On modelling of laser assisted machining: Forward and inverse problems for heat placement control

Abstract

Laser assisted machining (LAM) is one of the most efficient ways to improve the machinability of difficultto-cut materials (e.g. Nickel-based superalloys). In the conventional LAM process, the laser beam is focused ahead of the cutting area at a fixed location, which leads to a series of restrictions, e.g. small heating area and non-uniform heat distribution due to the limitation of beam size and energy distribution. In this paper, a novel spatially and temporally (S&T) controlled laser heating method was proposed, in which a large area can be heated up with a small laser spot by controlling the beam scanning, i.e., laser power, path and speed of scanning. The laser configuration for the prescribed HAZ (heat affected zone) was achieved by solving the inverse problem where the laser power together with either laser path or laser speed were optimised to achieve a particular temperature distribution in the chip to be removed by the following milling cutter. The proposed S&T laser heating method was thoroughly validated both for the forward and, the more important, inverse heating models by performing extensive temperature experiments by both infrared thermal camera and thermocouple array and further verified by laser assisted milling (LAMill) tests of Inconel 718 for large widths of cuts. The results showed that by applying path-optimised LAMill based on the inverse solution of the thermal problem, the peak and mean principal cutting forces were reduced by 55% and 47.8% respectively compared with the conventional dry milling process while the surface roughness improved by at least 14%. Moreover, after controlling the HAZ using the inverse thermal problem, a microstructure analysis of the machined surface showed that the proposed laser heating method avoids overheating of the workpiece below the planned depth of cut for the milling operation.

The Effects of Laser‐Assisted Ultrasonic Nanocrystal Surface Modification on the Microstructure and Mechanical Properties of 300M Steel

“…Similar problems had been encountered in laser‐assisted milling (LAM). Shang et al [ 35 ] had controlled a laser spot that oscillated following a specific track to obtain a bigger temperature‐affected area in LAM processing. However, unlike the LAM, although the laser spot was placed in front of the UNSM tip, a large portion of the laser spot still overlapped with the UNSM tip during processing.…”

“…As the combination of constant laser spot size and UNSM tip at different sizes could cause different temperature fields and plastic deformation fields in the surface of samples, it is necessary to explore the influence of different UNSM tip sizes in the LA‐UNSM processing on the basis of optimized laser power level. As mentioned in Shang et al, [ 35 ] when the UNSM tip size was much larger than the laser spot, the depth and uniformity of the SPD layer after LA‐UNSM processing would be destroyed. Therefore, based on the constant spot size of the laser (3 mm), three UNSM tips of different diameters (4.0, 2.4, and 1.5 mm) were used in this study.…”

Overview of Laser Applications in Manufacturing and Materials Processing in Recent Years

“…The dual heat source provided a more uniform temperature at the cutting zone and was shown to be most effective in tool wear reduction. Another new heating method was reported by Shang et al [140] based on spatially and temporally controlled laser scanning. The benefit includes a large heating area with a small laser spot size and is free from workpiece overheating below the depth of cut.…”

Experimental Investigation on Laser Assisted Diamond Turning of Binderless Tungsten Carbide by In-Process Heating

“…Li et al [ 17 ] compare the temperature field of Al 2 O 3 ceramic material with volumetric and surface laser heating sources. Shang et al [ 18 ] utilize the three-dimensional transient heat conduction model to predict the temperature distribution caused by a freeform laser trajectory, whose results inversely facilitate the laser parameter selections in the laser assisted milling. At present, there is no study has discussed the temperature field of binderless WC under spiral moving laser heating, which can guide the In-LAT laser parameters selection.…”