I’ve been struggling with this for quite some time and will be grateful if someone can help me. I have got the data for some tension and torsion tests performed on standard specimen- the tests were done by someone else- not me. I’m trying to do a material modelling based on the tests carried out. I computed the elastic modulus of from the tension tests by fitting a straight line to initial points on the curve of true stress vs true strain (see attached jpg file- modulus_of_elasticity) I now want to compute the shear modulus (modulus of rigidity) by results of torsion test. And I ought to be satisfying the relationship between elastic constants as well (just to make sure that I’ve done things correctly) that is: G = E / 2 (1+mu) Where; G = shear modulus E = modulus of elasticity mu = Poisson’s ratio. Actually, just like tension test, for torsion test too, I plotted shear stress vs shear strain - shear strain being = gamma /2 where gamma = angle of twist (in radians) * radius of the specimen / gauge length. I did this but could not satify the relation (difference being over 50!) G = E / 2 (1+mu) Before going into the details of the shear stress vs shear strain curve, I’m attaching the load set data for torsion test (refer file load_set.xls)given by the experimentologist and shall be grateful if someone shows me the computation of shear stress, angle of twist for just one reading of this set. I feel that I’m missing something here.