LS-DYNA FAQ CHN

LSTCrsquos Software Productions Introduction Published June 7th 2007 in LS-DYNA Tags No Tags

LSTCmdash为Livemore Software Technology Corp首字母缩写

LSTC公司创始人为Hallquist博士1976年当Hallquist博士在LLNL(Lawrence Livemore National Laboratory )任职时开发了DYNA3D早期主要应用于结构受各种各样冲击载荷时的应力分析同时二维版本DYNA2D也同时进行开发从76年到82年DYNA3D和DYNA2D一直由Hallquist博士进行版本更新1986年由Hallquist和Benson发布的版本增加了很多新的功能能运行于VAXVMSIBMUNIXCOS等软硬件平台从而扩大其应用且成为第一个拥有通用单面接触算法的代码1988年Hallquist博士创立LSTC公司进行DYNA3D商业化版本LS-DYNA3D的开发(后简称LS-DYNA)

早期的DYNA3D源代码是在公共网上发布的以供科研机构和公司应用与开发但从88版开始受美国政府相关法律限制不得发布于公共网之后DYNA3D继续由LLNL做开发早期公布的版本得到不少科研机构和公司的后续开发其中现在在显式动力分析方面的另两个主要软件RadiossPam-Crash均基于早期版本做的开发当然经过十多年的发展这两个软件也各有自己的新的功能和特色

LSTC公司的主要软件产品

LS-DYNA

LS-DYNA无疑是目前最为流行的显式动力分析软件支持目前大部分硬件和软件平台详细列表可参见httpwwwlstccompageshardwarehtm LS-DYNA求解器版本分为SMP(共享内存版)MPP(多机并行版)和PC版经过不断的代码优化其求解效率不断提升且随着硬件平台的技术更新大大缩短了大规模问题的求解时间适合的应用汽车碰撞amp乘员安全性板料成型液压成型锻造拉延成型多工序成型爆炸与穿甲鸟撞发动机叶片包容性和失效分析电子产品跌落分析运输容器设计玻璃成型注塑模流吹塑成型生物力学金属切削体育器材优化设计土木工程方面的海洋平台及公路护栏设计

目前最新的主版本号为971当然每一主版本号下都会有相应的子版本主要对应于不同的bug进行了修复应用时可以参考各子版本的release notes

值得注意的是LS-DYNA只是一个显式求解器目前LSTC公司跟相当多的主流CAE软件供应商进行了合作向他们提供相应的显示求解技术比较有名的是MSCSoftware将大部分LS-DYNA的显式求解技术集成到MSCDytran里面Ansys公司将部分LS-DYNA功能集成到AnsysLS-Dyna软件包里面ETA公司基于LS-DYNA求解技术开发了Dynaform软件包这些软件虽然不完全集成LS-DYNA的所有特性但也各有其优点

of 2LSTCs Software Productions Introduction | AiFEA

2007-8-26httpwwwaifeacomblogp=9

LS-OPT

LS-OPT是一个独立的设计优化和概率分析软件包与LS-DYNA有良好的接口早期开发一直在Linux和UNIX类系统下但从30版本开始LS-OPT支持Windows平台目前最新版本为32 LS-OPT优化功能基于RSM(Response Surface Methodology)和DOE(Design of Experiments)LS-OPT可以与大多前处理软件进行交互并且支持用CFortran语言进行扩展更详细信息参见httpwwwlstccompagesopthtm 典型应用包括优化设计系统识别概率分析

LS-Prepost

LS-Prepost是LSTC公司开发的一个免费的前后处理软件软件小巧但功能丰富同时支持大部分的平台目前最新版本为07年5月份的对于它的详细介绍和相关的demo可以由以下链接获得httpwwwlstccomlspp 注如果有需要LS-Prepost Windows平台最新版本可以发信给我(kevin[dot]zsc[at]163com)或者留下你的mail地址

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Page 2 of 2LSTCs Software Productions Introduction | AiFEA


LS-DYNA FAQ 中英文版-1Consistent system of units Published June 9th 2007 in LS-DYNA Tags consistent units

从今天开始陆续将LS-DYNA FAQ的英文版放上来并部分翻译成中文方便大家学习LS-DYNA Copyright of original english version owned by relative author Chinese version owned by AifeacomKevin

相信做仿真分析的人第一个需要明确的就是一致单位系统(Consistent Units)计算机只认识0amp1只懂得玩数字它才不管你用的数字的物理意义而工程师自己负责单位制的统一否则计算出来的结果没有意义不幸的是大多数老师在教有限元数值计算时似乎没有提到这一点

见下面LS-DYNA FAQ中的定义

Definition of a consistent system of units (required for LS-DYNA)

1 force unit = 1 mass unit 1 acceleration unit 1 力单位＝ 1 质量单位 times 1 加速度单位

1 acceleration unit = 1 length unit (1 time unit)^2 1 加速度单位 = 1 长度单位1 时间单位的平方

The following table provides examples of consistent systems of units As points of reference the mass density and Youngrsquos Modulus of steel are provided in each system of units ldquoGRAVITYrdquo is gravitational acceleration

MASS- LENGTH- TIME- FORCE- STRESS- ENERGY- DENSITY- YOUNGrsquos- Velocity(563KMPH) GRAVITY

kg m s N Pa Joule 783e+3 207e+11 1565 9806

kg cm s 1e-02N 783e-3 207e+09 156e+03 9806e+02

kg cm ms 1e+04N 783e-3 207e+03 156 9806e-04

kg cm us 1e+10N 783e-3 207e-03 156e-03 9806e-10

kg mm ms KN GPa KN-mm 783e-6 207e+02 1565 9806e-03

gm cm s dyne dycm2 erg 783e+0 207e+12 156e+03 9806e+02

gm cm us 1e+07N Mbar 1e7Ncm 783e+0 207e+00 156e-03 9806e-10 gm mm s 1e-06N Pa 783e-3 207e+11 156e+04 9806e+03

gm mm ms N MPa N-mm 783e-3 207e+05 1565 9806e-03

Page 1 of 2LS-DYNA FAQ 中英文版-1Consistent system of units | AiFEA


ton mm s N MPa N-mm 783e-9 207e+05 156e+04 9806e+03

lbfs2in in s lbf psi lbf-in 733e-4 300e+07 616e+02 386

slug ft s lbf psf lbf-ft 152e+1 432e+09 5133 3217

________________________________________________________________

kgfs2mm mm s kgf kgfmm2 kgf-mm 802e-10 207e+04 156e+04 (Japan)

kg mm s mN 1e3 Pa 783e-6 207e+08 9806e+02

gm cm ms 1e5 Pa 783e+0 207e+06 Kbui 3-11-97 JDay 1901

0 Responses to ldquoLS-DYNA FAQ 中英文版-1Consistent system of unitsrdquo

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Windows 平台下MPP LS-DYNA 并行计算设定 Published June 15th 2007 in LS-DYNA Tags No Tags

LS-DYNA 并行计算支持目前几乎所有的硬件和操作系统平台具体的SMPMPP版支持的平台可以在LSTC主页上查看（httpwwwlstccompageshardwarehtm）

尽管主流的LS-DYNA并行计算都是在LinuxUnix类平台（基于性能并行计算架构易用性和商业等原因）但有时候还是有需要在windows平台进行一些MPP-DYNA的并行计算（比如进行调试小规模的计算等）因此这里介绍一下windows平台下MPP DYNA运行的设定

1 下载MPICH软件

Windows平台下MPP DYNA的并行是基于MPICH 这个MPI软件包如果仅仅只有MPP版的LS-DYNA求解器而没有MPICH这个消息传递接口也无法实现并行计算MPICH目前的最新版本是20但Windows平台支持MPP-DYNA只支持MPICH125（or 126)可以在httpwww-unixmcsanlgovmpimpich1mpich-nt 下载mpichnt125exe (6 MB June 8 2003)这个可执行文件以管理员登陆后在每一台需要参与LS-DYNA并行计算的计算机上按缺省选项安装（如果机器空间有限也可以参考manual上进行手动安装会省一点点空间）

2 MPICH的帐号设置

用MPICH进行多机并行计算要进行帐号方面的配置帐号可以基于域帐号或者非域的帐号如果各机器不是加入到一个windows域进入CProgram FilesMPICHmpdbin 目录运行MPIRegisterexe会提示输入一个帐号accout这时输入一个用户帐号例如mppuser之后会让你输入密码并确认之后会提示ldquoDo you want this action to be presistent (yn)rdquo选yes 在每一台机器上都这样进行设置如果各机器是加入到一个windows域则可以按上面的方法输入一个帐号但输入方式是domainusername 或者也可以省略这一步直接在运行时输入域内帐号

3 MPICH 配置

点开始-gt程序-gtMPICH-gtmpd-gtMPICH Configuration Tool会弹出如下窗口

Page 1 of 3Windows 平台下MPP LS-DYNA 并行计算设定 | AiFEA


点击rdquoselectrdquo 按钮选择已经装好mpich的各台计算机在左边列表高亮显示各机器并选中然后按中间栏的rdquoApplyrdquo按钮

4 运行MPP DYNA

点击开始-gt程序-gtMPICH-gtmpd-gtmpirun



如果上一步配置成功在弹出的窗口右边会有计算机列表如果只是在本机运行点第一栏最右侧rdquohelliprdquo按钮选择本机上的mpp-dyna执行块并如上图输入dyna k文件及命令行参数如果是几台计算机并行计算则你需要将mpp-dyna执行块及k文件放在一个共享目录（开放运行读写权限）并从网络路径选择执行块这样选择后Application 路径类似hostnamesharepathmpp970exe i=inputk memory=100m （例如我机器会显示LENOVO-5081CA9Dtestmpp970_s_6763_intelsse_win32_mpich125exe i=contact_projectilek memory=10m）之后设定CPU数在右边选择参与计算的hosts（选中的会高亮）之后点击rdquoRunrdquo按钮（如果弹出输入用户和密码的窗口则按第2步的帐号输入）如果没有错误左边文本框会出现运行提示输出的提示信息

注意事项实际使用中对于windows2000用户只要上面的操作无误基本上不会出现问题而如果是windows XP用户则很有可能会因为防火墙开启等原因造成机器间通讯时间过长而超时退出解决方法是关闭防火墙或者在防火墙配置中例外mpi mpp程序另外如果有其它防火墙或者带网络监视能力的防病毒软件也应该进行设置允许mpich和mpp dyna的internet访问权限如果上面的设置都正确还是经常出现超时问题则折衷的方法是使用CMD方式使用无GUI的mpirun方式提交计算

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LS-DYNA FAQ 中英文版-2Mass Scaling 质量缩放 Published June 19th 2007 in LS-DYNA Tags 质量缩放 mass scaling

质量缩放指的是通过增加非物理的质量到结构上从而获得大的显式时间步的技术

在一个动态分析中任何时候增加非物理的质量来增大时间步将会影响计算结果（因为F=ma）有时候这种影响不明显在这种情况下增加非物理的质量是无可非议的比如额外的质量只增加到不是关键区域的很少的小单元上或者准静态的分析（速度很小动能相对峰值内能非常小）总的来说是由分析者来判断质量缩放的影响你可能有必要做另一个减小或消除了质量缩放的分析来估计质量增加对结果的灵敏度

你可以通过人工有选择的增加一个部件的材料密度来实现质量缩放这种手动质量缩放的方法是独立于通过设置Control_timestep卡DT2MS项来实现的自动质量缩放

当DT2MS设置为一个负值时质量只是增加到时间步小于TSSFAC|DT2MS|的单元上通过增加这些单元的质量它们的时间达到TSSFAC|DT2MS|有无数种TSSFAC和DT2MS的组合可以得到同样的乘积因而有相同的时间步但是对于每一种组合增加的质量将是不一样的一般的趋势是TSSFAC越小增加的质量越多作为回报当TSSFAC减小时计算稳定性增加（就像在没有做质量缩放的求解中一样）如果TSSFAC缺省的值09会导致稳定性问题可以试试08或者07 如果你减小TSSFAC你可以相应增加|DT2MS|这样还是可以保证时间步乘积不变

为了确定什么时候和位置质量自动增加了可以输出GLSTAT和MATSUM文件这些文件允许你绘出完整的模型或者单独部件所增加的质量对时间的曲线为了得到由壳单元组成的部件增加的质量云图将database_extent_binary卡的STSSZ项设置为3 这样你可以用ls-prepost绘出每个单元的质量增加量的云图具体方法是通过选择FcompgtMiscgttime step size

在control_timestep中设置DT2MS正值和负值的不同之处如下

负值初始时间步将不会小于TSSFAC-DT2MS质量只是增加到时间步小于TSSFAC|DT2MS|的单元上当质量缩放可接受时推荐用这种方法用这种方法时质量增量是有限的过多的增加质量会导致计算任务终止

正值初始时间将不会小于DT2MS 单元质量会增加或者减小以保证每一个单元的时间步都一样这种方法尽管不会因为过多增加质量而导致计算终止但更难以作出合理的解释

control_timestep卡中的参数MS1ST控制是否只是在初始化时增加一次质量（MS1ST=1）还是任何需要维持由DT2MS所指定的时间步时都增加质量（MS1ST=0)

你可以通过在control_termination卡片中设置参数ENDMAS来控制当质量增加到初始质量一定比率时终止计算（只对自动质量缩放有效）

－－－－－－－－－－－－－－－－－－－－－－－－－－可变形点焊梁的质量缩放

mat_spotweld卡的质量缩放参数DT只影响点焊单元如果control_timestep卡中没有指定质量缩放(DT2MS=0)而且时间由可变形点焊控制可以用参数DT来在初始化时增加惯量到点焊单元上来提高时间步达到DT指定的值当DT不为0时增加到可变形点焊梁元上的质量会输出到d3hsp文件里MATSUM 中动量和动能不受增加到可变形点焊上的质量的影响GSLTAT中DOES和总的KE受增加的质量的影响

考虑三种调用可变形点焊的质量缩放的情况 1当DT2MS为负值mat_spotweld卡DT＝0时尽管在d3hsp文件中可变形点焊质量增量百分比

Page 1 of 4LS-DYNA FAQ 中英文版-2Mass Scaling 质量缩放 | AiFEA


不真实下面几个值是正确的d3hsp中rdquoadded spotweld massrdquo 第一个时间步之后的rdquoadded massrdquo amp ldquopercentage increaserdquo glstat和matsum中的rdquoadded massrdquo

2 当DT2MS为负值且mat_spotweld卡DTne0时可变形点焊质量增加不会包含在d3hspglstatmatsum文件中的rdquoadded massrdquo里这非常容易令人误解用户必须检查d3hsp文件的rdquoadded spotweld massrdquo建议不要同时使用两种质量缩放标准推荐使用第一种方法（即负的DT2MSampDT=0）

3 如果DT2MS＝0且DTne0初始时间步将不考虑增加点焊的质量但是之后每一个周期时间步都会增加10直到时间步达到正确的值（考虑点焊质量增加）glstat amp matsum不包含rdquoadded massrdquo的行

注意质量增加会引起能量比率增长

English Version Mass-scaling refers to a technique whereby nonphysical mass is added to a structure in order to achieve a larger explicit timestep

Anytime you add nonphysical mass to increase the timestep in a dynamic analysis you affect the results (think of F = ma) Sometimes the effect is insignificant and in those cases adding nonphysical mass is justifiable Examples of such cases may include the addition of mass to just a few small elements in a noncritical area or quasi-static simulations where the velocity is low and the kinetic energy is very small relative to the peak internal energy In the end itrsquos up to the judgement of the analyst to gage the affect of mass scaling You may have to reduce or eliminate mass scaling in a second run to gage the sensitivity of the results to the amount of mass added

One can employ mass scaling in a selective manner by artificially increasing material density of the parts you want to mass-scale This manual form of mass scaling is done independently of the automatic mass scaling invoked with DT2MS in control_timestep

When DT2MS is input as a negative value mass is added only to those elements whose timestep would otherwise be less than TSSFAC |DT2MS| By adding mass to these elements their timestep becomes equal to TSSFAC |DT2MS| An infinite number of combinations of TSSF and DT2MS will give the same product and thus the same timestep but the added mass will be different for each of those combinations The trend is that the smaller the TSSF the greater the added mass In return stability may improve as TSSF is reduced (just as in non-mass-scaled solutions) If stability is a problem with the default TSSF of 09 try 08 or 07 If you reduce TSSF you can increase |DT2MS| proportionally so that the producttimestep is unchanged

To determine where and when mass is automatically added write GLSTAT and MATSUM files These files will allow you to plot added mass vs time for the complete model and for individual parts respectively To produce fringe plots of added mass in parts comprised of shell elements (DT2MS negative) set STSSZ=3 in database_extent_binary You can then fringe the added mass (per element) using LS-POST by choosing Fcomp gt Misc gt time step size (Here the label ldquotime step sizerdquo is really the element added mass)

The difference between using a positive or negative number for DT2MS in control_timestep is as follows

Negative Initial time step will not be less than TSSF -DT2MS



Mass is added to only those elements whose timestep would otherwise be less than TSSFabs(DT2MS) When mass scaling is appropriate I recommend this method The amount of mass that can be added using this method is limited lsquoExcessiversquo added mass will cause the job to terminate

Positive Initial time step will not be less than DT2MS Mass is added OR TAKEN AWAY from elements so that the timestep of every element is the same This method is harder to rationalize although it is not subject to termination from lsquoexcessiversquo added mass

The parameter MS1ST in control_timestep controls whether mass is added only once during initialization (MS1ST=1) or anytime as necessary to maintain the desired timestep specified via DT2MS (MS1ST=0)

You can use ENDMAS in control_termination to stop the calculation after a certain amount of mass has been added (active for automatic mass scaling only)

____________________________________________________________________________ Mass-scaling of deformable spotweld beams

The mass-scaling parameter in mat_spotweld (DT) affects only the spotwelds If no mass-scaling is invoked in control_timestep (DT2MS=0) AND the timestep is controlled by the deformable spotwelds DT can be used to add inertia to the spotwelds during intialization in order to increase the timestep to a value of DT When DT is nonzero mass added to spotweld beams is reported to d3hsp MATSUM momentum and KE does NOT factor in added mass to def spotwelds GLSTAT DOES factor in added mass to total KE (spotweldbeamtype9mscaleinitvelk)

Consider 3 cases of invoking mass-scaling in a model with deformable spotwelds

1 Although ldquopercentage mass increaserdquo under ldquoDeformable Spotweldsrdquo in d3hsp is bogus when DT2MS is neg and DT in mat_spotweld = 0 the following are correct ldquoadded spotweld massrdquo in d3hsp ldquoadded massrdquo and ldquopercentage increaserdquo in d3hsp AFTER the first time step ldquoadded massrdquo in glstat and matsum

2 Added spotweld mass controlled by DT in mat_spotweld is NOT INCLUDED in ldquoadded massrdquo given in d3hsp glstat or matsum when DT2MS is neg and DT in mat_spotweld is nonzero This can be quite misleading User must check for ldquoadded spotweld massrdquo in d3hsp Recommended Do not invoke both mass-scaling criteria Neg DT2MS with DT=0 (case 1 above) is preferred

3 If DT is nonzero and DT2MS=0 the initial timestep will NOT consider added spotweld mass but the time step will increase by 10 each cycle until the correct timestep (considering added spotweld mass) is achieved Glstat and matsum contain no ldquoadded massrdquo line item

The above can be illustrated using j5000a_2jdaytestweldspotweldbeamtype9mscalek __________________________________________________________________________________

Note that added mass may cause the energy ratio to rise (See j5000a_2jdaytesterodetaylormat3noerodemscalek)



1 Response to ldquoLS-DYNA FAQ 中英文版-2Mass Scaling 质量缩放rdquo

Pingback on Jun 23rd 2007 at 1115 pm 1 instability in lsdyna



LS-DYNA FAQ 中英文版-3Long run times 长分析时间 Published June 20th 2007 in LS-DYNA Tags long run time time scaling

当用显式时间积分时对于仿真非常小的部件而分析时间又要相当长时没有好的方法质量缩放(mass-scaling)增加了需要确认非物理质量的增加不会显著影响计算结果的负担当使用时间缩放(time-scaling)时也有同样的问题时间缩放(time-scaling)是指为了减小需要的时间步数通过增加加载速率而缩短仿真时间

要确认时间步不是仅由很少的小单元或者刚度大单元控制可以通过在d3hsp文件中搜索rdquosmallestrdquo来显示100个最小的时间步单元如果只有很少的几个单元控制时间步可以把那些单元及邻近区域重新remesh或者把它们变成刚体

可是仅运行必要长的时间是很明显的这意味着在一个跌落分析的情况时给跌落物体一个初速度把它放在离地面一个非常小的距离冲击之后仅运行足够得到需要的结果的时间

值得注意的是对于一个长时间的仿真如果时间步数超过了50万步最好使用双精度版本的LS-DYNA求解器使截断误差的影响最小化运行双精度版本要增加30的时间

对于长时间的分析自动显式隐式转换可能是一个选择使用这种方法用户可以指定在一个时间段内使用隐式积分隐式积分的优点是时间步不由单元尺寸控制所以可以得到大的时间步当然隐式计算也非常点用cpu时间而且目前并不是所有的LS-DYNA的功能和材料都在隐式分析中实现(大部分已经实现) 下面的FEA information newsletter里讨论了显式隐式转换(httpwwwfeapublicationscompagespdfnews3feadecpdf)

See also mass_scaling quasistatic

English Version

When yoursquore using explicit time integration there is no magic cure for long run times associated with simulating very small geometries over relatively long periods of time Mass-scaling carries a burden of having to confirm that the addition of nonphysical mass does not significantly affect the results (see attached file ldquomass_scalingrdquo) A similar burden exists when time-scaling is employed Time-scaling is a technique where the loading rate is increased and thus the simulation time is shortened in order to reduce the required number of timesteps

Make sure that your timestep is not being controlled by only a few small or stiff elements by searching in the d3hsp file for the string ldquosmallestrdquo If there are only a few controlling elements you can remesh in the vicinity of those elements or perhaps make them rigid

Though itrsquos rather obvious run only as long as is necessary This means in the case of a drop simulation assigning an initial velocity to the dropped object and placing it a very small distance from the landing surface After impact run only long enough to get the results you need

Page 1 of 2LS-DYNA FAQ 中英文版-3Long run times 长分析时间 | AiFEA


Be aware that for lengthy simulations where the number of timesteps goes above half a million or so yoursquod be well advised to use a double precision executable of LS-DYNA to minimize error due to roundoff Running double precision carries with it a cpu penalty of around 30

Automatic explicitimplicit switching may be an option Using this technique the user can specify time windows in which implicit time integration is used as opposed to explicit time integration An advantage of implicit time integration is that timesteps are not tied to element size and can thus be much larger Of course an implicit timestep is also much more expensive in terms of cpu Further not all LS-DYNA features and materials are implemented for implicit analysis at this time (though most are) Explicitimplicit switching is discussed in the following archived FEA Information newsletterhellip

httpwwwfeapublicationscompagespdfnews3feadecpdf See also mass_scaling quasistatic

0 Responses to ldquoLS-DYNA FAQ 中英文版-3Long run times 长分析时间rdquo

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LS-DYNA FAQ 中英文版-4Quasi-static 准静态 Published June 21st 2007 in LS-DYNA Tags quasi static

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

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-scalingmass-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rdquomass_scalingrdquo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_helliprdquo和Appendix M

See also gravitytxt readmepreload mass_scaling long_run_times implicitgeneral quick_initialization

Note[1] 初始化到预定义的几何 1 从第一次分析的最终状态输出一个节点位移文件（这一部分未按原文翻译）注意d3plot文件里不包含节点转动信息因此转动输出为0这对初始化壳和梁单元会是个问题 LS-Prepost有一个选项是输出节点位移在Output-gtNodal Displacements里但是这个输出是i83e16格式的但需要的是i83e15所以要注意修改一下

如果你做了一个正常的动态松驰分析来得到初始状态一个预定义位移和转动的drdispsif文件在DR阶段结束时会自动创建

2 在第二次分析时快速的初始化到第一步输出的预定义的几何你需要设置卡片control_dynamic_relaxation里的参数IDRFLG=2而且在命令行里指定rdquom=filenamerdquo(其中filename指第一步创建的文件)这样在瞬态分析之前LS-DYNA会自动做一个100步的预分析来使节点根据文件filename指定的数据移动到指定值

English Version

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

You can do a quasi-static analysis by running a regular explicit simulation invoking time- andor 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 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 ldquomass_scalingrdquo for more on mass-scaling

Page 1 of 3LS-DYNA FAQ 中英文版-4Quasi-static 准静态 | AiFEA


Or you can try an implicit static analysis using LS-DYNASee the commands control_implicit_hellip and Appendix M in the Userrsquos Manual There are examples of implicit analysis on our ldquouserrdquo ftp site in the ls-dynaexample directory See also gravitytxt readmepreload mass_scaling long_run_times implicitgeneral quick_initialization Note [1] Initializing to a prescribed geometry 1 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 lt execute s 1000 lt goes to final state deform lt write a file as described above t lt 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 gt Nodal Displacements but the output is i83e16 rather than the required i83e15 and hence the suggested use of LS-TAURUS LS-TAURUS is not available for Windows PCs Itrsquos free and available for Unix and Linux workstations

If you do a lsquoregularrsquo 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 (drdispsif)

Bug 2020 reported on 9222004 that rigid body nodes do not get initialized according to data in ldquom=pres_geom_filerdquo Additional example in homejdaytestcantileversolidtyp2sol_dr_nrbk (creates drdispsif) and typ2sol_presgeom_nrbk (m=drdispsif run) Nodes 11223344 are not initialized to whatrsquos in drdispsif 2 In your second run quickly initialize to the prescribed geometry written in step 1 You need to set IDRFLG=2 in control_dynamic_relaxation and include ldquom=filenamerdquo on the execution line where ldquofilenamerdquo is the file created in step 1 Before the transient run begins LS-DYNA will automatically run a precusor analysis of 100 timesteps wherein the nodse are displaced according to the data in ldquofilenamerdquo

revised 72103 jpd 72004

0 Responses to ldquoLS-DYNA FAQ 中英文版-4Quasi-static 准静态rdquo



LS-DYNA FAQ 中英文版-5Instability 计算不稳定 Published June 23rd 2007 in LS-DYNA Tags instability 不稳定

一些表示计算不稳定的消息如 ldquoout-of-range velocitiesrdquo 速度超出范围 ldquonegative volume in brick elementrdquo 体单元负体积 ldquotermination due to mass increaserdquo 因质量增加而终止

用来克服显式求解中的不稳定的方法如下

首先(也是最重要的)是使用可获得的最新的LS-DYNA版本最新的执行块可以从ftpuserftplstccom上下载(注前提是你有访问权限)联系LSTC获得user帐号的密码最新的BETA版执行块可以在ftpftplstccomoutgoingls971上找到(不需要密码但lstc公司对ftp访问有IP限制)

其次是增加d3plot的输出频率到可以显示出不稳定的出现过程这可以提供导致不稳定性发生的线索

其它的不些解决数值不稳定性的技巧试着用双精度LS-DYNA版本运行一次

试着减小时间步(timestep)缩放系数(即使使用了质量缩放mass-scaling)

单元类型和或沙漏(hourglass)控制对出现不稳定的减缩体和壳单元试着用沙漏控制type 4 和沙漏系数005

或者试着用类型16的壳单元沙漏控制type 8如果壳响应主要是弹性设置BWC=1 和 PROJ=1 (仅对B-T壳)

避免使用type=2体单元对体单元部件在厚度方向最少用两个体单元

接触设置接触的bucket sorts之间周期数为0这样会使用缺省的分类间隔如果参与接触的两个部件的相对速

度异常的大可能需要减小bucket sort的间隔(比如减小到52甚至1)

如果仿真过程中有明显的接触穿透出现转换到使用contact_automatic_surface_to_surface或者

contact_automatic_single_surface并设置SOFT=1 确保几何考虑了壳单元的厚度如果壳非常薄比如小于

1mm放大或者设置接触厚度到一个更加合理的值

避免冗余的接触定义也就是说不要对同样的两个部件定义多于一个的接触对

查找出现不稳定的部件的材料定义中的错误(比如误输入不一致的单位系统等)

关掉所有的damping

Page 1 of 3instability in lsdyna


这些技巧是一些通用的方法可能并不适合于所有的情况

See also negative_volume_in_brick_elementtipsshooting-nodes

English Version

Some messages that indicate an instability has occurred ldquoout-of-range velocitiesrdquo ldquonegative volume in brick elementrdquo ldquotermination due to mass increaserdquo

Approaches to combating instability of an explicit solution

First and foremost use the latest versionrevision of LS-DYNA available The latest production executables can be downloaded from ftpuserftplstccom Contact LSTC for the password to this ldquouserrdquo ftp account More recent BETA executables are found in ftpftplstccomoutgoingls971 (no password required)

The next step is to write plot states frequently enough to see the evolution of the instability This should offer clues into whatrsquos initiating the instability

Some other general tips toward resolving numerical instabilities

Try running a double precision LS-DYNA executable

Timestep Try reducing the timestep scale factor (even if mass-scaling is invoked)

Element formulation andor hourglass control For underintegrated solids or shells that go unstable try hourglass type 4 with a hourglass coefficient of 005 Or try shell formulation 16 with hourglass type 8 If response of shells is primarily elastic set BWC=1 and PROJ=1 (B-T shells only)

Avoid type 2 solids Use at least two solid elements thru the thickness of any solid part

Contact Set number of cycles between bucket sorts to zero so that the default sort interval will be used If the relative velocity between two parts in contact is exceptionally high it may be necessary to reduce the bucket sort interval (for instance to 5 2 or even 1)

If visible contact penetrations develop during the simulation switch to contact_automatic_surface_to_surface or contact_automatic_single_surface with SOFT set to 1 Make sure geometry takes into account thickness of shells If shells are VERY thin eg less than 1 mm scale up or set the contact thickness to a more reasonable value

Avoid redundant contact definitions that is donrsquot treat contact between the same two parts using more than one contact definition

Look for mistakes (typos inconsistent units etc) in material input of parts



that go unstable

Turn off all damping

These tips are of a general nature and may not be appropriate in all situations See also negative_volume_in_brick_elementtips shooting-nodes

0 Responses to ldquoLS-DYNA FAQ 中英文版-5Instability 计算不稳定rdquo

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LS-DYNA FAQ 中英文版-6Negative Volume 负体积 Published June 24th 2007 in LS-DYNA Tags Negative volume

泡沫材料的负体积(或其它软的材料)

对于承受很大变形的材料比如说泡沫一个单元可能变得非常扭曲以至于单元的体积计算得到一个负值这可能发生在材料还没有达到失效标准前对一个拉格朗日(Lagrangian)网格在没有采取网格光滑(mesh smoothing)或者重划分(remeshing)时能适应多大变形有个内在的限制LS-DYNA中计算得到负体积(negative volume)会导致计算终止除非在control_timestep卡里面设置ERODE选项为1而且在control_termination里设置DTMIN项为任何非零的值在这种情况下出现负体积的单元会被删掉而且计算继续进行(大多数情况)有时即使ERODE和DTMIN换上面说的设置了负体积可能还是会导致因错误终止

有助于克服负体积的一些方法如下简单的把材料应力－应变曲线在大应变时硬化这种方法会非常有效

有时候修改初始网格来适应特定的变形场将阻止负体积的形成此外负体积通常只对非常严重的变形情况是个问题而且特别是仅发生在像泡沫这样的软的材料上面

减小时间步缩放系数(timestep scale factor)缺省的09可能不足以防止数值不稳定

避免用全积分的体单元(单元类型2和3)它们在包含大变形和扭曲的仿真中往往不是很稳定全积分单元在大变形的时候鲁棒性不如单点积分单元因为单元的一个积分点可能出现负的Jacobian而整个单元还维持正的体积在计算中用全积分单元因计算出现负的Jacobian而终止会比单元积分单元来得快

用缺省的单元方程(单点积分体单元)和类型4或者5的沙漏(hourglass)控制(将会刚化响应)对泡沫材料首先的沙漏方程是如果低速冲击type 6系数10 高速冲击type 2或者3

对泡沫用四面体(tetrahedral)单元来建模使用类型10体单元

增加DAMP参数(foam model 57)到最大的推荐值05

对包含泡沫的接触用contact选项卡B来关掉shooting node logic

使用contact_interior卡用part set来定义需要用contact_interior来处理的parts在set_part卡1的第5项DA4来定义contact_interior类型缺省类型是1推荐用于单一的压缩在版本970里类型1的体单元可以设置type=2这样可以处理压缩和减切混合的模式

如果用mat_126尝试ELFORM=0

尝试用EFG方程(section_solid_EFG)因为这个方程非常费时所以只用在变形严重的地方而且只用于六面体单元

See also instability English Version

Page 1 of 3Negative volume in soft materials


Negative Volumes in Foams (or other soft materials)

In materials that undergo extremely large deformations such as soft foams an element may become so distorted that the volume of the element is calculated as negative This may occur without the material reaching a failure criterion There is an inherent limit to how much deformation a Lagrangian mesh can accommodate without some sort of mesh smoothing or remeshing taking place A negative volume calculation in LS-DYNA will cause the calculation to terminate unless ERODE in control_timestep is set to 1 and DTMIN in control_termination is set to any nonzero value in which case the offending element is deleted and the calculation continues (in most cases) Even with ERODE and DTMIN set as described a negative volume may cause an error termination (see erodenegvolk)

Some approaches that can help to overcome negative volumes include the following

- Simply stiffen up the material stress-strain curve at large strains This approach can be quite effective

- Sometimes tailoring the initial mesh to accomodate a particular deformation field will prevent formation of negative volumes Again negative volumes are generally only an issue for very severe deformation problems and typically occur only in soft materials like foam

- Reduce the timestep scale factor The default of 09 may not be sufficient to prevent numerical instabilities

- Avoid fully-integrated solids (formulations 2 and 3) which tend to be less stable in situations involving large deformation or distortion (The fully integrated element is less robust than a 1-point element when deformation is large because a negative Jacobian can occur at one of the integration points while the element as a whole maintains a positive volume The calculation with fully integrated element will therefore terminate with a negative Jacobian much sooner than will a 1-point element (lpb))

- Use the default element formulation (1 point solid) with type 4 or 5 hourglass control (will stiffen response) Preferred hourglass formulations for foams are type 6 with coef = 10 if low velocity impact types 2 or 3 if high velcocity impact

- Model the foam with tetrahedral elements using solid element formulation 10 (see ~pdfdubois-foam-tetspdf)

- Increase the DAMP parameter (foam model 57) to the maximum recommended value of 05

- Use optional card B of contact to turn shooting node logic off for contacts involving foam

- Use contact_interior A part set defines the parts to be treated by contact_interior Attribute 4 (DA4 = 5th field of Card 1) of the part set defines the TYPE of contact_interior used The default TYPE is 1 which is recommended for uniform compression In version 970 solid formulation 1



elements can be assigned TYPE=2 which treats combined modes of shear and compression

- If mat_126 is used try ELFORM = 0

- Try EFG formulation (section_solid_EFG) Use only where deformations are severe as this formulation is very expensive Use only with hex elements

See also instablitytips

0 Responses to ldquoLS-DYNA FAQ 中英文版-6Negative Volume 负体积rdquo

No Comments

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Distribution Opportunity



LS-DYNA隐式－显式自动转换例子 Published June 25th 2007 in LS-DYNA Tags implicit explicit switch

在LS-DYNA中可以通过卡片Control_implicit_general的选项imflag指定为一个负值(这个负值的绝对值为一条define_curve ID)来自动实现在指定的时间内作隐式或显式分析

这里的例子为一个一端固定平板另一端施加从0-001秒从0增加到100的力之后释放曲线ID3 指定从0-001秒内用隐式计算增量步为20步之后自动转为显式继续求解

下载input deck－》implicit_explicit_switchktxt

注意请用54345434a or 971版本运行上面的k文件不要用6763单精度或者双精度版本(这两个版本在implicit求解方面似乎存在bug隐式分析部分无法完成 )

0 Responses to ldquoLS-DYNA隐式－显式自动转换例子rdquo

No Comments

Page 1 of 1automatic implicit_explicit_switch


LS-DYNA中夹层板(sandwich)的模拟 Published June 27th 2007 in LS-DYNA Tags sandwich

在LS-DYNA中夹层板(sandwich plate)通常有三种方式来模拟 1 采用几层体单元来模拟当板比较薄沿厚度方向单元尺寸比较小时间步很难提高

2 中间的夹层材料用体单元模拟外面的包层材料用shell单元模拟在体单元和壳单元之间用Contact_tied (_offset)卡建立粘接关系

3 用一层壳单元来模拟对材料Mat_composite_damage和mat_enhanced_composite_damage打开层板理论选项(control_shell卡LAMSHT项设置为1)

对最后一种方式需要定义intergration_shell卡片例如下面这个层合板

点击放大

INTEGRATION_SHELL 180 -9722 02778 1 -9167 02778 1 -6667 22222 2 -2222 22222 2 2222 22222 2 6667 22222 2 9167 02778 3 9722 02778 3 PART material 1 1 11 PART material 2 1 12 PART material 3 1 11 SECTION_SHELL 1 2 00000000 80000000 000000 -1000000 0 18000000 18000000 18000000 18000000 00000000 mat_composite_damage 11 27e-6 734 734 734 032 032 032 278 278 278 1e9 1e9 1e9 1e9 mat_composite_damage 12 63e-7 0286 0286 0286 3 3 3 011 011 011 1e9 1e9 1e9 1e9

Page 1 of 2sandwich in ls-dyna


－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－其中intergration_shell卡片中第一项S表示板厚度方向积分点的规一化坐标值从-1到

1 积分点规一化坐标＝(积分点全局Z坐标－中面Z坐标)(thickness2) 第二项WF(Weighting factors)为与积分点关联的厚度与整个板厚度的比值WF和应该为1

第三项指向各层对应的part ID号这个part ID号仅用来指定这一层的材料

完整的一个实例如下shell8lam22rar

1 Response to ldquoLS-DYNA中夹层板(sandwich)的模拟rdquo

Jun 29th 2007 at 1219 am

这个例子非常好详细介绍了怎么定义integration_shell对我这样的新手帮助很大多谢了



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1 delubbi



LS-DYNA FAQ 中英文版-7Energy balance 能量平衡 Published June 28th 2007 in LS-DYNA Tags Energy Balance 能量平衡

GLSTAT(参见database_glstat)文件中报告的总能量是下面几种能量的和内能 internal energy 动能 kinetic energy 接触(滑移)能 contact(sliding) energy 沙漏能 houglass energy 系统阻尼能 system damping energy 刚性墙能量 rigidwall energy

GLSTAT中报告的弹簧阻尼能rdquoSpring and damper energyrdquo是离散单元(discrete elements)安全带单元

(seatbelt elements)内能及和铰链刚度相关的内能(constrained_joint_stiffnesshellip)之和而内

能rdquoInternal Energyrdquo包含弹簧阻尼能rdquoSpring and damper energyrdquo和所有其它单元的内能因此弹簧阻

尼能rdquoSpring and damper energyrdquo是内能rdquoInternal energyrdquo的子集

由SMP 5434a版输出到glstat文件中的铰链内能rdquojoint internal energyrdquo跟

constrained_joing_stiffness不相关它似乎与constrained_joint_revolute(_sphericaletc)的罚

值刚度相关连这是SMP 5434a之前版本都存在的缺失的能量项对MPP 5434a也一样这种现象在用拉格

朗日乘子(Lagrange Multiplier)方程时不会出现

与constrained_joint_stiffness相关的能量出现在jntforc文件中也包含在glstat文件中的弹簧和阻

尼能和内能中回想弹簧阻尼能rdquospring and damper energyrdquo不管是从铰链刚度还是从离散单元而来

总是包含在内能里面

在MATSUM文件中能量值是按一个part一个part的输出的(参见database_matsum)

沙漏能Hourglass energy仅当在卡片control_energy中设置HGEN项为2时才计算和输出同样刚性墙能

和阻尼能仅当上面的卡片中RWEN和RYLEN分别设置为2时才会计算和输出刚性阻尼能集中到内能里面质

量阻尼能以单独的行rdquosystem damping energyrdquo出现由于壳的体积粘性(bulk viscosity)

Page 1 of 7Energy Balance in LS-DYNA


而产生的能量耗散

(energy dissipated)在版本9704748之前是不计算的在后续子版本中设置TYPE=-2来在能量平衡中包含它

最理想的情况下能量平衡

总能量total energy ＝初始总能量＋外力功external work

换句话说如果能量比率energy ratio(指的是glstat中的total energyinitial energy实际上是

total energy(initial energy + external work)) 等于10注意质量缩放而增加质量可能会导致能

量比率增加

注意在LSprepost的HistorygtGlobal energies中不包含删掉的单元(eroded elements)的能量贡献然而

GLSTAT文件中的能量包含了它们注意它们的贡献可以通过ASCIIgtglstat中的rdquoEroded Kinetic Energyrdquo

amp ldquoEroded Internal Energyrdquo来绘制侵蚀能量(Eroded energy)是与删掉的单元相关的内能和删掉的节

点相关的动能典型来说如果没有单元删掉rdquoenergy ratio wo eroded energyrdquo等于1如果有单元被

删掉则小于1删掉的单元与rdquototal energyinitial energyrdquo比率没有关系总能量比率增加要归于其它

原因比如增加质量

重述一下将一个单元删掉时文件glstat中的内能和动能不会反映能量的丢失取而代之的是能量的丢

失记录在glstat文件的rdquoeroded internal energyrdquo amp ldquoeroded kinetic energyrdquo中如果用内能减

去rdquoeroded internal energyrdquo将得到分析中还存在的单元的内能对动能也一样 matsum文件中的内能和动能只包含余下(noneroded)的单元的贡献

注意如果在control_contact卡中将ENMASS设置为2则与删掉的单元的相关的节点不会删掉rdquoeroded

kinetic energyrdquo是0

在LSprepost中HistorygtGlobal 只是动能和内能的简单相加因此不包含接触能和沙漏能等的贡献－－－－－－－－－－壳的负内能



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为了克服这种不真实的效应－－关掉考虑壳的减薄(ISTUPD in control_shell) －－调用壳的体积粘性(set TYPE=-2 在control_bulk_viscosity卡中) －－对在matsum文件中显示为负的内能的parts使用damping_part_stiffness 先试着用一个小的值比如001 如果在control_energy中设置RYLEN=2因为刚性阻尼而能会计算且包含在内能中－－－－－－－－－－正的接触能当在接触定义中考虑了摩擦时将得到正的接触能摩擦将导致正的接触能如果没有设置接触阻尼和接触

摩擦系数你将会看到净接触能为零或者一个很小的值(净接触能＝从边和主边能量和) 所说的小是根

据判断－在没有接触摩擦系数时接触能为峰值内能的10内可以被认为是可接受的－－－－－－－－－－负的接触能突然增加的负接触能可能是由于未检测到的初始穿透造成的在定义初始几何时考虑壳的厚度偏置通常是

最有效的减小负接触能的步骤查阅LS-DYNA理论手册的2383amp2384节可得到更多接触能的信息

负接触能有时候因为parts之间的相对滑动而产生这跟摩擦没有关系这里说的负接触能从法向接触力

和法向穿透产生当一个穿透的节点从它原来的主面滑动到临近的没有连接的主面时如果穿透突然检测

到则产生负的接触能

如果内能为负接触能的镜像例如glstat文件中内能曲线梯度与负接触能曲线梯度值相等问题可能是非

常局部化的对整体求解正确性冲击较小你可以在LS-prepost中分离出有问题的区域通绘制壳单元部

件内能云图(Fcomp gt Misc gt Internal energy)实际上显示的是内能密度比如内能体积内能密

度云图中的热点通常表示着负的接触能集中于那里

如果有多于一个的接触定义sleout文件(database_sleout)将报告每一个接触对的接触能量因此缩小

了研究负接触能集中处的范围

克服负接触能的一般的建议如下－消除初始穿透(initial penetration)(在message文件中查找rdquowarningrdquo)

－检查和排除冗余的接触条件不应该在相同的两个parts之间定义多于一个的接触



－减小时间步缩放系数

－设置接触控制参数到缺省值SOFT=1 amp IGNORE=1除外(接触定义选项卡C)

－对带有尖的边的接触面设置SOFT=2(仅用于segment-to-segment接触)而且在版本970中推荐设置

SBOPT(之前的EDGE)为4对于部件之间有相对滑移的SOFT=2的接触为了改进edge-to-edge SOFT=2接触行

为设置DEPTH=5请注意SOFT=2接触增加了额外的计算开消尤其是当SBOPT或者DEPTH不是缺省值时

因此应该仅在其它接触选项(SOFT=0或者SOFT=1)不能解决问题时

模型的细节可能会指示可用其它的一些方法

English version

Total energy reported in GLSTAT (see database_glstat) is the sum of hellip

internal energy kinetic energy contact (sliding) energy hourglass energy system damping energy rigidwall energy

ldquoSpring and damper energyrdquo reported in the glstat file is the sum of internal energy of discrete elements seatbelt elements and energy associated with joint stiffnesses (constrained_joint_stiffnesshellip) ldquoInternal Energyrdquo includes ldquoSpring and damper energyrdquo as well as internal energy of all other element types Thus ldquoSpring and damper energyrdquo is a subset of ldquoInternal energyrdquo

The ldquojoint internal energyrdquo written to glstat by SMP 5434a is independent of the constrained_joint_stiffness It would appear to be associated with the penalty stiffness of constrained_joint_revolute (_spherical etc) This was a missing energy term prior to SMP rev 5434a It is still a missing energy term in MPP rev 5434a It does NOT appear when a Lagrange Multiplier formulation is used

The energy associated with constrained_joint_stiffness appears in the jntforc file and is included in glstat in ldquospring and damper energyrdquo and ldquointernal energyrdquo Recall that ldquospring and damper energyrdquo whether from joint stiffness or from discrete elements is always included in ldquointernal energyrdquo

Energy values are written on a part-by-part basis in MATSUM (see database_matsum)

Hourglass energy is computed and written only if HGEN is set to 2 in control_energy Likewise rigidwall energy and damping energy are computed and written only if RWEN and RYLEN respectively are set to 2



Stiffness damping energy is lumped into internal energyMass damping energy appears as a separate line item ldquosystem damping energyrdquo

Energy dissipated due to shell bulk viscosity was not calculated prior to revision 4748 of v 970 In subsequent revisions set TYPE=-2 to iclude this energy in the energy balance

The energy balance is perfect if total energy = initial total energy + external work or in other words if the energy ratio (referred to in glstat as ldquototal energy initial energyrdquo although it actually is total energy (initial energy + external work)) is equal to 10

Note that added mass may cause the energy ratio to rise (See ~testerodetaylormat3noerodemscalek)

The History gt Global energies do not include the contributions of eroded elements whereas the GLSTAT energies do include those contributions Note that these eroded contributions can be plotted as ldquoEroded Kinetic Energyrdquo and ldquoEroded Internal Energyrdquo via ASCII gt glstat Eroded energy is the energy associated with deleted elements (internal energy) and deleted nodes (kinetic energy) Typically the ldquoenergy ratio wo eroded energyrdquo would be equal to 1 if no elements have been deleted or less than one if elements have been deleted The deleted elements should have no bearing on the ldquototal energy initial energyrdquo ratio Overall energy ratio growth would be attributable to some other event eg added mass Restated when an element erodes the internal energy and kinetic energy in glstat do not reflect the energy loss Instead the energy losses are recorded as ldquoeroded internal energyrdquo and ldquoeroded kinetic energyrdquo in glstat If you subtract ldquoeroded internal energyrdquo from ldquointernal energyrdquo you have the internal energy of elements which remain in the simulation Likewise for kinetic energy The matsum filersquos internal energy and kinetic energy include only contributions from the remaining (noneroded) elements

An example is attached Note that if ENMASS in control_contact is set to 2 the nodes associated with the deleted elements are not deleted and the ldquoeroded kinetic energyrdquo is zero (See ~testm3ball2plate15k)

The total energy via History gt Global is simply the sum of KE and internal energies and thus doesnrsquot include such contributions as contact energy or hourglass energy Negative internal energy in shells

To combat this spurious effect - turn off shell thinning (ISTUPD) - invoke bulk viscosity for shells (set TYPE = -2 in control_bulk_viscosity) - use damping_part_stiffness for parts exhibiting neg IE in matsum



Try a small value first eg 01 If RYLEN=2 in control_energy then the energy due to stiffness damping is calculated and included in internal energy (See negative_internal_energy_in_shells for a case study) Positive contact energy

When friction is included in a contact definition positive contact is to be expected Friction SHOULD result in positive contact energy In the absence of contact damping and contact friction one would hope to see zero (or very small) net contact energy (net = sum of slave side energy and master side energy) ldquoSmallrdquo is a matter of judgement mdash 10 of peak internal energy might be considered acceptable for contact energy in the absence of contact friction (~testshl2solsphere_to_plateexamine_contact_damping_energyk appears to illustrate that contact damping (VDC = 0 30 90) produces positive sliding (or contact) energy)

Negative contact energy

Refer to p 314 315 of ldquoCrashworthiness Engineering Course Notesrdquo by Paul Du Bois Contact janelstccom to purchase these notes

Abrupt increases in negative contact energy may be caused by undetected initial penetrations Care in defining the initial geometry so that shell offsets are properly taken into account is usually the most effective step to reducing negative contact energy Refer to sections 2383 and 2384 in the LS-DYNA Theory Manual (May 1998) for more information on contact energy

Negative contact energy sometimes is generated when parts slide relative to each other This has nothing to do with friction mdash Irsquom speaking of negative energy from normal contact forces and normal penetrations When a penetrated node slides from its original master segment to an adjacent though unconnected master segment and a penetration is immediately detected negative contact energy is the result

If internal energy mirrors negative contact energy ie the slope of internal energy curve in glstat is equal and opposite that of the negative contact energy curve it could be that the problem is very localized with low impact on the overall validity of the solution You may be able to isolate the local problem area(s) by fringing internal energy of your shell parts (Fcomp gt Misc gt internal energy in LS-Prepost) Actually internal energy density is displayed ie internal energyvolume Hot spots in internal energy density usually indicate where negative contact energy is focused

If you have more than one contact defined the sleout file (database_sleout) will report contact energies for each contact and so the focus of the negative contact energy investigation can be narrowed

Some general suggestions for combating negative contact energy are as follows

- Eliminate initial penetrations (look for ldquoWarningrdquo in messag file)

- Check for and eliminate redundant contact conditions You should NOT have



more than one contact definition treating contact between the same two parts or surfaces

- Reduce the time step scale factor

- Set contact controls back to default except set SOFT=1 and IGNORE=1 (Optional Card C)

- For contact of sharp-edged surfaces set SOFT=2 (applicable for segment-to-segment contact only) Furthermore in v 970 setting SBOPT (formerly EDGE) to 4 is recommended for SOFT=2 contact where relative sliding between parts occurs For improved edge-to-edge SOFT=2 contact behavior set DEPTH to 5 Please note that SOFT=2 contact carries some additional expense particularly using nondefault values of SBOPT or DEPTH and so should be used only where other contact options (SOFT=0 or SOFT=1) are inadequate

The specifics of your model may dictate that some other approach be used

0 Responses to ldquoLS-DYNA FAQ 中英文版-7Energy balance 能量平衡rdquo

No Comments

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搭建LS-DYNA MPP版运行平台总结与探讨 Published June 29th 2007 in DYNA MPP Tags No Tags

随计算机硬件和网络设备技术的进步和价格的降低以及工业上对更精细的FE模型的需求MPP版LSDyna所点市场份额逐渐增加LSTC公司的Benson在关于DYNA history的presentation中甚至预测今后几年MPP会逐渐取代PCSMP版Dyna

目前LSTC公司硬件合作厂商(IBMHPSGISUNetc)都推出了商业化的LS-DYNA计算Cluster这些硬件厂商通常会投入相当一部分人力和财力在平台方面做开发和优化借着与LSTC良好的合作关系其平台上的MPP LS-DYNA加速比都能达到很理想的值Topcrunchorg网站给出了MPP DYNA 相关的两个Benchmark文件(一个单车前撞一个三车碰撞)并且专门收集用户在各种硬件平台上对这两个文件MPP LS-DYNA并行计算的速度信息其中不乏各硬件厂商提供且来测试的硬件平台信息包括CPU速度数目网络连接类型等从这些信息多们大致可以比较不同的DYNA版本不同的CPU不同的网络连接类型对MPP计算速度的影响

然而今天我要讨论的是自己搭建平台时需要注意的一些问题(前面的信息对我们会很有指导意义)商用平台固然好但并不是都能轻易得到有时候不得不自己组建这时候就得在选择配件时作好规划免得后达不到自己期望的并行效率(加速比)

影响MPP并行效率的几个关键因素－－网络连接－－选择的MPI和执行块－－模型的规模和domain decomposition

一个Dyna计算所花费的时间主要分成两块CPU计算时间及网络通信方面花费的时间对同一个分好块的domainCPU选定之后CPU计算时间基本上就确定了但在网络通信方面所花费的时间则根据网络设备和连接类型有大的关系从比较典型的汽车碰撞过程中对mpi消息的tracer发现平均每个处理器每个周期发送28条消息其中90的消息长度小于8K字节67小于1K字节[Ref 1]一条消息的通讯时间依赖于两个因素内部连接的带宽和响应时间(bandwidth amp latency)另外消息传递过程中存在着竞争当两个或多个处理器试图通过同一网络通路传送数据时就会产生竞争在基于IP的工作站网络中当两个机器试图同时通过同一路径进行通讯其中一条消息将延迟直到另一条传送完毕而这个延迟通常比实际直接传送两条消息所要的时间更多

网络设备的bandwith amp latency至关重要带宽大则传输同样数据所需时间少latency小则等待时间会降低同样有助减少通讯时间在同样的CPU配置下如果选择bandwidth小latency大的网络连接则花在通讯上的时间所点的总时间比率增加大部分时间内可能CPU要等待从别的CPU传过来的信息才能继续计算这样导致单机的CPU利用率不高总的加速比没办法提高就好比一部跑车开进了交通拥挤的低速道因此在选择网络设备时尽量选择bandwidth大latency小的硬件这也是为什么目前大型商用系统大多用myrinetinfiband替代GigE的原因除此之外设备的参数设置与驱动的tuning也会对加速比有所影响目前操作系统和网卡驱动通常是根据平常的网络浏览和交互进行参数设置的对这样的应用其效率比较高但对LS-DYNA MPP这样的应用其参数就不是优的前面已经提到在典型的LS-DYNA MPP计算过程中大量的消息为长度小于8K字节的短消息因此要对设备进行调谐以使得在短消息方面得到佳性能比如在我组建过的做LS-DYNA MPP并行计算的linux cluster上适当的进行网卡参数的设置缩短了总的计算时间在7左右

MPI的选择在linux平台可以有很多种HPMPIIntel-MPIMPICHLAMMPI前两者通常是接合特定的硬件平台和执行块进行优化而后两都对自己组建的Cluster更容易获得

Page 1 of 2搭建LS-DYNA MPP版运行平台总结与探讨 | AiFEA


从以前我自己组建的40CPUs 的Linux Cluster实际测试结果来看在GigE作为网络连接情况下同样参数设置和同样版本MPP Dyna执行块LAMMPI的计算效率要稍高于MPICHDYNA MPP版本在不断的更新过程中其不同版本的效率也不一样从topcrunch上也可以看出5434a版比3858执行效率就要高

计算模型的规模和domain decomposition也是两个影响比较大的方面规模小的模型如果分的domain多则很可能体现不出并行计算的优势因为这样分在每个CPU上的CPU计算时间与网络通讯时间之间的比率会下降CPU大部分时间可能在等待加速比在CPU超过一定数目时甚至会下降domain decomposition方法直接影响分配到各个CPU上的模型之间的公共节点的数目如果两个domain之间共用的节点数多则这两个domain分配到的CPU就计算过程中需要通讯的消息就多在做Domain decomposition时需要一些技桥巧和经验尽量将各个domain之间的交界面减少关于Domain decomposition方面的详细参数设置可以参考lsdyna keyword userrsquos manual中关于MPP的部分

上面只是自己搭建LS-Dyna MPP并行平台方面积累的一点点经验不能面面具道也可能会有些理解不对的地方欢迎交流

Reference

1 Message Passing and Advanced Computer Architectures

Brian Wainscott and Jason Wang LSTC

2 A Correlation Study between MPP LS-DYNA Performance and Various Interconnection Networks mdash a Quantitative Approach for Determining the Communication and Computation Costs Yih-Yih Lin Hewlett-Packard Company

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No Comments

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LS-DYNA FAQ 中英文版-8Hourglass control 沙漏控制 Published July 2nd 2007 in LS-DYNA Tags hourglass control 沙漏控制

沙漏(hourglass)模式是一种非物理的零能变形模式产生零应变和应力沙漏模式仅发生在减缩积分(单积分点)体壳和厚壳

单元上LS-DYNA里面有多种算法用于抑制沙漏模式缺省的算法(type 1)通常不是最有效的算法但却是最经济的

一种完全消除沙漏的方法是转换到全积分或者选择减缩积分(SR)方程的单元但这种方法是一种下策例如第一类型2体单

元比缺省的单点积分体单元计算开消大其二在大变形应用时更不稳定(更容易出现负体积)其三类型2体单元当单元形状比

较差时在一些应用中会趋向于剪切锁死(shear-lock)因而表现得过于刚硬

三角形壳和四面体单元没有沙漏模式但缺点是在许多应用中被认为过于刚硬

减小沙漏的一个好的方法是细化网格但这当然并不总是现实的

加载方式会影响沙漏程度施加压力载荷优于在单点上加载因为后者更容易激起沙漏模式

为了评估沙漏能在control_energy卡片中设置HGEN＝2而且用database_glstat和database_matsum卡分别输出系统和每一

个部件的沙漏能这一点是要确认非物理的沙漏能相对于每一个part的峰值内能要小(经验上来说lt10)对于壳单元可以绘制

出沙漏能密度云图但事先在database_extent_binary卡中设置SHGE=2然后在LS-Prepost中选择FcompgtMiscgthourglass

energy

对于流体部件缺省的沙漏系数通常是不合适的(太高)因此对于流体沙漏系数通常要缩小一到两个数量级对流体用基于粘

性的沙漏控制缺省的沙漏方程(type 1)对流体通常是可以的

对于结构部件一般来说基于刚性的沙漏控制(type 45)比粘性沙漏控制更有效通常当使用刚性沙漏控制时习惯于减小沙漏

系数到003~005的范围这样最小化非物理的硬化响应同时又有效抑制沙漏模式对于高速冲击即使对于固体结构部件推

荐采用基于粘性的沙漏控制(type 123)

粘性沙漏控制仅仅是抑制沙漏模式的进一步发展刚性沙漏控制将使单元朝未变形的方

Page 1 of 5hourglass control in ls-dyna


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向变形

类型8沙漏控制仅用于单元类型16的壳这种沙漏类型激活了16号壳的翘曲刚度因此单元的翘曲不会使解退化如果使用沙漏

控制816号壳单元可以用于解被称为扭曲梁(Twisted Beam)问题

对于单元类型1的体和减缩积分2D体(shell types 13 amp 15)类型6沙漏控制调用了一种假设应变协同转动方程使用沙漏控制类

型6和系数10一个弹性部件在厚度方向仅仅需要划分一层类型1的体单元就可以获得正确的弯曲刚度在隐式计算里面对于

类型1的体单元应该总是使用类型6的沙漏控制(实际上在V970里面这是自动设置的)

(More on type 6 HG control from Lee Bindeman) 类型6的沙漏控制与类型45不在于它用了一个假设应变场和材料属性来估算出假设应力场这个应力在单元封闭域内进行积分得

到沙漏力因此单元表现的像一个有同样假设应变场的全积分单元这种假设应变场设计成用来阻止纯弯曲中不真实的剪切变形

和近似不可压材料中的体积锁死

类型4和5的沙漏控制基于单元体积波速和密度像在LS-DYNA理论手册中方程321那样来计算沙漏刚度

沙漏类型6主要的改进是应力场在单元域内积分这使得当使用大的长细比或者歪斜形状的体单元时沙漏控制非常鲁棒类型4和

5的沙漏控制对大长细比和歪斜形状单元反应变不好它趋向于对某些沙漏模式反应的过于刚硬而对其它模式反应得过弱

沙漏控制类型6另一个理论上的优点是对在厚度方向只有一个单元的梁可以在弹性弯曲问题中得到准确的解要做到这一点设

置沙漏刚度参数为10同样对弹性材料方形截面杆的扭曲问题当沙漏系数设为10时可以用很少的单元来解然而对于非

线性材料用粗糙的网格得到好的结果是不可能的因为应力场不是像沙漏类型6假设的那样线性变化的在梁厚度方向上如果

没有更多积分点的话没有办法捕获应力场的非线性状态

对于选择沙漏控制下面几个问题要考虑对于单元有大的长细比或者明显歪斜(不管是初始还是变形过程中)推荐采用类型6

的沙漏控制类型6的沙漏控制通常对软的材料更好像泡沫或蜂窝材料在计算中会有非常明显的变形

在材料不是特别软或者单元有合理的形状且网格不是太粗糙时类型45和6沙漏控制似乎都能得到同样的结果这种情况推荐用



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类型4的沙漏控制因为它比其它的更快

类型6的沙漏控制在LS-DYNA Userrsquos Manual中参考的Belytschko和Bindeman的论文中有更详细的描述

English Version

Hourglass (HG) modes are nonphysical zero-energy modes of deformation that produce zero strain and no stress Hourglass modes occur only in under-intetgrated (single integration point) solid shell and thick shell elements LS-DYNA has various algorithms for inhibiting hourglass modes The default algorithm (type 1) while the cheapest is generally not the most effective algorithm

A way to entirely eliminate hourglass concerns is to switch to element formulations with fully-integrated or selectively reduced (SR) integration There can be a downside to this approach For example Type 2 solids are much more expensive than the single point default solid Secondly they are much more unstable in large deformation applications (negative volumes much more likely) Third type 2 solids have some tendency to rsquoshear-lockrsquo and thus behave too stiffly in applications where the element shape is poor

Triangular shells and tetrahedral solid elements do not have hourglassing modes but have drawbacks with regard to overly stiff behavior in many applications

A good way to reduce hourglassing is to refine your mesh but of course that isnrsquot always practical

The method of loading can affect the degree of hourglassing A pressure loading is preferred over loading individual nodes as the latter approach is more likely to excite hourglassing modes

To evaluate hourglass energy set HGEN to 2 in control_energy and use database_glstat and database_matsum to report the HG energy for the system and for each part respectively The point is to confirm that the nonphysical HG energy is small relative to peak internal energy for each part (lt10 as a rule-of-thumb) For shells only you can fringe hourglass energy density by first setting SHGE=2 in the LS-DYNA input deck (database_extent_binary) Then in LS-Prepost choose Fcomp gt Misc gt hourglass energy

For fluid parts the default HG coefficient is generally inappropriate (too high) Thus for fluids the hourglass coefficient should generally be scaled back one or two orders of magnitude Use only viscosity-based HG control for fluids The default HG formulation (type 1) is generally ok for fluids

Stiffness-based HG control (types 45) is generally more effective than viscous HG control for structural parts Usually when stiffness-based HG control is invoked I like to reduce the HG coefficient usually in the range of 03 to 05 soas to minimize nonphysical stiffening of the response and at the same time effectively inhibiting hourglass modes For high velocity impacts viscosity-based HG control (types 123) is recommended even for solidstructural parts ldquoViscous HG control only stops the HG mode from developing further Stiffness HG



Administrator
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control will push the element back toward its undeformed configurationCAUTION Stiffness hourglass control tends to be overly stiffrdquo (Paul Dubois)

Type 8 HG control applies only to shell formulation 16 This HG type activates warping stiffness in type 16 shells so that warping of the element does not degrade the solution Type 16 shells will solve the so-called Twisted Beam problem correctly if HG type 8 is invoked Type 6 HG control invokes an assumed-strain co-rotational formulation for type 1 solid elements and under-integrated 2D solids (shell types 13 and 15) With the HG type set to 6 and the hourglass coefficient set to 10 an elastic part need only be modeled with a single type 1 solid through its thickness to achieve the exact bending stiffness Type 6 HG control should always be used for type 1 solids in implicit simulations (in fact this is done automatically in v 970)

________________________________________________________________________ (More on type 6 HG control from Lee Bindeman) ldquoType 6 hourglass control for solid elements differs from types 4 and 5 because is uses an assumed strain field and material properties to evaluate an assumed stress field This stress is integrated in closed form over the element domain to obtain hourglass forces such that the element behaves like a fully integrated element with the same assumed strain field The assumed strain field is designed to prevent spurious shears during pure bending and volumetric locking for nearly incompressible material

Types 4 and 5 hourglass control calculate an hourglass stiffness based on the element volume wave speed and density as shown in equation 321 in the LS-DYNA Theoretical Manual

In my opinion the main improvement of hourglass type 6 is that the stress field is integrated over the element domain This makes the hourglass control quite robust when using solid elements with large aspect ratio or with skewed shapes Type 4 and 5 hourglass control tend to not respond appropriately for large aspect ratio or skewed shapes so they tend to become much too stiff in some hourglass modes and too soft in others

Another more academic advantage to type 6 hourglass control is that it is possible to obtain accurate results in elastic bending problems with beams made of 1 element through the thickness To do this set the hourglass stiffness parameter to 10 Similarly torsion of a rectangular bar of elastic material can be solved with very few elements when the hourglass stiffness parameter is set to 10 However with non-linear materials good coarse mesh results are impossible because the stress field does not vary linearly as is assumed with hourglass type 6 There is no way to capture the nonlinear nature of the stress field without more integration points through the beam thickness

To choose an hourglass control you need to consider the problem I would recommend type 6 hourglass control when elements have large aspect ratios (gt2) or are significantly skewed either initially or in a deformed configuration Type 6 hourglass control is usually better with soft materials such as foam or honeycomb material that deform



significantly during a calculation

In cases where the material is not particularly soft or elements are of reasonable shape and where the mesh is not too coarse types 4 5 and 6 hourglass control will likely all give about the same result in which case type 4 hourglass control is recommended since it is faster than the others

0 Responses to ldquoLS-DYNA FAQ 中英文版-8Hourglass control 沙漏控制rdquo

No Comments

Finite element program

SJ MEPLA - software for statics of glass structures wwwSJ-Softwarede



services



LS-DYNA FAQ 中英文版-9Damping 阻尼 Published July 6th 2007 in LS-DYNA Tags damping 阻尼

在LS-DYNA中阻尼完全是可选的通过使用一个DAMPING卡片来调用应该知道能量可以通过其它的非 DAMPING的方式耗散比如因为沙漏力产生的能量刚性墙的力产生的能量接触摩擦力产生的能量离散阻尼产生的内能等

有时候接触力可能将噪声引入到响应里在这种情况下通过CONTACT卡第二张卡的VDC参数来增加粘性阻尼从而帮助减小噪声VDC以临界阻尼的百分比输入典型的值是10到20

DAMPING卡片概览 LS-DYNA中的质量阻尼(Mass damping)包括damping_global amp damping_part_mass是用于抑止低频的结构振动模式但此外它有抑制刚体模式的效应因此对经受明显刚体运动的部件应该要么从质量阻尼中排除或者在部件经历大的刚体运动期间关掉质量阻尼或者使用damping_relative来替代通过使用 damping_relative仅仅相对指定刚体的运动振动被抑制

在质量阻尼情况下临界阻尼系数是4piT其中T是要抑制的模态的周期(通常是低阶(基频)模态)周期可以通过特征值分析(eigenvalue)或者从一个无阻尼的瞬态分析结果来估计如果选择使用质量阻尼建议使用小于临界阻尼系数的阻尼值取10的临界阻尼的值即输入04piT是相当典型的值可以选择用同样的阻尼系数抑制所有的部件(damping_global)或者对每一个部件指定不同的阻尼系数 (damping_part_mass)在任何一种情况下阻尼系数可能会随时间变化(在仿真中间关掉或打开阻尼时会有用)

damping_part_stiffness是为了抑制高频振动和数值振荡通常对结构振动没有明显的影响这种情况下阻尼系数COEF近似表示临界阻尼的一个系数典型的COEF值是01如果使用刚性阻尼产生不稳定消除阻尼或者减小COEF的值来使回复稳定(也许降低一个数量级或者在某些情况下更多)

质量和刚性阻尼在隐式瞬态分析中都实现了

在版本970中另一个可选的阻尼是频率不相关的阻尼选项它的目标是抑制一个范围的频率和一批部件 (damping_frequency_range)Damping_frequency_range是由Arup的Richard Sturt开发的它的理论细节是私有的它开发的意图是帮助LS-DYNA来适当地处理振动预测问题中的阻尼－－包括车辆 NVH时间历程分析某些地震问题和土木结构的振动问题

Page 1 of 4damping in ls-dyna


damping_frequency_range的关键点在于－仅使用很小的阻尼例如1到2 －处理阻尼将轻微的减小了响应的刚度那是因为阻尼力的应力滞后于理论上正确的阻尼力由于需要估计频率内容－用户指定的频率范围理想情况是不要超过高值和低值之间30在这个范围之外同样可以获得阻尼但阻尼值会减小这种阻尼是基于节点速度的所以可能会由于结构模态或者刚体转动而有振荡

在Rayleigh阻尼里阻尼矩阵表达为质量和刚度矩阵的线性组合 C = alpahM + betaK LS-DYNA为标准的非线性分析在单元级实现Rayleigh阻尼这是为了数值上的方便因为在显式方法里不需要生成刚度矩阵K取而代之通过简单的将应力在单元面积上积分得到内力Rayleigh阻尼作为这个应力的一个修正而实现

版本960中的刚性阻尼(stiffness damping)完全重新实现即使这样可以在960中提供COEF值这个值与 950中的BETA值是相符的其中COEF＝BETA(w2)

版本950和960中的刚性阻尼不完全相同在960中刚性阻尼方程在高频域提供一个近似的临界阻尼分数方程的详细信息是不公开的这个方程中的变化是因为使用旧版本方程时产生不稳定的频率而促使的在版本970的3510子版本(或者更高)中旧的950版本的刚性阻尼方程作为一个选项提供通过设置 COEF值为负值来调用这个参数之后被解释成V950用户手册中所指的BETA值

English Version

Damping is completely optional in LS-DYNA and is invoked using one the DAMPING commands Be aware that energy dissipation can occur through means other than DAMPING eg energy due to hourglass forces energy due to rigidwall forces energy due to contact friction forces internal energy from discrete dampers etc

Sometimes contact forces can introduce noise into the response In such cases adding viscous damping via the VDC parameter on Card 2 of contact may help reduce the noise VDC is input as a percentage of critical damping hellip a typical value is 10 to 20

___________________________________________________________ Overview of DAMPING commands

Mass damping in LS-DYNA which includes damping_global and damping_part_mass is intended to damp low-frequency structural modes but it has the added effect of damping rigid body modes Thus parts that undergo significant rigid body motion should EITHER be excluded from mass damping



OR the mass damping should be turned off during the time the part undergoes rigid body motion OR damping_relative should instead be used By using damping_relative only motionvibration that is relative to the motion of a particular rigid body is damped

The critical damping coefficient in the case of mass damping is 4piT where T is the period of the mode targeted for damping (usually the lowest frequency (fundamental) mode) The period can be determined from an eigenvalue analysis or estimated from results of an undamped transient analysis If the user elects to use mass damping a damping value less than the critical damping coefficient is suggested A value of 10 of critical damping input as 04piT is fairly typical You can choose to damp all parts using the same damping coefficient (damping_global) or to tailor the damping to the individual response characteristics of each part you can assign a different damping coefficient to each part (damping_part_mass) In either case the damping coefficient can vary with time (useful to turn damping off or on in the middle of a simulation)

damping_part_stiffness is intended to damp high frequency numerical oscillation and generally wonrsquot have much affect on structural vibrationoscillation The damping coefficient COEF in this case appproximately represents a fraction of critical damping A typical value of COEF is 01 If an instability results from using stiffness damping eliminate the damping or reduce COEF (by perhaps an order of magnitude or more in some cases) so that stability is restored

Both mass and stiffness damping are implemented for implicit transient analysis

Another damping alternative in version 970 is a frequency-independent damping option which targets a range of frequencies and a set of parts (damping_frequency_range) Damping_frequency_range was developed by Richard Sturt of Arup and its theoretical details are proprietary It was developed with the intent of helping LS-DYNA to handle damping in vibration prediction problems properly - including vehicle NVH time-history analysis as well as certain classes of seismic problems and civilstructural vibration problems The key points of damping_frequency_range are - Use for low amounts of damping only eg up to 1 or 2 - The damping treatment slightly reduces the stiffness of the response - thatrsquos because the applied damping force lags slightly behind the ldquotheoretically correctrdquo damping force due to the need to evaluate frequency content - The frequency range specified by the user should ideally be no more than a factor of 30 between highest and lowest Damping is still achieved outside the frequency range but the amount of damping reduces This damping is based on the nodal velocities these might oscillate due to structure modes or due to rigid body rotation __________________________________________________________________________ Additional commentary on damping hellip In Rayleigh damping the damping matrix is expressed as a linear combination of the mass and stiffness matricies



C = alphaM + betaK

The LS-DYNA implementation of Rayleigh damping for standard nonlinear analysis is done at the element level as you stated This is done for numerical convenience since in the explicit method we donrsquot need to form the stiffness matrix K Instead we compute internal forces by simply integrating stresses over the element area The Rayleigh damping terms are implemented as corrections to these stresses

The stiffness damping in version 960 is completely reformulated Even though you may provide a 960 COEF value which is consistent with the 950 BETA value that ishellip

COEF = BETA (w2)

hellipthe 950 stiffness damping and the 960 stiffness damping will not be exactly equivalent The 960 formulation of stiffness damping provides an APPROXIMATE fraction of critical damping in the high frequency domain The details of the formulation are proprietary The change in formulation was prompted by the frequent occurences of instability when using the old formulation

In rev 3510 (or higher) of v 970 the old 950-style stiffness damping formulation is available as an option and is invoked by setting the COEF parameter to a negative value The parameter is then interpreted as a BETA value as documented in the v 950 Userrsquos Manual

2 Responses to ldquoLS-DYNA FAQ 中英文版-9Damping 阻尼rdquo

Jul 17th 2007 at 205 am

Very good

Thanks

Jul 22nd 2007 at 1030 am

thank your effort

Turbine testing

Vibration measurement and modal analysis wwwoptonorcom

Noise Vibration Analyzer

4 channels handheld FFT for modal ODS balance

Data Collector Meter

1 delubbi

2 czj



LS-DYNA FAQ 中英文版-10ASCII output for MPP via binout Published July 17th 2007 in DYNA MPP and LS-DYNA Tags No Tags

从970版本开始有了二进制格式格式的所谓的ASCII output文件(matsumrcforcetc)－－注单机版和smp版输出的为文本格式的ASCII output文件

MPP-DYNA 不是直接写出ASCII输出文件而是输出二进制格式数据这些数据可以有两种格式dbout(参见V970用户手册Appendix LPL3)和binoutMPP缺省情况下会输出binout格式的数据卡片database_matsumdatabase_rcforcetc的第二个参数控制输出哪一种类型的数据

1= old format例如ASCII文件(SMP) 或者 dbout文件(MPP) 2= new binout格式(对MPP版这是缺省的) 3= both formats都输出

LS-Prepost可以直接读取binout数据而不需要转换但dbout文件需要用dumpbdb来转换成ASCII格式输出在LS-Prepost里选项页rdquo2Prime(启动界面右边的Group按钮下面)在CFD按钮下面有ldquoBinoutrdquo按钮点击之后在左下面出现的子面板中点击ldquoLoadrdquo按钮选择求解器输出的binout文件之后可以进行相关曲线的绘制（此处修改原文部分）

作为lsda软件包的一部分有两个程序可以获得(以用户账号登陆lstc ftp site在rdquolsdardquo目录下)一个是rdquol2ardquo它可以用来从binout文件中提取不同的ascii文件另一个是rdquoioqrdquo它是让你用来直接读取浏览binout文件的小工具

通常一个rdquol2ardquo执行块会包含在相应平台的MPP执行块的压缩包里但你也可以用那个l2a来操作任何ls-dyna执行块(MPP or SMP)产生的binout文件要从binout文件中提取ASCII输出文件在命令行执行l2a后面包含binout文件的名字例如rdquol2a binout0000Prime

Binout文件是平台无关的例如你可以在与输出binout数据的平台同一平台或者任何其它平台下处理binout数据

当MPP LS-DYNA执行块输出binout数据时将会有多于一个的文件以rdquobinoutrdquo作为根名字每一个这样的文件需要被独立的打开来得到所有需要的数据在d3hsp文件里你可以看到像如下的部分所示的信息告许你每一个binout文件包含哪些数据 gtThe following binary output file are being created gtand contain data equivalent to the indicated ascii output files gt binout0000(on processor 0) gt nodout gt matsum gt rcforc gt abstat gt rbdout gt sleout gt jntforc (type 0) gt binout0001(on processor 1) gt jntforc gt binout0003(on processor 3) gt deforc

Page 1 of 3ASCII output for MPP via binout


对MPP可选的控制输出格式的方法(from Jason)如果你在pfile中输入如下行 pfile gen dboutonly

to execute mpirun -np mpp970 i=hellip p=pfile

程序将像之前一样输出dbout文件(没有binout)之后你可以用dumpbdb来提取所有的ASCII文件

English Version

Starting with version 970 a binary format for the so-called ASCII output files (matsum rcforc etc) is available

MPP-DYNA runs do not write ASCII output files directly but instead write the data to binary database(s) There are two formats for this data dbout (see Appendix L p L3 in the v 970 Userrsquos Manual) and binout The default for MPP is to write the binout style of database The second input parameter of database_matsum database_rcforc etc controls what type of output will be written

1 = old format ie ASCII files (SMP) or dbout files (MPP) 2 = new binout format (this is the default for MPP) 3 = both formats written

LS-PrePost can read the binout data directly with no conversion by dumpbdb being required In LS-PrePost select the square button labeled ldquo2Prime (directly under the ldquoGrouprdquo button Next select ldquoBinoutrdquo and then from the bottom of the window select ldquoLoadrdquo From there itrsquos pretty self-explanatory

There are two programs that are available as part of our lsda package (see the ldquolsdardquo directory under the user account of our ftp site) One is ldquol2ardquo which will extract the various ascii files from a binout file The other is ldquoioqrdquo which is a small utility that lets you readexplore the binout file directly An ldquol2ardquo executable is generally included in the same tar file that contains the MPP executable for your platform but you can also use that l2a to operate on binout files produced by any LS-DYNA executable MPP or SMP To extract the ASCII files from a binout file execute l2a and include the name of the binout file on the execution line eg ldquol2a binout0000Prime

Binout files are platform-independent ie you can process binout data written by one platform on that same platform or on any other platform When a binout database is written by an MPP LS-DYNA executable there will be more than one file with the ldquobinoutrdquo rootname Each of these files must be opened individually to access all of the requested data In the d3hsp file yoursquoll see something like the following which tells



you what data is contained in each binout file

gt The following binary output files are being created gt and contain data equivalent to the indicated ascii output files gt binout0000 (on processor 0) gt nodout gt glstat gt matsum gt rcforc gt abstat gt rbdout gt sleout gt jntforc (type 0) gt binout0001 (on processor 1) gt jntforc gt binout0003 (on processor 3) gt deforc

Alternative control of output format for MPP (from Jason) if you put the following line in your pfile

pfile gen dboutonly


The program will output dbout as before and you can use dumpbdb to extract all the ASCII files

0 Responses to ldquoLS-DYNA FAQ 中英文版-10ASCII output for MPP via binoutrdquo

No Comments

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LS-DYNA FAQ 中英文版-11Contact Overview 接触概述 Published July 22nd 2007 in LS-DYNA Tags contact overview

这里提供LS-DYNA接触的一些简要信息讨论不包含所有的接触类型的接触选项更详细的LS-DYNA的接触回顾可以在wwwfeapublicatoinscom上找到FEA Information Newsletters中关于接触模型的由四个部分组成的系列文章这一系列文章的四部分分别在2001年的891012月份的新闻信里

Automatic vs Non-automatic 对大多数显式分析推荐用自动接触类型非自动接触类型(接触方向是重要的情况)有时用于金属成型仿真其中几何是非常直接的且接触面的方向在分析之间可以可靠的确定非自动接触通常推荐用于隐式分析

类型 Type 13接触(contact_automatic_single_surface)是一种单面接触(不需要定义主面)总是考虑壳的厚度且没有方向性因而参与接触的板壳面在建模的时候需要至少保持一个小的间隙为了避免初始穿透间隙不能小于潜在会发生接触的两个壳之间厚度的平均值体单元之间不需要有间隙接触类型13的接触搜索算法比接触类型3(contact_surface_to_surface)或者接触类型a3(contact_automatic_surface_to_surface)更加复杂例如type13可以处理例如壳边对面梁对壳面的情况和任何其它单面接触类型一样接触力不是直接从RCFORC文件中获取你必需要定义contact_force_transducer_penalty来获取接触力文章rdquocontact13vs26Prime提供了关于contact_automatic_single_surface 和contact_automatic_general对比的一些额外信息(之后会贴出敬请等待)

Type 3接触(contact_surface_to_surface)是双向的面对面接触其中壳的厚度考虑选项可以通过contact或者control_contact(contact优先)卡片打开或者关闭接触片的方向是很重要的因为这种接触类型只在一个方向来检测潜在的接触

在如面对面的一个双向接触中先检测从面侧的节点对主面的穿透然后再检测主面侧的节点对从面的穿透这种方法当用用设置SOFT=2来调用segment-based接触时会有例外

接触类型a3没有方向性(从壳的中面检测任一侧的潜在接触)而且总是考虑壳厚度从这一点考虑它非常类似于type 13的接触

接触参数的一些摘记 SOFT SOFT是contact选项卡A的第一个参数SOFT的缺省值是0SOFT=1除了在确定接触刚度方面之外与SOFT=0差不多是一样的SOFT=2与SOFT=0根本上是不一样的不但在确定接触刚度方法上而且在搜索穿透的产生的方法上也不一样SOFT=2会调用所谓的rdquosegment-based contactrdquo对于SOFT=1 amp 2接触的摘记可以分别参考文章rdquocontactsoft1Prime amp ldquocontactsoft2Prime(稍后推出敬请期待)

IGNORE 在仿真分析中的任何一个时间点如果一个节点突然检测到在面下面(比如说节点运动的非常快穿透之前没有检测到)原来的(IGNORE=0)算法仅仅是把节点移动到主面上不施加任何力(称之为rdquoshooting node logicrdquo)如果shooting node logic选项被关掉(SNLOG=1)会突然出现一个相当大的力而且产生负的接触能如果IGNORE设置为

Page 1 of 3contact overview in ls-dyna


1这样shooting node logic标志SNLOG没有作用相当于突然的穿透被留意到而且通过局部的调整接触厚度来补偿因此在任何分析的时间点如果检测到突然的穿透程序不会施加任何很大的力也不会移动任何节点但接触力会阻止进一步的穿透 English Version Provided herein are some very brief notes on LS-DYNA contact Not all the contact types or contact options are discussed

[For a comprehensive review of contact in LS-DYNA see the four-part series on contact modeling in the archived FEA information Newsletters available athellip wwwfeapublicationscom The four parts of the series are in the August September October and December 2001 newsletters]

Automatic vs Non-automatic Automatic contacts are recommended for most explicit simulations Non-automatic contacts (in which contact orientation is important) are sometimes used for metal forming simulations where the geometries are very straightforward and contact surface orientation can be reliably established before the simulation is conducted Non-automatic contacts are generally recommended for implicit simulations

TYPES Type 13 contact (contact_automatic_single_surface) is a single surface contact (no master surface is defined) that always considers shell thickness and has no orientation Thus itrsquos necessary that shell surfaces be modeled with at least a small gap between them To avoid initial penetrations the gap should be no less than the average thickness of the two shells potentially in contact No gap is necessary between solid elements The contact searching algorithm for type 13 contact is more complex than for type 3 (contact_surface_to_surface) or a3 (contact_automatic_surface_to_surface) ie type 13 can handle situations such as shell edge to surface and to some extent beam to shell surface As with any single surface contact type resultant forces are not directly retrievable in the RCFORC file one must define a contact_force_transducer_penalty in order to retrieve the contact forces The article ldquocontact13vs26Prime provides additional information on contact_automatic_single_surface and contrasts it to contact_automatic_general

Type 3 contact (contact_surface_to_surface) contact is a surface-to-surface (two-way) contact where shell thickness consideration can either be turned on or off either in contact or control_contact (contact has priority) The orientation of the contact segments is important with this contact type as the shell only looks in one direction for potential contact

In a two-way contact such surface_to_surface nodes on the slave side are first checked for penetration thru the master surface and then master nodes are checked for penetration thru the slave surface The exception is this approach is when segment-based contact is invoked by setting SOFT=2

Contact type a3 has no orientation (a shell looks for potential contact from either side of the shell



midplane) and always considers shell thickness so in this regarditrsquos quite similar to a type 13 contact

Table 61 in the 950 Keyword Userrsquos Manual lists the maximum penetration d that defines when a penetrating node is released from contact consideration This distance d is different for a type 3 contact than for a type 13 contact

Some notes on contact parameters

SOFT SOFT is the first parameter on Optional Card A of contacthellip The default value of SOFT is 0 SOFT=1 is more or less the same as SOFT=0 EXCEPT in the way the contact stiffness is determined SOFT=2 is a radical departure from SOFT=0 both in the way contact stiffness is determined but also in the manner that the search for penetration is conducted SOFT=2 invokes what is called ldquosegment-based contactrdquo For notes regarding contact with SOFT= 1 and 2 see the articles ldquocontactsoft1Prime and ldquocontactsoft2Prime respectively

IGNORE At any point during the simulation if a node is suddenly found to be below the surface (say it was moving very fast and wasnrsquot detected before penetration) the old style (IGNORE=0) algorithm just moves the node to the master surface without applying any forces (we term this ldquoshooting node logicrdquo) If the shooting node logic is turned off (SNLOG=1) then you get large forces suddenly appearing and negative contact energy If IGNORE is set to 1 then the shooting node logic flag SNLOG has no affect Rather the amount of sudden penetration is noted and compensated for by adjusting the contact thickness locally So at any time during the simulation if a sudden penetration is detected the program doesnrsquot apply any large forces nor are any nodes moved Contact forces however will resist FURTHER penetration jpd 122002 revised 42003 revised 92003 auto vs non-auto

0 Responses to ldquoLS-DYNA FAQ 中英文版-11Contact Overview 接触概述rdquo

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LS-OPT

LS-OPT是一个独立的设计优化和概率分析软件包与LS-DYNA有良好的接口早期开发一直在Linux和UNIX类系统下但从30版本开始LS-OPT支持Windows平台目前最新版本为32 LS-OPT优化功能基于RSM(Response Surface Methodology)和DOE(Design of Experiments)LS-OPT可以与大多前处理软件进行交互并且支持用CFortran语言进行扩展更详细信息参见httpwwwlstccompagesopthtm 典型应用包括优化设计系统识别概率分析

LS-Prepost

LS-Prepost是LSTC公司开发的一个免费的前后处理软件软件小巧但功能丰富同时支持大部分的平台目前最新版本为07年5月份的对于它的详细介绍和相关的demo可以由以下链接获得httpwwwlstccomlspp 注如果有需要LS-Prepost Windows平台最新版本可以发信给我(kevin[dot]zsc[at]163com)或者留下你的mail地址

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kg m s N Pa Joule 783e+3 207e+11 1565 9806

kg cm s 1e-02N 783e-3 207e+09 156e+03 9806e+02

kg cm ms 1e+04N 783e-3 207e+03 156 9806e-04

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准静态

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能量平衡

MPP

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kg m s N Pa Joule 783e+3 207e+11 1565 9806

kg cm s 1e-02N 783e-3 207e+09 156e+03 9806e+02

kg cm ms 1e+04N 783e-3 207e+03 156 9806e-04

kg cm us 1e+10N 783e-3 207e-03 156e-03 9806e-10










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C = alphaM + betaK



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长分析时间

准静态

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负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

接触概述




________________________________________________________________


kg mm s mN 1e3 Pa 783e-6 207e+08 9806e+02



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1 下载MPICH软件




3 MPICH 配置





4 运行MPP DYNA







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C = alphaM + betaK



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Jul 17th 2007 at 205 am

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产品介绍

单位制

并行计算设定

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长分析时间

准静态

计算不稳定

负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

接触概述




1 下载MPICH软件




3 MPICH 配置





4 运行MPP DYNA







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－－－－－－－－－－－－－－－－－－－－－－－－－－可变形点焊梁的质量缩放











































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产品介绍

单位制

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长分析时间

准静态

计算不稳定

负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

接触概述


4 运行MPP DYNA







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－－－－－－－－－－－－－－－－－－－－－－－－－－可变形点焊梁的质量缩放











































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长分析时间

准静态

计算不稳定

负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

接触概述




No Comments














－－－－－－－－－－－－－－－－－－－－－－－－－－可变形点焊梁的质量缩放











































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长分析时间

准静态

计算不稳定

负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

接触概述












－－－－－－－－－－－－－－－－－－－－－－－－－－可变形点焊梁的质量缩放











































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长分析时间

准静态

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负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

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C = alphaM + betaK



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长分析时间

准静态

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负体积


夹层板模拟

能量平衡

MPP

沙漏控制

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ASCII输出与MPP

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C = alphaM + betaK



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质量缩放

长分析时间

准静态

计算不稳定

负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

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C = alphaM + betaK



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质量缩放

长分析时间

准静态

计算不稳定

负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

接触概述

































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C = alphaM + betaK



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Jul 22nd 2007 at 1030 am

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Turbine testing





1 delubbi

2 czj

















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运算放大器































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计算机cpu







产品介绍

单位制

并行计算设定

质量缩放

长分析时间

准静态

计算不稳定

负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

接触概述

that go unstable




No Comments













































No Comments



services












No Comments








点击放大









Jun 29th 2007 at 1219 am




services

位移传感器



1 delubbi




























量比率增加















Administrator
高亮

























English version







































No Comments

Nuclear Energy


Forward Together



Custom Analysis
















Reference





No Comments



给世界听


















energy









Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮

向变形





















Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮



English Version











Administrator
高亮













No Comments





services

















English Version














C = alphaM + betaK



COEF = BETA (w2)




Jul 17th 2007 at 205 am

Very good

Thanks

Jul 22nd 2007 at 1030 am

thank your effort

Turbine testing





1 delubbi

2 czj

















English Version












pfile gen dboutonly




No Comments




运算放大器































No Comments

计算机cpu







产品介绍

单位制

并行计算设定

质量缩放

长分析时间

准静态

计算不稳定

负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

接触概述





































No Comments



services












No Comments








点击放大









Jun 29th 2007 at 1219 am




services

位移传感器



1 delubbi




























量比率增加















Administrator
高亮

























English version







































No Comments

Nuclear Energy


Forward Together



Custom Analysis
















Reference





No Comments



给世界听


















energy









Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮

向变形





















Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮



English Version











Administrator
高亮













No Comments





services

















English Version














C = alphaM + betaK



COEF = BETA (w2)




Jul 17th 2007 at 205 am

Very good

Thanks

Jul 22nd 2007 at 1030 am

thank your effort

Turbine testing





1 delubbi

2 czj

















English Version












pfile gen dboutonly




No Comments




运算放大器































No Comments

计算机cpu







产品介绍

单位制

并行计算设定

质量缩放

长分析时间

准静态

计算不稳定

负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

接触概述







No Comments








点击放大









Jun 29th 2007 at 1219 am




services

位移传感器



1 delubbi




























量比率增加















Administrator
高亮

























English version







































No Comments

Nuclear Energy


Forward Together



Custom Analysis
















Reference





No Comments



给世界听


















energy









Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮

向变形





















Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮



English Version











Administrator
高亮













No Comments





services

















English Version














C = alphaM + betaK



COEF = BETA (w2)




Jul 17th 2007 at 205 am

Very good

Thanks

Jul 22nd 2007 at 1030 am

thank your effort

Turbine testing





1 delubbi

2 czj

















English Version












pfile gen dboutonly




No Comments




运算放大器































No Comments

计算机cpu







产品介绍

单位制

并行计算设定

质量缩放

长分析时间

准静态

计算不稳定

负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

接触概述






点击放大









Jun 29th 2007 at 1219 am




services

位移传感器



1 delubbi




























量比率增加















Administrator
高亮

























English version







































No Comments

Nuclear Energy


Forward Together



Custom Analysis
















Reference





No Comments



给世界听


















energy









Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮

向变形





















Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮



English Version











Administrator
高亮













No Comments





services

















English Version














C = alphaM + betaK



COEF = BETA (w2)




Jul 17th 2007 at 205 am

Very good

Thanks

Jul 22nd 2007 at 1030 am

thank your effort

Turbine testing





1 delubbi

2 czj

















English Version












pfile gen dboutonly




No Comments




运算放大器































No Comments

计算机cpu







产品介绍

单位制

并行计算设定

质量缩放

长分析时间

准静态

计算不稳定

负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

接触概述






Jun 29th 2007 at 1219 am




services

位移传感器



1 delubbi




























量比率增加















Administrator
高亮

























English version







































No Comments

Nuclear Energy


Forward Together



Custom Analysis
















Reference





No Comments



给世界听


















energy









Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮

向变形





















Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮



English Version











Administrator
高亮













No Comments





services

















English Version














C = alphaM + betaK



COEF = BETA (w2)




Jul 17th 2007 at 205 am

Very good

Thanks

Jul 22nd 2007 at 1030 am

thank your effort

Turbine testing





1 delubbi

2 czj

















English Version












pfile gen dboutonly




No Comments




运算放大器































No Comments

计算机cpu







产品介绍

单位制

并行计算设定

质量缩放

长分析时间

准静态

计算不稳定

负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

接触概述


























量比率增加















Administrator
高亮

























English version







































No Comments

Nuclear Energy


Forward Together



Custom Analysis
















Reference





No Comments



给世界听


















energy









Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮

向变形





















Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮



English Version











Administrator
高亮













No Comments





services

















English Version














C = alphaM + betaK



COEF = BETA (w2)




Jul 17th 2007 at 205 am

Very good

Thanks

Jul 22nd 2007 at 1030 am

thank your effort

Turbine testing





1 delubbi

2 czj

















English Version












pfile gen dboutonly




No Comments




运算放大器































No Comments

计算机cpu







产品介绍

单位制

并行计算设定

质量缩放

长分析时间

准静态

计算不稳定

负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

接触概述

























English version







































No Comments

Nuclear Energy


Forward Together



Custom Analysis
















Reference





No Comments



给世界听


















energy









Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮

向变形





















Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮



English Version











Administrator
高亮













No Comments





services

















English Version














C = alphaM + betaK



COEF = BETA (w2)




Jul 17th 2007 at 205 am

Very good

Thanks

Jul 22nd 2007 at 1030 am

thank your effort

Turbine testing





1 delubbi

2 czj

















English Version












pfile gen dboutonly




No Comments




运算放大器































No Comments

计算机cpu







产品介绍

单位制

并行计算设定

质量缩放

长分析时间

准静态

计算不稳定

负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

接触概述






























No Comments

Nuclear Energy


Forward Together



Custom Analysis
















Reference





No Comments



给世界听


















energy









Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮

向变形





















Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮



English Version











Administrator
高亮













No Comments





services

















English Version














C = alphaM + betaK



COEF = BETA (w2)




Jul 17th 2007 at 205 am

Very good

Thanks

Jul 22nd 2007 at 1030 am

thank your effort

Turbine testing





1 delubbi

2 czj

















English Version












pfile gen dboutonly




No Comments




运算放大器































No Comments

计算机cpu







产品介绍

单位制

并行计算设定

质量缩放

长分析时间

准静态

计算不稳定

负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

接触概述














Reference





No Comments



给世界听


















energy









Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮

向变形





















Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮



English Version











Administrator
高亮













No Comments





services

















English Version














C = alphaM + betaK



COEF = BETA (w2)




Jul 17th 2007 at 205 am

Very good

Thanks

Jul 22nd 2007 at 1030 am

thank your effort

Turbine testing





1 delubbi

2 czj

















English Version












pfile gen dboutonly




No Comments




运算放大器































No Comments

计算机cpu







产品介绍

单位制

并行计算设定

质量缩放

长分析时间

准静态

计算不稳定

负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

接触概述













energy









Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮

向变形





















Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮



English Version











Administrator
高亮













No Comments





services

















English Version














C = alphaM + betaK



COEF = BETA (w2)




Jul 17th 2007 at 205 am

Very good

Thanks

Jul 22nd 2007 at 1030 am

thank your effort

Turbine testing





1 delubbi

2 czj

















English Version












pfile gen dboutonly




No Comments




运算放大器































No Comments

计算机cpu







产品介绍

单位制

并行计算设定

质量缩放

长分析时间

准静态

计算不稳定

负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

接触概述

向变形





















Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮
Administrator
高亮



English Version











Administrator
高亮













No Comments





services

















English Version














C = alphaM + betaK



COEF = BETA (w2)




Jul 17th 2007 at 205 am

Very good

Thanks

Jul 22nd 2007 at 1030 am

thank your effort

Turbine testing





1 delubbi

2 czj

















English Version












pfile gen dboutonly




No Comments




运算放大器































No Comments

计算机cpu







产品介绍

单位制

并行计算设定

质量缩放

长分析时间

准静态

计算不稳定

负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

接触概述



English Version











Administrator
高亮













No Comments





services

















English Version














C = alphaM + betaK



COEF = BETA (w2)




Jul 17th 2007 at 205 am

Very good

Thanks

Jul 22nd 2007 at 1030 am

thank your effort

Turbine testing





1 delubbi

2 czj

















English Version












pfile gen dboutonly




No Comments




运算放大器































No Comments

计算机cpu







产品介绍

单位制

并行计算设定

质量缩放

长分析时间

准静态

计算不稳定

负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

接触概述













No Comments





services

















English Version














C = alphaM + betaK



COEF = BETA (w2)




Jul 17th 2007 at 205 am

Very good

Thanks

Jul 22nd 2007 at 1030 am

thank your effort

Turbine testing





1 delubbi

2 czj

















English Version












pfile gen dboutonly




No Comments




运算放大器































No Comments

计算机cpu







产品介绍

单位制

并行计算设定

质量缩放

长分析时间

准静态

计算不稳定

负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

接触概述















English Version














C = alphaM + betaK



COEF = BETA (w2)




Jul 17th 2007 at 205 am

Very good

Thanks

Jul 22nd 2007 at 1030 am

thank your effort

Turbine testing





1 delubbi

2 czj

















English Version












pfile gen dboutonly




No Comments




运算放大器































No Comments

计算机cpu







产品介绍

单位制

并行计算设定

质量缩放

长分析时间

准静态

计算不稳定

负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

接触概述








C = alphaM + betaK



COEF = BETA (w2)




Jul 17th 2007 at 205 am

Very good

Thanks

Jul 22nd 2007 at 1030 am

thank your effort

Turbine testing





1 delubbi

2 czj

















English Version












pfile gen dboutonly




No Comments




运算放大器































No Comments

计算机cpu







产品介绍

单位制

并行计算设定

质量缩放

长分析时间

准静态

计算不稳定

负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

接触概述















English Version












pfile gen dboutonly




No Comments




运算放大器































No Comments

计算机cpu







产品介绍

单位制

并行计算设定

质量缩放

长分析时间

准静态

计算不稳定

负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

接触概述




pfile gen dboutonly




No Comments




运算放大器































No Comments

计算机cpu







产品介绍

单位制

并行计算设定

质量缩放

长分析时间

准静态

计算不稳定

负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

接触概述



























No Comments

计算机cpu







产品介绍

单位制

并行计算设定

质量缩放

长分析时间

准静态

计算不稳定

负体积


夹层板模拟

能量平衡

MPP

沙漏控制

阻尼

ASCII输出与MPP

接触概述

LS-DYNA FAQ CHN

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Transcript of LS-DYNA FAQ CHN