Week - 10 Hyperelastic Material Models

Aim: To calculate Mooney Rivlin and Ogden material constants and compare both using Stress-Strain data from a Dogbone specimen tensile test with 100% strain.

Hyperelastic material: Material where the strains can be recovered up to 500% strain.

Given data:

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Solution Procedure:

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Mooney Rivlin

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Step 1: Firstly dogbone specimen keyword file is loaded

Step 2: Stress-Strain Curve creation

The given table is converted to curve by using *DEFINE_CURVE as shown in the following figure.

Step 3: Since the length of specimen is 145 mm, we create a displacement curve equal to 100% strain or 1 strain value as shown in the following figure:

Step 4: Material card.

Hyperelastic material (*MAT_HYPERELASTIC_RUBBER) is created and LCID1 is assigned with previously defined stress-strain curve.

Step 5: Shell section creation

Step 6:Boundary Conditions:

1. Left side edge nodes are constrained in all directions except Y direction as shown.

2. middle node on either sides are contrained as shown.

3. Displacement is assigned to right side edge nodes using *PRESCRIBED_BOUNDARY_MOTION

Step 7: Implicit solutions cards

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Ogden Material creation for Ogden constant

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only material is changed in the next simulation as shown in below figure

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Results

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Constants obtained from d3hsp file

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Ogden Constants

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Stress Values Comparison

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Mooney-Rivlin

N=1

N=2

N=3

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Stress values after inputing the constants back in material cards

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N=1

N=2

N=3

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Ogden Constants before using the constants in the material card

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N=1

N=2

N=3

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Stress comparison after using Ogden constants in material card

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N= 1

N=2

N=3

Conclusions:

We performed uniaxial tensile test using MooneyRivlin and Ogden material constants

We obtained d3hsp file and extracted constants the we used the constants back in material card and performed the simulation again.

Hyperelastic material 77H yielded better results than 77O material.

We compared the stress values which agree with each other.