Using a PDV system to measure ejection debris velocity after a composite material impact

In this study, we developed modified photonic Doppler velocimetry (PDV) measurement system which can measure a wide range of flight velocities of ejecting debris. Using a utilized collimated probe with an iris, we can measure a target with a wide movement range and enhance the signal to noise ratio (SNR) by eliminating unwanted scattering light. The Doppler interference signal can be detected and recorded with an InGaAs photodetector and a high-speed oscilloscope. We found the beat frequency to be proportional to the detected velocity so that we could measure the flight velocity of ejecting debris. In order to localize the Doppler interference signal temporally, we used a continuous wavelet transform (CWT) to obtain a three-dimensional (3D) mapping of frequency, magnitude and time. The velocity line tracing algorithm (VLTA) was developed based on image processing algorithms to retrieve the flight velocity curve from the corresponding scalograms. Using a confocal microscope, our surface morphology observations, along with simulations, were used to verify the velocities measured on our PDV system.