Gravity — Welcome to LS-DYNA Examples

A simple model of a tire is placed under gravity loaded and bounces on a rigid wall.

Introduction

```*LOAD_BODY_Z
Tire Under Gravity Loading Bounces on a Rigid Wall
LS-DYNA Manual Section: *LOAD_BODY_Z

*RIGIDWALL_PLANAR Example: Tire Under Gravity Loading Bounces on a Rigid Wall

Description:
A simple model of a tire is placed under gravity loaded and bounces on a rigid
wall.

Model:
A positive gravity constant of 0.00981 mm/ms 2 is used to make the tire drop in
the negative z-direction. A *RIGIDWALL_PLANAR keyword is used to define the
ground. Nodes on the bottom of the tire are prevented from penetrating the
rigid wall by specifying them within the *RIGIDWALL_PLANAR command
(using a *SET_NODE_COLUMN keyword).

Results:
The rigid wall forces oscillate about the steady state, which is the weight of
the tire (W = 0.26 kN). Curiously, the tire damps out even though no damping is
specified within the model. See the example in *DAMPING_GLOBAL for an
explanation and fix.```

Keywords

```\$ * 2 discrete masses (10 kg each) at center of wheel to obtain proper weight
\$ * Gap between tire and ground = 0.2 mm
\$ * Mild steel (with strain rate effect)
\$ * Part 35 - wheel
\$ * Part 36 - tire
\$ * Shells (1 mm thick)
*CONTROL_ENERGY
*CONTROL_TERMINATION
*DATABASE_BINARY_D3PLOT
*DATABASE_BINARY_D3THDT
*DATABASE_GLSTAT
*DATABASE_HISTORY_NODE
*DATABASE_MATSUM
*DATABASE_NODOUT
*DATABASE_RWFORC
*DEFINE_CURVE
*ELEMENT_MASS
*ELEMENT_SHELL
*END
*KEYWORD
*MAT_PIECEWISE_LINEAR_PLASTICITY
*NODE
*PART
*RIGIDWALL_PLANAR
*SECTION_SHELL
*SET_NODE_COLUMN
*TITLE```

Reduced Input

```  *KEYWORD
*TITLE
A simple tire bouncing on the ground.
\$
\$  LSTC Example
\$
\$
\$  --- GRAVITY CHECK ---
\$
\$   steady state is reached around 150 ms
\$   m = 26.5534 kg ==> W = 0.26 kN
\$   Damping oscillations around s.s., which is 0.26 kN (from RWFORC file)
\$   Nodes demonstrate bouncing off ground (NODOUT)
\$
\$  Gravity modeled successfully using load curve and
\$     BASE ACCELERATION IN Z-DIRECTION - Body Load in Z
\$
\$ Note: The acceleration is in the negative z-direction even though
\$       all values needed to define acc. are positive.
\$
\$  * Shells (1 mm thick)
\$  * Mild steel (with strain rate effect)
\$  * Part 35 - wheel
\$  * Part 36 - tire
\$  * 2 discrete masses (10 kg each) at center of wheel to obtain proper weight
\$  * Gap between tire and ground = 0.2 mm
\$
\$  Units: mm, kg, ms, kN, GPa, kN-mm
\$
\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$
\$
\$\$\$\$  Control Ouput
\$
\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$
\$
\$...>....1....>....2....>....3....>....4....>....5....>....6....>....7....>....8
\$
*CONTROL_TERMINATION
\$   endtim    endcyc     dtmin    endeng    endmas
150.01         0       0.0       0.0       0.0
\$
*CONTROL_ENERGY
\$     hgen      rwen    slnten     rylen
2         2
\$
\$
*DATABASE_BINARY_D3PLOT
\$       dt       lcdt
10.0
\$
*DATABASE_BINARY_D3THDT
\$       dt       lcdt
999999
\$
*DATABASE_GLSTAT
\$       dt
0.2
\$
*DATABASE_MATSUM
\$       dt
0.2
\$
*DATABASE_NODOUT
\$       dt
0.2
\$
*DATABASE_HISTORY_NODE
\$      id1       id2       id3       id4       id5       id6       id7       id8
8914      8746      8918
\$
*DATABASE_RWFORC
\$       dt
0.2
\$
\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$
\$
\$\$\$\$  Gravity
\$
\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$
\$
\$...>....1....>....2....>....3....>....4....>....5....>....6....>....7....>....8
\$
\$
\$     lcid        df    lciddr        xc        yc        zc
1 9.810E-03
\$
\$
*DEFINE_CURVE
\$
\$     lcid      sidr      scla      sclo      offa      offo
1
\$
\$           abscissa            ordinate
0.00               1.000
1000.00               1.000
\$
\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$
\$
\$\$\$\$  Rigid Wall - The Ground
\$
\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$
\$
\$...>....1....>....2....>....3....>....4....>....5....>....6....>....7....>....8
\$
*RIGIDWALL_PLANAR
\$     nsid    nsidex     boxid
1         0         0
\$       xt        yt        zt        xh        yh        zh      fric
0.0       0.0    -279.2       0.0       0.0    -279.0       1.0
\$
\$
*SET_NODE_COLUMN
\$      sid
1
\$      nid
8901
8904
8911
8912
8913
8914
8919
8920
8921
8922
\$
\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$
\$
\$\$\$\$  Define Parts and Materials
\$
\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$
\$
\$...>....1....>....2....>....3....>....4....>....5....>....6....>....7....>....8
\$
*PART
\$      pid       sid       mid     eosid      hgid      grav    adpopt
wheel
35         1         1
tire
36         1         1
\$
\$
\$\$\$\$  Materials
\$
*MAT_PIECEWISE_LINEAR_PLASTICITY
\$...>....1....>....2....>....3....>....4....>....5....>....6....>....7....>....8
\$      mid        ro         e        pr      sigy      etan      eppf      tdel
1 0.783E-05     200.0       0.3     0.207               0.750
\$  Cowper/Symonds Strain Rate Parameters
\$        C         p      lcss      lcsr
40         5
\$  Plastic stress/strain curves
0.000     0.080     0.160     0.400     1.000
0.207     0.250     0.275     0.290     0.300
\$
\$
\$\$\$\$  Sections
\$
*SECTION_SHELL
\$...>....1....>....2....>....3....>....4....>....5....>....6....>....7....>....8
\$      sid    elform      shrf       nip     propt   qr/irid     icomp
1         2              3.0000
\$       t1        t2        t3        t4      nloc
1.00      1.00      1.00      1.00
\$
\$
\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$
\$
\$\$\$\$  Define Nodes and Elements
\$
\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$\$
\$
\$...>....1....>....2....>....3....>....4....>....5....>....6....>....7....>....8
\$
\$
\$\$\$\$\$\$\$  Nodal Mass Elements
\$
*ELEMENT_MASS
\$    eid     nid      mass
8730    8730      10.0
8746    8746      10.0
\$
*END```