Simple Evaluation of Superplastic Characteristic by Tensile Test Using R-Type Specimen

Abstract

Superplastic elongation is correlated positively with a value of strain-rate sensitivity index m. The measurement method of the value and the shape of specimen for uniaxial tensile test are various. Therefore, a special technique is required to measure the m-value. In this study, R-type specimens having no smoothed region were employed instead of smoothed test-pieces. A series of tests for various aluminum alloys sheets were carried out at elevated temperatures to evaluate superplasticity. It was difficult to measure the m-value using a single R-type specimen. However, the obtained value using more than three test-pieces was fairly in good agreement with the value of smoothed test-pieces. Furthermore, the total elongation of the gage length of 6mm in the bottom of R-part could replace that of the smoothed test-pieces. The obtained value was less scattered in comparison with the value of smoothed specimen. In conclusion, R-type specimen can be useful for simple evaluation of superplasticity.