Research

14 pages, 5057 KiB

Open AccessArticle

A Low-Cost Robotic Camera System for Accurate Collection of Structural Response

by Rolands Kromanis and Christopher Forbes

Inventions 2019, 4(3), 47; https://doi.org/10.3390/inventions4030047 - 21 Aug 2019

Cited by 12 | Viewed by 5920

Vision-based technologies are becoming ubiquitous when considering sensing systems for measuring the response of structures. Availability of proprietary camera systems has opened up the scope for many bridge monitoring projects. Even though structural response can be measured at high accuracies when analyzing target [...] Read more.

Vision-based technologies are becoming ubiquitous when considering sensing systems for measuring the response of structures. Availability of proprietary camera systems has opened up the scope for many bridge monitoring projects. Even though structural response can be measured at high accuracies when analyzing target motions, the main limitations to achieving even better results are camera costs and image resolution. Conventional camera systems capture either the entire structure or large/small part of it. This study introduces a low-cost robotic camera system (RCS) for accurate measurement collection of structural response. The RCS automatically captures images of parts of a structure under loading, therefore, (i) giving a higher pixel density than conventional cameras capturing the entire structure, thus allowing for greater measurement accuracy, and (ii) capturing multiple parts of the structure. The proposed camera system consists of a modified action camera with a zoom lens, a robotic mechanism for camera rotation, and open-source software which enables wireless communication. A data processing strategy, together with image processing techniques, is introduced and explained. A laboratory beam subjected to static loading serves to evaluate the performance of the RCS. The response of the beam is also monitored with contact sensors and calculated from images captured with a smartphone. The RCS provides accurate response measurements. Such camera systems could be employed for long-term bridge monitoring, in which strains are collected at strategic locations, and response time-histories are formed for further analysis. Full article

(This article belongs to the Special Issue Structural Health Monitoring and Their Applications Across Industry)

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18 pages, 7551 KiB

Open AccessArticle

A Semi-Supervised Based K-Means Algorithm for Optimal Guided Waves Structural Health Monitoring: A Case Study

by Abd Ennour Bouzenad, Mahjoub El Mountassir, Slah Yaacoubi, Fethi Dahmene, Mahmoud Koabaz, Lilian Buchheit and Weina Ke

Inventions 2019, 4(1), 17; https://doi.org/10.3390/inventions4010017 - 08 Mar 2019

Cited by 34 | Viewed by 7403

Abstract

This paper concerns the health monitoring of pipelines and tubes. It proposes the k-means clustering algorithm as a simple tool to monitor the integrity of a structure (i.e., detecting defects and assessing their growth). The k-means algorithm is applied on data collected experimentally, [...] Read more.

This paper concerns the health monitoring of pipelines and tubes. It proposes the k-means clustering algorithm as a simple tool to monitor the integrity of a structure (i.e., detecting defects and assessing their growth). The k-means algorithm is applied on data collected experimentally, by means of an ultrasonic guided waves technique, from healthy and damaged tubes. Damage was created by attaching magnets to a tube. The number of magnets was increased progressively to simulate an increase in the size of the defect and also, a change in its shape. To test the performance of the proposed method for damage detection, a statistical population was created for the healthy state and for each damage step. This was done by adding white Gaussian noise to each acquired signal. To optimize the number of clusters, many algorithms were run, and their results were compared. Then, a semi-supervised based method was proposed to determine an alarm threshold, triggered when a defect becomes critical. Full article

(This article belongs to the Special Issue Structural Health Monitoring and Their Applications Across Industry)

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17 pages, 4394 KiB

Open AccessArticle

Star Type Wireless Sensor Network for Future Distributed Structural Health Monitoring Applications

by James Meech, Christopher Crabtree and Zoltán Rácz

Inventions 2019, 4(1), 6; https://doi.org/10.3390/inventions4010006 - 23 Jan 2019

Cited by 2 | Viewed by 6422

Abstract

A star type wireless sensor network based on nine-axis micro-electromechanical inertial motion sensors with the potential to include up to 254 sensor nodes is presented, and an investigation into the mechanical and structural effects of bell ringing on bell towers is presented as [...] Read more.

A star type wireless sensor network based on nine-axis micro-electromechanical inertial motion sensors with the potential to include up to 254 sensor nodes is presented, and an investigation into the mechanical and structural effects of bell ringing on bell towers is presented as a possible application. This low-power and low-cost system facilitates the continual monitoring of mechanical forces exerted by swinging bells on their support and thus helps avoid structural degradation and damage. Each sensor measures bell rotation, and a novel method utilising only the instantaneous rotational angle is implemented to calculate the force caused by bell ringing. In addition, a commonly used, however, previously experimentally unconfirmed assumption that allows great simplification of force calculations was also proven to be valid by correlating predicted theoretical values with measurement data. Forces produced by ringing a 1425 kg bell in Durham Cathedral were characterised and found to agree with literature. The sensor network will form the basis of a toolkit that provides a scalable turnkey method to determine the exact mechanisms that cause excessive vibration in mechanical and architectural structures, and has the potential to find further applications in low-frequency distributed structural health monitoring. Full article

(This article belongs to the Special Issue Structural Health Monitoring and Their Applications Across Industry)

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11 pages, 6961 KiB

Open AccessArticle

Distributed Strain Sensing from Different Optical Fiber Configurations

by Daniel A. Drake, Rani W. Sullivan and J. Caleb Wilson

Inventions 2018, 3(4), 67; https://doi.org/10.3390/inventions3040067 - 25 Sep 2018

Cited by 11 | Viewed by 5968

Abstract

Strain distributions were obtained from optical fibers arranged in three different configurations on transversely-loaded cantilevered beams. Traditional strain measurement sensors, such as strain gauges, are limited to measuring strain at discrete points on a structural member. However, distributed optical fibers can measure high [...] Read more.

Strain distributions were obtained from optical fibers arranged in three different configurations on transversely-loaded cantilevered beams. Traditional strain measurement sensors, such as strain gauges, are limited to measuring strain at discrete points on a structural member. However, distributed optical fibers can measure high spatial (<1 mm spacing) strain or temperature distributions. In this study, optical fibers in spiral, grid, and rosette configurations were bonded to aluminum cantilevered beams subjected to tip loads. Strain distributions from optical fiber sensors were measured using a swept wavelength coherent interferometric technique. The optical fiber strain measurements show good agreement with strain gauge measurements. The attributes of each sensor configuration are discussed. Full article

(This article belongs to the Special Issue Structural Health Monitoring and Their Applications Across Industry)

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14 pages, 6164 KiB

Open AccessArticle

Experimental Investigation of Impact Localization in Composite Plate Using Newly Developed Imaging Method

by Mohammad Faisal Haider, Asaad Migot, Md Yeasin Bhuiyan and Victor Giurgiutiu

Inventions 2018, 3(3), 59; https://doi.org/10.3390/inventions3030059 - 27 Aug 2018

Cited by 12 | Viewed by 5148

Abstract

This paper focuses on impact localization of composite structures, which possess more complexity in the guided wave propagation due to the anisotropic behavior of composite materials. In this work, a composite plate was manufactured by using a compression molding process with proper pressure [...] Read more.

This paper focuses on impact localization of composite structures, which possess more complexity in the guided wave propagation due to the anisotropic behavior of composite materials. In this work, a composite plate was manufactured by using a compression molding process with proper pressure and temperature cycle. Eight layers of woven composite prepreg were used to manufacture the composite plate. A structural health monitoring (SHM) technique was implemented with piezoelectric wafer active sensors (PWAS) to detect and localize the impact on the plate. There were two types of impact event that were considered in this paper (a) low energy impact event (b) high energy impact event. Two clusters of sensors recorded the guided acoustic waves generated from the impact. The acoustic signals were then analyzed using a wavelet transform based time-frequency analysis. The proposed SHM technique successfully detected and localized the impact event on the plate. The experimentally measured impact locations were compared with the actual impact locations. An immersion ultrasonic scanning method was used to visualize the composite plate before and after the impact event. A high frequency 10 MHz 1-inch focused transducer was used to scan the plate in the immersion tank. Scanning results showed that there was no visible manufacturing damage in the composite plate. However, clear impact damage was observed after the high-energy impact event. Full article

(This article belongs to the Special Issue Structural Health Monitoring and Their Applications Across Industry)

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10 pages, 3496 KiB

Open AccessArticle

Nonlinear Vibrations of Innovative One-Way Clutch in Vehicle Alternator

by Xiaotian Xu, Gang Chen, Joshua Colley, Pengrui Li and Mohamad Qatu

Inventions 2018, 3(3), 53; https://doi.org/10.3390/inventions3030053 - 30 Jul 2018

Cited by 1 | Viewed by 6373

Abstract

One-way clutches have been proposed for vehicle alternators. The clutch can play an important role in reducing vibrations of the vehicle engine accessory system, but the severe vibrations of the clutch subsystem limit its stability and durability. This paper investigates the nonlinear vibrations [...] Read more.

One-way clutches have been proposed for vehicle alternators. The clutch can play an important role in reducing vibrations of the vehicle engine accessory system, but the severe vibrations of the clutch subsystem limit its stability and durability. This paper investigates the nonlinear vibrations of a one-way clutch between the accessory pulley and the alternator shaft. The one-way clutch is modelled as a discontinuous stiffness system, and the simplified model is analyzed using discontinuous transform to determine the periodic, primary resonance and the sub and super harmonic resonance solutions. The typical system model is numerically solved and the spectrum and phase plots are characterized. The results give a big picture of and insights into the nonlinear vibration features of one-way clutch system. A relevant US patent is pending. Full article

(This article belongs to the Special Issue Structural Health Monitoring and Their Applications Across Industry)

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12 pages, 3665 KiB

Open AccessArticle

A Uniform Strain Transfer Scheme for Accurate Distributed Optical Fiber Strain Measurements in Civil Structures

by Yang Du, Yizheng Chen, Yiyang Zhuang, Chen Zhu, Rex E. Gerald II and Jie Huang

Inventions 2018, 3(2), 30; https://doi.org/10.3390/inventions3020030 - 20 May 2018

Cited by 7 | Viewed by 5086

Abstract

We report a screw-like package design for an embeddable distributed optical fiber strain sensor for civil engineering applications. The screw-like structure is the exterior support for an optical fiber sensor. The bare optical fiber is embedded and secured in a longitudinal groove of [...] Read more.

We report a screw-like package design for an embeddable distributed optical fiber strain sensor for civil engineering applications. The screw-like structure is the exterior support for an optical fiber sensor. The bare optical fiber is embedded and secured in a longitudinal groove of the screw-like package using a rigid adhesive. Our packaging scheme prevents damage to the bare optical fiber and ensures that the packaged sensor is accurately and optimally sensing strain fields in civil structures. Moreover, our screw-like design has an equal area in a cross-section perpendicular to and along the screw axis, so strain field distributions are metered faithfully along the length of the embedded optical fiber. Our novel screw-like package optical fiber sensor, interfaced to a Rayleigh scattering-based optical frequency domain reflectometer system enables undistorted, accurate, robust, and spatially-distributed strain measurements in bridges, tunnels, pipelines, buildings, etc. along structural dimensions extending from centimeters to kilometers. Full article

(This article belongs to the Special Issue Structural Health Monitoring and Their Applications Across Industry)

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9 pages, 5072 KiB

Open AccessArticle

An Embeddable Strain Sensor with 30 Nano-Strain Resolution Based on Optical Interferometry

by Chen Zhu, Yizheng Chen, Yiyang Zhuang, Fujian Tang and Jie Huang

Inventions 2018, 3(2), 20; https://doi.org/10.3390/inventions3020020 - 04 Apr 2018

Cited by 6 | Viewed by 5789

Abstract

A cost-effective, robust and embeddable optical interferometric strain sensor with nanoscale strain resolution is presented in this paper. The sensor consists of an optical fiber, a quartz rod with one end coated with a thin gold layer, and two metal shells employed to [...] Read more.

A cost-effective, robust and embeddable optical interferometric strain sensor with nanoscale strain resolution is presented in this paper. The sensor consists of an optical fiber, a quartz rod with one end coated with a thin gold layer, and two metal shells employed to transfer the strain and orient and protect the optical fiber and the quartz rod. The optical fiber endface, combining with the gold-coated surface, forms an extrinsic Fabry–Perot interferometer. The sensor was firstly calibrated, and the result showed that our prototype sensor could provide a measurement resolution of 30 nano-strain (nε) and a sensitivity of 10.01 µε/µm over a range of 1000 µε. After calibration of the sensor, the shrinkage strain of a cubic brick of mortar in real time during the drying process was monitored. The strain sensor was compared with a commercial linear variable displacement transducer, and the comparison results in four weeks demonstrated that our sensor had much higher measurement resolution and gained more detailed and useful information. Due to the advantages of the extremely simple, robust and cost-effective configuration, it is believed that the sensor is significantly beneficial to practical applications, especially for structural health monitoring. Full article

(This article belongs to the Special Issue Structural Health Monitoring and Their Applications Across Industry)

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