Ultra-high-temperature fatigue test equipment for large-size expansion joint

Abstract

The invention provides ultrahigh-temperature fatigue test equipment for a large-size expansion joint. The ultrahigh-temperature fatigue test equipment comprises a loading system, a heating system, a cooling system and a pressurizing system, the loading system is composed of an execution mechanism, a guide mechanism, a load platform and a high-temperature pull rod assembly, and is used for applying a stable dynamic axial load; the heating system comprises a heating base plate, a low-temperature heating chamber provided with a transverse opening and closing mechanism and a high-temperature heating chamber provided with a vertical lifting mechanism, and rapid crossing of a material sensitization temperature area is achieved. The cooling system comprises a circulating water-cooling plate integrated on the heating chassis, a double-end water-cooling flange and a forced water-cooling jacket sleeved at the bottom of the high-temperature pull rod, and is used for blocking a heat conduction path; the pressurization system provides a protective atmosphere with the pressure fluctuation smaller than or equal to + / -10% through the gas circuit device. The equipment is suitable for testing the fatigue performance of the large-size expansion joint in an ultrahigh-temperature environment of 1000 DEG C, and meets the reliability evaluation requirements of materials such as nickel-based alloy and stainless steel.

Description

Technical Field

[0001] This invention belongs to the technical field of material mechanical property testing equipment, specifically relating to a special testing equipment for fatigue performance testing of large-size metal expansion joints in an ultra-high temperature environment of 1000℃, which is particularly suitable for reliability assessment of expansion joints used in high-temperature pipeline systems in the fields of petrochemical, nuclear power and aerospace. Background Technology

[0002] Expansion joints, as key compensation components in pipeline systems, endure alternating loads under high temperature and high pressure conditions for extended periods. Their fatigue performance directly impacts equipment operational safety. With the development of modern industry, the requirements for the high-temperature resistance of expansion joints are constantly increasing, especially in fields such as nuclear power and aerospace, where operating temperatures often exceed 800℃. This places higher demands on fatigue performance testing of expansion joints. Currently, the ultra-high temperature fatigue testing of large-size expansion joints both domestically and internationally faces the following technical challenges: First, conventional fatigue testing machines cannot simultaneously meet the requirements for large-size sample clamping and high load application, and the mechanical structure is prone to thermal deformation under high-temperature conditions, leading to inaccurate load application. Second, single heating zones cannot avoid the material sensitization range of 450~600℃, increasing the risk of intergranular corrosion by 37%, resulting in test results that do not accurately reflect actual operating conditions.

[0003] To address the aforementioned technical bottlenecks, this invention innovatively proposes a solution combining a zoned temperature-controlled heating system with a dual cooling structure. Through the coordinated operation of the low-temperature and high-temperature heating chambers, rapid crossing of the material's sensitization temperature range is achieved. The dual cooling design, employing a circulating water-cooled plate and a forced water-cooled jacket, effectively solves the thermal management challenges under high-temperature conditions. Multiple drive devices are arranged along the circumference of the expansion joint, and a displacement synchronization controller coordinates each drive unit to ensure synchronous loading displacement and avoid localized stress concentration. A high-precision gas path control system ensures the accuracy of environmental simulation during the testing process. Compared to existing technologies, this invention offers significant advantages such as high testing accuracy, stable temperature control, and high equipment reliability, filling a technological gap in the domestic field of ultra-high temperature fatigue testing equipment for large-size expansion joints. Summary of the Invention

[0004] The purpose of this invention is to provide a high-temperature fatigue testing equipment for large-size expansion joints, which solves the technical bottleneck of traditional equipment being unable to perform high-precision fatigue testing on large-size expansion joints (diameter ≥ 800 mm) in high-temperature environments of 800~1000℃. The equipment, through the synergistic innovation of the loading system, heating system, cooling system, and pressurization system, achieves rapid crossing of the material sensitization temperature range, stable application of dynamic loads, and precise control of high-temperature thermal management.

[0005] The technical solution provided by this invention is as follows:

[0006] A large-size expansion joint ultra-high temperature fatigue testing equipment is characterized by comprising a loading system, a heating system, a cooling system, and a pressurization system.

[0007] Furthermore, the loading system includes an actuator, a guide mechanism, a load platform, and a high-temperature tie rod assembly; the actuator includes a connecting plate and at least one loading unit acting on the connecting plate; the load platform is mounted on the guide mechanism; the high-temperature tie rod assembly includes a high-temperature tie rod and an adjustable anti-loosening sleeve.

[0008] Furthermore, the heating system includes a heating chassis, a low-temperature heating chamber, and a high-temperature heating chamber, each with its own independently installed heating unit; the heating chassis is fixedly installed on the load platform; the low-temperature heating chamber is equipped with a horizontal opening and closing mechanism to achieve horizontal opening and closing; and the high-temperature heating chamber is equipped with a vertical lifting mechanism to achieve vertical lifting and lowering.

[0009] Furthermore, the cooling system includes a double-ended water-cooled flange, a circulating water-cooled plate, and a forced water-cooled jacket; the double-ended water-cooled flange is installed on the circulating water-cooled plate; the circulating water-cooled plate is integrated inside the heating chassis; and the forced water-cooled jacket is installed at the bottom of the high-temperature tie rod.

[0010] Furthermore, the pressurization system includes a pressurization device and an air passage device, providing an inert protective atmosphere.

[0011] Furthermore, the loading unit adopts a uniform distribution design, which is evenly distributed on the connecting plate to eliminate off-center loading.

[0012] Furthermore, the connecting plate moves vertically along the guide mechanism with a displacement accuracy of ≤±0.5%FS, ensuring load coaxiality.

[0013] Furthermore, the heating unit consists of multiple independent temperature control modules, which can respectively regulate the low-temperature zone (maximum heating temperature 300℃) and the high-temperature zone (maximum heating temperature 1000℃).

[0014] Furthermore, the forced water cooling jacket is rigidly connected to the connecting plate, and the temperature difference between the inlet and outlet of the cooling water is ≤15℃, which effectively reduces the heat conduction from the high-temperature tie rod to the actuator.

[0015] Furthermore, the bottom of the expansion joint is fixed to the circulating water cooling plate by a double-headed water-cooled flange, and the middle part is connected to the high-temperature tie rod by a height-adjustable anti-loosening sleeve. The reciprocating motion of the actuator drives the high-temperature tie rod to achieve axial fatigue loading.

[0016] Furthermore, the heating system operates according to the following steps:

[0017] S1. Close the low-temperature heating chamber, heat the expansion joint to 300℃ and keep it at that temperature;

[0018] S2. Start the pressurization device to fill the expansion joint with a protective atmosphere, and the gas pressure fluctuation is ≤10% of the set value;

[0019] S3. Start the high-temperature heating chamber and heat to the test temperature of 800~1000℃;

[0020] S4. After the temperature stabilizes, open the low-temperature heating chamber through the horizontal opening and closing mechanism;

[0021] S5. The high-temperature heating chamber is lowered to the working position via a vertical lifting mechanism;

[0022] S6. The expansion joint is heated from 300°C to the test temperature within 5 minutes, spanning the sensitization temperature range of 450~600°C;

[0023] S7. Conduct fatigue tests at the test temperature.

[0024] This equipment achieves high-precision fatigue testing of large-size expansion joints at high temperatures of 800~1000℃ through a zoned temperature-controlled heating system, multiple cooling structures, multi-drive load-sharing synchronization technology, and adaptive clamping structure, filling a technological gap in this field. Attached Figure Description

[0025] Figure 1 This is a front view of a large-size expansion joint ultra-high temperature fatigue testing device according to the present invention.

[0026] Figure 2 This is a front view and sectional view (AA) of a large-size expansion joint ultra-high temperature fatigue testing equipment according to the present invention.

[0027] Figure 3 Figure (11) shows the actuator of a large-size expansion joint ultra-high temperature fatigue testing device according to the present invention.

[0028] Figure 4 Figure 14 shows a high-temperature tie rod assembly (14) of a large-size expansion joint ultra-high temperature fatigue testing equipment of the present invention.

[0029] In the figure: Loading system (1), Actuator (11), Guide mechanism (12), Load platform (13), High temperature tie rod assembly (14), Connecting plate (111), Loading unit (112), High temperature tie rod (141), Adjustable anti-loosening sleeve (142), Heating system (2), Heating chassis (21), Low temperature heating chamber (22), Horizontal opening and closing mechanism (221), High temperature heating chamber (23), Vertical lifting mechanism (231), Heating unit (24), Cooling system (3), Double-headed water-cooled flange (31), Circulating water-cooled plate (32), Forced water-cooled jacket (33), Pressurization system (4), Pressurization device (41), Air circuit device (42). Detailed Implementation

[0030] The present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some examples of the present invention, and not all examples.

[0031] In the large-size expansion joint ultra-high temperature fatigue testing equipment provided by the present invention, some directional terms are used for the convenience of description, such as "up", "down", "left", "right" etc., which indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of description and do not refer to the specific position that the device or component must be in. Therefore, they should not be construed as limiting the present invention.

[0032] Please see Figure 1 According to an embodiment of the present invention, a large-size expansion joint ultra-high temperature fatigue testing equipment is disclosed, including a loading system (1), a heating system (2), a cooling system (3), and a pressurization system (4). The loading system (1) consists of an actuator (11), a guide mechanism (12), a load platform (13), and a high-temperature tie rod assembly (14). In this embodiment, the actuator (11) uses three sets of hydraulic cylinders as loading units (112), which are evenly distributed on the connecting plate (111) to provide axial cyclic displacement. The cylinder thrust range is 0–1000kN, the stroke is ±160mm, and the displacement accuracy is ±0.5%. The guide mechanism (12) is a multi-column support structure, with the load platform (13) fixed at the upper end. The column surface is hardened to ensure that there is no radial offset when the connecting plate (111) moves up and down, ensuring the coaxiality of the loading. The extension and retraction of the loading unit (112) drives the connecting plate (111) to move up and down along the guide mechanism (12). The high-temperature tie rod assembly (14) includes a high-temperature tie rod (141) and an adjustable anti-loosening sleeve (142). The high-temperature tie rod (141) is made of nickel-based alloy with a temperature resistance of ≥1200℃. It runs through the heating chamber. The upper end is fastened to the test piece center plate through the adjustable anti-loosening sleeve (142), and the lower end is connected to the connecting plate (111) through a forced water cooling jacket (33). This effectively prevents the heat of the high-temperature tie rod (141) from being directly transferred to the connecting plate (111), thus protecting the actuator (11). The adjustable anti-loosening sleeve (142) is height-adjustable through a slot to adapt to different expansion joint center plate heights. The sleeve is embedded with a high-temperature graphite sealing ring to prevent loosening of the connection.

[0033] Load transfer path: Actuator (11) drives connecting plate (111) → guide mechanism (12) constrains motion trajectory → high temperature tie rod (141) drives expansion joint to axially stretch / compress through ferrule.

[0034] The heating system (2) includes a heating base (21), a low-temperature heating chamber (22), and a high-temperature heating chamber (23). The heating base (21) is fixed on the load platform (13) and has a built-in circulating water cooling plate (32) to reduce heat conduction to the load platform (13). The low-temperature heating chamber (22) is a symmetrical split type, with an outer stainless steel anti-scalding mesh, a middle rigid support layer, and an inner hard insulation layer (200–400 mm thick). The insulation layer has slots for embedding ring resistance wires, with a maximum heating temperature of 300℃. The low-temperature heating chamber (22) is opened and closed by a horizontal opening and closing mechanism (221). In this embodiment, the horizontal opening and closing mechanism (221) is driven by a hydraulic push rod. After closing, it forms a sealed chamber, and the temperature fluctuation during heat preservation is ≤ ±5℃. The high-temperature heating chamber (23) is an inverted cylindrical design, which is lifted vertically by a vertical lifting mechanism (231). It has a built-in heating wire heating element and multiple independent temperature control sections. The inner wall is covered with an ultra-high temperature ceramic reflective layer to reduce heat radiation loss. In this embodiment, the vertical lifting mechanism (231) is driven by a servo motor to drive the lead screw, with a working position positioning accuracy of ±0.1mm.

[0035] Temperature control logic:

[0036] The pressurization system (4) fills the test piece with inert gas (pressure fluctuation ≤10%).

[0037] Close the low-temperature chamber, heat it to 300℃ and keep it warm;

[0038] The high-temperature chamber is activated, and the temperature rises from 300°C to 1000°C within 5 minutes (spanning the 450–600°C sensitization range).

[0039] The low-temperature greenhouse opens horizontally, while the high-temperature greenhouse descends to its working position, maintaining a constant temperature of 1000℃.

[0040] The cooling system (3) adopts a multi-layer heat-blocking design, including a double-headed water-cooled flange (31), a circulating water-cooled plate (32), and a forced water jacket. The double-headed water-cooled flange (31) is installed on the circulating water-cooled plate (32), and the upper end is connected to the bottom flange of the expansion joint. The double-headed water-cooled flange (31) is made of high-temperature resistant material, which can prevent dimensional deformation during high-temperature tensile testing, and the flange size can be adjusted according to the size of the test piece. The circulating water-cooled plate (32) is integrated into the heating chassis (21), with a water channel coverage of ≥70%, and the temperature of the load platform (13) is stable below 45℃. The forced water-cooled jacket (33) is sleeved on the bottom of the high-temperature tie rod (141) and fixed to the connecting plate (111). The temperature difference between the cooling water inlet and outlet is ≤15℃, blocking the heat conduction from the tie rod to the actuator (11).

[0041] The pressurization system (4) introduces inert gas into the test piece. The pressurization system (4) includes a pressurization device (41) and a gas path device (42). In this embodiment, the main component of the pressurization device (41) is a variable frequency air pump with an output pressure of 0–10 MPa. The test pressure can be adjusted according to the set pressure curve. The gas path device (42) includes a pressure sensor, a pressure holding valve, an electromagnetic flow meter, etc., and controls the input of inert gas in real time. Inert gas is input and output into the test piece through the gas path device (42). When the expansion joint is subjected to axial displacement during the test, the internal volume changes, causing pressure fluctuations. The pressure holding valve dynamically compensates for the gas volume and maintains the pressure fluctuation ≤ ±1% of the set value.

[0042] Test procedure:

[0043] Example 1: Fatigue test of Φ1200mm expansion joint at 1000℃.

[0044] 1. Clamping and positioning

[0045] The bottom flange of the expansion joint is connected to the double-headed water-cooled flange (31) by high-temperature bolts;

[0046] Adjust the height of the adjustable anti-loosening sleeve (142) to the designed position (fits an expansion joint height of 1500mm), with a locking torque of 300 N·m.

[0047] 1. Staged heating control

[0048] step operate Parameter control 1 Close the low-temperature heating chamber (22) Keep warm at 300℃±5℃ for 30 minutes 2 Start the booster system (4) Argon pressure 2.0 MPa ± 0.2 MPa 3 Preheating high-temperature heating chamber (23) 1000℃±10℃ constant temperature 4 Open the low-temperature heating chamber (22) The lateral opening and closing mechanism (221) opens 800mm. 5 Lowering the high-temperature heating chamber (23) Positioning accuracy ±0.1mm 6 Rapid heating Heating rate 100℃ / min

[0049] 2. Fatigue loading

[0050] The actuator (11) uses three 1000kN hydraulic cylinders in displacement control mode;

[0051] Loading waveform: triangular wave (frequency 0.5Hz, stroke ±50mm);

[0052] Data acquisition: Record temperature gradient and pressure fluctuations in each cycle;

[0053] 3. Thermal management effect

[0054] Cooling components Temperature control effect Load platform (13) 41.2℃ (function of circulating water cooling plate (32)) Connecting plate (111) 76.5℃ (forced water cooling jacket (33) function) Implementing agency (11) <55℃ (oil temperature stable)

[0055] 4. Technical Effects

[0056] Improved testing efficiency: The cycle time for a single test has been shortened from the traditional 72 hours to 48 hours.

[0057] Data reliability: Temperature uniformity ≤20℃ and pressure fluctuation ≤1.5%.

[0058] The above embodiments demonstrate that the present invention fills the technical gap in ultra-high temperature fatigue testing of large-size expansion joints and provides accurate data support for the safe design of high-temperature pipelines.

[0059] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A large-size expansion joint ultra-high temperature fatigue testing equipment, characterized in that, include: Loading system (1): includes an actuator (11), a guide mechanism (12), a load platform (13), and a high-temperature tie rod assembly (14); the actuator (11) includes a connecting plate (111) and at least one loading unit (112) acting on the connecting plate; the load platform (13) is mounted on the guide mechanism (12); the high-temperature tie rod assembly includes a high-temperature tie rod (141) and an adjustable anti-loosening sleeve (142); Heating system (2): includes heating chassis (21), low temperature heating chamber (22) and high temperature heating chamber (23); heating chassis (21), low temperature heating chamber (22) and high temperature heating chamber (23) are respectively equipped with heating units (24); heating chassis (21) is fixedly installed on load platform (13); low temperature heating chamber (22) is equipped with a horizontal opening and closing mechanism (221) to realize horizontal opening and closing; high temperature heating chamber (22) is equipped with a vertical lifting mechanism (231) to realize vertical lifting; Cooling system (3): includes a double-headed water-cooled flange (31), a circulating water-cooled plate (32), and a forced water-cooled jacket (33); the double-headed water-cooled flange (31) is installed on the circulating water-cooled plate (32); the circulating water-cooled plate (32) is integrated into the heating chassis (21); the forced water-cooled jacket (33) is installed at the bottom of the high-temperature tie rod (141); The pressurization system (4) includes a pressurization device (41) and a gas path device (42) for providing the protective atmosphere required for the test.

2. The large-size expansion joint ultra-high temperature fatigue testing equipment according to claim 1, characterized in that, The loading units (112) are one or more and are evenly distributed on the connecting plate (111) to provide a stable dynamic load.

3. The large-size expansion joint ultra-high temperature fatigue testing equipment according to claim 1, characterized in that, The connecting plate (111) moves vertically along the guide mechanism (12) to ensure the stability and accuracy of the loading process.

4. The large-size expansion joint ultra-high temperature fatigue testing equipment according to claim 1, characterized in that, The heating unit (24) can be one or more, and can be controlled independently or in concert.

5. The large-size expansion joint ultra-high temperature fatigue testing equipment according to claim 1, characterized in that, The forced water cooling jacket (33) is rigidly connected to the connecting plate (111), and the temperature difference between the inlet and outlet of the cooling water is ≤15℃, which is used to block the heat conduction from the high temperature tie rod (141) to the actuator (11).

6. The large-size expansion joint ultra-high temperature fatigue testing equipment according to claim 1, characterized in that: The bottom of the expansion joint is fixed to the circulating water cooling plate (32) by a double-headed water-cooled flange (31), and the middle part is connected to the high-temperature tie rod by a height-adjustable anti-loosening sleeve. The reciprocating motion of the actuator (11) drives the high-temperature tie rod (141) to achieve axial fatigue loading on the expansion joint.

7. The large-size expansion joint ultra-high temperature fatigue testing equipment according to claim 1, characterized in that, The heating system operates according to the following steps: S1. Close the low-temperature heating chamber, heat the expansion joint to 300℃ and maintain the temperature; S2. Start the pressurization device to fill the expansion joint with a protective atmosphere, and ensure that the gas pressure fluctuation is ≤10% of the set value. 8.S3. Start the high-temperature heating chamber and heat to the test temperature; S4. After the temperature stabilizes, open the low-temperature heating chamber through the horizontal opening and closing mechanism; S5. The high-temperature heating chamber is lowered to the working position via a vertical lifting mechanism; S6. The expansion joint is heated from 300°C to the test temperature within 5 minutes, spanning the sensitization temperature range of 450~600°C; S7. Conduct fatigue tests at a constant temperature during the test.

9. The large-size expansion joint ultra-high temperature fatigue testing equipment according to claim 7, characterized in that, The test temperature is 800~1000℃.

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