A Novel Method for Impact Testing of Small Specimens - Numerical Simulation and Experiments

A novel method for dynamic testing of small specimens, based on impact loading, is proposed. This is motivated by the desire to elicit the dynamic mechanical response of single solder joints measuring 0.5 mm smaller in size. Impact loading is generated through impact of a tubular striker against a loading plate which is initially in contact with the specimen. The mechanical response of the specimen is derived from noting the stress waves generated in slender bars attached to the loading plate and specimen. Through this approach, dynamic tension or compression can be conveniently applied using the same test apparatus, and exact alignment of the slender bars attached is not critical. In addition, wave dispersion or attenuation in the bars (e.g., when polymer bars are used) has much less influence on the accuracy of results obtained. The equations governing this novel approach are derived and validated by finite element modeling. A prototype of a miniature impact tester was consequently fabricated, and tests on small aluminum specimens showed results comparable to that employing traditional split Hopkinson bar systems. The test arrangement was utilized for dynamic testing of lead-free single solder joint specimens, and initial results obtained are presented.