An Experimental Investigation of Yield Surfaces and Loading Surfaces of Pure Aluminum With Stress-Controlled and Strain-Controlled Paths of Loading

Tension-torsion tests with a computer controlled servohydraulic testing machine are reported. Yield surfaces were obtained during a load controlled path, which includes combined stress creep, as well as during a strain controlled path, which includes combined stress relaxation. These surfaces and their relation to the corresponding loading surfaces is discussed. The development of plastic strain increments and their relation to the yield surfaces and loading surfaces is also discussed.