COMPUTATION AND STORAGE EFFICIENT SPARSE MART ALGORITHM FOR 2D, 3D RECONSTRUCTION FROM FAN BEAM, CONE- BEAM PROJECTION DATA Sudhir Kumar Chaudhary and Prabhat Munshi Algebraic reconstruction algorithms are a better choice compared to transform-based algorithms whenever projection data is limited in nature. High computational costs and huge memory require- ments are two major downsides of iterative recon- struction methods. Among all algebraic techniques, the multiplicative algebraic reconstruction technique (MART) is most popular because it maximizes the entropy (of the image) in the limiting case. In the present work, our goal is to reduce computational complexity and cope with the huge storage scenario of the MART algorithm. We propose a new sparse MART algorithm (Sp-MART) and test it with 2D and 3D numerical data. A more accurate and efficient geometrical formula for calculating intersection length is also presented. Experimental projection data of human tooth and drip irrigation pipe is processed for further validation of the Sp-MART algorithm. Reconstructions of real specimens are also done using the FDK algorithm. The difference between the two algorithms is investigated by calcu- lating the structural similarity index and the L2 error of the results. https://doi.org/10.1080/09349847.2021.1928350 A NEURAL NETWORK SYSTEM FOR FAULT PREDICTION IN PIPELINES BY ACOUSTIC EMISSION TECHNIQUES Francesco Noseda, Luiza Ribeiro Marnet, Carlos Carlim, Luiz Rennó Costa, Natanael de Moura, Jr., Luiz Pereira Calôba, Sérgio Damasceno Soares, Thomas Clarke, and Ricardo Callegari Jacques The problem of evaluating the risk of failure associ- ated with the propagation of a crack in a pipe under pressure has great practical relevance, and it may be tackled with acoustic emission techniques. Artificial neural networks may be trained to classify the acoustic emissions generated by the crack according to the phase of propagation, and such a classifica- tion permits to evaluate the risk of maintaining a system in operation. In order to train the network, a human specialist has to estimate the transition times between any two consecutive phases by inspecting the results of a previous hydrostatic test, and such determination of the transition times has a high degree of subjectivity and uncertainty, affecting the classification performance of the network. In this paper, we propose a human-independent method for the estimation of the transition times, and we show successful applications to the data from two hydrostatic tests. For a test on a 2 m long pipe, the method exhibited 98% of correct-classification rate, an improvement of 8% over results obtained with human-determined transition times. For a 40 m long pipe, under experimental conditions compa- rable to those found in industrial applications, the method exhibited 91% of correct-classification rate. The proposed method provides a fully automated framework for the evaluation of the state of a crack. https://doi.org/10.1080/09349847.2021.1930305 BASELINE-FREE DAMAGE IDENTIFICATION METHOD FOR LATTICE SANDWICH STRUCTURES BASED ON OPERATIONAL DEFLECTION SHAPES Kan Feng, Qian Zhao, and Zheng Li A novel baseline-free damage identification method based on high-frequency operational deflection shapes (ODSs) is presented for debonding detection in lattice sandwich structures (LSSs). Two numerical models with different unit cells are constructed to analyze the vibration characteristics of a structure with a debonded defect in the high-frequency band. The mode shapes and ODSs are computed numerically to investigate the local defect vibration effects. The results show that there will be obvious local vibration at the damaged location at a certain and appropriate frequency band. A baseline-free damage index calculated from ODSs is proposed for damage imaging. For experimental validation, we suggested an intermittent periodic excitation signal for vibration actuating, which may excite multiple ODSs at different frequencies using one measure- ment that significantly improves the detection effi- ciency. The experimental results also indicated that the proposed damage identification method is effec- tive to locate the debonding damage in LSSs. The conclusions derived from this study are expected to provide an efficient vibration measurement tech- nique and a practical damage detection method for LSSs, as well as other plate-like structures. https://doi.org/10.1080/09349847.2021.1946224 IN SITU MEASUREMENT OF CONCRETE STATIC MODULUS OF ELASTICITY: PROOF OF CONCEPT IMPLEMENTATION David M. Mante, Zachary W. Coleman, Christopher Romano, and Tony Simmonds This paper reports a laboratory implementation of a prototype sensor for the measurement of in situ concrete static modulus of elasticity. Sensor measurements for a trial concrete mixture were generated, post-processed, and calibrated to best match the companion ASTM C469 modulus of elas- ticity testing performed on the same mixture for concrete aged up to 28 days. The sensor prototype measurements demonstrated close agreement with ASTM C469 testing with approximately 90% of cali- brated sensor prototype measurements within ±5% of companion testing. The initial sensor prototype implementation reported in this study affirms the feasibility of in situ concrete modulus of elasticity measurement and justifies further sensor develop- ment and implementation efforts. https://doi.org/10.1080/09349847.2021.1948154 CHARACTERISTICS OF EDDY CURRENT ATTENUATION IN METAL-CLAD PLATES AND MEASUREMENT OF CLADDING THICKNESS Quan Zhang, Jiayi Li, Yanfei Liao, Zhiwei Zeng, Junming Lin, and Yonghong Dai A metal-clad plate consists of a base layer and a clad layer of different materials. When testing clad plates using the eddy current technique, the variation of eddy current density along the thickness direction in clad plates is complicated owing to the interface between the layers. This paper attempts to inves- tigate the characteristics of the variation of eddy current density in the thickness direction in clad plates based on finite element analysis. The results are then used for revealing the mechanism of the relation between coil voltage and the thickness of the clad layer, which is essential for the measure- ment of cladding thickness. Thereupon, the experi- ment of measuring cladding thickness is performed, in which the testing frequency is selected based on the voltage-thickness relation. It is found that the measurement is accurate and the results have good linearity. https://doi.org/10.1080/09349847.2021.1930306 SCANNER | RNDEABSTRACTS RNDE Abstracts presents papers recently accepted to ASNT’s journal Research in Nondestructive Evaluation. To subscribe to RNDE visit asnt.org/store/rndemagazine. For individual paper access, visit the ASNT NDT Library at ndtlibrary.asnt.org. 20 M A T E R I A L S E V A L U A T I O N • A P R I L 2 0 2 2

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