SU1516817A1 - Method of vibratory check of single-dimensional structures - Google Patents

Abstract

This invention relates to non-destructive vibration control of a structure. The purpose of the invention is to increase the information content. For this purpose, the position of the defect is determined by the dependence of the measured amplitude of mass oscillations attached in the middle of the allocated zone between the damped sections. The oscillations excite a harmonic force applied to the mass. After detecting the position of the defect, the stiffness of the elastic element connecting the mass with the fixed base is changed to achieve a equality of the amplitudes of the oscillations of the mass when it is installed in the defective section and when installed in the defect-free area. By the change in the stiffness of the elastic element, the loss of stiffness of the controlled structure is judged. The connection of the mass with the base through an elastic element with adjustable stiffness and a change in the stiffness of the elastic element so that the amplitude of mass oscillations when attached to the structure under study in the defective section and defect-free zone, quantify the loss of rigidity of the structures in the defective section, which increases the information content of the method. 1 il.

Description

The invention relates to the control of defects in the structure, and in particular to methods of vibration control of beam structures.

The aim of the invention is to increase the information content.

The drawing shows a device that implements the method.

The method is carried out as follows.

The beam construction 1 under investigation is damped in two sections, for example, damped connecting sections with a fixed base 2. In the center

the allocated zone between the damped sections of the tested structure establish a mass of 3, 6, 5 times greater than the mass of the selected zone. The mass 3 is connected to the base 2 via an elastic element 4 with adjustable stiffness, made in the form of a corrugated elastic cylinder 5 filled with magnetorheological fluid 6 and enclosed by electric windings 7 connected to the source 8-voltage. Provide the stiffness of the elastic element equal to the bending stiffness of the selected zone when

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no defect in it. The oscillations of the allocated zone, applied to the mass 3 by means of the vibrator 9 connected through the amplifier 10 to the generator 11, are excited by the harmonic force of constant amplitude. The frequency of the exciting force is 5 times less than the resonant frequency of the bending oscillations of the selected zone. Using the sensor 12, connected through amplifier 13 with recorder I, measure the amplitude of mass oscillations 3. Change the position of the damped sections and mass 3 by moving the monitored design relative to the base 2. Find the dependence of the amplitude of mass oscillations 3 on its location on the investigated structure 1, which determines the location of the defect in the controlled structure 1. After identifying the location of the defect when mass 3 is located on the defective section, the stiffness of the elastic element C is changed to achieve equality a m is the amplitude of oscillations of mass 3 and the amplitude of oscillations of mass 3 when it is installed on a defect-free dedicated zone. The change in the stiffness of the elastic element, determined by the voltage of the source 8 connected to the winding 7, determines the loss of stiffness of the test structure 1 in the defective section.

The connection of the mass 3 with the fixed base 1 through the elastic element k with adjustable stiffness and the change in the rigidity of the elastic element so that the amplitudes of the oscillations of the mass 3 when attached to the structure 1 in the defective section and in the defect-free zone are equal, allows the structure to determine the loss of rigidity defective section, which increases the information content of the

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Example. The location of the defect and the loss of rigidity of the beam structure in the form of a steel rod 2.5 m long and 6 mm in diameter are determined. The base in the form of a bracket has a rigidity that is several tens of times greater than the rigidity of the controlled zone with a length of 0.2 m.

The controlled conformation is moved relative to the bracket and the attached mass 3. The elastic element 4 is made of a rubber corrugated pressurized cylinder, filled with c 5

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with kerosene with a small ferromagnet. The cylinder is covered by an electrical coil connected to a power source.

The total mass of the displacement transducer, one displacement mechanism and the added mass is 0.255 kg.

By applying voltage to the windings of the coil and increasing it, the rigidity of the controlled area of the structure and the mass of the rigidity are equal. According to the calibration curve, this rigidity, accepted as minimal and characterizing the intact structure, was C 15 | 62 40 N / M. Then determine the resonant frequency, which was 17b, 3 Hz. The elastic vibrations are excited at a frequency of 39 Hz. A crack-type defect is detected by a change in the amplitude recorded by the recorder. After that, when the attached mass is located in the zone of the defect, the voltage applied to the coil windings is increased, and the value of the variable stiffness at which the amplitude of oscillation decreased to the initial value is determined from the calibration characteristic. It amounted to N / M exceeded the initial value of stiffness by 20%.

Thus, due to a defect, the structure lost 2Q% of its initial stiffness.

Claims (1)

Invention Formula The method of vibration control of one-dimensional structures, according to which the structure under investigation is damped in two sections, is attached in the middle of the section. between the damped sections of the mass, 6.5 times the mass of the selected zone, changes the position of the damped sections and mass, maintains the distance between them, at each position of the damped sections and the masses excite oscillations of the allocated zone of the structure, applying harmonic to the mass the strength of a constant amplitude and a constant frequency, less than the critical frequency of the selected zone, measures the amplitude of mass oscillations, determines the dependence of the amplitude of mass oscillations on its position, over which d t about the position of the defect and the degree of defectiveness of the controlled end Structures, characterized in that, in order to increase the information content, the mass is connected to a fixed base through an elastic element with adjustable stiffness, when determining the position of the defect, the stiffness of the elastic element is set equal to the flexural rigidity of the defect-free selected zone, and after detecting the appearance of 16817 Defects change the stiffness of the elastic element, achieving equal amplitudes of the maso oscillations when installing it in a defective section and when installing in a defect-free area, and changing the stiffness of the elastic element to judge the loss of stiffness of the construction being fixed.