Study of short cracks under biaxial fatigue

P Lopez-Crespo,A Lopez-Moreno,J Zapatero,A Garcia-Gonzalez,B Moreno

doi:10.3221/igf-esis.30.31

P Lopez-Crespo, A Lopez-Moreno + Show 3 more

Open Access

https://doi.org/10.3221/igf-esis.30.31

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Abstract

In this paper a methodology for evaluating crack initiation under biaxial conditions is presented. The methodology consists of evaluating the crack length automatically with digital processing of highmagnification images of the crack. The methodology was applied to study five different strain conditions on a low carbon ferritic-pearlitic steel specimen with tubular shape. A hole of 150 ?m diameter was drilled to enforce the crack to initiate at a particular spot. Different combinations of axial and torsional strains were analysed during the initiation stage of the crack. The setup employed allowed detection of the crack to within 6 ?m from the edge of the hole on average and monitoring of the crack during early stages. Fatigue crack propagation curves clearly showed oscillations due to microstructure. It was also observed that these oscillations decreased as the torsional component of the strain was increased.

Highlights

U nderstanding the behaviour of engineering components under biaxial load is crucial for a number of industries, including aerospace, automobile and power generation industries
The aforementioned models for predicting crack propagation under biaxial loads no longer can be applied, because they are based on continuum mechanics
These are caused by grain and phase boundaries and other micro-structural features that continuum mechanics models do not take into account [9]

Summary

Introduction

U nderstanding the behaviour of engineering components under biaxial load is crucial for a number of industries, including aerospace, automobile and power generation industries. The aforementioned models for predicting crack propagation under biaxial loads no longer can be applied, because they are based on continuum mechanics. Fatigue crack growth is different to that predicted by the above mentioned models, and oscillations are commonly observed on the growth curves. These are caused by grain and phase boundaries and other micro-structural features that continuum mechanics models do not take into account [9]. The current work aims at studying the fatigue crack growth behaviour of small cracks under different biaxial conditions

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