Vol 53, No 3 (2017)

The type of changes in the total input conduction and its active and reactive components has been analyzed for an ultrasonic transducer with two independent piezoelectric plates separated by a dielectric layer as compared with the case of in-phase excitation of the transducer. Results of calculating the efficiency are considered for different transducer designs in accordance with a synthesisproblem solution that ensures a uniform amplitude-frequency response and a linear phase-frequency characteristic of emission.

A novel approach to calculating the acoustic tract in the method of acoustic reflectometry is suggested for inspection of heat-exchange pipes. Results of modeling and analysis of the acoustic tract are presented. The sensitivity of acoustic reflectometry to flaws in the form of through holes and deposits against the background of acoustic noises due to permissible deviations in the thickness of the pipe wall is estimated.

Results of research into magnetoelastic change of residual magnetization of cobalt steel annealed at 200—800°C are provided. The value of irreversible magnetoelastic demagnetization is shown to decrease with annealing temperature and become nearly zero after annealing at 600–800°C. In this case, a quasi-reversible (with nearly no hysteresis) change of magnetization is observed. It is explained by the processes of rotation of magnetization vectors when a load is applied.

Experimental results on studying the electromagnetic emission of uniaxially compressed dielectric composite materials based on epoxy adhesive with a filler are provided. Time instances of the response of mechanoelectrical transformations (MET) to an acoustic pulse have been recorded. Analysis of the results has shown that the linearity of the dependence of a criterion for testing the stress-strain state K_i on the pressure applied to a sample only manifests itself if the sample size contains an integer number of half-waves and the generated normal vibrations are standing waves. It has been established that the transverse symmetric and longitudinal antisymmetric waves render the main contribution to the MET response for the determined critical frequency values.

The design of the first domestic microfocus X-ray tube with massive target and electrostatic 200-kV electron-beam focusing is presented. A monoblock X-ray device based on this tube and intended for projection radiography is described. The main characteristics of the X-ray unit, including its fluoroscopic parameters, are estimated.

Experimental dependences are provided for the time growth of the areas of the indications of surface dead-end and through flaws with openings of 1–15 μm and depths of up to 12 mm during development under penetrant testing of stainless steel samples. A technique is proposed for estimating the depth of the surface flaws using the first derivative of the dependences 100 s after the beginning of development.

Micro-defect detection is an essential field of failure analysis for the assessment and reliability of engineering materials under various loading conditions. This paper illustrates the effect of thermal loading on micro crack formation in certain low modulus materials used for aerospace applications and further analysis. The demands of increased performance of polymeric materials have created a need for new experimental techniques for accurate measurements of their structural defects through non-destructive ways. The present work employs one such optical non-destructive technique such as Laser Speckle Interferometry (LSI) to study the micro crack formation in the low modulus material used as an insulator in solid rocket motors. The low modulus material used is a nitrile based rubber compound which, when thermally loaded to a differential temperature in the range of 20°C to 28°C generates an optimum fringe pattern for the analysis of defects. Extremely small defects in the micrometer scale can be detected by analyzing the anomalies in the generated fringe pattern.