Assignment 3-2D Element Formulation Challenge

Objective :-

• 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.

• In this objective we have to import crash beam file (_0000.rad) by using 'import solver desk' option
• Then change run time to 55 sec. for that we need to go 'Solver desk', 'ENGINE_KEYWORDS', Clicked on 'RUN' and change run time to 55 sec.

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

• To change the no of animation steps during simulation we have to go 'ENGINE_KEYWORDS', 'ANIM',Click on 'ANIM/DT' and put Tstart-25 and Tfreq-1

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

• In this objective we have to run simulation without changing any elemen properties.
• For that go to 'Radioss' in 'Analysis' tool, Save crash beam file (_0000.rad) in destination folder, put 'option' as '-nt 4' and hit 'Radioss'

• After that go to 'Hyperview', select .h3d file and hit Apply. we can see the way in which elements are deform via 3D animation
• By using contour option we get animation showing displacement contour during simulation.

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

• To check energy error and mass error open engine output file(0001.out) in notepad
• From this file we get energy error is -10.3% and mass error is `0.1659*10^-3`
• Acceptable tolerance for energy error is -15% to +5% and we got -10.3% means its acceptable.

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

• To plot rigid wall forces, internal energy, hourglass energy, contact energy, total energy of the simulations open hypergraph 2D.
• In hypergraphs need to input file 'T01', select the type of energy which we want on graph and hit Apply.

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

• In this case we have to perform simulaion with recommended shell properties
• Repeat process, import original engine file using solver desk and change the values of following properties and run the simulation

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.

• Go to 'Radioss' in 'Analysis' tool, Save crash beam file (_0000.rad) in destination folder, put 'option' as '-nt 4' and hit 'Radioss'

• After that go to 'Hyperview', select .h3d file and hit Apply. we can see the way in which elements are deform via 3D animation
• For animation of contour dislacement during simulation use contour option.

7. Follow steps 5 and 6.

• To plot rigid wall forces, internal energy, hourglass energy, contact energy, total energy of the simulations open hypergraph 2D.
• In hypergraphs need to input file 'T01', select the type of energy which we want on graph and hit Apply.

• To check energy error and mass error open engine output file(0001.out) in notepad
• From this file we get energy error is -0.1% and mass error is `0.1659*10^-3`
• Acceptable tolerance for energy error is -15% to +5% and we got -0.1% means its acceptable.

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.

• The difference in both simulations is the decrease in hourglass energy. The introduction of OEPH shell formulation (Ishell 24) in the second case, provides an artificial stiffness to the shell elements and helps counter hourglass formation. hence the simulation with recommended properties is better than simulation default properties
• The more realistic simulation also resulted in a different resultant force graph that represents the collision events more realistically.
• The formation of a kink at around 20 ms causes a sudden spike in case 1, whereas in the second simulation, as the QEPH shell formulation is used, there is no sudden spike as the elements are deformed in a much better manner. Understandably, there is a large force at the beginning, which happens at contact, and is the same in both cases.