Abstract
Keeping a coating–substrate system undamaged during heavy-load elastohydrodynamic lubrication (EHL) conditions is challenging. To overcome this problem, an EHL model with a coated gear pair was built. Firstly, based on the full-system finite element method, the effect of the coating elastic modulus on the oil film pressure was obtained. Secondly, the failure mode was predicted after the stress analysis. Finally, the surface/interface damage evolution behavior of the coating–substrate system was analyzed visually by embedding cohesive zone elements. In the numerical calculation, stiffer coatings tended to increase the film pressure and secondary pressure spike, compared with more compliant coatings. As the coating stiffness decreased, the maximum equivalent stress in the system reduced, and its location tended to develop close to or at the substrate. The coating cracking and interfacial delamination were individually caused by the shear stress in the coating and shear stress on the interface, and both of them initiated in the region of the secondary pressure peak. The interfacial delamination increased the crack failure probability of coating and vice versa. Therefore, through analyzing the EHL model, the exact damage growth location and its evolution in the coated solids can be determined, and the failure mechanism can be comprehensively revealed.
Highlights
As an effective way to achieve excellent surface load carrying capacity, coating technology has been widely employed in the field of rolling–sliding contact industrial friction pairs which are under heavy-duty elastohydrodynamic lubrication (EHL) conditions [1], such as gears, bearings, cams, etc. [2,3]
From the aspecton of nano-indentation coating–substrateor failure under the normal or tangential load, previous studies focused scratch characterization experiments load, previous studies mostly focused on nano-indentation or scratch characterization experiments combined with cohesive zone model (CZM) [11,12,13] or virtual crack closure technology (VCCT) [12]
The five oil pressure curves basically the thin coating, which means that its coating elastic modulus had little effect on the oil film pressure coincided because of the thin coating, which means that its coating elastic modulus had little effect distribution
Summary
As an effective way to achieve excellent surface load carrying capacity, coating technology has been widely employed in the field of rolling–sliding contact industrial friction pairs which are under heavy-duty elastohydrodynamic lubrication (EHL) conditions [1], such as gears, bearings, cams, etc. [2,3]. The lack of a method to analyze the failure behavior of the coating–substrate system under heavy-load EHL conditions is an urgent problem that needs to be solved. Liu et al [6] and Xiao et al [7] analyzed the EHL problem of line contact in coated gear transmissions. EHL the FE method combined with the solution of the Reynolds equation to solve the point contact issue for coated solids. From the aspecton of nano-indentation coating–substrateor failure under the normal or tangential load, previous studies focused scratch characterization experiments load, previous studies mostly focused on nano-indentation or scratch characterization experiments combined with cohesive zone model (CZM) [11,12,13] or virtual crack closure technology (VCCT) [12].
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