Laser treatment of aluminum composite and investigation of thermal stress field

Abstract

Laser surface melting of hot pressed aluminum composite tile, consisting of 90 % aluminum and 10 % WC, is carried out. Temperature and stress fields developed in the laser-treated region are modeled and predicted using ABAQUS finite element code in line with the experimental conditions. The spiral motion of the laser beam is incorporated at the surface during the laser scanning. This arrangement provides self-annealing effect on the initially formed laser scanning tracks through heat conduction from the lately formed laser scanning tracks. Surface temperature predictions are validated through the thermocouple data. Morphological and metallurgical changes in the laser-treated layer are examined using optical and electron scanning microscopes. It is found that the cooling rates in the central region of the workpiece remain low because of the self-annealing effect of the lately formed laser scanning tracks. This, in turn, lowers von Mises stress levels in this region. Stress peaks are formed below the surface because of the high thermal strain formed in this region during the cooling cycle. The spiral scanning of the laser beam causes oscillating stress levels in the surface region of the laser-treated layer; in which case, its amplitude reduces with the progressing time. Laser-treated layer is free from cracks and crack networks, which is associated with the self-annealing effect of the lately formed laser scanning tracks.

Thermomechanical modelling of laser surface glazing for H13 tool steel

“…In this study, strain developed due to thermal gradient has been accounted which considers evolution of the volume of material due to the coefficient of thermal expansion. This is called thermal strain which eventually induces elastic and plastic parts of the total strain [19,27]. Figure 7 illustrates the stress in both X (σ X ) and Y (σ Y ) directions on the surface element where maximum temperatures have been achieved which is in the centre of line heat source.…”

“…Yilbas et al modelled residual stress using ABAQUS FEM code of laser surface melting with aluminium composite. He considered the workpiece as an elastic body and used isotropic hardening to model rate-independent plasticity with temperature-dependent yield strength [19]. In another work of laser cladding by Paul et al, ABAQUS FEA software was used to model residual stress in H13 tool steel clad and substrate.…”

Why self-cleaning is important for solar thermal receivers?

“…In order to generate hierarchical surface texture by a high energy beam, melting and evaporation of the surface become necessary. In addition, to avoid surface cracking, self‐annealing effect needs be created on the textured surface . This involves with forming the closely spaced laser scanned tracks on the treated layer.…”

“…In addition, to avoid surface cracking, selfannealing effect needs be created on the textured surface. 1,5 This involves with forming the closely spaced laser scanned tracks on the treated layer. Hence, heat conduction from recently formed laser scanning tracks modifies the cooling rates in the initially formed neighboring tracks.…”