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ASSIGNMENT-4

RRenu Kumar17 Apr 2020

ASSIGNMENT-4

COMPARISON OF 7 CASES AS DISCUSSED IN LAST THREE SLIDES, IN A TABULATED FORMAT

OBJECTIVE:

The objective of ASSIGNMENT-4 is to comparison of 7 cases and we have to absorb the component that how it will behave at different material properties by changing the material card. and we have to absorb that the materials are being deleted or cracked. And we have to perform the following operations.

1. To identify the total number of cycles, Energy error, mass error and simulation time.
2. To notice the animation of all 5 and describe the animations in brief on the
basis of whether the elements are being deleted or cracked.
3. To Plot the energies and to notice any difference.
4. Based on all the results, TO know which case would represent the on-field scenario.

5. To list a case by case result and the conclusion.

The following are the 7 cases that we have to simulate, by modifying some corrections in the material card as well as in the property card.

JOHNSON COOK MATERIAL APPLICATION:

CASE-1:

Run the model as it is. Name the model as Law2_epsmax_failure.

CASE-2:

In /FAIL/JOHNSON, change Ifail_sh=1, Dadv=1,and Ixfem=1. Run the model as Law2_epsmax_crack.

CASE-3:

Delete /FAIL/JOHNSON card. Run the model as Law2_epsmax_nofail.

CASE-4:

Delete the value of EPS_p_max and run the model with the name Law2.

CASE-5:

Convert this material model to Law1 elastic with same density, E, nu and run.Check the results.

PLAST_BRIT MATERIAL APPLICATION:

CASE-6:

Open Law27_0000.rad.

change the shell properties to recommended shell properties.

Notice the material card. Johnson cook parameters, but different values for EPS based failure.

Run the model with name Law27.

PLAS_TAB MATERIAL APPLICATION:

CASE-7:

Creating a material card with Law36, and adding some details.

Case set up and Execution:

TASK-1 : Total number of cycles, Energy error, mass error and simulation time.

Importing the model: To start running the model first we have to import the model by using import solver deck.

FIG IMPORTING MODEL.

CASE-1: Run the model as it is. Name the model as Law2_epsmax_failure.

/MAT/LAW2 (PLAS_JOHNS) Johnson-Cook Material:This law represents an isotropic elasto-plastic material using the Johnson-Cook material model. This model expresses material stress as a function of strain, strain rate and temperature. A built-in failure criterion based on the maximum plastic strain is available.

Law Name Group Type Model Description Application Viscosity Orthotrop Embedded Thermal Option** Strain Rate Formulation
/MAT/LAW2 Elasto-plastic materials Metal Isotropic elasto-plastic material using the Johnson-Cook material model Metals, elasto-plastic materials, mild steels, strain rate dependent, temperature dependent, isotropic and kinematic hardening, duroplaste, low alloy steel, ST52, and DP600 No No Yes Yes Lagrange

In this model the material behaves as a linear-elastic material when the equivalent stress is lower than the plastic yield stress. For higher stress values, the material behavior is plastic, and the true stress is calculated as:

σ=(a+bεpn)(1+cln˙ε/˙ε0)(1−(T∗)m)
Where,
T*=T−Tr/Tmelt−Tr
Where,
εp = Plastic strain
ε˙ = Strain rate
T = Temperature
Tr = Ambient temperature
Tmelt = Melting temperature
Where the influence of temperature change and strain rate are neglected.
Procedure:
After importing the model we have to run the simulation. So without changing any material or shell properties run the simulation.
WHERE:
Rho initial = initial density
E = Youngs mobulu\'s
Nu = poissson ratio
Iflag = Input type flag
0 = Classic input for Johnson-Cook using parameters a, b, n.
1 = Simplified input type using σy\">σyσy , UTS, or εUTS\">εUTSεUTS .
SIGY or a = Yield stress
b = Plastic hardening parameter
n = Plastic hardening exponent
EPS_p_max = failure plastic strain is that at where my model going to fail after the yield point in the plastic region
in the terms of percent example given in the model is 0.151
my model will fail at 15.1% after the yield point in the plastic region.
SIG_max0 = maximum stress
c = strain rate cofficient
EPS_DOT_0 = Reference strain rate
ICC = Strain rate computation
Fsmooth = Strain rate smoothing flag.
Fcut = Cutoff frequency for strain rate smoothing.
Chard = Hardening coefficient (unloading)
m = temperature exponent
WHERE:
D1 = First parameter
D2 = second parameter
D3 = Third parameter
D4 = Fourth parameter
D5 = Fifth parameter
Epsilon_Dot_0 = reference strain rate
Ifail_sh = flag for shell failure model
Ifail_so = flag for solid failure model
Dadv = criterion for the crack advancement
Ixfem = XFEM flag
So go to analysis - radioss - and save the file in the respected folder with respected name. by keeping the options
export = all
run = analysis
run number = 1
options = -nt 4
After running the file open the FAILURE_JOHNSON_0001 and check for the energy error and mass error.
Total number of cycles = 49480 (as per radioss solver browser)
energy error = 0.2%
mass error = 0.000
simulation time = 99884.46s

ENERGY ERROR: Basically energy error must be negative and decreasing.The Error must be less than 15% at the end of computation, as per the condition. If the error is below 15% than the results could be acceptable.

So from the above figure, at the end of computation the energy error is 0.2% and mass error is 0.000 As per the condition the energy error is 0.2% which is below the 15% and the results could be acceptable for further simulation and ploting of graphs.

CASE-2: In /FAIL/JOHNSON, change Ifail_sh=1, Dadv=1,and Ixfem=1. Run the model as Law2_epsmax_crack.

In case-2, we have to change some parameters in /fail/johnson. such as:

Ifail_sh = 1 (shell is deleted or cracked)

Dadv = 1

Ixfem = 1

the reason behind changing the parameters is that we have to compare that how a model we behave at different parameters by changing some parameters.

so go to failure johnson and edit the parameters.

After editing the parameters run the model and save it in a respected folder. by doing following procedure.

So go to analysis - radioss - and save the file in the respected folder with respected name. by keeping the options
export = all
run = analysis
run number = 1
options = -nt 4
After running the file open the FAILURE_JOHNSON_0001 and check for the energy error and mass error.
Total number of cycles = 49397 (as per radioss solver browser)
energy error = 4.0%
mass error = 0.000
simulation time = 98014.70 s
So from the above figure, at the end of computation the energy error is 4.0% and mass error is 0.000 As per the condition the energy error is 0.2% which is below the 15% and the results could be acceptable for further simulation and ploting of graphs.

CASE-3: Delete /FAIL/JOHNSON card. Run the model as Law2_epsmax_nofail.

In case three we have to delete the johnson fail card. for this we have to go to the model option and select the failure and delete it.

After deleting the failure card run the model and save it in a respected folder. by doing following procedure.

So go to analysis - radioss - and save the file in the respected folder with respected name. by keeping the options
export = all
run = analysis
run number = 1
options = -nt 4
After running the file open the FAILURE_JOHNSON_0001 and check for the energy error and mass error.
Total number of cycles = 49405 (as per radioss solver browser)
energy error = 0.8%
mass error = 0.000
simulation time = 98703.56 s
So from the above figure, at the end of computation the energy error is 4.0% and mass error is 0.000 As per the condition the energy error is 0.2% which is below the 15% and the results could be acceptable for further simulation and ploting of graphs.

CASE-4: Delete the value of EPS_p_max and run the model with the name Law2.

In case-4, we have to delete the EPS_p_max. so go to material properties and select the EPS_p_max and keep it value as zero.

After keeping the value of EPS_p_max is zero, run the model and save it in a respected folder. by doing following procedure.

So go to analysis - radioss - and save the file in the respected folder with respected name. by keeping the options
export = all
run = analysis
run number = 1
options = -nt 4
After running the file open the FAILURE_JOHNSON_0001 and check for the energy error and mass error.
Total number of cycles = 48737 (as per radioss solver browser)
energy error = 3.0%
mass error = 0.000
simulation time = 92897.47s
So from the above figure, at the end of computation the energy error is 3.0% and mass error is 0.000 As per the condition the energy error is 0.2% which is below the 15% and the results could be acceptable for further simulation and ploting of graphs.

CASE-5: Convert this material model to Law1 elastic with same density, E, nu and run.Check the results.

In case-5 we have to convert the Law2 material card to Law1 material card for that we have to go to the material card and select the Law1 material.

AFTER selecting the material give some input values such as,

Density = 0.0028

E = 71000.0

nu = 0.33

After changing the law2 material card to law1 material card, run the model and save it in a respected folder. by doing following procedure.

So go to analysis - radioss - and save the file in the respected folder with respected name. by keeping the options
export = all
run = analysis
run number = 1
options = -nt 4
After running the file open the FAILURE_JOHNSON_0001 and check for the energy error and mass error.
Total number of cycles = 47969 (as per radioss solver browser)
energy error = 0.3%
mass error = 0.000
simulation time = 67754.14 s
So from the above figure, at the end of computation the energy error is 3.0% and mass error is 0.000 As per the condition the energy error is 0.2% which is below the 15% and the results could be acceptable for further simulation and ploting of graphs.

PLAST_BRIT MATERIAL APPLICATION:

Law Name Group Type Model Description Application Viscosity Orthotrop Embedded Thermal Option** Strain Rate Formulation

/MAT/LAW27

(PLAST_BRIT)

 Elasto-plastic materials Brittle Metal and Glass Aluminum, glass, etc. Hard steel, Dualphase steel, DP800, DP1000, casting, aluminum, magnesium, poly carbonate, and glass No No No Yes Lagrange

/MAT/LAW27 (PLAS_BRIT) Elasto-Plastic Material with Brittle Failure
• This law combines an isotropic elasto-plastic Johnson-Cook material model with an orthotropic brittle failure model. Material damage is accounted for prior to failure. Failure and damage occur only in tension. This law is applicable only for shells.

• Yield surface definition same as Johnson-Cook (Law2)

• Useful for modeling brittle failure of glass

CASE-6:

Open Law27_0000.rad.

change the shell properties to recommended shell properties.

Notice the material card. Johnson cook parameters, but different values for EPS based failure. We have to change the material parameters, which is diffferent for EPS based failure. The default card is to be Johnson cook parameters. change the values and run the model.

After changing the shell and material parameters, run the model and save it in a respected folder. by doing following procedure.

So go to analysis - radioss - and save the file in the respected folder with respected name. by keeping the options
export = all
run = analysis
run number = 1
options = -nt 4
After running the file open the FAILURE_JOHNSON_0001 and check for the energy error and mass error.

Total number of cycles = 62869 (as per radioss solver browser)
energy error = -1.9%
mass error = 0.000
simulation time = 87946.62 s
So from the above figure, at the end of computation the energy error is 3.0% and mass error is 0.000 As per the condition the energy error is 0.2% which is below the 15% and the results could be acceptable for further simulation and ploting of graphs.

PLAS_TAB MATERIAL APPLICATION:

Law Name Group Type Model Description Application Viscosity Orthotrop Embedded Thermal Option** Strain Rate Formulation

/MAT/LAW36

(PLAS_TAB)
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