Abstract
This paper developed a new ultrasonic computerized tomography (CT) method for damage inspections of a steel tube slab (STS) structure based on compressive sampling (CS). CS is a mathematic theory providing an approximate recovery for a sparse signal with minimal reconstruction error from under-sampled measurements. Considering the natural sparsity of the damage, CS algorithm is employed to image the defect in the concrete-filled steel tube of Shenyang Metro line 9 for reducing the work time. Thus, in the measurement stage, far fewer ultrasonic measurement paths were selected from the dense net of conventional ultrasonic CT techniques to capture the underlying damage information. Then, in the imaging stage, ℓ1-norm minimization algorithm of CS theory is selected to recover the internal damage via fusing measurement data and solving optimization problem. The functionality of the proposed method is validated by three numerical concrete tube models with various conditions. Additionally, both the conventional ultrasonic CT technique and the proposed one are employed for ultrasonic inspection of the STS structure in Shenyang Metro line 9. Both the numerical and experimental results indicate that the proposed ultrasonic CT improved by CS has a great potential for damage detection, which provides an alternative accurate and effective way for non-destructive testing/evaluation (NDT/E).
Highlights
Non-destructive testing (NDT) is an effective and compulsory method for the evaluation and testing of significant infrastructures in the civil engineering community
This study presents an improved ultrasonic computerized tomography (CT) technique based on the compressive sampling (CS) reconstruction algorithm
This study presents an improved ultrasonic CT technique based on the CS reconstruction algorithm and low‐rate randomly selected measurement paths
Summary
Non-destructive testing (NDT) is an effective and compulsory method for the evaluation and testing of significant infrastructures in the civil engineering community. The overarching goal of the research effort is to develop an effective and accurate ultrasonic inspecting method to reduce the workload and time for the assessment of the STS structures before their service To achieve this ambitious functionality, compressive sampling (CS) theory was proposed to improve both the measurement stage and the imaging stage of the conventional ultrasonic CT technique. The cross-section of the detected structure is the travel time of the ultrasonic waves via the external measurements, the internal situation of the divided into discrete microstructures. The value of travel time in one selected measuring path is determined by the travel path and the Ultrasonic CTinrepresents the acoustic method,relationship: which not microstructures the sectionanofimprovement the structure,inwhich can be transmission expressed as testing the following only performs the direct mode and stands for the traveling path of the ultrasonic waves affected by 1 net of the measured paths, each of which relates to a the damage in the structures. An improved measurement dense net is designed and proposed to develop the traditional ultrasonic CT technique and eliminate the drawbacks of the conventional algorithm, providing an equal accuracy
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