Том 54, № 12 (2018)
- Год: 2018
- Статей: 9
- URL: https://journals.rcsi.science/1061-8309/issue/view/11367
Electromagnetic Methods
Studying Field Dependence of Reversible Magnetic Permeability in Plastically Deformed Low-Carbon Steels
Аннотация
The field dependences of the signal U~ (Н) across the measuring winding of an induction transducer, which are proportional to reversible magnetic permeability, have been measured in lowcarbon St3 steel plastically deformed by stretching under reversal of its magnetization along the major hysteresis loop both when unloaded and under an elastic tensile load. A method is proposed for isolating the contribution rendered to the measured signal by the irreversible displacement of only 90-degree domain walls. The method consists in subtracting the curve U~ (Н) measured under the elastic tensile load of a magnitude sufficient to compensate for internal compressive residual stresses in the sample from the no-load U~ (Н) curve. It has been established that the induced magnetic anisotropy field obtained with this method is virtually no different from that produced by the method in which no-load U~ (Н) curves are approximated.
Distribution of Magnetic Flux in a Ferromagnetic Material in the Presence of a Nonferromagnetic Gap in the Composite Circuit
Аннотация
Comparative analysis of the distribution of magnetic-induction vector components over the volume of a bulk homogeneous sample of 40Kh steel has been carried out under its local magnetization by an attached magnetic device in the absence of a gap in the composite “attached magnetic device–sample” circuit and in the presence of a nonferromagnetic gap under both poles of the attached magnetic device. It is shown that with the gap present in the composite circuit, the most significant drop in the magnetic flux density in the interpole zone of the object near its surface occurs in a section that coincides with the inner face of the electromagnet pole. The influence of the size of the gap in the composite “attached magnetic device–sample” circuit on the magnetic flux density has been investigated at different depths from the sample surface.
Magnetic Method for Nondestructive Testing of Rebar in Concrete
Аннотация
It has been shown theoretically and experimentally that locally magnetizing rebar through a protective layer of concrete makes it possible to determine both the depth of the protective layer of concrete and the diameter of rebar based on stray magnetic fields regardless of the magnetic properties of steel that rebar is made of.
A Method of Pulsed Magnetic Testing for Discontinuities in Objects Made of Diamagnetic and Paramagnetic Metals Using a Magnetic Carrier
Аннотация
Experimental dependences of the electric voltage U (t) across an induction magnetic head as it scans a magnetic carrier containing the recordings of magnetic fields due to artificial continuity defects in aluminum plates with a thickness from 1.5 × 10–5 to 3.0 × 10–3 m are presented. The strength of the primary magnetic field in pulses created by a flat inductor varied in the range of (2–50) × 103 A/m. The rise time of the pulses with field spikes was in the range (1.5–100) × 10–6 s. A method for testing objects made of electroconductive materials has been developed that ensures the optimum geometrical dimensions of the inductor, the optimum amplitude, direction, rise time, and shape of the leading and trailing edges of the main field pulse, as well as the optimum amplitude, rise time, number, and polarity of field spikes. The method performs the operations of smoothing, computation, and extraction of desired signal with removal of background and recognizes information recorded on the magnetic carrier by comparing the obtained signal distributions with reference or design ones when establishing signals from minimum defects. The method improves the accuracy and increases the speed of testing by several times.
Solving the Inverse Geometric Problem of Magnetostatics for Corrosion Defects with Allowance for Nonlinear Properties of Ferromagnet
Аннотация
A method is proposed for solving the inverse problem of magnetostatics with allowance for a nonlinear dependence of the relative magnetic permeability of a ferromagnet on the applied external field. The method has been investigated for metal loss defects located on the ferromagnetic-plate side opposite to magnetic transducers, without imposing any conditions on defect shape. The ferromagnetic plate is magnetized in the direction of the abscissa axis; the dependence of the magnetic induction of metal on the applied external magnetic field corresponds to a nonlinear segment of the magnetization curve. The problem has been solved for the three-dimensional case. Defects were simulated and the direct problem was solved with software developed by the authors in FORTRAN language. The program for constructing lines of force and solving the inverse problem of reconstructing magnetic field components was written using the Scilab package of applied mathematical programs.
Acoustic Methods
Criterion Parameters for Assessing Degradation of Composite Materials by Acoustic Emission Testing
Аннотация
A concept of monitoring the degree of degradation in the multilayered structure of polymer composite package has been developed at the laboratory for modeling damage and failure of machines at Mechanical Engineering Research Institute, RAS. The concept is intended for real-time acousticemission testing of products and employs new criterion parameters that reflect the percentage of location pulses in energy clusters characterizing the processes of destruction of material structure at the micro-, meso-, and macro-scale levels. The developed procedure, algorithm, and software for monitoring the process of degradation in the multilayered structure of polymer composite material package and predicting the residual strength of the product have been successfully tried in static tensile bench tests with a structurally similar sample of aircraft panel containing a honeycomb polymer filler.
Distribution of Elastic Displacements and Mechanical Stresses in a Laminated Transducer with Amplitude-Phase Excitation
Аннотация
The paper considers how elastic displacements and mechanical stresses are distributed along a laminated transducer consisting of two piezoelectric plates with different amplitude-phase excitation that are separated by an intermediate layer and have their outer surfaces loaded on arbitrary input impedances. We analyze the extent to which the nature of the distribution of elastic displacements and mechanical stresses is affected by the geometry of the elements of the laminated transducer and its amplitude-phase excitation. This analysis is based on solving the problem of synthesis aimed at forming uniform amplitude-frequency and linear phase-frequency characteristics of radiation by this transducer in a wide frequency band. Calculation results are discussed for different laminated-transducer designs and compared with the maximum values of elastic displacements and mechanical stresses achieved by in-phase excitation of piezoelectric plates in these transducers.
Recognition of Corrosion Severity Using Modal Acoustic Emission on a Thin Plate
Аннотация
On the basis of theoretical and experimental studies about recognition of corrosion severity using modal acoustic emission on a thin plate, it found that when the degree of corrosion is slightly, the S0 is the main signals of the two modes, when the degree of corrosion is severity, the amplitude of A0 increases.