Case 1

Failure Johnson Card

Aluminum Property Card for Shell elements:

Material Card for Aluminum:

No change is done and performed radios Simulation

-nt 4 is applied for all simulations.

ELAPSED TIME     =         40.91 s

TOTAL NUMBER OF CYCLES  :   49380

MASS ERROR = 0.00 %

ENERGY ERROR = 0.8%

Max Von Mises Stress = 275 Mpa

Energy Curves:

At the end of the 5^th second. Those are energy levels

From energy levels and simulation we see that 27306 J of total 27375 J is caused by plastic deformation and 69.7 transformed into kinetic energy of deleted elements with velocity.

We see from the below graph that eps p max 0.151 lets elements to have max %15.1 plastic strain. Afterwards elements are getting deleted from the model.

Case 2

In the second case just three parameters are changed.

1. Ifail_sh from 2 to 1
2. Dadv from 0 to 1
3. Ixfem from 0 to 1

ELAPSED TIME     =         44.01 s

TOTAL NUMBER OF CYCLES  :   49217

MASS ERROR = 0.00 %

ENERGY ERROR = 4.1%

Report template used for comparison.

In this simulation we see that elements are getting cracked before they are getting deleted. Max stress exceeded to 295 Mpa

Case 3

Johnson Card is deleted from preprocessor and solved again.

ELAPSED TIME     =         41.82 s

TOTAL NUMBER OF CYCLES  :   49408

MASS ERROR = 0.00 %

ENERGY ERROR = 0.8%

In this simulation we see von mises stress of 270 Mpa

Out of 4 same element 1 reaches %15.1 epsmax value.

Case 4

EPS_p_max of %15.1 Strain is deleted from the model.

ELAPSED TIME     =         42.11 s

TOTAL NUMBER OF CYCLES  :   48737

MASS ERROR = 0.00 %

ENERGY ERROR = 3.0%

Since elements are not getting deleted from the model von mises stress rises up to 424 Mpa. It doesn’t exceed 425 Mpa which is defined in the material model

Case 5

LAW 2 changed to LAW1 “M1_ELAST”

ELAPSED TIME     =         39.39 s

TOTAL NUMBER OF CYCLES  :   47969

MASS ERROR = 0.00%

ENERGY ERROR = 1.3%

In this simulation von mises stress rises up to 10890 MPa and rises above 425 MPa because we changed from elastic plastic to elastic modelling.

There is no plastic strain as discussed above.

Case 6

LAW27.0000 Rad has been imported as solver deck. Property assignments have been done.

ELAPSED TIME     =         42.62 s

TOTAL NUMBER OF CYCLES  :   49508

MASS ERROR = 0.00%

ENERGY ERROR = 0.8%

Max von mises stress 287 Mpa.

Normally if we had a LAW2 eps p max of 0.151 Elements would be deleted after reaching %15.1 plastic strain but here we see there is more brittle plastic strain over the %15.1 plastic strain. Because in LAW27 we have a tensile stress for element deletion. Most probably this red curve element has subjected to a compressive stress.

Case 7

ELAPSED TIME     =         43.51 s

TOTAL NUMBER OF CYCLES  :   52217

MASS ERROR = 0.00%

ENERGY ERROR = -0.8%

Max von mises Stress is 587 Mpa

Since i selected eps max as 0.151 we see that after %15.1 plastic strain elements are deleted and don’t deform any further.

Comparison Table

From above results we see the importance of defining the max plastic strain, max plastic stress.

There is no mass and hourglass problem for all simulations because element properties are arranged accordingly. But some simulation have high energy values due to improper modelling such as case 4 and case 5.

We see that total energy should vary between 27000 – 30000 J. Best scenarios are Case 1, Case 2 and Case 6.

In terms of simulation time and cycle we don’t see a huge difference.

Element deletion and max plastic strain are affecting the simulations.

Max Stress definition is also very important parameter. For example there is no plastic strain limit but stress limit such as case 4,  it goes up to limit. In case 5 there is no such limit so stresses are unrealistic.