Abstract
On the basis of the tensile tests that were conducted on a Gleeble thermomechanical simulator at various temperatures and strain rates, the fracture behaviour of SA508-3 steel was investigated, and a model for predicting the occurrence of ductile fracture during hot deformation was established. In order to determine the critical fracture strain ϵf that initiates the necking of the material, a ‘virtual’ part of the specimen was created according to the constant volume condition to replace the necking volume of the specimen. Experimental results indicated that ϵf depends on temperature and strain rate, and subsequently, a model of ϵf was established. In conjunction with Oyane's fracture criterion, an evaluation method for predicting the fracture of SA508-3 during hot forming was reproduced. The model was verified by upsetting tests, and good coincidence was obtained. As an application, it was applied to a simulation of a forging stretching process, and the calculated results showed the model has preferable predication performance.
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