WCIŚLIK Wiktor Kielce University of Technology

The article describes an example of the numerical determination of the mean void nucleation strain which is the basic parameter of the Gurson-Tvergaard-Needleman (GTN) porous material model. The investigation was conducted for S355 steel, commonly used in civil engineering. Using criterion for the matrix-inclusion interface decohesion, developed by Argon et al, a numerical simulation of the void nucleation process was conducted, paying special attention to determine the values of stress and strain accompanying the formation of a void in a low level of stress state triaxiality ratio equal to 0.516. Axisymmetric model of rigid particle in the elastic-plastic matrix was used. The geometric parameters of the particles were adopted on the basis of microstructural analysis of the material. It was assumed that the critical radial stress at the interface between the particle and the matrix defines the moment of the void formation. The approach is different from that used by many authors, who set the GTN model parameters by adjusting the results of numerical simulation to experimental data. Critical strain equal to 0.2867 was obtained during the simulation. The parameter was used for the numerical simulation of tensile test of specimens with a ring notch. The results were compared to the force-elongation curves obtained experimentally for the specimens with the notch. The results of simulation using the determined value of nucleation strain were in good agreement with the experimental data.