Modelling of the damage in ductile steels

The nucleation, growth and coalescence of voids result in ductile fracture of materials. The first coalescence of voids defines crack initiation. In order to describe the initiation behaviour of a controlled rolled structural steel FeE 460 quantitatively, experimental investigations and micromechanical modelling were conducted. The tests were carried out at room temperature with axisymmetric notched tensile specimens under proportional loading. Specimen geometries containing different notch geometries leading to different stress triaxiality ratios were chosen. Taking into consideration the experimental procedure a failure curve which considers the local state of stress and strain at initiation was evaluated. Different criteria concerning initiation of the ductile failure process by reaching a critical void size Rc were proved with regard to the reproduction of the material behaviour.