Response of split Hopkinson pressure bars to end-surface damage

SHPB testing is one of the most widely used methods to characterize materials at high strain rates in order to provide data for the development of constitutive models. However, to produce reliable results, great care most be taken in data acquisition and processing. For example, during a routine test series, our surface bars were damaged. Control tests done on samples made of a well characterized Al 6061-T6 showed a significant alteration of the response of the system. Therefore, a study was initiated to understand the influence of surface damage on the response of the Hopkinson bar system. The results obtained from the damaged bar were compared with those from a test series using gaps that simulate potential damage defects. Results showed a similarity between data generated by gaps and damaged bars and suggested the importance of maintaining bars to a high quality surface finish. Comparisons of 3 lubricants were also done. Preliminary results showed a variation on the response ranging from negligible to significant. Finally, the influence of surface finish roughness ranging from RA4 to RA60 was investigated.