National Research Council of Canada

American Iron and Steel Institute

Daniel Levesque

Jean-Pierre Monchalin

Martin Lord

Andre Moreau

Alain Blouin

Christian Padioleau

Jean F Bussiere

Guy Lamouche

Silvio E Kruger

Luc Piche

Christian Neron

Marc Dubois

A method is disclosed for evaluating the physical properties of a sample, for example, the grain size in a polycrystalline material. An ultrasound field is generated in a local region of the sample with a non-contact source, such as a pulsed laser, such that the generated ultrasound diffuses away from said local region. After waiting until the generated ultrasound field has reached a diffusion regime, the resulting ultrasound field is measured with a non-contact detector. Parameters are adjusted in a mathematical model describing the predicted behaviour of the ultrasound field in the diffusion regime to fit the detected ultrasound field to the mathematical model. In this way, parameters dependent on the physical properties of the sample, such as the diffusion coefficient and absorption coefficient, can be derived. The grain size, for example, can be estimated from these parameters preferably by calibrating the diffusion coefficient to grain size.

Apparatus and method for evaluating the physical properties of a sample using ultrasonics

A method and system is provided for enhanced ultrasonic detection and imaging of small defects inside or at the surface of an object. The Synthetic Aperture Focusing Technique (SAFT) has been used to improve the detectability and to enhance images in conventional ultrasonics and this method has recently been adapted to laser-ultrasonics. In the present invention, an improved version of the frequency-domain SAFT (F-SAFT) based on the angular spectrum approach is described. The method proposed includes temporal deconvolution of the waveform data to enhance both axial and lateral resolutions, control of the aperture and of the frequency bandwidth to improve signal-to-noise ratio, as well as spatial interpolation of the subsurface images. All the above operations are well adapted to the frequency domain calculations and embedded in the F-SAFT data processing. The aperture control and the spatial interpolation allow also a reduction of sampling requirements to further decrease both inspection and processing times. This method is of particular interest when ultrasound is generated by a laser and detected by either a contact ultrasonic transducer or a laser interferometer.

Method and system for high resolution ultrasonic imaging of small

Apparatus and method for detecting shear resonances includes structure and steps for applying a radiation pulse from a pulsed source of radiation to an object to generate elastic waves therein, optically detecting the elastic waves generated in the object, and analyzing the elastic waves optically detected in the object. These shear resonances, alone or in combination with other information, may be used in the present invention to improve thickness measurement accuracy and to determine geometrical, microstructural, and physical properties of the object. At least one shear resonance in the object is detected with the elastic waves optically detected in the object. Preferably, laser-ultrasound spectroscopy is utilized to detect the shear resonances.

Laser-ultrasound spectroscopy apparatus and method with detection of

An ultrasonic interferometry technique for composite structures such as metal/polymer/metal structures exhibits high sensitivity to interfacial properties, even at usual ultrasonic wavelengths. A model for the ultrasonic response of multilayered media accounts for viscoelasticity. Results of numerical calculations point out scaling features for interfacial properties in terms of specific stiffness S. A method is provided for characterizing the interfacial adhesion in a multilayer composite in terms of the parameter S. The multilayer composite is ultrasonically irradiated with a pulsed signal to obtain a signal characteristic of the interfacial adhesion between the multilayers. A model is provided of the multilayer composite that includes at least two additional layers which model the behaviour of the interface between the composite layers. From the model, given various input parameters such as thickness of the two additional layers and the viscoelastic properties of the layers, a plurality of spectra, characteristic of interfacial adhesion between the modeled multilayer composite are obtained. The spectrum related to the ultrasonic signal is compared to the plurality of the modeled spectra and a best fit or match is obtained. The value of S relating to the best fit model is determined to be the value which characterizes the interfacial adhesion between layers of the irradiated composite.

High resolution ultrasonic interferometry for quantitative

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Terrebonne, Canada

Daniel Levesque