# Photoelasticity Problem

1. Mar 6, 2013

### MMCS

I am trying to calculate the nominal stress (theoretically) at the edge of the hole (east/west side) in a rectangular shaped sample with a hole in the centre. I have been told to use to equation

stress 1 - stress 2 = (f*n)/t
F = being the fringe stress coefficient (calculated from a previous circular sample)
n = fringe order (calculated from a previous circular sample)

My question is that, This formula does not take into account the reduction in area (like the F/A formula does) at the point of the hole so how can this be the correct formula to use?

Thanks

2. Mar 11, 2013

### afreiden

I believe it does take into account the area.

Your variable "t" is should be smaller for the cross-section where the hole is located, compared to other cross sections in your specimen. Therefore, even if the number of fringes, "n," stays the same, the stress is larger around the hole, as you'd expect.

In other words, your cross-sectional area is represented by "t," since I assume your out-of-plane thickness of your specimen is constant.