大型锻件内部空洞缺陷修复条件

介绍大型锻件内部空洞缺陷修复条件在理论研究和生产中的作用及研究现状.针对非线性粘性材料,建立以空洞周围速度场和远场应力、应变速率表示的泛函.对于由体积不可压缩材料构成的含有空洞的无限体而言,锻造过程中空洞周围的真实速度场总是使该泛函取极小值,借助泛函的变分可求得空洞边界速度与远场应力、应变的关系,锻造变形后空洞的形状.为使设计的速度场能表征空洞的变形特点,加快泛函极小化的收敛速度,采用叠加速度场.研究大型锻件镦粗工序中锻坯内部球形空洞的闭合情况.结果表明,随着空洞体积的减小,远场应力、应变迅速增大,仅靠远场应力的增大使空洞闭合是非常困难的,因此大锻件技术要求中应允许有未闭合的微小空洞存在.在理论分析的基础上进行试验研究,结果表明理论计算结果与实测结果相差不大.

Healing Conditions of Large Forgings Internal Voids Defect

Theoretic studies on the healing conditions of internal voids defect in large forgings and the application in workshop production are introduced. As far as nonlinear viscous materials are concerned a function, which is expressed with the velocity field, far-field stress and strain around voids, is presented. During the forging process of a infinite body with voids inside and made of incompressible material, the function with the condition of the actual velocity field always gets the minimum. According to this princi-ple, the relationship between the boundary velocity field and far-field stress and strain of a void is provided, thus, the void's shape after forging is predicted. Superimposed velocity field is employed to get the designed velocity field better represent the deforming characteristics and maximize the rate of convergence in which the function gets the minimum. By ways mentioned above, the healing of spherical internal voids inside the forging stock during upsetting is investigated. The results show that it is very difficult to heal voids only by increasing the far-filed stress because far-field stress and strain increase with the dwindling of the volume of the void. Therefore, it is reasonable that technical requirements for large forgings allow a certain amount of voids in large forgings. Based on the theoretic analysis, experiment is conducted and experimental results agree well with analytic calculations.