The general concept of equivalent stress and strain is examined with a view to its application in combined tension-torsion creep testing of polymers. A description of the apparatus used and the necessary refinements and precautions to give satisfactory results is given. Comparison of data using the equivalence concept generally supports its use as a method of simplifying data. Further results are given for both loading and unloading at various times during the creep test and the inherent problem of describing unloading is highlighted.
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