归一化参数蠕变模型的程序实现与验证

为了准确模拟实际构件的蠕变行为和应力松弛效应,在通用有限元程序环境下,利用其提供的用户可编程特性工具,将所发展的一种能完整描述蠕变3个阶段变形特征的归一化参数模型编制成用户子程序.考查了子程序计算结果与试验数据的差异、时间步长对计算结果的影响,并对不同规模有限元模型的计算耗时作了对比分析.针对变载(应力、温度)情形,在子程序中实现了时间硬化理论和应变硬化理论,并提出的介于两者之间的相对时间硬化理论.对带孔平板进行了实例计算,表明所发展的模型能够与有限元结果对实际结构进行蠕变模拟,计算结果的规律说明所发展的方法可较好地模拟实际构件的蠕变行为和应力松弛效应,验证了子程序的有效性. 

Implementation and validation of creep model based on normalized parameters

In order to numerically simulate creep behaviors and stress relaxation effects of realistic structural components under operating conditions in service,a model based on normalized parameters,which can be used to describe all the features of creep deformation in three stages,was presented and coded into a user's subroutine under the platform of a commercial finite element package by use of its user programmable features tools.The difference between the numerical results from the coded subroutine and the experimental data,and the effect of time step on numerical results,was investigated.The computer's time consuming for solution of finite element models in different scale was compared and analyzed.For a loading case with stress and/or temperature changing,the time hardening theory and the strain hardening theory,as well as the relative time hardening theory presented with its result between those of them,were implemented in the coded subroutine.Numerical results of a plate with a hole show that the coded subroutine can be used to simulate the creep behaviors and effects of stress relaxation in realistic structural components,and that the feasibility and effectiveness of the coded subroutine are validated.