1. The camera orientation for the greatest shear stress differed from the orientation where the extreme normal stresses occured. In fact, the two orientations differed by 45°.

2. As you recall, there was no shear stress on the principal stress planes (in other words, no red arrows). The converse of this situation is not true for the maximum shear stress state. In general, there will be a normal stress acting on the planes of maximum shear stress. This normal stress may be either tension or compression, but in either case, the normal stress will be the same magnitude and direction on all four maximum shear stress surfaces.

3. As we discovered in experiment one, the stresses originally measured in the x and y directions do not tell the complete story of the stress state in the pipe. As designers, we must be aware of the state of stress in all directions.