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  • 1
    In: Structural Health Monitoring, SAGE Publications, Vol. 22, No. 5 ( 2023-09), p. 3270-3285
    Abstract: Fatigue crack growth is one of the most common damage mechanisms of structural components and can result in a sudden and unexpected abrupt fracture which can cause catastrophic failure. Thus, monitoring of crack propagation is an important topic of structural health monitoring. For that reason, this work aims at the detection of crack propagation by the application of a high-frequency vibration-based method, using the electromechanical admittance (EMA). It enables the local monitoring of the coupled dynamic behavior of the structure and the piezoelectric transducer which changes, for example, due to damage. It is the purpose of this study to develop a method from the recorded data reflecting fatigue crack growth in weld zones. As it is known that the data are affected by temperature, a temperature compensation strategy is considered. In this study, a presentation of the coupled EMA data has been found, which allows the isolation of the crack propagation effects. Within the scope of fatigue experiments, fatigue cracks were introduced into threaded bolts of rail support points, welded onto base plates. In practice, they are embedded in a layer of mortar and, therefore, have poor accessibility. Electromechanical impedance measurements were carried out at different states of fatigue crack growth. The fatigue crack growth was validated by strain gauge measurements executed during the fatigue experiment. The proposed feature was calculated from the recorded EMA data. The technique produces promising results detecting fatigue cracks and can also be transferred to similar types of welded joints or rods where fatigue crack growth occurs.
    Type of Medium: Online Resource
    ISSN: 1475-9217 , 1741-3168
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2023
    detail.hit.zdb_id: 2101420-6
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  • 2
    In: Stahlbau, Wiley, Vol. 89, No. 4 ( 2020-04), p. 399-411
    Abstract: Damage detection using electromechanical impedance spectra – development and validation of a non‐destructive structure monitoring system Within a cooperational project of the University of Siegen between the “Applied Mechanics Group” (ATM) of the Department of Mechanical Engineering and the chair “Steel Construction and Composite Steel Construction” of the Department of Civil Engineering, a new monitoring method for non‐destructive damage detection on bolts was developed and tested according to its applicability on real life structures. The method is based on the measurement of electromechanical impedance spectra, which change varying influences on the structure. Therefore this method is suitable for identification of the structural state. The investigation method could be established in the monitoring of bridge structures. The investigations were carried out on threaded bolts welded onto steel plates. In order to determine the general behaviour of the electromechanical impedance spectra of the test specimens under varying conditions, preliminary investigations were carried out. The expected opposite development of the spectra under the influence of varying preloads and saw cuts was determined. The fatigue experiments which were carried out subsequently have shown the applicability on real life structures. In the article first experimental results are presented and the applicability of the measurement methodology for structural monitoring is discussed afterwards.
    Type of Medium: Online Resource
    ISSN: 0038-9145 , 1437-1049
    URL: Issue
    RVK:
    Language: German
    Publisher: Wiley
    Publication Date: 2020
    detail.hit.zdb_id: 2159000-X
    detail.hit.zdb_id: 240072-8
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  • 3
    In: ce/papers, Wiley, Vol. 4, No. 2-4 ( 2021-09), p. 203-209
    Abstract: Within a research project carried out at the Department of Civil Engineering and the Department of Mechanical Engineering of the University of Siegen, a new monitoring method for non‐destructive damage detection on bolts was developed and tested according to its applicability on real life structures. The so‐called EMI‐method is based on the measurement of electromechanical impedance spectra, which change with varying structural states and thus allow for a condition assessment. Structures vibrate in a combination of their natural modes, which can provide information about their structural condition. Their modal characteristics are system‐inherent quantities and are governed by geometry, system stiffnesses and mass allocation. If a system parameter changes, e.g. the bending stiffness of a bridge, this is reflected in the vibration analysis and the modal characteristics. To identify the modal characteristics of civil engineering structures, these are excited and the system response is measured. This principle is also used for damage detection by means of electro‐mechanical impedance spectra (EMI). The observed system‐inherent quantity is the frequency‐dependent mechanical impedance Zs(ω) of the structure. The method is based on the idea that the mechanical impedance of a structure or component to be measured changes as a result of damage (or loss of prestress in the case of bolts) and thus these changes can be detected. In the project, investigations were carried out on steel plates with orthogonally welded threaded bolts, which are used, for example, as fasteners for rail supporting points on bridges. Research objectives were on one hand the detection of the prestress stage and on the other hand the detection of fatigue damage in the weld seam. Within the scope of the project, it has been investigated to what extent a change of the prestressing load can be reliably detected by means of the EMI method. Furthermore, the influence of damage to the bolt on the impedance spectra was investigated.
    Type of Medium: Online Resource
    ISSN: 2509-7075 , 2509-7075
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 2894657-1
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  • 4
    Online Resource
    Online Resource
    Springer Science and Business Media LLC ; 2018
    In:  Psychological Research Vol. 82, No. 2 ( 2018-3), p. 324-336
    In: Psychological Research, Springer Science and Business Media LLC, Vol. 82, No. 2 ( 2018-3), p. 324-336
    Type of Medium: Online Resource
    ISSN: 0340-0727 , 1430-2772
    RVK:
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2018
    detail.hit.zdb_id: 1463034-5
    detail.hit.zdb_id: 2426389-8
    SSG: 5,2
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