Experimental Model Validation and Fatigue Behaviour of Cold-Formed High Strength Steel

Abstract

In the present paper, fatigue fracture behaviour of cold-formed High Strength Steel (HSS) S690QL are investigated. S690QL is often employed, in a pre-deformed state, for load-bearing applications, where cyclic service loads can be critical. Bending processes can induce residual plastic strain in bent areas and this changes the fatigue behaviour significantly. Traditional uniaxial dogbone testing cannot represent this multi-axial phenomenon properly and for this purpose a benchmark specimen is proposed, that is first bent and after subjected to fatigue loading. The bending process is modelled with a quasi-static Finite Element (FE) model, performed in the commercial code Abaqus. To validate the numerical model, a stereo Digital Image Correlation (DIC) set-up is used, capable of measuring the residual plastic strains in the specimen. The present article covers the validation of a cold-forming process followed by a preliminary fatigue analysis of S690QL.