Performing a simulation of a Sphere pressing on a plate for different material laws.

OBJECTIVES

1. To understand the different materials concern with Radioss Solver.
2. To assign recommended shell properties for crash analysis.
3. To understand the different classification of materials such as
4. To plot the different contours formed with use of various material laws and parameter change.

 

SLIDE 1

 

CASE 1 Run model FAILURE_JOHNSON_0000.rad as it is.

• Import the engine input file (FAILURE_JOHNSON_0000.rad) from the import tab in a solver deck.
• It will appears in wireframe mode.

 

 

 

• Click on the shaded mesh to view the mesh in shaded form

• Now click on analysis tab and select as Radioss as a solver.

 

• Give the input file destination as the solvers create a lot of instantaneous files, so better to save the files in a specific folder.
• The export option should be all – it will take all the components hidden too.
• Number of the run as 1 and Run option as analysis
• Options should be (-nt 4 means four CPU solves problems at a time)
• Click on the shaded mesh to view the mesh in shaded form.
• After completion of Radioss analysis, you will get the result card.

• Now change the mode from hyper mesh to hyper view
• Load the model of files created folder the file should be in form of .h3d
• .h3d file is an animation file that is a combined file of animation files( A01, A02, A03….)

                                

                                                                     

• Click on the contours option to get the different required result values of stress, displacement, hourglass energy, etc.
• The dynamic max-min result can be calculated.

• If you want to plot different graphs. Change the mode to hypergraph 2D.
• Hypergraph can be accessed with the file name with format(runname_T01). This file format should be in runname_T01

SLIDE 2

 

CASE 1 Run model as Law2_epsmax_failure

Johnson-Cook Plasticity Model (LAW2)

In this law the material behaves as linear elastic when the equivalent stress is lower than the yield stress.

For a higher value of stress, the material behavior is plastic. This law is valid for brick, shell, truss and beam elements. The relation between describing stress during plastic deformation is given in a closed-form.

Plastic strain at rupture

A typical stress-strain curve in the plastic region. When the maximum stress is reached during computation, the stress remains constant and material undergoes deformation until the maximum plastic strain. Element rupture occurs if the plastic strain is larger than ε_max . If the element is a shell, the ruptured element is deleted.

If the element is a solid element, the ruptured element has its deviatoric stress tensor permanently set to zero, but the element is not deleted. Therefore, the material rupture is modeled without any damage effect.

 

• Import the engine input file (FAILURE_JOHNSON_0000.rad) from import tab in a solver deck.
• It will appear in wireframe mode.

• Click on the shaded mesh to view the mesh in shaded form

• Now click on the analysis tab and select as Radioss as a solver.

• Give the input file destination as the solvers create lot of instantaneous files, so better to save the files in a specific folder.
• The export option should be all – it will take all the components hidden too.
• Number of the run as 1 and Run option as analysis
• Options should be (-nt 4 means four CPU solves problems at a time)
• Click on the shaded mesh to view the mesh in shaded form.
• After completion of Radioss analysis, you will get the result card.

• Now change the mode from hyper mesh to hyper view
• Load the model of files created folder the file should be in the form of .h3d
• .h3d file is an animation file that is a combined file of animation files( A01, A02, A03….)

• Click on the contours option to get the different required result values of stress, displacement, hourglass energy etc.
• The dynamic max-min result can be calculated.

• If you want to plot different graphs. Change the mode to hypergraph 2D.
• Hypergraph can be accessed with the file name with format(runname_T01). This file format should be in runname_T01

CASE 2 In /FAIL/JOHNSON, Change Ifail_sh =1, Dadv = 1 and  Ixfem = 1. Run the model as Law2_epsmax_crack

• Import the engine input file (FAILURE_JOHNSON_0000.rad) from the import tab in a solver deck.
• It will appear in wireframe mode.

• Click on the shaded mesh to view the mesh in shaded form

Click on the property card to change the

• Ifail_sh - Shell failure flag -  (Integer value)
• If Ixfem =0: failure - element deleted
• If Ixfem =1: failure - element cracked 2
• = 1: (Default) Shell is deleted or cracked.
• Dadv - Criterion for the crack advancement (Only active if with Ixfem =1)
• (Real between 0 and 1)
• = 1: (Default)
• Ixfem - XFEM flag (for /PROP/SHELL, /PROP/SH_SANDW, and /PROP/TYPE51 properties only)
• = 1 means - XFEM formulation 2
• = 0 (Default) menas - Without XFEM

Two different failures (rupture or crack) are introduced in this failure model. The failure criterion is calculated, as:

• Element rupture (Ixfem=0):

Element rupture (deleted) if D > 1

• Element crack (Ixfem=1):

Element cracked, if:

• This element has no failed neighbors and D > 1, then in this case, new crack initialization in element.
• This element has failed neighbors and D > Dadv, then in this case, crack advanced and Dadv used for crack advancement. Dadv will be used if existing crack arrives to a boundary of an element. Element deleted, if a second crack arrives to the same element.

• Now click on the analysis tab and select as Radioss as a solver.

• Give the input file destination as the solvers create lot of instantaneous files, so better to save the files in a specific folder.
• The export option should be all – it will take all the components hidden too.
• Number of run as 1 and Run option as analysis
• Options should be (-nt 4 means four CPU solves problems at a time)
• Click on the shaded mesh to view the mesh in shaded form.
• After completion of Radioss analysis you will get result card.

• Now change the mode from hyper mesh to hyper view
• Load the model of files created folder the file should be in the form of .h3d
• .h3d file is an animation file that is a combined file of animation files( A01, A02, A03….)

 

• Click on the contours option to get the different required result values of stress, displacement, hourglass energy etc.
• The dynamic max-min result can be calculated.

CASE 3 Delete the /FAIL/JOHNSON card. Run the model as Law2_epsmax_nofail

• Import the engine input file (FAILURE_JOHNSON_0000.rad) from the import tab in a solver deck.
• It will appears in wireframe mode.

• Click on the shaded mesh to view the mesh in shaded form

• Delete the /FAIL/JOHNSON card
• Applying these properties we can control the accuracy of and time required for simulation.

 

 

• Now click on the analysis tab and select as Radioss as a solver.

• Give the input file destination as the solvers create a lot of instantaneous files, so better to save the files in a specific folder.
• The export option should be all – it will take all the components hidden too.
• Number of run as 1 and Run option as analysis
• Options should be (-nt 4 means four CPU solves problems at a time)
• Click on the shaded mesh to view the mesh in shaded form.
• After completion of Radioss analysis you will get the result card.

• Now change the mode from hyper mesh to hyper view
• Load the model of files created folder the file should be in the form of .h3d
• .h3d file is an animation file that is a combined file of animation files( A01, A02, A03….)

• Click on the contours option to get the different required result values of stress, displacement, hourglass energy, etc.
• The dynamic max-min result can be calculated.

CASE 4 Delete the value of Eps_p_max and run the model as Law2

• Import the engine input file (FAILURE_JOHNSON_0000.rad) from the import tab in a solver deck.
• It will appear in wireframe mode.

• Click on shaded mesh to view the mesh in shaded form

• Delete the value of EPS_P_max.
• Ε_max_p = Failure plastic strain -- Default = 1030 (Real)
• Now click on analysis tab and select as Radioss as a solver.

• Give the input file destination as the solvers create a lot of instantaneous files, so better to save the files in a specific folder.
• The export option should be all – it will take the all the components hidden too.
• Number of the run as 1 and Run option as analysis
• Options should be (-nt 4 means four CPU solves problems at a time)
• Click on the shaded mesh to view the mesh in shaded form.
• After completion of Radioss analysis, you will get the result card.

• Now change the mode from hyper mesh to hyper view
• Load the model of files created folder the file should be in form of .h3d
• .h3d file is an animation file that is a combined file of animation files( A01, A02, A03….)

• Click on the contours option to get the different required result values of stress, displacement, hourglass energy, etc.
• The dynamic max-min result can be calculated.

CASE 5 convert this material model to Law 1 Elastic with the same density, E, nu and run.

• Import the engine input file (FAILURE_JOHNSON_0000.rad) from the import tab in a solver deck.
• It will appear in wireframe mode.

 

• Click on the shaded mesh to view the mesh in shaded form

• Change the material card to M1 which is only elastic material.
• This leads the material properties to be in the elastic zone only.

 

 

• Now click on analysis tab and select as Radioss as a solver.
• Give the input file destination as the solvers create lot of instantaneous files, so better to save the files in a specific folder.
• Export option should be all – it will take the all the components hidden too.
• Number of run as 1 and Run option as analysis
• Options should be (-nt 4 means four CPU solves problems at a time)
• Click on shaded mesh to view the mesh in shaded form.
• After completion of Radioss analysis you will get result card.

• Now change the mode from hyper mesh to hyper view.
• Load the model of files created folder the file should be in the form of .h3d
• .h3d file is an animation file that is a combined file of animation files( A01, A02, A03….)

• Click on the contours option to get the different required result values of stress, displacement, hourglass energy etc.
• The dynamic max-min result can be calculated.

SLIDE 3

CASE 6 convert this material model to Law 27.

• Import the engine input file (LAW27_0000.rad) from the import tab in a solver deck.
• It will appear in wireframe mode.

• Click on shaded mesh to view the mesh in shaded form

• Applying these properties we can control the accuracy of and time required for simulation.

 

 

 

 

• Now click on the analysis tab and select as Radioss as a solver.
• Give the input file destination as the solvers create lot of instantaneous files, so better to save the files in a specific folder.
• Export option should be all – it will take the all the components hidden too.
• Number of run as 1 and Run option as analysis
• Options should be (-nt 4 means four CPU solves problems at a time)
• Click on the shaded mesh to view the mesh in shaded form.
• After completion of Radioss analysis, you will get the result card.

• Now change the mode from hyper mesh to hyper view
• Load the model of files created folder the file should be in the form of .h3d
• .h3d file is an animation file that is a combined file of animation files( A01, A02, A03….)

• Click on the contours option to get the different required result values of stress, displacement, hourglass energy etc.
• The dynamic max-min result can be calculated.

 

 

COMPARISION

SR.NO	CASE NAME	TOTAL NO.OF CYCLE	ENERGY ERROR	MASS ERROR	SIMULATION TIME
1	CASE 1 Run model FAILURE_JOHNSON_0000.rad as it is.	49480	0.2%	0%	89.36 s
2	CASE 1 Run model as Law2_epsmax_failure	47969	0.3%	0%	58.56 s
3	CASE 2 In /FAIL/JOHNSON, Change Ifail_sh =1, Dadv = 1 and  Ixfem = 1. Run the model as Law2_epsmax_crack	49391	3.8%	0%	160.62 s
4	CASE 3 Delete the /FAIL/JOHNSON card. Run the model as Law2_epsmax_nofail	49405	0.8%	0%	67.78 s
5	CASE 4 Delete the value of Eps_p_max and run the model as Law2	49304	1.1%	0%	69.04 s
6	CASE 5 convert this material model to Law 1 Elastic with same density, E, nu and run.	49480	0.2%	0%	68.75 s
7	CASE 6 convert this material model to Law 27.	49541	1.2%	0%	72.34 s

 

The Energy Error computed by RADIOSS is a percentage.

• If the error is negative, it means that some energy has been dissipated.
• Negative Energy Error since it is not counted in the energy balance. The normal amount of Hourglass energy is about 10% to15%.
• If the error is positive, there is an energy creation. In case of using QEPH shell formulation or fully integrated elements, the Energy
• Error can be slightly positive since there is no Hourglass energy and the computation is much more accurate. An error of 1%or 2% will be acceptable.

 

The Mass error is 0% which is acceptable as no change has happened to mass.

The Simulation time for Law2_epsmax_crack is much more compared to others.

• In this case Dadv- Criterion for the crack advancement (Only active if with Ixfem =1), Ixfem- XFEM flag (for /PROP/SHELL) are introduced.
• When we are not using any failure criteria simulation time required is quite less as compared to others.

 

• The elastic material (M1) is not used that much because as force is removed it will come back to its original shape. Elastic materials obey the Hooks’s Law. The material is under the elastic limit.
• If we are using the failure_Johnson criteria using these properties we can control the accuracy of and time required for simulation. Recommended shell properties lead to better energy dissipations results in getting an accurate level of stress.

 

In law 2_eps_max_crack  we are using Failure plastic strain. If the value of eps_max is less than the induced plastic strain, the element gets deleted from the system. As shown in the figure. The other values in material card such as

• Ifail_sh - Shell failure flag -  (Integer value)
• If Ixfem =0: failure - element deleted
• If Ixfem =1: failure - element cracked 2
• = 1: (Default) Shell is deleted or cracked.
• Dadv - Criterion for the crack advancement (Only active if with Ixfem =1)
• (Real between 0 and 1)
• = 1: (Default)
• Ixfem - XFEM flag (for /PROP/SHELL, /PROP/SH_SANDW, and /PROP/TYPE51 properties only)
• = 1 means - XFEM formulation 2
• = 0 (Default) menas - Without XFEM
• If we are using the eps_max_ no fail criteria using these properties we can control the accuracy of and time required for simulation. Recommended shell properties leads to better energy dissipations results in getting an accurate level of stress. Elements get cracked and remain in the system.

 

• If we are using the eps_max_failure criteria using these properties we can control the accuracy of and time required for simulation. Recommended shell properties lead to better energy dissipations results in getting an accurate level of stress. Failure of plastic strain. If the value of eps_max is less than the induced plastic strain, the element gets deleted from the system. As shown in the figure.
• In law 2_eps_max_crack we are using Failure plastic strain. If the value of eps_max is less than the induced plastic strain, the element gets cracked or deleted from the system. As shown in the figure.

 

 

• This law allows the modeling of material damage and brittle failure in two principal directions.
• This law is only applicable to shell elements. It is compatible with Shell Property (/PROP/TYPE1) and Sandwich Shell Property (/PROP/TYPE11).
• The ICC flag defines the effect of strain rate on the maximum material stress σ_max. 

CONCLUSION:

1. There are two different types of radioss files namely engine file (runname_0001.rad) and starter file (runname_0000.rad).
2. Learn about how to change the materials using various types of material parameters of radioss files.
3. The use of different shell properties and their use. Creation of property cards of different shell elements.
4. QEPH cell formation for fully integrated elements the energy error can be slightly positive since there is no hourglass energy and the computation is much more accurate.
5. An error of one or two percent will be acceptable otherwise any positive energy error means energy has been created which indicates a model issue.
6. The Mass error is 0% which is acceptable as no change has happened to mass.
7. The Simulation time for Law2_epsmax_crack is much more compared to others.
8. To understand the different classification of materials such as

• Isotropic Elasticity • Isotropic Elasto-Plastic • Composite and Anisotropic • Viscous
• Hydrodynamic • Explosives

9. To plot the different contours formed with use of various material laws and parameter change.
10. Understand the various materials with their failure modes, crack generation, and propagation. Learned about the elements cracking and deleting from the system.
11. Changing the material parameter we can get the exact similar behavior of material failing.