Fatigue Life Prediction of S235 Details Based on Dislocation Density

Global approaches have been the main procedure to design structural details and components under fatigue loading. This procedure is easy to apply but it disregards not only the effect of the material type but also the influence of the geometry in complex components. On the other hand, local approaches rely on the specific local damage parameters that can be assessed for each type of material and detail geometry. The parameters derived from low cycle fatigue (LCF) tests are the most common damage parameters used to predict the fatigue life and establish reliable fatigue design approaches. Recently, Huffman proposed a fatigue damage model based on strain energy density and on the dislocation density of the material. In this regard, S235 was selected to perform a metallographic and mechanical assessment aiming to define the dislocation density of the material and to describe the fatigue behavior using the Huffman damage model. Additionally, fatigue tests on structural details (plate with hole) were conducted and results were compared with fatigue life predictions based on Huffman local approach. It was found that Huffman model based on dislocation density is a reliable approach to predict the fatigue life of structural steel details.