SU1582119A1 - Ultrasonic method of determining residual longevity of structure member - Google Patents

Abstract

The invention relates to methods of non-destructive testing, in particular, to the possibility of determining the durability of the elements of ships, in aviation and other fields of engineering. The aim of the invention is to reduce labor intensity and increase accuracy by controlling the surface layer of the product. In the proposed method for determining the residual durability of structural elements, the change in attenuation of surface waves of Rele is measured at two frequencies. The attenuation measurement is performed prior to the start of operation and at the time of monitoring the product during its operation. The change in attenuation characterizes the dynamics of the development of surface defects in relation to the initial state of the material and makes it possible to determine the residual durability of structural elements. 1 il.

Description

This invention relates to non-destructive methods. control, namely, the possibility of determining the durability of the elements of ships, in aviation and other fields of engineering.

The aim of the invention is to reduce labor intensity and increase accuracy by controlling the surface layer of the product.

The drawing shows the block diagram of the device for implementing the method.

The device consists of an ultrasound oscillator 1 connected to an emitter 2 installed on a controlled area of a product 3, a receiver 4 of ultrasonic oscillations connected in series with an amplifier 5 and a meter 6 of the amplitude of electrical oscillations.

The essence of the invention is that in the proposed method for determining the residual durability of structural elements, the change in attenuation of surface waves of Rele is measured at two frequencies. The attenuation measurement is performed prior to the start of operation and at the time of monitoring the product during its operation. The change in attenuation characterizes the dynamics of the development of surface defects in relation to the initial state of the material and allows determining the residual durability of structural elements.

The method is carried out as follows.

On the controlled area of the product 3 install the emitter 2 and

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fo

to

capacitor 4 at a selected distance (mm). the emitter is sequentially excited by oscillator 1 at frequencies of 20 MHz and f 3 MHz. After passing through the monitored section, the surface waves are converted into an electrical signal by receiver 4, amplified by amplifier 5 and fed to the meter 6 amplitude of electrical oscillations.

The choice of frequencies is due to the fact that in case of fatigue failure, the density of microdamages is formed in the surface layer with a thickness of 3 grain sizes within 10-15% of the durability of the structural element, which is close to critical. In the remaining thickness of the metal (controlled at the frequency fj), the critical density of microdamages is reached immediately before destruction.

The residual durability of the sample is calculated by a formula that can be expressed in terms of the measured amplitudes. The amplitude of the wave passing the distance L is calculated by the formula

A ° AQexp (-2c / L),

where A0 is the amplitude of the excited wave; d is the attenuation coefficient. The change in amplitude of the transmitted wave caused by material damage is described by the following formula:

A Aohr (+ do /),

where ud is the change in attenuation coefficient caused by damage to the material. Measuring the amplitude of the waves that have passed the distance L before the start of operation А ° and after some operating time A1, we obtain the value of the change in the attenuation coefficient

  -

Substitution of the o / v value for the residual durability at frequencies Ј1 and f 2 leads to the formula for residual durability through and across the surface waves measured before operation and after some time.

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 A comparison of the results of calculating the residual durability by the above formula with the accumulated number of cycles shows that the proposed control method makes it possible to predict the moment of destruction. As a criterion for the development of the resource should

Doesn't take an In ratio

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1 A

equal to 0.7. This corresponds to 70% of the exhaustion of the construction life and ensures safe operation.

The use of this method will improve the accuracy of the forecast by taking into account changes in the surface structure of the sample during fatigue failure. The reduction in labor intensity is achieved by reducing the work associated with the manufacture and installation of witness samples, and due to the fact that surface waves allow you to simultaneously control a large surface of the structure, determined by the distance between the receiving and radiating sensors. In addition, there is no need for work related to the measurement of loading and stresses operating in the control zone.

Claims (1)

The Ultrasonic Method for Determining the Residual Durability of Structural Elements, which consists in exciting and receiving ultrasonic vibrations that have passed through a controlled part of the structure, measures the parameters of the received oscillations, judging by the value of which the residual durability of the structural elements, characterized in that in order to reduce labor intensity and increase accuracy by controlling the surface layer of the product, a Rayleigh wave in a layer of no more than three thicknesses is successively excited In the grain and in a layer with a thickness of at least ten grain sizes, the material of the structure, the attenuation coefficient is measured as parameters of the received vibrations, and the residual life N is determined by the formula Nl 1 East A 1 ° g Where ; and ° (the values of the attenuation coefficient, respectively, prior to the start of operation in the i-th MO51582119 measurement element in a layer of a thickness not exceeding three grain sizes of the construction material; and ef is the same, in a layer of at least ten grain sizes of the material of construction.