积分迭代模式优化对侧翻一步碰撞算法的改进

Improvement of Onestep Rollover Collision Algorithm by Optimizations of Integration and Iteration Modes

针对侧翻一步碰撞初始算法中Mindlin壳单元面内四点全积分计算量大,广义失衡力迭代模式不合理且易剪切锁死,降低了算法计算精度和效率的问题。本文中从两方面入手,对初始算法进行优化。单元积分点模式优化方面,引入面内减缩积分和部分减缩积分方式,并在单元厚向采用五点、七点和九点3种积分方案,对单元面内和厚向积分方式进行匹配;广义失衡力迭代模式优化方面,采用力和力矩分离加权的方式计算失衡力“2”范数,通过计算时间-权重比曲线,确定合理的力和力矩的加权系数。最后选择某客车典型车身段作为实际算例,将改进算法、初始算法、LS-DYNA分析和侧翻试验结果进行对比,验证了本文所提改进方案的有效性。

In view of the poor calculation accuracy and low efficiency of the initial algorithm of one-step rollover collision due to the tremendous computing efforts in in-plane four-point integration of Mindlin shell element,the irrational iteration mode of generalized unbalanced force and being prone to shear lock,the initial algorithm is optimized from two aspects in this paper.For the optimization of element integration point mode,both inplane reduced integration and partial reduced integration are introduced,and three integration schemes,i.e.five point-,seven point-and nine point integrations are adopted along the direction of element thickness,which is then matched with in-plane integration.For the iteration mode optimization of generalized unbalanced forces,the separate weighting factor is defined for force and moment,respectively,to calculate the“2”norm of unbalanced force,and by means of calculation time-weighting factor ratio curve,the reasonable weighting factors for both force and moment are determined.Finally,the typical segment of a coach body is chosen as real calculation example,the results of improved algorithm,initial algorithm,LS-DYNA analysis and rollover test are compared,verifying the effectiveness of the improved scheme proposed.