Measurement method for stress–strain curve in a super-large strain range

Flow stress is an essential material property for metal forming. A stress–strain (SS) curve is generally measured by tensile testing or compression testing. In some metal forming processes, the maximum strain exceeds 5.0 (500%); however, standard testing methods can only measure an SS curve up to a strain of 1.0. Therefore, a new method was developed that enables us to measure an SS curve for strains up to 10.0. ressure torsion (HPT) was applied for the measurement. Using HPT, it is possible to deform a specimen without fracture. Therefore, larger strains can be introduced into a specimen than with conventional methods. An SS curve measurement was performed for pure aluminum. The measured torque during HPT and the average strain in the specimen were converted into an SS curve. The SS curve measured using the developed method was compared with that obtained using a compression test. It is confirmed that the flow stress was successfully measured up to a strain of 10.0. In addition, the results for the developed method correspond with those of the compression test up to a strain of 1.0.