Laser-beam welding

Steam and pnenmatic hammers Plate-bending machines Arc and gas welding Resistance welding Thermal metal-cntting machinery Electroslag welding Laser-beam welding Lathes... 

Ultrasonic welding Spot welding Plasma arc welding Laser beam welding Electron beam welding Furnace brazing Diffusion brazing Anaerobic Cyanoacrylate Epoxy resin Hot melt... 

This paper deals with the control of weld depth penetration for cylinders in gold-nickel alloy and tantalum. After introducing the experimental set-up and the samples description, the study and the optimization of the testing are presented for single-sided measurements either in a pulse-echo configuration or when the pump and the probe laser beams are shifted (influence of a thermal phenomenon), and for different kind of laser impact (a line or a circular spot). First, the ultrasonic system is used to detect and to size a flat bottom hole in an aluminium plate. Indeed, when the width of the hole is reduced, its shape is nearly similar to the one of a slot. Then, the optimization is accomplished for... 

In modelling the welding process, an optical model has been used to determine how the laser beam is attenuated in the course of passage. This information has been used as the basic input to a thermal model. 

In these approaches, several different forms of welding can be utilized such as resistance spot welding, gas tungsten spot welding, laser spot welding, and electron beam spot welding. However, resistance spot welding is the most popular and well accepted of these methods. 

Laser beam technologies can be applied with major efficiency during Nuclear Submarine (NS) dismantling operations for -cutting of metal constructions -welding of boron-containing-steel containers to store nuclear fuel and -decontaminating NS units and assemblies. 

Oxide layers are removed under the impact of laser beam 5-7 mm in diameter as distinct from cutting and welding procedures wherein concentrated beams 0.1-0.3 mm in diameter are applied oxide layers are removed under one-pulse impact allowing attaining acceptable decontamination rates (e g., at 50 Hz pulse-frequency the decontamination capacity can reach 3-5 m per hour). 

Since a laser beam can be focused down to a very small spot of light which can be absorbed very well at the surface of a material (be it metal, plastic, textile, etc.), the material can reach very high temperatures up to 9,032°F (5,000°C) and melt or even vaporize. In factories, laser systems are used to measure parts, inspect them for quality, and label, cut, weld, or resurface materials ranging from plastic film to sheet steel a quarter of an inch thick. 

The weaker lasers are used in such systems as CD players and recorders and in communications and distance-measuring devices. The more-intense laser beams are used for welding and cutting of metals, cloth, skin, etc. and have even been examined as a means of inducing thermonuclear fusion reactions. 

This method is called quasisimultaneous, because the laser beam scans at frequencies of several tens of Hertz, which is fast enough to almost-simultaneously melt the material all along the laser path. The pieces being joined can also be pressed together (Fig. 5.8.11), thereby squeezing out excess material. This eliminates the problems of gaps and nonuniform start/end points associated with classical laser welding. 

Beam Penetration and Material Removal. Welding with electron, plasma, or laser beams can be modeled by considering the movement of a vertical cavity (along with the surrounding molten film) through the material to be joined (Fig. 18.7). The cavity depth-to-width ratio is usually about 10, and, to first approximation, the outer boundary of the molten liquid can be represented by a cylinder whose surface is at the melting temperature Tm. 

S. Lathabai, K.J. Barton, D. Harris, P.G. Lloyd, D.M. Viano, and A. McLean, Welding and Weldability of AZ31B by Gas Tungsten Arc and Laser Beam Welding Processes, Magnesium Technology 2003, H.I. Kaplan, Ed., TMS, 2003... 

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