Evaluating Viscoelastic Creep and Tactile Probe Indentation during Elastomer Metrology
Tactile metrology of elastomers requires sub-0.02 N trigger forces and zero-load extrapolation to prevent viscoelastic creep from corrupting part dimensions.
Prony Series Relaxation
Meaning
Mathematical models describe the time-dependent stress reduction of viscoelastic materials held at a constant strain. Engineers utilize prony series relaxation to model how polymer seals and shock absorbers lose their holding force over time. The model represents the relaxation curve as a series of exponential decay terms.
Mathematical Formula
Computational representations utilize a sum of exponential decay terms to approximate how polymers release mechanical energy over extended periods. Viscoelastic models incorporate multiple relaxation times to capture the short-term and long-term behavior of the elastomer. Each term in the mathematical sequence corresponds to a specific molecular relaxation mechanism.
This formulation is highly efficient for finite element analysis calculations.
Material Behavior
Physical deformation tests measure the force decay curves necessary to fit the coefficient values for a specific elastomer formulation. Technicians place a polymer specimen under constant compression and monitor the decay of force over several hours or days. The resulting data is then fitted to the series using non-linear regression techniques.
Accurate coefficients are required to simulate how seals perform under the fluctuating thermal and mechanical loads of industrial machinery. Failing to capture this behavior can lead to early seal failures and fluid leaks in critical factory equipment.
Component Simulation
Structural simulations use these calculated coefficients to predict the sealing pressure of gaskets under long-term compression. Designers adjust the elastomer geometry to ensure it maintains a minimum force over its planned operating life. This step is necessary to verify the durability of the assembly.