چكيده لاتين
Damage mechanics, as one of the emerging branches in the science of mechanics, is considered a powerful tool for failure mechanics. All materials inherently have defects in the form of cracks, holes and defects. These defects can be formed during the production of the material or during loading. The main goal of damage mechanics is to investigate the growth of all defects and their effect on the mechanical strength of the material. Simulating damage growth in ductile materials and predicting the time and location of failure in these materials is one of the most important fields for designers in shaping processes. By taking into account the effect of hydrostatic pressure and the third deviatoric stress on the process of material plastic deformation, Wierzbicki proposed a new concept of material damage model. Bai-Wierzbick damage criterion is a powerful model for damage prediction in known ductile metals and covers a wide range of triaxial stresses. Today, one of the important parts of software based on the finite element method, such as Abaqus software, is the ability to predict the place and time of failure in different loads. Some damage models, such as Wierzbickiʹs damage criterion, are not available in this software. For this purpose, a subrotine in the software should be used. This damage model uses triaxial stress effects and lode angle parameter in its formulation. To check this damage criterion, it is necessary to develop this criterion in the form of VUMAT subrotine in the software. To simulate this model, two materials, aluminum 2024-T351 and steel 1045, which are available in the references, have been used. In order to verify the performance and check the damage prediction results, smooth, grooved round samples and grooved plates are used and the results are compared with the experimental results. To check the sub-rotine and verify its performance in sheet forming mode, the prepared algorithm was modified for two-dimensional mode and to check the results, the subrotine was applied on the flat sample under tension. At the end, to investigate the effects of the lode angle parameter on the results, simulation is performed on the grooved sample. The results obtained from the above simulations show that this criterion provides a good prediction of failure and its location. Also, the results obtained in the 2D mode are very close to the three-dimensional mode. The solution time in the 2D mode compared to the 3D mode also showed an acceptable reduction. At the end, in order to finalize the performance of the prepared subrotine, the results were checked on the deep drawing process. The results obtained from the simulation were compared with the experimental results, which shows the good performance of this criterion in predicting the damage in the deep drawing forming process
