Meaning
Linear relationship between the mechanical stress in a transparent polymer and its optical birefringence. Stress optical law allows technicians to calculate internal frozen-in tensions by observing the colored patterns in a part under polarized light. It remains valid as long as the material stays within its elastic limit and does not undergo plastic deformation.
Light Rays
Radiation traveling through a stressed plastic splits into two rays that move at different velocities. This difference creates an interference pattern that corresponds to the intensity of the force applied during the moulding process. Results arrive.
Measuring the fringe order gives a numerical value for the stress at any point in the component.
Polariscopes Visualization
Tooling technicians use this principle to see how a gate location or a cooling rate affects the final part. When technicians apply the stress optical law, they can identify areas prone to cracking or warping before the part fails in the field. Patterns emerge.
This technique works for both virgin resins and transparent blends, provided the optical constants of the material are known. It is useful for checking lenses and medical housings where clarity and structural integrity are both required.
Residual Stresses
Residual stresses often cause long-term dimensional drift.
