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Contact II

A hemispherical ball of brick elements is displaced into a plate of brick elements. The plate is supported around its edges. Download is available in the download section of this document

Introduction

LS-DYNA Implicit Workshop

Problem #11: Ball Pressed Into Plate

Objectives
* Learn when implicit methods can run faster than explicit
methods.
* Learn to troubleshoot contact and convergence problems.

Problem Description
A hemispherical ball of brick elements is displaced into a
plate of brick elements. The plate is supported around its edges.

Input Filename: hemi.k

Procedure
Copy the input file to your local directory. The simulation
is initially set up to run explicitly. Start the job and
estimate how long it will take to finish. Stop the job
using stop when your patience runs thin.

1. How long will the explicit job take to run?

Edit the input deck and activate the implicit method.
Run the simulation and postprocess the results.

2. Does the problem run to completion?

3. What is the meaning of the negative eigenvalue warning message?

Modify the input deck to perform an eigenvalue analysis.
Extract the lowest 30 modes.

4. Are any zero or rigid body modes detected?

5. What was the problem with this model?

6. Why did this model run as an explicit analysis?

Use *BOUNDARY_SPC_SET to add appropriate constraints to the
ball (use the existing node set ID #1.) Repeat the simulation.

7. Examine the contact condition (HINT: cut a section plane
normal to the Y-direction using SPLANE buttons). How deeply
does the ball penetrate the plate?

To reduce penetration, use the penalty scale factor to
increase the contact interface penalty stiffness by 10x
(SLSFAC=1.0 on *CONTROL_CONTACT). Repeat the simulation.

8. How long does the simulation take to run using implicit
method?

Is the penetration problem improved?

Keywords

*BOUNDARY_PRESCRIBED_MOTION_SET
*BOUNDARY_SPC_SET
*CONTACT_SURFACE_TO_SURFACE
*CONTROL_CONTACT
*CONTROL_HOURGLASS
*CONTROL_IMPLICIT_AUTO
*CONTROL_IMPLICIT_DYNAMICS
$*CONTROL_IMPLICIT_EIGENVALUE
*CONTROL_IMPLICIT_GENERAL
*CONTROL_IMPLICIT_SOLUTION
*CONTROL_IMPLICIT_SOLVER
*CONTROL_TERMINATION
*DATABASE_BINARY_D3PLOT
*DATABASE_GLSTAT
*DATABASE_RCFORC
*DEFINE_CURVE
*ELEMENT_SOLID
*END
*KEYWORD
*MAT_ELASTIC
*MAT_ELASTIC
*NODE
*PART
*SECTION_SOLID
*SECTION_SOLID
*SET_NODE_LIST
*TITLE

Reduced Input

  *KEYWORD 
  *TITLE
  half ball impact problem
  $
  $ Units: m, s, kg, N
  $
  $ A. Tabiei
  $
  *CONTROL_TERMINATION
  $   ENDTIM   
        1.00
  $
  $========1=========2=========3=========4=========5=========6=========7=========8
  $
  *CONTROL_IMPLICIT_GENERAL
  $   imflag       dt0      iefs   nstepsb      igso
           0     0.010         0         0         0
  $
  *CONTROL_IMPLICIT_SOLUTION
  $  nlsolvr    ilimit    maxref     dctol     ectol     rctol     lstol
           0         0         0       0.0       0.0         0         0
  $    dnorm   divflag   inistif   nlprint
           0         0         0         0
  $
  *CONTROL_IMPLICIT_SOLVER
  $   lsolvr   prntflg    negeig
           0         0         0
  $
  *CONTROL_IMPLICIT_AUTO
  $    iauto    iteopt    itewin     dtmin     dtmax
           1        30         0       0.0       0.1
  $
  *CONTROL_IMPLICIT_DYNAMICS
  $    imass     gamma      beta
           0       0.0       0.0
  $$
  $*CONTROL_IMPLICIT_EIGENVALUE
  $$    neigv
  $        30
  $$
  $========1=========2=========3=========4=========5=========6=========7=========8
  $
  *CONTROL_CONTACT
  $   SLSFAC    RWPNAL    ISLCHK    SHLTHK    PENOPT    THKCHG     ORIEN
      0.1000                   0         1         0         0         0
  $   USRSTR    USRFAC     NSBCS    INTERM    XPENEN
           0         0         0         0      0.00
  $
  *CONTACT_SURFACE_TO_SURFACE
  $     SSID      MSID     SSTYP     MSTYP    SBOXID    MBOXID       SPR       MPR
           1         2         3         3         0         0         0         0
  $       FS        FD        DC         V       VDC    PENCHK        BT        DT
   0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00         0 0.000E+00 0.000E+00
  $      SFS       SFM       SST       MST      SFST      SFMT       FSF       VSF
   0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00 0.000E+00
  $ optional card A
  $     soft
           0
  $ optional card B
  $   penmax    thkopt    shlthk     snlog
         0.0         0         0         0
  $
  $---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
  $
  *DATABASE_BINARY_D3PLOT    
  5.0000E-03
  $
  *DATABASE_RCFORC
  1.0000E-06
  $
  *DATABASE_GLSTAT
  1.0000E-06
  $
  $---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
  $
  *MAT_ELASTIC                        
           1  7.850E+3  210.0E+9       0.3       
  *MAT_ELASTIC 
           2  7.850E+3  210.0E+9       0.3                                  
  *PART
   elastic plate                                                                  
           1         1         1      
  *PART
   elastic ball                                                                   
           2         2         2      
  *SECTION_SOLID                     
           1         0      
  *SECTION_SOLID                    
           2         0     
  *CONTROL_HOURGLASS
           5
  $---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
  *BOUNDARY_PRESCRIBED_MOTION_SET
           1         3         2         1       1.0
  *DEFINE_CURVE
           1 
        0.00000000E+00      0.00000000E+00
        1.00000000E+00      5.00000000E-01
        2.00000000E+00      5.00000000E-01
  $---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
  *SET_NODE_LIST                           
           1       
         515       518       521       524       527       530       533       536
         539       560       563       566       569       572       575       590
         593       596       599       602       605       631       633       635
         637       667       669       671       673       691       693       695
         697       704       707       710       713       716       719       745
         747       749       751       781       783       785       787       805
         807       809       811       817       819       821       823       829
         831
  $---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8 
  $$
  *BOUNDARY_SPC_SET
  $     NSID       CID      DOFX      DOFY      DOFZ     DOFRX     DOFRY     DOFRZ
           1         0         1         1         0         0         0         0
  $$
  $---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8 
  *END

Figures

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Animated Result

Result