Influence of micro asperity contact and radial clearance on the tribological properties of crankpin bearings

A new hybrid numerical method that couples the dynamic slider-crank mechanism(SCM)and crankpin bearing(CB)lubrication models is proposed to analyze the effect of micro asperity contact on the tribological properties of a CB.In the hybrid model,the dynamic equations of the SCM are established based on the Newton method,while the lubrication equations of the CB are established on the basis of the Reynolds equation.Experimental data of the engine are also used in simulation analyses to enhance the reliability of the results.The load-bearing capacity(LBC)and friction force of the CB are selected as objective functions.Results show that the LBC has a negligible effect on the tribological properties of the CB,but the friction force greatly affects the resistance of the bearing under different radial clearances and surface roughness values.In particular,the maximum friction force in the asperity contact region accounts for 40.5%of the maximum total friction force at a radial clearance of 5μm and 77.7%of the maximum total friction of the CB with a surface roughness of 10μm.

Application of Fractal Contact Model in Dynamic Performance Analysis of Gas Face Seals

Fractal theory provides scale?independent asperity contact loads and assumes variable curvature radii in the contact analyses of rough surfaces, the current research for which mainly focuses on the mechanism study. The present study introduces the fractal theory into the dynamic research of gas face seals under face?contacting conditions. Structure?Function method is adopted to handle the surface profiles of typical carbon?graphite rings, proving the fractal con?tact model can be used in the field of gas face seals. Using a numerical model established for the dynamic analyses of a spiral groove gas face seal with a flexibly mounted stator, a comparison of dynamic performance between the Majumdar?Bhushan(MB) fractal model and the Chang?Etsion?Bogy(CEB) statistical model is performed. The result shows that the two approaches induce differences in terms of the occurrence and the level of face contact. Although the approach distinctions in film thickness and leakage rate can be tiny, the distinctions in contact mechanism and end face damage are obvious. An investigation of fractal parameters D and G shows that a proper D(nearly 1.5) and a small G are helpful in raising the proportion of elastic deformation to weaken the adhesive wear in the sealing dynamic performance. The proposed research provides a fractal approach to design gas face seals.

Elastohydrodynamic Lubrication Interface Stiffness and Damping Considering Asperity Lateral Contact

Elastohydrodynamic lubrication(EHL)point contact occurs between two rough surfaces at the mesoscopic level,while the interaction of rough surfaces involves contact between asperities at the microscale level.In most cases,the contact between asperities within an interface takes the form of lateral contact rather than peak contact.Regions devoid of contact asperities are filled with lubricating oil.However,conventional models often oversimplify lateral contact forms as interactions between asperities and a smooth,rigid plane.These simplifications fail to accurately represent the true contact conditions and can lead to inaccuracies in the analysis of EHL’s contact performance.To address this issue,we have developed a novel EHL interface model comprising two rough surfaces.This model allows us to explore the influence of asperity height,contact angle,and contact azimuth angle on EHL interface performance.

A mathematical model of rough surface contact characterization in spot welding

Based on the elastic-plastic mechanics and the contact mechanics, an asperity contact model for the resistance spot welding of the rough surface is presented. The numerical results indicate that the real contact area is only a small section of the nominal contact area. The value of the real contact area is randomly fluctuating within 20%. The real contact area’s distribution and each point’s deformation can also be obtained from this model, which is primary in the calculation of the contact resistance and the temperature field of the spot welding.