Long Term Interconnect Creep and Weld Fatigue under Cyclic Thermal Load in Heavy Formats
Thermal expansion and cell swell induce cyclic shear stresses that trigger weld fatigue and interconnect creep, requiring compliance flexure loops.
Norton Bailey Law
Meaning
Mathematical equations that describe the rate of steady-state creep deformation in metals and alloys under constant stress and high temperatures guide the evaluation of structural materials in battery cells. Applying the Norton Bailey law allows engineers to predict the long-term mechanical deformation of current collectors and casing materials. This calculation is crucial for assessing the durability of internal cell connections and preventing electrical open-circuits in heavy-duty applications.
Creep Analysis
Electrode materials and tabs experience sustained mechanical loads during the swelling of active materials. Using the Norton Bailey law, designers calculate the rate of plastic deformation in the metal foils over years of operation. This ensures that electrical contact is maintained throughout the life of the battery.
Thermal Influence
Higher operating temperatures accelerate the rate of material creep, increasing the risk of structural failure. The exponents in the Norton Bailey law are fitted using experimental data obtained at different temperature ranges. This characterization helps select alloys that remain stable under thermal and mechanical stress.
Structural Integrity
Cell designers use these predictions to size the internal support structures and terminal welds. Incorporating the Norton Bailey law into finite element models ensures that weld joints do not fail due to creep-induced fatigue. This prevents premature open-circuit failures in the field.