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Study on ameliorating friction noise of ABS materials by lubrication
Polymer Testing 82 (2020) 106307
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Study on ameliorating friction noise of ABS materials by lubrication Lin Wang a, b, Hui He a, *, Rongtao Lin b, Zhiqiang Wu b, Qi Wang b, Bo Yang b, Rui Chen b a
School of Materials Science and Engineering, South China University of Technology, No 381, Wushan Road, Tianhe District, Guangzhou, 510640, People’s Republic of China b National-certified Enterprise Technology Center, Kingfa Science and Technology Co., Ltd, No.33 Kefeng Road, Science Town, Guangzhou, 510663, People’s Republic of China
A R T I C L E I N F O
A B S T R A C T
Keywords: Friction noise Lubrication Stick-slip phenomenon
In this study, the stick-slip mechanism of ABS resin friction noise and the effect of different lubricants on the friction noise were investigated by means of friction coefficient test instrument and self-designed noise test method. It was found that different types of lubricants have different effects on ameliorating the noise and stickslip phenomena of ABS material. As the content of lubricant increased, the friction noise and stick-slip phe nomenon of ABS were reduced. According to the study, reducing the dynamic and static friction △F was the key factor to reduce the stick-slip phenomenon and reduce the friction noise.
1. Introduction ABS resin is a terpolymer formed by copolymerization of acryloni trile, butadiene and styrene. Due to the special chemical and physical combination mode, the ABS resin has excellent heat resistance, chemical resistance, low-temperature impact resistance, rigidity and toughness balance and good processing performance, so that the ABS resin is widely applied to the fields of household appliances, office equipment, automobiles, communication and the like. The application of ABS in the automobile field mainly comprises pillar, air conditioner grille, acces sories of instrumental panel as well as door panel and other parts. These parts may be assembled with various metal or plastic parts to form the parts assembly (such as the whole dashboard, the whole door panel) in the vehicle, and the contact between different parts is unavoidable. This presents a problem that the two plastic parts often produce a noticeable and unpleasant creaking noise [1–3] as a result of sliding friction against each other when the vehicle is braking, turning sharply or driving on a bumpy road. In recent years, with the development of automobile sound insu lation technology, the noise such as tire noise, wind noise and the like from the outside of the automobile is effectively attenuated, and the noise level in the automobile is greatly reduced, but the friction noise between components in the automobile is audible, so that the automo bile sound insulation technology is widely concerned. These noises can be removed by some conventional ways like mounting felt pads or
smearing lube oil between the contact surfaces of different parts, but these methods have the disadvantage, namely increasing the manufacturing process and cost of automobiles. Therefore, how to reduce friction noise through material modification has been paid more attention by material researchers. At present, the research at home and abroad shows that there are three main mechanisms of noise generation caused by friction: the stickslip mechanism, the sprag-slip mechanism and the mode-coupling in stabilities mechanism [4]. Most of the studies [5–8] show that the creaking is due to the stick-slip phenomenon occurring during the mutual sliding of the plastic parts. The characteristic of the phenomenon is that the relative sliding of the two parts (the surface of the part has a certain degree of elastic freedom) is discontinuous, with the occurrence of the sliding, the fric tion force presents the trend of sawtooth waves [9,10]. Ohara [11,12] believed that this motion was the result of a combination of surface roughness and material surface elasticity. It could be understood that when two polymers in contact tend to slide relative to each other under an external force, the van der Waals force between the two polymer molecules and the surface roughness made the two polymers adhere to each other on the contact surface, thus generating a friction force, and limiting the relative sliding. This caused deformation of the microscopic surface of the polymer and the material accumulates potential energy due to the deformation. But as the external force was further increased, the accumulative potential energy was large enough to overcome the
* Corresponding author. College of Materials Science and Engineering, South China University of Technology, No 381, Wushan Road, Tianhe District, Guangzhou, 510640, People’s Republic of China. E-mail address: [email protected] (H. He). https://doi.org/10.1016/j.polymertesting.2019.106307 Received 12 October 2019; Received in revised form 4 December 2019; Accepted 18 December 2019 Available online 19 December 2019 0142-9418/© 2019 Published by Elsevier Ltd.
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adhesion, and the two materials would move relative to each other. At the same time, the release of potential energy caused the vibration of the material and ambient air, and then creaking noise was produced. The key factor for the occurrence of stick-slip motion is generally considered to be a large difference between the static coefficient of friction and the dynamic coefficient of friction or a negative correlation between the dynamic coefficient of friction and the relative sliding speed during the sliding process [11–16]. When the two plastic parts are about to slide relative to each other, if the difference between the dynamic friction force and static friction force is small, the transition from static state to sliding state will be very steady. In contrast, if the static friction force is significantly greater than the dynamic friction force, the friction force will drop abruptly at the moment of sliding, and this sudden change will easily result in unstable sliding and stick-slip motion. Similarly, when the relative sliding of the material has just occurred, the relative sliding speed increases, but the frictional force decreases, that is, the coefficient of dynamic friction is negatively correlated with the relative sliding speed until the frictional force is small enough to overcome the intermolecular adhesion, and the sliding is suppressed, resulting in unstable sliding. This phenomenon is similar to a physical model in which a slider attached to a wall by a spring slides relative to the rough ground. The research of Eiss Jr. shows that the surface roughness, the load, the relative sliding speed between ABS parts and ABS material itself can affect the above-mentioned unstable sliding phenomenon [17]. The smooth-smooth contact surfaces are easier to occur stick-slip phenom enon than the rough-rough contact surfaces; With the increase of the load (i.e. the mutual compressive force of the two contact surfaces is increased), the phenomenon of stick-slip is more significant; Compared to the material without the addition of silicone oil, the material added with silicone oil has no stick-slip phenomenon, and the author considers that the surface energy of the polymer is lowered by silicon, so that the surface adhesion of the polymer is lowered. Norman [17] proposed that the rectangular wave phenomenon of friction observed in stick-slip motion (described by the phenomenon of peak-to-peak force variation in the friction curve) is related to the noise level, and he believes that noise can be accepted when the corresponding coefficient of friction (COF) at the friction peak is less than 0.4. His research shows that when fiberglass-added polypropylene (FPP) sliding with polycarbonate (PC) or a fiber-filled styrene-maleic anhydride polymer (SMAC), the stick-slip phenomena are more slight than those of FPP and FPP, PC and PC, SMAC and SMAC. On the one hand, the glass fiber improves the rigidity and hardness of the material, so that the surface of the material is difficult to accumulate deformation potential energy. On the other hand, the glass fiber modification and the combination of the surfaces of different ma terials form a very small surface roughness, so that the COF is reduced. Ganguly found that adding MA-g-SEBS to ABS could ameliorate the stick-slip phenomenon of ABS. He observed that the addition of MA-g-SEBS increased the surface friction of ABS and the results were characterized through DMA and SEM, He believed that the addition of MA-g-SEBS gave the ABS proper surface morphology and damping properties, and thus the stick-slip phenomenon was ameliorated. In practical application, the method for reducing the stick-slip phe nomenon by changing the surface roughness of the polymer and improving the damping performance of the material is not necessarily applicable. For example, in the automobile industry, there is a gloss requirement for ABS materials used to make automobile decorations, but increasing the surface roughness of ABS tends to result in loss of surface gloss. And the method for improving the damping performance of the material is that additives such as rubber and the like are added to the polymer, so that the overall rigidity of the material is reduced. Therefore, the research wants to find a surface modification method which has less influence on the surface roughness to ameliorate the stick-slip phenomenon of the ABS material and to further solve the friction noise problem of the ABS material. The friction force is mainly caused by the adhesion of the real contact
surface [18]. Erhard’s research [19] also showed that the surface energy (which is closely related to the intermolecular interaction force at the contact surface) of the polymer has a good correlation with the friction adhesion. Therefore, by adding the lubricating modifier and allowing it to migrate to the surface of the material, the surface energy of the polymer can be changed, the surface adhesion can be reduced, and this method can be used as an effective and economical method for changing the friction characteristics of the surface of the polymer. Ohara, K [20] ameliorates the stick-slip phenomenon by blending silicone oil or PTFE with ABS resin. Although it was not pointed out by the author, the idea is to use the incompatibility of silicone oil or PTFE with ABS to migrate them to the ABS surface, then to improve surface energy and reduce adhesion. Jareenuch Rojsatean [17] reduces the dynamic and static friction coefficient of the material and the magnitude of the bimodal vibration of the stick-slip curve by adding ethylene bis-stearamide (EBS) and polyethylene-octene copolymer (POE). However, macromolecular materials like PTFE and POE have poor compatibility with ABS and can bring great reduction of ABS properties. In contrast, small molecules of silicone oil and EBS could be better choices. Yaogang Wang et al. [21, 22] had investigated properties of different nanofluids by analyzing a frictional test and a grinding experiment. They had also studied the application effect of different volume concentrations of Al2O3 nanofluids on force ratio, specific energy, G-ratio and surface quality, wheel morphology, chip formation and viscosity and contact angle during the MQL (Minimum Quantity Lubrication) grinding of Ni-based alloy (Inconel718). Unlike pure oil MQL grinding, Al2O3 nanofluid MQL grinding can form thin protective oil forms on the grinding wheel and workpiece surface. These films improve the tribological performance of grinding wheel/workpiece interfaces significantly. SEM and EDX anal ysis further prove the existence of the lubrication film. Therefore, no matter what material or industry it is, such as metal and polymer, lu bricants could be very important for the improvement of the tribological performance. In this study, a friction coefficient tester and a self-designed noise tester are also adopted to characterize the dynamic and static friction coefficients, the stick-slip motion and the friction noise of different modified materials, so as to explore the generating mechanism of the friction noise and the key factors for controlling the friction noise. 2. Experimental 2.1. Experimental materials Ordinary ABS resin: Melt flow index 16g/10min(220 � C,10 kg), Vicat softening point temperature 110 � C, made by Kingfa SCI. & TECH. CO., LTD. Low noise ABS material: Melt flow index 18g/10min (220 � C, 10 kg), Vicat softening point 110 � C, made by Kingfa SCI. & TECH. CO., LTD. Silicone lubricant TP-200E(Molecular weight ¼ 600000 Da), made by Zhejiang Java Specialty Chemicals Co., Ltd. Ethylene bis stearamide (Molecular weight ¼ 593 Da), made by PT. CMS Chemical Indonesia. Polyethylene wax (140 � C, viscosity 800 Pa∙s), Clariant Specialty Chemicals. Fatty acid lubricant(Molecular weight ¼ 200–1000 Da), Struktol Company of America, LLC. 2.2. Experimental equipment and instruments Double screw extruder: SHJ-30, Nanjing Ruiya Chemical Equipment Co., Ltd. Injection molding machine: B-920, Zhejiang Haitian Plastic Machinery Co., Ltd. Sealing strip wear-resistance testing machine, Dongguan Maisheng Electronic Equipment Co., Ltd. Quadratic element imager, Dongguan Yuanxin optical instrument. Scanning electronic microscopy: S-3400, Hitachi High-Technologies (Shanghai) Co., Ltd. Stick-slip tester: SSP-03, Ziegler-Instruments GmbH Co., Ltd. Time-ofFlight secondary ion mass spectrometry: Model 2100 Trifft II, Physical Electronics. 2
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2.3. Sample preparation
the material was continuously subjected to repeated deformation and rebound processes, so that the noise could be generated. Quadratic element imager and scanning electronic microscopy (SEM) test: The samples which were used in friction noise performance test were observed on the surface to observe scratch marks with a quadratic element imager (Fig. 3 left) and S-3400 scanning electron microscope (Fig. 3 right). The scratch marks firstly studied under the quadratic element imager under a magnification of 150 times then observed under SEM with a magnification of 1000 times. Before SEM observation, gold spray on sample surface was required to ensure clear image acquirement of the scratch marks. Stick-slip test: the stick-slip properties of different materials were tested using an SSP-03 stick-slip test instrument from ZIGLER Corpora tion (Fig. 4). The tests were conducted in accordance with the VDA 230206 standard. The principle was similar to friction coefficient test which is talked above. Two test samples were separately stuck to a stator and a slider. The slider could move from left to right circularly, relative movement occurred between two samples and data which included load, slide speed as well as acceleration were acquired. Further risk priority number (RPN) could be calculated to depict the risk of slip-stick occurrence. RPN was graded from level 1 to level 10. Wherein the higher the grade is, the more serious the stick-slip phenomenon is. Three levels of load (2.4 N, 40 N and 80 N) as well as three level of speed (1 mm/s, 6 mm/s and 12 mm/s) were set as parameters and cross-studied in order to cover almost possible “squeak-generated” situation in the cars. Time-of-Flight secondary ion mass spectrometry (TOF-SIMS) test: element analysis of sample surface was studied and linked to friction noise with TOF-SIMS Model 2100, made by physics electronics (Fig. 5). Analysis process was conducted according to ASTM E 1078 and 1829. Gallium LMIG was used as initial ion beam and an initial energy was set as 25 keV. Silicone modified ABS sample was studied with this instrument to study dispersion and effect of silicon.
The preparation method comprises the following steps: weighing ABS (80–84 wt%), heat-resistant master batch (15 wt%), pigment (0.5 wt%), antioxidant (0.5 wt%) and lubricants(0–4 wt%), uniformly mix ing, melting, blending, extruding and granulating by using a doublescrew extruder at the temperature of 240–250 � C The resulting pellets were dried in an oven at 80 � C for 2 h, and then were made into square plates of 100 mm � 100 mm � 2 mm and ISO standard mechanical specimens through injection molding machine for later testing. 2.4. Testing and characterization Friction coefficient test: The friction coefficient of the modified sample was measured by FT-1 friction coefficient test equipment (pro duced by AMETEK) according to standard GB 10006-88. Fig. 1 showed the schematic of the test. Two test samples made from the same material was separately stuck to a slider with double-side tape while the other was stuck to the instrument base of the equipment. When the force sensor rose by a certain speed, it dragged the slider moved from left to right. Meanwhile, the drag force against distance could be recorded. In further calculation, dynamic and static friction coefficients against dis tance were obtained. Direction force FN and movement speed were set as 2 N and 100 mm/min according to the GB 10006-88. Friction noise performance test: According to the literature and experiment, we set up the material friction noise test equipment. Fig. 2 is the test process and the test schematic diagram. As shown in Fig. 2, the test instrument generates noise by sliding friction between an upper plate vertically fixed to the jig and a lower plate fixed to the stage under a certain load. The upper plate was a flat plate with a size of 20 mm in width, 40 mm in height and 2 mm in thickness and the lower plate was 2 mm in thickness. The load FN was applied to the upper plate by fixing a 20 N weight on the bracket during the test. In the sliding process, the decibel value is recorded by using a decibel gauge, namely, the Biaokang HT-80A, and the decibel gauge and the friction interface are always kept at a distance of 2–4 cm so as to record the noise generated in the friction process. Simultaneously a sound collecting device was used to collect noise signals. The collected noise signal was processed by Adobe Audience. As shown in Fig. 2, the upper plate was deformed due to the friction force in the sliding process, namely, the upper plate was bent along the direction subjected to the friction force, the material was continuously bent and deformed along with the relative sliding process, and when the resilience force generated by the deformation exceeded the friction force, the material would spring back to its original shape, and vibration could be generated when
3. Results and discussion 3.1. The relationship between friction noise and stick-slip phenomenon of ABS materials Fig. 6 shows the results of testing ordinary ABS and a low friction noise ABS material using a friction coefficient testing platform. It could be seen from the test curve that the friction force of the ordinary ma terial changed periodically in the sliding process and the curve was zigzag. The sliding block could be observed to advance in a jumping mode in the test process and obvious stick-slip phenomenon was shown.
Fig. 1. Principle of the friction coefficient tester. 3
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Fig. 2. Friction noise performance test schematic diagram.
Fig. 3. Quadratic element imager (left) and scanning electronic microscopy (right).
Fig. 4. Schematic diagram of SSP-3 stick-slip instrument.
As can be seen from the test curve of the low noise material, as the rope was tightened, the friction force was gradually increased until the block starts sliding. The friction force was kept stable when the block slid and no stick-slip phenomenon took place. So this friction test could reflect the stick-slip tendency of the material to some extent. In the friction test curve, the ratio of the maximum friction force FS to the applied load (FN) that the sliding block was subjected to in stationary was the static fric tion coefficient (μs), and the ratio of the friction force FD to the load that the sliding block was subjected to during sliding was the dynamic fric tion coefficient (μD). It can be seen from Fig. 6 (a) that the friction force of the sliding block was constantly changing during sliding, and the dynamic friction coefficient was the ratio of the average value of the dynamic friction force of the sliding section to the load. In order to characterize the degree of stick-slip of materials, the amplitude △F of the stick-slip motion was introduced in, that was, the difference between the average value of the maximum value of the friction force and the average value of the minimum value of the friction force during the
sliding process in the friction test. The larger △F indicated the greater the amplitude of the jumping advance of the sliding block, and the greater the tendency of the stick-slip motion took place. Fig. 7 is the noise testing results of different materials according to the experimental section noise test method. It could be seen that the noise of ordinary materials was very loud. In the audio curve output by Adobe Audition, there were many sharp noise peaks and the maximum decibel was 82 dB according to the decibel meter. The audio curve of the low noise material was very stable and had almost no strong and sharp noise peak, and the maximum decibel was only 62 dB according to the decibel meter. The results of ordinary materials and low noise materials were consistent with those of noise test and stick-slip test, which indi cated that the friction noise was related to the stick-slip motion. Spe cifically, the friction creaking noise was generated by two objects contacting each other and sliding toward each other, and when the sliding was in an unstable state, the stick-slip motion was extremely easy to occur. The stick-slip motion occurs on the contact surface of two 4
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Fig. 5. Time-of-Flight secondary ion mass spectrometry.
Fig. 7. Noise test results of different materials (a) Ordinary ABS Material (b) Low Noise ABS Material.
deformed, and the material accumulates potential energy due to the deformation. With the further increase of the external force, when the accumulated potential energy is large enough to overcome the adhesion, the two materials can generate relative displacement, which is “slip”. At the same time, the release of potential energy causes vibration of the material and the surrounding air, causing a creaking sound [23]. Fig. 8 is the graphs of morphology of the bottom plate after the noise test of both materials using quadratic and scanning electron microscopy. As can be seen from Fig. 8 (A), the surface of the bottom plate had distinct stripes perpendicular to the direction of friction, which was caused by the stick-slip phenomenon with the upper plate, the noise was produced by the constant deformation-rebound vibration of the material during the unstable sliding, but the surface of the low noise material only had obvious striation parallel to the sliding direction, which indi cated that the relative sliding motion of the two plates was in a steady state, and the stick-slip phenomenon completely disappeared. The observation of the surface morphology of the sample after scraping directly confirmed the existence of the stick-slip phenomenon in the noise testing process, and also proved that the stick-slip phenomenon was the cause of the noise’s generation, which was consistent with the results of other researchers. By observing the scraped sample under an electron microscope, the change of the morphology after scraping could be observed more directly, and the result was shown in Fig. 8 (C). As can be seen from the figure, for the ordinary material, the dent perpendic ular to the friction direction is relatively narrow, only 40 μm, but deeper, which indicates that the degree of adhesion was very high, the defor mation amount of the material was increased due to the strong adhesion, the potential energy storage was increased, and the noise was more easily caused; However, as shown in Fig. 8 (D), the dent of the low noise material became unobvious, and the distance became significantly larger by 90 μm, which was also shallower, indicating that the adhesive force is not strong, and the material rebound was mild. The above results could further confirm the action mechanism of stick-slip phenomenon, and indicate that the main means to avoid the generation of friction noise is to reduce stick-slip.
Fig. 6. The stick-slip test curves for different materials (a) Normal ABS Material (b) Low Noise ABS Material.
mutually contacted objects, and under the condition of the same surface morphology, the interaction between the two polymer molecules cause the two to adhere on the contact surface so as to generate friction force and limit the relative sliding. At this time, the two objects are relatively stationary, which is “stick”. The microscopic surface of the polymer is
3.2. The relationship between surface tribological characteristics of ABS material and friction noise The research shows that the creaking noise of the automobile parts can be effectively ameliorated by covering those parts with grease or the 5
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Fig. 8. The bottom plate’s surface morphology after the noise test: (A) The quadratic image photograph of ordinary material; (B) The quadratic mage photograph of low noise material; (C) The SEM picture of ordinary material; (D) The SEM picture of low noise material.
coating with low friction coefficient. However, due to the complexity of its procedures and the possibility of introducing sporadic substances to pose a safety hazard to the health of drivers and passengers, they are not widely accepted [24]. In the modification process, different kinds of lubricants are added to influence the friction performance of polymer injection molded products so as to ameliorate the creaking noise of parts, which becomes a new research direction. In this research, the lubricant was used to modify ABS, and the self-designed noise test equipment was used to test the noise performance of ABS material modified by lubricating promoter. As ABS is a kind of polar polymer, some non-polar substances, especially those with small molecular weight, could be used as external lubricants for ABS. Common non-polar lubricants for ABS include silicone, ethylene bis-stearamide, esters of fatty acid, polyethylene wax and so on. Theoretically these lubricants tend to migrate to surface of ABS, forming a thin lubricating layer,
resulting in more easily relative motion between ABS samples [21,22]. Fig. 9 is the audio chart of noise test of the typical samples. It can be seen that the noise performance of ordinary material was not good, the noise decibel value was 82 dB, the noise performance of a silicone lubricant modified ABS material was improved, and the noise decibel value was reduced to a certain extent; The modified ABS material of polyethylene wax was completely free of noise, which indicated it has the capability of completely eliminating the friction noise between ABS parts. As for the difference in the amelioration of the stick-slip phenomenon of different lubricants, we presumed that it was caused by the difference in the degree of improvement of ABS surface energy by different lubricants. The results of dynamic and static friction coefficient, the coefficient difference △μ, the amplitude △F and noise of materials modified by different lubricants during sliding process are listed in Table 1. As can be seen, compared with the unmodified ordinary materials, the dynamic
Fig. 9. Noise performance test results of ABS materials modified by different lubricating promoters: (A) unmodified ABS; (B) ABS modified by ethylene bis stear amide; (C) ABS modified by Silicone; (D) ABS modified by Polyethylene wax. 6
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and static friction coefficients of the modified ABS materials were obviously reduced after different lubricating modification promoters were added (Fig. 10). According to Fig. 10 and Table 1, the dynamic and static friction coefficients of ordinary materials were both large, and the stick-slip phenomenon was obvious, the △F reached 0.302 N. After the lubricant was added, the stick-slip phenomenon was weakened to different degrees, and the amplitude of the stick-slip phenomenon was obviously reduced or even disappeared, which indicated that the modification effects of different lubricating modifiers were different. Among them, the effect of polyethylene wax was the best and the figure of the noise test result was the lowest (Fig. 11). In general, the lubri cating effect of the lubricant is achieved by reducing the coefficient of friction, in particular the coefficient of dynamic friction, whereas for frictional noise, the effect of only reducing the coefficient of friction is not ideal. As shown in Table 1, the addition of silicone-based modifi cation promoters greatly reduced the μs and μd of the ABS material, especially the coefficient of kinetic friction μd was reduced to 0.216, which was the lowest in all samples. So it was an important reason why silicone compounds could be used as polymer scratch-resistant agents. However, the stick-slip phenomenon was very obvious in the friction test, the amplitude △F reached 0.213 N, and the noise test result was 74 dB, which was only slightly lower than that of the unmodified ABS material. This was consistent with the results of Ronald A.L. Rorrer and others [4]. The stick-slip phenomenon of the material is not simply related to the dynamic and static friction coefficient, but to the differ ence between the two, which is consistent with the results presented in Table 1. The coefficient difference △μ of ordinary unmodified materials was about 0.082. The dynamic and static friction coefficients of poly ethylene wax were reduced, and the difference △μ of dynamic and static friction coefficients was also reduced to 0.018, so the stick-slip tendency of the materials was reduced. Although the dynamic friction coefficient of the material modified by the polyethylene wax was not the lowest, the static friction coefficient μs of the material was reduced more greatly. So the difference △ μ between the dynamic friction coefficient and the static friction coefficient was reduced obviously. Therefore, regarding the ameliorating of the friction noise performance of the material through the lubricating promoters, we need to pay more attention to the overall change of the static and dynamic friction coef ficient of the material rather than only to the change of the dynamic friction coefficient μd. For this phenomenon, Martin Trapp gave the explanation: The key to solve the creaking noise problem was to eliminate the stick-slip motion, which was described by the following stick-slip equation [24]: From the equation, the stick-slip motion was closely related to the difference between the load and the dynamic-static friction coefficient. Load was often determined by component design and operating condi tions. When the creaking noise occurred, the load could not be changed, so the dynamic and static friction coefficients became the only optimi zation direction. Therefore, the characteristic of the low dynamic and static friction coefficient of the polyethylene wax was the key to solve the problem of creaking noise.
Fig. 10. Effect of different lubricants on friction coefficient of ABS.
Fig. 11. Relationship of △μ and sound intensity (squeak noise) performed by modifying ABS with different lubricants.
The stick-slip performance of ABS modified by polyethylene wax with different contents was systematically studied, and the results are shown in Fig. 12. As can be seen from the figure, the dynamic and static friction coefficients of the modified ABS material were gradually reduced with the increase of the addition amount, the stick-slip degree of the material was gradually reduced, and the noise test result was gradually reduced too. When the addition amount reached 2% or more, the stick-slip phenomenon in the friction test was very weak and could hardly be observed, and the noise decibel value was also reduced to 67 dB. Table 2 and Fig. 13 show the friction coefficient data of ABS mate rials modified by polyethylene wax at different contents, and it could be seen that the dynamic and static friction coefficients of the materials were reduced with the increase of the content of modifying promoters and the decrease of the difference of the dynamic and static friction coefficient △μ greatly reduced the viscosity-slip tendency of the ma terial. Fig. 14 is a graph showing the surface morphology of the noise test base plate of the ABS modified with polyethylene wax at different contents, and it could be seen that as the amount of addition increased, the adhesion streaks perpendicular to the scraping direction decreased until disappearing, indicating that the stick-slip motion gradually decreased, which is in accordance with the results of the noise test. Fig. 15 is the attenuated total reflection (ATR) spectrum of different amounts of ethylene wax. It can be seen that the polyethylene wax has a very significant absorption peak at 1470 cm 1, which is the bending
Table 1 Friction coefficient and noise test results of ABS materials modified by adding 4 wt% of different lubricating modification promoters. Lubricating modifier
Static friction coefficient μs
Dynamic friction μd
△μ
△F/ N
Sound Intensity/ dB
None Silicone Ethylene bisstearamide Esters of fatty acid Polyethylene wax
0.507 0.292 0.321
0.425 0.216 0.275
0.082 0.076 0.046
0.302 0.213 0.184
82 74 71
0.246
0.217
0.029
<0.02
62
0.247
0.229
0.018
<0.02
58
7
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vibration peak of methylene. The peak in the surface is stronger than the inner layer compared to the surface’s and inner layer’s infrared spec trum of the 96% ABS/4% wax, which indicating the higher content of wax in the surface. The wax migrated to the surface to lubricate the surface of the ABS, reducing the friction coefficient of the material and further reducing the noise. The stick-slip tendency of lubrication-free and polyethylene wax modified ABS materials was characterized by SPP-03 stick-slip tester. The results are shown in Table 3. The RPN values of the unmodified materials were all higher than those of the modified ABS materials, particularly under the conditions of 40 N load, 1mm/s speed, 80 N load and 6mm/s speed, the lubrication-free materials reached the higher grades to level 6 and level 9, and the modified materials only reach to level 2 and level 1, which indicated that the modification by poly ethylene wax substantially reduced the stick-slip tendency of the material. Rojsatean’s study [17] indicates that static friction coefficient is related to static adhesion, and further studies suggest that static adhe sion is closely related to polymer composition characteristics, that is, the surface energy. The critical surface tension of the polymer material will be changed when the H atoms in the polymer hydrocarbon chain are replaced by other elements or when other elements are introduced into the compound chain. Generally, except the F halogen atom, an atom in the halogen element replaces the H atom in the polymer or to introduce a N atom or an O atom into the polymer chain will result in an increase in the critical surface tension of the polymer (the surface hydrophobicity was decreased), the order of some common elements increasing surface free energy is: N > O > I > Br > Cl > H > Si > F. Since the ABS matrix contains acrylonitrile bond, its surface energy is high, and the risk of generating stick-slip is very high. The free energy of the H element is far less than N element. After the ethylene-octene copolymer is added into the ABS matrix [18], a small amount of the ethylene-octene copolymer migrates to the surface of the ABS material, thereby reducing the surface energy of the ABS, weakening the adhesion force and achieving the
Fig. 12. Friction curve and noise test results of ABS modified by polyethylene wax with different contents. Table 2 Stick-slip test results. Load (N)
Speed (mm/s)
2.4 2.4 2.4 40 40 40 80 80 80
1 6 12 1 6 12 1 6 12
RPN Lubricant-free
4 wt% Polyethylene Wax
Level 2 Level 2 Level 2 Level 6 Level 2 Level 2 Level 9 Level 2 Level 3
Level Level Level Level Level Level Level Level Level
1 1 1 2 1 1 1 1 1
Fig. 13. Friction coefficient and noise test results of ABS modified by poly ethylene wax.
Fig. 15. ATR study on the surface of ABS samples modified with different content of polyethylene wax.
Fig. 14. Surface morphology of modified ABS noise test plate with different content of polyethylene wax. 8
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ion mass spectrometry mass spectrometry. It can be seen from the figure that the silicon element distribution was not uniform, while the ABS sample coated with the silicon coating had a very uniform distribution of silicon on the surface. Correspondingly, the ABS sample coated with the silicon-coated coating had the lowest surface energy and the value of the difference between the dynamic and static friction coefficients was close to zero, so that the effect of improving the click noise was the most excellent. In summary, the key to eliminating click noise is to eliminate the stick-slip motion and one of the methods to solve the stick-slip motion is to attach a uniform low surface energy material to the surface of the polymer matrix.
Table 3 Contact angle and surface energy of different modified ABS. Modifier
Blank Silicone Ethylene bis stearamide Fatty acid ester
Contact angle
Surface energy
Water
Diiodomethane
Polar force
Dispersion force
Total
86.16 100.12 97.14
25.45 24.58 19.64
1.009 0.06 0.004
45.99 36.58 45.35
47 36.64 45.35
99.39
17.67
0.08
37.07
37.15
purpose of reducing the difference between the static friction coefficient and the dynamic-static friction coefficient, thereby eliminating the stick-slip motion. Compared with the ethylene-octene copolymer, the addition of the PE wax has less influence on the mechanical property of the ABS material. Meanwhile, the low viscosity of PE wax enables itself to be easily gathered on the surface in injection molding process to form a PE-rich wax skin, which has a better effect of reducing the surface energy. Table 3 shows the surface energy test results. It can be seen from the table that the surface energy of silicone, ethylene bis-stearamide and fatty acid modified ABS decreased significantly and the surface energy of the fatty acid modified ABS reduced most obviously. This was in agreement with the test results of friction noise. As decrease of surface energy resulted in the reduction of adhesion between materials and thus the difference between the dynamic and static friction coefficients, thereby reducing the frictional noise caused by the stick-slip vibration. It was worth noting that the silicone modified ABS showed the lowest energy, but the noise improvement was normal. It was mainly because the silicone was a high molecular weight material, which could not be uniformly dispersed in the ABS matrix and was easily surface-enriched. As shown in Fig. 16 below, the silicone-added ABS template was tested for the distribution of Si element on the surface by flight time-secondary
4. Conclusion The consistency of the results of friction performance test and noise test and the results of surface morphology of the noise test plate proved that the friction noise of the ABS material was mainly caused by the stick-slip phenomenon. There is a significant correlation between the noise and the friction force variation △F during relative sliding of the two parts. Decreasing △F can reduce the noise caused by friction. It was found that different types of lubricants have different effects on ameliorating the noise and stick-slip phenomena of ABS material. By adding lubricant to the ABS material, most of the lubricants evaluated could reduce the △F to different degrees, thereby reducing stick-slip phenomenon and friction noise. Among those lubricants, fatty acid ester and polyethylene wax are the most effective. The difference in the effect of different lubricants on ameliorating stick-slip should be related to the degree of influence of lubricants on the surface energy of ABS materials. It could be inferred that reducing the dynamic and static friction △F was the key factor to reduce the stick-slip phenomenon and reduce the friction noise.
Fig. 16. Ion mass spectrum of silicone modified ABS Graph 1 Graph2. 9
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Author statement
[8] S. Ahmadi, P. Nassiri, I. Ghasemi, M.R.M. Esmaeilpoor, Iran. Polym. J. (Engl. Ed.) v24 (2015), https://doi.org/10.1007/s13726-015-0353-0. [9] S.N. Patek, J.E. Baio, The acoustic mechanics of stick slip friction in the California spiny lobster (Panulirus interruptus), J. Exp. Biol. v210 (2007), https://doi.org/ 10.1242/jeb.009084. [10] K. Nakano, Two dimensionless parameters controlling the occurrence of stick-slip motion in a 1-DOF system with Coulomb friction, Tribol. Lett. v24 (2006), https:// doi.org/10.1007/s11249-006-9107-7. [11] A. Elmaian, F. Gautier, C. Pezerat, J.M. Duffal, Improving dynamic and tribological behaviours by means of a Mn–Cu damping alloy with grooved surface features, Appl. Acoust. v76 (2014), https://doi.org/10.1016/j.apacoust.2013.09.004. [12] N.S. Eiss, B.P. McCann, Frictional instabilities in polymer-polymer sliding, Tribol. Trans. v36 (1993), https://doi.org/10.1080/10402009308983211. [13] E.L.N. Eiss, M. Trapp, Frictional behavior of automotive interior polymeric material pairs, SAE Technical Papers (1997), https://doi.org/10.4271/972056. [14] J.H. Norman, S. Eiss, Stick–slip friction in dissimilar polymer pairs used in automobile interiors, Tribol. Int. v31 (1998), https://doi.org/10.1016/s0301-679x (98)00092-9. [15] R.A.L. Rorrer, V. Juneja, Friction-induced vibration and noise generation of instrument panel matrial pairs, Tribol. Int. v35 (2002), https://doi.org/10.1016/ S0301-679x(02)00047-6. [16] H. Jiang, Q. Cheng, C. Jiang, J. Zhang, L. Yonghua, Effect of stick-slip on the scratch performance of polypropylene, Tribol. Int. v91 (2015), https://doi.org/ 10.1016/j.triboint. 2015.06.024. [17] J. Rojsatean, Experimental bench for studying the relation between the dynamic characteristics of the frictional motion and the electric potential at the surface of polymer slabs in sliding conformal contact, Tribol. Int. v109 (2016), https://doi. org/10.1016/j.triboint. 2016. 12.055. [18] Z. Rymuza, Tribology of polymers, Archives of Civil and Mechanical Engineering v4 (2007), https://doi.org/10.1016/s1644-9665(12)60235-0. [19] G. Erhard, Sliding friction behavior of Polymer-Polymer material combinations, Wear v84 (1983), https://doi.org/10.1016/0043-1648(83)90262-4. [20] K. Ohara, Stick-Slip motion and surface deformation, Wear v50 (1978), https:// doi.org/10.1016/0043-1648(78)90077-7. [21] Y.G. Wang, Comparative evaluation of the lubricating properties of vegetable-oilbased nanofluids between frictional test and grinding experiment, J. Manuf. Process. v26 (2017), https://doi.org/10.1016/j.jmapro.2017.02.001. [22] Y.G. Wang, Experimental evaluation on tribological performance of the wheel/ workpiece interface in minimum quantity lubrication grinding with different concentrations of Al2O3 nanofluids, J. Clean. Prod. v142 (2017), https://doi.org/ 10.1016/j.jclepro. 2016.10.110. [23] K. Ohara, Observations of surface profiles and the nature of contact between Polymer films by multiple beam interferometry, Wear v39 (1976), https://doi.org/ 10.1016/0043-1648 (76) 90053-3. [24] M. Trapp, F. Chen, Automotive Buzz, Squeak and Rattle: Mechanisms, Analysis, Evaluation and Prevention, Elsevier Science, Burlington, 2012, https://doi.org/ 10.1016/b978-0-7506-8496-5.00001-4.
I have made substantial contributions to the conception or design of the work and I have drafted the work or revised it critically for important intellectual content. I agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. Declaration of competing interest The authors declare no conflict of interest. Acknowledgements Thanks for the device supports from National-certified Enterprise Technology Center, Kingfa Science and Technology Co., Ltd., and the financial supports by the National Key Research and Development Program of China (2016YFB0302005). References [1] R. Johnsson, J. Odelius, M. Rantatalo, A new test track for automotive squeak and rattle (S&R) detection, Appl. Acoust. v80 (2014), https://doi.org/10.1016/j. apacoust.2014.01.010. [2] M.L. Ridder, P. Khosropanah, R.A. Hijmering, T. Suzuki, M.P. Bruijn, H.F. C. Hoevers, J.R. Gao, M.R. Zuiddam, J. Low Temp. Phys. v184 (2015), https://doi. org/10.1007/s10909-015-1381-z. [3] S.H. Shin, J.G. Ih, T. Hashimoto, S. Hatano, Sound quality evaluation control of car interior noise, Appl. Acoust. v70 (2008), https://doi.org/10.1016/j. apacoust.2008.03.009. [4] A. Elmaian, F. Gautier, C. Pezerat, How can automotive friction-induced noises be related to physical mechanisms, Appl. Acoust. v76 (2014), https://doi.org/ 10.1016/j.apacoust.2013.09. 004. [5] F.C.C. Ciofi, C. Pace, G. Scandurra, High sensitivity instrumentation for low frequency noise measurements, IEEE Transactions on Instrumentayion and Measurement v52 (2003), https://doi.org/10.1109/Tim.2003.817913. [6] A.L. Bot, E.B. Chakra, Improving Dynamic and tribological behaviours by means of a Mn–Cu damping alloy with grooved surface features, Iridology Letters v37 (2009), https://doi.org/10.1007/s11249-009-9521-8. [7] P.J. Wei, P.W. Tsai, J.F. Lin, Analysis based on microcontact mechanism for the roughness dependent stick–slip motion, Wear v266 (2009), https://doi.org/ 10.1016/j.wear. 2008.07.002.
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Study on ameliorating friction noise of ABS materials by lubrication Lin Wang a, b, Hui He a, *, Rongtao Lin b, Zhiqiang Wu b, Qi Wang b, Bo Yang b, Rui Chen b a
School of Materials Science and Engineering, South China University of Technology, No 381, Wushan Road, Tianhe District, Guangzhou, 510640, People’s Republic of China b National-certified Enterprise Technology Center, Kingfa Science and Technology Co., Ltd, No.33 Kefeng Road, Science Town, Guangzhou, 510663, People’s Republic of China
A R T I C L E I N F O
A B S T R A C T
Keywords: Friction noise Lubrication Stick-slip phenomenon
In this study, the stick-slip mechanism of ABS resin friction noise and the effect of different lubricants on the friction noise were investigated by means of friction coefficient test instrument and self-designed noise test method. It was found that different types of lubricants have different effects on ameliorating the noise and stickslip phenomena of ABS material. As the content of lubricant increased, the friction noise and stick-slip phe nomenon of ABS were reduced. According to the study, reducing the dynamic and static friction △F was the key factor to reduce the stick-slip phenomenon and reduce the friction noise.
1. Introduction ABS resin is a terpolymer formed by copolymerization of acryloni trile, butadiene and styrene. Due to the special chemical and physical combination mode, the ABS resin has excellent heat resistance, chemical resistance, low-temperature impact resistance, rigidity and toughness balance and good processing performance, so that the ABS resin is widely applied to the fields of household appliances, office equipment, automobiles, communication and the like. The application of ABS in the automobile field mainly comprises pillar, air conditioner grille, acces sories of instrumental panel as well as door panel and other parts. These parts may be assembled with various metal or plastic parts to form the parts assembly (such as the whole dashboard, the whole door panel) in the vehicle, and the contact between different parts is unavoidable. This presents a problem that the two plastic parts often produce a noticeable and unpleasant creaking noise [1–3] as a result of sliding friction against each other when the vehicle is braking, turning sharply or driving on a bumpy road. In recent years, with the development of automobile sound insu lation technology, the noise such as tire noise, wind noise and the like from the outside of the automobile is effectively attenuated, and the noise level in the automobile is greatly reduced, but the friction noise between components in the automobile is audible, so that the automo bile sound insulation technology is widely concerned. These noises can be removed by some conventional ways like mounting felt pads or
smearing lube oil between the contact surfaces of different parts, but these methods have the disadvantage, namely increasing the manufacturing process and cost of automobiles. Therefore, how to reduce friction noise through material modification has been paid more attention by material researchers. At present, the research at home and abroad shows that there are three main mechanisms of noise generation caused by friction: the stickslip mechanism, the sprag-slip mechanism and the mode-coupling in stabilities mechanism [4]. Most of the studies [5–8] show that the creaking is due to the stick-slip phenomenon occurring during the mutual sliding of the plastic parts. The characteristic of the phenomenon is that the relative sliding of the two parts (the surface of the part has a certain degree of elastic freedom) is discontinuous, with the occurrence of the sliding, the fric tion force presents the trend of sawtooth waves [9,10]. Ohara [11,12] believed that this motion was the result of a combination of surface roughness and material surface elasticity. It could be understood that when two polymers in contact tend to slide relative to each other under an external force, the van der Waals force between the two polymer molecules and the surface roughness made the two polymers adhere to each other on the contact surface, thus generating a friction force, and limiting the relative sliding. This caused deformation of the microscopic surface of the polymer and the material accumulates potential energy due to the deformation. But as the external force was further increased, the accumulative potential energy was large enough to overcome the
* Corresponding author. College of Materials Science and Engineering, South China University of Technology, No 381, Wushan Road, Tianhe District, Guangzhou, 510640, People’s Republic of China. E-mail address: [email protected] (H. He). https://doi.org/10.1016/j.polymertesting.2019.106307 Received 12 October 2019; Received in revised form 4 December 2019; Accepted 18 December 2019 Available online 19 December 2019 0142-9418/© 2019 Published by Elsevier Ltd.
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adhesion, and the two materials would move relative to each other. At the same time, the release of potential energy caused the vibration of the material and ambient air, and then creaking noise was produced. The key factor for the occurrence of stick-slip motion is generally considered to be a large difference between the static coefficient of friction and the dynamic coefficient of friction or a negative correlation between the dynamic coefficient of friction and the relative sliding speed during the sliding process [11–16]. When the two plastic parts are about to slide relative to each other, if the difference between the dynamic friction force and static friction force is small, the transition from static state to sliding state will be very steady. In contrast, if the static friction force is significantly greater than the dynamic friction force, the friction force will drop abruptly at the moment of sliding, and this sudden change will easily result in unstable sliding and stick-slip motion. Similarly, when the relative sliding of the material has just occurred, the relative sliding speed increases, but the frictional force decreases, that is, the coefficient of dynamic friction is negatively correlated with the relative sliding speed until the frictional force is small enough to overcome the intermolecular adhesion, and the sliding is suppressed, resulting in unstable sliding. This phenomenon is similar to a physical model in which a slider attached to a wall by a spring slides relative to the rough ground. The research of Eiss Jr. shows that the surface roughness, the load, the relative sliding speed between ABS parts and ABS material itself can affect the above-mentioned unstable sliding phenomenon [17]. The smooth-smooth contact surfaces are easier to occur stick-slip phenom enon than the rough-rough contact surfaces; With the increase of the load (i.e. the mutual compressive force of the two contact surfaces is increased), the phenomenon of stick-slip is more significant; Compared to the material without the addition of silicone oil, the material added with silicone oil has no stick-slip phenomenon, and the author considers that the surface energy of the polymer is lowered by silicon, so that the surface adhesion of the polymer is lowered. Norman [17] proposed that the rectangular wave phenomenon of friction observed in stick-slip motion (described by the phenomenon of peak-to-peak force variation in the friction curve) is related to the noise level, and he believes that noise can be accepted when the corresponding coefficient of friction (COF) at the friction peak is less than 0.4. His research shows that when fiberglass-added polypropylene (FPP) sliding with polycarbonate (PC) or a fiber-filled styrene-maleic anhydride polymer (SMAC), the stick-slip phenomena are more slight than those of FPP and FPP, PC and PC, SMAC and SMAC. On the one hand, the glass fiber improves the rigidity and hardness of the material, so that the surface of the material is difficult to accumulate deformation potential energy. On the other hand, the glass fiber modification and the combination of the surfaces of different ma terials form a very small surface roughness, so that the COF is reduced. Ganguly found that adding MA-g-SEBS to ABS could ameliorate the stick-slip phenomenon of ABS. He observed that the addition of MA-g-SEBS increased the surface friction of ABS and the results were characterized through DMA and SEM, He believed that the addition of MA-g-SEBS gave the ABS proper surface morphology and damping properties, and thus the stick-slip phenomenon was ameliorated. In practical application, the method for reducing the stick-slip phe nomenon by changing the surface roughness of the polymer and improving the damping performance of the material is not necessarily applicable. For example, in the automobile industry, there is a gloss requirement for ABS materials used to make automobile decorations, but increasing the surface roughness of ABS tends to result in loss of surface gloss. And the method for improving the damping performance of the material is that additives such as rubber and the like are added to the polymer, so that the overall rigidity of the material is reduced. Therefore, the research wants to find a surface modification method which has less influence on the surface roughness to ameliorate the stick-slip phenomenon of the ABS material and to further solve the friction noise problem of the ABS material. The friction force is mainly caused by the adhesion of the real contact
surface [18]. Erhard’s research [19] also showed that the surface energy (which is closely related to the intermolecular interaction force at the contact surface) of the polymer has a good correlation with the friction adhesion. Therefore, by adding the lubricating modifier and allowing it to migrate to the surface of the material, the surface energy of the polymer can be changed, the surface adhesion can be reduced, and this method can be used as an effective and economical method for changing the friction characteristics of the surface of the polymer. Ohara, K [20] ameliorates the stick-slip phenomenon by blending silicone oil or PTFE with ABS resin. Although it was not pointed out by the author, the idea is to use the incompatibility of silicone oil or PTFE with ABS to migrate them to the ABS surface, then to improve surface energy and reduce adhesion. Jareenuch Rojsatean [17] reduces the dynamic and static friction coefficient of the material and the magnitude of the bimodal vibration of the stick-slip curve by adding ethylene bis-stearamide (EBS) and polyethylene-octene copolymer (POE). However, macromolecular materials like PTFE and POE have poor compatibility with ABS and can bring great reduction of ABS properties. In contrast, small molecules of silicone oil and EBS could be better choices. Yaogang Wang et al. [21, 22] had investigated properties of different nanofluids by analyzing a frictional test and a grinding experiment. They had also studied the application effect of different volume concentrations of Al2O3 nanofluids on force ratio, specific energy, G-ratio and surface quality, wheel morphology, chip formation and viscosity and contact angle during the MQL (Minimum Quantity Lubrication) grinding of Ni-based alloy (Inconel718). Unlike pure oil MQL grinding, Al2O3 nanofluid MQL grinding can form thin protective oil forms on the grinding wheel and workpiece surface. These films improve the tribological performance of grinding wheel/workpiece interfaces significantly. SEM and EDX anal ysis further prove the existence of the lubrication film. Therefore, no matter what material or industry it is, such as metal and polymer, lu bricants could be very important for the improvement of the tribological performance. In this study, a friction coefficient tester and a self-designed noise tester are also adopted to characterize the dynamic and static friction coefficients, the stick-slip motion and the friction noise of different modified materials, so as to explore the generating mechanism of the friction noise and the key factors for controlling the friction noise. 2. Experimental 2.1. Experimental materials Ordinary ABS resin: Melt flow index 16g/10min(220 � C,10 kg), Vicat softening point temperature 110 � C, made by Kingfa SCI. & TECH. CO., LTD. Low noise ABS material: Melt flow index 18g/10min (220 � C, 10 kg), Vicat softening point 110 � C, made by Kingfa SCI. & TECH. CO., LTD. Silicone lubricant TP-200E(Molecular weight ¼ 600000 Da), made by Zhejiang Java Specialty Chemicals Co., Ltd. Ethylene bis stearamide (Molecular weight ¼ 593 Da), made by PT. CMS Chemical Indonesia. Polyethylene wax (140 � C, viscosity 800 Pa∙s), Clariant Specialty Chemicals. Fatty acid lubricant(Molecular weight ¼ 200–1000 Da), Struktol Company of America, LLC. 2.2. Experimental equipment and instruments Double screw extruder: SHJ-30, Nanjing Ruiya Chemical Equipment Co., Ltd. Injection molding machine: B-920, Zhejiang Haitian Plastic Machinery Co., Ltd. Sealing strip wear-resistance testing machine, Dongguan Maisheng Electronic Equipment Co., Ltd. Quadratic element imager, Dongguan Yuanxin optical instrument. Scanning electronic microscopy: S-3400, Hitachi High-Technologies (Shanghai) Co., Ltd. Stick-slip tester: SSP-03, Ziegler-Instruments GmbH Co., Ltd. Time-ofFlight secondary ion mass spectrometry: Model 2100 Trifft II, Physical Electronics. 2
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2.3. Sample preparation
the material was continuously subjected to repeated deformation and rebound processes, so that the noise could be generated. Quadratic element imager and scanning electronic microscopy (SEM) test: The samples which were used in friction noise performance test were observed on the surface to observe scratch marks with a quadratic element imager (Fig. 3 left) and S-3400 scanning electron microscope (Fig. 3 right). The scratch marks firstly studied under the quadratic element imager under a magnification of 150 times then observed under SEM with a magnification of 1000 times. Before SEM observation, gold spray on sample surface was required to ensure clear image acquirement of the scratch marks. Stick-slip test: the stick-slip properties of different materials were tested using an SSP-03 stick-slip test instrument from ZIGLER Corpora tion (Fig. 4). The tests were conducted in accordance with the VDA 230206 standard. The principle was similar to friction coefficient test which is talked above. Two test samples were separately stuck to a stator and a slider. The slider could move from left to right circularly, relative movement occurred between two samples and data which included load, slide speed as well as acceleration were acquired. Further risk priority number (RPN) could be calculated to depict the risk of slip-stick occurrence. RPN was graded from level 1 to level 10. Wherein the higher the grade is, the more serious the stick-slip phenomenon is. Three levels of load (2.4 N, 40 N and 80 N) as well as three level of speed (1 mm/s, 6 mm/s and 12 mm/s) were set as parameters and cross-studied in order to cover almost possible “squeak-generated” situation in the cars. Time-of-Flight secondary ion mass spectrometry (TOF-SIMS) test: element analysis of sample surface was studied and linked to friction noise with TOF-SIMS Model 2100, made by physics electronics (Fig. 5). Analysis process was conducted according to ASTM E 1078 and 1829. Gallium LMIG was used as initial ion beam and an initial energy was set as 25 keV. Silicone modified ABS sample was studied with this instrument to study dispersion and effect of silicon.
The preparation method comprises the following steps: weighing ABS (80–84 wt%), heat-resistant master batch (15 wt%), pigment (0.5 wt%), antioxidant (0.5 wt%) and lubricants(0–4 wt%), uniformly mix ing, melting, blending, extruding and granulating by using a doublescrew extruder at the temperature of 240–250 � C The resulting pellets were dried in an oven at 80 � C for 2 h, and then were made into square plates of 100 mm � 100 mm � 2 mm and ISO standard mechanical specimens through injection molding machine for later testing. 2.4. Testing and characterization Friction coefficient test: The friction coefficient of the modified sample was measured by FT-1 friction coefficient test equipment (pro duced by AMETEK) according to standard GB 10006-88. Fig. 1 showed the schematic of the test. Two test samples made from the same material was separately stuck to a slider with double-side tape while the other was stuck to the instrument base of the equipment. When the force sensor rose by a certain speed, it dragged the slider moved from left to right. Meanwhile, the drag force against distance could be recorded. In further calculation, dynamic and static friction coefficients against dis tance were obtained. Direction force FN and movement speed were set as 2 N and 100 mm/min according to the GB 10006-88. Friction noise performance test: According to the literature and experiment, we set up the material friction noise test equipment. Fig. 2 is the test process and the test schematic diagram. As shown in Fig. 2, the test instrument generates noise by sliding friction between an upper plate vertically fixed to the jig and a lower plate fixed to the stage under a certain load. The upper plate was a flat plate with a size of 20 mm in width, 40 mm in height and 2 mm in thickness and the lower plate was 2 mm in thickness. The load FN was applied to the upper plate by fixing a 20 N weight on the bracket during the test. In the sliding process, the decibel value is recorded by using a decibel gauge, namely, the Biaokang HT-80A, and the decibel gauge and the friction interface are always kept at a distance of 2–4 cm so as to record the noise generated in the friction process. Simultaneously a sound collecting device was used to collect noise signals. The collected noise signal was processed by Adobe Audience. As shown in Fig. 2, the upper plate was deformed due to the friction force in the sliding process, namely, the upper plate was bent along the direction subjected to the friction force, the material was continuously bent and deformed along with the relative sliding process, and when the resilience force generated by the deformation exceeded the friction force, the material would spring back to its original shape, and vibration could be generated when
3. Results and discussion 3.1. The relationship between friction noise and stick-slip phenomenon of ABS materials Fig. 6 shows the results of testing ordinary ABS and a low friction noise ABS material using a friction coefficient testing platform. It could be seen from the test curve that the friction force of the ordinary ma terial changed periodically in the sliding process and the curve was zigzag. The sliding block could be observed to advance in a jumping mode in the test process and obvious stick-slip phenomenon was shown.
Fig. 1. Principle of the friction coefficient tester. 3
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Fig. 2. Friction noise performance test schematic diagram.
Fig. 3. Quadratic element imager (left) and scanning electronic microscopy (right).
Fig. 4. Schematic diagram of SSP-3 stick-slip instrument.
As can be seen from the test curve of the low noise material, as the rope was tightened, the friction force was gradually increased until the block starts sliding. The friction force was kept stable when the block slid and no stick-slip phenomenon took place. So this friction test could reflect the stick-slip tendency of the material to some extent. In the friction test curve, the ratio of the maximum friction force FS to the applied load (FN) that the sliding block was subjected to in stationary was the static fric tion coefficient (μs), and the ratio of the friction force FD to the load that the sliding block was subjected to during sliding was the dynamic fric tion coefficient (μD). It can be seen from Fig. 6 (a) that the friction force of the sliding block was constantly changing during sliding, and the dynamic friction coefficient was the ratio of the average value of the dynamic friction force of the sliding section to the load. In order to characterize the degree of stick-slip of materials, the amplitude △F of the stick-slip motion was introduced in, that was, the difference between the average value of the maximum value of the friction force and the average value of the minimum value of the friction force during the
sliding process in the friction test. The larger △F indicated the greater the amplitude of the jumping advance of the sliding block, and the greater the tendency of the stick-slip motion took place. Fig. 7 is the noise testing results of different materials according to the experimental section noise test method. It could be seen that the noise of ordinary materials was very loud. In the audio curve output by Adobe Audition, there were many sharp noise peaks and the maximum decibel was 82 dB according to the decibel meter. The audio curve of the low noise material was very stable and had almost no strong and sharp noise peak, and the maximum decibel was only 62 dB according to the decibel meter. The results of ordinary materials and low noise materials were consistent with those of noise test and stick-slip test, which indi cated that the friction noise was related to the stick-slip motion. Spe cifically, the friction creaking noise was generated by two objects contacting each other and sliding toward each other, and when the sliding was in an unstable state, the stick-slip motion was extremely easy to occur. The stick-slip motion occurs on the contact surface of two 4
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Fig. 5. Time-of-Flight secondary ion mass spectrometry.
Fig. 7. Noise test results of different materials (a) Ordinary ABS Material (b) Low Noise ABS Material.
deformed, and the material accumulates potential energy due to the deformation. With the further increase of the external force, when the accumulated potential energy is large enough to overcome the adhesion, the two materials can generate relative displacement, which is “slip”. At the same time, the release of potential energy causes vibration of the material and the surrounding air, causing a creaking sound [23]. Fig. 8 is the graphs of morphology of the bottom plate after the noise test of both materials using quadratic and scanning electron microscopy. As can be seen from Fig. 8 (A), the surface of the bottom plate had distinct stripes perpendicular to the direction of friction, which was caused by the stick-slip phenomenon with the upper plate, the noise was produced by the constant deformation-rebound vibration of the material during the unstable sliding, but the surface of the low noise material only had obvious striation parallel to the sliding direction, which indi cated that the relative sliding motion of the two plates was in a steady state, and the stick-slip phenomenon completely disappeared. The observation of the surface morphology of the sample after scraping directly confirmed the existence of the stick-slip phenomenon in the noise testing process, and also proved that the stick-slip phenomenon was the cause of the noise’s generation, which was consistent with the results of other researchers. By observing the scraped sample under an electron microscope, the change of the morphology after scraping could be observed more directly, and the result was shown in Fig. 8 (C). As can be seen from the figure, for the ordinary material, the dent perpendic ular to the friction direction is relatively narrow, only 40 μm, but deeper, which indicates that the degree of adhesion was very high, the defor mation amount of the material was increased due to the strong adhesion, the potential energy storage was increased, and the noise was more easily caused; However, as shown in Fig. 8 (D), the dent of the low noise material became unobvious, and the distance became significantly larger by 90 μm, which was also shallower, indicating that the adhesive force is not strong, and the material rebound was mild. The above results could further confirm the action mechanism of stick-slip phenomenon, and indicate that the main means to avoid the generation of friction noise is to reduce stick-slip.
Fig. 6. The stick-slip test curves for different materials (a) Normal ABS Material (b) Low Noise ABS Material.
mutually contacted objects, and under the condition of the same surface morphology, the interaction between the two polymer molecules cause the two to adhere on the contact surface so as to generate friction force and limit the relative sliding. At this time, the two objects are relatively stationary, which is “stick”. The microscopic surface of the polymer is
3.2. The relationship between surface tribological characteristics of ABS material and friction noise The research shows that the creaking noise of the automobile parts can be effectively ameliorated by covering those parts with grease or the 5
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Fig. 8. The bottom plate’s surface morphology after the noise test: (A) The quadratic image photograph of ordinary material; (B) The quadratic mage photograph of low noise material; (C) The SEM picture of ordinary material; (D) The SEM picture of low noise material.
coating with low friction coefficient. However, due to the complexity of its procedures and the possibility of introducing sporadic substances to pose a safety hazard to the health of drivers and passengers, they are not widely accepted [24]. In the modification process, different kinds of lubricants are added to influence the friction performance of polymer injection molded products so as to ameliorate the creaking noise of parts, which becomes a new research direction. In this research, the lubricant was used to modify ABS, and the self-designed noise test equipment was used to test the noise performance of ABS material modified by lubricating promoter. As ABS is a kind of polar polymer, some non-polar substances, especially those with small molecular weight, could be used as external lubricants for ABS. Common non-polar lubricants for ABS include silicone, ethylene bis-stearamide, esters of fatty acid, polyethylene wax and so on. Theoretically these lubricants tend to migrate to surface of ABS, forming a thin lubricating layer,
resulting in more easily relative motion between ABS samples [21,22]. Fig. 9 is the audio chart of noise test of the typical samples. It can be seen that the noise performance of ordinary material was not good, the noise decibel value was 82 dB, the noise performance of a silicone lubricant modified ABS material was improved, and the noise decibel value was reduced to a certain extent; The modified ABS material of polyethylene wax was completely free of noise, which indicated it has the capability of completely eliminating the friction noise between ABS parts. As for the difference in the amelioration of the stick-slip phenomenon of different lubricants, we presumed that it was caused by the difference in the degree of improvement of ABS surface energy by different lubricants. The results of dynamic and static friction coefficient, the coefficient difference △μ, the amplitude △F and noise of materials modified by different lubricants during sliding process are listed in Table 1. As can be seen, compared with the unmodified ordinary materials, the dynamic
Fig. 9. Noise performance test results of ABS materials modified by different lubricating promoters: (A) unmodified ABS; (B) ABS modified by ethylene bis stear amide; (C) ABS modified by Silicone; (D) ABS modified by Polyethylene wax. 6
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and static friction coefficients of the modified ABS materials were obviously reduced after different lubricating modification promoters were added (Fig. 10). According to Fig. 10 and Table 1, the dynamic and static friction coefficients of ordinary materials were both large, and the stick-slip phenomenon was obvious, the △F reached 0.302 N. After the lubricant was added, the stick-slip phenomenon was weakened to different degrees, and the amplitude of the stick-slip phenomenon was obviously reduced or even disappeared, which indicated that the modification effects of different lubricating modifiers were different. Among them, the effect of polyethylene wax was the best and the figure of the noise test result was the lowest (Fig. 11). In general, the lubri cating effect of the lubricant is achieved by reducing the coefficient of friction, in particular the coefficient of dynamic friction, whereas for frictional noise, the effect of only reducing the coefficient of friction is not ideal. As shown in Table 1, the addition of silicone-based modifi cation promoters greatly reduced the μs and μd of the ABS material, especially the coefficient of kinetic friction μd was reduced to 0.216, which was the lowest in all samples. So it was an important reason why silicone compounds could be used as polymer scratch-resistant agents. However, the stick-slip phenomenon was very obvious in the friction test, the amplitude △F reached 0.213 N, and the noise test result was 74 dB, which was only slightly lower than that of the unmodified ABS material. This was consistent with the results of Ronald A.L. Rorrer and others [4]. The stick-slip phenomenon of the material is not simply related to the dynamic and static friction coefficient, but to the differ ence between the two, which is consistent with the results presented in Table 1. The coefficient difference △μ of ordinary unmodified materials was about 0.082. The dynamic and static friction coefficients of poly ethylene wax were reduced, and the difference △μ of dynamic and static friction coefficients was also reduced to 0.018, so the stick-slip tendency of the materials was reduced. Although the dynamic friction coefficient of the material modified by the polyethylene wax was not the lowest, the static friction coefficient μs of the material was reduced more greatly. So the difference △ μ between the dynamic friction coefficient and the static friction coefficient was reduced obviously. Therefore, regarding the ameliorating of the friction noise performance of the material through the lubricating promoters, we need to pay more attention to the overall change of the static and dynamic friction coef ficient of the material rather than only to the change of the dynamic friction coefficient μd. For this phenomenon, Martin Trapp gave the explanation: The key to solve the creaking noise problem was to eliminate the stick-slip motion, which was described by the following stick-slip equation [24]: From the equation, the stick-slip motion was closely related to the difference between the load and the dynamic-static friction coefficient. Load was often determined by component design and operating condi tions. When the creaking noise occurred, the load could not be changed, so the dynamic and static friction coefficients became the only optimi zation direction. Therefore, the characteristic of the low dynamic and static friction coefficient of the polyethylene wax was the key to solve the problem of creaking noise.
Fig. 10. Effect of different lubricants on friction coefficient of ABS.
Fig. 11. Relationship of △μ and sound intensity (squeak noise) performed by modifying ABS with different lubricants.
The stick-slip performance of ABS modified by polyethylene wax with different contents was systematically studied, and the results are shown in Fig. 12. As can be seen from the figure, the dynamic and static friction coefficients of the modified ABS material were gradually reduced with the increase of the addition amount, the stick-slip degree of the material was gradually reduced, and the noise test result was gradually reduced too. When the addition amount reached 2% or more, the stick-slip phenomenon in the friction test was very weak and could hardly be observed, and the noise decibel value was also reduced to 67 dB. Table 2 and Fig. 13 show the friction coefficient data of ABS mate rials modified by polyethylene wax at different contents, and it could be seen that the dynamic and static friction coefficients of the materials were reduced with the increase of the content of modifying promoters and the decrease of the difference of the dynamic and static friction coefficient △μ greatly reduced the viscosity-slip tendency of the ma terial. Fig. 14 is a graph showing the surface morphology of the noise test base plate of the ABS modified with polyethylene wax at different contents, and it could be seen that as the amount of addition increased, the adhesion streaks perpendicular to the scraping direction decreased until disappearing, indicating that the stick-slip motion gradually decreased, which is in accordance with the results of the noise test. Fig. 15 is the attenuated total reflection (ATR) spectrum of different amounts of ethylene wax. It can be seen that the polyethylene wax has a very significant absorption peak at 1470 cm 1, which is the bending
Table 1 Friction coefficient and noise test results of ABS materials modified by adding 4 wt% of different lubricating modification promoters. Lubricating modifier
Static friction coefficient μs
Dynamic friction μd
△μ
△F/ N
Sound Intensity/ dB
None Silicone Ethylene bisstearamide Esters of fatty acid Polyethylene wax
0.507 0.292 0.321
0.425 0.216 0.275
0.082 0.076 0.046
0.302 0.213 0.184
82 74 71
0.246
0.217
0.029
<0.02
62
0.247
0.229
0.018
<0.02
58
7
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vibration peak of methylene. The peak in the surface is stronger than the inner layer compared to the surface’s and inner layer’s infrared spec trum of the 96% ABS/4% wax, which indicating the higher content of wax in the surface. The wax migrated to the surface to lubricate the surface of the ABS, reducing the friction coefficient of the material and further reducing the noise. The stick-slip tendency of lubrication-free and polyethylene wax modified ABS materials was characterized by SPP-03 stick-slip tester. The results are shown in Table 3. The RPN values of the unmodified materials were all higher than those of the modified ABS materials, particularly under the conditions of 40 N load, 1mm/s speed, 80 N load and 6mm/s speed, the lubrication-free materials reached the higher grades to level 6 and level 9, and the modified materials only reach to level 2 and level 1, which indicated that the modification by poly ethylene wax substantially reduced the stick-slip tendency of the material. Rojsatean’s study [17] indicates that static friction coefficient is related to static adhesion, and further studies suggest that static adhe sion is closely related to polymer composition characteristics, that is, the surface energy. The critical surface tension of the polymer material will be changed when the H atoms in the polymer hydrocarbon chain are replaced by other elements or when other elements are introduced into the compound chain. Generally, except the F halogen atom, an atom in the halogen element replaces the H atom in the polymer or to introduce a N atom or an O atom into the polymer chain will result in an increase in the critical surface tension of the polymer (the surface hydrophobicity was decreased), the order of some common elements increasing surface free energy is: N > O > I > Br > Cl > H > Si > F. Since the ABS matrix contains acrylonitrile bond, its surface energy is high, and the risk of generating stick-slip is very high. The free energy of the H element is far less than N element. After the ethylene-octene copolymer is added into the ABS matrix [18], a small amount of the ethylene-octene copolymer migrates to the surface of the ABS material, thereby reducing the surface energy of the ABS, weakening the adhesion force and achieving the
Fig. 12. Friction curve and noise test results of ABS modified by polyethylene wax with different contents. Table 2 Stick-slip test results. Load (N)
Speed (mm/s)
2.4 2.4 2.4 40 40 40 80 80 80
1 6 12 1 6 12 1 6 12
RPN Lubricant-free
4 wt% Polyethylene Wax
Level 2 Level 2 Level 2 Level 6 Level 2 Level 2 Level 9 Level 2 Level 3
Level Level Level Level Level Level Level Level Level
1 1 1 2 1 1 1 1 1
Fig. 13. Friction coefficient and noise test results of ABS modified by poly ethylene wax.
Fig. 15. ATR study on the surface of ABS samples modified with different content of polyethylene wax.
Fig. 14. Surface morphology of modified ABS noise test plate with different content of polyethylene wax. 8
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ion mass spectrometry mass spectrometry. It can be seen from the figure that the silicon element distribution was not uniform, while the ABS sample coated with the silicon coating had a very uniform distribution of silicon on the surface. Correspondingly, the ABS sample coated with the silicon-coated coating had the lowest surface energy and the value of the difference between the dynamic and static friction coefficients was close to zero, so that the effect of improving the click noise was the most excellent. In summary, the key to eliminating click noise is to eliminate the stick-slip motion and one of the methods to solve the stick-slip motion is to attach a uniform low surface energy material to the surface of the polymer matrix.
Table 3 Contact angle and surface energy of different modified ABS. Modifier
Blank Silicone Ethylene bis stearamide Fatty acid ester
Contact angle
Surface energy
Water
Diiodomethane
Polar force
Dispersion force
Total
86.16 100.12 97.14
25.45 24.58 19.64
1.009 0.06 0.004
45.99 36.58 45.35
47 36.64 45.35
99.39
17.67
0.08
37.07
37.15
purpose of reducing the difference between the static friction coefficient and the dynamic-static friction coefficient, thereby eliminating the stick-slip motion. Compared with the ethylene-octene copolymer, the addition of the PE wax has less influence on the mechanical property of the ABS material. Meanwhile, the low viscosity of PE wax enables itself to be easily gathered on the surface in injection molding process to form a PE-rich wax skin, which has a better effect of reducing the surface energy. Table 3 shows the surface energy test results. It can be seen from the table that the surface energy of silicone, ethylene bis-stearamide and fatty acid modified ABS decreased significantly and the surface energy of the fatty acid modified ABS reduced most obviously. This was in agreement with the test results of friction noise. As decrease of surface energy resulted in the reduction of adhesion between materials and thus the difference between the dynamic and static friction coefficients, thereby reducing the frictional noise caused by the stick-slip vibration. It was worth noting that the silicone modified ABS showed the lowest energy, but the noise improvement was normal. It was mainly because the silicone was a high molecular weight material, which could not be uniformly dispersed in the ABS matrix and was easily surface-enriched. As shown in Fig. 16 below, the silicone-added ABS template was tested for the distribution of Si element on the surface by flight time-secondary
4. Conclusion The consistency of the results of friction performance test and noise test and the results of surface morphology of the noise test plate proved that the friction noise of the ABS material was mainly caused by the stick-slip phenomenon. There is a significant correlation between the noise and the friction force variation △F during relative sliding of the two parts. Decreasing △F can reduce the noise caused by friction. It was found that different types of lubricants have different effects on ameliorating the noise and stick-slip phenomena of ABS material. By adding lubricant to the ABS material, most of the lubricants evaluated could reduce the △F to different degrees, thereby reducing stick-slip phenomenon and friction noise. Among those lubricants, fatty acid ester and polyethylene wax are the most effective. The difference in the effect of different lubricants on ameliorating stick-slip should be related to the degree of influence of lubricants on the surface energy of ABS materials. It could be inferred that reducing the dynamic and static friction △F was the key factor to reduce the stick-slip phenomenon and reduce the friction noise.
Fig. 16. Ion mass spectrum of silicone modified ABS Graph 1 Graph2. 9
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Author statement
[8] S. Ahmadi, P. Nassiri, I. Ghasemi, M.R.M. Esmaeilpoor, Iran. Polym. J. (Engl. Ed.) v24 (2015), https://doi.org/10.1007/s13726-015-0353-0. [9] S.N. Patek, J.E. Baio, The acoustic mechanics of stick slip friction in the California spiny lobster (Panulirus interruptus), J. Exp. Biol. v210 (2007), https://doi.org/ 10.1242/jeb.009084. [10] K. Nakano, Two dimensionless parameters controlling the occurrence of stick-slip motion in a 1-DOF system with Coulomb friction, Tribol. Lett. v24 (2006), https:// doi.org/10.1007/s11249-006-9107-7. [11] A. Elmaian, F. Gautier, C. Pezerat, J.M. Duffal, Improving dynamic and tribological behaviours by means of a Mn–Cu damping alloy with grooved surface features, Appl. Acoust. v76 (2014), https://doi.org/10.1016/j.apacoust.2013.09.004. [12] N.S. Eiss, B.P. McCann, Frictional instabilities in polymer-polymer sliding, Tribol. Trans. v36 (1993), https://doi.org/10.1080/10402009308983211. [13] E.L.N. Eiss, M. Trapp, Frictional behavior of automotive interior polymeric material pairs, SAE Technical Papers (1997), https://doi.org/10.4271/972056. [14] J.H. Norman, S. Eiss, Stick–slip friction in dissimilar polymer pairs used in automobile interiors, Tribol. Int. v31 (1998), https://doi.org/10.1016/s0301-679x (98)00092-9. [15] R.A.L. Rorrer, V. Juneja, Friction-induced vibration and noise generation of instrument panel matrial pairs, Tribol. Int. v35 (2002), https://doi.org/10.1016/ S0301-679x(02)00047-6. [16] H. Jiang, Q. Cheng, C. Jiang, J. Zhang, L. Yonghua, Effect of stick-slip on the scratch performance of polypropylene, Tribol. Int. v91 (2015), https://doi.org/ 10.1016/j.triboint. 2015.06.024. [17] J. Rojsatean, Experimental bench for studying the relation between the dynamic characteristics of the frictional motion and the electric potential at the surface of polymer slabs in sliding conformal contact, Tribol. Int. v109 (2016), https://doi. org/10.1016/j.triboint. 2016. 12.055. [18] Z. Rymuza, Tribology of polymers, Archives of Civil and Mechanical Engineering v4 (2007), https://doi.org/10.1016/s1644-9665(12)60235-0. [19] G. Erhard, Sliding friction behavior of Polymer-Polymer material combinations, Wear v84 (1983), https://doi.org/10.1016/0043-1648(83)90262-4. [20] K. Ohara, Stick-Slip motion and surface deformation, Wear v50 (1978), https:// doi.org/10.1016/0043-1648(78)90077-7. [21] Y.G. Wang, Comparative evaluation of the lubricating properties of vegetable-oilbased nanofluids between frictional test and grinding experiment, J. Manuf. Process. v26 (2017), https://doi.org/10.1016/j.jmapro.2017.02.001. [22] Y.G. Wang, Experimental evaluation on tribological performance of the wheel/ workpiece interface in minimum quantity lubrication grinding with different concentrations of Al2O3 nanofluids, J. Clean. Prod. v142 (2017), https://doi.org/ 10.1016/j.jclepro. 2016.10.110. [23] K. Ohara, Observations of surface profiles and the nature of contact between Polymer films by multiple beam interferometry, Wear v39 (1976), https://doi.org/ 10.1016/0043-1648 (76) 90053-3. [24] M. Trapp, F. Chen, Automotive Buzz, Squeak and Rattle: Mechanisms, Analysis, Evaluation and Prevention, Elsevier Science, Burlington, 2012, https://doi.org/ 10.1016/b978-0-7506-8496-5.00001-4.
I have made substantial contributions to the conception or design of the work and I have drafted the work or revised it critically for important intellectual content. I agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. Declaration of competing interest The authors declare no conflict of interest. Acknowledgements Thanks for the device supports from National-certified Enterprise Technology Center, Kingfa Science and Technology Co., Ltd., and the financial supports by the National Key Research and Development Program of China (2016YFB0302005). References [1] R. Johnsson, J. Odelius, M. Rantatalo, A new test track for automotive squeak and rattle (S&R) detection, Appl. Acoust. v80 (2014), https://doi.org/10.1016/j. apacoust.2014.01.010. [2] M.L. Ridder, P. Khosropanah, R.A. Hijmering, T. Suzuki, M.P. Bruijn, H.F. C. Hoevers, J.R. Gao, M.R. Zuiddam, J. Low Temp. Phys. v184 (2015), https://doi. org/10.1007/s10909-015-1381-z. [3] S.H. Shin, J.G. Ih, T. Hashimoto, S. Hatano, Sound quality evaluation control of car interior noise, Appl. Acoust. v70 (2008), https://doi.org/10.1016/j. apacoust.2008.03.009. [4] A. Elmaian, F. Gautier, C. Pezerat, How can automotive friction-induced noises be related to physical mechanisms, Appl. Acoust. v76 (2014), https://doi.org/ 10.1016/j.apacoust.2013.09. 004. [5] F.C.C. Ciofi, C. Pace, G. Scandurra, High sensitivity instrumentation for low frequency noise measurements, IEEE Transactions on Instrumentayion and Measurement v52 (2003), https://doi.org/10.1109/Tim.2003.817913. [6] A.L. Bot, E.B. Chakra, Improving Dynamic and tribological behaviours by means of a Mn–Cu damping alloy with grooved surface features, Iridology Letters v37 (2009), https://doi.org/10.1007/s11249-009-9521-8. [7] P.J. Wei, P.W. Tsai, J.F. Lin, Analysis based on microcontact mechanism for the roughness dependent stick–slip motion, Wear v266 (2009), https://doi.org/ 10.1016/j.wear. 2008.07.002.
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