Abstract
In multi-pass welding, there is increasing motivation to move towards in-process defect detection to enable real-time repair; thus avoiding deposition of more layers over a defective weld pass. All defect detection techniques require a consistent and repeatable approach to calibration to ensure that measured defect sizing is accurate. Conventional approaches to calibration employ fixed test blocks with known defect sizes, however, this methodology can lead to incorrect sizing when considering complex geometries, materials with challenging microstructure, and the significant thermal gradients present in materials during the inter-pass inspection period. To circumvent these challenges, the authors present a novel approach to calibration and introduce the concept of in-process calibration applied to ultrasonic Non-Destructive Testing (NDT). The new concept is centred around the manufacturing of a second duplication sample, containing intentionally-embedded tungsten inclusions, with identical process parameters as the main sample. Both samples are then inspected using a high-temperature robotic NDT process to allow direct comparative measurements to be established between the real part and the calibration sample. It is demonstrated that in-process weld defect detection using the in-process calibration technique can more reliably identify defects in samples which would otherwise pass the acceptance test using a traditional calibration.
Highlights
IntroductionAccurate defect sizing is not possible without a controlled and repeatable calibration process in which the signal received from the component defects are compared with a known signal already captured during the inspection of a standard calibration block [4]
The authors present a novel approach to calibration and introduce the concept of in-process calibration applied to ultrasonic NonDestructive Testing (NDT)
Accurate defect sizing is not possible without a controlled and repeatable calibration process in which the signal received from the component defects are compared with a known signal already captured during the inspection of a standard calibration block [4]. This calibration sample requires to be manufactured from as close to identical a material as the component under test and the artificial-defect size and shape must be comparable to the expected defects [5], i.e., a ø1 mm longitudinal lack of fusion in the weld can be represented by a ø1 mm drilled hole in the calibration block
Summary
Accurate defect sizing is not possible without a controlled and repeatable calibration process in which the signal received from the component defects are compared with a known signal already captured during the inspection of a standard calibration block [4]. This calibration sample requires to be manufactured from as close to identical a material as the component under test and the artificial-defect size and shape must be comparable to the expected defects [5], i.e., a ø1 mm longitudinal lack of fusion in the weld can be represented by a ø1 mm drilled hole in the calibration block
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