FEA White Paper, Part 1: Material Properties

Photo: Design Engineer Thomas Morgan uses modeling software for Finite Element Analysis of an electrical connector gasket

This white paper explores the importance of understanding material properties when performing Finite Element Analysis (FEA) on elastomer seals.

Here’s a summary of what you’ll find in this white paper, which we originally published as a three-part series in 2022:

Why Use FEA?

FEA helps in predicting the durability of seals by simulating stresses and strains under extreme environmental and temperature conditions. This allows for faster iterations during the design process, reducing the need for physical prototypes and real-world testing. It also enables precise adjustments to design without the risk of production delays.

What is FEA?

FEA is a simulation that predicts how parts will behave under real-world conditions by creating a mathematical model of the part's shape, discretized into finite elements. These elements approximate the properties of the material, and the interaction between nodes determines how the part reacts to external forces and deformations.

Material Properties and Testing

Rubber is a highly non-linear, hyperelastic material, meaning it can undergo significant deformations without permanent damage and return to its original shape. To capture this in FEA, labs perform various tests (uniaxial, planar, and biaxial tension, and compression tests) to understand the material's behavior under different types of strain.

Approximation Equations

To simulate elastomer behavior in FEA, approximation equations are used. Early models like Neo-Hooke and Mooney-Rivlin equations were limited in capturing the non-linear nature of elastomers. Modern models, like the Ogden model, are more versatile and accurate, especially at higher strain rates.

Compressive Stress Relaxation (CSR)

CSR is the long-term reduction in the force exerted by elastomers due to molecular changes and heat. Over time, seals lose their ability to maintain sealing force, especially in extreme environments. Engineers must account for CSR in design by considering both fresh and aged material properties to ensure long-term seal performance.

This white paper is part one of a series, with subsequent papers focusing on simulation setup and real-world application. To read the other parts of this series, check out these links:

FEA White Paper Part 2 -setup

FEA White Paper Part 3 - results