Resolution Improvement of Ultrasonic Signals Using Sparse Deconvolution and Variational Mode Decomposition Algorithms
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COUSTIC METHODS
Resolution Improvement of Ultrasonic Signals Using Sparse Deconvolution and Variational Mode Decomposition Algorithms Benammar Abdessalema, *, ** and Chibane Farida, b a b
Research Center in Industrial Technologies CRTI, P.O. Box 64, Cheraga, Algiers, 16014 Algeria Electrification of Industrial Enterprises Laboratory, University of Boumerdes, Boumerdes, Algeria *e-mail: [email protected] **e-mail: [email protected] Received November 23, 2019; revised December 13, 2019; accepted December 20, 2019
Abstract—Over the past few years, the use of ultrasonic arrays for nondestructive testing (NDT) applications has grown rapidly and led to use new algorithms of signal processing. The present paper’s main objective is to improve the resolution of defect detection and make the detection process as fast and accurate as possible. This paper introduces a novel method to improve the resolution of ultrasonic phased array. The proposed method is based on the variational decomposition of signal and on a deconvolution method. To reduce the level of signal’s noise, a method based on the variational mode decomposition (VMD) is used and to improve the resolution, a sparse deconvolution algorithm optimized using the majorization-minimization (MM) method is used. A simulation study has been carried out simulating a block of stainless steel containing several defects in different positions. Experimental tests were performed on a sample of stainless steel containing several defects. The obtained results show that the proposed method can improve the quality of ultrasonic data which enhances the localization of defects. Keywords: ultrasonic phased array, empirical mode decomposition, variational mode decomposition, sparse deconvolution, MM algorithm DOI: 10.1134/S1061830920060029
1. INTRODUCTION In recent years, the ultrasonic phased array acquisition is performed automatically and can carry out multiple inspections without the need of reconfiguration of instrument, which gives a large coverage of inspected area [1]. Phased arrays have many advantages over single element transducers in terms of sensitivity and inspection performance [2]. Even with all these advances, the images provided by the phased array instrument have a low resolution, which suggests the introduction of new algorithms in order to enhance the quality of images [2–4]. Often in ultrasonic phased array testing of materials, the inspectors use the ultrasonic B-scan images which are composed of multiple stacked A-scans. The resolution of A-scans can be significantly improved nowadays by using the signal processing algorithms and techniques that have been the object of numerous researches during the last ten years [1, 4, 5]. The received A-scans signals contain useful information, including amplitude and time delays, which can used to quantify the size and depth of the defects [6]. Nevertheless, the performances of ultrasonic inspections of some materials such as stainless steel are degraded because of its coarse grain structure, which leads to attenuation
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