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Effect of temperature on wear performance of aircraft tire tread rubber
Polymer Testing 79 (2019) 106037
Contents lists available at ScienceDirect
Polymer Testing journal homepage: www.elsevier.com/locate/polytest
Test Method
Effect of temperature on wear performance of aircraft tire tread rubber a,⁎
a
a
a,⁎⁎
Jian Wu , Long Chen , Youshan Wang , Benlong Su a b
a
, Zhibo Cui , Diyuan Wang
b
T
Center for Rubber Composite Materials and Structures, Harbin Institute of Technology, Weihai, 264209, China China COMAC Shanghai Aircraft Manufacturing Co., Ltd, 200000, China
ARTICLE INFO
ABSTRACT
Keywords: Aircraft tire Temperature Wear Surface morphology Finite element simulation
Wear performance of tread rubber directly affect the service life of aircraft tires, especially for lateral sliding and high temperature conditions. Temperature of aircraft tire tread rises rapidly during takeoff and landing due to high-speed friction, which greatly affects the wear performance. Therefore, wear tests of aircraft tire tread materials under different temperatures and slip angles have been carried out; then, wear surface morphology and wear mechanism have been discussed; finally, Further research of wear mechanism has been detailed based on the finite element model of rubber wheel. Results indicate that slip angle has a greatly effect on the wear rate when temperature is lower than 45 °C and slip angle is greater than 10°; wear mechanism is different, when temperature is greater than 65 °C; roughness of wear surface decreases with the increasement of temperature. Besides, wear rate and frictional power density have a good correlation, which lays the foundation for the next work of wear prediction.
1. Introduction Aircraft tire is the key component of aircraft, and its wear performance is crucial to the safety of aircraft [1,2]. Under the high-speed landing condition, temperature of tire tread rises rapidly due to highspeed friction [3,4], Wear performance of aircraft tire is directly correlated to temperature. Therefore, it is essential to study the influence of temperature on wear properties. Wear performance of rubber have been widely studied. However, researches on the high-temperature wear mechanism of aircraft tires are insufficient in recent years. Schallamach [5] and Shingo [6] developed the relation between wear rate and various parameters based on wear tests, then the wear rate of tire was calculated based on the linear wear hypothesis and the Schallamach theory formula. Wear resistance is an important index of many rubber products, especially for the aircraft tire. Wear tests of tread materials were carried out for studying the wear resistance [7], results indicated that the micro texture of pavement significantly affected the wear resistance of tire. As concluded by Bhattacharya [8], wear rate of natural rubber nanocomposites also decreases sharply when the content of nanofiber increases. Besides, the wear rate can be characterized by the wavelength of rubber materials based on the Laboratory of Surface Phenomena of USP [9]. Temperature has a great influence on the wear mechanism and surface characteristics of rubber [10], especially in high temperature.
⁎
Roughness increased when the temperature increased; the surface morphology and wear characteristics of rubber materials can be characterized by the fractal theory [11]. A power function wear model of tread rubber blocks with frictional energy dissipation was developed based on the laboratory testing of rubber wear [12]. Finite element method has become a useful tool for wear performance simulation of rubber. Under the condition of steady rolling, finite element model was developed based on Archard wear model for predicting the tire wear [13]. A relationship between the frictional energy and the indoor tread wear has been established by finite element method [14]. A tire wear predicted model was also developed by explicit finite element simulation based on the frictional energy dissipation [15]. Knisley [16] also developed a relationship between frictional energy and tread wear rate at the rolling tire contact surface. Prior to this work, finite element model of tread blocks has been developed [17]. In this paper, wear mechanism of tread rubber is studied under different temperatures. Firstly, wear tests of aircraft tire tread materials are carried out by high-temperature Akron abrasion tester GT-7012-AH under different temperatures and different slip angles. Then, the surface topography wear of rubber wheel and wear debris are studied based on DSX510 Optical digital microscope. Finally, the finite element wear model of rubber wheel is developed and the relation between wear rate and friction power density is obtained.
Corresponding author. Corresponding author. E-mail addresses: [email protected] (J. Wu), [email protected] (B. Su).
⁎⁎
https://doi.org/10.1016/j.polymertesting.2019.106037 Received 20 May 2019; Received in revised form 11 August 2019; Accepted 12 August 2019 Available online 13 August 2019 0142-9418/ © 2019 Elsevier Ltd. All rights reserved.
Polymer Testing 79 (2019) 106037
J. Wu, et al.
(50 phr), which were provided by Shandong Linglong Tire Co., Ltd. Wear tests have been carried out by strip specimens according to the BS 903 A9, the phenomenon of "debonding" was observed when temperature above 45 °C, seen in Fig. 1. For solving this problem, tread rubber wheel (including the strip thickness according to GB/T 1689-2014) is cured by vulcanization mold in a flat-panel press under pressure 15 MPa, and temperature 150 °C for 25 min, as shown in Fig. 2(a), Fig. 2(b) shows the dimension of rubber wheel with thickness of 12.7 mm. Fig. 3 shows the high-temperature Akron abrasion tester GT-7012AH. The GH-300D electronic balance with the accuracy of 0.001g is used to measure the wear rate. Experimental parameters are shown in Table 1. Four rubber wheels are performed at each condition. 2.2. Surface topography Surface topography of wear is measured by the DSX510 optical digital microscope, seen in Fig. 4. Then, three-dimensional map and roughness are obtained. Fig. 5 shows the morphological characteristic of 25 °C and the slip angle of 15°. Wear debris are digitally processed by MATLAB software, and shape factors can be obtained.
Fig. 1. Debonding phenomenon of strip specimen.
3. Result and discussion 3.1. Effect of temperature Wear characteristics of tread materials are sensitive to the external environments, such as velocity, tire pressure, temperature, etc. Here, the effects of temperature on wear rate are analyzed by tests. Fig. 6 shows the relationship between wear rate and temperature. It can be seen that wear rate decreases rapidly when the slip angle is larger than 10°. Fig. 7 shows surface topographies of rubber wheel under different temperatures and the slip angle of 15°. The region A represents the inner position of rubber wheel is in contact with abrasive disk, the region B represents the intermediate position and the region C represents the outer position. Results indicate that tread material has the different wear surfaces due to the increase temperature. When the temperature increases, wear of regions B and C are changed, and the texture of wear on the rubber wheel surface is more intensive (seen in Fig. 7). Because temperature increases, the material properties are changed [18]. Besides, the smooth region of rubber wheel increases when the temperature increases, which results in the decrease of the wear rate when the slip angle is 15°, as shown in Fig. 6. The distance between protrudes under the slip angle of 15° and different temperatures are shown in Table 2, which are obtained by ten points at a same region, as shown h in Fig. 7(b). Results indicate that distance between protrudes of a same region decreases with increasing temperature, and from region A to region C, it also decreases under a same temperature, resulting in the rubber wheel with smoother surface when temperature increases, as shown in Fig. 7. When the temperature is larger than 65 °C, the distance of protrudes in region C is smaller than that with no wear; when the temperature increases, the distance of protrudes decreases. Slice processing is used for the surface of region C, then two-dimensional map, three-dimensional map and roughness are obtained. At the view of (500umX500um), the number of protrudes increases with temperature increases, and roughness decreases (the height of the protrudes decreases) when the temperature increases. The roughness is significantly less than that with no wear when the temperature is higher than 65 °C, seen in Table 3.
Fig. 2. (a) Vulcanization mold (b) The dimensions of rubber wheel.
Fig. 3. High-temperature Akron abrasion tester. Table 1 Experimental parameters used in wear tests. Experimental parameters Temperature(°C) Slip angle(°)
25,45,65,75,85 0, 2.5, 5, 7.5, 8.5, 10,15, 17.5, 20, (Rated load:26.7 N, Mileage:1 km)
2. Experiment set up 2.1. Materials and wear tests
3.2. Effect of slip angle
The tread rubber materials mainly contained natural rubber (100 phr), ZnO (3 phr), stearicacid (2 phr), sulphur (2 phr), and carbon blacks
Seen in Fig. 8, when the temperature is below 45 °C, wear rate under the
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Fig. 4. Optical digital microscope.
Fig. 5. 3D surface topography of rubber wheel.
Fig. 7. Wear morphology under different temperatures.
Fig. 6. The variation of wear rate with temperature.
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Table 2 Distance between protrudes in different temperatures. Temperature (°C)
25(No wear) 25 45 65 75 85
Distance between protrudes (mm) The inner position (A)
The intermediate position (B)
The outer position (C)
Average value
Standard deviation
Average value
Standard deviation
Average value
Standard deviation
0.503 1.143 0.757 0.613 0.602 0.574
0.015 0.013 0.023 0.014 0.016 0.019
0.494 1.057 0.568 0.536 0.415 0.327
0.016 0.024 0.019 0.021 0.019 0.017
0.486 0.828 0.512 0.415 0.262 0.112
0.015 0.015 0.017 0.012 0.018 0.011
Table 3 Characteristic parameters from region C under different temperatures.
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Fig. 9 shows the surface topography at 25 °C under different slip angles. Results show that no obvious furrow and adhesion are observed on the surface when the slip angle is 0°, which is consistent with the surface with no wear. Oily substance is produced when the slip angle is larger than 10°. Slice processing for the region C is similar to the previous method under different slip angles. Table 4 shows distance between protrudes in different slip angles. Distance between protrudes decreases from region A to region C under a same slip angle. When the slip angle increases at a same region, the distance between protrudes increases, which is consistent with the surface topography measured by optical digital microscope shown in Fig. 9. Fig. 10 shows the roughness in different slip angles at 25 °C. It can be seen that when the slip angle increases, roughness increases (the height of the protrudes increases). 3.3. Wear debris analysis Fig. 8. The variation of wear rate with slip angle.
Wear debris is the direct result of wear, which is of great significance to study the wear mechanism. Shape factor [19] is used to characterize appearance of wear debris, which depends on the equivalent area S, the projection area of wear debris A, and the circumference of wear debris L
G=
S 4 = 2 A L
(1)
where A and L are obtained from MATLAB software, 5 wear debris are discussed for each condition of 26.7 N/15°/25 °C. The average of 5 shape factors in different temperatures and slip angles are shown in Fig. 11. Results indicate that shape factor decreases in the range of 0.1–0.3 when the temperature and slip angle increase, that is, stick or columnar wear debris increases with increase of temperature and slip angle [19]. The temperature has great influence on the wear debris and the change of the surface characteristics of wear. Fig. 12 presents the surface morphology of wear debris in different temperatures and the slip angle of 15°. It can be seen that the Oily substance increases when the temperature increases, and more and more wear debris with small size appear and adhere to when the temperature increases (seen in Fig. 12(a)). Tire scrap is more likely to happen in summer after long wear, which is consistent with the actual occurrence [20]. Based on results of wear tests, surface topography and wear debris, and combine the 'Competition' mechanism theory [18]. The mechanism of the Akron wear at high temperature is mainly the wear of debris, which is determined by the condition of wear. 4. Finite element simulation 4.1. Constitutive model Temperature of aircraft tire tread rises rapidly during takeoff and landing due to the high-speed friction, which directly affects mechanical properties of material (Seen in Fig. 13). Here, material properties of tread rubber materials are characterized by Yeoh strain energy function [21], the strain density function is given by:
Fig. 9. Wear morphology under different slip angles.
condition of a small slip angle is enhanced but less than that with a large slip angle. Over the range from 65 °C to 85 °C, wear rate increases slightly with increasing slip angle. It can be seen that the slip angle is a leading factor on wear performance of tread material at a low temperature.
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Table 4 Distance between protrudes in different slip angles. Slip angles (°)
0(No wear) 0 10 15 20
Distance between protrudes (mm) The inner position (A)
The intermediate position (B)
The outer position (C)
Average value
Standard deviation
Average value
Standard deviation
Average value
Standard deviation
0.543 0.503 1.053 1.143 2.212
0.012 0.013 0.027 0.013 0.022
0.514 0.494 0.685 1.057 1.457
0.015 0.019 0.017 0.024 0.027
0.486 0.486 0.543 0.828 1.121
0.018 0.021 0.019 0.015 0.029
Fig. 10. Relation curve of roughness and slip angle.
Fig. 12. Wear debris and enlarged view of surface in different temperatures.
Fig. 13. Strain–stress curve in different temperatures.
W = C10 (I1 = 2[(1 + )
3) + C20 (I1 (1 + ) 2]
3)2 + C30 (I1
3)3
C10 + 2C20 [(1 + )2 + 2(1 + ) 1 3C30 [(1 + )2 + 2(1 + ) 1 3]2
3+] (2)
where W is the strain density, I1 is the first invariant of the deviatoric strain tensor, C10, C20 and C30 are the rubber material constants determined from experiments. Table 5 provides material constants in different temperatures.
Fig. 11. Effect of temperature and slip angle on the shape factor.
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Table 5 Material constants in different temperatures. Temperature(°C)
C10
C20
C30
25 45 65 75 85
0.38 0.38 0.35 0.34 0.33
−4.46 −5.14 −4.11 −4.32 −4.17
7.03 7.31 5.28 5.18 4.87
to the reference node RP-1 of rubber wheel. The grinding wheel is fixed in all displacement DOF and X, Z turn DOF. Under the load, rubber wheel and grinding wheel are rotated in Y direction. 4.3. Frictional power density In the analysis of aircraft tire contact characteristics, the distributions of contact shear stress and slip displacement are the focus of attention for the aircraft designer, which play a great part in aircraft tire performance. Fig. 16 shows the contact results under the temperature of 25 °C and the slip angle of 15°. Results show that a large slip displacement and contact shear stress are generated on the rubber wheel surface, which was caused by the slip angle. When the slip angle increases, the contact shear stress decreases, and the slip displacement has a significant increasement. Then, the frictional power density is obtained by the product of slip displacement and contact shear stress. Based on the simulation results and numeral calculations. Under the condition of wear 1 km and the slip angle is larger than 10°, the frictional power density decreases with increase of temperature. Frictional power density increases when the slip angle increases (seen in Fig. 17). Fig. 18 shows the instantaneous distribution of frictional power density at 25 °C, 85 °C, and slip angle of 5°. It can be seen that the maximum frictional power densities at different temperatures are concentrated in the region C, and increases with the increasement of temperature. Besides, the higher the temperature, the smaller is its the area of longitudinal nodes, and the larger is its the area of transverse nodes.
Fig. 14. Finite element model of rubber wheel.
4.2. Meshing and boundaries Fig. 14(a) shows 2D finite element model of rubber wheel. CGAX4H element is used for rubber wheel meshing, including 406 nodes and 364 elements. 3D finite element model is obtained based on the 2D model, and finer mesh is required in the region contacted with grinding wheel. The grinding wheel is modeled by discrete rigid body. Seen in Fig. 14(b). Steady-state rolling is adopted in finite element analysis according the working conditions of abrasion tester GT-7012-AH, as illustrated in Fig. 15. Surface A represents the contact surface between rubber wheel and plate, which is fixed in Y direction displacement degrees of freedom (DOF) and X turn DOF, then a concentrated force FZ = 27.6 N is applied
Fig. 15. 3D finite element model of rubber wheel.
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Fig. 17. Relation of temperature, slip angle and frictional power density.
Fig. 19 shows relation between wear rate and frictional power density at 5°. It can be seen that when the temperature increases, wear rate and frictional power density increase synchronization. The simulation result of the rubber wheel is in good agreement with the experimental data, which provides the basis for the further research on the wear prediction of aircraft tread material. 5. Conclusions Upon takeoff and landing with high speed, the properties of aircraft tire tread are affected by temperature. The wear characteristics of tread materials under different temperatures have been studied in this paper. Wear tests under different temperatures and slip angles have been carried out. Furthermore, the morphological characteristics of rubber surface and wear debris have been discussed in detail. According the results, main conclusions gained are as follows: (1) Effects of temperature on wear rate and surface topography is significantly when the slip angle is larger than 10°. The wear patterns of rubber wheel surface are more intensive with increase of temperature. And the roughness is less than that of no wear when the temperature is higher than65 °C; (2) Slip angle is a leading factor on wear performance of tread materials at the low temperature. The distance between protrudes
Fig. 16. Contact results of contact shear stress and slip displacement.
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increases with increasement of slip angle. Besides, oily substance is produced when slip angle is larger than 10°; (3) The Akron wear at high temperature is mainly the wear of debris. Number of stick wear debris increases with increase of temperature and slip angle; (4) The wear rate has a correlation with simulation result of friction power density. Acknowledgements This work is funded by Major Program of National Natural Science Foundation of China (51790502), Natural Science Foundation of Shandong Province,China (ZR2018QEE004) and Weihai technology development program,China (2017DXGJ11). References [1] A.J. Tuononen, Digital Image Correlation to analyse stick-slip behaviour of tyre tread block, Tribol. Int. 69 (69) (2014) 70–76. [2] H.C. Zhou, G.L. Wang, J. Yang, K.X. Xue, Numerical simulation of tire hydroplaning and its influencing factors, Appl. Mech. Mater. 602–605 (2014) 580–585. [3] A.A. Alroqi, W. Wang, Y. Zhao, Aircraft tire temperature at touchdown with wheel prerotation, J. Aircr. 54 (3) (2016). [4] M. Bennett, S.M. Michael, A. Graham, B.S. Thomas, V. Vishnyakov, Composition of smoke generated by landing aircraft, Environ. Sci. Technol. 45 (8) (2011) 3533–3538. [5] A. Schallamach, The velocity and temperature dependence of rubber friction, Proc. Phys. Soc. 66 (5) (1954) 386–392. [6] S. Kohmura, H. Nakamura, J. Komura, Y. Tanakeal, Estimation method of tire treadwear on a vehicle, SAE Tech. Pap. 910168 (1991). [7] F.A. Cardoso, A.L.D.A. Costa, D.K. Tanaka, Durability performance of tire tread rubber compounds as a function of road pavement, Tecnol. Metal. Mater. Mineracao 1124 (2010) 375–387. [8] M. Bhattacharya, A.K. Bhowmick, Analysis of wear characteristics of natural rubber nanocomposites, Wear 269 (1) (2010) 152–166. [9] T. Vieira, R.P. Ferreira, A.K. Kuchiishi, L.L.B. Bernucci, A. Sinatora, Evaluation of friction mechanisms and wear rates on rubber tire materials by low-cost laboratory tests, Wear 328–329 (2015) 556–562. [10] Y. Li, S. Zuo, L. Lei, X. Yang, X. Wu, Analysis of impact factors of tire wear, J. Vib. Control 18 (6) (2012) 833–840. [11] Z. Wang, S. Hu, Z. Miao, L. Ma, Application of multifractal spectrum calculation Program in rubber wear under high temperature, Wirel. Pers. Commun. 36 (2018) 1–9. [12] J.R. Cho, J.H. Choi, Y.S. Kim, Abrasive wear amount estimate for 3D patterned tire utilizing frictional dynamic rolling analysis, Tribol. Int. 44 (7) (2011) 850–858. [13] R. Sreeraj, V. Sandeep, R. Gokul, P. Baskar, Tire wear analysis using ABAQUS, Int. J. Innov. Res. Sci. Eng. Technol. 5 (8) (2016) 14403–14410. [14] K.R. Smith, Prediction of tire profile wear by steady-state FEM, Tire Sci. Technol. 36 (4) (2008) 290–303. [15] J.C. Cho, B.C. Jung, Prediction of tread pattern wear by an explicit finite element model, Tire Sci. Technol. 35 (4) (2007) 276–299. [16] S. Knisley, A correlation between rolling tire contact friction energy and indoor tread wear, Tire Sci. Technol. 30 (2) (2002) 83–99. [17] J. Wu, Y.S. Wang, B.L. Su, J.Y. Dong, Z.B. Cui, B.K. Gond, Prediction of tread pattern block deformation in contact with road, Polym. Test. 58 (2017) 208–218. [18] A.N. Gent, C.T.R. Pulford, Mechanisms of rubber abrasion, J. Appl. Polym. Sci. 28 (3) (2010) 943–960. [19] T.B. Kirk, D. Panzera, R.V. Anamalay, Z.L. Xu, Computer image analysis of wear debris for machine condition monitoring and fault diagnosis, Wear s181–183 (95) (1995) 717–722. [20] X. Hu, S. Zhan, S. Zheng, Study of grey relational grade identification for ferrography based on characteristic analysis of wear debris, Lubr. Sci. 11 (1) (2010) 57–67. [21] O.H. Yeoh, Characterization of elastic properties of carbon-black-filled rubber vulcanizates, Rubber. Chem. Technol. 63 (5) (1990) 792–805.
Fig. 18. Distribution of frictional power density.
Fig. 19. Comparison between experiment and simulation in wear rate and frictional power density.
9
Contents lists available at ScienceDirect
Polymer Testing journal homepage: www.elsevier.com/locate/polytest
Test Method
Effect of temperature on wear performance of aircraft tire tread rubber a,⁎
a
a
a,⁎⁎
Jian Wu , Long Chen , Youshan Wang , Benlong Su a b
a
, Zhibo Cui , Diyuan Wang
b
T
Center for Rubber Composite Materials and Structures, Harbin Institute of Technology, Weihai, 264209, China China COMAC Shanghai Aircraft Manufacturing Co., Ltd, 200000, China
ARTICLE INFO
ABSTRACT
Keywords: Aircraft tire Temperature Wear Surface morphology Finite element simulation
Wear performance of tread rubber directly affect the service life of aircraft tires, especially for lateral sliding and high temperature conditions. Temperature of aircraft tire tread rises rapidly during takeoff and landing due to high-speed friction, which greatly affects the wear performance. Therefore, wear tests of aircraft tire tread materials under different temperatures and slip angles have been carried out; then, wear surface morphology and wear mechanism have been discussed; finally, Further research of wear mechanism has been detailed based on the finite element model of rubber wheel. Results indicate that slip angle has a greatly effect on the wear rate when temperature is lower than 45 °C and slip angle is greater than 10°; wear mechanism is different, when temperature is greater than 65 °C; roughness of wear surface decreases with the increasement of temperature. Besides, wear rate and frictional power density have a good correlation, which lays the foundation for the next work of wear prediction.
1. Introduction Aircraft tire is the key component of aircraft, and its wear performance is crucial to the safety of aircraft [1,2]. Under the high-speed landing condition, temperature of tire tread rises rapidly due to highspeed friction [3,4], Wear performance of aircraft tire is directly correlated to temperature. Therefore, it is essential to study the influence of temperature on wear properties. Wear performance of rubber have been widely studied. However, researches on the high-temperature wear mechanism of aircraft tires are insufficient in recent years. Schallamach [5] and Shingo [6] developed the relation between wear rate and various parameters based on wear tests, then the wear rate of tire was calculated based on the linear wear hypothesis and the Schallamach theory formula. Wear resistance is an important index of many rubber products, especially for the aircraft tire. Wear tests of tread materials were carried out for studying the wear resistance [7], results indicated that the micro texture of pavement significantly affected the wear resistance of tire. As concluded by Bhattacharya [8], wear rate of natural rubber nanocomposites also decreases sharply when the content of nanofiber increases. Besides, the wear rate can be characterized by the wavelength of rubber materials based on the Laboratory of Surface Phenomena of USP [9]. Temperature has a great influence on the wear mechanism and surface characteristics of rubber [10], especially in high temperature.
⁎
Roughness increased when the temperature increased; the surface morphology and wear characteristics of rubber materials can be characterized by the fractal theory [11]. A power function wear model of tread rubber blocks with frictional energy dissipation was developed based on the laboratory testing of rubber wear [12]. Finite element method has become a useful tool for wear performance simulation of rubber. Under the condition of steady rolling, finite element model was developed based on Archard wear model for predicting the tire wear [13]. A relationship between the frictional energy and the indoor tread wear has been established by finite element method [14]. A tire wear predicted model was also developed by explicit finite element simulation based on the frictional energy dissipation [15]. Knisley [16] also developed a relationship between frictional energy and tread wear rate at the rolling tire contact surface. Prior to this work, finite element model of tread blocks has been developed [17]. In this paper, wear mechanism of tread rubber is studied under different temperatures. Firstly, wear tests of aircraft tire tread materials are carried out by high-temperature Akron abrasion tester GT-7012-AH under different temperatures and different slip angles. Then, the surface topography wear of rubber wheel and wear debris are studied based on DSX510 Optical digital microscope. Finally, the finite element wear model of rubber wheel is developed and the relation between wear rate and friction power density is obtained.
Corresponding author. Corresponding author. E-mail addresses: [email protected] (J. Wu), [email protected] (B. Su).
⁎⁎
https://doi.org/10.1016/j.polymertesting.2019.106037 Received 20 May 2019; Received in revised form 11 August 2019; Accepted 12 August 2019 Available online 13 August 2019 0142-9418/ © 2019 Elsevier Ltd. All rights reserved.
Polymer Testing 79 (2019) 106037
J. Wu, et al.
(50 phr), which were provided by Shandong Linglong Tire Co., Ltd. Wear tests have been carried out by strip specimens according to the BS 903 A9, the phenomenon of "debonding" was observed when temperature above 45 °C, seen in Fig. 1. For solving this problem, tread rubber wheel (including the strip thickness according to GB/T 1689-2014) is cured by vulcanization mold in a flat-panel press under pressure 15 MPa, and temperature 150 °C for 25 min, as shown in Fig. 2(a), Fig. 2(b) shows the dimension of rubber wheel with thickness of 12.7 mm. Fig. 3 shows the high-temperature Akron abrasion tester GT-7012AH. The GH-300D electronic balance with the accuracy of 0.001g is used to measure the wear rate. Experimental parameters are shown in Table 1. Four rubber wheels are performed at each condition. 2.2. Surface topography Surface topography of wear is measured by the DSX510 optical digital microscope, seen in Fig. 4. Then, three-dimensional map and roughness are obtained. Fig. 5 shows the morphological characteristic of 25 °C and the slip angle of 15°. Wear debris are digitally processed by MATLAB software, and shape factors can be obtained.
Fig. 1. Debonding phenomenon of strip specimen.
3. Result and discussion 3.1. Effect of temperature Wear characteristics of tread materials are sensitive to the external environments, such as velocity, tire pressure, temperature, etc. Here, the effects of temperature on wear rate are analyzed by tests. Fig. 6 shows the relationship between wear rate and temperature. It can be seen that wear rate decreases rapidly when the slip angle is larger than 10°. Fig. 7 shows surface topographies of rubber wheel under different temperatures and the slip angle of 15°. The region A represents the inner position of rubber wheel is in contact with abrasive disk, the region B represents the intermediate position and the region C represents the outer position. Results indicate that tread material has the different wear surfaces due to the increase temperature. When the temperature increases, wear of regions B and C are changed, and the texture of wear on the rubber wheel surface is more intensive (seen in Fig. 7). Because temperature increases, the material properties are changed [18]. Besides, the smooth region of rubber wheel increases when the temperature increases, which results in the decrease of the wear rate when the slip angle is 15°, as shown in Fig. 6. The distance between protrudes under the slip angle of 15° and different temperatures are shown in Table 2, which are obtained by ten points at a same region, as shown h in Fig. 7(b). Results indicate that distance between protrudes of a same region decreases with increasing temperature, and from region A to region C, it also decreases under a same temperature, resulting in the rubber wheel with smoother surface when temperature increases, as shown in Fig. 7. When the temperature is larger than 65 °C, the distance of protrudes in region C is smaller than that with no wear; when the temperature increases, the distance of protrudes decreases. Slice processing is used for the surface of region C, then two-dimensional map, three-dimensional map and roughness are obtained. At the view of (500umX500um), the number of protrudes increases with temperature increases, and roughness decreases (the height of the protrudes decreases) when the temperature increases. The roughness is significantly less than that with no wear when the temperature is higher than 65 °C, seen in Table 3.
Fig. 2. (a) Vulcanization mold (b) The dimensions of rubber wheel.
Fig. 3. High-temperature Akron abrasion tester. Table 1 Experimental parameters used in wear tests. Experimental parameters Temperature(°C) Slip angle(°)
25,45,65,75,85 0, 2.5, 5, 7.5, 8.5, 10,15, 17.5, 20, (Rated load:26.7 N, Mileage:1 km)
2. Experiment set up 2.1. Materials and wear tests
3.2. Effect of slip angle
The tread rubber materials mainly contained natural rubber (100 phr), ZnO (3 phr), stearicacid (2 phr), sulphur (2 phr), and carbon blacks
Seen in Fig. 8, when the temperature is below 45 °C, wear rate under the
2
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Fig. 4. Optical digital microscope.
Fig. 5. 3D surface topography of rubber wheel.
Fig. 7. Wear morphology under different temperatures.
Fig. 6. The variation of wear rate with temperature.
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Table 2 Distance between protrudes in different temperatures. Temperature (°C)
25(No wear) 25 45 65 75 85
Distance between protrudes (mm) The inner position (A)
The intermediate position (B)
The outer position (C)
Average value
Standard deviation
Average value
Standard deviation
Average value
Standard deviation
0.503 1.143 0.757 0.613 0.602 0.574
0.015 0.013 0.023 0.014 0.016 0.019
0.494 1.057 0.568 0.536 0.415 0.327
0.016 0.024 0.019 0.021 0.019 0.017
0.486 0.828 0.512 0.415 0.262 0.112
0.015 0.015 0.017 0.012 0.018 0.011
Table 3 Characteristic parameters from region C under different temperatures.
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Fig. 9 shows the surface topography at 25 °C under different slip angles. Results show that no obvious furrow and adhesion are observed on the surface when the slip angle is 0°, which is consistent with the surface with no wear. Oily substance is produced when the slip angle is larger than 10°. Slice processing for the region C is similar to the previous method under different slip angles. Table 4 shows distance between protrudes in different slip angles. Distance between protrudes decreases from region A to region C under a same slip angle. When the slip angle increases at a same region, the distance between protrudes increases, which is consistent with the surface topography measured by optical digital microscope shown in Fig. 9. Fig. 10 shows the roughness in different slip angles at 25 °C. It can be seen that when the slip angle increases, roughness increases (the height of the protrudes increases). 3.3. Wear debris analysis Fig. 8. The variation of wear rate with slip angle.
Wear debris is the direct result of wear, which is of great significance to study the wear mechanism. Shape factor [19] is used to characterize appearance of wear debris, which depends on the equivalent area S, the projection area of wear debris A, and the circumference of wear debris L
G=
S 4 = 2 A L
(1)
where A and L are obtained from MATLAB software, 5 wear debris are discussed for each condition of 26.7 N/15°/25 °C. The average of 5 shape factors in different temperatures and slip angles are shown in Fig. 11. Results indicate that shape factor decreases in the range of 0.1–0.3 when the temperature and slip angle increase, that is, stick or columnar wear debris increases with increase of temperature and slip angle [19]. The temperature has great influence on the wear debris and the change of the surface characteristics of wear. Fig. 12 presents the surface morphology of wear debris in different temperatures and the slip angle of 15°. It can be seen that the Oily substance increases when the temperature increases, and more and more wear debris with small size appear and adhere to when the temperature increases (seen in Fig. 12(a)). Tire scrap is more likely to happen in summer after long wear, which is consistent with the actual occurrence [20]. Based on results of wear tests, surface topography and wear debris, and combine the 'Competition' mechanism theory [18]. The mechanism of the Akron wear at high temperature is mainly the wear of debris, which is determined by the condition of wear. 4. Finite element simulation 4.1. Constitutive model Temperature of aircraft tire tread rises rapidly during takeoff and landing due to the high-speed friction, which directly affects mechanical properties of material (Seen in Fig. 13). Here, material properties of tread rubber materials are characterized by Yeoh strain energy function [21], the strain density function is given by:
Fig. 9. Wear morphology under different slip angles.
condition of a small slip angle is enhanced but less than that with a large slip angle. Over the range from 65 °C to 85 °C, wear rate increases slightly with increasing slip angle. It can be seen that the slip angle is a leading factor on wear performance of tread material at a low temperature.
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Table 4 Distance between protrudes in different slip angles. Slip angles (°)
0(No wear) 0 10 15 20
Distance between protrudes (mm) The inner position (A)
The intermediate position (B)
The outer position (C)
Average value
Standard deviation
Average value
Standard deviation
Average value
Standard deviation
0.543 0.503 1.053 1.143 2.212
0.012 0.013 0.027 0.013 0.022
0.514 0.494 0.685 1.057 1.457
0.015 0.019 0.017 0.024 0.027
0.486 0.486 0.543 0.828 1.121
0.018 0.021 0.019 0.015 0.029
Fig. 10. Relation curve of roughness and slip angle.
Fig. 12. Wear debris and enlarged view of surface in different temperatures.
Fig. 13. Strain–stress curve in different temperatures.
W = C10 (I1 = 2[(1 + )
3) + C20 (I1 (1 + ) 2]
3)2 + C30 (I1
3)3
C10 + 2C20 [(1 + )2 + 2(1 + ) 1 3C30 [(1 + )2 + 2(1 + ) 1 3]2
3+] (2)
where W is the strain density, I1 is the first invariant of the deviatoric strain tensor, C10, C20 and C30 are the rubber material constants determined from experiments. Table 5 provides material constants in different temperatures.
Fig. 11. Effect of temperature and slip angle on the shape factor.
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Table 5 Material constants in different temperatures. Temperature(°C)
C10
C20
C30
25 45 65 75 85
0.38 0.38 0.35 0.34 0.33
−4.46 −5.14 −4.11 −4.32 −4.17
7.03 7.31 5.28 5.18 4.87
to the reference node RP-1 of rubber wheel. The grinding wheel is fixed in all displacement DOF and X, Z turn DOF. Under the load, rubber wheel and grinding wheel are rotated in Y direction. 4.3. Frictional power density In the analysis of aircraft tire contact characteristics, the distributions of contact shear stress and slip displacement are the focus of attention for the aircraft designer, which play a great part in aircraft tire performance. Fig. 16 shows the contact results under the temperature of 25 °C and the slip angle of 15°. Results show that a large slip displacement and contact shear stress are generated on the rubber wheel surface, which was caused by the slip angle. When the slip angle increases, the contact shear stress decreases, and the slip displacement has a significant increasement. Then, the frictional power density is obtained by the product of slip displacement and contact shear stress. Based on the simulation results and numeral calculations. Under the condition of wear 1 km and the slip angle is larger than 10°, the frictional power density decreases with increase of temperature. Frictional power density increases when the slip angle increases (seen in Fig. 17). Fig. 18 shows the instantaneous distribution of frictional power density at 25 °C, 85 °C, and slip angle of 5°. It can be seen that the maximum frictional power densities at different temperatures are concentrated in the region C, and increases with the increasement of temperature. Besides, the higher the temperature, the smaller is its the area of longitudinal nodes, and the larger is its the area of transverse nodes.
Fig. 14. Finite element model of rubber wheel.
4.2. Meshing and boundaries Fig. 14(a) shows 2D finite element model of rubber wheel. CGAX4H element is used for rubber wheel meshing, including 406 nodes and 364 elements. 3D finite element model is obtained based on the 2D model, and finer mesh is required in the region contacted with grinding wheel. The grinding wheel is modeled by discrete rigid body. Seen in Fig. 14(b). Steady-state rolling is adopted in finite element analysis according the working conditions of abrasion tester GT-7012-AH, as illustrated in Fig. 15. Surface A represents the contact surface between rubber wheel and plate, which is fixed in Y direction displacement degrees of freedom (DOF) and X turn DOF, then a concentrated force FZ = 27.6 N is applied
Fig. 15. 3D finite element model of rubber wheel.
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Fig. 17. Relation of temperature, slip angle and frictional power density.
Fig. 19 shows relation between wear rate and frictional power density at 5°. It can be seen that when the temperature increases, wear rate and frictional power density increase synchronization. The simulation result of the rubber wheel is in good agreement with the experimental data, which provides the basis for the further research on the wear prediction of aircraft tread material. 5. Conclusions Upon takeoff and landing with high speed, the properties of aircraft tire tread are affected by temperature. The wear characteristics of tread materials under different temperatures have been studied in this paper. Wear tests under different temperatures and slip angles have been carried out. Furthermore, the morphological characteristics of rubber surface and wear debris have been discussed in detail. According the results, main conclusions gained are as follows: (1) Effects of temperature on wear rate and surface topography is significantly when the slip angle is larger than 10°. The wear patterns of rubber wheel surface are more intensive with increase of temperature. And the roughness is less than that of no wear when the temperature is higher than65 °C; (2) Slip angle is a leading factor on wear performance of tread materials at the low temperature. The distance between protrudes
Fig. 16. Contact results of contact shear stress and slip displacement.
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increases with increasement of slip angle. Besides, oily substance is produced when slip angle is larger than 10°; (3) The Akron wear at high temperature is mainly the wear of debris. Number of stick wear debris increases with increase of temperature and slip angle; (4) The wear rate has a correlation with simulation result of friction power density. Acknowledgements This work is funded by Major Program of National Natural Science Foundation of China (51790502), Natural Science Foundation of Shandong Province,China (ZR2018QEE004) and Weihai technology development program,China (2017DXGJ11). References [1] A.J. Tuononen, Digital Image Correlation to analyse stick-slip behaviour of tyre tread block, Tribol. Int. 69 (69) (2014) 70–76. [2] H.C. Zhou, G.L. Wang, J. Yang, K.X. Xue, Numerical simulation of tire hydroplaning and its influencing factors, Appl. Mech. Mater. 602–605 (2014) 580–585. [3] A.A. Alroqi, W. Wang, Y. Zhao, Aircraft tire temperature at touchdown with wheel prerotation, J. Aircr. 54 (3) (2016). [4] M. Bennett, S.M. Michael, A. Graham, B.S. Thomas, V. Vishnyakov, Composition of smoke generated by landing aircraft, Environ. Sci. Technol. 45 (8) (2011) 3533–3538. [5] A. Schallamach, The velocity and temperature dependence of rubber friction, Proc. Phys. Soc. 66 (5) (1954) 386–392. [6] S. Kohmura, H. Nakamura, J. Komura, Y. Tanakeal, Estimation method of tire treadwear on a vehicle, SAE Tech. Pap. 910168 (1991). [7] F.A. Cardoso, A.L.D.A. Costa, D.K. Tanaka, Durability performance of tire tread rubber compounds as a function of road pavement, Tecnol. Metal. Mater. Mineracao 1124 (2010) 375–387. [8] M. Bhattacharya, A.K. Bhowmick, Analysis of wear characteristics of natural rubber nanocomposites, Wear 269 (1) (2010) 152–166. [9] T. Vieira, R.P. Ferreira, A.K. Kuchiishi, L.L.B. Bernucci, A. Sinatora, Evaluation of friction mechanisms and wear rates on rubber tire materials by low-cost laboratory tests, Wear 328–329 (2015) 556–562. [10] Y. Li, S. Zuo, L. Lei, X. Yang, X. Wu, Analysis of impact factors of tire wear, J. Vib. Control 18 (6) (2012) 833–840. [11] Z. Wang, S. Hu, Z. Miao, L. Ma, Application of multifractal spectrum calculation Program in rubber wear under high temperature, Wirel. Pers. Commun. 36 (2018) 1–9. [12] J.R. Cho, J.H. Choi, Y.S. Kim, Abrasive wear amount estimate for 3D patterned tire utilizing frictional dynamic rolling analysis, Tribol. Int. 44 (7) (2011) 850–858. [13] R. Sreeraj, V. Sandeep, R. Gokul, P. Baskar, Tire wear analysis using ABAQUS, Int. J. Innov. Res. Sci. Eng. Technol. 5 (8) (2016) 14403–14410. [14] K.R. Smith, Prediction of tire profile wear by steady-state FEM, Tire Sci. Technol. 36 (4) (2008) 290–303. [15] J.C. Cho, B.C. Jung, Prediction of tread pattern wear by an explicit finite element model, Tire Sci. Technol. 35 (4) (2007) 276–299. [16] S. Knisley, A correlation between rolling tire contact friction energy and indoor tread wear, Tire Sci. Technol. 30 (2) (2002) 83–99. [17] J. Wu, Y.S. Wang, B.L. Su, J.Y. Dong, Z.B. Cui, B.K. Gond, Prediction of tread pattern block deformation in contact with road, Polym. Test. 58 (2017) 208–218. [18] A.N. Gent, C.T.R. Pulford, Mechanisms of rubber abrasion, J. Appl. Polym. Sci. 28 (3) (2010) 943–960. [19] T.B. Kirk, D. Panzera, R.V. Anamalay, Z.L. Xu, Computer image analysis of wear debris for machine condition monitoring and fault diagnosis, Wear s181–183 (95) (1995) 717–722. [20] X. Hu, S. Zhan, S. Zheng, Study of grey relational grade identification for ferrography based on characteristic analysis of wear debris, Lubr. Sci. 11 (1) (2010) 57–67. [21] O.H. Yeoh, Characterization of elastic properties of carbon-black-filled rubber vulcanizates, Rubber. Chem. Technol. 63 (5) (1990) 792–805.
Fig. 18. Distribution of frictional power density.
Fig. 19. Comparison between experiment and simulation in wear rate and frictional power density.
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