RD-V: 0220 Foam Material (LAW70)

Foam material law under compression and tensile load cases.

The analysis shows the behavior of the foam material /MAT/LAW70 under compression and tensile load cases.

A cube (100mm*100mm*100mm) is modeled with solid elements.

The analysis is run for 4 cases:
  • With compression load case for a material without strain rate dependency and unloading curve
  • With compression load case for a material without strain rate dependency and hysteresis parameters
  • With tensile load case for a material without strain rate dependency and hysteresis parameters
  • With compression load case for a material with strain rate dependency and hysteresis parameters

The reaction force result is extracted from the rigid bodies which model the anchorage and loading condition.

Options and Keywords Used

Input Files

Before you begin, copy the file(s) used in this problem to your working directory.

Model Description

Units: Mg, s, mm, MPa

A cube (100mm*100mm*100mm) modeled with solid elements (/PROP/SOLID) and foam material (/MAT/LAW70) is compressed or extended in the vertical direction.

The nodes of the cube top surface are defined in a rigid body (/RBODY) with a vertical imposed displacement defined with a smooth function (/FUNCT_SMOOTH).

The nodes of the cube lower surface are also defined in a rigid body and its main node is clamped using a boundary condition (/BCS).

The secondary nodes of the rigid bodies are selected with a node set (/GRNOD) defined by box (/BOX).


Figure 1. Foam cube with rigid bodies

The material is defined with engineering stress versus engineering strain with several curves for the strain rate dependency.

The tensile behavior is defined with the scaling factor versus engineering strain curve multiplied by the compression engineering stress versus engineering strain curve(s).


Figure 2. Compression engineering stress versus engineering strain curve


Figure 3. Compression curve multiply by the tensile scaling factor curve
Model
Description
0220_foam_LAW70_0
Compression up to 95% of the initial solid block height
Single engineering stress versus engineering strain loading curve
Single unloading curve which the loading curve scaled by 0.2
0220_foam_LAW70_1
Compression up to 95% of the initial solid block height
Single engineering stress versus engineering strain loading curve
Unloading is defined with hysteresis parameters
0220_foam_LAW70_2
Tensile up to 50% of the initial solid block height
Single engineering stress versus engineering strain loading curve
Unloading is defined with hysteresis parameters
Tensile scale factor curve
0220_foam_LAW70_3
Compression up to 95% of the initial solid block height
Three engineering stress versus engineering strain loading curves
Unloading is defined with hysteresis parameters
Tensile scale factor curve

Results



Figure 4. Results

The engineering stress versus engineering stress computed from the rigid body force and nodal displacement give results which overlay exactly the input curve from the material.

The unloading behavior with model with the unloading curve (0220_foam_LAW70_0) is less realistic than the model with hysteresis behavior (0220_foam_LAW70_1).