Abstract
Interest in laser beam welding for aerospace applications is continuously growing, mainly for aluminum alloys. The joints quality is usually assessed by non-destructive inspection (NDI). In this work, bead on plate laser welds on 1.6 mm thick AA6013 alloy sheets, using a 2 kW Yb-fiber laser were obtained and inspected by pulse/echo ultrasonic phased-array technique. Good and poor quality welds were inspected in order to verify the limits of inspection, comparing also to X-ray radiography and metallographic inspections. The results showed that ultrasonic phased array technique was able to identify the presence of grouped porosity, through the attenuation of the amplitude of the echo signal. This attenuation is attributed to the scattering of the waves caused by micro pores, with individual size below the resolution limit of the equipment, but when grouped, can cause a perceptive effect on the reflection spectra.
Highlights
Laser beam welding (LBW) is an attractive joining process for aluminum structures, due to its high production rate, associated with high quality welds
Bead on plate welds were performed on the alloy AA6013-T4 (Al-Mg-Si-Cu), 1.6 mm thick sheets
Ultrasonic phased array inspection has been investigated for the detection of defects in thin aluminum laser beam welded sheets
Summary
Laser beam welding (LBW) is an attractive joining process for aluminum structures, due to its high production rate, associated with high quality welds. The high concentrated energy (around 106 W.cm–2) in a precision controlled spot enables welding in key-hole mode, at welding speeds up to 10 m/min in thin sheets, resulting in a very narrow heat affected zone. Those characteristics are attractive for both automotive and aerospace industries. The use of welded structures on airframes demands a qualified and robust welding process, including a reliable defect control system, based on NDI techniques. The inspection technique should be performed rapidly and preferably during the welding (in process inspection), to not become the bottleneck of the process
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