CN111579361A - Test fixture and method for three-point bending and four-point bending of rock - Google Patents
Test fixture and method for three-point bending and four-point bending of rock Download PDFInfo
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- CN111579361A CN111579361A CN202010545332.3A CN202010545332A CN111579361A CN 111579361 A CN111579361 A CN 111579361A CN 202010545332 A CN202010545332 A CN 202010545332A CN 111579361 A CN111579361 A CN 111579361A
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- 238000012360 testing method Methods 0.000 title claims abstract description 59
- 238000013001 point bending Methods 0.000 title claims abstract description 58
- 238000000034 method Methods 0.000 title abstract description 8
- 238000003825 pressing Methods 0.000 claims description 63
- 238000004519 manufacturing process Methods 0.000 claims description 14
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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
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- G01N3/04—Chucks
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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
- G01N3/20—Investigating strength properties of solid materials by application of mechanical stress by applying steady bending forces
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Abstract
The invention discloses a test fixture and a method for three-point bending and four-point bending of a rock, wherein the fixture comprises a base, an auxiliary support plate, an upper pressure head, a lower pressure head and a fixed pressure head, wherein support rods and fixing parts are arranged at two ends of the base; the middle parts of the upper surface and the lower surface of the auxiliary support plate are symmetrically provided with fixed pressure heads, a loading pressure head is arranged above the fixed pressure heads on the upper surface of the auxiliary support plate, auxiliary support plate tracks are arranged on two sides of the auxiliary support plate, and two upper pressure heads are movably connected in the auxiliary support plate tracks; symmetrical scales are correspondingly arranged on the same side of the base and the auxiliary carrier plate; the specification and size of the auxiliary support plate are consistent with those of the base, and when the upper pressure head is fixed with the auxiliary support plate, the upper pressure head is positioned right above the groove.
Description
Technical Field
The invention belongs to the field of rock mechanical property testing, and particularly relates to a clamp and a method for three-point bending and four-point bending tests of a rock.
Background
The fracture toughness of the rock is one of important indexes of rock mechanical properties, a three-point bending test is generally used for measuring the type I fracture toughness of a rock sample and researching the type I/II composite crack propagation behavior, and a four-point bending test is generally used for measuring the type I fracture toughness and the type II fracture toughness of the rock sample. The loading mode of the three-point bending test is simple and the application is wide. Compared with a three-point bending test, the four-point bending test has the advantages that two more pressure heads and one auxiliary carrier plate are arranged, the structure of the pressure clamp is complex, the bending moment is uniformly distributed, and the test result is more accurate. Both need to obtain required rock mechanics parameter through accurate control pressure head interval.
In the actual operation process, the existing clamp for the three-point and four-point bending tests mainly has three defects, so that the testing capability is reduced. Firstly, a pressure head and an auxiliary carrier plate need to be disassembled to realize the conversion of a three-point bending test and a four-point bending test; secondly, the distance between the upper pressure heads in the four-point bending test needs to be measured manually, and the deviation of the position of each pressure head can cause the error increase and even the failure of the test; thirdly, the control of the auxiliary carrier plate is not flexible, and the measurement of the II fracture toughness in the four-point bending test of the rock cannot be realized. Therefore, designing an integrated comprehensive clamp for the three-point and four-point bending test of the rock is very key to improving the test efficiency and accuracy.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a test fixture and a test method for three-point bending and four-point bending of a rock.
The purpose of the invention is realized by the following technical scheme:
a test fixture for three-point bending and four-point bending of rocks comprises a base, an auxiliary support plate, upper press heads, lower press heads and fixed press heads, wherein support rods and fixing parts are arranged at two ends of the base;
the middle parts of the upper surface and the lower surface of the auxiliary carrier plate are symmetrically provided with fixed pressing heads, two sides of the auxiliary carrier plate are provided with auxiliary carrier plate tracks, auxiliary carrier plate ball guide rails are arranged in the auxiliary carrier plate tracks, two upper pressing heads are movably connected in the auxiliary carrier plate tracks, and the upper pressing heads are provided with convex sliding blocks matched with the auxiliary carrier plate tracks in shape; the middle part of the upper pressure head is provided with a connecting hole, the middle parts of the two ends of the auxiliary support plate are provided with threaded holes, and the upper pressure head is fixed through a screw, the connecting hole and the threaded holes;
symmetrical scales are correspondingly arranged on the same side of the base and the auxiliary carrier plate; the auxiliary support plate is consistent with the base in specification and size, and when the upper pressure head is fixed with the auxiliary support plate, the upper pressure head is located right above the groove.
Furthermore, the upper pressure head and the lower pressure head are both composed of a cuboid-shaped pressing block and a semi-cylindrical pressing body, the pressing block is fixedly installed at two ends of the pressing body, and the convex sliding block is correspondingly installed on the pressing block; the fixed pressure head is of a semi-cylindrical structure; the semi-cylindrical diameter of the pressing body is larger than that of the fixed pressing head.
The other technical scheme provided by the invention is as follows:
a manufacturing method of a test fixture for three-point bending and four-point bending of rocks comprises the following steps:
(301) manufacturing an auxiliary carrier plate, wherein the main body of the auxiliary carrier plate is cuboid, screw holes with the same size are formed in four end parts of the auxiliary carrier plate, threaded holes with the same size are formed in the left end and the right end of the auxiliary carrier plate, symmetrical scales are arranged at the front end of the auxiliary carrier plate, the measurement precision is 0.1mm, a fixed pressure head is arranged in the center of the auxiliary carrier plate, and auxiliary carrier plate rails and auxiliary carrier plate ball guide rails which slide left and right are arranged at the front end and the rear end of the auxiliary carrier plate;
(302) manufacturing two upper pressing heads, wherein convex sliding blocks matched with the auxiliary carrier plate in shape are arranged on pressing blocks on two sides of the upper pressing heads; a connecting hole with the same diameter as the threaded hole on the auxiliary carrier plate in the step (301) is formed in the middle of the pressing body of the upper pressing head, and the upper pressing head is a loading pressing head on the top of the rock sample;
(303) manufacturing a base, wherein the main body of the base is a cuboid with the same size as the auxiliary carrier plate, screw holes with the same diameter as that in the step (301) are formed in the four end parts of the base, two grooves with the same size are formed in the left side and the right side of the cuboid base, the width of each groove is larger than the diameter of the middle pressing body of the upper pressing head, base rails and base ball guide rails are arranged at the front end and the rear end of the cuboid base, the specifications of the base rails and the auxiliary carrier plate rails are the same, and the specifications of the base ball guide rails and the auxiliary carrier plate ball; the front end of the base is provided with symmetrical scales with the same scale specification as those on the auxiliary support plate, and the 0 scale mark of the symmetrical scales in the base, the 0 scale mark of the symmetrical scales in the auxiliary support plate and the circle center of the fixed pressure head are on the same vertical line so as to ensure the precision;
(304) manufacturing two lower pressing heads, wherein convex sliding blocks matched with the base track in shape are arranged on pressing blocks on two sides of the lower pressing heads; the lower pressure head is a supporting pressure head at the bottom of the rock sample;
(305) manufacturing four screws, wherein the diameter of each screw is smaller than that of each screw hole, so that no friction is generated between each screw hole and each screw when a rock sample is loaded;
(306) sliding the convex sliding blocks of the two lower pressing heads into the inner cavity of the base track from the groove of the base along the end part of the base track to be in contact with the ball guide rail of the base, and adjusting the positions of the convex sliding blocks according to the symmetrical scales by sliding the lower pressing heads;
(307) sliding the convex sliding blocks of the two upper pressure heads into the inner cavity of the auxiliary carrier plate ball track along the end part of the auxiliary carrier plate ball track to be in contact with the auxiliary carrier plate ball guide rail, and performing position adjustment according to the symmetrical scales by sliding the upper pressure heads; the upper pressure head is fixed through the threaded hole and the screw;
(308) inserting one ends of the four screws into four screw holes of the base, and fixing the four screws respectively by nuts; and then the auxiliary carrier plate is fixed on the same height of the four screw rods through nuts to complete the manufacture.
The other technical scheme provided by the invention is as follows:
a test method of a test fixture for three-point bending and four-point bending of rock comprises the following steps:
placing a rock sample on a lower pressure head of the base, aligning a connecting hole of an upper pressure head with a threaded hole of the auxiliary carrier plate by sliding the upper pressure head, and fixing the upper pressure head by a screw to ensure that the upper pressure head is not contacted with the rock sample; the auxiliary carrier plate moves downwards along the screw rod, so that the upper surface of the rock sample is contacted with the fixed pressing heads on the lower surface of the auxiliary carrier plate, and the lower surface of the rock sample is contacted with the two lower pressing heads on the base;
contacting a loading pressure head of the servo press machine with a fixed pressure head on the upper surface of the auxiliary support plate, starting the loading pressure head of the servo press machine, and pressurizing according to a set loading rate until the rock sample is damaged, so that the three-point bending test of the rock sample can be completed;
placing a rock sample on a lower pressure head of the base, moving the auxiliary carrier plate downwards along the screw rod, enabling the upper surface of the rock sample to be in contact with two upper pressure heads on the auxiliary carrier plate through sliding the upper pressure heads and the lower pressure heads, enabling the lower surface of the rock sample to be in contact with the two lower pressure heads on the base, pressurizing according to a set loading rate, and completing the four-point bending test of the rock sample until the rock sample is damaged.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
1. the auxiliary support plate is provided with the fixed pressure head and the slidable pressure head, so that the conversion of three-point and four-point bending tests can be quickly realized, the problem that the conversion of the three-point and four-point bending tests is realized by disassembling the pressure head and the auxiliary support plate is solved, the test time is saved, and the integration rate of the test equipment is improved.
2. The end edge of vice support plate and base is equipped with the symmetry scale, because three, four-point bending test require the diverse to the loading span, so the concrete position of pressure head can be according to the accurate regulation of symmetry scale more than, down, can not only practice thrift the manpower centering and adjust and measure the time of span, can also improve the rate of accuracy of test result.
3. The upper pressure head and the lower pressure head are flexibly controlled through the ball guide rail, so that the clamp disclosed by the invention can also realize the measurement of the II-type fracture toughness of the rock sample in a four-point bending test, and the comprehensive testing capability of the device disclosed by the invention is greatly improved.
4. The clamp is suitable for a common servo press, and only the base is arranged on a loading platform of the servo press to pressurize according to a set loading rate, so that the clamp is easy to popularize and apply.
Drawings
FIG. 1 is a schematic perspective view of a clamp according to the present invention;
fig. 2a and fig. 2b are a schematic plan structure diagram and a schematic perspective structure diagram of the secondary carrier plate, respectively;
fig. 3a and 3b are a schematic plan structure diagram and a schematic perspective structure diagram of the upper pressure head respectively;
fig. 4a and 4b are a schematic plan view and a schematic perspective view of the base, respectively;
FIGS. 5a and 5b are a schematic plane view and a schematic loading view of a three-point bending type I fracture test of a pre-cracked rock sample respectively;
FIGS. 6a and 6b are a schematic plane view and a schematic loading view of a four-point bending type I fracture test of a pre-cracked rock sample, respectively;
fig. 7a and 7b are a schematic plan view and a schematic loading view of a four-point bending type II fracture test of a pre-cracked rock specimen, respectively.
Reference numerals: 1-loading ram, 2-screw, 3-nut, 4-screw, 5-sub-carrier, 6-upper ram, 7-lower ram, 8-base, 9-groove, 10-fixed ram, 11-sub-carrier screw hole, 12-threaded hole, 13-sub-carrier ball guide, 14-symmetrical scale, 15-convex slider, 16-threaded hole, 17-press, 18-base screw hole, 19-base ball guide, 20-symmetrical scale, 21-pre-crack rock specimen, 22-pre-crack.
Detailed Description
The invention is described in further detail below with reference to the figures and specific examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In the description of the present invention, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", and the like indicate orientations or positional relationships based on the orientations or positions shown in the drawings, and are only for convenience and simplicity in describing the present patent.
As shown in fig. 1 to 4b, the invention provides a test fixture for three-point bending and four-point bending of a rock, which comprises a base 8, an auxiliary support plate 5, an upper pressure head 6, lower pressure heads 7 and a fixed pressure head 10, wherein screw rods 2 are mounted at four end parts of the base 8, the auxiliary support plate 5 can move on the screw rods and is fastened through nuts 3, grooves 9 are formed in the upper surfaces of two ends of the base 8, base rails are arranged at the front side and the rear side of the base between the grooves 9, base ball guide rails 19 are arranged in the base rails, the two lower pressure heads 7 are movably connected in the base rails, and convex sliding blocks 15 matched with the shapes of the base rails are arranged on the lower pressure heads 7;
the middle parts of the upper surface and the lower surface of the auxiliary support plate 5 are symmetrically provided with fixed press heads 10, the upper part of the fixed press head 10 on the upper surface of the auxiliary support plate 5 is used for contacting with a loading press head 1 of a servo press, auxiliary support plate tracks are arranged on the front side and the rear side of the auxiliary support plate, auxiliary support plate ball guide rails 13 are arranged in the auxiliary support plate tracks, two upper press heads 6 are movably connected in the auxiliary support plate tracks, and convex slide blocks 15 matched with the auxiliary support plate tracks in shape are arranged on the upper press heads 6; the middle part of the upper pressure head 6 is provided with a threaded hole 16, the middle parts of the two ends of the auxiliary carrier plate 5 are provided with threaded holes 12, and the upper pressure head can be fixed through the screw 4, the threaded hole 16 and the threaded hole 12;
the same sides of the auxiliary carrier plate 5 and the base 8 are respectively and correspondingly provided with symmetrical scales 14 and symmetrical scales 20; the specification and the size of the auxiliary carrier plate 5 are consistent with those of the base 8, and when the upper pressure head is fixed with the auxiliary carrier plate, the upper pressure head 6 is positioned right above the groove 9.
The upper pressure head 6 and the lower pressure head 7 are both composed of a cuboid-shaped pressing block and a semi-cylindrical pressing body 17, the pressing block is fixedly installed at two ends of the pressing body 17, and the convex sliding block 15 is correspondingly installed on the pressing block; the fixed pressure head 10 is of a semi-cylindrical structure; the semi-cylindrical diameter of the pressing body 17 is larger than that of the fixed pressing head 10.
Example 1-three point bending type I fracture test:
based on a servo press loading system, the clamp disclosed by the invention is used for testing the fracture toughness of the rock. The method comprises the following steps:
step 101, as shown in fig. 1, firstly assembling the clamp of the present invention, inserting four screws 2 into the base screw holes 18 shown in fig. 4b, and fixing with four nuts 3;
102, respectively taking four nuts 3, screwing the four nuts into the same height from the other end of the screw 2, inserting the auxiliary carrier plate screw holes 11 shown in fig. 2a and 2b into the upper parts of the four nuts 3 along the screw 2, and taking the four nuts 3 again to fix the auxiliary carrier plate 5;
103, as shown in fig. 3a and 3b, sliding the convex sliding blocks 15 of the two upper pressing heads 6 into the two sides of the auxiliary carrier plate 5 along the ends of the ball guide rails 13 of the auxiliary carrier plate as shown in fig. 2a and 2b, aligning the threaded holes 12 of the auxiliary carrier plate with the threaded holes 16 of the upper pressing heads, and fixing the threaded holes with the screws 4;
104, as shown in the figures 3a and 3b, sliding the convex sliding blocks 15 of the two lower pressing heads 7 into two sides of the base 8 from the base groove 9 along the end parts of the base ball guide rails 19 shown in the figures 4a and 4b, and completing the assembly of the clamp disclosed by the invention, as shown in the figure 1, the length range, the width range and the thickness range of the measurable rock sample are 100-400 mm, 40-200 mm and 40-200 mm, so that the recommended test size requirements at home and abroad are met;
105, placing the pre-crack rock sample 21 on the lower pressure head 7, aligning the pre-crack 22 with the 0 scale of the base symmetrical scale 20, enabling the bottom span to slide the lower pressure head 7, and adjusting to the required span according to the base symmetrical scale 20;
106, screwing the nut 3 at the lower end of the auxiliary carrier plate 5 to the bottom as shown in FIG. 1, wherein the diameter of the screw hole 11 of the auxiliary carrier plate is larger than that of the screw 2, so that friction cannot be generated between the auxiliary carrier plate and the screw during loading;
step 107, the pre-crack rock sample 21 is in contact with the fixed pressure head 10 on the auxiliary carrier plate 5, the upper pressure head 6 is fixed and aligned with the base groove 9, the upper pressure head 6 is ensured not to be in contact with the pre-crack rock sample 21, and a three-point bending I-type fracture test shown in fig. 5a and 5b can be realized;
step 108, adjusting the lower pressure head 7 in the step 105 to the required span of the three-point bending I-shaped fracture test, and starting the servo pressThe loading pressure head 1 is pressurized according to a set loading rate, and when the pre-cracked rock sample 21 is damaged, the three-point bending I-type fracture toughness K of the rock can be calculated according to the following formulaIC：
In the formula: s is the span at the bottom of the rock sample, P is the peak load, a is the length of the pre-crack, W, t is the width and thickness of the pre-crack rock sample,
is a relative length factor of the pre-crack.
Example 2 four-point bending type I fracture test:
based on a servo press loading system, the clamp disclosed by the invention is used for testing the fracture toughness of the rock. The method comprises the following steps:
step 201, as shown in fig. 1, firstly assembling the clamp of the present invention, inserting four screws 2 into the base screw holes 18 shown in fig. 4b, and fixing with four nuts 3;
step 202, screwing the four nuts 3 to the same height from the other end of the screw 2, inserting the auxiliary carrier plate screw holes 11 shown in fig. 2a and 2b into the upper parts of the four nuts 3 along the screw 2, and fixing the auxiliary carrier plate 5 by using the four nuts 3;
step 203, as shown in fig. 3a and fig. 3b, sliding the convex sliding blocks 15 of the two upper press heads 6 into the two sides of the auxiliary carrier plate 5 along the end parts of the auxiliary carrier plate ball guide rails 13 shown in fig. 2, aligning the auxiliary carrier plate threaded holes 12 with the upper press head threaded holes 16, and fixing with screws 4;
step 204, as shown in fig. 3a and 3b, sliding the convex sliding blocks 15 of the two lower pressing heads 7 into two sides of the base 8 from the base groove 9 along the end parts of the base ball guide rails 19 shown in fig. 4a and 4b, and completing assembly of the clamp disclosed by the invention, as shown in fig. 1, the length range of the measurable rock sample is 100-400 mm, the width range is 40-200 mm, and the thickness range is 40-200 mm, so that the recommended test size requirements at home and abroad are met;
step 205, placing the pre-crack rock sample 21 on the lower pressure head 7, aligning the pre-crack 22 with the 0 scale of the base symmetric scale 20, enabling the bottom span to slide the lower pressure head 7, and adjusting to the required span according to the base symmetric scale 20;
step 206, removing the screws 4 of the auxiliary carrier plate 5 shown in fig. 1, removing the fixing constraint of the upper pressure head 6, adjusting the top span to the required span by sliding the upper pressure head 6 according to the symmetrical scales 14 of the auxiliary carrier plate, and ensuring that the fixed pressure head 10 is not contacted with the pre-crack rock sample 21 because the semi-cylindrical pressure body 17 of the upper pressure head 6 is larger than the fixed pressure head 10;
step 207, screwing the nut 3 at the lower end of the auxiliary carrier plate 5 shown in fig. 1 to the bottom, wherein the diameter of a screw hole 11 of the auxiliary carrier plate is larger than that of a screw 2, so that friction cannot be generated between the auxiliary carrier plate and the screw hole during loading, the pre-crack rock sample 21 is in contact with the upper pressure head 6, and a four-point bending I-shaped fracture test shown in fig. 6a and 6b can be realized;
and step 208, adjusting the lower pressure head 7 and the upper pressure head 6 in the step 205 to the required span of the four-point bending I-type fracture test, starting the servo press to load the pressure head 1 to pressurize according to the set loading rate, and when the pre-cracked rock sample 21 is damaged, calculating the I-type fracture toughness K of the rock according to the following formulaIC：
In the formula: s1For horizontal span from the bottom support point of the pre-cracked rock specimen to the pre-crack, S2The horizontal span from the top load point of the pre-cracked rock specimen to the pre-crack, P is the peak load, a is the pre-crack length, W, t is the pre-crack rock specimen width and thickness respectively,
is a relative length factor of the pre-crack.
Example 3-four point bending type II fracture test:
based on a servo press loading system, the clamp disclosed by the invention is used for testing the fracture toughness of the rock. The method comprises the following steps:
step 301, as shown in fig. 1, assembling the fixture of the present invention, inserting four screws 2 into the base screw holes 18 shown in fig. 4b, and fixing with four nuts 3;
step 302, screwing the four nuts 3 to the same height from the other end of the screw 2, inserting the auxiliary carrier plate screw holes 11 shown in fig. 2a and 2b into the upper parts of the four nuts 3 along the screw 2, and fixing the auxiliary carrier plate 5 by using the four nuts 3;
step 303, as shown in fig. 3a and 3b, sliding the convex sliding blocks 15 of the two upper pressing heads 6 into the two sides of the auxiliary carrier plate 5 along the end parts of the ball guide rails 13 of the auxiliary carrier plate as shown in fig. 2a and 2b, aligning the threaded holes 12 of the auxiliary carrier plate with the threaded holes 16 of the upper pressing heads, and fixing the threaded holes with the screws 4;
step 304, as shown in figures 3a and 3b, sliding the convex sliding blocks 15 of the two lower pressing heads 7 into two sides of the base 8 from the base groove 9 along the end parts of the base ball guide rails 19 shown in figures 4a and 4b, and completing the assembly of the clamp disclosed by the invention, as shown in figure 1, the length range of the measurable rock sample is 100-400 mm, the width range is 40-200 mm, and the thickness range is 40-200 mm, so that the recommended test size requirements at home and abroad are met;
step 305, placing the pre-crack rock sample 21 on the lower pressure head 7, aligning the pre-crack 22 with the 0 scale of the base symmetric scale 20, enabling the bottom span to slide the lower pressure head 7, and adjusting to the required span according to the base symmetric scale 20;
step 306, removing the screws 4 of the auxiliary carrier plate 5 shown in fig. 1, removing the fixing constraint of the upper pressure head 6, adjusting the top span to the required span according to the symmetrical scales 14 of the auxiliary carrier plate, and ensuring that the fixed pressure head 10 is not contacted with the pre-crack rock sample 21 because the semi-cylindrical pressure head 17 of the upper pressure head 6 is larger than the fixed pressure head 10;
307, screwing the nut 3 at the lower end of the auxiliary carrier plate 5 shown in the figure 1 to the bottom, wherein the diameter of a screw hole 11 of the auxiliary carrier plate is larger than that of a screw 2, so that friction cannot be generated between the auxiliary carrier plate and the screw hole during loading, and the pre-crack rock sample 21 is in contact with the upper pressure head 6, so that a four-point bending II-type fracture test shown in figures 7a and 7b can be realized;
step 308, adjusting the lower pressure head 7 and the upper pressure head 6 in the step 305 to the required span of the four-point bending II-type fracture test, starting the servo press to load the pressure head 1 to pressurize according to the set loading rate, and when the pre-cracked rock sample 21 is damaged, calculating the rock II-type fracture toughness K according to the following formulaIIC：
In the formula: s1、S2Respectively bottom support point or top load point to horizontal short span and long span of the pre-crack, P is peak load, a is pre-crack length, W, t is pre-crack rock specimen width and thickness, respectively, YIIThe dimensionless geometric factor can be calculated by a finite element program.
The present invention is not limited to the above-described embodiments. The foregoing description of the specific embodiments is intended to describe and illustrate the technical solutions of the present invention, and the above specific embodiments are merely illustrative and not restrictive. Those skilled in the art can make many changes and modifications to the invention without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (4)
1. A test fixture for three-point bending and four-point bending of rocks is characterized by comprising a base, an auxiliary support plate, upper press heads, lower press heads and fixed press heads, wherein support rods and fixing parts are arranged at two ends of the base;
the middle parts of the upper surface and the lower surface of the auxiliary carrier plate are symmetrically provided with the fixed pressure heads, two sides of the auxiliary carrier plate are provided with auxiliary carrier plate tracks, auxiliary carrier plate ball guide rails are arranged in the auxiliary carrier plate tracks, two upper pressure heads are movably connected in the auxiliary carrier plate tracks, and the upper pressure heads are provided with convex slide blocks matched with the auxiliary carrier plate tracks in shape; the middle part of the upper pressure head is provided with a connecting hole, the middle parts of the two ends of the auxiliary support plate are provided with threaded holes, and the upper pressure head is fixed through a screw, the connecting hole and the threaded holes;
symmetrical scales are correspondingly arranged on the same side of the base and the auxiliary carrier plate; the auxiliary support plate is consistent with the base in specification and size, and when the upper pressure head is fixed with the auxiliary support plate, the upper pressure head is located right above the groove.
2. The test fixture for three-point bending and four-point bending of the rock as claimed in claim 1, wherein the upper pressure head and the lower pressure head are both composed of a cuboid-shaped pressing block and a semi-cylindrical pressing body, the pressing block is fixedly installed at two ends of the pressing body, and the convex sliding block is correspondingly installed on the pressing block; the fixed pressure head is of a semi-cylindrical structure; the semi-cylindrical diameter of the pressing body is larger than that of the fixed pressing head.
3. A manufacturing method of a test fixture for three-point bending and four-point bending of a rock is characterized by comprising the following steps:
(301) manufacturing an auxiliary carrier plate, wherein the main body of the auxiliary carrier plate is cuboid, screw holes with the same size are formed in four end parts of the auxiliary carrier plate, threaded holes with the same size are formed in the left end and the right end of the auxiliary carrier plate, symmetrical scales are arranged at the front end of the auxiliary carrier plate, the measurement precision is 0.1mm, a fixed pressure head is arranged in the center of the auxiliary carrier plate, and auxiliary carrier plate rails and auxiliary carrier plate ball guide rails which slide left and right are arranged at the front end and the rear end of the auxiliary carrier plate;
(302) manufacturing two upper pressing heads, wherein convex sliding blocks matched with the auxiliary carrier plate in shape are arranged on pressing blocks on two sides of the upper pressing heads; a connecting hole with the same diameter as the threaded hole on the auxiliary carrier plate in the step (301) is formed in the middle of the pressing body of the upper pressing head, and the upper pressing head is a loading pressing head on the top of the rock sample;
(303) manufacturing a base, wherein the main body of the base is a cuboid with the same size as the auxiliary carrier plate, screw holes with the same diameter as that in the step (301) are formed in the four end parts of the base, two grooves with the same size are formed in the left side and the right side of the cuboid base, the width of each groove is larger than the diameter of the middle pressing body of the upper pressing head, base rails and base ball guide rails are arranged at the front end and the rear end of the cuboid base, the specifications of the base rails and the auxiliary carrier plate rails are the same, and the specifications of the base ball guide rails and the auxiliary carrier plate ball; the front end of the base is provided with symmetrical scales with the same scale specification as those on the auxiliary support plate, and the 0 scale mark of the symmetrical scales in the base, the 0 scale mark of the symmetrical scales in the auxiliary support plate and the circle center of the fixed pressure head are on the same vertical line so as to ensure the precision;
(304) manufacturing two lower pressing heads, wherein convex sliding blocks matched with the base track in shape are arranged on pressing blocks on two sides of the lower pressing heads; the lower pressure head is a supporting pressure head at the bottom of the rock sample;
(305) manufacturing four screws, wherein the diameter of each screw is smaller than that of each screw hole, so that no friction is generated between each screw hole and each screw when a rock sample is loaded;
(306) sliding the convex sliding blocks of the two lower pressing heads into the inner cavity of the base track from the groove of the base along the end part of the base track to be in contact with the ball guide rail of the base, and adjusting the positions of the convex sliding blocks according to the symmetrical scales by sliding the lower pressing heads;
(307) sliding the convex sliding blocks of the two upper pressure heads into the inner cavity of the auxiliary carrier plate ball track along the end part of the auxiliary carrier plate ball track to be in contact with the auxiliary carrier plate ball guide rail, and performing position adjustment according to the symmetrical scales by sliding the upper pressure heads; the upper pressure head is fixed through the threaded hole and the screw;
(308) inserting one ends of the four screws into four screw holes of the base, and fixing the four screws respectively by nuts; and then the auxiliary carrier plate is fixed on the same height of the four screw rods through nuts to complete the manufacture.
4. A test method of a test fixture for three-point bending and four-point bending of rock is characterized by comprising the following steps:
placing a rock sample on a lower pressure head of the base, aligning a connecting hole of an upper pressure head with a threaded hole of the auxiliary carrier plate by sliding the upper pressure head, and fixing the upper pressure head by a screw to ensure that the upper pressure head is not contacted with the rock sample; the auxiliary carrier plate moves downwards along the screw rod, so that the upper surface of the rock sample is contacted with the fixed pressing heads on the lower surface of the auxiliary carrier plate, and the lower surface of the rock sample is contacted with the two lower pressing heads on the base;
contacting a loading pressure head of the servo press machine with a fixed pressure head on the upper surface of the auxiliary support plate, starting the loading pressure head of the servo press machine, and pressurizing according to a set loading rate until the rock sample is damaged, so that the three-point bending test of the rock sample can be completed;
placing a rock sample on a lower pressure head of the base, moving the auxiliary carrier plate downwards along the screw rod, enabling the upper surface of the rock sample to be in contact with two upper pressure heads on the auxiliary carrier plate through sliding the upper pressure heads and the lower pressure heads, enabling the lower surface of the rock sample to be in contact with the two lower pressure heads on the base, pressurizing according to a set loading rate, and completing the four-point bending test of the rock sample until the rock sample is damaged.
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| CN112161879A (en) * | 2020-09-19 | 2021-01-01 | 太原理工大学 | Device and method for measuring three-point bending fracture toughness of static semicircular disc in warm-pressing environment |
| CN112557181A (en) * | 2020-12-01 | 2021-03-26 | 郑州大学 | Clamp for realizing four-point bending and four-point shearing fatigue of positive and negative stress ratios of rock concrete |
| CN112611629A (en) * | 2020-12-09 | 2021-04-06 | 华侨大学 | Multifunctional stone curtain wall connecting node bearing capacity test device |
| CN113092244A (en) * | 2021-03-31 | 2021-07-09 | 天津大学 | Movable press head type bending clamp and bending device for on-site bending of pipe |
| CN113358473A (en) * | 2021-06-21 | 2021-09-07 | 重庆交通大学 | Special testing device for rock fracture toughness convenient for direct field work |
| CN113405896A (en) * | 2021-06-10 | 2021-09-17 | 北京理工大学 | Four sides simply support restraint rectangular plate mechanical testing clamping device |
| CN113418772A (en) * | 2021-06-08 | 2021-09-21 | 北京航空航天大学 | Structure-load-transmission integrated composite material three-point bending fixture and use method |
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| CN116973209A (en) * | 2023-09-25 | 2023-10-31 | 中国林业科学研究院木材工业研究所 | Continuous on-line detection device and method for strength grade of sawn timber for structure |
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| CN112611629A (en) * | 2020-12-09 | 2021-04-06 | 华侨大学 | Multifunctional stone curtain wall connecting node bearing capacity test device |
| CN113092244A (en) * | 2021-03-31 | 2021-07-09 | 天津大学 | Movable press head type bending clamp and bending device for on-site bending of pipe |
| CN113418772A (en) * | 2021-06-08 | 2021-09-21 | 北京航空航天大学 | Structure-load-transmission integrated composite material three-point bending fixture and use method |
| CN113405896A (en) * | 2021-06-10 | 2021-09-17 | 北京理工大学 | Four sides simply support restraint rectangular plate mechanical testing clamping device |
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| CN113358473B (en) * | 2021-06-21 | 2023-10-27 | 重庆交通大学 | Special test device of rock fracture toughness convenient to direct field work |
| CN115200986A (en) * | 2022-07-29 | 2022-10-18 | 华侨大学 | Three-point bending test fixture capable of automatically aligning |
| CN116973209A (en) * | 2023-09-25 | 2023-10-31 | 中国林业科学研究院木材工业研究所 | Continuous on-line detection device and method for strength grade of sawn timber for structure |
| CN116973209B (en) * | 2023-09-25 | 2023-12-08 | 中国林业科学研究院木材工业研究所 | Continuous on-line detection device and method for strength grade of sawn timber for structure |
| CN117147331A (en) * | 2023-10-27 | 2023-12-01 | 中国石油大学(华东) | Three-point bending test device and test method suitable for ultrathin brittle material |
| CN117147331B (en) * | 2023-10-27 | 2024-01-26 | 中国石油大学(华东) | Three-point bending test device and test method suitable for ultrathin brittle material |
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