RD-E: 5200 Creep and Stress Relaxation
The purpose of this example is to introduce how to use typical visco-elastic material to simulate creep and stress relaxation tests.
![ex_52_creep_stress](../../../images/solvers/ex_52_creep_stress.png)
Figure 1.
Options and Keywords Used
- /MAT/LAW40 (KELVINMAX)
- Boundary condition (/BCS)
- Rigid body (/RBODY)
- Concentrated force load (/CLOAD)
- Imposed displacement (/IMPDISP)
Input Files
Refer to Access the Model Files to download the required model file(s).
The model files used in this example are available in:
/radioss/example/52_cylinder_creep
Model Description
- For stress relaxation test: The foam sample has been compressed until a given strain and kept in this state.
- For creep test: The foam sample has been tensile under constant force.
![ex_52_creep_stress](../../../images/solvers/ex_52_creep_stress.png)
Figure 2. Problem Description
Units: mm, s, Mg, N, MPa
- Material Properties
- Initial density
- 2e-9 [Mg/mm3]
- Bulk modulus
- 66.67
- Long time shear modulus Ginf
- 10
- Shear modulus G1
- 90
- Decay constant
- 1 = 0.01 [1/ms]
Model Method
![ex_52_creep_test](../../../images/solvers/ex_52_creep_test.png)
Figure 3. Stress Relaxation Test under Constant Displacement and Creep Test under Constant Force
For stress relaxation test: The foam sample has been compressed under constant displacement (/IMPDISP).
For creep test: The foam sample has been tensile under constant force (/CLOAD).
Results
![ex_52_stress](../../../images/solvers/ex_52_stress.png)
Figure 4.
![ex_52_stress2](../../../images/solvers/ex_52_stress2.png)
Figure 5. Stress Relieved with Different Decay Constant in Stress Relaxation Test under Constant Displacement
![ex_52_sample](../../../images/solvers/ex_52_sample.png)
Figure 6.
![ex_52_sample2](../../../images/solvers/ex_52_sample2.png)
Figure 7. Sample Deformed with Decay Constant in Creep Test under Constant Force
![](../../../images/solvers/embim48.png)
![mat40_relax_time](../../../images/solvers/mat40_relax_time.png)
![ex_52_ti](../../../images/solvers/ex_52_ti.png)
The general case of viscous materials represents time-dependent in elastic behavior. Creep is time-depended deformation and stress relaxation is a time-depended decrease in stress. Viscous material can describe these two phenomenons. In Radioss, the following material laws describe viscous:
Visco-elastic Law
- /MAT/LAW34
- Visco-elastic generalized Maxwell model, Boltzmann (solids)
- /MAT/LAW35
- Visco-elastic generalized Maxwell-Kelvin-Voigt (shells + solids)
- /MAT/LAW38
- Visco-elastic tabulated (solids)
- /MAT/LAW40
- Visco-elastic generalized Maxwell-Kelvin (solids)
- /MAT/LAW42
- Ogden/Mooney-Rivlin with Prony viscosity (Hyperelastic materials)
- /MAT/LAW62
- Ogden (Hyperelastic materials)
- /MAT/LAW70
- Visco-elastic tabulated (solids)
- /MAT/LAW77
- Visco-elastic tabulated with porosity and air flow
Visco-elastic Plastic Law
- /MAT/LAW33
- Visco-elastic plastic (solids) and user-defined yield function
- /MAT/LAW52
- Gurson, visco-elasto-plastic porous metals, and strain rate dependent
- /MAT/LAW66
- Semi-analytical plastic model. Yield surface built from curves in tension, compression and shear + /VISC/PRONY
![ex_52_maxwell_model](../../../images/solvers/ex_52_maxwell_model.png)
Figure 8. Maxwell Model
![ex_52_kelvin_voigt_model](../../../images/solvers/ex_52_kelvin_voigt_model.png)
Figure 9. Kelvin_Voigt Model