S. V. Len’kov

Torsional waves excited by electromagnetic–acoustic transducers during guided-wave acoustic inspection of pipelines

A theory of propagation of torsional waves excited by an electromagnetic–acoustic transducer in a pipe is proposed. This theory takes into account the excitation parameters, geometry, viscosity, and the elastic characteristics of an object. The main testing parameters (the frequency and geometry of the transducer) that determine the possibilities of guided-wave testing of pipelines of various dimensions using torsional waves are theoretically substantiated.

Factors that affect the excitation effectiveness of torsional waves during waveguide inspection of pipes

The results of theoretical and experimental studies of the features and excitation effectiveness of torsional waves in pipes depending on the parameters of excitation, the properties of the pipe material, and the dimensions of an object are given. The results can be used for the evaluation of the possibility of waveguide quality control of pipelines during the development of inspection procedures using torsional waves.

Increasing the estimation accuracy of correlation functions of discrete signals

An improved algorithm is proposed to calculate the mutual correlation functions (MCFs) of signals using the fast Fourier transform, the quadrature formulas of the trapezoidal method, and the Simpson method. The calculation error of MCFs is analyzed by comparing MCFs obtained for continuous finite signal samples and MCFs obtained using improved calculation algorithms for discrete signal samples. It is shown that these algorithms for calculating MCFs provide a more accurate primary estimate of MCFs. Improved calculation algorithms are described.

An instrument for measuring acoustic wave velocities in metals and alloys

A circuit and principle of operation of the instrument for measuring ultrasonic-wave propagation times, which is based on the autocirculation method using up-to-date electronics, are described. The circuit solutions, allowing one to sufficiently decrease the measurement error, are presented. The methods that ensure a high determination accuracy of ultrasonic-wave velocities in steel samples are considered. Areas of instrument applications are shown.

Resonance measurement technique for viscoelastic properties of damping materials of the porous closed cellular PE foam type

Theoretical and experimental studies of longitudinal and lateral vibrations in a 2D cavity filled with foam viscoelastic material were performed; measurement methods of Lame parameters, as well as viscosity parameters with longitudinal and lateral resonance vibrations in cellular polypropylene loaded by a final mass were proposed. Measurements of the visco-elastic properties of samples from the porous closed cellular polyethylene of a PE foam and EVA ultrathene types were made.

A magnetic field in a conducting half-space during permanent magnet motion above it

The problem of calculating magnetic-field attenuation in a conducting medium in the process of permanent magnet motion above it is considered.

Peculiarities of Changes in the Desired Signal of a Magnetic Anisometer under Rotation of Its Attachable Sensor

The way the rotation and speed of the sensor in a permanent-magnet anisometer affect its readings when inspecting the stress-strained state of ferromagnetic articles has been studied. Regularities of changes in the longitudinal and transverse magnetic-field strength components during sensor rotation have been revealed. A degree to which both components depend on the rotation speed has been demonstrated.

Correlation of rail structure with the Rayleigh-wave velocity and the coercive force

The velocity of Rayleigh waves is correlated with the depth of the decarburized layer and the hardness of rail steel. With increase in the depth of the decarburized layer and decrease in the hardness, the velocity of Rayleigh waves increases. Conversely, in the same conditions, the coercive force of the rail steel declines. The thickness of the decarburized layer is determined by this method and confirmed by direct measurements.

Evaluating the Structure of a Ferromagnetic Material Based on Magnetic-Field Strength between the Poles of an Attached Two-Pole Magnetizing Device

The possibility for using a magnetic structoroscope with a two-pole permanent-magnet magnetizing device to test mechanical properties of stressed-deformed state of articles made of ferromagnetic materials has been investigated. Dependences of equipment readings on the geometrical dimensions of the structuroscope sensor and on the deformation of ferromagnetic material of a sample in tension in the elastic loading–unloading domain are presented for samples made of different ferromagnetic materials.

Factors affecting attenuation of torsional waves in pipes loaded on contact viscoelastic media

Results of theoretical and experimental studies of the attenuation of torsional waves in pipes depending on the conditions of loading on viscoelastic media, pipe dimensions, and excitation frequency are presented. The results can be used for justification of pipe testing parameters such as insonification range and sensitivity when developing guided-wave techniques for pipelines of different sizes under various service conditions.