Dynamic Testing Technique Based on Multi-channel Photonic Doppler Velocimetry for Investigating the Dynamic Behavior of Materials

Abstract

In the present paper, more attention is paid to develop a new optical measurement approach of split-Hopkinson pressure bar (SHPB) and wave propagation inverse analysis (WPIA) by using multi-channel photonic Doppler velocimetry (PDV). Based on the particle velocities measured by PDV, the dynamic stress–strain curve of material is obtained in SHPB tests. The strain is determined by the radial particle velocity of specimen, and the stress is determined by the free surface particle velocity of the transmitted bar. The results obtained by the new method coincide with those obtained by the conventional strain gauge measurements. The new method is non-intrusive and insensitive to electrical noise, making it significantly more reliable than strain gauges. Using the oblique incidence of laser beam, a series of particle velocity wave propagation signals for long rod specimen are measured simultaneously. Based on the measurements of particle velocity profile, the dynamic constitutive response of polymethyl methacrylate (PMMA) is determined by WPIA method. The comparison between the dynamic stress–strain curve and the quasi-static one indicates that the strain-rate effect must be taken into account for PMMA.