Stress-strain curve measurements of aluminum alloy and carbon steel by unconstrained-type high-pressure torsion testing

Publication date: 15 May 2017
Source:Materials & Design, Volume 122
Author(s): Yasuhiro Yogo, Masatoshi Sawamura, Noritoshi Iwata, Nobuyuki Yukawa
In measurements of stress-strain (SS) curves, it is difficult to achieve a large strain, i.e., 5 (500%), which is introduced in actual metal forming processes. Recently, a constrained-type high-pressure torsion test was applied and allowed measurement of the SS curve up to a strain of 10. However, the testing method cannot be used for steel specimens, because a compression pressure of over 3GPa has to be applied to a specimen via the dies, which leads to brakeage of the dies due to the stress concentration. Therefore, an unconstrained-type high-pressure torsion was applied for measurement of the SS curves of carbon steel. With this method, the rotation angle of the upper die and torque curve could be measured without breakage of the dies. After development of the methodology to convert the rotation angle-torque curve to a SS curve, the SS curves of an aluminum alloy and carbon steel were measured. The validity of the measured SS curves was examined by comparing the SS curves measured by the compression test, the constrained and unconstrained-type high-pressure torsion test. It was also confirmed that the difference of the unconstrained-type high-pressure torsion test was less than 10% compared to the other methods.

Graphical abstract

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