Tension Testing
Tension testing in a Split Hopkinson Pressure Bar (SHPB) is more complex due to a variation of loading methods and specimen attachment to the incident and transmission bar. The first tension bar was designed and tested by Harding et al. in 1960; the design involved using a hollow weight bar that was connected to a yoke and threaded specimen inside of the weight bar. A tensile wave was created by impacting the weight bar with a ram and having the initial compression wave reflect as a tensile wave off the free end Another breakthrough in the SHPB design was done by Nichols who used a typical compression setup and threaded metallic specimens on both the incident and transmission ends, while placing a composite collar over the specimen. The specimen had a snug fit on the incident and transmission side in order to bypass an initial compression wave. Nichols setup would create an initial compression wave by an impact in the incident end with a striker, but when the compression wave reached the specimen, the threads would not be loaded. The compression wave would ideally pass through the composite collar and then reflect off the free end in tension. The tensile wave would then pull on the specimen. The next loading method was revolutionized by Ogawa in 1984. A hollow striker was used to impact a flange that is threaded to end on an incident bar. This striker was propelled by using either a gas gun or a rotating disk. The specimen was once again attached to the incident and transmission bar via threading.
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