Hyperelastic Rubber Material in ANSYS APDL

Introduction of Hyperelastic Rubber Material in ANSYS APDL
What is Hyperelastic Material?
Linear Elastic vs Hyperelastic Material
Mechanical Properties of Rubber Material
Linear Elastic Rubber Material in ANSYS APDL
Hyperelastic Rubber Material in ANSYS APDL
Hyperelastic Material Models
Mooney-Rivlin Material Model
Neo-Hookean Material Model
Ogden Material Model
Yeoh Material Model
Arruda-Boyce Material Model
Experimental Material Testing
Curve Fitting for Hyperelastic Materials
Hyperelastic Material Constants
Choosing the Best Hyperelastic Model
Rubber Material for Seismic Base Isolation
Download Project Files

Introduction

Modeling rubber and elastomeric materials is one of the most challenging tasks in ANSYS APDL because these materials exhibit highly nonlinear mechanical behavior even under relatively small strains. Unlike steel or concrete, rubber does not follow Hooke’s law over a wide deformation range.

This project demonstrates how to define Hyper Elastic (Rubber) Material in ANSYS APDL using both linear and nonlinear constitutive models. In addition, the project explains how experimental test results can be converted into material constants suitable for finite element analysis..

Hyperelastic Rubber Material in ANSYS APDL

If you are working on:

Seismic Base Isolation
Rubber Bearings
Elastomeric Pads
Rubber Dampers
Rubber Bushings
Composite Rubber Components

this project will provide the complete workflow required for accurate material modeling.

What is Hyperelastic Material?

Hyperelastic materials are a class of nonlinear materials capable of undergoing extremely large elastic deformations while returning to their original shape after unloading.

Hyperelastic Rubber Material in ANSYS APDL

Typical Hyperelastic materials include:

Natural Rubber
Synthetic Rubber
Silicone Rubber
Elastomers
Polyurethane
Rubber Bearings
Seismic Isolators

Unlike linear elastic materials, Hyperelastic materials require strain-energy density functions instead of a single Young’s Modulus.

Linear Elastic vs Hyperelastic Material

The project first compares two approaches for defining rubber material in ANSYS APDL.

Linear Elastic Method

The simplest method assumes linear behavior and requires only:

Young’s Modulus (E)
Poisson’s Ratio (ν)
Density (ρ)

Although this method is simple, it is only suitable for very small strains.

Hyperelastic Method

For realistic analysis, Hyperelastic behavior must be defined.

The workflow consists of:

Mechanical Property Definition
Selection of Hyperelastic Model
Material Constant Identification
Experimental Curve Fitting
Verification of Material Response

Mechanical Properties of Rubber Material

Rubber materials cannot be described accurately using only:

Young’s Modulus (E)
Poisson’s Ratio (ν)
Density (ρ)

Instead, ANSYS APDL requires Hyperelastic material constants derived from laboratory testing. Hyperelastic Rubber Material in ANSYS APDL

Hyperelastic Material Models in ANSYS APDL

This project introduces the most commonly used Hyperelastic constitutive models:

Neo-Hookean
Mooney-Rivlin
Yeoh
Ogden
Arruda-Boyce

Each model has different levels of accuracy depending on the deformation level and available experimental data.

Mooney-Rivlin Material Model

One of the most widely used Hyperelastic models is the Mooney-Rivlin Model.

In this project, the material is defined using parameters such as:

These coefficients describe the nonlinear stress-strain response of rubber under large deformation.

Experimental Material Testing

Accurate Hyperelastic modeling requires experimental testing.Hyperelastic Rubber Material in ANSYS APDL

Typical laboratory tests include:

Uniaxial Tension Test
Uniaxial Compression Test
Planar Shear Test
Biaxial Test
Volumetric Compression Test

These experiments provide the stress-strain data required for parameter identification.

Curve Fitting Procedure

Instead of manually estimating material constants, the stress-strain curves obtained from experiments are fitted using optimization techniques.

The project explains how Curve Fitting is used to identify:

for the selected Hyperelastic constitutive model.

Choosing the Best Hyperelastic Model

Different applications require different material models.

For example:

Neo-Hookean → Simple deformation
Mooney-Rivlin → Moderate deformation
Yeoh → Large deformation
Ogden → Very accurate nonlinear response
Arruda-Boyce → Polymer chain behavior

Selecting the proper constitutive model significantly improves numerical accuracy.

Rubber Material for Seismic Base Isolation

One of the most important engineering applications of Hyperelastic material modeling is the analysis of Rubber Seismic Base Isolators.

Since base isolators experience large shear deformation during earthquakes, accurate Hyperelastic material models are essential for realistic finite element simulations.

The techniques presented in this project are directly applicable to: