WO2018190042A1 - Method for measuring residual stress - Google Patents
Method for measuring residual stress Download PDFInfo
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- WO2018190042A1 WO2018190042A1 PCT/JP2018/008965 JP2018008965W WO2018190042A1 WO 2018190042 A1 WO2018190042 A1 WO 2018190042A1 JP 2018008965 W JP2018008965 W JP 2018008965W WO 2018190042 A1 WO2018190042 A1 WO 2018190042A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/25—Measuring force or stress, in general using wave or particle radiation, e.g. X-rays, microwaves, neutrons
Definitions
- the present invention relates to a method for measuring the residual stress of an object to be inspected.
- X-ray diffraction method and acoustoelastic method are known as non-destructive methods for measuring the residual stress of an object to be inspected as disclosed in Patent Document 1 and the like.
- the X-ray diffraction method is a method for evaluating the state of residual stress of the inspection object based on the result of diffraction of X-rays irradiated to the inspection object.
- the acoustoelastic method is a method for evaluating the state of residual stress of the object to be inspected based on the time until ultrasonic waves (surface SH waves or the like) incident on the object to be inspected are received.
- the X-ray diffraction method can measure the value (absolute value) of the residual stress of the object to be inspected, but can only evaluate the extreme surface layer (in the range of several ⁇ m from the surface) of the object to be inspected. It takes a relatively long time to set up the equipment used in the method and to measure the residual stress.
- the acoustoelastic method has a shorter measurement time than the X-ray diffraction method and can evaluate a deep range from the surface of the object to be inspected.
- Each parameter (acoustic velocity and acoustoelastic constant) is generally determined by measuring the initial acoustic velocity with a sample before applying stress under the same conditions as the object to be inspected, and further changing the acoustic velocity according to the applied stress. It is obtained by measuring.
- a residual stress measurement method is a method for measuring a residual stress of an object to be inspected, and is an X-ray diffraction method of the object to be inspected or the object to be inspected made of the same material as the object to be inspected.
- This residual stress measurement method includes a residual stress value measurement step, a converted stress value measurement step, a calibration coefficient calculation step, and a calibration step.
- a residual stress value ⁇ which is a residual stress value (absolute value) of a specific part of the inspection object 1 is measured by an X-ray diffraction method.
- the converted stress value ⁇ ′ of a specific portion (the same portion measured in the residual stress value measuring step) of the inspection object 1 is obtained by the acoustoelastic method. Measured.
- the converted stress value ⁇ ′ is a stress value having a correlation with the residual stress value ⁇ .
- the residual stress value ⁇ is represented by the product of the converted stress value ⁇ ′ and a calibration coefficient k described later.
- the acoustic elastic constant (rate of change in sound speed according to the applied stress) caused by the material of the device under test 1 can be converted into the residual stress value ⁇ .
- the converted stress value is measured by surface waves (surface SH waves and Rayleigh waves) that propagate on the surface of the inspection object 1 or in the vicinity thereof (hereinafter referred to as “surface region”).
- ⁇ ′ is measured.
- the converted stress value ⁇ ′ is calculated based on the time until the ultrasonic wave transmitted from the transmitting unit 10 propagates to the receiving unit 20 as a surface wave.
- the surface region means a region corresponding to a depth of about 1 to 2 wavelengths of surface waves from the surface of the inspection object 1.
- the calibration coefficient k is calculated based on the residual stress value ⁇ measured in the residual stress value measuring step and the converted stress value ⁇ ′ measured in the converted stress value measuring step.
- the following relational expression is obtained.
- a specific part of the inspection object 1 is measured by two methods of the X-ray diffraction method and the acoustoelastic method, so that the residual stress value of the part is measured. Since ⁇ and the converted stress value ⁇ ′ correlated therewith are obtained, a calibration coefficient k for converting the converted stress value ⁇ ′ to the residual stress value ⁇ is calculated based on the residual stress value ⁇ and the converted stress value ⁇ ′. .
- each converted stress value ⁇ ′ obtained by the measurement is calculated as a calibration coefficient. It is possible to approximate the residual stress value ⁇ by using k. Therefore, in this residual stress measurement method, the X-ray diffraction method alone is used for inspection without performing the preliminary measurement of the test object 1 necessary for calculating the absolute value of the residual stress of the test object 1 by the acoustoelastic method.
- an average value of the residual stress values ⁇ of a plurality of parts (for example, measurement point A and measurement point B in FIG. 2) of the inspection object 1 is calculated, and in the converted stress value measuring step, An average value of the converted stress values ⁇ ′ of the plurality of parts of the inspection object 1 is calculated, and based on the average value of the residual stress values ⁇ and the average value of the converted stress values ⁇ ′ in the calibration coefficient calculating step.
- the calibration coefficient k may be calculated.
- the calibration coefficient k is calculated by measuring the test object made of the same material as the test object 1 and in the same stress state by the X-ray diffraction method and the acoustoelastic method, and the calibration coefficient k is used in the calibration process. May be. That is, in the residual stress value measuring step, a specific residual stress value ⁇ of the test object is calculated, and in the converted stress value measuring step, the specific part of the test object (the part measured in the residual stress value measuring process) The converted stress value ⁇ ′ of the same part) is calculated, and in the calibration coefficient calculating step, the calibration coefficient k is calculated based on the residual stress value ⁇ and the converted stress value ⁇ ′.
- each converted stress value ⁇ ′ obtained by the measurement may be calibrated to the residual stress value ⁇ based on the calibration coefficient k.
- the residual stress value measurement step as the residual stress value ⁇ , ultrasonic waves (surfaces) used as a residual stress value ⁇ from the surface of the part to be inspected 1 by the acoustoelastic method.
- the average value ⁇ ave of each residual stress value ⁇ measured by the X-ray diffraction method is measured for a plurality of portions in the range of the propagation depth (in this embodiment, the depth corresponding to one wavelength of the surface wave).
- the residual stress value ⁇ on the surface of the inspection object 1 is measured by the X-ray diffraction method.
- the device under test 1 is polished by electrolytic polishing from the surface of the device under test 1 by the first depth d1.
- the residual stress value ⁇ of the new surface is again measured by the X-ray diffraction method.
- the calibration coefficient k is calculated based on the average value ⁇ ave and the converted stress value ⁇ ′ measured by the acoustoelastic method in the converted stress value measurement step.
- the average value ⁇ ave is used in the calibration coefficient calculation step. That is, the residual stress value used in the calibration coefficient calculation step is a value corresponding to the ultrasonic wave propagation depth used in the converted stress value measurement step. Therefore, in the calibration coefficient calculation step, the calibration coefficient k is calculated based on the residual stress value ⁇ of the surface layer of the specific part (the part shallower than the depth at which the ultrasonic wave used in the acoustoelastic method propagates). The accuracy of the calibration coefficient k is increased. Therefore, the accuracy of calibration in the calibration process is increased.
- the measurement method of the present embodiment is particularly effective when the residual stress value has a gradient in the depth range in which the ultrasonic wave used in the acoustoelastic method propagates from the surface of the device under test 1.
- the specific stress differs by using a plurality of ultrasonic waves (surface waves) having different frequencies as the converted stress value ⁇ ′.
- a stress value function F indicating the relationship between the depth of the specific part and the converted stress value ⁇ ′ based on the measurement of a plurality of converted stress values ⁇ ′ by the acoustoelastic method for the depth and the measured values (FIG. 5). (See).
- the surface wave propagates deeper from the surface of the object 1 to be inspected as the frequency is low, the surface area of the object 1 to be inspected can be determined by measuring the specific portion with surface waves having a plurality of different frequencies.
- the stress value function F It is possible to grasp the stress gradient at (determine the stress value function F). Specifically, a surface wave of the first frequency is transmitted from the transmission unit 10 to the specific part and is received by the reception unit 20. Based on this propagation time, the reduced stress value ⁇ ′1 is measured. Next, a surface wave having a frequency lower or higher than the first frequency is transmitted from the transmission unit 10 and received by the reception unit 20. The converted stress value ⁇ ′2 is measured based on this propagation time. Then, the stress value function F is calculated based on each converted stress value ⁇ ′.
- the calibration coefficient k is calculated based on the converted stress value ⁇ ′ and the residual stress value ⁇ when the depth is zero in the stress value function F, so that the specific portion is single-accurated by the acoustoelastic method.
- the calibration coefficient k is calculated based on the converted stress value ⁇ ′ measured at the frequency and the residual stress value ⁇ , that is, the calibration coefficient k is calculated based on the stress values at different depths. Compared to the case, the accuracy of the calibration coefficient k is increased. Therefore, the accuracy of calibration in the calibration process is increased.
- the stress value function F may be obtained based on a plurality of converted stress values ⁇ ′ measured by three or more surface waves having different frequencies. In this way, the accuracy of the calibration coefficient k is further increased.
- the residual stress value measurement process of the second embodiment will be described with reference to FIG.
- a steel material was used as the object to be inspected 1, and an ultrasonic wave having a frequency of 5 MHz was used in the converted stress value measurement step.
- the propagation depth of the inspected object 1 of ultrasonic waves (surface waves) used in the acoustoelastic method is in the range of about one wavelength from the surface of the inspected object 1.
- the propagation range of the surface wave is a range having a depth of about 0.6 mm from the surface of the object 1 to be inspected.
- the residual stress value measuring step of this example first, the residual stress value ⁇ of the surface of a specific part of the inspection object 1 was measured by the X-ray diffraction method. The measurement result was ⁇ 300 MPa. Since compressive stress was applied to this part, the residual stress value was a negative value.
- the test object 1 was polished from the surface of the test object 1 by electrolytic polishing by a first depth d1 (150 ⁇ m in this example). And the residual stress value (sigma) of the new surface was measured. The measurement result was ⁇ 250 MPa. Similarly, the residual stress value at the second depth d2 (300 ⁇ m in this embodiment) from the surface of the inspection object 1 is ⁇ 200 MPa, and the third depth d3 (this embodiment from the surface of the inspection object 1). In the example, the residual stress value at the site of 450 ⁇ m was ⁇ 150 MPa, and the residual stress value at the site of the fourth depth d4 (600 ⁇ m in this example) from the surface of the inspection object 1 was ⁇ 100 MPa. As a result, the average value ⁇ ave of the residual stress values in the specific part of the device under test 1 was ⁇ 200 MPa. The position and number of measurement points are not limited to the above example.
- the average value ⁇ ave of the depth range in which the surface wave propagates is obtained as the residual stress value ⁇ of the specific part of the inspection object 1, thereby obtaining the residual stress value ⁇ on the surface of the specific part. It was confirmed that the accuracy of the calibration coefficient k is higher than when the calibration coefficient k is calculated.
- the converted stress value ⁇ ′ of the specific part was measured by ultrasonic waves (surface waves) having a frequency of 5 MHz and ultrasonic waves (surface waves) having a frequency of 2 MHz. .
- the measured value of the converted stress value ⁇ ′ by ultrasonic waves (surface waves) having a frequency of 5 MHz was a value at a position where the depth from the surface of the DUT 1 was about 0.6 mm, and was ⁇ 500 MPa.
- the measured value of the converted stress value ⁇ ′ by ultrasonic waves (surface waves) having a frequency of 2 MHz was a value at a position where the depth from the surface of the DUT 1 was about 1.5 mm, and was ⁇ 400 MPa. From this, the stress value function F was obtained.
- the converted stress value ⁇ ′ (about ⁇ 567 MPa in this embodiment) when the depth is zero in the stress value function F and the residual stress value measured in the residual stress value measurement step.
- the calibration coefficient k was calculated based on ⁇ ( ⁇ 700 MPa in this example).
- the calibration coefficient k is calculated on the basis of the converted stress value ⁇ ′ and the residual stress value ⁇ when the depth is zero in the stress value function F, so that the specific portion is single-accurated by the acoustoelastic method.
- the calibration coefficient k is calculated based on the converted stress value ⁇ ′ ( ⁇ 400 MPa, ⁇ 500 MPa, etc.) measured at the frequency of and the residual stress value ⁇ ( ⁇ 700 MPa)
- the accuracy of the calibration coefficient k is higher. It was confirmed that it would increase.
- a propagation time ratio having a correlation with the residual stress value ⁇ measured by the X-ray diffraction method may be measured as the converted stress value ⁇ ′.
- the propagation time ratio means the ratio of the time that the surface SH wave propagates from the transmission unit 10 to the reception unit 20 to the time that the Rayleigh wave propagates from the transmission unit 10 to the reception unit 20.
- the residual stress measurement method of the above embodiment is a method of measuring the residual stress of the object to be inspected, and is a method for specifying the object to be inspected or the object under test made of the same material as the object to be inspected by X-ray diffraction.
- a residual stress value measuring step for measuring a residual stress value which is a residual stress value of a part and a converted stress value which is a stress value of the specific part and has a correlation with the residual stress value are measured by a acoustoelastic method.
- the converted stress value is converted into the residual stress value based on the converted stress value measuring step, the residual stress value measured in the residual stress value measuring step, and the converted stress value measured in the converted stress value measuring step.
- a calibration coefficient calculation step for calculating a calibration coefficient to be converted into a plurality of converted stress values obtained by measuring a plurality of parts of the object to be inspected by the acoustoelastic method, respectively, based on the calibration coefficient Calibration to calibrate to Including the extent, the.
- the residual stress value of a part to be inspected or a specific part of the specimen to be measured is measured by two methods, the X-ray diffraction method and the acoustoelastic method, and a converted stress having a correlation therewith. Since the value is obtained, a calibration coefficient for converting the converted stress value into the residual stress value is calculated based on the residual stress value and the converted stress value. Therefore, by measuring a plurality of parts of the object to be inspected by the acoustoelastic method which can be measured in a shorter time than the X-ray diffraction method, each converted stress value obtained by the measurement is retained by using the calibration coefficient. It is possible to approximate the stress value.
- the specific part of the object to be inspected is measured in the residual stress value measuring step and the converted stress value measuring step.
- the residual stress value measuring step as the residual stress value, the X-rays are obtained for a plurality of parts in a depth range in which ultrasonic waves used in the acoustoelastic method propagate from the surface of the part for the specific part. It is preferable to measure the average value of each residual stress value measured by the diffraction method.
- the residual stress value used in the calibration coefficient calculation step becomes a value corresponding to the propagation depth of the ultrasonic wave used in the converted stress value measurement step, the surface layer of the specific part in the calibration coefficient calculation step Compared to the case where the calibration coefficient is calculated based on the residual stress value (part shallower than the depth at which the ultrasonic wave used in the acoustoelastic method propagates), the accuracy of the calibration coefficient is increased. Therefore, the accuracy of calibration in the calibration process is increased.
- This method is particularly effective when the residual stress value has a gradient in the depth range in which the ultrasonic wave used in the acoustoelastic method propagates from the surface of the object to be inspected.
- the converted stress value measuring step a plurality of values are measured by the acoustoelastic method for different depths of the specific part by using a plurality of ultrasonic waves having different frequencies as the converted stress value. And obtaining a stress value function indicating a relationship between the depth of the specific part and the converted stress value based on each measured value, and in the calibration coefficient calculating step, the residual stress value and the stress value It is preferable to calculate the calibration coefficient based on the converted stress value when the depth is zero in the function.
- the calibration coefficient is calculated on the basis of the converted stress value and the residual stress value when the depth is zero in the stress value function in the calibration coefficient calculation step, so that the specific part is obtained by the acoustoelastic method.
- the calibration coefficient is calculated based on the converted stress value measured at a single frequency and the residual stress value, that is, compared to the case where the calibration coefficient is calculated based on each stress value at different depths.
- the accuracy of the calibration coefficient is increased. Therefore, the accuracy of calibration in the calibration process is increased.
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Abstract
A method for measuring residual stress, wherein the method includes: a residual stress value measurement step for measuring a residual stress value, which is a value of residual stress at a specific location on a specimen or test object, through an X-ray diffraction method; a conversion stress value measurement step for measuring a conversion stress value, which is a value of stress at the specific location and has a correlation with the residual stress value, through an acoustoelasticity method; a correction coefficient calculation step for calculating a correction coefficient for converting the conversion stress value to the residual stress value on the basis of the residual stress value measured in the residual stress value measurement step and the conversion stress value measured in the conversion stress value measurement step; and a correction step for correcting conversion stress values obtained by measuring a plurality of locations on the specimen through the acoustoelasticity method to respective residual stress values on the basis of the correction coefficient.
Description
本発明は、被検査体の残留応力を測定する方法に関するものである。
The present invention relates to a method for measuring the residual stress of an object to be inspected.
従来、非破壊で被検査体の残留応力を測定する方法として、特許文献１等に見られるように、Ｘ線回折法や音弾性法が知られている。Ｘ線回折法は、被検査体に照射されたＸ線の回折の結果に基づいて当該被検査体の残留応力の状態を評価する方法である。音弾性法は、被検査体に入射した超音波（表面ＳＨ波等）が受信されるまでの時間に基づいて当該被検査体の残留応力の状態を評価する方法である。
Conventionally, X-ray diffraction method and acoustoelastic method are known as non-destructive methods for measuring the residual stress of an object to be inspected as disclosed in Patent Document 1 and the like. The X-ray diffraction method is a method for evaluating the state of residual stress of the inspection object based on the result of diffraction of X-rays irradiated to the inspection object. The acoustoelastic method is a method for evaluating the state of residual stress of the object to be inspected based on the time until ultrasonic waves (surface SH waves or the like) incident on the object to be inspected are received.
Ｘ線回折法では、被検査体の残留応力の値（絶対値）の測定が可能であるが、被検査体の極表層（表面から数μｍの範囲）しか評価できず、また、Ｘ線回折法に用いる装置のセッティングや残留応力の計測に比較的多くの時間を要する。一方、音弾性法は、Ｘ線回折法に比べて計測時間が短く、また、被検査体の表面から深い範囲の評価が可能であるものの、計測結果から残留応力の絶対値を得るためには、被検査体の材料に起因する各パラメータ（音速や音弾性定数）の事前測定が必要となる。なお、各パラメータ（音速や音弾性定数）は、一般的に、被検査体と同じ条件で応力が印加される前のサンプルにより初期音速が測定され、さらに応力の付与に応じた音速の変化を測定することにより求められる。
The X-ray diffraction method can measure the value (absolute value) of the residual stress of the object to be inspected, but can only evaluate the extreme surface layer (in the range of several μm from the surface) of the object to be inspected. It takes a relatively long time to set up the equipment used in the method and to measure the residual stress. On the other hand, the acoustoelastic method has a shorter measurement time than the X-ray diffraction method and can evaluate a deep range from the surface of the object to be inspected. In addition, it is necessary to previously measure each parameter (acoustic velocity and acoustoelastic constant) caused by the material of the object to be inspected. Each parameter (acoustic velocity and acoustoelastic constant) is generally determined by measuring the initial acoustic velocity with a sample before applying stress under the same conditions as the object to be inspected, and further changing the acoustic velocity according to the applied stress. It is obtained by measuring.
本発明の目的は、音弾性法によって被検査体の残留応力の絶対値を算出するのに必要な被検査体の各パラメータ（音速や音弾性定数）の事前測定をすることなく、比較的短時間で被検査体の残留応力の絶対値を測定することが可能な残留応力測定方法を提供することである。
It is an object of the present invention to perform comparatively short measurement without prior measurement of each parameter (sound speed and acoustoelastic constant) of an inspected object necessary for calculating the absolute value of the residual stress of the inspected object by the acoustoelastic method. It is an object of the present invention to provide a residual stress measurement method capable of measuring the absolute value of the residual stress of an object to be inspected over time.
本発明の一局面に従う残留応力測定方法は、被検査体の残留応力を測定する方法であって、Ｘ線回折法によって、前記被検査体又は前記被検査体と同材料からなる被試験体の特定の部位の残留応力の値である残留応力値を測定する残留応力値測定工程と、音弾性法によって、前記特定の部位の応力の値であって前記残留応力値と相関を有する換算応力値を測定する換算応力値測定工程と、前記残留応力値測定工程で測定された前記残留応力値と前記換算応力値測定工程で測定された前記換算応力値とに基づいて前記換算応力値を前記残留応力値に変換する校正係数を算出する校正係数算出工程と、前記被検査体の複数の部位を前記音弾性法で測定することにより得られた各換算応力値を前記校正係数に基づいてそれぞれ残留応力値に校正する校正工程と、を含む。
A residual stress measurement method according to an aspect of the present invention is a method for measuring a residual stress of an object to be inspected, and is an X-ray diffraction method of the object to be inspected or the object to be inspected made of the same material as the object to be inspected. Residual stress value measurement step of measuring a residual stress value that is a residual stress value of a specific part, and a converted stress value that is a value of the stress of the specific part and has a correlation with the residual stress value by an acoustoelastic method The converted stress value is measured based on the converted stress value measuring step, the residual stress value measured in the residual stress value measuring step, and the converted stress value measured in the converted stress value measuring step. A calibration coefficient calculation step for calculating a calibration coefficient to be converted into a stress value, and respective converted stress values obtained by measuring a plurality of parts of the object to be inspected by the acoustoelastic method based on the calibration coefficient Calibrate to stress values Including a calibration step.
以下、本発明の好ましい実施形態について、図面を参照しながら説明する。
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
（第１実施形態）
本発明の第１実施形態の残留応力測定方法について、図１及び図２を参照しながら説明する。本残留応力測定方法は、残留応力値測定工程と、換算応力値測定工程と、校正係数算出工程と、校正工程と、を含んでいる。 (First embodiment)
The residual stress measurement method according to the first embodiment of the present invention will be described with reference to FIGS. This residual stress measurement method includes a residual stress value measurement step, a converted stress value measurement step, a calibration coefficient calculation step, and a calibration step.
本発明の第１実施形態の残留応力測定方法について、図１及び図２を参照しながら説明する。本残留応力測定方法は、残留応力値測定工程と、換算応力値測定工程と、校正係数算出工程と、校正工程と、を含んでいる。 (First embodiment)
The residual stress measurement method according to the first embodiment of the present invention will be described with reference to FIGS. This residual stress measurement method includes a residual stress value measurement step, a converted stress value measurement step, a calibration coefficient calculation step, and a calibration step.
残留応力値測定工程では、図１に示されるように、Ｘ線回折法によって、被検査体１の特定の部位の残留応力の値（絶対値）である残留応力値σが測定される。
In the residual stress value measuring step, as shown in FIG. 1, a residual stress value σ, which is a residual stress value (absolute value) of a specific part of the inspection object 1 is measured by an X-ray diffraction method.
換算応力値測定工程では、図１に示されるように、音弾性法によって、前記被検査体１の特定の部位（残留応力値測定工程で測定した部位と同じ部位）の換算応力値σ′が測定される。換算応力値σ′は、残留応力値σと相関を有する応力の値である。具体的に、残留応力値σは、換算応力値σ′と後述する校正係数ｋとの積によって表される。なお、本実施形態の測定方法を適用せず、通常の音弾性法のみで測定する場合には、換算応力値σ′は、被検査体１に応力が印加される前の状態（無応力状態）における初期音速や、被検査体１の材料に起因する音弾性定数（印加する応力に応じた音速の変化の割合）に基づいて残留応力値σに変換されることが可能である。本実施形態の換算応力値測定工程では、被検査体１の表面ないしその近傍の領域（以下、「表面領域」と称する。）を伝播する表面波（表面ＳＨ波やレーリー波）によって換算応力値σ′が測定される。具体的に、この換算応力値σ′は、送信部１０から送信された超音波が表面波として受信部２０に伝播するまでの時間に基づいて算出される。なお、表面領域は、被検査体１の表面から表面波の約１～２波長の深さに相当する領域を意味する。
In the converted stress value measuring step, as shown in FIG. 1, the converted stress value σ ′ of a specific portion (the same portion measured in the residual stress value measuring step) of the inspection object 1 is obtained by the acoustoelastic method. Measured. The converted stress value σ ′ is a stress value having a correlation with the residual stress value σ. Specifically, the residual stress value σ is represented by the product of the converted stress value σ ′ and a calibration coefficient k described later. When the measurement method according to the present embodiment is not applied and the measurement is performed only by the normal acoustoelastic method, the converted stress value σ ′ is a state before the stress is applied to the inspection object 1 (no stress state). ) And the acoustic elastic constant (rate of change in sound speed according to the applied stress) caused by the material of the device under test 1 can be converted into the residual stress value σ. In the converted stress value measurement process of the present embodiment, the converted stress value is measured by surface waves (surface SH waves and Rayleigh waves) that propagate on the surface of the inspection object 1 or in the vicinity thereof (hereinafter referred to as “surface region”). σ ′ is measured. Specifically, the converted stress value σ ′ is calculated based on the time until the ultrasonic wave transmitted from the transmitting unit 10 propagates to the receiving unit 20 as a surface wave. The surface region means a region corresponding to a depth of about 1 to 2 wavelengths of surface waves from the surface of the inspection object 1.
校正係数算出工程では、残留応力値測定工程で測定された残留応力値σと換算応力値測定工程で測定された換算応力値σ′とに基づいて校正係数ｋを算出する。校正係数ｋは、換算応力値σ′を残留応力値σに変換する係数である。例えば、図２の測定点ＡにおいてＸ線回折法によって測定された残留応力値σと同測定点Ａにおいて音弾性法により測定された換算応力値σ’とに基づいて、σ＝ｋ×σ’の関係式が得られる。
In the calibration coefficient calculating step, the calibration coefficient k is calculated based on the residual stress value σ measured in the residual stress value measuring step and the converted stress value σ ′ measured in the converted stress value measuring step. The calibration coefficient k is a coefficient for converting the converted stress value σ ′ into the residual stress value σ. For example, σ = k × σ ′ based on the residual stress value σ measured by the X-ray diffraction method at the measurement point A in FIG. 2 and the converted stress value σ ′ measured by the acoustoelastic method at the measurement point A. The following relational expression is obtained.
校正工程では、図２に示されるように、被検査体１の複数の（図２では５つの）部位Ａ～Ｅを前記音弾性法で測定するとともに、その測定で得られた各換算応力値σ′を校正係数ｋに基づいてそれぞれ残留応力値σに校正する。これにより、被検査体１の複数の部位Ａ～Ｅにおける残留応力値σが得られる。
In the calibration process, as shown in FIG. 2, a plurality (five in FIG. 2) of parts A to E of the inspected object 1 are measured by the acoustoelastic method and each converted stress value obtained by the measurement is measured. Each σ ′ is calibrated to a residual stress value σ based on the calibration coefficient k. As a result, residual stress values σ at a plurality of portions A to E of the device under test 1 are obtained.
以上に説明したように、本実施形態の残留応力測定方法では、被検査体１の特定の部位をＸ線回折法及び音弾性法の２つの方法で測定することにより、その部位の残留応力値σ及びそれと相関のある換算応力値σ′が求まるので、これら残留応力値σと換算応力値σ′とに基づいて換算応力値σ′を残留応力値σに変換する校正係数ｋが算出される。よって、Ｘ線回折法よりも短時間で計測可能な音弾性法によって被検査体１の複数の部位Ａ～Ｅを測定することにより、その測定で得られた各換算応力値σ′を校正係数ｋを用いることによって残留応力値σに近似することが可能となる。したがって、本残留応力測定方法では、音弾性法によって被検査体１の残留応力の絶対値を算出するのに必要な被検査体１の事前測定をすることなく、Ｘ線回折法のみで被検査体１の複数の部位Ａ～Ｅを測定する場合よりも短時間で、かつ、Ｘ線回折法による測定と同程度の精度で被検査体１の複数の部位Ａ～Ｅの残留応力値σを求めることができる。
As described above, in the residual stress measurement method of the present embodiment, a specific part of the inspection object 1 is measured by two methods of the X-ray diffraction method and the acoustoelastic method, so that the residual stress value of the part is measured. Since σ and the converted stress value σ ′ correlated therewith are obtained, a calibration coefficient k for converting the converted stress value σ ′ to the residual stress value σ is calculated based on the residual stress value σ and the converted stress value σ ′. . Therefore, by measuring a plurality of portions A to E of the object 1 to be measured by the acoustoelastic method which can be measured in a shorter time than the X-ray diffraction method, each converted stress value σ ′ obtained by the measurement is calculated as a calibration coefficient. It is possible to approximate the residual stress value σ by using k. Therefore, in this residual stress measurement method, the X-ray diffraction method alone is used for inspection without performing the preliminary measurement of the test object 1 necessary for calculating the absolute value of the residual stress of the test object 1 by the acoustoelastic method. The residual stress values σ of the plurality of portions A to E of the body 1 to be inspected in a shorter time than when measuring the plurality of portions A to E of the body 1 and with the same accuracy as the measurement by the X-ray diffraction method. Can be sought.
なお、残留応力値測定工程において、被検査体１の複数の部位（例えば、図２における測定点Ａ及び測定点Ｂ）の残留応力値σの平均値が算出され、換算応力値測定工程において、被検査体１の前記複数の部位の換算応力値σ′の平均値が算出され、校正係数算出工程において、前記残留応力値σの平均値と前記換算応力値σ′の平均値とに基づいて校正係数ｋが算出されてもよい。
In the residual stress value measuring step, an average value of the residual stress values σ of a plurality of parts (for example, measurement point A and measurement point B in FIG. 2) of the inspection object 1 is calculated, and in the converted stress value measuring step, An average value of the converted stress values σ ′ of the plurality of parts of the inspection object 1 is calculated, and based on the average value of the residual stress values σ and the average value of the converted stress values σ ′ in the calibration coefficient calculating step. The calibration coefficient k may be calculated.
また、被検査体１と同じ材料からなりかつ同じ応力状態にある被試験体をＸ線回折法及び音弾性法で測定することによって校正係数ｋが算出され、校正工程においてその校正係数ｋが用いられてもよい。つまり、残留応力値測定工程において、前記被試験体の特定の残留応力値σが算出され、換算応力値測定工程において、被試験体の前記特定の部位（残留応力値測定工程で測定した部位と同じ部位）の換算応力値σ′が算出され、校正係数算出工程において、前記残留応力値σと前記換算応力値σ′とに基づいて校正係数ｋが算出され、校正工程において、被検査体１の複数の部位Ａ～Ｅが音弾性法で測定されるとともに、その測定で得られた各換算応力値σ′が校正係数ｋに基づいてそれぞれ残留応力値σに校正されてもよい。このことは、以下の第２実施形態及び第３実施形態においても同様である。
Further, the calibration coefficient k is calculated by measuring the test object made of the same material as the test object 1 and in the same stress state by the X-ray diffraction method and the acoustoelastic method, and the calibration coefficient k is used in the calibration process. May be. That is, in the residual stress value measuring step, a specific residual stress value σ of the test object is calculated, and in the converted stress value measuring step, the specific part of the test object (the part measured in the residual stress value measuring process) The converted stress value σ ′ of the same part) is calculated, and in the calibration coefficient calculating step, the calibration coefficient k is calculated based on the residual stress value σ and the converted stress value σ ′. Are measured by the acoustoelastic method, and each converted stress value σ ′ obtained by the measurement may be calibrated to the residual stress value σ based on the calibration coefficient k. The same applies to the following second and third embodiments.
（第２実施形態）
次に、本発明の第２実施形態の残留応力測定方法について説明する。なお、第２実施形態では、第１実施形態と異なる部分についてのみ説明を行い、第１実施形態と同じ工程、作用及び効果の説明は省略する。 (Second Embodiment)
Next, a residual stress measurement method according to the second embodiment of the present invention will be described. In the second embodiment, only different parts from the first embodiment will be described, and descriptions of the same steps, operations, and effects as those in the first embodiment will be omitted.
次に、本発明の第２実施形態の残留応力測定方法について説明する。なお、第２実施形態では、第１実施形態と異なる部分についてのみ説明を行い、第１実施形態と同じ工程、作用及び効果の説明は省略する。 (Second Embodiment)
Next, a residual stress measurement method according to the second embodiment of the present invention will be described. In the second embodiment, only different parts from the first embodiment will be described, and descriptions of the same steps, operations, and effects as those in the first embodiment will be omitted.
図３に示されるように、本実施形態では、残留応力値測定工程において、残留応力値σとして、被検査体１の特定の部位について当該部位の表面から音弾性法で用いられる超音波（表面波）が伝播する深さ（本実施形態では表面波の１波長分の深さ）の範囲の複数の部位についてＸ線回折法で測定された各残留応力値σの平均値σａｖｅを測定する。
As shown in FIG. 3, in the present embodiment, in the residual stress value measurement step, as the residual stress value σ, ultrasonic waves (surfaces) used as a residual stress value σ from the surface of the part to be inspected 1 by the acoustoelastic method. The average value σave of each residual stress value σ measured by the X-ray diffraction method is measured for a plurality of portions in the range of the propagation depth (in this embodiment, the depth corresponding to one wavelength of the surface wave).
具体的には、図３に示されるように、まずは、Ｘ線回折法によって被検査体１の表面の残留応力値σを測定する。その後、被検査体１の表面から第１深さｄ１分だけ電解研磨によって被検査体１を研磨する。そして、再びＸ線回折法によって新出面の残留応力値σを測定する。この操作を複数回繰り返すことにより、音弾性法で用いられる超音波（表面波）が伝播する深さの範囲の複数の部位についてＸ線回折法で測定された各残留応力値σの平均値σａｖｅを算出する。
Specifically, as shown in FIG. 3, first, the residual stress value σ on the surface of the inspection object 1 is measured by the X-ray diffraction method. Thereafter, the device under test 1 is polished by electrolytic polishing from the surface of the device under test 1 by the first depth d1. Then, the residual stress value σ of the new surface is again measured by the X-ray diffraction method. By repeating this operation a plurality of times, the average value σ ave of the residual stress values σ ave measured by the X-ray diffraction method for a plurality of portions in the depth range in which the ultrasonic waves (surface waves) used in the acoustoelastic method propagate. Is calculated.
そして、校正係数算出工程では、その平均値σａｖｅと換算応力値測定工程において音弾性法によって測定された換算応力値σ′とに基づいて校正係数ｋを算出する。
In the calibration coefficient calculation step, the calibration coefficient k is calculated based on the average value σave and the converted stress value σ ′ measured by the acoustoelastic method in the converted stress value measurement step.
以上のように、本実施形態では、校正係数算出工程において前記平均値σａｖｅが用いられる。すなわち、校正係数算出工程において用いられる残留応力値が換算応力値測定工程で用いられる超音波の伝播深さに対応する値となる。このため、校正係数算出工程において前記特定の部位の表層（音弾性法で用いられる超音波が伝播する深さよりも浅い部位）の残留応力値σに基づいて校正係数ｋが算出される場合に比べ、校正係数ｋの精度が高まる。よって、校正工程における校正の精度が高まる。本実施形態の測定方法は、被検査体１の表面から音弾性法で用いられる超音波が伝播する深さの範囲において残留応力値に勾配がある場合に特に有効である。
As described above, in the present embodiment, the average value σave is used in the calibration coefficient calculation step. That is, the residual stress value used in the calibration coefficient calculation step is a value corresponding to the ultrasonic wave propagation depth used in the converted stress value measurement step. Therefore, in the calibration coefficient calculation step, the calibration coefficient k is calculated based on the residual stress value σ of the surface layer of the specific part (the part shallower than the depth at which the ultrasonic wave used in the acoustoelastic method propagates). The accuracy of the calibration coefficient k is increased. Therefore, the accuracy of calibration in the calibration process is increased. The measurement method of the present embodiment is particularly effective when the residual stress value has a gradient in the depth range in which the ultrasonic wave used in the acoustoelastic method propagates from the surface of the device under test 1.
（第３実施形態）
次に、本発明の第３実施形態の残留応力測定方法について説明する。なお、第３実施形態においても、第１実施形態と異なる部分についてのみ説明を行い、第１実施形態と同じ工程、作用及び効果の説明は省略する。 (Third embodiment)
Next, a residual stress measurement method according to a third embodiment of the present invention will be described. In the third embodiment, only the parts different from the first embodiment will be described, and the description of the same steps, operations, and effects as those in the first embodiment will be omitted.
次に、本発明の第３実施形態の残留応力測定方法について説明する。なお、第３実施形態においても、第１実施形態と異なる部分についてのみ説明を行い、第１実施形態と同じ工程、作用及び効果の説明は省略する。 (Third embodiment)
Next, a residual stress measurement method according to a third embodiment of the present invention will be described. In the third embodiment, only the parts different from the first embodiment will be described, and the description of the same steps, operations, and effects as those in the first embodiment will be omitted.
図４に示されるように、本実施形態では、換算応力値測定工程において、換算応力値σ′として、互いに異なる周波数を有する複数の超音波（表面波）を用いることにより前記特定の部位の異なる深さについて音弾性法で複数の換算応力値σ′を測定することと、各測定値に基づいて前記特定の部位の深さと換算応力値σ′との関係を示す応力値関数Ｆ（図５を参照）を求めることと、を行う。なお、周波数が低い程、表面波は被検査体１の表面から深い範囲を伝播するので、互いに異なる複数の周波数の表面波によって前記特定の部位を測定することにより、被検査体１の表層近傍における応力勾配を把握すること（前記応力値関数Ｆを求めること）ができる。具体的には、前記特定の部位に対し、送信部１０から第１周波数の表面波を送信し、これを受信部２０で受信する。この伝播時間に基づいて換算応力値σ′１を測定する。次に、第１周波数よりも低い又は高い周波数を有する表面波を送信部１０から送信し、これを受信部２０で受信する。この伝播時間に基づいて換算応力値σ′２を測定する。そして、各換算応力値σ′に基づいて前記応力値関数Ｆを算出する。
As shown in FIG. 4, in the present embodiment, in the converted stress value measurement step, the specific stress differs by using a plurality of ultrasonic waves (surface waves) having different frequencies as the converted stress value σ ′. A stress value function F indicating the relationship between the depth of the specific part and the converted stress value σ ′ based on the measurement of a plurality of converted stress values σ ′ by the acoustoelastic method for the depth and the measured values (FIG. 5). (See). In addition, since the surface wave propagates deeper from the surface of the object 1 to be inspected as the frequency is low, the surface area of the object 1 to be inspected can be determined by measuring the specific portion with surface waves having a plurality of different frequencies. It is possible to grasp the stress gradient at (determine the stress value function F). Specifically, a surface wave of the first frequency is transmitted from the transmission unit 10 to the specific part and is received by the reception unit 20. Based on this propagation time, the reduced stress value σ′1 is measured. Next, a surface wave having a frequency lower or higher than the first frequency is transmitted from the transmission unit 10 and received by the reception unit 20. The converted stress value σ′2 is measured based on this propagation time. Then, the stress value function F is calculated based on each converted stress value σ ′.
続いて、校正係数算出工程では、前記応力値関数Ｆにおいて深さがゼロのときにおける換算応力値σ′と残留応力値測定工程においてＸ線回折法によって測定された残留応力値σとに基づいて校正係数ｋを算出する。
Subsequently, in the calibration coefficient calculation step, based on the converted stress value σ ′ when the depth is zero in the stress value function F and the residual stress value σ measured by the X-ray diffraction method in the residual stress value measurement step. A calibration coefficient k is calculated.
ここで、Ｘ線回折法では、被検査体１の極表層の部位（実質的に深さがゼロと評価可能な部位）の残留応力値が測定される。よって、前記応力値関数Ｆにおいて深さがゼロのときの換算応力値σ′と残留応力値σとに基づいて校正係数ｋが算出されることにより、前記特定の部位について音弾性法によって単一の周波数で測定された換算応力値σ′と前記残留応力値σとに基づいて校正係数ｋが算出される場合、つまり、互いに異なる深さにおける各応力値に基づいて校正係数ｋが算出される場合に比べ、校正係数ｋの精度が高まる。したがって、校正工程における校正の精度が高まる。
Here, in the X-ray diffraction method, a residual stress value of a portion of the extreme surface layer of the inspection object 1 (a portion where the depth can be evaluated to be substantially zero) is measured. Therefore, the calibration coefficient k is calculated based on the converted stress value σ ′ and the residual stress value σ when the depth is zero in the stress value function F, so that the specific portion is single-accurated by the acoustoelastic method. When the calibration coefficient k is calculated based on the converted stress value σ ′ measured at the frequency and the residual stress value σ, that is, the calibration coefficient k is calculated based on the stress values at different depths. Compared to the case, the accuracy of the calibration coefficient k is increased. Therefore, the accuracy of calibration in the calibration process is increased.
なお、換算応力値測定工程では、３以上の互いに異なる周波数の表面波によって測定された複数の換算応力値σ′に基づいて前記応力値関数Ｆが求められてもよい。このようにすれば、より校正係数ｋの精度が高まる。
In the converted stress value measuring step, the stress value function F may be obtained based on a plurality of converted stress values σ ′ measured by three or more surface waves having different frequencies. In this way, the accuracy of the calibration coefficient k is further increased.
次に、第２実施形態の残留応力値測定工程について、図３を参照しながら説明する。この実施例では、被検査体１として鋼材が用いられ、また、換算応力値測定工程では、５ＭＨｚの周波数を有する超音波が用いられた。音弾性法で用いられる超音波（表面波）の被検査体１の伝播深さは、被検査体１の表面から約１波長分の範囲である。この実施例では、被検査体１として鋼材が用いられるため、表面波の伝播範囲は、被検査体１の表面から約０．６ｍｍの深さの範囲となる。
Next, the residual stress value measurement process of the second embodiment will be described with reference to FIG. In this example, a steel material was used as the object to be inspected 1, and an ultrasonic wave having a frequency of 5 MHz was used in the converted stress value measurement step. The propagation depth of the inspected object 1 of ultrasonic waves (surface waves) used in the acoustoelastic method is in the range of about one wavelength from the surface of the inspected object 1. In this embodiment, since a steel material is used as the object 1 to be inspected, the propagation range of the surface wave is a range having a depth of about 0.6 mm from the surface of the object 1 to be inspected.
この実施例の残留応力値測定工程では、まず、Ｘ線回折法によって被検査体１の特定の部位の表面の残留応力値σが測定された。この測定結果は、－３００ＭＰａであった。なお、この部位には圧縮応力が印加されているため、残留応力値はマイナスの値となった。
In the residual stress value measuring step of this example, first, the residual stress value σ of the surface of a specific part of the inspection object 1 was measured by the X-ray diffraction method. The measurement result was −300 MPa. Since compressive stress was applied to this part, the residual stress value was a negative value.
次に、被検査体１の表面から第１深さｄ１（この実施例では１５０μｍ）だけ電解研磨によって被検査体１が研磨された。そして、その新出面の残留応力値σが測定された。この測定結果は、－２５０ＭＰａであった。同様に、被検査体１の表面から第２深さｄ２（この実施例では３００μｍ）の部位における残留応力値は、－２００ＭＰａであり、被検査体１の表面から第３深さｄ３（この実施例では４５０μｍ）の部位における残留応力値は、－１５０ＭＰａであり、被検査体１の表面から第４深さｄ４（この実施例では６００μｍ）の部位における残留応力値は、－１００ＭＰａであった。これより、被検査体１の前記特定の部位における残留応力値の平均値σａｖｅは、－２００ＭＰａとなった。なお、測定点の位置や数は、上記の例に限られない。
Next, the test object 1 was polished from the surface of the test object 1 by electrolytic polishing by a first depth d1 (150 μm in this example). And the residual stress value (sigma) of the new surface was measured. The measurement result was −250 MPa. Similarly, the residual stress value at the second depth d2 (300 μm in this embodiment) from the surface of the inspection object 1 is −200 MPa, and the third depth d3 (this embodiment from the surface of the inspection object 1). In the example, the residual stress value at the site of 450 μm was −150 MPa, and the residual stress value at the site of the fourth depth d4 (600 μm in this example) from the surface of the inspection object 1 was −100 MPa. As a result, the average value σave of the residual stress values in the specific part of the device under test 1 was −200 MPa. The position and number of measurement points are not limited to the above example.
以上より、被検査体１の特定の部位の残留応力値σとして表面波が伝播する深さの範囲の平均値σａｖｅが求められることにより、前記特定の部位の表面の残留応力値σに基づいて校正係数ｋが算出される場合に比べ、校正係数ｋの精度が高まることが確認された。
As described above, the average value σave of the depth range in which the surface wave propagates is obtained as the residual stress value σ of the specific part of the inspection object 1, thereby obtaining the residual stress value σ on the surface of the specific part. It was confirmed that the accuracy of the calibration coefficient k is higher than when the calibration coefficient k is calculated.
続いて、第３実施形態の換算応力値測定工程について、図４及び図５を参照しながら説明する。この実施例においても、被検査体１として鋼材が用いられた。
Subsequently, the converted stress value measurement process of the third embodiment will be described with reference to FIGS. 4 and 5. Also in this example, a steel material was used as the object 1 to be inspected.
この実施例の換算応力値測定工程では、５ＭＨｚの周波数を有する超音波（表面波）と２ＭＨｚの周波数を有する超音波（表面波）とによって前記特定の部位の換算応力値σ′が測定された。５ＭＨｚの周波数を有する超音波（表面波）による換算応力値σ′の測定値は、被試験体１の表面からの深さが約０．６ｍｍの位置の値であり、－５００ＭＰａであった。２ＭＨｚの周波数を有する超音波（表面波）による換算応力値σ′の測定値は、被試験体１の表面からの深さが約１．５ｍｍの位置の値であり、－４００ＭＰａであった。これより、前記応力値関数Ｆが求められた。
In the converted stress value measuring step of this example, the converted stress value σ ′ of the specific part was measured by ultrasonic waves (surface waves) having a frequency of 5 MHz and ultrasonic waves (surface waves) having a frequency of 2 MHz. . The measured value of the converted stress value σ ′ by ultrasonic waves (surface waves) having a frequency of 5 MHz was a value at a position where the depth from the surface of the DUT 1 was about 0.6 mm, and was −500 MPa. The measured value of the converted stress value σ ′ by ultrasonic waves (surface waves) having a frequency of 2 MHz was a value at a position where the depth from the surface of the DUT 1 was about 1.5 mm, and was −400 MPa. From this, the stress value function F was obtained.
次に、校正係数算出工程では、前記応力値関数Ｆにおいて深さがゼロのときの換算応力値σ′（この実施例では約－５６７ＭＰａ）と、残留応力値測定工程で測定された残留応力値σ（この実施例では－７００ＭＰａ）と、に基づいて校正係数ｋが算出された。
Next, in the calibration coefficient calculation step, the converted stress value σ ′ (about −567 MPa in this embodiment) when the depth is zero in the stress value function F and the residual stress value measured in the residual stress value measurement step. The calibration coefficient k was calculated based on σ (−700 MPa in this example).
以上より、応力値関数Ｆにおいて深さがゼロのときの換算応力値σ′と残留応力値σとに基づいて校正係数ｋが算出されることにより、前記特定の部位について音弾性法によって単一の周波数で測定された換算応力値σ′（－４００ＭＰａや－５００ＭＰａ等）と前記残留応力値σ（－７００ＭＰａ）とに基づいて校正係数ｋが算出される場合に比べ、校正係数ｋの精度が高まることが確認された。
As described above, the calibration coefficient k is calculated on the basis of the converted stress value σ ′ and the residual stress value σ when the depth is zero in the stress value function F, so that the specific portion is single-accurated by the acoustoelastic method. Compared with the case where the calibration coefficient k is calculated based on the converted stress value σ ′ (−400 MPa, −500 MPa, etc.) measured at the frequency of and the residual stress value σ (−700 MPa), the accuracy of the calibration coefficient k is higher. It was confirmed that it would increase.
なお、今回開示された実施形態は、すべての点で例示であって制限的なものではないと考えられるべきである。本発明の範囲は、上記した実施形態の説明ではなく特許請求の範囲によって示され、さらに特許請求の範囲と均等の意味および範囲内でのすべての変更が含まれる。
In addition, it should be thought that embodiment disclosed this time is an illustration and restrictive at no points. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.
例えば、換算応力値測定工程では、換算応力値σ′として、Ｘ線回折法で測定された残留応力値σと相関を有する伝播時間比が測定されてもよい。伝播時間比は、表面ＳＨ波が送信部１０から受信部２０まで伝播する時間のレーリー波が送信部１０から受信部２０まで伝播する時間に対する割合を意味する。
For example, in the converted stress value measurement step, a propagation time ratio having a correlation with the residual stress value σ measured by the X-ray diffraction method may be measured as the converted stress value σ ′. The propagation time ratio means the ratio of the time that the surface SH wave propagates from the transmission unit 10 to the reception unit 20 to the time that the Rayleigh wave propagates from the transmission unit 10 to the reception unit 20.
ここで、上記実施形態について概説する。
Here, the above embodiment will be outlined.
上記実施形態の残留応力測定方法は、被検査体の残留応力を測定する方法であって、Ｘ線回折法によって、前記被検査体又は前記被検査体と同材料からなる被試験体の特定の部位の残留応力の値である残留応力値を測定する残留応力値測定工程と、音弾性法によって、前記特定の部位の応力の値であって前記残留応力値と相関を有する換算応力値を測定する換算応力値測定工程と、前記残留応力値測定工程で測定された前記残留応力値と前記換算応力値測定工程で測定された前記換算応力値とに基づいて前記換算応力値を前記残留応力値に変換する校正係数を算出する校正係数算出工程と、前記被検査体の複数の部位を前記音弾性法で測定することにより得られた各換算応力値を前記校正係数に基づいてそれぞれ残留応力値に校正する校正工程と、を含む。
The residual stress measurement method of the above embodiment is a method of measuring the residual stress of the object to be inspected, and is a method for specifying the object to be inspected or the object under test made of the same material as the object to be inspected by X-ray diffraction. A residual stress value measuring step for measuring a residual stress value which is a residual stress value of a part and a converted stress value which is a stress value of the specific part and has a correlation with the residual stress value are measured by a acoustoelastic method. The converted stress value is converted into the residual stress value based on the converted stress value measuring step, the residual stress value measured in the residual stress value measuring step, and the converted stress value measured in the converted stress value measuring step. A calibration coefficient calculation step for calculating a calibration coefficient to be converted into a plurality of converted stress values obtained by measuring a plurality of parts of the object to be inspected by the acoustoelastic method, respectively, based on the calibration coefficient Calibration to calibrate to Including the extent, the.
本残留応力測定方法では、被検査体又は被試験体の特定の部位をＸ線回折法及び音弾性法の２つの方法で測定することにより、その部位の残留応力値及びそれと相関のある換算応力値が求まるので、これら残留応力値と換算応力値とに基づいて換算応力値を残留応力値に変換する校正係数が算出される。よって、Ｘ線回折法よりも短時間で計測可能な音弾性法によって被検査体の複数の部位を測定することにより、その測定で得られた各換算応力値を前記校正係数を用いることによって残留応力値に近似することが可能となる。したがって、本残留応力測定方法では、音弾性法によって被検査体の残留応力の絶対値を算出するのに必要な被検査体の各パラメータ（音速や音弾性定数）の事前測定をすることなく、Ｘ線回折法のみで被検査体の複数の部位を測定する場合よりも短時間で、かつ、Ｘ線回折法による測定と同程度の精度で被検査体の複数の部位の残留応力値を求めることができる。
In this residual stress measurement method, the residual stress value of a part to be inspected or a specific part of the specimen to be measured is measured by two methods, the X-ray diffraction method and the acoustoelastic method, and a converted stress having a correlation therewith. Since the value is obtained, a calibration coefficient for converting the converted stress value into the residual stress value is calculated based on the residual stress value and the converted stress value. Therefore, by measuring a plurality of parts of the object to be inspected by the acoustoelastic method which can be measured in a shorter time than the X-ray diffraction method, each converted stress value obtained by the measurement is retained by using the calibration coefficient. It is possible to approximate the stress value. Therefore, in this residual stress measurement method, without performing prior measurement of each parameter (sound velocity or acoustoelastic constant) of the inspected object necessary for calculating the absolute value of the residual stress of the inspected object by the acoustoelastic method, The residual stress values of the plurality of parts of the object to be inspected are obtained in a shorter time and with the same accuracy as the measurement by the X-ray diffraction method, compared with the case of measuring the plurality of parts of the object to be inspected only by the X-ray diffraction method. be able to.
この場合において、前記残留応力値測定工程及び前記換算応力値測定工程では、前記被検査体の前記特定の部位が測定されることが好ましい。
In this case, it is preferable that the specific part of the object to be inspected is measured in the residual stress value measuring step and the converted stress value measuring step.
このようにすれば、校正工程における測定対象である被検査体と同一の被検査体の測定結果に基づいて校正係数が求められるので、校正係数の精度が高まる。よって校正工程における校正の精度が高まる。
In this way, since the calibration coefficient is obtained based on the measurement result of the same object to be inspected as the object to be measured in the calibration process, the accuracy of the calibration coefficient is increased. Therefore, the accuracy of calibration in the calibration process is increased.
また、記残留応力値測定工程では、前記残留応力値として、前記特定の部位について当該部位の表面から前記音弾性法で用いられる超音波が伝播する深さの範囲の複数の部位について前記Ｘ線回折法で測定された各残留応力値の平均値を測定することが好ましい。
In the residual stress value measuring step, as the residual stress value, the X-rays are obtained for a plurality of parts in a depth range in which ultrasonic waves used in the acoustoelastic method propagate from the surface of the part for the specific part. It is preferable to measure the average value of each residual stress value measured by the diffraction method.
このようにすれば、校正係数算出工程において用いられる残留応力値が換算応力値測定工程で用いられる超音波の伝播深さに対応する値となるので、校正係数算出工程において前記特定の部位の表層（音弾性法で用いられる超音波が伝播する深さよりも浅い部位）の残留応力値に基づいて校正係数が算出される場合に比べ、校正係数の精度が高まる。よって、校正工程における校正の精度が高まる。この方法は、被検査体の表面から音弾性法で用いられる超音波が伝播する深さの範囲において残留応力値に勾配がある場合に特に有効である。
In this way, since the residual stress value used in the calibration coefficient calculation step becomes a value corresponding to the propagation depth of the ultrasonic wave used in the converted stress value measurement step, the surface layer of the specific part in the calibration coefficient calculation step Compared to the case where the calibration coefficient is calculated based on the residual stress value (part shallower than the depth at which the ultrasonic wave used in the acoustoelastic method propagates), the accuracy of the calibration coefficient is increased. Therefore, the accuracy of calibration in the calibration process is increased. This method is particularly effective when the residual stress value has a gradient in the depth range in which the ultrasonic wave used in the acoustoelastic method propagates from the surface of the object to be inspected.
また、前記換算応力値測定工程では、前記換算応力値として、互いに異なる周波数を有する複数の超音波を用いることにより前記特定の部位の異なる深さについて前記音弾性法で複数の値を測定することと、各測定値に基づいて前記特定の部位の深さと前記換算応力値との関係を示す応力値関数を求めることと、を行い、前記校正係数算出工程では、前記残留応力値と前記応力値関数において深さがゼロのときの換算応力値とに基づいて前記校正係数を算出することが好ましい。
In the converted stress value measuring step, a plurality of values are measured by the acoustoelastic method for different depths of the specific part by using a plurality of ultrasonic waves having different frequencies as the converted stress value. And obtaining a stress value function indicating a relationship between the depth of the specific part and the converted stress value based on each measured value, and in the calibration coefficient calculating step, the residual stress value and the stress value It is preferable to calculate the calibration coefficient based on the converted stress value when the depth is zero in the function.
この態様では、校正係数算出工程において前記応力値関数において深さがゼロのときの換算応力値と残留応力値とに基づいて校正係数が算出されることにより、前記特定の部位について音弾性法によって単一の周波数で測定された換算応力値と前記残留応力値とに基づいて校正係数が算出される場合、つまり、互いに異なる深さにおける各応力値に基づいて校正係数が算出される場合に比べ、校正係数の精度が高まる。したがって、校正工程における校正の精度が高まる。
In this aspect, the calibration coefficient is calculated on the basis of the converted stress value and the residual stress value when the depth is zero in the stress value function in the calibration coefficient calculation step, so that the specific part is obtained by the acoustoelastic method. Compared to the case where the calibration coefficient is calculated based on the converted stress value measured at a single frequency and the residual stress value, that is, compared to the case where the calibration coefficient is calculated based on each stress value at different depths. The accuracy of the calibration coefficient is increased. Therefore, the accuracy of calibration in the calibration process is increased.
Claims (4)
- 被検査体の残留応力を測定する方法であって、
Ｘ線回折法によって、前記被検査体又は前記被検査体と同材料からなる被試験体の特定の部位の残留応力の値である残留応力値を測定する残留応力値測定工程と、
音弾性法によって、前記特定の部位の応力の値であって前記残留応力値と相関を有する換算応力値を測定する換算応力値測定工程と、
前記残留応力値測定工程で測定された前記残留応力値と前記換算応力値測定工程で測定された前記換算応力値とに基づいて前記換算応力値を前記残留応力値に変換する校正係数を算出する校正係数算出工程と、
前記被検査体の複数の部位を前記音弾性法で測定することにより得られた各換算応力値を前記校正係数に基づいてそれぞれ残留応力値に校正する校正工程と、を含む、残留応力測定方法。 A method for measuring the residual stress of an object to be inspected,
A residual stress value measuring step of measuring a residual stress value, which is a residual stress value of a specific part of the test object or a test object made of the same material as the test object, by an X-ray diffraction method;
A converted stress value measuring step of measuring a converted stress value that is a value of the stress of the specific part and has a correlation with the residual stress value by the acoustoelastic method,
A calibration coefficient for converting the converted stress value into the residual stress value is calculated based on the residual stress value measured in the residual stress value measuring step and the converted stress value measured in the converted stress value measuring step. Calibration coefficient calculation process;
A calibration step of calibrating each converted stress value obtained by measuring a plurality of parts of the object to be inspected by the acoustoelastic method to a residual stress value based on the calibration coefficient, respectively. . - 請求項１に記載の残留応力測定方法において、
前記残留応力値測定工程及び前記換算応力値測定工程では、前記被検査体の前記特定の部位が測定される、残留応力測定方法。 The residual stress measurement method according to claim 1,
The residual stress measurement method in which the specific part of the inspection object is measured in the residual stress value measurement step and the converted stress value measurement step. - 請求項１又は２に記載の残留応力測定方法において、
前記残留応力値測定工程では、前記残留応力値として、前記特定の部位について当該部位の表面から前記音弾性法で用いられる超音波が伝播する深さの範囲の複数の部位について前記Ｘ線回折法で測定された各残留応力値の平均値を測定する、残留応力測定方法。 In the residual stress measuring method according to claim 1 or 2,
In the residual stress value measuring step, as the residual stress value, the X-ray diffraction method is used for a plurality of parts in a range in which ultrasonic waves used in the acoustoelastic method propagate from the surface of the specific part for the specific part. A residual stress measurement method for measuring an average value of each residual stress value measured in step 1. - 請求項１又は２に記載の残留応力測定方法において、
前記換算応力値測定工程では、前記換算応力値として、互いに異なる周波数を有する複数の超音波を用いることにより前記特定の部位の異なる深さについて前記音弾性法で複数の値を測定することと、各測定値に基づいて前記特定の部位の深さと前記換算応力値との関係を示す応力値関数を求めることと、を行い、
前記校正係数算出工程では、前記残留応力値と前記応力値関数において深さがゼロのときの換算応力値とに基づいて前記校正係数を算出する、残留応力測定方法。 In the residual stress measuring method according to claim 1 or 2,
In the converted stress value measuring step, as the converted stress value, measuring a plurality of values by the acoustoelastic method for different depths of the specific part by using a plurality of ultrasonic waves having different frequencies from each other; Obtaining a stress value function indicating a relationship between the depth of the specific part and the converted stress value based on each measurement value,
The residual stress measurement method, wherein, in the calibration coefficient calculation step, the calibration coefficient is calculated based on the residual stress value and a converted stress value when the depth is zero in the stress value function.
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| JP6362533B2 (en) * | 2013-12-24 | 2018-07-25 | 株式会社神戸製鋼所 | Residual stress evaluation method and residual stress evaluation apparatus |
| JP6529887B2 (en) * | 2015-10-22 | 2019-06-12 | 株式会社神戸製鋼所 | Residual stress evaluation method |
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2017
- 2017-04-12 JP JP2017078700A patent/JP6793086B2/en not_active Expired - Fee Related
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2018
- 2018-03-08 WO PCT/JP2018/008965 patent/WO2018190042A1/en active Application Filing
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| JPS62294926A (en) * | 1986-06-16 | 1987-12-22 | Hitachi Ltd | Measurement of stress by ultrasonic surface wave |
| JPH05142067A (en) * | 1991-09-25 | 1993-06-08 | Toshiba Corp | Measuring method for distribution of concentrated stress |
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| SONG, WENTAO ET AL.: "Nondestructive Testing and Characterization of Residual Stress Field Using an Ultrasonic Method", CHINESE JOURNAL OF MECHANICAL ENGINEERING, vol. 29, no. 2, 2016, pages 365 - 371, XP035891316, ISSN: 1000-9345, DOI: doi:10.3901/CJME.2015.1023.126 * |
| TANAKA, SHUNICHIRO ET AL.: "Measurement of residual stress distribution in vicinity of ceramic bond interface by micro x-ray method and ultrasonic microscope method", LECTURE PROCEEDINGS OF REGULAR GENERAL MEETING CONFERENCE OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS KANSAI BRANCH, vol. 67, no. 1, March 1992 (1992-03-01), pages 7 - 9 * |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110793855A (en) * | 2019-11-13 | 2020-02-14 | 北京理工大学 | Evaluation method for intercrystalline stress of polycrystalline alloy with cubic structure |
| CN111537127A (en) * | 2020-05-13 | 2020-08-14 | 西北工业大学 | Full-range calibration method of X-ray stress gauge |
| CN111537127B (en) * | 2020-05-13 | 2022-03-11 | 西北工业大学 | Full-range calibration method of X-ray stress gauge |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2018179718A (en) | 2018-11-15 |
| JP6793086B2 (en) | 2020-12-02 |
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