X-ray diffraction measuring device and residual stress calculation method using x-ray diffraction measuring device

Abstract

To provide an X-ray diffraction measuring device and a residual stress calculation method using the X-ray diffraction measuring device capable of accurately calculating residual stress of a measuring object OB even when an imaging surface is not orthogonal to an X ray.SOLUTION: A method includes steps of: detecting a diffraction ring of a first sample having a previously known diffraction angle; detecting a diffraction ring of a second sample having a previously known diffraction angle that is different from that of the first sample; determining gravity center position coordinates of the first diffraction ring and gravity center position coordinates of the second diffraction ring; determining an X-ray optical axis inclination as an inclination of an X-ray optical axis relative to an imaging surface using the gravity center position coordinates of the diffraction ring of the first sample and the gravity center position coordinates of the diffraction ring of the second sample; determining exit point coordinates of an X ray on the imaging surface with distances between the imaging surface and the first and second samples set as zero; detecting a diffraction ring of a measuring object using the calculated X-ray optical axis inclination and the exit point coordinates of the X ray on the imaging surface; and correcting the gravity center coordinates of the diffraction ring of the measuring object to calculate residual stress of the measuring object.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an X-ray diffraction measurement device that emits X-rays toward a measurement object to calculate residual stress in the measurement object, and a residual stress calculation method using the X-ray diffraction measurement device. [Background technology]

[0002] Conventionally, there has been known an X-ray diffraction measurement device that irradiates an object to be measured with X-rays at a predetermined angle of incidence, causes the X-rays diffracted by the object to form an X-ray diffraction ring (hereinafter referred to as a diffraction ring) on ​​the imaging surface, detects the shape of the formed diffraction ring, and performs analysis using the cos α method to measure the residual stress of the object to be measured.

[0003] This type of X-ray diffraction measurement device uses an imaging plate as the imaging surface, irradiates the object to be measured with X-rays to image a diffraction ring on the imaging plate, and then irradiates the imaging plate with a laser beam while scanning it, detecting the emission intensity along with the scanning position, thereby detecting the shape of the imaged diffraction ring.

[0004] For example, the diffraction ring forming device disclosed in Patent Document 1 includes a case incorporating an X-ray emitter for irradiating an object to be measured with X-rays and an imaging plate for recording the diffraction ring. The case has plane walls that are perpendicular to each other, parallel plane walls that intersect with the plane walls at an angle of approximately 45 degrees, and a plane wall that is perpendicular to the plane wall. The X-ray emitters are arranged in the case so that the optical axes of the X-rays emitted from the X-ray emitters are included in planes that are perpendicular to the plane walls, are parallel to the plane walls, and are located near the intersection lines formed by extending the plane walls, at a predetermined angle relative to the plane walls.

[0005] In addition, the X-ray diffraction device of Patent Document 2 is installed on the rail by attaching the mounting unit to the rail, and the X-ray incidence angle ψ0 is set to a single incidence angle. The X-ray diffraction device is stopped at any measurement point on the rail, and X-rays generated by the X-ray generator are irradiated from the X-ray irradiation unit to the X-ray irradiation point on the top surface. As a result, diffracted X-rays from the rail are incident on the imaging plate, and an entire image of the diffraction ring is captured and recorded by the imaging plate. When the imaging plate is then removed from the X-ray diffraction device and attached to a reading device, image information of the diffraction ring is read from the imaging plate. An evaluation device analyzes this image information of the diffraction ring to evaluate the residual stress of the rail 1. Patent Document 2 also explains an example of measuring stress in railway rails using the cos α method. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2014 / 128874 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-241308 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the diffraction ring forming device of Patent Document 1 and the X-ray diffraction device of Patent Document 2, the X-ray emission angle is precisely adjusted and controlled in advance inside the device, including by modifying the case, etc., so there is no uncertainty in the X-ray emission angle and no errors occur in residual stress, etc. However, if the X-ray emitter is detachable, it is difficult to precisely adjust and control the X-ray emission angle, and the uncertainty in the X-ray emission angle may result in errors in residual stress, etc.

[0008] The present invention has been made in consideration of the above circumstances, and aims to provide an X-ray diffraction measurement device and a residual stress calculation method using an X-ray diffraction measurement device that can correctly calculate the residual stress of a measurement object OB even when the imaging surface and the X-ray are not perpendicular to each other. [Means for solving the problem]

[0009] The X-ray diffraction measurement device according to claim 1 comprises a correction calculation means for calculating information on the positional relationship between the optical axis of the X-rays and the imaging surface to be used in the residual stress calculation means, wherein the diffraction ring formation detection means detects a first diffraction ring of a first sample whose diffraction angle is known in advance, and detects a second diffraction ring of a second sample whose diffraction angle is known in advance and whose diffraction angle is different from that of the first sample, and the correction calculation means calculates the coordinates of the center of gravity of the first diffraction ring and the coordinates of the center of gravity of the second diffraction ring, and the correction calculation means calculates the coordinates of the center of gravity of the diffraction ring of the first sample. The apparatus comprises an X-ray optical axis tilt calculation means for calculating the X-ray optical axis tilt, which is the tilt of the X-ray optical axis with respect to the imaging surface, from the position coordinates and the coordinates of the center of gravity of the diffraction ring of the second sample, and an X-ray emission point coordinate calculation means for calculating the coordinates of the X-ray emission point on the imaging surface when the distance from the imaging surface to the first sample and the second sample is set to zero, and is characterized in that the residual stress calculation means corrects the coordinates of the center of gravity of the diffraction ring of the measurement object detected by the diffraction ring formation detection means using the X-ray optical axis tilt calculated by the correction calculation means and the coordinates of the X-ray emission point on the imaging surface, thereby calculating the residual stress of the measurement object.

[0010] The X-ray diffraction measurement device according to claim 2 has the same features as claim 1, and is characterized in that the residual stress calculation means determines the provisional centroid coordinates and average radius of the diffraction ring of the object to be measured detected by the diffraction ring formation detection means, determines the deviation of the provisional centroid coordinates from the centroid coordinates in the case where there is no tilt of the X-ray optical axis using a known diffraction angle in the case where there is no residual stress in the object to be measured, calculates the corrected centroid coordinates by adding the centroid coordinate deviation to the coordinates of the X-ray emission point, resets the corrected centroid coordinates as the origin to determine the corrected diffraction angle for the entire circumference of the diffraction ring, and calculates the residual stress of the object to be measured from the corrected diffraction angle.

[0011] The X-ray diffraction measurement device according to claim 3 has the same configuration as claim 1 or 2, and is characterized in that the residual stress calculation means calculates the residual stress using the cos α method.

[0012] The residual stress calculation method for an X-ray diffraction measurement device according to claim 4 includes detecting a first diffraction ring of a first sample whose diffraction angle is known in advance, and detecting a second diffraction ring of a second sample whose diffraction angle is known in advance and different from that of the first sample, calculating the coordinates of the center of gravity of the first diffraction ring and the coordinates of the center of gravity of the second diffraction ring, calculating the tilt of the X-ray optical axis, which is the tilt of the X-ray optical axis with respect to the imaging plane, from the coordinates of the center of gravity of the diffraction ring of the first sample and the coordinates of the center of gravity of the diffraction ring of the second sample, calculating the coordinates of the X-ray exit point on the imaging plane when the distance from the imaging plane to the first sample and the distance from the second sample to the imaging plane are set to zero, detecting the diffraction ring of the measurement object using the calculated tilt of the X-ray optical axis and the coordinates of the X-ray exit point on the imaging plane, and correcting the coordinates of the center of gravity of the detected diffraction ring of the measurement object to calculate the residual stress of the measurement object.

[0013] The residual stress calculation method for an X-ray diffraction measurement device according to claim 5 has the same features as claim 4, and is characterized in that it determines the provisional centroid coordinates and average radius of the diffraction ring of the detected object to be measured, determines the deviation of the provisional centroid coordinates from the centroid coordinates in the case where there is no tilt of the X-ray optical axis using a known diffraction angle in the case where there is no residual stress in the object to be measured, calculates the corrected centroid coordinates by adding the deviation of the centroid coordinates to the coordinates of the X-ray emission point, resets the corrected centroid coordinates as the origin to determine the corrected diffraction angle for the entire circumference of the diffraction ring, and calculates the residual stress of the object to be measured from the corrected diffraction angle.

[0014] A method for calculating residual stress in an X-ray diffraction measurement device according to claim 6 is characterized in that, in addition to the features of claim 4 or 5, the residual stress is calculated using the cos α method. [Effects of the Invention]

[0015] According to the present invention, even when the imaging surface and the X-ray are not perpendicular to each other, the residual stress of the measurement object OB can be calculated correctly. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is an explanatory diagram showing an example of an X-ray diffraction measurement device according to the present invention. [Figure 2]FIG. 2 is an explanatory diagram showing the configuration of an X-ray diffraction measurement unit of the X-ray diffraction measurement device. [Figure 3] FIG. 2 is an explanatory diagram showing the configuration of an X-ray diffraction measurement unit of the X-ray diffraction measurement device. [Figure 4] FIG. 2 is an explanatory diagram showing the positional relationship of an imaging plate (IP) in the X-ray diffraction measurement device. [Figure 5] FIG. 2 is an explanatory diagram showing the deviation of the center of gravity of the diffraction ring of the X-ray diffraction measurement device. [Figure 6] FIG. 2 is an explanatory diagram showing the correction process of the X-ray diffraction measurement device. [Figure 7] FIG. 2 is an explanatory diagram showing details of the correction process of the X-ray diffraction measurement device. [Figure 8] FIG. 2 is an explanatory diagram showing details of the correction process of the X-ray diffraction measurement device. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Fig. 1 is an explanatory diagram showing an example of an X-ray diffraction measurement device according to the present invention. Fig. 2 is an explanatory diagram showing the configuration of the X-ray diffraction measurement unit of the same X-ray diffraction measurement device. Fig. 3 is an explanatory diagram showing the configuration of the X-ray diffraction measurement unit of the same X-ray diffraction measurement device. Fig. 4 is an explanatory diagram showing the positional relationship of the imaging plate (IP) of the same X-ray diffraction measurement device. Fig. 5 is an explanatory diagram showing the deviation of the center of gravity of the diffraction ring of the same X-ray diffraction measurement device. Fig. 6 is an explanatory diagram showing the correction process of the same X-ray diffraction measurement device. Figs. 7 and 8 are explanatory diagrams showing the details of the correction process of the same X-ray diffraction measurement device.

[0018] The X-ray diffraction measurement apparatus 1 according to the present invention emits X-rays toward a target object OB to calculate the residual stress of the target object OB. The X-ray diffraction measurement apparatus 1 includes an X-ray emitter 20 that emits X-rays toward the target object OB, a diffraction ring formation detection means that irradiates the target object OB with X-rays from the X-ray emitter 20, receives the diffracted X-ray light generated by the target object OB on an imaging plane that intersects with the optical axis of the X-rays emitted from the X-ray emitter 20, forms a diffraction ring, which is an image of the diffracted X-ray light, on the imaging plane, and detects the diffraction ring, and a residual stress calculation means that calculates the residual stress of the target object OB using data on the diffraction ring detected by the diffraction ring formation detection means.

[0019] The configuration of an X-ray diffraction measurement apparatus 1 including a diffraction ring forming device 10 will be described with reference to FIGS. 1 to 3. In order to measure the residual stress of a measurement object OB, this X-ray diffraction measurement apparatus 1 irradiates the measurement object OB with X-rays and detects the shape of a diffraction ring formed by diffracted X-rays emitted from the measurement object OB by the irradiation of the X-rays. In this embodiment, the measurement object OB is a metal member. The physical configuration shown in FIGS. 1 to 3 is an example.

[0020] The X-ray diffraction measurement apparatus 1 is composed of a diffraction ring forming device 10 and other components. The diffraction ring forming device 10 is provided, within a housing 12, with an X-ray emitter 20 that emits X-rays, a table 52 for mounting an imaging plate 50 on which a diffraction ring is formed by diffracted X-rays, a table drive mechanism 30 that rotates and moves the table 52, a laser detection device 70 for measuring the shape of the diffraction ring formed on the imaging plate (IP) 50, the X-ray emitter 20, the imaging plate 50, the table 52, the table drive mechanism 30, and the laser detection device 70. The X-ray diffraction measurement apparatus 1 also includes a computer device 100 and a high-voltage power supply 110.

[0021] The diffraction ring forming device 10 also contains various circuits connected to the X-ray emitter 20, table 52, table drive mechanism 30, and laser detection device 70 to control their operation and input detection signals, and the various circuits shown outside the diffraction ring forming device 10 (housing 12) in Fig. 1 are contained within the two-dot chain line inside the diffraction ring forming device 10. Note that circuit boards, electric wires, fixtures, cooling fans, etc. are omitted from Figs. 1 to 3.

[0022] 1, the housing 12 of the diffraction ring forming device 10 has a rectangular parallelepiped shape with a sloped bottom surface to eliminate corners and a stepped bottom structure. Specifically, the housing 12 has a first bottom wall 12a, a second bottom wall 12c, a front wall 12b, a rear wall 12e, a top wall 12f, side walls (not shown), a sloped bottom wall 12g connecting the first bottom wall 12a and the second bottom wall 12c, and a connecting wall 12d provided to eliminate corners where the second bottom wall 12c and the front wall 12b intersect. The second bottom wall 12c has a circular hole 12c1 through which X-rays emitted from the X-ray emitter 20 and diffracted X-rays generated by the measurement object OB pass.

[0023] 1, the X-ray emitter 20 is formed in an elongated shape, extends in the left-right direction in the figure at an upper part inside the housing 12, and is fixed to the housing 12. It receives a high voltage supply from a high-voltage power supply 110 and is controlled by an X-ray control circuit 200 to emit X-rays downward (toward the lower left in the figure) from an exit port 22. The direction of the exit port 22 is such that the optical axis of the emitted X-rays is approximately perpendicular to the second bottom wall 12c. When the surface of the measurement object OB and the connecting wall 12d are parallel, the angle of incidence of the X-rays with respect to the surface of the measurement object OB is approximately 45 degrees.

[0024] The X-ray control circuit 200 is controlled by a controller 102 constituting a computer device 100 (described later), and controls the drive current and drive voltage supplied from the high-voltage power supply 110 to the X-ray emitter 20 so that the X-ray emitter 20 emits X-rays of a constant intensity. The X-ray emitter 20 also includes a cooling device (not shown), and the X-ray control circuit 200 also controls the drive signal supplied to this cooling device. This keeps the temperature of the X-ray emitter 20 constant.

[0025] As shown in FIGS. 1 to 3 , the table drive mechanism 30 includes a moving stage 32 below the X-ray emitter 20. The moving stage 32 is movable by a feed motor 34 and a screw rod 36 in a direction perpendicular to the optical axis of the X-rays within a plane formed by the optical axis of the X-rays emitted from the X-ray emitter 20 and a normal to the measurement object OB. The feed motor 34 is fixed within the table drive mechanism 30 and is immovable relative to the housing 12. The screw rod 36 extends in a direction perpendicular to the optical axis of the X-rays emitted from the X-ray emitter 20, and one end of the screw rod 36 is connected to the output shaft of the feed motor 34. The other end of the screw rod 36 is rotatably supported by a bearing 38 provided within the table drive mechanism 30.

[0026] The moving stage 32 is sandwiched between a pair of opposing plate-like guides 40, 40 fixed within the table drive mechanism 30, and is movable along the axial direction of the screw rod 36. That is, when the feed motor 34 is driven forward or reverse, the rotational motion of the feed motor 34 is converted into linear motion of the moving stage 32. An encoder 34a is incorporated within the feed motor 34. The encoder 34a outputs a pulse train signal that alternates between high and low levels to the position detection circuit 202 and the feed motor control circuit 204 each time the feed motor 34 rotates by a predetermined small rotation angle.

[0027] The position detection circuit 202 and the feed motor control circuit 204 start operating in response to a command from the controller 102. Immediately after the start of measurement, the feed motor control circuit 204 drives the feed motor 34 to move the moving stage 32 toward the feed motor 34. When the pulse train signal output from the encoder 34a is no longer input to the position detection circuit 202, the position detection circuit 202 outputs a signal indicating that the moving stage 32 has reached the movement limit position to the feed motor control circuit 204 and sets the count value to "0." When the feed motor control circuit 204 receives a signal from the position detection circuit 202 indicating that the movement limit position has been reached, it stops outputting the drive signal to the feed motor 34. The movement limit position is set as the origin position of the moving stage 32. Therefore, when the moving stage 32 moves in the upper left direction in FIG. 1 and reaches the movement limit position, the position detection circuit 202 outputs a position signal representing "0", and when the moving stage 32 moves in the lower right direction from the movement limit position, the position detection circuit 202 counts the pulse train signal from the encoder 34a and outputs a signal representing the movement distance x from the movement limit position as a position signal.

[0028] When a set value indicating the destination position of the moving stage 32 is input from the controller 102 to the feed motor control circuit 204, the feed motor 34 is driven to rotate forward or reverse in accordance with the set value. The position detection circuit 202 counts the number of pulses in the pulse signal output by the encoder 34a. The position detection circuit 202 then uses the counted number of pulses to calculate the current position of the moving stage 32 (movement distance x from the movement limit position) and outputs this to the controller 102 and the feed motor control circuit 204. The feed motor control circuit 204 drives the feed motor 34 until the current position of the moving stage 32 input from the position detection circuit 202 matches the destination position input from the controller 102.

[0029] The feed motor control circuit 204 also receives a set value representing the movement speed of the moving stage 32 from the controller 102. The feed motor control circuit 204 then calculates the movement speed of the moving stage 32 using the number of pulses per unit time of the pulse signal received from the encoder 34a, and drives the feed motor 34 so that the calculated movement speed of the moving stage 32 becomes the movement speed received from the controller 102.

[0030] The upper ends of the pair of guides 40, 40 are connected by a plate-shaped upper wall 42. As shown in Fig. 3, the upper wall 42 has a through-hole 42a formed therein, and the center position of the through-hole 42a faces the center position of the emission port 22 of the X-ray emitter 20. The X-rays emitted from the X-ray emitter 20 enter the table drive mechanism 30 through the emission port 22 and the through-hole 42a.

[0031] When an imaging plate 50 (described later) is in the diffraction ring imaging position (the state shown in FIGS. 1 to 3), a through-hole 32a is formed in the moving stage 32 at a position opposite the through-hole 42a. A spindle motor 44 is attached to the moving stage 32 and has an output shaft 44a whose center of rotation is the central axis of the exit port 22 and the through-holes 42a, 32a. The output shaft 44a is cylindrical and has a through-hole 44a1 with a circular cross section and whose central axis is the center of rotation. A through-hole 44b is provided on the opposite side of the output shaft 44a of the spindle motor 44 and whose central axis is the center of the through-hole 44a1. A cylindrical passage member 46 is fixed to the inner circumferential surface of the through-hole 44b to reduce the inner diameter of a portion of the through-hole 44b.

[0032] An encoder 44c similar to the encoder 34a is also incorporated within the spindle motor 44. The encoder 44c outputs a pulse train signal that alternates between high and low levels each time the spindle motor 44 rotates by a predetermined small rotation angle to the spindle motor control circuit 206 and the rotation angle detection circuit 208. Furthermore, the encoder 44c outputs an index signal that switches from low to high for a predetermined short period each time the spindle motor 44 rotates once to the controller 102 and the rotation angle detection circuit 208.

[0033] The spindle motor control circuit 206 and the rotation angle detection circuit 208 begin operation in response to a command from the controller 102. The spindle motor control circuit 206 receives a set value representing the rotation speed of the spindle motor 44 from the controller 102. The spindle motor control circuit 206 then calculates the rotation speed of the spindle motor 44 using the number of pulses per unit time of the pulse signal received from the encoder 44c, and supplies a drive signal to the spindle motor 44 so that the calculated rotation speed becomes the rotation speed (set value) received from the controller 102. The rotation angle detection circuit 208 counts the number of pulses in the pulse train signal received from the encoder 44c, and uses the count value to calculate the rotation angle of the spindle motor 44, i.e., the rotation angle θp of the imaging plate 50, and outputs the calculated value to the controller 102. When the rotation angle detection circuit 208 receives an index signal received from the encoder 44c, it sets the count value to "0." That is, the position where the index signal is received is the reference position where the rotation angle is 0 degrees.

[0034] The table 52 is formed in a circular shape and is fixed to the tip of the output shaft 44a of the spindle motor 44. The central axis of the table 52 and the central axis of the output shaft 44a of the spindle motor 44 coincide with each other. The table 52 has an integral protrusion 54 that protrudes downward from the center of the bottom surface, and a screw thread is formed on the outer circumferential surface of the protrusion 54. The central axis of the protrusion 54 coincides with the central axis of the output shaft 44a of the spindle motor 44. An imaging plate 50 is attached to the bottom surface of the table 52.

[0035] The imaging plate 50 is a circular plastic film with a surface coated with a phosphor. The lower surface of the imaging plate 50 (the surface facing the measurement object OB) serves as the imaging surface on which the diffraction ring is formed. A through-hole 50a is provided in the center of the imaging plate 50. A protrusion 54 is passed through this through-hole 50a, and a nut-shaped fixture 56 is screwed onto the outer circumferential surface of the protrusion 54, thereby sandwiching and fixing the imaging plate 50 between the fixture 56 and the table 52. The fixture 56 is a cylindrical member, and its inner circumferential surface is formed with threads that correspond to the threads of the protrusion 54.

[0036] Through holes 52a, 54a, 56a are also provided in the table 52, the protrusion 54, and the fixture 56, respectively, and the central axes of the through holes 52a, 54a, 56a are the same as the central axis of the table 52, and the inner diameter of the through hole 56a is smaller than those of the through holes 52a, 54a, and is the same as the inner diameter of the aforementioned passage member 46. Therefore, the X-rays emitted from the output shaft 44a of the spindle motor 44 are emitted through the through holes 52a, 54a, 56a and also through the circular hole 12c1 provided in the second bottom wall 12c toward the measurement object OB located externally below. In this case, since the inner diameter of the passage member 46 and the inner diameter of the through-hole 56a are small, the X-rays that enter the through-holes 44b, 44a1, 52a, and 54a through the passage member 46 are slightly diffused, but the X-rays that exit the through-hole 56a become parallel rays parallel to the axis of the through-hole 44a1 and are emitted from the circular hole 12c1.

[0037] The imaging plate 50 is driven by the feed motor 34 to move together with the movable stage 32, spindle motor 44, and table 52 from the origin position to a diffraction ring imaging position where an image of the diffraction ring is captured. As described above, at this diffraction ring imaging position, the X-rays emitted from the X-ray emitter 20 are irradiated onto the measurement object OB on the table TB. The imaging plate 50 is also driven by the spindle motor 44 to rotate, while also moving together with the movable stage 32, spindle motor 44, and table 52, through a diffraction ring reading area where the captured diffraction ring is read and a diffraction ring erasure area where the diffraction ring is erased. Note that during this movement of the imaging plate 50, the central axis of the imaging plate 50 moves in a direction perpendicular to the optical axis of the X-rays, while being maintained within a plane defined by the optical axis of the X-rays emitted from the X-ray emitter 20 and the normal to the measurement object OB.

[0038] The laser detection device 70 irradiates the imaging plate 50, which has captured the image of the diffraction ring, with laser light and detects the intensity of the light incident from the imaging plate 50. The laser detection device 70 is located sufficiently farther toward the feed motor 34 from the measurement object OB and the imaging plate 50, which is located at the diffraction ring imaging position. In other words, when the imaging plate 50 is located at the diffraction ring imaging position, the X-rays diffracted by the measurement object OB are not blocked by the laser detection device 70. The laser detection device 70 includes a laser light source 72, a collimating lens 74, a reflecting mirror 76, a polarizing beam splitter 78, a quarter-wave plate 80, and an objective lens 82.

[0039] The laser light source 72 is controlled by a laser drive circuit 210 to emit laser light that is irradiated onto the imaging plate 50. The laser drive circuit 210 is controlled by the controller 102 to control and supply a drive signal so that laser light of a predetermined intensity is emitted from the laser light source 72. The laser drive circuit 210 receives a light-receiving signal output from a photodetector 94 (described later) and controls the drive signal output to the laser light source 72 so that the intensity of the light-receiving signal becomes a predetermined intensity. This maintains a constant intensity of the laser light irradiated onto the imaging plate 50.

[0040] The collimating lens 74 converts the laser light emitted from the laser light source 72 into parallel light. The reflecting mirror 76 reflects the laser light converted into parallel light by the collimating lens 74 toward the polarizing beam splitter 78. The polarizing beam splitter 78 transmits most (e.g., 95%) of the laser light incident from the reflecting mirror 76 as is. The quarter-wave plate 80 converts the laser light incident from the polarizing beam splitter 78 from linearly polarized light to circularly polarized light. The objective lens 82 focuses the laser light incident from the quarter-wave plate 80 on the surface of the imaging plate 50. The optical axis of the laser light emitted from this objective lens 82 is in a plane formed by the optical axis of the X-rays emitted from the X-ray emitter 20 and the normal to the measurement object OB, and is parallel to the optical axis of the X-rays, i.e., perpendicular to the movement direction of the moving stage 32.

[0041] A focus actuator 84 is attached to the objective lens 82. The focus actuator 84 is an actuator that moves the objective lens 82 in the optical axis direction of the laser light. When the focus actuator 84 is not energized, the objective lens 82 is located at the center of its movable range.

[0042] When the laser light focused by the objective lens 82 is irradiated onto the portion of the surface of the imaging plate 50 where the diffraction ring is imaged, the photo-stimulated luminescence phenomenon occurs. That is, when the imaging plate 50 is irradiated with laser light after the diffraction ring is imaged, the phosphor of the imaging plate 50 emits light corresponding to the intensity of the diffracted X-rays and having a wavelength shorter than that of the laser light. The reflected light of the laser light irradiated onto and reflected from the imaging plate 50 and the light emitted from the phosphor pass through the objective lens 82 and the quarter-wave plate 80 and are reflected by the polarizing beam splitter 78.

[0043] A condenser lens 86, a cylindrical lens 88, and a photodetector 90 are provided in the reflection direction of the polarizing beam splitter 78. The condenser lens 86 condenses the light incident from the polarizing beam splitter 78 onto the cylindrical lens 88. The cylindrical lens 88 generates astigmatism in the transmitted light. The photodetector 90 is composed of a quadrant light-receiving element consisting of four identical square light-receiving elements separated by dividing lines, and outputs detection signals of magnitudes proportional to the intensity of light incident on the four light-receiving regions arranged clockwise as four light-receiving signals to the amplifier circuit 212.

[0044] The amplifier circuit 212 amplifies the four light receiving signals output from the photodetector 90 by the same amplification factor to generate four light receiving signals, which are then output to the focus error signal generation circuit 214 and the SUM signal generation circuit 216. In this embodiment, focus servo control using the astigmatism method is used. The focus error signal generation circuit 214 generates a focus error signal by calculation using the amplified four light receiving signals. That is, the focus error signal generation circuit 214 performs a predetermined calculation and outputs the result of this calculation to the focus servo circuit 218 as a focus error signal. The focus error signal represents the amount of deviation of the focal position of the laser light from the surface of the imaging plate 50.

[0045] The focus servo circuit 218 is controlled by the controller 102, and generates a focus servo signal based on the focus error signal and outputs it to the drive circuit 220. The drive circuit 220 drives the focus actuator 84 in response to this focus servo signal to displace the objective lens 82 in the optical axis direction of the laser light. In this case, by generating a focus servo signal so that the value of the focus error signal is always a constant value (for example, zero), it is possible to continuously focus the laser light on the surface of the imaging plate 50.

[0046] The SUM signal generating circuit 216 adds up the four amplified light receiving signals to generate a SUM signal, which is output to the A / D conversion circuit 222. The intensity of the SUM signal corresponds to the combined intensity of the laser light reflected by the imaging plate 50 and the intensity of the light generated by photostimulated luminescence, but because the intensity of the laser light reflected by the imaging plate 50 is approximately constant, the intensity of the SUM signal corresponds to the intensity of the light generated by photostimulated luminescence. In other words, the intensity of the SUM signal corresponds to the intensity of the diffracted X-rays incident on the imaging plate 50. The A / D conversion circuit 222 is controlled by the controller 102, receives the SUM signal from the SUM signal generating circuit 216, converts the instantaneous value of the received SUM signal into digital data, and outputs the digital data to the controller 102.

[0047] The laser detection device 70 also includes a condenser lens 92 and a photodetector 94. The condenser lens 92 condenses a portion of the laser light emitted from the laser light source 72, which is reflected without passing through the polarizing beam splitter 78, onto the light-receiving surface of the photodetector 94. The photodetector 94 is a light-receiving element that outputs a light-receiving signal corresponding to the intensity of the light condensed on its light-receiving surface. Therefore, the photodetector 94 outputs a light-receiving signal corresponding to the intensity of the laser light emitted by the laser light source 72 to the laser drive circuit 210.

[0048] An LED light source 96 is provided adjacent to the objective lens 82. The LED light source 96 is controlled by an LED drive circuit 224 to emit visible light and eliminate the diffraction rings imaged on the imaging plate 50. The LED drive circuit 224 is controlled by the controller 102 to supply a drive signal to the LED light source 96 to generate visible light of a predetermined intensity.

[0049] 2 and 3, the diffraction ring forming device 10 also has an LED light source 60. The LED light source 60 is fixed to the underside of one end of a plate 62 arranged between the X-ray emitter 20 and the upper wall 42 of the table drive mechanism 30. The upper surface of the other end of the plate 62 is fixed to an output shaft 64a of a motor 64 fixed inside the housing 12. Rotation of the motor 64 causes the plate 62 to rotate in a plane parallel to the upper wall 42 of the table drive mechanism 30. Stopper members 68a and 68b are provided on the upper wall 42 of the table drive mechanism 30. The stopper member 68a restricts the rotation of the plate 62 so that, when the plate 62 is rotated, the LED light source 60 comes to rest at a position (position P) facing the exit port 22 of the X-ray emitter 20 and the through-hole 42a in the upper wall 42 of the table drive mechanism 30.

[0050] On the other hand, the stopper member 68b restricts the rotation of the plate 62 so that when the plate 62 is rotated, the plate 62 comes to rest at a position (position S) where the plate 62 does not block the passage between the emission port 22 of the X-ray emitter 20 and the through-hole 42a of the upper wall 42 of the table drive mechanism 30. In other words, the position P is a position where the plate 62 is in the state shown in FIGS. 1 to 3 , and is a position where the LED light emitted from the LED light source 60 enters the passage of the passage member 46 provided in the through-hole 44a1 of the spindle motor 44. The position S is a position where the X-rays emitted from the X-ray emitter 20 are not blocked by the plate 62.

[0051] The LED light source 60 emits LED light in response to a drive signal from an LED drive circuit 226 whose operation is controlled by the controller 102. The LED light is diffused visible light, and when the plate 62 is in position P, a portion of the LED light passes through through holes 42a, 32a, the passage of the passage member 46, and through hole 44b, enters through hole 44a1 of the output shaft 44a of the spindle motor 44, and is then emitted from through holes 52a, 54a, 56a and the circular hole 12c1 of the second bottom wall 12c. In the case of this LED light, the inner diameters of the passage member 46 and the through hole 56a are small, so that the X-rays that enter through holes 44b, 44a1, 52a, 54a through the passage member 46 are somewhat diffused, but the LED light emitted from through hole 56a becomes parallel light parallel to the axis of through hole 44a1 and is emitted from circular hole 12c1. Therefore, the LED light source 60, the passage member 46, the through-hole 56a, etc. constitute a visible light emitter of the present invention that emits collimated visible light to the measurement object OB.

[0052] The motor 64 is equipped with an encoder 64b similar to the encoders 34a and 44c, and the encoder 64b outputs a pulse train signal that alternates between high and low levels to the rotation control circuit 228 each time the motor 64 rotates a predetermined small rotation angle. When a rotation direction and rotation start instruction is input from the controller 102, the rotation control circuit 228 outputs a drive signal to the motor 64 to rotate the motor 64 in the instructed direction. When the input of the pulse train signal from the encoder 64b stops, the output of the drive signal stops. This allows the plate 62 to rotate to the above-mentioned P position and S position, respectively.

[0053] An imaging lens 24 is provided on the bottom inclined wall 12g of the housing 12, and an imager 26 is provided inside the housing 12. The imager 26 is composed of a CCD light receiver or a CMOS light receiver in which a large number of image sensors are arranged in a matrix, and outputs a light reception signal (image signal) of a magnitude corresponding to the intensity of light received by each image sensor to a sensor signal extraction circuit 230. The imaging lens 24 and the imager 26 capture an image of an area centered on the emission point of the LED light on the measurement object OB, which is located at a set position relative to the imaging plate 50.

[0054] That is, the imaging lens 24 and the imager 26 function as a digital camera that captures an image of the measurement object OB. The position set with respect to the imaging plate 50 is a position where the vertical distance L from the emission point (irradiation point) of the X-rays and LED light on the measurement object OB to the imaging plate 50 is a predetermined distance Lo. In this case, the depth of field of the imaging lens 24 and the imager 26 is set to a range before and after the emission point. The sensor signal extraction circuit 230 outputs a light receiving signal (image capturing signal) from each image capturing element of the imager 26 to the controller 102 together with data indicating the position (i.e., pixel position) of each image capturing element. Therefore, image data representing an image of the vicinity of the irradiation point, including the irradiation point of the LED light on the measurement object OB, is output to the controller 102.

[0055] The computer system 100 comprises a controller 102, an input device 104, and a display device 106. The controller 102 is an electronic control device whose main component is a microcomputer equipped with a CPU, ROM, RAM, a large-capacity storage device, etc., and controls the operation of the X-ray diffraction measurement system 1 by executing various programs stored in the large-capacity storage device. The controller 102 also implements the diffraction ring formation detection means, residual stress calculation means, correction calculation means, sample diffraction ring center of gravity position coordinate calculation means, X-ray optical axis tilt calculation means, and X-ray emission point coordinate calculation means, which will be described later. The input device 104 is connected to the controller 102 and is used by an operator to input various parameters, work instructions, etc. The display device 106 displays on its display screen an image including the irradiation point captured by the imager 26, as well as marks for properly setting the position and orientation of the housing 12 relative to the measurement object OB. Furthermore, the display device 106 visually informs the operator of various setting conditions, operating conditions, measurement results, etc. The high-voltage power supply 110 supplies the X-ray emitter 20 with a high voltage and current for emitting X-rays.

[0056] When calculating residual stress in an object (OB) using the X-ray diffraction measurement system 1 configured as described above, the positional relationship between the imaging plate (IP) 50, which forms the imaging surface, and the X-rays significantly affects the resulting value. This is particularly important when using the socα method. When X-rays strike the object (OB), they are diffracted and reflected in a cone shape centered on the apparent X-ray axis (see Figure 4). If the object (OB) contains stress, the reflected cone appears to shift, making the positional relationship between the imaging plate (IP) 50 and the X-rays problematic. In conventional X-ray diffraction measurement systems, the optimal positional relationship between the imaging plate and the X-rays for residual stress calculation is established during the manufacturing, assembly, and initial adjustment stages of the X-ray diffraction measurement system, and this positional relationship is then strictly fixed to prevent errors in subsequent measurements.

[0057] Specifically, if the distance between the object to be measured OB and the imaging plate (IP) 50 (hereinafter referred to as the sample distance) is fixed, the imaging surface (IP) 50 and the X-rays do not necessarily need to be perpendicular. However, if they are not perpendicular, the positional relationship between the imaging plate (IP) 50 and the X-ray irradiation point changes, and the center of gravity of the diffraction ring changes. As shown in Figures 4 and 5, when considering two samples with different diffraction angles, namely, a first sample (sample A) and a second sample (sample B), the center of gravity (X0, Y0) of the diffraction ring A (RDA) of sample A and the center of gravity (XDB0, YDB0) of the diffraction ring B (RDB) of sample B are different from the center of gravity (X0, Y0) of the diffraction ring when the imaging plate (IP) 50 is ideally positioned (perpendicular to the X-rays). To prevent this misalignment of the centers of gravity of the diffraction rings, conventional X-ray diffraction measurement devices adjust the imaging plate (IP) 50 so that it is perpendicular to the X-rays. As will be described below, the present invention is intended to accurately calculate the residual stress of the object to be measured OB even when the imaging plate (IP) 50 and the X-ray are not perpendicular (the imaging surface is approximately perpendicular to the optical axis of the X-ray (although it is approximately perpendicular, it is not perpendicular in the calculation of residual stress, but is managed to be not perpendicular enough to allow for more accurate calculation of residual stress).

[0058] The present invention will now be described in detail. First, a specific method for determining the residual stress of an object to be measured OB by forming a diffraction ring and detecting its shape, which is a conventional basic means of an X-ray diffraction measurement apparatus 1, will be described. In measuring this residual stress, the X-ray diffraction measurement apparatus 1 is configured as shown in FIGS. 1 to 3, and operation of the X-ray diffraction measurement apparatus 1 is initiated by turning on the power. Then, the object to be measured OB is placed on a table TB, and the diffraction ring formation detection means and residual stress calculation means are put into operation.

[0059] The diffraction ring formation detection means operates the X-ray emitter 20 to irradiate the measurement object OB with X-rays, thereby recording the diffraction ring on the imaging plate 50, and operates the laser detection device 70 to read the diffraction ring recorded on the imaging plate 50. Here, the description will be given for the measurement object OB, but the same applies to samples A and B. Then, the LED light source 96 is operated to erase the diffraction ring recorded on the imaging plate 50, and the residual stress calculation means calculates the residual stress of the measurement object OB using data representing the read diffraction ring. Note that the residual stress calculation means of the present application uses the cos α method as a method for calculating the residual stress, but is not limited to the cos α method.

[0060] Below, we will explain corrections for correctly calculating the residual stress of the measurement object OB even when the imaging plate (IP) 50 of the present invention and the X-rays are not perpendicular to each other (see FIGS. 4 to 8 for the symbols in the following explanations and calculation formulas. Also, the symbols X, Y, x, and y indicate the dimensions of the X-axis and Y-axis, respectively). The X-ray diffraction measurement device 1 of the present application has a diffraction ring formation detection means and a residual stress calculation means that have the functions described below in addition to conventional functions, and also has a correction calculation means that calculates information on the positional relationship between the optical axis of the X-rays and the imaging plane (IP) to be used in the residual stress calculation means.

[0061] The functional configuration is such that the diffraction ring formation detection means detects diffraction ring A (RDA) (first diffraction ring) of sample A, which is a first sample whose diffraction angle is known in advance, and also detects diffraction ring B (RDB) (second diffraction ring) of sample B, which is a second sample whose diffraction angle is known in advance and is different from that of the first sample (note that RD represents the average radius of each diffraction ring). The correction calculation means also includes a sample diffraction ring center of gravity position coordinate calculation means for calculating the coordinates (XDA0, YDA0) of the center of gravity of the diffraction ring A and the coordinates (XDB0, YDB0) of the center of gravity of the diffraction ring B, an X-ray optical axis tilt calculation means for calculating the X-ray optical axis tilt (ρx, ρy), which is the tilt of the X-ray optical axis with respect to the imaging plane, from the coordinates (XDA0, YDA0) of the center of gravity of the diffraction ring A and the coordinates (XDB0, YDB0) of the center of gravity of the diffraction ring B, and an X-ray emission point coordinate calculation means for calculating the coordinates (X0, Y0) of the X-ray emission point on the imaging plane when the distances from the imaging plane (IP) to sample A and sample B are set to zero.

[0062] The residual stress calculation means then corrects the centroid coordinates of the diffraction ring of the object OB detected by the diffraction ring formation detection means using the X-ray optical axis tilt (ρx, ρy) calculated by the correction calculation means and the X-ray exit point coordinates (X0, Y0) on the imaging plane (IP) to calculate the residual stress of the object OB. Specifically, the residual stress calculation means calculates a provisional centroid coordinate and average radius RD of the diffraction ring of the object OB detected by the diffraction ring formation detection means, calculates a deviation between the provisional centroid coordinates and the centroid coordinate in the case where there is no X-ray optical axis tilt using a known diffraction angle in the case where there is no residual stress of the object OB, adds the centroid coordinate deviation to the X-ray exit point coordinates (X0, Y0) to calculate the corrected centroid coordinates (XD0, YD0), resets the corrected centroid coordinates (XD0, YD0) to the origin to calculate the corrected diffraction angle for the entire circumference of the diffraction ring, and calculates the residual stress of the object OB from the corrected diffraction angle.

[0063] The operation flow is as follows: first, diffraction ring A (RDA) of sample A is detected, and the second diffraction ring of sample B (RDB) is detected. Then, the coordinates of the center of gravity of diffraction ring A (XDA0, YDA0) and the coordinates of the center of gravity of diffraction ring B (XDB0, YDB0) are calculated. Next, the X-ray optical axis tilt (ρx, ρy), which is the tilt of the X-ray optical axis with respect to the imaging plane (IP), is calculated from the coordinates of the center of gravity of diffraction ring A (XDA0, YDA0) and the coordinates of the center of gravity of diffraction ring B (XDB0, YDB0) of sample B. Next, the coordinates (X0, Y0) of the X-ray emission point on the imaging plane (IP) are calculated when the distance from the imaging plane (IP) to sample A and sample B is set to zero. Then, the diffraction ring of the measurement object OB is detected using the calculated X-ray optical axis tilt (ρx, ρy) and the coordinates of the X-ray emission point on the imaging surface (X0, Y0), and the coordinates of the center of gravity of the detected diffraction ring of the measurement object OB are corrected to calculate the residual stress of the measurement object OB.

[0064] The specific process for correcting the centroid coordinates of the detected diffraction ring of the measured object OB and calculating the residual stress of the measured object OB is as follows: First, the provisional centroid coordinates and average radius RD of the detected diffraction ring of the measured object OB are determined. Then, using the known diffraction angle when the measured object OB has no residual stress, the deviation between the provisional centroid coordinates and the centroid coordinate when there is no tilt of the X-ray optical axis is determined. The centroid coordinate deviation is added to the X-ray emission point coordinates (X0, Y0) to obtain the corrected centroid coordinates (XD0, YD0). The corrected centroid coordinates (XD0, YD0) are then reset as the origin to obtain the corrected diffraction angle for the entire circumference of the diffraction ring, and the residual stress of the measured object OB is calculated from the corrected diffraction angle.

[0065] Next, the flow of operation will be explained using formulas. First, when considering the X-axis direction (similarly for the Y-axis direction), it is assumed that the actual imaging plane (IP) is tilted by ρx in the X-axis direction with respect to an ideal plane (with no tilt, i.e., an imaging plane when the imaging plane and the X-ray are perpendicular) (see FIG. 6). If the centers of gravity of diffraction rings A and B when converted to the ideal plane are XA0 and XB0, and the coordinate of the X-ray emission point is X0, the coordinate transformation formulas can be shown in FIGS. 7 and 8 and the following formulas. Now, when considering the transformation of the coordinate system to the ideal plane, the following formulas 1 and 2 and formula 3 for the X-coordinate of the center on the ideal plane can be established (note that P and M mean plus and minus, respectively, and plus indicates the right side in FIG. 6).

[0066]

number

[0067]

number

[0068]

number

[0069] Considering the X coordinate, if we let XA be the deviation of the center of diffraction ring A on the ideal surface when the imaging plane (IP) is tilted, and XB be the deviation of the center of diffraction ring B on the ideal surface when the imaging plane (IP) is tilted, then the measured XA0 and XB0 are the X-ray emission point + tilt deviation amount, and so we obtain the following equations 4 and 5, which lead to equation 6.

[0070]

number

[0071]

number

[0072]

number

[0073] XA0 can be calculated by substituting RP=RAP and RM=RAM from the conversion formula between the measured value and the ideal surface, and then we obtain equations 7, 8, and 9. Note that since diffraction ring B is the same as diffraction ring A, equation 10 can be derived.

[0074]

number

[0075]

number

[0076]

number

[0077]

number

[0078] Substituting numbers 9 and 10 into number 6 gives number 11, from which number 12 can be found.

[0079]

number

[0080]

number

[0081] Number 14 can be derived from number 13, which is obtained by substituting number 9 into number 4.

[0082]

number

[0083]

number

[0084] Substituting the number 10 into the number 5 also gives the number 15.

[0085]

number

[0086] From this series of equations, the coordinates (X0, Y0) of the X-ray emission point and the tilt of the X-ray optical axis (ρx, ρy) can be found.

[0087] The complement angle 2η of the diffraction angle of the object OB is known from its material, and the average radius RD of the diffraction rings of the object OB obtained by the diffraction ring formation detection means is determined. Note that the calculation of the average radius RD of each diffraction ring can be performed using any known method, and is not particularly limited. Then, the X-ray emission point coordinates (X0, Y0), the X-ray optical axis tilt (ρx, ρy), and Equation 13 are used to obtain Equations 16, 17, and similarly Equation 18, which determine the corrected center of gravity coordinates (XD0, YD0) of the object OB.

[0088]

number

[0089]

number

[0090]

number

[0091] Then, the residual stress calculation means determines the corrected diffraction angle for the entire circumference of the diffraction ring by resetting the corrected center of gravity coordinates (XD0, YD0) as the origin, and calculates the residual stress of the measurement object OB from the corrected diffraction angle.

[0092] According to the X-ray diffraction measurement apparatus 1 configured and operated as described above, even if the imaging plate (IP) 50, which is the imaging surface, and the X-rays are not perpendicular to each other, the residual stress of the measurement object OB can be calculated correctly.

[0093] The present invention allows various embodiments and modifications without departing from the broad spirit and scope of the present invention. Furthermore, the above-described embodiments are intended to explain the present invention and do not limit the scope of the present invention. That is, the scope of the present invention is defined by the claims, not the embodiments. Various modifications made within the scope of the claims and the meaning of the invention equivalent thereto are considered to be within the scope of the present invention. [Industrial Applicability]

[0094] As described above, according to the present invention, it is possible to provide an X-ray diffraction measurement device and a residual stress calculation method using an X-ray diffraction measurement device that can correctly calculate the residual stress of a measurement object OB even when the imaging surface and the X-ray are not perpendicular to each other. [Explanation of symbols]

[0095] 1. X-ray diffraction measurement device 10. Diffraction ring forming device 12. Enclosure 12a...1st bottom wall 12b...Front wall 12c...Second bottom wall 12c1 Circular hole 12d... Connecting wall 12e...Rear wall 12f...Top wall 12g...Bottom inclined wall 20...X-ray emitter 22......Outlet 24. Imaging lens 26. Imager 30 Table drive mechanism 32. Moving stage 32a...Through hole 34 Feed motor 34a Encoder 36 Screw rod 38...Bearing section 40 Guide 42 Upper wall 42a...Through hole 44 Spindle motor 44a Output shaft 44b...Through hole 44c encoder 44a1...Through hole 46 Passageway member 50 Imaging Plate 50a...Through hole 52 Table 52a...Through hole 54...Protrusion 54a...Through hole 56...Fixing fixture 56a...Through hole 60...LED light source 62 Plate 64 Motor 64a Output shaft 64b encoder 68a... Stopper member 68b Stopper member 70 Laser detection device 72 Laser light source 74 Collimating lens 76...Reflector 78 Polarizing Beam Splitter 80...1 / 4 wavelength plate 82 Objective lens 84 Focus actuator 86...Condenser lens 88 Cylindrical Lens 90 Photodetector 92...Condenser lens 94 Photodetector 96...LED light source 100. Computer equipment 102 Controller 104 Input device 106...Display device 110 High-voltage power supply 200 X-ray control circuit 202 Position detection circuit 204 Feed motor control circuit 206 Spindle motor control circuit 208 Rotation angle detection circuit 210 Laser driver circuit 212 Amplifier circuit 214...Focus error signal generating circuit 216...SUM signal generation circuit 218 Focus servo circuit 220 Drive circuit 222 A / D conversion circuit 224 LED drive circuit 226 LED drive circuit 228 Rotation control circuit 230 Sensor signal extraction circuit

Claims

1. an X-ray diffraction measurement apparatus comprising: an X-ray emitter that emits X-rays toward a measurement object to be measured; a diffraction ring formation detection means that irradiates the X-rays from the X-ray emitter toward the measurement object, receives diffracted light of the X-rays generated at the measurement object on an imaging plane that intersects approximately perpendicularly with an optical axis of the X-rays emitted from the X-ray emitter, forms a diffraction ring that is an image of the diffracted light of the X-rays on the imaging plane, and detects the diffraction ring; and a residual stress calculation means that calculates residual stress in the measurement object using data on the diffraction ring detected by the diffraction ring formation detection means, a correction calculation means for calculating information on the positional relationship between the optical axis of the X-ray and the imaging surface to be used in the residual stress calculation means; The diffraction ring formation detection means Detecting a first diffraction ring of a first sample having a known diffraction angle, and detecting a second diffraction ring of a second sample having a known diffraction angle that is different from that of the first sample; The correction calculation means a sample diffraction ring centroid position coordinate calculation means for calculating the centroid position coordinate of the first diffraction ring and the centroid position coordinate of the second diffraction ring; an X-ray optical axis tilt calculation means for calculating an X-ray optical axis tilt, which is the tilt of the optical axis of the X-ray with respect to the imaging plane, from the coordinates of the center of gravity of the diffraction ring of the first sample and the coordinates of the center of gravity of the diffraction ring of the second sample; an X-ray emission point coordinate calculation means for calculating the coordinates of the emission point of the X-ray on the imaging surface when the distance from the imaging surface to the first sample and the distance from the imaging surface to the second sample are set to zero; the residual stress calculation means corrects the coordinates of the center of gravity of the diffraction ring of the measurement object detected by the diffraction ring formation detection means using the tilt of the X-ray optical axis calculated by the correction calculation means and the coordinates of the exit point of the X-ray on the imaging surface, thereby calculating the residual stress of the measurement object.

2. The residual stress calculation means determining a provisional center of gravity coordinate and an average radius of the diffraction ring of the measurement object detected by the diffraction ring formation detection means; a deviation between the provisional centroid coordinates and the centroid coordinates in the case where there is no tilt of the X-ray optical axis is calculated using a known diffraction angle in the case where there is no residual stress of the measurement object; adding the deviation of the centroid coordinates to the coordinates of the exit point of the X-rays to obtain corrected centroid coordinates; 2. The X-ray diffraction measurement apparatus according to claim 1, wherein the corrected center of gravity coordinates are reset as the origin to determine a corrected diffraction angle for the entire circumference of the diffraction ring, and the residual stress of the measurement object is calculated from the corrected diffraction angle.

3. 3. The X-ray diffraction measurement apparatus according to claim 1, wherein the residual stress calculation means calculates the residual stress using a cos α method.

4. A residual stress calculation method for an X-ray diffraction measurement apparatus includes: irradiating an X-ray from an X-ray emitter that emits X-rays toward a target object to be measured, receiving diffracted light of the X-rays generated in the object on an imaging plane that intersects approximately perpendicularly with an optical axis of the X-rays emitted from the X-ray emitter, forming a diffraction ring that is an image of the diffracted light of the X-rays on the imaging plane, detecting the diffraction ring, and calculating residual stress of the object from data of the detected diffraction ring, Detecting a first diffraction ring of a first sample having a known diffraction angle, and detecting a second diffraction ring of a second sample having a known diffraction angle that is different from that of the first sample; determining a coordinate of a center of gravity of the first diffraction ring and a coordinate of a center of gravity of the second diffraction ring; determining an X-ray optical axis tilt, which is a tilt of the optical axis of the X-ray with respect to the imaging plane, from the coordinates of the center of gravity of the diffraction ring of the first sample and the coordinates of the center of gravity of the diffraction ring of the second sample; determining coordinates of the emission point of the X-ray on the imaging surface when the distances from the imaging surface to the first sample and the second sample are set to zero; Using the calculated tilt of the X-ray optical axis and the coordinates of the emission point of the X-ray on the imaging surface, A residual stress calculation method using an X-ray diffraction measurement device, characterized by detecting the diffraction ring of the measurement object, correcting the coordinates of the center of gravity of the detected diffraction ring of the measurement object, and calculating the residual stress of the measurement object.

5. determining a provisional center of gravity coordinate and an average radius of the diffraction ring of the detected measurement object; a deviation between the provisional centroid coordinates and the centroid coordinates in the case where there is no tilt of the X-ray optical axis is calculated using a known diffraction angle in the case where there is no residual stress of the measurement object; adding the deviation of the centroid coordinates to the coordinates of the exit point of the X-rays to obtain corrected centroid coordinates; 5. A residual stress calculation method using an X-ray diffraction measurement apparatus according to claim 4, wherein the corrected center of gravity coordinates are reset as the origin to determine a corrected diffraction angle for the entire circumference of the diffraction ring, and the residual stress of the measurement object is calculated from the corrected diffraction angle.

6. 6. The method for calculating residual stress using an X-ray diffraction measurement device according to claim 4, wherein the residual stress is calculated using a cos α method.

Images