Dynamic hardness testing using a Split Hopkinson Pressure Bar apparatus


  • Nilsson Martin

Publish date: 2002-01-01

Report number: FOI-R--0447--SE

Pages: 35

Written in: English


To provide high strain and high strain rate data for new materials it is necessary to develop new and better testing methods. Indentation offers an attractive method because of ease of use, low costs, low material consumption and simple manufacturing of samples. The goal of this work has been to develop dynamic, hardness-testing device using elastic waves for loading and elastic wave theory for measurement. The materials tested are 7075-T6 aluminium, SIS 2541-03 steel and SiAION. The set-up is similar to a traditional Hopkinson Pressure Bar. A projectile is propelled on to the transmitter bar by a air gun. The force acting on the indenter diamond and the indentation depth is calculated using the two strain method for non-uniform bars. The experiments show that it is possible to measure hardness of metals and ceramics and fracture toughness of ceramics at higher strain rates with the apparatus. However, no definite conclusions can be made concerning the hardness of the materials tested. The number of samples is too small and the method has to be further evaluated. The calculated permanent indentation depth is, in most cases, lower than the measured permanent indentation depth. Otherwise, the curves are correct in the sense that the loading phase is overlapping for different loads and the indentation is always recovering elastically with a similar slope when the applied load is declining.