LU504724B1 - Device and method for testing static and dynamic direct tensile strength of annular core - Google Patents

Device and method for testing static and dynamic direct tensile strength of annular core Download PDF

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Publication number
LU504724B1
LU504724B1 LU504724A LU504724A LU504724B1 LU 504724 B1 LU504724 B1 LU 504724B1 LU 504724 A LU504724 A LU 504724A LU 504724 A LU504724 A LU 504724A LU 504724 B1 LU504724 B1 LU 504724B1
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Luxembourg
Prior art keywords
loading
block
annular core
tensile strength
press
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LU504724A
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German (de)
Inventor
Tianzuo Wang
Mingcheng Cai
Ruiwen Jiang
Fei Xue
Mingfeng Zhang
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Univ Shaoxing
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Publication of LU504724B1 publication Critical patent/LU504724B1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/02—Details
    • G01N3/04—Chucks
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/32—Investigating strength properties of solid materials by application of mechanical stress by applying repeated or pulsating forces
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0001—Type of application of the stress
    • G01N2203/0003—Steady
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0001—Type of application of the stress
    • G01N2203/0005—Repeated or cyclic
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0014—Type of force applied
    • G01N2203/0016—Tensile or compressive
    • G01N2203/0017—Tensile
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0014—Type of force applied
    • G01N2203/0026—Combination of several types of applied forces
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/003—Generation of the force
    • G01N2203/0032—Generation of the force using mechanical means
    • G01N2203/0037—Generation of the force using mechanical means involving a rotating movement, e.g. gearing, cam, eccentric, or centrifuge effects
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0058—Kind of property studied
    • G01N2203/006—Crack, flaws, fracture or rupture
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0058—Kind of property studied
    • G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
    • G01N2203/0073—Fatigue
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0058—Kind of property studied
    • G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
    • G01N2203/0075—Strain-stress relations or elastic constants
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/02—Details not specific for a particular testing method
    • G01N2203/04—Chucks, fixtures, jaws, holders or anvils
    • G01N2203/0435—Chucks, fixtures, jaws, holders or anvils modifying the type of the force applied, e.g. the chuck transforms a compressive machine for applying a bending test

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  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)

Abstract

The invention relates to a device and a method for testing static and dynamic direct tensile strength of annular core. The device comprises: two fixed bearing platforms with fixed guide rails are fixedly connected to the left part and the right part of the upper end of a bottom support seat at intervals. The press-pull transfer mechanism consists of a sliding bearing platform, a transfer block and a loading unit. The lower end of the sliding bearing platform is provided with a chute. The inner end of that transfer block is provided with a guide inclined plane. The loading unit consists of a strip-shaped connecting block and a semicircular loading head. The left and right sides of the lower end of the wedge-shaped loading block are provided with loading inclined planes, the lower end of the wedge-shaped loading block is arranged between the upper ends of the two transfer blocks.

Description

DESCRIPTION LU504724
DEVICE AND METHOD FOR TESTING STATIC AND DYNAMIC DIRECT
TENSILE STRENGTH OF ANNULAR CORE
TECHNICAL FIELD
The invention relates to the technical field of rock mechanics, in particular to a device and a method for testing static and dynamic direct tensile strength of annular core.
BACKGROUND
Determination of rock strength under various loading conditions (compression, tension and shear) is one of the main problems in rock mechanics. Because the tensile strength of rock materials is very low compared with the compressive strength, most rocks and even rock-like materials are often more vulnerable to tensile failure. Therefore, the tensile strength of rock is an important parameter in rock mass engineering stability evaluation, tunnel boring machine design and hydraulic fracturing construction. The evaluation of rock tensile strength needs a suitable sample and test procedure. At present, the existing tensile strength testing methods can be divided into indirect testing method and direct testing method.
Indirect testing methods mainly include Brazilian splitting method, ring compression splitting method, three-point bending method and four-point bending method, and the test rock samples used generally need to be processed into disc, ring and strip. Brazilian splitting method is a method recommended by the International Society of Rock
Mechanics, and it is the most widely used tensile strength testing method at present.
During the testing process, the processed disc-shaped specimen is placed between two strip or arc loading plates, and then a load is applied to make the specimen split along the center, so as to obtain its tensile strength.
In the three-point or four-point bending tensile test, the strip-shaped specimen with/504724 rectangular cross section is placed on the bending device, and the span is adjusted and loaded, so that the specimen is stretched and broken at the lower edge of the beam. No matter which kind of indirect tensile strength test is adopted, the tensile strength of rock is obtained indirectly through the splitting fracture load obtained from the test. Due to the tensile stress in some areas of the sample caused by compressive load, the sample generally splits along the area with the largest induced tensile stress rather than along the part with the smallest bearing capacity, so the obtained tensile strength value has certain deviation from the actual tensile strength.
Different from the above-mentioned indirect testing methods, direct tensile testing is a direct method to measure the tensile strength of rocks. During the tensile process, the tested sample is under the action of pure tensile stress, which can ensure the specimen to break along the weakest bearing capacity, so that the tensile strength of rocks can be truly reflected during the testing process, and the measurement results obtained are more accurate than those obtained by indirect testing methods. The commonly used direct testing methods mainly include bonding method and clamping method. It is necessary to make the rock into cylindrical or dumbbell-shaped samples first. When testing, the two ends of the sample are fixed with the fixture by bonding or clamping, and then the corresponding tensile strength is determined by stretching the fixture to rupture the sample. However, there are some difficulties in the actual test, such as debonding at the bonding site or clamping failure at the clamping site due to stress concentration. At the same time, it is necessary to eliminate the influence of eccentric loading during the test, which greatly limits the practical application and popularization of the direct test method.
To sum up, there is an urgent need for a direct tensile testing device with simple structure and convenient operation, which can be applied to the conventional rock mechanics testing machine, so as to obtain the tensile strength parameters of rocks more accurately by direct tensile method.
SUMMARY LU504724
Aiming at the problems existing in the prior art, the invention provides a device and a method for testing static and dynamic direct tensile strength of annular core. The device is reasonable in structure and convenient to operate, and can obtain the tensile strength parameters of rocks more accurately through direct stretching, truly reflect the tensile strength of rocks and effectively improve the accuracy of measurement results.
This method is simple in steps and operation, and can effectively directly test the tensile strength of rock samples in the horizontal direction, and can obtain the tensile strength parameters of rocks more accurately.
In order to achieve the above purpose, the invention provides a device for testing static and dynamic direct tensile strength of annular core, which comprises a bottom support seat, a fixed bearing platform, a press-pull transfer mechanism and a wedge-shaped loading block; the fixed bearing platform is horizontally arranged, and the upper end of the fixed bearing platform is fixedly connected with a fixed guide rail extending in the left-right direction; two fixed bearing platforms are fixedly connected to the left part and the right part of the upper end of the bottom support seat at left and right intervals; the number of the press-pull transfer mechanisms is two, and the press-pull transfer mechanisms are composed of a sliding bearing platform, a transfer block and a loading unit; the sliding bearing platform is horizontally arranged, and the lower end of the sliding bearing platform is provided with a chute extending in the left-right direction; the transfer block is fixedly connected to the upper part of the inner end of the sliding bearing platform, and the inner end of the transfer block is provided with a guide inclined plane which is higher outside and lower inside; the loading unit consists of a strip-shaped connecting block and a semicircular loading head; the front end of the strip-shaped connecting block is fixedly connected to the rear end face of the inner end of the transfer block; the inner end of the loading head is fixedly connected with the rear end of the strip-shaped connecting block; two press-pull transfer mechanisms are arranged above the two fixed bearing platforms in a left-right direction, and the sliding bearing platform is slidably sleeved on the fixed guide rail through the chute, so as to realize the sliding HU504724 between the press-pull transfer mechanism and the fixed bearing platform in the left-right direction; when the two press-pull transfer mechanisms slide into contact, the two loading heads form a circular loading ring. the upper end of the wedge-shaped loading block has a planar structure, and two loading inclined planes with an outer high and an inner low are symmetrically arranged on the left and right sides of the lower end; the lower end of the wedge-shaped loading block is arranged between the upper ends of the two transfer blocks, and the loading inclined surfaces on both sides are in sliding fit with the guide inclined planes of the two transfer blocks respectively.
As a preference, the bottom support seat is composed of a supporting bottom plate, two supporting top plates and two vertical brackets, wherein the two supporting top plates are oppositely arranged at the left and right parts above the supporting bottom plate; two vertical brackets are correspondingly arranged below the two supporting top plates, and the upper ends of the vertical brackets are fixedly connected with the lower end faces of the supporting top plates, and the lower ends of the vertical brackets are fixedly connected with the upper end faces of the supporting bottom plate; the middle part of the upper end of the supporting bottom plate is fixedly connected with a limiting block between two vertical brackets, and the height of the limiting block is lower than that of the vertical brackets.
Further, in order to facilitate assembly and separation, the supporting bottom plate is provided with a bolt hole | at the periphery, which is matched with the platform of the pressure testing machine; the supporting top plate is provided with a plurality of bolt holes Il; the fixed bearing platform is provided with a plurality of bolt holes Ill, and is fixedly connected with the bottom support seat through connecting bolts | which penetrate the bolt holes Ill and bolt holes Il.
Further, in order to facilitate assembly and separation, the sliding bearing platform is provided with a plurality of bolts IV; the transfer block is provided with a plurality of bolt holes V, and is fixedly connected with the sliding bearing platform through a connecting bolt Il penetrating the bolt holes IV and the bolt holes V.
Further, in order to ensure the stability and reliability of the sliding fit between tHdJ504724 press-pull transfer mechanism and the fixed bearing platform, the sections of the fixed guide rail and the chute are both dovetail-shaped.
Further, in order to ensure reliable connection strength, the rear end of the strip-shaped connecting block extends to the rear end of the inner cambered surface of the loading head, and the rear end of the strip-shaped connecting block is fixedly connected to the middle of the inner cambered surface of the loading head.
As a preference, the strip-shaped connecting block and the loading head have an integrated structure.
Further, in order to apply the vertical load gently during the test, the inclination angles of the guide inclined plane and the loading inclined plane are consistent.
In the invention, through the arrangement of the bottom support seat, stable and reliable support can be provided for the testing device. The upper end of the bottom support seat is fixedly connected with a fixed bearing platform with a fixed guide rail, and the bottom of the sliding bearing platform in the press-pull transfer mechanism is provided with a chute matched with the fixed guide rail, so that the lateral sliding of the press-pull transfer mechanism and the fixed bearing platform in the left and right directions can be realized. A wedge-shaped groove can be formed between two press-pull transfer mechanisms by arranging a guide inclined plane at the inner end of the transfer table in the press-pull transfer mechanism, and meanwhile, loading inclined planes are arranged at both sides of the lower end of the wedge-shaped loading block, so that the vertical load applied to the top of the wedge-shaped loading block can be converted into the lateral load acting on the two press-pull transfer mechanisms transversely, and thus the compressive load on the top of the wedge-shaped loading block can be converted into a pair of tensile loads acting on the inner surface of the annular core.
So that a pure tensile load can be applied to the rock sample without adopting l&/504724 bonding or clamping mode, and the situation that the existing direct tensile testing method is easy to cause bonding failure at the bonding place or clamping failure at the clamping place due to stress concentration is avoided; and meanwhile, the tensile load is applied through the annular loading head matched with the inner surface of the annular core to be tested, so that the problem of eccentric stretching in the direct tensile testing by the bonding or clamping method is avoided. In addition, because the invention only needs the testing machine to provide the compression load, the requirements for testing equipment are low, and the testing machine does not need to have the tensile function, so it can be widely applied to universal testing machines of various specifications, and the static direct tensile strength test of rocks can be realized. At the same time, the invention can also be installed in a drop hammer testing machine, and the impact force formed by the drop hammer can be converted into dynamic tensile force, so that the dynamic direct tensile strength of rocks can also be obtained. The invention provides a device for testing static and dynamic direct tensile strength of annular core by pressure-tension conversion loading. The device is simple in structure and convenient to operate, and is convenient to be popularized and applied to various conventional rock mechanics testing machines. At the same time, it can realize the tensile strength testing of rocks under direct tensile conditions, truly reflect the tensile strength of rocks, and effectively improve the accuracy of tensile strength parameter testing.
The invention provides a method for testing static and dynamic direct tensile strength of annular core, which comprises the following steps: step 1: processing the obtained core into an annular core; step 2: firstly, fixing the supporting bottom plate on the platform of the rock mechanics pressure testing machine through fastening bolts to fix the bottom support seat; then connecting two fixed bearing platforms respectively and fixedly to the upper ends of two supporting top plates by connecting bolts |; then, assembling two press-pull transfer mechanisms on two fixed bearing platforms in a sliding way, and the inner ends of the two press-pull transfer mechanisms are in the initial position of abutting each other;
step 3: sleeving the prepared annular core outside the circular loading ring formed/504724 by the loading heads on the two press-pull transfer mechanisms, and ensuring that the annular core is coaxial with the circular loading ring, then placing the wedge-shaped loading block in the wedge-shaped groove formed between the transfer blocks on the two press-pull transfer mechanisms, and ensuring that the upper end of the wedge-shaped loading block is in a horizontal position; step 4: starting the pressure testing machine to apply a compressive load on the top of the wedge-shaped loading block, and the wedge-shaped loading block converts the compressive load P into a pair of symmetrical tensile loads T acting on the inner surface of the annular core through the press-pull transfer mechanism, and by recording the vertical pressure and vertical displacement applied by the pressure testing machine, obtaining the horizontal tensile force and horizontal tensile displacement of the annular core, and calculating the tensile strength oy of the rock by formula (1):
FRE, DRE LN | ét where: P is the maximum compressive load when the annular core is broken by tension, and the unit is N; t is the thickness of the annular core in m; do is the radius of the outer ring of the annular core, in m; di is the radius of the inner ring of the annular core, and the unit is m.
The method has simple steps, and can convert the vertical pressure into two horizontal tensile forces acting on the inner surface of the annular core, so that the annular core is subjected to direct tensile failure, so that the tensile strength of the rock sample in the horizontal direction can be effectively directly tested, the technical problems of bond failure, stress concentration and eccentric tension in the existing direct tensile test are overcome, and the tensile strength parameters of the rock can be obtained more accurately. At the same time, the invention is convenient to operate, can be applied to various conventional rock mechanics testing machines, and has great popularization and application value.
BRIEF DESCRIPTION OF THE FIGURES LU504724
FIG. 1 is a structural schematic diagram of the present invention;
FIG. 2 is an assembly schematic diagram of the invention connected with an annular core;
FIG. 3 is a schematic structural view of the present invention after removing the wedge-shaped loading block and the right-side press-pull transfer mechanism;
FIG. 4 is a schematic structural diagram of the medium-pressure pulling and transferring mechanism of the present invention:
FIG. 5 is a schematic structural view of the bottom support seat in the present invention:
FIG. 6 is an assembly schematic diagram of the bottom support seat and two fixed bearing platforms in the present invention:
FIG. 7 is a schematic structural diagram of a wedge-shaped loading block in the present invention;
FIG. 8 is a schematic structural diagram of a transfer block in the present invention.
In the drawings: 1. bottom support seat, 2. supporting bottom plate, 3. wedge-shaped loading block, 4. fixed bearing platform, 5. supporting top plate, 6. vertical bracket, 7. fixed guide rail, 8. press-pull transfer mechanism, 9. sliding bearing platform, 10, chute, 11, transfer block, 12. loading unit, 13. guide inclined plane, 14. strip-shaped connecting block, 15. loading head, 16. loading inclined plane, 17. annular core, 18. bolt hole |, 19. bolt hole Il, 20. bolt hole Ill, 21. limiting block, 22. vertical plane, 23. transfer support plate, 24. loading block.
DESCRIPTION OF THE INVENTION LU504724
The invention will be further explained with the attached drawings.
As shown in FIG. 1 to FIG. 8, the invention provides a device for testing static and dynamic direct tensile strength of annular core, which comprises a bottom support seat 1, a fixed bearing platform 4, a press-pull transfer mechanism 8 and a wedge-shaped loading block 3; the length direction of the bottom support seat 1 extends in the left-right direction.
The fixed bearing platform 4 is horizontally arranged, and the upper end of the fixed bearing platform 4 is fixedly connected with a fixed guide rail 7 extending in the left-right direction, the left and right ends of the fixed guide rail 7 are arranged flush with the left and right ends of the fixed bearing platform 4, and the fixed guide rail 7 is located in the center of the fixed bearing platform 4 in the width direction. Two fixed bearing platforms 4 are fixedly connected to the left part and the right part of the upper end of the bottom support seat 1 at left and right intervals.
The number of the press-pull transfer mechanisms 8 is two, and the press-pull transfer mechanisms 8 are composed of a sliding bearing platform 9, a transfer block 11 and a loading unit 12. The sliding bearing platform 9 is horizontally arranged, and the lower end of the sliding bearing platform 9 is provided with a chute 10 extending in the left-right direction. The transfer block 11 is fixedly connected to the upper part of the inner end of the sliding bearing platform 9, and the inner end of the transfer block 11 is provided with a guide inclined plane 13 which is higher outside and lower inside. As a priority, the transfer block 11 consists of a transfer support plate 23 at the bottom and a loading block 24 fixedly connected to the upper end of the transfer support plate 23, and the guide inclined plane 13 is formed at the inner end of the loading block 24. As a preference, the transfer support plate 23 and the loading block 24 are integrated. The loading unit 12 consists of a strip-shaped connecting block 14 and a semicircular loading head 15. The front end of the strip-shaped connecting block 14 is fixedly connected to the rear end face of the inner end of the transfer block 11. The inner end of the loading head 15 is fixedly connected with the rear end of the strip-shaped connecting block 14.
Two press-pull transfer mechanisms 8 are arranged above the two fixed bearing)504724 platforms 4 in a left-right direction, and the sliding bearing platform 9 is slidably sleeved on the fixed guide rail 7 through the chute 10, so as to realize the sliding fit between the press-pull transfer mechanism 8 and the fixed bearing platform 4 in the left-right direction.
When the two press-pull transfer mechanisms 8 slide into contact, the two loading heads form a circular loading ring. As a preference, in order to make the loading head 15 adapt to the annular cores 17 with different inner diameters, semi-circular pad plates can also be arranged, and the inner diameter of the semi-circular pad plates is adapted to the outer diameter of the loading head 15 and is arranged on the outer surface of the loading head 15, and the number of the semi-circular pad plates is two, and the semi-circular pad plates are arranged on the outer surfaces of the two loading heads 15 in opposite directions.
The upper end of the wedge-shaped loading block 3 has a planar structure, and two loading inclined planes 16 with an outer high and an inner low are symmetrically arranged on the left and right sides of the lower end, the bottom ends of the loading inclined planes 16 intersect to form a V-shaped structure. The lower end of the wedge-shaped loading block 3 is arranged between the upper ends of the two transfer blocks 11, and the loading inclined surfaces 16 on both sides are in sliding fit with the guide inclined planes 13 of the two transfer blocks 11 respectively. As a preference, both the upper left end and the upper right end of the wedge-shaped loading block 3 are provided with vertical planes 22, and the lower end of the vertical planes 22 is connected with the upper end of the loading inclined plane 16.
As a preference, the bottom support seat 1 is composed of a supporting bottom plate 2, two supporting top plates 5 and two vertical brackets 6, wherein the two supporting top plates 5 are oppositely arranged at the left and right parts above the supporting bottom plate 2. Two vertical brackets 6 are correspondingly arranged below the two supporting top plates 5, and the upper ends of the vertical brackets 6 are fixedly connected with the lower end faces of the supporting top plates 5, and the lower ends of the vertical brackets 6 are fixedly connected with the upper end faces of the supporting bottom plate 2.
The middle part of the upper end of the supporting bottom plate 2 is fixedly504724 connected with a limiting block 21 between two vertical brackets 6, and the height of the limiting block 21 is lower than that of the vertical brackets 6.
In order to facilitate assembly and separation, the supporting bottom plate 2 is provided with a bolt hole | 18 at the periphery, which is matched with the platform of the pressure testing machine. The supporting top plate 5 is provided with a plurality of bolt holes Il 19. The fixed bearing platform 4 is provided with a plurality of bolt holes III 20, and is fixedly connected with the bottom support seat 1 through connecting bolts | which penetrate the bolt holes II! 20 and bolt holes II 19.
In order to facilitate assembly and separation, the sliding bearing platform 9 is provided with a plurality of bolts IV. The transfer block 11 is provided with a plurality of bolt holes V, and is fixedly connected with the sliding bearing platform 9 through a connecting bolt Il penetrating the bolt holes IV and the bolt holes V.
In order to ensure the stability and reliability of the sliding fit between the press-pull transfer mechanism and the fixed bearing platform, the sections of the fixed guide rail 7 and the chute 10 are dovetail-shaped.
In order to ensure reliable connection strength, the rear end of the strip-shaped connecting block 14 extends to the rear end of the inner cambered surface of the loading head 15, and the rear end of the strip-shaped connecting block 14 is fixedly connected to the middle of the inner cambered surface of the loading head 15.
As a preference, the strip-shaped connecting block 14 and the loading head 15 have an integrated structure.
In order to apply the vertical load smoothly during the test, the inclination angles of the guide inclined plane 13 and the loading inclined plane 16 are consistent.
In the invention, through the arrangement of the bottom support seat, stable and reliable support can be provided for the testing device.
The upper end of the bottom support seat is fixedly connected with a fixed bearing)504724 platform with a fixed guide rail, and the bottom of the sliding bearing platform in the press-pull transfer mechanism is provided with a chute matched with the fixed guide rail, so that the lateral sliding of the press-pull transfer mechanism and the fixed bearing platform in the left and right directions can be realized.
A wedge-shaped groove can be formed between two press-pull transfer mechanisms by arranging a guide inclined plane at the inner end of the transfer table in the press-pull transfer mechanism, and meanwhile, loading inclined planes are arranged at both sides of the lower end of the wedge-shaped loading block, so that the vertical load applied to the top of the wedge-shaped loading block can be converted into the lateral load acting on the two press-pull transfer mechanisms transversely, and thus the compressive load on the top of the wedge-shaped loading block can be converted into a pair of tensile loads acting on the inner surface of the annular core.
So that a pure tensile load can be applied to the rock sample without adopting a bonding or clamping mode, and the situation that the existing direct tensile testing method is easy to cause bonding failure at the bonding place or clamping failure at the clamping place due to stress concentration is avoided; and meanwhile, the tensile load is applied through the annular loading head matched with the inner surface of the annular core to be tested, so that the problem of eccentric stretching in the direct tensile testing by the bonding or clamping method is avoided.
In addition, because the invention only needs the testing machine to provide the compression load, the requirements for testing equipment are low, and the testing machine does not need to have the tensile function, so it can be widely applied to universal testing machines of various specifications, and the static direct tensile strength test of rocks can be realized.
At the same time, the invention can also be installed in a drop hammer testing machine, and the impact force formed by the drop hammer can be converted into dynamic tensile force, so that the dynamic direct tensile strength of rocks can also be obtained.
The invention provides a device for testing static and dynamic direct tensile strength of annular core by pressure-tension conversion loading.
The device is simple in structure and convenient to operate, and is convenient to be popularized and applied to various conventional rock mechanics testing machines.
At the same time, it can realize the tensile strength testing of rocks under dirett504724 tensile conditions, truly reflect the tensile strength of rocks, and effectively improve the accuracy of tensile strength parameter testing.
The invention also provide a method for testing that static and dynamic direct tensile strength of an annular core, which comprise the following steps: step 1: processing the obtained core into an annular core 17 with a thickness of 40-50 mm and inner and outer diameters of 50-70 mm and 70-140 mm respectively; step 2: firstly, fixing the supporting bottom plate 2 on the platform of the rock mechanics pressure testing machine through fastening bolts to fix the bottom support seat 1; then respectively and fixedly connecting the two fixed bearing platforms 4 to the upper ends of the two supporting top plates 5 by connecting bolts |; then, slidably assembling the two press-pull transfer mechanisms 8 on the two fixed bearing platforms 4, and making the inner ends of the two press-pull transfer mechanisms 8 in the initial position of abutting each other; step 3: sleeving the prepared annular core 17 outside the circular loading ring formed by the loading heads 15 on the two press-pull transfer mechanisms 8, and ensuring that the annular core 17 is coaxial with the circular loading ring, and then placing the wedge-shaped loading block 3 in the wedge-shaped groove formed between the transfer blocks 11 on the two press-pull transfer mechanisms 8, and ensuring that the upper end of the wedge-shaped loading block 3 is in a horizontal position; step 4: starting the pressure testing machine to apply a compressive load on the top of the wedge-shaped loading block 3, and converting the compressive load P into a pair of symmetrical tensile loads T acting on the inner surface of the annular core 17 through the press-pull transfer mechanism 8 by the wedge-shaped loading block 3, and obtaining the horizontal tensile force and horizontal tensile displacement of the annular core 17 by recording the vertical pressure and vertical displacement applied by the pressure testing machine, and the tensile strength ot of the rock can be calculated by formula 1;
where: P is the maximum compressive load when the annular core 17 is broken ByJ504724 tension, and the unit is N; t is the thickness of the annular core 17 in m; do is the radius of the outer ring of the annular core 17, in m; di is the radius of the inner ring of the annular core 17, and the unit is m.
The method has simple steps, and can convert the vertical pressure into two horizontal tensile forces acting on the inner surface of the annular core, so that the annular core is subjected to direct tensile failure, so that the tensile strength of the rock sample in the horizontal direction can be effectively directly tested, the technical problems of bond failure, stress concentration and eccentric tension in the existing direct tensile test are overcome, and the tensile strength parameters of the rock can be obtained more accurately. At the same time, the invention is convenient to operate, can be applied to various conventional rock mechanics testing machines, and has great popularization and application value.

Claims (9)

CLAIMS LU504724
1. A device for testing static and dynamic direct tensile strength of annular core, comprising a bottom support seat (1), wherein the length direction of the bottom support seat (1) extends in the left-right direction; characterized by also comprising a fixed bearing platform (4), a press-pull transfer mechanism (8) and a wedge-shaped loading block (3); the fixed bearing platform (4) is horizontally arranged, and the upper end of the fixed bearing platform (4) is fixedly connected with a fixed guide rail (7) extending in the left-right direction; two fixed bearing platforms (4) are fixedly connected to the left part and the right part of the upper end of the bottom support seat (1) at left and right intervals; the number of the press-pull transfer mechanisms (8) is two, and the press-pull transfer mechanisms (8) are composed of a sliding bearing platform (9), a transfer block (11) and a loading unit (12); the sliding bearing platform (9) is horizontally arranged, and the lower end of the sliding bearing platform (9) is provided with a chute (10) extending in the left-right direction; the transfer block (11) is fixedly connected to the upper part of the inner end of the sliding bearing platform (9), and the inner end of the transfer block (11) is provided with a guide inclined plane (13) which is higher outside and lower inside; the loading unit (12) consists of a strip-shaped connecting block (14) and a semicircular loading head (15); the front end of the strip-shaped connecting block (14) is fixedly connected to the rear end face of the inner end of the transfer block (11); the inner end of the loading head (15) is fixedly connected with the rear end of the strip-shaped connecting block (14); two press-pull transfer mechanisms (8) are arranged above the two fixed bearing platforms (4) in a left-right direction, and the sliding bearing platform (9) is slidably sleeved on the fixed guide rail (7) through the chute (10), so as to realize the sliding fit between the press-pull transfer mechanism (8) and the fixed bearing platform (4) in the left-right direction; when the two press-pull transfer mechanisms (8) slide into contact, the two loading heads (15) form a circular loading ring;
the upper end of the wedge-shaped loading block (3) has a planar structure, arid)504724 two loading inclined planes (16) with an outer high and an inner low are symmetrically arranged on the left and right sides of the lower end; the lower end of the wedge-shaped loading block (3) is arranged between the upper ends of the two transfer blocks (11), and the loading inclined surfaces (16) on both sides are in sliding fit with the guide inclined planes (13) of the two transfer blocks (11) respectively.
2. The device for testing static and dynamic direct tensile strength of annular core according to claim 1, characterized in that the bottom support seat (1) is composed of a supporting bottom plate (2), two supporting top plates (5) and two vertical brackets (6), wherein the two supporting top plates (5) are oppositely arranged at the left and right parts above the supporting bottom plate (2); two vertical brackets (6) are correspondingly arranged below the two supporting top plates (5), and the upper ends of the vertical brackets (6) are fixedly connected with the lower end faces of the supporting top plates (5), and the lower ends of the vertical brackets (6) are fixedly connected with the upper end faces of the supporting bottom plate (2); the middle part of the upper end of the supporting bottom plate (2) is fixedly connected with a limiting block (21) between two vertical brackets (6), and the height of the limiting block (21) is lower than that of the vertical brackets (6).
3. The device for testing static and dynamic direct tensile strength of annular core according to claim 1 or 2, characterized in that the supporting bottom plate (2) is provided with a bolt hole | (18) at the periphery, which is matched with the platform of the pressure testing machine; the supporting top plate (5) is provided with a plurality of bolt holes II (19); the fixed bearing platform (4) is provided with a plurality of bolt holes III (20), and is fixedly connected with the bottom support seat (1) through connecting bolts which penetrate the bolt holes Ill (20) and bolt holes II (19).
4. The device for testing static and dynamic direct tensile strength of annular cotéJ504724 according to claim 3, characterized in that the sliding bearing platform (9) is provided with a plurality of bolts IV; the transfer block (11) is provided with a plurality of bolt holes V, and is fixedly connected with the sliding bearing platform (9) through a connecting bolt II penetrating the bolt holes IV and the bolt holes V.
5. The device for testing static and dynamic direct tensile strength of annular core according to claim 4, characterized in that the sections of the fixed guide rail (7) and the chute (10) are both dovetail-shaped.
6. The device for testing static and dynamic direct tensile strength of annular core according to claim 5, characterized in that the rear end of the strip-shaped connecting block (14) extends to the rear end of the inner cambered surface of the loading head (15), and the rear end of the strip-shaped connecting block (14) is fixedly connected to the middle of the inner cambered surface of the loading head (15).
7. The device for testing static and dynamic direct tensile strength of annular core according to claim 6, characterized in that the strip-shaped connecting block (14) and the loading head (15) have an integrated structure.
8. The device for testing static and dynamic direct tensile strength of annular core according to claim 7, characterized in that the inclination angles of the guide inclined plane (13) and the loading inclined plane (16) are consistent.
9. A method for testing static and dynamic direct tensile strength of annular corëU504724 comprising the following steps:
step 1: processing the obtained core into an annular core (17);
step 2: firstly, fixing the supporting bottom plate (2) on the platform of the rock mechanics pressure testing machine through fastening bolts to fix the bottom support seat (1); then connecting two fixed bearing platforms (4) respectively and fixedly to the upper ends of two supporting top plates (5) by connecting bolts I; then, assembling two press-pull transfer mechanisms (8) on two fixed bearing platforms (4) in a sliding way, and the inner ends of the two press-pull transfer mechanisms (8) are in the initial position of mutual abutment;
step 3: sleeving the prepared annular core (17) outside the circular loading ring formed by the loading heads (15) on the two press-pull transfer mechanisms (8), and ensuring that the annular core (17) is coaxial with the circular loading ring, then placing the wedge-shaped loading block (3) in the wedge-shaped groove formed between the transfer blocks (11) on the two press-pull transfer mechanisms (8), and ensuring that the upper end of the wedge-shaped loading block (3) is in a horizontal position;
step 4: starting the pressure testing machine to apply a compressive load on the top of the wedge-shaped loading block (3), and the wedge-shaped loading block (3) converts the compressive load P into a pair of symmetrical tensile loads T acting on the inner surface of the annular core (17) through the press-pull transfer mechanisms (8), and by recording the vertical pressure and vertical displacement applied by the pressure testing machine, obtaining the horizontal tensile force and horizontal tensile displacement of the annular core (17), and calculating the tensile strength oi of the rock by formula (1):
SRE, VAE LN / 3 En wherein P is the maximum compressive load when the annular core (17) is broken by tension, and the unit is N; t is the thickness of the annular core (17) in m; do is the radius of the outer ring of the annular core (17), in m; di is the radius of the inner ring of the annular core (17), and the unit is m.
LU504724A 2023-07-12 2023-07-12 Device and method for testing static and dynamic direct tensile strength of annular core LU504724B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
LU504724A LU504724B1 (en) 2023-07-12 2023-07-12 Device and method for testing static and dynamic direct tensile strength of annular core

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
LU504724A LU504724B1 (en) 2023-07-12 2023-07-12 Device and method for testing static and dynamic direct tensile strength of annular core

Publications (1)

Publication Number Publication Date
LU504724B1 true LU504724B1 (en) 2024-01-15

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LU504724A LU504724B1 (en) 2023-07-12 2023-07-12 Device and method for testing static and dynamic direct tensile strength of annular core

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