LS Dyna

LS Dyna

Quasistatic analysis with LS-DYNA

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    • goktug.yilmaz
      Subscriber

      Hello!

      I want to do a crashbox simulation in LS-DYNA. I will use an aluminum profile and compress it with a very low velocity such as 100 mm/min.

      I have used implicit analysis for it and selected static analysis from implicit dynamics. However, how could I be sure that I am really doing a quasistatic analysis? I have uploaded my .k file with an extension of .txt for you to check it.

    • Aniket
      Ansys Employee
      Ansys staff can not download any files on the forum, so if you want to reach a larger audience to get answers from, please insert inline images describing your problem.n-AniketnHow to access Ansys help linksnGuidelines for Posting on Ansys Learning Forumn
    • goktug.yilmaz
      Subscriber
      Thank you for reminding me. If you look at images below, you can see what kind of analysis I am trying to do. This compression analysis must be a quasi static analysis since the press has a very low velocity in real life. nI gave motion to my rigid plate (Boundary Condition) and used implicit solver. I think that this analysis was a quasi static analysis since I selected implicit dynamics-static analysis by keeping the value of IMASS at zero which I show you with a red frame. However, I want to be sure that this is a quasi static analysis. In brief, my question is how could I understand I am really doing a quasi static analysis?.n
    • goktug.yilmaz
      Subscriber
      Thank you for reminding me. If you look at images below, you can see what kind of analysis I am trying to do. This compression analysis must be a quasi static analysis since the press has a very low velocity in real life. nI gave motion to my rigid plate (Boundary Condition) and used implicit solver. I think that this analysis was a quasi static analysis since I selected implicit dynamics-static analysis by keeping the value of IMASS equal to zero which I show you with a red frame. However, I want to be sure that this is a quasi static analysis. In brief, my question is how could I understand I am really doing a quasi static analysis?.n
    • goktug.yilmaz
      Subscriber
      I also want to share the content of my keyword file.$# LS-DYNA Keyword file created by LS-PrePost(R) V4.7.17 - 08Jul2020n$# Created on Mar-06-2021 (21:10:50)n*KEYWORDn*TITLEn$# titlenLS-DYNA keyword deck by LS-PrePostn*CONTROL_ACCURACYn$# osu inn pidosu iacc n 1 4 3 1n*CONTROL_IMPLICIT_AUTOn$# iauto iteopt itewin dtmin dtmax dtexp kfail kcyclen 1 11 5 0.0 0.0 0.0 0 0n*CONTROL_IMPLICIT_DYNAMICSn$# imass gamma beta tdybir tdydth tdybur irate alphan 0 0.5 0.25 0.01.00000E281.00000E28 0 0.0n*CONTROL_IMPLICIT_GENERALn$# imflag dt0 imform nsbs igs cnstn form zero_vn 1 0.001 2 1 2 0 0 0n*CONTROL_IMPLICIT_SOLUTIONn$# nsolvr ilimit maxref dctol ectol rctol lstol abstoln 12 11 15 0.001 0.011.00000E10 0.91.0000E-10n$# dnorm diverg istif nlprint nlnorm d3itctl cpchk n 2 1 1 0 2 0 0n$# arcctl arcdir arclen arcmth arcdmp arcpsi arcalf arctimn 0 0 0.0 1 2 0 0 0n$# lsmtd lsdir irad srad awgt sred n 4 2 0.0 0.0 0.0 0.0n*CONTROL_IMPLICIT_SOLVERn$# lsolvr lprint negev order drcm drcprm autospc autotoln 2 0 2 0 4 0.0 1 0.0n$# lcpack mtxdmp iparm1 rparm1 rparm2 n 2 0 5001.00000E-9 0.001n$# emxdmp rdcmem n 0 0.85n*CONTROL_TERMINATIONn$# endtim endcyc dtmin endeng endmas nosol n 1.0 0 0.0 0.01.000000E8 0n*DATABASE_BNDOUTn$# dt binary lcur ioopt n 0.001 0 0 1n*DATABASE_NODFORn$# dt binary lcur ioopt n 0.001 0 0 1n*DATABASE_NODOUTn$# dt binary lcur ioopt option1 option2 n 0.001 0 0 1 0.0 0n*DATABASE_RBDOUTn$# dt binary lcur ioopt n 0.001 0 0 1n*DATABASE_RCFORCn$# dt binary lcur ioopt n 0.001 0 0 1n*DATABASE_BINARY_D3PLOTn$# dt lcdt beam npltc psetid n 0.01 0 0 0 0n$# ioopt rate cutoff window type pset n 0 0.0 0.0 0.0 0 0n*DATABASE_NODAL_FORCE_GROUPn$# nsid cid n 3 0n*BOUNDARY_PRESCRIBED_MOTION_RIGID_IDn$# id headingn 0RigidPlateDisplacementn$# pid dof vad lcid sf vid death birthn 4 3 2 1 -1.0 01.00000E28 0.0n*BOUNDARY_SPC_SET_IDn$# id headingn 0FixedNodesn$# nsid cid dofx dofy dofz dofrx dofry dofrzn 3 0 1 1 1 1 1 1n
    • Andreas Koutras
      Ansys Employee
      Hi goktug,nthanks for your question. To run a static analysis, make sure that IMFLAG=1 (in CONTROL_IMPLICIT_GENERAL) and IMASS=0 (in CONTROL_IMPLICT_DYNAMICS). The latter is the default value if IMFLAG=1. Appendix P of the manual vol 1 provides several recommendations on the parameters for implicit analysis. nTo confirm that you are running a static analysis, you can, for example, apply a vertical force at the top plate and then rapidly drop the force value to zero, and compare the response between IMASS=0 and IMASS=1. IMASS=1 will produce free vibration. Make sure the plate has sufficient density.nRegards,nakn
    • goktug.yilmaz
      Subscriber
      Thank you very much for your answer. If I just want to control energy, and observe that internal energy is greater than kinetic energy, would it be enough to make sure that the analysis is quasi static? n
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