Multiaxial Critical Plane Strain Life Analysis for Conformal Cooled Tooling
Multiaxial critical plane strain-life analysis models out-of-phase thermal and pressure fatigue on internal conformal cooling walls to prevent die failure.
Brown-Miller
Meaning
A multiaxial fatigue criterion calculates the operational lifetime of metallic components subjected to complex, multi-directional strain states. The Brown-Miller algorithm evaluates how combined shear and normal strains on a specific plane determine the initiation of cracks in cell casings and current collectors. It establishes a mathematical relation where the maximum shear strain governs failure, modified by the normal strain acting on the same plane.
This approach defines the limits of physical endurance under combined vibrational and thermal loads in pouch or prismatic cells.
Fatigue Assessment
Analysis of stress states in current collector foils requires multi-axial calculations due to the anisotropic forces generated during cell expansion. The brown-miller formulation allows engineers to predict when structural failure will occur in the copper or aluminum foils under cyclic expansion. It calculates fatigue life by combining tension and shear into a single representative strain value.
Foil Durability
Mechanical wear in electrode foils accelerates under high-rate cycling where volume changes are localized and non-uniform. The use of the brown-miller method in design workflows identifies weak points where stress concentrations might otherwise cause premature tearing. Finite element analysis models utilize this criterion to evaluate the risk of current collector fracture.
Structural Integrity
Sourcing decisions for foil thickness and temper rely on fatigue simulations that utilize these multi-axial strain calculations. The resulting durability predictions establish the minimum material standards for mechanical robustness in long-life batteries. Heavy duty applications utilize these metrics to ensure pack integrity over ten years.