A torsion experiment is performed on rods made from glass, a ductile metal and wood. What failure criteria would you use, what do you expect the failure surfaces to look like (including orientation) and why?

The sum of the normal stresses does not change as the stress state rotates through an angle. a)-trune b)- false

Plot schematically the tensile stress versus strain curves for a typical thermoplastic material at a temperature below its glass transition temperature (tg and at a temperature above its tg, respectively. do the same for a typical thermosetting material. list in a table any differences or similarities between the two materials at t> tg and t < tg, respectively, and relate them to the structures of the two types of polymers

Different between right hand turning tool and left hand turning tool ?