JP6185447B2 - Stress measuring apparatus and stress measuring method - Google Patents

Description

  The present invention relates to a technique for evaluating stress inside a sliding surface of a member that slides with a counterpart member.

  For example, in a metal belt type CVT transmission mechanism, it is an important problem to prevent wear of a contact portion of a pulley with respect to a belt element. According to Non-Patent Document 1, due to the sliding of the belt element with respect to the pulley, a refined structure layer is generated from the surface to a depth of several μm on the surface of the pulley, and the boundary between the base martensite structure and the refined structure In the vicinity, cracks originating from the surface are observed. It has also been observed that cracks originating from the inside occur at a depth of about 15 μm from the surface. It is presumed that the wear occurs when the generated cracks progress and the surface peels off. Therefore, grasping the internal strain or internal stress of the sliding surface of the pulley, which causes cracks, is important in taking measures for suppressing pulley wear.

  Neutron stress measurement methods and acoustoelastic methods are known as methods for measuring strain inside metal, but these are difficult to use in general industrial applications. The internal strain that affects the wear exists from the sliding surface to a depth of about several hundred μm, and such strain cannot be measured by means of direct measurement such as a strain gauge. There was nothing but to calculate by a calculation method such as the finite element method.

  Non-Patent Document 2 introduces a method for measuring the stress of a metal member using an electrodeposited copper thin film. In this measuring method, a thin film of electrodeposited copper is plated on a metal member, and a load is repeatedly applied to the metal member in the plane direction of the thin film. Thereby, a repeated load acts on the thin film, and crystals are generated and grow on the thin film. Since the maximum shear stress dominates crystal growth, it has been reported that the maximum shear stress can be measured from the crystal generation density and the principal stress can be measured from the crystal orientation.

Honda Technical Review Vol26-No. 1 New Proposal of Stress Measurement Method Using Copper Thin Film (Yuichi Ono, Department of Mechanical and Space Engineering, Graduate School of Engineering, Tottori University 2012)

  However, in the technique described in Non-Patent Document 2, although the shear stress and shear strain on the surface of the metal member can be obtained, the stress inside the metal member cannot be obtained, and the inside of the sliding surface cannot be obtained. Stress evaluation could not be performed. Therefore, an object of the present invention is to provide a stress measuring device and a stress measuring method capable of evaluating the stress inside the sliding surface.

The present invention relates to a stress measuring apparatus for reciprocally sliding an opposing test piece in contact with a sliding surface of a test piece and analyzing the internal stress of the test piece. A metal thin film is provided in the vertical direction, and an analysis means for analyzing the metal thin film is provided.

  When the mating test piece is brought into contact with the sliding surface of the test piece and slid back and forth, the test piece is repeatedly loaded and particles are generated in the metal thin film. Since the growth of the particles is governed by the maximum shear stress generated in the test piece, the density of crystals generated in the metal thin film is an index indicating the maximum shear. In the present invention, since the metal thin film extends inward from the sliding surface side, the maximum shear stress and principal stress inside the test piece can be measured by measuring the density and orientation of the crystal. .

  Here, as the metal thin film, various metals such as copper, nickel, chromium, gold, and platinum can be used, but copper is preferable. The metal thin film can be made amorphous by forming it by a thin film forming method that does not undergo solidification, such as electrolytic plating, electroless plating, or sputtering. The thickness of the metal thin film is desirably 10 to 30 μm. The metal thin film is preferably amorphous. This makes it easier to capture the generation and growth of crystals and improve the accuracy of stress analysis.

  The metal thin film may be orthogonal to the sliding surface or may be inclined. The measurement results are affected when the mating test piece comes into contact with the metal thin film, so if the metal thin film is immersed inward from the sliding surface or exposed to the sliding surface, the metal thin film of the mating test piece It is desirable to provide a recess at the position.

  A test piece is provided with the recessed part opened to a sliding surface, and can provide a metal thin film in the one or both of the side surface of a recessed part. By providing the metal thin film only on one of the side surfaces of the recess, a space is formed in front of the metal thin film, the influence of the test piece on the metal thin film can be reduced, and the measurement accuracy can be increased. Moreover, when a metal thin film is provided on both side surfaces of the concave portion, in addition to such an effect, it is possible to obtain an effect of grasping variation in measurement.

  The present invention is a test piece for stress measurement having the above characteristics. Further, the present invention is a stress evaluation method using the above-described stress measuring device, wherein the surface of the metal thin film of the test piece that has been reciprocated is analyzed by EBSD (Electron Backscatter Diffraction), and the crystal of the metal thin film is analyzed. It is a stress evaluation method characterized in that the maximum shear stress is obtained from the generation density and the principal stress is obtained from the crystal orientation.

  ADVANTAGE OF THE INVENTION According to this invention, the stress measuring apparatus and stress measuring method which can evaluate the stress inside a sliding surface are provided.

It is a sectional side view which shows the test piece for stress measurement in 1st Embodiment of this invention. It is a sectional side view which shows the modification of the test piece for stress measurement of 1st Embodiment of this invention. It is a sectional side view which shows the test piece for stress measurement in 2nd Embodiment of this invention. It is a sectional side view which shows the test piece for stress measurement in 2nd Embodiment of this invention. It is a sectional side view which shows the modification of the test piece for stress measurement in 2nd Embodiment of this invention. It is a perspective view explaining the method of a reciprocating sliding test. It is a sectional side view which shows the example which applied this invention to the pulley of a metal belt type CVT transmission mechanism.

1. First Embodiment Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 10 denotes a test piece. The test piece 10 is a model of a pulley of a metal belt type CVT transmission mechanism, and a metal block having a copper thin film (metal thin film) 12 electrodeposited on one side surface or both side surfaces is placed with the copper thin films 12 facing each other. The metal blocks are joined by an appropriate method such as combination or welding. A mating test piece 20 is pressed against the sliding surface 13 of the test piece 10.

  The mating test piece 20 is a belt element of a metal belt type CVT transmission mechanism, and a plurality of grooves 21 serving as lubricating oil flow paths are formed on the side surfaces thereof. The groove 21 faces the copper thin film 12, so that the copper thin film 12 is not in contact with the mating test piece 20.

  In the stress measuring apparatus having the above-described configuration, lubricating oil is supplied to the sliding surface 13 of the test piece 10 and a vertical load directed to the test piece 10 is applied to the mating test piece 20. Reciprocate in the orthogonal direction. When the predetermined number of repetitions is reached, the test piece 10 is disassembled and the surface of the copper thin film 12 is analyzed by EBSD. The generation density (growth particle generation area / measurement area area) and crystal orientation of the metal thin film are obtained by EBSD analysis, and the maximum shear stress and principal stress are obtained using the mathematical formula described in Non-Patent Document 2.

  In the stress measuring apparatus having the above configuration, the maximum shear stress and the main stress in a desired portion inside the sliding surface 13 can be measured. In particular, in the above embodiment, since the copper thin film 12 is not in contact with the mating test piece 20, there is no influence from the mating test piece 20, and accurate measurement is possible.

  FIG. 2 is a diagram showing a modification of the first embodiment. In this modification, the interval between the copper thin films 12 is not constant, and the end of the copper thin film 12 is submerged inside the test piece 10. Even in such a modified example, since the copper thin film 12 is not in contact with the mating test piece 20, there is no influence from the mating test piece 20, and accurate measurement is possible.

2. Second embodiment
FIG. 3 is a diagram showing a second embodiment of the present invention. As shown in FIG. 3 (A), the test piece 30 is a combination of a first test piece 30a and a second test piece 30b. On the side surface of the first test piece 30a, a copper thin film (metal thin film) 32 is formed by electrodeposition plating over the entire length in the vertical direction (entire surface or a part thereof). In addition, an inclined surface 34 is formed at the corner of the second test piece 30 b, and a space is formed in front of the copper thin film 32. Such a test piece 30 can be obtained by forming the copper thin film 32 on the first test piece 30a and then joining the first and second test pieces 30a and 30b by welding or the like. The first and second test pieces 30a and 30b may be fastened with bolts or the like. In such a test piece 30, since the space is formed in front of the copper thin film 32, the influence on the copper thin film 32 from the test piece 30 is reduced, and accurate measurement can be performed.

  FIG. 3B is a modification of FIG. 3A, in which a rectangular notch 35 is provided at the corner of the test piece 30c, and the same effect as the test piece 30 shown in FIG. Can be obtained. In addition, the shape of the notch 35 is arbitrary, For example, it can also form in arc shape.

  In the embodiment shown in FIG. 3C, inclined surfaces 34 are formed at corners of the first test piece 30d and the second test piece 30e, and a copper thin film 32 is formed on each inclined surface 34. Such a test piece 30 has two copper thin films 32 in addition to the effects of the test piece 30 shown in FIGS. 3A and 3B, so that it is possible to grasp variations in measurement. An effect is obtained.

  In the embodiment shown in FIG. 3D, rectangular cutouts 35 are provided at the corners of the first test piece 30f and the second test piece 30g, and a copper thin film 32 is provided on the side surface of each cutout 35. The same effect as that of the test piece 30 shown in FIG.

  FIG. 4 (A) shows a state in which the counterpart test piece 40 is brought into contact with the test piece 30 shown in FIG. 3 (D). A groove 41 is formed in the counterpart test piece 40, and the width of the groove 41 is set wider than the interval between the copper thin films 32. As a result, contact between the copper thin film 32 and the mating test piece 40 is avoided, there is no influence on the copper thin film 32 from the mating test piece 40, and a space is formed in front of the copper thin film 32. The influence on the copper thin film 32 from the piece 30 is reduced, and the accuracy of measurement is increased. As shown in FIG. 4B, the relationship between the position of the contact portion and the internal stress can be obtained by changing the distance between the groove 41 and the copper thin film 32.

  In FIG. 4B, the copper thin film 32 is provided over the entire length (entire surface or a part thereof) of the side surface of the notch 35. The depth from the sliding surface where the stress can be measured is shown in FIG. Since there is a limit, as shown in FIG. 5A, the copper thin film 32 may be provided up to a measurable range. Or, contrary to the test piece 30 shown in FIG. 5 (A), as shown in FIG. 5 (B), the copper thin film 32 can be provided only in a portion away from the sliding surface. If the stress measurable range is unknown, as shown in FIG. 5C, the measurable range can be found by dividing the copper thin film 32 in the depth direction.

  FIG. 6 is a diagram showing the procedure of the reciprocating sliding test. First, a metal block in which a copper thin film is formed on one side by electrolytic plating is combined with the copper thin film to obtain a test piece 50. Next, the test piece 50 is inserted into the frame 60. In this case, if there is a gap between the frame 60 and the test piece 50, use a shim to adjust the gap to zero, or apply external force to the frame 60 to deform it so that the gap is zero. You may adjust.

  Next, the frame 60 is mounted on a reciprocating sliding test device. In this case, the sliding direction is adjusted so that the groove provided in the mating test piece coincides with the copper thin film of the test piece 50 throughout the sliding stroke. Next, a reciprocating sliding test is started by applying a load to the counterpart test piece. When the prescribed number of repetitions is completed, the reciprocating sliding test is terminated.

  Next, the test piece 50 is taken out from the frame 60, and the surface of the copper thin film is analyzed by EBSD. When a repeated load is applied to the copper thin film, crystals are generated and grow on the copper thin film. Since the maximum shear stress acting on the copper thin film controls the crystal growth, the maximum shear stress is measured from the crystal generation density, and the principal stress is measured from the crystal orientation.

  FIG. 6 is a view showing an example in which the test piece of the present invention is applied to a pulley 70 of a metal belt type CVT transmission mechanism. The pulley 70 is configured by fitting a ring-shaped outer peripheral member 73 to the outer periphery of the pulley body 71 and fixing with a bolt 74. A copper thin film 72 is formed on the outer periphery of the pulley body 71 by electrolytic plating. The copper thin film 72 is provided at a place where the stress of the pulley 70 is to be evaluated. The copper thin film 72 is provided on the entire circumference of the pulley body 71 or a part in the circumferential direction. The belt element (counter test piece) 80 is fixed to the pulley 70 by an appropriate method in a pressed state, and a reciprocating sliding test can be performed by reciprocatingly rotating the pulley.

  INDUSTRIAL APPLICABILITY The present invention can be used for measuring the stress of a part that slides with a mating part such as a pulley of a metal belt type CVT transmission mechanism.

DESCRIPTION OF SYMBOLS 10 ... Test piece, 12 ... Copper thin film (metal thin film), 13 ... Sliding surface, 20 ... Opposite test piece,
21 ... groove, 30 ... test piece, 32 ... copper thin film (metal thin film), 35 ... notch, 40 ... mating test piece, 41 ... groove, 50 ... test piece, 60 ... frame, 70 ... pulley,
80: Belt element (counter specimen).

Claims (7)

In the stress measuring device for reciprocally sliding the mating test piece in contact with the sliding surface of the test piece and analyzing the internal stress of the test piece,
A stress measurement apparatus comprising: an analysis unit configured to analyze the metal thin film by providing a metal thin film on the test piece from the sliding surface side in a depth direction of the test piece.   The stress measurement apparatus according to claim 1, wherein the metal thin film is a copper thin film.   The stress measuring apparatus according to claim 1, wherein the metal thin film is amorphous.   The stress measuring apparatus according to claim 1, wherein the metal thin film is exposed on the sliding surface, and the counterpart test piece has a recess at a position of the metal thin film.   The stress measurement apparatus according to claim 1, wherein the metal thin film is immersed inward from the sliding surface.   The stress measuring device according to claim 1, wherein the test piece includes a recess opening in the sliding surface, and the metal thin film is provided on one or both of the side surfaces of the recess. . In the stress measurement method for analyzing the internal stress of the test piece by reciprocally sliding the mating test piece in contact with the sliding surface of the test piece,
A stress measurement method characterized in that a metal thin film is provided on the test piece from the sliding surface side in the depth direction of the test piece and the metal thin film is analyzed.

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