Week - 10 Hyperelastic Material Models

Objective: To perform a tensile test with 100% strain for both Mooney Rivilin and ogden material constant using given stress-strain data.

Procedure:

A. Choosing a hyperelastic material for the model

B. Specifying experiment data into the material model

C. Extract material constant and curve fit data for each order of polynomial from the D3 HSP file.

D. Extract stress-strain curve from the simulation for each order of the polynomial.

E. Comparing the stress-strain curve with experimental data.

1. MOONLEY RIVLIN MATERIAL 

Specifying Material data in Material Model 

the stress and strain values are in engineering stress and strain format so we need not convert them.

open the define_drive card and enter the values

Material card

enter 

1. MID=1

2. RO=0.0010

3. PR= 0.491

4. N= Number of constant to solve for =1-3 for each case

5. LCSS Loard curve ID defining Engineering stress versus engineering strain LCID from define_curve

TENSILE TEST 

The material is graphite iron casting for the meshed dogbone specimen 

Boundary Condition 

for the tensile test, one end is fixed, one at centers and the other end is given displacement Hence 3BCS

1. Boundary condition

Constraint one end of the specimen in all direction except for y because when it elongate in x direction the width along with y contracts.

Select the mid-nodes on both ends and constrain them for the y direction.

2. Boundary_Prescribed_Motion_Set

A node-set is created at the other end of the speciemen. In the tensile test, the strain should be at 100% so the displacement is given at 145mm, the same  length as the specimen.

3. control implicit Auto Parameters like general, solution solver are set.

4. data base binary d3plot and ASCll cards -GLSTAT cards are created for knowing strain history.

5. The simulation with a given load curve is run Mooney constants are obtained 

N=1

Mooney constant c1 = 0.1768E+00

Mooney constant c2 = 0.1474E+00

N=2

N=3

6. The fitted curve is verified and compared with given engineering stress and strain values.

7. The stretch is then converted to engineering strain (engineering strain=1-stretch)

8. True stress is also converted to engineering stress ( engineering stress=true stress/(1+engineering strain)

9. from the graph obtained, we can find that the fitted data curve follow the given data.

10. Taking the constant into consideration, the tensile test is simulated and validated 

11. The stress-strain data is plotted after simulation and the data is converted to engineering stress-strain values and plotted and compared with given data.

12. using ogden material, a similar process is carried out to validate the curve.

13. The graph is plotted and compared

14. The constant are noted down and a tensile test is performed on the model to validate the derived constant.

15. The simulation data from the tensile test follows the data and is hence validated.

Conclusion:

1. The hyperelastic material modeling is simulation for the tensile test with given load curve data.

2. The constant we obtained found out that the material curve is valid for the uniaxial stress data derived from the stress-strain element history curve

3. The graph for n=1,n=2,n=3 is plotted and compared with experimental data.