Quasi-Static 准静态

动态松驰(Dynamic relaxation) 并不是有意为一般的准静态(Quasi-Static) 分析设置的。它适合于当预载只产生小的弹情况应变的施加预载,或者初始化系统到一个预定义的几何形状 [1]。但对其它更多情况并不适合。

Dynamic relaxation is not intended for general quasistatic analysis. It’s ok for applying preload when the preload produces only small elastic strains or for initializing a system to a prescribed geometry[1] but it’s not good for much else.

你可以通过做一个常规的显示仿真来模拟准静态分析,通过按需要调用时间 / 质量缩放(time-scaling,mass-scaling) 来在可接受的时间内得到结果,但这种方法是需要技巧地。你必须监测系统动能按希望的使惯性效应最小化。

You can do a Quasi-Static analysis by running a regular explicit simulation, invoking time- and/or mass-scaling as necessary to crank out the results in a reasonable timeframe, but this approach can be tricky. You have to keep an eye on the kinetic energy in the system as you want to minimize the inertial effects. 

基本上动能相对内能应该保持在一个较小的值。时间缩放是指加载比在准静态实验里更快,以减少总的仿真时间。关于质量缩放更多内容可以看”mass_scaling”一节。或者你可以尝试用 LS-DYNA 运行一个隐式静力分析。可以看用户手册里的卡片 *control_implicit_……”和 Appendix M。

Basically, the kinetic energy should remain small relative to the internal energy. (By time-scaling, I mean applying the load more quickly than in the Quasi-Static experiment in order to reduce the simulation time.) See the file“mass_scaling”for more on mass-scaling.
Or, you can try an implicit, static analysis using LS-DYNA. See the commands *control_implicit_…… and Appendix M in the User’s Manual. There are examples of implicit analysis on our“user”FTP site in the LS-DYNA/example directory. 
See also: gravity.txt, readme.preload, mass_scaling, long_run_times, implicit.general, quick_initialization.

Note[1]:初始化到预定义的几何

Write a file of nodal displacements from the final state of your first run. To get this data in the necessary format, use LS-TAURUS as follows:
ls-taurus g=d3plot < executes 1000 < goes to final state deform < write a file as described above t < termimate LS-TAURUS
Note the d3plot does not contain nodal rotations and thus the rotations are written as zero. This could be a real problem for initialization of shells and beams.
LS-Prepost has an option to write the displacements using Output > Nodal Displacements but the output is i8,3e16 rather than the required i8,3e15 and hence the
suggested use of LS-TAURUS.
LS-TAURUS is not available for Windows PCs. It’s free and available for Unix and Linux workstations.
If you do a‘regular’dynamic relaxation run to get to the initialized state, a file of prescribed displacements and rotations will automatically be written at the conclusion of the DR phase (drdisp.sif).
Bug #2020 reported on 9/22/2004 that rigid body nodes do not get initialized according to data in“m=pres_geom_file”。 Additional example in /home/jday/test/cantilever/solid/typ2sol_dr_nrb.k (creates drdisp.sif) and typ2sol_presgeom_nrb.k (m=drdisp.sif run). Nodes 11,22,33,44 are not initialized to what’s in drdisp.sif

1. 从第一次分析的最终状态输出一个节点位移文件。

  • 发表于 · 2017.09.16 07:58 · 阅读 · 3062

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