Assignment 4-RADIOSS Material Laws Challenge

Aim:- Run cras analysis on the given model by applying different material laws available in Radioss and post-process the result.

Case 1:-Import the FAILURE_JOHNSON_0000.rad file and run the model as it is. Give the title name as Law2_epsmax_failure.

• Open Hypermesh go import> solver deck option>browser file and import file. The FAILURE_JOHNSON_0000.rad is selected as show in image.

• We check the unit using Bring card as show in image.

• In this case,we run the simulation with default property. so we don't change any value in file.

• To rune the simulation we go Analysis >Radioss> here we need to save file in new folder. so that we can access easily. After saving file tick the include connector and type -nt 4 in the option text boxe as show below
• By clicking 'RADIOSS' we get the solver window as so the below. After a few minutes radioss do the job and you can check all the file in folder that you save.

• The simulation is complete, now we need to visualize it . so we need to switch to hyperview as show in image.

• After access hyperview, we need to h3d file that was generated when radioss processed the starter file.After select file click apply.
• We can change visualization after clicking apply select contour option from toolbar. now we can change result type 'von mises' and change averaging method to simple.as show in below

• Next step is to carry out energy error and mass error check and this is done by analyzing the radioss engine output file. This can be accessed frome same directory as the stater and engine file that is denoted by '0001.out' and open in any text editor.
• After open the file and scroll down in the end we see the final energy error.

• final energy error is 0.8%, which is acceptable. It is closer to 0. that is better and there is no mass error.
• Now plote the graph we switch hypergraph2D using client selector option in the toolbar.
• In hypergraph section,we need to input a file.we will be using the resule file that is generated by radioss solver this file denoted by 'T01' file.

Case2:-

• Import the case 1 rad file, named “Law2_epsmax_failure” and perform the simulation with failure plastic strain (EPS_p_max) and fail_Johson card enabled.
• Changes to be made in /FAIL/JOHNSON card:

• ifail_sh= 1
• Dadv= 1
• Ixfem= 1

• Use the recommended values for the property card.
• Give the title name as Law2_epsmax_crack.

• First import FAILURE_JOHNSON_0000.rad via the solver dick. This time we make some chenges to the fail/johnson card. It can be accessed via the model tab under the failure submenu.
• The following value are assigne as show the below

Ifail=1:- which determines the shell element failure merhod. so there are two ways in which we can see element failure the element will either get delete or in some cases the cracing occure according to the material property.

Dadv=1:- it gets actavited when we have taken Ixfem=1. we are going to taken Dadv=1. which gives quality criteria. that how much an element can get break into small picese. if it goes beyound the limet element get deleted.

Ixfem=1:- In this we can choose that if there any element that is failling we want that element to delete or element to be crack. we are going to take Ixfem=1 which allowed to failed element to crack not to deleted.

• Now run the analysis and file is saved as "Law2_epsmax_crack_0000.rad"with connector taked and '-nt 4' typed in the options box. we can click on the radioss buotton to run analysis.

• After the completes solver window analysis. switch to hyperview window and run h3d file of the current analysis Law2_epsmax_crack.h3d and set the von mises stress contours.

• Now check the energy and mass error on the radioss output file Law2_epsmax_crack_0001.out

• The energy error is decent enough and it lesser than 5% and mass error non existent. we can go ahead and swetch to hpyergraph2D to plote the graph.

Case 3:- Import the case 2 rad file, named “Law2_epsmax_crack” and perform the simulation by removing the fail_Johnson failure card. Give the title name as Law2_epsmax_nofail.

• Again open hyperwork and import second case file Law2_epsmax_crack_0000.rad and delete fail/johnson card. Go to failure> failure_johnson_1.

• Now run the analysis and file is saves as Law2_epsmax_nofail_0000.rad with connectors takes and -nt 4 typed in the option box. we click on the radioss button to run the analysis.

• After completes the solver run switch to hyperview window and run h3d file of the current analysis Law2_epsmax_nofail.h3d and set von mises stress contours.

• Now check the energy and mass error on the radioss output file Law2_epsmax_nofail_0001.out

• The energy is almost zero and mass error non existent. now we can switch to hypergraph to plots the graphs.

Case 4:- Import the case 3 rad file, named “Law2_epsmax_nofail” and perform the simulation by removing both the failure plastic strain (EPS_p_max) and the fail_Jhonson failure card.

• Now import the case 3 rad file Law2_epsmax_nofail_0000.rad . this time delete the EPS_p_max value (make it 0). Going to the model tab, we can go to materials>Aluminium as show in below.

• After that we can go analysis> rasdioss save file as Law2_0000.rad and check connector and type -nt 4 in option text box and run the analysis by clicking radioss.

• After completes the analysis we can switch to hyperview window and run Law2.h3d file and actavated von mises stress contours.

• Now we check the energy and mass error on the radioss output file Law2_0001.out.

• The energy error is less than 5% and non mass error existent.

Case 5 :- Import the case 4 rad file and perform the simulation by changing the material card to Law 1. Keep the same value for rho, E, and nu values.

• Import the case 4 rad file after that go materials card > Aluminium and change the card image M1_ELAST, which is Law1. and don't change rho, E and nu values.

• Now we go analysis > radioss and save as file Law1_0000.rad and enable connector and types -nt 4 in option text box and run the analysis by clicking radioss.

• After completes the analysis we can switch to hyperview window and run Law1.h3d file and actavated von mises stress contours.

• Now we check the energy and mass error on the radioss output file Law1_0001.out.

• The energy error is less than 5% and non mass error existent. we can switch to hypergraph2D to plote the graphsfor this simulation.

Case 6:- Import the case 1 rad file, named “Law2_epsmax_failure” and perform the simulation with the law 36 material card. Refer to the video titled "Materials 7" for further information.

• In this case import case 1 rad file and we nees to recommended shell property go to property> 5nip. Now we can look at the utility and set the following attributes as following.

Ishell=24,ismstr=2,ish3n=2,n=5,ithick=1,iplas=1

• Now we run the analysis via the radioss tools. and save file as Law27_0000.rad and enable connector and types -nt 4 in option text box and run the analysis by clicking radioss.

• After completes the analysis we can switch to hyperview window and run Law27.h3d file and actavated von mises stress contours.

• we can chack the energy and mass error via Law27_0001.out.

• the energy error is too close to 0 and mass error no existent.

Case 7:- Open the Law27_0000.rad file and perform the simulation with the law 27 material card. Use the recommended shell properties.

• In this case import Law27_0000.rad file. Go to the model tab and here, we shall be creating a new curve right click>create> curve

• initially there are 4 curves , we are adding a new curve named case7.
• Now go to materials>Aluminium and change the card to M36_PLAS-TAB(LAW36). After that set the values of roh_initial, E and Nu as follows.

Roh_initial=0.0027,E=71000.00,Nu=0.33

• Then we can add the curve using the N_funct attributes. we can change it's values to 1 and by diong so, it lets us select the reference curve. we shell select the one we just made.
• Now we run the analysis via the radioss tools. and save file as Law36_0000.rad and enable connector and types -nt 4 in option text box and run the analysis by clicking radioss.

• After completes the analysis we can switch to hyperview window and run Law36.h3d file and actavated von mises stress contours and we can view the simulation.

An energy error of -1.6% is acceptable. The mass error no existent.

• Now we can switch hypergraph2D to plote the graph.

Observation

Case 1:-

1. In this case fail/johnson card as well as EPS_P_max value assigned with ixfem value as 0. This means that the elements are deleted as soon as they cross the EPS_p_max thersold. which we can see in the above simulation.
2. Internal energy, as well as rigid forces, are reaction to the forces generated by the sphere on the sheet energy increase linearly unit many element are deleted at around the 4ms thersold.This probably create some vibration and that result in a sugar of kinetic energy at the same point.
3. The rigid forces fluctuate when the element are deleted and a large chunk of element are deleted at 4ms ,there aren't many element opposing the forces of the sphere. the most of the element in its path have been deleted at that point.

Case2:-

1. in this case we have used ifail_sh,Dadv,and ixfem as part of the fail/johnson card. Ixfem is especially important here because it decides the way of the element react. with its value equal to 1 here,it means the element will crack and fail. along wiht Dadv crack propagation can also be seen here,with element being deleted only when the element crack reaches them as a result this is a more realistic depction
2. In this case rigid wall is moving. so to move any object there should be same external force is applying to the object. so that is why the rigid wall forces start increasing from zero and when it collided with the plate, the energy get transfered to the element that's the reason the rigid wall forces get decreased agian to zero.

Case3:-

1. in this case we delete fail/johnson card that the onus is on EPS_P_max to be the factor for element deletion. As we can see in the following it's value is 0.151 meaning element will be deleted if the strain on any integration point with in said element reaches 15.1% of the plastic strain. the element, in this case fail rapidly when compared to the elements in case 2 due to xfem crack formulation there.
2. There is a linear increase in internal and total energy until a bulk of the element are deleted from the element model. This is expected since the energy absorbed by these elements go to the waste due to their deletion.
3. This also explains the sudden drop in rigid wall forces at the same timestamp due to most elements that were in contact with the sphere during collision being deleted.The rigid wall force is basically a measure of the opposing force generated by the metal sheet against the sphere. Fluctuations occur when elements are deleted. when there are no elements to oppose the incoming sphere, there wan't be any rigid wall forces.

Case4:-

1. Law 2 (plas_johns) expresses material stress as a function of strain,strain rate and temperature.
2. The metal sheet is able to withstand a large amount of stress and avoid element deletion primarilu due to the fact that the value for EPS_P_max was deleted. since it was deleted, radioss assigns it the default value of 10^30. In addition to that, the fail/johnson card was deleted. The marterial behaves like a pseudo-elastic(also called elasto-plastic) material since it has a very high EPS_P_max threshold and elements cannot be deleted due to no failure cards.
3. with the value of c(strain rate coefficient)=0, there is no strain rate (neither does temperature play a role here). As a result, the stress, in this case, is purely a function of strain generared in the material.
4. Added, the kinetic energy generated in this case is almost negligible(2.5-4 ms) compared to the internal (and total )energy here. the total energy increase is almost linear over time.

Case5:-

1. in this case, the plate is defined with a Law-1 material which defines the basic properties of elastic material.This model considers only the elastic phase of the material, there is no plasticity involved which results in linear deformation.
2. This case makes use of the M1_Elast card and as we can see, the metal sheet absorbs the full impact of the sphere. This material law is used to model purely elastic materials. This explains why there are no element deletions nor ruptures. Due to its elasticity, it also can absorb an extremely large amount of energy which explains the peak at the end of the kinetic energy plot below. Absorbing a lot of energy also results in very high stresses the maximum stress observed in the metal sheet is 10890mpa, which is a massive value compared to the same in Law 2.
3. The kinetic energy gradually increases as the plate is stretched to the maximum limit for the applied load.
4. Also, due to the elastic nature, the internal energy(and rigid wall forces) keep increasing exponentially. the internal energy of the metal sheet increases due to the absoption of the kinetic energy from the impacting sphere and drops down once the plate returns to the original shape.

Case6:-

1. In this case the use of the M27_plas_brit material card that is used for isotropic elastoplastic johnson-cook material model an orthotropic brittle failure model. the sheet (compared to case 7) absorbs more force and resorts to more deformation before the element are deleted(at around 4ms).
2. with the loss if energy through deleted elements we notice the graph plateaus at around the 4 ms mark.
3. Whit several elements deleted and none to stop the incoming sphere, the rigrd wall force graph drops at the same timestamp of 4ms. the spikes are formed when an element is deleted and is characterized by a trough and crest but with so many ekements deleted, the trough is massive at the 4ms mark.

case7:-

1. In this case, from the simulation we can say that this material exhibits strong brittle behaviour. it does not bend as much in response to the applied force and immediately disintegrates. there seems to be not much cracking and the region of elements deletion take the shape of the spher. Another thing that we can notice is that the stress concentration is localized around the region of impact and these stresses are not dissipated throughout the whole metal plate.
2. There is an almost linear relation between internal energy and time till past the 3ms mark where many elements get deleted at once. when the elements are deleted, the energy on each element goes to waste, which results in the plateauing of the curve.
3. on the topic of energy wastage and element deletion, it is more particularly visible in the rigid wall force graph. Each of the spikes is due to an element deletion. the resultant force gradually increases past the same 3ms mark which is when the sheet gives way and lets the sphere through. with not much of the sheet in the way, the rigid wall forces are drastically reduced, and that results in that drop at the 3ms mark. the first drop occurs when the sheet ruptures the first time.

case	no.of cycles	mass error	final energy error	solver simulation processing time in second	condition of elements under excessive stress
case1(Law2_espmax_failure)	49780	0	0.8%	190.60s	Deleted
case2(Law2_espmax_crack)	49217	0	4.1%	262.69s	elements under go crack formation and than deletion
case3(Law2_espmax_nofail)	49408	0	0.8%	119.03s	deleted
case4(Law2)	48737	0	3.0%	152.00s	can not be deleted due to lack of failure and high default EPS_p_max valur
case5(Law1)	47969	0	1.3%	115.06s	can't be deleted due to elastic card property
case6(Law27)	49508	0	0.8%	130.79s	deleted
case7(Law36)	53157	0	-1.6%	149.13s	deleted

Conclusion:-

1. Learn about different type of material cards
2. Learn about failure card in hypermesh
3. Learn about different type of energy

In a simulation selecting a correct material card play a important role. if you select a worng material cad it give you result but it will not represent the actual situation.