动力松弛法对加载曲线有什么要求？

superllback

问题：假如考虑一个压力容器，内壁面承受5MPa的静压，然后分析容器受到子弹撞击过程。

出于某些原因，希望全程用LSDYNA求解。因此容器在5MPa内压下的应力分析采用Dynamic relaxation方法，并将该应力作为预应力保留。

现在遇到的问题：

1，关键字：除了*DEFINE_CURVE, *CONTROL_DYNAMIC_RELAXATION之外，还需要其他的吗？

2，5MPa加载曲线形状应该是一段斜线与一段水平线。但斜线的斜率应如何确定？
水平线究竟延伸多长？曲线的横坐标是真实时间还是虚拟时间？
如果是虚拟时间，是否只需要给出3个位置的时间坐标与纵坐标？即原点、斜线与水平线的交点、水平线的结束点这3个点的位置坐标。
另外，虚拟时间的话，迅速上升到5MPa与缓慢上升到5MPa有无差异？

3，如何保证动力松弛法计算结束后，预应力一直保留，并与后续的动力学计算叠加？

上述问题，希望有经验的大神们出手相助！不胜感激！

empty4585

1, When SIDR=1 or  2 in "*Define_curve", the program will execute "Dynamic Relaxation", "*Control_D_R" is even an additional option. Furtermore for some loads,  such as "Load_body_{option}", "Load_thermal_load_curve", "Airbag_simple_pressure_volume" and so on, there is an option "LCIDDR" devoted to input the "DR" curve.

2,  There is no strict limit to the slope of the "DR" curve. It depends on the convergence of your problem. The more steeper slope will cause more difficulties.
"DR" contains two aspects: "explicit" and "implicit". For the former, the time is the real time but it doesn't matter. 1000 or more cycles for the oblique line section is recommanded in my opinion. For the latter, the time is not real, you can think about the incremental method in impicilt.
And then, the termination of abcissa is not important for most cases, the section of "slope = 0" will be automatically extended. (for "BPM" it is not)

3, yes.

378698619

楼主问题解决了吗，我也是想问这些同样的问题

hiteryu

empty4585 发表于 2016-5-11 10:11
1, When SIDR=1 or  2 in "*Define_curve", the program will execute "Dynamic Relaxation", "*Control_D_ ...

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