Micromechanical damage model for plasticity of materials to predict failure under ‎shear loads

The present work, deals with the Gurson-Tvergaard-Needleman (GTN) micromechanics based damage model ‎to add the ability to predict and calculate damage under shear loads; and use it in modeling damage and failure ‎under shear dominated loading conditions. In the development of GTN model, since different damages have ‎different physical concepts and attenuation effects, so an independent shear damage parameter was presented as a ‎function of equivalent plastic strain of the matrix. The modified GTN damage model was implemented by ‎developing the VUMAT code in the Abaqus software environment. To use the GTN model developed in VUMAT ‎format for damage analysis, 16 input parameters of the model were determined for the material under study. ‎After developing the model, the code and determining the input parameters for it, the modified model was first ‎tested on a single element. The results of the developed model showed complete agreement with the results of the ‎basic GTN model and analytical solutions under tensile and shear loads, respectively. Finally, the developed model ‎was tested in shear loading on a shear sample. It was observed that the modified model under shear load ‎eliminates the weakness of the base GTN model and well predicts the occurrence of damage and weakening of the ‎mechanical properties of the material under the prevailing shear conditions.‎