SU1516831A1 - Method of vibration diagnostics of mechanisms - Google Patents

Abstract

The invention relates to mechanical engineering and can be used to diagnose the elements of machines and equipment, in particular rolling bearings. The purpose of the invention is to expand the field of use and locate the defect. The method is based on analyzing the coherence of vibration at two points of the mechanism by measuring the spatial coefficient of the coherence of vibration in the near zone of the source at several pairs of points. The points are separated from each other in one pair by less than 10% of the vibration wavelength and are separated from the source of driving forces at a distance comparable to the wavelength. The small distances between measurement points in one pair of points allows detecting defects in small-sized nodes, and a comparison of measurement results in different pairs of points makes it possible to determine the location of a defect in large-sized mechanisms and nodes. 2 Il.

Description

The invention relates to mechanical engineering and can be used to diagnose the elements of machines and equipment, in particular rolling bearings.

The aim of the invention is to expand the scope of use of the method of vibration diagnostics, including due to its extension to small-sized units of mechanisms and determining the location of the defect.

FIG. Figures 1a and 2b show graphs explaining the proposed method; .on FIG. 2 is a diagram for implementing the method.

FIG. 1a (curve 1) shows the dependence of the modulus of the spatial coherence coefficient of a high frequency three-octave vibration on the distance D1 of a defect-free mechanism at points remote from the vibration source where pseudo-vibration is almost absent.

The distance between the measurement points of the spatial coherence coefficient is expressed in wavelengths, the vibration A with the average frequency of the selected components in the material from which the controlled assembly is made. As can be seen from the curve, at distances x, 1 is the coefficient of coherence of vibration with no

but

00

with

The VII of pseudo-vibration almost coincides with the unit.

FIG. 16 (curve 2) - the dependence of the modulus of the spatial coefficient of coherence of the high-frequency one-third octave vibration of the mechanism, measured directly at the node-source of vibration, is given. As can be seen from the curve, pseudo-vibration is present in the measured signal, since Ri is til) 1 over the distance x 1 -c7v / 1U.

FIG. IB shows a comparison of the spatial coherence moduli () of the vibration coherence factor of bearing assemblies for defect-free (curve 3) and defective (curve 4) bearings at small distances. As can be seen from the curves, the modulus of the coherence coefficient strongly depends on the technical condition of the bearing, especially for & 1: and, 1 L.

The method can also be used to detect defects in various structures, such as bolted, welded and other joints, cracks, etc., in which the phase relationships of the vibration displacements during wave propagation change abruptly. To solve these problems, it is advisable to excite the vibration from an external source of random vibration forces. The use of a source of harmonic forces, as shown by experimental studies, does not provide the required sensitivity of detecting and localizing structural defects.

No less important is the area of application of the APB method, the detection of defects in the flow creation package; and flux-conducting systems in which the presence of intense local noise sources in the medium changes the value of the normalized mutual spectral density of vibrations of the walls of pipelines, casings, etc. in the near zone of the source.

The method can be implemented using the device shown in FIG. 2

The device consists of two channels, including measuring vibration transducers 1 connected in series, band-pass filters 2 and amplifiers 3 with an automatic gain control device 4. The outputs of the amplifiers are connected to the inputs of the multiplier 5 signals, to which

The integrator 6 is sequentially connected to the latter, the output of the latter is connected to interconnected blocks of the reference signals 7 and memory 8, and the outputs of these blocks are connected to the inputs of the indicator 9.

The device works as follows.

QTwo measuring vibration transducers 1 are set at a distance less than A / S. From the transformed signals, the random vibration components in one (e.g., octave) frequency band with a rather high (more than 5 kHz) average frequency are separated by band-pass filters 2.

The selected components increase in amplifier 3 to a certain (normalized) value specified by the automatic gain control circuit 4, and the normalized signals are multiplied in a signal multiplier 5 and averaged by the integrator

5 6- The received signal is compared in block 7 of the reference values of the signals with a standard determined by a set of measurements of defect-free nodes, and if it turns out to be lower than the standard, is stored in the storage device 8 and returned to the indicator 9. a distance more and the measurements are repeated keeping the result obtained. After measuring the measurements in the block of threshold values, an additional comparison of the results obtained between themselves is made and the sign of the difference in the measurement results is displayed on the indicator, indicating the direction of further movement of the measuring vibration transducers.

As a result of repeated measurements, the bearing area is determined for which the product of the signals M1 is minimum. The resulting location determines the coordinates of the defect, and the magnitude of the output signal determines the degree of development of the defect.

Claims (1)

Invention Formula The vibration diagnostics method of 5 mechanisms, which consists in simultaneously converting the vibration of a single pair of test points into electrical signals, remove them 0 five 0 five 0 515 the part containing the components in the same frequency band generates a signal proportional to their product, determines the average value of the latter, compares it with the reference values, and determines the magnitude of the defect from the comparison results, characterized in that defect locations, convert the vibrations into electrical signals in several pairs of test points, from each pair of simultaneously converted signals, select the part containing 31 the components in the same frequency band, form signals proportional to the product of the selected components in each pair, determine their average values, compare them with each other and with the reference values for each pair of points, and compare the magnitude and location of the defect using the results. the distance between the vibration control points is chosen in each pair of not more than 10%, and between pairs of at least 25% of the vibration wavelength with the average frequency of the selected components, oh well S 0,6 he 0.1 about 0.8 0.4 0.2 / L UA 0.6 0.8 Fiz.1 / L W / J dH VA 5D L 1.0 1