I have recently done a lab at university which studied the effects of combined bending and torsion. It was conducted using a Hi-tech HSM.11 piece of equipment. We applied loads at a series of angles, 0deg, 45deg and 90deg. We then worked out our priciple stresses and yields. One of the questions is to copmpare our results to those predicted by von mises and tresca. This is where my knowledge struggles as for example at 45deg my sigma1yield I calculated was 0.5MN/m2 and sigma2yield was -0.5MN/m2. When I calculated Von Mises I came up with an answer of 0.75, tresca was 1. What do these results tell me? What would my comparison be?