*Article* **Characteristics of Flyer Velocity in Laser Impact Welding**

## **Huimin Wang 1 and Yuliang Wang 2,3,\***


Received: 11 January 2019; Accepted: 26 February 2019; Published: 1 March 2019

**Abstract:** The flyer velocity is one of the critical parameters for welding to occur in laser impact welding (LIW) and plays a significant role on the welding mechanism study of LIW. It determines the collision pressure between the flyer and the target, and the standoff working distance. In this study, the flyer velocity was measured with Photon Doppler Velocimetry under various experimental conditions. The laser energy efficiency was compared with measured flyer velocity for various laser energy and flyer thickness. In order to reveal the standoff working window, the peak flyer velocity and flyer velocity characteristic before and after the peak velocity and the flyer velocity was measured over long distance. In addition, the rebound behavior of the flyer was captured to confirm the non-metallurgical bonding in the center of the weld nugge<sup>t</sup> in LIW. Furthermore, the flyer size and confinement layer effect on the flyer velocity were investigated.

**Keywords:** flyer velocity; energy efficiency; peak velocity; flyer rebound; flyer size; confinement layer
