Lukasz Farbaniec

Influence of Triaxial Stress State on Ductile Fracture Strength of Polycrystalline Nickel

In this contribution, the effect associated with stress triaxiality on ductile damage evolution in high purity nickel has been investigated from both experimental and theoretical points of view. Tensile tests on smooth and notched round bar specimens were performed to calibrate the fracture strain in a wide range of stress triaxiality. The capability of the Gurson model to reproduce and predict physical failure behaviour was examined. It was shown that stress triaxiality played a major role on damage evolution as demonstrated by the progressive reduction of material ductility under increasing triaxial states of stress.

Prediction of Ductile Fracture Through Small-Size Notched Tensile Specimens

In this study, a combined experimental and numerical procedure that based on extended analysis of stresses, strains, and damage of the specimen notch region, was proposed to investigate high-strength steel and pure nickel metals. Miniaturized notched tensile specimens with different notch radii were used to generate various levels of triaxial stress, and to evaluate stress-dependent failure. It was shown that the triaxiality plays a major role in the damage evolution demonstrated by decreasing ductility. The experimental investigation was supplemented by scanning electron microscopy observations of fractured surfaces. The deformation mechanisms leading to the failure ware linked with the extensions of the Gurson model for porous ductile metals. The evolution of damage in both materials was compared and discussed.