Estimation of the plastic zone in fatigue through the thickness based on synchrotron diffraction data

Abstract

In this work we present a novel methodology to analyse the extent of crack tip plasticity inside engineering materials. The plastic zone developed ahead of a fatigue crack in a bainitic steel compact tension specimen is studied. The bulk of the steel is probed with synchrotron X-ray diffraction technique to measure the elastic strain field deep inside the material. The procedure involves combining the experimental synchrotron data with numerical data to obtain the equivalent strain map. This map is then converted into a stress field where the boundary of the plastic zone can be directly extracted. The procedure is tested on a real fatigue crack and the results are compared to plane stress and plane strain models. The promising results will enable key progress on understanding the mechanisms that generate the damage at the tip of fatigue cracks in engineering components.