A Planar Simple Shear Test and Flow Behavior
in a Superplastic Al-Mg Alloy
Superplasticity is generally studied by performing tensile and gas-pressure-bulge tests. In formed
parts, however, a variety of strain states, including in-plane shear, are encountered. The understanding
of the mechanical response in shear is helpful in the study of superplastic metal forming. In this study,
a device for a planar simple shear test was designed and used to perform tests on a superplastic Al-Mg
alloy sheet at the elevated temperatures of 500 °C (773K) and 550 °C (823K). In such a test, the incremental
rotation of the principal strain axes and specimen-end effects during deformation can complicate
the determination of true mechanical response. The possible approximations regarding the
strain state in the specimen gage have been investigated. The e-e curves developed based on a simple-
shear assumption show a lower flow stress than that under uniaxial tension, and strain hardening
is related to dynamic grain growth. The rate of strain hardening at a fixed level is essentially the
same for both uniaxial tension and shear, but the difference in the effective stress between uniaxial
tension and shear depends upon strain rate and temperature. This study marks the first known attempt
to characterize large strain response for superplastic metals under conditions of simple shear.
in a Superplastic Al-Mg Alloy
Superplasticity is generally studied by performing tensile and gas-pressure-bulge tests. In formed
parts, however, a variety of strain states, including in-plane shear, are encountered. The understanding
of the mechanical response in shear is helpful in the study of superplastic metal forming. In this study,
a device for a planar simple shear test was designed and used to perform tests on a superplastic Al-Mg
alloy sheet at the elevated temperatures of 500 °C (773K) and 550 °C (823K). In such a test, the incremental
rotation of the principal strain axes and specimen-end effects during deformation can complicate
the determination of true mechanical response. The possible approximations regarding the
strain state in the specimen gage have been investigated. The e-e curves developed based on a simple-
shear assumption show a lower flow stress than that under uniaxial tension, and strain hardening
is related to dynamic grain growth. The rate of strain hardening at a fixed level is essentially the
same for both uniaxial tension and shear, but the difference in the effective stress between uniaxial
tension and shear depends upon strain rate and temperature. This study marks the first known attempt
to characterize large strain response for superplastic metals under conditions of simple shear.