阅读说明：本技术 应力测定方法 (Stress measuring method ) 是由 高松弘行 福井利英 松田真理子 兜森达彦 于 2018-04-06 设计创作，主要内容包括：本发明的应力测定方法是对由金属构成的、包括表面以及凹部的被检查体的凹部的应力进行测定的方法,所述应力测定方法包括：检测工序,使X射线向凹部入射,并且利用二维检测器对通过所述X射线在凹部衍射而形成的衍射X射线的衍射环进行检测；以及计算工序,基于检测工序的检测结果来计算凹部的应力,在检测工序中,对被检查体的凹部内的多个部位分别入射X射线,并且利用二维检测器对通过各X射线在凹部衍射而形成的衍射环进行检测。(The stress measuring method of the present invention is a method for measuring a stress in a concave portion of a test object made of a metal and including a surface and a concave portion, the method including: a detection step of causing an X-ray to enter the recess and detecting a diffraction ring which is formed by the X-ray diffracting in the recess by a two-dimensional detector; and a calculation step of calculating stress of the concave portion based on a detection result of the detection step, wherein in the detection step, X-rays are incident on each of a plurality of portions in the concave portion of the object, and a diffraction ring formed by diffraction of each X-ray in the concave portion is detected by a two-dimensional detector.)

1. A method for measuring stress of a concave portion of a test object made of metal and including a surface and the concave portion having a shape recessed from the surface and extending in a groove shape, wherein,

the stress measuring method comprises the following steps:

a detection step of causing an X-ray to enter the recess and detecting a diffraction ring of a diffracted X-ray formed by the X-ray diffracting in the recess by a two-dimensional detector; and

a calculation step of calculating the stress of the concave portion based on a detection result of the detection step,

in the detection step, X-rays are incident on each of a plurality of portions in the concave portion of the subject, and the diffraction ring formed by the diffraction of each X-ray in the concave portion is detected by the two-dimensional detector.

2. The stress measuring method according to claim 1,

in the detection step, as the plurality of portions, portions continuously connected in the concave portion are selected, and X-rays are continuously incident on the portions.

3. The stress measuring method according to claim 2,

in the detection step, as the continuous portion, a portion continuously continuous along the extending direction of the concave portion is selected.

4. The stress measurement method according to claim 2 or 3,

in the detection step, X-rays are continuously incident on the continuously connected portions, and a single diffraction ring obtained by overlapping a plurality of diffraction rings formed by diffracting each X-ray at the portions is detected by the two-dimensional detector.

5. The stress measuring method according to claim 1,

in the detecting step, the X-ray is made incident on the recess so that the total of irradiation areas of the X-ray to the recess is equal to or larger than a predetermined multiple of an area of the crystal grain of the object.

6. The stress measuring method according to claim 1,

in the detection step, each X-ray is made incident on the concave portion at a low incident angle of 20 ° or less.

7. A method for measuring stress of a concave portion of a test object made of metal and including a surface and the concave portion having a shape recessed from the surface and extending in a groove shape, wherein,

the stress measuring method comprises the following steps:

a detection step of detecting a diffraction ring of the diffracted X-rays formed by the X-rays diffracting in the concave portion by a two-dimensional detector while allowing the X-rays to enter the concave portion; and

a calculation step of calculating the stress of the concave portion based on a detection result of the detection step,

in the detection step, X-rays are incident on a single portion in the concave portion of the object at a plurality of different incident angles, and a diffraction ring formed by diffraction of each X-ray in the concave portion is detected by the two-dimensional detector.

8. The stress measuring method according to claim 7,

in the detecting step, the plurality of incident angles are selected from a range in which an incident angle increased by a predetermined angle with respect to a specific incident angle is set as an upper limit value and an incident angle decreased by the predetermined angle with respect to the specific incident angle is set as a lower limit value.

9. The stress measuring method according to claim 8,

in the detecting step, the specific incident angle is selected from low incident angles of 20 ° or less.

Technical Field

The present invention relates to a method for measuring stress of an object to be inspected.

Background

In recent years, as a method for nondestructively measuring the stress (residual stress) of a test object made of a metal, a two-dimensional detection method (so-called cos α method) using a two-dimensional detector has been widely used as disclosed in patent document 1 and the like. This method is a method for measuring stress based on a diffraction ring of diffracted X-rays generated by diffraction of X-rays incident on an object to be inspected at a specific incident angle Ψ within the object. Since the measurement accuracy in this two-dimensional detection method is approximately proportional to sin2 Ψ, the measurement accuracy decreases as the incident angle Ψ of the X-ray incident on the subject changes from 45 °. Therefore, in the two-dimensional detection method, the incident angle Ψ of the X-ray to the subject is usually set to be 25 ° to 65 °. In patent document 1, the incident angle Ψ is set to 30 °.

Although the two-dimensional detection method can measure the stress of a relatively flat portion of the subject with high accuracy, it is difficult to measure the stress of a concave portion of the subject with high accuracy. Specifically, when the measuring section of the subject has a concave portion recessed in a concave shape from the surface of a portion around the measuring section, incident X-rays and diffracted X-rays interfere with the subject, and thus a clear diffraction ring cannot be detected, or even if a diffraction ring is detected, the accuracy of the diffracted X-rays passing through a portion near the subject in the diffraction ring is lowered. Therefore, it is difficult to ensure that the incident angle Ψ of the incident X-ray is sufficiently large. This makes it difficult to measure the stress of the concave portion with high accuracy by a two-dimensional detection method. In other words, when it is required to measure the stress of the concave portion with high accuracy, it is generally difficult to apply a two-dimensional detection method.

Prior art documents

Patent document

Patent document 1: japanese patent laid-open publication No. 2011-

Disclosure of Invention

The present invention aims to provide a stress measurement method capable of measuring the stress of a concave portion of a subject with high accuracy by using a two-dimensional detection method.

A stress measuring method according to an aspect of the present invention is a method of measuring a stress of a concave portion of a test object made of metal and including a surface and the concave portion having a shape recessed from the surface and extending in a groove shape, the method including: a detection step of causing an X-ray to enter the recess and detecting a diffraction ring of a diffracted X-ray formed by the X-ray diffracting in the recess by a two-dimensional detector; and a calculation step of calculating the stress of the concave portion based on a detection result of the detection step, wherein in the detection step, X-rays are incident on each of a plurality of portions in the concave portion of the object, and a diffraction ring formed by diffraction of each X-ray in the concave portion is detected by the two-dimensional detector.

A stress measuring method according to another aspect of the present invention is a method of measuring a stress of a concave portion of a test object made of a metal and including a surface and the concave portion having a shape recessed from the surface and extending in a groove shape, the method including: a detection step of detecting a diffraction ring of the diffracted X-rays formed by the X-rays diffracting in the concave portion by a two-dimensional detector while allowing the X-rays to enter the concave portion; and a calculation step of calculating stress of the concave portion based on a detection result of the detection step, wherein in the detection step, X-rays are incident on a single portion in the concave portion of the object at a plurality of incident angles different from each other, and a diffraction ring formed by diffraction of each X-ray in the concave portion is detected by the two-dimensional detector.

Drawings

Fig. 1 is a schematic view showing a detection step of the stress measurement method according to the first embodiment of the present invention.

Fig. 2 is a schematic view showing a detection step of the stress measurement method according to the second embodiment of the present invention.

Fig. 3 is a diagram showing an example of the moving direction of incident X-rays in the first embodiment.

Fig. 4 is a graph showing the relationship between the irradiation area of incident X-rays and the reliability (CrMo-based low alloy steel).

Fig. 5 is a graph showing the relationship between the irradiation area of incident X-rays and the reliability (NiCrMo-based low alloy steel).

Fig. 6 is a graph showing a relationship between the oscillation angle of incident X-rays and reliability (CrMo-based low alloy steel).

Detailed Description

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

(first embodiment)

A stress measurement method according to a first embodiment of the present invention will be described with reference to fig. 1. In this stress measurement method, a two-dimensional detector (not shown) is used to measure the stress of the concave portion 3 of the object 1 (such as a crankshaft) made of a metal such as a steel material. As shown in fig. 1, the concave portion 3 has a shape recessed from the surface 2 of the object 1 and extending like a groove. The stress measuring method includes a detecting step and a calculating step.

In the detection step, X-rays irradiated from the irradiation unit 4 capable of irradiating X-rays are made incident on the concave portion 3, and the diffraction ring R of diffracted X-rays formed by the diffraction of the X-rays in the concave portion 3 is detected by a two-dimensional detector. Specifically, in this detection step, X-rays are incident on a plurality of locations in the recess 3 at a fixed incident angle Ψ, and the diffraction ring R formed by the diffraction of each X-ray in the recess 3 is detected by a two-dimensional detector. In this case, the irradiation unit 4 may be moved with the subject 1 fixed, or the subject 1 may be moved with the irradiation unit 4 fixed. Further, as the plurality of portions, portions continuously connected in the concave portion 3 are selected. More preferably, as the plurality of portions, portions continuously connected in the extending direction of the recess 3 are selected. In this detection step, X-rays are continuously incident on the continuously connected portions from the irradiation unit 4 at a constant incident angle Ψ, and a single diffraction ring R obtained by overlapping a plurality of diffraction rings R formed by diffracting each X-ray at the portions is detected by a two-dimensional detector. The area of the X-ray irradiated to the continuously connected portion in the recess 3 is preferably set to be equal to or larger than a predetermined multiple (e.g., 18000 times) of the area of the crystal grain of the object 1. In the present embodiment, the incident angle Ψ of the X-ray to the recess 3 is set to a low incident angle of 5 ° to 20 °.

In the calculation step, the stress of the concave portion 3 is calculated based on the detection result (the single diffraction ring R) in the detection step.

As described above, in the stress measurement method according to the present embodiment, in the detection step, since the two-dimensional detector detects the plurality of diffraction rings R corresponding to the respective X-rays incident on the plurality of portions in the concave portion 3, the diffraction information (information on the crystal contributing to diffraction) included in the detection result in the detection step is larger than that in the case where only the single diffraction ring corresponding to the single X-ray incident in the concave portion 3 is detected. This improves the accuracy of calculation of the stress of the concave portion 3 in the calculation step. Therefore, even when X-rays enter the concave portion 3 at a low incident angle of, for example, 5 ° or more and 20 ° or less, the stress of the concave portion 3 can be measured with high accuracy. Thus, in the stress measurement method of the present embodiment, even when the object 1 has a shape in which it is difficult to secure a sufficiently large incident angle Ψ of the incident X-ray to the concave portion 3 (when the incident angle Ψ is increased, the incident X-ray or the diffracted X-ray interferes with the object 1, the irradiation unit 4 interferes with the object 1, or the like), it is possible to effectively avoid interference between the incident X-ray and the diffracted X-ray and the object 1, and to measure the stress of the concave portion 3 with high accuracy.

In the detection step, since the plurality of portions are selected as the portions continuously connected in the extending direction of the concave portion 3, the measurement accuracy of the stress of the concave portion 3 is further improved. Specifically, since the stress of the concave portion 3 is considered to be almost uniform along the extending direction of the concave portion 3, the measurement accuracy is improved by detecting the diffraction rings R at the portions continuously connected along the direction.

In the detection step, as the plurality of portions in the concave portion 3 on which the X-ray is incident, portions arranged at intervals along the extending direction of the concave portion 3 may be selected, and the plurality of diffraction rings R formed by diffraction of the incident X-ray on each portion may be detected. In this case, in the calculation step, an average value of a plurality of detection values (stress values) obtained from the respective diffraction rings R is calculated. However, as in the above-described embodiment, by selecting, as the plurality of portions, portions that are continuously continuous in the extending direction of the concave portion 3 and continuously receiving X-rays at the selected portions, it is not necessary to set measurement conditions for each measurement portion, as compared with the case where X-rays are received at a plurality of portions that are arranged at intervals in the concave portion 3, and therefore, the work of the detection step is simplified.

(second embodiment)

Next, a stress measurement method according to a second embodiment of the present invention will be described with reference to fig. 2. In the second embodiment, only the portions different from the first embodiment will be described, and the description of the same configurations, operations, and effects as those of the first embodiment will be omitted.

In the present embodiment, as shown in fig. 2, in the detection step, X-rays are made incident from the irradiation section 4 at a plurality of different incident angles Ψ for a single location within the recess 3, and the diffraction ring R formed by the diffraction of each X-ray in the recess 3 is detected by a two-dimensional detector. The plurality of incident angles Ψ are selected from a range in which an incident angle increased by a predetermined angle (on the order of 3 ° to 7 °) with respect to a specific incident angle Ψ selected from the low incident angles (5 ° or more and 20 ° or less) is defined as an upper limit value and an incident angle decreased by the predetermined angle with respect to the specific incident angle is defined as a lower limit value. In the present embodiment, in the detection step, X-rays are made to continuously enter the recess 3 from the lower limit value to the upper limit value or from the upper limit value to the lower limit value of the range, and a single diffraction ring obtained by overlapping a plurality of diffraction rings formed by the diffraction of each X-ray in the recess 3 is detected by a two-dimensional detector.

As described above, in the stress measurement method according to the present embodiment, in the detection step, since the plurality of diffraction rings R corresponding to the plurality of X-rays incident on the single portion of the concave portion 3 at the different incident angles Ψ are detected by the two-dimensional detector, the diffraction information (information on the crystal contributing to diffraction) included in the detection result in the detection step is increased as compared with the case where only the single diffraction ring R corresponding to the X-ray incident on the concave portion 3 at the single incident angle is detected. Specifically, when the incident angle Ψ of the incident X-ray is different, the depth of the recess 3 into which the X-ray enters is different, and thus the X-ray enters the recess 3 at a plurality of incident angles Ψ, whereby the diffraction information included in the detection result of the detection process increases. This improves the accuracy of calculation of the stress of the concave portion 3 in the calculation step.