S. Yu. Gurevich

On the theory of Lamb wave excitation in metals by pulsed laser radiation

The problem of pulsed photoacoustic transformation is solved for ferromagnetic metal plates. The effect of the temperature dependence of the thermal coefficient of linear expansion on the spectrum of Lamb waves excited by pulsed laser is revealed.

Analysis of ultrasonic waves excited in a metal plate by nanosecond laser pulses

Laser excitation of ultrasonic waves in ferromagnetic plates has been experimentally studied. The obtained results can be recommended for use in the development of methods and equipment for testing thin-walled metal articles.

A photothermal emitter and an EMA receiver of ultrasonic Lamb waves

Results of an investigation into the general characteristics of ultrasonic Lamb waves that are excited by a photothermal emitter in metallic plates as a function of its geometric and energy parameters are given. A metal surface area heated during irradiation by nanosecond optical pulses is such an ultrasonic emitter. Excited Lamb waves were recorded using a special wide-band EMA receiver. These findings can be used in the development of devices for the noncontact ultrasonic quality control of thin metalware.

Diffraction of Surface Waves by the Edge of a Wedge

Conditions of propagation of Rayleigh waves over an elastic wedge are considered. Refraction factors are determined for conversion of the initial wave into secondary volume and surface waves. Calculation results for the modules of the refraction coefficient agree well with published experimental data.

On boundaries between mechanisms of thermoacoustic conversion of laser pulses to ultrasound in metals

A technique based on experimental data has been suggested for determination of threshold energies at which hydrodynamic and evaporation mechanisms of ultrasound generation in metals set in.

Experimental study of directional characteristics of a pulsed laser thermoacoustic radiator

Results of experimental research on revealing the dependence of directional characteristics of a pulsed laser thermoacoustic radiator of body ultrasonic waves on the radiator’s energy and geometry parameters are provided. Experimental bench and measurement procedure are described. The results can be used in developing tools for noncontact ultrasonic inspection of metal materials and products.

Studying the temperature dependences of the parameters of laser-generated lamb waves

The process of laser generation of pulses of symmetrical and antisymmetrical Lamb waves in a ferromagnetic plate due to the thermoelastic effect was experimentally studied. The temperature dependences of the shape, amplitude, duration, and vibration frequency of acoustic pulses and the velocities of their propagation in the plate were investigated.

Thickness Gauging of Thin Metalware with Ultrasound Excited by Laser Nanopulses

It has been established that an ultrasonic pulse is split when Lamb ultrasonic waves are excited in thin metalware by a thermosonic emitter 3 mm or more in diameter. This makes it possible to measure the group velocity of ultrasonic waves. A technique is proposed for thickness gauging of articles based on the dependence of the velocity on the vibration frequency and article thickness (dispersion curves).

Directional Characteristics of a Laser Pulsed Thermoacoustic Emitter in Nonmagnetic Metals

Results of experiments on studying the dependence of the directivity of a pulsed laser thermoacoustic emitter of longitudinal and transverse ultrasonic waves that operates in a nonmagnetic conducting medium on the surface density of laser-radiation heat power are presented. The results can be recommended for nondestructive testing of nonmagnetic materials and articles with laser ultrasonic sources.

Laser generation and electromagnetic detection of normal acoustic waves in ferromagnetic metals

Noncontact generation and detection of normal acoustic waves in a ferromagnetic metal sheet made of the 32NKD alloy are experimentally studied. The main relationships of the parameters of such processes are determined.