Abstract: Experimental investigation on the mechanism of the void closing in a large ingot during forging processes was carried out. It was found that the closure of a void along the direction of maximum compressive strain ε1 consists of three steps, I.E.1) deformation; 2) connection; 3) welding. Results of measurement of the strain distribution in the deformed billets showed that the top value of the maximum compressive strainε1 would regularly change its position along OY axis with the changing of anvil width to billet height ratio. For successive operations, there was a small strain zone in the billet centre axis between two operations due to the effect of friction.

Key words: 闭合指数, 孔洞闭合度, 临界闭合压下量, 最大压应变