Evaluation of Forming Limit Diagram Damage Criterion in Fracture Prediction of Thin Sheet Metals

One of the simple criteria for estimating the formability of sheet metals is use of forming limit diagram (FLD). Determining the amount of accuracy and the range of proper prediction of this criterion is one of the most important challenges of researchers and engineers. In the present research first, employing the forming limit diagram of St14 steel, number of practical experiments such as tensile test of standard, notched, and opened specimens, tube hydroforming and deep drawing processes are simulated, and possibility of crack initiation and fracture in them are predicted. Then, to evaluate the forming limit diagram damage criterion, the above experiments are also practically performed and the practical results are achieved. Finally, comparing the results of numerical simulations and empirical observations, the amount of accuracy and proper range for fracture prediction of sheet metals by the FLD damage criterion is revealed.