Assignment 3-2D Element Formulation Challenge

Aim: 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.

Open hypercrash and radioss solver ,

open geometry

Expand card in tree module and go to ENG_RUN

Set Tstop =55

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

go to ENG_ANIM_DT and change Tstart =25

Property of HAT_SECTION as below

Card image : P1_Shell
Ishell: 0
Ismstr: 0
iSH3n: default
N: 5
Hm: 0.01
Hf:0.01
Hr: 0.01
Istrain : 0
thick : 1.5
Ashear: 0.877
Ithick : 1
Iplas: 1

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

now run the simulation
go to ANALIZE> RADIOSS

set Path : where simultion result save
Export option : all
Option : -nt 4

Click on radioss to run the simulation

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

Now open .H3d file in hyperview mode. and divide the screen in two part and open T01 file in 2nd screen

Displacement and internal energy

To check energy error and mass error open engine output file(0001.out) in notepad

from this file we get below result

Result :
ERROR I-ENERGY :-10.3%
MAS.ERR : 0.1659E-03

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

NOw open .H3d file in hyperview

Simulation file result :

Velocity:

Hour glass enegery :

Mass change

Plastic Strain

Specific energy

Von misess (Stress)

for graph open T01 file in hypergraph 2d

set init as Kg/Mm/Ms

Internal energy

Kinetic energy

Hour glass energy

TOtal energy

contact energy

Rgid wall normal force( a-axis)

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

Open new geometry and change Tstop and Tstart as above

and Open property tab and open Hat_section

Change as per given critera

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.

now run the simulation again in ANALYSIS > radioss > select the path

click on radioss

after simulation completed

we get below value

Error Internal energy: -3.8%
MAS.ERR : 0.1659E-03

Open Hyperview and select .H3d file to view the animation files

displacement:

Velocity :

Hourglass enegry:

Max change:

Plastic strain:

Specific energy:

VOn misses Stress

Internal ENergy

Kinetic energy

Contact energy

Hour glass energy

Total energy

Rigid wall : total resultant force

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

		Case 1	Case 2
Displacement	Max (Mag)	6.75E+02	7.72E+02
	Min (Mag)	9.76E-03	0
Velocity	Max	1.34E+01	2.39E+01
	Min	0.00E+00	0
hourglass energy	Max	1.67E+04	3.24E+04
	Min	-8.54E+00	0
Mass change	Max	3.66E-01	7.84E-01
	Min	0.00E+00	0
Plastic strain	Max	4.46E-01	9.89E-01
	Min	2.84E-03	0
Specific energy	Max	1.96E+04	4.09E+04
	Min	1.58E+02	1.28E+01
Von Misess Stress	Max	3.50E+02	3.50E+02
	Min	2.71E+01	0.00E+00

Pictures: Graf comparison

Internal energy

Kinetic energy

Contact pressure

Hourglass energy

Total energy

Total resultant force on rigid wall

COnclusion :

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