Numerical Simulation of Engagement of a Wet Clutch With Skewed Surface Roughness

2001 ◽  
Vol 124 (2) ◽  
pp. 305-312 ◽  
Author(s):  
H. Gao ◽  
G. C. Barber ◽  
M. Shillor
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Weibull Distribution ◽  
Height Distribution ◽  
Asperity Contact ◽  
Friction Characteristic ◽  
Friction Materials ◽  
Wet Friction ◽  
Torque Response ◽  
Wet Clutch

The engagement of a wet clutch with skewed surface roughness was investigated. A Weibull asperity height distribution rather than a Gaussian one was utilized in the asperity contact pressure model. The combined effects of surface roughness and skewness on the friction coefficient were studied for new, run-in and glazed wet friction materials. The results show that the engagement time predicted by the Weibull distribution is greater than that obtained using the Gaussian distribution. A torque spike at the beginning of engagement occurs using the Weibull distribution by taking the skewness into account. A positively sloped curve of friction coefficient versus velocity can reduce the torque increase near the end of the engagement. The strain value at the end of engagement obtained by including the skewness is lower than that predicted by excluding it. The surface topography and the friction characteristics change with the engagement wear and thermal glazing. The torque response and the phase plane are presented for the run-in and the glazed wet friction materials as a function of surface roughness, skewness, and friction characteristic.

scholarly journals A new kind of resin-based wet friction material: Non-woven fabrics with isotropic fiber networks as preforms

Friction ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 92-103 ◽  
Author(s):  
Yewei Fu ◽  
Le Zhou ◽  
Tao Yin ◽  
Zhongyao Luo ◽  
Hejin Li ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Low Cost ◽  
Static Friction ◽  
Friction Material ◽  
Woven Fabrics ◽  
Mechanical And Thermal Properties ◽  
Friction Materials ◽  
Dynamic Friction Coefficient ◽  
Wet Friction ◽  
Long Fibers

AbstractAs an alternative to short fibers, non-woven fabrics (NWFs) were made using different types of long fibers to optimize the performance of paper-based friction materials and their technology. In this investigation, the fillers and resin were impregnated into these NWFs to prepare three kinds of wet friction material. The tribological, mechanical, and thermal properties of the new wet friction material were studied. The results indicate that the dynamic friction coefficient of the new friction material is approximately 0.12 and the static friction coefficient is approximately 0.15; the better wear rate is 0.81334 × 10-14 m3·(N·m)-1. In addition, the temperature for 10% mass loss yielded 100 °C enhancement and the tensile strength was improved by 200%, compared to previously reported values. Most importantly, the advantages include a simple preparation flow, low cost, and resource conservation. This is a promising approach for the future development of paper-based friction materials.

Thermohydrodynamic Analysis of Submerged Oil Journal Bearings Considering Surface Roughness Effects

1997 ◽  
Vol 119 (1) ◽  
pp. 100-106 ◽  
Author(s):  
J. Ramesh ◽  
B. C. Majumdar ◽  
N. S. Rao
Keyword(s):  
Surface Roughness ◽  
Thermal Effects ◽  
Hydrodynamic Pressure ◽  
Height Distribution ◽  
Asperity Contact ◽  
Roughness Effects ◽  
State Behavior ◽  
Total Load ◽  
Contact Loads ◽  
Effect Of Surface

A theoretical study of a submerged oil journal bearing is made considering surface roughness and thermal effects. The total load-supporting ability under such condition is due to the thermohydrodynamic as well as the asperity contact pressure. The effect of surface roughness and viscosity-temperature dependency on hydrodynamic pressure has been found by solving the average Reynolds equation, energy equation and heat conduction equations simultaneously. The cavitation model of Jacobsson-Floberg has been modified to take the surface roughness effects into consideration. A parametric study of steady-state behavior has been carried out. Finally, the isothermal, thermohydrodynamic, and contact loads for a model bearing have been calculated, assuming the surface height distribution as Gaussian.

Modelling the influence of velocity on wet friction-element friction in clutches

2018 ◽  
Vol 70 (1) ◽  
pp. 42-50
Author(s):  
Yanzhong Wang ◽  
Chao Guo ◽  
Yuan Li ◽  
Guoxing Li
Keyword(s):  
Friction Coefficient ◽  
Surface Topography ◽  
Friction Model ◽  
Content Type ◽  
Friction Element ◽  
Lubrication Film ◽  
Mixed Friction ◽  
Wet Friction ◽  
Clutch Engagement ◽  
Wet Clutch

Purpose This study aims to establish a friction coefficient model relative to the rotation speed of a wet clutch engagement, which can predict friction coefficient under different stages of slipping velocity and different load pressures. In particular, the model has been improved by accounting the speed effect for the perdition of wet friction-element boundary friction, which is significant for understanding the friction mechanisms and for supporting the development of more efficient and related products. Design/methodology/approach This research investigated the mechanism of wet friction in a wet clutch engagement. A mixed friction model is established based on the asperity model and Newton’s law of viscosity. To obtain a friction coefficient computed by the model, the normal load shared by both asperities and lubrication fluid needs to be determined. Therefore, rough surface contact mechanism is analysed; a surface topography model is established; and surface parameters are obtained by means of surface topography measurement and reconstruction. Finally, verification of the mixed friction model is achieved. Findings Friction will be generated by both the asperity contact and the lubrication film shear relative to the rotation speed. And, the higher the relative speed, the larger the shearing power of lubrication film. It is caused by decrease in contact area of asperity. Surface morphology of a sintered bronze friction disk was obtained by a Laser-Micro-Test. The predicted results by the established model show that the total friction coefficient slightly reduced and then increased suddenly with speed. The surface topography model is responsible for the nonlinear behaviour of the asperity friction. Results of the simulation model are in agreement with those of the wet clutch engagement experiments. Originality/value This research is original and it is supported by the national defence project. The wet friction element which is applied on tracked vehicles is analysed for the first time. Through the model, the trend of the friction coefficient can be more accurately predicted. The problem of the wet friction plate modelling difficult is solved by using the mixed friction model.

Microcontact Model for Paper-Based Wet Friction Materials

2001 ◽  
Vol 124 (2) ◽  
pp. 414-419 ◽  
Author(s):  
H. Gao ◽  
G. C. Barber
Keyword(s):  
Surface Roughness ◽  
Density Distribution ◽  
Friction Material ◽  
Friction Materials ◽  
The Real ◽  
Real Area Of Contact ◽  
Wet Friction ◽  
Gaussian Density ◽  
Negative Skewness ◽  
Real Area

This paper is focused on the real area of contact for paper-based wet friction materials during the engagement of wet clutches. The deformation of the wet friction material is identified as elastic during the engagement. A microcontact model is proposed considering both surface roughness and skewness. A Weibull density distribution is employed in the model rather than a Gaussian density distribution. This model is compared with the Greenwood-Williamson (GW) model for the cases of positive skewness, zero skewness and negative skewness. The real areas of contact of new, run-in and glazed wet friction materials were investigated using this microcontact model. Both surface roughness and skewness were found to have a great effect on the real area of contact.

On the Behavior of Friction in Lubricated Point Contact With Provision for Surface Roughness

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
H. Sojoudi ◽  
M. M. Khonsari
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Numerical Solutions ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Hydrodynamic Pressure ◽  
Operating Conditions ◽  
Asperity Contact ◽  
Type Curve ◽  
Lift Off

This paper presents a simple approach to predict the behavior of friction coefficient in the sliding lubricated point contact. Based on the load-sharing concept, the total applied load is supported by the combination of hydrodynamic film and asperity contact. The asperity contact load is determined in terms of maximum Hertzian pressure in the point contact while the fluid hydrodynamic pressure is calculated through adapting the available numerical solutions of elastohydrodynamic lubrication (EHL) film thickness formula for smooth surfaces. The simulations presented cover the entire lubrication regime including full-film EHL, mixed-lubrication, and boundary-lubrication. The results of friction, when plotted as a function of the sum velocity, result in the familiar Stribeck-type curve. The simulations are verified by comparing the results with published experimental data. A parametric study is conducted to investigate the influence of operating condition on the behavior of friction coefficient. A series of simulations is performed under various operating conditions to explore the behavior of lift-off speed. An equation is proposed to predict the lift-off speed in sliding lubricated point contact, which takes into account the surface roughness.

scholarly journals Response Characteristics of Dynamic Torque for Wet Clutch Engagement: A Numerical and Experimental Study

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Zhigang Zhang ◽  
Ling Zou ◽  
Hang Liu ◽  
Jin Feng ◽  
Zhige Chen
Keyword(s):  
Elastic Modulus ◽  
Applied Pressure ◽  
Asperity Contact ◽  
Oil Film ◽  
Response Characteristics ◽  
Clutch Engagement ◽  
Torque Response ◽  
Wet Clutch ◽  
Friction Lining ◽  
Lubricant Viscosity

To determine the factors affecting the dynamic transmitted torque response characteristics of the wet clutch, the oil film pressure, the asperity contact pressure, the applied pressure, and the dynamic transmitted torque model were established, using the fourth-order Runge–Kutta numerical method to couple the oil film thickness and the speed difference to obtain the change curve of the joint pressure and the transmitted torque. The established model was used to study the influence of the pressure hysteresis time, lubricant viscosity, friction lining permeability, friction pair equivalent elastic modulus, and surface combined roughness RMS on the dynamic transmitted torque response during the wet clutch engagement. The results indicate that the longer the pressure hysteresis time, the smaller the permeability of the friction lining, the smaller the equivalent elastic modulus, the greater surface combined roughness RMS, the more delayed the response of the transmitted torque, and the smaller the level of jerk of the wet clutch engagement. Also, the lower the lubricant viscosity, the greater the permeability of the friction lining, and the smaller the equivalent elastic modulus is and the greater surface combined roughness RMS is, the more sensitive the transmitted torque response is to pressure response changes.

Application of Elastic-Plastic Static Friction Model to Rough Surface With Asymmetric Asperity Distribution

2008 ◽  
Author(s):  
Chul-Hee Lee ◽  
Andreas A. Polycarpou
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Static Friction ◽  
Friction Model ◽  
Experimental Measurements ◽  
Height Distribution ◽  
Elastic Plastic ◽  
Static Friction Coefficient ◽  
Non Gaussian ◽  
Asperity Distribution

The asymmetric height distribution in surface roughness is usually indispensable in engineering surfaces prepared by specific manufacturing process. Moreover, the running-in process develops severe asymmetric roughness distribution in the surface interfaces. In this paper, the effect of asymmetric asperity distribution on static friction coefficient is investigated theoretically and by comparing it with experimental results. In order to generate a probability density function of non-Gaussian surface roughness, the Pearson system of frequency curves was used. Subsequently, the Kogut and Etsion (KE) model of elastic-plastic static friction was modified to calculate the contacting interfacial forces. For the experiments, actual roller and housing surfaces from a CV (Constant Velocity) joint were prepared to measure the static friction coefficient as it clearly shows the asymmetry of roughness distribution due to the manufacturing and also running-in process. The experimental measurements were subsequently compared with the modified KE static friction model with Gaussian as well as Pearson distributions of asperity heights. It was found that the model with Pearson distribution captures the experimental measurements well in terms of the surface conditions.

Performance of Spur Gears Considering Surface Roughness and Shear Thinning Lubricant

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
S. Akbarzadeh ◽  
M. M. Khonsari
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Film Thickness ◽  
Elastohydrodynamic Lubrication ◽  
Shear Thinning ◽  
Asperity Contact ◽  
Spur Gears ◽  
Lubricant Film Thickness ◽  
Lubrication Regime ◽  
Effect Of Surface

A model is developed for predicting the performance of spur gears with provision for surface roughness. For each point along the line of action, the contact of pinion and gear is replaced by that of two cylinders. The radii of cylinders, transmitted load, and contact stress are calculated, and lubricant film thickness is obtained using the load-sharing concept of Johnson et al. (1972, “A Simple Theory of Asperity Contact in Elastohydrodynamic Lubrication,” Wear, 19, pp. 91–108) To validate the analysis, the predicted film thickness and the friction coefficient are compared to published theoretical and experimental data. The model is capable of predicting the performance of gears with non-Newtonian lubricants—such as that of shear thinning lubricants—often used in gears. For this purpose, a correction factor for shear thinning film thickness introduced by Bair (2005, “Shear Thinning Correction for Rolling/Sliding Electrohydrodynamic Film Thickness,” Proc. Inst. Mech. Eng., Part J: J. Eng. Tribol., 219, pp. 1–6) has been employed. The results of a series of simulations presenting the effect of surface roughness on the friction coefficient are presented and discussed. The results help to establish the lubrication regime along the line of action of spur gears.

Influence of surface roughness, friction coefficient, and wrap angle on clinching joint strength and its correlation with belt friction phenomenon

2021 ◽  
pp. 135065012110253
Author(s):  
Santosh Kumar ◽  
Vimal Edachery ◽  
Swamybabu Velpula ◽  
Avinash Govindaraju ◽  
Sounak K. Choudhury ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Joint Strength ◽  
Joint Interface ◽  
Cross Sectional ◽  
Lap Shear ◽  
Mathematical Correlation ◽  
Mechanical Clinching ◽  
Wrap Angle

Clinching is an economical sheet joining technique that does not require any consumables. Besides, after its usage, the joints can be recycled without much difficulty, making clinching one of the most sustainable and eco-friendly manufacturing processes and a topic of high research potential. In this work, the influence of surface roughness on the load-bearing capacity (strength) of joints made by the mechanical clinching method in cross-tensile and lap-shear configuration is explored. Additionally, a correlating mathematical model is established between the joint strength and its surface parameters, namely, friction coefficient and wrap angle, based on the belt friction phenomenon. This correlation also explains the generally observed higher strength in lap-shear configuration compared to cross-tensile in clinching joints. From the mathematical correlation, through friction by increasing the average surface roughness, it is possible to increase the strength of the joint. The quality of the thus produced joint is analyzed by cross-sectional examination and comparison with simulation results. Experimentally, it is shown that an increment of >50% in the joint strength is achieved in lap-shear configuration by modifying the surface roughness and increasing the friction coefficient at the joint interface. Further, the same surface modification does not significantly affect the strength in cross-tensile configuration.

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