JP5450905B1 - A method for predicting the remaining creep life of bainite structure. - Google Patents
A method for predicting the remaining creep life of bainite structure. Download PDFInfo
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Abstract
【課題】ベイナイト組織のクリープ余寿命の予測方法を提供する。
【解決手段】電磁超音波探触子を用いて、ベイナイト組織内に非接触で超音波を励起させることによって、ベイナイト組織において超音波共鳴を発生させる工程と、超音波共鳴の共鳴周波数を測定する工程と、共鳴周波数における超音波の変移を測定する工程と、共鳴周波数における音速を求める工程と、超音波の変移から前記ベイナイト組織の第1損傷率を求める工程と、音速からベイナイト組織の第2損傷率を求める工程と、第1損傷率及び第2損傷率に基づいてベイナイト組織の補正損傷率を求める工程とを含む、クリープ余寿命の予測方法とする。A method for predicting the remaining creep life of a bainite structure is provided.
An electromagnetic ultrasonic probe is used to excite ultrasonic waves in a bainite structure in a non-contact manner to generate ultrasonic resonance in the bainite structure, and to measure the resonance frequency of the ultrasonic resonance. A step of measuring an ultrasonic wave transition at a resonance frequency, a step of determining a sound velocity at the resonance frequency, a step of determining a first damage rate of the bainite structure from the ultrasonic wave shift, and a second of the bainite structure from the sound velocity. The creep remaining life prediction method includes a step of obtaining a damage rate and a step of obtaining a corrected damage rate of the bainite structure based on the first damage rate and the second damage rate.
Description
本発明は、ベイナイト組織のクリープ余寿命の予測方法に関する。 The present invention relates to a method for predicting the creep remaining life of a bainite structure.
火力発電設備や原子力発電設備等において用いられる機械部品は、長期間に渡って高温・高圧条件におかれることから、徐々に塑性変形を起こし、クリープ寿命に達すると破断してしまう。従って、火力発電設備や原子力発電設備を安全かつ経済的に運転するためには、用いられている機械部品のクリープ余寿命を的確に予測することによって、最適な時期に機械部品の交換を行うことが求められる。 Mechanical parts used in thermal power generation facilities, nuclear power generation facilities, and the like are subjected to high temperature and high pressure conditions for a long period of time, so that they gradually undergo plastic deformation and break when the creep life is reached. Therefore, in order to operate thermal power generation facilities and nuclear power generation facilities safely and economically, the machine parts must be replaced at the optimal time by accurately predicting the remaining creep life of the machine parts used. Is required.
このような機械部品に使用されている耐熱鋼のクリープ余寿命を予測する方法としては、例えば、目視検査、磁粉探傷検査、超音波探傷検査及び放射線探傷検査等の寿命末期に発生する亀裂を検出する方法、並びに、レプリカ法によるクリープボイドや微視亀裂を検出する方法が知られているが、これらの方法では、亀裂が生じる前の余寿命を予測することができない。また、特開昭63−235861号公報が示すように、実際に稼動している火力発電設備や原子力発電設備の機械部品の耐熱鋼から試験片を切り出して、クリープ破断試験を行い、その破断時間から余寿命を予測する方法が知られているが、この方法では、実際に稼動している設備から試験片を切り出して長時間に渡って試験をする必要があり、煩雑である。
これらの方法に対して、特開2001−343368号公報が示すように、亀裂が生じる前の余寿命を予測することができ、実際に稼動している設備から試験片を切り出す必要もない方法として、磁性を有する耐熱鋼に非接触で超音波を励起させることによって超音波共鳴を発生させ、この超音波共鳴の減衰具合から余寿命を予測する方法が報告されている。As a method of predicting the remaining creep life of heat-resistant steel used in such machine parts, for example, detection of cracks occurring at the end of life such as visual inspection, magnetic particle inspection, ultrasonic inspection, and radiation inspection There are known methods for detecting creep voids and microcracks by the replica method, but these methods cannot predict the remaining life before cracks are generated. Moreover, as disclosed in Japanese Patent Laid-Open No. 63-235861, a specimen is cut out from a heat-resistant steel of a mechanical part of a thermal power generation facility or a nuclear power generation facility that is actually in operation, and a creep rupture test is performed. However, in this method, it is necessary to cut out a test piece from a facility that is actually in operation and perform a test for a long time, which is complicated.
For these methods, as disclosed in JP-A-2001-343368, it is possible to predict the remaining life before a crack occurs, and there is no need to cut out a test piece from an actually operating facility. In addition, a method has been reported in which ultrasonic resonance is generated by exciting ultrasonic waves in a magnetic heat-resistant steel in a non-contact manner and the remaining life is predicted from the attenuation of the ultrasonic resonance.
本発明は、ベイナイト組織のクリープ余寿命の予測方法を提供することを目的とする。 An object of the present invention is to provide a method for predicting the remaining life of creep of a bainite structure.
本発明に係るクリープ余寿命の予測方法は、電磁超音波探触子を用いて、ベイナイト組織内に非接触で超音波を励起させることによって、ベイナイト組織において超音波共鳴を発生させる工程と、超音波共鳴の共鳴周波数を測定する工程と、共鳴周波数における超音波の変移を測定する工程と、共鳴周波数における音速を求める工程と、超音波の変移からベイナイト組織の第1損傷率を求める工程と、音速からベイナイト組織の第2損傷率を求める工程と、第1損傷率及び第2損傷率に基づいてベイナイト組織の補正損傷率を求める工程とを含む。 The creep remaining life prediction method according to the present invention includes a step of generating ultrasonic resonance in a bainite structure by exciting non-contact ultrasonic waves in the bainite structure using an electromagnetic ultrasonic probe, A step of measuring a resonance frequency of the acoustic resonance, a step of measuring a transition of the ultrasonic wave at the resonance frequency, a step of obtaining a sound velocity at the resonance frequency, a step of obtaining a first damage rate of the bainite structure from the transition of the ultrasonic wave, A step of obtaining a second damage rate of the bainite structure from the speed of sound, and a step of obtaining a corrected damage rate of the bainite structure based on the first damage rate and the second damage rate.
第1損傷率が複数存在する場合に、第1損傷率の中から、第2損傷率に最も近い第1損傷率を選択する工程を更に含み、第2損傷率に最も近い第1損傷率及び第2損傷率に基づいて、補正損傷率を求めることが好ましい。
第1損傷率と第2損傷率とを平均することによって、補正損傷率を求めることが好ましい。When there are a plurality of first damage rates, the method further includes selecting a first damage rate closest to the second damage rate from among the first damage rates, the first damage rate closest to the second damage rate, and It is preferable to obtain a corrected damage rate based on the second damage rate.
It is preferable to obtain the corrected damage rate by averaging the first damage rate and the second damage rate.
超音波の変移から減衰係数を算出し、減衰係数から第1損傷率を求めることが好ましく、または、超音波の変移から非線形超音波量を算出し、非線形超音波量から第1損傷率を求めることが好ましい。 It is preferable to calculate the attenuation coefficient from the change of the ultrasonic wave and obtain the first damage rate from the attenuation coefficient, or to calculate the non-linear ultrasonic amount from the change of the ultrasonic wave and obtain the first damage rate from the non-linear ultrasonic amount. It is preferable.
本発明によって、ベイナイト組織のクリープ余寿命の予測方法を提供することが可能となった。 According to the present invention, it is possible to provide a method for predicting the creep remaining life of a bainite structure.
以下、上記知見に基づき完成した本発明の実施の形態を詳細に説明する。なお、本発明の目的、特徴、利点、および、そのアイデアは、本明細書の記載により、当業者には明らかであり、本明細書の記載から、当業者であれば容易に本発明を再現できる。以下に記載された発明の実施の形態及び具体的な実施例などは、本発明の好ましい実施態様を示すものであり、例示又は説明のために示されているのであって、本発明をそれらに限定するものではない。本明細書で開示されている本発明の意図並びに範囲内で、本明細書の記載に基づき、様々な改変並びに修飾ができることは、当業者にとって明らかである。 Hereinafter, an embodiment of the present invention completed based on the above knowledge will be described in detail. The objects, features, advantages, and ideas of the present invention will be apparent to those skilled in the art from the description of the present specification, and those skilled in the art can easily reproduce the present invention from the description of the present specification. it can. The embodiments and specific examples of the invention described below show preferred embodiments of the present invention and are shown for illustration or explanation, and the present invention is not limited to them. It is not limited. It will be apparent to those skilled in the art that various modifications and variations can be made based on the description of the present specification within the spirit and scope of the present invention disclosed herein.
本発明に係るベイナイト組織のクリープ余寿命の予測方法は、電磁超音波探触子を用いて、ベイナイト組織内に非接触で超音波を励起させることによって、ベイナイト組織において超音波共鳴を発生させる工程と、超音波共鳴の共鳴周波数を測定する工程と、共鳴周波数における超音波の変移を求める工程と、共鳴周波数における音速を求める工程と、前記超音波の変移からベイナイソ組織の第1損傷率を求める工程と、音速からベイナイト組織の第2損傷率を求める工程と、第1損傷率及び第2損傷率に基づいてベイナイト組織の補正損傷率を求める工程とを含む。 The method for predicting the creep remaining life of a bainite structure according to the present invention is a step of generating ultrasonic resonance in a bainite structure by exciting non-contact ultrasonic waves in the bainite structure using an electromagnetic ultrasonic probe. Measuring a resonance frequency of ultrasonic resonance, obtaining a change in ultrasonic wave at the resonance frequency, obtaining a sound velocity at the resonance frequency, and obtaining a first damage rate of the beina iso tissue from the change in the ultrasonic wave. A process, a step of obtaining a second damage rate of the bainite structure from the speed of sound, and a step of obtaining a corrected damage rate of the bainite structure based on the first damage rate and the second damage rate.
本発明者等は、ベイナイト組織を測定対象とした場合に、電磁超音波探触子を用いて非接触で超音波を励起させた場合に得られる、減衰係数や非線形超音波量などの共鳴周波数における超音波の変移と、損傷率などの時間との関係が1対1対応にならないことを見出した。即ち、ある減衰係数または非線形超音波量に対応する損傷率が、複数存在することを見出した。このような場合、減衰係数または非線形超音波量のみからでは、対応する損傷率を求めることができないという問題が生じた。
このような問題を解決するために発明された、本発明に係るベイナイト組織のクリープ余寿命の予測方法によって、電磁超音波共鳴法(Electromagnetic Acoustic Rosonance、以下「EMAR法」ともいう)によって共鳴周波数における超音波の変移から第1損傷率を求め、EMAR法によって測定された音速から第2損傷率を求め、第1損傷率を第2損傷率で補正すれば、より精度が優れた補正損傷率を求めることが可能になる。ここで、共鳴周波数における超音波の変移から、共鳴周波数における減衰係数、または、共鳴周波数における非線形超音波量を求めることが好ましく、いずれから第1損傷率を求めてもよい。The present inventors, when the bainite structure is the measurement object, obtain resonance frequencies such as attenuation coefficient and nonlinear ultrasonic quantity, which are obtained when non-contact ultrasonic waves are excited using an electromagnetic ultrasonic probe. It was found that the relationship between the transition of the ultrasonic wave and the time such as the damage rate does not have a one-to-one correspondence. That is, it has been found that there are a plurality of damage rates corresponding to a certain attenuation coefficient or nonlinear ultrasonic quantity. In such a case, there arises a problem that the corresponding damage rate cannot be obtained only from the attenuation coefficient or the nonlinear ultrasonic quantity.
In order to solve such a problem, the method for predicting the remaining life of creep of a bainite structure according to the present invention, the electromagnetic ultrasonic resonance method (electromagnetic acoustic resonance, hereinafter also referred to as “EMAR method”) at the resonance frequency. If the first damage rate is obtained from the transition of the ultrasonic wave, the second damage rate is obtained from the speed of sound measured by the EMAR method, and the first damage rate is corrected by the second damage rate, a corrected damage rate with higher accuracy can be obtained. It becomes possible to ask. Here, it is preferable to obtain the attenuation coefficient at the resonance frequency or the amount of nonlinear ultrasonic waves at the resonance frequency from the transition of the ultrasonic wave at the resonance frequency, and the first damage rate may be obtained from either of them.
EMAR法は、電磁超音波探触子(Electromagnetic Acoustic Rosonance、以下「EMAT」ともいう)と超音波共鳴法とを組み合わせた、非破壊的に材料特性を測定する方法である。EMATは、電磁気的な作用(ローレンツ力または磁歪)によって非接触で超音波を送受信できるため、音響結合剤や遅延剤を必要としない。このため、EMATを用いるEMAR法は、測定する材料内のエネルギ損失だけを正確に測定することができる。さらに、EMAR法は、EMATに超音波共鳴法を組み合わせることによって、共鳴状態での同位相の多重エコーを受信してEMATのS/N比を向上させることができるため、低いことが知られるEMATの変換効率を大幅に改善させることができる。 The EMAR method is a non-destructive method for measuring material properties by combining an electromagnetic ultrasonic probe (hereinafter also referred to as “EMAT”) and an ultrasonic resonance method. Since EMAT can transmit and receive ultrasonic waves in a non-contact manner by an electromagnetic action (Lorentz force or magnetostriction), it does not require an acoustic coupling agent or a retarder. For this reason, the EMAR method using EMAT can accurately measure only energy loss in the material to be measured. Furthermore, the EMAT method is known to be low because EMAT can be combined with the ultrasonic resonance method to receive multiple echoes in the same phase in the resonance state and improve the S / N ratio of the EMAT. Conversion efficiency can be greatly improved.
EMATとしては、ローレンツ力型のEMATを用いても良く、磁歪型のEMATを用いても良いが、強磁性を有するベイナイト組織を予測対象とすることから、磁歪型のEMATを用いることが好ましい。磁歪型のEMATとして、例えば、磁歪型の軸対称SH波を送受信するEMATなどを用いても良い。
以下、磁歪型の軸対称SH波を送受信するEMATを用いる場合を例として、本発明に係るベイナイト組織のクリープ余寿命の予測方法を説明する。As the EMAT, a Lorentz force type EMAT may be used, or a magnetostrictive type EMAT may be used. However, since a bainite structure having ferromagnetism is targeted for prediction, it is preferable to use a magnetostrictive type EMAT. As the magnetostrictive EMAT, for example, an EMAT that transmits and receives a magnetostrictive axisymmetric SH wave may be used.
Hereinafter, the method for predicting the remaining life of creep of a bainite structure according to the present invention will be described by taking as an example the case of using EMAT that transmits and receives magnetostrictive axisymmetric SH waves.
図1が示すように、磁歪型の軸対称SH波を送受信するEMAT1は、測定対象である試験片2の長軸方向に沿った静磁場を与えるソレイドコイル3と、円周方向に動磁場を与える蛇行コイル4とを備える。EMAT1が、軸対称SH波を発生させる原理は、以下の通りである。まず、ソレノイドコイル3に直流電流を流すことによって、試験片2の長軸方向に静磁場Hοを生じさせる。次に、蛇行コイル4に高周波電流を流すことによって、蛇行コイル4の直下において、静磁場に直交する方向に変動磁場Hωを励起させる。このため、図2が示すように、試験片2の表面は、これら2つの磁場の合成磁場Ht(Hο+Hω)によって磁化される。なお、図2における蛇行コイル4の矢印の向きは、電流の流れる方向を示している。合成磁場を周期的に変動させると、磁歪のため周期的に試験片2の表面がせん断変形し、これが超音波源となって、軸対称SH波5を発生させることができる。
As shown in FIG. 1, an
軸対称SH波は、試験片2の長軸方向に偏向し、円周方向に伝播する表面SH波である。軸対称SH波の長軸方向の変位を、r、θ及びzで表される円筒座標系で、uz(r,θ,z)とおくと、均質等方媒体に対する運動方程式は、下記式(1)で表される。
(式中、ρは密度であり、μは剛性率である。)The axially symmetric SH wave is a surface SH wave that is deflected in the major axis direction of the test piece 2 and propagates in the circumferential direction. If the displacement in the major axis direction of an axisymmetric SH wave is represented by u z (r, θ, z) in a cylindrical coordinate system represented by r, θ and z, the equation of motion for a homogeneous isotropic medium is It is represented by (1).
(Where ρ is the density and μ is the stiffness)
また、周期境界条件である、uz(θ)=uz(θ+2π)を適用すると、変位uzは、式(2)で表される。
(式中、R(r)は半径rに依存する変位振幅であり、ωはSH波の角速度であり、nは整数である。)Further, when the periodic boundary condition u z (θ) = u z (θ + 2π) is applied, the displacement u z is expressed by Expression (2).
(Where R (r) is the displacement amplitude depending on the radius r, ω is the angular velocity of the SH wave, and n is an integer.)
式(2)を式(1)に代入して整理すると、式(3)になる。
(式中、Vsは横波の音速であり、√(μ/ρ)である。)Substituting equation (2) into equation (1) and rearranging results in equation (3).
(In the formula, Vs is the speed of sound of the transverse wave and is √ (μ / ρ).)
式(3)は、ベッセルの微分方程式であることから、その一般解は、c1及びc2を用いて式(4)のように表すことができる。
(式中、Jn及びYnは、それぞれ、n次の第一種及び第二種ベッセル関数であり、r’は、rω/Vsとした。)Since Equation (3) is a Bessel differential equation, its general solution can be expressed as Equation (4) using c 1 and c 2 .
(In the formula, J n and Y n are nth-order first-type and second-type Bessel functions, respectively, and r ′ is rω / V s .)
ここで、試験片2として中空の棒を用いる場合には、内外周表面では応力が0であるとの境界条件から、式(5)で表される振動数方程式が得られる。
(式中、Ra及びRbは、それぞれ、中空の棒の外半径及び内半径である。)Here, when a hollow rod is used as the test piece 2, the frequency equation represented by the equation (5) is obtained from the boundary condition that the stress is 0 on the inner and outer peripheral surfaces.
(Wherein R a and R b are the outer radius and the inner radius of the hollow rod, respectively)
一方で、試験片2として中実の棒を用いる場合には、棒の中心でR(r’)が有限値となるようにc2=0であり、また、棒の表面で応カが0であるとの境界条件から、式(6)で表される振動数方程式が得られる。
(式中、Ksは波数であり、ω/Vsである。また、Raは、中実の棒の半径である。)On the other hand, when a solid bar is used as the test piece 2, c 2 = 0 so that R (r ′) becomes a finite value at the center of the bar, and the stress is 0 on the surface of the bar. From the boundary condition that is, the frequency equation represented by the equation (6) is obtained.
(Where K s is the wave number and is ω / V s , and R a is the radius of the solid bar.)
式(5)及び式(6)において、nは、蛇行コイル4のターン数であり、式(7)によって決まる1以上の整数である。
(式中、δは、蛇行コイル4の平行部分の間隔であり、Raは、中空の棒の外半径または中実の棒の半径である。)
例えば、δ=0.9mmの蛇行コイル4を用いた場合には、中空の棒(外径φ56.5mm)を用いるとnは99となり、中実の棒(直径φ6mm)では10となる。
式(5)または式(6)を解くことによって、共鳴周波数fm (n)(但し、mは、1以上の整数である)が得られる。In Expressions (5) and (6), n is the number of turns of the meandering coil 4 and is an integer of 1 or more determined by Expression (7).
(Where δ is the spacing between the parallel portions of the serpentine coil 4 and R a is the outer radius of the hollow rod or the radius of the solid rod.)
For example, when the meandering coil 4 of δ = 0.9 mm is used, n is 99 when a hollow rod (outer diameter φ56.5 mm) is used, and 10 when a solid rod (diameter φ6 mm) is used.
By solving Equation (5) or Equation (6), the resonance frequency f m (n) (where m is an integer of 1 or more) is obtained.
共鳴周波数における減衰係数は、以下の方法で求めることができる。まず、EMATに高出力のバースト波信号を入力することによって、試験片2に超音波を励起させる。なお、高出力のバースト波信号は、当業者であれば適宜適切に設定することができるが、例えば、50μs以下であっても良く、音速でバースト波の時間で2、3周周回するように設定しても良い。SH波が伝播し、蛇行コイル4の真下を通る度に、同じ蛇行コイル4によって受信される。周波数を掃引して受信信号の振幅を測定すると、例えば、図3に示すような、複数の共鳴ピークが観測できる。共鳴周波数fm (n)は、式(5)または式(6)から求めることができる。なお、図3は、実施例で示すように、蛇行コイル4としてδが0.9mmのものを用い、試験片2として、ベイナイト組織を有するクロムモリブデン鉄鋼鋼材から作られた中空の棒(外径φ56.5mm、内径47.5mm)を用いた際の結果である。
単位時間当たりの超音波の減衰を表す減衰係数は、図4に示すように、各共鳴周波数において超音波を励起させて共鳴状態を作った後、超音波の残響を測定することによって図5に示すような減衰曲線を得、さらに、この減衰曲線に指数関数を近似することによって求めることができる。The attenuation coefficient at the resonance frequency can be obtained by the following method. First, the ultrasonic wave is excited in the test piece 2 by inputting a high-output burst wave signal to EMAT. A high-power burst wave signal can be appropriately set by those skilled in the art. For example, the high-power burst wave signal may be 50 μs or less, and may circulate a few times in the burst wave time at the speed of sound. May be set. The SH wave propagates and is received by the same meandering coil 4 every time it passes directly under the meandering coil 4. When the amplitude of the received signal is measured by sweeping the frequency, for example, a plurality of resonance peaks as shown in FIG. 3 can be observed. The resonance frequency f m (n) can be obtained from the equation (5) or the equation (6). In addition, FIG. 3 shows a hollow rod (outside diameter) made of a chromium molybdenum steel material having a bainite structure as a test piece 2 using a meandering coil 4 having a δ of 0.9 mm as shown in the examples. It is a result at the time of using (phi) 56.5mm, internal diameter 47.5mm).
As shown in FIG. 4, the attenuation coefficient representing the attenuation of the ultrasonic wave per unit time is shown in FIG. 5 by measuring the reverberation of the ultrasonic wave after exciting the ultrasonic wave at each resonance frequency to create a resonance state. It is possible to obtain an attenuation curve as shown and further approximate the exponential function to this attenuation curve.
共鳴周波数における音速は、式(5)および式(6)から求めることができる。 The speed of sound at the resonance frequency can be obtained from Equation (5) and Equation (6).
このようにして得られたベイナイト組織における、減衰係数及び損傷率の関係、並びに、音速及び損傷率の関係は、図6のようになる。図6が示すように、ある減衰係数においては、対応する損傷率が複数存在する。このため、減衰係数のみからでは、ベイナイト組織の損傷率を求めることができない。そこで、減衰係数から第1損傷率を求め、さらに、音速から第2損傷率を求め、これら第1損傷率と第2損傷率との両方に基づくことによって、精度が優れた補正損傷率を求めることができる。
補正損傷率を求める方法は、特に限定されないが、例えば、複数存在する第1損傷率のいずれか1つと第2損傷率とを平均することによって求めても良く、また、複数存在する第1損傷率の中から第2損傷率に最も近いものを選択し、この第2損傷率に最も近い第1損傷率と第2損傷率とを平均することによって、求めることが好ましい。
このようにして得られた補正損傷率から、ベイナイト組織のクリープ寿命を精度良く予測することができる。FIG. 6 shows the relationship between the attenuation coefficient and the damage rate and the relationship between the sound speed and the damage rate in the bainite structure thus obtained. As shown in FIG. 6, there are a plurality of corresponding damage rates for a certain attenuation coefficient. For this reason, the damage rate of a bainite structure cannot be calculated | required only from an attenuation coefficient. Accordingly, the first damage rate is obtained from the attenuation coefficient, the second damage rate is obtained from the sound velocity, and a corrected damage rate with excellent accuracy is obtained based on both the first damage rate and the second damage rate. be able to.
The method for obtaining the corrected damage rate is not particularly limited. For example, the correction damage rate may be obtained by averaging any one of the plurality of first damage rates and the second damage rate. It is preferable to obtain by selecting the one closest to the second damage rate from the rates and averaging the first damage rate and the second damage rate closest to the second damage rate.
From the corrected damage rate thus obtained, the creep life of the bainite structure can be accurately predicted.
上記の方法では、減衰係数から第1損傷率を求めたが、非線形超音波量から第1損傷率を求めても良い。
非線形超音波量は、EMRA法を用いて、共鳴周波数の移動を測定することによって求める(Nonlinear Resonant Ultrasound Spectroscopy、以下「NRUS法」ともいう)。具体的には、試験片2を比較的低振幅、例えば、10−6オーダーのひずみ振幅、で加振し、加振力の変化に伴う試験片2の共鳴周波数の移動を測定する。試験片2として未損傷の試料を用いた場合には、図7に示すように、共鳴周波数の移動は観測されないが、試験片2として損傷している試料を用いた場合には、図8に示すように、共鳴周波数の移動が観測される。この共鳴周波数の移動量Δfを、図7に示すような振幅依存性がない共鳴周波数f0で割ることによって、非線形超音波量を求めることができる。In the above method, the first damage rate is obtained from the attenuation coefficient. However, the first damage rate may be obtained from the amount of nonlinear ultrasonic waves.
The amount of nonlinear ultrasonic waves is determined by measuring the shift of the resonance frequency using the EMRA method (Nonlinear Resonant Ultraspectometry, hereinafter also referred to as “NRUS method”). Specifically, the test piece 2 is vibrated with a relatively low amplitude, for example, a strain amplitude of the order of 10 −6 , and the movement of the resonance frequency of the test piece 2 accompanying a change in the excitation force is measured. When an undamaged sample is used as the test piece 2, no resonance frequency shift is observed as shown in FIG. 7, but when a damaged sample is used as the test piece 2, FIG. As shown, resonance frequency shift is observed. The amount of nonlinear ultrasonic waves can be obtained by dividing the amount of movement Δf of the resonance frequency by the resonance frequency f 0 having no amplitude dependency as shown in FIG.
このようにして得られたベイナイト組織における非線形超音波量及び損傷率の関係を、音速及び損傷率の関係と並べて、図9に示す。減衰係数の場合と同様に、ある非線形超音波量においては、対応する損傷率が複数存在する。このため、非線形超音波量のみからでは、ベイナイト組織の損傷率を求めることができない。そこで、非線形超音波量から第1損傷率を求め、さらに、音速から第2損傷率を求め、これら第1損傷率と第2損傷率との両方に基づくことによって、精度が優れた補正損傷率を求めることができる。
補正損傷率を求める方法は、減衰係数から第1損傷率を求めた場合と同様である。このようにして得られた補正損傷率から、ベイナイト組織のクリープ寿命を精度良く予測することができる。The relationship between the nonlinear ultrasonic quantity and the damage rate in the bainite structure thus obtained is shown in FIG. 9 along with the relationship between the sound speed and the damage rate. As in the case of the attenuation coefficient, there are a plurality of corresponding damage rates in a certain nonlinear ultrasonic quantity. For this reason, the damage rate of a bainite structure cannot be calculated | required only from the amount of nonlinear ultrasonic waves. Accordingly, the first damage rate is obtained from the nonlinear ultrasonic quantity, and the second damage rate is obtained from the sound velocity. Based on both the first damage rate and the second damage rate, the corrected damage rate with excellent accuracy is obtained. Can be requested.
The method for obtaining the corrected damage rate is the same as that for obtaining the first damage rate from the attenuation coefficient. From the corrected damage rate thus obtained, the creep life of the bainite structure can be accurately predicted.
ベイナイト組織を有するクロムモリブデン鉄鋼鋼材から作られた中空の棒(外径φ56.5mm、内径47.5mm、長さ35.0mm)を試料として、温度が550℃、応力が145MPaの条件下での、試料の長さ10.0mmの箇所における、共鳴周波数、減衰係数及び非線形超音波量を測定した。併せて、試料の長さ10.0mmの箇所における外径及び肉厚を測定した。
減衰係数は、磁歪型の軸対称SH波を送受信するEMAT(蛇行コイルの平行部分の間隔δ0.9mm)及びRITEC社製RAM10000を用いて測定した。非線形超音波量は、磁歪型の軸対称SH波を送受信するEMATとRITEC社製RAM5000を用いて、加振力を10〜100まで10単位で変化させることによって測定した。試料の外径は、試料に酸化被膜がついたままの状態でノギスを用いて測定した。試料の厚さは、試料の酸化被膜を除去してから、パナメトリック社製Model26MG−XTを用いて測定した。Using a hollow rod (outer diameter 56.5 mm, inner diameter 47.5 mm, length 35.0 mm) made of chromium molybdenum steel having a bainite structure as a sample, the temperature was 550 ° C. and the stress was 145 MPa. The resonance frequency, the attenuation coefficient, and the amount of nonlinear ultrasonic waves were measured at a 10.0 mm length of the sample. In addition, the outer diameter and the wall thickness at the 10.0 mm length of the sample were measured.
The attenuation coefficient was measured using EMAT (spacing of parallel portion of meander coil δ 0.9 mm) that transmits and receives magnetostrictive axisymmetric SH waves and RAM10000 manufactured by RITEC. The amount of nonlinear ultrasonic waves was measured by changing the excitation force from 10 to 100 in 10 units using EMAT that transmits and receives magnetostrictive axisymmetric SH waves and RAM5000 manufactured by RITEC. The outer diameter of the sample was measured using a vernier caliper with the oxide film still attached to the sample. The thickness of the sample was measured using a Model 26MG-XT manufactured by Panametric after removing the oxide film of the sample.
試料の外径及び肉厚の測定結果、並びに、f1 (99)及びf2 (99)における共鳴周波数及び減衰係数の測定結果を表1に示す。また、f1 (99)における減衰係数の測定結果を、図10にグラフとして示す。Table 1 shows the measurement results of the outer diameter and thickness of the sample, and the measurement results of the resonance frequency and attenuation coefficient at f 1 (99) and f 2 (99) . Moreover, the measurement result of the attenuation coefficient in f 1 (99) is shown as a graph in FIG.
図10から明らかなように、ベイナイト組織を測定対象とした場合には、例えば0.005μs−1のようなある減衰係数においては、対応する損傷率が複数存在し、減衰係数のみからではベイナイト組織の損傷率を求められないことが示された。As is apparent from FIG. 10, when the bainite structure is a measurement object, for example, a certain attenuation coefficient such as 0.005 μs −1 has a plurality of corresponding damage rates. It was shown that the damage rate cannot be obtained.
また、f1 (99)における、各振幅力に対する共鳴周波数を正規化することによって求めた、共鳴周波数の相対的移動量を図11に示す。さらに、加振力10の時の共鳴周波数を振幅依存性がない共鳴周波数であるf0とし、加振力が100の時の共鳴周波数をfmaxとして、Δf=f0−fmaxを求めることによって、図11を非線形超音波量(Δf/f0)x100に変換した結果を図12に示す。
図12から明らかなように、ベイナイト組織を測定対象とした場合には、例えば0.10のようなある減衰係数においては、対応する損傷率が複数存在し、非線形超音波量のみからではベイナイト組織の損傷率を求められないことが示された。In addition, FIG. 11 shows the relative shift amount of the resonance frequency obtained by normalizing the resonance frequency for each amplitude force in f 1 (99) . Further, Δf = f 0 −f max is obtained by setting the resonance frequency when the excitation force is 10 as f 0 which is a resonance frequency having no amplitude dependence, and setting the resonance frequency when the excitation force is 100 as f max. FIG. 12 shows the result of converting FIG. 11 into a nonlinear ultrasonic quantity (Δf / f 0 ) × 100 by the above.
As is apparent from FIG. 12, when the bainite structure is the measurement object, for example, a certain attenuation coefficient such as 0.10 has a plurality of corresponding damage rates. It was shown that the damage rate cannot be obtained.
1 EMAT
2 試験片
3 ソレイドコイル
4 蛇行コイル
5 軸対称SH波1 EMAT
2
Claims (3)
前記超音波共鳴の共鳴周波数を測定する工程と、
前記共鳴周波数における超音波の変移を測定する工程と、
前記共鳴周波数における音速を求める工程と、
前記超音波の変移から前記ベイナイト組織の第1損傷率を求める工程と、
前記音速から前記ベイナイト組織の第2損傷率を求める工程と、
第1損傷率及び第2損傷率に基づいて前記ベイナイト組織の補正損傷率を求める工程とを含み、
前記超音波の変移から非線形超音波量を算出し、前記非線形超音波量から第1損傷率を求める、クリープ余寿命の予測方法。 Using an electromagnetic ultrasonic probe to generate ultrasonic resonance in the bainite structure by exciting non-contact ultrasonic waves in the bainite structure; and
Measuring the resonance frequency of the ultrasonic resonance;
Measuring the transition of the ultrasound at the resonance frequency;
Obtaining a sound velocity at the resonance frequency;
Obtaining a first damage rate of the bainite structure from the transition of the ultrasonic wave;
Obtaining a second damage rate of the bainite structure from the sound velocity;
A step of based on the first damage rate and the second damage rate obtaining the correction damage rate of the bainite seen including,
A method for predicting a remaining creep life , wherein a nonlinear ultrasonic amount is calculated from the change of the ultrasonic wave, and a first damage rate is obtained from the nonlinear ultrasonic amount .
第2損傷率に最も近い第1損傷率及び第2損傷率に基づいて、補正損傷率を求めることを特徴とする、請求項1に記載の方法。 Selecting a first damage rate closest to the second damage rate from the first damage rates when there are a plurality of first damage rates;
The method according to claim 1, wherein the corrected damage rate is obtained based on the first damage rate and the second damage rate that are closest to the second damage rate.
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