TL;DR: In this article, a carburized 316 stainless steel was studied under rotary bending in laboratory air and in 3% NaCl aqueous solution using materials with two different case depths.
TL;DR: In this paper, the case depth of a three pct Cr-Mo steel with and without the formation of a surface compound layer was investigated and the influence of this compound layer on the fatigue limit was described.
Abstract: The plasma nitriding conditions necessary to treat a three pct Cr-Mo steel with and without the formation of a surface compound layer have been investigated and the influence of this compound layer on the fatigue limit is described. The nitrided case depth has been varied as a function of time at a constant temperature of 480 °C and the corresponding rotating bending fatigue strength evaluated. This data has been used to develop a simple model to describe the influence of the case depth on the fatigue limit.
TL;DR: In this paper, the problem of fatigue crack propagation in surface treated specimens similar to gear teeth is analyzed, and two numerical approaches are followed: the finite element method and the weight function technique.
Abstract: — The problem of fatigue crack propagation in surface treated specimens similar to gear teeth is analysed. Experimental fatigue tests were carried out on carburized, and carburized and shot peened, specimens. In order to predict crack propagation and to consider the effect of the treatments, different models of the cracked specimens were realized. Two numerical approaches were followed: the finite element method and the weight function technique. Two- and three-dimensional finite element models were constructed, and the stress-intensity factors were evaluated by considering the effect of both the load and the residual stresses due to the treatments. The agreement between these and those obtained through the weight function technique is good. The weight function approach was used directly in the computer software package (which allows crack propagation predictions) and considered the effects of hardness and residual stresses. The comparison between theoretical predictions and experimental results validated the approach followed.
TL;DR: In this paper, an analytical model for bending fatigue life prediction of carburized gear steel specimens based on strain-life approach is proposed, where Multilayer method and hardness method are used for estimating strain life fatigue properties.
TL;DR: In this paper, the authors present experimental and analytical results on fatigue behavior of case-hardened steel and use linear elastic fracture mechanics (LEFM) to predict crack nucleation sites as well as fatigue lives.
Abstract: This paper presents experimental and analytical results on fatigue behaviour of case-hardened 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.