The Axial Stability test evaluates the ability of wire/ cable insulation to resist longitudinal dimensional change while cycling between high and low temperatures.
A test sample undergoes five cycles of exposure to heat, cold, and room temperature, remaining at each temperature for the amount of time it takes for the sample to reach thermal equilibrium with its surroundings. After all five cycles are completed, any elongation or shrink-back of each layer of insulation is measured.