TORSION TESTING OF MILD STEEL MATERIAL: ENIAPb steel SPECIMEN: Nominally 17.1 mm dia. But exact diameter should be noted. TORSIOMETER: Dial indicator type, 0.001 radians/division, gauge length 81mm (L) - this

measures angle of twist. PROCEDURE: 1. Insert the specimen into the jaws/grips of the Torque Tester and using the torque scale 0-750 Nm load the specimen up to 200 Nm in steps of 25 Nm noting the angle of twist at each torque increment. 2. Unload specimen to zero torque in 25 Nm increments again noting the angle of twist at each torque increment. 3. Repeat Step 1. 4. Continue noting measurements of torque/angle of twist to beyond yield removing the extensometer at, say, 350 Nm. 5. Change gear from 314%/min to 90%/min and note the time to fracture. POST-TEST ANALYSIS • For "elastic torsion" of a circular shaft: T T GO 7-7-2 = = JR L • Using the data obtained in 1, 2, and 3 draw a graph of torque (7) in Nm against angle of twist (0) in radians find the shear modulus (G): T GO T GJ TL It ; therefore: G = G = slope of 07 = Trearrange: 0 • Estimate the yield strength in shear, Ty • Estimate the total angle of twist to fracture TENSILE TESTING/TORSION TESTING OF MILD STEEL Knowing relationship between tensile modulus, E, shear modulus, G, and Poisson's ratio, v E-2G(1+v) TL "Estimate" a value of Poisson's ratio for steel./nExperimentation Precise details of items under test, and of the testing system, are required. Sketches, circuit diagrams, and/or CAD drawings are often required in this section. All equipment should be specified fully (i.e. using model numbers, and reference numbers if possible) with the exception of minor ancillary equipment such as a metre rule, protractor etc. This specification may also include the accuracy of the equipment used. Always remember that at some future date the experimental results may be subject to severe scrutiny and the more accurately the system has been specified the less the doubt concerning the test, and the better the chance of remedial action. Concise details of the operations performed should be presented mentioning factors which are of special significance. Trivial statements however should be avoided, but, for example, where the order of performing a number of steps is considered to be important such information should be concisely presented. The writing style should resemble a recipe in a cookbook. It is particularly useful to refer to special precautions taken as this can often eliminate possible doubts in a future enquiry. The purpose of this section is to define the experimental techniques employed without ambiguity, and thus in a way which would permit a complete identical "re-test". Remember it was done in the past.