Development of a dynamic torsion testing system
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The aim of this thesis is to design and build a torsional Kolsky bar apparatus for testing cylindrical specimens in torsion at high strain-rates. In addition to well-established designs, this testing apparatus will include a conical mirror combined with a high speed camera that allows time-resolved optical observation of the shear deformation on the surface of the specimen. The basic design of a Kolsky bar consists of a loading bar, input bar, specimen, and output bar. The experiment is conducted by storing torque in the loading bar and then releasing the torque by breaking the clamp and sending a shear wave pulse through the apparatus into the specimen. This shear wave pulse is monitored by strain gages mounted on the input and output bars. Analysis of the strain waves in the input and output bar is used to extract the shear stress - shear strain profile of the specimen. Several experiments were conducted on 6061-O and 1100-O aluminum with wall thicknesses ranging from 0.3 to 1.5 mm.