说明：  采用子程序实现单元删除。子程序采用定义场变量、状态的方式，通过判断单元应力是否达到规定的限值，从而实现单元的删除。有需要的可以下载
(Subroutine is used to implement cell deletion. Subroutine to define the field variable, the state of the way, by determining whether the unit stress reaches the specified limit, in order to achieve the deletion of the unit. There is a need to download)