OS-E: 0150 Large Displacement Analysis of Chassis

Demonstrates the use of 2D plate (shell) elements with large displacement analysis.



Figure 1. FE Model

Model Description

This example is of a chassis modeled with shell elements and solves for large displacement analysis with the load steps:
1
Front torsional stiffness
2
Rear torsional stiffness
3
Vertical bending stiffness
Rail and Cross members modeled with shell elements, 7 are connected via rigid elements.

Displacements (translations and rotations), which are large enough to render small deformation theory invalid; therefore, the initial stiffness matrix is not suitable to represent the problem. This may result in either small or large (finite) strains. Large displacements are those that are greater than the characteristic dimension of the model (thickness of the beam plate or shell). This is always a nonlinear problem. A typical rule of thumb, if strains exceed 5%, always switch LGDISP=1.

Large deformations (geometric nonlinearity) we update our stiffness matrix after each loading increment. If you switch LGDISP=1, then the recent stiffness that is taken to the next increment is already updated. Therefore, by having this on, the deformed geometry or an updated stiffness matrix will be taken into the next step.
FE Model
Element Types
CQUAD4
The linear material properties are:
MAT1
Young’s Modulus
2.1E5 MPA
Poisson Ratio
0.3
Density
7.85E-9
MATS1
YIELD Point
350

Results



Figure 2. Stress Contour and Plastic Strain Plot

Model Files

The model files used in this example include:

<install_directory>/demos/hwsolvers/optistruct/examples/SHELL_LGDISP.fem