Week - 10 Hyperelastic Material Models

HPERELASTIC MATERIAL MODEL

OBJECTIVE:

In this challenge with the given material data below, calculate the Mooney Rivlin and Ogden material constants and compare both using stress-strain data from a Dogbone specimen tensile test with 100 percent strain. The given data is the engineering stress-strain in MPa/(mm/mm). The comparison should be shown from the d3hsp file and using simulation.

PROCEDURE:

• First, we have to extract engineering stress and strain data from the give data and feed that into excel.

• With the extracted data define the stress-strain curve in Ls-prepost.
• Then create a section for the dog_bone specimen.

• Then define the displacement curve for 100% displacement and stress-strain curve.

• Then create MAT_077 material card and MAR_007_ O and assign the stress-strain curve.

• For the boundary condition, we have to constrain one node in all direction and then create a node-set and constrain them in all direction except y so that the specimen compress in y-axis while expanding.

• Then create a prescribed motion in the opposite direction of SPC and constrained in all directions except X-axis and assign the displacement curve to it.

• then assign the sec and MAT in part id.

• Then create control implicit_auto, implicit_general, and termination card so that the stimulation run in the implicit analysis.

• In the database create an extend_binary card and assign STRFLG as 1 so that the strain value can be plotted.

• Then run the stimulation in the Ls-Dyna solver.
• then extract stress and strain in X-direction and compare them with the raw data.

RESULTS

CASE1

In MAT_077 card and MAT_077_O material cards, we have to simulate with varying N1, N2, and N3 number constant to solve and extract the true stress and true strain.

077_MAT_HPERELASTIC_RUBBER

077_O_OGDEN_RUBBER

We have noted the constant C10, C01, C11, C20, C02, C30 in MAT_077 and mu, alpha values in MAT_077_O.

Then the true stress and true strain are converted in engineering stress and eng. strain data and compared with raw data, which merely fit each other.

077_MAT_HPERELASTIC_RUBBER

077_O_OGDEN_RUBBER

CASE2

In this case, we have to simulate by using the constant values C, mu, and alpha constant.

077_MAT_HPERELASTIC_RUBBER

077_O_OGDEN_RUBBER

Then the true stress and true strain are converted in engineering stress and eng. strain data and compared with raw data, which is slightly lesser than Raw data, because the curve trace the path with constants and tries to fit it with.

077_MAT_HPERELASTIC_RUBBER

077_O_OGDEN_RUBBER

CONCLUSION

• from this challenge, we concluded that in both cases N1 is a perfect fit for the data we provided.
• The accuracy is depending on the problems we are doing.
• The knowledge of the hyperelastic material model is obtained
• Mooney Rivlin and Ogden's material constant are determined.