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1983

Signal Processing

Articles 1 - 7 of 7

Full-Text Articles in Mechanical Engineering

Ultrasonic Signal Processing For Multilayered Nde, Ramesh Shankar, Stephen S. Lane, Jeffrey M. Warren Jan 1983

Ultrasonic Signal Processing For Multilayered Nde, Ramesh Shankar, Stephen S. Lane, Jeffrey M. Warren

Review of Progress in Quantitative Nondestructive Evaluation

The interpretation of ultrasonic signals in the inspection for flaws in bonded regions of multilayered specimens is difficult because of signal energy loss due to material attenuation, undesired reverberations within certain layers, and overlapping responses from different interfaces because of finite transducer bandwidth. The flaws are usually air gaps, lack of adhesion, and porosity within the bonding agent.

While ultrasonic NDE signal interpretation can always be improved with appropriate instrumentation — broader bandwidth transducers for increased resolution, for example — signal processing allows for further enhancement using a digital computer. Material attenuation can be compensated for by using digital filters that preferentially ...


Interferometric Techniques Using Embedded Optical Fibers For The Quantitative Nde Of Composites, Janet C. Wade, Richard O. Claus Jan 1983

Interferometric Techniques Using Embedded Optical Fibers For The Quantitative Nde Of Composites, Janet C. Wade, Richard O. Claus

Review of Progress in Quantitative Nondestructive Evaluation

Optical interferometric techniques using single mode optical fiber waveguide embedded in composites and other layered materials have been used to measure one- and two-dimensional stress distributions and acoustic emission caused by applied point source loads. By interferometrically comparing the phases of coherent optical signals propagated through an embedded sample fiber and a bypass reference fiber, a signal proportional to the instantaneous strain integrated along the embedded length of the sample fiber has been detected. System calibration has been obtained by applying a one-dimensional dc strain field to a cantilever beam containing the fiber. Using this calibrated system, an array of ...


A Computerized Ultrasonic Scanning Bridge For Defect Imaging: Composite Materials, Donald Boyd, William Mcdonald, Andrew Simmons Jan 1983

A Computerized Ultrasonic Scanning Bridge For Defect Imaging: Composite Materials, Donald Boyd, William Mcdonald, Andrew Simmons

Review of Progress in Quantitative Nondestructive Evaluation

A computerized ultrasonic scanning bridge has been developed for the scanning and imaging of defects in structures. The raster scaning pattern can be implemented with any pair of the six available axes. The digitized ultrasonic signal can be imaged using a Peritek Graphic system. Details of the ultrasonic scanning bridge and imaging system will be reviewed.

Examples of the evaluation of a graphite epoxy component will be reviewed. The scanning of the composite part requires the use of the two angulation axis for the raster scanning. The correlation of the ultrasonic inspection with failure pressure of the graphite epoxy component ...


Nondestructive Evaluation With Beamforming Transducer Arrays, M. Simaan Jan 1983

Nondestructive Evaluation With Beamforming Transducer Arrays, M. Simaan

Review of Progress in Quantitative Nondestructive Evaluation

If a nondestructive evaluation system is designed to detect the presence or absence of a flaw in a material, typically one transducer may be sufficient. If, however, a characterization of the flaw is desired, then an array of transducers is in most cases required. Besides the capability of two and three dimensional imaging, array data has the advantages of increased resolution, improved signal-to-noise ratio after preprocessing and sharper focusing.

In any NDE system, the acquisition of data is only one step towards the final objective of flaw characterization. The other step is that of processing the data in order to ...


Subsurface Broadband Acoustic Microscopy Of Solids Using Aperture Lenses, M. Nikoonahad, Yue Guangqi, E. A. Ash Jan 1983

Subsurface Broadband Acoustic Microscopy Of Solids Using Aperture Lenses, M. Nikoonahad, Yue Guangqi, E. A. Ash

Review of Progress in Quantitative Nondestructive Evaluation

The imaging of interior planes in a solid object involves difficulties with spherical aberration, with the elimination of the front surface echo, and with the need in some cases to use signal processing techniques in order to enhance the signal-to-noise ratio. This paper shows that suitably designed spherical lenses can be used to minimize the spherical aberration. The elimination of the front surface echo requires careful time-gating and very short, broadband pulses. It is shown by using extended chirp pulses, the signal-to-noise ratio for subsurface objects can be very greatly improved. A number of examples of the use of these ...


High Resolution Arma Model Reconstruction For Nde Ultrasonic Imaging, Yoh-Han Pao, Victor Chen, Ahmed El-Sherbini Jan 1983

High Resolution Arma Model Reconstruction For Nde Ultrasonic Imaging, Yoh-Han Pao, Victor Chen, Ahmed El-Sherbini

Review of Progress in Quantitative Nondestructive Evaluation

Ultrasonic imaging is of use in a number of important areas, including nondestructive testing and medicine. The field has grown considerably in the past ten years and remains an active and growing area of research. For nondestructive evaluation of materials (NDE), the aim is to provide means for obtaining estimates of the size, shape and orientation of flaws in sufficiently a quantitative manner so that failure of mechanical structural parts can be predicted.1,2 As an imaging technique, ultrasonic imaging is appropriate whenever the medium considered is opaque to other sources of radiation, such as optical radiation. It is ...


Real Time Signal Processing In An Ultrasonic Imaging System, Michael J. Moore, Frank J. Dodd Jan 1983

Real Time Signal Processing In An Ultrasonic Imaging System, Michael J. Moore, Frank J. Dodd

Review of Progress in Quantitative Nondestructive Evaluation

Reliable and repeatable flaw detection and accurate flaw characterization are critical to reliable evaluation of component serviceability. Digital filtering and signal processing techniques can be used in real time to reliably and repeatedly detect flaws even at low signal-to-noise ratios. The same techniques provide near optimum flaw resolution and dimensional precision using standard unfocused transducers. This paper describes these techniques and demonstrates their effectiveness with sample data. The data was processed and collected by an ultra-high-speed general purpose programmable signal processor which is used to detect, locate, and generate images of the component with flaw locations.