| 1. |
- Bhalla, Suresh, et al.
(författare)
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Piezo-impedance transducers for residual fatigue life assessment of bolted steel joints
- 2012
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Ingår i: Structural Health Monitoring. - : SAGE Publications. - 1475-9217 .- 1741-3168. ; 11:6, s. 733-750
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Tidskriftsartikel (refereegranskat)abstract
- This article presents a new approach for fatigue life assessment of bolted steel joints using the equivalent stiffness determined by surface-bonded piezo-impedance transducers. The piezo transducers acquire electromechanical admittance signatures comprising the conductance (real part) and the susceptance (imaginary part), from which the equivalent system parameters of the joint are identified. The equivalent stiffness, one of the identified parameters, is experimentally found to be related to the residual stiffness of the joint and is correlated with the remaining life of the component in terms of the cycles of loading that can be further sustained by the joint. Through tests on three prototype steel joints, empirical equations are derived to relate the residual fatigue life to the loss of equivalent identified stiffness. The most promising feature of the proposed approach is that it employs the admittance signature of the surface-bonded piezo transducers directly, thereby circumventing the determination of the in situ stiffness of the joint.
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| 2. |
- Engholm, Marcus, 1977-, et al.
(författare)
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Direction of Arrival Estimation of Lamb Waves Using Circular Arrays
- 2011
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Ingår i: Structural Health Monitoring. - : SAGE Publications. - 1475-9217 .- 1741-3168. ; 10:5, s. 467-480
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Tidskriftsartikel (refereegranskat)abstract
- Uniform circular arrays (UCAs) with 360 degrees azimuthal coverage are very useful for structural health monitoring (SHM) of large planar structures. Difficulties encountered when working with Lamb waves include their dispersive and multi-modal nature. In this paper three different methods for estimating the direction-of-arrival (DOA) of incoming Lamb waves are compared and verified using simulated and experimental data. The previously proposed phase-mode excitation based beamformer is compared with two high-resolution spectral estimation techniques, the Capon method and the multiple signal classification method (MUSIC). Design consideration and guidelines for UCAs are presented. To experimentally evaluate the performance of the considered DOA methods a prototype array consisting of 16 separate pinducers arranged in a ring was constructed. The array was provided with an analog multiplexer that enabled recording signals received by the individual elements using a digital oscilloscope. The array was used for the reception of ultrasonic pulses sent by broadband piezoelectric transmitters and propagating in an aluminum plate. A selection of simulation and experimental results is presented showing the superior performance of the Capon beamformer.
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| 3. |
- Farhan, Muhammad, et al.
(författare)
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Predictive information and maintenance optimization based on decision theory : a case study considering a welded joint in an offshore wind turbine support structure
- 2022
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Ingår i: Structural Health Monitoring. - : SAGE Publications. - 1475-9217 .- 1741-3168. ; 21:1, s. 185-207
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Tidskriftsartikel (refereegranskat)abstract
- Predictive information and maintenance optimization for deteriorating structures is concerned with scheduling (a) the collection of information by inspection and monitoring and (b) maintenance actions such as repair, replacement, and retrofitting based on updated predictions of the future condition of the structural system. In this article, we consider the problem of jointly identifying—at the beginning of the service life—the optimal inspection time and repair strategy for a generic welded joint in a generic offshore wind turbine structure subject to fatigue. The optimization is performed based on different types of decision analyses including value of information analyses to quantify the expected service life cost encompassing inspection, repair, and fatigue damage for all relevant combinations of inspection time, repair method, and repair time. Based on the analysis of the expected service life cost, the optimal inspection time, repair method, and repair time are identified. Possible repair methods for a welded joint in an offshore environment include welding and grinding, for which detailed models are formulated and utilized to update the joint’s fatigue performance. The decision analyses reveal that an inspection should be scheduled approximately at mid-service life of the welded joint. A repair should be performed in the same year after an indication and measurement of a fatigue crack given an optimal inspection scheduling. This article concludes with a discussion on the results obtained from the decision and value of information analyses.
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| 4. |
- Fernandez, Ignasi, 1984, et al.
(författare)
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Monitoring of new and existing stainless-steel reinforced concrete structures by clad distributed optical fibre sensing
- 2023
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Ingår i: Structural Health Monitoring. - : SAGE Publications. - 1475-9217 .- 1741-3168. ; 22:1, s. 257-275
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Tidskriftsartikel (refereegranskat)abstract
- The implementation of structural health monitoring systems in existing civil engineering structures could contribute to a safer and more resilient infrastructure as well as important savings. Due to their light weight, small size, and high resistance to the environment, distributed optical fibre sensors (DOFS) stand out as a very promising technology for damage detection and quantification in reinforced concrete structures. This dataset includes information of DOFS featuring an external polymeric cladding with rough surface, deployed in a stainless-steel reinforced concrete beam subjected to four-point bending. Several sensor positions, both embedded in the concrete and attached to the surface, are included in a multilayer configuration. The data of the sensors includes two series of test, first cyclic loading under service loads and lastly cyclic loading to failure. Additionally, data from Digital Image Correlation and the actuator recordings are included for cross-validation purposes.
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| 5. |
- Fröjd, Patrik, et al.
(författare)
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Continuous wave measurements in a network of transducers for structural health monitoring of a large concrete floor slab
- 2016
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Ingår i: Structural Health Monitoring. - : SAGE Publications. - 1475-9217 .- 1741-3168. ; 15:4, s. 403-412
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Tidskriftsartikel (refereegranskat)abstract
- Local, superficial damage was detected and localized on an 8 × 2-m concrete floor slab using a structural health monitoring system. A total of 30 piezoelectric transducers, placed in a grid, transmitted and received continuous ultrasonic waves that were measured using a lock-in amplifier. Tomography was used to create images from the measured amplitude and phase of the continuous waves between all possible transducer pairs. The location of damage induced by impact hits was visible in the resulting images. The signals could easily be detected even between the most distant transducer pairs, indicating the possibility of monitoring even very large concrete structures.
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| 6. |
- Fröjd, Patrik, et al.
(författare)
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Detecting damage events in concrete using diffuse ultrasound structural health monitoring durinbg strong environmental variations
- 2018
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Ingår i: Structural Health Monitoring. - : SAGE Publications. - 1475-9217 .- 1741-3168. ; 17:2, s. 410-419
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Tidskriftsartikel (refereegranskat)abstract
- Diffuse ultrasonic wave measurements used in structural health monitoring applications can detect damage in concrete. However, the accuracy is very susceptible to environmental variations. In this study, a large concrete floor slab was monitored using diffuse wave fields that were generated by continuous-wave transmissions between ultrasonic transducers. The slab was monitored for several weeks while being subjected to changes in environmental conditions. Subsequently, it was damaged using impact hits, resulting in centimeter-scale cracking. The variations caused by the environment masked the effects of the damage in the measurements. To address this issue, the Mahalanobis distance was used to distinguish between the influence of the damage and the influence of the environmental variations. The Mahalanobis model uses amplitude and phase measurements of continuous waves at a set of different frequencies as inputs. A moving window approach was applied to the baseline data set to account for slow trends. This study shows that this technique greatly suppresses most of the variations caused by environmental conditions. All damage events in our data set have been detected.
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| 7. |
- Gil Berrocal, Carlos, 1986, et al.
(författare)
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Assessment and visualization of performance indicators of reinforced concrete beams by distributed optical fibre sensing
- 2021
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Ingår i: Structural Health Monitoring. - : SAGE Publications. - 1475-9217 .- 1741-3168. ; 20:6, s. 3309-3326
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Tidskriftsartikel (refereegranskat)abstract
- The implementation of structural health monitoring systems in civil engineering structures already in the construction phase could contribute to safer and more resilient infrastructure. Due to their lightweight, small size and high resistance to the environment, distributed optical fibre sensors stand out as a very promising technology for damage detection and quantification in reinforced concrete structures. In this article, the suitability of embedding robust distributed optical fibre sensors featuring a protective sheath to accurately assess the performance indicators, in terms of vertical deflection and crack width, of three reinforced concrete beams subjected to four-point bending is investigated. The results revealed that a certain strain attenuation occurs in embedded robust distributed optical fibre sensors compared to commonly used thin polyimide-coated distributed optical fibre sensors bonded to steel reinforcement bars. However, the presence of the protective sheath prevented the appearance of strain reading anomalies which has been a frequently reported issue. Performance wise, the robust distributed optical fibre sensors were able to provide a good estimate of the beam deflections with errors of between 12.3% and 6.5%. Similarly, crack widths computed based on distributed optical fibre sensor strain measurements differed by as little as ±20 µm with results from digital image correlation, provided individual cracks could be successfully detected in the strain profiles. Finally, a post-processing procedure is presented to generate intuitive contour plots that can help delivering critical information about the element’s structural condition in a clear and straightforward manner.
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| 8. |
- Leturiondo, Urko, et al.
(författare)
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Validation of a physics-based model of a rotating machine for synthetic data generation in hybrid diagnosis
- 2017
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Ingår i: Structural Health Monitoring. - : Sage Publications. - 1475-9217 .- 1741-3168. ; 16:4, s. 458-470
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Tidskriftsartikel (refereegranskat)abstract
- Diagnosis and prognosis are key issues in the application of condition based maintenance. Thus, there is a need to evaluate the condition of a machine. Physics-based models are of great interest as they give the response of a modelled system in different operating conditions. This strategy allows for the generation of synthetic data that can be used in combination with real data acquired by sensors to improve maintenance. The article presents an electromechanical model for a rotating machine, with special emphasis on the modelling of rolling element bearings. The proposed model is validated by comparing the simulation results and the experimental results in different operating conditions and different damaged states. This comparison shows good agreement, obtaining differences of up to 10% for the modelling of the whole rotating machine and less than 0.6% for the model of the bearing.
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| 9. |
- Neves, Ana C., et al.
(författare)
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The influence of frequency content on the performance of artificial neural network–based damage detection systems tested on numerical and experimental bridge data
- 2021
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Ingår i: Structural Health Monitoring. - : SAGE Publications. - 1475-9217 .- 1741-3168. ; 20:3, s. 1331-1347
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Tidskriftsartikel (refereegranskat)abstract
- The method herein proposed provides a novel perspective about data processing within structural health monitoring, which is essential for automated real-time monitoring and assessment of civil engineering structures. The low- and high-frequency contents of the forced vibration response of a structure are used to train and test artificial neural networks for the purpose of damage detection. In the context of several damage scenarios, the different versions of the networks are compared with each other with the aim of verifying which are the most efficient regarding novelty detection (one-class classification). The data related with the high-frequency response showed to contain more useful information for the proposed damage detection algorithm, when compared with the low-frequency response data (typically modal). In view of that, high frequencies should be given more attention in future research about their application in connection with structural health monitoring systems.
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| 10. |
- Neves, Ana C., et al.
(författare)
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The influence of frequency content onthe performance of artificial neural network–based damage detectionsystems tested on numerical andexperimental bridge data
- 2020
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Ingår i: Structural Health Monitoring. - 1475-9217 .- 1741-3168.
-
Tidskriftsartikel (refereegranskat)abstract
- The method herein proposed provides a novel perspective about data processing within structural health monitoring,which is essential for automated real-time monitoring and assessment of civil engineering structures. The low- and highfrequencycontents of the forced vibration response of a structure are used to train and test artificial neural networksfor the purpose of damage detection. In the context of several damage scenarios, the different versions of the networksare compared with each other with the aim of verifying which are the most efficient regarding novelty detection (oneclassclassification). The data related with the high-frequency response showed to contain more useful information forthe proposed damage detection algorithm, when compared with the low-frequency response data (typically modal). Inview of that, high frequencies should be given more attention in future research about their application in connectionwith structural health monitoring systems.
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