时间步长对爆破模拟结果的影响研究

摘要

为提高LS-DYNA软件模拟工程爆破时的精度,从理论上改进了确定极限时间步长Δte的方法,结合已有的数据对本方法的合理性进行了验证,并通过实例探讨了时间步长Δt对爆破模拟结果的影响.研究表明:Δte仅与炸药的爆速、炸药最小单元的最小边长以及计算时间步长比例因子有关,在网格划分时,炸药单元不能取过小或过于狭长;Δt对土体中爆炸空腔半径形成的影响不大,而对压力峰值的影响显著,且具有一定的规律性;随着比例距离Z的增加,压力峰值误差呈现由小到大,再由大到小的趋势.当计算区域范围在Z<0.5 m·kg-1/3时,Δt可取为1~3倍Δte;当Z≥0.5 m·kg-1/3时,时间步长Δt可适当放宽,取为3~5倍Δte.对于一般的爆破模拟,考虑到经济性,Δt取为1~3倍Δte即可满足大多数工程计算精度的要求.%In order to improve the precision of simulation blasting with LS-DYNA software,the method of determining limit time stepΔte is improved forward theoretically,the rationality of the method is verified using the existing data,and the influ-ence of time stepΔt on blasting simulation results is discussed through engineering examples.Results shows thatΔte is only associated with the detonation velocity of explosive,the minimum side length of explosive unit and the scale factor of calcula-tion time step.The explosive element cannot be too small or too narrow when the meshing grid is made.Δt has little effect on the formation of the cavity radius in the soil,but it exerts a significant effect on the peak pressure and has a certain regularity. With increasing the proportional distance Z,the pressure peak error increases firstly and then decreases.When the calculating scope is in the range of 0~0.5 m·kg-1/3 ,Δt can be taken as 1~3 timesΔte .When it exceeds 0.5 m·kg-1/3 ,Δt can be ap-propriately increased,taking 3~5 timesΔte .For the general blasting simulation,by taking into account the economy,Δt is taken as 1~3 timesΔte .And it may meet the requirements of calculation accuracy for most engineering practices.