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Plateau honing of a diesel engine cylinder with special topography and reasonable machining time
Tribology International 146 (2020) 106204
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Plateau honing of a diesel engine cylinder with special topography and reasonable machining time Babak Sadizade a, *, Alireza Araee a, Samad Nadimi Bavil Oliaei b, Vahid Rezaeizad Farshi c a
School of Mechanical Engineering, University of Tehran, Tehran, 11155/4563, Iran Department of Mechanical Engineering, ATILIM University, Ankara, Turkey c Motorsazan Co, Tabriz, Iran b
A R T I C L E I N F O
A B S T R A C T
Keywords: Diesel engine cylinder bore surface Linear regression Plateau honing Surface roughness
Deep valleys and flattened peaks are essential characteristics of the finished cylinder bore surface, which is known as the plateau surface. Generally, a honing process is done in three steps to achieve a plateau surface, which is costly and time-consuming and acts as a bottleneck for cylinder block machining line. The real challenge is to select optimum levels of honing process parameters to achieve desired surface characteristics with minimum machining time. The aim of this study is to examine the influence of the input parameters of the honing process on the surface texture of diesel engine cylinder bore. The Rk family parameters are used for surface roughness evaluation and the honing crosshatch angle, in accordance with engine design requirements, which was fixed for all experiments. Optimization by means of the desirability function technique allowed determining most appropriate conditions to desirable roughness (surface quality) and/or minimize machining time (productivity). Based on the findings of this study the conventional three-stage honing process has been replaced by the twostage process. Using the proposed two-stage honing process the intended plateau surface in cylinder bores are achieved and a remarkable reduction in the honing process time is obtained. Consequently, the process efficiency is improved significantly.
1. Introduction In order to fulfill the requirements of international environmental standards and to improve fuel efficiency, the production of engines with lower fuel consumption and emissions has received considerable attention in recent years [1]. The surface roughness and texture of the inner surface of engine cylinder bores should be designed in a way to possess excellent wear resistance, low friction with better oil retention along with reduced oil consumption and break-in period. A surface with such desired specifications is usually achieved through a multi-stage honing operation to generate plateau surface that consists of deep grooves for the retention of oil and fine plateau surface to improve load bearing capacity [2–6]. Generally, a three step process is implemented which consists of rough, base and plateau honing stages. The first stage is a rough honing process carried out by coarse honing stones targeted to improve the surface finish, shape and to eliminate the surface variations that originate from the previous fine boring operation. The rough honing operation is intended to create a geometrically correct cylinder bore and is intended to construct a suitable base surface finish for the following
steps. The second process, base honing, which is accomplished using medium size abrasive grits, aims to improve the surface texture closer to the final product requirements. Finally, plateau honing is carried out with very fine abrasive grits to modify the roughness peaks and generate a fine surface texture that resembles ‘run-in’ surfaces [2]. Fig. 1 illus trates the surface roughness profiles of the cylinder bores after rough and plateau honing operations. A rough honed surface is characterized by high peaks, while a plateau honed surface is composed of smoothed peaks and deep valleys. As shown in Fig. 2 to penetration of cutting particles of tool stone into the work piece, metal cutting and continue of material removal, three essential components of honing tool movement is as follows: (i) Feed or expansion movement of the honing tool stones (ii) Rotational movement around the bore axis (iii) Tool stroke movement along the bore axis The depth of engagement of the abrasive particles is provided by the axial movement of the tool feeding cone, which is translated into a radial
* Corresponding author. E-mail address: [email protected] (B. Sadizade). https://doi.org/10.1016/j.triboint.2020.106204 Received 24 August 2019; Received in revised form 8 November 2019; Accepted 18 January 2020 Available online 23 January 2020 0301-679X/© 2020 Elsevier Ltd. All rights reserved.
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Experimental and simulation studies indicate that honing crosshatch angle, α, influences the lubrication distribution on the cylinder bore surfaces [6]. Therefore, this is one of the engine design specifications that is defined with a tolerance range and must be taken into account in adjusting honing tool velocities. Therefore, in order to study the effect of cutting velocity on the output of the honing process while maintaining the desired honing angle, it is necessary to maintain a constant stroke to - rotational speeds ratio to any cutting velocity level. In the design of the experiment carried out in this study, this is followed. Currently, five surface roughness profile parameters based on ma terial ratio curve (ISO 13565-2 [7]) namely reduced peak height (Rpk), core roughness depth (Rk), reduced valley depth (Rvk), material ratio 1 at the peak zone (Mr1) and material ratio 2 at the valley zone (Mr2) are used in almost all of the engine block machining shops as the surface roughness specification of the cylinder liner surface. The parameter Rk is a measure of roughness height after a running-in process that defines the load-bearing capacity of a surface, while the parameter Rvk is used to evaluate the oil retention capacity of a honed surface. Rpk shows the top section of the roughness that will be removed after running–in the process [2–6]. The correlation and regression analyses of parameters included in ISO 13565-2 (Rk group) standards show that Rk, Rvk, and Mr2 are mutually independent and rather great stability on surfaces. The Rk parameter is correlated with Rpk and Mr1 is correlated with Mr2 [5]. The productivity and quality of the final cylinder surface are the two main concerns at the engine cylinder block honing station. Compre hensive theoretical and empirical studies are needed to modeling and optimization (increase productivity while maintaining and improving finished surface quality) of process. A complete understanding of the input parameters and the effect of each on the output of the process is required. Effective input parameters to the honing can be divided into two groups of process parameters (tool rotational speed, tool stroke speed, honing time at each step, cutting force …) and non-process pa rameters (work piece material, machine, tool, abrasive stone specifica tion, …). The fact that such a great number of parameters influence surface finish obtained complicates use of analytical methods for modeling roughness and material removal rate. For this reason, in the present work experimental tests were performed so as to obtain math ematical models from regression analysis. Process parameters such as honing tool expansion force (honing pressure) in each stage, cutting velocity as the sum of revolution and stroke speed of the tool, honing time especially in plateau honing stage is the commonly considered as input independent parameters in the studies of cylinder honing. Pawlus et al. [5] reported rough honing pressure and plateau honing time have a great influence on cylinder liner surface topography parameters but the effect of plateau honing pressure is negligible. The Rk and Rvk parameters are proportional to rough honing pressure, but inverse proportional to plateau honing time. Corral and co [8,10]. described that roughness of honed cylinders in creases mainly with abrasive grain size, followed by honing pressure but cutting speed influences roughness slightly. In same grain size, higher pressure causes higher roughness, because abrasive grains dig into the workpiece surface and makes deeper marks on it. For high and medium grain size, the higher cutting speed makes cutting easier that results in the lower roughness. For low grain size, the honed surface is finer and therefore the influence of vibrations will be more significant. Increased vibration with cutting speed result in slightly increasing in roughness. Rvk, Rpk, and Rt roughness parameters show the Maximum variability in a honed surface that significantly reduced when Increase the number of measurements in each workpiece. Corral et all in another article [14] reported the influence of grain size, density of abrasive, tangential speed of cylinders, linear speed of honing head and pressure of abrasive stones on surface roughness and material removal rate (productivity) in the rough honing process of steel cylinder. They found that, roughness de pends mainly on grain size, pressure and density of abrasive but material removal rate depends on grain size and pressure, followed by tangential speed. They used optimization by means of the desirability function
Fig. 1. Surface roughness profiles: (a) Rough honed, (b) Plateau honed.
Fig. 2. Engine cylinder block, liner, cross-hatched honing angle (α) and ve locity components of the abrasive particles.
movement of the honing stone (section A-A of Fig. 2) towards the workpiece. The expansion motion is decisive for the results of the honing process. The stroke motion of the tool is carried out at a constant speed in midway along the bore length and with variable speed in reversal points at two ends of its stroke. In honing a simultaneous rotating and reciprocating action of the stone (Fig. 2) results in a characteristic crosshatch lay pattern. This combination of motion gives the stones a figure eight travel path. Angle between the crosshatched grooves is known as honing angle (α) and is illustrated in as shown in Fig. 2. Ac cording to eq. (1) α is related to peripheral speed (Vr) and stroke speed (Vs) of the honing tool. The peripheral speed (Vr) and cutting speed (Vc) can be defined as follows in eq. (2) and eq. (3) [4]: �α� Vs tan (1) ¼ Vr 2 vr ¼ π∅Rev
(2)
pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi Vc ¼ Vr2 þ Vs2
(3)
In these relations ∅ is the inner diameter of the liner (in this study is equal to 0.1 m) and Rev is the number of honing tool revolution in 1 min. 2
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Table 1 Bore surface roughness average amount of sequence.
Fig. 3. The operational sequence of cylinder blocks machining line.
Parameters
Unit
Fine boring
Rough honing
Plateau honing
acceptable limits
Ra R3z Rpk Rk Rvk Mr1 Mr2
μm μm μm μm μm
4.23 18.24 3.81 14.34 4.32 7.79 89.78
1.25 7.68 3.17 3.39 3.50 11.74 87.37
0.75 4.80 0.99 2.05 2.00 8.52 85.16
– – 0–0.2 0.2–0.6 0.8–1.8 0–10 65–85
% %
to two, machining time and tool change time in relevant stage will be saved. This way, the honing station will no longer be a bottleneck in the engine block machining line. The aim of this study is to investigate the capability of a two-step honing process compared to a three-step honing process in achieving the desired plateau surface. Rough honing time is minimized with the use of two sequences honing pressure named rough and low pressures. The hydraulic pressure, which determines the feed force, is had been changed in during of the rough honing without interrupting the process. High rough pressure used in the process initiation with the aim of high material removal rate and geometrical correction of the cylinder bore. Low pressure, with a shorter time, is used to improve the surface roughness and to get a surface with characteristics closer to the final product and also, to prepare the bore surface for plateau honing stage. Optimization of two stage plateau honing process is done with desir ability function approach that one of the most widely used methods in industry for the optimization of multiple response processes. Linear regression modeling and determining operable settings of input pa rameters to reach desirable amounts of surface roughness quality and process productivity is done in design expert software. According to the results of this study, to generate a desirable plateau surface in engine bore, the optimized two-stage honing process could be adequate. This can result in lower machining time and can significantly increase manufacturing process efficiency.
technique allowed determining most appropriate conditions to mini mize roughness (surface quality) and/or maximize material removal rate (productivity). Salj� e et al. [19] studied internal and external honing on cast iron and Al–Si alloy workpieces. They reported that in low cut ting velocities, the material removal rate increases with cutting velocity and then after reaching a certain amount this effect reversed. The peak of the material removal rate - cutting speed curve, varies with the abrasive particles size. They attribute this phenomenon to the slide bearing effect (higher peripheral speed results a lubricating film which hinder the penetration of abrasive particles into work piece). They found that roughness increased linearly with increase of ratio tangential force over normal force, while material removal rate was related to tangential force. They reported the origin of insufficient reproducibility of honed engine cylinders quality is the inappropriate performance of the feed drive system and the variation of sharpening condition of tool stones. Hoffmeistera and co [9]. introduced the new kind of lid burr so-called” Blech mantel” extending into the pore cavities at honing with high pressure can negatively affect the tribological properties of the cylinder running surfaces. Despite a well-known and controlled honing process, variation in surface roughness cannot be avoided and topography variations do exist at one cylinder bore to next one and even in different location of one bore. This low reproducibility in the roughness measurement could be the result of the workpiece materials structure variation, tool dynamics as an inherent specification of this process (at two reversal point of stroke the longitudinal speed will zero) [11] and tool/workpiece contact area decreasing in two ends of stroke course (result to increasing of cutting pressure on abrasive particles) [12]. In this study, in order to obtain the correct results indicating the roughness conditions of the whole workpiece surface, multiple roughness measurements was per formed in different given areas of the workpiece. Cabanettes et al. [13] found that the honing tool wears down, the cylinder liner surface gets rougher plateau or peaks and sharper asperities indicating that plowing occurs instead of cutting. In multi-stage processes (as plateau honing) study, the method of recognizing the acceptable and optimum level of parameters is very important. Lawrence and co [3]. used the combining of robust process design and grey-relational analysis (Taguchi-Grey relational analysis) to evolve the operating levels of honing process parameters in rough, finish and plateau honing stages targeting to meet multiple surface topographic specifications on the final running surface of the cylinder bores. A general sequence of operations in a cylinder block bore machining is shown in Fig. 3. Mono spindle vertical honing machines mostly used in cylinder block machining line. At each stage of the honing (Rough, Base and Plateau) the corresponding tool is mounted on the machine mandrel and the cylinder bores are individually honed. After honing the last bore at the end of each stage, the tool is returned to the reference position and replaced with the next honing stage tool. The same steps are repeated in each stage. This three-step honing process is quite costly and timeconsuming, so it is considered as the bottleneck of cylinder machining line. Any solution which helps to reduce honing time while maintaining surface specifications intact seems to be essential and of vital impor tance. By reducing the number of stages at the honing station from three
2. Materials and methods The current investigation involves a series of experiments and opti mization desirability function approach to study the possibility of reaching the desired plateau surface with two steps honing, instead of the common three steps honing. To do so, the optimization of machining time in 6-cylinder diesel engine block honing station with mono spindle vertical honing machine is considered. Cylinder blocks after pressing and boring of liners in machining line delivered to honing station with 99.86–99.88 mm dia. and maximum cylindricity tolerance of 0.015 mm. According to the design requirements, the final surface of the engine liners in plateau honing must be reached to roughness with parameters in the range listed in Table 1 and a honing angle, ⍺ ¼ 30� –35� . It is worth mentioning that, whenever surface roughness of the cylinder liner was out of the specified range, a dramatic reduction in the engine perfor mance and increased emissions have been observed during engine per formance tests [21–28]. Honing process capability is effective in engine performance and emission in addition to the valuable studies mentioned above, this effect has always been clearly seen in the engine test cell. In order to evaluate the conditions in a diesel engine company facing a piston jump problem in the test cell, the roughness changes of the cyl inder surface at various machining stages are evaluated and summarized in Table 1. The values specified in the acceptable limit’s column are adapted to the company’s internal technical data. It is clear from this table that the parameters Rpk, Rk, and Rvk deviate from acceptable tolerance limits. The specifications of the honing machine, tools, coolant, and surface roughness measuring device used in the experiments are summarized in Table 2. Cylinder block in the honing station and honing tool in 3
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Table 2 Equipment, Materials and Conditions used in experiment. Equipment
Rough honing
Honing Machine Honing No. of stick tool Abrasive type
Nagel, Model: VS-10-120 LA 8 8 Diamond Carbide D151 AC20 M560C 320/40V51 01 MS 3 � 5 � 100 8 � 8 � 100
Sizing method
Stick Dimension (W � H � L) mm
coolant Depth of cut Surface roughness measurement
Air sizing
Plateau honing
Number of strokes
ECOCUT HFN 5 100–140 μm 6 μm Mahr - Marsurf PS1- Stylus diameter is 2 μm, U cut off wavelength 2.5 mm 6 cylinder cast iron engine block with liner
workpiece
Fig. 5. Surface roughness measurement positions. Arrow indicates the direc tion of stylus travel (dimensions in mm).
experiments is used for plateau honing process. The peripheral speed (Vr), stroke speed (Vs), rough pressure (Pr), low pressure (Pl) and lowpressure application time in rough honing stage (Tl) and the plateau pressure (Ppl) and plateau stroke number (SNpl) in plateau honing stage considered as input parameters. The selection of the input parameters and their levels were based on the prior pilot tests and production experience in the cylinder bore machining line. At the end of the process, the cutting speed and the groove angle can no longer be maintained because the direction of the motion has to be inverted. According to engine design requirements, the honing angle (⍺), should be 30� –35� when measured midway along the bore length. Therefore, the ratio of Vs to Vr should be kept constant and equal to 0.09 to fulfill the requirements. Hence whereas of these two speeds, three levels of cutting speed Vc (sum of them) are studied in experiments (Table 5). The maximum adjustable pressure of the hydraulic system of the machine mandrel is 30 bar. The values of Pr, Pl, and Ppl are set to a fraction of maximum achievable pressure. The hydraulic pressure de termines the applied expansion force to the honing tool. Low pressure, Pl, is the reduced pressure that executed at the end of the rough honing operation and honing ledge pressed on the bore wall of constant force for a time period of Tl. With respect to the independence of the parameters in two honing stages in all of the rough honing experiments, plateau honing parameters are kept constant and equal to SNpl ¼ 15 and Ppl ¼ 5% and in plateau honing experiments the workpiece was machined with constant rough honing parameters including to Vc ¼ 72 m/min, Pr ¼ 60%, Pl ¼ 15% and Tl ¼ 7 s. Linear regression is used to model the relationship between input and response parameters. Operable ranges of inner parameters are predicted so that response parameters will be within the desired toler ance range so that the optimized level of each parameter is achieved. The validation of optimum settings of parameters was certified by additional experiments.
Fig. 4. Cylinder block and rough honing tool in honing station. Table 3 Chemical composition of liners material. Element
C
Si
Mn
Cr
P
Cu
S
% By Weight
3.35
2.52
0.99
0.55
0.41
0.22
0.11
machining position are shown in Fig. 4. Regardless of the material removal conditions at the interface of the tool and bore surface, the force of expansion is kept constant by adjusting honing pressure throughout the honing process. As rough honing of 6-cylinder bores finished, spindle returns to the start point and operation is continued after changing the tool for plateau honing. The liners used as experiments workpiece have a bore diameter of 99.9 mm and a length of 222 mm. The chemical compositions of the grey cast iron are shown in Table 3. The inner surface of cylinder liners has a hardness of 217–302 HB. According to the results of metallography (ASTM A247), the material of liners is cast iron with pearlite matrix and a little amount of the steadite (iron phosphide eutectic network), typical graphite form is type I (strongest nodular graphite), graphite distribu tion pattern A, E and graphite size is 4,5. In the experiment, the Rk family, Ra, R3z topographic specifications and rough honing time is measured. Besides that, the roughness profiles are obtained and visually analyzed. Surface roughness measurement is done at three axial locations within the cylinder bore in respect of upper ring reversal, intermediate between upper and lower ring reversal and lower ring reversal. As shown in Fig. 5 six axial measurements of two circumferential locations 90� apart in each bore are accomplished. As shown in Table 5 in order to study the effect of input parameters on output characteristics, L18 orthogonal Taguchi design of experiments are used for rough honing and full factorial orthogonal design of
2.1. Modeling and optimization The five surface roughness parameters and a rough honing time, are constitute the six output parameters considered in this study. When the optimization procedure involves more than one response, it is not possible to optimize each one in a separate way, because a number of solutions equal to the variables under study would be gathered. The 4
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overall solution must be included in an optimal region, leading to a certain degree of compliance with the proposed criteria for each variable of the system; namely, a compromise solution must be found [16]. The desirability function approach is one of the most widely used methods in industry for the optimization of multiple response processes [18–20]. It is based on the idea that the “quality” of a product or process that has multiple quality characteristics, with one of them outside of some “desired” limits, is completely unacceptable. The method finds oper ating conditions x that provide the “most desirable” response values. For each response Yi(x), a desirability function di (Yi) assigns numbers
Table 4 Optimization constraint values of response parameters. Parameter
Goal
Lower Limit
Upper Limit
Rough honing time [sec.] Rpk [micro m.] Rk [micro m.] Rvk [micro m.] Mr1 [%] Mr2 [%]
minimize minimize is in range is in range minimize is in range
0 0.0 0.2 0.8 0 65
450 0.2 0.6 1.8 10 85
Table 5 Design of experiments and results. Input parameters
Rough honing
Plateau honing
Min Max Av. St. d St. deviation/mean
Response parameters
Test No.
Vc
Pr
Pl
Tl
Ppl
SNpl
honing time
Ra
Rpk
Rk
Rvk
Mr1
Mr2
Unit
m/min.
%
%
Sec.
%
No
Sec.
μm
μm
μm
μm
%
%
μm
t1 t2 t3 t4 t5 t6 t7 t8 t9 t10 t11 t12 t13 t14 t15 t16 t17 t18 t19 t20 t21 t22 t23 t24 t25 t26 t27
54
40 60 80 40 60 80 40 60 80 40 60 80 40 60 80 40 60 80 60
20 50 70 20 50 70 50 70 20 70 20 50 50 70 20 70 20 50 15
2
5
15
2 5 8 2 5 8 2 5 8 2 8 5 1
10
1220 524 432 855 376 264 614 308 232 738 682 277 882 430 370 716 484 294 410 410 410 410 410 410 410 410 410 232 1220 539 267 0.50
0.24 0.34 0.27 0.24 0.24 0.24 0.29 0.31 0.33 0.37 0.23 0.32 0.37 0.40 0.33 0.33 0.26 0.28 0.33 0.31 0.29 0.29 0.23 0.24 0.21 0.18 0.18 0.18 0.40 0.28 0.06 0.20
0.25 0.25 0.26 0.23 0.22 0.33 0.25 0.39 0.24 0.32 0.18 0.31 0.27 0.45 0.29 0.28 0.22 0.23 0.28 0.25 0.25 0.26 0.26 0.23 0.21 0.20 0.19 0.18 0.45 0.26 0.06 0.23
0.60 0.61 0.65 0.58 0.60 0.66 0.63 0.67 0.59 0.69 0.57 0.69 0.73 0.73 0.64 0.70 0.60 0.67 0.77 0.74 0.67 0.56 0.54 0.52 0.48 0.47 0.46 0.46 0.77 0.62 0.08 0.13
0.72 0.78 0.84 0.67 0.83 0.96 1.01 1.17 0.92 1.34 0.75 1.02 1.32 1.79 1.11 1.15 0.87 1.06 0.85 0.82 0.78 0.93 0.79 0.69 0.74 0.62 0.60 0.60 1.79 0.93 0.26 0.28
7.42 7.22 6.33 7.15 6.67 6.05 7.29 6.98 7.58 6.89 7.15 7.83 6.11 7.45 7.59 6.28 7.24 8.16 7.30 7.18 7.32 8.08 8.38 8.22 8.36 8.19 7.66 6.05 8.38 7.34 0.67 0.09
84.00 81.93 82.73 84.03 82.37 84.85 82.77 82.23 82.90 82.90 84.73 81.43 76.00 77.30 82.33 80.70 84.33 81.57 84.00 83.55 84.78 83.85 84.35 84.22 84.10 84.08 84.90 76.00 84.90 82.85 2.13 0.03
2.10 2.65 2.38 2.02 2.33 2.04 2.42 2.73 2.25 2.69 1.93 3.03 2.84 3.16 2.75 2.89 2.13 2.47 2.40 2.27 2.08 1.88 1.89 1.92 1.74 1.53 1.62 1.53 3.16 2.30 0.43 0.19
72 90 54 72 90 72
54 90 72 12
40 80 60 14
15 70 36 23
5
7
2 7 5 2
15 20 10 20 15 2
Vr: Peripheral speed of the abrasive particles (m/min). Vs: Stroke speed of the abrasive particles (m/min). Vc: Cutting speed of the abrasive particle (m/min). Pr: Hydraulic pressure on honing tool in rough stage (%). Pl: Low hydraulic pressure on honing tool in rough stage (%). Tl: Low time in rough honing stage (sec). Ppl: Hydraulic pressure on honing tool in plateau stage (%). SNpl: Plateau honing stroke number.
5
R3z
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Fig. 6. Effect of input parameters on response parameters.
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between 0 and 1 to the possible values of Yi, with di (Yi) ¼ 0 repre senting a completely undesirable value of Yi and di (Yi) ¼ 1 representing a completely desirable or ideal response value. The individual de sirabilities are then combined using the geometric mean, which gives the overall desirability D [17,18]:
Table 6 Linear regression model. Parameter
Linear Regression Model
honing time ¼ Ra ¼ Rpk ¼ Rk ¼ Rvk ¼ R3z ¼
1891–3.3 Pl 5.7 Vc 13.1 Pr 0.45 þ 0.0012 Pl - 0.0012 Ppl - 0.012 SNpl 0.27 þ 0.00195 Pl þ 0.00615 Tl – 0.0045 Ppl – 0.00574 SNpl 0.99 þ 0.00186 Pl – 0.00954 Ppl 0.0259 SNpl 0.38 þ 0.0097 Pl þ 0.042 Tl 2.76 þ 0.013 Pl - 0.062 SNpl
D ¼ dr11 � dr22 � … � drnn
�P1 ri
¼
�Yn
d ri i¼1 i
�P1 ri
(4)
where ri is the importance of each variable relative to the others. If any response Yi is completely undesirable (di (Yi) ¼ 0), then the overall
Fig. 7. Response surface plots for output parameters (based on regression model). Level of fixed input parameters in each graph: Pr ¼ 80%, Pl ¼ 15%, Tl ¼ 7 Sec., Vc ¼ 72 m/min., Ppl ¼ 8%, SNpl ¼ 20.
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1. Conduct experiments and fit response models for all output parameters. 2. Define individual desirability functions for each response. 3. Maximize the overall desirability D with respect to the input parameters. Based on the requirements and experiences from machining line, the optimization constraint values were selected according to Table 4. In calculating the desirability factor (eq. (4)) the importance, ri, equal to three are taken into account for all response parameters. Optimization by means of the desirability function technique allowed determining most appropriate conditions to keep five roughness parameters in desired range (surface quality) and minimum machining b i are used in time (productivity). In practice, fitted response values Y
place of the Yi. In the regression model for each output parameter, the Analysis of variance (ANOVA) table is used and the models F-value implies the model is significant. There is only a 0.01% chance that a “Model F-Value” could occur due to noise. Values of “Prob > F00 less than 0.05 indicate that model terms are significant. In modeling by means of least squares method it is tried to obtain the simplest linear regression model that has maximum agreement with the experimental results. To examine the model significance, following diagnostic plots are investi gated for each model [15,18]: � Normal probability plot of the studentized residuals to check for normality of residuals. � Studentized residuals versus predicted values for constant error. � Externally studentized residuals for outliers, i.e., influential values. � Box-Cox plot for power transformations. In this study the Design-expert was used for statistical analysis. 3. Results and discussion The main objective of this research is reaching high productivity and quality in diesel engine cylinder bores honing. For this purpose, the results of the experiments have been analyzed, regression modeling has been performed and a few applicable input process parameters have been determined. Results of experiments in rough honing with Taguchi L18 DOE and plateau honing with full factorial DOE are shown in Table 5. The average of every roughness parameter in six measurements location is mentioned as a result. With respect to the orthogonal design of experiments, we were able to study the individual effect of input parameters on re sponses; the results are presented in Fig. 6. The standard deviation to mean ratio is reported in Table 5 and graphs in Fig. 6 indicates that material ratio parameters (Mr1 and Mr2) are not significantly affected from the variation of input parameters and the amount of these two response parameters are in desirable tolerance range in all experiments. It seems that these two parameters which characterize the ratio of ma terials in the valley and peak section of surface roughness are more influenced by non-process parameters such as abrasive particle size, which were unchanged in this study. The results show that the size and concentration of the abrasive particles used in this experiment is appropriate. As expected, the rough pressure variation has the main effect on rough honing time, cutting speed and the effect of low pressure is less significant. Among rough honing parameters, the low pressure has the most significant effect on the configuration of surface roughness. To reach the fixed desired honing angle, the quantity of Vs to Vr fraction kept to 0.09 in all experiments. The increase in Vs, results in rougher surfaces and this is on the contrary for Vr. Therefore, the effect of variation in Vc is not bold on surface roughness. Plateau honing input parameters, stroke number and plateau pressure are the same effect on surface roughness so that increasing to these parameters causes to smoother honed surface. It is worth mentioning that the effect of plateau
Fig. 8. Operability Area of input parameters. Constant parameters quantity in each graph is: Pl ¼ 15%, Tl ¼ 7 s, Ppl ¼ 8%, SNpl ¼ 20, Vc ¼ 72 m/min, Pr ¼ 80%., Pl ¼ 15%.
desirability is zero. Depending on whether a particular response Yi is to be maximized, minimized, or assigned a target value, different desir ability functions di (Yi) can be used [17,18]. The desirability approach consists of the following steps:
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Table 7 Optimum levels of parameters and resultant responses from model and experiment. Process parameters Vc
Pr
Measured Parameters Pl
m/min % % 72 80 15 Models predicted dif. between model and experiment.
Tl
Ppl
SNpl
honing time
Ra
Rpk
Rk
Rvk
Mr1
Mr2
R3z
Sec. 7
% 8
No. 20
Sec. 364 383 5%
μm
μm
μm
μm
% 7.2 – –
% 83 – –
μm
0.19 0.21 10%
0.18 0.19 6%
0.44 0.42 4%
0.84 0.82 2%
1.91 1.72 11%
unstable and unwanted vibrations increase dramatically, so the inter mediate level of this parameter is appropriately detected. The results of surface roughness measurements of this set of experiments were in the desired range. The sample roughness profile in the selected level of honing parameters is illustrated in Fig. 9, deep narrow valleys and proper bearing area at peaks of roughness profile are evident that engine cylinder liners surface roughness is suitable for its duty. Experimental measurements performed at the optimum set showed that the model error for different output parameters was in the range of 2–11%, indi cating acceptable accuracy of the proposed model. To illustrate the shape of the roughness, the height of the roughness on the vertical axis is shown by 100x magnification. From the results of experiments, the variation of roughness in one cast iron cylinder bore’s different positions is very excessive. As shown in Fig. 10 the shape and distribution of graphite has important role in roughness variation. Therefore, in this study to obtain real results, sur face roughness of each machined specimen was measured at six specific locations.
Fig. 9. The roughness profile in surface honed with selected levels of input parameters.
strokes number is more than plateau pressure. With increasing honing pressure, abrasive particles compressed with a higher force to the workpiece surface so higher feed force lead to more penetration and the material removal rate are favorably increased but on the other hand the surface roughness parameters will be out of desirable range. The modeling of relations between input and output parameters is done with linear regression technique in Design-expert. The best models for each response parameter are presented in Table 6. From the models most influential factors on process quality (surface roughness parame ters) as well as on productivity (honing time) were determined within the range studied. The variations in Mr1 and Mr2 is not significant, therefore, they are not included in the models. Based on regression model, response surface plots for output parameters are shown in Fig. 7. Based on the models of Table 6, and the tolerance limits of response parameters according to engine design requirements, optimization is done and overlay graphs created (Fig. 8). These graphs show the applicable range of input parameters to meet all the targets listed in Table 4 in green. According to the results of optimization, the set of input parameters with desirability equal to 0.886 (Table 7) are selected as optimum setting. At high cutting velocities, the process becomes
4. Conclusions Using the desirability technique, a set of optimized parameters in two honing stages, instead of common three honing stages, to reach the desired plateau surface (high quality) with least machining time (high productivity) are introduced. Rough honing time is minimized with the use of two sequence honing pressure named rough and low pressures in the rough honing stage without interrupting of process. The high rough pressure used in the rough honing initiation phase results in high ma terial removal rate and ease of geometrical correction of the cylinder bore, which could reduce honing time. Low pressure in a short period of time, which is used for the rest of the rough honing stage, makes it possible to achieve a surface roughness close to the final product. It also prepares the bore surface for plateau honing stage. The material ratio roughness parameters (Mr1 and Mr2) are not significantly affected by variation in honing process parameters. These response parameters, always are in the desired tolerance range. In order to get the desired honing angle in all settings, the ratio of stoke velocity (Vs) and rotational velocity (Vr) must be kept constant. At high cutting velocities, the
Fig. 10. SEM image of engine cylinder (workpiece) surface after plateau honing (a) Cross section (b) cylindrical inner surface. 9
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unwanted vibrations increase dramatically so the intermediate level of this parameter is appropriately detected. High phosphorus grey cast iron is one of the most widely used materials in diesel engine cylinder liners, so the results of this study can be useful for many diesel engine manu facturers in cylinder block machining line. The results of this study revealed that, by replacing a three-stage honing process with an opti mized two-stage process without sacrificing surface qualities, a threefold reduction in the whole honing process time can be achieved.
[10] Corral Irene Buj, De Lamob Lourdes Rodero, Marco Almagro Lluís. Use of results from honing test machines to determine rough-ness in industrial honing machines. J Manuf Process 2017;28:60–9. [11] Schmitt Christina. Analysis of the process dynamics for the precision honing of bores. CIRP 2014;17:692–7. [12] Moos Uwe, Bahre Dirk. Analysis of process forces for the precision honing of small bores. Procedia CIRP 2015;31:387–92. [13] Cabanettes F, Dimkovski Z, Ros�enSchool B-G. Roughness variations in cylinder liners induced by honing tools’ wear. Precis Eng 2015;41:40–6. [14] Buj-Corral Irene, Vivancos-Calvet Joan, Coba-Salcedo Milton. Modelling of surface finish and material removal rate in rough honing. Precis Eng 2014;38:100–8. [15] Montgomery DC. Design and analysis of experiments. New York: John Wileyand Sons, Inc.; 2003. [16] Venkata Subbaiah K, Raju Ch, Pawade RS, Suresh Ch. Machinability investigation with wiper ceramic insert and optimization during the hard turning of AISI 4340 steel. Mater Today: Proceedings 2019;18:445–54. [17] Singh Sangwan Kuldip, Sihag Nitesh. Multi-objective optimization for energy efficient machining with high productivity and quality for a turning process. Procedia CIRP 2019;80:67–72. [18] Candioti Luciana Vera, DeZan María M, C� amara María S, Goicoechea H�ector C. Experimental design and multiple response optimization. Using the desirability function in analytical methods development. Talanta 2014;124:123–38. [19] Salj� e E, von See M. Process-optimization in honing. CIRP Ann - Manuf Technol 1987;36:235–9. [20] Venkata Subbaiah K, Raju Ch, Pawade RS, Suresh Ch. Machinability investigation with wiper ceramic insert and optimization during the hard turning of AISI 4340 steel. Mater Today: Proceedings 2019;18:445–54. [21] EduardoTomanik Mohamed El Mansori, Roberto Souza, Profito Francisco. Effect of waviness and roughness on cylinder liner friction. Tribol Int 2018;120:547–55. [22] Grabon Wieslaw, Pawlus Pawel, Wos Slawomir, Koszela Waldemar, Wieczorowski Michal. Evolutions of cylinder liner surface texture and tribological performance of piston ring-liner assembly. Tribol Int 2018;127:545–56. [23] Ali Usman, Park Cheol Woo. Optimizing the tribological performance of textured piston ring–liner contact for reduced frictional losses in SI engine: warm operating conditions. Tribol Int 2016;99:224–36. [24] Koszela Waldemar, Pawlus Pawel, Reizer Rafal, Liskiewicz Tomasz. The combined effect of surface texturing and DLC coating on the functional properties of internal combustion engines. Tribol Int 2018;127:470–7. [25] Xiang Rao, Sheng Chenxing, Guo Zhiwei, Yuan Chengqing. Effects of thread groove width in cylinder liner surface on performances of diesel engine. Wear 2019; 426–427:1296–303. [26] Soderfjall Markus, Herbst Hubert M, Larsson Roland. Andreas Almqvist. Influence on friction from piston ring design, cylinder liner roughness and lubricant properties. Tribol Int 2017;116:272–84. [27] Prakash Chandra Mishra. Modeling the root causes of engine friction loss: transient elasto hydrodynamics of a piston subsystem and cylinder liner lubricated contact. Appl Math Model 2015;39:2234–60. [28] Kim Eun-Seok, Kim Seung-Mok, Lee Young-Ze. The effect of plateau honing on the friction and wear of cylinder liners. Wear 2018;400–401:207–12.
Declaration of competing interest The authors whose names are listed immediately below certify that they have NO affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consul tancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript. References [1] Karpuschewskia B, Welzel F, Risse K, Schorgel M, Kreter S. Potentials for improving efficiency of combustion engines due to cylinder liner surface engineering. Procedia CIRP 2016;46:258–65. [2] Haasis G. An introduction to plateau honing of engine cylinder bores. Nagel Technical Report; 1982. [3] Lawrence KD, Ramamoorthy B. Multi-surface topography targeted plateau honing for the processing of cylinder liner surfaces of automotive engines. Appl Surf Sci 2016;365:19–30. [4] El Mansori M, Goeldel B, Sabri L. Performance impact of honing dynamics on surface finish of precoated cylinder bores. Surf Coating Technol 2013;215:334–9. [5] Pawlus P, Cieslak T, Mathia T, Mater J. The study of cylinder liner plateau honing process. Process. Technol. 2009;209:6078–86. [6] Mezghani S, Demirci I, Yousfi M, EL Mansori M. Mutual influence of crosshatch angle and superficial roughness of honed surfaces on friction in ring-pack tribo – system. Tribol Int 2013;66:54–9. [7] ISO 13565-2. Geometrical Product Specifications (GPS)-Surface texture: profile method; Surface having stratified functional proper-ties-Part 2: height characterization using the linear material ratio curve. [8] Corral Irene Buj, Calvet Joan Vivancos. Roughness variability in the honing process of steel cylinders with CBN metal bonded tools. Precis Eng 2011;35:289–93. [9] Hoffmeistera H-W, Grossea T, Gerdesa A. Investigation of the influence of different process setting parameters on the surface formation at honing of thermally sprayed layers. Procedia CIRP 2012;1:371–6.
10
Contents lists available at ScienceDirect
Tribology International journal homepage: http://www.elsevier.com/locate/triboint
Plateau honing of a diesel engine cylinder with special topography and reasonable machining time Babak Sadizade a, *, Alireza Araee a, Samad Nadimi Bavil Oliaei b, Vahid Rezaeizad Farshi c a
School of Mechanical Engineering, University of Tehran, Tehran, 11155/4563, Iran Department of Mechanical Engineering, ATILIM University, Ankara, Turkey c Motorsazan Co, Tabriz, Iran b
A R T I C L E I N F O
A B S T R A C T
Keywords: Diesel engine cylinder bore surface Linear regression Plateau honing Surface roughness
Deep valleys and flattened peaks are essential characteristics of the finished cylinder bore surface, which is known as the plateau surface. Generally, a honing process is done in three steps to achieve a plateau surface, which is costly and time-consuming and acts as a bottleneck for cylinder block machining line. The real challenge is to select optimum levels of honing process parameters to achieve desired surface characteristics with minimum machining time. The aim of this study is to examine the influence of the input parameters of the honing process on the surface texture of diesel engine cylinder bore. The Rk family parameters are used for surface roughness evaluation and the honing crosshatch angle, in accordance with engine design requirements, which was fixed for all experiments. Optimization by means of the desirability function technique allowed determining most appropriate conditions to desirable roughness (surface quality) and/or minimize machining time (productivity). Based on the findings of this study the conventional three-stage honing process has been replaced by the twostage process. Using the proposed two-stage honing process the intended plateau surface in cylinder bores are achieved and a remarkable reduction in the honing process time is obtained. Consequently, the process efficiency is improved significantly.
1. Introduction In order to fulfill the requirements of international environmental standards and to improve fuel efficiency, the production of engines with lower fuel consumption and emissions has received considerable attention in recent years [1]. The surface roughness and texture of the inner surface of engine cylinder bores should be designed in a way to possess excellent wear resistance, low friction with better oil retention along with reduced oil consumption and break-in period. A surface with such desired specifications is usually achieved through a multi-stage honing operation to generate plateau surface that consists of deep grooves for the retention of oil and fine plateau surface to improve load bearing capacity [2–6]. Generally, a three step process is implemented which consists of rough, base and plateau honing stages. The first stage is a rough honing process carried out by coarse honing stones targeted to improve the surface finish, shape and to eliminate the surface variations that originate from the previous fine boring operation. The rough honing operation is intended to create a geometrically correct cylinder bore and is intended to construct a suitable base surface finish for the following
steps. The second process, base honing, which is accomplished using medium size abrasive grits, aims to improve the surface texture closer to the final product requirements. Finally, plateau honing is carried out with very fine abrasive grits to modify the roughness peaks and generate a fine surface texture that resembles ‘run-in’ surfaces [2]. Fig. 1 illus trates the surface roughness profiles of the cylinder bores after rough and plateau honing operations. A rough honed surface is characterized by high peaks, while a plateau honed surface is composed of smoothed peaks and deep valleys. As shown in Fig. 2 to penetration of cutting particles of tool stone into the work piece, metal cutting and continue of material removal, three essential components of honing tool movement is as follows: (i) Feed or expansion movement of the honing tool stones (ii) Rotational movement around the bore axis (iii) Tool stroke movement along the bore axis The depth of engagement of the abrasive particles is provided by the axial movement of the tool feeding cone, which is translated into a radial
* Corresponding author. E-mail address: [email protected] (B. Sadizade). https://doi.org/10.1016/j.triboint.2020.106204 Received 24 August 2019; Received in revised form 8 November 2019; Accepted 18 January 2020 Available online 23 January 2020 0301-679X/© 2020 Elsevier Ltd. All rights reserved.
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Experimental and simulation studies indicate that honing crosshatch angle, α, influences the lubrication distribution on the cylinder bore surfaces [6]. Therefore, this is one of the engine design specifications that is defined with a tolerance range and must be taken into account in adjusting honing tool velocities. Therefore, in order to study the effect of cutting velocity on the output of the honing process while maintaining the desired honing angle, it is necessary to maintain a constant stroke to - rotational speeds ratio to any cutting velocity level. In the design of the experiment carried out in this study, this is followed. Currently, five surface roughness profile parameters based on ma terial ratio curve (ISO 13565-2 [7]) namely reduced peak height (Rpk), core roughness depth (Rk), reduced valley depth (Rvk), material ratio 1 at the peak zone (Mr1) and material ratio 2 at the valley zone (Mr2) are used in almost all of the engine block machining shops as the surface roughness specification of the cylinder liner surface. The parameter Rk is a measure of roughness height after a running-in process that defines the load-bearing capacity of a surface, while the parameter Rvk is used to evaluate the oil retention capacity of a honed surface. Rpk shows the top section of the roughness that will be removed after running–in the process [2–6]. The correlation and regression analyses of parameters included in ISO 13565-2 (Rk group) standards show that Rk, Rvk, and Mr2 are mutually independent and rather great stability on surfaces. The Rk parameter is correlated with Rpk and Mr1 is correlated with Mr2 [5]. The productivity and quality of the final cylinder surface are the two main concerns at the engine cylinder block honing station. Compre hensive theoretical and empirical studies are needed to modeling and optimization (increase productivity while maintaining and improving finished surface quality) of process. A complete understanding of the input parameters and the effect of each on the output of the process is required. Effective input parameters to the honing can be divided into two groups of process parameters (tool rotational speed, tool stroke speed, honing time at each step, cutting force …) and non-process pa rameters (work piece material, machine, tool, abrasive stone specifica tion, …). The fact that such a great number of parameters influence surface finish obtained complicates use of analytical methods for modeling roughness and material removal rate. For this reason, in the present work experimental tests were performed so as to obtain math ematical models from regression analysis. Process parameters such as honing tool expansion force (honing pressure) in each stage, cutting velocity as the sum of revolution and stroke speed of the tool, honing time especially in plateau honing stage is the commonly considered as input independent parameters in the studies of cylinder honing. Pawlus et al. [5] reported rough honing pressure and plateau honing time have a great influence on cylinder liner surface topography parameters but the effect of plateau honing pressure is negligible. The Rk and Rvk parameters are proportional to rough honing pressure, but inverse proportional to plateau honing time. Corral and co [8,10]. described that roughness of honed cylinders in creases mainly with abrasive grain size, followed by honing pressure but cutting speed influences roughness slightly. In same grain size, higher pressure causes higher roughness, because abrasive grains dig into the workpiece surface and makes deeper marks on it. For high and medium grain size, the higher cutting speed makes cutting easier that results in the lower roughness. For low grain size, the honed surface is finer and therefore the influence of vibrations will be more significant. Increased vibration with cutting speed result in slightly increasing in roughness. Rvk, Rpk, and Rt roughness parameters show the Maximum variability in a honed surface that significantly reduced when Increase the number of measurements in each workpiece. Corral et all in another article [14] reported the influence of grain size, density of abrasive, tangential speed of cylinders, linear speed of honing head and pressure of abrasive stones on surface roughness and material removal rate (productivity) in the rough honing process of steel cylinder. They found that, roughness de pends mainly on grain size, pressure and density of abrasive but material removal rate depends on grain size and pressure, followed by tangential speed. They used optimization by means of the desirability function
Fig. 1. Surface roughness profiles: (a) Rough honed, (b) Plateau honed.
Fig. 2. Engine cylinder block, liner, cross-hatched honing angle (α) and ve locity components of the abrasive particles.
movement of the honing stone (section A-A of Fig. 2) towards the workpiece. The expansion motion is decisive for the results of the honing process. The stroke motion of the tool is carried out at a constant speed in midway along the bore length and with variable speed in reversal points at two ends of its stroke. In honing a simultaneous rotating and reciprocating action of the stone (Fig. 2) results in a characteristic crosshatch lay pattern. This combination of motion gives the stones a figure eight travel path. Angle between the crosshatched grooves is known as honing angle (α) and is illustrated in as shown in Fig. 2. Ac cording to eq. (1) α is related to peripheral speed (Vr) and stroke speed (Vs) of the honing tool. The peripheral speed (Vr) and cutting speed (Vc) can be defined as follows in eq. (2) and eq. (3) [4]: �α� Vs tan (1) ¼ Vr 2 vr ¼ π∅Rev
(2)
pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi Vc ¼ Vr2 þ Vs2
(3)
In these relations ∅ is the inner diameter of the liner (in this study is equal to 0.1 m) and Rev is the number of honing tool revolution in 1 min. 2
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Table 1 Bore surface roughness average amount of sequence.
Fig. 3. The operational sequence of cylinder blocks machining line.
Parameters
Unit
Fine boring
Rough honing
Plateau honing
acceptable limits
Ra R3z Rpk Rk Rvk Mr1 Mr2
μm μm μm μm μm
4.23 18.24 3.81 14.34 4.32 7.79 89.78
1.25 7.68 3.17 3.39 3.50 11.74 87.37
0.75 4.80 0.99 2.05 2.00 8.52 85.16
– – 0–0.2 0.2–0.6 0.8–1.8 0–10 65–85
% %
to two, machining time and tool change time in relevant stage will be saved. This way, the honing station will no longer be a bottleneck in the engine block machining line. The aim of this study is to investigate the capability of a two-step honing process compared to a three-step honing process in achieving the desired plateau surface. Rough honing time is minimized with the use of two sequences honing pressure named rough and low pressures. The hydraulic pressure, which determines the feed force, is had been changed in during of the rough honing without interrupting the process. High rough pressure used in the process initiation with the aim of high material removal rate and geometrical correction of the cylinder bore. Low pressure, with a shorter time, is used to improve the surface roughness and to get a surface with characteristics closer to the final product and also, to prepare the bore surface for plateau honing stage. Optimization of two stage plateau honing process is done with desir ability function approach that one of the most widely used methods in industry for the optimization of multiple response processes. Linear regression modeling and determining operable settings of input pa rameters to reach desirable amounts of surface roughness quality and process productivity is done in design expert software. According to the results of this study, to generate a desirable plateau surface in engine bore, the optimized two-stage honing process could be adequate. This can result in lower machining time and can significantly increase manufacturing process efficiency.
technique allowed determining most appropriate conditions to mini mize roughness (surface quality) and/or maximize material removal rate (productivity). Salj� e et al. [19] studied internal and external honing on cast iron and Al–Si alloy workpieces. They reported that in low cut ting velocities, the material removal rate increases with cutting velocity and then after reaching a certain amount this effect reversed. The peak of the material removal rate - cutting speed curve, varies with the abrasive particles size. They attribute this phenomenon to the slide bearing effect (higher peripheral speed results a lubricating film which hinder the penetration of abrasive particles into work piece). They found that roughness increased linearly with increase of ratio tangential force over normal force, while material removal rate was related to tangential force. They reported the origin of insufficient reproducibility of honed engine cylinders quality is the inappropriate performance of the feed drive system and the variation of sharpening condition of tool stones. Hoffmeistera and co [9]. introduced the new kind of lid burr so-called” Blech mantel” extending into the pore cavities at honing with high pressure can negatively affect the tribological properties of the cylinder running surfaces. Despite a well-known and controlled honing process, variation in surface roughness cannot be avoided and topography variations do exist at one cylinder bore to next one and even in different location of one bore. This low reproducibility in the roughness measurement could be the result of the workpiece materials structure variation, tool dynamics as an inherent specification of this process (at two reversal point of stroke the longitudinal speed will zero) [11] and tool/workpiece contact area decreasing in two ends of stroke course (result to increasing of cutting pressure on abrasive particles) [12]. In this study, in order to obtain the correct results indicating the roughness conditions of the whole workpiece surface, multiple roughness measurements was per formed in different given areas of the workpiece. Cabanettes et al. [13] found that the honing tool wears down, the cylinder liner surface gets rougher plateau or peaks and sharper asperities indicating that plowing occurs instead of cutting. In multi-stage processes (as plateau honing) study, the method of recognizing the acceptable and optimum level of parameters is very important. Lawrence and co [3]. used the combining of robust process design and grey-relational analysis (Taguchi-Grey relational analysis) to evolve the operating levels of honing process parameters in rough, finish and plateau honing stages targeting to meet multiple surface topographic specifications on the final running surface of the cylinder bores. A general sequence of operations in a cylinder block bore machining is shown in Fig. 3. Mono spindle vertical honing machines mostly used in cylinder block machining line. At each stage of the honing (Rough, Base and Plateau) the corresponding tool is mounted on the machine mandrel and the cylinder bores are individually honed. After honing the last bore at the end of each stage, the tool is returned to the reference position and replaced with the next honing stage tool. The same steps are repeated in each stage. This three-step honing process is quite costly and timeconsuming, so it is considered as the bottleneck of cylinder machining line. Any solution which helps to reduce honing time while maintaining surface specifications intact seems to be essential and of vital impor tance. By reducing the number of stages at the honing station from three
2. Materials and methods The current investigation involves a series of experiments and opti mization desirability function approach to study the possibility of reaching the desired plateau surface with two steps honing, instead of the common three steps honing. To do so, the optimization of machining time in 6-cylinder diesel engine block honing station with mono spindle vertical honing machine is considered. Cylinder blocks after pressing and boring of liners in machining line delivered to honing station with 99.86–99.88 mm dia. and maximum cylindricity tolerance of 0.015 mm. According to the design requirements, the final surface of the engine liners in plateau honing must be reached to roughness with parameters in the range listed in Table 1 and a honing angle, ⍺ ¼ 30� –35� . It is worth mentioning that, whenever surface roughness of the cylinder liner was out of the specified range, a dramatic reduction in the engine perfor mance and increased emissions have been observed during engine per formance tests [21–28]. Honing process capability is effective in engine performance and emission in addition to the valuable studies mentioned above, this effect has always been clearly seen in the engine test cell. In order to evaluate the conditions in a diesel engine company facing a piston jump problem in the test cell, the roughness changes of the cyl inder surface at various machining stages are evaluated and summarized in Table 1. The values specified in the acceptable limit’s column are adapted to the company’s internal technical data. It is clear from this table that the parameters Rpk, Rk, and Rvk deviate from acceptable tolerance limits. The specifications of the honing machine, tools, coolant, and surface roughness measuring device used in the experiments are summarized in Table 2. Cylinder block in the honing station and honing tool in 3
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Table 2 Equipment, Materials and Conditions used in experiment. Equipment
Rough honing
Honing Machine Honing No. of stick tool Abrasive type
Nagel, Model: VS-10-120 LA 8 8 Diamond Carbide D151 AC20 M560C 320/40V51 01 MS 3 � 5 � 100 8 � 8 � 100
Sizing method
Stick Dimension (W � H � L) mm
coolant Depth of cut Surface roughness measurement
Air sizing
Plateau honing
Number of strokes
ECOCUT HFN 5 100–140 μm 6 μm Mahr - Marsurf PS1- Stylus diameter is 2 μm, U cut off wavelength 2.5 mm 6 cylinder cast iron engine block with liner
workpiece
Fig. 5. Surface roughness measurement positions. Arrow indicates the direc tion of stylus travel (dimensions in mm).
experiments is used for plateau honing process. The peripheral speed (Vr), stroke speed (Vs), rough pressure (Pr), low pressure (Pl) and lowpressure application time in rough honing stage (Tl) and the plateau pressure (Ppl) and plateau stroke number (SNpl) in plateau honing stage considered as input parameters. The selection of the input parameters and their levels were based on the prior pilot tests and production experience in the cylinder bore machining line. At the end of the process, the cutting speed and the groove angle can no longer be maintained because the direction of the motion has to be inverted. According to engine design requirements, the honing angle (⍺), should be 30� –35� when measured midway along the bore length. Therefore, the ratio of Vs to Vr should be kept constant and equal to 0.09 to fulfill the requirements. Hence whereas of these two speeds, three levels of cutting speed Vc (sum of them) are studied in experiments (Table 5). The maximum adjustable pressure of the hydraulic system of the machine mandrel is 30 bar. The values of Pr, Pl, and Ppl are set to a fraction of maximum achievable pressure. The hydraulic pressure de termines the applied expansion force to the honing tool. Low pressure, Pl, is the reduced pressure that executed at the end of the rough honing operation and honing ledge pressed on the bore wall of constant force for a time period of Tl. With respect to the independence of the parameters in two honing stages in all of the rough honing experiments, plateau honing parameters are kept constant and equal to SNpl ¼ 15 and Ppl ¼ 5% and in plateau honing experiments the workpiece was machined with constant rough honing parameters including to Vc ¼ 72 m/min, Pr ¼ 60%, Pl ¼ 15% and Tl ¼ 7 s. Linear regression is used to model the relationship between input and response parameters. Operable ranges of inner parameters are predicted so that response parameters will be within the desired toler ance range so that the optimized level of each parameter is achieved. The validation of optimum settings of parameters was certified by additional experiments.
Fig. 4. Cylinder block and rough honing tool in honing station. Table 3 Chemical composition of liners material. Element
C
Si
Mn
Cr
P
Cu
S
% By Weight
3.35
2.52
0.99
0.55
0.41
0.22
0.11
machining position are shown in Fig. 4. Regardless of the material removal conditions at the interface of the tool and bore surface, the force of expansion is kept constant by adjusting honing pressure throughout the honing process. As rough honing of 6-cylinder bores finished, spindle returns to the start point and operation is continued after changing the tool for plateau honing. The liners used as experiments workpiece have a bore diameter of 99.9 mm and a length of 222 mm. The chemical compositions of the grey cast iron are shown in Table 3. The inner surface of cylinder liners has a hardness of 217–302 HB. According to the results of metallography (ASTM A247), the material of liners is cast iron with pearlite matrix and a little amount of the steadite (iron phosphide eutectic network), typical graphite form is type I (strongest nodular graphite), graphite distribu tion pattern A, E and graphite size is 4,5. In the experiment, the Rk family, Ra, R3z topographic specifications and rough honing time is measured. Besides that, the roughness profiles are obtained and visually analyzed. Surface roughness measurement is done at three axial locations within the cylinder bore in respect of upper ring reversal, intermediate between upper and lower ring reversal and lower ring reversal. As shown in Fig. 5 six axial measurements of two circumferential locations 90� apart in each bore are accomplished. As shown in Table 5 in order to study the effect of input parameters on output characteristics, L18 orthogonal Taguchi design of experiments are used for rough honing and full factorial orthogonal design of
2.1. Modeling and optimization The five surface roughness parameters and a rough honing time, are constitute the six output parameters considered in this study. When the optimization procedure involves more than one response, it is not possible to optimize each one in a separate way, because a number of solutions equal to the variables under study would be gathered. The 4
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overall solution must be included in an optimal region, leading to a certain degree of compliance with the proposed criteria for each variable of the system; namely, a compromise solution must be found [16]. The desirability function approach is one of the most widely used methods in industry for the optimization of multiple response processes [18–20]. It is based on the idea that the “quality” of a product or process that has multiple quality characteristics, with one of them outside of some “desired” limits, is completely unacceptable. The method finds oper ating conditions x that provide the “most desirable” response values. For each response Yi(x), a desirability function di (Yi) assigns numbers
Table 4 Optimization constraint values of response parameters. Parameter
Goal
Lower Limit
Upper Limit
Rough honing time [sec.] Rpk [micro m.] Rk [micro m.] Rvk [micro m.] Mr1 [%] Mr2 [%]
minimize minimize is in range is in range minimize is in range
0 0.0 0.2 0.8 0 65
450 0.2 0.6 1.8 10 85
Table 5 Design of experiments and results. Input parameters
Rough honing
Plateau honing
Min Max Av. St. d St. deviation/mean
Response parameters
Test No.
Vc
Pr
Pl
Tl
Ppl
SNpl
honing time
Ra
Rpk
Rk
Rvk
Mr1
Mr2
Unit
m/min.
%
%
Sec.
%
No
Sec.
μm
μm
μm
μm
%
%
μm
t1 t2 t3 t4 t5 t6 t7 t8 t9 t10 t11 t12 t13 t14 t15 t16 t17 t18 t19 t20 t21 t22 t23 t24 t25 t26 t27
54
40 60 80 40 60 80 40 60 80 40 60 80 40 60 80 40 60 80 60
20 50 70 20 50 70 50 70 20 70 20 50 50 70 20 70 20 50 15
2
5
15
2 5 8 2 5 8 2 5 8 2 8 5 1
10
1220 524 432 855 376 264 614 308 232 738 682 277 882 430 370 716 484 294 410 410 410 410 410 410 410 410 410 232 1220 539 267 0.50
0.24 0.34 0.27 0.24 0.24 0.24 0.29 0.31 0.33 0.37 0.23 0.32 0.37 0.40 0.33 0.33 0.26 0.28 0.33 0.31 0.29 0.29 0.23 0.24 0.21 0.18 0.18 0.18 0.40 0.28 0.06 0.20
0.25 0.25 0.26 0.23 0.22 0.33 0.25 0.39 0.24 0.32 0.18 0.31 0.27 0.45 0.29 0.28 0.22 0.23 0.28 0.25 0.25 0.26 0.26 0.23 0.21 0.20 0.19 0.18 0.45 0.26 0.06 0.23
0.60 0.61 0.65 0.58 0.60 0.66 0.63 0.67 0.59 0.69 0.57 0.69 0.73 0.73 0.64 0.70 0.60 0.67 0.77 0.74 0.67 0.56 0.54 0.52 0.48 0.47 0.46 0.46 0.77 0.62 0.08 0.13
0.72 0.78 0.84 0.67 0.83 0.96 1.01 1.17 0.92 1.34 0.75 1.02 1.32 1.79 1.11 1.15 0.87 1.06 0.85 0.82 0.78 0.93 0.79 0.69 0.74 0.62 0.60 0.60 1.79 0.93 0.26 0.28
7.42 7.22 6.33 7.15 6.67 6.05 7.29 6.98 7.58 6.89 7.15 7.83 6.11 7.45 7.59 6.28 7.24 8.16 7.30 7.18 7.32 8.08 8.38 8.22 8.36 8.19 7.66 6.05 8.38 7.34 0.67 0.09
84.00 81.93 82.73 84.03 82.37 84.85 82.77 82.23 82.90 82.90 84.73 81.43 76.00 77.30 82.33 80.70 84.33 81.57 84.00 83.55 84.78 83.85 84.35 84.22 84.10 84.08 84.90 76.00 84.90 82.85 2.13 0.03
2.10 2.65 2.38 2.02 2.33 2.04 2.42 2.73 2.25 2.69 1.93 3.03 2.84 3.16 2.75 2.89 2.13 2.47 2.40 2.27 2.08 1.88 1.89 1.92 1.74 1.53 1.62 1.53 3.16 2.30 0.43 0.19
72 90 54 72 90 72
54 90 72 12
40 80 60 14
15 70 36 23
5
7
2 7 5 2
15 20 10 20 15 2
Vr: Peripheral speed of the abrasive particles (m/min). Vs: Stroke speed of the abrasive particles (m/min). Vc: Cutting speed of the abrasive particle (m/min). Pr: Hydraulic pressure on honing tool in rough stage (%). Pl: Low hydraulic pressure on honing tool in rough stage (%). Tl: Low time in rough honing stage (sec). Ppl: Hydraulic pressure on honing tool in plateau stage (%). SNpl: Plateau honing stroke number.
5
R3z
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Fig. 6. Effect of input parameters on response parameters.
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between 0 and 1 to the possible values of Yi, with di (Yi) ¼ 0 repre senting a completely undesirable value of Yi and di (Yi) ¼ 1 representing a completely desirable or ideal response value. The individual de sirabilities are then combined using the geometric mean, which gives the overall desirability D [17,18]:
Table 6 Linear regression model. Parameter
Linear Regression Model
honing time ¼ Ra ¼ Rpk ¼ Rk ¼ Rvk ¼ R3z ¼
1891–3.3 Pl 5.7 Vc 13.1 Pr 0.45 þ 0.0012 Pl - 0.0012 Ppl - 0.012 SNpl 0.27 þ 0.00195 Pl þ 0.00615 Tl – 0.0045 Ppl – 0.00574 SNpl 0.99 þ 0.00186 Pl – 0.00954 Ppl 0.0259 SNpl 0.38 þ 0.0097 Pl þ 0.042 Tl 2.76 þ 0.013 Pl - 0.062 SNpl
D ¼ dr11 � dr22 � … � drnn
�P1 ri
¼
�Yn
d ri i¼1 i
�P1 ri
(4)
where ri is the importance of each variable relative to the others. If any response Yi is completely undesirable (di (Yi) ¼ 0), then the overall
Fig. 7. Response surface plots for output parameters (based on regression model). Level of fixed input parameters in each graph: Pr ¼ 80%, Pl ¼ 15%, Tl ¼ 7 Sec., Vc ¼ 72 m/min., Ppl ¼ 8%, SNpl ¼ 20.
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1. Conduct experiments and fit response models for all output parameters. 2. Define individual desirability functions for each response. 3. Maximize the overall desirability D with respect to the input parameters. Based on the requirements and experiences from machining line, the optimization constraint values were selected according to Table 4. In calculating the desirability factor (eq. (4)) the importance, ri, equal to three are taken into account for all response parameters. Optimization by means of the desirability function technique allowed determining most appropriate conditions to keep five roughness parameters in desired range (surface quality) and minimum machining b i are used in time (productivity). In practice, fitted response values Y
place of the Yi. In the regression model for each output parameter, the Analysis of variance (ANOVA) table is used and the models F-value implies the model is significant. There is only a 0.01% chance that a “Model F-Value” could occur due to noise. Values of “Prob > F00 less than 0.05 indicate that model terms are significant. In modeling by means of least squares method it is tried to obtain the simplest linear regression model that has maximum agreement with the experimental results. To examine the model significance, following diagnostic plots are investi gated for each model [15,18]: � Normal probability plot of the studentized residuals to check for normality of residuals. � Studentized residuals versus predicted values for constant error. � Externally studentized residuals for outliers, i.e., influential values. � Box-Cox plot for power transformations. In this study the Design-expert was used for statistical analysis. 3. Results and discussion The main objective of this research is reaching high productivity and quality in diesel engine cylinder bores honing. For this purpose, the results of the experiments have been analyzed, regression modeling has been performed and a few applicable input process parameters have been determined. Results of experiments in rough honing with Taguchi L18 DOE and plateau honing with full factorial DOE are shown in Table 5. The average of every roughness parameter in six measurements location is mentioned as a result. With respect to the orthogonal design of experiments, we were able to study the individual effect of input parameters on re sponses; the results are presented in Fig. 6. The standard deviation to mean ratio is reported in Table 5 and graphs in Fig. 6 indicates that material ratio parameters (Mr1 and Mr2) are not significantly affected from the variation of input parameters and the amount of these two response parameters are in desirable tolerance range in all experiments. It seems that these two parameters which characterize the ratio of ma terials in the valley and peak section of surface roughness are more influenced by non-process parameters such as abrasive particle size, which were unchanged in this study. The results show that the size and concentration of the abrasive particles used in this experiment is appropriate. As expected, the rough pressure variation has the main effect on rough honing time, cutting speed and the effect of low pressure is less significant. Among rough honing parameters, the low pressure has the most significant effect on the configuration of surface roughness. To reach the fixed desired honing angle, the quantity of Vs to Vr fraction kept to 0.09 in all experiments. The increase in Vs, results in rougher surfaces and this is on the contrary for Vr. Therefore, the effect of variation in Vc is not bold on surface roughness. Plateau honing input parameters, stroke number and plateau pressure are the same effect on surface roughness so that increasing to these parameters causes to smoother honed surface. It is worth mentioning that the effect of plateau
Fig. 8. Operability Area of input parameters. Constant parameters quantity in each graph is: Pl ¼ 15%, Tl ¼ 7 s, Ppl ¼ 8%, SNpl ¼ 20, Vc ¼ 72 m/min, Pr ¼ 80%., Pl ¼ 15%.
desirability is zero. Depending on whether a particular response Yi is to be maximized, minimized, or assigned a target value, different desir ability functions di (Yi) can be used [17,18]. The desirability approach consists of the following steps:
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Table 7 Optimum levels of parameters and resultant responses from model and experiment. Process parameters Vc
Pr
Measured Parameters Pl
m/min % % 72 80 15 Models predicted dif. between model and experiment.
Tl
Ppl
SNpl
honing time
Ra
Rpk
Rk
Rvk
Mr1
Mr2
R3z
Sec. 7
% 8
No. 20
Sec. 364 383 5%
μm
μm
μm
μm
% 7.2 – –
% 83 – –
μm
0.19 0.21 10%
0.18 0.19 6%
0.44 0.42 4%
0.84 0.82 2%
1.91 1.72 11%
unstable and unwanted vibrations increase dramatically, so the inter mediate level of this parameter is appropriately detected. The results of surface roughness measurements of this set of experiments were in the desired range. The sample roughness profile in the selected level of honing parameters is illustrated in Fig. 9, deep narrow valleys and proper bearing area at peaks of roughness profile are evident that engine cylinder liners surface roughness is suitable for its duty. Experimental measurements performed at the optimum set showed that the model error for different output parameters was in the range of 2–11%, indi cating acceptable accuracy of the proposed model. To illustrate the shape of the roughness, the height of the roughness on the vertical axis is shown by 100x magnification. From the results of experiments, the variation of roughness in one cast iron cylinder bore’s different positions is very excessive. As shown in Fig. 10 the shape and distribution of graphite has important role in roughness variation. Therefore, in this study to obtain real results, sur face roughness of each machined specimen was measured at six specific locations.
Fig. 9. The roughness profile in surface honed with selected levels of input parameters.
strokes number is more than plateau pressure. With increasing honing pressure, abrasive particles compressed with a higher force to the workpiece surface so higher feed force lead to more penetration and the material removal rate are favorably increased but on the other hand the surface roughness parameters will be out of desirable range. The modeling of relations between input and output parameters is done with linear regression technique in Design-expert. The best models for each response parameter are presented in Table 6. From the models most influential factors on process quality (surface roughness parame ters) as well as on productivity (honing time) were determined within the range studied. The variations in Mr1 and Mr2 is not significant, therefore, they are not included in the models. Based on regression model, response surface plots for output parameters are shown in Fig. 7. Based on the models of Table 6, and the tolerance limits of response parameters according to engine design requirements, optimization is done and overlay graphs created (Fig. 8). These graphs show the applicable range of input parameters to meet all the targets listed in Table 4 in green. According to the results of optimization, the set of input parameters with desirability equal to 0.886 (Table 7) are selected as optimum setting. At high cutting velocities, the process becomes
4. Conclusions Using the desirability technique, a set of optimized parameters in two honing stages, instead of common three honing stages, to reach the desired plateau surface (high quality) with least machining time (high productivity) are introduced. Rough honing time is minimized with the use of two sequence honing pressure named rough and low pressures in the rough honing stage without interrupting of process. The high rough pressure used in the rough honing initiation phase results in high ma terial removal rate and ease of geometrical correction of the cylinder bore, which could reduce honing time. Low pressure in a short period of time, which is used for the rest of the rough honing stage, makes it possible to achieve a surface roughness close to the final product. It also prepares the bore surface for plateau honing stage. The material ratio roughness parameters (Mr1 and Mr2) are not significantly affected by variation in honing process parameters. These response parameters, always are in the desired tolerance range. In order to get the desired honing angle in all settings, the ratio of stoke velocity (Vs) and rotational velocity (Vr) must be kept constant. At high cutting velocities, the
Fig. 10. SEM image of engine cylinder (workpiece) surface after plateau honing (a) Cross section (b) cylindrical inner surface. 9
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unwanted vibrations increase dramatically so the intermediate level of this parameter is appropriately detected. High phosphorus grey cast iron is one of the most widely used materials in diesel engine cylinder liners, so the results of this study can be useful for many diesel engine manu facturers in cylinder block machining line. The results of this study revealed that, by replacing a three-stage honing process with an opti mized two-stage process without sacrificing surface qualities, a threefold reduction in the whole honing process time can be achieved.
[10] Corral Irene Buj, De Lamob Lourdes Rodero, Marco Almagro Lluís. Use of results from honing test machines to determine rough-ness in industrial honing machines. J Manuf Process 2017;28:60–9. [11] Schmitt Christina. Analysis of the process dynamics for the precision honing of bores. CIRP 2014;17:692–7. [12] Moos Uwe, Bahre Dirk. Analysis of process forces for the precision honing of small bores. Procedia CIRP 2015;31:387–92. [13] Cabanettes F, Dimkovski Z, Ros�enSchool B-G. Roughness variations in cylinder liners induced by honing tools’ wear. Precis Eng 2015;41:40–6. [14] Buj-Corral Irene, Vivancos-Calvet Joan, Coba-Salcedo Milton. Modelling of surface finish and material removal rate in rough honing. Precis Eng 2014;38:100–8. [15] Montgomery DC. Design and analysis of experiments. New York: John Wileyand Sons, Inc.; 2003. [16] Venkata Subbaiah K, Raju Ch, Pawade RS, Suresh Ch. Machinability investigation with wiper ceramic insert and optimization during the hard turning of AISI 4340 steel. Mater Today: Proceedings 2019;18:445–54. [17] Singh Sangwan Kuldip, Sihag Nitesh. Multi-objective optimization for energy efficient machining with high productivity and quality for a turning process. Procedia CIRP 2019;80:67–72. [18] Candioti Luciana Vera, DeZan María M, C� amara María S, Goicoechea H�ector C. Experimental design and multiple response optimization. Using the desirability function in analytical methods development. Talanta 2014;124:123–38. [19] Salj� e E, von See M. Process-optimization in honing. CIRP Ann - Manuf Technol 1987;36:235–9. [20] Venkata Subbaiah K, Raju Ch, Pawade RS, Suresh Ch. Machinability investigation with wiper ceramic insert and optimization during the hard turning of AISI 4340 steel. Mater Today: Proceedings 2019;18:445–54. [21] EduardoTomanik Mohamed El Mansori, Roberto Souza, Profito Francisco. Effect of waviness and roughness on cylinder liner friction. Tribol Int 2018;120:547–55. [22] Grabon Wieslaw, Pawlus Pawel, Wos Slawomir, Koszela Waldemar, Wieczorowski Michal. Evolutions of cylinder liner surface texture and tribological performance of piston ring-liner assembly. Tribol Int 2018;127:545–56. [23] Ali Usman, Park Cheol Woo. Optimizing the tribological performance of textured piston ring–liner contact for reduced frictional losses in SI engine: warm operating conditions. Tribol Int 2016;99:224–36. [24] Koszela Waldemar, Pawlus Pawel, Reizer Rafal, Liskiewicz Tomasz. The combined effect of surface texturing and DLC coating on the functional properties of internal combustion engines. Tribol Int 2018;127:470–7. [25] Xiang Rao, Sheng Chenxing, Guo Zhiwei, Yuan Chengqing. Effects of thread groove width in cylinder liner surface on performances of diesel engine. Wear 2019; 426–427:1296–303. [26] Soderfjall Markus, Herbst Hubert M, Larsson Roland. Andreas Almqvist. Influence on friction from piston ring design, cylinder liner roughness and lubricant properties. Tribol Int 2017;116:272–84. [27] Prakash Chandra Mishra. Modeling the root causes of engine friction loss: transient elasto hydrodynamics of a piston subsystem and cylinder liner lubricated contact. Appl Math Model 2015;39:2234–60. [28] Kim Eun-Seok, Kim Seung-Mok, Lee Young-Ze. The effect of plateau honing on the friction and wear of cylinder liners. Wear 2018;400–401:207–12.
Declaration of competing interest The authors whose names are listed immediately below certify that they have NO affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consul tancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript. References [1] Karpuschewskia B, Welzel F, Risse K, Schorgel M, Kreter S. Potentials for improving efficiency of combustion engines due to cylinder liner surface engineering. Procedia CIRP 2016;46:258–65. [2] Haasis G. An introduction to plateau honing of engine cylinder bores. Nagel Technical Report; 1982. [3] Lawrence KD, Ramamoorthy B. Multi-surface topography targeted plateau honing for the processing of cylinder liner surfaces of automotive engines. Appl Surf Sci 2016;365:19–30. [4] El Mansori M, Goeldel B, Sabri L. Performance impact of honing dynamics on surface finish of precoated cylinder bores. Surf Coating Technol 2013;215:334–9. [5] Pawlus P, Cieslak T, Mathia T, Mater J. The study of cylinder liner plateau honing process. Process. Technol. 2009;209:6078–86. [6] Mezghani S, Demirci I, Yousfi M, EL Mansori M. Mutual influence of crosshatch angle and superficial roughness of honed surfaces on friction in ring-pack tribo – system. Tribol Int 2013;66:54–9. [7] ISO 13565-2. Geometrical Product Specifications (GPS)-Surface texture: profile method; Surface having stratified functional proper-ties-Part 2: height characterization using the linear material ratio curve. [8] Corral Irene Buj, Calvet Joan Vivancos. Roughness variability in the honing process of steel cylinders with CBN metal bonded tools. Precis Eng 2011;35:289–93. [9] Hoffmeistera H-W, Grossea T, Gerdesa A. Investigation of the influence of different process setting parameters on the surface formation at honing of thermally sprayed layers. Procedia CIRP 2012;1:371–6.
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