摘要:

A pulsed laser ultrasonic source and an electromagnetic acoustic (EMAT) detector have been used to produce images of artificial defects in aluminium samples. Three different imaging techniques have been investigated: reflection tomography, the synthetic aperture focusing technique (SAFT) and transmission tomography

ISSN:1058-9759    

DOI:10.1080/10589759008952957

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Laser techniques for ultrasonic generation and reception have potential for a wide range of non-contact measurements, chiefly because they can be used for defect detection and materials characterisation at elevated temperatures. However, these techniques have other advantages. Unlike contact transducers, they do not disturb elastic wave propagation by loading the surface of the specimen. They are also capable of much higher temporal and spatial resolution than can be obtained by most conventional techniques.

ISSN:1058-9759    

DOI:10.1080/10589759008952958

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Laser-based systems for non-contact generation and detection of ultrasound are being investigated at the CEGB's Marchwood Engineering Laboratories for application to remote non-destructive inspection problems. These include the in-situ inspection of the graphite bricks that make up the cores of Advanced Gas-Cooled Reactors (AGR's). The propagation of laser-generated ultrasonic pulses in AGR graphite has been studied using a laboratory system incorporating a Q-switched ruby laser generator and Michelson interferometer detector

ISSN:1058-9759    

DOI:10.1080/10589759008952959

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The generation of ultrasound in metals and plastics by a pulsed TEA CO2laser is reported. In the case of metals a technique of laser induced air breakdown above the metal surface produces a rapidly expanding plasma which applies a normal force, with approximately Heaviside time dependence, to the surface resulting in the generation of an ultrasonic pulse. In plastics the ultrasound is generated by the absorption of C02 radiation producing a buried thermoelastic source close to the sample surface. In both cases the interaction leaves no surface damage

ISSN:1058-9759    

DOI:10.1080/10589759008952960

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A new imaging interferometer system is described which has been designed with industrial applications in mind. Based on CCD image array detection and Digital signal processing of interferograms in a quadrature optical system, high sensitivity (≈ 1nm) detection of ultrasonic transients and fast data analysis can be achieved. Details of the system are discussed and the results of initial feasibility tests with clean and speckle pattern data presented

ISSN:1058-9759    

DOI:10.1080/10589759008952961

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

An overview is presented of optical techniques used to detect ultrasound propagating in solids. Typically, the sensor system may be based on a beam deflection technique, a Michelson interferometer or a Fabry-Perot interferometer. In some cases, the systems offer a flat wideband frequency response up to frequencies in excess of 100 MHz. The techniques used are non-contacting and possess none of the ultrasonic ringing characteristics associated with more conventional ultrasonic sensors. Estimates of some minimum displacement sensitivities are presented

ISSN:1058-9759    

DOI:10.1080/10589759008952962

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Our laboratory is involved in the development of non-conventional techniques for the non-destructive evaluation of metallic materials. Our technological and scientific developments in progress include

ISSN:1058-9759    

DOI:10.1080/10589759008952963

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A non-contacting and non-destructive testing method using laser techniques was evaluated by theoretical and experimental research. As the inspection of thin layers was of main interest, the opto-acoustical generation and detection of surface acoustic waves were studied.

ISSN:1058-9759    

DOI:10.1080/10589759008952964

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A technique for calculating the response of finite transducers to surface waves is described. Calculations for laser generated surface waves are presented and compared with experimental waveforms recorded by two types of electromagnetic transducer

ISSN:1058-9759    

DOI:10.1080/10589759008952965

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The National Nondestructive Testing Centre has been active in the development of electromagnetic acoustic transducers (EMATs) for some years. Applications range from laboratory tools to industrial thickness monitoring equipment. Some projects are briefly described to give an indication of the range of work undertaken. New data is presented on the effect of reflector inclination on the signal strength detected by an SV EMAT

ISSN:1058-9759    

DOI:10.1080/10589759008952966

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor