The market for process instruments generally requires low cost devices that are robust, small in size, portable, and usable in-plant. Ultrasonic torsional guided wave sensors have received much attention by researchers for measurement of viscosity and/or density of fluids in recent years. The supporting electronic systems for these sensors providing many different settings of sine-wave signals ...

A representative area of concern for fatigue crack growth in aircraft occurs in multi-layered metallic structures. Ultrasonic plate waves are currently being investigated by multiple initiatives to detect these types of flaws with a minimal number of sensors to enable Structural Health Monitoring (SHM). Previous work has focused on structures with one or two layers, coupled with modeling of the...

The inspection of a storage tank floor is a time consuming and expensive procedure, mainly due to necessity to empty and to clean the tank before an inspection. For this purpose a long range ultrasonic technique based on Lamb waves may be applied. Such an approach is used for inspection of pipes and can cover the distances up 100m. However the storage tanks are much more complicated structures ...

A representative area of concern for fatigue crack growth in aircraft occurs in multi-layered metallic structures. Ultrasonic plate waves are currently being investigated by multiple initiatives to detect these types of flaws with a minimal number of sensors to enable Structural Health Monitoring (SHM). Previous work has focused on structures with one or two layers, coupled with modeling of the...

The issue of non-destructive characterization of material microstructure with respect to precursors to macroscale damage initiation is addressed. Ultrasonic guided waves are known to be sensitive to material nonlinearity, which is evident through the generation of higher harmonic modes. Thus, nonlinear guided waves have strong potential to identify precursors to macroscale damage and revolution...

ABSTRACT Conventional methods of ultrasonic non-destructive evaluation (NDF.) use liquids to couple sound waves into the test sample. This either requires immersion of the parts to he examined or the use of complex and bulky water squirting systems that must be scanned over the structure. Air-coupled ultrasonic systems eliminate these requirements if the losses at air-solid interfaces are toler...

Corrosion in pipe work is a major problem. While most plants have reliable information on most equipment, the least data available is always with respect to their piping. Significant portions of plant piping and pipelines are insulated or buried and hence, even external corrosion cannot be readily observed. Ultrasonic guided waves in the pipe wall provide an attractive solution as the waves are...

Pavel Fomitchov Sridhar Krishnaswamy, MEMBER SPIE Northwestern University Center for Quality Engineering and Failure Prevention 2137 North Sheridan Road Evanston, Illinois 60208 E-mail: [email protected] Abstract. A fiber Bragg grating (FBG) sensor for detection of ultrasonic waves in liquids and solid structures is investigated. The sensor contains a fiber probe with a FBG, a tunable narr...

Lamb waves are often used in ultrasonic applications for non-destructive testing of large constructions. The difficulty in the analysis of Lamb waves is their dispersive characteristics, especially their frequency dependent phase and group velocities. This article focuses on the separation of the first symmetric mode S0 and the first asymmetric mode A0 and the reliable estimation of their group...

The monitoring of liquid-filled tubes with respect to the formation of soft deposition layers such as biofilms on the inner walls calls for non-invasive and long-term stable sensors, which can be attached to existing pipe structures. For this task a method is developed, which uses an ultrasonic clamp-on device. This method is based on the impact of such deposition layers on the propagation of c...