RU2392610C1 - Method for radiation control of object status - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: usage for radiation control of an object status. One performs transmission of an object with X-rays or gamma-rays, detector registration of intensity of the radiation having penetrated through the object and re-transmission. Re-transmission of the control object proceeds with the angle of the radiation beam incidence modified by a value from 0.5° to 10°. One registers intensity at re-transmission, compares distribution of radiation intensity across the detector surface in the both cases and estimates presence or absence of defects in the object based on match or mismatch of the relative positioning of the increased intensity areas.

EFFECT: enhanced authenticity of radiation control results including for complicated shape objects.

4 cl, 2 dwg, 1 ex

Description

The invention relates to non-destructive testing methods, namely to the field of radiation defectoscopy using x-ray or gamma radiation.

A known method of X-ray flaw detection, including the transmission of an object, including complex shape, X-rays and recording the result on an X-ray film with its subsequent manifestation (Rumyantsev SV "Radiation defectoscopy." - M .: ATOMIZDAT, 1974, p. .510) - an analogue.

In accordance with the known method, a sign of a defect is the presence on the film of areas ("spots") with increased or decreased optical density compared with the optical density of the image of the defect-free part of the object. In this case, it is believed that areas with increased optical density (darker on the film) correspond to pores, cracks, and other defects. A disadvantage of the known solution is that this method does not take into account the possibility of dark spots for a reason not related to metallurgical defects, namely, due to the diffraction phenomenon during transmission.

A known method of non-destructive monitoring of the state of an object, which includes repeated x-ray photography of the object, during which the detector, in particular the cassette with the x-ray film, is brought into direct contact with the control object. The conclusion about the presence or absence of defects is made after comparing two images. When re-illuminated, the position of the object relative to the radiation source is unchanged, and the cassette with the film is moved until it is in direct contact with the site of the object where spots with high optical density are detected (RF patent No. 2304766, G01N 23/18, publication 2007.08.20) - prototype.

A disadvantage of the known method is its limited scope, for example, the known solution cannot be used with the necessary reliability if the object has a complex geometric shape that excludes the contact of the cartridge with a controlled section of the product.

The technical result, to which the claimed invention is directed, is to increase the reliability of the results of radiation monitoring for objects, including complex shapes.

The specified technical result is achieved by the fact that in the method of radiation monitoring the state of the object, including its transmission by X-ray or gamma radiation, registration of the distribution of the intensity of the radiation transmitted through the object using a detector, processing of the transmission results and assessment of the presence of defects in the monitoring object and repeated transmission, to increase the reliability of the control is repeated transmission of the test object at a change in the angle of incidence of the beam of radiation on it from 0.5 to 10 ° values, record the intensity during repeated transmission, compare the distribution of the transmitted radiation intensity over the surface of the detector during both surveys, by which the presence or absence of defects in the object is estimated based on the coincidence or mismatch of the location of the areas of increased intensity.

In the inventive method, a change in the angle of incidence of the radiation beam on the test object by up to 10 ° can be carried out by moving the test object by 1-30 mm from its original position, and, in particular, a cassette with an x-ray film or a film with an x-ray sensitive can be used as a detector " phosphoric coating.

In the method, the assessment of the presence of defects in the control object can be carried out based on the coincidence of the relative location of the areas of high intensity according to the results of both transmissions.

The method is based on the following. When the voltage on the x-ray tube in the range U = 40-400 kV, usually used for flaw detection purposes, the wavelength corresponding to the maximum radiation intensity is λ ~ 1.24 × 1.5 / U nm, or λ ~ 0.05-0.005 nm, and taking into account the dispersion of the spectrum λ ~ 0.1-0.003 nm. For crystalline lattice periods a = 0.25-0.5 nm, which are usual for most materials, the most intense diffraction reflections of X-ray waves come from crystallographic planes with distances between them d / n ~ 0.15-0.25 nm.

The deviation of the diffracted (reflected) rays 20 from the primary beam is described by the Wulf-Bragg equation θ = (arcsin (λ / 2 / (d / n)), or at small angles 2θ = λ / (d / n). For the above values of λ and d / n, these angles are in most cases from 1 to 20 °, and the most intense reflections occur in the range of 1-5 °. At the same time, another geometric diffraction condition must be fulfilled: the angles of the primary and reflected rays to the reflecting plane must be equal and lie in the same plane as the normal to the reflecting plane. Phenomenon is determined by the perfection of the crystal lattice and usually does not exceed 1-1.5 °.

X-ray diffraction spots are formed by reflections from the crystallographic planes of each individual grain and have sizes on the order of grain sizes. This is the cause of errors, since defects (pores, etc.) often have the same dimensions of ~ 0.1-1 mm. Since the irradiated volume of the object contains many grains, diffraction spots from a sufficiently coarse-grained object (especially during X-ray inspection of molten parts) form a chaotic picture, each of which has its own wavelength and angle of reflection.

If, as proposed in the claimed solution, the direction of the primary X-ray beam relative to the object is changed by a certain angle, the diffraction conditions change, while the previously obtained diffraction spots disappear (go out) and new ones appear at different angles, generally formed by the components of the primary beam with different lengths waves and reflected from other crystallographic planes. Accordingly, the mutual arrangement of spots, as well as their position relative to the geometric elements of the controlled product, will radically change.

The claimed range of variation of the angle of incidence of the radiation beam on the object is due, on the one hand, to the diffraction width of the reflection: the angle must be large enough (at least 1 °) to remove only grains and (or) some crystallographic planes of these grains from the reflecting position and introduce reflective position of other grains and planes. On the other hand, the angle should not be too large so as not to cause geometric distortions of the object in the picture. The range boundary depends on the geometry of the controlled object and, as a rule, does not exceed 10 °, and in the claimed method, the location of the detector (film cassette) relative to the object remains unchanged, in contrast to the decision adopted for the prototype.

Concrete example

The block of turbine nozzle blades, cast from the heat-resistant alloy ChS104, undergoes X-ray control; the section is the hook of the large block shelf at a distance between the casting surface and the cartridge of ~ 25 mm. Pictures were taken twice with the casting displaced relative to the primary x-ray beam by a distance of 30 mm at a focal length of 1300 mm, which corresponds to a change in the angle of 30 × 57.4 / 1300 = 1.3 °. In the image of the casting (conventionally shown by two bold lines), there are many dark spots in both images, however, the location of the spots in these images does not coincide, which indicates the absence of real defects. Diffraction spots from one grain are located along ellipses, each of which corresponds to a certain zone of crystallographic planes. In general, diffraction from many grains forms a chaotic picture. The experimental design is shown in FIGS. 1 and 2, where the vertical long arrow schematically depicts an X-ray beam, and the short inclined arrows indicate the directions of the diffracted beams. The result was verified using the method of destructive testing, namely, a metallographic study, based on which it was concluded that there were no real defects in the object under study.

Claims (4)

1. A method of radiation monitoring the state of an object, including its transmission by X-ray or gamma radiation, registration with the aid of a detector of the intensity of radiation transmitted through the object and repeated scanning, characterized in that to increase the reliability of the control, repeated scanning of the control object is carried out at a value of 0, 5 to 10 ° the angle of incidence of the radiation beam on it, the intensity is recorded during repeated transmission, the intensity distribution over the surface of the detector is compared and radiation at both, and evaluate the presence or absence of defects in the object based on the coincidence or mismatch of the relative location of the areas of high intensity. 2. The method according to claim 1, characterized in that the change in the angle of incidence of the radiation beam on the control object by a value from 0.5 to 10 ° is carried out by moving the control object by 1-30 mm from the initial position. 3. The method according to claim 1, characterized in that an X-ray film is used as a detector. 4. The method according to claim 1, characterized in that as the detector using a plastic film with a phosphorus coating.

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