大型锻件锻造镦粗表面无开裂条件

On Upsetting Conditions of Large Forgings without Cylinder Surface Cracking

为描述镦粗过程变形的不均匀程度,将损伤力学的临界空穴扩张比理论用于镦粗变形表面开裂的研究中。引入了瞬时鼓形系数的概念,数值计算表明:在给定的端面摩擦条件下,相对压下量是影响瞬时鼓形系数大小的因素;镦粗过程中鼓形顶点处纬向应力、经向应力仅是瞬时鼓形系数的函数。得到了损伤力学变量应力三轴度与不均匀变形程度变量瞬时鼓形系数的关系。借助临界空穴扩张比理论和塑性力学方程,建立大型锻件锻造镦粗表面无开裂条件,并通过实验证明了该条件的正确性。

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 experiments indicate the conditions are correct.