Misalignment effect of Split Hopkinson Pressure Bar (SHPB) / Zurri Adam Mohd Adnan ... [et al.]

Split Hopkinson Pressure Bar (SHPB) testing set-up is one of the mechanical testing that commonly used to determine the dynamic stress behaviour of materials. The most important step in order to get accurate and reliable data is the quality of calibration process. Even though the test has been widely used, but there is still lack of information on how the testing set-up being calibrated. This paper is focused on misalignment calibration of SHPB test set-up. Tests were conducted using 200 mm striker bar at velocity of 22m/s without specimen. Results with misalignment and without misalignment cases were compared. The results with misalignment shows major fluctuation occur at the baseline for incident bar signal due to the height offset misalignment between the bars. Then, the incident bar is adjusted to a height of 156.78mm to ensure not in misalignment position using levelling gauge which results in good trapezoidal shape of bar signal with minor fluctuating baseline. Similar shape and baseline were achieved for both cases up until 368 µɛ, however major fluctuation in negative incident strain called reflected strain occur due to height offset misalignment. The magnitude of bar signal, µɛ (micro strain) are similar up to 368 µɛ for both cases due to similar impact velocity. Misalignment of SHPB bar contributes to fluctuation of the wave beyond 368 µɛ.