Material Model comparison Law1 Law 2 Law 36 Law 27
OBJECTIVE:
To Analyse the failure behaviour of model using different material model :
Law1, Law 2 , Law 36 & Law 27.
Case setup, Execution and result:
CASE 1: Law2_epsmax_failure
Below is the Material card & Failure card
No Of cycles : 49480
Simulation time : 71.39 S
Energy Error : 0.2% is acceptable since the value is less than 5%
Mass Error : 0
Max Von mises stress is 287.6 MPa and failure take place by deletion of elements (Ixfem = 0) and failure occurs when strain is 15% of plastic strain (since Eps_p_max = .0.151) .
Energy: The Kinetic energy is zero and the whole of the kinetic energy of sphere is converted into internal energy of the plate and the max value absorbed is 27500 J
Case 2: Law2_epsmax_crack
The Above case is run by changing the below values in failure card.
No Of cycles : 49391
Simulation time : 185.68 S
Energy Error : 3.8% is acceptable since the value is less than 5%
Mass Error : 0
Max Von mises stress is 306.7 MPa and failure take place by cracking of elements (since Ixfem = 1 & Ish_fail =1) and failure occurs when strain is 15% of plastic strain (since Eps_p_max = .0.151)
Energy: The Kinetic energy is zero and the whole of the kinetic energy of sphere is converted into internal energy of the plate and the max value absorbed is 30625 J
Case 3: Law2_epsmax_nofail
The Above case is run by deleting failure card
No Of cycles : 49405
Simulation time : 73.15 S
Energy Error : 0.8% is acceptable since the value is less than 5%
Mass Error : 0
Max Von mises stress is 270.5 MPa and failure take place by deletion of elements (NO failure card) and failure occurs when strain is 15% of plastic strain (since Eps_p_max = .0.151)
Energy: The Kinetic energy is zero and the whole of the kinetic energy of sphere is converted into internal energy of the plate and the max value absorbed is 27000 J.
Case 4: Law2
The Above case is run by deleting failure card & Eps_p_max
No Of cycles : 48737
Simulation time : 7374 S
Energy Error : 3% is acceptable since the value is less than 5%
Mass Error : 0
Max Von mises stress is 424.7 MPa and failure does not occur since failure card and Eps_p_max is not defined and default value is 10E30.
Energy: The Kinetic energy is zero and the whole of the kinetic energy of sphere is converted into internal energy of the plate and the max value absorbed is 65000 J. More energy is absorbed compared to previous cases.
Case 5: Law 1
The Above case is run by creating material model for law1 (elastic property) . Density, Elastic modules and poisson\'s ratio is kept same as above cases.
No Of cycles : 47969
Simulation time : 76.27 S
Energy Error : 0.3% is acceptable since the value is less than 5%
Mass Error : 0
Max Von mises stress is 1086 MPa. Since the plate is elastic , it keeps on deforming and is able to withstand higher stress. once the plate is elastic , once the load is removed , it return back to orginal configuration.
Energy: The Kinetic energy is zero and the whole of the kinetic energy of sphere is converted into internal energy of the plate and the max value absorbed is 8.55e5 J. More energy is absorbed compared to previous cases.the plate is now having higher strength , It is capable of absorbing greater amount of energy.
Case 5: Law 36
Material model is converted to Law 36 with below property and function
No Of cycles : 53149
Simulation time : 80.13 S
Energy Error : 1.1% is acceptable since the value is less than 5%
Mass Error : 0
Max Von mises stress is 1297 MPa. elements gets deleted when strain reaches 16% of plastic strain.
Energy: The Kinetic energy is zero and the whole of the kinetic energy of sphere is converted into internal energy of the plate and the max value absorbed is 105000 J.
Case 7: Law 27
Law27_0000.rad file is run with given property. Law 27 combines isotropic elasto-plastic Johnson-Cook material model with an orthotropic brittle failure model.
No Of cycles :41208
Simulation time : 59.94 S
Energy Error : -4.3% is acceptable
Mass Error : 0
Max Von mises stress is 385.8 MPa. elements gets deleted when strain reaches 15% of plastic strain.
Energy: The Kinetic energy is zero and the whole of the kinetic energy of sphere is converted into internal energy of the plate and the max value absorbed is 29250 J.
CONCLUSION:
1. Law 1 should be used when the displacement is not the purpose of the analysis like vibration.
2. The Real life scenario for ductile material is showcased by case2: law2 with eps_p_max value and Ixfem=1. since in real world the failure happens with crack and no the element deletion.
3. For brittle material Law 27 is the best model.