ASTM A938 Torsion Testing of Wire

Scope:

The standard test method, Torsion Testing of Wire ASTM A938, is a valuable technique for measuring wire ductility under torsional loading. The complex stress and strain conditions that arise in the sample throughout the test are sensitive to tiny differences in materials. A torsion test is used to examine how a sample reacts when it is twisted or subjected to torsional stresses due to the applied moments that create shear stress along the axis.

Procedure:

The ASTM A938 specimen is clamped along its longitudinal axis. The specimen is prevented from deflecting away from the axis of rotation during twisting by applying tensile force. Excessive speed results in a lower torsion value, and the specimen is placed in the machine. The clamp is rotated at a constant speed until the test specimen is fractured. 

Specimen size:

For ASTM A938, the recommended test length (distance between clamping heads) is 8 in. (203 mm).

Result:

The test specimen is judged to have passed the test if the number of turns is satisfactory.

Conclusion:

The standard test method, Torsion Testing of Wire ASTM A938, is a valuable technique for measuring wire ductility under torsional loading.