Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
FATIGUE CRACK GROWTH IN LASER-TREATED AA2198-T851 ALLOY UNDER ZERO-TO-TENSION LOADING
Submission Author:
Cauê Carvalho , SP
Co-Authors:
Cauê Carvalho, Gabriel Cotrim de Cesare Peinado, João Pascon, Milton Sergio Fernandes de Lima, Carlos Antonio Reis Pereira Baptista
Presenter: Cauê Carvalho
doi://10.26678/ABCM.COBEM2023.COB2023-0535
Abstract
Laser heating treatment (LHT) is a residual-stress-based approach reported to exhibit satisfactory efficiency in enhancing the lifespan of aluminium alloy components. The technique involves local heating followed by fast cooling, inducing compressive residual stresses near this area. As an ongoing technique, the understanding of some questions like how the load ratio R affects the fatigue crack growth (FCG) rate of laser-treated material, their fracture behaviour, and even the influence of microstructural changes remains unresolved. The current study focused on M(T) specimens made of 2.0 mm thick AA2198-T851 alloy sheets with L-T and T-L crack orientations. The specimens were treated with a fibre laser (power 200 W, scanning speed 1 mm/s) to produce heating lines ahead of the crack. Electrical resistance strain gauges were strategically bonded to measure strain during crack growth. FCG tests involved zero-to-tension (R = 0) constant amplitude loading, followed by fractographic analysis using scanning electron microscopy (SEM). Microhardness profiling and X-ray diffraction (XRD) were used to evaluate the influence of microstructural changes on method efficiency. The experimental results indicated significant FCG retardation, particularly in the L-T orientation, in laser-treated specimens. Only LHT specimens showed evidence of secondary cracks, further supporting the FCG retardation effect. The microhardness profile exhibited a decline in a wide range near the heating lines, while XRD analysis revealed the dissolution of certain hardening precipitates. Compared with strain gauge measurements, the results suggest that introduced residual stresses overshadow any potential effects of microstructural changes on FCG.
Keywords
Laser surface treatment, Laser heating, fatigue crack growth, AA2198-T851, Fractography
