A miniature impact tester for dynamic testing of small specimens

Abstract

A novel dynamic testing methodology was conceptualized and a portable miniature impact tester was fabricated for obtaining the dynamic force-displacement or stress-strain response of small specimens such as single solder joint. The tester comprises an input and an output bar; a tubular striker impinges an impact plate initially in contact with the specimen to generate a tensile or compressive load. Careful alignment is required only for the striker, the impact plate and the ends of the two bars adjacent to the specimen. The mechanical response of a specimen is derived from the stress waves in bars, and wave dispersion or attenuation in bars has less influence on the results compared to a split Hopkinson bar system. Theoretical derivation and interpretation of the governing equations was presented, with respect to calculation of results from recorded wave signals. FEM simulation was performed to examine the loading wave generated at the impact plate and its planar nature during propagation along the bars was verified. Experimental tests on cylindrical aluminum specimens showed that the results obtained using the miniature impact tester are comparable to those obtained from a split Hopkinson bar system, validating its performance. © The Society for Experimental Mechanics, Inc. 2013.