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：一种对由金属构成的被检查体的应力进行测定的方法,该方法包括：检测工序,使X射线从照射部向被检查体入射,并且利用二维检测器对X射线在被检查体衍射而形成的衍射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被检查体的应力,在检测工序中,在将照射部以向被检查体入射的入射角处于5°以上且20°以下的范围内的方式相对于被检查体倾斜的状态下,使X射线从该照射部分别向被检查体的多个部位入射,并且利用二维检测器对各X射线在被检查体衍射而形成的衍射环进行检测。(A method of measuring stress of an object to be inspected made of metal, the method comprising: a detection step of causing an X-ray to enter the subject from the irradiation unit and detecting a diffraction ring of the diffracted X-ray, which is formed by the X-ray being diffracted by the subject, by a two-dimensional detector; and a calculation step of calculating the stress of the subject based on the detection result of the detection step, wherein in the detection step, in a state in which the irradiation section is tilted with respect to the subject so that the incident angle to the subject is in a range of 5 ° to 20 °, the X-rays are incident on a plurality of portions of the subject from the irradiation section, and the diffraction ring formed by the diffraction of each X-ray on the subject is detected by a two-dimensional detector.)

1. A stress measuring method for measuring a stress of a test object made of a metal,

the stress measuring method comprises the following steps:

a detection step of causing an X-ray to enter the subject from an irradiation unit capable of irradiating the subject with the X-ray and detecting a diffraction ring of a diffracted X-ray formed by diffraction of the X-ray on the subject by a two-dimensional detector; and

a calculation step of calculating the stress of the object to be inspected based on the detection result of the detection step,

in the detection step, the irradiation unit is tilted with respect to the subject such that an incident angle of the X-rays incident on the subject is in a range of 5 ° or more and 20 ° or less, the X-rays are incident on a plurality of portions of the subject from the irradiation unit, and a diffraction ring formed by each X-ray diffracting on the subject 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, continuously connected portions in the subject are selected, and X-rays are continuously incident on the selected portions.

3. The stress measuring method according to claim 2,

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.

4. The stress measuring method according to any one of claims 1 to 3,

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

5. A stress measuring method for measuring a stress of a test object made of a metal,

the stress measuring method comprises the following steps:

a detection step of causing an X-ray to enter the subject from an irradiation unit capable of irradiating the subject with the X-ray and detecting a diffraction ring of a diffracted X-ray formed by diffraction of the X-ray on the subject 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, the X-rays are made incident from the irradiation unit to a specific portion of the subject at a plurality of different incident angles including a specific incident angle selected from a range of 5 ° to 20 °, and the diffraction ring formed by the diffraction of each X-ray at the specific portion is detected by the two-dimensional detector.

6. The stress measuring method according to claim 5,

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

7. The stress measuring method according to claim 1,

in the detection step, an object having a shape as follows is used as the object to be inspected: the X-ray detector interferes with the irradiation unit inclined with respect to the subject so that an incident angle of the X-ray irradiated from the irradiation unit to the subject is larger than 25 ° or with a diffracted X-ray formed by diffraction of the X-ray irradiated from the irradiation unit on the subject, and is separated from the X-ray diffracted by the irradiation unit inclined with respect to the subject so that an incident angle of the X-ray irradiated to the subject is 25 ° or smaller or the X-ray irradiated from the irradiation unit.

8. The stress measuring method according to claim 5,

in the detection step, an object having a shape as follows is used as the object to be inspected: the X-ray detector interferes with the irradiation unit inclined with respect to the subject so that an incident angle of the X-ray irradiated from the irradiation unit to the subject is larger than 25 ° or with a diffracted X-ray formed by diffraction of the X-ray irradiated from the irradiation unit on the subject, and is separated from the X-ray diffracted by the irradiation unit inclined with respect to the subject so that an incident angle of the X-ray irradiated to the subject is 25 ° or smaller or the X-ray irradiated from the irradiation unit.

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. 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 at which the X-ray is incident on the subject is usually set to 25 ° to 65 °. In patent document 1, the incident angle Ψ is set to 30 °.

In the two-dimensional detection method, when the incident angle Ψ of the X-ray incident on the subject is within the range of 25 ° to 65 °, high-precision measurement is possible, but an appropriate incident angle may not be secured due to the shape of the subject, or the like. For example, if the irradiation unit capable of irradiating X-rays is tilted with respect to the subject so that the incident angle Ψ for the X-rays to enter the subject is within the above range, the X-rays may be diffracted or the irradiation unit itself may interfere with the subject. In such a case, it is difficult to measure the stress of the subject with high accuracy. Further, as the incident angle Ψ of the X-ray becomes larger, the influence of the surface roughness of the object becomes more likely to occur, and thus an appropriate incident angle Ψ may not be secured. Further, in order to measure the stress in the deep part of the subject, it is necessary to reduce the incident angle Ψ, but as described above, the measurement accuracy of this measurement method is approximately proportional to sin2 Ψ, and therefore, the measurement accuracy decreases as the incident angle Ψ becomes smaller. Therefore, when the incident angle Ψ at which the X-ray is incident on the subject cannot be set within the range of 25 ° to 65 °, particularly when the incident angle Ψ needs to be set within a range smaller than 25 ° (low incident angle), it is generally difficult to apply the two-dimensional detection method.

Prior art documents

Patent document

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

Disclosure of Invention

An object of the present invention is to provide a stress measurement method capable of measuring the stress of an object to be examined with high accuracy by using a two-dimensional detection method when the incident angle of X-rays to the object is in the range of 5 ° or more and 20 ° or less.

A stress measurement method according to an aspect of the present invention is a method of measuring a stress of a test object made of a metal, the method including: a detection step of causing an X-ray to enter the subject from an irradiation unit capable of irradiating the subject with the X-ray and detecting a diffraction ring of a diffracted X-ray formed by diffraction of the X-ray on the subject by a two-dimensional detector; and a calculation step of calculating a stress of the subject based on a detection result of the detection step, wherein in the detection step, the irradiation unit is inclined with respect to the subject so that an incident angle of the X-ray to the subject is in a range of 5 ° or more and 20 ° or less, the X-ray is incident on each of a plurality of portions of the subject from the irradiation unit, and a diffraction ring formed by diffraction of each X-ray on the subject is detected by the two-dimensional detector.

In addition, a stress measuring method according to another aspect of the present invention is a method of measuring a stress of a test object made of a metal, the method including: a detection step of causing an X-ray to enter the subject from an irradiation unit capable of irradiating the subject with the X-ray and detecting a diffraction ring of a diffracted X-ray formed by diffraction of the X-ray on the subject 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 made to enter a specific portion of the subject from the irradiation unit at a plurality of different incident angles including a specific incident angle selected from a range of 5 ° to 20 °, and each X-ray is detected by the two-dimensional detector as a diffraction ring formed by diffracting each X-ray at the specific portion.

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 a relationship between an irradiation area of incident X-rays and a slope error (CrMo-based low alloy steel).

Fig. 5 is a graph showing a relationship between the oscillation angle of incident X-rays and reliability (CrMo-based low alloy steel).

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

(first embodiment)

A stress measurement method according to a first embodiment of the present invention will be described with reference to fig. 1. This stress measurement method is a method of measuring the stress of the object 1 (such as a crankshaft) made of a metal such as a steel material using a two-dimensional detector (not shown). The subject 1 has a shape that interferes with the irradiation unit 4 inclined with respect to the subject 1 so that an incident angle of the X-ray irradiated from the irradiation unit 4 capable of irradiating the X-ray to the subject 1 is larger than 25 °, or a diffraction X-ray formed by diffraction of the X-ray irradiated from the irradiation unit 4 on the subject 1, and is separated from the irradiation unit 4 inclined with respect to the subject 1 so that the incident angle of the X-ray incident on the subject 1 is 25 ° or smaller, or a diffraction X-ray formed by diffraction of the X-ray irradiated from the irradiation unit 4 on the subject 1. Specifically, as shown in fig. 1, the device 1 has a front surface 2 and a concave portion 3 having a shape recessed from the front surface 2 and extending in a groove shape. In the present embodiment, a case of measuring the stress of the concave portion 3 of the device under test 1 will be described. That is, in the present embodiment, when the irradiation part 4 is inclined with respect to the concave part 3 so that the incident angle Ψ of the X-ray is larger than 25 °, the irradiation part 4 interferes with the surface 2 of the object 1, or the diffracted X-ray interferes with the boundary between the concave part 3 and the surface. However, the measurement site is not limited to the recess 3. 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, in a state where the irradiation unit 4 is tilted with respect to the subject 1 so that the incident angle Ψ at which the X-rays are incident on the concave portion 3 is within a range of 5 ° to 20 ° (low incident angle), the X-rays are incident on a plurality of locations in the concave portion 3 from the irradiation unit 4 at a constant incident angle Ψ, and the diffraction ring R formed by the diffraction of each X-ray on the concave portion 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 a predetermined multiple (for example, 15000 times) or more of the area of the crystal grain of the object 1.

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 of the present embodiment, since the irradiation unit 4 is tilted with respect to the subject 1 so that the incident angle of the X-ray incident on the subject 1 is within the range of 5 ° or more and 20 ° or less (low incident angle) in the detection step, even when the subject 1 has a shape in which the irradiation unit 4 interferes with the subject 1 when the irradiation unit 4 is tilted with respect to the subject 1 so that the incident angle of the X-ray incident on the subject 1 is greater than 25 °, the stress of the subject 1 can be measured efficiently. In addition, since the plurality of diffraction rings R corresponding to the respective X-rays respectively incident on the plurality of portions of the subject 1 are detected in the detection step, 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 single X-ray incident on the subject 1 is detected. Therefore, the accuracy of calculation of the stress of the object 1 in the calculation step is improved.

In addition, in the detection step, since the plurality of portions are selected as 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 substantially uniform along the extending direction of the concave portion 3, the measurement accuracy is improved by detecting the diffraction ring R with respect to the portion 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 along 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 operation 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, incident X-rays are made to enter from the irradiation section 4 at a single position in the recess 3 at a plurality of different incident angles Ψ including a specific incident angle Ψ selected from a range of 5 ° to 20 ° and, 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 is selected from a range having the specific incident angle Ψ as a lower limit value and an incident angle Ψ increased by a prescribed angle with respect to the specific incident angle Ψ as an upper limit value. In the present embodiment, in the detection step, X-rays are made to continuously enter the concave portion 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 respective X-rays diffracting in the concave portion 3 is detected by a two-dimensional detector.

As described above, in the stress measurement method of the present embodiment, since the X-ray is irradiated to the subject 1 at the plurality of different incident angles Ψ including the specific incident angle Ψ selected from the range of 5 ° to 20 ° in the detection step, even when the subject 1 has a shape in which the irradiation part 4 interferes with the subject 1 when the irradiation part 4 is tilted with respect to the subject 1 so that the incident angle at which the X-ray is incident on the subject 1 is larger than 25 °, the stress of the subject 1 can be effectively measured. In the detection step, since the two-dimensional detector detects the plurality of diffraction rings R corresponding to the plurality of X-rays respectively incident at the plurality of incident angles Ψ different from each other, 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 a single diffraction ring corresponding to the X-ray incident on the object 1 at a single incident angle is detected. Therefore, the accuracy of calculation of the stress of the concave portion 3 in the calculation step is improved.

In the detection process, the plurality of incident angles Ψ are selected from a range in which the specific incident angle Ψ is set to a lower limit value and the incident angle Ψ, which is increased by a predetermined angle with respect to the specific incident angle Ψ, is set to an upper limit value, so that more diffraction information can be obtained in the vicinity of the irradiation site of the X-ray incident at the specific incident angle Ψ. Thus, the measurement accuracy is improved.