Fatigue behaviour and life predictions of case‐hardened steels

Abstract

A B S T R A C T This paper presents experimental and analytical results on fatigue behaviour of casehardened steel. Fully reversed strain-controlled constant amplitude axial fatigue tests were performed on through-hardened case, through-hardened core and case-hardened steel specimens. Surface versus sub-surface cracking and the role of residual stresses and their relaxation are discussed. Multi-layer models of the case-hardened specimens were used to predict crack nucleation sites as well as fatigue lives, and the predictions corresponded well with the experimental results. Linear elastic fracture mechanics (LEFM) was also used to conduct fatigue crack growth analysis to further explain the experimental observations from the fracture surfaces of the case-hardened specimens. A fatigue strength estimation method based on hardness and inclusion size was used to estimate the fatigue limit of the materials investigated. Fractography of fracture surfaces and crack nucleation location are also presented.

Experimental analysis of bending fatigue strength of plain and notched case-hardened gear steels

“…It is worth noting that strain-life approaches have also been utilized for material testing as well as design of case-hardened steel components [39,40]. The experimental campaign conduced in the present paper may form the basis to apply the specimen-based approaches mentioned in the (normative) Annex of ISO Standard [1].…”

Probabilistic cumulative damage model to estimate fatigue life

“…This scatter, especially in terms of fatigue life, is described assuming a Weibull distribution or lognormal distribution. [1][2][3][4] In this paper, the Palmgren-Miner linear damage hypothesis has been used to address this issue. The cumulative distribution function (CDF) for the failure of components submitted to three levels of stress amplitude was obtained.…”

“…Furthermore, fatigue life data show a considerable scatter, and for engineering purposes a proper description of this scatter is imperative. This scatter, especially in terms of fatigue life, is described assuming a Weibull distribution or lognormal distribution …”

Influence of Case Hardening on Fatigue Resistance of Models of Hollow Shafts with Production Surface Defects

“…The case hardening (carburizing) should contribute to the solution of this problem because it produces a high carbon martensite case with the good fatigue and wear resistance whereas core is low-carbon and tough. In addition, the case hardening develops surface compressive residual stresses, which should avoid or retard initiation and growth of fatigue cracks from the surface defects [1,2].…”