Monitoring of Structural Integrity
结构完整性监测
The conventional approach to evaluating structural integrity – rule-of-thumb guidelines, with excessive safety margins – no longer makes sense in today’s highly competitive business climate. On the other hand, new materials are used without sufficient life test data support. We are hence facing the problems to ensure the long term reliability of components that have been designed without sufficient confidence due to the lack of data. The only possibility to achieve a safe operation of the plants is to detect the defects or damages in the components in time by frequent inspection and/or on-line monitoring. The trend of integration of monitoring techniques and assessment approaches has been facilitated in recent years. The ability to monitor minute changes in plant or infrastructure condition with a high degree of confidence has led to continuous advances in structural integrity technology and risk based assessment.
Structural Integrity monitoring (SIM) is a broad field that encompasses a number of synergetic technologies brought together to provide a system that can potentially identify and characterize the damage of a structural system. The SIM process involves the observation of a system over time using periodically sampled dynamic response measurements from an array of sensors, the extraction of damage-sensitive features from these measurements, and the statistical analysis of these features to determine the current state of system health. The traditional integrity approaches are either visual or localized experimental methods such as acoustic or ultrasonic methods, magnetic field methods, radiograph, eddy-current methods and thermal field methods. All of these experimental techniques require that the location of the damage is known a priori and that the portion of the structure being inspected is readily accessible. The need for quantitative global damage detection methods that can be applied to large complex structures has led to research into SIM methods that examine changes in the dynamic characteristics of the complex structure. The basic premise of these global SIM methods is that damage will alter the stiffness, mass or energy dissipation properties of a system, which, in turn, alter the measured dynamic response of the system. An advanced SIM system may comprise of following components:
(1) Embedded networked sensing with active Micro-Electro Mechanical Systems (MEMS).
(2) Data interrogation with statistical pattern recognition algorithms to identify the damage.
(3) Data correlation techniques to locate the damage.
(4) Integrated software in the sensing unit through a programmable micro-processing chip.
(5) A wireless data transmission system that transmits the data output from the sensing units to a central location.
(6) The structural integrity assessment in the central workstation.
To be able to develop a robust and cost-effective SIM system one should integrate and extend the technologies from various engineering and information technology disciplines. The development of sensors alone may cover a broad spectrum of disciplines, such as mechanics, materials, optics, acoustics, electronics, chemistry, heat and mass transfer, and machine design and so on. The data processing and transmission also represent a multidisciplinary approach that combines the mathematics, computer science, and communication technology. It can thus be anticipated that more multidisciplinary and interdisciplinary researches will be needed in the future development of holistic approach to structural integrity.
Further research opportunities 未来研究方向
l Sensor technology: Low cost multifunctional sensors, Wireless sensors, Mobile robotic sensors, Mobile AE sensors, Self powered sensors
l Interpretation of data: Cross correction between sensor output and catastrophic failure; Mathematical modelling and experimental studies and predictive models; Real time structured integrity assessment using condition monitoring data
l Long term performance and reliability of sensor systems and instrumentation
l Self diagnostic structures
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