Vol 54, No 3 (2018)

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).

An original waveguide design has been proposed that makes it possible to carry out acousticemission inspection, diagnostics, and monitoring of industrial objects operating at temperatures above 85°С. The waveguide ensures higher heat-dissipation characteristics, with minimum acoustic losses, than the known clamped-type waveguides. Its application involves no changes to the test object and requires no special permissions from supervising authorities. The underlying physical operating principles, specific features of embodiment, application possibilities, and results of the full cycle of research into how waveguide design features influence heat-dissipation and acoustic characteristics are described. The use of such waveguides widens the application field for the acoustic-emission method as an express technique for evaluating the technical condition of high-temperature objects both during operation and before decommissioning them for technical diagnostics with the aim to identify active (hazardous) areas and include them into the program of testing with other nondestructive methods.

The problem of how one or several rectilinear cracks intersecting at a point affect eddy-currents and electromotive force (e.m.f.) induced in a current loop has been considered. The loop is located above a nonmagnetic infinite plate, orthogonally to the crack lines. Under these conditions, when the plate is geometrically thin and can be replaced with a conductive surface, the problem is solved analytically. The calculation data, which are illustrated by the graphs of how the e.m.f. depends on the proximity to the crack when the current frequency and loop location height are varied, show that crack’s contribution to the magnetic reaction virtually fades at distances exceeding the sum of the linear loop length and its height. Results of conducted physical experiments prove the adequacy of the developed mathematical model and its applicability to the solution of such problems.

Digital radiography is currently a genuine alternative to the laborious and uneconomical method of X-ray diffraction in nondestructive testing. The processes of forming optical images on a radiographic film and on a flat-panel detector are different. The input action on a detector, whether a radiographic film or a digital transducer, is the so-called radiation image, the X-ray radiation generated by an X-ray tube and transmitted through a test object. The object attenuates radiation depending on its own thickness and material density. The main parameters of the radiation image are its contrast, definition, and signal-to-noise ratio (SNR). In order to achieve the most efficient conversion of the X-ray image into an optical one, one needs to choose the optimum combination of the listed parameters depending on which detector is being used. In this study, theoretical research and practical evaluation of its results have been carried out. Conditions have been determined for the best adaptation of a radiation image to the employed detector that ensure the prescribed quality indicators of the optical image of the test object. Results of the research that was carried out within the framework of scientific field 2.3 “Developing methods for automated nondestructive testing and the reliability of its results” (“Strategic directions of development of materials and technologies of their processing for a period of up to 2030”) are provided.

A new Doppler-effect–based method for nondestructive testing of the condition of the inner walls of pipelines using a flowing fluid is considered. An optical method has been used to reveal specific features in the structure of the fluid-medium flow in a circular-section pipeline. A new technique that makes use of laser radiation scattered on flowing-fluid particles has been proposed for determining the coordinates of a flawed zone on the inner pipeline wall. The technique makes it possible to determine the zone coordinates along the length and diameter of the pipeline.