Nonlinear Creep Damage Parameter Extraction for AA3003 Coolant Plate Joints
Extracting AA3003 braze joint creep damage parameters requires DIC strain mapping under multiaxial stress to prevent premature cold plate fluid leakage.
Norton-Bailey Creep Law
Meaning
Phenomenological power law constitutive equations describe the secondary steady state deformation rate of metallic materials exposed to constant stress and elevated temperature. The Norton-Bailey creep law models time dependent inelastic strain rate as a function of stress magnitude and accumulated time or strain. Structural engineers apply this formulation to forecast high temperature stress relaxation and deformation in power electronics solders and structural fastenings.
The basic formulation assumes constant temperature and isotropic material response, limiting direct application to non isothermal thermal cycling without temperature dependent coefficient modifications.
Empirical Formulation
Stress exponents and time multipliers fit experimental creep curve data across specified stress ranges. Applying the Norton-Bailey creep law requires empirical calibration against uniaxial tensile creep test results. Material constants vary with operating temperature.
Primary Stage
Strain hardening options adjust strain rate calculations during initial transient creep phases. Utilizing the Norton-Bailey creep law in strain hardening form accurately models primary creep deceleration under constant load. Material work hardening resists rapid early deformation.
Structural Application
Finite element simulations compute long term relaxation in copper busbars and cooling plate braze lines. Implementing the Norton-Bailey creep law enables prediction of bolt load retention loss in clamped thermal interfaces. Sustained clamping force loss reduces contact conductance across module cooling assemblies.
Applying the Norton-Bailey creep law predicts long term joint retention forces across thermal cycling regimes.