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MECH3315 Mechanics Laboratory
Mechanical Engineering
University of New Haven
Torsion Testing
During this experiment a specimen is loaded into a torsion testing machine and tested to failure. A shear
stress-shear strain diagram is plotted for the specimen, which characterizes the torsional behavior of the sample
and material. Mechanical properties such as torsional yield strength, shear modulus and maximum shear strength
are determined using the shear stress-shear strain diagram.
Outcomes:
 Determination of the torsional properties of a ductile steel test sample using a standard torsion test.
 Observation the behavior of the material under torsion and report observations.
 Study the fracture surface characteristics and report observations.
 Gain familiarity with torsion testing procedures and testing equipment.
The specific items to be determined are:
1. Shearing Proportional Limit: the point where the shear stress and shear strain are no longer linear,
note that some initial chuck tightening might cause a shift in the data while still in the linear range.)
2. Yield Shear Stress using 0.04 radians/meter of gage length. This is determined in the same manner
as the tensile yield strength where the 0.2% offset is replaced by an offset based on the length of
the sample.
3. Probable Tensile Strength: Ultimate and Shear have a rough relation where Shear Strength at
failure = 0.45 to 0.65 of the ultimate tensile strength.
4. Experimental Shear Modulus- G, determined with the slope of the shear stress vs shear strain in the
linear region.
5. Maximum Elastic Shear Strain (useful for torsion spring design)
6. Maximum Shear Strain to failure
7. Type and character of fracture
Equipment:
1. Tinius Olsen Lo-Torq Bench Model Torsion Testing Machine with 10,000 NM torsion load cell and
200 deg resistive encoder. Model 290 display.
2. Steel Specimen
3. Micrometer Caliper & ruler
4. Output device for recording data (printer or computer)