Abstract
In the 1st report, the appropriate evaluation factors for void closure were revealed to be true strain εz in the z direction and the hydrostatic stress ratio σm /σeq. However, those results were obtained under the condition of single-path forging, and were not confirmed for multipass forging. In this paper, we investigated whether εz or εeq is appropriate as the evaluation factor for void closure by numerical experiments of multipath forging. The following results were obtained. 1) εeq cannot because to evaluate the void closure in multipath forging, but εz can. 2) The main factor of εz required for void closure in multipass forging is the void shape at the start of the final pass. 3) If εz required for void closure in multipass forging is less than the value of the single-pass forging, the void closure of the multipass forging can be evaluated by the single-path forging.
