Combined Bending & Torsion

[pauljackson77]

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 principle 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?

 

[LightHero]

The comparison between the von Mises and Tresca results can tell you how much more or less stress the material can take before yielding. The von Mises yield criterion is known to overestimate the yield strength of materials, so if your calculated yield strength value is lower than the von Mises prediction, then the material is likely capable of withstanding more stress before yielding. On the other hand, if the calculated yield strength value is higher than the Tresca prediction, then the material is likely capable of withstanding less stress before yielding. In your case, your calculated yield strength values are 0.5MN/m2 and -0.5MN/m2, respectively, which are lower than the von Mises prediction of 0.75 and the Tresca prediction of 1. Therefore, this suggests that the material is capable of withstanding more stress before yielding.