High temperature fatigue test device of nested induction-resistance composite heating

Abstract

The utility model discloses a nested inductive-resistance composite heating's high temperature fatigue test device relates to high temperature fatigue test device technical field, including sample passageway pipe, inner layer resistance heating area, high frequency induction heating layer and thermal expansion compensation structure, and inner layer resistance heating area includes the resistance heating band of strip distribution, and the corrugated compensation groove for absorbing its radial thermal expansion deformation is set up on resistance heating band, and high frequency induction heating layer includes high frequency induction coil, and thermal expansion compensation structure includes at least one setting in the outer layer ceramic locating ring between inner layer resistance heating area and high frequency induction heating layer, the utility model discloses the resistance and induction coil combination mode heating can take into account the heating rate and temperature uniformity, and adopts ceramic locating ring and corrugated compensation groove and cooperates the control thermal expansion gap of heat.

Description

Technical Field

[0001] This utility model relates to the technical field of high-temperature fatigue testing devices, and in particular to a high-temperature fatigue testing device with nested induction-resistance composite heating. Background Technology

[0002] High-temperature fatigue testing machines are core equipment for evaluating the mechanical properties of materials under high temperature and alternating loads, and have important applications in aerospace, energy and power, and new energy vehicles.

[0003] Currently, mainstream high-temperature fatigue testing machines mainly employ two heating methods: resistance heating and induction heating. Resistance heating heats the sample by generating Joule heat through the flow of current through a resistive element. Its advantage is good temperature control uniformity, but its disadvantage is a very low heating rate and low testing efficiency. Induction heating utilizes a high-frequency alternating magnetic field to generate eddy currents and heat the metal sample. Its advantage is an extremely fast heating rate, but its disadvantage is a large temperature difference between the sample surface and core, i.e., a large temperature gradient, leading to an uneven temperature field and seriously affecting the accuracy and reliability of the test data.

[0004] To combine the advantages of both, some technical solutions attempt to simply wrap the induction coil and the resistance heating element together. However, due to the significant difference in the coefficients of thermal expansion between the induction coil and the resistance element, the structure is prone to deformation under high-temperature cycling, which can cause the induction coil to come into contact with other components, leading to short circuit faults. This results in poor equipment reliability and makes it difficult to meet the needs of complex and long-term testing.

[0005] Therefore, existing technologies face the following pressing problems in heating control for high-temperature fatigue testing:

[0006] 1) A single heating method cannot simultaneously achieve both heating rate and temperature uniformity;

[0007] 2) Simple composite heating methods are prone to short circuits due to thermal expansion mismatch, resulting in low reliability. Utility Model Content

[0008] This invention aims to solve the technical problems existing in the prior art. To this end, this invention proposes a nested induction-resistance composite heating high-temperature fatigue testing device, which uses a combination of resistance and induction coil heating to balance heating rate and temperature uniformity, and uses a ceramic positioning ring and a corrugated compensation groove to control the thermal expansion gap.

[0009] The high-temperature fatigue testing device with nested induction-resistance composite heating according to a first aspect embodiment of the present invention includes:

[0010] Sample channel tube;

[0011] An inner resistance heating zone is coaxially disposed outside the sample channel tube. The inner resistance heating zone includes strip-shaped resistance heating strips, and the resistance heating strips are provided with wavy compensation grooves for absorbing their radial thermal expansion deformation.

[0012] A high-frequency induction heating layer is coaxially disposed outside the inner layer resistance heating region, and the high-frequency induction heating layer includes a high-frequency induction coil.

[0013] The thermal expansion compensation structure includes at least one outer ceramic positioning ring disposed between the inner resistance heating zone and the high-frequency induction heating layer to maintain the distance between them.

[0014] In some embodiments, an inner ceramic positioning ring is further provided between the sample channel tube and the inner resistance heating zone, wherein the inner ceramic positioning ring and the outer ceramic positioning ring together constitute a double-layer positioning structure.

[0015] In some embodiments, both the inner ceramic positioning ring and the outer ceramic positioning ring are three-lobed silicon nitride ceramic rings composed of at least three fan-shaped rings evenly distributed circumferentially.

[0016] In some embodiments, the resistance heating band is made of molybdenum disilicide material, and the high-frequency induction coil is wound from a hollow copper tube.

[0017] In some embodiments, a nano-aerogel insulation layer is filled in the annular gap formed between the inner resistive heating region and the high-frequency induction heating layer.

[0018] In some embodiments, the nano-aerogel insulation layer is alumina nano-aerogel.

[0019] In some embodiments, a layer of reflective aluminum foil is further disposed between the outer side of the resistance heating strip and the inner side of the high-frequency induction coil.

[0020] In some embodiments, the corrugated compensation groove is formed on the side of the resistance heating band opposite to the sample channel tube.

[0021] In some embodiments, an outer protective layer is further included covering the high-frequency induction heating layer, the outer protective layer including a multi-layer heat insulation shell and a hydraulic water cooling jacket embedded in the heat insulation shell.

[0022] In some embodiments, the sample channel tube is a corundum ceramic tube.

[0023] The nested induction-resistance composite heating high-temperature fatigue testing device according to an embodiment of the present invention has at least the following features:

[0024] Beneficial effects:

[0025] This invention employs a coaxial nested design of induction heating and resistance heating. The outer induction coil achieves rapid heating (up to 800℃ / min), while the inner resistance band provides precise temperature compensation and uniform heating, ensuring temperature uniformity within ±5℃ in the test area. This simultaneously resolves the contradiction between the slow heating of traditional resistance heating and the uneven temperature distribution of induction heating, significantly improving experimental efficiency and data reliability.

[0026] This invention significantly improves the reliability and service life of the equipment. Addressing the core challenge of short circuits caused by thermal expansion in composite heating, this invention employs a dual dynamic thermal expansion compensation design: a ceramic positioning ring and a compensation groove. The double-layered, three-lobed ceramic positioning ring precisely and stably maintains a safe gap between the heating components; the wavy compensation groove on the back of the resistance band effectively absorbs its own thermal expansion deformation, reducing thermal stress. This design reduces thermal expansion gap fluctuations by 60%, increases the equipment's thermal cycle life by 5 times, and significantly reduces test failures caused by thermal deformation.

[0027] This invention significantly reduces the energy consumption of the equipment. By filling the space between the induction coil and the resistance band with a nano-aerogel insulation layer and adding reflective aluminum foil, radial heat conduction and radiation from the inner resistance band to the outer induction coil are effectively blocked. This highly efficient heat insulation design not only protects the induction coil and cooling system but also significantly reduces heat loss, resulting in a 35% reduction in the overall energy consumption of the device, meeting the requirements of energy conservation and environmental protection.

[0028] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0030] Figure 1 This is a cross-sectional view of a nested induction-resistance composite heating high-temperature fatigue testing device according to some embodiments of the present invention.

[0031] Figure 2 This is a front view of a high-temperature fatigue testing device with nested induction-resistance composite heating according to some embodiments of the present invention.

[0032] Figure label:

[0033] 1000-type high-temperature fatigue testing device with nested induction-resistance composite heating;

[0034] Sample channel tube 100;

[0035] Resistance heating element 200;

[0036] 300 high-frequency induction coil, 310 nano-aerogel heat insulation layer, 320 reflective aluminum foil, 330 outer protective layer, 341 heat insulation shell, 342 hydraulic water cooling jacket;

[0037] Outer ceramic positioning ring 400, inner ceramic positioning ring 410. Detailed Implementation

[0038] Reference Figure 1 and Figure 2 As shown, this utility model proposes a high-temperature fatigue testing device 1000 with nested induction-resistance composite heating, which aims to solve the technical problems in the prior art where it is difficult to balance heating rate and temperature uniformity, and composite heating structures are prone to short-circuit failure due to thermal expansion.

[0039] The overall structure of the device adopts a multi-layered coaxial nested design from the inside out, with clear layers and coordinated functions. From the inside out, it includes: a sample channel tube 100, an inner resistance heating zone, a middle high-frequency induction heating layer, and an outer protective layer 330.

[0040] The sample channel tube 100 is located at the very center of the apparatus. This sample channel tube 100 is preferably made of high-purity corundum ceramic (Al2O3), and its inner diameter can be designed from Φ25mm to Φ50mm, depending on the size of a typical fatigue specimen. Corundum ceramic is chosen as the material for the sample channel tube 100 based on its excellent high-temperature performance: it has an extremely high melting point, good chemical stability, and high-temperature mechanical strength. In high-temperature fatigue testing, the sample channel tube 100 not only guides and precisely positions the specimen, but more importantly, its high-temperature rigidity effectively resists and constrains any thermal deformation or torsion that may occur at high temperatures, thus ensuring the accurate application of the test load and providing the first layer of protection for the accuracy of the test data.

[0041] Secondly, adjacent to the outer side of the sample channel tube 100 is the inner resistance heating zone. This area is crucial for achieving high-precision and uniform temperature control; its main function is to provide a stable and uniform base temperature field for the sample through resistance Joule heating. This zone includes the inner ceramic positioning ring 410, the resistance heating band 200, and the reflective aluminum foil 320.

[0042] Specifically, the inner ceramic positioning ring 410 is directly fixed to the outer wall of the sample channel tube 100. This positioning ring can adopt a three-lobed fan-shaped structure, which is composed of three fan-shaped ring plates evenly distributed and spliced ​​around the circumference. This segmented design facilitates installation and can provide an expansion gap for itself during thermal cycling. The positioning ring is preferably made of silicon nitride (Si3N4) ceramic material with a thickness of 2mm. Silicon nitride ceramic has excellent thermal shock resistance, high strength, and excellent electrical insulation, making it an ideal high-temperature structural and insulating material. In the axial direction, multiple such positioning rings are evenly distributed at a spacing of 50mm, which together form a precise support skeleton. Its core function is to ensure that a constant annular gap of 1.0±0.1mm is formed between the subsequently installed resistance heating strip 200 and the outer wall of the sample channel tube 100. Precise control of this gap is crucial: if the gap is too small, a short circuit is likely to occur under thermal expansion; if the gap is too large, the heat transfer efficiency of resistance heating will be reduced.

[0043] The resistance heating strip 200 can be made of MoSi2 (molybdenum disilicide), and the strip can be a strip structure with a thickness of 1 mm and a length × width of 60 × 20 mm. MoSi2 is an excellent high-temperature heating element that can operate stably for a long time in an oxidizing atmosphere. These resistance strips are distributed in a circumferential strip shape and connected to the power supply in parallel. To eliminate cold zones between strips, a 10% to 15% overlap area is set between adjacent resistance strips. In this way, the entire circumferential inner wall forms a seamless and uniform heating surface, providing uniform heating to the sample through the Joule effect.

[0044] To address the significant thermal expansion of MoSi2 material at high temperatures, this invention innovatively incorporates a corrugated compensation groove on the back side of the resistance heating strip 200 (i.e., the side furthest from the sample channel tube 100). This corrugated compensation groove is radially oriented, with a width of 0.3 mm and a depth of 1.2 mm (greater than the thickness of the resistance strip), and is spaced 20 mm apart along the length of the resistance strip. When the resistance strip expands radially due to heat, the unique structure of these corrugated grooves allows for elastic deformation, acting like miniature springs. This effectively absorbs and buffers the stress generated by thermal expansion, significantly reducing the peak thermal stress within the resistance strip and preventing cracking or damage due to excessive stress. This is one of the key design features for achieving long-term stable operation of the device.

[0045] On the outermost side of this area, right next to the back of the resistance heating band 200, a layer of reflective aluminum foil 320 is laid. Utilizing the high reflectivity of the aluminum foil surface to thermal radiation, it can effectively reflect most of the heat radiated outward from the resistance band back into the heating zone, thereby improving energy utilization and reducing the thermal impact on the external induction coil.

[0046] Secondly, there is the intermediate high-frequency induction heating layer located outside the inner resistance heating zone. This region is the core for achieving rapid heating; its main function is to directly generate eddy current heat inside the sample through the principle of electromagnetic induction, thereby achieving an extremely high heating rate. This layer mainly includes an outer ceramic positioning ring 400, a high-frequency induction coil 300, and a nano-aerogel insulation layer 310 filling the space between them.

[0047] The outer ceramic positioning ring 400 has a similar structure to the inner ring, also employing a three-lobed Si3N4 fan-shaped ring structure with reinforcing ribs, but its thickness is increased to 5mm to provide stronger support and positioning capabilities. These outer positioning rings are also evenly distributed with an axial spacing of 50mm. Their inner diameter precisely matches the outermost diameter of the inner resistance heating zone, while their outer diameter provides a positioning reference for the high-frequency induction coil 300. The inner and outer ceramic positioning rings work together to form a bidirectional, dual-layer precision spacing control system.

[0048] The high-frequency induction coil 300 is the power source for rapid heating. It is made of a hollow copper tube with an outer diameter of Φ6mm, spirally wound. The hollow design allows cooling water to circulate inside the tube, promptly removing heat generated by the coil's own resistance and external thermal radiation, preventing the coil from overheating and melting. The coil is connected to a 20-50kHz high-frequency power supply, generating a high-frequency alternating magnetic field that penetrates all layers and acts directly on the metal sample.

[0049] Between the inner resistance heating zone (specifically, the outer side of the reflective aluminum foil 320) and the high-frequency induction coil 300, there exists an annular gap defined by inner and outer ceramic positioning rings. In this embodiment, the width of this gap is 1.0–1.5 mm. To achieve efficient thermal insulation, this gap is completely filled with a nano-aerogel insulation layer 310. The nano-aerogel insulation layer 310 can be alumina nano-aerogel (Al2O3). Nano-aerogel is one of the solid materials with the lowest known thermal conductivity. Its filling here plays a crucial multiple roles: First, it effectively blocks the conductive and convective heat generated during the operation of the inner resistance zone from being transferred to the outer induction coil with its extremely low thermal conductivity, protecting the safety of the coil; second, as a porous medium, it can also effectively block the interference of high-pressure airflow (under certain experimental conditions) on the induction coil; finally, it, together with the aforementioned reflective aluminum foil 320, constitutes a highly efficient composite thermal insulation system of "reflection + blocking".

[0050] Finally, the outermost layer of the device is the outer protective layer 330. The main functions of this layer are safety protection, final thermal insulation, and auxiliary cooling. It mainly consists of a multi-layered thermal insulation shell 341 and a hydraulic water-cooled jacket 342. The multi-layered thermal insulation shell 341, from the inside out, includes: a 0.1mm thick molybdenum foil reflective layer to reflect the small amount of heat radiation leaking from the induction coil; a 20mm thick Al2O3 fiber felt in the middle, serving as the main volumetric thermal insulation material; and an outermost 304 stainless steel shell, providing structural support, corrosion resistance, and final electromagnetic shielding. This multi-layered thermal insulation system effectively isolates the internal high temperatures of thousands of degrees, keeping the surface temperature of the shell within a safe range. To further enhance the cooling effect, a hydraulic water-cooled jacket 342 with spiral flow channels is directly machined or embedded in the inner wall of the stainless steel shell. Cooling water flows through it, providing secondary cooling for the induction coil and effectively controlling the temperature of the entire heating furnace, while maintaining the normal operating temperature of components such as the hydraulic actuator connected to the testing machine.

[0051] In summary, this invention organically combines resistance heating and induction rapid heating technologies through the aforementioned precise nested structural design. During operation, the high-frequency induction coil 300 is first activated, causing the sample temperature to rapidly rise to near the target temperature within a short time (e.g., at a rate of 800℃ / min). Subsequently, the power of the inner MoSi2 resistance heating strip 200 is precisely controlled to fine-tune and compensate the temperature field, thereby achieving high-precision uniform temperature control of ±5℃. Simultaneously, the synergistic design of the "bidirectional three-lobed ceramic positioning ring" and the "wave-shaped compensation groove on the back of the resistance strip" cleverly solves the problem of thermal expansion mismatch under complex thermal environments, ensuring the structural stability and long lifespan of the device. Furthermore, the composite thermal insulation design of "nano-aerogel + reflective aluminum foil 320" greatly improves energy efficiency. Ultimately, this invention achieves the technical effects of rapid heating, uniform temperature control, high reliability, and low energy consumption.

[0052] Examples of the embodiments described above are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described above with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0053] In the description of this utility model, it should be understood that the directional descriptions, such as up, down, front, back, left, right, etc., indicate the directional or positional relationship based on the directional or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0054] In the description of this utility model, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. If "first" or "second" is used in the description, it is only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0055] In the description of this utility model, unless otherwise explicitly defined, terms such as "setting," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this utility model in conjunction with the specific content of the technical solution.

[0056] The embodiments of the present utility model have been described in detail above with reference to the accompanying drawings. However, the present utility model is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present utility model.

Claims

1. A high temperature fatigue testing apparatus of nested induction-resistance composite heating, characterized by, include: Sample channel tube; An inner resistance heating zone is coaxially disposed outside the sample channel tube. The inner resistance heating zone includes strip-shaped resistance heating strips, and the resistance heating strips are provided with wavy compensation grooves for absorbing their radial thermal expansion deformation. A high-frequency induction heating layer is coaxially disposed outside the inner layer resistance heating region, and the high-frequency induction heating layer includes a high-frequency induction coil. The thermal expansion compensation structure includes at least one outer ceramic positioning ring disposed between the inner resistance heating zone and the high-frequency induction heating layer to maintain the distance between them.

2. The nested induction-resistive composite heating high-temperature fatigue testing device according to claim 1, characterized in that, It also includes an inner ceramic positioning ring disposed between the sample channel tube and the inner resistance heating zone, the inner ceramic positioning ring and the outer ceramic positioning ring together forming a double-layer positioning structure.

3. The nested induction-resistive composite heating high-temperature fatigue testing apparatus according to claim 2, wherein Both the inner ceramic positioning ring and the outer ceramic positioning ring are three-lobed silicon nitride ceramic rings composed of at least three fan-shaped rings evenly distributed circumferentially.

4. The nested induction-resistive composite heating high-temperature fatigue testing device of claim 1, wherein, The resistance heating strip is made of molybdenum disilicide material, and the high-frequency induction coil is wound from a hollow copper tube.

5. The nested induction-resistive composite heating high-temperature fatigue testing apparatus of claim 1, wherein, A nano-aerogel insulation layer is filled in the annular gap formed between the inner resistive heating zone and the high-frequency induction heating layer.

6. The nested induction-resistive composite heating high-temperature fatigue testing device of claim 5, wherein, The nano-aerogel insulation layer is alumina nano-aerogel.

7. The nested induction-resistive composite heating high-temperature fatigue testing device of claim 1, wherein, A layer of reflective aluminum foil is also provided between the outer side of the resistance heating strip and the inner side of the high-frequency induction coil.

8. The nested induction-resistive composite heating high-temperature fatigue testing device of claim 1, wherein, The wavy compensation groove is located on the side of the resistance heating band that is away from the sample channel tube.

9. The nested induction-resistive composite heating high-temperature fatigue testing device of claim 1, wherein, It also includes an outer protective layer covering the high-frequency induction heating layer, the outer protective layer comprising a multi-layer heat insulation shell and a hydraulic water cooling jacket embedded in the heat insulation shell.

10. The nested induction-resistive composite heating high-temperature fatigue testing device of claim 1, wherein, The sample channel tube is a corundum ceramic tube.

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