Pulsed laser induced mechanical behavior of Zircaloy-4
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Pulsed laser induced mechanical behavior of Zircaloy-4 Sooil Kim, Woo-Ju Lee, Quhon Han, and Dongchoul Kima) Department of Mechanical Engineering, Sogang University, Mapo-go, Seoul 121-742, Republic of Korea (Received 8 May 2014; accepted 9 December 2014)
The mechanical behavior of a Zircaloy-4 sheet as induced by a pulsed laser was studied with an accurately developed computational process that was validated with experiments. A modified Gaussian model of the heat source and the use of experimentally obtained thermal and mechanical properties of Zircaloy-4 in the computational process provided reliable simulation results of the phase transition and mechanical deformation of Zircaloy-4. A parametric study of the pulsed laser welding conditions of Zircaloy-4 was undertaken using the developed computational process. The analyzed parameters were the laser power, pulse duration, and pulse frequency. The simulation results revealed that the deformation was significantly dependent on the geometry of the molten zone and the heat-affected zone, which can be designed by the analyzed laser parameters.
I. INTRODUCTION
Contributing Editor: Jürgen Eckert a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2014.390
method to derive the ultimate tensile strength of the welding spot of Mg alloys.3 Dandras et al. characterized the dependence of the melt pool diameter and welding quality on various laser-welding factors, such as the assist gas and preheat temperature.4 Most of these studies primarily focused on critical manufacturing defects caused by thermal deformation. However, the welding conditions that minimize these defects have been conventionally investigated by experience-based experiments. This is because of the complicated mechanisms and the impractical time and high costs required. In recent years, more efficient numerical methods have been developed for parametric studies to investigate the relationship between the temperature of the welding pool and the specimen behavior. Most welding models are based on the analytical solution of Rosenthal.5 Mazumder and Steen developed the first finite difference model of continuous laser welding using a Gaussian heat source model.6 Frewin and Scott constructed the first simulation model for analyzing the temperature of workpieces during pulsed welding using a finite element method (FEM).7 By means of the model, they investigated the time-dependent temperature distribution of the specimen, the diameter of the molten zone (MZ), and the HAZ. De et al. analyzed the spot laser welding process with a 150 ms pulse duration using a double ellipsoidal model.8 He et al. developed a numerical model for stainless spot welding that incorporated the heat transfer and fluid flow.9 Most of these theoretical studies on welding have focused on analyzing the temperature distribution at the welding spot, including the HAZ, and have given information limited to the shape of the MZ. Several researchers have recently analyzed residual stress and deformation based on the ca
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