Evaluation of Ductile Damage Criteria in Hot Forming Processes

The process of ductile fracture which occurs due to the accumulation, growth and combination of defects or cracks of material is called ductile damage. Failure in materials can be predicted, using damage mechanics and damage criteria. On the other hand, most of the materials depended to the manufacturing process, are formed in warm or hot conditions so that; the temperature also affects on the probable damage initiation. In this study, a number of conventional hot forming processes of aluminum alloys such as forming process by tail gas, hydroforming, and blank forming with punch are simulated by finite element method and different damage criteria, and damage initiation in them is predicted. Then, the obtained numerical results are compared with the experimental results, achieved from empirical experiments and are validated. Finally, the damage criteria are classified based on the accuracy of the predicted results and the most appropriate criteria for predicting the damage in hot forming processes is introduced. It is concluded that Brozzo and Ayada damage criteria are the most proper criteria for predicting the damage initiation in the hot forming processes.