RU1793343C - Method of working piece surface structure x-ray analyzing - Google Patents

Description

The invention relates to x-ray structural analysis and can be used in non-destructive analysis of the structure of industrial products, including in the field.

A known X-ray return camera (CROS) comprising an X-ray source, a circular aperture diaphragm forming a direct beam of X-rays with a small divergence angle, a sample holder and a flat film cassette located between the source and the holder perpendicular to the incident beam.

The incident beam has a circular spot on the sample of a small area (several mm2), a conical beam diffracted from the surface of the sample is formed and recorded on the film as a diffraction circle. Exposure when shooting a single x-ray is significant (from one to several hours). The chamber allows the use of small samples and is not applicable for non-destructive testing.

The closest in technical essence is the method of studying the texture of the inner surfaces of cylindrical products, which consists in sending a conical x-ray beam cut from a wide-dispersed beam of a point source to the studied inner surface, registering it with a reflection detector from the annular part of the product and using the diffraction pattern judges the structure of the inner surface of the article. .

The use of diverging conical beams and the axis of symmetry of the survey geometry, which distinguish this method, make it possible to quickly and without destruction of the product analyze the structure of the inner surface. When using a film as a detector, the exposure time is several tens of minutes, and the area of the surface under analysis is several thousand mm2,

In this way, sections of the article having the shape of internal surfaces of revolution can be examined; it is not applicable to external surfaces. In addition, it is not possible to establish an unambiguous correspondence between the area of the investigated surface and the diffraction pattern obtained from it, because the conical diffraction beams from each point on the irradiated annular region intersect at a common point lying on the symmetry axis of the device where they are detected by the detector. Therefore, the detector accumulates

summarized information on the structure of the entire irradiated annular region without its detailing in the individual sections composing this region.

An object of the invention is to enable local analysis of the structural state of the outer surface of articles over a large area at the same time.

This goal is achieved in that the X-ray source with a widely diverging beam is located above the analyzed surface of the product, a conical beam is cut out using a screen, projecting onto the surface of the product in the form of a ring, and the conical beam is positioned relative to the surface under study so that its axis symmetries perpendicular to the surface, and

0 diffracted radiation is recorded in a circle formed by the focal points on the surface, equidistant analyzed. While moving the source and detector along the surface, the entire product is scanned.

In FIG. 1 illustrates the essence of the method; in FIG. 2 - adjusting the geometry of the survey during the implementation of the method, and also explains how to set

0 unambiguous correspondence between the area of the investigated surface and the diffraction pattern obtained from it; in FIG. 3 is a portion of an x-ray taken by the proposed method.

5 The proposed method can be implemented as follows.

X-ray source 1 is located above the surface 2 of the product, the diaphragm 3 with an annular slot set so

0 way to ensure a given angle 2 a of the solution of the conical beam 4, as well as the perpendicularity of the axis of symmetry of the conical beam to the investigated surface 2 of the product, diffraction beams 5, which

5 converge at corresponding points on the focusing circles 6, register with a detector 7, which can be used as a film in a cassette or a two-dimensional ionization counter.

0 Focusing of diffraction radiation in any plane containing the 00 axis occurs in a geometrically equivalent way to a point lying at a distance R from the 00 axis and at a distance H from the analyzed surface. Focusing in the plane corresponds to the Zeeman-Bolin principle of focusing known in radiography.

Due to the axial symmetry of the method (axis 00), the geometrical location of the focus points will be a curve lying in a plane equidistant to the analyzed surface. For a flat surface, the sample is the circle described by the relations

+ tg a);

tg2 (20-a) + 1 where z R is the radius of the circle of focused radiation;

h is the distance from the radiation source to the analyzed surface;

a - the half-angle of the falling conic

: whom beam;

in - diffraction angle; H is the distance between the analyzed surface and the circle of focusing radiation.

Diffraction cones with an angular aperture of $ 4 from all sections of the irradiated surface touch this circle. Therefore, with a detector set up to contain a circle of focused radiation, this circumference and traces of diffracted cones touching it are recorded. Angle about. and the distance h defines the size of the irradiated annular region, and therefore, determine the area of the analyzed surface. With increasing a and h, the dimensions of the irradiated surface increase.

An unambiguous correspondence between the individual sections of the analyzed surface and the diffraction pattern obtained from it. Is ensured by the 4jc incident beam So and the diffraction beam S / hedgehog in the same plane passing through axis 00 and the point of incidence of the beam S0 on the surface of the analyzed product . The intersection of this plane with the detector indicates the area where rays scattered from a given surface area are recorded. Therefore, each point lying on

0

5

0

5

0

5

0

5

the circle of focused rays corresponds to a single point on the analyzed surface. This makes it possible to unambiguously determine the location of regions with a changed structural state on the analyzed surface.

To detect focused diffraction radiation, the detector can be set in various ways.

The following two options are most technically simple: on a surface evidistant to be analyzed at a distance H from it, as shown in FIG. 1, and along a cylindrical surface of radius R with the axis of the cylinder 00. In FIG. Figure 3 shows an X-ray diffraction pattern obtained in the second embodiment of the arrangement of the film. The weld zone of two Al sheets with different structures was investigated. Radiation, exposure time 20 min, RT-1 film, photocassette radius 80 mm, (111) and (200) reflections with diffraction angles of 19.32 ° and 22.43, respectively, are focused. It is seen that the x-ray can be conditionally divided into three zones. Zone A characterizes the metal of the first sheet: the recrystallized structure gives clear diffraction reflections from individual grains, in zone B the diffraction pattern corresponds to a seam with a coarse-grained structure, with slightly diffuse reflections indicating residual deformation in the grains, and zone B refers to the metal of the second sheet with a deformed structure which results in almost complete smearing of the diffraction spots. It can be seen that individual sections of the investigated surface are well localized on the x-ray. It must be emphasized that with any installation of the detector, the diffraction radiation is focused at the points forming a curve that is equidistant to the analyzed surface, and the specific shape of the curve is determined by the local shape of the analyzed surface.

Claims (1)

SUMMARY OF THE INVENTION A method for X-ray diffraction analysis of a surface of an article, which consists in irradiating the analyzed surface with a conical x-ray beam of the best, cut out screen from a wide-spread beam of a point source and projected onto the irradiated surface in the form of a ring, the radiation diffracted by the irradiated section and the nature of the diffraction pattern court of structural state of the product’s surface, characterized in that, in order to enable local analysis of the structural state of the product’s surface, the conical beam is positioned relative to the surface under study so that its axis of symmetry is perpendicular to the surface and the diffracted radiation is recorded around the circle formed by the focus points on surface equidistant analyzed. Editor E. Savina Compiled by V. Koshelev Tehred M. Morgenthal Corrector. O. Gusti