JP2938443B1 - Buckling test method for rod-shaped body and jig for mounting rod-shaped specimen - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To insert a rod-shaped test piece into a transparent pipe and perform a buckling test while restraining the buckling of the test piece to a certain extent. Provided are a buckling test method for a rod-shaped body and a rod-shaped test piece mounting jig which can be sufficiently reduced. SOLUTION: A transparent cylindrical body 7 which has a transparent outer cylinder and a transparent inner cylinder movably connected to each other and which can expand and contract together with a rod-shaped test piece.
Is mounted on the base 4, the rod-shaped test piece 2 is inserted into the transparent cylindrical body, and the outer peripheral surface of the rod-shaped test piece is made to be able to be restrained through a predetermined gap by the transparent cylindrical body. Hold both ends of the holding jig 3, 11 between the base side and the pressing device.
A buckling test method for a rod-shaped test piece in which a rod-shaped test piece is buckled in a transparent cylinder by applying an axial load through a load meter by a pressing device 21 and a rod-shaped test piece used in this method Test piece mounting jig.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tubular (hollow) body or columnar body having various cross-sectional shapes used for construction of structures, for example, a drilling steel pipe used for extracting oil or natural gas, and the like. (Solid) body or the like, whose outer peripheral surface is constrained by constraining bodies having various inner peripheral surface shapes via gaps,
The present invention relates to a buckling test method for a rod-shaped body (hereinafter, referred to as a “rod-shaped body”) subjected to an axial load and a jig for mounting a rod-shaped test piece.

[0002]

2. Description of the Related Art For example, in the field of oil extraction, in recent years, the state of oil reserves underground has changed,
Excavation conditions are becoming more severe, and buckling of excavating steel pipes, which has not been a problem in the past, has become a problem. Conventionally, excavation is performed using an empirical formula or a theoretical formula. However, buckling occurs in a steel pipe for excavation, making it impossible to continue excavation, and in some cases, excavation must be abandoned. In this case, since the damage is enormous, in order not to cause such inconvenience, some experiments have recently been attempted to evaluate the conventionally used empirical formula or theoretical formula.

However, since these experiments are mainly conducted on actual pipes for excavating underground, it is difficult to sufficiently observe the buckling behavior, and the data obtained is extremely limited. Since the cost burden is large, it is not practical. More recently, attempts have been made to create test specimens and perform the buckling test in a long, completely fixed, transparent pipe that mimics the drilling environment. Attempts have also been made to lay the device and vibrate the test piece.

[0004]

However, in the buckling test using the above test piece, the test piece undergoes deformation such as compression, bending and torsion, but a transparent pipe into which the test piece is inserted is fixed. Therefore, the contact friction between the inner surface of the transparent pipe and the deformed test piece increases in various directions, and the test accuracy is significantly reduced. In the buckling test in which the test piece is vibrated, by vibrating the test piece,
Although there is an effect of removing some contact friction, as the test piece becomes longer, the removing effect is greatly reduced. Further, since the test piece itself is vibrated, there is a problem that an error of the test result is increased. Here, in order to eliminate the contact between the deformed test piece and the transparent pipe, the inner diameter may be increased, but the buckling environment becomes far from the actual excavation conditions, and the data obtained by this buckling test actually Evaluation cannot be made in a regular manner.

[0005] Therefore, the present invention provides a method for preparing a test piece and inserting a buckling test into a transparent pipe, while restricting the buckling of the test piece to some extent with the transparent pipe. A rod-like shape that allows the buckling test to be performed under conditions close to the actual buckling environment without excessive load on the test specimen by the transparent pipe by sufficiently reducing the axial and circumferential contact friction of the specimen An object of the present invention is to provide a buckling test method for a body and a jig for mounting a rod-shaped test piece.

[0006]

The features of the present invention are as follows. (1) to (6) relate to a buckling test method for a rod-shaped body, and (7) to (14) relate to (1) to
It is positioned as an example of a rod-shaped test piece mounting jig used for performing the rod-shaped buckling test method of (6).

[0007] (1) A transparent cylindrical body, which is movably connected to a transparent outer cylinder and a transparent inner cylinder, is mounted on a base with a rod-shaped test piece that can expand and contract, and the rod-shaped test piece is inserted into the transparent cylinder. Then, the outer peripheral surface of the rod-shaped test piece is made to be capable of being restrained by a transparent cylinder via a predetermined gap, and both ends of the rod-shaped test piece are restrained via a holding jig between the base side and the pressing device. Then, the rod-shaped test piece was buckled in a transparent cylinder by applying an axial load via a load meter by a pressing device,
A buckling test method for a rod-like body, wherein a buckling strength characteristic is evaluated from a deformation state and a load amount. (2) The method according to (1), characterized in that one end or both ends of the rod-shaped test piece is variably held, and an axial load is applied with both ends constrained. (3) In (1) or (2), when applying a load in the axial direction, the transparent cylinder is rotated to reduce friction. (4) In any one of (1) to (3), both ends of the rod-shaped test piece are fixed to a rotatable holding jig, and during the buckling test,
It is characterized in that a predetermined torsional force is applied to the rod-shaped test piece via a gripping jig by the torsional force applying device. (5) In any one of (1) to (3), both ends of the rod-shaped test piece are fixed to a rotatable holding jig, and during the buckling test,
The torsion force generated in the rod-shaped test piece is measured by a torque meter via a gripping jig. (6) In any one of (1) to (5), at least two video cameras are arranged at equal intervals outside the transparent cylinder, and attached to a rod-shaped test piece in the transparent cylinder during a buckling test. The position of the identified identification mark is continuously or intermittently photographed, and the photographed image is subjected to image processing to automatically quantitatively analyze the deformation history and the twist amount history of the rod-shaped test piece.

(7) A transparent cylinder which is movably connected to a transparent outer cylinder and a transparent inner cylinder, and which can be extended and contracted together with a rod-shaped test piece, a base supporting the transparent cylinder, and A support provided so as to surround the transparent cylindrical body, and an annular support provided on the support and slidably supporting the outer peripheral surface of at least the intermediate portion of the transparent outer cylinder in the axial direction and the circumferential direction, A bar test comprising: a holding jig provided on the base side and the pressurizing device side for holding and fixing an end of a bar-shaped test piece; and a load meter for measuring an axial load on the bar-shaped test piece. Single mounting jig. (8) In (7), the gripping jig for gripping / fixing the tip of the rod-shaped test piece has a gripping / fixing structure for changing the direction of the tip of the rod-shaped test piece. (9) In (7) or (8), the transparent outer cylinder arranged in the middle part can move freely in the longitudinal direction of the rod-shaped test piece, but does not move freely except in the longitudinal direction of the test piece. It is characterized by being supported by an annular support portion. (10) In any one of the constitutions (7) to (9), the thickness of the transparent inner cylinder in the transparent cylinder is formed to be smaller than the thickness of the transparent outer cylinder. (11) In any one of (7) to (10), a scale or an identification mark for observing the deformation state of the rod-shaped test piece is drawn on the peripheral surface of the transparent cylinder, the support, and the rod-shaped test piece. The rod-shaped test piece mounting jig according to any one of claims 6 to 9, wherein: (12) In any one of (7) to (11), one gripping jig for fixing both ends of the rod-shaped test piece is rotatably supported, and the torsion force on the rod-shaped test piece is measured by the gripping jig. A torsion force measuring device having a torque meter and a speed reducer is connected. (13) In any one of (7) to (12), one gripping jig for fixing both ends of the rod-shaped test piece is rotatably supported, and a deceleration (transmission) device and a torque meter are mounted on the gripping jig. The torsion force providing device provided is connected. (14) In any one of the constitutions (7) to (13), the positions of the marks which are arranged at equal intervals in the circumferential direction on the outer side of the transparent cylinder and are attached to the rod-shaped test pieces in the transparent cylinder are continuously or intermittently determined. Shooting, at least two or more video cameras, an image processing apparatus for processing the captured image from the video camera, a deformation history of the rod-shaped test piece by a signal from the image processing apparatus, an arithmetic unit for calculating the amount of twist, A recording and display device is provided for recording and displaying the deformation history of the rod-shaped test piece based on a signal from the arithmetic unit.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a rod-shaped test piece made of a tubular (hollow) or columnar (solid) body having various cross-sectional shapes by processing a material corresponding to a rod-like body actually used, for example. (Hereinafter referred to as a “rod-shaped test piece”),
In the case where the buckling test of the rod-shaped test piece is performed by inserting the rod-shaped test piece into the transparent cylinder forming the jig for mounting the rod-shaped test piece, the outer peripheral surface of the buckling portion of the rod-shaped test piece is sufficiently restrained by the transparent cylinder. Another object of the present invention is to sufficiently reduce axial and circumferential contact friction with the inner surface of a transparent cylinder when a rod-shaped test piece is deformed.

The main point of the means for solving this problem lies in the structure of the transparent cylinder forming the rod-shaped test piece mounting jig. That is, the transparent cylindrical body is made of a transparent material such as an acrylic resin which has a high strength and does not crack easily and which is stable in accuracy and safety so that the buckling behavior of the rod-shaped test piece inserted therein can be easily observed. In the state of being formed and supported by the support, the bar-shaped test piece is made to be able to expand and contract in the longitudinal direction together with the bar-shaped test piece. This is because the cylindrical body is freely moved (expanded and contracted) in the axial direction so that the contact friction with the rod-shaped test piece is reduced.

More specifically, the transparent cylindrical body is made of a material, a mechanical property, a shape, and a size of a rod-shaped test piece to be subjected to a buckling test.
Consists of a transparent outer cylinder and a transparent inner cylinder manufactured to a predetermined size corresponding to the conditions of actual use conditions, allowable deformation state, etc., and extends and contracts the length by connecting multiple transparent outer cylinders and transparent inner cylinders alternately It has a possible structure.

When a rod-shaped test piece is inserted into the transparent cylinder, a gap between the inner peripheral surface of the transparent inner cylinder and the outer peripheral surface of the rod-shaped test piece is formed.
The dimensions of the transparent inner cylinder and the transparent outer cylinder are set such that a predetermined gap corresponding to the allowable deformation state is formed. When the inner peripheral surface of the transparent cylindrical body and the outer peripheral surface of the rod-shaped test piece are circular, the ratio of the inner diameter of the transparent cylindrical body to the outer diameter of the rod-shaped test piece is set to be about 1.5 to 3, When an axial load is applied and the rod-shaped test piece buckles, even if the inner peripheral surface of the transparent inner cylinder contacts the outer peripheral surface of the rod-shaped test piece, the ideal buckling behavior of this rod-shaped test piece is not hindered as much as possible. Like that.

However, a transparent cylinder (transparent outer cylinder and transparent inner cylinder)
Is not limited to the same shape. A combination of shapes such as a circle, a square, a polygon, or a shape similar to these shapes can be selected according to the combination of the shapes of the rod-like body and the restraining body actually used.

One of the transparent outer cylinders arranged on the base side is fixed to the base side, and the other is fixed to the holding plate fixed to the load transmitting portion of the pressurizing device. The transparent inner cylinder to be inserted into the transparent outer cylinder can move freely in the axial direction while ensuring that a part is always inserted into the inner peripheral surface of the transparent outer cylinder, but do not move freely except in the axial direction. Connected to transparent outer cylinder.

The transparent cylindrical body must have a strength capable of withstanding the load due to the buckling deformation of the rod-shaped test piece, and it is preferable that the transparent outer cylinder having a large diameter is thicker than the transparent inner cylinder.
Further, in order to minimize the contact friction that hinders the buckling deformation of the rod-shaped test piece, it is preferable to minimize the unevenness of the inner peripheral surface of the transparent cylindrical body.

The transparent cylinder is formed of a transparent material.
This is to enable the buckling behavior of the rod-shaped test piece inserted in the buckling test to be easily observed visually or with a sensor. The buckling state (position, deformation state) of the rod-shaped test piece during the buckling test ), It is more effective that scales and identification marks are drawn on the peripheral surface of the transparent cylinder, the support, or the peripheral surface of the rod-shaped test specimen in order to observe the buckling strength characteristics in more detail. It is. This scale is effective for quantitatively observing the deformation of the rod-shaped specimen during the buckling test. This observation may be visual observation, or, during the buckling test, the time history of changes in the shape of the scale and rod-shaped test piece is captured and recorded with a video video camera, and quantitative analysis is performed using a computer system that includes image processing. It is also possible.

Further, identification marks are provided at regular intervals in the longitudinal direction of the rod-shaped test piece, and the position change of the identification marks is continuously or intermittently photographed by a plurality of video cameras during the buckling test. It is also effective to automatically perform quantitative analysis on the deformation history and torsion amount history of the rod-shaped test piece by performing image processing on the photographed image.

When performing a buckling test, it is necessary to change the outer diameter and length of the rod-shaped test piece, and the required inner diameter and length of the transparent cylindrical body. It is effective to prepare a buckling tester equipped with For example, for a change in the length of the rod-shaped test piece, a plurality of transparent outer cylinders having different lengths and having a connectable and detachable structure and a plurality of transparent inner cylinders are prepared so that the number of assembly steps can be increased or decreased. It is effective to

The rod-shaped test piece is made of the same material as the actually used steel pipe for excavation, for example, in a predetermined size.
This rod-shaped test piece is gripped and fixed at one end to a gripping jig provided on the base side, and the other end is mounted on a holding plate fixed to a load transmission plate of a load applying device with a load meter interposed. Hold and fix with a jig. In this case, for example,
As a fixing structure, a spherical seat is provided on the base side, and a structure in which a gripping jig having a spherical surface is rotatably supported on the spherical seat is used to hold and fix the bar-shaped test piece when it buckles. It is also effective to be able to freely change the direction of the tip of the rod-shaped test piece.

The change in the gripping / fixing structure of the rod-shaped test piece tip is important in considering various actual conditions. For example, when simulating a fixed building structure, it is effective to use a fixed type, and when simulating a steel pipe for drilling (drill pipe), it is effective to use a spherical seat type. As described above, it is effective to prepare a gripping jig having various necessary gripping / fixing structures so that various gripping / fixing structures can be easily changed, and to be able to exchange the gripping jigs. .

Further, for example, the tip of the rod-shaped test piece is fixed to a gripping jig so that a buckling test can be performed in a state where a predetermined torsional force is applied to the rod-shaped test piece. It is also effective that a predetermined twisting force can be applied by connecting and rotating. Also,
For example, fix the tip of a rod-shaped test piece to a gripping jig, connect this gripping jig to a torsion measuring device, rotate it, measure this rotational force, and determine the torsional force generated in the rod-shaped test piece during the buckling test. It is also effective to enable measurement.

An embodiment of the present invention will be described below with reference to FIGS.
Details will be described based on (b). FIGS. 1 (a) and 1 (b) show the mounting of a rod-shaped test piece of the present invention used to perform a buckling test on a rod-shaped test piece made of a material corresponding to a steel pipe for excavation using a vertical buckling test apparatus. FIG. 3 conceptually shows a structural example of a jig.

The rod-shaped test piece mounting jig 1 of this embodiment has a base 4 into which a replaceable lower gripping jig 3 for supporting the lower end of the rod-shaped test piece 2 is fitted, and a support standing upright on the base. 5
A transparent inner cylinder 7b is vertically slidably connected to a transparent outer cylinder 7a movably supported by an annular support portion (ball bearing) 6 of the support, and the length L is transparent. A cylindrical body 7, a holding plate 10 attached to the upper end side of the transparent cylindrical body 7 with bolts and nuts 9 via mounting portions 8, a replaceable upper gripping jig 11 fitted into the holding plate; The transparent cylinder 7 is inserted into the transparent cylindrical body 7 so as to have predetermined gaps a and b between the inner peripheral surface and the lower end of the transparent cylindrical body 7 via the cap 3c. The gripping jig 11 includes a bar-shaped test piece 2 which is gripped and fixed, and a load cell (load cell) 12 disposed between the upper gripping jig 11 of the rod-shaped test piece 2 and the holding plate 10.

Here, the transparent cylinder 7 is composed of three transparent outer cylinders 7a and two transparent inner cylinders 7b, and is formed by connecting the transparent outer cylinders 7a and the transparent inner cylinder 7b alternately. ing.
More specifically, a ball bearing 13 is mounted on the outer periphery of the end of the transparent inner cylinder 7b, and the transparent inner cylinder 7b slides vertically on the inner peripheral surface of the transparent outer cylinder 7a via the ball bearing 13. It is mounted so that it can rotate in the circumferential direction.

A pin hole (not shown) is provided on the inner peripheral surface at the end of the transparent outer cylinder 7a. The ball bearing 13 of the transparent inner cylinder 7b is inserted into the transparent outer cylinder 7a, and the pin 14 is inserted into the pin hole. As a result, the transparent cylinder 7b becomes transparent outer cylinder 7a.
From falling out. Of the transparent outer cylinder 7a,
The lower transparent outer cylinder 7a is attached to the base 4 with a bolt and nut 16 via a mounting portion 15 at the lower portion thereof.
The upper transparent outer cylinder 7a can slide up and down and can rotate in the circumferential direction via an annular support (ball bearing) 6 attached to a fixed arm 5a of a support 5 erected on the base 1. It is supported by.

Here, the lower gripping jig 3 fitted into the base 4 has a spherical (concave) seat 3a formed thereon, and the spherical seat has a hemisphere fixed to the lower end of the rod-shaped test piece 2. A gripping cap 3c is supported rotatably. Therefore, the direction of the lower end of the rod-shaped test piece 2 can be changed via the gripping cap 3c during the buckling test. Depending on the test object, the gripping cap 3c may have a structure in which the orientation of the lower end of the rod-shaped test piece 2 is fixed.
In that case, the gripping jig 3 is replaced with another gripping cap 3c. In the case of the upper gripping jig 11, the lower gripping jig 3
The same holding / fixing structure as in the case of may be adopted.

As described above, the rod-shaped test piece 2 is inserted into the transparent cylindrical body 7 so that appropriate gaps a and b are formed between the outer peripheral surface and the inner peripheral surface of the transparent cylindrical body 7. When the both ends of the rod-shaped test piece 2 are restrained by the holding plate 10 and the base 4 via the upper gripping jig 11 and the lower gripping jig 3 and buckled by pressing vertically, the transparent cylinder 7 When the allowable deformation state set in the above is exceeded, the outer peripheral surface of the buckling portion of the rod-shaped test piece 2 comes into contact with the inner peripheral surface of the transparent cylindrical body 7 and is restrained. At the upper end of the support 5, a mounting portion 17 for the buckling test device is formed. This support 5
May be formed in a transparent cylindrical shape.

Using the bar-shaped test piece mounting jig 1 according to the present invention configured as described above, the bar-shaped test piece 2 of the present invention can be mounted on a buckling test device to perform a buckling test.
FIG. 2 (a) shows the results of a buckling test of a rod-shaped test piece.
1 shows a state in which a rod-shaped test piece mounting jig 1 according to the present invention is mounted on a buckling test device. The jig 1 for mounting a bar-shaped test piece on which the bar-shaped test piece 2 is mounted has its base 4 placed on a test table 18 of a buckling test apparatus, and a mounting portion 1 at the upper end of a support 5.
7 is fixed by bolts and nuts 20 to a support portion 19 provided above and below a test table 18 of the buckling test device so as to be able to move up and down.

In this state, the upper surface of the holding plate 10 holding and fixing the upper holding jig 11 holding the tip of the rod-shaped test piece 2 via the load cell 12 is disposed on the support portion 16 of the buckling test device. The pressure transmitting device 22 is in contact with the load transmitting unit 22 of the pressurizing device 21. In this state, the holding plate 1 is
0, by applying an axial load W to the rod-shaped test piece 2 via the load cell 12 and the upper holding jig 11, FIG.
As shown in (b), a buckling test in which the rod-shaped test piece 2 is buckled in the transparent cylindrical body 7 in a constrained state can be performed. Can be evaluated. At this time, the transparent cylindrical body 7 expands and contracts together with the rod-shaped test piece 2, and its length is from L to L in FIG.
changes to x.

When a scale 23 in the circumferential direction is drawn on the peripheral surface of the transparent cylindrical body 7 as shown in FIG.
When the vertical scale 24 is drawn on the support 5 as shown in (b), the buckling behavior can be visually observed, and FIG.
As shown in (c), when, for example, a plurality of color-coded identification marks 25 are provided at equal intervals in the length direction of the bar-shaped test piece 2, the relative positions of the scales 23 and 24 and the identification marks 25 are determined. The deformation of the rod-shaped test piece 2 can be quantified by observation.

Further, as shown in FIG. 4, the position change of the identification mark 25 is determined by two video cameras 26 arranged outside the transparent cylinder 7 at intervals of, for example, 90 degrees in the circumferential direction of the rod-shaped test piece. The photographed images are continuously or intermittently photographed, the photographed images are subjected to image processing by the image processing device 27, the deformation history and the twist amount history of the rod-shaped test piece are automatically and quantitatively analyzed by the arithmetic unit 28, and the recorded / display device 29 is provided. It can also be recorded and displayed.

Note that the buckling test here is not performed on actual pipes actually used, but is performed on test pieces having different small shapes. The results of the buckling test are converted to those of actual pipes. However, this conversion method is established separately.For example, a buckling position, a deformed state, a buckling shape, etc. are detected by a sensor, and an arithmetic unit is used. By patterning the directional load and the buckling behavior, it becomes possible to precisely evaluate the buckling strength characteristics similar to those of an actual pipe.

In the buckling test, the rod-shaped test piece 2 was used.
The torsion amount can be measured, but the torsional force cannot be measured. Therefore, when the torsional force needs to be measured, for example, as shown in FIG. The lower gripping jig 3 to be fixed by rotation is rotatably supported on a base 4 via a bearing (not shown), and the gripping jig is provided with a torque meter (not shown) for measuring a torsional force on the rod-shaped test piece 2. By connecting the torsion force measuring device 30, the torsion force generated in the bar-shaped test piece 2 during the buckling test can be measured.

When there is a request to perform a buckling test in a state where a predetermined torsional force is applied to the rod-shaped test piece 2, for example, as shown in FIG. Is rotatably supported on a base 4 via a bearing (not shown), and a torsion force applying device 32 equipped with a speed reducer 31 and a torque meter (not shown) is connected to this gripping jig to obtain a rod-shaped test. A buckling test can be performed in a state where a predetermined twisting force is applied to the piece 2.

The present invention is not limited to the above example. For example, although the above example assumes a steel pipe for excavation, the present invention, in addition to a steel pipe for excavation, is used for construction of a structure.
The present invention is also applicable to a buckling test using a rod-shaped test piece assuming a metal rod-shaped body mainly used for constructing a structure subjected to an axial load.

Further, the shape of the rod-shaped test piece of the present invention, the structure of the jig for mounting the rod-shaped test piece (including vertical type and horizontal type), the shape of the transparent cylindrical body (outer cylinder, inner cylinder), and the buckling test apparatus The structure (including the vertical type and the horizontal type), the mounting structure of the rod-shaped test piece mounting jig to the buckling test device, and the like are changed within a range satisfying the scope of the claims.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a buckling test example of a rod-shaped body according to the present invention will be described. In this example, an SS40 rod-shaped test piece having a diameter of 3 mm and a length of 2000 mm was mounted on the rod-shaped test piece mounting jig 1 according to the present invention shown in FIG. In this case, the rod-shaped test piece is attached to a rod-shaped buckling test apparatus as shown in FIG.

Here, the transparent cylinder has an outer diameter of 8 mm and an inner diameter of 6 mm.
mm, a transparent inner cylinder of 300 mm in length, and two transparent outer cylinders of 20 mm in outer diameter, 10 mm in inner diameter, and 500 mm in length. The transparent outer cylinder and the transparent inner cylinder are connected so as to be wrapped within a range of 25 to 400 mm, and both ends of a rod-shaped test piece having a maximum length of 2000 mm are gripped and fixed by a fixed-type gripping jig, The rod-shaped test piece was sufficiently compressed.

As described above, in the buckling test apparatus of the present invention, the rod-shaped test piece is inserted with the gap a formed in the transparent cylinder, and both ends are held by the holding jig on the pressing device side and the holding jig on the base side. 50kgf with a pressure device while holding and fixing
An experiment was performed in which the rod-shaped test piece 2 was buckled by applying an axial load W of up to. The experimental results will be described below with reference to FIGS. 7 and 8 together with the case of the conventional example.

(1) As shown in FIG. 7, in the experimental example of the present invention, the buckling behavior was smoothly performed, and the axial load was 0.2 kgf.
At this time, the outer peripheral surface of the buckling portion of the rod-shaped test piece 2 started to contact the inner surface of the transparent inner cylinder. However, since the transparent cylindrical body can slide in the vertical direction and can rotate in the circumferential direction, the rod-shaped Since the contact friction between the test piece and the inner surface of the transparent cylinder is alleviated, the buckling behavior proceeds slowly and naturally until the load in the axial direction reaches 50 kgf. The bending behavior could be reproduced.

(2) On the other hand, in the case of a conventional buckling test in which the rod-shaped test piece 2 is inserted into an integral transparent pipe 7 'having a length enough to buckle the rod-shaped test piece. When the axial load is 0.2 kgf in the same manner as above, the outer peripheral surface of the buckling portion of the rod-shaped test piece starts to contact the inner surface of the transparent pipe 7 ′, and then, as shown in FIG. Pipe 7 '
Due to the contact friction with the inner surface, when the axial load exceeds 10 kgf, the deformation at the upper end begins to become prominent from the point where the rod-shaped test piece 2 comes into contact with the transparent pipe, and the axial load rapidly rises and fluctuates. As shown in FIG. 8B, good buckling behavior could hardly be reproduced. This rapid increase and fluctuation of the axial load is due to an increase in the frictional force with the transparent pipe 7 ', and this result gives an extra cause for use in the analysis, making accurate analysis impossible. I have.

(3) As shown in FIG. 5, in the experimental example of the present invention in which the torsional force was measured on the rod-shaped test piece 2 during the buckling test by the torsional force measuring device 30, the transparent cylindrical body and the rod-shaped specimen were used. Since the contact friction with the test piece was reduced, the effect of torsion could be analyzed separately from the axial load.

(4) Further, as shown in FIG. 6, in the experimental example of the present invention in which a buckling test was performed while applying a predetermined torsional force to the bar-shaped test piece by the torsional force applying device 32, the influence of torsion was observed. Was separated from the axial load, and analysis was also possible for some parameters (for example, changes in the diameter of the rod-shaped test piece and the distance a from the transparent cylinder).

(5) As shown in FIG. 4, two video cameras 26 are arranged in two directions 90 degrees apart from each other with respect to a bar-shaped test piece having identification marks 25 provided at equal intervals in the length direction. In the embodiment of the present invention described above, the deformation history can be automatically analyzed quantitatively by observing the position of the identification mark of the rod-shaped test piece 2 during the buckling test with the two video cameras.

[0045]

According to the present invention, the contact friction between the transparent cylindrical body and the rod-shaped test piece can be sufficiently reduced without giving an extra action to the rod-shaped test piece, and the buckling behavior by the buckling test is obtained. It is possible to accumulate a good database by collecting the data in detail. In addition, since the transparent cylinder is used, the buckling behavior can be visually observed or can be observed with a sensor or the like. Then, based on the various databases obtained in the buckling test, a buckling quantitative evaluation can be performed to derive a reliable buckling strength evaluation formula. Detailed drilling path design and determination of grades and dimensions of materials used enabled drilling with a lower safety factor and no digging problems due to buckling.

[Brief description of the drawings]

1A is a cross-sectional explanatory view showing a structural example of a rod-shaped test piece mounting jig according to the present invention, and FIG. 1B is a cross-sectional explanatory view taken along the line Aa-Ab in FIG.

FIG. 2A is a cross-sectional explanatory view showing a state in which the rod-shaped test piece mounting jig of FIG. 1 is mounted on a buckling test device (example);
FIG. 2B is an explanatory cross-sectional view showing a state in which the rod-shaped test piece is buckled by applying an axial load from the state of FIG.

3A is a three-dimensional explanatory view showing a transparent cylindrical body with a scale according to the present invention, FIG. 3B is a three-dimensional explanatory view showing a support with a scale according to the present invention, and FIG. , A three-dimensional explanatory view showing a rod-shaped test piece with an identification mark.

FIG. 4 is a conceptual plan view showing an example of an apparatus for quantitatively analyzing the deformation state of a rod-shaped test piece used in the rod-shaped test piece mounting jig of the present invention.

FIG. 5 is a partially cut-away side sectional view showing an example of a torsional force measuring device used in the rod-shaped test piece mounting jig of the present invention.

FIG. 6 is a partially cutaway side sectional explanatory view showing an example of a torsion force applying device used in the rod-shaped test piece mounting jig of the present invention.

FIG. 7 is a conceptual explanatory diagram showing a relationship between an axial load and a buckling amount on a rod-shaped test piece in an experimental example of the present invention and an experimental example according to a conventional example.

FIG. 8 is an explanatory side view conceptually showing a modified example of a rod-shaped test piece in an experimental example of the present invention and an experimental example according to a conventional example.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 rod-shaped test piece mounting jig 2 rod-shaped test piece 3 lower gripping jig 3a spherical seat 3c gripping cap 4 base 5 support 5a fixed arm 6 annular support 7 transparent cylinder 7a transparent outer cylinder 7b transparent inner cylinder 7 'transparent Pipe 8 Mounting part 9 Bolt / nut 10 Holding plate 11 Upper holding jig 11a Holding cap 12 Load cell 13 Ball bearing 14 Pin 15 Mounting part 16, 20 Bolt / nut 17 Mounting part 18 Test stand 19 Support part 21 Pressurizing device 22 Load Transmission unit 23, 24 Scale 25 Identification mark 26 Video camera 27 Image processing device 28 Computing unit 29 Recording / display device 30 Torsional force measuring device 31 Deceleration (transmission) device 32 Torsional force applying device

Claims (14)

(57) [Claims] 1. A transparent cylindrical body which is movably connected to a transparent outer cylinder and a transparent inner cylinder, is mounted on a base and has a rod-shaped test piece which can be extended and contracted, and a rod-shaped test piece is inserted into the transparent cylindrical body. Then, the outer peripheral surface of the rod-shaped test piece is made to be capable of being restrained by a transparent cylinder through a predetermined gap, and both ends of the rod-shaped test piece are restrained via a holding jig between the base side and the pressing device. A rod-shaped test piece is buckled in a transparent cylinder by applying an axial load via a load meter with a pressurizing device, and the buckling strength characteristic is evaluated from the deformation state and the load amount. Body buckling test method. 2. The buckling test of a rod-shaped test piece according to claim 1, wherein one end or both ends of the rod-shaped test piece is variably gripped and an axial load is applied with both ends constrained. Method. 3. The buckling test method for a rod-shaped body according to claim 1, wherein, when an axial load is applied, the transparent cylinder is rotated to reduce static friction. 4. A rod-shaped test piece is fixed at both ends to a rotatable gripping jig, and a predetermined torsional force is applied to the rod-shaped test piece via the gripping jig by a torsion force applying device during the buckling test. The buckling test method for a rod-shaped body according to any one of claims 1 to 3, characterized in that: 5. A method in which both ends of a rod-shaped test piece are fixed to a rotatable gripping jig, and a torsion force generated in the rod-shaped test piece during a buckling test is measured by a torsion force measuring device via the gripping jig. The buckling test method for a rod-shaped body according to any one of claims 1 to 3, characterized in that: 6. At least two video cameras are arranged at equal intervals on the outside of the transparent cylinder to continuously or intermittently position the identification mark on the rod-shaped test piece in the transparent cylinder during the buckling test. The photographed image is image-processed, and the deformation history and the torsion amount history of the rod-shaped test piece are automatically quantitatively analyzed by performing image processing on the photographed image. The method according to any one of claims 1 to 5, wherein Buckling test method for rods. 7. A transparent cylindrical body, which is formed by movably connecting a transparent outer cylinder and a transparent inner cylinder, and is capable of extending and contracting with a rod-shaped test piece, a base supporting the transparent cylindrical body, and a transparent base. A support provided so as to surround the cylindrical body, an annular support provided on the support and slidably supporting the outer peripheral surface of at least the intermediate portion of the transparent outer cylinder in the axial and circumferential directions, and a base. Jig provided on the side and the pressurizing device side, comprising a gripping jig for gripping and fixing an end of the rod-shaped test piece, and a load meter for measuring an axial load on the rod-shaped test piece. Mounting jig. 8. The rod-shaped specimen according to claim 7, wherein the gripping jig for gripping / fixing the tip of the rod-shaped test piece has a gripping / fixing structure capable of changing the direction of the tip of the rod-shaped test piece. Test piece mounting jig. 9. A transparent outer cylinder disposed at an intermediate portion is freely movable in the longitudinal direction of the rod-shaped test piece, but is supported by the annular support portion so as not to move freely except in the longitudinal direction of the rod-shaped test piece. 9. The method according to claim 7, wherein
The rod-shaped test piece mounting jig according to the description. 10. The thickness of the transparent inner cylinder of the transparent cylinder is
The rod-shaped test piece mounting jig according to any one of claims 7 to 9, wherein the jig is formed to be thinner than the thickness of the transparent outer cylinder. 11. A scale or an identification mark for observing a deformation state of the rod-shaped test piece is drawn on the peripheral surface of the transparent cylinder, the support, and the rod-shaped test piece.
The rod-shaped test piece mounting jig according to any one of claims 10 to 10. 12. A rotatable supporting jig for fixing both ends of a bar-shaped test piece, a torque meter for measuring a torsional force on the bar-shaped test piece, and a deceleration (speed change) on the holding jig.
The rod-shaped test piece mounting jig according to any one of claims 7 to 11, wherein a torsional force measuring device provided with a vessel is connected. 13. A gripping jig for fixing both ends of a rod-shaped test piece is rotatably supported, and a torsional force applying device equipped with a speed reducer and a torque meter is connected to the gripping jig. The rod-shaped test piece mounting jig according to any one of claims 7 to 12. 14. At least two or more videos which are arranged at equal intervals in the circumferential direction outside the transparent cylindrical body and continuously or intermittently photograph the positions of the identification marks attached to the rod-shaped test pieces in the transparent cylindrical body. A camera, an image processing device for processing a captured image from the video camera, an arithmetic unit for calculating a deformation history and a twist amount of the rod-shaped test piece based on a signal from the image processing device, and a rod-shaped test based on a signal from the arithmetic unit. The rod-shaped test piece mounting jig according to any one of claims 7 to 13, further comprising a record display device that records and displays the deformation history of the piece.