RU2619812C1 - Method of non-destructive testing of hidden defects in technically complex structural element which is not accessible and device for its implementation - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: structural element, which is accessible, is mechanically loaded and moved. Then, the parameters of the moving process of the accessible structural element are measured. Then, they are compared with the same parameters of the structural element, the level of defects of which are taken as acceptable. Moreover, before loading the structural element, which is accessible, a rigid connection with the inaccessible structural element is done for the provision of a common resonance. The device contains an exciter and a receiver of free oscillations, each of which has a piezoelectric element connected to an oscillation generator or a measurement indicator. The exciter and the receiver of free oscillations consist of length-separated steel rods and have a set of removable elements that have a wide range of operating frequencies.

EFFECT: non-destructive testing of technically complex structural elements and non-destructive testing of technically complex structural elements that are not accessible.

2 cl, 1 dwg

Description

The invention relates to non-destructive methods and means of inspection of technically complex structural elements. It can be used, for example, when monitoring the state of structural elements in an assembly that are not accessible.

Known "Impulse impedance method of defectoscopy of objects" patent RU No. 2078339, C1 IPC G01N 29/16, publ. 04/27/1997), according to which a combined impedance transducer with one zone of contact with the controlled object periodically excites elastic vibrations in the transducer-controlled object system using the transducer emitter and measures the amplitude of the electric signal at the transducer receiver, which is used to judge the defectiveness of objects, characterized in that the converter is excited by radio pulses with a given carrier frequency, as an information parameter in the electrical signal of the receiver, In addition, the phase difference in the signals of the emitter and receiver is additionally measured, and the defectiveness of objects is judged together by the amplitude and phase difference.

The disadvantage of this method is that it does not allow non-destructive testing of structural elements to which there is no access.

The integral method of free vibrations is also known (Non-Destructive Testing. In 5 books. Book 2. Acoustic Control Methods: A Practical Guide / I.N. Ermolov, N.P. Aleshin, A.I. Potapov; Edited by V.V. Sukhorukov. - M.: Higher School., 1991. - 283 p. For 163 s.),

 which consists in the fact that the vibrations of the control object are excited by a hammer blow, recorded by a microphone, amplified and fed to an information processing system whose task is to measure the fundamental frequency of free vibrations. For complex control objects, the fundamental frequency is determined experimentally at benign control objects. The duration of the oscillations is judged on the attenuation of sound in the material of the object. Duration also decreases under the influence of multiple small defects.

The disadvantage of this method is that it does not allow non-destructive testing of structural elements to which there is no access.

The well-known "Method of non-destructive testing of latent defects in the structure and device for its implementation" (patent RU No. 1389422, A1 IPC G01N 3/00, publ. 02.27.1996), according to which the structure is loaded with a variable mechanical load and cause its movement, measure process parameters displacements of the structure and compare them with the same parameters of the structure, the level of defects of which is taken as permissible; before loading, connect the moving section of the structure with an elastic element characterized by negative stiffness, with measurable in absolute value with the rigidity of the tested structure, but less than it. This method is selected as a prototype.

The disadvantage of the method chosen for the prototype is that this method does not allow non-destructive testing of structural elements to which there is no access.

A device is known, described in patent SU No. 251890 (IPC G011, publ. 09/10/1969) "Device for determining the solidity of products", containing a causative agent of free vibrations and a receiver of free vibrations, which are made in the form of steel rods divided along the length, each of which has a layer of piezoelectric elements, for example, of barium titanate, respectively connected to a sound purity generator and a measurement indicator. This device is selected as a prototype.

The disadvantage of the device selected as a prototype is the inability to vary the frequency of the natural oscillations of the device.

The objective of the invention is to provide the possibility of non-destructive testing of technically complex structural elements and structural elements to which there is no access, and creating a new device design that allows for this non-destructive testing.

To solve this problem, a non-destructive flaw detection method for technically complex structural elements is proposed, which allows to eliminate the shortcomings of the closest analogue and provide the following technical result:

- non-destructive testing of technically complex structural elements;

- the implementation of non-destructive testing of technically complex structural elements located in the assembly, to which there is no access.

The specified technical result is achieved as follows. The structural element to which there is access is loaded with a variable mechanical load and cause its movement. Measure the parameters of the process of moving the structural element to which there is access. Then, they are compared with the same parameters of the structural element, the level of defects of which is taken as permissible. Moreover, before loading a structural element to which there is access, a rigid connection is established that provides general resonance with a structural element to which there is no access.

Unlike the closest analogue, this method allows non-destructive testing of a structural element to which there is no access.

Moreover, a device for non-destructive testing of technically complex structural elements is made in the form of a pathogen and a receiver of free vibrations, each of which has a piezoelectric element connected to an oscillation generator or a measurement indicator. The causative agent and the receiver of free vibrations consist of steel rods divided along the length. In this case, the pathogen and the receiver of free vibrations are made collapsible and have a set of removable elements that have a wide range of operating frequencies.

The significance of differences in terms of the proposed device from the closest analogue is determined by the addition to the device design of a set of removable elements that have a wide range of operating frequencies, allowing you to adjust the natural frequencies of free vibrations of the pathogen and receiver to the natural frequencies of the controlled structural element, to which there is no access.

The essence of the claimed invention is illustrated by the drawing (Fig. 1), which shows a device for non-destructive testing of latent defects in structural elements to which there is no access.

In FIG. 1 shows a device comprising a steel rod 1, a detached element along the length, a removable element 2, a piezoelectric element 3.

The method of non-destructive testing of latent defects in structural elements to which there is no access, and the operation of the proposed device are as follows.

An exciter and a receiver of free oscillations (described in paragraph 2 of the formula) are separately connected to a device that fixes the frequency of natural oscillations. First, the free-oscillation pathogen is installed on a controlled internal structural element, and the free-oscillation receiver is installed on an external, accessible for control, structural element. The receiver of free vibrations is installed at points dynamically connected with the internal controlled structural element, i.e. at those points at which the maximum amplitude of the form of natural oscillations is observed, having points of maximum amplitude on the internal controlled element. The frequency of natural oscillations is fixed.

Next, the receiver and the causative agent of free vibrations are interchanged and the frequency of natural vibrations is fixed. The values of the frequency of natural vibrations in both cases should coincide. If the amplitude of the oscillations is not large enough and differs in frequency from the frequency of the natural vibrations of the causative agent of free vibrations, then select the removable element 2 and the steel rods 1 of the exciter and the free vibrations receiver divided along the length so that the frequency of the natural vibrations of the pathogen and the free vibrations receiver is as close as possible to measured frequency of free vibrations. After the measurement data, the controlled structural elements are installed in their places in the structure. On the external structural element, two points are determined having the maximum amplitude of the found natural vibration frequency. The causative agent of free vibrations is installed in one of them, the receiver of free vibrations in the other and the value of the frequency of natural vibrations is controlled, and through it the state of the internal controlled structural element. After the design is assembled, some change in the controlled value of the frequency of free vibrations is possible. If these changes are significant, it is necessary to repeat the process of selecting the frequency of free vibrations of the pathogen and the receiver of free vibrations.

Thus, the considered method allows to provide the possibility of non-destructive testing of technically complex structural elements and structural elements to which there is no access. And also created a new device design, allowing for the implementation of this non-destructive flaw detection.

Claims (2)

1. The method of non-destructive testing of latent defects in structural elements to which there is no access, which consists in the fact that the structural element to which there is access is loaded with a variable mechanical load and cause its movement, measure the parameters of the process of moving the structural element to which there is access, and compare them with the same parameters of the structural element, the level of defects of which is taken as permissible, characterized in that before loading the structural element, to which there is access, establish the same tkuyu communication, providing a common resonance structure with the element to which no access. 2. A device for non-destructive testing of latent defects in the structure, including a pathogen and a receiver of free vibrations, each of which has a piezoelectric element connected to an oscillation generator or measurement indicator, the pathogen and a receiver of free vibrations consist of steel rods divided along the length, characterized in that the pathogen and the receiver of free oscillations is made collapsible and have a set of removable elements that have a wide range of operating frequencies.

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