一种新的简化延性层裂模型

重新定义损伤、应用Cochran-Banner模型中的强度函数,提出了一种新的简化延性层裂模型。新模型抛弃了Cochran和Banner为计算他们所定义的损伤所作的基本假设:一旦微损伤形成,使微损伤演化远远易于使固体进一步发生体积应变。从而修正了差分微元中固体比容的计算。强调指出,选定重新定义的损伤以及强度函数或应力松弛方程提供了确定损伤的可能,排除了任何外加的损伤演化方程。在新的简化延性层裂模型中,一旦拉伸应力达到层裂强度,重新定义的损伤将由强度函数确定的应力松弛方程、计及损伤的能量守恒方程、状态方程以及本构方程等一系列封闭方程组确定。若干平板撞击致层裂实验的理论计算与实验结果已被比较。新模型中仅含两个参数:层裂强度及临界损伤度,它们的确定能使在一定初、边值条件下的层裂试验数值计算结果与实验测得的靶自由面速度历史或靶-低阻抗材料界面应力历史以及回收观测的层裂面上的损伤一致。

A NEW SIMPELIFIED DUCTILE SPALL MODEL

A new simplified ductile spall model is presented using the redefined damage and the strength function given by Cochran-Banner.The correction concerning the volume of the mesh cells is realized by abandoning the assumption of Cochran and Banner to calculate the damage:it is much easier to open microcracks once they are formed than to strain the solid further.It is noted that choosing the redefined damage and a strength function or a stress relaxation equation provides a possibility of determining the damage and excludeing any extra equation of damage evolution.Once the spall strength is reached,the redefined damage in the new simplified ductile spall model will only be determined by a series of closed equations including the stress relaxation relationship given by the strength function,the energy conservation equation,the equation of state and the constitutive equations for the damaged aggregate.Comparison of the theoretical and experimental results for some plane spall tests is performed.The determination of the spall strength and the critical damage included in the presented spall model should make the computed results of spall tests under the appropriate initial and boundary conditions consistent with the experimental free surface velocity profile of target or the stress profile of interfacebetween target and low impedance buffer and the observed damage at spall plane for spall tests.