Week - 10 Hyperelastic Material Models

Objective

To calculate the Mooney Rivlin and Ogden material constants and compare the both using stress-strain data from a Dogbone specimen tensile test with 100 percent strain.

Procedue

The given data is the engineering stress-strain are tabulated and the values are plotted as shown in the fig below

The given dogbone model is imported in LS-Dyna PrePost

Then Assign MAT_HYPERELASTIC_RUBBER ,*MAT_OGDEN_RUBBER and section below

The Boundary condition are attached at end side

The above highlighted nodes all the DOF are arrested for translation along Y axis

The above highlighted nodes all the DOF are arrested for translation along Y axis

Displacement curve id is plotted below

Control cards

(CONTROL_IMPLICIT_GENERAL

It activates Implicit analysis and define control parameters

IMFLG – Implicit/Explicit analysis type flag1- Implicit analysis

DTO- Intial time steps size for implicit analysis 0.01

IMFORM – Element formulation flag for seamless spring back : 2 retain original elements

*CONTROL_IMPLICIT_SOLVER

LSolver: LInear equation solver method: 6 (Double precision solver)

*CONTROL_IMPLICIT_AUTO

IAUTO set automatically adjust time step size

ITEOPT Optimum equilibrium iteration count per time step 11

ITEWIN Allowable iteration window 5

.

CONTROL TERMINATION

End time = 1

Analysis setup for material model

The d3hp file for each mat model is opened in notepad and the material constants of Mooney –Rivlin and Ogden as well as sinal fit data

From the output files

MAT_HYPERELASTIC

The Mooney Rivlin constants are

N=1

Mooney Constant C1 = 0.1768E+00

Mooney Constant C2 = 0.1474E+00

N=2

Hyperelastic constant C10 =0.2595E+00

Hyperelastic constant c01 =0.4594E-01

Hyperelastic constant C11 =-0.2092E-01

Hyperelastic constant C20 =0.2913E-02

Hyperelastic constant C02 =0.1016E-02

Hyperelastic constant C30 =0.0000E+00

N=3

Hyperelastic constant C10 =0.2611E+00

Hyperelastic constant c01 =0.4420E-01

Hyperelastic constant C11 =-0.6076E-01

Hyperelastic constant C20 =-0.2667E-02

Hyperelastic constant C02 =-0.9966E-02

Hyperelastic constant C30 =0.1565E-03

MAT_OGDEN_RUBBER

N=1

mu(1)=9.1076024661337E-01

alpha(1)=1.3427238801352

N=2

mu(1)=9.1564732574773E-01

mu(2)=2.2259557306956

alpha(1)=1.3399091914039

alpha(2)=1.843702588226E-03

N=3

mu(1)=-3.1842578658820E-02

mu(2)=2.6137553189304E-01

mu(3)=6.8199192355946E-01

alpha(1)=1.9263321421638

alpha(2)=1.5503405397784

alpha(3)=1.2887820955417

Conclusion

The Money Rivlin and Ogden materials constants are compared and optained /verfied from the d3hsp file.

Money Rivlin and Ogden materials constants using stress-strain data from a Dogbone specimen tensile test with 100 percent strain from the d3hsp file and from the simulation as well ,from comparing the define curve by using constant values we can obtain the same results from the materialscard.Boundary conditions is an another important factors which need to make an implicit simulation stable .hence the model needs to be constrained in all possible ways.Learned how to verify and validate the hyperelastic material model for an given material data.