JP2014235039A - Fatigue testing method for wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fatigue testing method for a wire capable of easily and quickly preparing an S-N diagram of the wire with high accuracy by performing a rotating and bending fatigue testing of the wire within 0.02 to 1 mm in diameter with high accuracy and high efficiency.SOLUTION: The fatigue testing method of a wire makes both sides of a wire 11 in a bent state synchronously rotate with a central axis 15 of the wire 11 as a rotation center while holding the wire 11 having a circular cross-section within a plane in a bent state, repeatedly loads a tensile stress and a compression stress to a bent part 12 of the wire 11, and prepares an S-N diagram by determining a relationship between a stress amplitude value S repeatedly loaded to the wire 11 and a repetition number N up to a destruction. A diameter d of the wire 11 is set within 0.02 to 1 mm, and the stress amplitude value S is determined by adjusting a bent radius R of the bent part 12, and the S-N diagram is prepared.

Description

The present invention provides, for example, a wire rod used for a robot cable with high accuracy and high efficiency, and an SN diagram of the wire can be created simply, quickly and with high accuracy. The present invention relates to a fatigue test method.

As the robot operation speeds up, the robot cable is required to have high bending fatigue resistance. Therefore, as an evaluation of the bending fatigue resistance characteristics of the robot cable, for example, a cable bending fatigue test is performed in which the robot cable is bent 90 ° to the left and right. However, from the cable bending fatigue test, it is not possible to evaluate the bending fatigue resistance of the stranded wire constituting the robot cable and the bending fatigue resistance of the strand forming the stranded wire. On the other hand, since a strand is a unit component of a cable or a stranded wire, accurately grasping the bending fatigue resistance characteristics of the strand is the development of the conductor material that forms the strand, the manufacture of the strand This greatly contributes to process development and manufacturing process development for producing stranded wires (cables). Therefore, a fatigue test piece, for example, a small thin piece test piece, is manufactured using the same conductor material as the element wire, and the fatigue test is performed to obtain the bending fatigue resistance characteristic. It is used as a substitute for bending fatigue characteristics.

Here, when producing a strand and a thin piece test piece using the same conductor material, the formation of the strand is mainly a three-dimensional process in which a large process is applied in the wire drawing direction. The structure is characterized in that the structure becomes finer in the wire drawing direction, and the formation of the thin specimen is mainly two-dimensional processing. Therefore, the structure of the thin specimen is fine in the thickness direction. It has the characteristic that crystallization occurs. For this reason, when the wire diameter is reduced as in the case of a wire used for a robot cable, the difference between the structure state of the wire and the structure state of the thin specimen increases, and the bending fatigue resistance of the thin specimen is reduced. It becomes impossible to substitute for the bending fatigue resistance of the wire.
Moreover, when a strand is formed with a composite metal conductor such as a tin-plated copper wire or a copper-coated aluminum wire, a thin piece test piece having a composite structure similar to the composite structure formed on the strand is prepared. It is impossible to obtain the bending fatigue resistance of the thin metal specimen of the composite metal conductor, and cannot substitute for the bending fatigue resistance of the composite metal conductor. For this reason, there exists a problem that the bending fatigue-proof characteristic of the strand of a composite metal conductor cannot be evaluated.

On the other hand, a rotating bending fatigue test has been conventionally performed as a fatigue test of a wire, but in a fatigue test of a wire using a conventional rotating bending fatigue tester, while gripping one end of the wire and applying a rotational force, Since the other end side is only freely supported so as to be rotatable, when the wire diameter of the wire becomes small, the influence of the torsional moment acting on the wire along with the rotation cannot be ignored. For this reason, variation in fatigue test results becomes large and accurate data cannot be obtained. When a conventional rotary bending fatigue tester is used, the lower limit of the wire diameter is, for example, about 2 mm for steel wires. Therefore, in order to accurately perform a rotating bending fatigue test of a wire rod (thin wire) having a wire diameter of less than 2 mm, a rotational force is introduced from both directions to a portion (bending portion) where a repeated load is applied to the wire rod. There has been proposed a wire fatigue test method that prevents the torsional moment from acting (see, for example, Patent Document 1).

JP-A-6-235589

Here, when conducting a wire fatigue test using a conventional rotating bending fatigue testing machine, when the wire rod has a wire diameter of about 0.1 to 0.2 mm, if the wire rotation speed is increased, the center axis of the wire is rotated. A state in which the bending portion moves from a state in which the bending portion is not moved from a state in which the bending portion is moved (the gripping portion on one end side of the wire rod and the free support portion on the other end side are respectively fixed portions, respectively. There is a problem that the central region of the wire including the wire changes to a state in which the wire moves. Further, in the case of a wire having a wire diameter of 0.1 mm or less, if the wire rotation speed is increased, there is a problem that the wire cannot be stably rotated because the rigidity of the wire is insufficient. Therefore, a straight line having a central axis that is in the same direction as a tangent line that is arranged in a state where a bent wire is arranged at the center of the wire, and is connected to both sides of the bent portion, and is in contact with the end of the bent portion. If the rotational force is synchronously applied to both sides of the wire, that is, the end side of each linear portion, as in the invention of Patent Document 1, the wire diameter of the wire is 0. It has been found that even when the thickness is less than 1 mm, the wire can be stably rotated at a high speed with the center axis of the wire as the center of rotation, making up for insufficient rigidity of the wire. However, when the wire diameter is 0.2 mm or less, the bending state of the wire is always set accurately every time the wire fatigue test is performed, that is, the bending radius ( (Radius of curvature) and the inclination angle of the straight part with respect to the bent part are difficult to set accurately, and it is very difficult to conduct a fatigue test on the wire while accurately changing the tensile stress and compressive stress values generated in the bent part. There is a problem that is difficult.

The present invention has been made in view of such circumstances, and a rotating bending fatigue test of a wire having a wire diameter in the range of 0.02 to 1 mm is performed with high accuracy and high efficiency, and an SN diagram of the wire is obtained. An object of the present invention is to provide a fatigue test method for a wire that can be easily, rapidly and highly accurately produced.

The fatigue test method for a wire according to the present invention that meets the above-described object is to hold a wire having a circular cross section in a bent state in a plane while synchronizing both sides of the wire in a bent state with the central axis of the wire as a rotation center. Rotating, repeatedly applying tensile stress and compressive stress to the bent portion of the wire, and obtaining the relationship between the stress amplitude value S repeatedly applied to the wire and the number of repetitions N until failure, and an SN diagram A fatigue test method for a wire to be created,
The wire diameter d is in the range of 0.02 to 1 mm, the bending radius R of the bent portion is adjusted, the stress amplitude value S is determined, and the SN diagram is created.

In the wire rod fatigue test method according to the present invention, at least two wire diameters d of the wire used in the fatigue test method are set, and the SN diagram is obtained for each of the wire rods having different wire diameters d. It is preferable to create it using fatigue test data composed of the stress amplitude value S and the repetition number N.

In the fatigue test method for a wire according to the present invention, the bent wire has the semicircular bent portion and linear portions connected to both sides of the bent portion and arranged in parallel to each other. It is preferable.

In the fatigue test method for a wire according to the present invention, the bent wire may include the bent portion having an arc angle of less than 180 degrees and linear portions connected to both sides of the bent portion. .

In the fatigue test method for a wire according to the present invention, the wire may be a strand having a wire diameter of 20 to 180 μm.

In the fatigue test method for a wire according to the present invention, the wire may be a stranded wire obtained by twisting a plurality of strands having a wire diameter of 20 to 180 μm.
Here, the number of strands to be twisted is, for example, the number when forming a stranded wire having a wire diameter of 0.15 to 1 mm. In particular, when the strand becomes a very thin wire (for example, the wire diameter is 50 μm or less), the twisting difference between the strands with respect to bending deformation applied to the strands when twisting can be ignored, and the twisting difference can be ignored. Along with this, the difference in stress amplitude generated in each strand during the rotating bending fatigue test can be ignored, so that the stranded wire can be integrally evaluated as one wire.

In the fatigue test method for a wire according to the present invention, the element wire can be formed of a single metal conductor.
Here, the single metal conductor refers to, for example, copper, copper alloy, aluminum, aluminum alloy or the like.

In the fatigue test method for a wire according to the present invention, the strand may be formed of a composite metal conductor in which two or more dissimilar metals are concentrically arranged.
Here, the composite metal conductor refers to, for example, tin-plated copper, tin-plated copper alloy, copper-coated aluminum, copper-coated aluminum alloy, and the like.

In the fatigue test method for a wire according to the present invention, the wire has a wire diameter of 20 to 180 μm, and a core material comprising a single metal conductor or a composite metal conductor in which two or more dissimilar metals are concentrically stacked. And a wire formed by an insulating coating layer disposed on the outer peripheral side of the core material.
Here, the single metal conductor refers to, for example, copper, copper alloy, aluminum, aluminum alloy, and the like, and the composite metal conductor includes, for example, tin-plated copper, tin-plated copper alloy, copper-coated aluminum, and copper-coated aluminum. The insulating coating layer is made of, for example, a fluororesin, polyethylene, or vinyl chloride, and has a thickness of, for example, 50 to 300 μm.

In the fatigue test method for a wire according to the present invention, since a rotating bending fatigue test of a wire having a wire diameter in the range of 0.02 to 1 mm is performed, for example, a thin strand used for a robot cable or the like, An SN diagram of a thin twisted wire formed by twisting strands can be created. Thereby, it can contribute to the development of the conductor material which forms a strand, the manufacturing process development of a strand, and the manufacturing process development of a twisted wire.

In the wire fatigue test method according to the present invention, when at least two types of the wire diameter d of the wire used in the fatigue test method are set, the wire bending radius R is adjusted to determine the mounting condition for the wire fatigue tester. If the Young's modulus of the wire is E, the stress amplitude value S applied to the wire during the fatigue test is Ed / (2R). Therefore, a different stress amplitude value S can be obtained simply by changing the wire diameter d of the wire. It can be set accurately, and the rotating bending fatigue test of the wire can be performed easily and accurately.
When the SN diagram is created using the fatigue test data composed of the stress amplitude value S and the repetition number N obtained for each wire having a different wire diameter d, a highly accurate SN diagram is obtained. Can be created efficiently.

In the fatigue test method for a wire according to the present invention, when the wire in a bent state has a semicircular bent portion and straight portions connected to both sides of the bent portion and arranged in parallel to each other, the bent portion and the straight line It is possible to prevent unexpected stress from being applied to the connection region of the part, and it is possible to obtain accurate data while suppressing variations in the fatigue test results.

In the wire rod fatigue test method according to the present invention, when the bent wire has a bent portion having an arc angle of less than 180 degrees (less than π) and straight portions connected to both sides of the bent portion, By adjusting the angle, the stress amplitude value S applied to the bent portion can be easily adjusted, and unexpected stress can be prevented from being applied to the connection region between the bent portion and the straight portion, thereby suppressing variations in fatigue test results. Accurate data can be obtained.

In the wire fatigue test method according to the present invention, when the wire is a strand having a wire diameter of 20 to 180 μm, for example, an SN diagram of a strand of a robot cable is not possible. Can be created directly.

In the wire fatigue test method according to the present invention, when the wire is a stranded wire obtained by twisting a plurality of strands having a wire diameter of 20 to 180 μm, for example, twisting of a robot cable is not possible. An SN diagram of the line can be created directly. This makes it possible to predict the life when the stranded wire is actually used as a robot cable, and it is possible to collect practical data. Furthermore, it is possible to select a twisting method for reducing the frictional force generated between the strands, and to optimize the type and layer thickness of the lubricant interposed between the single wires.

In the wire fatigue test method according to the present invention, when the strand is formed of a single metal conductor, the strand is formed of a composite metal conductor in which two or more dissimilar metals are stacked concentrically. In the case of being present, from the result of the rotating bending fatigue test (the SN diagram of the strand), the conductor material development of the strand and the manufacturing process development of the strand can be performed efficiently.

In the fatigue test method for a wire according to the present invention, the wire has a wire diameter of 20 to 180 μm, and a core material composed of a single metal conductor or a composite metal conductor in which two or more dissimilar metals are stacked concentrically. In the case of a strand formed with an insulating coating layer disposed on the outer peripheral side of the core material, the conductor material of the strand (core material) from the rotating bending fatigue test result (SN diagram of the strand) Development and manufacturing process development of strands can be carried out efficiently. Furthermore, it is suitable for preventing deflection and twisting of strands (higher rigidity of strands) and preventing damage to strands (core material) due to gripping. Each insulating coating layer can be selected.

1A and 1B are a plan view and a side view, respectively, of a wire fatigue test apparatus to which the wire fatigue test method according to the first embodiment of the present invention is applied. It is explanatory drawing of the bending state of a wire. It is a top view of the fatigue test apparatus of the wire which concerns on a modification. It is a SN diagram calculated | required with the fatigue test method of the wire based on the 1st Embodiment of this invention. It is a top view of the fatigue test apparatus of the wire to which the fatigue test method of the wire which concerns on the 2nd Embodiment of this invention is applied.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
A wire fatigue test apparatus 10 (hereinafter simply referred to as a fatigue test apparatus 10) to which the wire fatigue test method according to the first embodiment of the present invention is applied is shown in FIGS. 1 (A) and 1 (B). Further, while holding the wire 11 having a circular cross section and a straight shape (the wire diameter d is 0.02 to 1 mm) in a bent state in a plane, the wire 11 is bent by rotating around the central axis 15 of the wire 11. It is an apparatus that creates an SN diagram by repeatedly applying tensile stress and compressive stress to the part 12 and determining the relationship between the stress amplitude value S repeatedly applied to the wire 11 and the number of repetitions N until failure. The bent wire 11 includes a semicircular bent portion 12 and straight portions 13 and 14 connected to both sides of the bent portion 12 in parallel with each other (that is, the direction of a tangent line contacting the end of the bent portion 12). And straight portions 13 and 14) having a central axis 15 in the same direction. The fatigue test apparatus 10 holds the straight portions 13 and 14 of the wire 11 and connects to the support members 16 and 17 arranged in parallel and horizontally at the same height position, and the support members 16 and 17, respectively. Rotation rods 18 and 19 for transmitting the rotation driving force, rotation driving means 20 for rotating the rotation rods 18 and 19 in synchronization, and a counter 21 for measuring the total number of rotations of the rotation rods 18 and 19. doing.

When the linear portions 13 and 14 of the wire 11 are fixed to the support members 16 and 17, respectively, the axial center positions of the central axis 15 of the linear portion 13 of the wire 11 and the rotation central axis of the support member 16 are made to coincide with each other. The axial center positions of the central shaft 15 and the rotation central shaft of the support member 17 are matched. The support member 16 and the rotating rod 18 are connected to each other with the axial center positions of the rotation center axes coinciding with each other, and both sides of the rotating rod 18 are mounted on the base 22 with a distance from each other. 24 is rotatably held via a bearing (not shown). Further, the support member 17 and the rotating rod 19 are connected to each other so that the axial center positions of the rotation center axes coincide with each other, and both sides of the rotating rod 19 are mounted on the base 22 with a distance from each other. 26 is rotatably held via a bearing (not shown). And in the direction along the rotation center axis of the supporting members 16 and 17, the rotating rods 18 and 19 are disposed via the mounting members 23 to 26 so that the tips of the supporting members 16 and 17 are in the same position as viewed from the side. It is arranged on the base 22. Since the support members 16 and 17 are arranged in parallel, the rotating rods 18 and 19 are parallel.

The rotation driving means 20 includes a motor 27 whose output shaft is coupled to one of the rotating rods 18 and 19, for example, one end of the rotating rod 19 (an end protruding from the mounting member 26), and the rotating rods 18 and 19. The first and second gear members 28 and 28a are attached to the respective intermediate positions in the longitudinal direction and the outer peripheral portions thereof are screwed together. The counter 21 is mounted side by side with the second gear member 28 a at an intermediate position of the rotary rod 19, and a disk member 29 having one hole (not shown) formed on the outer peripheral side, and a radius of the disk member 29. A slit 29a that is disposed on the outer side in the direction and through which the outer peripheral side of the rotating disk member 29 passes is formed in the center, and a measuring unit 30 having a light emitting part and a light receiving part on both sides of the slit 29a, and the disk member 29 A calculation unit (not shown) that calculates an integrated rotational speed of the disk member 29 (rotating rod 19) from a detection signal output when the light receiving unit detects light from the light emitting unit that has passed through the hole; ing. Reference numeral 31 denotes a fixing member for fixing the motor 27 to the base 22, reference numeral 32 denotes a support member for fixing the measuring unit 30 to the base 22, and reference numeral 33 denotes a signal cable for transmitting a detection signal from the measuring unit 30 to the arithmetic unit. It is.

As shown in FIG. 2, when the bending radius of the bent portion 12 is R, the distance between the rotation center axes of the support member 16 (rotating rod 18) and the supporting member 17 (rotating rod 19) is 2R. Therefore, the rotary rods 18 and 19 are fixed on the base 22 via the mounting members 23, 24, 25, and 26 in advance so that the distance between the rotation center axes of the rotary rod 18 and the rotary rod 19 is 2R. At the same time, when the length of the straight portions 13 and 14 fixed to the support members 16 and 17 is set to L, and the wire 11 having a length adjusted to πR + 2L is attached to the fatigue test apparatus 10, the wire 11 is bent at a radius R. A bent state having a semicircular bent portion 12 can be obtained.

When the wire 11 is in the bent state shown in FIG. 2, a tensile strain of d / (2R) is present at the convex central portion of the bent portion 12 and d / (2R) is present at the concave central portion of the bent portion 12. Each compressive strain occurs. For this reason, when the Young's modulus of the wire 11 is E, the tensile stress of Ed / (2R) is applied to the central portion of the bent portion 12 on the convex side, and the compression of Ed / (2R) is applied to the concave central portion of the bent portion 12. Stress is generated. Accordingly, when both sides of the bent wire 11 are rotated synchronously with the central axis 15 as the center of rotation, tensile stress and compressive stress are repeatedly applied to the bent portion 12, and the stress amplitude value S at that time is Ed / ( 2R).

Here, the stress amplitude value S is a variable using the wire diameter d of the wire 11 and the bending radius R of the bent portion 12 as parameters, respectively, but the bending radius of the bent portion 12 is set to R as shown in FIG. The stress amplitude value S can be changed by changing the wire diameter d of the wire 11. For this reason, when the rotation bending is performed using the P (2 ≦ P) type wire 11 having the same material configuration and different wire diameter d, the stress amplitude value S _i (i = 1) for each wire 11 having a different wire diameter d. , P) and the number of repetitions N _i (i = 1, 2,..., P) are obtained. Therefore, when the obtained P pieces of fatigue test data are synthesized, that is, when P pieces of fatigue test data are plotted on a coordinate plane with the vertical axis representing the stress amplitude value and the horizontal axis representing the number of repetitions, the S- An N diagram can be created.

FIG. 3 shows a fatigue test apparatus 34 according to a modification of the fatigue test apparatus 10.
Compared with the fatigue test apparatus 10, the fatigue test apparatus 34 is connected to a support member 35 to which the linear portion 13 of the bent wire 11 is fixed and rotatably supports a rotating rod 36 that transmits a rotational driving force. The members 37 and 38 and the attachment members 41 and 42 that rotatably support the rotating rod 40 that transmits the rotational driving force by being connected to the support member 39 to which the linear portion 14 of the bent wire 11 is fixed are different from each other. The motor 45 is attached to one end of the rotating rod 36 (the end protruding from the mounting member 38) so that the rotating rods 36 and 40 are rotated in synchronization with being erected on the bases 43 and 44. The motor 46 is provided at one end (the end protruding from the mounting member 42), and the bases 43 and 44 are arranged along the direction orthogonal to the rotation center axis of the rotating rods 36 and 40. It is the distinctive feature is movable on a rail 47 and 48. Reference numerals 45a and 46a denote fixing members for fixing the motors 45 and 46 to the bases 43 and 44, respectively. With such a configuration, the distance between the rotation center axes of the support member 35 (rotating rod 36) and the support member 39 (rotating rod 40) can be adjusted by changing the distance between the bases 43 and 44. The wire 11 can be in a bent state having a semicircular bent portion 12 in which a bending radius is arbitrarily set.

The rotating rod 36 is mounted on the base via the mounting members 37 and 38 so that the tips of the supporting members 35 and 39 are in the same position as viewed from the side in the direction along the rotation center axis of the supporting members 35 and 39. The rotating rod 40 is disposed on a base 44 via attachment members 41 and 42. Further, the axis positions of the rotation center axes of the support member 35 and the rotation rod 36 coincide with each other, and the axis positions of the rotation center axes of the support member 39 and the rotation rod 40 coincide with each other. Further, the axial center positions of the central axis 15 passing through the linear portion 13 and the rotational central axis of the support member 35 coincide with each other, and the axial center positions of the central axis 15 passing through the linear portion 14 and the rotational central axis of the supporting member 39 are one. I'm doing it.

The distance between the rotation center axes of the support member 35 (rotating rod 36) and the support member 39 (rotating rod 40) was set to 2R, and the lengths of the straight portions 13 and 14 fixed to the support members 35 and 39 were set to L, respectively. In this case, when the wire 11 having a length adjusted to πR + 2L is attached to the fatigue test apparatus 34, the wire 11 is brought into a bent state having a semicircular bent portion 12 having a bending radius R as shown in FIG. it can. As a result, Ed / (2R) tensile stress is generated at the convex central portion of the bent portion 12 of the wire 11, and Ed / (2R) compressive stress is generated at the concave central portion of the bent portion 12. Therefore, when it is desired to change the tensile stress (compressive stress) generated in the bent portion 12 of the wire 11, the wire diameter d of the wire 11 is made constant and the distance between the rotation center axes of the support member 35 and the support member 39 is changed. Thus, by changing the bending radius R of the bent portion 12, the stress generated in the bent portion 12 can be easily adjusted. It is also possible to change both the wire diameter d of the wire 11 and the bending radius R of the bent portion 12.

Then, the fatigue test method of the wire which concerns on the 1st Embodiment of this invention is demonstrated.
As shown in FIGS. 2 and 3, the wire fatigue test method has a circular cross section and a straight wire 11 held in a bent state in a plane, while both sides of the wire 11 are centered on the central axis 15 respectively. The tensile stress and the compressive stress are repeatedly applied to the bent portion 12 of the wire 11 by rotating (rotating and bending), and the relationship between the stress amplitude value S repeatedly applied to the wire 11 and the number N of repetitions until breakage is obtained. This is a fatigue test method for a wire rod to obtain an SN diagram. The both sides of the bent wire 11 are rotated synchronously, that is, the rotational force is applied to the end sides of the straight portions 13 and 14 that are connected to both sides of the bent portion 12 arranged at the center of the wire 11. When given synchronously, the wire 11 having a wire diameter d in the range of 0.02 to 1 mm is stably rotated at high speed with the center axis 15 of the wire 11 as the center of rotation, making up for insufficient rigidity of the wire 11. Can be made.

Here, the wire 11 has a wire diameter d of 0.02 to 0.18 mm (20 to 180 μm) and is formed using a single metal conductor (for example, copper, copper alloy, aluminum, or aluminum alloy). A composite metal conductor (for example, tin-plated copper, tin-plated copper alloy, copper-coated aluminum, or the like) formed by concentrically laminating two or more dissimilar metals with a wire diameter d of 20 to 180 μm A wire formed using a copper-coated aluminum alloy) or a wire diameter d of 20 to 180 μm, and a core material made of a single metal conductor or a composite metal conductor, and disposed on the outer peripheral side of the core material It can be a strand formed with an insulating coating layer (for example, a fluororesin coating layer, a polyethylene coating layer, or a vinyl chloride coating layer). The wire 11 is made of a single metal conductor or a composite metal conductor, and a stranded wire obtained by twisting a plurality of strands having a wire diameter d of 20 to 180 μm, or a core material made of a single metal conductor or a composite metal conductor. And a stranded wire formed by twisting a plurality of strands formed of an insulating coating layer (for example, a fluororesin coating layer, a polyethylene coating layer, or a vinyl chloride coating layer) disposed on the outer peripheral side of the core material You can also.

For adjusting the stress amplitude value S generated in the bent portion 12 of the wire 11, (1) a method of changing the bending radius R of the bent portion 12 while keeping the wire diameter d of the wire 11 constant, and (2) bending of the wire 11. There are a method of changing the wire diameter d while keeping the bending radius R of the portion 12 constant, and (3) a method of changing the wire diameter d of the wire 11 and the bending radius R of the bent portion 12 respectively.

In the method (1), since the wire diameter d is constant, the rotating bending fatigue test can be performed with the structure state of the wire 11 being constant. Here, FIG. 4 shows an SN diagram obtained by performing a rotating bending fatigue test on the wire 11 having a wire diameter d of 80 μm formed using hard copper and annealed copper, respectively. In addition, the average crystal grain size of the wire 11 which is a strand of hard copper is 300 nm, and the average crystal grain size of the wire 11 which is a strand of annealed copper is 810 nm. FIG. 4 is obtained from a conventional rotating bending fatigue test performed for a wire made of a pure copper material and a wire made of a pure copper material (hereinafter referred to as an ECAP material) obtained by repeating ECAP (Equal Channel Angular Pressing) four times. The SN diagram is also shown. Here, the conventional rotating bending fatigue test was obtained using an Ono type rotating bending fatigue tester (bending moment of 14.7 Nm, repetition rate of 60 Hz). The average crystal grain sizes of the pure copper wire and the ECAP wire are 50 μm and 300 nm, respectively.

From FIG. 4, it is considered that the wire 11 that is a strand of soft copper has a longer fatigue life than the wire 11 that is a strand of hard copper. Moreover, when the result of the wire 11 which is an elemental wire of soft copper and the result of the wire of the pure copper obtained by the conventional rotating bending fatigue test are compared, when the stress amplitude value S is 100 MPa, the number N of repetitions until failure is close. It is a value. Moreover, since the plot (SN diagram) of the wire 11 which is a strand of hard copper exists between the plot of the pure copper wire and the wire of the ECAP material (SN diagram), It is understood that an appropriate rotational bending fatigue test has been performed on the wire 11 that is a hard copper wire and the wire 11 that is a soft copper wire.

In the method (2), when it is desired to add a small stress amplitude value to the bent portion 12 of the wire 11, instead of increasing the bend radius R of the bent portion 12, rotational bending is performed using the wire 11 having a small wire diameter d. It is possible to set the bending radius R of the bent portion 12 of the wire 11 to a range that can be accurately controlled, and to add the intended stress amplitude value S to the bent portion 12.
Further, the method (3) makes it possible to adjust the stress generated in the bent portion 12 of the wire 11 over a wide range. Thereby, the fatigue test by the rotation bending of the wire 11 can be performed with high accuracy and high efficiency, and the SN diagram of the wire 11 can be created simply, quickly, and with high accuracy.

As shown in FIG. 5, a wire fatigue test apparatus 49 to which the wire fatigue test method according to the second embodiment of the present invention is applied has a straight wire 50 with a circular cross section (the wire diameter d is 0. 0). 2 to 1 mm), while maintaining the bent state in the plane, the both sides of the bent wire 50 are rotated synchronously with the central axis 54 of the wire 50 as the rotation center, and the surface of the bent portion 51 of the wire 50 is It is an apparatus that creates an SN diagram by repeatedly applying tensile stress and compressive stress and determining the relationship between the stress amplitude value S repeatedly applied to the wire 50 and the number of repetitions N until failure. The bent wire 50 is composed of a bent portion 51 having a bending radius R and straight portions 52 and 53 that are connected to both sides of the bent portion 51, respectively.

Here, the central axis 54 passing through the straight portions 52, 53 intersects on the convex side of the bent portion 51, and the direction of the central axis 54 of the straight portion 52 is at the end of the bent portion 51 to which the straight portion 52 is connected. The direction of the tangent line is the same as the direction of the tangent, and the direction of the central axis 54 of the straight line portion 53 is the same as the direction of the tangent line that touches the end of the bent portion 51 to which the straight line portion 53 is connected. For this reason, the fatigue test apparatus 49 holds the straight portions 52 and 53 of the wire 50, has the same height, and is disposed at symmetrical positions with the bent portion 51 at the center, Rotation drive means 59 including motors 57 and 58 that are connected to the members 55 and 56 and rotate the support members 55 and 56 in synchronization with each other, and a counter 60 that measures the integrated rotational speed of the support members 55 and 56. Have.

When the linear portions 52 and 53 of the wire 50 are fixed to the support members 55 and 56, respectively, the axial center positions of the central axis 54 of the linear portion 52 of the wire 50 and the rotation central axis of the support member 55 are made to coincide with each other. The axial center positions of the central shaft 54 and the rotation central shaft of the support member 56 are matched. The motor 57 of the rotation driving means 59 is fixed to the mounting member 62 erected on the first base 61 so that the center position of the output shaft coincides with the rotation center position of the support member 55, and is driven to rotate. The motor 58 of the means 59 is fixed to a mounting member 64 erected on the second base 63 so that the center position of the output shaft coincides with the rotation center position of the support member 56. Further, the rotation driving means 59 is provided with a controller 65 that rotates the motors 57 and 58 in synchronization.

For example, the counter 60 is erected on the first base 61 so as to be positioned outside the side portion of the support member 55 and the plate member 66 provided to protrude from the side portion of the support member 55. A slit 67 through which the front side of the plate member 66 that rotates together with 55 passes is formed in the center, and a measuring unit 68 having a light emitting unit and a light receiving unit on both sides of the slit 67, and a light receiving unit that receives light from the light emitting unit through the plate member 66. A calculation unit 69 that calculates an integrated rotation speed of the plate member 66 (support member 55) from a detection signal that is output by detecting that the light incident on the unit is blocked.

Furthermore, the fatigue test apparatus 49 includes rail members 70 and 71 arranged in parallel at a distance, and first and second carriages 72 and 73 that run on the rail members 70 and 71. Here, the first and second bases 61 and 63 are respectively disposed on the first and second carriages 72 and 73 and on the surfaces of the first and second carriages 72 and 73 via pin members 74. It is rotatably mounted. Here, the first and second carriages 72 and 73 include rotation lock means (not shown) for preventing the rotation of the first and second bases 61 and 63, respectively, and the first and second bases. A display means (not shown) is provided for the rotation angle of the bases 61 and 63 (for example, the angle formed between the rotation center axis of the support members 55 and 56 and the center axis along the longitudinal direction of the rail members 70 and 71). The first and second carriages 72 and 73 are provided with movement locking means (not shown) for preventing the movement of the first and second carriages 72 and 73, respectively. The first and second carriages 72 and 73 are moved synchronously between the two carriages 72 and 73 (for example, when the first carriage 72 is moved in a direction approaching (moving away from) the second carriage 73, In conjunction with this, the second carriage 73 moves in a direction approaching (moving away from) the first carriage 72). Moving means (not shown) is provided.

The wire fatigue test method according to the second embodiment of the present invention is different from the wire fatigue test method according to the first embodiment of the present invention except that the bending state of the wire 50 is different. A fatigue test method can be performed in the same manner. For this reason, a method of attaching the wire 50 to the fatigue test apparatus 49, that is, a method of bringing the wire 50 into a bent state will be described, and description of a method of creating an SN diagram of the wire 50 will be omitted.

As shown in FIG. 5, when the bending radius of the bent portion 51 of the wire 50 is R and the center angle (arc angle) of the bent portion 51 is 2θ (2θ <π), the first and second bases 61 and 63 are provided. , The distance between the rotation center of the tip of the support member 55 and the rotation center of the tip of the support member 56 is 2Rsinθ, and the length of the bent portion 51 is 2Rθ. Therefore, in advance, the rail member is set so that the rotation angle of the first and second bases 61 and 63 is θ, and the distance between the rotation center of the tip of the support member 55 and the rotation center of the tip of the support member 56 is 2Rsinθ. The linear portions 52 fixed to the support members 55 and 56 are fixed while fixing the positions of the first and second carriages 72 and 73 on the 70 and 71 and the rotation angles of the first and second bases 61 and 63. , 53 is set to H, and the wire 50 having a length adjusted to 2Rθ + 2H is attached to the fatigue testing apparatus 49, the wire 50 is brought into a bent state having a bent portion 51 having a bending radius R and a central angle 2θ. Can do.

The straight portions 52 and 53 of the wire 50 are fixed with the central axes 54 of the straight portions 52 and 53 aligned with the axial center positions of the rotation central axes of the support members 55 and 56, respectively. Holding member for assisting maintenance, for example, the linear portion 52, via a pipe or bearing in which the inner peripheral surface side through which the linear portions 52, 53 are inserted is made of a low friction material such as vinyl chloride, nylon, or fluororesin 53 may be supported on the support members 55 and 56, and both ends of the linear portions 52 and 53 may be fixed to the support members 55 and 56, respectively. Further, when a pipe is used as the holding member, an air current swirling along the inner peripheral surface from one side to the other side is introduced into the pipe, or the pipe disposed on the support members 55 and 56 is operated at a high speed. It is also possible to hold the straight portions 52 and 53 in the pipe in a non-contact state by forming a swirl flow along the inner peripheral surface in the pipe.

As described above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the configuration described in the above-described embodiment, and the matters described in the scope of claims. Other embodiments and modifications conceivable within the scope are also included.
Further, the present invention also includes a combination of components included in the present embodiment and other embodiments and modifications.

DESCRIPTION OF SYMBOLS 10: Fatigue test apparatus, 11: Wire rod, 12: Bending part, 13, 14: Linear part, 15: Center axis, 16, 17: Support member, 18, 19: Rotating rod, 20: Rotation drive means, 21: Counting , 22: base, 23, 24, 25, 26: mounting member, 27: motor, 28: first gear member, 28a: second gear member, 29: disk member, 29a: slit, 30: Measuring unit, 31: fixing member, 32: support member, 33: signal cable, 34: fatigue testing device, 35: support member, 36: rotating rod, 37, 38: mounting member, 39: supporting member, 40: rotating rod , 41, 42: mounting member, 43, 44: base, 45: motor, 45a: fixing member, 46: motor, 46a: fixing member, 47, 48: rail, 49: fatigue test device, 50: wire rod, 51 : Bent part, 52, 53: Direct Part, 54: central shaft, 55, 56: support member, 57, 58: motor, 59: rotational drive means, 60: counter, 61: first base, 62: mounting member, 63: second base 64, mounting member, 65: controller, 66: plate member, 67: slit, 68: measurement unit, 69: calculation unit, 70, 71: rail member, 72: first carriage, 73: second Dolly, 74: Pin member

Claims (9)

While holding the wire having a circular cross section in a bent state in a plane, the both sides of the bent wire are rotated synchronously with the central axis of the wire as the center of rotation, and tensile and compressive stress are applied to the bent portion of the wire. Is a fatigue test method for a wire, in which a relationship between the stress amplitude value S repeatedly applied to the wire and the number N of repetitions until failure is obtained to create a SN diagram,
The wire diameter d of the wire is in the range of 0.02 to 1 mm, the bending radius R of the bent portion is adjusted, the stress amplitude value S is determined, and the SN diagram is created. Fatigue test method for wire. The wire rod fatigue test method according to claim 1, wherein at least two wire diameters d of the wire used in the fatigue test method are set, and the SN diagram is obtained for each of the wire rods having different wire diameters d. A fatigue test method for a wire, which is created using fatigue test data composed of the stress amplitude value S and the repetition number N. 3. The wire fatigue test method according to claim 1, wherein the bent wire has a semicircular bent portion and straight portions that are connected to both sides of the bent portion and arranged in parallel to each other. A fatigue test method for a wire, characterized by 3. The wire fatigue test method according to claim 1, wherein the wire in a bent state has the bent portion having an arc angle of less than 180 degrees and linear portions connected to both sides of the bent portion. A method for fatigue testing of wires characterized by 5. The wire fatigue test method according to claim 1, wherein the wire is a strand having a wire diameter of 20 to 180 μm. 5. The wire rod fatigue test method according to claim 1, wherein the wire is a stranded wire in which a plurality of strands having a wire diameter of 20 to 180 μm are twisted together. Fatigue test method. 7. The wire fatigue test method according to claim 5, wherein the wire is formed of a single metal conductor. The wire fatigue test method according to claim 5 or 6, wherein the wire is formed of a composite metal conductor in which two or more dissimilar metals are laminated in a concentric manner. . The wire rod fatigue test method according to any one of claims 1 to 4, wherein the wire rod has a wire diameter of 20 to 180 µm, and a single metal conductor or two or more dissimilar metals are stacked in a concentric manner. A wire fatigue test method, characterized in that the wire is formed of a core material made of a composite metal conductor and an insulating coating layer disposed on the outer peripheral side of the core material.

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