Temporal Superposition
Temporal alignment of mechanical data sets collected at different temperatures creates a single plot representing material behavior across many decades of time. Performing master curve construction relies on the principle that time and temperature have an equivalent effect on the molecular relaxation of polymers. Data segments are shifted horizontally along the frequency axis to form a continuous line.
This method is valid only for thermorheologically simple materials where all relaxation mechanisms have the same temperature dependence.
Shifting Procedure
Performing the shift involves selecting a reference temperature and moving the other data sets until they overlap. The amount of shift is recorded as a factor that follows the Williams-Landel-Ferry equation.
Data Alignment
Data collected at high temperatures represent the long term behavior of the material at the reference temperature. Conversely, low temperature data show how the material reacts to very high frequencies.
Curve Validity
Validation of the result requires that the individual segments form a smooth and continuous curve without vertical offsets. This combined plot allows engineers to predict the stiffness of a part over several years of service using only a few days of laboratory testing. Accurate construction prevents the failure of structural components under long term load.
