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17 pages, 6947 KB

Open AccessArticle

A Vision-Based Bolt Looseness Detection Method for a Multi-Bolt Connection

by Lin Deng, Ye Sa, Xiufang Li, Miao Lv, Sidong Kou and Zhan Gao

Appl. Sci. 2024, 14(11), 4385; https://doi.org/10.3390/app14114385 - 22 May 2024

Cited by 14 | Viewed by 3132

Many vision-based bolt looseness detection methods that directly observe the bolts have been developed. However, these methods have many limitations in terms of the conditions and processes of their implementation. To address these problems, this paper proposed a fully automated vision-based bolt looseness detection method for a rigid multi-bolt connection. The proposed method combines digital shearing speckle pattern interferometry (DSSPI) and recurrent neural network (RNN) and involves capturing speckle fringe patterns under various looseness cases using the DSSPI system and classifying these patterns with an RNN model to detect the loose bolts. The proposed method can detect all the bolts within the measured surface at one time, which is efficient. On the other hand, it eliminates the need for prior information such as the initial angle and position of each bolt. It can even detect unseen bolts in multi-bolt connections, making it applicable for connections in complex structures in which occlusion often occurs. Additionally, the method eliminates the complex process of distortion rectification. These features make the method achieve a single-judgment time (four bolts at one detection) of only 4.70 millisecond with a detection accuracy over 99%, which has potential for the real-time detection of loose bolts in multi-bolt connections. Full article

(This article belongs to the Section Optics and Lasers)

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14 pages, 6829 KB

Open AccessArticle

Denoising of Wrapped Phase in Digital Speckle Shearography Based on Convolutional Neural Network

by Hao Zhang, Dawei Huang and Kaifu Wang

Appl. Sci. 2024, 14(10), 4135; https://doi.org/10.3390/app14104135 - 13 May 2024

Cited by 8 | Viewed by 1982

Abstract

Speckle-shearing technology is widely used in defect detection due to its high precision and non-contact characteristics. However, the wrapped-phase recording defect information is often accompanied by a lot of speckle noise, which affects the evaluation of defect information. To solve the problems of traditional denoising algorithms in suppressing speckle noise and preserving the texture features of wrapped phases, this study proposes a speckle denoising algorithm called a speckle denoising convolutional neural network (SDCNN). The proposed method reduces the loss of texture information and the blurring of details in the denoising process by optimizing the loss function. Different from the previous simple assumption that the speckle noise is multiplicative, this study proposes a more realistic wrapped image-simulation method, which has better training results. Compared with representative algorithms such as BM3D, SDCNN can handle a wider range of speckle noise and has a better denoising effect. Simulated and real speckle-noise images are used to evaluate the denoising effect of SDCNN. The results show that SDCNN can effectively reduce the speckle noise of the speckle-shear wrapping phase and retain better texture details. Full article

(This article belongs to the Special Issue Innovative Applications of Artificial Intelligence in Multidisciplinary Sciences: Latest Advances and Prospects)

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22 pages, 12722 KB

Open AccessArticle

Dynamic ESPI Evaluation of Deformation and Fracture Mechanism of 7075 Aluminum Alloy

by Shun Takahashi, Sanichiro Yoshida, Tomohiro Sasaki and Tyler Hughes

Materials 2021, 14(6), 1530; https://doi.org/10.3390/ma14061530 - 20 Mar 2021

Cited by 10 | Viewed by 3890

Abstract

The deformation and fracture mechanism in 7075 aluminum alloy is discussed based on a field theoretical approach. A pair of peak-aged and overaged plate specimens are prepared under the respective precipitation conditions, and their plastic deformation behaviors are visualized with two-dimensional electronic speckle pattern interferometry (ESPI). The in-plane velocity field caused by monotonic tensile loading is monitored continuously via the contour analysis method of ESPI. In the plastic regime, the peak-aged specimen exhibits a macroscopically uniform deformation behavior, while the annealed specimen exhibits non-uniform deformation characterized by a localized shear band. The occurrence of the shear band is explained by the transition of the material’s elastic resistive mechanism from the longitudinal force dominant to shear force dominant mode. The shear force is interpreted as the frictional force that drives mobile dislocations along the shear band. The dynamic behavior of the shear band is explained as representing the motion of a solitary wave. The observed decrease in the solitary wave’s velocity is accounted for by the change in the acoustic impedance with the advancement of plastic deformation. Full article

(This article belongs to the Special Issue Mechanics and Analysis of Advanced Materials and Structures)

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10 pages, 4119 KB

Open AccessArticle

Digital Shearing Speckle Pattern Interferometry Based on Rochon Prism and Its Application

by Xu Wang, Zhan Gao, Chenjia Gao, Jieming Zhao, Yuhao Niu, Zihui Liu, Yuan Zhang and Yuchen Liu

Appl. Sci. 2019, 9(12), 2554; https://doi.org/10.3390/app9122554 - 22 Jun 2019

Cited by 4 | Viewed by 4301

Abstract

This paper presents improved digital shearing speckle pattern interferometry based on Rochon Prism. The advantage of this method is that it avoids the shadow noise caused by transmission light, which improves the shearography accuracy. By reducing the angle of divergence and coordinating the measuring distance and the precision coordinate, the beam-splitting path of the interference optical path is improved. Experimental results prove that the improved method contributes to the practical and instrumental application of shearography. Full article

(This article belongs to the Section Mechanical Engineering)

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7 pages, 1330 KB

Open AccessProceeding Paper

Investigating Hydrofracture Evolution of Quasi-Brittle Material Using a Post-Peak Control Technique Associated with Speckle-Shearing Interferometry

by Wei-Chih Chen, Li-Hsien Chen, Shyh-Tsong Lin and Yao-Chung Chen

Proceedings 2018, 2(8), 452; https://doi.org/10.3390/ICEM18-05326 - 12 Jun 2018

Cited by 1 | Viewed by 1822

Abstract

This paper presents the experimental results obtained with a post-peak loading device of hydraulic fracture controlled by setting circumferential deformation of a specimen to be a closed-loop feedback signal during servo-water-driven and monitored with the optical technique of speckle-shearing interferometry (SSI). The macro-scale complete loading curve obtained by the post-peak loading system indicate the stiffness, peak strength and post-peak behavior of quasi-brittle material subjected to borehole water pressure. The micro-scale out-of-plane displacement (OPD) obtained by SSI corresponding to complete loading curve was exhibited where the internal crack tip was located. The complete hydrofracture evolution from displacement continuity to displacement discontinuity was investigated. The test results provide a better understanding of the hydraulic fracture mechanism which is helpful for the development of theoretical and numerical solutions related to hydraulic fractures. Full article

(This article belongs to the Proceedings of The 18th International Conference on Experimental Mechanics)

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