Predictive Modeling of Creep Driven Pore Growth under Cyclic High Temperature Tooling Loads
Predictive creep modeling quantifies elevated temperature pore evolution in solid state cell tooling to establish precise hold times and prevent yield loss.
Yield Stress Relaxation
Meaning
Time dependent mechanical phenomenon where the internal stress of a material decreases over time while it is held at a constant state of deformation. Yield stress relaxation is a critical factor in the long term stability of battery pack seals and structural bonds. It describes how the holding force of a gasket or adhesive degrades during the life of the product.
Molecular Process
Polymer chains within the material gradually rearrange themselves to reach a lower energy state under the applied strain. During yield stress relaxation the macroscopic dimensions remain fixed but the pressure exerted by the material against its container drops. This process is accelerated by high temperatures.
Engineering Risk
Loss of tension in a bolted joint or a compressed seal can lead to fluid leaks or mechanical rattling. If yield stress relaxation occurs too quickly, the pack may lose its ingress protection rating against water and dust. Designers must account for this loss when calculating the initial clamping force.
Testing Standard
Laboratory tests use a load cell to track the decay of force in a sample held at a specific percentage of its yield point. This yield stress relaxation curve allows the manufacturer to select materials that maintain at least seventy percent of their original sealing force over the life of the vehicle. Long term data ensures that the battery remains safe and dry in all operational environments.
Proper material characterization prevents the need for expensive recalls due to structural loosening.