JP6772715B2 - Fatigue test method and fatigue test equipment - Google Patents
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本発明は、金属材料等の試験片に超音波振動を与えて疲労強度の試験を行う疲労試験方法及び疲労試験装置に関し、詳しくは、比較的小径の試験片の疲労試験に好適な疲労試験方法及び疲労試験装置に関する。 The present invention relates to a fatigue test method and a fatigue test apparatus for testing fatigue strength by applying ultrasonic vibration to a test piece of a metal material or the like. Specifically, a fatigue test method suitable for a fatigue test of a test piece having a relatively small diameter. And fatigue test equipment.
近年、金属材料の疲労強度を評価する疲労試験として、超音波を用いた疲労試験が広く用いられている。この疲労試験は、例えば、特許文献１に記載されているように、超音波の発生に必要な電力を供給する発振機と、発振機の出力を受けて超音波振動を発振する超音波振動子と、超音波振動子が発振する振動と共振して振動を増幅し、増幅した振動を略柱体状の試験片に与えるホーンとを備えた疲労試験装置を用いて、試験片をホーンの振動と共振させ、試験片の軸方向に、引張と圧縮の繰返し応力を発生させて疲労破壊を生じさせて疲労強度を評価する試験である。 In recent years, a fatigue test using ultrasonic waves has been widely used as a fatigue test for evaluating the fatigue strength of a metal material. In this fatigue test, for example, as described in Patent Document 1, an oscillator that supplies power necessary for generating ultrasonic waves and an ultrasonic vibrator that oscillates ultrasonic vibrations by receiving the output of the oscillator. And, using a fatigue test device equipped with a horn that resonates with the vibration oscillated by the ultrasonic vibrator, amplifies the vibration, and gives the amplified vibration to the substantially columnar test piece, the test piece is vibrated by the horn. This is a test in which fatigue strength is evaluated by generating fatigue failure by repeatedly generating tensile and compressive stresses in the axial direction of the test piece.
通常、試験片として用いる標準試験片は、図６に示すように、試験片１０の軸方向の中間部に、疲労強度を評価する評価対象部位としての括れ部１０ａを設けた、いわゆる、サーキュラテーパ型（砂時計型）に形成されていて、括れ部１０ａに、最大応力を発生させる構造となっている。 As shown in FIG. 6, a standard test piece normally used as a test piece has a so-called circular taper in which a constricted part 10a as an evaluation target part for evaluating fatigue strength is provided in an axially intermediate part of the test piece 10. It is formed in a mold (hourglass shape) and has a structure that generates maximum stress in the constricted portion 10a.
試験片１０は、上端側に突設した雄ねじ部１０ｂを、ホーンの下端側に設けた雌ねじ孔に螺挿させることで、ホーンの下端側に連結されるが、標準試験片（外径Ｄ１：１０ｍｍ、括れ部の外径Ｄ２：３ｍｍ）は、雄ねじ部１０ｂが直径６ｍｍに設定されていて、現在、広く知られている一般的な疲労試験機においては、ホーンの雌ねじ孔が、雄ねじ部の径に適合する大きさの径に形成されている。 The test piece 10 is connected to the lower end side of the horn by screwing the male screw portion 10b projecting from the upper end side into the female screw hole provided on the lower end side of the horn, but the standard test piece (outer diameter D1: 10 mm, the outer diameter of the constricted part D2: 3 mm), the male screw part 10b is set to a diameter of 6 mm, and in a general fatigue tester currently widely known, the female screw hole of the horn is the male screw part. It is formed with a diameter that matches the diameter.
試験対象が、特定の金属材料又は金属製品等である場合、例えば、特定径の棒鋼や線材、又は、金属製品の一部分である場合、その金属材料等に切削等の加工を加えて試験片を成形するが、このとき、疲労試験を行いたい金属材料が、外径６ｍｍ未満の比較的小径の棒鋼や線材等である場合、又は、各種金属製品等において、疲労試験を行いたい部分が小さくて、６ｍｍの外径を取ることができない場合、直径６ｍｍの雄ねじ部を形成できないため、ホーンに取付けることができず、疲労試験を行なうことができない。 When the test target is a specific metal material or metal product, for example, a steel bar or wire rod with a specific diameter, or a part of a metal product, the metal material or the like is processed by cutting or the like to form a test piece. At this time, when the metal material to be subjected to the fatigue test is a steel bar or wire rod having a relatively small diameter of less than 6 mm, or in various metal products, the portion to be subjected to the fatigue test is small. If an outer diameter of 6 mm cannot be obtained, a male screw portion having a diameter of 6 mm cannot be formed, so that the metal cannot be attached to the horn and a fatigue test cannot be performed.
また、疲労試験を行う際、試験片において、疲労破壊を生じさせる括れ部の体積、即ち、評価体積が小さいと、括れ部の内部に存在して、内部破壊の起点となる介在物の量が小量となって、疲労破壊が生じ難くなるので、評価体積となる括れ部の体積を、十分に確保する必要がある。 Further, when performing a fatigue test, if the volume of the constricted portion that causes fatigue fracture, that is, the evaluation volume is small in the test piece, the amount of inclusions existing inside the constricted portion and becoming the starting point of internal fracture is large. Since the amount is small and fatigue fracture is less likely to occur, it is necessary to secure a sufficient volume of the constricted portion, which is the evaluation volume.
そうすると、小径の試験片においては、括れ部の径が、他の部分の外径よりも細くなり、括れ部の体積、即ち、評価体積が小さくなってしまうので、何らかの方法でホーンに取付けることができたとしても、疲労によって破壊する確率が著しく低下してしまい、正確、かつ、迅速な疲労試験を行うことができない。 Then, in the test piece having a small diameter, the diameter of the constricted portion becomes smaller than the outer diameter of the other portion, and the volume of the constricted portion, that is, the evaluation volume becomes smaller. Therefore, it can be attached to the horn by some method. Even if it can be done, the probability of destruction due to fatigue is significantly reduced, and an accurate and quick fatigue test cannot be performed.
この問題を解消するため、図７（ａ）に示すように、括れ部の外径を可能な範囲で太くしたり、軸方向長さを長くしたりして、試験片の評価体積を大きくすることが考えられるが、そのように評価体積を増やした場合には、図７（ｂ）に示すように、評価体積部分に発生する最大応力が低下するので、疲労強度の正確な評価を行う疲労試験に必要な応力が得られない。したがって、小径の試験片については、単純に評価体積を大きくするだけでは、疲労強度を正確に評価することができない。 In order to solve this problem, as shown in FIG. 7A, the evaluation volume of the test piece is increased by increasing the outer diameter of the constricted portion as much as possible or increasing the axial length. However, when the evaluation volume is increased in this way, as shown in FIG. 7B, the maximum stress generated in the evaluation volume portion decreases, so that fatigue for accurate evaluation of fatigue strength is performed. The stress required for the test cannot be obtained. Therefore, for a test piece having a small diameter, the fatigue strength cannot be accurately evaluated by simply increasing the evaluation volume.
本発明は、従来、超音波疲労試験装置で疲労試験を行うことができなかった比較的小径の試験片の疲労強度を正確に評価することを課題とし、該課題を解決する疲労試験方法及び疲労試験装置を提供することを目的とする。 An object of the present invention is to accurately evaluate the fatigue strength of a test piece having a relatively small diameter, which could not be conventionally subjected to a fatigue test with an ultrasonic fatigue test apparatus, and a fatigue test method and fatigue to solve the problem. It is an object of the present invention to provide a test apparatus.
本発明者らは、上記課題を解決する手法につて鋭意検討した。その結果、ホーンの下端部に、ホーンの振動と共振しホーンで増幅した振動を、疲労試験に必要な応力を試験片に発生させる振幅以上に増幅する補助ホーンを取り付け、補助ホーンに試験片を取り付けて、試験片を補助ホーンの振動と共振させると、比較的小径の試験片の疲労強度を正確に評価できることを見いだした。 The present inventors have diligently studied a method for solving the above problems. As a result, an auxiliary horn that resonates with the vibration of the horn and amplifies the vibration amplified by the horn to an amplitude greater than the amplitude that generates the stress required for the fatigue test on the test piece is attached to the lower end of the horn, and the test piece is attached to the auxiliary horn. It was found that the fatigue strength of a relatively small-diameter test piece can be accurately evaluated by attaching it and resonating the test piece with the vibration of the auxiliary horn.
本発明は、上記知見に基づいてなされたもので、その要旨は次のとおりである。 The present invention has been made based on the above findings, and the gist thereof is as follows.
（１）発振器から出力した電力により、超音波振動子に、上下方向の超音波振動を発振させ、その振動を、下端側に行くに従って細くなる柱体状のホーンによって増幅して、試験対象の柱体状の試験片に与え、試験片の疲労強度を評価する疲労試験方法であって、
上記ホーンの下端部に、上端部の外径が該ホーンの下端部の外径と同等以下で、かつ、下端部の外径が上端部よりも小径な柱体状に形成され、ホーンの振動と共振する補助ホーンを装着し、上記補助ホーンにより、ホーンで増幅した振動を、疲労試験に必要な応力を試験片に発生させる振幅以上に増幅するとともに、
試験片の上端部に突設した試験片取付用の雄ねじ部を、上記補助ホーンの下端部に設けた、該雄ねじ部に適合する試験片取付用の雌ねじ孔に螺挿して、試験片を補助ホーンに取付けて、試験片を補助ホーンの振動と共振させることにより、
試験片において、疲労強度の評価を行う評価対象部位に最大応力を発生させ、かつ、評価対象部位の全長に亘って、疲労試験に必要な応力を発生させる
ことを特徴とする疲労試験方法。
(1) The electric power output from the oscillator causes the ultrasonic vibrator to oscillate ultrasonic vibrations in the vertical direction, and the vibrations are amplified by a columnar horn that becomes thinner toward the lower end side to be tested. It is a fatigue test method that is given to a pillar-shaped test piece and evaluates the fatigue strength of the test piece.
At the lower end of the horn, the outer diameter of the upper end is equal to or less than the outer diameter of the lower end of the horn, and the outer diameter of the lower end is formed in a columnar shape smaller than the upper end, and the horn vibrates. An auxiliary horn that resonates with is attached, and the vibration amplified by the horn is amplified by the above auxiliary horn to an amplitude that causes the stress required for the fatigue test to be generated in the test piece.
The male screw portion for mounting the test piece, which protrudes from the upper end of the test piece, is screwed into the female screw hole for mounting the test piece, which is provided at the lower end of the auxiliary horn and is compatible with the male screw portion, to assist the test piece. By attaching to the horn and resonating the test piece with the vibration of the auxiliary horn,
A fatigue test method characterized in that a maximum stress is generated in an evaluation target part for evaluating fatigue strength in a test piece, and a stress required for a fatigue test is generated over the entire length of the evaluation target part.
（２）前記試験片における軸方向の中間部に、上端部側及び下端部側よりも小径で、かつ、疲労強度を評価するのに必要な体積を有する評価対象部位としての括れ部を形成して、該括れ部の軸方向中央部に、最大応力を発生させることを特徴とする前記（１）に記載の疲労試験方法。 (2) An axially intermediate portion of the test piece is formed with a constricted portion as an evaluation target portion having a diameter smaller than that of the upper end portion side and the lower end portion side and having a volume necessary for evaluating fatigue strength. The fatigue test method according to (1) above, wherein a maximum stress is generated at the central portion in the axial direction of the constricted portion.
（３）前記補助ホーンの形状を、下端部側に行くに従って指数関数曲線をなすように湾曲する外周面の先細り形状とすることを特徴とする前記（１）又は（２）に記載の疲労試験方法。 (3) The fatigue test according to (1) or (2) above, wherein the shape of the auxiliary horn is a tapered shape of an outer peripheral surface that curves so as to form an exponential curve toward the lower end side. Method.
（４）前記補助ホーンの形状を、下端部側に行くに従って次第に小径となる円錐台状、又は、下端側が段状に細くなる形状とすることを特徴とする前記（１）又は（２）に記載の疲労試験方法。 (4) The shape of the auxiliary horn is characterized by having a truncated cone shape in which the diameter gradually decreases toward the lower end side, or a shape in which the lower end side gradually becomes thinner (1) or (2). The fatigue test method described.
（５）超音波の発生に必要な電力を供給する超音波発振器と、該超音波発振器の出力を受けて超音波振動を上下方向に発振する超音波振動子と、下端側に行くに従って次第に細くなる柱体状に形成されて、上記超音波振動子が発振した振動を増幅するホーンとを有し、柱体状の試験片に振動を与え、該試験片の疲労強度を評価する疲労試験装置において、
上記ホーンの下端部に、上端部の外径が該ホーンの下端部の外径と同等以下で、かつ、下端部が上端部よりも小径な柱体状に形成され、ホーンの振動と共振して、該ホーンで増幅された振動を、上記試験片の疲労強度を評価する評価対象部位に最大応力を発生させるとともに、該評価対象部位の全長に亘って疲労試験に必要な応力を発生させる振幅以上に増幅する補助ホーンが装着され、
上記補助ホーンの下端部に、上記試験片の上端部に突設した試験片取付用の雄ねじ部を螺挿して、該試験片を取付けることができる試験片取付用の雌ねじ孔が形成されている
ことを特徴とする疲労試験装置。
(5) An ultrasonic oscillator that supplies the power required to generate ultrasonic waves, an ultrasonic oscillator that receives the output of the ultrasonic oscillator and oscillates ultrasonic vibrations in the vertical direction, and gradually becomes thinner toward the lower end side. A fatigue test device that is formed in a columnar shape and has a horn that amplifies the vibration oscillated by the ultrasonic vibrator, applies vibration to the columnar test piece, and evaluates the fatigue strength of the test piece. In
At the lower end of the horn, the outer diameter of the upper end is equal to or less than the outer diameter of the lower end of the horn, and the lower end is formed in a pillar shape having a smaller diameter than the upper end, and resonates with the vibration of the horn. The vibration amplified by the horn generates the maximum stress at the evaluation target portion for evaluating the fatigue strength of the test piece, and the amplitude that generates the stress required for the fatigue test over the entire length of the evaluation target portion. Auxiliary horn that amplifies above is attached,
A female screw hole for mounting a test piece is formed in the lower end of the auxiliary horn by screwing a male screw portion for mounting the test piece projecting from the upper end of the test piece to mount the test piece. Fatigue test equipment characterized by this.
（６）前記評価対象部位が、上端部側及び下端部側よりも小径で、かつ、疲労強度を評価するのに必要な体積を有し、前記評価対象部位の軸方向中央部に最大応力を発生させる括れ部を備えることを特徴とする前記（５）に記載の疲労試験装置。 (6) The evaluation target portion has a smaller diameter than the upper end side and the lower end side, has a volume necessary for evaluating fatigue strength, and exerts a maximum stress at the axial center portion of the evaluation target portion. The fatigue test apparatus according to (5) above, which comprises a constricted portion to be generated.
本発明によれば、超音波疲労試験装置のホーンに、試験片取付用の雌ねじ孔を有する補助ホーンを取り付け、従来、直接、ホーンに取り付けることが難しかった小径の試験片の上端部に試験片取付用の雄ねじ部を突設して、該雄ねじ部を、補助ホーンの試験片取付用の雌ねじ孔に螺挿することにより、試験片を、補助ホーンを介してホーンに取り付けることができるので、小径の試験片でも、確実に疲労試験を行うことができる。 According to the present invention, an auxiliary horn having a female screw hole for attaching a test piece is attached to the horn of the ultrasonic fatigue test device, and the test piece is attached to the upper end of a small-diameter test piece which has been difficult to be directly attached to the horn in the past. By projecting the male threaded portion for mounting and screwing the male threaded portion into the female screw hole for mounting the test piece of the auxiliary horn, the test piece can be mounted on the horn via the auxiliary horn. Fatigue tests can be reliably performed even with small-diameter test pieces.
さらに、本発明によれば、補助ホーンは、上端部の外径が、ホーンの下端部の外径と同等以下で、かつ、下端部の外径が、上端部よりも小径の柱体状に形成されているので、ホーンによって増幅した超音波振動を、さらに、補助ホーンで増幅することができ、最終的に、超音波振動の振幅を、試験片の評価対象部位に疲労試験に必要な応力を発生させる振幅以上に増幅することができるので、試験片の評価対象部位の外径を太くしたり、又は、軸方向長さを長くしたりして、疲労強度の評価に必要な評価体積を増大しなくても、疲労破壊に必要な応力を発生させることが可能となり、従来、困難であった小径の試験片の疲労試験を確実に行うことができ、疲労強度を正確に評価することができる。 Further, according to the present invention, the auxiliary horn has a pillar shape in which the outer diameter of the upper end portion is equal to or less than the outer diameter of the lower end portion of the horn and the outer diameter of the lower end portion is smaller than that of the upper end portion. Since it is formed, the ultrasonic vibration amplified by the horn can be further amplified by the auxiliary horn, and finally, the amplitude of the ultrasonic vibration is applied to the evaluation target part of the test piece to the stress required for the fatigue test. Since it can be amplified beyond the amplitude that causes the fatigue strength, the evaluation volume required for the evaluation of fatigue strength can be increased by increasing the outer diameter of the evaluation target part of the test piece or increasing the axial length. Even if it does not increase, it is possible to generate the stress required for fatigue failure, and it is possible to reliably perform fatigue tests on small-diameter test pieces, which was difficult in the past, and to accurately evaluate fatigue strength. it can.
本発明の疲労試験方法（以下「本発明方法」ということがある。）は、
発振器から出力した電力により、超音波振動子に、上下方向の超音波振動を発振させ、その振動を、下端側に行くに従って細くなる柱体状のホーンによって増幅して、試験対象の柱体状の試験片に与え、試験片の疲労強度を評価する疲労試験方法であって、
上記ホーンの下端部に、上端部の外径が該ホーンの下端部の外径と同等以下で、かつ、下端部の外径が上端部よりも小径な柱体状に形成され、ホーンの振動と共振する補助ホーンを装着し、上記補助ホーンにより、ホーンで増幅した振動を、疲労試験に必要な応力を試験片に発生させる振幅以上に増幅するとともに、
試験片の上端部に突設した試験片取付用の雄ねじ部を、上記補助ホーンの下端部に設けた、該雄ねじ部に適合する試験片取付用の雌ねじ孔に螺挿して、試験片を補助ホーンに取付けて、試験片を補助ホーンの振動と共振させることにより、
試験片において、疲労強度の評価を行う評価対象部位に最大応力を発生させ、かつ、評価対象部位の全長に亘って、疲労試験に必要な応力を発生させる
ことを特徴とする。
The fatigue test method of the present invention (hereinafter, may be referred to as "the method of the present invention") is
The electric power output from the oscillator causes the ultrasonic vibrator to oscillate ultrasonic vibrations in the vertical direction, and the vibrations are amplified by a columnar horn that becomes thinner toward the lower end, and the columnar shape to be tested. It is a fatigue test method that is given to the test piece and evaluates the fatigue strength of the test piece.
At the lower end of the horn, the outer diameter of the upper end is equal to or less than the outer diameter of the lower end of the horn, and the outer diameter of the lower end is formed in a columnar shape smaller than the upper end, and the horn vibrates. An auxiliary horn that resonates with is attached, and the vibration amplified by the horn is amplified by the above auxiliary horn to an amplitude that causes the stress required for the fatigue test to be generated in the test piece.
The male screw portion for mounting the test piece, which protrudes from the upper end of the test piece, is screwed into the female screw hole for mounting the test piece, which is provided at the lower end of the auxiliary horn and is compatible with the male screw portion, to assist the test piece. By attaching to the horn and resonating the test piece with the vibration of the auxiliary horn,
The test piece is characterized in that the maximum stress is generated in the evaluation target portion for which the fatigue strength is evaluated, and the stress required for the fatigue test is generated over the entire length of the evaluation target portion.
本発明の疲労試験装置（以下「本発明装置」ということがある。）は、
超音波の発生に必要な電力を供給する超音波発振器と、該超音波発振器の出力を受けて超音波振動を上下方向に発振する超音波振動子と、下端側に行くに従って次第に細くなる柱体状に形成されて、上記超音波振動子が発振した振動を増幅するホーンとを有し、柱体状の試験片に振動を与え、該試験片の疲労強度を評価する疲労試験装置において、
上記ホーンの下端部に、上端部の外径が該ホーンの下端部の外径と同等以下で、かつ、下端部が上端部よりも小径な柱体状に形成され、ホーンの振動と共振して、該ホーンで増幅された振動を、上記試験片の疲労強度を評価する評価対象部位に最大応力を発生させるとともに、該評価対象部位の全長に亘って疲労試験に必要な応力を発生させる振幅以上に増幅する補助ホーンが装着され、
上記補助ホーンの下端部に、上記試験片の上端部に突設した試験片取付用の雄ねじ部を螺挿して、該試験片を取付けることができる試験片取付用の雌ねじ孔が形成されている
ことを特徴とする。
The fatigue test apparatus of the present invention (hereinafter, may be referred to as "the apparatus of the present invention") is
An ultrasonic oscillator that supplies the power required to generate ultrasonic waves, an ultrasonic oscillator that receives the output of the ultrasonic oscillator and oscillates ultrasonic vibrations in the vertical direction, and a pillar that gradually becomes thinner toward the lower end side. In a fatigue test apparatus having a horn formed in a shape and amplifying the vibration oscillated by the ultrasonic vibrator, the pillar-shaped test piece is vibrated, and the fatigue strength of the test piece is evaluated.
At the lower end of the horn, the outer diameter of the upper end is equal to or less than the outer diameter of the lower end of the horn, and the lower end is formed in a pillar shape having a smaller diameter than the upper end, and resonates with the vibration of the horn. The vibration amplified by the horn generates the maximum stress at the evaluation target portion for evaluating the fatigue strength of the test piece, and the amplitude that generates the stress required for the fatigue test over the entire length of the evaluation target portion. Auxiliary horn that amplifies above is attached,
A female screw hole for mounting a test piece is formed in the lower end of the auxiliary horn by screwing a male screw portion for mounting the test piece projecting from the upper end of the test piece to mount the test piece. It is characterized by that.
以下、本発明方法及び本発明装置について図面に基づいて説明する。 Hereinafter, the method of the present invention and the apparatus of the present invention will be described with reference to the drawings.
図１に、本発明の疲労試験装置の態様（左図）、及び、疲労試験装置の各位置での振幅及び応力（右図）を示す。図１に示す疲労試験装置は、外径が６ｍｍ未満、具体的には２．５〜５ｍｍ程度の試験片、即ち、標準的な試験片に比べ、比較的小径の試験片の疲労試験に適したものとなっている。 FIG. 1 shows an aspect of the fatigue test apparatus of the present invention (left figure) and the amplitude and stress at each position of the fatigue test apparatus (right figure). The fatigue test device shown in FIG. 1 is suitable for a fatigue test of a test piece having an outer diameter of less than 6 mm, specifically a test piece having an outer diameter of about 2.5 to 5 mm, that is, a test piece having a relatively small diameter as compared with a standard test piece. It has become a thing.
図１の左図に示す本発明装置は、超音波の発生に必要な電力を供給する超音波発振器１と、超音波発振器１の出力を受けて超音波振動を上下方向に発振する超音波振動子２と、超音波振動子２が発振した振動を増幅するホーン３とを有している。 The apparatus of the present invention shown on the left side of FIG. 1 has an ultrasonic oscillator 1 that supplies power required for generating ultrasonic waves, and an ultrasonic vibration that oscillates ultrasonic vibrations in the vertical direction by receiving the output of the ultrasonic oscillator 1. It has a child 2 and a horn 3 that amplifies the vibration oscillated by the ultrasonic vibrator 2.
ホーン３の下端部には、ホーン３によって増幅された振幅を、さらに増幅する補助ホーン４が装着され、補助ホーン４の下端部には、疲労試験の対象の試験片５が取り付けられている。ホーン３及び補助ホーン４を通じて試験片５に振動を加えることにより、試験片５に、軸方向の引張及び圧縮の繰り返し応力を発生させて、試験片５の疲労強度を評価する。 An auxiliary horn 4 that further amplifies the amplitude amplified by the horn 3 is attached to the lower end of the horn 3, and a test piece 5 to be tested for fatigue is attached to the lower end of the auxiliary horn 4. By applying vibration to the test piece 5 through the horn 3 and the auxiliary horn 4, a repeated axial stress of tension and compression is generated in the test piece 5, and the fatigue strength of the test piece 5 is evaluated.
試験片５の下方には、試験片５の振幅を測定する変位計（図示なし）が設置されている。図１の右図（疲労試験装置の各位置での振幅及び応力を示す）において、実線及び一点鎖線は応力を、破線及び二点鎖線は振幅（変位）を表していて、図１の右図は、破線で表す振幅が生じている時には、実線で表す応力が発生し、一点鎖線で表す振幅が生じている時には、二点鎖線で表す応力が発生していることを示している。 A displacement meter (not shown) for measuring the amplitude of the test piece 5 is installed below the test piece 5. In the right figure of FIG. 1 (indicating the amplitude and stress at each position of the fatigue test device), the solid line and the alternate long and short dash line represent the stress, and the broken line and the alternate long and short dash line represent the amplitude (displacement). Indicates that the stress represented by the solid line is generated when the amplitude represented by the broken line is generated, and the stress represented by the two-dot chain line is generated when the amplitude represented by the alternate long and short dash line is generated.
超音波振動子２は、ランジュバン式のピエゾ素子を備えていて、超音波発振器１からの出力によって、上下方向に振動する超音波振動を発生させ、超音波振動は、超音波振動を増幅させるブースター２ａを介してホーン３に伝達される。例えば、超音波振動子２は、２０ｋＨｚの超音波振動を発振するように設定されている。 The ultrasonic vibrator 2 is provided with a Langevin type piezo element, and the output from the ultrasonic oscillator 1 generates ultrasonic vibration that vibrates in the vertical direction, and the ultrasonic vibration is a booster that amplifies the ultrasonic vibration. It is transmitted to the horn 3 via 2a. For example, the ultrasonic vibrator 2 is set to oscillate ultrasonic vibration of 20 kHz.
ホーン３は、超音波振動子２の下端部（実際には、ブースター２ａの下端部）に取付けられていて、断面が略円形状で、かつ、下端側に行くに従って次第に細くなる柱体状に形成されていて、超音波振動子２から発振された超音波振動に共振して、超音波振動を増幅する。例えば、ホーンは２０ｋＨｚで共振するように設定されている。 The horn 3 is attached to the lower end of the ultrasonic vibrator 2 (actually, the lower end of the booster 2a), has a substantially circular cross section, and has a pillar shape that gradually becomes thinner toward the lower end side. It is formed and resonates with the ultrasonic vibration oscillated from the ultrasonic vibrator 2 to amplify the ultrasonic vibration. For example, the horn is set to resonate at 20 kHz.
なお、超音波発振器１、超音波振動子２、及び、ホーン３は、周知の超音波疲労試験装置（例えば、特許文献１に記載、参照）の構成と略同じであるから、詳細な説明は省略する。 The ultrasonic oscillator 1, the ultrasonic oscillator 2, and the horn 3 have substantially the same configurations as those of a well-known ultrasonic fatigue test apparatus (see, for example, Patent Document 1). Omit.
補助ホーン４は、上端部の外径がホーン３の下端部の外径と同等以下（図１は、同等の場合を示している。）で、かつ、下端部が上端部よりも小径な柱体状に形成されていて、ホーン３と同じ周波数特性に設定されているので、ホーン３の振動に共振する。 A pillar in which the outer diameter of the upper end of the auxiliary horn 4 is equal to or less than the outer diameter of the lower end of the horn 3 (FIG. 1 shows the same case), and the lower end is smaller than the upper end. Since it is formed in a body shape and has the same frequency characteristics as the horn 3, it resonates with the vibration of the horn 3.
補助ホーン４がホーン３の振動と共振すると、ホーン３で増幅された振動がさらに増幅されるので、補助ホーン４は、最終的には、超音波振動を、試験片５の括れ部６（後述する）に疲労試験に必要な応力を発生させる振幅以上に増幅する。 When the auxiliary horn 4 resonates with the vibration of the horn 3, the vibration amplified by the horn 3 is further amplified. Therefore, the auxiliary horn 4 finally applies ultrasonic vibration to the constricted portion 6 of the test piece 5 (described later). Amplify above the amplitude that generates the stress required for the fatigue test.
疲労試験に必要な応力は、疲労試験の対象となる金属材料の用途等による要求特性（耐疲労性）に基づき、所定の負荷回数で破損しない（又は、疲労破壊する）応力を求める場合等、疲労試験の目的により適宜決定するものであるが、その必要な応力に基づいて補助ホーン４の振幅をどの程度の大きさにすればよいか、又は、ホーン３からの振動の振幅を補助ホーン４でどの程度増幅する必要があるか等が判断され、その結果に基づいて、補助ホーン４の最終的な形状が設定される。なお、補助ホーン４が振動を増幅する原理は、基本的に、ホーン３と同じである。 The stress required for the fatigue test is based on the required characteristics (fatigue resistance) depending on the application of the metal material subject to the fatigue test, such as when obtaining a stress that does not break (or fatigue breaks) within a predetermined number of loads. It is determined as appropriate according to the purpose of the fatigue test, but how large the amplitude of the auxiliary horn 4 should be based on the required stress, or the amplitude of vibration from the horn 3 is determined by the auxiliary horn 4. It is determined how much amplification is necessary, and the final shape of the auxiliary horn 4 is set based on the result. The principle that the auxiliary horn 4 amplifies the vibration is basically the same as that of the horn 3.
図２に、本発明の補助ホーンの一態様（上段部が左側、下端部が右側）を示す。補助ホーン４は、図２に示すように、下端部（右側）に行くに従って指数関数曲線をなすように湾曲する外周面を備える先細り状に形成され、断面が略円形状である（以下、「指数型」ということがある。）。指数型の補助ホーン４は、外周面がなだらかに細くなるので、補助ホーン内での最大応力を低く抑制できるという利点を有している。 FIG. 2 shows one aspect of the auxiliary horn of the present invention (the upper portion is on the left side and the lower end portion is on the right side). As shown in FIG. 2, the auxiliary horn 4 is formed in a tapered shape having an outer peripheral surface that curves so as to form an exponential curve toward the lower end (right side), and has a substantially circular cross section (hereinafter, "" It is sometimes called "exponential type".) Since the outer peripheral surface of the exponential type auxiliary horn 4 is gently thinned, there is an advantage that the maximum stress in the auxiliary horn can be suppressed low.
指数型の補助ホーン４は、振動方程式が次式で表され、ホーン３と２０ｋＨｚで共振するように設定されている。 The exponential type auxiliary horn 4 has a vibration equation expressed by the following equation and is set to resonate with the horn 3 at 20 kHz.
上記（１）式において、ｌは、補助ホーンの軸方向長さ、Ｓ１は、下端側（小径側）の断面積、Ｓ２は、上端側（大径側）の断面積、ωは、角振動数（ｒａｄ／ｓ）、ｃは、超音波振動の速度（ｍ／ｓ）である。 In the above equation (1), l is the axial length of the auxiliary horn, S1 is the cross-sectional area of the lower end side (small diameter side), S2 is the cross-sectional area of the upper end side (large diameter side), and ω is the angular vibration. The number (rad / s) and c are the velocities of ultrasonic vibration (m / s).
指数型の補助ホーン４においては、Ｓ１及びＳ２を設定し、ホーン３の振動の周波数と共振する長さｌを上記（１）式で決定すれば、指数関数の曲線に倣って外周面の軸方向の曲がり具合を算出することができる。 In the exponential type auxiliary horn 4, if S1 and S2 are set and the length l that resonates with the vibration frequency of the horn 3 is determined by the above equation (1), the axis of the outer peripheral surface follows the curve of the exponential function. The degree of bending in the direction can be calculated.
図２に示す補助ホーンの場合、下端側の直径が６ｍｍ、上端側の直径が１９ｍｍ、軸方向長さ１が３０．７１ｍｍに設定されており、外周面は、補助ホーンの径方向をｙ軸、軸方向をｘ軸とした場合、外周面は、ｙ＝３ｅｘｐ（８．８７２ｘ）で表される指数関数の曲線状をなすように形成されている。 In the case of the auxiliary horn shown in FIG. 2, the diameter on the lower end side is set to 6 mm, the diameter on the upper end side is set to 19 mm, and the axial length 1 is set to 30.71 mm, and the outer peripheral surface is set to the y-axis in the radial direction of the auxiliary horn. When the axial direction is the x-axis, the outer peripheral surface is formed so as to form a curved shape of an exponential function represented by y = 3exp (8.872x).
指数型の補助ホーン４の増幅率Ｔは、下記（２）式で表される。下記（２）式において、Ｓ１は、下端側（小径側）の断面積、Ｓ２は、上端側（大径側）の断面積である。 The amplification factor T of the exponential type auxiliary horn 4 is expressed by the following equation (2). In the following equation (2), S1 is the cross-sectional area of the lower end side (small diameter side), and S2 is the cross-sectional area of the upper end side (large diameter side).
上記（２）式により増幅率Ｔを決定すれば、試験片５の疲労試験に最低限必要とされる応力を発生させる振幅を得るために、超音波振動子２及びホーン３の振幅、さらに、超音波発振器１の出力を設定することができる。図２に示す補助ホーン４の場合、増幅率は約３．１７倍程度である。 If the amplification factor T is determined by the above equation (2), the amplitudes of the ultrasonic oscillator 2 and the horn 3 and further, in order to obtain the amplitude for generating the minimum stress required for the fatigue test of the test piece 5, are further determined. The output of the ultrasonic oscillator 1 can be set. In the case of the auxiliary horn 4 shown in FIG. 2, the amplification factor is about 3.17 times.
図３に、疲労試験の対象となる試験片（上段部が左側、下端部が右側）の態様を示す。試験片５は、図３に示すように、軸方向の中間部に、上端部側及び下端部側の外径よりも小径の括れ部６が形成された、サーキュラテーパ型（砂時計型）の形状の試験片である。括れ部６の中央を中心に上下対称であり、上端部には、補助ホーン４への取付けに供する試験片取付用の雄ねじ部５ａ（後述する）が突設されている。 FIG. 3 shows an aspect of a test piece (the upper part is on the left side and the lower end part is on the right side) to be subjected to a fatigue test. As shown in FIG. 3, the test piece 5 has a circular taper type (hourglass type) shape in which a constriction portion 6 having a diameter smaller than the outer diameter of the upper end portion side and the lower end portion side is formed in the intermediate portion in the axial direction. It is a test piece of. It is vertically symmetrical with respect to the center of the constricted portion 6, and a male screw portion 5a (described later) for attaching a test piece to be attached to the auxiliary horn 4 is provided at the upper end portion.
試験片５は、ホーン３及び補助ホーン４と同じ周波数特性を有していて、ホーン３及び補助ホーン４の振動と同じ周波数で共振する。 The test piece 5 has the same frequency characteristics as the horn 3 and the auxiliary horn 4, and resonates at the same frequency as the vibration of the horn 3 and the auxiliary horn 4.
括れ部６は、疲労強度の評価を行う評価対象部位となる部分を含んでいる。補助ホーン４の振動と共振すると（図１、参照）、括れ部のほぼ中央に、補助ホーン４によって増幅された振動の節が位置し、この部分に、最大応力が発生する。試験片５は、下記（３）式の振動方程式に従って、補助ホーン４と２０ｋＨｚで共振するように設計されている。 The constricted portion 6 includes a portion to be evaluated to evaluate the fatigue strength. When it resonates with the vibration of the auxiliary horn 4 (see FIG. 1), a vibration node amplified by the auxiliary horn 4 is located substantially in the center of the constricted portion, and a maximum stress is generated in this portion. The test piece 5 is designed to resonate with the auxiliary horn 4 at 20 kHz according to the vibration equation of the following equation (3).
上記（３）式において、Ｄ１は、外径（ｍｍ）、Ｄ２は、括れ部の外径（ｍｍ）、Ｌは、括れ部の軸方向長さ（ｍｍ）、ｌは、試験片の端部から括れ部の一番近い端部までの軸方向長さ（ｍｍ）、ρは、密度（ｋｇ／ｍ3）、Ｅは、ヤング率（Ｎ／ｍ2）、ωは、角振動数（ｒａｄ／ｓ）、ｃは、超音波振動の速度（ｍ／ｓ）である。 In the above equation (3), D1 is the outer diameter (mm), D2 is the outer diameter (mm) of the constricted portion, L is the axial length (mm) of the constricted portion, and l is the end portion of the test piece. Axial length (mm) from to the nearest end of the constriction, ρ is density (kg / m 3 ), E is Young ratio (N / m 2 ), ω is angular frequency (rad) / S) and c are the velocities of ultrasonic vibration (m / s).
試験片５は、外径、括れ部の径、及び、括れ部の軸方向長さを設定することにより、上記（３）式から、試験片の端部から括れ部の端までの軸方向長さｌを決定することができれば、試験片全体の形状を決定することができる。 By setting the outer diameter, the diameter of the constricted portion, and the axial length of the constricted portion, the test piece 5 has an axial length from the end of the test piece to the end of the constricted portion from the above equation (3). If the diameter can be determined, the shape of the entire test piece can be determined.
試験片５の括れ部６は、疲労強度を評価するために必要な体積（評価対象部位の体積）、即ち、評価体積Ｖを有しており、評価体積Ｖは下記（４）式で算出される。 The constricted portion 6 of the test piece 5 has a volume (volume of the evaluation target portion) required for evaluating the fatigue strength, that is, an evaluation volume V, and the evaluation volume V is calculated by the following equation (4). To.
上記（４）式において、Ｄ１は、外径（ｍｍ）、Ｄ２は、括れ部の外径（ｍｍ）、Ｌは、括れ部の軸方向長さ（ｍｍ）である。 In the above equation (4), D1 is the outer diameter (mm), D2 is the outer diameter (mm) of the constricted portion, and L is the axial length (mm) of the constricted portion.
サーキュラテーパ型の試験片の疲労破壊は、多くの場合、発生する最大応力の約９０％以上の大きさの応力が発生する範囲で生じることが既に知られている。したがって、評価体積を決定する際には、最大応力の約９０％以上の大きさの応力が発生する範囲（評価対象部位）が括れ部内に位置するように、括れ部の外径や、軸方向長さを設定する必要がある。 It is already known that fatigue fracture of a circular taper type test piece often occurs in a range where a stress having a magnitude of about 90% or more of the maximum stress generated occurs. Therefore, when determining the evaluation volume, the outer diameter of the constricted portion and the axial direction so that the range in which the stress of about 90% or more of the maximum stress is generated (evaluation target portion) is located in the constricted portion. You need to set the length.
小径の試験片の場合、括れ部の外径は変更する余地が少ないことから、多くの場合、括れ部の軸方向長さを長くすることで、評価体積を大きくすることになる。 In the case of a test piece having a small diameter, there is little room for changing the outer diameter of the constricted portion. Therefore, in many cases, the evaluation volume is increased by increasing the axial length of the constricted portion.
評価体積の大きさは、できるだけ大きい方が望ましいが、実際は、括れ部に発生させることができる最大応力の大きさ、即ち、ホーン３や補助ホーン４によって増幅できる超音波振動の振幅との関係で決定され、括れ部６に最大応力の約９０％以上の大きさの応力が発生する範囲内で設定される。 The size of the evaluation volume is preferably as large as possible, but in reality, it is related to the size of the maximum stress that can be generated in the constricted portion, that is, the amplitude of the ultrasonic vibration that can be amplified by the horn 3 and the auxiliary horn 4. It is determined and set within a range in which a stress having a magnitude of about 90% or more of the maximum stress is generated in the constricted portion 6.
試験片５の括れ部６に発生する最大応力（最大公称応力）Ｓは、下記（５）式で表される。 The maximum stress (maximum nominal stress) S generated in the constricted portion 6 of the test piece 5 is represented by the following equation (5).
上記（５）式において、ａは、試験片の下端部での振幅（変位：ｍ）、Ｅは、ヤング率（Ｎ／ｍ2）であり、β及びｂは、上記（３）式におけるβ及びｂである。 In the above equation (5), a is the amplitude (displacement: m) at the lower end of the test piece, E is the Young's modulus (N / m 2 ), and β and b are β in the above equation (3). And b.
最大応力は、変位計で測定した、試験片５の下端部の変位量を、上記（５）式に代入して算出することができる。上記（５）式から解るように、最大応力は振幅に比例するから、上記（５）式で算出する最大応力が、括れ部６を疲労試験するのに必要な応力以上となるよう、試験片５に与える振動の振幅を、補助ホーンで増幅する。 The maximum stress can be calculated by substituting the displacement amount of the lower end portion of the test piece 5 measured by the displacement meter into the above equation (5). As can be seen from the above equation (5), the maximum stress is proportional to the amplitude. Therefore, the test piece so that the maximum stress calculated by the above equation (5) is equal to or greater than the stress required for the fatigue test of the constricted portion 6. The amplitude of the vibration given to 5 is amplified by the auxiliary horn.
図３に示す試験片５は、外径が５ｍｍ、括れ部の外径が３ｍｍ、括れ部の軸方向長さが６０ｍｍに設定されている。評価体積は１２８ｍｍ3で、標準試験片の評価体積の約４倍程度の体積であり、補助ホーン４の使用により、約１６７４ＭＰａ程度の最大応力が発生する。 The test piece 5 shown in FIG. 3 has an outer diameter of 5 mm, an outer diameter of the constricted portion of 3 mm, and an axial length of the constricted portion of 60 mm. The evaluation volume is 128 mm 3, which is about four times the evaluation volume of the standard test piece, and the use of the auxiliary horn 4 generates a maximum stress of about 1674 MPa.
補助ホーン４は、補助ホーン４の上端部に突設した補助ホーン取付用の雄ねじ部４ａが、ホーン３の下端部に設けた補助ホーン取付用の雌ねじ孔（図示なし）に螺挿されることにより、ホーン３に連結、装着されている。 The auxiliary horn 4 is formed by inserting a male screw portion 4a for mounting an auxiliary horn projecting from the upper end portion of the auxiliary horn 4 into a female screw hole (not shown) for mounting the auxiliary horn provided at the lower end portion of the horn 3. , Connected to and attached to the horn 3.
ホーン３には、通常、上端部に直径６ｍｍの雄ねじ部を突設し標準試験片が取付けられるので、標準試験片の雄ねじ部を螺挿する直径６ｍｍの雌ねじ孔が下端部に形成されている。それ故、ホーン３へ補助ホーン４を装着する際には、補助ホーン４の雄ねじ部４ａの直径は６ｍｍとし、ホーン３の雌ねじ孔を、補助ホーン取付用として、そのまま利用するのが好ましい。 Since a standard test piece is usually attached to the horn 3 by projecting a male screw portion having a diameter of 6 mm at the upper end portion, a female screw hole having a diameter of 6 mm for screwing the male screw portion of the standard test piece is formed at the lower end portion. .. Therefore, when mounting the auxiliary horn 4 on the horn 3, it is preferable that the diameter of the male screw portion 4a of the auxiliary horn 4 is 6 mm and the female screw hole of the horn 3 is used as it is for mounting the auxiliary horn.
試験片５は、試験片５の上端部に突設した試験片取付用の雄ねじ部５ａが、補助ホーン４の下端部に設けた試験片取付用の雌ねじ孔４ｂに螺挿して、補助ホーン４に連結されて、補助ホーン４に取付けられる。 In the test piece 5, the male screw portion 5a for mounting the test piece projecting from the upper end portion of the test piece 5 is screwed into the female screw hole 4b for mounting the test piece provided at the lower end portion of the auxiliary horn 4, and the auxiliary horn 4 is inserted. It is connected to and attached to the auxiliary horn 4.
補助ホーン４の試験片取付用の雌ねじ孔４ｂは、試験片５の雄ねじ部５ａと適合する大きさに形成されている。疲労試験の対象が、外径２．５〜５ｍｍの試験片の場合、試験片取付用の雄ねじ部５ａの外径は２ｍｍに設定され、試験片取付用の雌ねじ孔４ｂも直径２ｍｍに設定されている。 The female screw hole 4b for attaching the test piece of the auxiliary horn 4 is formed to have a size compatible with the male screw portion 5a of the test piece 5. When the target of the fatigue test is a test piece with an outer diameter of 2.5 to 5 mm, the outer diameter of the male screw portion 5a for mounting the test piece is set to 2 mm, and the female screw hole 4b for mounting the test piece is also set to 2 mm in diameter. ing.
試験片５の雄ねじ部５ａの外径が６ｍｍ未満で、ホーン３の雌ねじ孔に螺挿できず、試験片５を、直接、ホーン３に取付けられない場合、補助ホーン４がアタッチメントとして機能して、試験片５を、間接的にホーン３に装着することができ、標準試験片よりも小径の試験片でも、疲労試験を行うことが可能となる。 If the outer diameter of the male screw portion 5a of the test piece 5 is less than 6 mm, the test piece 5 cannot be screwed into the female screw hole of the horn 3, and the test piece 5 cannot be directly attached to the horn 3, the auxiliary horn 4 functions as an attachment. , The test piece 5 can be indirectly attached to the horn 3, and the fatigue test can be performed even with a test piece having a diameter smaller than that of the standard test piece.
なお、図１に示すように、補助ホーン４とホーン３の連結部分、及び、補助ホーン４と試験片５の連結部分は、いずれも、振動の振幅の腹に当たり、振幅自体は大きいものの、発生する応力は略０となるので、これらの連結部分において、疲労破壊は生じ難い。 As shown in FIG. 1, the connecting portion between the auxiliary horn 4 and the horn 3 and the connecting portion between the auxiliary horn 4 and the test piece 5 both hit the antinodes of the vibration amplitude, and although the amplitude itself is large, the occurrence occurs. Since the stress to be applied is substantially 0, fatigue fracture is unlikely to occur at these connecting portions.
図１に示す疲労試験装置で疲労試験を行う際には、ホーン３の下端部に共振する補助ホーン４を装着するとともに、試験片５の試験片取付用の雄ねじ部５ａを、補助ホーン４の下端部に設けた、該雄ねじ部５ａに適合する試験片取付用の雌ねじ孔４ｂに螺挿して、試験片５を補助ホーン４に取り付け、その後、超音波振動子２を振動させて、２０ｋＨｚの超音波振動を発振し、ホーン３、補助ホーン４、及び、試験片５を、２０ｋＨｚで共振させる。 When performing a fatigue test with the fatigue test apparatus shown in FIG. 1, an auxiliary horn 4 that resonates with the lower end of the horn 3 is attached, and a male screw portion 5a for attaching the test piece of the test piece 5 is attached to the auxiliary horn 4. The test piece 5 is attached to the auxiliary horn 4 by screwing it into the female screw hole 4b for attaching the test piece that fits the male thread portion 5a provided at the lower end portion, and then the ultrasonic transducer 2 is vibrated to 20 kHz. The ultrasonic vibration is oscillated, and the horn 3, the auxiliary horn 4, and the test piece 5 are resonated at 20 kHz.
このとき、超音波振動子２からの振動をホーン３によって増幅し、さらに、ホーン３の振動を、補助ホーン４によって、ホーン３で増幅された振動の振幅よりも増幅する。最終的に、超音波振動の振幅を、補助ホーン４によって、疲労試験に必要な応力を発生させる振幅以上に増幅し、補助ホーン４の振動と共振させた試験片５の括れ部６に、疲労試験に必要な応力を発生させる。この発生した応力により、試験片５の疲労強度を評価することができる。 At this time, the vibration from the ultrasonic vibrator 2 is amplified by the horn 3, and the vibration of the horn 3 is further amplified by the auxiliary horn 4 more than the amplitude of the vibration amplified by the horn 3. Finally, the amplitude of the ultrasonic vibration is amplified by the auxiliary horn 4 to be greater than the amplitude that generates the stress required for the fatigue test, and the constricted portion 6 of the test piece 5 that resonates with the vibration of the auxiliary horn 4 is fatigued. Generate the stress required for the test. The fatigue strength of the test piece 5 can be evaluated by the generated stress.
このように、試験片５を、試験片５の試験片取付用の雄ねじ部５ａに適合する試験片取付用の雌ねじ孔４ｂを有する補助ホーン４に取付けることにより、試験片５は、補助ホーン４を介してホーン３に取付けられるので、従来、超音波疲労試験装置のホーンに、直接取付けることが難しかった小径の試験片でも、確実に疲労試験を行うことができる。 In this way, by attaching the test piece 5 to the auxiliary horn 4 having the female screw hole 4b for mounting the test piece that matches the male screw portion 5a for mounting the test piece of the test piece 5, the test piece 5 becomes the auxiliary horn 4. Since it is attached to the horn 3 via the above, even a small-diameter test piece, which has been difficult to attach directly to the horn of the ultrasonic fatigue test device, can be reliably subjected to the fatigue test.
さらに、補助ホーン４により、超音波振動の振幅が疲労試験に必要な応力を発生させる振幅以上に増幅することができるので、評価対象部位の括れ部６の評価体積を増大しても、括れ部６に、疲労試験に必要な応力を発生させることが可能となる。したがって、従来きわめて困難であった、小径の試験片の疲労試験を確実に行うことができ、小径の試験片の疲労強度を正確に評価することができる。 Further, since the auxiliary horn 4 can amplify the amplitude of the ultrasonic vibration to be larger than the amplitude that generates the stress required for the fatigue test, even if the evaluation volume of the constricted portion 6 of the evaluation target portion is increased, the constricted portion 6. It is possible to generate the stress required for the fatigue test. Therefore, the fatigue test of the small-diameter test piece, which has been extremely difficult in the past, can be reliably performed, and the fatigue strength of the small-diameter test piece can be accurately evaluated.
補助ホーンは、指数型の形状以外の形状の補助ホーンでもよい。図４に、円錐台状の補助ホーンの態様（上段部が左側、下端部が右側）を示す。図５に、下端側が段状に細くなる形状の補助ホーンの態様（上段部が左側、下端部が右側）を示す。 The auxiliary horn may be an auxiliary horn having a shape other than the exponential shape. FIG. 4 shows an aspect of the truncated cone-shaped auxiliary horn (the upper part is on the left side and the lower end part is on the right side). FIG. 5 shows an aspect of an auxiliary horn having a shape in which the lower end side is tapered in a stepped manner (the upper part is on the left side and the lower end part is on the right side).
図４に示す円錐台状の補助ホーン７は、下記（６）式の振動方程式に従って、指数型の補助ホーンと同様に、ホーン３と、２０ｋＨｚで共振するように設計されており、指数型の補助ホーンに比べ成形し易いという利点を有している。 The truncated cone-shaped auxiliary horn 7 shown in FIG. 4 is designed to resonate with the horn 3 at 20 kHz in the same manner as the exponential type auxiliary horn according to the vibration equation of the following equation (6), and is of the exponential type. It has the advantage of being easier to mold than the auxiliary horn.
上記（６）式において、ｌは、補助ホーンの軸方向長さ、Ｓ１は、下端側（小径側）の断面積、Ｓ２は、上端側（大径側）の断面積、ωは、角振動数（ｒａｄ／ｓ）、ｃは、超音波振動の速度（ｍ／ｓ）である。 In the above equation (6), l is the axial length of the auxiliary horn, S1 is the cross-sectional area of the lower end side (small diameter side), S2 is the cross-sectional area of the upper end side (large diameter side), and ω is the angular vibration. The number (rad / s) and c are the velocities of ultrasonic vibration (m / s).
図４に示す補助ホーン７は、下端側の直径が６ｍｍ、上端側の直径が１９ｍｍ、軸方向長さが１２７．３７ｍｍに設定されており、上端部には、直径６ｍｍの補助ホーン取付用の雄ねじ部７ａが、下端部には、直径２ｍｍの試験片取付用の雌ねじ孔７ｂが設けられている。 The auxiliary horn 7 shown in FIG. 4 has a diameter of 6 mm on the lower end side, a diameter of 19 mm on the upper end side, and an axial length of 127.37 mm, and is set at the upper end portion for mounting an auxiliary horn having a diameter of 6 mm. A male screw portion 7a is provided, and a female screw hole 7b for attaching a test piece having a diameter of 2 mm is provided at the lower end portion.
円錐台状型の補助ホーン７の増幅率Ｔは、下記（７）式で表される。下記（７）式において、ｌは、補助ホーンの軸方向長さ、Ｓ１は、下端側（小径側）の断面積、Ｓ２、は上端側（大径側）の断面積、ωは、角振動数（ｒａｄ／ｓ）、ｃは、超音波振動の速度（ｍ／ｓ）である。 The amplification factor T of the truncated cone-shaped auxiliary horn 7 is expressed by the following equation (7). In the following equation (7), l is the axial length of the auxiliary horn, S1 is the cross-sectional area of the lower end side (small diameter side), S2 is the cross-sectional area of the upper end side (large diameter side), and ω is the angular vibration. The number (rad / s) and c are the velocities of ultrasonic vibration (m / s).
上記（７）式により増幅率Ｔを決定すれば、試験片５の疲労試験に最低限必要な応力を発生させる振幅を得るために、超音波振動子２及びホーン３の振幅、さらに、超音波発振器１の出力を設定することができる。補助ホーン７の場合、増幅率は約３．２０倍程度である。 If the amplification factor T is determined by the above equation (7), the amplitudes of the ultrasonic oscillator 2 and the horn 3 and the ultrasonic waves are obtained in order to obtain the amplitude that generates the minimum stress required for the fatigue test of the test piece 5. The output of oscillator 1 can be set. In the case of the auxiliary horn 7, the amplification factor is about 3.20 times.
図５に示す補助ホーン８は、軸方向の略中間部に段部８ａが形成されていて、上端部側が下端部側より細く、全体として、外径の異なる円柱が結合したような段状型の補助ホーンである。 The auxiliary horn 8 shown in FIG. 5 has a stepped portion 8a formed in a substantially intermediate portion in the axial direction, the upper end portion side is thinner than the lower end portion side, and as a whole, a stepped type in which cylinders having different outer diameters are connected. Auxiliary horn.
下記（８）が振動方程式であり、ホーン３と２０ｋＨｚで共振するように設定されている。補助ホーン８は、成形が比較的簡単で、増幅率が指数型に比べて高いという利点を有するが、段状に細くなる部分で、補助ホーン内での最大応力が指数型と比較して大きくなる。 The following (8) is a vibration equation, which is set to resonate with the horn 3 at 20 kHz. The auxiliary horn 8 has the advantages of being relatively easy to mold and having a higher amplification factor than the exponential type, but the maximum stress in the auxiliary horn is larger than that of the exponential type in the stepwise thinned portion. Become.
上記（８）式において、ｌは、補助ホーンの軸方向長さ、ｆは、振動数（Ｈｚ）、ｃは、超音波振動の速度（ｍ／ｓ）である。 In the above equation (8), l is the axial length of the auxiliary horn, f is the frequency (Hz), and c is the speed of ultrasonic vibration (m / s).
図５に示す補助ホーン８は、下端側（細径側）の直径が１０ｍｍ、上端側（太径側）の直径が１８ｍｍ、太径側の軸方向長さが６１ｍｍ、全体の軸方向長さが１２２ｍｍに設定されている。 The auxiliary horn 8 shown in FIG. 5 has a lower end side (small diameter side) diameter of 10 mm, an upper end side (large diameter side) diameter of 18 mm, a large diameter side axial length of 61 mm, and an overall axial length. Is set to 122 mm.
指数型の補助ホーン、及び、円錐台状型の補助ホーンと同様に、補助ホーン８の上端部には、直径６ｍｍの補助ホーン取付用の雄ねじ部８ｂが設けられ、下端部には、直径３ｍｍの試験片取付用の雌ねじ孔８ｃが設けられている。 Similar to the exponential type auxiliary horn and the truncated cone type auxiliary horn, the upper end portion of the auxiliary horn 8 is provided with a male screw portion 8b for attaching the auxiliary horn having a diameter of 6 mm, and the lower end portion has a diameter of 3 mm. A female screw hole 8c for mounting the test piece is provided.
段状型の補助ホーン８の増幅率Ｔは、下記（９）式で表される。下記（９）式において、Ｓ１は、下端側（小径側）の断面積、Ｓ２は、上端側（大径側）の断面積である。 The amplification factor T of the stepped auxiliary horn 8 is represented by the following equation (9). In the following equation (9), S1 is the cross-sectional area of the lower end side (small diameter side), and S2 is the cross-sectional area of the upper end side (large diameter side).
上記（９）式により増幅率Ｔを決定すれば、試験片５の疲労試験に最低限必要な応力を発生させる振幅を得るために、超音波振動子２及びホーン３の振幅、さらに、超音波発振器１の出力を設定することができる。補助ホーン８の増幅率は約３．２４倍程度である。 If the amplification factor T is determined by the above equation (9), the amplitudes of the ultrasonic oscillator 2 and the horn 3 and the ultrasonic waves can be obtained in order to obtain the amplitude that generates the minimum stress required for the fatigue test of the test piece 5. The output of oscillator 1 can be set. The amplification factor of the auxiliary horn 8 is about 3.24 times.
これまで、該径が６ｍｍ未満の、標準試験片の外径より小径の試験片の疲労試験について説明したが、本発明方法及び本発明装置は、基本的に、試験片の試験片取付用の雄ねじ部を、補助ホーンの試験片取付用の雌ねじ孔に螺挿できる試験片に適用することができる。また、試験片に、通常よりも大きな応力を発生させたい場合にも、本発明方法及び本発明装置を適用することができる。 So far, the fatigue test of a test piece having a diameter of less than 6 mm and a diameter smaller than the outer diameter of the standard test piece has been described, but the method of the present invention and the apparatus of the present invention are basically for mounting the test piece of the test piece. The male thread portion can be applied to a test piece that can be screwed into the female thread hole for mounting the test piece of the auxiliary horn. Further, the method of the present invention and the apparatus of the present invention can also be applied when it is desired to generate a stress larger than usual on the test piece.
前述したように、本発明によれば、超音波疲労試験装置のホーンに、試験片取付用の雌ねじ孔を有する補助ホーンを取り付け、従来、直接、ホーンに取り付けることが難しかった小径の試験片の上端部に試験片取付用の雄ねじ部を突設して、該雄ねじ部を、補助ホーンの試験片取付用の雌ねじ孔に螺挿し、試験片を、補助ホーンを介してホーンに取り付けることができるので、小径の試験片でも、確実に疲労試験を行うことができる。 As described above, according to the present invention, an auxiliary horn having a female screw hole for attaching a test piece is attached to the horn of the ultrasonic fatigue test device, and it is conventionally difficult to directly attach the test piece to the horn. A male screw portion for mounting a test piece is projected from the upper end portion, the male screw portion is screwed into a female screw hole for mounting a test piece of an auxiliary horn, and the test piece can be mounted on the horn via the auxiliary horn. Therefore, the fatigue test can be reliably performed even with a test piece having a small diameter.
また、本発明によれば、ホーンによって増幅した超音波振動を、さらに、補助ホーンで増幅し、最終的に、超音波振動の振幅を、試験片の評価対象部位に疲労試験に必要な応力を発生させる振幅以上に増幅することができるので、試験片の評価対象部位の外径を太くしたり、又は、軸方向長さを長くしたりして、疲労強度の評価に必要な評価体積を増大しなくても、疲労破壊に必要な応力を発生させることが可能となり、従来、困難であった小径の試験片の疲労試験を確実に行うことができ、疲労強度を正確に評価することができる。よって、本発明は、疲労試験を必要とする各種産業において利用可能性が高いものである。 Further, according to the present invention, the ultrasonic vibration amplified by the horn is further amplified by the auxiliary horn, and finally the amplitude of the ultrasonic vibration is applied to the evaluation target portion of the test piece to apply the stress required for the fatigue test. Since it can be amplified beyond the generated amplitude, the evaluation volume required for fatigue strength evaluation can be increased by increasing the outer diameter of the evaluation target part of the test piece or increasing the axial length. It is possible to generate the stress required for fatigue failure without doing so, and it is possible to reliably perform a fatigue test on a small-diameter test piece, which was difficult in the past, and to accurately evaluate fatigue strength. .. Therefore, the present invention is highly applicable in various industries requiring fatigue testing.
１ 超音波発振器
２ 超音波振動子
２ａ ブースター
３ ホーン
４、７、８ 補助ホーン
４ａ、７ａ、８ｂ 補助ホーン取付用の雄ねじ部
４ｂ、７ａ、８ｃ 補助ホーン取付用の雌ねじ孔
５ 試験片
５ａ 試験片取付用の雄ねじ部
６ 括れ
1 Ultrasonic oscillator 2 Ultrasonic oscillator 2a Booster 3 Horn 4, 7, 8 Auxiliary horn 4a, 7a, 8b Male screw part for mounting auxiliary horn 4b, 7a, 8c Female screw hole for mounting auxiliary horn 5 Test piece 5a Test piece Male thread for mounting 6 Constriction
Claims (4)
前記ホーンの下端部に、上端部の外径が該ホーンの下端部の外径と同等以下で、かつ、下端部の外径が上端部よりも小径な柱体状に形成され、ホーンの振動と共振する補助ホーンを装着し、前記補助ホーンにより、前記ホーンで増幅した振動を、疲労試験に必要な応力を試験片に発生させる振幅以上に増幅するとともに、
試験片の上端部に突設した試験片取付用の雄ねじ部を、前記補助ホーンの下端部に設けた、該雄ねじ部に適合する試験片取付用の雌ねじ孔に螺挿して、試験片を補助ホーンに取付けて、試験片を補助ホーンの振動と共振させ、
前記試験片における軸方向の中間部に、該試験片の上端部側及び下端部側よりも小径で、かつ、疲労強度を評価するのに必要な体積を有する評価対象部位としての括れ部を形成して、該括れ部の軸方向中央部に最大応力を発生させ、かつ、前記評価対象部位の全長に亘って、疲労試験に必要な応力を発生させることを特徴とする疲労試験方法。 The electric power output from the oscillator causes the ultrasonic vibrator to oscillate ultrasonic vibrations in the vertical direction, and the vibrations are amplified by a columnar horn that becomes thinner toward the lower end, and the columnar shape to be tested. It is a fatigue test method that is given to the test piece and evaluates the fatigue strength of the test piece.
The lower end of the front Symbol horn, an outer diameter of the upper end portion is equal to or less than the outer diameter of the lower end of the horn, and the outer diameter of the lower end portion is formed in the small-diameter pillar-like than the upper end portion, of the horn an auxiliary horn resonating with vibration mounted, by pre-Symbol aid horn, a vibration amplified by the horn, amplifies than the amplitude for generating a stress necessary for fatigue test specimen,
A male screw portion of the test piece for attachment protruding from the upper end of the test piece, before SL provided at the lower end of the auxiliary horn, and screwed into the female screw hole for matching the test piece attached to the male screw portion, the test specimen Attached to the auxiliary horn, the test piece resonates with the vibration of the auxiliary horn ,
An axially intermediate portion of the test piece is formed with a constricted portion as an evaluation target site having a diameter smaller than that of the upper end side and the lower end side of the test piece and having a volume necessary for evaluating fatigue strength. to, to generate maximum stress in the axial center portion of the該括Re parts and over the entire length of the evaluation target part, the fatigue test wherein the generating the stress required to fatigue testing.
前記ホーンの下端部に、上端部の外径が該ホーンの下端部の外径と同等以下で、かつ、下端部が上端部よりも小径な柱体状に形成され、該ホーンの振動と共振して、該ホーンで増幅された振動を、前記試験片の疲労強度を評価する評価対象部位に最大応力を発生させるとともに、該評価対象部位の全長に亘って疲労試験に必要な応力を発生させる振幅以上に増幅する補助ホーンが装着され、
前記補助ホーンの下端部に、前記試験片の上端部に突設した試験片取付用の雄ねじ部を螺挿して、該試験片を取付けることができる試験片取付用の雌ねじ孔が形成され、
前記評価対象部位が、上端部側及び下端部側よりも小径で、かつ、疲労強度を評価するのに必要な体積を有し、前記評価対象部位の軸方向中央部に最大応力を発生させる括れ部を備えることを特徴とする疲労試験装置。 An ultrasonic oscillator that supplies the power required to generate ultrasonic waves, an ultrasonic oscillator that receives the output of the ultrasonic oscillator and oscillates ultrasonic vibrations in the vertical direction, and a pillar that gradually becomes thinner toward the lower end side. Jo to be formed, prior SL and a horn ultrasonic transducers to amplify the vibrations oscillate, giving vibration to the pillar-shaped test piece, the fatigue test apparatus for evaluating the fatigue strength of the test piece,
The lower end of the front Symbol horn, an outer diameter of the upper end portion is equal to or less than the outer diameter of the lower end of the horn, and the lower end portion is formed in the small-diameter pillar-like than the upper end portion, and the vibration of the horn resonance to the vibration amplified by the horn, together with generating the maximum stress in the evaluation target site to assess the fatigue strength before Symbol specimen, the stress required to fatigue tests over the entire length of the evaluation target part An auxiliary horn that amplifies more than the generated amplitude is attached,
The lower end of the front Symbol auxiliary horn, and screwed to the male screw portion of the test piece for attachment protruding from the upper end of the front Symbol specimens, female screw hole of the test piece attachment which can be attached to the test piece is formed ,
The evaluation target part has a smaller diameter than the upper end side and the lower end side, has a volume necessary for evaluating fatigue strength, and is constricted to generate a maximum stress in the axial center part of the evaluation target part. A fatigue test device characterized by having a part .
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