Bending and Torsion Testing Equipment

Abstract

To provide a bending and twisting test device which can apply both a bending moment and a twisting moment to a test piece by using a single driving unit.SOLUTION: A bending and twisting test device 1 comprises a first lever 23, a second lever 33, jigs 50, 60 and a driving unit 42. The first lever 23 is provided so as to be rotatable around a first central axis thereof, and provided so as to be swingable around a first oscillation shaft orthogonal to the first central axis at a base end thereof. The second lever 33 is provided so as to be rotatable around a second central axis thereof, and provided so as to be swingable around a second oscillation shaft orthogonal to the second central axis at a base end thereof. Both ends of the test piece 2 are fixed at tips of the levers 23, 33. The jigs 50, 60 support a radial load of the test piece 2. The driving unit 42 displaces the jigs 50, 60 in an orthogonal direction of the central axis of the test piece 2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a bending-torsion testing device that applies both bending and torsional moments to a test specimen using a single driving unit. [Background technology]

[0002] Piping in power plants and other facilities expands thermally due to heating by the fluid inside and is subjected to internal pressure from the fluid. Such pipes are subjected to bending and torsional moments due to the thermal expansion and internal pressure. Furthermore, as the temperature and internal pressure of the pipes change, the bending and torsional moments also change, causing the pipes to fatigue. Therefore, it is necessary to predict the fatigue life of the pipes due to bending and torsional moments by conducting tests using mechanical testing equipment to apply bending and torsional moments to a pipe specimen. An example of such testing equipment is disclosed in Patent Document 1. The testing equipment disclosed in Patent Document 1 includes a jig for fixing one end of the specimen, a torsional load applying device for applying a torsional load around the axis of the specimen to the other end of the specimen, and a bending load applying device for applying a bending load perpendicular to the axis of the specimen to the center of the specimen. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-156021 Summary of the Invention [Problem to be solved by the invention]

[0004] The testing device described in Patent Document 1 is expensive because it requires two actuators to apply both a bending moment and a torsion moment to the test piece.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its main object is to provide a bending-torsion testing device that can apply both bending and torsional moments to a test specimen using a single driving unit. [Means for solving the problem]

[0006] In order to solve the above problems, a test instrument is provided, comprising: a first lever extending from a first base end to a first tip end, rotatably provided around a first central axis extending from the first base end to the first tip end, and swingable at the first base end around a first swing axis perpendicular to the first central axis, one end of a columnar or hollow columnar test body being fixed to the first tip end so that the central axis of the test body is perpendicular to the first central axis; and a second lever extending from a second base end to a second tip end in a direction parallel to and opposite to the direction in which the first lever extends from the first base end to the first tip end, and rotatably provided around a second central axis extending from the second base end to the second tip end, and the second lever being swingable at the first base end around a first swing axis perpendicular to the first central axis. A bending / torsion testing device is provided, comprising: a second lever that is provided at its base end so as to be swingable around a second oscillation axis perpendicular to the second central axis, and the other end of the test body is fixed to the second tip end so that the central axis of the test body is perpendicular to the second central axis; a pair of jigs that are separated from each other in the direction of the central axis of the test body and support a radial load of the test body so that the test body can rotate about the central axis of the test body; and a drive unit that displaces the pair of jigs in a direction perpendicular to the central axis of the test body so as to swing the first lever and the second lever about the first oscillation axis and the second oscillation axis, respectively.

[0007] According to the above, when the drive unit displaces the pair of jigs in a direction perpendicular to the central axis of the test piece, the test piece bends and a bending moment is generated in the test piece. Because the first lever is rotatable about its first central axis and the second lever is rotatable about its second central axis, the test piece bends significantly. Furthermore, when the drive unit displaces the pair of jigs in a direction perpendicular to the central axis of the test specimen, the first lever swings around a first swing axis at its first base end, and the second lever swings around a second swing axis at its second base end. Because the direction in which the first lever extends from its first base end to its first tip is opposite the direction in which the second lever extends from its second base end to its second tip, the direction in which the first lever swings around the first swing axis is opposite the direction in which the second lever swings around the second swing axis. As a result, the test specimen twists, and a torsional moment is generated in the test specimen. Therefore, both bending and torsional moments can be applied to the test specimen by a single driving unit. [Effects of the Invention]

[0008] A single drive unit can apply both bending and torsional moments to the test specimen. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a front view of a bending-torsion test device. [Figure 2] FIG. 1 is a side view of a bending-torsion test device. [Figure 3] FIG. 1 is a perspective view of the main part of a bending / torsion test device. [Figure 4] FIG. 1 is a perspective view of the main part of a bending / torsion test device. [Figure 5] FIG. 1 is a front view of the main parts of a bending / torsion testing device. [Figure 6] FIG. 1 is a front view of the main parts of a bending / torsion testing device. [Figure 7] FIG. 1 is a front view of the main parts of a bending / torsion testing device. [Figure 8] FIG. 1 is a side view of the main part of a bending / torsion test device. [Figure 9] 1 is a graph showing a waveform of a load per cycle. [Figure 10] 10 is a graph showing experimental results of the relationship between the number of cycles and the displacement. [Figure 11] 10 is a graph showing experimental results of the relationship between the number of cycles and the deflection angle. [Figure 12] 10 is a graph showing experimental results of the relationship between the number of cycles and the torsion angle. [Figure 13] 1 is a photograph showing the state of cracks that occurred in a test specimen. [Figure 14] 10 is a graph showing experimental results of the relationship between deflection angle and equivalent bending moment. [Figure 15] 10 is a graph showing experimental results of the relationship between the torsion angle and the equivalent bending moment. [Figure 16] 1 is a graph showing experimental results of the relationship between the number of cycles to fatigue failure and the equivalent bending moment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments described below are subject to various limitations that are technically preferable for implementing the present invention, but the scope of the present invention is not limited to the following embodiments and illustrated examples.

[0011] 1. Bending and torsion testing equipment FIG. 1 is a front view of the bending-torsion test apparatus 1. FIG. 2 is a side view of the bending-torsion test apparatus 1. FIGS. 3 and 4 are perspective views of the main parts of the bending-torsion test apparatus 1. FIGS. 5 to 7 are front views of the main parts of the bending-torsion test apparatus 1. FIG. 8 is a side view of the main parts of the bending-torsion test apparatus 1. In each figure, the X-axis, Y-axis, and Z-axis, which are mutually perpendicular, are shown as auxiliary lines indicating directions. The X-axis and Y-axis are horizontal, and the Z-axis is vertical. Since the X-axis extends left and right, the Y-axis extends front and back, and the Z-axis extends up and down, the X-axis, Y-axis, and Z-axis directions are also referred to as the left-right direction, the front-back direction, and the up-down direction, respectively. Here, in FIG. 5, the test specimen 2 set in the bending-torsion test apparatus 1 is not deformed. In FIG. 6, the test specimen 2 is bent in a downward convex shape. In FIG. 7, the test specimen 2 is bent in an upward convex shape. In the initial state where the test specimen 2 set in the bending-torsion test device 1 is not deformed, the central axis of the test specimen 2 is parallel to the X-axis.

[0012] The bending-torsion test device 1 applies two-point loads to a cylindrical or hollow cylindrical test piece 2, thereby generating a bending moment and a torsion moment in the test piece 2, and measures the deflection angle θ and torsion angle φ generated in the test piece 2. The bending-torsion test device 1 can be used not only for static bending-torsion tests, but also for creep-fatigue tests, fatigue tests, and creep tests.

[0013] Here, the deflection angle θ refers to the angle between the central axis of the test specimen 2 in its initial state at the end of the test specimen 2 and the central axis of the test specimen 2 after deformation. The torsion angle φ refers to the angular displacement from the initial state around the central axis of the test specimen 2 at the end of the test specimen 2. The two-point load refers to a bending load applied to the test specimen 2 from two points. The test specimen 2 may be made of metal or resin. When the test specimen 2 is hollow cylindrical, two metal round tubes butt-welded together may be used as the test specimen 2.

[0014] The bending-torsion test apparatus 1 includes a support base 10, a first linear guide 12, a second linear guide 13, a first lever mechanism 20, a second lever mechanism 30, a loading device 40, a load cell 70, a deflection angle sensor 81, a torsion angle sensor 82, and a heating furnace 90. Note that when the bending-torsion test apparatus 1 is used for a static bending-torsion test or a fatigue test, the heating furnace 90 does not need to be provided. In Figure 4, the heating furnace 90 is not shown so that the entire test specimen 2 and first lever mechanism 20 can be shown.

[0015] (1) Support stand The support base 10 supports the weight of the first linear guide 12, the second linear guide 13, the first lever mechanism 20, the second lever mechanism 30, the load device 40, the load cell 70, the deflection angle sensor 81, the torsion angle sensor 82, and the heating furnace 90. The support base 10 is installed on an experimental table (not shown) via a plurality of adjusters for adjusting the height in the Z-axis direction. By adjusting the height of these adjusters, the upper surface of the support base 10 can be adjusted to be horizontal.

[0016] (2) Linear guide The first linear guide 12 is attached to the support base 10. The first linear guide 12 guides a first lever mechanism 20 (described later) in the left-right direction. The direction in which the first linear guide 12 guides the first lever mechanism 20 is parallel to the central axis of the test piece 2 in its initial state set in the bending-torsion test device 1.

[0017] The second linear guide 13 is attached to the support base 10 at a position away from the first linear guide 12 and to the rear right. The second linear guide 13 guides the second lever mechanism 30 (described later) in the left-right direction. The direction in which the second linear guide 13 guides the second lever mechanism 30 is parallel to the central axis of the test piece 2.

[0018] (3) First lever mechanism The first lever mechanism 20 is provided on the support base 10 via a first linear guide 12. The first lever mechanism 20 holds one end of the test specimen 2 so that the one end can be swung up and down around a first pivot 22 (described later) as a fulcrum, and so that the one end of the test specimen 2 can tilt around the central axis of a first lever 23 (described later). The first lever mechanism 20 has a first pole 21, a first pivot 22, a first lever 23, a first chuck 24, a first support bar 25, and a first counterweight 26.

[0019] The first pole 21 is provided upright on the support base 10 via a first linear guide 12. The first pole 21 is guided in the left-right direction relative to the support base 10 by the first linear guide 12. As the first pole 21 is guided by the first linear guide 12, the first pivot 22, the first lever 23, the first chuck 24, the first support bar 25, and the first counterweight 26 are also guided in the left-right direction.

[0020] The first pivot 22 is attached to the upper end of the first pole 21 via a bearing or the like so that its central axis is parallel to the left-right direction. The axial load and radial load of the first pivot 22 are supported by the bearing, and the first pivot 22 is rotatable around its central axis.

[0021] The first lever 23 has a central axis that extends from the base end of the first lever 23 on the first pivot 22 side to the tip of the first lever 23. The base end of the first lever 23 corresponds to the "first base end," the tip of the first lever 23 corresponds to the "first tip," and the central axis of the first lever 23 corresponds to the "first central axis."

[0022] The base end of the first lever 23 is attached to the first pivot 22 via a bearing or the like so that the central axis of the first lever 23 is perpendicular to the central axis of the first pivot 22. The first lever 23 extends from the first pivot 22 in a direction perpendicular to the central axis of the first pivot 22. Specifically, the first lever 23 extends rearward from the first pivot 22. The axial load and radial load of the first lever 23 are supported by the bearing, and the first lever 23 is rotatable around its central axis. Here, because the first pivot 22 is rotatable around its central axis as described above, the first lever 23 is provided so as to be swingable up and down around the central axis of the first pivot 22, with the central axis of the first pivot 22 as a fulcrum. The central axis of the first pivot 22 corresponds to the "first swing axis."

[0023] The first chuck 24 is attached to the tip of the first lever 23. The first chuck 24 fixes one end of the test specimen 2 to the tip of the first lever 23 so that the central axis of the test specimen 2 is perpendicular to the central axis of the first lever 23.

[0024] The base end of first support bar 25 is attached to the base end of first lever 23 or to first pivot 22 so that the central axis of first support bar 25 is coaxial with the central axis of first lever 23. First support bar 25 extends from first pivot 22 in a direction perpendicular to the central axis of first pivot 22. Specifically, first support bar 25 extends forward from first pivot 22.

[0025] The first counterweight 26 is attached to the first support bar 25. The position of the first counterweight 26 is adjustable along the first support bar 25.

[0026] (4) Second lever mechanism The second lever mechanism 30 is provided on the support base 10 via a second linear guide 13. The second lever mechanism 30 is configured to be symmetrical to the first lever mechanism 20 with respect to a vertical axis. The second lever mechanism 30 holds the other end of the test specimen 2 so that the other end of the test specimen 2 can be swung up and down around a second pivot 32 (described later) as a fulcrum, and so that the other end of the test specimen 2 can tilt around the central axis of a second lever 33 (described later). The second lever mechanism 30 has a second pole 31, a second pivot 32, a second lever 33, a second chuck 34, a second support bar 35, and a second counterweight 36.

[0027] The second pole 31 is provided upright on the support base 10 via a second linear guide 13, at a position spaced apart to the rear and right of the first pole 21. The second pole 31 is guided in the left-right direction relative to the support base 10 by the second linear guide 13. As the second linear guide 13 guides the second pole 31, a second pivot 32, a second lever 33, a second chuck 34, a second support bar 35, and a second counterweight 36, which will be described later, are also guided in the left-right direction.

[0028] The second pivot 32 is attached to the upper end of the second pole 31 via a bearing or the like so that its central axis is parallel to the left-right direction. The axial load and radial load of the second pivot 32 are supported by the bearing, and the second pivot 32 is rotatable around its central axis.

[0029] The second lever 33 has a central axis that extends from the base end of the second lever 33 on the second pivot 32 side to the tip of the second lever 33. The base end of the second lever 33 corresponds to the "second base end," the tip of the second lever 33 corresponds to the "second tip," and the central axis of the second lever 33 corresponds to the "second central axis."

[0030] The base end of the second lever 33 is attached to the second pivot 32 via a bearing or the like so that the central axis of the second lever 33 is perpendicular to the central axis of the second pivot 32. The second lever 33 extends from the second pivot 32 in a direction perpendicular to the central axis of the second pivot 32. Specifically, the second lever 33 extends forward from the second pivot 32. The axial load and radial load of the second lever 33 are supported by the bearing, and the second lever 33 is rotatable around its central axis. Here, in the initial state in which the test specimen 2 is not deformed, the direction in which the second lever 33 extends from its base end to its tip is parallel to and opposite to the direction in which the first lever 23 extends from its base end to its tip.

[0031] As described above, the second pivot 32 is rotatable about its central axis, and therefore the second lever 33 is provided so as to be able to swing up and down around the central axis of the second pivot 32, with the central axis of the second pivot 32 as a fulcrum. The central axis of the second pivot 32 corresponds to the "second swing axis."

[0032] The second chuck 34 is attached to the tip of the second lever 33. The second chuck 34 fixes the other end of the test specimen 2 to the tip of the second lever 33 so that the central axis of the test specimen 2 is perpendicular to the central axis of the second lever 33.

[0033] The base end of the second support bar 35 is attached to the base end of the second lever 33 or the second pivot 32 so that the central axis of the second support bar 35 is coaxial with the central axis of the second lever 33. The second support bar 35 extends from the second pivot 32 in a direction perpendicular to the central axis of the second pivot 32. Specifically, the second support bar 35 extends rearward.

[0034] The second counterweight 36 is attached to the second support bar 35. The position of the second counterweight 36 is adjustable along the second support bar 35.

[0035] Both ends of the test specimen 2 are fixed to the tips of the levers 23 and 33 by chucks 24 and 34, respectively, so that the assembly of the test specimen 2 and the levers 23 and 33 forms a crank shape. In the initial state where the test specimen 2 is not deformed, the weights of the counterweights 26 and 36 balance the levers 23 and 33 and the test specimen 2 horizontally.

[0036] (5) Loading device and load cell The loading device 40 applies a two-point load to the test piece 2 . The load cell 70 measures the sum of the two-point loads applied by the loading device 40. The load cell 70 outputs an output signal representing the measurement value of the sum of the two-point loads to a data logger or computer connected to the load cell 70. The data logger or computer inputs the output signal from the load cell 70 and stores the measurement value of the sum of the two-point loads measured by the load cell 70 in chronological order.

[0037] The load device 40 includes a base 41, a drive unit 42, a head 43, third linear guides 44 and 45, tilting mechanisms 46 and 47, and jigs 50 and 60.

[0038] The stand 41 is a gate-shaped structure consisting of an upper part and a column part. The stand 41 is installed on the support base 10. Lever mechanisms 20 and 30 are disposed on the left and right sides of the stand 41, respectively, and the test specimen 2 is passed through the area surrounded by the stand 41 in the left-right direction.

[0039] The driving unit 42 is attached to the top of the stand 41. The driving unit 42 is an actuator, more specifically, a hydraulic servo cylinder. The driving unit 42 can perform both displacement control and load control. The driving unit 42 may also be an air cylinder or an electromagnetic solenoid.

[0040] The head 43 is connected to the drive unit 42 via a load cell 70. The head 43 is driven in the vertical direction by the drive unit 42. As the head 43 moves up and down, third linear guides 44 and 45, tilting mechanisms 46 and 47, and jigs 50 and 60, which will be described later, also move up and down. The load applied to the head 43 from the drive unit 42 is measured by the load cell 70, and this load is equal to the sum of the two-point loads.

[0041] The third linear guides 44, 45 are attached to the underside of the head 43, lined up on the left and right. The third linear guides 44, 45 guide tilting mechanisms 46, 47 (described later) in the left and right directions, respectively, and the left and right movable ranges of the tilting mechanisms 46, 47 are set by the third linear guides 44, 45. The third linear guides 44, 45 are provided with centering springs, which position the tilting mechanisms 46, 47 in the center of their left and right movable ranges. When the tilting mechanisms 46, 47 are positioned, the midpoint between jigs 50, 60 (described later) is located directly below the drive unit 42 and the load cell 70.

[0042] The tilting mechanisms 46 and 47 are attached to the head 43 via third linear guides 44 and 45, respectively. Each of the tilting mechanisms 46 and 47 is composed of a single-axis pivot joint. The tilting mechanisms 46 and 47 support jigs 50 and 60 (described below) so that they can tilt about an axis perpendicular to both the displacement direction of the head 43 and the central axis of the test piece 2. In other words, the tilting mechanisms 46 and 47 support the jigs 50 and 60 so that they can tilt about an axis extending forward and backward.

[0043] The jigs 50 and 60 are attached to tilting mechanisms 46 and 47, respectively. The jigs 50 and 60 support the radial load of the test specimen 2 so that the test specimen 2 can rotate around its central axis. Because the test specimen 2 can rotate around its central axis relative to the jigs 50 and 60, the jigs 50 and 60 do not provide resistance to torsion of the test specimen 2. The jigs 50 and 60 are spaced apart from each other in the direction of the central axis of the test piece 2. The distance from one end of the test piece 2 to the jig 50 is equal to the distance from the other end of the test piece 2 to the jig 60. The position of the midpoint between the jigs 50 and 60 is aligned with the position of the midpoint between both ends of the test piece 2.

[0044] The jigs 50 and 60 will now be described in detail. The jig 50 includes a first block 51, a pair of first rollers 52, a second block 53, a pair of second rollers 54, and a pair of screw-type fasteners 55.

[0045] The first block 51 is connected to the tilting mechanism 46. The first block 51 is provided so as to be tiltable left and right by the tilting mechanism 46.

[0046] A pair of first rollers 52 are attached below the first block 51, lined up in front and behind. When the first block 51 is not tilted, the rotation axes of the first rollers 52 are parallel to the left-right direction. These first rollers 52 are applied to the outer peripheral surface of the test specimen 2 from above.

[0047] The first block 52 and the second block 53 are assembled together with the test specimen 2 disposed therebetween. A threaded fastener 55 secures the second block 53 to the first block 51.

[0048] A pair of second rollers 54 are attached to the top of the second block 53, lined up front and back. When the first block 51 and the second block 53 are not tilted, the rotation axis of the second rollers 54 is parallel to the left-right direction. These second rollers 54 are placed against the outer surface of the test specimen 2 from below, and the test specimen 2 is sandwiched between the first roller 52 and the second roller 54.

[0049] The screw-type fastener 55 tightens the second block 53 to the first block 51, generating a clamping force that clamps the test specimen 2 between the first roller 52 and the second roller 54. This clamping force restricts the relative movement of the test specimen 2 with respect to the jig 50 in the direction of its central axis.

[0050] The jig 60 has the same configuration as the jig 50, and therefore a detailed description of the jig 60 will be omitted.

[0051] When the drive unit 42 displaces the head 43, the third linear guides 44, 45, the tilting mechanisms 46, 47, and the jigs 50, 60 downward, a downward load is applied from the jigs 50, 60 to the test piece 2, causing the test piece 2 to bend downward and convexly, and the levers 23, 33 to rotate around their respective central axes, as shown in Figure 6. As the levers 23, 33 rotate, the chucks 24, 34 tilt in an inverted V shape, and the tilt angle of the chucks 24, 34 is equal to the deflection angle θ.

[0052] When the test specimen 2 bends convexly downward, the jigs 50, 60 are tilted by the tilting mechanisms 46, 47 so that the lower portions of the jigs 50, 60 move away from each other. At this time, the levers 23, 33 are swung down so as to rotate in opposite directions around the pivots 22, 32, respectively, causing the test specimen 2 to twist. The swing angle of the levers 23, 33 is equal to the torsional angle φ of the test specimen 2.

[0053] Conversely, when the drive unit 42 displaces the head 43, the third linear guides 44, 45, the tilting mechanisms 46, 47, and the jigs 50, 60 upward, and an upward load is applied from the jigs 50, 60 to the test specimen 2, the test specimen 2 bends upward in a convex shape, and the levers 23, 33 rotate around their respective central axes, causing the chucks 24, 34 to tilt in a V-shape, as shown in Figure 7. Due to the bending of the test specimen 2, the jigs 50, 60 are tilted by the tilting mechanisms 46, 47 so that the lower portions of the jigs 50, 60 approach each other. At this time, the levers 23, 33 are swung up to rotate in opposite directions about the pivots 22, 32, respectively, causing the test specimen 2 to twist.

[0054] As the test piece 2 bends, the gap between both ends of the test piece 2 narrows, and the lever mechanisms 20 and 30 move closer to each other, guided by the linear guides 12 and 13. When the test piece 2 is no longer bent, the lever mechanisms 20 and 30 move away from each other.

[0055] (6) Deflection angle sensor and torsion angle sensor The deflection angle sensor 81 and the torsion angle sensor 82 are attached to the tip of the first lever 23 via the first chuck 24. The deflection angle sensor 81 and the torsion angle sensor 82 may be attached to the second chuck 34. The deflection angle sensor 81 and the torsion angle sensor 82 are formed by tilt sensors.

[0056] The deflection angle sensor 81 measures the rotation angle of the first lever 23 around the central axis of the first lever 23, i.e., the deflection angle θ of the test piece 2 and the tilt angle of the first chuck 24. The deflection angle sensor 81 outputs an output signal representing the measurement value of the deflection angle θ to a data logger or computer connected to it. The data logger or computer inputs the output signal of the deflection angle sensor 81 and stores the measurement values ​​of the deflection angle θ measured by the deflection angle sensor 81 in chronological order.

[0057] The torsion angle sensor 82 measures the swing angle of the first lever 23 around the central axis of the first pivot 22, centered on the first pivot 22, and the torsion angle φ of the test piece 2. The torsion angle sensor 82 outputs an output signal representing the measurement value of the torsion angle φ to a data logger or computer connected thereto. The data logger or computer inputs the output signal of the torsion angle sensor 82 and stores the measurement values ​​of the torsion angle φ measured by the torsion angle sensor 82 in chronological order.

[0058] (7) Heating furnace The heating furnace 90 is attached to the head 43 so as to hang down from the head 43, and moves up and down integrally with the head 43. The heating furnace 90 may be detachable from the head 43. The heating furnace 90 is tubular and has an internal space. The left and right ends of the heating furnace 90 are open, and the test specimen 2 is passed through these openings, with the center of the test specimen 2 housed in the heating furnace 90. With the test specimen 2 passing through the opening of the heating furnace 90, the gap between the outer surface of the test specimen 2 and the edge of the opening is sealed with insulating material. The heating furnace 90 is an electric furnace, and an electric heater and a temperature sensor are provided in the heating furnace 90. The electric heater heats the internal space of the heating furnace 90 and the test specimen 2. The temperature sensor measures the temperature inside the heating furnace 90. The electric heater and temperature sensor are connected to a temperature control circuit outside the heating furnace 90. The temperature control circuit feedback-controls the electric heater according to the temperature measured by the temperature sensor to maintain a constant temperature inside the heating furnace 90.

[0059] The heating furnace 90 is composed of an upper half and a lower half so that it can be separated into upper and lower halves. A groove with a semicircular cross section is formed on the underside of the upper half, and a groove with a semicircular cross section is formed on the upper surface of the lower half. The upper and lower halves are combined to form the heating furnace 90. The upper half is attached to the head 43.

[0060] 2. Bending moment, torsional moment and equivalent bending moment When the test specimen 2 is a hollow cylinder, i.e., a round tube, when two-point loads are applied to the test specimen 2 from the jigs 50 and 60, the bending moment, torsional moment, and equivalent bending moment generated in the test specimen 2 are as follows.

[0061]

number

[0062] where M [Nm] is the bending moment, T [Nm] is the torsional moment, and M e[N] is the equivalent bending moment, P [N] is the two-point load applied to the test piece 2 from the jigs 50 and 60, L [m] is the length of the test piece 2, and L1 [m] is the distance from the end of the test piece 2 to the jig 50.

[0063] 3. Test specimen setup The method by which an operator sets the test specimen 2 in the bending / torsion test device 1 will be described.

[0064] First, the screw fasteners 55 of the jig 50 are loosened to remove the second block 53 from the first block 51. The same is done for the jig 60. The lower half of the heating furnace 90 is removed from the upper half.

[0065] Next, one end of the test specimen 2 is fixed to the first chuck 24 of the lever mechanism 20. By adjusting the position of the first counterweight 26 of the lever mechanism 20, the weight of the first counterweight 26 and the weight of the test specimen 2 balance the first lever 23 of the lever mechanism 20 horizontally.

[0066] Next, the other end of the test specimen 2 is fixed to the second chuck 34 of the lever mechanism 30. By adjusting the position of the second counterweight 36 of the lever mechanism 30, the second lever 33 of the lever mechanism 30 is balanced horizontally by the weight of the second counterweight 36 and the weight of the test specimen 2. Therefore, the weights of the counterweights 26 and 36 balance the levers 23 and 33 and the test specimen 2 horizontally.

[0067] Next, the lever mechanisms 20 and 30 are moved left and right along the linear guides 12 and 13, and the positions of the lever mechanisms 20 and 30 are adjusted so that the middle of the test piece 2 is positioned directly below the drive unit 42 and the load cell 70.

[0068] Next, the drive unit 42 is operated to lower the head 43 until the first roller 52 of the jig 50 and the first roller of the jig 60 come into contact with the test piece 2 .

[0069] Next, the second block 53 of the jig 50 is assembled to the first block 51, and the test specimen 2 is sandwiched between the first roller 52 and the second roller 54. Then, a screw-type fastener 55 is attached to the second block 53 and the first block 51, and the second block 53 is fastened to the first block 51 by the screw-type fastener 55. In this way, the jig 50 is assembled, and the test specimen 2 is rotatably supported by the jig 50. Similarly, the jig 60 is assembled, and the test specimen 2 is supported by the jig 60.

[0070] Next, the lower half of the heating furnace 90 is attached to the upper half, and the center of the test specimen 2 is placed in the heating furnace 90. Next, the gap between the edge of the opening at the end face of the heating furnace 90 and the outer peripheral surface of the test piece 2 is closed with a heat insulating material. This completes the setting of the test specimen 2.

[0071] 4. Static bending and torsion test method A static bending-torsion test method using the bending-torsion test device 1 will be described.

[0072] The test specimen 2 is set in the bending / torsion test device 1 as described above. Next, the deflection angle sensor 81 and the torsion angle sensor 82 are calibrated to their zero points.

[0073] Next, the driving unit 42 is started, and operates under displacement control or load control, thereby driving the head 43 to raise or lower it. As the displacement of the head 43 increases, the two-point load applied to the test specimen 2 from the jigs 50 and 60 increases. This causes the test specimen 2 to bend and twist, and the deflection angle θ and the torsion angle φ increase. The driving unit 42 may operate until the test specimen 2 breaks, or the driving unit 42 may remove the two-point load before the test specimen 2 breaks.

[0074] While the test specimen 2 is being deflected and twisted, the load cell 70 measures the sum of the two-point loads, and the deflection angle sensor 81 and torsion angle sensor 82 measure the deflection angle θ and torsion angle φ, respectively. The load cell 70, deflection angle sensor 81, and torsion angle sensor 82 output the measured values ​​of the sum of the two-point loads, the deflection angle θ, and the torsion angle φ to a data logger or a computer. The data logger or computer records the measured values ​​of the sum of the two-point loads, the deflection angle θ, and the torsion angle φ in chronological order.

[0075] The loading device 40 may apply a two-point load to the test specimen 2 while the heating furnace 90 is heating the test specimen 2. The loading device 40 may apply a two-point load to the test specimen 2 while the temperature inside the heating furnace 90 is at room temperature due to the heating furnace 90 being stopped.

[0076] 5. Creep-Fatigue Test Method A creep-fatigue test method using the bending-torsion test device 1 will be described.

[0077] The test specimen 2 is set in the bending / torsion test device 1 as described above. Next, when the power to the heating furnace 90 is turned on, the temperature control circuit feedback controls the electric heater of the heating furnace 90 based on the temperature measured by the temperature sensor of the heating furnace 90. This heats the inside of the heating furnace 90 and maintains the temperature of the heating furnace 90 at a predetermined temperature. Next, the deflection angle sensor 81 and the torsion angle sensor 82 are calibrated to their zero points.

[0078] Next, when the driving unit 42 operates under load control or displacement control, the driving unit 42 repeatedly raises and lowers the head 43. As a result, a two-point load is repeatedly applied to the test piece 2 from the jigs 50 and 60. As a result, the test piece 2 repeatedly bends in a downward or upward convex shape, or the test piece 2 repeatedly bends in a downward convex shape and an upward convex shape alternately. Note that during each cycle, the state in which the two-point load is maximized may be maintained for a certain period of time. Alternatively, during each cycle, the state in which the two-point load is minimized may be maintained for a certain period of time.

[0079] While the test piece 2 is repeatedly deflected, the load cell 70 measures the sum of the two-point loads, and the deflection angle sensor 81 and the torsion angle sensor 82 measure the deflection angle θ and the torsion angle φ, respectively. The load cell 70, the deflection angle sensor 81, and the torsion angle sensor 82 output the measured values ​​of the sum of the two-point loads, the deflection angle θ, and the torsion angle φ to a data logger or a computer. The data logger or the computer records the measured values ​​of the sum of the two-point loads, the deflection angle θ, and the torsion angle φ in chronological order.

[0080] While the test specimen 2 is heated by the heating furnace 90, two-point loads are repeatedly applied to the test specimen 2, causing creep to occur in the test specimen 2. In other words, as the number of cycles increases, the maximum deflection angle θ and maximum torsion φ of the test specimen 2 during each cycle also increase.

[0081] The drive unit 42 may operate until the test specimen 2 experiences creep fatigue failure, or the repeated loading may be stopped or temporarily interrupted by stopping the drive unit 42 before the test specimen 2 experiences creep fatigue failure.

[0082] 6. Fatigue Test Method The fatigue test method is the same as the creep-fatigue test method described above, except that the test specimen 2 is not heated by the heating furnace 90.

[0083] 7. Creep Test Method A creep test method using the bending-torsion test device 1 will be described.

[0084] The test specimen 2 is set in the bending / torsion test device 1 as described above. Next, when the power to the heating furnace 90 is turned on, the temperature control circuit feedback controls the electric heater of the heating furnace 90 based on the temperature measured by the temperature sensor of the heating furnace 90. This heats the inside of the heating furnace 90 and maintains the temperature of the heating furnace 90 at a predetermined temperature. Next, the deflection angle sensor 81 and the torsion angle sensor 82 are calibrated to their zero points.

[0085] Next, when the drive unit 42 operates under load control, the drive unit 42 raises or lowers the head 43, thereby applying a constant two-point load from the jigs 50, 60 to the test specimen 2. As a result, the test specimen 2 bends in a convex shape downward or upward. Since the constant two-point load is applied to the test specimen 2 while the test specimen 2 is heated by the heating furnace 90, a creep phenomenon occurs in the test specimen 2. In other words, the maximum deflection angle θ and the maximum torsion angle φ of the test specimen 2 increase over time.

[0086] While the creep phenomenon of test specimen 2 is progressing, load cell 70 measures the sum of the two-point loads, and deflection angle sensor 81 and torsion angle sensor 82 measure the deflection angle θ and torsion angle φ, respectively. Load cell 70, deflection angle sensor 81, and torsion angle sensor 82 output the measured values ​​of the sum of the two-point loads, deflection angle θ, and torsion angle φ to a data logger or computer. The data logger or computer records the measured values ​​of the sum of the two-point loads, deflection angle θ, and torsion angle φ in chronological order.

[0087] 8. Beneficial Effects (1) When the jigs 50 and 60 are displaced up and down by the driving unit 42, two-point loads are applied from the jigs 50 and 60 to the test specimen 2, causing the test specimen 2 to bend. At this time, the levers 23 and 33 swing so as to rotate in opposite directions around the pivots 22 and 32, respectively, causing the test specimen 2 to twist. Therefore, both bending moment and torsional moment can be applied to the test specimen 2 by the single driving unit 42. Furthermore, since the test specimen 2 is modeled after actual piping in a power plant or the like, a mechanical state that approximates the state in which the actual piping is bent and twisted can be realized in the test specimen 2.

[0088] (2) The bending-torsion test device 1 can be provided at low cost because the actuator used in the bending-torsion test device 1 is a single drive unit 42. In addition, since the bending and twisting of the test specimen 2 are generated by the power of the single drive unit 42, there is no time lag between the timing of the bending and the timing of the twisting of the test specimen 2.

[0089] (3) Because the first lever 23 is rotatable about its central axis and the second lever 33 is rotatable about its central axis, the test specimen 2 is subject to large deflections. Here, the test specimen 2 is modeled after actual piping in a power plant or the like, and because the actual piping has a long span, the piping is subject to large deflections due to thermal expansion and internal pressure. Therefore, the large deflection of the test specimen 2 due to the rotation of the levers 23 and 33 simulates the deflection of actual piping.

[0090] (4) Since the test specimen 2 can rotate around the central axis of the test specimen 2 relative to the jigs 50 and 60, the jigs 50 and 60 do not provide resistance to the torsion of the test specimen 2.

[0091] (5) When the test specimen 2 is bent, the distance between both ends of the test specimen 2 becomes shorter. Even in such a case, the lever mechanisms 20 and 30 are guided left and right by the linear guides 12 and 13, so the distance between the tips of the levers 23 and 33 is adjusted to match the distance between both ends of the test specimen 2.

[0092] (6) Because the relative movement of the test piece 2 in the central axis direction with respect to the jigs 50 and 60 is restricted, when the test piece 2 bends, the distance between the jigs 50 and 60 changes. Even in such a case, the jigs 50 and 60 are guided left and right by the third linear guides 44 and 45, so the distance between the jigs 50 and 60 is adjusted according to the bending of the test piece 2.

[0093] (7) When the test piece 2 is bent, the jigs 50 and 60 are tilted by the tilting mechanisms 46 and 47, and the jigs 50 and 60 are moved left and right by the third linear guides 44 and 45. Therefore, the shape of the deflection curve of the test piece 2 is not unique in the jigs 50 and 60.

[0094] 9. Experiments using bending and torsion testing equipment and their results Creep-fatigue tests were carried out using the bending-torsion test device 1. The details of the tests and their results are explained below.

[0095] (1) Test specimen The ends of two metal round tubes of equal length were welded together to prepare specimen 2. The length of specimen 2 was 900 mm, the inner diameter of specimen 2 was 38.14 mm, and the outer diameter of specimen 2 was 48.3 mm.

[0096] (2) Heating temperature The temperature inside the heating furnace 90 was controlled to be constant at 923K.

[0097] (3) Loading conditions FIG. 9 shows the waveform of the load P applied by the drive unit 42 during one cycle by load-controlling the drive unit 42. In FIG. 9, the vertical axis represents the load P, and the horizontal axis represents time. The maximum value P of the load P max , retention time t h , the increasing speed of the load P is V i and the load reduction rate V d is shown in Table 1. Here, the load P is the sum of the two point loads, and the holding time t h is the load P at its maximum value P max is the time to hold the i is the load P from the minimum value (near zero) to the maximum value P max The load P per unit time is changed from d is the load P at its maximum value P max This is the variation of the load P per unit time when changing from the maximum value to the minimum value. When the load when the drive unit 42 was subjected to load control was measured by the load cell 70, it was confirmed that the measured value was in accordance with the settings shown in FIG.

[0098] [Table 1]

[0099] Creep-fatigue tests were carried out under the above loading conditions (a) to (f).

[0100] (4) Change in displacement Figure 10 is a graph showing the experimental results of the relationship between the number of cycles and the displacement under the load condition (b). In Figure 10, the horizontal axis represents the number of cycles, and the vertical axis represents the time when the load P reaches the maximum value Pmax The displacement of the head 43 when the head 43 descends from the initial position is negative.

[0101] As is clear from Figure 10, as the number of cycles increases, the absolute values ​​of the displacement at both the maximum load and the minimum load increase. This indicates that creep occurs in specimen 2. Furthermore, when the number of cycles slightly exceeds 2000, cracks appear in test specimen 2, and the fatigue life of test specimen 2 is reached.

[0102] (5) Change in deflection angle Fig. 11 is a graph showing the experimental results of the relationship between the number of cycles and the deflection angle θ under the load condition (b). In Fig. 11, the horizontal axis represents the number of cycles, and the vertical axis represents the maximum value P of the load P. max 11, the deflection angle θ at the maximum load and the deflection angle θ at the minimum load both increase as the number of cycles increases.

[0103] (6) Change in torsion angle Fig. 12 is a graph showing the experimental results of the relationship between the number of cycles and the torsion angle φ under the load condition (b). In Fig. 12, the horizontal axis represents the number of cycles, and the vertical axis represents the time when the load P reaches the maximum value P max 12, the torsional angle φ at the maximum load and the torsional angle φ at the minimum load both increase as the number of cycles increases.

[0104] (7) Observation of cracks Figure 13 is a photograph showing the cracks that occurred in test specimen 2 under loading condition (b). As shown in Figure 13, it can be seen that a crack occurred at the interface between the end of the metal round tube and the weld.

[0105] (8) Relationship between deflection angle and equivalent bending moment Figure 14 is a graph showing the experimental results of the relationship between deflection angle θ and equivalent bending moment. In Figure 14, the horizontal axis represents deflection angle θ, and the vertical axis represents equivalent bending moment. As is clear from Figure 14, hysteresis occurs in the deflection angle θ at each cycle. It is also clear that the residual deflection angle θ increases as the number of cycles increases. This indicates that creep is occurring in test specimen 2.

[0106] (9) Relationship between torsion angle and equivalent bending moment Figure 15 is a graph showing the experimental results of the relationship between the torsion angle φ and the equivalent bending moment. In Figure 15, the horizontal axis represents the torsion angle φ, and the vertical axis represents the equivalent bending moment. As shown in Figure 15, it can be seen that hysteresis occurs in the torsion angle φ at each cycle. It can also be seen that the remaining torsion angle φ increases as the number of cycles increases. This indicates that creep occurs in test specimen 2.

[0107] (10) Relationship between equivalent bending moment and fatigue life Fig. 16 is a graph showing the experimental results of the relationship between the number of cycles at which fatigue failure was reached and the equivalent bending moment. In Fig. 16, the horizontal axis represents the number of cycles at which fatigue failure was reached, and the vertical axis represents the equivalent bending moment. In Fig. 16, the holding time t h The results for 1 minute are plotted as white circles, and the retention time t h The results for a retention time of t 10 min are plotted as black circles. h The fatigue life when the holding time t h It can be seen that the fatigue life is lower than that of 1 minute. From this, the load P is set to the maximum value P max It can be seen that the torsional creep phenomenon caused by holding the specimen at a constant temperature affects the fatigue life, and the more pronounced the creep phenomenon, the shorter the fatigue life. [Explanation of symbols]

[0108] 1...Bending and torsion testing equipment 12...First linear guide (first guide) 13...Second linear guide (second guide) 23...First lever 33...Second lever 42...Drive unit 44, 45...Third linear guide (third guide) 46,47…Tilt mechanism 50,60...jig 51...1st Block 52...First roller 53...Second Block 54...Second roller 55...Threaded fasteners (fasteners) 81... Deflection angle sensor 82...Torsion angle sensor

Claims

1. a first lever extending from a first base end to a first tip end, rotatable about a first central axis extending from the first base end to the first tip end, and swingable at the first base end about a first swing axis perpendicular to the first central axis, one end of a columnar or hollow columnar test body being fixed to the first tip end so that the central axis of the test body is perpendicular to the first central axis; a second lever extending from a second base end to a second tip end in a direction parallel to and opposite to the direction in which the first lever extends from the first base end to the first tip end, being rotatable about a second central axis extending from the second base end to the second tip end, and being swingable at the second base end about a second swing axis perpendicular to the second central axis, the other end of the test body being fixed to the second tip end so that the central axis of the test body is perpendicular to the second central axis; a pair of jigs spaced apart from each other in the direction of the central axis of the test body and supporting a radial load on the test body so that the test body can rotate around the central axis of the test body; a drive unit that displaces the pair of jigs in a direction perpendicular to the central axis of the test piece so as to swing the first lever and the second lever around the first swing axis and the second swing axis, respectively.

2. a first guide that guides the first lever in a direction parallel to the central axis of the test body; 2. The bending / torsion test device according to claim 1, further comprising: a second guide that guides the second lever in a direction parallel to the central axis of the test piece.

3. 3. A bending / torsion testing device according to claim 1, further comprising a pair of tilting mechanisms that support the pair of jigs so that the pair of jigs can be tilted about axes that are perpendicular to both the displacement direction of the pair of jigs and the central axis of the test piece.

4. 4. The bending / torsion testing device according to claim 3, further comprising a pair of third guides that respectively guide the pair of tilting mechanisms in a direction parallel to the central axis of the test piece.

5. The jig is The first block, a first roller attached to the first block so as to be rotatable about an axis parallel to the central axis of the test piece, the first roller being in contact with an outer peripheral surface of the test piece; a second block assembled to the first block with the test specimen interposed between the first block and the second block; a second roller attached to the second block so as to be rotatable about an axis parallel to the central axis of the test piece, the second roller being in contact with the outer peripheral surface of the test piece; a fastener that fastens the first block and the second block and generates a clamping force that clamps the test specimen between the first roller and the second roller. A bending and torsion testing device according to any one of claims 1 to 4.

6. 6. The bending / torsion test device according to claim 1, further comprising a deflection angle sensor provided at the first tip of the first lever or the second tip of the second lever, the deflection angle sensor measuring the deflection angle of the test piece.

7. 7. The bending / torsion test device according to claim 1, further comprising a torsion angle sensor provided at the first tip of the first lever or the second tip of the second lever, the torsion angle sensor measuring the torsion angle of the test piece.

8. 8. The bending and torsion testing device according to claim 1, further comprising a heating furnace that accommodates a portion of the test specimen between the pair of jigs.

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