JP2019007822A - X-ray stress measuring device - Google Patents

Abstract

To shorten the time required for measuring the stress value of a sample and obtain an accurate stress value irrespective of the type of sample.SOLUTION: Provided is a device for measuring the stress of a sample utilizing a diffraction phenomenon that occurs when a polycrystalline sample is irradiated with an X-ray, comprising: an X-ray irradiation unit 110 for irradiating a sample S with an X-ray that is held by a sample holding unit 113; an X-ray detection unit 116 for detecting the intensity of diffracted X-ray of the X-ray with which the sample S is irradiated, and provided with a plurality of X-ray detection elements unidimensionally arranged in a prescribed direction; a rotary unit for rotating each of the X-ray irradiation unit, the X-ray detection unit and the sample holding unit so that the angle formed by an X-ray incident on the surface of the sample and the surface and the angle formed by a diffracted X-ray diffracted by the sample and heading toward the X-ray detection unit 116 and the surface maintain a prescribed relationship; and a stress measurement unit for rotating one of the X-ray irradiation unit and X-ray detection unit and the sample holding unit so that the angle formed by an X-ray incident on the surface of the sample and the surface changes while maintaining the physical relationship of the X-ray irradiation unit and the X-ray detection unit and measuring the stress value of the sample.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an X-ray stress measurement apparatus that measures the stress of a sample such as a metal using an X-ray diffraction phenomenon.

One method for measuring the residual stress of a sample made of a polycrystal is to irradiate the sample with X-rays and use the X-ray diffraction phenomenon that occurs at that time (Non-patent Document 1). The measurement principle of this method (hereinafter referred to as X-ray stress measurement method) will be described with reference to FIG. A polycrystal is a substance composed of a large number of crystal grains (single crystal). In FIG. 1, for convenience of explanation, a crystal grain having a lattice plane perpendicular to the sample surface is present on the sample surface. I'm drawing. FIG. 1 shows a situation in which the distortion in the normal OP direction of the lattice plane of the crystal grain in the plane Z-O-X created by the normal of the sample surface and the direction of the stress to be measured is shown. In FIG. 1, the angle ψ is the angle formed by the normal (OZ) of the sample surface and the normal OP of the lattice surface, the angle θ is the angle formed by the incident X-ray and the lattice surface, and the angle ψ ₀ is the method of the sample surface. The angle between the line and the incident X-ray (referred to as “incident angle”), the angle η is the angle between the grating plane normal OP and the incident X-ray, and the angle between the grating plane normal OP and the diffracted X-ray Represents. The angle η corresponds to the incident angle of X-rays with respect to the lattice plane of the crystal grain. The angle formed by the extended line of incident X-rays and the diffracted X-rays is 2θ.

Considering the case where X-rays having a wavelength of λ are incident on crystal grains whose lattice plane is parallel to the sample surface (that is, angle ψ = 0 °), the angle θ formed by the incident X-ray and the lattice plane is Bragg's equation. The intensity of the diffracted X-ray is maximized when (2dsinθ = nλ, d is the interval between the lattice planes, and n is an integer). Accordingly, the intensity of the diffracted X-rays emitted in the direction of 2θ when the X-rays are irradiated toward the sample while sequentially changing the angle θ is measured, and the angle 2θ When the relationship of X-ray intensity is obtained, an intensity distribution curve of diffracted X-rays as shown in FIG. 2A is obtained. The angle 2θ ₀ (the angle θ ₀ ) at which the intensity is maximum in the diffraction X-ray intensity distribution curve is an angle that satisfies the Bragg equation described above. The angle 2θ ₀ at this time is the diffraction angle (specifically, the angle ψ = (Diffraction angle at 0 °).

The above phenomenon is the same when X-rays are incident on a crystal grain whose lattice plane is inclined by an angle ψ with respect to the sample surface as shown in FIG. 1. In this case, the angle ψ = 0 °. Further, by irradiating the sample with X-rays inclined at an angle ψ, a diffraction X-ray intensity distribution curve similar to that shown in FIG. 2A can be obtained. The angle 2θ at which the intensity is maximum in the X-ray diffraction intensity curve is different for each angle ψ. Since there are many crystal grains in the X-ray irradiation region and the inclination of the lattice plane of these crystal grains varies, by obtaining the X-ray diffraction intensity curve while sequentially changing the angle ψ, the angle ψ The angle 2θ at which the intensity becomes maximum every time, that is, the diffraction angle can be obtained. Hereinafter, the diffraction angle at the angle _ψ is expressed as 2θ _ψ .

The diffraction angle 2θ _ψ depends on the interval d between the lattice planes of the crystal grains, and the diffraction angle θ _ψ decreases as the interval d between the lattice planes increases. Further, when tensile stress acts on the sample, the crystal grains having a larger angle ψ have a larger lattice spacing d, and the larger the tensile stress, the larger the spread. Therefore, in the X-ray stress measurement, the diffraction angle 2θ _ψ for each angle _ψ is obtained, and the residual stress of the sample is estimated from this. Specifically, the diffraction angle 2θ _ψ obtained for each angle ψ is plotted on a 2θ-sin ² ψ diagram (see FIG. 2B) showing the relationship between the diffraction angle 2θ _ψ and sin ² ψ. An expression representing a straight line connecting each point is obtained by the method of least squares, and the stress is calculated from the coefficient (gradient of the straight line). For example, when the equation representing the straight line is Y = A + M * X, the stress value σ is obtained from the following equation (1). In the formula, K represents a stress constant.
σ = K * M (1)

  In the conventional X-ray stress measurement method, a sample (X-ray stress measurement device) as shown in FIG. 3 is used to irradiate a sample with X-rays, and the intensity of diffraction X-rays generated at that time is measured. The line intensity distribution curve is obtained. In the X-ray stress measurement apparatus, the X-ray tube 10 and the irradiation side slit 11 are fixed to the outer periphery of the goniometer 17, and the sample S is installed so that the surface thereof is the center of the goniometer 17. X-rays emitted from the X-ray tube 10 are irradiated to the sample S placed on the sample holder 13 through the irradiation side slit 11. X-rays diffracted by the sample S are introduced into the X-ray detector 16 through the exit side slit 15. Usually, the X-ray detector 16 is a scintillation tube or a proportional counter tube filled with gas, and a detection signal corresponding to the incident X-ray intensity is obtained.

  In order to detect the diffracted X-rays by the X-ray detection unit 16, the angle θ formed by the incident X-rays and the surface (lattice plane) of the sample S, the surface of the sample S, and the sample S head from the sample S toward the X-ray detection unit 16. It is necessary to scan the angle θ within a predetermined angle range while maintaining the relationship that the angle θ formed by X-rays is always equal. Therefore, in the goniometer 17, the holding part of the sample holder 13 (the inner peripheral part of the goniometer 17), the X-ray detection part 16, and the emission side slit 15 are coaxial and have different drive shafts, and these drive shafts are each θ: It is driven to rotate at a ratio of 2θ, that is, 1: 2.

  Conventionally, the sample holder 13 and the X-ray detector 16 are mechanically driven using the goniometer 17 to measure the diffraction X-ray intensity while sequentially changing the X-ray angle θ for each angle ψ. Since the diffraction angle was obtained based on the result, it took time to obtain the stress acting on the sample S.

  On the other hand, there is a method of measuring stress using a position sensitive detector (PSD) as a diffracted X-ray detector. Since PSD can simultaneously measure the X-ray intensity at a diffraction angle within a certain range, scanning of the angle θ is unnecessary, and the time required for stress measurement can be shortened (Patent Document 1).

However, the conventional method using PSD has the following problems.
There are various materials for the sample to be subjected to the X-ray stress measurement method. For example, in the case of a sample made of an iron-based material, it is known that the half-value width of the peak appearing in the diffraction X-ray intensity distribution curve increases as the residual stress increases. It has been. Specifically, in the case of α iron, the half width of the peak (peak position 2θ = about 156 deg) of the diffraction X-ray intensity distribution curve obtained when the (211) plane is irradiated with the characteristic X-ray Cr—Kα ray is It may reach 8-9deg. In contrast, the PSD measurement angle range is at most about 18 deg (when the goniometer radius is 200 mm), and the peak of the diffraction X-ray intensity distribution curve does not fall within the PSD measurement angle range for samples such as α-iron. (See FIG. 4).

JP 2001-324392 A

X-ray stress measurement method standard (2002 edition) = Iron and Steel =, published by Japan Society for Materials Science, Planning Japan Society for Materials Science X-ray Material Strength Committee, JSMD-SD-5-02

  The position where the intensity is maximum in the diffracted X-ray intensity distribution curve (that is, the position of the peak top) is usually measured up to the background range beyond the both sides of the peak waveform, and the ends on both sides of the peak waveform are specified. The straight line connecting these end portions is used as the base line, and after subtracting this from the peak waveform, the remaining waveform is normalized and obtained. However, as described above, the PSD measurement angle range is narrow, and the X-ray intensity in the angle range exceeding both ends of the peak waveform cannot be measured. Therefore, for convenience, a straight line connecting both ends of the peak waveform in the measurement angle range is regarded as a base line, and subtraction processing is performed to obtain the peak top position.

As shown in FIG. 4, in the case of the curve A in which the peak top position is approximately in the center of the PSD measurement angle range, the slope of the straight line (dashed line) regarded as the base line by the above method is the original base line. There is no significant difference. However, when the peak top position deviates from the center of the PSD measurement angle range, the slope of the straight line regarded as the baseline is different from the slope of the original baseline, so after subtracting the baseline from the peak waveform The position of the peak top obtained from the waveform of is shifted from the original position. Since the displacement of the peak top leads to a change in the slope of the 2θ-sin ² ψ diagram, there is a problem that the stress value cannot be obtained correctly.

  The problem to be solved by the present invention is that the time required for measuring the stress value of the sample can be shortened, and the stress value of the sample can be set regardless of the type of material of the sample to be subjected to X-ray stress measurement. It is to calculate accurately.

The present invention made to solve the above-mentioned problems is an X-ray stress measuring apparatus for measuring the stress of a sample using a diffraction phenomenon generated when a sample made of a polycrystal is irradiated with X-rays. There,
a) a sample holder;
b) an X-ray irradiation unit that irradiates the sample held by the sample holding unit with X-rays;
c) A plurality of X-ray detection elements arranged one-dimensionally in a predetermined direction, and X-rays radiated on the sample from the X-ray irradiation unit are X-rays diffracted in a predetermined angle range in the sample An X-ray detector for detecting the intensity of a certain diffracted X-ray;
d) The angle formed between the X-ray incident on the surface of the sample held by the sample holding portion and the surface, and the angle formed by the diffracted X-ray diffracted by the sample and directed to the X-ray detection portion. A rotation unit that rotates the X-ray irradiation unit, the X-ray detection unit, and the sample holding unit, respectively, so as to maintain a predetermined relationship,
e) While maintaining the positional relationship between the X-ray irradiation unit and the X-ray detection unit, the angle formed by the X-ray incident on the surface of the sample held by the sample holding unit and the surface is changed. A stress measuring unit configured to measure the stress value of the sample by rotating any one of the X-ray irradiation unit, the X-ray detecting unit, and the sample holding unit;

  In the present invention, since the X-ray detection unit includes a large number of X-ray detection elements that are centrally arranged in a predetermined direction, the X-ray detection unit is incident on the sample and diffracted in a predetermined angle range in the crystal grains in the sample. X-ray intensity can be detected simultaneously. For this reason, the stress value of the sample can be measured only by rotating any one of the X-ray irradiation unit, the X-ray detection unit, and the sample holding unit, and the time for stress measurement can be shortened.

Further, in the present invention, the stress measuring unit is
f) When the sample held by the sample holder is in an unstressed state, an angle θ ₀ between an incident X-ray that is an X-ray incident on the sample and the surface of the sample satisfies the Bragg equation In addition, an outgoing X-ray having an angle of 2θ ₀ with the extended line of the incident X-ray out of the outgoing X-ray emitted from the sample enters the X-ray detection element at the center of the X-ray detection unit. The sample holder, the X-ray irradiator, and the X-ray detector are arranged so that X-rays are incident on the sample from the X-ray irradiator, and the X-ray detectors at that time have a plurality of X-rays. A first measuring unit for _{obtaining a} temporary diffraction angle 2θ _ψ0 from the detection value of the line detection element;
g) An angle formed between the incident X-ray and the surface of the sample while maintaining the positional relationship between the X-ray irradiation unit and the X-ray detection unit when the first measurement unit obtains the temporary diffraction angle 2θ _ψ0. Rotate at least one of the X-ray irradiation unit, the X-ray detection unit, and the sample holding unit so that X ₀ + ψ _n becomes, so that X-rays are incident on the sample from the X-ray irradiation unit, A second measurement unit for _{obtaining a} provisional diffraction angle 2θ _ψn from detection values of a plurality of X-ray detection elements of the X-ray detection unit at that time;
h) the temporary diffraction angles 2 [Theta] _.phi.0 and the angle 0 ° of the set, and to create a diffraction angle 2 [Theta] _Pusaienu and the angle [psi _n set tentative 2θ-sin ² ψ diagram from the temporary, the angle in FIG. 0 ° and the diffraction angle calculating unit for obtaining temporary diffraction angle _2θ ψ1 ~2θ _ψn-1 respectively in the angular ψ ₁ ~ψ _n-1 to an angle [psi _n from
i) An angle formed between the incident X-ray and the surface of the sample while maintaining the positional relationship between the X-ray irradiation unit and the X-ray detection unit when the first measurement unit obtains the provisional diffraction angle 2θ _ψ0. as but a _{θ 0 + ψ 1 ~θ 0 +} ψ n-1, the sample from the turn is pivoted by the X-ray irradiation unit at least one of the X-ray irradiation unit and said sample holder and the X-ray detector to be incident X-ray, the calculated peak top position from the detection value of the plurality of X-ray detection elements of the X-ray detector at that time, which angle ψ ₁ ~ψ true diffraction angle in _{n-1 2θ ψ1} ~ It is preferable to include a stress calculation unit that creates a true 2θ-sin ² ψ diagram as 2θ _ψn-1 and obtains the stress value of the sample from the true 2θ-sin ² ψ diagram.

In the present invention, in order to confirm the linearity of the sin ² ψ diagram, it is preferable to select 50 ° as the angle ψ _n . In this case, as the angles ψ _{1 to} ψ _n−1 , an arbitrary plurality of angles from 0 ° to 50 ° are selected. Angle is set as an angle ψ ₁ ~ψ _n-1 is preferably a plurality of angles obtained by equally dividing the angle range of angle ψ ₁ ~ψ _n-1, but is not limited thereto.

In the above configuration, the first measurement unit and the second measurement unit have an angle ψ of 0 ° (= ψ ₀ ) among the crystal grains in the sample held by the sample holding unit, that is, the sample surface and the lattice plane are parallel. Diffraction angles 2θ _ψ0 and 2θ _ψn when X-rays are incident on a crystal grain and a crystal grain whose lattice plane is tilted at an angle ψ _{n with} respect to the surface of the sample under the conditions satisfying the Bragg equation Calculate as a corner. Then, the diffraction angle calculation unit creates a 2θ-sin ² ψ diagram from the tentative diffraction angle obtained in this way, and from this, the tentative angle in the angle ψ _{1 to} ψ _n-1 between the angle 0 ° and the angle ψ _n is obtained. obtaining diffraction angle _2θ ψ1 ~2θ _ψn-1, respectively.

Next, the stress calculation unit maintains the positional relationship between the X-ray irradiation unit and the X-ray detection unit when the first measurement unit obtains the temporary diffraction angle 2θ _ψ0 , and as the angle between the surface becomes _{θ 0 + ψ 1 ~θ 0 +} ψ n-1, the X-ray by sequentially rotating at least one of the X-ray irradiation unit and said sample holder and the X-ray detector X-rays are incident on the sample from the irradiation unit. And the peak top position is calculated | required from the detected value of the several X-ray detection element of the X-ray detection part at that time. In the present invention, in advance since seeking diffraction angle _2θ ψ1 ~2θ _ψn-1 provisional at an angle ψ ₁ ~ψ _n-1, the peak top position is almost the center of the measurement angle range of the X-ray detector, an accurate The peak top position can be obtained.

  In the present invention, the first measurement unit and the second measurement unit are configured to set the detected values of the plurality of X-ray detection elements of the X-ray detection unit as vertical axes and the angles of the diffracted X-rays incident on the X-ray detection elements. The peak top position can be obtained by creating a graph with the horizontal axis and subjecting the graph to profile fitting processing. As a technique used for the profile fitting process, a Levenberg-Marquardt method (Levenberg-Marquardt method), which is a kind of calculation method of the least square method, can be cited. As a function used for profile fitting processing, for example, a Gaussian function, a Lorentz function, or a combination thereof can be used.

Further, in the present invention, the first measurement unit and the second measurement unit may detect the detected values of the plurality of X-ray detection elements of the X-ray detection unit on the vertical axis, and the diffracted X-rays incident on the X-ray detection elements. A graph having the diffraction angle as the horizontal axis may be created, a baseline in the graph may be obtained, and the peak top position may be obtained by normalizing the remaining graph waveform that has been subtracted from the graph. As described above, in the present invention, since the peak top position is approximately the center of the measurement angle range of the X-ray detection unit, the accurate peak top position can be obtained also by subtraction processing for subtracting the baseline.
It is characterized by

According to the X-ray stress measurement apparatus according to the present invention, since the detector having a large number of X-ray detection elements arranged in a predetermined direction as the X-ray detection unit is employed, It is possible to simultaneously detect the intensity of X-rays diffracted in a predetermined angle range in the inside crystal grains. For this reason, the stress value of the sample can be measured only by rotating any one of the X-ray irradiation unit, the X-ray detection unit, and the sample holding unit, and the time for stress measurement can be shortened. Also, determine the diffraction angle _2θ ψ1 ~2θ _ψn-1 provisional at an angle ψ ₁ ~ψ _n-1, to determine the arrangement of the X-ray irradiation unit and the X-ray detection unit based on this, the peak top position is X-ray It is possible to avoid a significant deviation from the center of the measurement angle range of the detection unit. For this reason, since an accurate peak top position can be obtained regardless of the type of sample material to be subjected to X-ray stress measurement, the stress value acting on the sample can be accurately obtained.

Explanatory drawing of the principle of X-ray stress measurement. (A) is an X-ray diffraction intensity curve, (b) is a 2θ-sin ² ψ diagram. The schematic block diagram of the conventional X-ray stress measuring apparatus. The figure which shows the example of the diffraction X-ray intensity distribution curve obtained with the conventional X-ray stress measuring apparatus. 1 is a schematic configuration diagram of an X-ray stress measurement apparatus according to an embodiment of the present invention. The principle explanatory drawing of the X-ray stress measurement using the X-ray stress measuring apparatus of a present Example. The flowchart of a stress measurement process. Angle [psi ₀ and the angle [psi diffraction angles obtained for _n 2 [Theta] _.phi.0, determined from 2θ-sin ² ψ diagram showing an example of a 2θ-sin ² ψ diagram is created based on _2θ ψn (a), and (a) angle ψ ₁ ~ψ _n-1 and shows the relationship between diffraction angle _2θ ψ1 ~2θ _ψn-1 provisional being. The figure which shows the example of the X-ray intensity distribution curve obtained by adjusting arrangement | positioning of an X-ray irradiation part, an X-ray detection part, and a sample stage based on a temporary diffraction angle. The figure which shows the result of having measured the stress value using the conventional apparatus. The figure which shows the result of having measured the stress value using the X-ray-stress measuring apparatus of a present Example. The figure which shows collectively the stress value obtained using the conventional apparatus and the X-ray-stress measuring apparatus of a present Example.

Hereinafter, an X-ray stress measuring apparatus according to an embodiment of the present invention will be described with reference to FIGS.
FIG. 5 shows a schematic configuration of the X-ray stress measuring apparatus according to the present embodiment. The X-ray stress measurement apparatus includes a goniometer 117, a sample stage 113 attached to the center of the goniometer 117, and an X-ray irradiation unit 110 and an X-ray detection unit 116 attached to the outer periphery of the goniometer 117. ing. The X-ray detection unit 116 includes a large number of minute X-ray detection elements arranged on a line. The X-ray irradiation unit 110 includes an X-ray tube 110a and generates X-rays having a specific wavelength according to the material of the target.

  The goniometer 117 is used as an angle θ formed by the incident X-rays from the X-ray irradiation unit 110 to the sample S and the surface of the sample S, and the X-ray detection element at the center of the surface of the sample S and the sample S from the sample S. The sample stage 113, the X-ray irradiation unit 110, and the X-ray detection unit 116 are coaxially connected to each other by different drive axes while maintaining the relationship in which the angle θ formed by the X-rays that are directed is always equal. Each of the line detectors 116 is driven to rotate. Therefore, these drive shafts are rotationally driven at a ratio of θ: 2θ, but in this embodiment, each drive shaft can be further rotationally driven independently.

  When X-rays enter the X-ray detection element of the X-ray detection unit 116, the X-ray detection unit 116 generates a detection signal corresponding to the intensity. The detection signal obtained by the X-ray detection unit 116 is sent to the data processing unit 120 through the amplifier 118. The data processing unit 120 includes a data collection unit 121, a diffraction angle calculation unit 122, a stress value calculation unit 123, and the like. The data collection unit 121 corresponds to the first and second measurement units of the present invention. The control unit 100 controls the operation of each unit of the X-ray stress measurement apparatus. Results such as graphs obtained by processing by the data processing unit 120 are transmitted to the control unit 100 and output to the display unit 101. In addition to the display unit 101, the control unit 100 includes an input unit 102 for an operator to make appropriate settings and support. The control unit 100 and the data processing unit 120 use a personal computer as a software resource, and execute the dedicated control / processing software installed in the personal computer, thereby realizing the functional blocks as described above. It can be.

  Next, the stress measurement operation of the sample S made of a polycrystalline body using this X-ray stress measurement apparatus will be described with reference to FIGS. Here, it is assumed that the sample stage 113 is fixed and the positions of the X-ray irradiation unit 110 and the X-ray detection unit 116 are changed around the sample S held on the sample stage 113. The X-ray detection unit 116 may be fixed and the surface inclination of the sample S may be changed. Further, the positions of both the X-ray irradiation unit 110 and the X-ray detection unit 116 and the sample stage 113 may be changed. In short, it is sufficient that the sample stage 113, the X-ray irradiation unit 110, and the X-ray detection unit 116 hold a predetermined positional relationship. In the following description, the XY plane is positioned on the surface of the sample S, and the normal line on the surface of the sample S is represented by the Z axis.

  Prior to the execution of the stress measurement operation of the sample S, the measurer operates the input unit 102 to bring the sample stage 113 to the position shown in FIG. 5 and rotate the drive shaft of the goniometer 117 to detect the surface of the sample S and the surface of the sample S. Is the angle formed by the X-rays incident on the X-ray, and the angle formed by the X-rays emitted from the surface of the sample S and incident on the X-ray detection element located at the center of the X-ray detection unit 116 is θ. As described above, the X-ray irradiation unit 110 and the X-ray detection unit 116 are arranged. In the following description, the positions of the X-ray irradiation unit 110 and the X-ray detection unit 116 at this time are set as initial positions. The angle θ is an angle satisfying the Bragg equation when X-rays having a wavelength λ are incident on crystal grains constituting the sample S in an unstressed state, and is an angle specific to the material of the sample S. Therefore, X-rays incident on crystal grains existing on the surface portion of the sample S in an unstressed state and having an angle ψ of 0 ° (that is, crystal grains in which the surface of the sample S and the lattice plane are parallel) are The Bragg equation is satisfied. The arrangement of the sample stage 113, the X-ray irradiation unit 110, and the X-ray detection unit 116 may be automatically adjusted when the measurer inputs the material of the sample S through the input unit 102. The person may adjust manually.

When the adjustment is completed and the measurer instructs the start of the stress measurement operation, the control unit 100 executes the stress measurement operation according to the flowchart shown in FIG.
In step S1, when the X-ray irradiation unit 110 and the X-ray detector 116 is in the initial position shown in FIG. 5, and the two states when in therefrom at a position obtained by angle [psi _n rotation, each diffracted X-ray An operation of creating an intensity distribution curve is executed (step S1). In both of these states, the sample stage 113 is in the position described above. Therefore, when the X-ray irradiation unit 110 and the X-ray detection unit 116 are in the initial positions, the angle formed between the surface of the sample S and the X-rays incident thereon is θ, and the X-ray irradiation unit 110 and the X-ray detection unit When 116 is at a position rotated by an angle ψ _n from the initial position, the angle formed by the surface of the sample S and the X-ray incident thereon is θ + ψ _n . That is, when the X-ray irradiation unit 110 and the X-ray detection unit 116 are in the initial positions, Bragg's equation is used for the crystal grains having the angle ψ = 0 ° among the crystal grains on the surface portion of the unstressed sample S. When the X-ray to be filled is incident from the X-ray irradiation unit 110 and the X-ray irradiation unit 110 and the X-ray detection unit 116 are at a position rotated by an angle ψ _n from the initial position, the surface of the sample S in a stress-free state is applied. X-rays satisfying the Bragg equation are incident from the X-ray irradiation unit 110 to crystal grains having an angle ψ = ψ _n among certain crystal grains.

In any state, the X-rays incident on the surface of the sample S are diffracted by crystal grains existing near the surface of the sample S as shown in FIG. Since a large number of crystal grains exist in the X-ray incident region on the surface of the sample S, the X-rays diffracted by each crystal grain enter the X-ray detection element located at a position corresponding to the diffraction angle 2θ. The X-ray detection unit 116 generates a detection signal corresponding to the intensity of the X-ray input to each X-ray detection element. The detection signals of many X-ray detection elements show the relationship between the angle 2θ and the X-ray intensity. Therefore, when the data processing unit 120 receives the detection signals of the respective X-ray detection elements through the amplifier 118, the data collection unit 121 collects these signals and diffracted X-ray intensity distribution curves showing the relationship between the angle 2θ and the X-ray intensity. Create And the diffraction angle calculation part 122 calculates this distribution curve, and calculates | requires the position of the peak top where X-ray intensity becomes the maximum (step S2). The peak top position at which the X-ray intensity at the angle ψ = ψ ₀ (= 0 °) and the angle ψ = ψ _n becomes the maximum becomes the temporary diffraction angles 2θ _ψ0 and 2θ _ψn .

  In steps S1 and S2, the arrangement of the X-ray irradiation unit 110 and the X-ray detection unit 116 is selected using an angle θ that satisfies the Bragg equation when the sample S is in an unstressed state. Depending on the size, the peak top position of the diffraction X-ray intensity distribution curve is shifted from the center of the measurement angle range of the X-ray detection unit 116 as shown by the curve B shown in FIG. Therefore, here, the diffraction angle calculation unit 122 does not obtain the peak top position by subtraction processing and normalization processing using the baseline, but obtains the peak top position by profile fitting processing.

Further, the diffraction angle calculation unit 122 _creates a temporary 2θ-sin ² ψ diagram using the obtained diffraction angles 2θ _ψ0 , 2θ _ψn and the corresponding angles ψ ₀ , ψ _n (step S3). the 2θ-sin ² ψ diagram from an angle [psi ₀ and [psi _n the diffraction angle _2θ ψ1 ~2θ _ψn-1 provisional at an angle ψ ₁ ~ψ _n-1 of between calculated respectively (step S4). FIG. 8A shows a temporary 2θ-sin ² ψ diagram created from diffraction angles 2θ _ψ0 , 2θ _ψn and angles ψ ₀ , ψ _n . Further, FIG. 8 (b) shows a diffraction angle _2θ ψ1 ~2θ _ψn-1 provisional obtained from 2θ-sin ² ψ diagram provisional.
The operation so far is the operation content of the first and second measurement units of the present invention.

Subsequently, the control unit 100, obtained in step S4, on the basis of the diffraction angle _2θ ψ1 ~2θ _ψn-1 provisional at an angle ψ ₁ ~ψ _n-1, the X-ray irradiation unit 110 and the X-ray detector 116 5 is rotated from the initial position shown in FIG. 5 by angles ψ ₁ to ψ _n−1 , and a diffraction X-ray intensity distribution curve creation operation is executed at each position (step S5). At this time, the control unit 100 controls the drive shaft, X-rays are incident at an angle _θ ψ1 ~θ _ψn-1 to the surface of the sample S, an angle _θ ψ1 ~θ _ψn-1 relative to the surface The arrangement of the X-ray irradiation unit 110 and the X-ray detection unit 116 is adjusted so that the emitted diffracted X-rays enter the X-ray detection element at the center of the X-ray detection unit 116. As a result, X-rays are incident on the sample S under conditions satisfying the Bragg equation in crystal grains existing on the surface of the sample S and having a lattice plane with an angle ψ of ψ ₁ to ψ _n−1. In addition, the diffracted X-rays are incident on the X-ray detection element at substantially the center of the X-ray detection unit 116. Thereafter, as described above, the detection signal of each X-ray detection element is output from the X-ray detection unit 116 to the data processing unit 120, and the diffracted X-ray intensity for each of the angles ψ _{1 to} ψ _n-1 based on the detection signal. A distribution curve is created. An example of the diffraction X-ray intensity distribution curve created at this time is shown in FIG. As shown in FIG. 9, here, a diffraction X-ray intensity distribution curve is created such that the peak top is located approximately at the center of the measurement angle range of the X-ray detection unit 116, and the angles ψ ₁ to ψ are generated from the curve. true diffraction angle _2θ ψ1 ~2θ _ψn-1 in _n-1 is calculated (step S6).

Then, the stress value calculation unit 123 and the angle ψ ₁ ~ψ _n-1, the diffraction angle _2θ ψ1 ~2θ based on _ψn-1 to create the 2θ-sin ² ψ diagram at that time (step S7). Then, a stress value σ (= K * M, where K is a stress constant) is obtained from the slope M of a straight line (formula Y = A + M * X) connecting the points of the 2θ-sin ² ψ diagram (step S8).

  Next, experimental results of measuring specific sample stress values using the X-ray stress measurement apparatus and the conventional apparatus will be described with reference to FIGS. Here, an iron-based sample (iron-based high stress test piece) having a peak half-value width of 4.5 to 5.2 ° was used as a sample, and an experiment was performed at n = 10.

  FIG. 10 shows the stress value obtained using the conventional apparatus, and FIG. 11 shows the stress value obtained using the X-ray stress measuring apparatus. FIG. 12 is a table summarizing the results obtained with the conventional apparatus and the X-ray stress measuring apparatus. In the experiment, an X-ray detector having a measurement angle range of 9.02 ° and an X-ray detector having a measurement angle range of 18.33 ° were used. 10 (a) and 11 (a) show the results using an X-ray detector with a measurement angle range of 9.02 °, and FIGS. 10 (b) and 11 (b) show a measurement angle range of 18.33 °. The result using an X-ray detection part is shown.

  As is clear from FIGS. 10A and 10B, in the conventional apparatus, the stress value obtained by the difference in the measurement angle range of the X-ray detector changes. On the other hand, as shown in FIGS. 11A and 11B, in the X-ray stress measurement apparatus of this example, even when the measurement angle ranges of the X-ray detectors are different, the stress values having substantially the same value were obtained. From the above results, it was confirmed that the apparatus according to the present example can obtain an accurate stress value even if the measurement angle range is narrow.

DESCRIPTION OF SYMBOLS 10 ... X-ray tube 110 ... X-ray irradiation part 11, 111 ... Irradiation side slit 13 ... Sample holder 113 ... Sample stage 15 ... Output side slit 16, 116 ... X-ray detection part 17, 117 ... Goniometer 100 ... Control part 101 ... Display unit 102 ... Input unit 120 ... Data processing unit 121 ... Data collection unit 122 ... Diffraction angle calculation unit 123 ... Stress value calculation unit S ... Sample

Claims (4)

An X-ray stress measurement device that measures the stress of a sample using a diffraction phenomenon that occurs when X-rays are irradiated to a sample made of a polycrystalline body,
a) a sample holder;
b) an X-ray irradiation unit that irradiates the sample held by the sample holding unit with X-rays;
c) A plurality of X-ray detection elements arranged one-dimensionally in a predetermined direction, and X-rays radiated on the sample from the X-ray irradiation unit are X-rays diffracted in a predetermined angle range in the sample An X-ray detector for detecting the intensity of a certain diffracted X-ray;
d) The angle formed between the X-ray incident on the surface of the sample held by the sample holding portion and the surface, and the angle formed by the diffracted X-ray diffracted by the sample and directed to the X-ray detection portion. A rotation unit that rotates the X-ray irradiation unit, the X-ray detection unit, and the sample holding unit, respectively, so as to maintain a predetermined relationship,
e) While maintaining the positional relationship between the X-ray irradiation unit and the X-ray detection unit, the angle formed by the X-ray incident on the surface of the sample held by the sample holding unit and the surface is changed. An X-ray stress measurement apparatus comprising: an X-ray irradiation unit, a stress measurement unit that rotates any one of the X-ray detection unit and the sample holding unit to measure a stress value of the sample. In the X-ray stress measuring device according to claim 1,
The stress measuring unit is
f) When the sample held by the sample holder is in an unstressed state, an angle θ ₀ between an incident X-ray that is an X-ray incident on the sample and the surface of the sample satisfies the Bragg equation In addition, an outgoing X-ray having an angle of 2θ ₀ with the extended line of the incident X-ray out of the outgoing X-ray emitted from the sample enters the X-ray detection element at the center of the X-ray detection unit. The sample holder, the X-ray irradiator, and the X-ray detector are arranged so that X-rays are incident on the sample from the X-ray irradiator, and the X-ray detectors at that time have a plurality of X-rays. A first measuring unit for _{obtaining a} temporary diffraction angle 2θ _ψ0 from the detection value of the line detection element;
g) The angle formed between the incident X-ray and the surface of the sample while maintaining the positional relationship between the X-ray irradiation unit and the X-ray detection unit when the first measurement unit obtains the temporary diffraction angle 2θ _ψ0. Rotate at least one of the X-ray irradiation unit, the X-ray detection unit, and the sample holding unit so that X ₀ + ψ _n becomes, so that X-rays are incident on the sample from the X-ray irradiation unit, A second measurement unit for _{obtaining a} provisional diffraction angle 2θ _ψn from detection values of a plurality of X-ray detection elements of the X-ray detection unit at that time;
h) the temporary diffraction angles 2 [Theta] _.phi.0 and the angle 0 ° of the set, and to create a diffraction angle 2 [Theta] _Pusaienu and the angle [psi _n set tentative 2θ-sin ² ψ diagram from the temporary, the angle in FIG. 0 ° and the diffraction angle calculating unit for obtaining temporary diffraction angle _2θ ψ1 ~2θ _ψn-1 respectively in the angular ψ ₁ ~ψ _n-1 to an angle [psi _n from
i) An angle formed between the incident X-ray and the surface of the sample while maintaining the positional relationship between the X-ray irradiation unit and the X-ray detection unit when the first measurement unit obtains a temporary diffraction angle 2θ _ψ0. as but a _{θ 0 + ψ 1 ~θ 0 +} ψ n-1, the sample from the turn is pivoted by the X-ray irradiation unit at least one of the X-ray irradiation unit and said sample holder and the X-ray detector to be incident X-ray, the calculated peak top position from the detection value of the plurality of X-ray detection elements of the X-ray detector at that time, which angle ψ ₁ ~ψ true diffraction angle in _{n-1 2θ ψ1} ~ A true 2θ-sin ² ψ diagram is created as 2θ _ψn-1 , and a stress calculation unit for _obtaining a stress value of the sample from the true 2θ-sin ² ψ diagram is provided. measuring device.   The first measurement unit and the second measurement unit have detection values of a plurality of X-ray detection elements of the X-ray detection unit as vertical axes, and diffraction angles of diffracted X-rays incident on the X-ray detection elements as horizontal axes. The X-ray stress measurement apparatus according to claim 2, wherein the peak top position is obtained by creating a graph to be processed and performing profile fitting processing on the graph.   The first measurement unit and the second measurement unit have detection values of a plurality of X-ray detection elements of the X-ray detection unit as vertical axes, and diffraction angles of diffraction X-rays incident on the X-ray detection elements as horizontal axes. 3. The X top according to claim 2, wherein a graph is generated, a baseline in the graph is obtained, and a remaining graph waveform obtained by subtracting the baseline from the graph is normalized to obtain a peak top position. Line stress measuring device.

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