SU1310710A1 - Method of quality control of acoustic contact in ultrasonic flaw detection - Google Patents

Abstract

This invention relates to the field of acoustic non-destructive testing methods. The aim of the invention is to increase the reliability of monitoring by receiving ultrasonic (UL) oscillations reflected from the prism working surface at the first critical angle and recording the signal amplitude sharply decreasing when the transducer is loaded due to ray shift due to a jump in the phase of the reflection coefficient on the prism working surface. The beam of longitudinal ultrasonic vibrations emitted by the working piezoplastics of a prismatic transducer includes rays incident on the working surface of the prism at the first critical angle. In the absence of acoustic contact, ultrasound beams propagating at the first critical angle are specularly reflected from the working surface of the prism. In the presence of acoustic contact, ultrasound rays propagating at the first critical angle are reflected from the working surface of the prism with a discontinuous displacement. The offset of the oscillations reflected at the first critical angle is recorded by the receiving piezoplate. 1 il. i cl 00 about vi

Description

The invention relates to the field of acoustical methods of non-destructive testing and can be used in ultrasonic (US) testing for controlling the quality of acoustic contact.

The purpose of the invention is to increase the reliability of control over the reception of ultrasonic vibrations reflected from the working surface of the prism under the first critical node.

The drawing shows an inclined transducer that implements the method of controlling the quality of acoustic contact during ultrasonic flaw detection,

The converter contains a prism 1, a working piezo plate 2 and a receiving piezo plate 3. The number 4 on the drawing indicates the working surface of the prism 2, position 5 is the product under test, and position 6 is the layer of contact liquid.

The method of controlling the quality of acoustic contact with an ultrasonic flaw detector is as follows.

Apply surface controllable. product layer of contact fluid and set on it an inclined transducer.

A beam of longitudinal ultrasonic vibrations is emitted into a prism and an ultrasonic beam reflected from the working surface of the prisms is received at the first critical angle. The amplitude of the received oscillations is measured and the quality of the contact is determined with its help. When a prism – contact layer is incident on the boundary (if the latter is present) at the first critical angle, beams from a beam of longitudinal oscillations experience a non-specular reflection, shifting along the interface,

As a result, part of the wave beam energy is removed from this region of space, where it was transferred by the wave upon reflection from the free surface (in the absence of acoustic contact). The front of the reflected wave beam turns out to be phase modulated, and therefore, when averaged over a certain angle range containing phase discontinuity points, the amplitude of the resulting field is further reduced compared to the case of reflection from the free surface.

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The method of quality control of acoustic contact during ultrasonic flaw detection is carried out as follows. Apply a layer 6 of contact liquid, for example an oil, on the surface of the test article 5 and install it. there is an inclined transducer on it. With the help of piezoplates 2, a beam of longitudinal ultrasonic vibrations is emitted into a prism 1. This beam includes rays that go under the first critical-. If there is no acoustic contact, ultrasonic rays propagating at an angle od xp are mirrored from the working surface 4 of the prism 1 at the boundary of the material of the prism 1 - air. Mirroring from the surface 4, the ultrasonic vibrations fall on the receiving piezoplate 3, which converts them into an electrical signal. In the presence of acoustic contact, ultrasound rays propagating at an oi-ivp angle are reflected from the working surface 4 of the prism 1 at the boundary of the material of the prism 1 - the contact layer 6 of the material of the test article 5 with a jump-like displacement and fall on the partial piezo plate 3 partially. The electrical signal from the piezoplate 3 enters the measuring unit (not shown), for example, an ultrasonic flaw detector, which is used to measure the amplitude of the received ultrasonic vibrations, 5, using the amplitude of the received oscillations, determine the quality of the acoustic contact of the prism 1 with the monitored product 5: an increase in amplitude indicates a deterioration in the quality of contact. In this case, using a piezoplast 2, a flaw detector is carried out.

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For transducers with prism angles of 40–54, commonly used in ultrasonic testing of welds, the amplitude density of the spatial spectrum of the incident beam in the vicinity of the first critical angle (for basic metals in the range 27–32 is relatively small. This disadvantage is compensated by the fact that instead of the receiving plate 3, the prism has a reflector in the form of a flat-bottomed hole, whose axis is located in the vertical plane of symmetry of the converter at an angle to the vertical, equal to the first critical angle, and passes through the next central

ultrasonic beam on the working surface of the prism. A flat-bottomed hole with a diameter of 2-3 wavelengths in the material of the prism is deepened to the border of the ultrasonic beam. The signal emitted by the reflector falls on the working surface of the prism in the region of the trace of the central beam of the probe ultrasonic beam at the first critical angle and is received by the piezo-plate 2,

For an inclined transducer with a prism angle of Plexiglas 40, a PTS-19 plate with a diameter of 12 mm on a specimen made of steel OH18H9T with a surface roughness R, the following differences dA of the amplitudes of the signal quality of the contact in the loaded and unloaded states of the transducer are obtained for different contact.

liquids: for water YES 7.1 dB, for oil L A 8.3 dB, for glycerin D A 12 dB,

Claims (1)

5 claims The method of controlling the quality of acoustic contact with ultrasonic flaw detection, which consists in emitting ultrasonic vibrations into the prism, receiving ultrasonic vibrations reflected from the working surface of the prism, measuring the amplitude of the received vibrations, and determining its quality tact, characterized in that, for the purpose of increasing the reliability of the control, oscillations are received that fall on the working surface of the prism at the first critical angle. Compiled by V.Gondarevsky Editor A.Revin Tehred I., Popovich Proofreader A.Obruchar Order 1884/40 Circulation 777 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, Projecto st., 4,