Numerical Tests for Shear Mechanisms Based on Two Different Calibration Points

Abstract

In this paper, a numerical comparative study for shear mechanisms is performed, based on two different calibration points. The assessment is motivated due to the fact that the accuracy of the results obtained by coupled damage models is strongly dependent on the calibration point. Hence, the numerical results obtained by these models are more realistic and in agreement with experimental evidence when the external loading conditions are close to the calibration point. By the way, shear mechanisms proposed by Xue and Nahshon &
Hutchison were selected and added into damage variable of Gurson-TvergaardNeedleman model (GTN), in order to give ability to predict crack formation when shear
loading condition is presented. In the first part of this paper, both mechanisms are presented as well as the GTN model. Besides that, the numerical strategy is introduced, based on an implicit integration algorithm. In the following section, a point in high and other in low stress triaxialities are taken as calibration points and by an inverse method, the material parameters are obtained. In order to analyze the dependence of the results in relation to the calibration point, numerical tests are carried out for pure shear and combined shear/tensile loading conditions using first, the material parameters obtained by the first calibration point and then, using the properties which resulted by the second calibration point. Both numerical results are compared with experimental data and the ability to predict the correct fracture location. At the end, the equivalent plastic strain and displacement at fracture are analyzed for each calibration condition. The numerical tests have shown that for the loading conditions applied, the material properties obtained by the shear calibration point was more appropriate than the material properties taken for high stress triaxiality calibration point.