|Mar16-12, 01:32 AM||#1|
Determination of elastic modulii (tension and torsion tests)
Iíve 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.
Iím 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 Iíve done things correctly) that is:
G = E / 2 (1+mu)
G = shear modulus
E = modulus of elasticity
mu = Poissonís 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, Iím 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 Iím missing something here.
|Mar28-12, 09:45 PM||#2|
I see you have no replies..
1) There appears to be damage (plasticity?) occurring in your tension test. None of the equations that you posted apply to plasticity.
2) If you are only considering the elastic portion, which does appear to be linear and small ("infinitesimal") strain, then you are correct: your check on the value of G should match.
You mention shear stress.. but in your Excel file you have torque and angle of twist.. You could write G as a function of the torque and angle of twist, right? Otherwise, how are you obtaining shear stress?
|Similar Threads for: Determination of elastic modulii (tension and torsion tests)|
|Tension in elastic cord at low point||Introductory Physics Homework||3|
|Relation between Frenet-Serret torsion and the torsion tensor?||Differential Geometry||2|
|elastic modulii relation for a sphere||Atomic, Solid State, Comp. Physics||3|
|Elastic energy stored in a shaft under torsion?||Engineering, Comp Sci, & Technology Homework||3|
|Change of entropy for an elastic ribbon under a tension||Advanced Physics Homework||0|