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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.

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.

The in vitro response of the mouse fibroblast cell line 3T3 on the surface of ultrafine grained titanium [produced by a severe plastic deformation (SPD) process] has been studied in this work. SPD Ti showed much higher strength than the coarse grained Ti and equivalent to that of Ti-6Al-4V alloy. Better cell proliferation was observed on SPD Ti compared to conventional Ti and Ti-6Al-4V alloy. This could be attributed to the increased surface free energy by reduction in the grain size and possibly the presence of a large number of nano size grooves at the triple point junctions in SPD Ti sample. There was no significant difference in the results of cytotoxicity tests of fine and coarse grained materials.