Avaliação e comparação de diferentes modelos de fadiga na estimativa de vida em metais sujeitos a carregamentos multiaxiais

Abstract

The present work aims to evaluate different fatigue models in estimating the fatigue life of metals subjected to multiaxial loadings. Mechanical components often experience dynamic loads, which might result in the initiation of cracks due to fatigue damage, which is responsible for nearly 90% of all failures in mechanical components. In this setting, it is important to evaluate and validate fatigue models capable of predicting these failures. This work evaluates three different multiaxial fatigue models, namely: the Smith, Watson and Topper (SWT) model, the Modified Wöhler Curve Method (MWCM) and a model based on equivalent stresses associated with Goodman's criterion. In order to evaluate and conduct a comparative analysis among them, they were implemented and life estimate results were compared with experimental observations available in the literature. In this case, it was possible to verify the response of each model in terms of the following loading parameters: multiaxiality, mean stress and phase difference. Concerning the implemented models, the MWCM, in general, provided the best estimates. Most of its life estimates were under a factor 4 error region, with a conservative tendency. The SWT model systematically failed to capture the mean stress effect, leading to very optimistic estimates in some cases. The equivalent stress-based model, despite its simplicity, provided satisfactory results overall speaking. However, this model tends to provide overly conservative predictions when in presence of mean stresses.