Assignment 3-2D Element Formulation Challenge

Aim:-

Recommended properties:

Parameters		Comment
Ishell =24		QEPH 4 nodes shells are best combination of cost and accuracy.
Ismstr=2		Full geometric nonlinearities (default)with possible small strain formulation activation in RADIOSS Engine.
Ish3n=2		Standard 3 noded shell (C0)with modification for large rotation(default)
N=5		Number of integration points set to 5 for accuracy bending.
Ithick=1		Thickness change is taken into account for accuracy.
Iplas=1		Iterative plasticity for good accuracy.

Questions:

Comparison of results with base simulation and improved shell element properties

1.Using the crash beam file from the previous assignment, change the run time to 55 ms.

2. Change the number of animation steps during simulation to a minimum of 25 and maximum of 60.

3. Run the base simulation without any modification to element properties.

4. At the end of the simulation, do the energy error and mass error checks and determine whether results would be acceptable.

5. If acceptable, Plot rigid wall forces, internal energy, hourglass energy, contact energy, total energy of the simulations.

6. Change all the shell elements properties to recommended properties, save this as separate, rad files and run the simulation.

7. Follow steps 5 and 6.

8. Create a brief report comparing all the results from steps 5 and 6 for both simulations.

9. Comment whether there is any change in the results and why there is any change in the result.

Solution

Q1:-change the run time to 55 ms.

• First open the file in Radioss solver, Go import menu> import solver deck, Here you select file which you want to bring here this file is called starter input deck file that ends with 0000.rad.  

• To change run time to 55ms. Go solver tab(view>browser>hypermesh>solver)>engin_keywords>run, now we ready to change run time to 55ms.

Q2:-Change the number of animation steps during simulation to a minimum of 25 and maximum of 60.

• To change animation time you go engine_keywords>anim>anim/dt, we can change Tstartvalue to 25 to maximum 60, Tfreq can be set as 1.0 show in blow.

Q3:-Run the base simulation without any modification to element properties.

• we go Analysis>Radioss.

 

• In Radioss option you can save file and change the file name before  running it in solver.During save change file name so that you don't confusion.

• It is recommended to be write as a "-nt 4" as show in the image. it means assigning the task to 4 cores in the system, to performs simulation faster.It depends upon the processor our system. where "tn" means number of threads and 4 use for quard-cores processor systems and 8 use for octa-cores processor,after that click on Radioss in order to simulation.

• Now simulation is complete,we need to visualize it. so we go hyperview utility.
• To open hyperview go hypermesh>hyperview according to image that given blow.

• After accessing hyperview,we should input simulation file. for this use h3d file that was generated when Radioss processed the started file.

• After simulation we use contour option in the toollbar for representation.

Q4:-At the end of the simulation, do the energy error and mass error checks and determine whether results would be acceptable.

• To check the obtained value of energy error lik interal energy, total energy, mass enetgy from the engine output file (0001.out).

• when you go down in the engine file, you can seen maximum energy error -10.3% , internal energy 0.1933e+8 , kinetic energy 0.3562e+8
• The acceptable energy tolerance for energy error is -15% to +5%.The closer to 0 is better.

Q5:- If acceptable, Plot rigid wall forces, internal energy, hourglass energy, contact energy, total energy of the simulations.

• To plot rigid wall and any other energy graph we can use Hypergraph2D as show in image.

• in hypergraph, we need input a file. for this we will be use result file that generated by Radioss solver that is 'T01' file. 

Kinetic energy:- we know that kinetic energy is 1/2 mv^2.we can seen in the graph in inital state  velocity will be higher but it decrease with respect to time due to the deformation within the rail component. so the kinetic energy directly proportional to the velocity.This is the resion why kinetic energy decrease gradually as shwon in graph.

Internal energy:- we know that internal energy is U=Q*W (W=F*D) In the beginning there is no displacement (D=0) within the component,so that internal energy starts form zero.when it is subjected to acceleration there will be a displacement. As the displacement will be increase internal energy also increase.

Hourglass energy:- In this case recommended property is not specified.there will be a deformation undergo of element with respect to strain is not recorded. the element undergo an hourglass effect and there will be no physical stabilization.So, to balanced the energy artifical energy required.That is hourglass energy. so there is a lot of hourglass energy needed. so that hourglass energy start from origin and goes on increasing as show in graph 

Total energy :- As the hourglass energy increase more amount of energy is not recorded.so that total energy decreased as the graph progress.

• Now we create a new plote for rigid wall force using rigid wall/rwall force-4 rigid wall-1 resultant force show in graph 

Q6:-Change all the shell elements properties to recommended properties, save this as separate, rad files and run the simulation.

• Here we create new case with recommended shall element prorerties. first import the file and change the value Tstop=55ms, Tstart=25, Tfreq=1 in solver deck.

• Now edit the property as show in image.

• now run the simulation again and save file in different folder.

• we can switch hyperview to generate simulation. here we need h3d file that generate during radioss procedure open it in hyperview and click on apply.

Q7:-Follow steps 5 and 6.

• In this case we check the obtained value for energy error, internal energy,totel energy, mass energy from engine output file (00001.out).

 

• we can see here drastic reduction in the energy error.Earlier hourglass energy is -10.3%, now it become 0.1% which is almost zero

Hourglass energy In the starting of deformation hourglass energy gradually increase because of default porperty ; 0-DEF SHALL has a single integration point and it has no stabilized property.

• Whereas recommended property ie- QEPH-4 the hourglass energy is zero because the property of element has  improved with 4 node integration piont and it has physical haurglass stabilization property.these it avoid the hourglass completely in this case.
• now we generate graph by switch hypergraph and select this simulation T01file.

Q8:-Create a brief report comparing all the results from steps 5 and 6 for both simulations.

Now we will open both cases simultaneously as show in image. This makes comparison easy.

The obvious difference in both simulation is the reduction in hourglass energy. in the seciond case we use QEPH shall foumulation (shall=24) that provides an artificial stiffness to the shall element and helps counter the hourglass formulation.

Attributs	default property	Recommended property
Energy error	-10.3�ceptiable	-0.1% it almost zero that is goos number
kinetic energy	0.3562e+8	0.4376e+8
internal energy	0.1933e+8	0.1750e+8
hourglass energy	hourglass energy increase over time and it have no physical stabilization with default property	hourglass is zero. since they have all recommended property
total energy	the hourglass energy increase and more amount of energy is not recorded so total energy is decrease as show in graph	curve remain constant because ther is no hourglass energy lost

 

The formation of a kink at around 20 ms cause a sudden spike in case 1, whereas in second simulation, as the QEPH shall formulation used so there is no sudden spike as the element deforme in a much better manner. 

Concolusion  :-

• Learned about different property setting used for better simulation result in Hypermesh Radioss user profile.
• carried out simulation for both default and recommended value in hypermesh.
• Plotted all require graphs using hypergraph2D 

After comparing both cases,we can say there is difference in the value of hourglass energy, internal energy, kinetic energy and rigid wall force. Recommended setting helps reduced drastically due to the introducetion of physical stabilization method that is deployed by QEPH element  deformation occurred under recommended setting.