Assignment 4-RADIOSS Material Laws Challenge
AIM:
To run the simualtion for the plate and rigid ball by using Jhonson Cook Material and Elasto Plastic Material with Brittle Failure as per the cases using Radioss solver.
OBJECTIVE:
1. Law 2 (file: FAILURE_JOHNSON_0000.rad) - base simulation.
2. Law 2 (file: FAILURE_JOHNSON_0000.rad) with Ifail_sh = 1, Dadv = 1, and Ixfem = 1.
3. Law 2 (file: starter file for case 2) with fail/JOHNSON card deleted.
4. Law 2 (file: starter file for case 3) with EPS_p_max value deleted
5. Law 1 (file: FAILURE_JOHNSON_0000.rad) with fail/JOHNSON card deleted and values for density, E, nu assigned
6. Law 27 (file: LAW27_0000.rad) with recommended shell properties
7. Law 36 (file: LAW27_0000.rad) with recommended shell properties and given reference curve.
THEORY:
In FEA,the materials are specified to conduct simulations and analyze how a particular material behaves under certain stress and loading conditions.
The attention should be provided to the material type chosen and the material properties provided. There could be different material properties needed as input to fully characterize a material for analysis purposes. Any unclear or illogical data provided during material characterization will lead to uncertain results.
Choosing the right material and providing the reliable material data in performing a simulation is very important.
RADIOSS provides one of the most comprehensive material and rupture libraries in the industry. The material laws and rupture criteria span across definitions for concrete, foam, rubber, steel, composites,biomaterials, and more. In Radioss,We are specifying the materials and type,The materials are categorized in two forms,
1) In the form of Material Cards [Material Laws]:
- Law 1 – Elastic.
- Law 2 – Johnson-Cook.
- Law 27 – Elastic-Plastic Brittle.
- Law 36 – Elastic-Plastic Tabulated.
- Law 42 – Ogden (Visco Hyperelastic).
- Law 70 – Foam.
2) In the form of Material Properties:
- Isotropic Elasticity.
- Isotropic Elasto-Plastic.
- Composite and Anisotropic.
- Viscous.
- Hydrodynamic.
- Explosives.
Law 1 [Isotropic Elasticity]:
This Law /MAT/ELAST defines an isotropic, linear elastic material using Hooke’s law. This law represents a linear relationship between stress and strain. It is available for truss, beam (type 3 only), shell and solid elements.
Useful for elements attached to rigid body.This material law is used to model purely elastic materials.
This law is only applicable for small deformations.
The material stiffness is determined by only two values: the Young’s modulus (E), and Poisson’s ratio (`nu`). The shear modulus (G) can be computed using E and `nu`.
`G=E/2(1+nu)`
Isotropic Elastic Plastic Piecewise Linear Material [Law36] :
This is a Isotropic elasto-plastic material.
It's a user-defined function for the work-hardening portion of the stress-strain curve.
It's available for brick and shell elements.
Elastic portion of material stress-strain curve defined by Young modulus and Poisson’s ratio.
Material plasticity curves can be given for up an arbitrary number of strain rates.
Linear interpolation of strain-stress curve.
i) For a given strain rate.
ii) For a given plastic strain.
In order to avoid poor curve extrapolation during the strain calculation, a dummy curve defined for a high strain rate value can be added in the model—typically the highest strain rate curve is repeated.
The curves have to be defined such as they don’t intersect themselves in the strain range being used. Otherwise the calculation may fail.
Elasto-Plastic Material with Brittle Failure [Law27] :
This law combines an isotropic elasto-plastic Johnson-Cook material model with an orthotropic brittle failure model. Material damage is accounted for prior to failure. Failure and damage occur only in tension. This law is applicable only for shells.
Yield surface definition same as Johnson-Cook (Law2).
Useful for modeling brittle failure of glass.
Damage and rupture defined with 4 parameters for each principal direction:
`e_t` = Strain at the beginning of tensile failure.
`e_m` = Maximum tensile strain at which the stress in the element is set to a value dependent on dmax1.
`d_max` = Maximum damage factor ef = Maximum tensile strain for element deletion.
Viscous Material:
The viscous materials are classified into two types called:
1) Hyper Elastic [/MAT/OGDEN or /MAT/LAW42 : Ogden, Mooney-Rivlin]:
They are Visco Hyperelastic behavior (non-linear elastic).
This law is generally used to model incompressible rubbers, polymers, foams, and elastomers.
This material can be used with shell and solid elements.
Generally used to model polymers and elastomers.
2) Tabulated Foam [/MAT/FOAM_TAB or /MAT/LAW70: Tabulated Foam]:
Visco-elastic behavior
Stress – strain relationship defined by functions according to strain rate
Unloading behavior defined by:
`***`Curves.
`***`Hysteresis Parameters.
PROCEDURE:
Phase 1-Import the Starter File into the Solver Deck Radioss.
While opening hypermesh software,A user profile window will pop up,Switch to the radioss user profile as shown in below figure and start importing the model into the solver deck.
Now after switch the user profile to radioss,import the model (starter file) into the radioss solver deck.
To import the model,Go to Standard Panel >> Import >> Import Solver Deck.
Import Solver Deck option should be selected to import the radioss starter file.
Here the import browser will appear as shown, Select the appropriate starter file to import into GUI.
Switch the File Type to Radioss Block and import the model into GUI.
Here the model is in wireframe mode,Switch to the shaded mode as shown.
To switch to shaded mode,Go to Visualization Tab >> Shaded Elements and Mesh Lines.
Visualization Tab to Switch to the Shaded Elements and Mesh Lines.
Case 1-Running the Simulation as it is default:
Now after importing the model into the GUI,Go to the solver browser and select the begin card to inorder to check the unit system,which is shown.
Now go and check the material card by selecting it in model browser inorder to check whether the appropriate properties have been assigned or not,The material property card is shown.
Now go and check the property card.In the property the parameters have been assigned to the material given,Which is shown.
Now run the simulation,To run simulation,Go to Analysis Panel as shown.
Go to Analysis Panel >> Radioss >> Select the Input File >> Save it in Different Folder and Rename it as Case-1 >> Run.
Check the Include Connectors,If there are any connectors in the model,The connectors will also be taken into account.
Type -NT 4 in options tab,This will make the simulation faster.
Where NT indicates No of threads,4 indicates assigning the task to 4 cores in the system.
Here save the input file in a different folder, and rename it as case-1 which is shown in below figure 30.
Now run the solver by hitting on radioss.
After completing the simulation,the radioss will pop up a solver window stating Radioss Job Completed which indicates the simulation has been completed,Which is shown.
After running the simulation,The animation files will be generated where we specified a location to store the files which is shown.
Now go and open the 00001.out file with notepad.
The obtained values for Energy Error,Mass Error,Internal Energy Error,Kinetic Energy Error and Contact Energy Error has been shown.
Obtained values for Energy Error,Mass Error,Internal Energy Error,Kinetic Energy Error and Contact Energy Error.
The values obtained for this cycle are
`***`Energy Error-0.8%
`***`Internal Energy-0.2730E+05
`***`Kinetic Energy-67.81
`***`External Work-0.2721E+05
`***`Elapsed Time-95.36s
`***`Mass Error-0
`***`Total No of Cycles-49380
Next the 00001.rad file is opened to see the Tstop and Tfrequency value which is shown.
Phase 5 - Postprocessing
1) Review the Simulation using HyperView :
Hyperview allows for loading and viewing result files obtained from several sources.
Based on the solver type of the files and the results you would like to visualize and analyze,there are differnt ways to load the input deck and their corresponding results into hyperview.
First to begin the postprocessing in the Hypermesh,Split the Screen as shown.
Import the animation file .h3d into the hyperview.
And then activate the Client HyperView.
To access the load model panel, Select Load Model Button from the HyperView Panel and open .h3d file as shown.
After loading the model into hyperview,It will be represented as shown.
After importing the .h3d file into the GUI,Enable the contour.
The contour tool create contour plots of a model graphically visualize the analysis results.
To enable contour,Go to Results ToolBar >> Contour.
Now switch to the Von Misses Stress in result type and select the component,select the averaging method as simple and
then click apply as shown.
After applying ,Run the Simulation,The Simulation animation is shown.
2) Plot the graphs using -Hypergraph 2D:
Now plot the graphs using Hypergraph 2D,We are plotting the graphs to see what is happening in the rail component.
Hypergraph 2D is a powerful data analysis and plotting tool with interfaces to many popular file formats.
It is sophisicated math engine capable of processing even the most complex mathematical expressions.
Hypergraph 2D combines these features with high quality presentation output and customization capabilities to create a complete data analysis system for any organization.
Here switch to the Hypergraph 2D to plot the graphs.
To switch,Go to Client Selector >> Choose the Hypergraph 2D as shown.
The first graph is plotted for the Rigid Wall Forces.
To plot the graph,Go to Hypergraph 2D >> Data File >>Element_Formulation-Shell-3_assignmentT01 >> Apply.
Select the Appropriate T01 File.
Plotting Graph for Rigid Wall Forces:
Here the graph has been plotted for the Rigid Wall Forces as shown in below Figure 30.
There are various parameters in Rigid Wall like Normal Force,Tangent Force,FX-X Total Force,FY-Y Total Force,FZ-Z Total Force,Total Resultant Force.
We are selecting only Total Resultant Force,Because we don't know the exact axis of the component placed,So that's why we are selecting Total Resultant Force and then plotting the graph.
While plotting the graph,Units profile window will pop up,There select solver units and then plot the graph,Because the graphs will be plotted according to the solver units.
Now plot the graph for the rigid wall forces which is shown.
Rigid Wall Forces:
All Energies Graph:
All Energies Graph Animation:
Internal Energy:
Kinetic Energy:
Total Energy:
Contact Energy:
Hourglass Energy:
Case 2-Change the Values in Jhonson Failure Card:
Here the Jhonsons Failure card is edited,and the values have been given in the failure card as per the values given the question.
But the law is same [LAW 2],Only the failure card is edited.
The values which are to be changed are Ifail_sh=1,Dadv=1,Ixfem=1.
The values have been given in the failure card which is shown.
Now run the simulation using radioss,After running the simulation,The animation and TH files will be obtained in a required location,which is shown.
Now go and open the 00001.out file with notepad. The obtained values for Energy Error,Mass Error,Internal Energy Error,Kinetic Energy Error and Contact Energy Error has been shown.
Obtained values for Energy Error,Mass Error,Internal Energy Error,Kinetic Energy Error and Contact Energy Error.
The values obtained for this cycle are
`***`Energy Error-4.1%
`***`Internal Energy-0.3082E+05
`***`Kinetic Energy-141.9
`***`External Work-0.2980E+05
`***`Elapsed Time-134.34s
`***`Mass Error-0
`***`Total No of Cycles-49217
1) Review the Simulation using -HyperView:
After completion of running the simulation,Switch to the hyperview.
Open the appropriate .h3d file to review the simulation.
The .h3d file is loaded and it is shown
2) Plot the graphs using-Hypergraph 2D:
Now switch to the Hypergraph 2D and plot the graphs.
The rigid wall forces graph is plotted which is shown
Case 3-Delete the Failure Jhonson Card :
Here the failure card is deleted to see any changes happening the result.
Delete Failure Card.
Now run the simulation using radioss,After running the simulation,The animation and TH files will be obtained in a required location,which is shown.
Now go and open the 00001.out file with notepad.
The obtained values for Energy Error,Mass Error,Internal Energy Error,Kinetic Energy Error and Contact Energy Error has been shown
Obtained values for Energy Error,Mass Error,Internal Energy Error,Kinetic Energy Error and Contact Energy Error.
The values obtained for this cycle are
`***`Energy Error-0.8%
`***`Internal Energy-0.2744E+05
`***`Kinetic Energy-87.08
`***`External Work-0.2736E+05
`***`Mass Error-0
`***`Elapsed Time- 96.79 s
`***`Total No of Cycles-49407
1) Review the Simulation using -HyperView:
After completion of running the simulation,Switch to the hyperview.
Open the appropriate .h3d file to review the simulation.
The .h3d file is loaded and it is shown in below Figure 52.
Here the shell elements are getting deleted,when it reaches the maximum plastic strain epsmax value which is shown.
2) Plot the graphs using-Hypergraph 2D:
Now switch to the Hypergraph 2D and plot the graphs.
The rigid wall forces graph is plotted which is shown
Case 4 - Delete the EPS_P_Max Value from the Material Card:
Here delete the value of EPS_P_Max value and run the model with the name LAW2 but the same material card.
The value of plastic strain is removed which is shown.
Now run the simulation using radioss,After running the simulation,The animation and TH files will be obtained in a required location,which is shown.
Now go and open the 00001.out file with notepad.
The obtained values for Energy Error,Mass Error,Internal Energy Error,Kinetic Energy Error and Contact Energy Error has been shown.
Obtained values for Energy Error,Mass Error,Internal Energy Error,Kinetic Energy Error and Contact Energy Error.
The values obtained for this cycle are
`***`Energy Error-1.1%
`***`Internal Energy-0.3879E+05
`***`Kinetic Energy-3.931
`***`External Work-0.3838E+05
`***`Mass Error-0
`***`Elapsed Time- 131.47s
`***`Total No of Cycles-49303
1) Review the Simulation using -HyperView:
After completion of running the simulation,Switch to the hyperview.
Open the appropriate .h3d file to review the simulation.
The .h3d file is loaded and it is shown in below Figure 62.
Here EPS_P_Max=0,So the shell elements will not be deleted which is shown
2) Plot the graphs using-Hypergraph 2D:
Now switch to the Hypergraph 2D and plot the graphs.
The rigid wall forces graph is plotted which is shown
Case 5 - Change the Material Card to LAW1:
Here change the material card to LAW1,Here it will be elastic behaviour.
Don't change any material properties,Use default material properties like `rho`density,`E`youngs modulus and `nu`poissons ratio.
Now run the simulation using radioss,After running the simulation,The animation and TH files will be obtained in a required location,which is shown.
Now go and open the 00001.out file with notepad. The obtained values for Energy Error,Mass Error,Internal Energy Error,Kinetic Energy Error and Contact Energy Error has been shown.
Obtained values for Energy Error,Mass Error,Internal Energy Error,Kinetic Energy Error and Contact Energy Error.
The values obtained for this cycle are
`***`Energy Error- -7.4%
`***`Internal Energy-0.7195E+06
`***`Kinetic Energy-425.7
`***`External Work-0.7780E+06
`***`Mass Error-0
`***`Elapsed Time- 117.85s
`***`Total No of Cycles-47900
1) Review the Simulation using -HyperView:
After completion of running the simulation,Switch to the hyperview.
Open the appropriate .h3d file to review the simulation.
The .h3d file is loaded and it is shown in below.
Here EPS_P_Max=0,So the shell elements will not be deleted which is shown in below.
The elements will not even split during the collison,Cause the LAW1 material card is assigned to the rupture plate.
So there will be an elastic behaviour[Ability to regain its original size and shape].
2) Plot the graphs using-Hypergraph 2D:
Now switch to the Hypergraph 2D and plot the graphs.
The rigid wall forces graph is plotted which is shown.
Case 6-Change the Material Card to LAW27 :
Here change the material card to LAW27 and change the shell properties to the recommended shell peroperties.
It is an isotropic elastoplastic jhonson cook material model with an orthographic brittle failure model.
Now run the simulation using radioss,After running the simulation,The animation and TH files will be obtained in a required location,which is shown.
Now go and open the 00001.out file with notepad.
The obtained values for Energy Error,Mass Error,Internal Energy Error,Kinetic Energy Error and Contact Energy Error has been shown.
Obtained values for Energy Error,Mass Error,Internal Energy Error,Kinetic Energy Error and Contact Energy Error.
The values obtained for this cycle are
`***`Energy Error- 0.8%
`***`Internal Energy-0.2954E+05
`***`Kinetic Energy-65
`***`External Work-0.2940E+05
`***`Mass Error-0
`***`Elapsed Time- 155.47s
`***`Total No of Cycles-49506
1) Review the Simulation using -HyperView:
After completion of running the simulation,Switch to the hyperview.
Open the appropriate .h3d file to review the simulation.
The .h3d file is loaded and it is shown in below Figure 82.
Here the shell elements will be deleted due to brittleness which is shown.
2) Plot the graphs using-Hypergraph 2D:
Now switch to the Hypergraph 2D and plot the graphs.
The rigid wall forces graph is plotted which is shown.
Case 7- Change the Material Card to LAW36 :
Here change the material card to LAW36.
A shell paremeters are changed to the recommended parameters.
It's a elasto plastic piecewise linear material.
Changed Material Card and Shell Element Parametrs.
After Defining the material card,We have to define a stress strain curve for this material.
We only want plastic region out of it,So we have to define a curve using given plastic strain and post-yield stress value manually.
The curve will be defined based on the values given which is shown.
To create a Curve,Right Click on the Model Browser >> Create >> Curve >> Window Will Pop Up >> Define a Curve using Platic Strains and Post-Yield Stress Values.
Now run the simulation using radioss,After running the simulation,The animation and TH files will be obtained in a required location,which is shown.
Now go and open the 00001.out file with notepad.
The obtained values for Energy Error,Mass Error,Internal Energy Error,Kinetic Energy Error and Contact Energy Error has been shown in below.
Obtained values for Energy Error,Mass Error,Internal Energy Error,Kinetic Energy Error and Contact Energy Error.
The values obtained for this cycle are
`***`Energy Error- 0.7%
`***`Internal Energy-0.7078E+05
`***`Kinetic Energy-21.31
`***`External Work-0.7046E+05
`***`Mass Error-0
`***`Elapsed Time-143.60s
`***`Total No of Cycles-49053
1) Review the Simulation using -HyperView:
After completion of running the simulation,Switch to the hyperview.
Open the appropriate .h3d file to review the simulation.
The .h3d file is loaded and it is shown in below Figure 95.
Here the shell elements will be deleted once it reaches maximum plastic strain which is shown in below Figure 95.
Cause the material is assigned with both elastic and plastic.
2) Plot the graphs using-Hypergraph 2D:
Now switch to the Hypergraph 2D and plot the graphs.
The rigid wall forces graph is plotted which is shown.
Comparison of all the 7 Cases :
|
Cases |
Energy Error |
Internal Energy |
Kinetic Energy |
External Work |
Mass Error |
Elapsed Time |
Total Number of Cycles |
Material Used |
Changes in Material Parameters |
Element Failure Behaviour |
|
Case-1 |
0.8% |
0.2730E+05 |
67.81 |
0.2721E+05 |
0 |
95.36s |
49380 |
Jhoonson- Cook [LAW2] |
Used Default Shell Parameters and Runned the Simulation. |
Elements Deleted. |
|
Case-2 |
4.1% |
0.3082E+05 |
141.9 |
0.2980E+05 |
0 |
134.34s |
49217 |
Jhoonson- Cook [LAW2] |
Changed the Values for Ifail_sh,Dadv,Ixfem in the Failure Card. |
Elements will be Cracked and Deleted. |
|
Case-3 |
0.8% |
0.2744E+05 |
87.08 |
0.2736E+05 |
0 |
96.79 s |
49407 |
Jhoonson- Cook [LAW2] |
Deleted the Failure Card from the Model Browser. |
Elements Deleted. |
|
Case- 4 |
1.1% |
0.3879E+05 |
3.931 |
0.3838E+05 |
0 |
131.47s |
49303 |
Jhoonson- Cook [LAW2] |
Changed the Value for Maximum Plastic Strain [Eps_Max=0]. |
Elements Deformed,Cracked but not Deleted. |
|
Case-5 |
7.4% |
0.7195E+06 |
425.7 |
0.7780E+06 |
0 |
117.85s |
47900 |
Elastic [LAW1] |
Changed the Material Card to LAW1 and Kept the Same Material Properties. |
Eleme |
nts |
|
Deformed,Cracked but not Deleted. |
|||||||||||
|
Case- 6 |
0.8% |
0.2954E+05 |
65 |
0.2940E+05 |
0 |
155.47s |
49506 |
ElastoPlastic- Brittle [LAW27] |
Assigned the Rupture Parameters for the Plate and Used Recommended Element Parameters. |
Elements Deleted. |
|
|
Case-7 |
0.7% |
0.7078E+05 |
21.31 |
0.7046E+05 |
0 |
143.60s |
49053 |
ElastoPlasticTabulated [LAW36]. |
Created a Plastic Stress Strain Curve by Using Plastic Strains and Yield Stress Values. |
Elements Deleted. |
|
CONCLUSION:
Hence the simulation for all the cases were carried out with different materials laws.
Hence the simulation for all the cases were runned successfully.
Law 1 is used to model purely elastic materials or materials that remain in the elastic range. To model this we require Poisson's ratio and Young's modulus. This law represents a linear relationship between stress and strain.
Law 2: In this law, the material behaves as linear elastic when equivalent stress is lower than the yield stress. For a higher value of stress, the material behaves like plastic. Failure can be captured better with the help of an optional Fail_Johnson card.
Law 27: Used for brittle materials.
Law 36: The elastic-plastic behavior of isotropic material is modeled with user-defined functions. The stress-strain curve is modeled using E and Poisson's ratio.Therefore, it is the best card because we cannot know the exact failing condition of the material in the other cases, but we can define the stress-strain curve, and then we can decide where the material is failing.