In this blog I thought we could do a small dive into hyper- and viscoelastic materials and how to model these in Abaqus. Many elastomers, rubbers and biological soft tissues exhibit such behaviors.  

The “Introduction to Finite Element Analysis for Rubbers” Workshop is a free event for anyone dealing with Rubbers, who has beginner or advanced experience in simulation and FEA, but would like to look at extending the scope of the work they do. This workshop is an ideal way to understand what advanced simulation can offer and find out how easy it is to perform a real world non-linear analysis on rubber materials or products. This event will be held this Friday the 23rd of April.

In this blog, we’ll take a look at an air spring (Figure 1). This device is used for vibration isolation as well as suspension, for example in heavy weight vehicle applications.

Figure 1: Example of an air spring.

The example shown here consists of a convoluted bellows (two convolutions), with steel plates on each end. In practice, one to three convolutions are used. The bellows is made of rubber that is reinforced with fibres. A steel girdle hoop helps to keep it in shape when it is filled with compressed air.

To model the behaviour of rubbers and rubber-like materials, typically hyperelastic material models are used. A hyperelastic material is elastic: after unloading, the material returns to its original shape. The material state therefore does not depend on the history or the rate of deformation, but only on the current loading. The model is based on a strain energy potential, which is a function of the (invariants of the) current strain.

In this blog, the hyperelastic behaviour modelling in Abaqus will be discussed.  This will be implemented by fitting relevant experimental data with appropriate strain potential energy functions that are built-in in Abaqus and deciding on the function that best models the rubber materials behaviour. Additionally a finite element model will be demonstrated, wherein the designated material behaviour will be show cased.

Last but not least, in the process of explaining relevant aspects  of hyperelastic material modelling with Abaqus, various suggestions and good practices will be shared.

In this blog we will focus on the capabilities of Simulia Abaqus to assist in modelling rubber like materials.
Rubber materials such as thermoplastics are largely used in the industry; to list some of the areas where these materials can be found we can mention tyre industry, consumer pack goods, medical or sealing solutions but rubbers are also present in many others engineering fields. Today I will dedicate the next lines to the sealing market due to its beneficial ratio between ease to explain-build up a model and the high end capabilities that Abaqus can provide.