Page 6 - ДисертСемак2

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It is estimated the thickness of the material layer, which can be characterized by

determining the velocity of the Rayleigh wave of a certain frequency. This analysis is

based on the depth distribution of the Rayleigh wave energy. A criterion is proposed

according to which wave velocity is determined by a layer of material with a

thickness of 0,6 Λ (Λ is the wavelength).

To ensure the required resolution of measuring of changes in the surface acoustic

Rayleigh wave parameters in thickness, it is justified the use of long-term probing

radio pulses, which are narrowband. The width of the allowable spectrum of Rayleigh

wave acoustic pulse and its connection with depth separation are analyzed. It is

shown that for high separation it is necessary to use probing acoustic pulses with

duration one and half orders of magnitude for the period of high-frequency signal

filling.

A method for measuring the velocity of surface acoustic Rayleigh waves based

on the use of long-term probing radio pulses has been developed. Rigidly connected

piezoelectric transducers are used to measure the speed of Rayleigh surface acoustic

waves, and the measurement is performed by determining the time offset of the

probing signal relative to the reference sinusoidal signal.

To determine the distribution of surface layer parameters by thickness based on

probing surface acoustic Rayleigh waves with different frequencies, the inverse

problem is solved, which includes determining the effective penetration depth of the

surface acoustic Rayleigh wave and the algorithm for determining surface layer

thickness parameters which is based on velocity changes of acoustic surface

Rayleigh wave with different frequency.

This method has been tested on two types of control objects - sills and objects

with abrasive blasting, which confirmed the manufacturability and efficiency of its

use.

A method for studying the parogon material has been developed and local

sections of the parogon in which the Rayleigh wave velocity decreases have been

identified, and the dependence of this decrease on the wave frequency is also