Meaning
The findley power law acts as a mathematical model to predict the creep behavior of polymers under constant stress over extended periods. This relationship assumes that the creep strain accumulates at a rate determined by a power function of time. It effectively maps how plastic parts deform when subjected to static loads while remaining within the limits of linear viscoelasticity.
The utility of the calculation ends once material degradation or extreme environmental shifts render the linear assumption invalid.
Creep Prediction
Engineers employ the findley power law to estimate the long-term dimensional stability of moulded components. It relates the total strain at time t to the instantaneous elastic strain plus a time dependent component. Practitioners set the model constants by performing short-term stress tests at elevated temperatures to extrapolate performance over years of service.
A reliable calculation accounts for the non-linear response of resins when exposed to high load cycles. The accuracy of the estimate rests upon the consistency of the material grade and the precision of the stress level application.
Moulding Variance
Processors differentiate between the datasheet values obtained through standard testing and the actual behaviour of injected parts. Differences arise because the internal stress distribution inside a complex part depends upon the cooling rate and the gate location. Virgin resin typically follows the predicted power law curve with higher accuracy than regrind because the molecular weight distribution stays more uniform.
Moulders use this insight to adjust the gate dimensions or the cooling cycles to minimize residual stresses that could accelerate creep.
Structural Impact
Deviations from the expected power law output often signal a failure in the structural integrity of the assembly. When a part exhibits higher creep than the model predicts, the cause involves either incorrect material selection or an error in the design of the wall thickness. An increased creep rate results in loose fasteners and poor seal contact in housings.
The findley power law defines the boundary between a component that stays rigid and one that fails through gradual structural fatigue.
