A new type of flat-bar specimen for non-proportional mixed-mode crack tip loading under uniaxial tension

Abstract

Non-proportional cyclic loading is a challenging issue for numerical crack path predictions. Principal stress axes and the vector of the J-integral rotate during loading and the mixed-mode ratio of stress intensity factors changes within a load period. Reliable criteria for crack deflection, accounting for arbitrary loading and boundary conditions under non-proportional loading, have not yet been found. Experimental research in this field nowadays requires expensive set-ups and multiaxial testing equipment such as hydraulic biaxial or tension-torsion testing machines. In this paper, a specimen is presented, suitable for uniaxial testing, however providing conditions of non-proportional loading. Finite element simulations show that the variance of mixed-mode parameters is sufficiently large to cover the range of KII/KI-ratios required for investigating crack deflection criteria.