Challenge

Assignment 4

COMPARING DIFFERENCE MATERIAL LAWS IN RADIOSS

OBJECTIVES:

In this assignment we have to Compare 7 cases as discussed in last 3 slides, in a tabulated format on the basis of:

CASE1 AND CASE2:

In this comparison we have to compare two Johnson cook material model failure card.
Johnson cook material is used for isotropic elastic-plastic material.
In case1 ifail_sh = 0, Dadv = 0, ixfem = 0 (default) while in case2 ifail_sh = 1, Dadv = 1, ixfem = 1.

Dadv and ixfem is for crack, due to that in case1 elements will deleted without crack while in case 2 elements will crack first then deleted.
Due to crack in elements case 2 take more time then case 1.
The stress generated in case 1 is less than case 2 because crack is generated in case2.

case1 case2

In case 1 the elements are deleted first so the kinetic force have sudden hike but in case 2 it has more smother than case 1 because of the crack will form first.

case1 case2

In both the cases the internal energy increases linearly and become sustain because initially both has elastic strain.

case1 case2

case1 case2

CASE3 AND CASE4:

In this comparison we have to deleted the Johnson failure card in case 2 and then delete the epsmax value in case4.

Epsmax value is the maximum strain percentage value of the material.
In case 3 epsmax value is given hence there is deletion of elements but in case 4 there is no epsmax value hence it has infinite deformation.
Due to deletion of elements stress in case 3 is less than case4.

case4 case3

In case 3 the kinetic energy is sudden hike due to element deletion while in case 4 initially a sudden hike is there but after that it almost constant.

case3 case4

In both the case the internal energy is increases exponentially but in case 3 in become almost constant after the elements are get deleted.

case3 case4

case3 case4

CASE5:

The law1 is based on the parameters density, young’s modulus and poission ratio.
1. Density = 0.0027
2. E= 71000
3. Poission ratio = 0.33
In law1 there is no deletion of elements the deformation will be until the failure plastic strain reaches the epsmax 16%.
It is mainly used in large deformations.

CASE6:

Law 27 is used for brittle failure where equivalent stress is lower than the plastic yield stress.
Failure and damage occur only in tension.
This law is applicable only in shell.
Due to eps_f1=0.151 the material breaks like glass.
Hourglass is zero because of QEPH.

CASE7:

This model is an isotropic elastro-plastic material using user-defined for stress and strain curve.

case	Material model/Law	Number of cycle	Energy error	Mass error	Cycle time (s)	on-field scenario
Case1	Failure Johnson cook law2	49479	-0.3% to 1%	0	129.07	Elastic equivalent stress is less than yield stress
Case2	Failure Johnson cook law2	49369	-0.3% to 5.8%	0	138.45	Elastic equivalent stress is less than yield stress
Case3	Johnson cook law2 with epsmax	49404	-0.3% to 1.2%	0	126.86	Elastic equivalent stress is less than yield stress
Case4	Johnson cook law2 without epsmax	48736	-0.3% to 3%	0	126.77	Elastic equivalent stress is less than yield stress
Case5	Law1 elastro plastic	47968	-0.3% to 4%	0	125.00 s	Purely elastic material
Case6	Law27 plas_brit	41854	-4.4% to 0.6%	0	109.28	Brittle material
Case7	Law36 plas_tab	41854	-4.4% to 0.6%	0	113.22	Elastic plastic material – isotropic material

RESULT AND CONCLUSION:

In this assignment learnt about the different material laws in RADIOSS and how to assign them.

Ship work like this
in your own course.