Kenneth Edwards

Laser forming: overview of the controlling factors in the temperature gradient mechanism

Abstract Laser forming (LF) offers the industrial promise of controlled shaping of metallic and non-metallic components for prototyping, the correction of design shape or distortion, and precision adjustment applications. The potential process advantages include precise incremental adjustment, flexibility of application, and no mechanical ‘spring-back’ effect. To date, there has been a considerable amount of work carried out on two-dimensional LF, using multi-pass straight-line scan strategies to produce a reasonably controlled bend angle in a number of materials, including aerospace alloys. A key area, however, where there is a limited understanding, is the variation in the bend angle per pass during multi-pass temperature gradient mechanism-based LF along a single irradiation track, in particular, the decrease in the bend angle per pass after many irradiations for a given set of process parameters. Understanding this is essential if the process is to be fully controlled for a manufacturing environment. The research presented in this paper through empirical data and numerical simulation of the LF of sheet mild steel, Ti6Al4V and AA5251, by CO2 laser offers a novel coherent picture of the key influencing factors and at which point in the bend evolution each is dominant, which has not been presented before.

Laser peen forming for 2D shaping and micro adjustment

Laser peen forming has been carried out on 0.075mm thick steel samples, using relatively low power Nd:YAG lasers at 1064nm, 532nm and 355nm wavelengths. The process was found to produce a bend angle up to approximately 20 degrees, depending upon the amount of passes and laser parameters used. The results from these experiments have been compared to samples formed using continuous wave thermal forming. The results showed that laser peen forming could take place with a pulsed Nd:YAG laser, which uses less energy than a laser used for thermal forming, and that the laser peen formed samples do not have evidence of heat affected zones or changes to the bulk material, both seen with laser thermal forming. This indicates that the laser peen forming process is largely athermal or non-thermal, as there is very little heat input into the samples except for decolorisation of the surface due to the plasma generated in the process. A parameter window has been established for laser peen forming on 0.075mm thick steel using a 1064nm wavelength. The effect that the process has on the surface of the material is also being analysed using optical interferomety and scanning probe microscopy.Laser peen forming has been carried out on 0.075mm thick steel samples, using relatively low power Nd:YAG lasers at 1064nm, 532nm and 355nm wavelengths. The process was found to produce a bend angle up to approximately 20 degrees, depending upon the amount of passes and laser parameters used. The results from these experiments have been compared to samples formed using continuous wave thermal forming. The results showed that laser peen forming could take place with a pulsed Nd:YAG laser, which uses less energy than a laser used for thermal forming, and that the laser peen formed samples do not have evidence of heat affected zones or changes to the bulk material, both seen with laser thermal forming. This indicates that the laser peen forming process is largely athermal or non-thermal, as there is very little heat input into the samples except for decolorisation of the surface due to the plasma generated in the process. A parameter window has been established for laser peen forming on 0.075mm thick steel u...