Fretting Fatigue

Pottirayil

Menezes

et al. 2008

Directionality of grinding marks influences the coefficient of friction during sliding. Depending on the sliding direction the coefficient of friction varies between maximum and minimum for textured surfaces. For random surfaces without any texture the friction coefficient becomes independent of the sliding direction. This paper proposes the concept of a friction tensor analogous to the heat conduction tensor in anisotropic media. This implies that there exists two principal friction coefficients μ 1,2 analogous to the principal conductivities k 1,2 . For symmetrically textured surfaces the principal directions are orthogonal with atleast one plane of symmetry. However, in the case of polished single crystalline solids in relative sliding motion, crystallographic texture controls the friction tensor.

Section: Discussionmentioning

confidence: 72%

Friction tensor concept for textured surfaces

Pottirayil

Menezes

et al. 2008

“…The literature on fretting fatigue in the high frequency regime is generally limited, except in the recent years. The motivation for studying of fretting fatigue at higher frequency is to investigate the implications of contact dynamics on fretting and fatigue lives and the evolution of coefficient of friction Farris et al 2003). Also fretting fatigue tests at high frequencies provide an alternative method for conventional testing by accelerating the testing process, which otherwise would take considerably longer time.…”

Section: Introductionmentioning

confidence: 99%

Wave propagation in coated cylinders with reference to fretting fatigue

Ramesh

Kailas

2008

Fretting fatigue is the phenomenon of crack initiation due to dynamic contact loading, a situation which is commonly encountered in mechanical couplings subjected to vibration. The study of fretting fatigue in high frequency regime has gained importance in recent years. However the stress wave effects at high frequency loading is scanty in the literature. The objective of present investigation is to study stress wave propagation in cylinders with reference to high frequency fretting. The case of a coated cylinder is considered since coating is often provided to improve tribological properties of the component. Rule of mixtures is proposed to understand the dispersion phenomenon in coated or layered cylinder knowing the dispersion relation for the cases of homogeneous cylinders made of coating and substrate materials separately. The possibility of stress wave propagation at the interface with a particular phase velocity without dispersion is also discussed. Results are given for two different thicknesses of coating.

“…Fretting is essentially a contact fatigue phenomenon wherein the failure is predominantly localised near the surface (Farris et al 2003). This is indeed the case at least during the initial stages until the bulk stresses dominate and fatigue damage penetrates into the bulk material.…”

Section: Introductionmentioning

confidence: 99%

Axisymmetric fretting analysis in coated cylinder

Ramesh

Kailas

2008

Fretting is essentially a contact fatigue phenomenon, although bulk stresses and material properties contribute to final failure. The near surface state of stress developed under oscillatory contact between machine elements plays a major role in deciding the severity of fretting. It is possible to enhance tribological properties by coating the surface. There is rather scanty literature available on fretting analysis of coated components. Presence of such coatings has a large influence on the near surface state of stress. The effect of coatings on the severity of fretting is the focus of this paper. Results obtained for both hard and soft coatings are compared with the results obtained for the homogeneous case. The component geometry and loading are chosen to be cylindrical to enable 3D elastic axisymmetric fretting analysis. The results are compared with 2D models (strip and half-plane) to examine their utility and validity for understanding axisymmetric fretting. Contact pressure and frictional shear loading cases are solved separately and superposed appropriately depending on the coefficient of friction considered. Results for different values of coefficient of friction and elastic mismatch are illustrated through contour plots of stresses and strains. These results are expected to be helpful for identifying fretting failure zones and fracture mechanisms in coated components. Analytical results presented here could serve as useful benchmarks for calibrating numerical codes and experimental techniques.