Concrete temperature stress testing machine for compensating ambient temperature

Abstract

The invention discloses a concrete temperature stress testing machine for compensating ambient temperature, which belongs to the technical field of concrete temperature strain test and comprises a testing machine host, a heat insulation box, a sealing sleeve, a water-cooling temperature control system and an active compensation system. Through the combination of the heat preservation box and the sealing sleeve, the concrete test block, the fixed-end universal joint, the movable-end universal joint, the fixed chuck, the movable chuck, the load sensor and other core test parts are sealed in the heat preservation box and the sealing sleeve, an independent internal constant-temperature test area is constructed, and the idealized premise that temperature changes of all the parts are consistent in the prior art is broken through; meanwhile, a water-cooling temperature control system composed of a first water cavity, a through groove, a second water cavity, a water injection pipe and a water drainage pipe is arranged among the first fixing base, the second fixing base and the sliding rod, it is ensured that the external temperature is constant, and the water-cooling effect is good. The problem of superposition of external deformation and deformation of the test piece and the internal part is thoroughly avoided.

Description

Technical Field

[0001] This invention relates to a temperature stress testing machine, and more particularly to a concrete temperature stress testing machine that compensates for ambient temperature, belonging to the field of concrete temperature strain testing technology. Background Technology

[0002] Mass concrete is widely used in major projects such as water conservancy, bridges, and high-rise building foundations. Temperature cracks caused by the release of heat of hydration and changes in ambient temperature in the early stages are a core issue threatening the safety and durability of engineering structures. The temperature stress testing machine for concrete (TSTM), as a comprehensive evaluation device, can simulate fully constrained conditions in the laboratory and simultaneously measure key mechanical parameters such as the elastic modulus, creep, stress relaxation, cracking stress, and characteristic fracture temperature of concrete. It can establish the correlation between laboratory data and the crack resistance performance of engineering structures, and become a core experimental means to solve the problem of cracking in mass concrete.

[0003] It is worth noting that although existing technologies have compensation schemes for temperature deformation of testing machines (such as the "material-length matching compensation method" proposed in prior art CN106092724B), their core design premise is that all components involved in the deformation calculation are under the same temperature change environment. This scheme uses 4J36 indium steel (α1: 0.5~2.5×10) with a low expansion coefficient for the slide rod, fixed seat, and universal joint. -6 The clamp and load cell are made of 45 steel with a high coefficient of thermal expansion (α2: 10~12×10 m / ℃). -6 The components were manufactured at m / ℃, and specific component lengths were designed (total length of the optical bar L1: 3120~3450mm, total length of the fixed end + universal joint L2: 1190~1320mm, total length of the chuck + load sensor L3: 210~300mm) to ensure that the total temperature deformation difference △L1 (optical bar deformation) - △L2 (fixed end + universal joint deformation) - △L3 (chuck + load sensor deformation) = 0, thereby offsetting temperature deformation. However, in the actual "dual temperature zone" environment of the test, the premise of this compensation scheme is completely invalid:

[0004] Inconsistent temperature change parameters lead to deformation calculation failure: The compensation formula in the comparison document is based on "the same temperature change △T for all components", that is, △L1=α1×△T×L1, △L2=α1×△T×L2, △L3=α2×△T×L3; however, in reality, the deformation of the light bar and the fixed end is △L1'=α1×△Touter×L1, △L2'=α1×△TInner×L2, and the deformation of the clamp and the load sensor is △L3'=α2×△TInner×L3. Since △Touter ≠ △TInner, the total deformation difference △L1'-△L2'-△L3'≠0, and the compensation mechanism completely fails.

[0005] Temperature difference deformation introduces additional errors: The deformation of the external host components (light bar, fixed end) caused by △T will be transmitted to the concrete specimen in the sealed box through the universal joint and clamp. This deformation is superimposed on the deformation caused by the temperature change of the specimen itself and the deformation caused by the temperature change of the components in the box. As a result, the "concrete deformation" measured by the testing machine is actually a mixture of the three types of deformation, and it is impossible to distinguish the true mechanical response of the concrete itself.

[0006] To address this issue, a concrete temperature stress testing machine that compensates for ambient temperature was designed. Summary of the Invention

[0007] The main objective of this invention is to provide a concrete temperature stress testing machine that compensates for ambient temperature. By combining an insulated chamber and a sealing sleeve, the core testing components, including the concrete specimen, fixed-end universal joint, movable-end universal joint, fixed clamp, movable clamp, and load sensor, are sealed inside, creating an independent "internal constant temperature testing zone." This breaks the ideal premise of "uniform temperature change of all components" in existing technologies, effectively isolating external main components such as the first fixed seat, second fixed seat, and slide rod from internal temperature exchange. Simultaneously, a water-cooled temperature control system consisting of a first water chamber, a through groove, a second water chamber, a water injection pipe, and a drainage pipe is provided between the first fixed seat, second fixed seat, and slide rod to ensure a constant external temperature, completely avoiding the problem of "external deformation superimposed with the deformation of the specimen and internal components." Combined with an active compensation system consisting of a push rod, servo motor, screw, and laser displacement sensor, when internal temperature changes cause minor deformation, the servo motor can drive the push rod in real time to move the load sensor, using mechanical displacement to offset the difference in internal temperature deformation. Compared to the existing technology's "passive length matching compensation," this method offers a more comprehensive solution. The drawback of fixed material parameters and failure due to inconsistent temperature changes is addressed by this active compensation method, which eliminates the assumption of "constant temperature change" and dynamically adjusts the compensation amount. This ensures that the load sensor accurately captures the true mechanical response of the concrete specimen, solving the problem of "indistinguishable deformation mixtures." It significantly improves the testing accuracy of key parameters such as elastic modulus and cracking stress. By setting a water flow regulation mechanism consisting of a guide tube, piston, water hole, return spring, and air hole between the top of the sealing sleeve and the water injection pipe, this mechanism can automatically adjust the flow rate of the circulating medium in the water chamber according to the real-time temperature difference between the inside and outside of the insulation box. When the ambient temperature outside the box rises and the temperature difference between the outside and inside the box increases, the water flow regulation mechanism expands the water hole channel through piston displacement, accelerating the medium circulation rate to enhance heat dissipation and prevent the temperature of the fixed seat and slide rod from rising with the environment. When the temperature difference decreases, the return spring returns to its original position, shrinking the water hole and reducing the flow rate to maintain temperature stability. This "temperature difference adaptive" water flow control method eliminates the need for manual intervention to keep the temperature of the external support structure constant, improving the adaptability and stability of the equipment in complex environments and indirectly ensuring the consistency of internal test data.

[0008] The objective of this invention can be achieved by adopting the following technical solution:

[0009] A concrete temperature stress testing machine that compensates for ambient temperature includes a main testing machine, an insulation chamber, a sealing sleeve, a water-cooled temperature control system, and an active compensation system.

[0010] The main body of the testing machine includes a first fixed base and a second fixed base arranged opposite to each other, and a slide rod whose two ends are respectively connected to the first fixed base and the second fixed base;

[0011] The insulation box is set between the first fixed seat and the second fixed seat, and the end of the insulation box is fixed to the inner side of the first fixed seat. The inside of the insulation box is sealed to accommodate the concrete test block, the fixed end universal joint, the movable end universal joint, the fixed clamp, the movable clamp and the load sensor. One end of the fixed end universal joint is connected to the inner side wall of the insulation box and the other end is connected to the fixed clamp. One end of the movable end universal joint is connected to the load sensor and the other end is connected to the movable clamp. The concrete test block is clamped between the fixed clamp and the movable clamp.

[0012] The side wall of the insulated box has a first opening, and the sealing sleeve is slidably disposed at the end of the insulated box. The outer end face of the sealing sleeve is tightly fitted with the inner side of the second fixed seat. The side wall of the sealing sleeve has a second opening for the load sensor to slide.

[0013] The second fixed base is equipped with an active compensation system that controls the load sensor to move away from the concrete test block, in order to compensate for the temperature changes of the concrete test block, the fixed end universal joint, the movable end universal joint, the fixed clamp, the movable clamp and the load sensor.

[0014] A water-cooled temperature control system is provided between the first fixed seat, the second fixed seat, and the slide rod to ensure that the temperature of the first fixed seat, the second fixed seat, and the slide rod remains constant.

[0015] Preferably, both ends of the outer side of the insulated box are equipped with limiting rings, and the limiting rings are sleeved on the sliding rod.

[0016] Preferably, both ends of the sealing sleeve are provided with slip rings fitted on the slide rod, and a compression spring is provided between the slip ring and the limiting ring, with the slide rod passing through the inside of the compression spring.

[0017] Preferably, the active compensation system includes a push rod, a servo motor, a screw, a vertical plate, and a laser displacement sensor. The push rod is linearly slidably disposed between two sliding channels inside the second fixed base, and the end of the push rod extends into the interior of the sealing sleeve. The load sensor is fixedly installed on the push rod. A servo motor with its output end connected to the screw is installed on the top of the main testing machine. A vertical plate is vertically fixed on the top of the push rod near the servo motor. A laser displacement sensor is provided on the second fixed base opposite the vertical plate. The output end of the laser displacement sensor is connected to a controller through a wire. The output end of the controller is electrically connected to the servo motor.

[0018] Preferably, the end of the push rod near the load sensor is provided with heat insulation cotton, which wraps around the outside of the load sensor and fits against the inner wall of the second port.

[0019] Preferably, the water-cooled temperature control system includes a first water chamber, a through groove, a second water chamber, a water injection pipe, a water flow regulating mechanism, and a drain pipe. The first water chamber is located inside the second fixed seat, the through groove is located inside the slide rod, and the second water chamber is located inside the first fixed seat. The first water chamber, the through groove, and the second water chamber are interconnected. The top of the second fixed seat is provided with a water injection pipe that communicates with the inside of the first water chamber. A water flow regulating mechanism is provided between the sealing sleeve and the water injection pipe. The first fixed seat is provided with a drain pipe that communicates with the second water chamber.

[0020] Preferably, the water flow regulating mechanism includes a conduit, a piston, a water hole, a return spring, and an air hole. The conduit is connected between the top of the sealing sleeve and the water injection pipe. An air hole is provided at the end of the conduit. A piston is horizontally slidably installed inside the conduit. A water hole that cooperates with the water injection pipe is provided on the piston. A return spring is provided between the piston and the end of the conduit.

[0021] Preferably, the first water cavity includes a sun-shaped water cavity and an annular water cavity, the annular water cavity is sleeved on the outside of the push rod, and the sun-shaped water cavity and the annular water cavity are connected.

[0022] Preferably, the second water cavity is shaped like a grid, and the drain pipe is connected to the center of the second water cavity.

[0023] The beneficial effects of this invention are as follows:

[0024] This invention provides a concrete temperature stress testing machine that compensates for ambient temperature. Through a combination of an insulated chamber and a sealing sleeve, core testing components such as concrete test blocks, fixed-end universal joints, movable-end universal joints, fixed clamps, movable clamps, and load sensors are sealed inside, creating an independent "internal constant temperature testing zone." This breaks the ideal premise of existing technologies that require "uniform temperature changes in all components," effectively isolating external main components such as the first fixed seat, second fixed seat, and slide rod from internal temperature exchange. Simultaneously, a water-cooled temperature control system consisting of a first water chamber, a through groove, a second water chamber, a water injection pipe, and a drainage pipe is provided between the first fixed seat, second fixed seat, and slide rod to ensure a constant external temperature and completely avoid "..." To address the issue of "external deformation superimposed on the deformation of the specimen and internal components," an active compensation system composed of a push rod, servo motor, screw, and laser displacement sensor is used. When internal temperature changes cause minor deformations, the servo motor can drive the push rod in real time to move the load sensor, using mechanical displacement to offset the difference in internal temperature deformation. Compared to the existing technology of "passive length matching compensation," which relies on fixed material parameters and fails due to inconsistent temperature changes, this active compensation does not require the assumption of "constant temperature change" and can dynamically adjust the compensation amount to ensure that the load sensor accurately captures the true mechanical response of the concrete specimen. This solves the pain point of "indistinguishable mixed deformation" and significantly improves the testing accuracy of key parameters such as elastic modulus and cracking stress.

[0025] By setting a water flow regulating mechanism consisting of a conduit, piston, water hole, return spring, and air hole between the top of the sealing sleeve and the water injection pipe, the mechanism can automatically adjust the flow rate of the circulating medium in the water chamber according to the real-time temperature difference between the inside and outside of the insulation box. When the ambient temperature outside the box rises and the temperature difference between the outside and inside the box increases, the water flow regulating mechanism expands the water hole channel through piston displacement to accelerate the medium circulation rate and enhance heat dissipation, preventing the temperature of the fixed seat and slide rod from rising with the environment. When the temperature difference decreases, the return spring returns to its original position and shrinks the water hole, reducing the flow rate to maintain temperature stability. This "temperature difference adaptive" water flow control method makes the temperature of the external support structure constant no longer dependent on manual intervention, improving the adaptability and stability of the equipment in complex environments and indirectly ensuring the consistency of internal test data. Attached Figure Description

[0026] Figure 1 This is a front view of a preferred embodiment of a concrete temperature stress testing machine that compensates for ambient temperature according to the present invention.

[0027] Figure 2 This is a top sectional view of a preferred embodiment of a concrete temperature stress testing machine that compensates for ambient temperature according to the present invention.

[0028] Figure 3 This is a preferred embodiment of a concrete temperature stress testing machine that compensates for ambient temperature according to the present invention. Figure 1 Enlarged view of point A in the middle;

[0029] Figure 4 This is a side view of the sealing sleeve in a preferred embodiment of a concrete temperature stress testing machine for compensating for ambient temperature according to the present invention.

[0030] Figure 5 This is a diagram of the water flow adjustment mechanism in a preferred embodiment of a concrete temperature stress testing machine that compensates for ambient temperature according to the present invention.

[0031] Figure 6 This is a cross-sectional view of the second fixed base in a preferred embodiment of a concrete temperature stress testing machine that compensates for ambient temperature according to the present invention.

[0032] Figure 7 This is an internal sectional view of the first fixed base in a preferred embodiment of a concrete temperature stress testing machine for compensating for ambient temperature according to the present invention.

[0033] In the diagram: 1. Main unit of the testing machine; 101. First fixed seat; 102. Second fixed seat; 103. Sliding rod;

[0034] 2. Insulated box; 201. Limiting ring;

[0035] 3. Fixed end universal joint; 4. Fixed chuck;

[0036] 5. Push rod; 501 heat insulation cotton;

[0037] 6. Servo motor; 7. Screw; 8. Load sensor; 9. Universal joint at movable end; 10. Movable chuck; 11. First port; 12. Sealing sleeve; 13. Second port; 14. Slip ring; 15. Compression spring; 16. First water chamber; 17. Through groove; 18. Second water chamber; 19. Water injection pipe;

[0038] 20. Water flow regulating mechanism; 2001. Guide tube; 2002. Piston; 2003. Water hole; 2004. Return spring; 2005. Air hole;

[0039] 21. Drainage pipe; 22. Vertical plate; 23. Laser displacement sensor. Detailed Implementation

[0040] To enable those skilled in the art to more clearly understand the technical solution of the present invention, the present invention will be further described in detail below with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0041] Example 1

[0042] like Figures 1-7 As shown, this embodiment provides a concrete temperature stress testing machine that compensates for ambient temperature, including a main testing machine 1, an insulation box 2, a sealing sleeve 12, a water-cooled temperature control system, and an active compensation system;

[0043] The main body of the testing machine 1 includes a first fixed seat 101 and a second fixed seat 102 arranged opposite to each other, and a slide rod 103 whose two ends are respectively connected to the first fixed seat 101 and the second fixed seat 102;

[0044] The insulation box 2 is set between the first fixed seat 101 and the second fixed seat 102, and the end of the insulation box 2 is fixed to the inner side of the first fixed seat 101. The insulation box 2 is sealed to contain concrete test blocks, fixed end universal joint 3, movable end universal joint 9, fixed clamp 4, movable clamp 10 and load sensor 8. One end of the fixed end universal joint 3 is connected to the inner side wall of the insulation box 2, and the other end is connected to the fixed clamp 4. One end of the movable end universal joint 9 is connected to the load sensor 8, and the other end is connected to the movable clamp 10. The concrete test block is clamped between the fixed clamp 4 and the movable clamp 10.

[0045] The side wall of the heat preservation box 2 is provided with a first opening 11, and the sealing sleeve 12 is slidably disposed at the end of the heat preservation box 2. The outer end face of the sealing sleeve 12 is tightly fitted with the inner side of the second fixed seat 102. The side wall of the sealing sleeve 12 is provided with a second opening 13 for the load sensor 8 to slide.

[0046] The second fixed base 102 is equipped with an active compensation system that controls the load sensor 8 to move away from the concrete test block, in order to compensate for the temperature changes of the concrete test block, the fixed end universal joint 3, the movable end universal joint 9, the fixed clamp 4, the movable clamp 10 and the load sensor 8.

[0047] A water-cooled temperature control system is provided between the first fixed seat 101, the second fixed seat 102 and the slide rod 103 to ensure that the temperature of the first fixed seat 101, the second fixed seat 102 and the slide rod 103 is constant.

[0048] General working principle: Before the test begins, the assembly and debugging of the core components are completed: The main body 1 of the testing machine consists of a first fixed seat 101, a second fixed seat 102 and a sliding rod 103 connecting the two ends, forming the basic support frame of the equipment. The insulation box 2 is set between the first fixed seat 101 and the second fixed seat 102, and the end of the insulation box 2 is fixed to the inside of the first fixed seat 101. Its interior is sealed to accommodate the concrete test block, the fixed end universal joint 3, the movable end universal joint 9, the fixed clamp 4, the movable clamp 10 and the load sensor 8. One end of the fixed end universal joint 3 is connected to the inner wall of the insulation box 2 and the other end is connected to the fixed clamp 4. One end of the movable end universal joint 9 is connected to the load sensor 8 and the other end is connected to the movable clamp 10. The concrete test block is stably clamped between the fixed clamp 4 and the movable clamp 10. The fixed end universal joint 3 and the movable end universal joint 9 can eliminate the additional stress caused by the clamping eccentricity and ensure the initial stress state of the concrete test block is stable.

[0049] The first opening 11 on the side wall of the insulation box 2 and the second opening 13 on the side wall of the sealing sleeve 12 form a through channel, providing space for the movement of the load sensor 8 and the subsequent push rod 5; the sealing sleeve 12 is slidably set at the end of the insulation box 2, and its outer end face is tightly fitted with the inner side of the second fixed seat 102, together with the insulation box 2 to form an independent "internal constant temperature test area", effectively isolating the temperature exchange between the external host components such as the first fixed seat 101, the second fixed seat 102, and the slide rod 103 and the internal test components, breaking the ideal premise of "all components have the same temperature change" in the existing technology.

[0050] After the test was started, the two core systems operated synchronously:

[0051] The water-cooled temperature control system operates as follows: The water-cooled temperature control system injects a circulating medium (such as constant-temperature water) at a constant temperature into the first water cavity 16 inside the second fixed seat 102 through the water injection pipe 19. The medium flows along the through groove 17 inside the slide rod 103 and finally enters the second water cavity 18 inside the first fixed seat 101. It is then discharged from the drain pipe 21, which is connected to the second water cavity 18, forming a complete medium circulation loop. During the circulation process, the medium absorbs or releases heat from the first fixed seat 101, the second fixed seat 102, and the slide rod 103 through heat exchange, ensuring that the temperature of these three external support components remains constant. This prevents deformation caused by changes in ambient temperature from being transferred to the internal test area, thus completely solving the problem of "external deformation superimposed on the deformation of the specimen and internal components".

[0052] Active compensation system workflow: When the internal test components (concrete test block, fixed end universal joint 3, movable end universal joint 9, fixed clamp 4, movable clamp 10, load sensor 8) undergo slight deformation due to their own temperature change;

[0053] According to the displacement compensation formula: ΔL compensation=α1×l1×ΔT1+α2×l2×ΔT2+α3×l3×ΔT3, the temperature change can be calculated.

[0054] In the formula, α1, α2 and α3 represent the linear expansion coefficients of the materials of the universal joint, the clamp and the load sensor 8, respectively; l1, l2 and l3 represent the lengths of the universal joint, the clamp and the load sensor 8, respectively; ΔT1, ΔT2 and ΔT3 represent the temperature changes of the universal joint, the clamp and the load sensor 8 as measured by the temperature sensor, respectively.

[0055] Then, the calculated temperature change is sent to the controller. The controller analyzes the signal and calculates the compensation displacement required to offset the temperature deformation according to the preset algorithm. Then, it outputs a control signal to the servo motor 6 on the top of the main unit 1 of the testing machine. After receiving the signal, the servo motor 6 runs and its output end drives the screw 7 to rotate. The screw 7 converts the rotational motion into linear motion through the threaded engagement, which pulls the push rod 5, which is linearly slidably set between the two sides of the second fixed seat 102, to move. The end of the push rod 5 extends outward from the sealing sleeve 12, and the load sensor 8 is fixedly installed on the push rod 5. Therefore, the push rod 5 can drive the load sensor 8 to move along the second opening 13 in a direction away from the concrete specimen. The laser displacement sensor 23 accurately detects the displacement distance and accurately offsets the temperature deformation difference of the internal components through mechanical displacement.

[0056] Ultimately, the load sensor 8 only captures the stress changes of the concrete specimen itself due to mechanical response (such as elastic deformation and stress accumulation before cracking), avoiding interference from temperature deformation, and achieving high-precision testing of key parameters such as elastic modulus, creep, and cracking stress of the concrete specimen, thus solving the pain point of existing technology that "deformation mixtures cannot be distinguished".

[0057] Example 2

[0058] The solution in Example 1 will be further described below with reference to its specific working method.

[0059] In this embodiment, both ends of the outer side of the heat preservation box 2 are provided with limiting rings 201, and the limiting rings 201 are sleeved on the slide rod 103.

[0060] Local working principle: The limiting rings 201 at both ends of the outer side of the insulation box 2 are sleeved on the slide rod 103. The slide rod 103 provides axial guidance and radial support for the limiting rings 201. Through the tight cooperation between the limiting rings 201 and the slide rod 103, the radial displacement and axial movement of the insulation box 2 during the test are restricted, ensuring that the insulation box 2 is always in the preset position between the first fixed seat 101 and the second fixed seat 102. This avoids the internal concrete test block clamping misalignment and the force imbalance between the fixed end universal joint 3 and the movable end universal joint 9 caused by the displacement of the insulation box 2, and provides a stable structural foundation for subsequent deformation compensation and stress detection.

[0061] In this embodiment, both ends of the sealing sleeve 12 are provided with slip rings 14 sleeved on the slide rod 103, and compression springs 15 are provided between the slip rings 14 and the limiting ring 201, with the slide rod 103 passing through the inside of the compression springs 15.

[0062] Local working principle: The compression spring 15 generates a continuous preload in its natural state, which pushes the slip ring 14 to move the sealing sleeve 12 toward the second fixed seat 102, so that the outer end face of the sealing sleeve 12 is always tightly fitted with the inner side of the second fixed seat 102, ensuring the sealing performance of the "internal constant temperature test area" formed by the sealing sleeve 12 and the heat preservation box 2, preventing external air from entering or the internal constant temperature environment from leaking. At the same time, when the active compensation system drives the push rod 5 to move the sealing sleeve 12 slightly, the compression spring 15 can adaptively adjust the position of the sealing sleeve 12 through elastic deformation, always maintaining the sealing state and ensuring the stability of the internal test environment.

[0063] In this embodiment, the active compensation system includes a push rod 5, a servo motor 6, a screw 7, a vertical plate 22, and a laser displacement sensor 23. The push rod 5 is linearly slidably disposed between the two sliding channels inside the second fixed base 102, and the end of the push rod 5 extends into the interior of the sealing sleeve 12. The load sensor 8 is fixedly installed on the push rod 5. The top of the main unit 1 of the testing machine is equipped with a servo motor 6 whose output end is connected to the screw 7. The top of the push rod 5 near the servo motor 6 is vertically fixed with a vertical plate 22. The laser displacement sensor 23 is provided on the second fixed base 102 opposite to the vertical plate 22. The output end of the laser displacement sensor 23 is connected to a controller through a wire. The output end of the controller is electrically connected to the servo motor 6.

[0064] Local working principle: When internal temperature changes cause deformation, the amount of displacement to be compensated is calculated, and an operation signal is output to the servo motor 6. The servo motor 6 drives the screw 7 to rotate. The threaded engagement between the screw 7 and the push rod 5 converts the rotational motion into linear motion, pushing the push rod 5 to slide axially along the second fixed seat 102. The push rod 5 drives the load sensor 8 to move along the second port 13 of the sealing sleeve 12. The laser displacement sensor 23 accurately detects the displacement distance. The mechanical displacement of the load sensor 8 offsets the temperature deformation of the internal components, ensuring that the load sensor 8 only bears the stress generated by the mechanical response of the concrete specimen itself, thus improving the accuracy of the test data.

[0065] In this embodiment, the end of the push rod 5 near the load sensor 8 is provided with heat insulation cotton 501, which wraps around the outside of the load sensor 8 and fits against the inner wall of the second opening 13.

[0066] Local working principle: The heat insulation cotton 501 not only completely wraps the outside of the load sensor 8, but also fits tightly against the inner wall of the second opening 13 of the sealing sleeve 12. On the one hand, the heat insulation cotton 501 has excellent heat insulation performance, which can block the heat transfer between the push rod 5 and the load sensor 8, prevent the external environment from being transferred to the load sensor 8 through the push rod 5, and avoid measurement errors caused by temperature fluctuations in the load sensor 8. On the other hand, the heat insulation cotton 501 fills the gap between the push rod 5 and the second opening 13, further enhancing the sealing performance of the sealing sleeve 12, reducing the heat exchange between the "internal constant temperature test area" and the outside, and maintaining the internal temperature stability.

[0067] In this embodiment, the water-cooled temperature control system includes a first water chamber 16, a through groove 17, a second water chamber 18, a water injection pipe 19, a water flow regulating mechanism 20, and a drain pipe 21. The first water chamber 16 is located inside the second fixed base 102, the through groove 17 is located inside the slide rod 103, and the second water chamber 18 is located inside the first fixed base 101. The first water chamber 16, the through groove 17, and the second water chamber 18 are interconnected. The top of the second fixed base 102 is provided with a water injection pipe 19 that is connected to the inside of the first water chamber 16. A water flow regulating mechanism 20 is provided between the sealing sleeve 12 and the water injection pipe 19. The first fixed base 101 is provided with a drain pipe 21 that is connected to the second water chamber 18.

[0068] Local working principle: During the test, a circulating medium at a constant temperature is injected into the first water chamber 16 from the water injection pipe 19 at the top of the second fixed seat 102. The medium flows fully in the first water chamber 16 and exchanges heat with the second fixed seat 102. Then, it flows along the through groove 17 inside the slide rod 103 to the second water chamber 18 of the first fixed seat 101. After completing heat exchange with the first fixed seat 101 in the second water chamber 18, it is discharged from the drain pipe 21 on the first fixed seat 101. Throughout the entire circulation process, the medium maintains the temperature of the first fixed seat 101, the second fixed seat 102, and the slide rod 103 at a preset constant value through continuous heat exchange. This prevents these external components from deforming due to changes in ambient temperature, thereby preventing deformation from being transmitted to the internal test area and interfering with the test data.

[0069] In this embodiment, the water flow regulating mechanism 20 includes a conduit 2001, a piston 2002, a water hole 2003, a return spring 2004, and an air hole 2005. The conduit 2001 is connected between the top of the sealing sleeve 12 and the water injection pipe 19. An air hole 2005 is provided at the end of the conduit 2001. The piston 2002 is horizontally slidably disposed inside the conduit 2001. A water hole 2003 that cooperates with the water injection pipe 19 is provided on the piston 2002. A return spring 2004 is provided between the piston 2002 and the end of the conduit 2001.

[0070] Local working principle: When the internal ambient temperature of the insulation box 2 rises, causing the temperature difference between the insulation box 2 and the outside to increase, the temperature of the sealing sleeve 12 rises with the internal environment. The heat is transferred to the internal air through the conduit 2001, causing the air inside the conduit 2001 to expand due to heat. The expanded air pushes the piston 2002 to slide towards the return spring 2004, compressing the return spring 2004. At this time, the overlapping area of ​​the water hole 2003 on the piston 2002 and the water injection pipe 19 increases, the medium flow cross section expands, and the medium flow rate increases, enhancing the heat dissipation effect on the first fixed seat 101, the second fixed seat 102, and the slide rod 103, preventing their temperature from rising. When the temperature difference between the inside and outside of the insulation box 2 decreases, the air inside the conduit 2001 contracts, and the return spring 2004 releases elastic potential energy to push the piston 2002 to return to its original position. The overlapping area of ​​the water hole 2003 and the water injection pipe 19 decreases, and the medium flow rate decreases, avoiding excessive heat dissipation that could cause temperature fluctuations in external components. This achieves "temperature difference adaptive" water flow regulation, maintaining a constant temperature for external components without manual intervention.

[0071] In this embodiment, the first water cavity 16 includes a shaped water cavity and an annular water cavity. The annular water cavity is sleeved on the outside of the push rod 5, and the shaped water cavity and the annular water cavity are connected.

[0072] Local working principle: The first water cavity 16 is composed of a H-shaped water cavity and an annular water cavity. The annular water cavity is sleeved outside the push rod 5, and the H-shaped water cavity and the annular water cavity are interconnected. The medium injected by the water injection pipe 19 first enters the H-shaped water cavity. The H-shaped structure makes the medium evenly distributed inside the second fixed seat 102, expands the contact area between the medium and the second fixed seat 102, ensures sufficient heat exchange in all parts of the second fixed seat 102, and avoids local excessively high or low temperatures. Then the medium flows into the annular water cavity. The annular water cavity is set around the push rod 5, which can perform 360° circumferential heat exchange on the push rod 5, block the heat transfer between the push rod 5 and the second fixed seat 102, and prevent the temperature of the push rod 5 from being affected by the second fixed seat 102 and transferred to the internal load sensor 8, further ensuring the stability of the working environment of the load sensor 8.

[0073] In this embodiment, the second water cavity 18 is shaped like a grid, and the drain pipe 21 is connected to the center of the second water cavity 18.

[0074] Local working principle: Under the guidance of the grid-shaped structure, the medium flows evenly through all areas inside the first fixed seat 101, avoiding local stagnation of the medium inside the first fixed seat 101, ensuring sufficient heat exchange and uniform temperature in all parts of the first fixed seat 101. At the same time, the drain pipe 21 is set at the center of the second water cavity 18, so that the medium is evenly gathered from all areas of the second water cavity 18 to the center for discharge, ensuring smooth medium circulation, maintaining stable heat exchange efficiency, and ensuring constant temperature of the first fixed seat 101.

[0075] Example 3

[0076] The solutions in Embodiments 1 and 2 will be further described below with reference to their specific working methods.

[0077] Before starting the test, the equipment assembly and specimen clamping are completed: the concrete specimen is placed inside the insulation box 2, and the inner wall of the insulation box 2 is connected to the fixed clamp 4 through the fixed end universal joint 3. The movable end universal joint 9 is connected to the load sensor 8 and the movable clamp 10. The distance between the fixed clamp 4 and the movable clamp 10 is adjusted to stably clamp the concrete specimen. The fixed end universal joint 3 and the movable end universal joint 9 eliminate the clamping eccentric stress and ensure that the initial force on the concrete specimen is uniform. Under the pre-tightening force of the compression spring 15, the outer end face of the sealing sleeve 12 is tightly attached to the inner side of the second fixed seat 102, forming a closed "internal constant temperature test area" together with the insulation box 2. The heat insulation cotton 501 on the push rod 5 wraps the load sensor 8 and is attached to the inner wall of the second opening 13 to enhance the sealing and heat insulation.

[0078] Once the experiment officially began, the water-cooled temperature control system and the active compensation system worked together to ensure test accuracy.

[0079] The water-cooled temperature control system operates as follows: A constant-temperature medium is injected from the water injection pipe 19 into the first water cavity 16 of the second fixed seat 102. The medium first undergoes heat exchange in the second fixed seat 102 through the H-shaped water cavity, then insulates the push rod 5 through the annular water cavity, and subsequently flows into the second water cavity 18 of the first fixed seat 101 through the through groove 17 of the slide rod 103. The H-shaped structure ensures sufficient heat exchange in all parts of the first fixed seat 101. Finally, the medium is discharged from the drain pipe 21. During this process, the water flow adjustment mechanism 20 adaptively adjusts the flow rate according to the temperature difference: when the temperature difference increases, the air in the guide tube 2001 expands, pushing the piston 2002 to slide, enlarging the water hole 2003 and increasing the flow rate; when the temperature difference decreases, the return spring 2004 pushes the piston 2002 to return to its original position, narrowing the water hole 2003 and reducing the flow rate, ensuring that the temperature of the first fixed seat 101, the second fixed seat 102, and the slide rod 103 remains constant.

[0080] The active compensation system adjusts in real time: When the internal test component deforms due to temperature change, the temperature change is calculated according to the displacement compensation formula: ΔL compensation=α1×l1×ΔT1+α2×l2×ΔT2+α3×l3×ΔT3;

[0081] In the formula, α1, α2 and α3 represent the linear expansion coefficients of the materials of the universal joint, the clamp and the load sensor 8, respectively; l1, l2 and l3 represent the lengths of the universal joint, the clamp and the load sensor 8, respectively; ΔT1, ΔT2 and ΔT3 represent the temperature changes of the universal joint, the clamp and the load sensor 8 as measured by the temperature sensor, respectively.

[0082] Then, the calculated temperature change is sent to the controller. The controller analyzes the signal and calculates the compensation displacement required to offset the temperature deformation according to the preset algorithm. Then, it outputs a control signal to the servo motor 6 on the top of the main unit 1 of the testing machine. After receiving the signal, the servo motor 6 runs and its output end drives the screw 7 to rotate. The screw 7 converts the rotational motion into linear motion through the threaded engagement, which pulls the push rod 5, which is linearly slidably set between the two sides of the second fixed seat 102, to move. The end of the push rod 5 extends outward from the sealing sleeve 12, and the load sensor 8 is fixedly installed on the push rod 5. Therefore, the push rod 5 can drive the load sensor 8 to move along the second opening 13 in a direction away from the concrete specimen. The laser displacement sensor 23 accurately detects the displacement distance and accurately offsets the temperature deformation difference of the internal components through mechanical displacement.

[0083] Throughout the experiment, all components and systems worked closely together to completely solve the problems of "deformation superposition" and "deformation confusion" in existing technologies, achieving high-precision testing of key mechanical parameters of concrete and providing reliable data support for the study of crack resistance performance of large-volume concrete.

[0084] The above description is merely a further embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope disclosed in the present invention, based on the technical solution and concept of the present invention, shall fall within the scope of protection of the present invention.

Claims

1. A concrete temperature stress testing machine for compensating for ambient temperature, characterized in that, Includes the main unit of the testing machine (1), the heat preservation box (2), the sealing sleeve (12), the water-cooled temperature control system and the active compensation system; The main body of the testing machine (1) includes a first fixed seat (101) and a second fixed seat (102) arranged opposite to each other, and a slide rod (103) with its two ends connected to the first fixed seat (101) and the second fixed seat (102) respectively; The insulation box (2) is set between the first fixed seat (101) and the second fixed seat (102), and the end of the insulation box (2) is fixed to the inner side of the first fixed seat (101). The insulation box (2) is sealed inside to accommodate concrete test blocks, fixed end universal joint (3), movable end universal joint (9), fixed clamp (4), movable clamp (10) and load sensor (8). One end of the fixed end universal joint (3) is connected to the inner wall of the insulation box (2), and the other end is connected to the fixed clamp (4). One end of the movable end universal joint (9) is connected to the load sensor (8), and the other end is connected to the movable clamp (10). The concrete test block is clamped between the fixed clamp (4) and the movable clamp (10). The side wall of the heat preservation box (2) is provided with a first opening (11), the sealing sleeve (12) is slidably disposed at the end of the heat preservation box (2), and the outer end face of the sealing sleeve (12) is tightly fitted with the inner side of the second fixed seat (102). The side wall of the sealing sleeve (12) is provided with a second opening (13) for the load sensor (8) to slide. The second fixed base (102) is equipped with an active compensation system that controls the load sensor (8) to move away from the concrete test block, in order to compensate for the temperature changes of the concrete test block, the fixed end universal joint (3), the movable end universal joint (9), the fixed clamp (4), the movable clamp (10) and the load sensor (8). A water-cooled temperature control system is provided between the first fixed seat (101), the second fixed seat (102), and the slide rod (103) to ensure that the temperature of the first fixed seat (101), the second fixed seat (102), and the slide rod (103) remains constant.

2. The concrete temperature stress testing machine for compensating for ambient temperature according to claim 1, characterized in that: Both ends of the outer side of the insulated box (2) are provided with limiting rings (201), and the limiting rings (201) are sleeved on the slide rod (103).

3. A concrete temperature stress testing machine for compensating for ambient temperature according to claim 2, characterized in that: Both ends of the sealing sleeve (12) are provided with slip rings (14) fitted on the slide rod (103). A compression spring (15) is provided between the slip ring (14) and the limiting ring (201). The slide rod (103) passes through the inside of the compression spring (15).

4. A concrete temperature stress testing machine for compensating for ambient temperature according to claim 1, characterized in that: The active compensation system includes a push rod (5), a servo motor (6), a screw (7), a vertical plate (22), and a laser displacement sensor (23). The push rod (5) is linearly slidably disposed between the two sliding channels inside the second fixed seat (102), and the end of the push rod (5) extends into the interior of the sealing sleeve (12). The load sensor (8) is fixedly installed on the push rod (5). The top of the main unit (1) of the testing machine is equipped with a servo motor (6) whose output end is connected to the screw (7). The top of the push rod (5) near the servo motor (6) is vertically fixed with a vertical plate (22). The laser displacement sensor (23) is provided on the second fixed seat (102) directly opposite the vertical plate (22). The output end of the laser displacement sensor (23) is connected to a controller through a wire. The output end of the controller is electrically connected to the servo motor (6).

5. A concrete temperature stress testing machine for compensating for ambient temperature according to claim 4, characterized in that: The push rod (5) is provided with heat insulation cotton (501) at one end near the load sensor (8). The heat insulation cotton (501) is wrapped around the outside of the load sensor (8) and fits against the inner wall of the second opening (13).

6. A concrete temperature stress testing machine for compensating for ambient temperature according to claim 1, characterized in that: The water-cooled temperature control system includes a first water chamber (16), a through groove (17), a second water chamber (18), a water injection pipe (19), a water flow regulating mechanism (20), and a drain pipe (21). The first water chamber (16) is located inside the second fixed seat (102), the through groove (17) is located inside the slide rod (103), and the second water chamber (18) is located inside the first fixed seat (101). The first water chamber (16), the through groove (17), and the second water chamber (18) are interconnected. The top of the second fixed seat (102) is provided with a water injection pipe (19) that is connected to the inside of the first water chamber (16). A water flow regulating mechanism (20) is provided between the sealing sleeve (12) and the water injection pipe (19). The first fixed seat (101) is provided with a drain pipe (21) that is connected to the second water chamber (18).

7. A concrete temperature stress testing machine for compensating for ambient temperature according to claim 6, characterized in that: The water flow regulating mechanism (20) includes a conduit (2001), a piston (2002), a water hole (2003), a return spring (2004), and an air hole (2005). The conduit (2001) is connected between the top of the sealing sleeve (12) and the water injection pipe (19). An air hole (2005) is provided at the end of the conduit (2001). A piston (2002) is horizontally slidably arranged inside the conduit (2001). A water hole (2003) that cooperates with the water injection pipe (19) is provided on the piston (2002). A return spring (2004) is provided between the piston (2002) and the end of the conduit (2001).

8. A concrete temperature stress testing machine for compensating for ambient temperature according to claim 6, characterized in that: The first water cavity (16) includes a sun-shaped water cavity and an annular water cavity. The annular water cavity is fitted outside the push rod (5), and the sun-shaped water cavity and the annular water cavity are connected.

9. A concrete temperature stress testing machine for compensating for ambient temperature according to claim 6, characterized in that: The second water chamber (18) is shaped like a grid, and the drain pipe (21) is connected to the center of the second water chamber (18).

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