WH Leong

Bio: WH Leong is an academic researcher from University of Sheffield. The author has contributed to research in topics: Modal analysis & Lamb waves. The author has an hindex of 1, co-authored 1 publications receiving 211 citations.

Structural health monitoring using scanning laser vibrometry: II. Lamb waves for damage detection

Abstract: Guided ultrasonic waves have shown great potential for structural health monitoring. Various types of transducer can be used for actuating and sensing of these waves. This includes non-contact approaches such as optical/laser techniques. Classical laser methods usually involve high energy interferometers. The paper demonstrates that a commercial laser vibrometer, designed for vibration/modal analysis, can be used for crack detection in metallic structures. The study involves a simple fatigue test in order to initiate and grow a crack. Lamb waves generated by one bonded piezoceramic transducer were sensed using a multi-point scanning laser vibrometer. The results demonstrate the potential of laser vibrometry for simple, rapid and robust detection of fatigue cracks in metallic structures.

1059 physical activity among older people admitted to a university hospital in malaysia

Abstract: Physical inactivity is prevalent among hospitalised older people and is associated with poor outcomes. This study aims to determine activity levels in a Malaysian university hospital. Direct observation of patients admitted to the geriatric medicine ward over 2 weeks between the hours of 8 am-8 pm was performed. Data was collated onto an observation diary which was piloted, and changes made iteratively. A taxonomy of inpatient activity and healthcare staff interaction was created. Observer training was done to ensure familiarity and consistency in the recording. Data was presented descriptively and comparison made between weekday/weekend. Minutes of activity time per-hour (mins/hr) was use to report findings. Ninety-one patients were observed over 1918.8 hours (weekday, 1579.67 hours; weekends, 363.87 hours). The observed median (Q1,Q3) was 15.1 (9.4, 30.1) hours per-patient. 32.6 minutes per day on average was spent upright, with the rest spent either sitting or lying down. 78.9% of patients’ time was spent doing nothing. Patients’ position was different between weekdays vs weekends, lying, 35.7 vs 40.8 mins/hr; sitting, 23.3 vs 18.2 mins/hr; and standing, 1.1 vs 1.0 mins/hr. Patients spent significantly less proportion of time active at the weekends (weekdays, 28.3% vs weekends, 19.9%). When individual activities were analysed, patients were doing less walking (weekend, 0.4 vs weekday, 0.01 mins/hr, p = 0.01) therapy-supervised exercise (1.1 vs 0.02 mins/hr, p < 0.01), and nursing care (0.6 vs 0.1 mins/hr, p < 0.01) over the weekend. There was also less doctor interaction (weekday, 1.1 vs 0.5 mins/hr, p = 0.04) and no therapist interaction at the weekend. Nursing input was unchanged. Older people admitted to a university hospital in Malaysia were very inactive. There was further reduction in activity levels and healthcare interaction at the weekend. Maintaining physical activity during hospitalisation is required to ensure best possible recovery from their acute illness.

Structural health monitoring using scanning laser vibrometry: I. Lamb wave sensing

Abstract: Structural health monitoring using Lamb waves is based on guided waves introduced to a structure at one point and sensed at a different location. Actuation and sensing can be accomplished using various types of transducer. The paper demonstrates a non-contact method for low-frequency Lamb wave sensing. The technique utilizes a laser Doppler velocimeter. Lamb wave responses are enhanced using data smoothing and filtering procedures. The results are validated using classical piezoceramic-based sensing and numerical simulations. The study shows the potential of laser vibrometry for Lamb wave sensing.

Fatigue crack detection in metallic structures with Lamb waves and 3D laser vibrometry

Abstract: The paper presents the application of ultrasonic guided waves for fatigue crack detection in metallic structures. The study involves a simple fatigue test performed to introduce a crack into an aluminium plate. Lamb waves generated by a low-profile, surface-bonded piezoceramic transducer are sensed using a tri-axis, multi-position scanning laser vibrometer. The results demonstrate the potential of laser vibrometry for simple, rapid and robust detection of fatigue cracks in metallic structures. The method could be used in quality inspection and in-service maintenance of metallic structures in aerospace, civil and mechanical engineering industries.