Simultaneous Particle Tracking Velocimetry And Pyrometry Of Spatter Particles Ejected During The Laser Power-Bed Fusion Process Using A Spectral Plenoptic Camera

Abstract

This paper aims to provide a method for simultaneous 3D particle tracking velocimetry and dual-wavelength pyrometry using a single spectral plenoptic camera for uses in spray and flow diagnostics. The spectral plenoptic camera can capture spatial, angular, and spectral information of light from the scene using a single main lens and sensor. Particle tracking is conducted using the Light-Field Ray Bundling algorithm paired with a four-frame best estimate-enhanced track initialization algorithm to generate 3D high-resolution spatial locations and velocity of particles. Secondly, a dual-wavelength pyrometry method was developed to use particle locations from Light-Field Ray Bundling to find the particle spectra for each wavelength, and then calculate temperature using the spectral intensities. This method achieves 3D particle tracking and temperature measurements using a single lens and sensor, which can be applicable for many different flow measurements. The method was applied to the spatter particle generation caused by the Laser Powder-Bed Fusion process, where spatter particles have been found to be detrimental to the manufactured parts. The calculated speeds of the spatter particles are within the expected range, and the tracks show a complex 3D process. The temperature measurements indicate that the detected particles are in the liquid phase, with temperatures greater than 2000ºC. The simultaneous measurements demonstrate an overall deceleration and cooling of particles during their flight. Therefore, this is a viable technique for simultaneous tracking and temperature measurements.