Simple Evaluation of Superplasticity Using a Tensile Test with R-type Specimens

Abstract

Superplastic elongation depends heavily on a value of strain-rate sensitivity index m. The value of m is obtained by various methods, using specimens of various shapes for uniaxial tensile tests. A special technique is required to measure the m-value. In this study, R-type specimens having no smoothed region were employed instead of ordinary smoothed specimens. A series of tests for various aluminum alloy sheets and titanium alloy bars 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 specimens was in fairly good agreement with the value of smoothed specimen. Furthermore, the total elongation of the gauge length of mm at the bottom of the R-part could replace that of the smoothed test-pieces. The obtained value was less scattered in comparison with the value of the smoothed specimens. Consequently, R-type specimen can be useful for simple evaluation of superplasticity.