Theoretical Mechanism
Viscoplastic constitutive relations provide the framework for analyzing rate dependent inelastic deformation in solder connections during high temperature cycles. Within computational mechanics, the anand model defines the flow stress as a function of temperature and loading rate using a single internal state variable. The boundary of its application sits at approximately half the melting point of the alloy where creep and plasticity combine into a single response.
Constitutive Variable
Hardening and dynamic recovery occur within the material lattice as a single evolution equation. Integration of the anand model requires specific sensitivity constants that define strain rate dependency and hardening coefficients. These values change according to the specific alloy composition such as standard solder blends.
Experimental Verification
Accurate prediction of mechanical fatigue depends upon constant strain rate tests conducted at multiple temperatures. Engineers verify the anand model by comparing simulated hysteresis loops against stress data from physical tests. Calibration is complete once the internal resistance to deformation aligns with physical samples.
Stress Calculation
Integration of the plastic flow occurs throughout the virtual thermal cycle to calculate energy density. The anand model allows for the assessment of reliability without identifying a separate yield criterion. Total damage accumulates per cycle.
