High stress self-locking load holding device

Abstract

The utility model discloses a high stress self -locking holding device, including rigid bearing frame, self -locking jack, stress sensor, rigid bearing frame includes by the parallel arrangement of the lower to upper pressing plate no.

Description

Technical Field

[0001] This utility model relates to a testing device for civil engineering materials, specifically a high-stress self-locking bearing device. Background Technology

[0002] Stress corrosion cracking (SCC) is a significant cause of performance degradation in concrete materials under the combined effects of sustained high stress and corrosive environments. Simulating this process in the laboratory presents a core challenge: applying a sustained high stress exceeding 70% of the concrete specimen's compressive strength and maintaining that load stability over a corrosion test period lasting months or even years. Existing laboratory loading techniques suffer from the following prominent problems: 1. While hydraulic servo loading systems can precisely control the load, they are expensive, energy-intensive, require continuous external power support, and components such as hydraulic oil are easily damaged in corrosive environments, making them unsuitable for long-term stability testing; 2. Simple mechanical loading (such as springs or levers) is susceptible to material relaxation and concrete creep, making it difficult to maintain load stability over test periods lasting months, with load attenuation rates often exceeding 10%; stress levels are limited, making it difficult to achieve high stress loading exceeding 70% of the concrete's compressive strength; and stress relaxation is significant, resulting in poor load retention and low data reliability. Summary of the Invention

[0003] Purpose of the invention: The purpose of this utility model is to provide a high-stress self-locking load-bearing device that is stable in load, simple in structure, and safe and reliable.

[0004] Technical solution: The high-stress self-locking bearing device of this utility model includes a rigid bearing frame, a self-locking jack, and a stress sensor; the rigid bearing frame includes a pressure plate 1, a pressure plate 2, a pressure plate 3, and a pressure plate 4 arranged in parallel from bottom to top, as well as a screw and a fastening nut that connect all the pressure plates; the test block is placed between pressure plate 1 and pressure plate 2, and the self-locking jack and the stress sensor are respectively placed between each pair of pressure plates of pressure plate 2, pressure plate 3, and pressure plate 4.

[0005] Furthermore, disc spring assemblies are installed between the pressure plate and the fastening nut. Each disc spring assembly is composed of several interlocking disc springs. These assemblies provide elastic compensation force and compression stroke to absorb and compensate for stress losses caused by factors such as concrete creep and slight bolt elongation.

[0006] Furthermore, the piston rod of the self-locking jack is threadedly engaged with the self-locking nut. The mechanical self-locking function of the self-locking jack can lock the position at any stroke, effectively preventing loosening and unloading.

[0007] Furthermore, the self-locking jack is connected to a hydraulic pump via a high-pressure oil pipe to provide stress loading.

[0008] Furthermore, the stress sensor is connected to a data acquisition device for recording load changes. The high-precision stress sensor is used to monitor the load value applied to the test specimen in real time and accurately, while the data acquisition device records load changes.

[0009] Furthermore, pressure plates one, two, three, and four are all made of 316 stainless steel plates that have undergone quenching and tempering treatment. The tensile strength and yield strength of the 316 stainless steel plates are both not less than 100MPa, and the surface flatness error is less than 0.02mm. Through holes are correspondingly opened on the four sides or corners of pressure plates one, two, three, and four. The pressure plate material is selected from alloy steel plates with high strength, hardness, and corrosion resistance. The surface of the pressure plates is ground smooth to ensure uniform stress distribution. The through holes are used for the threaded rod to pass through and connect the pressure plates.

[0010] Furthermore, the screw and fastening nut have an anti-corrosion coating; the surfaces are treated with Dacromet or epoxy coating for corrosion protection.

[0011] Furthermore, all screws are made of 316 stainless steel with a tensile strength of not less than 100MPa. The screws are symmetrically and vertically distributed on the four sides or corners of the pressure plate, forming a load-bearing structure by tightening nuts.

[0012] Furthermore, a protective cover is installed around the self-locking jack and stress sensor to prevent corrosive media from splashing and affecting the monitoring accuracy and service life of the equipment.

[0013] Working Principle: This invention utilizes a rigid load-bearing frame, a self-locking jack, a stress sensor, and a disc spring assembly to achieve long-term high-stress loading, holding, and constant load on the test block under corrosive conditions. A hydraulic pump drives the jack to apply axial pressure to the test piece. The load passes through the rigid load-bearing frame, employing a redundancy load (1.05~1.10 times the target load). The mechanical self-locking of the jack, combined with the elastic buffering compensation of the disc spring assembly, ensures load stability and effectively compensates for stress relaxation, locking the load within the frame. The device requires no external continuous function, provides stable load, improves the reliability of test data and operational safety, and enables standardized loading, locking, and data monitoring, ensuring test repeatability and accuracy. It effectively solves the problems of high-stress loading and large load attenuation in long-term stress corrosion testing of concrete using traditional methods.

[0014] Beneficial effects: Compared with the prior art, this utility model has the following features: (1) The rigid load-bearing frame has high load capacity. The selection of high-strength materials and the frame structure design can withstand high stress loading. The structure is simple and saves equipment and maintenance costs; (2) The elastic deformation of the disc spring group can continuously compensate for stress relaxation; (3) The structure is safe and there is no risk of hydraulic oil leakage or electrical failure. The jack and self-locking nut can prevent accidental unloading; (4) The device surface is sprayed with anti-corrosion coating suitable for corrosive environments. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of this utility model;

[0016] Figure 2 This is a schematic diagram of the structure of the pressure plate of this utility model;

[0017] Figure 3 This is a schematic diagram of the structure of the pressure plate 14, screw 15, disc spring assembly 4 and fastening nut 16 of this utility model;

[0018] Figure 4 This is a schematic diagram of the piston rod 21 and self-locking nut 5 of the self-locking jack 2 of this utility model. Detailed Implementation

[0019] The test object was a 100mm cube of C40 concrete, with a target continuous compressive stress of 30MPa (i.e., a total load of 300kN). The screw 15 of the high-stress self-locking bearing device was made of 316 stainless steel, with a tensile strength of not less than 100MPa. The screw 15 had a diameter of 30mm and a height of 350mm. The pressure plates 11, 12, 13, and 14 were all Q361 grade high-strength alloy steel plates that had undergone quenching and tempering treatment. The tensile strength and yield strength of the 316 stainless steel plates were not less than 100MPa, and the surface flatness error was less than 0.02mm. The length, width, and thickness of the pressure plates were 300.5mm, 300.5mm, and 20mm, respectively, and through holes 101 with a diameter of 30.5mm were opened on all four sides. The material surfaces were treated with Dacromet or epoxy coating for corrosion protection.

[0020] like Figure 1 As shown, a high-stress self-locking bearing device for concrete stress corrosion testing is assembled, such as... Figure 2 As shown, through holes 101 are opened at the center of each of the four sides of the pressure plate. Four screws 15 are passed through the through holes 101 on the first pressure plate 11, ensuring the pressure plate 11 is placed horizontally. The upper surface of the first pressure plate 11 is cleaned. The concrete specimen to be tested is precisely centered on the pressure plate 11. Four screws 15 are passed through the through holes 101 on the second pressure plate 12, ensuring their centers are aligned with the specimen. The self-locking jack 2 is placed on the second pressure plate 12, ensuring it is aligned with the specimen. The third pressure plate 13 is covered, and the stress sensor 3 is placed at the center of the third pressure plate 13. The fourth pressure plate 14 is then covered. Figure 3As shown, a pre-assembled disc spring assembly 4 is fitted onto each screw 15. The disc spring assembly 4 is composed of several disc springs combined together. Specifically, the disc springs are made of 304 stainless steel, with an outer diameter of 63mm, an inner diameter of 31mm, a thickness of 3.5mm, and a strength of not less than 205Mpa. Then, fastening nuts 16 are tightened onto each screw 15 in sequence, and the rigid load-bearing frame 1 is assembled.

[0021] To perform excess loading and locking, the self-locking jack 2 is connected to the hydraulic pump via a high-pressure oil pipe. Slowly start the hydraulic pump, as... Figure 4 As shown, the piston rod 21 of the self-locking jack 2 extends outward. The piston rod 21 has external threads and is threadedly connected to the self-locking nut 5. The extended piston rod 21 presses against the upper and lower pressure plates, tightening the screw 15 and applying pressure to the test piece. The stress sensor 3 monitors the load value in real time. Specifically, the stress sensor 3 is model HZC-HT-50T with a range of 50T. The stress sensor 3 is connected to a data acquisition instrument to closely observe the readings. The designed margin of error is 1.05:1, therefore, the load is increased to 420kN. During the loading process, the self-locking nut 5 is tightened to ensure it remains in close contact with the lower surface of the pressure plate 13. When the load reaches 315kN, the pressure is maintained for about 5 minutes to allow the initial relaxation of the system to be fully released. After loading is completed, the self-locking mechanism of the self-locking jack 2 is operated to lock the piston rod.

[0022] Depressurize and verify the hydraulic pump by slowly releasing the pressure through the pressure relief valve. Observe the reading on the data acquisition instrument; it should drop from 315kN. Due to the compensation effect of the disc spring assembly 4, the final value will stabilize. If this value is higher than the target load of 300kN, adjust it precisely to 300kN by fine-tuning the self-locking jack 2 (applying slight pressure and then re-locking) or slightly loosening the self-locking nut 5. If it is lower than 300kN, the redundancy loading step must be repeated. After confirming that the load is stable within 300kN ± 2%, remove the hydraulic pump and high-pressure oil pipe.

[0023] For long-term testing, the entire device was moved into a corrosion test chamber to begin long-term stress corrosion testing. Controlling the device's height in the solution prevents the self-locking jack 2 and stress sensor 3 on the upper layer from being submerged. Ideally, protective covers are installed around the self-locking jack 2 and stress sensor 3. Load values ​​are recorded periodically using a data acquisition instrument to verify its stability. The device achieves truly long-term high-stress stable loading, providing a reliable experimental method for studying the mechanism of concrete stress corrosion. The device is highly versatile, adaptable to different stress levels and specimen sizes by replacing the rigid load-bearing frame 1 and disc spring assembly 4 with different specifications.

Claims

1. A high-stress self-locking load-bearing device, characterized in that: The system includes a rigid bearing frame (1), a self-locking jack (2), and a stress sensor (3). The rigid bearing frame (1) includes a pressure plate 1 (11), a pressure plate 2 (12), a pressure plate 3 (13), and a pressure plate 4 (14) arranged in parallel from bottom to top, as well as a screw (15) and a fastening nut (16) that connect all the pressure plates. The test block is placed between the pressure plate 1 (11) and the pressure plate 2 (12), and the self-locking jack (2) and the stress sensor (3) are placed between the two pressure plates of the pressure plate 2 (12), the pressure plate 3 (13), and the pressure plate 4 (14), respectively.

2. The high-stress self-locking bearing device according to claim 1, characterized in that: Disc spring assemblies (4) are provided between the pressure plate (14) and the fastening nut (16), and the disc spring assemblies (4) are composed of several disc springs combined together.

3. The high-stress self-locking bearing device according to claim 1, characterized in that: The piston rod (21) of the self-locking jack (2) is threadedly engaged with the self-locking nut (5).

4. The high-stress self-locking bearing device according to claim 1, characterized in that: The self-locking jack (2) is connected to the hydraulic pump via a high-pressure oil pipe.

5. The high-stress self-locking bearing device according to claim 1, characterized in that: The stress sensor (3) is connected to a data acquisition instrument for recording load changes.

6. The high-stress self-locking bearing device according to claim 1, characterized in that: The pressure plate one (11), pressure plate two (12), pressure plate three (13) and pressure plate four (14) are all 316 stainless steel plates that have been quenched and tempered. The tensile strength and yield strength of the 316 stainless steel plates are not less than 100MPa and the surface flatness error is less than 0.02mm. The four sides or corners of the pressure plate one (11), pressure plate two (12), pressure plate three (13) and pressure plate four (14) are respectively opened with through holes (101).

7. The high-stress self-locking bearing device according to claim 1, characterized in that: The screw (15) and fastening nut (16) have anti-corrosion coatings on their surfaces.

8. The high-stress self-locking bearing device according to claim 1, characterized in that: The screws (15) are all made of 316 stainless steel with a tensile strength of not less than 100MPa.

9. The high-stress self-locking bearing device according to claim 1, characterized in that: The self-locking jack (2) and the stress sensor (3) are surrounded by protective covers.

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