Abstract
In-plane torsional shear testing is a well-established material testing technique in the metal forming community. The corresponding specimen is designed to be machined from sheet metal with a continuous annular shear zone intended to deform in simple shear. Consequently, there are no geometric discontinuities or “edge-effects” to induce volumetric changes or instabilities with the result that large true plastic strains up to 1.0 can be achieved. This paper presents an extension of the in-plane torsional shear test to the dynamic regime. Dynamic experiments were performed using a torsional split Hopkinson bar (TSHB) on specimens manufactured from Al 1050 H14. The experimental results show that the adopted technique can be used to determine the material behavior accurately and reliably in the dynamic regime.
Highlights
The accurate determination of material properties of sheet metal forms the basis for numerical process analysis [1]
According to Yin et al [4], an ideal mechanical test should have an in-plane pure shear stress state, a controlled location for crack initiation, and the shear stress and shear strain should be determined without the need to revert to an inverse procedure
The torsional split Hopkinson bar (TSHB) system allows for reliable high strain rate testing of materials up to 104 /s [7]
Summary
The accurate determination of material properties of sheet metal forms the basis for numerical process analysis [1]. Experimental tests are required to determine stress vs strain values, and to do so up to high values of true strain This is significant in sheet metal forming where strain reaches values beyond 1 [1]. The in-plane torsional test meets all these requirements It was first introduced by Marciniak and Kolodziejski to investigate ductile failure in planar sheets [5]. The specimen allows for the testing of thick sheets due to the reduced cross-section requiring a lower shearing torque and large shear strain data can be obtained to support numerical analysis without the need for flow curve extrapolation. The torsional split Hopkinson bar (TSHB) system allows for reliable high strain rate testing of materials up to 104 /s [7].
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