High Frequency Guided Wave Phased Array Focusing in Pipe
Abstract
Ultrasonic non-destructive evaluation is used a industry because of its excellent defect detection potential. Long range ultrasonic guided waves have intrigued investigators for years because of an ability to test structures over a long distance from a single sensor position. Guided waves have much more complex wave behavior than bulk waves in infinite media. The Lamb type guided waves in hollow cylinders spread out and wrap around the circumference when propagating in an axial direction. Focusing at a certain point in a hollow cylinder is implemented by utilizing the non-axisymmetric energy distributions of flexural wave modes. There are two types of focusing in pipes: natural focusing and phased array focusing. When a partially loaded excitation is used to generate guided waves in cylindrical shells, the excited flexural modes lead to ultrasonic energy naturally focused at certain positions. This special natural focusing phenomenon can be used to improve guided wave inspection results in hollow cylinders. By applying input time delays and amplitudes for a multi-channel ultrasonic signal generation system, one can focus the guided waves at a pre-selected position. The input parameters of the ultrasonic phased array are calculated by implementing a deconvolution computations of the displacement angular profiles excited by one excitation channel. Theoretical and experitmental results show the power of focusing in the long range ultrasonic guided wave inspection of pipe. Excellent results and superb inspection potential are shown.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 31, 2005
- Accession Number
- ADA444978
Entities
People
- Joseph L. Rose
- Li Zhang
Organizations
- Pennsylvania State University