Week - 10 Hyperelastic Material Models
AIM:The main aim of this week challenge is to use the given stress-strain curve data and create a material modelof hyperelastic rubber and ogden rubber. Validate the create material model card by performing a tensile test on a Dogbone specimen and Finally compare the result of the simulation with the given data.
PROCEDURE:
With the given stress and strain data import the values into the excel and plot a curve with the stress and strain values.
Now use this curve as an input to define the material card.
STEP 1: Open the LS-DYNA pre post and import the basic file containing the nodes and element.
STEP 2:Now create material and section cards for the part.
STEP 3:Open the keyword manager and check the all button.Under the MAT keyword select the MAT 77 H-HYPERELASTIC MATERIAL.
STEP 4:Open the keyword manager and check the all button.Under the SECTION keyword select the SHELL card for wall.Now give the properties of shell as desired.
STEP 5: Now go to PART keyword and assign the part with the desired material and section cards.
STEP 6:The nodes at the fixed end is constrained in the Xand Z direction only and the Y direction is not constrained because of lateral expansion during the tensile test.
The nodes at the middle is constrained in the Y-direction since the neutral axis passes through the middle of the specimen in the X-direction.
STEP 7:Now define a curve in order to give the displacement boundary condition.
STEP 8:Open the keyword manager and check the all button.Under the DEFINE keyword select the CURVE.
STEP 9:Open the keyword manager and check the all button.Under the BOUNDARY keyword select the PRESCRIBED_MOTION_SET.
STEP 10:Open the keyword manager and check the all button.Under the CONTROL keyword and select TERMINATION.Now give the total time of the simulation.
STEP 11:Open the keyword manager and check the all button.Under the DATABASE keyword and select D3PLOT,ASCII option
Once after running the model for N=1,2 and 3 get the value of Mooney Rivlin constant and put the values for those constant with N=0 and then again run the simulation.
N=1
N=2
N=3
Now after running the simulation compare the stress strain plot you got from the simulation with the given data.
STRESS OUTPUT
N=1
N=2
N=3
STRAIN OUTPUT:
N=1
N=2
N=3
Similar to the hyper elastic materials the validate the material card for the ogden rubber material.
Now with all the value same as previous case put n=8 and get the values for all the 8 constants
These are the value of constant that we got from running the simulation.
Now input these values in the material card and run the simulation again.
OUTPUT PLOTS:
STRESS PLOTS
STRAIN PLOTS:
Now plot the stress strain curvefor n=8 and compare it with the given data
CONCLUSION:
Thus the material card for the two material has been created and validated. Both materials exhibit almost similar Properties but the ogden material has a better fit than the hyperelastic material and it can be better controlled as it has 8 constants.The Results Obtained may change in accordance with Poisson's ratio.