Prediction of ductile fracture in cold forging of aluminum alloy

In this paper; the limitation and applicability of the ductile fracture cri teria based on a work hypothesis and Cockcroft and Latham were investigated For this purpose, experimental and numerical investigations for simple ups etting were conducted for aluminum alloys Al1100-O, Al2024-T3, Al6061-T4, a nd Al7075-T4. As a result, the fracture merle of each alloy was observed. T he study was extended for pin-shape cold forging of Al100-O and Al6061-T4 I n compare the likeliness of fracturing according to two criteria. Based on experimental data of simple upsetting, the damage factors for the same two criteria were calculated hy adopting rigid-viscoplastic finite element anal ysis. With this approach, the prediction of surface cracking was attempted hy comparing the calculated limiting damage factors between simple upsettin g and pin-shape forging. It was observed in simple upsetting that Cockcroft and Latham's criterion gave a more reasonable prediction for crack initiat ion site than work hypothesis, but the limiting damage factors differ depen ding on the process. In spite of the differences, however, Cockcroft and La tham's criterion might be useful in designing upsetting-like cold forging p rocesses in which the influence of the induced circumferential tensile stre ss on failure is dominant.