The influence of stick–slip transitions in mixed-friction predictions of heavily loaded cam–roller contacts

Abstract

A load-sharing-based mixed lubrication model, applicable to cam-roller contacts, is developed. Roller slippage is taken into account by means of a roller friction model. Roughness effects in the dry asperity contact component of the mixed lubrication model are taken into account by measuring the real surface topography. The proportion of normal and tangential load due to asperity interaction is obtained from a dry contact stick-slip solver. Lubrication conditions in a cam-roller follower unit, as part of the fuel injection equipment in a heavy-duty diesel engine, are analyzed. Main findings are that stick-slip transitions (or variable asperity contact friction coefficient) are of crucial importance in regions of the cam where the acting contact forces are very high. The contact forces are directly related to the sliding velocity/roller slippage at the cam-roller contact and thus also to the static friction mechanism of asperity interactions. Assuming a constant asperity contact friction coefficient (or assuming that gross sliding has already occurred) in highly loaded regions may lead to large overestimation in the minimal required cam-roller contact friction coefficient in order to keep the roller rolling. The importance of including stick-slip transitions into the mixed lubrication model for the cam-roller contact is amplified with decreasing cam rotational velocity.

A new numerical model for investigating the effect of surface roughness on the stick and slip of contacting surfaces with identical materials

“…Although the Coulomb's friction law is universally applied in frictional contact modelling, there are different complementary conditions applied in the partial slip modelling which result in the presence of different algorithms as listed in Table 1. For example, some of the recent literature [19][20][21]35] in Table 1 used the following criteria expressed by: Equation 16…”

“…Roughness Method Coulomb's friction law Guyot et al [13] No FEM+BEM Equation 15Chen and Wang [19] No SAM Equation 16Gallego et al [1] No SAM Equation 15Wang et al [20] No SAM Equation 16Spinu and Amarandei [21] No SAM Equation 16Botto et al [27] No FEM Equation 15Dong et al [28] Yes SAM Equation 15Bazrafshan et al [29] Yes BEM Equation 15Alakhramsing et al [35] Yes FEM+BEM Equation 16Table 1 List of some of work on the partial slip modelling based on Coulomb's law…”

“…It is noteworthy that the reason why the equal sign in the complementary condition is discarded is mainly related to the definition of the residual of the linear system. If the complementary condition in the literature (Equation 16) [19][20][21]35] is applied here, the former estimation of the tangential rigid body approach is challenging to achieve as in the step 2 the identification of stick nodes is required where the information about slip distance of the node is necessary. However, it is also the residual of the linear system being calculated based on the estimated rigid body approach.…”

Modeling and simulation for wear prediction in planar mechanical systems with multiple clearance joints

“…Also, the Archard wear equation not only represents a macroscopic model, but also expresses microscopic effects between the contact bodies. In addition, this model has been successfully applied to the wear prediction of cam [70], follower [35] [36], revolute pair [37,38,41] and helical gear [71]. In this paper, the Archard model is employed to predict the wear of the revolute joint with clearance in the mechanical system, which can be described as:…”

Modeling and Simulation for Wear Prediction in Planar Mechanical Systems with Multiple Clearance Joints

“…Also, the Archard wear equation not only represents a macroscopic model, but also expresses microscopic effects between the contact bodies. In addition, this model has been successfully applied to the wear prediction of cam [70], follower [35] [36], revolute pair [37,38,41] 11 and helical gear [71]. In this paper, the Archard model is employed to predict the wear of the revolute joint with clearance in the mechanical system, which can be described as:…”