DPIV method of measurement of powder stream of co-axial feeding for laser manufacturing

Laser direct manufacturing and re-fabricating by co-axis feeding have been widely used in space, aircraft and power station. Due to lack of evaluation method of powder stream, its industrial application is limited in. A new Digital Particle Image Velocimetry (DPIV) system has been developed to measure the powder stream outside co-axis feeding head. The DPIV system is as follows: A double pulse Nd+:YAG laser, lambda=532mn, single pulse energy 220mJ, pulse repeat frequency 10Hz, pulse width 6ns; Nd+:YAG laser beam shaping device; Frame straddle CCD camera, 30 frames/s, 8bit image plate and special image software. The transverse and longitudinal distributions of concentration and velocity fields have been measured by CCD camera respectively. It is shown that the focus parameters (focus diameter, focus length), concentration field, flow velocity field of powder stream can be successfully evaluated by the DPIV technique.