Coupled Thermomechanical Strain Life FEA for Large Format Gigacast Tray Molds
Coupled thermomechanical strain-life FEA predicts thermal checking and insert fatigue life in gigacast tray molds using non-linear elastoplastic plasticity models.
Bauschinger Effect
Meaning
Strain hardening behavior characterized by a decrease in yield strength when the direction of plastic deformation is reversed. During the high-speed roll-to-roll processing of current collector foils, the bauschinger effect lowers the threshold at which copper or aluminum substrates undergo plastic deformation under reverse tension. This mechanical softening dictates the tension limits required to prevent web creasing and foil rupture during slitting or coating.
The phenomenon applies exclusively to polycrystalline metals undergoing asymmetric or cyclic strain paths.
Yield Asymmetry
Microstructural dislocation pile-ups created during primary tension generate directional back-stresses inside the metallic crystal lattice. Upon load reversal, these internal stresses assist dislocation movement in the opposite direction, forcing the material to yield at a lower stress magnitude than observed during original loading. Thin current collector foils subjected to complex bending over roller arrays experience localized reverse yielding along their microstructural grain boundaries.
Web Distortion
Substrate tension adjustments compensate for reduced directional yield strength.
Calendering Limit
Roller compaction of coated electrode sheets generates intense shear forces at the interface between the active material and the underlying foil substrate. When tension forces fluctuate across the roll-to-roll line, the bauschinger effect causes localized elongation in the metallic foil while the rigid ceramic electrode layer resists deformation. This differential strain degrades interfacial adhesion and induces edge waves across the finished electrode web.
Controlling maximum line tension within narrow operating margins preserves foil planarity.