Biaxial Strain Hardening Metrics for High Draw Ratio Amorphous Sheet Thermoforming
Biaxial strain hardening metrics dictate wall thickness uniformity in high draw thermoforming; matching plug dynamics to material hardening prevents blowout.
Mooney Rivlin Model
Meaning
Mathematical modeling provides a way to characterize the elasticity of elastomers under moderate deformation. Engineers use the mooney rivlin model to simulate the response of seals and gaskets in various loading conditions. It assumes the material is isotropic and incompressible.
Strain Energy
Density of the stored energy is expressed as a function of the strain invariants. In the mooney rivlin model the simplest form uses two coefficients to describe the relationship between stress and stretch. This formulation captures the linear behavior seen at low to medium strains.
Material Constant
Empirical data from tensile and compression tests are used to determine the specific values for a resin grade. Applying the mooney rivlin model requires careful calibration against the actual batch of elastomer being used. These constants reflect the cross-link density and the stiffness of the polymer.
Predictive Accuracy
Limitations of the theory become apparent when the material is stretched beyond its initial limits. While the mooney rivlin model is excellent for small deformations it fails to account for the hardening seen at high extension. Designers must choose more complex models when the part undergoes extreme stretching.
The simplicity of the two parameter version makes it a popular choice for quick estimations in industrial design. This mathematical tool remains a standard feature in most commercial structural analysis software.