Experimental Study on Hidden Corrosion/Delamination Detection with Ultrasonic Guided Waves

Hidden corrosion detection is critical in the aerospace industry. Occurring on the inside surfaces or at the interfaces of an aircraft’s skin, the corrosion must be detected from the outside surface. Surface waves are, therefore, not suitable for detecting such defects/failures. Ultrasonic bulk wave methods can be used to detect the corrosion caused thinning in the wall or a delamination of a structure [1,2]. However, since the method is based on point-by-point testing, it becomes a tedious time consuming procedure for large area inspection. Guided wave methods are being developed to tackle this problem [3–6]. An experimental study of hidden corrosion/delamination detection in single/multiple layer aluminum plates is conducted with specially selected ultrasonic guided wave modes. Both corrosion simulation specimens by machine cutting, and real corrosion specimens by electrochemical processing, Two-layer specimens have been prepared with such corroded sheets to form an artificial interface corrosion/delamination. Various wave modes are subsequently generated on these specimens to examine the implications of thinning on mode cutoff, group velocity changes, mode frequency shifts, and transmission and reflection amplitudes. Finally, a practical problem of skin to honeycomb core delamination detection with guided waves is also addressed.</p

Temperature and Viscosity in-Situ Sensor for Hostile Processes

Viscosity of a fluid is known to affect the reflection of shear waves from a solid/fluid interface. In this paper, we will discuss the experimental work to simultaneously measure both temperature and viscosity of a fluid at very high temperatures using a buffer rod technique. The sensor is based on the effect of melt viscosity on ultrasonic shear wave reflections from the solid-melt interface. We have used refractory materials for the solid buffer rod delay line which is water cooled. The sensor has been calibrated using various calibration samples and has been tested for repeatability. A portable instrument and a database has been created for temperatures up to 1500 degree Celcius. The results based on this sensor and their interpretations will be discussed. This sensor can find applications both as a process monitor as well as a tool for improving melter design for high temperature melt processes

Evaluation of fiber-reinforced composites using noncontact laser air- transducer system

Ultrasonic evaluation of materials using a non-contact system is sometimes desirable, for example when the material is moving too quickly to allow conventional fluid couplants to be used, is contained in a hostile environment, or the material itself is absorbent or toxic. In such situations, a pulsed laser is ideal for generating a variety of ultrasonic transients [1], as longitudinal, shear, surface (Rayleigh) waves and plate (Lamb) waves are generated simultaneously. Several types of non-contact detector are also available, including various optical devices [2] such as interferometers and beam deflectors. The disadvantages of an entirely laser based system are cost, and the optical quality of the test material must be reasonably high

Aspergillus infection of the orbital apex masquerading as tolosa-hunt syndrome

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