Experimental and Numerical Investigation of Torsion Fatigue of Bearing Steel

Abstract

This paper presents the results of torsion fatigue of widely used bearing steels (through hardening with bainite, martensite heat treatments, and case hardened). An MTS torsion fatigue test rig (TFTR) was modified with custom mechanical grips and used to evaluate torsional fatigue life and failure mechanism of bearing steel specimen. Tests were conducted on the TFTR to determine the ultimate strength in shear (Sus) and stress cycle (S-N) results. Evaluation of the fatigue specimens in the high cycle regime indicates shear driven crack initiation followed by normal stress driven propagation, resulting in a helical crack pattern. A 3D finite element model was then developed to investigate fatigue damage in torsion specimen and replicate the observed fatigue failure mechanism for crack initiation and propagation. In the numerical model, continuum damage mechanics (CDM) were employed in a randomly generated 3D Voronoi tessellated mesh of the specimen to provide unstructured, nonplanar, interelement, and inter/transgranular paths for fatigue damage accumulation and crack evolution as observed in micrographs of specimen. Additionally, a new damage evolution procedure was implemented to capture the change in fatigue failure mechanism from shear to normal stress assisted crack growth. The progression of fatigue failure and the stress-life results obtained from the fatigue damage model are in good agreement with the experimental results. The fatigue damage model was also used to assess the influence of topological microstructure randomness accompanied by material inhomogeneity and defects on fatigue life dispersion.

An anisotropic damage model for tensile fatigue

“…This formulation of damage has been extensively used to characterize tensile fatigue, 28,29 torsion fatigue, 52 and rolling contact fatigue. This formulation of damage has been extensively used to characterize tensile fatigue, 28,29 torsion fatigue, 52 and rolling contact fatigue.…”

“…This method has been extensively used in damage mechanics-based simulations of tensile fatigue, 28,29 torsion fatigue, 52 and rolling contact fatigue. This method has been extensively used in damage mechanics-based simulations of tensile fatigue, 28,29 torsion fatigue, 52 and rolling contact fatigue.…”

“…where Δσ is the critical stress range, σ r and n are temperature dependent material parameters that need to be empirically determined. This formulation of damage has been extensively used to characterize tensile fatigue, 28,29 torsion fatigue, 52 and rolling contact fatigue. 19,23,26,45,46 For the damage tensor approach in this paper the dissipation potential function ϕ is a scalar function of the Damage…”

Microstructure evolution and torsional fretting fatigue damage mechanism of 316L austenitic stainless steel at different torques

“…Due to the requirements of the device, the specimens are designed and machined like a bone shape (see Figure 2). 13,14 Before the experiment, the specimens were treated with three steps: Firstly, the specimens were annealed at 1100 C for 10 h. Secondly, the specimens were quenched in water at room temperature. Finally, in order to prevent rust, all the specimens were dipped in oil.…”

Effect of non-metallic inclusions on butterfly wing initiation, crack formation, and spall geometry in bearing steels

“…So, the crack initiation and development mechanisms as well as fatigue life assessment with uniaxial fatigue tests may be inaccurate. As a new approach, some researchers [13,14] have recently used torsion fatigue as an analogy to RCF because the failure is shear dominated in both cases. However, in torsion fatigue tests only the outer layer of the shaft is subjected to the critical shear stress value and the probability of crack initiation due to inclusions and defects is less.…”