Laser shock peening and conventional mechanical shot peening are both comparable processes generally applicable to surface treat various metals and alloys. Commercial advantages offered by the laser systems such as flexibility, deep penetration of laser-induced shocks with precise control of the thermal pulses, shorter process times, high speeds, accuracy and aesthetics are attractive in comparison with the mechanical shot peening technique. Laser shock peening in the recent years has proved to be successful with steels, aluminium and titanium surfaces and metallic alloys in general. Nevertheless, minimal research has been conducted on laser shock peening and mechanical shot peening of technical grade ceramics. This article presents an update of the theory and to-date relevant literature within the two subject areas, as well as a comparison and a contrast between the mechanical and laser shock peening techniques. In addition, various gaps in knowledge are identified to propose further research for the development of both the techniques applicable to the surface treatment of technical grade ceramics.

The present paper is concerned with hybrid laser-arc welding processes. Previous work is reviewed, and attention is then focused on plasma augmented laser welding. Features, application parameters, and mechanisms of the process are discussed, followed by a summary of the research and development work undertaken by the present authors, concentrating on application areas where the process can offer distinct advantages, such as tailor welded blanks, lap welding of coated steels, welding using additional filler material, and high speed welding of thin sheet metals.

No abstract

A hybrid laser arc welding system incorporating a plasma arc in a triangulated configuration (plasma augmented laser welding -PALW) was used to produce bead on plate welds in 6 mm low carbon steel. Laser powers up to 5 kW and arc currents up to 150 A were investigated. Plasma augmented laser welding allowed an increase in full penetration welding speed of 100% or an increase in penetration of between 25 and 100%, compared with the laser alone. At speeds of 2 m min 21 and above, PALW and laser alone were found to be equal with respect to fusion zone area per kW (mm 2 kW 21 ). Plasma augmented laser welding was equivalent in terms of welding energy utilisation (mm 3 J 21 of fusion zone) at 2 m min 21 and superior above 2 m min 21 . Full penetrating PALW allows significant energy losses via the keyhole root exit. Only when the keyhole root closes can the full benefits of the hybrid process be manifested in the workpiece.

A welding process that combined plasma arc welding with laser welding was used to make autogenous bead on plate welds on a sheet stock of a carbon steel. A wide range of welding parameters (arc current, laser power, weld speed) was employed. The experimental weld pool shapes were analysed and the data were used to train a neural network to predict weld pool shape as a function of process conditions. The predictions of the neural network model showed excellent agreement with the experimental results, indicating that a neural network model is a viable means for predicting weld pool shape. Using the model, a parametric study was carried out to examine the influence of process conditions on the final weld pool profile.