A Kolsky Bar for High-Rate Indentation
Tóm tắt
A Kolsky Bar for high-rate indentation has been developed. Samples are adhered to the end of the input bar and the indenter is mounted/machined directly on the end of the output bar, in a way that only negligibly affects the output bar’s otherwise uniform impedance. When the input pulse reaches the sample, the sample is driven into the output bar and loaded. By properly choosing the lengths and impedances of the bars and striker, the maximum load and loading duration can be reliably controlled. It can furthermore be ensured that the sample is only subjected to a single loading; i.e., the sample is not reloaded due to later stress-wave reverberations in the bars even though momentum trapping is not used. Depending on the sample and desired indentation load, unusually small output bars (less than 2 mm diameter) may be needed. For this reason, the output bar is instrumented with a normal displacement interferometer on the free-end. This provides an accurate measurement of the motion of the indenter tip and the indentation force. The sample face is instrumented with an additional displacement interferometer and these two displacement measurements are used to determine indentation depth. The method is applied to Vickers indentation of OFHC Cu and Ti–6Al–4V, and spherical indentation of 6061-T6 aluminum. An additional application is given with the aluminum alloy where a specially designed striker bar is used to partially unload the sample during loading, a technique that allows the contact area between the sample and the indenter to be estimated. In general, the method is applicable to a wide range of materials and indenter shapes and has the potential for loading times less than 5 μs.
Tài liệu tham khảo
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