1,721,178 research outputs found
Carbon nanotube coated piezoelectric ceramic for self-health-monitoring
No full textThe sensor signal of Lead Zirconate Titanate (PZT) piezoelectric sensors/actuator surface mounted to a structure with a thin adhesive layer is known to be influenced by the bondline quality and integrity. Monitoring the bondline health of sensor/actuators integrated into structures is becoming a major concern to guarantee the success and reliability of Structural Health Management systems. The design of a carbon-nanotube-coated PZT (CPZT) sensor was presented in earlier work shown that the bondline of CPZTs mounted on a structure, can be up to 274% stronger than that of conventional PZTs. A CPZT consists of a standard PZT surface coated with a high-density array of oriented CNTnanoelectrodes (CNTs-NEA). The CNTs-NEA in the interface plays the role of electrodes and of reinforcing filler material. This paper presents results indicating that CPZTs have better performance than conventional PZTs because CNTs in the interface can additionally allow monitoring the bondline integrity during manufacturing and in-service life of a structure. Tests were performed on CPZTs surface mounted on a metal structure with a thin nonconductive adhesive layer. CNTs in the interface were used to monitor adhesive curing by detecting electrical resistance variations of the interface due to phase changes in the adhesive during curing. Crack and debond formation in the interface were monitored in a similar approach.The CPZT is unique in that it is the only existing PZT that, not only has a stronger interface, but is also capable of self-monitoring the health of its bondline which is essential for accurate and reliable SHM systems
Influence of interface degradation on the performance of piezoelectric actuators
No full textAn experimental and numerical study was performed to investigate the effects of interface debonding on the performance of piezoelectric (PZT) ceramic actuators for structural health monitoring (SHM) systems. Interface degradation of PZT actuators may occur over time during the in-service life of the structure compromising the performance and reliability of the SHM system. Energy losses and signal changes should be understood to guarantee the reliability of the SHM systems during the life-time of the structure. Here we present the first systematic study on the performance of PZT actuators with a partially degraded interface. The electro-mechanical coupling between PZT actuators and a hosting aluminium plate was found to vary with the interface debonding over a wide frequency range affecting the amplitude and phase of the actuators signal. A signal delay and an amplitude decrease were observed for: increasing debonding area, different debond shape, and location underneath the PZT actuators. Changes were found to be dependent on the actuation frequency with respect to the PZT resonance frequency. A spectral element-based code integrated with a coupled electro-mechanical field solver was used to verify the experimental results by simulating the propagation of ultrasonic Lamb waves in an aluminum plate with built-in PZT sensors/actuators
A large area flexible expandable network for structural health monitoring
No full textAn investigation was performed to develop a flexible sensor network that can be stretched and expanded to cover structures with an order of magnitude larger than its original unexpanded size. The increasing need to cover large areas with a high number of sensors, networks, and electronic devices for structural health monitoring leads to this study. In this paper a flexible polymer with ultra- high stretching capability (linear expansions larger than 1000% the original length) is designed, fabricated and tested for sensor network applications. The stretchabihty of the polymer is achieved by engineering thousands of micronodes, which house the sensors and electronics, interconnected by extendable and flexible polymer microwires. The extendable microwires are the key element to perform uniform expansions of the network in all directions, to allow precise location of the nodes, to maximize the polymer expansion per unit area and to allow translation only of the nodes. With the proposed microwire design, a linear elongation wider than 1000% was achieved for a 256 nodes network, avoiding failure of the microwires and micronodes during fabrication and extension. It is believed that the proposed flexible, expandable polymer design is a cost-effective approach to integrate networks of thousands of sensors, actuators and electronic devices into large structures
sj-pdf-1-lup-10.1177_09612033221100908 – Supplemental Material for Comorbidities of systemic lupus erythematosus prior to and following diagnosis in different age-at-onset groups
No full textSupplemental Material, sj-pdf-1-lup-10.1177_09612033221100908 for Comorbidities of systemic lupus erythematosus prior to and following diagnosis in different age-at-onset groups by Cheng-Ya Yu, Chang-Fu Kuo, I-Jun Chou, Jung-Sheng Chen, Hung-Yi Lu, Chao-Yi Wu, Li-Chen Chen, Jing-Long Huang and Kuo-Wei Yeh in Lupus</p
On the Challenges of Upscaling Damage Monitoring Methodologies for Stiffened Composite Aircraft Panels
No full textHealth management methodologies for condition-based maintenance are often developed using sensor data collected during experimental tests. Most tests performed in laboratories focus on a coupon level or flat panels, while structural component testing is less commonly seen. As researchers, we often consider our experimental tests to be representative of a structure in a final application and consider the developed methodologies to be transferrable to these real-life structures. Yet, structures in their final applications such as wind turbines or aircraft are often larger, more complex, might contain various assembly details, and are loaded in complex conditions. These factors might influence the performance of developed diagnostic and prognostic methodologies and should therefore not be ignored.In our work, we consider the aspects of upscaling structural health monitoring (SHM) methodologies for stiffened composite panels with the design of the panels inspired by an aircraft wing structure. For this, we examine two levels of panels, namely a single- and multi-stiffener composite panel, where we consider the single-stiffener panel to be a representative lower-level version of the multi-stiffener panel. Multiple SHM sensors (acoustic emission, Lamb waves, strain sensing) were installed on both composite panels to monitor damage propagation during testing. We identify and analyse challenges and further discuss considerations that must be taken during upscaling of diagnostics and prognostics, and with that, aid in the development of health management methodologies for condition-based maintenance.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Structural Integrity & Composite
Using optical fibre sensors for structural health monitoring of Tsing Ma Bridge
No full textOptical fibre sensors have been extensively employed as real-time damage detection tools in advanced aircraft and space vehicles. However, the practical applications of this kind of sensors to real civil engineering structures have not been widely adopted. A structural health monitoring system - Wind and Structural Health Monitoring System (WASHMS) for the Tsing Ma Bridge has been operated since the bridge commissioning in May 1997. This paper presents a study using fiber Bragg grating sensors to measure strain responses of the Tsing Ma Bridge and compare the results with those obtained from W ASHMS using traditional resistive strain gauges. The measurement results using FBG sensors were in excellent agreement with those acquired by WASHMS
Structural health monitoring of adhesively-bonded hybrid joints by acoustic emission
No full textThe increasing use of Adhesively-bonded joints in industrial applications resulted in more attention to damage assessment in these joints. The aim of the present study is to characterize the damage in bi-material double-lap adhesively-bonded joints by Acoustic Emission (A E). Two different structural adhesives, representing a ductile (Methacrylate-based) and brittle (epoxy-based) types, were used to bond C F R P skins to a steel core. The fabricated joints were loaded in tension while damage evolution was monitored by A E . Due to the difference in the fracture nature of the adhesives "brittle vs. ductile", different damage mechanisms occurred in the specimens; including adhesive layer failure, steel deformation, adhesive/adherends interfacial debonding and delamination in the C F R P skin. In order to distinguish and classify these damage types by A E, the AE features of each damage mechanism were first obtained by conducting some standard tests on the individual constituent materials. Then, these AE reference patterns were used to train an ensemble decision tree classifier. Finally, the trained model classified the AE signals of the double-lap tests and the images captured by camera were utilized to verify AE results. This study demonstrates the potential of AE technique for damage characterization of the adhesively-bonded bi-material joints.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Structural Integrity & Composite
A spider-web-like highly expandable sensor network for multifunctional materials
No full textA multiscale method that allows a noninvasive and precise integration of thousands of nano- or microscale electronic devices into large macroscopic materials or structures of any 3D shape and rigidity is demonstrated. An array of microsensors (for strain and temperature) is built on a spider-web-like, highly expandable and flexible polyimide substrate that is engineered in such a way as to allow unique area dilatations. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
An Experimental Benchmark Problem in Structural Health Monitoring
No full textThis paper focuses on the goals of the second phase of the activities of the IASC-ASCE
Structural Health Monitoring Task Group, involving the application of structural
health monitoring techniques to data obtained from a four story steel frame
structure tested July 19–21, 2000 at the University of British Columbia. Damage was
simulated by removing bracing within the structure. An electromagnetic shaker and
mass on the top floor of the structure were used to excite the structure. Accelerometers
were placed throughout the structure to provide measurements of the structural
responses. Three excitation cases were considered, including one ambient vibration
level in which the shaker was turned off
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