Basics III

A tip load is applied to a cantilevered beam made of shell elements. The tip of the beam is constrained to be rigid.

LS-DYNA Implicit Workshop

Problem #3: Rigid Tip

Objective
* Learn the limitations of a linear approximation using a simple example.

Problem Description
A tip load is applied to a cantilevered beam made of shell elements. The tip of the
beam is constrained to be rigid.


Procedure
Copy the input file to your local directory Using an editor, view the input file and
answer the following questions:

1. How is the rigid tip modeled?
2. How long is the beam?

Run the simulation using the original input file.

3. What type of analysis was performed?

4. What is the tip deflection?

5. What is the angle of rotation of the rigid body (Note: rotations in the RBDOUT file
are given in radians)?

6. What is the maximum X-stress at the supported end?

7. What is the maximum X-stress in the rigid elements?

Copy the input file to a new directory. Modify the input
file to perform a nonlinear analysis, and re-run the simulation.

8. What is the tip deflection?

9. What is the angle of rotation of the rigid body?

10. What is the maximum X-stress at the supported end?

11. What is the maximum X-stress in the rigid elements?

Copy the input file to a new directory. Modify the input file to again perform a linear
analysis, but with the constrained nodal rigid body removed. Run the simulation.

12. What is the tip deflection?

13. What is the maximum X-stress at the supported end?

14. What is the maximum X-stress in the tip elements?

Why does stress develop in the rigid elements during the linear analysis? (Hint: plot
the (axial) X-displacement along the length of the beam for each simulation.)

*BOUNDARY_SPC_NODE
*CONSTRAINED_NODAL_RIGID_BODY
*CONTROL_IMPLICIT_GENERAL
*CONTROL_IMPLICIT_SOLUTION
*CONTROL_TERMINATION
*DATABASE_BINARY_D3PLOT
*DATABASE_RBDOUT
*DEFINE_CURVE
*ELEMENT_SHELL
*END
*KEYWORD
*LOAD_NODE_POINT
*MAT_ELASTIC
*NODE
*PART
*SECTION_SHELL
*SET_NODE_LIST
*TITLE

  *KEYWORD
  $
  *TITLE
  cantilevered shell strip w/ nodal rigid body end
  $
  $--------------
  $
  *CONTROL_TERMINATION
  $#  endtim    endcyc     dtmin    endeng    endmas    
    1.000000         0       0.0       0.0       0.0
  $
  $--------------
  $
  *CONTROL_IMPLICIT_GENERAL
  $#  imflag       dt0    imform      nsbs       igs     cnstn      form      
           1  1.000000
  $
  *CONTROL_IMPLICIT_SOLUTION
  $#  nsolvr    ilimit    maxref     dctol     ectol     rctol     lstol     
           1         0         0       0.0       0.0       0.0       0.0
  $#   dnorm    diverg     istif   nlprint    nlnorm    
           0         0         0         0         0
  $
  $--------------
  $
  *DATABASE_RBDOUT
  $#      dt    binary    
    1.000000
  $
  *DATABASE_BINARY_D3PLOT
  $#      dt      lcdt      beam     npltc     
    1.000000
  $
  $--------------
  $
  *CONSTRAINED_NODAL_RIGID_BODY
  $#     pid       cid      nsid     pnode      iprt    drflag    rrflag    
          99         0         1
  $
  *SET_NODE_LIST
  $#     sid       da1       da2       da3       da4       
           1       0.0       0.0       0.0       0.0
  $#    nid1      nid2      nid3      nid4      nid5      nid6      nid7      nid8
          15        31        32        16        14        30        46        47
          48
  $
  $--------------
  $
  *BOUNDARY_SPC_NODE
  $#     nid       cid      dofx      dofy      dofz     dofrx     dofry     dofrz
           1         0         1         1         1         1         1         1
          17         0         1         1         1         1         1         1
          33         0         1         1         1         1         1         1
  $
  $--------------
  $
  *LOAD_NODE_POINT
  $#     nid       dof      lcid        sf       cid        m1        m2        m3
          16         2         1  0.500000
          32         2         1  1.000000
          48         2         1  0.500000
  $
  *DEFINE_CURVE
  $#    lcid      sidr       sfa       sfo      offa      offo    dattyp    
           1         0       0.0       0.0       0.0       0.0
  $#                a1                  o1                  
                   0.0                 0.0
            1.00000000          5.00000000
            2.00000000          5.00000000
  $
  $--------------
  $
  *PART
  $# title                                                                        
  cantilevered shell                                                              
  $#     pid     secid       mid     eosid      hgid      grav    adpopt      tmid
           1         1         1
  $
  *SECTION_SHELL
  $#   secid    elform      shrf       nip     propt   qr/irid     icomp     setyp
           1        21  0.833300         3         3       0.0
  $#      t1        t2        t3        t4      nloc     marea     
    0.100000  0.100000  0.100000  0.100000         0       0.0
  $
  *MAT_ELASTIC
  $#     mid        ro         e        pr        da        db  not used  
           17.0000e-043.0000e+07  0.300000       0.0       0.0       0.0
  $
  *PART
  $# title                                                                        
  cantilevered shell                                                              
  $#     pid     secid       mid     eosid      hgid      grav    adpopt      tmid
           2         1         2
  $
  *MAT_ELASTIC
  $#     mid        ro         e        pr        da        db  not used  
           27.0000e-043.0000e+07  0.300000       0.0       0.0       0.0
  $
  $--------------
  $
  *END