Assignment 4-RADIOSS Material Laws Challenge

OBJECTIVE:

• To apply the various cases as mentioned in the above question on the given failure johnson cook material.
• To plot the graphs(Post-processing) with respect to the obtained values from those cases.
• To compare the obtained results, from those cases.

Procedure: 

Case 1 (Running the simulation without any change):

• Initially, after opening the HyperWorks software the user profile should be selected. For this challenge since analysis should be performed, Radioss is chosen as a user profile. After choosing the user profile, The solver deck should be imported. The file should be selected & click on the import 

• After importing the solver deck

• As it is seen in wireframe mode for better visualization, enable the option named "Shaded elements with mesh lines". After enabling it

• The material card is the next card to be verified, inorder to see the properties assigned to the material.

• The next card to be verified is the property card. In the property card, the properties assigned to the given material are seen.

• As mentioned, this case is to be run as usual with the base values. i.e., running the model without changing any value. The model can be run with the help of a command named "radioss" in the analysis panel. After opening the radioss panel, the file should be assigned within some location. Then by clicking "save as", the files will be saved in that locations. 
• As the running is completed, the location is assigned before running. In that location, the files are stored. These files in that specified location 

 

• Among those files, the 0001.out file is opened in the notepad, which indicates the results in the form of numerical values(such as energy error, mass error, kinetic energy, internal energy,etc)

• The obtained last cycle values are:
• energy error = 0.8%
• Internal energy = 0.2730E+05 KJ
• Kinetic energy = 67.81 KJ
• External work = 0.2721E+05 KJ
• Mass error = 0
• elapsed time = 112.27 s
• Total number of cycles = 49379
• Then the 0001.rad file is opened in the note pad, which shows the Tfrequency, run time(Tstop) values 

• The next step is to view the simulation. This is done by switching on to another window. In this window, the h3d file is imported and applied in the hyper view. The hyper view panel

Note:

• Always when we switched on to a new window, the hyper view panel is enabled by default. To plot the graphs(i.e., post-processing), the hypergraph 2D panel should be enabled by the user.
• The h3d file is a combination of all animation files. 

 

• To run the simulation, the contour panel should be enabled.  In this panel, the parameters such as result type as von misses, selection of components, selection of averaging method, and click on apply. 

 

• After applying, the model is ready for simulation. The obtained simulation appears as shown in the below animation. Which results in deleting the elements, because the circular plate is assigned with law 2. As it is assigned with material law 2, the plate possesses both elastic & plastic behavior. The maximum von-mises stress is seen in the below animation.

 

Post-processing:

• The next step is to do the post-processing, by plotting the obtained results in the form of various graphs. The first graph to be plotted is rigid wall forces. This is done by switching into the new window & enabling the Hypergraph 2D panel. In this panel, T01(Time history) file is imported. And the parameters required for obtaining the result with respect to the rigid wall are selected 

 

• After selecting to apply, a pop-up appears. Which depicts to mention the unit system. As per the unit system seen in begin card from the solver browser, the units selected are length(millimeter), Time(milliseconds), Mass(kilograms).

 

• Soon after applying the unit system, the graph is plotted which indicates the rigid wall total resultant force. Initially, the elements start observing the energy, when the spherical-shaped rigid sphere hits the given component(Plate shaped). And due to this energy absorption, the forces will reach a peak value. And after reaching the peak value, the elements will start deleting, Which is shown in the fall of the rigid wall forces.

 

• The next step is to plot the graph for the energies such as internal energy, kinetic energy, Total energy, hourglass energy. So for that, the parameters are selected in the hypergraph 2D panel. This should be done in the new window. 

 

• The obtained graph with respect to the requested energies. As in this case, the johson cook material with law 2 is applied and represented by a,b,n, eps_max(plastic strain), the elements get deleted. The reasons for obtaining the below graph are explained below:
• Usually, the internal energy starts from the origin, And it increases because of the increase in displacement.
• The kinetic energy will slightly vary at the time of element breakage.
• The total energy is the combination of all energies. So, it will increase.
• The hourglass energy is constant throughout the process. Because, the property card is assigned with the recommended values such as Ishell:24, Ismstr:2, Ish3n:2, Iplas:1, Ithick:1, N=5.

 

Case 2(Changing the values in failure card):-

• In this case, the failure card is edited with respect to the given values. But the material law is the same(i.e., law 2). Before changing the values in the failure card. The values to be changed are Ifail_sh = 1, Dadv = 1, Ixfem = 1.              

• After changing the values in the failure card.

• The next step is to run the simulation by using the radioss. After running the simulation, the obtained files(Animation files, time history files) in the specified location 

 

• The next step is to view the 0001.out file. In order to check for the energy errors, mass errors, etc. The 0001.out file with the maximum values 

 

The obtained last cycle values are:

• energy error = 0.2%
• Internal energy = 0.3082E+05 KJ
• Kinetic energy = 141.9KJ
• External work = 0.2980E+05 KJ
• Mass error = 0
• elapsed time = 114.38 s
• Total number of cycles = 49216
• The obtained h3d file is imported in the hyper view, in order to simulate. The obtained simulation appears as shown in the below animation.

 

Post-processing:

• The obtained rigid wall force is represented in the form of a graph. The total resultant force reaches a peak value due to the impact of the rigid sphere towards the circular plate.

 

• Go to Hyper graph 2D >> Select T01(Time history file) >> Select x-type = Time >> Y-type = Global variable >> Y-request = Internal, kinetic, contact, Hour glass and Total energies >> MAG(Magnitude) >> Apply

Case 3(Deleting the failure of johnson card):-

• In this case, the failure card is deleted to see any changes in the result.

• Now, the simulation is run without changing any further parameters. After running it, the files obtained in the saved location 

 

• Then by opening the 0001.out file energy errors, mass errors, etc. The 0001.out file with the maximum values 

 

The obtained maximum values are:

• energy error = 0.8%
• Internal energy = 0.2744E+05 KJ
• Kinetic energy = 87.08 KJ
• External work = 0.2736E+05 KJ
• Mass error = 0
• elapsed time = 112.73 s
• Total number of cycles = 49407
• Then the obtained h3d file has imported into another window, In order to view the simulation. The obtained simulation in terms of von-mises is shown below animation.

 

• From the above animation, noticed thing is that the elements break because the circular plate is assigned with elastoplastic material.

Post-processing:

• The next step is to view the results, by the obtained graphs. These graphs are obtained by importing the obtained  T01 file in the next window. Initially, the rigid wall forces are obtained. 

 

• Go to Hyper graph 2D >> Select T01(Time history file) >> Select x-type = Time >> Y-type = Global variable >> Y-request = Internal, kinetic, contact, Hour glass and Total energies >> MAG(Magnitude) >> Apply

Case 4(Deleting the eps_max value from the material card):-

• In this case for the same material card, the plastic strain(eps_max) value which is 0.151, is removed(eps_max).

• After removing the value for plastic strain, the material card 

• Then the simulation is run using radioss. After running the obtained animation files stored in the specified location 

 

• Then the obtained 0001.out file is opened. In order to view the obtained results in the form of values. The obtained values for the last cycles 

 

The obtained last cycle values are:

• energy error = 1.1%
• Internal energy = 0.3879E+05 KJ
• Kinetic energy = 3.931 KJ
• External work = 0.3838E+05 KJ
• Mass error = 0
• elapsed time = 141.41 s
• Total number of cycles = 49304
• Then the obtained h3d file has imported into another window, In order to view the simulation. The obtained simulation in terms of von-mises is shown below animation. As the eps_max value (plastic strain) is zero, the elements will not break.

 

• The elements are not getting deleted. 

Post-processing:

• The obtained rigid wall force graph. The rigid wall force increases & decreases gradually. And reshes to the peak value at the last moment of collision & decreases.

 

• Go to Hyper graph 2D >> Select T01(Time history file) >> Select x-type = Time >> Y-type = Global variable >> Y-request = Internal, kinetic, contact, Hour glass and Total energies >> MAG(Magnitude) >> Apply

 

Case 5(Changing the material card to law 1):-

• In this case, the material law is changed to law 1, which possesses only the elastic behavior. Before changing the material law, it was in material law 2
• After changing the material card, And the values of E,`rho`,`mu` will remain the same.

• Then the simulation is run. After running the simulation, the obtained animation files

 

• Then the obtained 0001.out file is opened, in order to view the energy errors, mass errors. The obtained values 

 

The obtained values for last cycle are:

• energy error = 1.3%
• Internal energy = 0.8632E+06 KJ
• Kinetic energy = 1677 KJ
• External work = 0.8568E+06 KJ
• Mass error = 0
• elapsed time = 107.94 s
• Total number of cycles = 47968
• Then the obtained h3d file has imported another window, In order to view the simulation. The obtained simulation in terms of von-mises is shown below animation. The elements will not even split during the collision. Because law 1 is assigned to the circular plate. So, it possesses elasticity (i.e., the ability to regain its original size & shape).

 

Post-processing:

• Then the graphs are plotted to view the results. The total resultant force of the rigid wall force increases gradually till the end. Because there is no plastic behavior seen in this case. The obtained rigid wall force graph 

 

• Then the internal energy graph is obtained. Internal energy also increases gradually. But the graph will be some what dissimilar to that of the previous cases
• Go to Hyper graph 2D >> Select T01(Time history file) >> Select x-type = Time >> Y-type = Global vairiable >> Y-request = Internal, kinetic, contact, Hour glass and Total energies >> MAG(Magnitude) >> Apply

Case 6(Changing the material card to law 27):-

• In this case, the material card is changed to law 27(Which possesses brittleness) & to change the parameters in the property card with the recommended values. For example aluminum & glass etc. This law combines the elastoplastic johnson-cook material with an orthographic brittle failure model. Before changing the parameters, the property card 
• After changing the parameters in the property card.

• Then the simulation is run. After running the simulation, the obtained animation files in the specified location 

 

• Then the 00001.out file is opened, in order to view the energy errors, mass errors. The obtained values 

The obtained values for last cycle are:

• energy error = 0.8%
• Internal energy = 0.2954E+05 KJ
• Kinetic energy = 65.00 KJ
• External work = 0.2940E+05 KJ
• Mass error = 0
• elapsed time = 112.75 s
• Total number of cycles = 49506
• Then the obtained h3d file has imported another window, In order to view the simulation. The obtained simulation in terms of von-mises is shown below animation. Here the elements will break due to their brittle property.

 

Post-processing:

• The obtained rigid wall forces graph. The rigid wall forces will reach a peak value at the time of impact and decreases gradually.

 

• Goto Hyper graph 2D >> Select T01(Time history file) >> Select x-type = Time >> Y-type = Global variable >> Y-request = Internal, kinetic, contact, Hour glass and Total energies >> MAG(Magnitude) >> Apply

Case 7(Changing the material card to law 36 & parameters in the property card):-

• In this case, the material card is changed to law 36(possess elastoplastic piecewise linear material). And the shell parameters in the property card are changed to the recommended properties. Before changing the parameters, the property card
• After changing the values, the material card

• While defining the material card as law 36, a function should be represented to define the curves. Initially, there will be some curves are defined. But a new curve is defined, the values are given by the user. A curve will be generated based on the given values.

• Higher the curve> Higher the strain rate > But earlier the failure takes place.
• The process of creating the curve is: create> curve> New> assign a name> proceed> shows the curve with values & graph.
• Then the simulation is run, by using radios. After running the simulation, the 0001.out file is opened to view the obtained results in the form of values.

 

The obtained values for last cycle are:

• energy error = 1.8%
• Internal energy = 0.3850E+05 KJ
• Kinetic energy = 234.5KJ
• External work = 0.3982E+05 KJ
• Mass error = 0
• elapsed time = 121.3s
• Total number of cycles = 52174
• Then the obtained h3d file has imported another window, In order to view the simulation. The obtained simulation in terms of von-mises is shown in the below animation

 

• In this case, also the elements will break. Because the material card assigned possesses both elastic & plastic material.

Post-processing:

• The rigid wall forces obtained are shown in the form of a graph 

 

•  Go to Hyper graph 2D >> Select T01(Time history file) >> Select x-type = Time >> Y-type = Global variable >> Y-request = Internal, kinetic, contact, Hour glass and Total energies >> MAG(Magnitude) >> Apply

 

Comparsion of 7 cases:

Basis of comparsion	case 1	case 2	case 3	case 4	case 5	case 7	case 6
energy error(%)	0.8%	0.2%	0.8%	1.1%	1.3%	1.8%	0.8%
Internal energy(KJ)	0.2730E+05	0.3082E+05	0.2744E+05	0.3879E+05	0.8632E+06	0.3850E+05	0.2954E+05
Kinetic energy(KJ)	67.81	141.9	87.08	3.931	1677	234.5	65
External work(KJ)	0.2721E+05	0.2980E+05	0.2736E+05	0.3838E+05	0.8568E+06	0.3982E+06	0.2940E+05
Mass error	0	0	0	0	0	0	0
elapsed time(S)	112.27	114.38	112.73	141.41	107.94	121.3	112.75
Total number of cycles	49379	49216	49407	49304	47968	52174	49506
Elements deletion	will be deleted	will be deleted	will be deleted	will not be deleted	will not be deleted	will be deleted	will be deleted
Material law used	Law 2 with a, b,n values	Law 2 by changing the value in failure card	Law 2 by deleting the failure johnson  card	Law 2 by removing plastic strain(eps_max) value	Law 1	Law 36	Law 27

CONCLUSION:

Simulation of all the 7 cases are ran using the Hypermesh and the results are viewed in Hyperview and graphs are plotted in Hypergraph.

Also all the cases are compared with each other and came up with the conclusion that

• In case 2, the energy error is near to 5%, which is near to the ideal value.
• In case 7, the values from the actual testing can be used for co-ordinates of the graph, so that the accuracy of the result is increased.
• In case 5, LAW1 material card is used, hence the components are subjected to load within the elastic limit ,so it doesnt fail and at the same time, it saves time and energy.
• EPS based failures are efficient in cases where some amount of plastic strain is allowed.

BASED ON ALL THE RESULTS, WHICH CASE WOULD REPRESENT THE ON-FIELD SCENERIO?

LAW36:

• In LAW36, the energy error is between -1.8% to 0.7% which is acceptable since both the values are near to zero.
• Also the values we used are the actual values from labs based on real life experiments.
• The plastic region is from the lab values and the elastic region can be occupied using the young's modulus and Poisson's ratio.
• These reasons make LAW36 more similiar to real life compared to the others.