关键词: 大锻件;锻造;镦粗;损伤力学

Abstract:

Instantaneous drum coefficient was given to describe the degree of inhomogeneous deformation during upsetting.The theory of critical hole expansion ratio in damage mechanics was used in the study of cylinder surface cracking.Numerical calculation shows that,with invariable end surface friction condition,the relative pressing volume influences the value of instantaneous drum coefficient.Longitudinal stress and latitude
stress are as function of instantaneous drum coefficient during upsetting.
Then,the relation between the stress triaxiality and instantaneous drum coefficient is obtained.By means of the theory of critical hole expansion ratio and plastic equation,upsetting conditions of large forgings without cylinder surface cracking are obtained.The

Key words: experiments indicate the conditions are correct. large forgings;forge;upsetting;damage mechanics