Thermalmodellingoflaserweldingandrelatedprocessesaliteraturereview..doc

Thermal modelling of laser welding and related processes: a literature review??Original Research ArticleOptics Laser Technology Reinforcing cracked aluminum structures with composite patches have been recognized as an efficient and economical method to extend the service life of cracked aluminum components. To further enhance the effectiveness of composite patches, it is envisioned that the crack can be first fused by laser welding to remove the high stress concentration at the crack front before applying the composite patch. In this paper, the feasibility of the envisioned fusion repair is investigated. A systematic approach for the fusion process design is proposed to overcome challenges related to alloy strength recovery, crack tracing, focusing position, welding speed, plate flatness, shielding gas pressure, thin-sheet factors, and skewed cracks. A thick-sheet, partial penetration model is first used to determine the starting point of laser welding conditions. A systematic approach to transfer the thick-sheet condition to successful thin-sheet welding is then presented. Based on successfully fused crack samples of AA 7075-T6, the ultimate tensile strength tests show that in average 74% of the alloys original strength was recovered for a single-pass repair and 68% for a double-pass repair and the results are highly repeatable. It should be clear to see the benefit of the crack fusion because without crack fusion, the composite patch is bonded to a part with zero UTS at the crack region and with a high stress intensity factor at the crack front. Article Outline 1. Introduction 1.1. Fatigue cracks 1.2. Crack repair using laser welding 1.3. Challenges in aluminum crack fusion by laser welding 2. Laser welding of aluminum alloys 3. Fiber laser welding 4. Initial process parameter selection via modelling 4.1. A model for low-speed, thick-sheet, partial penetration laser welding 5. Experimental setup 5.1. Laser setup 5.2. Cracked sample preparation 6. Process de