Hydraulic direct loading type UHPC (Ultra High Performance Concrete) anti-drawing test device

Abstract

The invention relates to a hydraulic direct loading type UHPC (Ultra High Performance Concrete) anti-drawing test device, which effectively solves the problems that a drawing test device is easy to cause local damage of a sample, the rigidity of the device is poor, and the tension is easy to be eccentric. According to the technical scheme, the device comprises a sample, a cylinder body and connecting structures located at the two ends of the cylinder body, the cylinder body is a cylinder with two open ends, oil holes are formed in the side wall of the cylinder body, the sample is of a dumbbell-shaped structure with two thick ends and a thin middle, the sample is coaxially arranged in the cylinder body, and the two ends of the sample are matched with the cylinder body through the connecting structures. The connecting structures can realize sealing fit between the inner wall of the cylinder body and the outer wall of the sample, the connecting structures and the sample are relatively fixed, and the connecting mechanism at each end can axially slide outwards relative to the cylinder body; hydraulic oil directly acts on the end part of the sample, uniform distribution of pressure on the bearing surface of the sample and the resultant force direction along the axial direction of the sample can be ensured, local damage of the sample or influence of bending moment or shearing force on the sample on the test is avoided, and the rigidity of the whole device is better.

Description

Technical Field

[0001] The present invention relates to the field of concrete performance testing, and specifically to a hydraulic direct loading type UHPC tensile pull-out test device. Background Art

[0002] UHPC is a concrete material with ultra-high strength, high toughness and high durability. It has an extremely dense microstructure, and the porosity is much lower than that of traditional concrete. Its dense structure gives it extremely strong impermeability. Moreover, the high fluidity and high self-compacting performance of UHPC can avoid the defects of surface honeycombing and pitting. After pouring, the surface is as flat as a mirror, and the surface smoothness can reach the level of decorative materials.

[0003] The pull-out test is used to test the tensile pull-out performance of UHPC. The current pull-out test devices generally adopt the method of clamping both ends of the specimen with clamps and then applying tensile force simultaneously. For example, the invention patent with the application number: CN202210356394.9 discloses a clamping device for the tensile strength detection of dog-bone specimens. The specimen is set in the shape of a dog bone with enlarged ends at both ends, and then the two ends of the specimen are clamped by two groups of clamps, and tensile force is applied.

[0004] In the above-mentioned method of rigid clamping through a mechanical clamping mechanism, the stress points are concentrated at the local contact between the clamp and the specimen, and the stress position is concentrated, so the specimen is prone to local damage. Moreover, the two groups of clamps are respectively located outside both ends of the specimen, and the axial dimension of the device is large, and the rigidity of the whole device is relatively poor, and it is easy to deform during large-load loading. Moreover, affected by the clamping accuracy of the clamp and the surface position accuracy of the specimen, the tensile force direction is prone to be non-coincident with the specimen axis during pull-out, causing the specimen to bear bending moment or shear force, affecting the test results.

[0005] Based on the fact that UHPC has an extremely low porosity and a high-quality formed surface, it has the possibility of directly bearing the pressure of hydraulic oil as a mechanical part in a short time during the test without transmitting the pull-out force through other rigid clamps, which provides a new direction for the tensile pull-out test of UHPC specimens.

[0006] The invention patent with the application number CN201310533896.5 discloses a device and method for testing the forming performance of pipes under the combined action of internal and external pressure. It applies hydraulic pressure to the pipe wall through hydraulic chambers inside and outside the pipe wall, clamps the workpiece through a piston and a punch, and then applies a drawing force to the test piece through the clamping force. Although this patent directly applies hydraulic pressure to the workpiece, the hydraulic pressure directly applies only a radial force, and the axial force still relies on the mechanical clamping of the piston and the punch for loading. Therefore, it is still impossible to directly apply the hydraulic pressure to the workpiece to load the axial force. In addition, as a concrete casting, the UHPC test piece has much lower geometric tolerance and dimensional tolerance than metal test pieces and does not meet the conditions to be used as a mechanical part. Therefore, there is no solution in the field to directly apply hydraulic pressure to concrete test pieces, especially for axial force loading. To implement this technical concept, it is first necessary to break the inherent thinking in the field, overcome technical biases, and then effectively solve technical problems such as the design of kinematic pairs and sealing. Summary of the Invention

[0007] The present invention provides a UHPC tensile and drawing test device with direct hydraulic loading, aiming to solve the problems that the drawing test device is prone to cause local damage to the specimen, has poor rigidity of the device, and the tensile force is prone to eccentricity.

[0008] The technical solution it adopts includes a specimen, a cylinder body, and connection structures located at both ends of the cylinder body. The cylinder body is a cylindrical shape with openings at both ends, and there are oil holes on the side wall of the cylinder body. The specimen is in a dumbbell shape with thick ends and a thin middle, and the specimen is coaxially placed inside the cylinder body. The two ends of the specimen are cooperated with the cylinder body through the connection structures. The connection structures can achieve a sealed fit between the inner wall of the cylinder body and the outer wall of the specimen. The connection structures are relatively fixed to the specimen, and each connection mechanism at each end can axially slide outward relative to the cylinder body.

[0009] The specimen consists of heads at both ends and a rod part in the middle. The rod part is a cylindrical shape with a uniform diameter and is connected to the heads at both ends respectively. Each head includes a first cone, and the small end of the first cone is connected to the end of the rod part.

[0010] The connection structure includes a sliding sleeve. The outer wall of the sliding sleeve fits and seals with the inner wall of the cylinder body. The sliding sleeve can slide outward relative to the cylinder body, and the inner wall of the sliding sleeve seals and cooperates with the outer wall of the head of the specimen.

[0011] A limit ring is screwed at each end of the cylinder body. There is a limit edge at the outer end of the inner wall of the limit ring. The inner diameter of the limit edge is smaller than the outer diameter of the sliding sleeve, and there is a gap between the limit edge and the outer end of the sliding sleeve.

[0012] The head of the specimen further includes a second cone. The second cone is located at the outer end of the first cone and has its small end facing outward. The outer end of the inner wall of the sliding sleeve is a conical surface with its small end facing outward, and the second cone cooperates with the inner wall of the sliding sleeve.

[0013] A screw is embedded at the outer end of the specimen. A limit disk is sleeved on the screw, and a compression nut is screwed on the screw outside the limit disk to press the limit disk against the end of the specimen. The outer edge of the limit disk presses against the outer end of the sliding sleeve.

[0014] Axial glue injection holes are formed on the outer end face of the sliding sleeve. The lower ends of the glue injection holes are located on the inner wall conical surface of the sliding sleeve. Sealant can be injected between the sliding sleeve and the outer wall of the second cone at the head of the specimen through the glue injection holes. After the sealant solidifies, a post-filled sealing layer is formed.

[0015] The taper of the second cone is smaller than the taper of the inner wall of the sliding sleeve.

[0016] The head of the specimen further includes a connecting section located between the first cone and the second cone. The connecting section is cylindrical, and a sealing ring is installed between the outer wall of the connecting section and the inner wall of the sliding sleeve.

[0017] The present invention utilizes the material characteristics of the UHPC specimen with dense texture and high surface forming quality, combines with the good filling property of the sealing layer formed by post-injecting sealant, and the wedge-shaped gap between the specimen and the sliding sleeve to ensure the reliable sealing between the specimen and the sliding sleeve. Thus, the specimen can be directly used as the piston part of the hydraulic system, and the pressure of the hydraulic oil directly acts on the end of the specimen. Different from the traditional rigid contact or clamping loading method, the hydraulic oil can ensure the uniform distribution of pressure on the bearing surface of the specimen and the resultant force direction along the axis of the specimen, avoiding local damage of the specimen or the influence of the specimen bearing bending moment or shear force on the test.

[0018] In addition, since the present invention does not require clamping mechanisms and loading mechanisms outside the two ends of the specimen, the axial dimension of the whole device is greatly reduced, making the rigidity of the whole device better and not prone to flexural deformation; moreover, the whole device has a regular cylindrical shape and is more simple and compact in structure. Description of the Drawings

[0019] Figure 1 It is the front view cross-sectional view of the present invention.

[0020] Figure 2 It is Figure 1 The enlarged view of position A in

[0021] Figure 3 It is the top view of the present invention.

[0022] Figure 4 It is the sectional view of the assembly sequence of the present invention.

[0023] Figure 5 It is the three-dimensional view of the assembly sequence of the present invention.

[0024] Figure 6 It is the three-dimensional view of the specimen.

[0025] Figure 7 It is a three-dimensional view of the sliding sleeve. Specific embodiments

[0026] Combined with the attached drawings, the present invention includes a specimen 1, a cylinder block 2, and connection structures located at both ends of the cylinder block 2. The cylinder block 2 is in the shape of a cylinder with openings at both ends. An oil hole 3 is provided on the side wall of the cylinder block 2, and the oil hole 3 is externally connected to an oil circuit for controlling the inflow and outflow of hydraulic oil into and out of the cylinder block 2. The specimen 1 is in the shape of a dumbbell with thick ends and a thin middle. The specimen 1 is coaxially placed inside the cylinder block 2. Both ends of the specimen 1 are cooperated with the cylinder block 2 through the connection structures. The connection structures can achieve a sealed fit between the inner wall of the cylinder block 2 and the outer wall of the specimen 1. The connection structures are relatively fixed to the specimen 1, and each end connection mechanism can slide axially outward relative to the cylinder block 2; that is to say, the connection structures do not apply an axially inward binding force to the specimen 1 to avoid affecting the test results. When hydraulic oil is pumped into the cylinder block 2 for pressurization, the hydraulic pressure acts on both ends of the specimen 1, so that both ends of the specimen 1 are simultaneously subjected to an axially outward pressure, thereby realizing the loading of the pulling force on the specimen 1.

[0027] The specimen 1 is composed of heads 4 at both ends and a rod part 5 in the middle. The rod part 5 is in the shape of a cylinder with a uniform diameter and is connected to the heads 4 at both ends respectively. The head 4 includes a first cone 6. The small end of the first cone 6 is connected to the end of the rod part 5, and the connection part is smoothly transitioned through a fillet to avoid stress concentration; the rod part 5 is the position where the specimen 1 breaks, and the conical surface of the first cone 6 of the head 4 is the acting surface of the hydraulic pressure.

[0028] The connection structure includes a sliding sleeve 7. The outer wall of the sliding sleeve 7 fits and seals with the inner wall of the cylinder block 2. The sliding sleeve 7 can slide outward relative to the cylinder block 2. The inner wall of the sliding sleeve 7 is in sealed fit with the outer wall of the head 4 of the specimen 1. Through the cooperation between the sliding sleeve 7 and the cylinder block 2 and the cooperation between the sliding sleeve 7 and the specimen 1, while the end of the cylinder block 2 is sealed, no axially inward binding force is applied to the end of the specimen 1.

[0029] A limit ring 8 is screwed at each end of the cylinder block 2. A limit edge 9 is provided at the outer end of the inner wall of the limit ring 8. The inner diameter of the limit edge 9 is smaller than the outer diameter of the sliding sleeve 7, and there is a gap between the limit edge 9 and the outer end of the sliding sleeve 7. The limit edge 9 can limit the distance that the sliding sleeve 7 slides outward to prevent the sliding sleeve 7 from slipping out of the cylinder block 2.

[0030] The head 4 of the specimen 1 further includes a second cone 10. The second cone 10 is located at the outer end of the first cone 6 and the small end faces outward. The outer end of the inner wall of the sliding sleeve 7 is a conical surface with the small end facing outward. The second cone 10 cooperates with the inner wall of the sliding sleeve 7; through the cooperation of the conical surfaces, when the specimen 1 is subjected to an axially pulling force, it cannot move outward relative to the sliding sleeve 7, and the specimen 1 can be prevented from slipping out of the cylinder block 2.

[0031] A screw rod 11 is embedded in the outer end of the sample 1, and a limit plate 12 is passed through the screw rod 11. A clamping nut 13 located on the outside of the limit plate 12 is screwed on the screw rod 11, and the limit plate 12 is pressed against the end of the sample 1, and the outer edge of the limit plate 12 is pressed against the outer end of the sleeve 7; the limit plate 12 prevents the sleeve 7 from moving outward relative to the sample 1; through the cooperation of the conical surface and the limitation of the limit plate 12, the positions of the sample 1 and the sleeve 7 are relatively fixed, which can greatly reduce the difficulty of sealing between the two and greatly reduce the possibility of sealing failure.

[0032] An axial glue injection hole 14 is opened on the outer end surface of the sliding sleeve 7, and the lower end of the glue injection hole 14 is located on the inner wall conical surface of the sliding sleeve 7. The glue injection hole 14 can be used to press the sealant between the sliding sleeve 7 and the outer wall of the second cone 10 of the head 4 of the sample 1. After the sealant solidifies, a post-filled sealing layer 15 is formed; the sealing layer 15 can densely fill the gap between the sample 1 and the sliding sleeve 7, thereby forming an effective sealing layer 15.

[0033] The taper of the second cone 10 is smaller than that of the inner wall of the sleeve 7, so that the gap between the sample 1 and the sleeve 7 is wedge-shaped with a narrow outer end and a wide inner end. When the sealing layer 15 in the gap is subjected to the liquid pressure in the cylinder 2, it can be further compressed to ensure effective sealing.

[0034] The head 4 of the sample 1 also includes a connecting section 16, which is located between the first cone 6 and the second cone 10. The connecting section 16 is cylindrical, and a sealing ring 17 is installed between the outer wall of the connecting section 16 and the inner wall of the sleeve 7; on the one hand, the sealing ring 17 and the sealing layer 15 formed by the injection of glue form a two-level seal to improve the sealing reliability. On the other hand, the sealing ring 17 serves as the bottom seal of the gap to intercept the sealant during the injection of glue, thereby preventing the sealant from leaking from the lower end of the sleeve 7 and ensuring that the glue in the gap is liquid-injected and dense.

[0035] When the present invention is used for testing, the sample 1 needs to be assembled into the cylinder body 2 first, and the specific assembly sequence is as follows: first place the sample 1 in the cylinder body 2, and then install the sleeve 7 into the end of the cylinder body 2. Since the sleeve 7 and the cylinder body 2 are in a conventional sliding fit, a conventional sealing ring can be used for sealing; while the sleeve 7 is assembled into the cylinder body 2, the sleeve 7 is sleeved on the head 4 of the sample 1, and then the upper limit plate 12 is installed on the screw 11 at the end of the sample 1 and the clamping nut 13 is screwed on, the limit plate 12 is pressed against the end of the sample 1 to limit the sleeve 7, and finally the limit ring 8 is screwed onto the end of the cylinder body 2 to complete the assembly.

[0036] After assembly, sealant is injected into the gap between the sliding sleeve 7 and the specimen 1 through the sealant injection hole 14 at the end of the sliding sleeve 7. During injection, the pressure is maintained for ten to twenty minutes to densely fill the gap between the sliding sleeve 7 and the specimen 1. After the sealant solidifies, a sealing layer 15 will be formed between the specimen 1 and the sliding sleeve 7. Multiple sealant injection holes 14 can be arranged circumferentially. On the one hand, the multi-point injection method is conducive to the dense filling of the glue; on the other hand, when injecting sealant through one of the injection holes 14, the remaining injection holes 14 can be used as vent holes.

[0037] Before assembly, a waterproof coating can be applied to the outer wall of the head 4 of the specimen 1 to form a waterproof layer. The waterproof coating can better fill and repair the tiny defects on the surface of the specimen 1, further improving the sealing effect between the sealant and the outer wall of the specimen 1.

[0038] After the sealant solidifies and forms, hydraulic oil is pumped into the cylinder block 2 through the oil inlet. The hydraulic pressure acts on the end of the specimen 1 through the first conical surface, and at the same time, an outward axial force is applied to both ends of the specimen 1, thereby forming a pulling force. As the pressure in the cylinder block 2 increases, the pulling force gradually increases until the rod part 5 of the specimen 1 breaks. The pressure sensor records the pressure in the cylinder block 2 at the moment when the specimen 1 breaks. The product of this pressure and the projected area of the conical surface of the first cone 6 of the specimen 1 in the axial direction is the pulling force value when the specimen 1 breaks.

[0039] At the moment when the specimen 1 breaks, the sliding sleeve 7 and the broken specimen 1 will pop out outward until they contact the limit edge 9. The limit edge 9 can prevent potential safety hazards and hydraulic oil leakage caused by the sliding sleeve 7 or the broken specimen 1 slipping out of the cylinder block 2. After the specimen 1 breaks, the pressure in the cylinder block 2 can be steadily relieved.

[0040] Since the inner wall of the sliding sleeve 7 is injected with sealant, after the test is completed and the specimen 1 is removed, it is necessary to scrape and clean the residual glue on the inner wall of the sliding sleeve 7, or the sliding sleeve 7 can be replaced during the next test.

[0041] In the present invention, the specimen 1 directly serves as the piston part of the hydraulic system, enabling the pressure of the hydraulic oil to directly act on the end of the specimen 1, which can ensure the uniform distribution of the pressure on the bearing surface of the specimen 1 and the resultant force direction along the axis of the specimen 1, avoiding local damage of the specimen 1 or the influence of the specimen 1 bearing bending moment or shear force on the test.

[0042] In addition, since the present invention does not require clamping mechanisms and loading mechanisms outside both ends of the specimen 1, the axial dimension of the entire device is greatly reduced, making the entire device have better rigidity and not prone to flexural deformation; moreover, the overall shape of the device is a regular column, and the structure is simpler and more compact.

Claims

1. A hydraulic direct loading UHPC tensile test device, characterized in that: The invention comprises a sample (1), a cylinder body (2) and connecting structures located at both ends of the cylinder body (2); the cylinder body (2) is cylindrical with openings at both ends, an oil hole (3) is provided on the side wall of the cylinder body (2); the sample (1) is a dumbbell-shaped structure with thick ends and a thin middle; the sample (1) is coaxially placed in the cylinder body (2); both ends of the sample (1) cooperate with the cylinder body (2) through the connecting structure; the connecting structure can achieve a sealed cooperation between the inner wall of the cylinder body (2) and the outer wall of the sample (1); the connecting structure and the sample (1) are relatively fixed, and the connecting mechanism at each end can slide outwardly relative to the cylinder body (2) in the axial direction.

2. A hydraulic direct loading UHPC tensile test device according to claim 1, characterized in that: The sample (1) is composed of heads (4) at two ends and a rod (5) in the middle. The rod (5) is cylindrical with a uniform diameter and is connected to the head (4) at both ends. The head (4) includes a first cone (6). The small end of the first cone (6) is connected to the end of the rod (5).

3. A hydraulic direct loading UHPC tensile test device according to claim 2, characterized in that: The connection structure comprises a sliding sleeve (7), the outer wall of the sliding sleeve (7) is in close contact with the inner wall of the cylinder body (2) and is sealed. The sliding sleeve (7) can slide outward relative to the cylinder body (2), and the inner wall of the sliding sleeve (7) is in close contact with the outer wall of the head (4) of the sample (1).

4. A hydraulic direct loading UHPC tensile test device according to claim 3, characterized in that: A limiting ring (8) is screwed onto each end of the cylinder body (2) via a thread, and a limiting edge (9) is provided at the outer end of the inner wall of the limiting ring (8). The inner diameter of the limiting edge (9) is smaller than the outer diameter of the sliding sleeve (7), and a gap is left between the limiting edge (9) and the outer end of the sliding sleeve (7).

5. The hydraulic direct loading UHPC tensile test device according to claim 3 is characterized in that: The head (4) of the specimen (1) further comprises a second cone (10), which is located at the outer end of the first cone (6) with the small end facing outwards. The outer end of the inner wall of the sliding sleeve (7) is a conical surface with the small end facing outwards. The second cone (10) cooperates with the inner wall of the sliding sleeve (7).

6. A hydraulic direct loading UHPC tensile test device according to claim 3, characterized in that: A screw rod (11) is embedded in the outer end of the sample (1), a limit plate (12) is passed through the screw rod (11), and a clamping nut (13) is screwed onto the screw rod (11) and is located outside the limit plate (12). The limit plate (12) is pressed against the end of the sample (1), and the outer edge of the limit plate (12) is pressed against the outer end of the sliding sleeve (7).

7. A hydraulic direct loading UHPC tensile test device according to claim 4, characterized in that: An axial glue injection hole (14) is formed on the outer end surface of the sliding sleeve (7), and the lower end of the glue injection hole (14) is located on the inner wall conical surface of the sliding sleeve (7). Through the glue injection hole (14), sealant can be injected between the sliding sleeve (7) and the outer wall of the second cone (10) of the head (4) of the sample (1). After the sealant solidifies, a post-filling sealing layer (15) is formed.

8. A hydraulic direct loading UHPC tensile test device according to claim 7, characterized in that: The taper of the second cone (10) is smaller than the taper of the inner wall of the sliding sleeve (7).

9. The hydraulic direct loading UHPC tensile test device according to claim 5, characterized in that: The head (4) of the sample (1) further comprises a connecting section (16), the connecting section (16) being located between the first cone (6) and the second cone (10), the connecting section (16) being cylindrical, and a sealing ring (17) being installed between the outer wall of the connecting section (16) and the inner wall of the sliding sleeve (7).

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