Abstract
Small cracks are common defects in steel and often lead to catastrophic accidents in industrial applications. Various nondestructive testing methods have been investigated for crack detection; however, most current methods focus on qualitative crack identification and image processing. In this study, eddy current pulsed thermography (ECPT) was applied for quantitative crack detection based on derivative analysis of temperature variation. The effects of the incentive parameters on the temperature variation were analyzed in the simulation study. The crack profile and position are identified in the thermal image based on the Canny edge detection algorithm. Then, one or more trajectories are determined through the crack profile in order to determine the crack boundary through its temperature distribution. The slope curve along the trajectory is obtained. Finally, quantitative analysis of the crack sizes was performed by analyzing the features of the slope curves. The experimental verification showed that the crack sizes could be quantitatively detected with errors of less than 1%. Therefore, the proposed ECPT method was demonstrated to be a feasible and effective nondestructive approach for quantitative crack detection.
Highlights
Steel is a widely used metal in industry and plays a vital role in the aerospace, transportation, weapon, and energy fields [1]
The use of eddy current pulsed thermography (ECPT) for crack detection based on temperature analysis was investigated using simulation and experimental studies
A quantitative crack detection method was proposed based on derivative analysis, and cracks of different sizes were quantitatively analyzed
Summary
Steel is a widely used metal in industry and plays a vital role in the aerospace, transportation, weapon, and energy fields [1]. As one of the basic technologies for crack detection and identification, nondestructive testing has been playing an increasingly important role in ensuring the quality of products and engineering structures These approaches avoid destruction of the internal structure of the objects and instead rely on physics-based methods to determine the surface and internal properties and to verify whether internal discontinuities (defects) are present. Oswald and Tian analyzed the surface defects of metallic materials using ECPT to investigate the effect of the eddy penetration depth on the temperature [16]. The main target of this study was to develop a quantitative evaluation method for crack size detection based on ECPT technology.
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