Residual stress determination method

Abstract

The object of the present invention is to provide a residual stress measuring method capable of measuring the residual stress of a fillet portion with high accuracy. In the residual stress measuring method according to one embodiment of the present invention, when the incident angle of X-rays is Ψ[°], the fillet radius is R[mm], the fillet angle is θ[°], the upper and lower widths of the housing of the X-ray stress measuring device are W[mm], the width of the detection area of ​​the two-dimensional detector is D[mm], the complementary angle of the Bragg angle is η[°], and the interval between the flange portion and the virtual straight line passing through the center of the fillet and parallel to the flange portion is a[mm], the following formula 1 is satisfied, when Ψ≥0, the irradiation distance L[mm] of the X-rays in the calculation step based on the two-dimensional detector satisfies the following formula 2, and when Ψ<0, the irradiation distance L satisfies the following formula 3. The incident angle Ψ is positive when it is inclined toward the shaft portion side relative to the virtual straight line passing through the measurement portion and the center of the fillet, and is negative when it is inclined toward the flange portion side. D≤W···1

Description

Technical Field

[0001] The present invention relates to a residual stress measuring method. Background Art

[0002] In recent years, the technology of measuring residual stress using X-rays has become popular. This technology uses X-rays to measure the lattice strain generated inside a test object having a crystal structure and converts the measurement result into residual stress.

[0003] As a residual stress measurement method using X-rays, the cosα method is known. In the cosα method, the object to be inspected is irradiated with X-rays at a specific incident angle, the intensity of diffracted X-rays generated by the reflection of the X-rays on the object to be inspected is detected two-dimensionally, and the residual stress is measured based on the diffraction rings formed by the intensity distribution of the detected diffracted X-rays (refer to JP-A-5-72061).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 5-72061 Summary of the invention

[0007] Problems to be solved by the invention

[0008] When the incident angle of the X-ray is set to Ψ [°], the measurement accuracy of the cosα method is roughly proportional to sin2Ψ. Therefore, in the cosα method, the measurement accuracy decreases as the incident angle Ψ of the X-ray to the object to be inspected moves away from 45°. For example, if the incident angle Ψ of the X-ray becomes less than 15°, the measurement accuracy deteriorates sharply. In addition, as the incident angle Ψ of the X-ray increases, it becomes easily affected by the surface roughness of the object to be inspected. Therefore, in the cosα method, the incident angle Ψ of the X-ray to the object to be inspected is usually set to be greater than 15° and less than 65°, and is preferably set to 35°.

[0009] However, if the residual stress of the fillet portion of a structure having a cylindrical shaft portion and a flange portion (plate-shaped portion) protruding radially from the shaft portion, and a fillet portion for relieving stress concentration is to be measured, it is difficult to set the incident angle Ψ to the desired angle. That is, if the incident angle Ψ of the X-ray is set to be greater than 15° and less than 65°, the measuring device may interfere with the object to be inspected. In this case, in the past, the incident angle Ψ of the X-ray was set to an appropriate angle outside the desired range to measure the residual stress. However, according to this existing method, it is difficult to measure the residual stress of the object to be inspected with good accuracy.

[0010] The present invention has been made based on the above circumstances, and an object of the present invention is to provide a residual stress measuring method capable of measuring the residual stress of a fillet portion with high accuracy.

[0011] Means for solving problems

[0012] A residual stress measuring method according to one embodiment of the present invention proposed to solve the above-mentioned problems is a residual stress measuring method for a fillet portion of a metal structure, wherein the metal structure has a shaft portion and a flange portion protruding in a radial direction from the shaft portion, and the fillet portion is provided at a connection portion between the shaft portion and the flange portion, and the residual stress measuring method comprises the following steps: using an X-ray stress measuring device and calculating the residual stress by a cosα method, wherein the X-ray stress measuring device has an irradiation portion for irradiating X-rays, and a flange portion for detecting the residual stress of the fillet portion by the X-rays irradiated from the irradiation portion. A two-dimensional detector that produces diffraction rings due to lattice diffraction, and a housing equipped with the irradiation unit and the two-dimensional detector, when the incident angle of the X-ray is set to Ψ[°], the fillet radius of the fillet portion is set to R[mm], the fillet angle of the fillet portion is set to θ[°], the upper and lower widths of the housing are set to W[mm], the width of the detection area of ​​the two-dimensional detector is set to D[mm], the complementary angle of the Bragg angle is set to η[°], and the interval between an imaginary straight line passing through the center of the fillet and parallel to the flange portion and the flange portion is set to a[mm], the following formula 1 is satisfied.

[0013] [Mathematical formula 1]

[0014]

[0015] And, in In the case of Ψ<0, the irradiation distance L [mm] of the X-rays in the above calculation step based on the above two-dimensional detector satisfies the following formula 2. In the case of Ψ<0, the above irradiation distance L in the above calculation step satisfies the following formula 3:

[0016] [Mathematical formula 2]

[0017]

[0018] [Mathematical formula 3]

[0019]

[0020] The incident angle Ψ is positive when it is inclined toward the shaft portion with respect to a virtual straight line passing through the measurement location and the center of the fillet, and is negative when it is inclined toward the flange portion.

[0021] According to the residual stress measuring method, when measuring the residual stress of the fillet portion formed at the connection portion between the shaft portion and the flange portion, the incident angle Ψ of the X-ray can be made close to the desired angle. Therefore, according to the residual stress measuring method, the residual stress of the fillet portion can be measured with high accuracy.

[0022] It may be that, when the rounded corner portion has a plurality of regions with different diameters, the center of curvature and the radius of curvature of the region with the largest diameter among the plurality of regions are determined as the center of the rounded corner and the radius of the rounded corner. In this way, when the rounded corner portion has a plurality of regions with different diameters, by determining the center of curvature and the radius of curvature of the region with the largest diameter among the plurality of regions as the center of the rounded corner and the radius of the rounded corner, the residual stress of the rounded corner portion can be measured easily and with high accuracy.

[0023] It may be that, when the rounded corner portion has a plurality of regions with different diameters, the center of curvature and the radius of curvature of the region with the longest arc among the plurality of regions are determined as the center of the corner and the radius of the corner of the rounded corner portion. In this way, when the rounded corner portion has a plurality of regions with different diameters, by determining the center of curvature and the radius of curvature of the region with the longest arc among the plurality of regions as the center of the corner and the radius of the corner of the rounded corner portion, the residual stress of the rounded corner portion can be measured easily and with high accuracy.

[0024] The calculation step may include the step of adjusting the irradiation distance L so that the incident angle Ψ is close to a set value within a range satisfying the above-mentioned formulas 1 to 3, and arranging the above-mentioned X-ray stress measuring device relative to the above-mentioned fillet portion. The residual stress measuring method can arrange the above-mentioned X-ray stress measuring device at a desired position based on the above-mentioned formulas 1 to 3, thereby being able to easily and accurately measure the residual stress of the above-mentioned fillet portion.

[0025] The setting value is preferably 35° or −35°. When the setting value is the above value, the residual stress in the fillet portion can be measured easily and with high accuracy.

[0026] In the present invention, the term "center of fillet" refers to the center of curvature of the fillet. The term "radius of fillet" refers to the radius of curvature of the fillet. The term "angle of fillet" refers to the imaginary straight line passing through the center of fillet and orthogonal to the axis (see Figure 1 The imaginary straight line V) and the imaginary straight line passing through the measurement site and the center of the fillet (reference Figure 1 The so-called "upper and lower width of the housing" refers to the side of the housing adjacent to the shaft (reference Figure 1 The lower surface 3a) and the surface opposite to the surface and adjacent to the flange portion (reference Figure 1 The width of the upper surface 3b) (reference Figure 1 The "interval between the flange and an imaginary straight line passing through the center of the fillet and parallel to the flange" refers to the average value of the intervals between the imaginary straight line and any five points of the flange (but excluding the fillet). The "detection area of ​​the two-dimensional detector" refers to the area in the two-dimensional detector that can detect diffraction rings.

[0027] Effects of the Invention

[0028] As described above, the residual stress measuring method according to one embodiment of the present invention can measure the residual stress of the fillet portion with high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic side view showing a state where the residual stress of a fillet portion is measured by the residual stress measuring method according to one embodiment of the present invention.

[0030] Figure 2 This is a graph showing the relationship between the X-ray irradiation distance and the fillet angle of the fillet portion in the residual stress measurement method according to one embodiment of the present invention.

[0031] Figure 3 This is a graph showing the relationship between the X-ray irradiation distance and the fillet radius of the fillet portion in the residual stress measurement method according to one embodiment of the present invention.

[0032] Figure 4 This is a graph showing the relationship between the upper and lower widths of the housing and the fillet angle of the fillet portion in the residual stress measuring method according to the embodiment of the present invention.

[0033] Figure 5 This is a graph showing the relationship between the upper and lower widths of the housing and the fillet radius of the fillet portion in the residual stress measuring method according to the embodiment of the present invention.

[0034] Figure 6 It is a schematic diagram used to explain the process of determining the fillet center and fillet radius.

[0035] Figure 7 It is used to explain the difference between determining the fillet center and fillet radius Figure 6 Schematic diagram of the process.

[0036] Figure 8 It is used to explain the difference between determining the fillet center and fillet radius Figure 6 as well as Figure 7 Schematic diagram of the process.

[0037] Fig. 9This is a graph showing the relationship between the incident angle of X-rays and the irradiation distance of X-rays in Examples and Comparative Examples.

[0038] Fig.10 This is a graph showing the maximum value of the incident angle of X-rays for each fillet angle in Examples and Comparative Examples. DETAILED DESCRIPTION

[0039] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0040] [Residual stress measurement method]

[0041] like Figure 1 As shown in FIG. 1 , the residual stress measuring method is a method for measuring the residual stress of a fillet portion 13 of a metal structure M, wherein the metal structure M has a shaft portion 11 and a flange portion 12 protruding in a radial direction from the shaft portion 11, and has a fillet portion 13 at a connection portion between the shaft portion 11 and the flange portion 12. The flange portion 12 protrudes in a direction perpendicular to the central axis of the shaft portion 11. The residual stress measuring method includes a step (calculation step) of calculating the residual stress by a cosα method using an X-ray stress measuring device 10, wherein the X-ray stress measuring device 1 includes an irradiation portion 1 for irradiating X-rays, a two-dimensional detector 2 for detecting diffraction rings generated by Bragg diffraction of the X-rays irradiated from the irradiation portion 1 to the fillet portion 13, and a housing 3 equipped with the irradiation portion 1 and the two-dimensional detector 2.

[0042] The X-ray stress measuring device 10 is configured to detect diffraction rings by irradiating the metal structure M with X-rays. The housing 3 is, for example, roughly rectangular. The housing 3 has: a lower surface 3a adjacent to the shaft portion 11; and an upper surface 3b opposite to the lower surface 3a and adjacent to the flange portion 12. In the housing 3, if the incident angle Ψ shifts to the positive side, the lower surface 3a is close to the shaft portion 11, and if the incident angle Ψ shifts to the negative side, the upper surface 3b is close to the flange portion 12. The two-dimensional detector 2 is provided at the end of the housing 3 on the X-ray emission surface side. That is, the two-dimensional detector 2 is provided at the end on the side opposite to the measurement site S. A calculator (not shown) that can use the above-mentioned diffraction rings and calculate the residual stress by the cosα method is connected to the housing 3. As the two-dimensional detector 2, an imaging plate can be cited, for example.

[0043] In this residual stress measuring method, the incident angle of the above-mentioned X-ray is set to Ψ[°], the fillet radius of the fillet portion 13 is set to R[mm], the fillet angle of the fillet portion 13 is set to θ[°], the upper and lower widths of the shell 3 are set to W[mm], the width of the detection area of ​​the two-dimensional detector 2 is set to D[mm], the complementary angle of the Bragg angle is set to η[°], and the interval between the imaginary straight line V passing through the center P of the fillet and parallel to the flange portion 12 and the flange portion 12 is set to a[mm]. In this case, the following formula 1 is satisfied.

[0044] [Formula 4]

[0045]

[0046] In the residual stress measurement method, the whole image or a part of the diffraction ring is captured by the two-dimensional detector 2 to measure the residual stress of the fillet portion 13. Therefore, as shown in the above formula 1, it is necessary to set the width D of the detection area of ​​the two-dimensional detector 2 to be less than the upper and lower width W of the housing 3. In addition, the so-called "width of the detection area of ​​the two-dimensional detector" refers to the width of the detection area of ​​the two-dimensional detector in the upper and lower directions of the housing (i.e., the upper and lower width of the detection area of ​​the two-dimensional detector).

[0047] In addition, in this residual stress measurement method, In the case of , the X-ray irradiation distance L [mm] based on the two-dimensional detector 2 in the above calculation step satisfies the following formula 2.

[0048] [Formula 5]

[0049]

[0050] Furthermore, in this residual stress measuring method, when Ψ<0, the X-ray irradiation distance L [mm] based on the two-dimensional detector 2 in the above-mentioned calculation step satisfies the following formula 3.

[0051] [Mathematical formula 6]

[0052]

[0053] The incident angle Ψ of the X-ray refers to the angle between the X-ray and the imaginary straight line N passing through the measurement site S and the fillet center P. The incident angle Ψ is positive when it is inclined toward the shaft 11 side relative to the imaginary straight line N passing through the measurement site S and the fillet center P, and negative when it is inclined toward the flange 12 side.

[0054] In this residual stress measurement method, if the X-ray irradiation distance L is too small, when the housing 3 is tilted so that the incident angle Ψ of the X-ray becomes a desired value, the housing 3 may interfere with the shaft portion 11 or the flange portion 12. On the other hand, in this residual stress measurement method, by increasing the X-ray irradiation distance L, the incident angle Ψ of the X-ray can be set within a relatively wide range. However, in this case, if the X-ray irradiation distance L is too large, the two-dimensional detector 2 can no longer detect the peak of the diffracted X-ray at the diffraction angle η.

[0055] Based on this point of view, when the shell 3 is tilted toward the shaft 11 side relative to the imaginary straight line N passing through the measurement position S and the center of the fillet P (that is, when the incident angle Ψ of the X-ray is positive), the lower limit value of the X-ray irradiation distance L is represented by the following formula 4 based on the condition that the shell 3 is not in contact with the shaft 11, and the upper limit value of the X-ray irradiation distance L is represented by the following formula 5 based on the condition that the peak value of the diffraction ring can be detected in the two-dimensional detector 2.

[0056] [Formula 7]

[0057]

[0058] [Mathematical formula 8]

[0059]

[0060] On the other hand, when the shell 3 is tilted toward the flange 12 side relative to the imaginary straight line N passing through the measuring position S and the center of the fillet P (that is, when the incident angle Ψ of the X-ray is negative), the lower limit value of the X-ray irradiation distance L is represented by the following formula 6 based on the condition that the shell 3 is not in contact with the flange 12, and the upper limit value of the X-ray irradiation distance L is represented by the following formula 7 based on the condition that the peak value of the diffraction ring can be detected in the two-dimensional detector 2.

[0061] [Mathematical formula 9]

[0062]

[0063] [Formula 10]

[0064]

[0065] <Measurement Conditions>

[0066] refer to Figure 2 to Figure 5 The measurement conditions in this residual stress measurement method will be described.

[0067] (Irradiation distance)

[0068] First, refer to Figure 2 as well as Figure 3 The following describes the range of the X-ray irradiation distance L in the residual stress measurement method. Generally, in the cosα method, if the incident angle Ψ of the X-ray to the measurement site S is less than ±15° (i.e., more than -15° and less than +15°), the measurement accuracy will deteriorate sharply. Figure 2 as well as Figure 3 In the following, the X-ray irradiation distance L using the above equations 1 to 3 is described when the X-ray incident angle Ψ is set to ±15°. Figure 2In the example, the fillet radius R of the fillet portion 13 is set to 18 mm, the upper and lower width W of the housing 3 is set to 44 mm, the width D of the detection area of ​​the two-dimensional detector 2 is set to 40 mm, the interval a between the imaginary straight line V passing through the fillet center P and parallel to the flange portion 12 and the flange portion 12 is set to 2 mm, and the complementary angle η of the Bragg angle is set to 23.6°. In this case, the range Q1 that the irradiation distance L of the X-ray can take is shown in relation to the fillet angle θ. In addition, in Figure 3 In, for Figure 2 The range Q2 that the X-ray irradiation distance L can take is shown by the relationship with the fillet radius R when the fillet angle θ is set to 60° and the fillet radius R is made variable.

[0069] exist Figure 2 In the case where the fillet angle θ of the fillet portion 13 is 57°, the range Q1 that the irradiation distance L of the X-ray can take is most limited. Figure 2 It is known that when the fillet angle θ is less than 57°, the housing 3 is preferably tilted toward the shaft portion 11 so that the incident angle Ψ of the X-ray becomes positive. It is also known that when the fillet angle θ exceeds 57°, the housing 3 is preferably tilted toward the flange portion 12 so that the incident angle Ψ of the X-ray becomes negative.

[0070] exist Figure 3 In the case where the fillet radius R of the fillet portion 13 is 21 mm, the range Q2 that the X-ray irradiation distance L can take is most limited. Figure 3 It can be seen that when the fillet radius R is less than 21 mm, the housing 3 is preferably tilted toward the flange 12 so that the incident angle Ψ of the X-ray becomes negative. In addition, it can be seen that when the fillet radius R exceeds 21 mm, the housing 3 is preferably tilted toward the shaft 11 so that the incident angle Ψ of the X-ray becomes positive.

[0071] (Up and down width of the housing)

[0072] refer to Figure 4 as well as Figure 5 The following describes the range of the upper and lower widths W of the housing 3 in the residual stress measurement method. Figure 4 In the embodiment, the upper and lower widths W of the housing 3 are set to be equal to Figure 2 Under the same conditions, the range of the upper and lower widths W of the housing 3 can be shown by the relationship between the fillet angle θ and the X-ray irradiation distance L when the X-ray irradiation distance L is set to the maximum value. Figure 5 In, for Figure 4 , the range of the upper and lower widths W of the housing 3 is shown by the relationship with the fillet radius R when the fillet angle θ is set to 60° and the fillet radius R is made variable.

[0073] exist Figure 4In the case where the fillet angle θ of the fillet portion 13 is 57°, the range of the upper and lower widths W of the housing 3 is most limited. Figure 4 It can be seen that when the fillet angle θ is less than 57°, by making the housing 3 face the shaft portion 11, even when the upper and lower width W of the housing 3 is relatively large, the measurement can be performed under the desired conditions. In addition, it can be seen that when the fillet angle θ exceeds 57°, by making the housing 3 tilt toward the flange portion 12, even when the upper and lower width W of the housing 3 is relatively large, the measurement can be performed under the desired conditions.

[0074] exist Figure 5 In the case where the fillet radius R of the fillet portion 13 is 21 mm, the range of the upper and lower widths W of the housing 3 is most limited. Figure 5 It can be seen that when the fillet radius R is less than 21 mm, by tilting the housing 3 toward the flange portion 12, even when the upper and lower width W of the housing 3 is relatively large, the measurement can be performed under the desired conditions. In addition, it can be seen that when the fillet radius R exceeds 21 mm, by tilting the housing 3 toward the shaft portion 11, even when the upper and lower width W of the housing 3 is relatively large, the measurement can be performed under the desired conditions.

[0075] <Setting the fillet center and fillet radius>

[0076] like Figure 6 As shown in FIG. 1 , in this residual stress measurement method, when the curvature of the fillet portion 13 is constant, the fillet center P and the fillet radius R are set corresponding to the curvature. In contrast, in the fillet portion 13, there are sometimes a plurality of regions with different diameters. Figure 7 as well as Figure 8 An example of a method of setting the fillet center and the fillet radius when a plurality of regions having different diameters exist in the fillet portion will be described.

[0077] Figure 7 The fillet portion 13a has: a first region Y1 having a first curvature radius R1; and a second region Y2 having a second curvature radius R2 smaller than the first curvature radius R1. In this case, the curvature center P1 and the curvature radius R1 of the first region Y1 having the largest curvature radius can be determined as the fillet center and fillet radius of the fillet portion 13a. By determining the fillet center and fillet radius of the fillet portion 13a in this way, the residual stress of the fillet portion 13a can be measured easily and with high accuracy.

[0078] Figure 8The fillet portion 13b has: a first region Y1' having a first arc C1; a second region Y2' having a second arc C2 shorter than the first arc; and a third region Y3' having a third arc C3 shorter than the second arc C2. In this case, the center of curvature P1' and the radius of curvature R1' of the first region Y1' having the longest arc can be determined as the fillet center and fillet radius of the fillet portion 13b. By determining the fillet center and fillet radius of the fillet portion 13b in this way, the residual stress of the fillet portion 13b can be measured easily and with high accuracy.

[0079] <Measurement of residual stress>

[0080] The calculation step preferably includes the steps of adjusting the X-ray irradiation distance L within the range satisfying the above-mentioned formulas 1 to 3 so that the incident angle Ψ of the X-ray is close to the set value, and arranging the X-ray stress measurement device 10 with respect to the fillet portion 13, 13a, 13b (arranging step). That is, the calculation step preferably includes the steps of deriving the arrangement conditions of the X-ray stress measurement device 10 using the above-mentioned formulas 1 to 3 (deriving step); arranging the X-ray stress measurement device 10 with respect to the fillet portion 13, 13a, 13b based on the conditions derived in the above-mentioned deriving step (arranging step); and calculating the residual stress of the fillet portion 13, 13a, 13b under the arrangement in the above-mentioned arrangement step (residual stress calculating step), wherein the above-mentioned arrangement step adjusts the X-ray irradiation distance L within the range satisfying the above-mentioned formulas 1 to 3 so that the incident angle Ψ of the X-ray is close to the set value, and arranging the X-ray stress measurement device 10 with respect to the fillet portion 13, 13a, 13b. In the above arrangement step, for example, the tilt direction of the housing 3 and the X-ray irradiation distance L are adjusted so that the X-ray incident angle Ψ approaches the set value. In this residual stress measurement method, the residual stress of the fillet portions 13, 13a, and 13b can be easily and accurately measured by including the above calculation step and the above arrangement step.

[0081] As the setting value in the arrangement step, 35° or −35° is preferable. According to this configuration, the residual stress of the fillet portions 13 , 13 a , and 13 b can be measured with higher accuracy.

[0082] In the above-mentioned derivation process, it is preferable to derive a condition satisfying the above-mentioned set value as a configuration condition of the X-ray stress measuring device 10. However, depending on the shape of the fillet portion 13, 13a, 13b, it is considered that the condition satisfying the above-mentioned set value may not be derived in the above-mentioned derivation process. In the case where the condition satisfying the above-mentioned set value cannot be derived in the above-mentioned derivation process, the residual stress measuring method has a significant advantage over the existing measurement method that determines the configuration of the X-ray stress measuring device 10 by trial and error. In the residual stress measuring method, for example, the incident angle Ψ of the X-ray derived in the above-mentioned derivation process may be within ±30° (i.e., greater than -30° and less than 30°), or within ±15° (i.e., greater than -15° and less than 15°). Even in such a case, the residual stress measuring method can measure the residual stress of the fillet portion 13, 13a, 13b more easily and with higher accuracy than the existing measurement method.

[0083] <Advantages>

[0084] According to this residual stress measurement method, when measuring the residual stress of the fillet portions 13, 13a, 13b formed at the connection portion between the shaft portion 11 and the flange portion 12, the incident angle Ψ of the X-ray can be made close to a desired angle. Therefore, according to this residual stress measurement method, the residual stress of the fillet portions 13, 13a, 13b can be measured with high accuracy.

[0085] [Other embodiments]

[0086] The above embodiments do not limit the structure of the present invention. Therefore, the above embodiments can be based on the description of this specification and technical common sense to omit, replace or add the components of each part of the above embodiments, which should be interpreted as belonging to the scope of the present invention.

[0087] In this residual stress measurement method, when the fillet portion has a plurality of regions having different diameters, for example, the fillet center and the fillet radius may be obtained for each measurement location.

[0088] Example

[0089] The present invention will be described in detail below based on examples, but the present invention is not to be construed in a limited manner based on the description of the examples.

[0090] The residual stress of the fillet of a metal structure having a shaft and a flange protruding in the radial direction from the shaft was measured using an X-ray stress measuring device with a detection area width D of 70 mm for a two-dimensional detector and a housing width of 102 mm from top to bottom, using the cosα method. The fillet radius R of the fillet was 29 mm, the complementary angle η of the Bragg angle was 23.6°, and the interval a between the flange and an imaginary straight line passing through the center of the fillet and parallel to the flange was 8 mm.

[0091] [Comparative Example]

[0092] Visual inspection was performed to ensure that the housing was not in contact with the shaft and flange, and an X-ray stress measuring device was configured to make the incident angle Ψ of the X-ray as large as possible. In this comparative example, the configuration of the X-ray stress measuring device was changed six times for the cases where the fillet angle θ of the fillet was 45°, 50°, and 55°, and the residual stress of the fillet was measured. Fig. 9 The relationship between the incident angle Ψ of the X-ray and the irradiation distance L of the X-ray in the comparative example is shown. Fig.10 The maximum value of the incident angle Ψ of the X-ray for each fillet angle θ is shown.

[0093] [Example]

[0094] For the cases where the fillet angle θ is 45°, 50°, and 55°, the configuration of the X-ray stress measuring device is determined using the above-mentioned formulas 1 to 3, respectively. In the embodiment, the configuration of the X-ray stress measuring device is determined using the above-mentioned formulas 1 to 3 so that the incident angle Ψ of the X-ray is close to ±35°. In the embodiment, regardless of whether the fillet angle θ is 45°, 50°, or 55°, the housing is tilted toward the shaft side relative to the imaginary straight line passing through the measurement site and the center of the fillet. Fig. 9 The relationship between the incident angle Ψ of the X-ray and the irradiation distance L of the X-ray in the embodiment is shown. Fig.10 The incident angle Ψ of the X-ray with respect to each fillet angle θ is shown.

[0095] like Fig. 9 as well as Fig.10 As shown, the incident angle Ψ of the X-ray is increased in the embodiment compared with the comparative example. It is understood that the embodiment can measure the residual stress of the fillet portion with higher accuracy than the comparative example.

[0096] Industrial Applicability

[0097] As described above, the residual stress measuring method according to one embodiment of the present invention is suitable for measuring the residual stress of a fillet portion.

[0098] Description of Reference Numerals

[0099] 1 irradiation part

[0100] 2. 2D detector

[0101] 3. Housing

[0102] 3a Lower surface

[0103] 3b Upper surface

[0104] 10 X-ray stress measurement device

[0105] 11 Shaft

[0106] 12 Flange

[0107] 13, 13a, 13b Rounded corners

[0108] a The distance between the flange and an imaginary straight line passing through the center of the fillet and parallel to the flange

[0109] C1 1st arc

[0110] C2 Arc 2

[0111] C3 The third arc

[0112] D is the width of the detection area of ​​the 2D detector.

[0113] LX-ray irradiation distance

[0114] M Metal Structure

[0115] N An imaginary straight line passing through the measurement point and the center of the fillet

[0116] P Fillet center

[0117] P1, P1' Center of curvature

[0118] Q1, Q2 X-ray irradiation distance range

[0119] R Corner radius

[0120] R1 1st radius of curvature

[0121] R1' Radius of curvature

[0122] R2 Second radius of curvature

[0123] S Measurement site

[0124] V An imaginary straight line passing through the center of the fillet and parallel to the flange

[0125] W: Upper and lower width of the housing

[0126] Y1, Y1' Area 1

[0127] Y2, Y2' 2nd area

[0128] Y3' Area 3

[0129] θ Fillet angle

[0130] Ψ X-ray incident angle

[0131] η is the complementary angle of the Bragg angle.

Claims

1. A residual stress measuring method, which is a residual stress measuring method for a fillet portion of a metal structure, wherein the metal structure comprises a shaft portion and a flange portion protruding in a radial direction from the shaft portion, and the fillet portion is provided at a connection portion between the shaft portion and the flange portion, wherein the residual stress measuring method comprises the following steps: The residual stress is calculated by a cos α method using an X-ray stress measuring device, wherein the X-ray stress measuring device includes an irradiation unit for irradiating X-rays, a two-dimensional detector for detecting diffraction rings generated by Bragg diffraction of the X-rays irradiated from the irradiation unit to the fillet portion, and a housing equipped with the irradiation unit and the two-dimensional detector. When the incident angle of the X-ray is Ψ, the fillet radius of the fillet portion is R, the fillet angle of the fillet portion is θ, the upper and lower widths of the housing are W, the width of the detection area of ​​the two-dimensional detector is D, the complementary angle of the Bragg angle is η, and the interval between the imaginary straight line passing through the center of the fillet and parallel to the flange portion and the flange portion is a, the following formula 1 is satisfied: [Mathematical formula 1] Furthermore, when Ψ≧0, the X-ray irradiation distance L based on the two-dimensional detector in the calculation step satisfies the following equation 2: When Ψ<0, the irradiation distance L in the calculation step satisfies the following formula 3: [Mathematical formula 2] [Mathematical formula 3] in, The incident angle Ψ is positive when it is inclined toward the shaft side relative to an imaginary straight line passing through the measuring position and the center of the fillet, and is negative when it is inclined toward the flange side. The units of Ψ, θ, and η are degrees, and the units of R, W, D, a, and L are mm.

2. The residual stress measuring method according to claim 1, characterized in that: When the rounded portion has a plurality of regions with different diameters, the center of curvature and the radius of curvature of the region with the largest diameter among the plurality of regions are determined as the center of curvature and the radius of curvature of the rounded portion.

3. The residual stress measuring method according to claim 1, characterized in that: When the rounded corner portion has a plurality of regions with different diameters, the center of curvature and the radius of curvature of the region with the longest arc among the plurality of regions are determined as the center of curvature and the radius of curvature of the rounded corner portion.

4. The residual stress measuring method according to claim 2 or 3, characterized in that: The calculation step includes the steps of adjusting the irradiation distance L within a range satisfying the equations 1 to 3 so that the incident angle Ψ approaches a set value, and arranging the X-ray stress measurement device relative to the fillet portion.

5. The residual stress measuring method according to claim 4, characterized in that: The set value is 35° or -35°.

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