![]() ![]() The UGW is a rapidly emerging SHM technique for inspection of metallic/composite structures. A schematic view of active and passive SHM methods is shown in Figure 1. Like NDE, the SHM sensors detect and quantify the structural defect but in the latter technique sensors are permanently fixed/embedded in structures to provide health monitoring data on need basis. Contrary, the active SHM is a direct health assessment method for detection and estimation of structural defects using health detection act structures actuators/sensors. However, the passive SHM does not provide the root cause(s) of the problem and the opportunity for a thorough examination of the defect. It requires external excitation source to produce elastic waves in structures and utilize the functioning parameters such as vibration and stress levels for health assessment. The passive SHM is an examining method used in static/dynamic and rotating equipment. The SHM is generally performed by two methods: the passive and active SHM. The GWs have the potential to be used inside curved structures thus suitable for inspection of various shapes and geometries over a longer distance. They are also known as long-range ultrasonic testing (LRU), introduced initially to determine the integrity assessment of large and continuous pipelines. The guided wave (GW) has a unique ability to confine itself inside the thin-wall structures, therefore, they can propagate over large distances with minimal attenuation and loss of energy. The guided waves ultrasonic testing (GWUT) potentially offers a smart alternative solution to conventional approach towards NDE and SHM. However, majority of these techniques tend to be slow and cumbersome, especially in case of large structures (pipelines, marine, ships, and aerospace). Numerous health assessment techniques such as bulk wave ultrasonic, X-rays, infrared thermography, and eddy current are used effectively for non-destructive evaluation (NDE) of structures. The SHM approach involves collecting data from various sensors installed on structures and interpreting the findings to make reliable and cost-effective and CBM decisions for structures under different operating conditions. In recent years, the significance of structural health monitoring (SHM) techniques has been enhanced in the health assessment, remaining useful life (RUL) prediction, and condition-based maintenance (CBM) of degrading structures. The inspection and maintenance of mechanical structures were performed mainly in accordance with a preventive (time-based) approach in the past. The extent and severity of these mechanisms depend on the applied static/dynamic loads, operating conditions, and material properties such as corrosion resistance, microstructural features, the crystallographic orientation and the grain-boundary structure. The structural degradation processes may occur in different forms of corrosion, fatigue cracks, erosion, and strength reduction. Mechanical structures and their reliability deteriorate continuously under the influence of operating and ambient environmental conditions. A framework for an empirical model may be considered to determine these structural flaws. We also propose an experimental research work assisted by numerical simulations to investigate the response of UGWs upon interaction with cracks in different shapes and orientations. ![]() It has been observed that no significant research work has been convened to identify the shape and orientation of defects in plate-like structures. This paper reviews the research literature on UGWs and their application in defect diagnosis and health monitoring of metallic structures. These parameters become even more important in cases where the crack intensity is associated with the safety of men, environment, and material, such as ship’s hull, aero-structures, rail tracks and subsea pipelines. The shape and orientation of structural defects are critical parameters during the investigation of crack propagation, assessment of damage severity, and prediction of remaining useful life (RUL) of structures. ![]() Because of its excellent long-range diagnostic capability, this method is effective in detecting cracks, material loss, and fatigue-based defects in isotropic and anisotropic structures. Ultrasonic guided wave (UGW) is one of the most commonly used technologies for non-destructive evaluation (NDE) and structural health monitoring (SHM) of structural components.
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