Fatigue characterization of a crankshaft steel: Use and interaction of new models

Abstract

The peculiar geometrical shape and working conditions of crankshafts make fatigue becoming responsible for most of the failure cases in such components. Therefore, improvement of crankshaft performance requires enhancing its fatigue life. In this work, the fatigue behavior of a D38MSV5S steel, used for crankshafts in compact vehicles, is investigated according to two traditional ways of analysis, namely the stress based and the fracture mechanics based approaches, though using advanced design models: On the one side, a probabilistic Weibull regression S-N model is assessed for experimental results obtained from fatigue resonance tests. On the other side, the crack growth rate curve is calculated from crack growth tests, carried out on SENB specimens, using a normalizing procedure. Specific Matlab programs are developed to facilitate the evaluation process. The information gained from both models will contribute to provide a probabilistic interpretation to the Kitagawa-Takahashi diagram.

Prediction of fatigue crack growth life under variable-amplitude loading using finite element analysis

“…In fact, the S-N and FCGR models were applied without using any similarity or self-similarity assumptions. According to these models, ten specimens and suitable test planning would be enough to achieve a good estimation of the fatigue endurance limit [32]. This method is simple, but it is not accurate enough.…”

Report of Committee III.2: Fatigue and fracture

“…A general fatigue life prediction procedure was presented in (Correia et al, 2016), which was based on the CCS crack growth rate model (Blasón et al, 2015) and the proposed approach was used to obtain the fatigue data of a notched plate made of P355NL1 steel, in which the Equivalent Initial Flaw Size (EIFS) concept had been employed. As the EIFS concept assumes that materials had defects acting like initial cracks, this EIFS was usually smaller than the crack initiation concept of the local/Fracture Mechanics integrated approaches.…”