KR20160141261A

KR20160141261A - Test method for direct tensile strength measurement utilizing hollow hole and testing device for tensile strength using thereof

Info

Publication number: KR20160141261A
Application number: KR1020150076303A
Authority: KR
Inventors: 손무락
Original assignee: 대구대학교 산학협력단
Priority date: 2015-05-29
Filing date: 2015-05-29
Publication date: 2016-12-08
Also published as: KR101748809B1

Abstract

The present invention is intended to more conveniently and accurately measure the tensile strength of various materials constituting the ground or facilities, and it is an object of the present invention to solve the difficulties and troubles of the conventional method of producing and testing specimens of a direct tensile strength test, , The test procedure is more convenient and the test result can be measured more accurately and the safe use of the test result in the practical use of the test result will lead to the safe design and construction of the ground or facilities. It is a useful invention that has a special advantage that can pursue economy through it.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of measuring tensile strength by using a hollow hole, and a method of testing tensile strength using the hollow hole.

The present invention relates to a test method for measuring a direct tensile strength using a hollow hole and an apparatus for testing a tensile strength using the same. More particularly, the present invention relates to a method for testing a tensile strength test apparatus using a cement, The present invention relates to a direct tensile strength measurement test method and a tensile strength test apparatus using the hollow hole,

Construction work for installing various facilities (buildings, railways, roads, port facilities, breakwater, etc.) on or under the ground is being carried out in various places in and around the country. In order for these various facilities to be safely installed, the ground and the materials constituting the facilities supporting the facilities must have sufficient strength to withstand various loads such as the weight of the facility and any additional added load and wind loads. Otherwise, the ground or facilities may be destroyed or excessive deformation may occur, causing various damages such as cracks in the facilities.

Therefore, the strength of the materials constituting the ground and the facilities must be checked to ensure that they have sufficient strength as they are directly related to the safety of the facilities.

The strength of the materials constituting these grounds and facilities is investigated through the compressive strength test, the tensile strength test, and the shear strength test.

The tensile strength test applied to the conventional method is largely a direct tensile strength test and an indirect tensile strength test, which are a folding tensile strength test and a bending tensile strength test.

First, the existing direct tensile strength test is carried out by preparing a test specimen in a mold and then releasing the mold, installing a jig for tensile test on the demolded specimen, applying epoxy to both ends of the specimen and attaching a device for tensile test There are ways to do the test.

Such test methods require a lot of effort and time, such as making test specimens separately, attaching devices for testing, and then performing tests, and the test procedure is difficult and troublesome. In order to compensate for these problems, the recycled tensile test method in which the test specimen is demolded from the mold, the specimen is laid down, the compressive force is applied, and the flexural tensile test method in which the specimen is formed into the beam shape and the load is applied are frequently used as the indirect tensile strength test method . These test methods indirectly estimate the tensile strength of specimens using empirical equations of applied compressive load and tensile strength. However, the tensile strength through these methods is significantly different from the tensile strength of the actual specimen, and there are various problems in using the test results directly.

On the other hand, as a conventional device for measuring the tensile strength, Patent No. 1074976 entitled " Compression and Tensile Strength Measuring Apparatus "is disclosed in Patent Document 1 (see Patent Document 1).

The "compression and tensile strength measuring apparatus 100" of the above-mentioned Japanese Patent No. 1074976 includes an upper frame 30 for processing a loading point as shown in FIG. 1; An actuator (20) mounted on a loading point of the upper frame (30); A load cell (60) having one end mounted on the lower end of the actuator (20) and the other end passing through the upper frame (30); A first specimen holder 70 mounted at the lower end of the load cell 60; A second specimen holder 71 positioned in a direction opposite to the first specimen holder 70; A lower frame (40) having at least one screw-coupled and height-adjustable pedestal (90) on which the second specimen holder (71) is mounted; A support bar 50 penetratingly fixed to the lower frame 40 and the upper frame 30; And a plurality of spacer blocks 80 stacked on the support bar 50. The lower end of the support bar 50 is fixed to the lower frame 40, And the upper part is screwed with the upper frame 30 after the space block 80 is stacked. The space block 80 has a semi-cylindrical block fastened to the support bar 50 A cylindrical body coupled by a sphere; And first and second coupling protrusions protruding from both ends of the body portion.

However, such a compression and tensile strength measuring apparatus 100 has a problem in that tensile strength can be measured only with a specimen prepared so as to be easily pulled.

Patent Document 1: Japanese Patent Publication No. 1074976

The present invention has been made to solve the various problems caused by the conventional tensile strength test as described above, and it is an object of the present invention to provide a method and apparatus for solving the difficulties and troubles of the process of manufacturing and testing a specimen, And a tensile strength test apparatus using the same.

Another object of the present invention is to provide a direct tensile strength measurement test method using a hollow hole capable of solving the inaccuracy of direct utilization of test results, which is a problem of the conventional indirect tensile strength test, and a tensile strength test apparatus using the same.

In other words, it is an object of the present invention to provide a method of measuring tensile strength of a material constituting a ground or a facility by taking advantage of the advantages obtained by eliminating the drawbacks caused by the conventional direct and indirect tensile strength tests, A tensile strength measurement test method and a tensile strength test apparatus using the same.

In order to achieve the above object, there is provided an apparatus for measuring a direct tensile strength using a hollow hole according to the present invention, comprising: a material specimen (S) having a hollow hollow (H) A separable cylindrical body (1) inserted into the hollow hole (H); The end portions of the external load transmitting piston rods 3 operated by the hydraulic or air pressure generating device 2 are placed in the spherical grooves 1a formed at both central portions of the cylindrical body 1 to measure the tensile strength of the specimens .

In order to achieve the above object, the apparatus for directly measuring tensile strength using hollow holes according to the present invention is characterized in that a cylindrical hollow hole (H) is formed at the center of a material specimen (S) The external load acting device is provided with a tube 1 'made of a flexible material which can be inflated by hydraulic pressure or air pressure, a hydraulic or air pressure generating pump 2' for generating a hydraulic pressure or an air pressure in the tube 1 ' ), And a hose (3 ') for injecting hydraulic or air pressure into the tube (1').

In order to accomplish the above object, there is provided a method of directly measuring a tensile strength using a hollow hole according to the present invention, comprising: preparing a material specimen having a cylindrical hollow hole at the center thereof; (S2) of installing an external load acting device on the hollow hole (H) and a tensile strength measuring step (S3) of measuring the tensile strength of the material specimen by operating the external load acting device .

The present invention can solve the difficulties and troubles of the process of manufacturing and testing a specimen, which is a problem of the conventional direct tensile strength test, and has a special advantage that can solve the inaccuracies of the direct utilization of the test result, which is a problem of the conventional indirect tensile strength test .

1 is a perspective view of a conventional compression and tensile strength measuring apparatus,
FIG. 2 is a view showing a direct tensile strength measurement test apparatus according to a first embodiment of the present invention,
FIG. 3 is a sectional view showing the use state of a direct tensile strength measuring apparatus according to a first embodiment of the present invention,
4 is a use state plan view of a direct tensile strength measurement apparatus according to the first embodiment of the present invention,
5 is a diagram showing a direct tensile strength measurement test apparatus according to a second embodiment of the present invention,
FIG. 6 is a sectional view showing the use state of a direct tensile strength measuring apparatus according to a second embodiment of the present invention,
FIG. 7 is a plan view showing the use state of a direct tensile strength measurement apparatus according to a second embodiment of the present invention.

Hereinafter, a direct tensile strength measurement test method using the hollow hole of the present invention and a tensile strength test apparatus using the same will be described in detail with reference to the accompanying drawings.

FIG. 2 is a view showing a direct tensile strength testing apparatus according to a first embodiment of the present invention, FIG. 3 is a sectional view of the apparatus for testing a direct tensile strength according to the first embodiment of the present invention, FIG. 5 is a diagram showing a direct tensile strength measurement test apparatus according to a second embodiment of the present invention, FIG. 6 is a view showing a second embodiment of the present invention And FIG. 7 is a plan view illustrating a direct tensile strength measurement apparatus according to a second embodiment of the present invention. In FIG. 7, The tensile strength measurement tester includes a material specimen S having a hollow hollow H at the center thereof; A separable cylindrical body (1) inserted into the hollow hole (H); The end portions of the external load transmitting piston rods 3 operated by the hydraulic or air pressure generating device 2 are placed in the spherical grooves 1a formed at both central portions of the cylindrical body 1 to measure the tensile strength of the specimens .

An external load acting on both central portions of the cylindrical body 1 uses an oil pressure or an air pressure and a load generated by an oil pressure or an air pressure is generated by an oil pressure or air pressure generating device 2, An air pressure cylinder 3a, and a piston rod 3.

Inductive grooves may be formed on both sides of the center of the cylindrical body 1 and above and below the spherical grooves 1a. The piston rod 3 may be bi-directionally driven by hydraulic or air pressure, .

The piston rod 3 is positioned in a spherical groove 1a formed in a central portion of the cylindrical body 1 so that the spherical shape of the piston rod 3 can act as a hinge so as not to cause eccentricity during a load transfer process have.

The piston rod 3 is integrally formed in the inner spherical groove 1a of the cylindrical body 1 or can be positioned along the induction groove formed in the cylindrical body 1. [

A flexible rubber 1b is attached to the outside of the cylindrical body 1 in order to make the contact with the surface of the material specimen S uniform during a load operation.

The apparatus for testing a direct tensile strength using the hollow hole of the present invention according to the second embodiment is characterized in that a cylindrical hollow hole H is formed at the center of the material specimen S and an external load acting device The external load acting device is provided with a tube 1 'made of a flexible material that can be inflated by hydraulic pressure or air pressure, a hydraulic or pneumatic generating pump 2' for injecting hydraulic pressure or air pressure into the tube 1 ' , And a hose 3 'for injecting hydraulic or pneumatic pressure into the tube. At this time, a measuring device (not shown) for measuring the magnitude of the hydraulic pressure or the air pressure injected into the tube 1' So that the size of the hydraulic pressure or air pressure injected into the tube can be known.

Here, the external load acting on the hollow hole H is formed by inserting the tube 1 'made of a flexible material capable of expanding by the hydraulic pressure or the air pressure into the hollow hole H, and the hydraulic or air pressure generating pump 2' Is injected into the tube 1 'through a hose 3' for injecting hydraulic pressure or air pressure generated in the tube 1 '.

Meanwhile, the method for measuring the direct tensile strength using the hollow hole of the present invention according to the first embodiment includes a material specimen preparing step (S1 step) of preparing a material specimen having a cylindrical hollow hole (H) at the center thereof; (S2) of installing an external load acting device on the hollow hole (H) and a tensile strength measuring step (S3) of measuring the tensile strength of the material specimen by operating the external load acting device Lt; / RTI >

The material specimen prepared in the material preparation specimen step (S1 step) can be any shape such as a cylindrical shape, a cubic shape, a rectangular parallelepiped shape, and a spherical shape. In the tensile strength measurement step (S3 step) A cylindrical body 1 whose external load is detachable in the hollow hole H is provided and a spherical groove 1a is formed at both central portions of the cylindrical body 1 to act on the spherical groove 1a.

In the tensile strength measuring step (S3), an external load acting device for providing an external load acting as a hydraulic or pneumatic pressure to the central portion of the cylindrical body 1 may be a hydraulic or air pressure generating device 2, And an induction groove is formed above and below the spherical groove 1a on both sides of the inner center of the cylindrical body 1 .

The piston rod 3 is formed in a spherical groove 1a formed in the center of the inner periphery of the cylindrical body 1, So that the shape of the spherical shape during the load transfer can serve as a hinge so as not to cause eccentricity in the load transfer process.

A flexible rubber is attached to the outside of the cylindrical body 1 in order to make the contact with the surface of the material specimen S uniform during load application.

The method for directly measuring a tensile strength using the hollow hole of the present invention according to the second embodiment includes: preparing a material specimen having a cylindrical hollow hole (H) at the center thereof (S1 step); (S2) of installing an external load acting device on the hollow hole (H) and a tensile strength measuring step (S3) of measuring the tensile strength of the material specimen by operating the external load acting device Lt; / RTI >

The material specimen prepared in the material preparation specimen step (S1 step) can be any shape such as a cylindrical shape, a cubic shape, a rectangular parallelepiped shape, and a spherical shape. In the tensile strength measurement step (S3 step) An external load exerts a tube 1 'on the hollow hole H and acts within the tube 1'.

In addition, in the tensile strength measuring step (S3), the external load acting device for providing an external load acting as a hydraulic pressure or an air pressure in the tube 1 'is a tube 1' made of a flexible material capable of expanding by hydraulic pressure or air pressure A hydraulic or air pressure generating pump 2 'for generating an oil pressure or an air pressure in the tube 1', and a hose 3 'for injecting hydraulic or air pressure into the tube 1'.

Example One

The tensile strength of the material specimen (S) was measured using the direct tensile strength measuring apparatus according to the first embodiment of the present invention.

First, as shown in FIG. 2 and FIG. 3, a material specimen S having a hollow hole H is prepared, and a cylindrical body (not shown) having a hydraulic or pneumatic cylinder 3a of the external load acting device and a piston rod 3 (1) was inserted into the hollow hole (H).

Then, the tensile strength of the material specimen S was measured by operating the external load acting device. That is, when the external load acting device is operated, the hydraulic pressure or the air pressure generated in the hydraulic or air pressure generating device 2 is supplied to the hydraulic or pneumatic cylinder 3a through the hydraulic or air pressure transmitting means 2a, The separable cylindrical body 1 is pushed outward while being pulled out in both directions shown by the arrows in Fig. 4 from the hydraulic or pneumatic cylinder 3a.

The action force transmitted to the center of the cylindrical body 1 is transmitted to the cylinder 3a when the material specimen S is destroyed without further resisting the force transmitted from the cylindrical body 1 while gradually increasing the hydraulic pressure and the air pressure The direct tensile strength of the material specimen S is calculated in consideration of the applied force and the contact area between the cylindrical body 1 and the material specimen S [ Sectional area of the specimen center perpendicular to the direction of the force except for the force / hollow hole).

Example 2

The tensile strength of the material specimen (S) was measured by using a direct tensile strength measuring apparatus according to the second embodiment of the present invention.

First, as shown in FIGS. 5 and 6, a material specimen S having a hollow hole H is prepared, and the hydraulic or air pressure generating pump 2 ', hydraulic pressure or air pressure of the external load acting device is injected into the tube A tube 1 'made of a flexible material capable of expanding by hydraulic pressure or air pressure having a hose 3' is inserted into the hollow hole H.

At this time, the hydraulic or air pressure generating pump 2 'is provided with a measuring device capable of measuring the magnitude of the hydraulic pressure or the air pressure injected into the tube 1', so that the size of the hydraulic pressure or the air pressure injected into the tube 1 ' .

Then, the tensile strength of the material specimen S was measured by operating the external load acting device. That is, when the external load acting device is operated, the hydraulic pressure or the air pressure generated in the hydraulic or air pressure generating pump 2 'is injected into the tube 1' through the hose 3 'so that the tube 1' (S) in the radial direction shown by the arrow in Fig.

The tensile stress generated at an arbitrary point of the material specimen S when the material specimen S is broken without further resisting the expansion pressure of the tube 1 'can be expressed by the following equations (1) and As calculated by the co-expansion theory.

here,

: Tensile stress on specimen

a: Radius of hollow hole

p: Hydraulic or pneumatic pressure generated in the tube

b: Distance from the center of the hollow hole to the outermost part of the specimen

and r is the distance from the center of the hollow hole to the arbitrary point of the specimen.

When r is equal to a in the above equation, the above equation is further simplified as shown in the following equation (2).

The calculated tensile stress is used as the tensile strength of the specimen S to be measured. If the center of the hollow hole H of the material specimen S is located eccentrically in the center of the specimen S, then the tensile strength at this time is calculated by the following equation (3).

From the above Examples 1 and 2, it was confirmed that the tensile strength of various materials can be more conveniently and accurately measured by using the test method for measuring tensile strength by using the hollow hole of the present invention and the tensile strength testing apparatus using the same.

While the present invention has been described with reference to the preferred embodiments, it is to be understood that the present invention is not limited thereto and various changes and modifications may be made without departing from the scope of the invention.

1: Cylindrical body 1 ': tube
1a: spherical groove 1b: flexible rubber
2: Hydraulic or air pressure generating device 2 ': Hydraulic or air pressure generating pump
2a: Hydraulic or pneumatic transmission means 3: Piston rod
3 ': Hose 3a: Hydraulic or pneumatic cylinder
S: material specimen H: hollow hole

Claims

A material specimen preparation step (S1 step) of preparing a material specimen having a cylindrical hollow hole (H) at the center thereof; (S2) of installing an external load acting device on the hollow hole (H) and a tensile strength measuring step (S3) of measuring the tensile strength of the material specimen by operating the external load acting device Wherein the tensile strength is measured by a tensile test.

The method according to claim 1, wherein the material specimen prepared in the material preparation specimen step (S1) is a cylindrical shape, a cube shape, a rectangular shape, or a spherical shape.

The method according to claim 2, wherein the cylindrical body (1) is provided with an external load acting on the hollow hole (H) in the hollow hole (H) in the tensile strength measurement step (S3) Wherein the spherical grooves (1a) are formed in both central portions of the spherical grooves (1a, 1b) and act on the spherical grooves (1a).

4. The apparatus according to claim 3, wherein in the tensile strength measuring step (S3), an external load acting device for providing an external load acting as a hydraulic or pneumatic pressure to the central portion of the cylindrical body (1) Or air pressure transmitting means (2a), a hydraulic or pneumatic cylinder (3a), and a piston rod (3).

5. The method according to claim 4, wherein induction grooves are formed on both sides of the spherical groove (1a) on both sides of the inner center of the cylindrical body (1).

The method of claim 4, wherein the piston rod (3) can be propelled in both directions by hydraulic pressure or air pressure, and both ends are formed in a spherical shape.

The piston rod (3) according to claim 6, wherein the piston rod (3) is placed in a spherical groove (1a) formed in a central portion of the cylindrical body (1) and serves as a hinge so that the spherical shape does not cause eccentricity during the load transfer process Wherein the tensile strength is measured by a tensile test.

The piston rod according to claim 7, wherein the piston rod (3) is integrally formed in the inner spherical groove (1a) of the cylindrical body (1) or is arranged so as to be positioned along the induction groove formed in the cylindrical body Wherein the tensile strength is measured by a tensile test.

9. The method according to claim 8, characterized in that a flexible rubber (1b) is attached to the outside of the cylindrical body (1) to equalize the contact with the surface of the material specimen (S) Tensile strength measurement test method.

2. The apparatus according to claim 1, wherein the external load acting device provided in the hollow hole (H) comprises a tube (1 ') made of a flexible material capable of expanding by hydraulic pressure or air pressure, , And a hose (3 ') for injecting the hydraulic or pneumatic pressure generating pump (2'), the hydraulic pressure or the air pressure into the tube (1 ').

The apparatus as claimed in claim 10, wherein the hydraulic or pneumatic pressure generating pump (2 ') is provided with a measuring device capable of measuring the magnitude of hydraulic pressure or air pressure injected into the tube (1'), Wherein the hollow hole is formed so as to be able to know the size of the air pressure.

11. The method according to claim 10, wherein a tube (1 ') made of a flexible material capable of expanding by an oil pressure or an air pressure is inserted into the hollow hole (H) Is a load acting by being injected into the tube (1 ') through a hose (3') injecting hydraulic pressure or air pressure generated in the tube (2 ').

A material specimen S having a cylindrical hollow hole H formed at the center thereof; A separable cylindrical body (1) inserted into the hollow hole (H); The end portions of the external load transmitting piston rods 3 operated by the hydraulic or air pressure generating device 2 are placed in the spherical grooves 1a formed at both central portions of the cylindrical body 1 to measure the tensile strength of the specimens And the tensile strength of the hollow hole is measured.

The apparatus according to claim 13, wherein the external load acting on both central portions of the cylindrical body (1) uses hydraulic pressure or air pressure, and the external load operating device for providing hydraulic pressure or air pressure is a hydraulic or air pressure generating device (2) And a piston rod (3). The apparatus for measuring tensile strength of a direct tensile strength using a hollow hole according to claim 1,

15. The apparatus for measuring tensile strength of a direct tensile strength using a hollow hole according to claim 14, characterized in that induction grooves are formed on both sides of the center of the cylindrical body (1).

15. The apparatus of claim 14, wherein the piston rod (3) can be propelled in both directions by hydraulic pressure or air pressure, and both ends are spherically formed.

The piston rod (3) according to claim 16, wherein the piston rod (3) is placed in a spherical groove (1a) formed in the center of the cylindrical body (1) and serves as a hinge so that the spherical shape does not cause eccentricity during load transfer And the tensile strength of the hollow hole is measured.

The piston rod according to claim 17, wherein the piston rod (3) is integrally formed in the inner spherical groove (1a) of the cylindrical body (1) or is arranged so as to be positioned along the induction groove formed in the cylindrical body And the tensile strength of the hollow hole is measured.

19. The method according to claim 18, wherein the outer surface of the cylindrical body (1) is provided with a flexible rubber for uniform contact with the surface of the material specimen (S) Test equipment.

A cylindrical hollow hole H is formed at the center of the material specimen S and an external load acting device is provided in the hollow hole H. The external load acting device is made of a flexible material capable of expanding by hydraulic pressure or air pressure A hydraulic or pneumatic pressure generating pump 2 'for generating hydraulic pressure or air pressure in the tube 1', and a hose 3 'for injecting hydraulic pressure or air pressure into the tube 1' Wherein the tensile strength is measured by a tensile test.

The apparatus according to claim 20, wherein a measuring device capable of measuring the magnitude of the hydraulic pressure or the air pressure injected into the tube (1 ') is provided in the hydraulic or pneumatic pressure generating pump (2') so that the magnitude of the hydraulic pressure or the air pressure injected into the tube And the tensile strength of the hollow hole is measured.

21. The method according to claim 20, characterized in that the tube (1 ') made of a flexible material capable of expanding by external pressure acting on the hollow hole (H) is inserted into the hollow hole (H) Is a load acting by being injected into the tube (1 ') through a hose (3') injecting hydraulic pressure or air pressure generated in the tube (2 ').