Distribution of the Stress Birefringence. In order to get the stress distribution and make a comparison with the experimental results given by the stress birefringence distribution, we use the formula in  to compute the numerical stress birefringence, which is given as follows:
Here, [DELTA]n is the stress birefringence. is the stress-optical coefficient, which is a constant for linear stress-optical principle, and we take C = 1.
Figure 5 shows the distribution of the stress birefringence at t = 1.05 in the simulation.
Figure 7 gives the change of the stress birefringence from the tail of the insert until the end of the cavity, which is in accordance qualitatively with the experiment in , that is, the stress birefringence increases quickly near the weld line district and then decreases gradually until reaching the tail of the mold cavity.