A heating device for high temperature hopkinson bar experiment

Abstract

The application discloses a heating device for high-temperature Hopkinson bar experiment and belongs to the technical field of material mechanical property research. The preheating cavity is provided with an opening cover and two openings for the incident rod and the transmission rod of the Hopkinson bar experiment device to pass through; the mixed heating cavity is communicated with the preheating cavity; the air outlet of the speed-regulating fan is communicated with the mixed heating cavity through the air supply inlet arranged on the mixed heating cavity; the electric heater is arranged in the mixed heating cavity; and the controller is signal-connected with the electric heater, the speed-regulating fan and the temperature measuring element for measuring the temperature of the sample to be tested. The heating device can stably heat the non-conductive nonmetallic material or the sample to be tested with poor conductivity and avoid obvious temperature gradient in the sample to be tested.

Description

Technical Field

[0001] This invention belongs to the field of material mechanical property research technology, specifically relating to a heating device for high-temperature Hopkinson bar experiments. Background Technology

[0002] The split Hopkinson bar test technique is the most important and reliable experimental method for studying the mechanical properties of materials under high strain rates, and it is an important component of explosion and shock dynamics experimental techniques. As research and practical needs continue to expand, the service performance of materials under extreme conditions also requires further investigation and verification. Therefore, based on the Hopkinson bar test technique, researchers have designed various supplementary devices to meet experimental requirements under different conditions. For example, to study the dynamic mechanical behavior of materials under high-temperature conditions, different heating methods are often selected based on the properties of different materials. Currently, these can be mainly divided into heat conduction heating and electromagnetic induction heating.

[0003] For conductive materials, such as metals, electromagnetic induction is typically used to heat the sample. The alternating current generated by the induction heating power supply passes through an inductor to produce an alternating magnetic field. The sample is placed within this field, generating an alternating current within it. Eddy currents cause the atoms within the sample to move at high speeds and randomly, colliding and rubbing against each other to generate heat, thus heating the sample. This method is highly efficient but cannot be used to heat non-conductive non-metallic materials. For non-conductive or poorly conductive materials, such as fiberglass and soil, heating wires are typically fixed around the sample, utilizing thermal radiation to reach the desired temperature. However, this method does not ensure uniform temperature distribution within the sample.

[0004] In addition, other equipment is used to preheat the test sample. When the required temperature is reached, the test sample is quickly fixed in the clamping position. This method involves heating the test sample before the test. When the test sample comes into contact with the incident rod and transmission rod at the ambient temperature, heat transfer will occur, resulting in a significant temperature gradient inside the test sample (i.e., uneven temperature inside the test sample). Summary of the Invention

[0005] In view of this, the present invention provides a heating device for high-temperature Hopkinson bar experiments, which can stably heat non-conductive non-metallic materials or test samples with poor conductivity, and avoid the appearance of obvious temperature gradients inside the test sample.

[0006] The present invention adopts the following technical solution:

[0007] A heating device for high-temperature Hopkinson bar experiments includes a housing, a speed-regulating fan, an electric heater, and a controller;

[0008] The housing has a preheating chamber and a mixing chamber. The preheating chamber has a cover and two through circular openings on its two opposite sides for the incident rod and transmission rod of the Hopkinson rod test apparatus to pass through from the opposite sides. The test sample can be sandwiched between the incident rod and the transmission rod that pass through the preheating chamber. When the Hopkinson rod test apparatus applies an impact load to the test sample through the incident rod, the incident rod and the transmission rod can move axially in the circular openings. The mixing chamber is connected to the preheating chamber.

[0009] The outlet of the variable speed fan is connected to the mixing chamber through the air inlet provided on the mixing chamber;

[0010] The electric heater is disposed inside the mixing chamber;

[0011] The controller is signal-connected to the electric heater, the speed-regulating fan, and the temperature measuring element for measuring the temperature of the test sample, and is used to adjust the heating power of the electric heater and the speed of the speed-regulating fan according to the collected temperature of the test sample.

[0012] Furthermore, the preheating chamber is located above the mixing chamber;

[0013] The air inlet on the mixing chamber is located below the electric heater.

[0014] Furthermore, the test sample is misaligned with the air inlet on the mixing chamber.

[0015] Furthermore, temperature measuring elements connected to the controller signal are provided at the positions corresponding to the incident rod and the transmission rod in the circular opening of the preheating cavity, on the inner wall surface of the preheating cavity above the test sample, and on the incident rod and the transmission rod extending into the preheating cavity.

[0016] Furthermore, the distance between the two circular openings of the preheating cavity and the test sample is more than 3 cm.

[0017] Furthermore, the inner walls of the preheating chamber and the mixing chamber are provided with thermal insulation material.

[0018] Furthermore, the electric heater is an electric heating wire.

[0019] Furthermore, the temperature sensing element is a thermocouple.

[0020] Furthermore, it also includes an incident rod bracket and a transmission rod bracket disposed outside the housing to support the incident rod and the transmission rod.

[0021] Beneficial effects:

[0022] 1. The chamber has a preheating chamber and a mixing chamber. The preheating chamber has a cover and two through circular openings on its two opposite sides for the insertion of the incident rod and the transmission rod of the Hopkinson rod test apparatus. The test sample can be sandwiched between the incident rod and the transmission rod that penetrate the preheating chamber. When the Hopkinson rod test apparatus applies an impact load to the test sample through the incident rod, the incident rod and the transmission rod can move axially within the circular openings. The mixing chamber is connected to the preheating chamber. The outlet of the variable speed fan is connected to the mixing chamber through the air inlet provided on the mixing chamber. The electric heater is located inside the mixing chamber. The controller is connected to the electric heater, the variable speed fan, and the temperature measuring element used to measure the temperature of the test sample.

[0023] In this way, the variable-speed fan can direct the air from the mixing chamber heated by the electric heater to the preheating chamber and out from both ends of the preheating chamber, thereby heating the test sample in the preheating chamber. That is, the device uses convective heat transfer, which has a higher heat transfer efficiency than thermal radiation, as the heating method. The device uses a variable-speed fan to disturb the hot air to maintain a constant temperature in the preheating chamber and the mixing chamber. At the same time, in order to ensure the stability of the temperature field and keep the test sample at the set temperature, the device can use a temperature sensing element to monitor the temperature of the test sample in real time and transmit the temperature information to the controller to adjust the speed of the variable-speed fan and the thermal power of the electric heater. This achieves stable heating of non-conductive non-metallic materials or test samples with poor conductivity. Furthermore, the incident rod and transmission rod extending into the preheating chamber are heated together with the test sample, avoiding a significant temperature gradient inside the test sample.

[0024] 2. The preheating chamber is located above the mixing chamber; the air inlet on the mixing chamber is located below the electric heater. In this way, hot air can flow from bottom to top, thereby achieving a more uniform heating effect on the test sample in the preheating chamber.

[0025] 3. The air inlets on the test sample and the mixing chamber are offset. This allows for more thorough mixing between the preheating chamber and the mixing chamber compared to a variable-speed fan blowing hot air directly onto the test sample, resulting in a smaller temperature gradient inside the test sample.

[0026] 4. Temperature measuring elements connected to the controller signal are installed at the circular opening of the preheating chamber corresponding to the incident rod and the transmission rod, on the inner wall surface of the preheating chamber above the test sample, and on the incident rod and the transmission rod extending into the preheating chamber.

[0027] In this way, the power of the electric heater and the speed of the variable speed fan can be adjusted based on more comprehensive and reliable real-time monitoring of the temperature around the test sample, thereby keeping the temperature of the test sample stable and creating a smaller temperature gradient inside the test sample.

[0028] 5. The distance between the two openings of the preheating chamber and the test sample is more than 3cm, which can make the temperature gradient inside the test sample smaller.

[0029] 6. The inner walls of the preheating chamber and the mixing chamber are lined with thermal insulation material, which can further reduce the temperature gradient inside the test sample. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the heating device for high-temperature Hopkinson bar experiments provided by the present invention in use.

[0031] Figure 2 yes Figure 1 Schematic diagram of the internal structure of the intermediate mixing chamber and the preheating chamber;

[0032] Figure 3 yes Figure 1 A schematic diagram of the mechanism connecting the medium-speed regulating fan to the mixing chamber;

[0033] Figure 4 This is a schematic diagram of the temperature control principle of the heating device for high-temperature Hopkinson bar experiments provided by the present invention;

[0034] Among them, 1-incident rod, 2-incident rod support, 3-speed regulating fan, 4-mixing box, 5-controller, 6-transmission rod support, 7-transmission rod, 8-preheating box, 9-first thermocouple, 10-test sample, 11-second thermocouple, 12-third thermocouple, 13-electric heater. Detailed Implementation

[0035] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0036] Reference Figures 1-4 A heating device for high-temperature Hopkinson bar experiments, used for strain rates of 1000 s⁻¹. -1 The above describes a uniaxial compression test at temperatures ranging from 85 to 200°C. Its structural components include a housing, a speed-regulating fan 3, an electric heater 13, and a controller 5.

[0037] The chamber has a preheating chamber and a mixing chamber. The preheating chamber has a cover and a through circular opening on opposite sides, allowing the incident rod 1 and the transmission rod 7 of the Hopkinson rod experimental device to pass through from opposite sides. After opening the cover, the test sample 10 can be clamped between the incident rod 1 and the transmission rod 7 that pass through the circular opening of the preheating chamber. After the test sample 10 is clamped, when the Hopkinson rod experimental device applies an impact load to the test sample 10 through the incident rod 1, the incident rod 1 and the transmission rod 7 can move axially in the circular opening, that is, the diameter of the circular opening is larger than that of the incident rod 1 and the transmission rod 7. In this embodiment, the diameters of the incident rod 1 and the transmission rod 7 are 18 mm, and the diameter of the circular opening is 5-10 mm larger than the diameters of the incident rod 1 and the transmission rod 7. The mixing chamber is connected to the preheating chamber. The air outlet of the speed-regulating fan 3 is connected to the mixing chamber through the air inlet provided on the mixing chamber. The electric heater 13 is disposed in the mixing chamber. The controller 5 is connected to the electric heater 13, the speed-regulating fan 3, and the temperature measuring element that can measure the temperature of the test sample 10. The controller 5 is used to adjust the heating power of the electric heater 13 and the speed of the speed-regulating fan 3 according to the collected temperature of the test sample 10.

[0038] Thus, the variable-speed fan 3 allows the air in the mixing chamber heated by the electric heater 13 to flow into the preheating chamber and out from both ends of the circular opening of the preheating chamber (the circular opening allows the incident rod 1 and the transmission rod 7 to enter the preheating chamber, and also allows the hot air to flow out of the preheating chamber), thereby heating the test sample 10 in the preheating chamber. That is, the device uses convection heat transfer, which has a higher heat transfer efficiency than thermal radiation, as the heating method. The device uses the variable-speed fan 3 to disturb the hot air to maintain a constant temperature in the preheating chamber and the mixing chamber. At the same time, in order to ensure the preheating chamber and the mixing chamber... The stability of the temperature field in the cavity ensures that the test sample 10 is kept at the set temperature. The device uses a temperature sensing element to monitor the temperature of the test sample 10 in real time and transmits the temperature information to the controller 5 to adjust the speed of the speed regulating fan 3 and the heat power of the electric heater 13. This achieves stable heating of the non-conductive non-metallic material or the test sample 10 with poor conductivity. Furthermore, the incident rod 1 and the transmission rod 7 extending into the preheating cavity are heated together with the test sample 10, avoiding a significant temperature gradient inside the test sample 10.

[0039] As an improvement, the preheating chamber is positioned above the mixing chamber, and the air inlet of the mixing chamber is positioned below the electric heater 13. This allows hot air to flow from bottom to top, achieving a more uniform heating effect on the test sample 10 in the preheating chamber. Furthermore, the test sample 10 and the air inlet of the mixing chamber are offset, meaning the air inlet of the mixing chamber does not directly face the test sample 10. This allows for more thorough mixing between the preheating chamber and the mixing chamber compared to the variable-speed fan 3 directly blowing hot air onto the test sample, resulting in a more uniform internal temperature (i.e., a smaller temperature gradient) for the test sample 10.

[0040] Furthermore, in this embodiment, not only are temperature sensing elements provided on the test sample 10, but at least five temperature sensing elements are also provided at other locations within the preheating chamber. Specifically, temperature sensing elements connected to the controller 5 are provided at the positions corresponding to the incident rod 1 and the transmission rod 7 at the circular opening of the preheating chamber, on the inner wall surface of the preheating chamber above the test sample 10, and on the incident rod 1 and the transmission rod 7 extending into the preheating chamber. This allows for more comprehensive and reliable real-time monitoring of the temperature surrounding the test sample 10, enabling the adjustment of the power of the electric heater 13 and the speed of the speed-regulating fan 3, thereby maintaining a stable temperature for the test sample 10 and ensuring a small temperature gradient inside the test sample 10.

[0041] As a further improvement, after the test sample 10 is sandwiched between the incident rod 1 and the transmission rod 7 that penetrate the circular opening preheating cavity, the distance between the two circular openings of the preheating cavity and the test sample 10 is more than 3cm. This distance can make the temperature gradient inside the test sample 10 smaller.

[0042] Specifically, in this embodiment, the electric heater 13 is an electric heating wire; the temperature sensing element is a Class I precision nickel-chromium constantan thermocouple with a measurement range of -200 to 900°C. Nickel-chromium constantan thermocouples have extremely high sensitivity, are inexpensive, have strong oxidation resistance, and are suitable for long-term operation in high-speed airflow. (Refer to...) Figure 1 and Figure 2 The thermocouple positioned above the test sample 10 is the first thermocouple 9, the thermocouple positioned on the test sample 10 is the second thermocouple, and the thermocouple positioned on the transmission rod 7 is the third thermocouple 12. Additionally, refer to... Figure 1 In the heating device used for the high-temperature Hopkinson rod experiment, an incident rod support 2 located outside the chamber is provided to support the incident rod 1, and a transmission rod support 6 located outside the chamber is provided to support the transmission rod 7.

[0043] More specifically, in this embodiment, the test sample 10 has a diameter of 8 mm and a thickness of 4 mm. The enclosure includes a mixing chamber 4 and a preheating chamber 8 with interconnected chambers. The chamber of the mixing chamber 4 is the aforementioned mixing cavity, and the chamber of the preheating chamber 8 is the aforementioned preheating cavity. Furthermore, the mixing chamber 4 is a rectangular box with a length × width × height × thickness of 200 mm × 100 mm × 70 mm × 10 mm, and the preheating chamber 8 is a rectangular box with a length × width × height × thickness of 100 mm × 45 mm × 40 mm × 10 mm. In addition, thermal insulation material is provided on the inner walls of the preheating cavity and the mixing cavity, thereby further reducing the temperature gradient inside the test sample 10.

[0044] This heating device for high-temperature Hopkinson bar experiments can be used to test non-conductive or poorly conductive materials such as fiberglass, soil, and insulating polymers at strain rates up to 1000 s⁻¹. -1 The above refers to uniaxial compression tests conducted at temperatures ranging from 85 to 200°C.

[0045] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A heating device for high-temperature Hopkinson's rod experiments, characterized in that, Includes housing, speed-regulating fan, electric heater, and controller; The housing has a preheating chamber and a mixing chamber. The preheating chamber is located above the mixing chamber and has a cover. Two opposite sides of the preheating chamber have through-hole circular openings for the incident rod and transmission rod of the Hopkinson rod experimental device to pass through from opposite sides. The test sample can be sandwiched between the incident rod and the transmission rod that pass through the preheating chamber. The distance between the two circular openings of the preheating chamber and the test sample is greater than 3 cm. When the Hopkinson rod experimental device applies an impact load to the test sample through the incident rod, the incident rod and the transmission rod can move axially within the circular openings. The mixing chamber is connected to the preheating chamber. The outlet of the variable speed fan is connected to the mixing chamber through the air inlet provided on the mixing chamber. The air inlet on the mixing chamber is located below the electric heater. The test sample is offset from the air inlet on the mixing chamber. The electric heater is disposed inside the mixing chamber; Temperature measuring elements connected to the controller signal are provided at the positions corresponding to the incident rod and the transmission rod in the circular opening of the preheating cavity, the inner wall surface of the preheating cavity above the test sample, and the incident rod and the transmission rod extending into the preheating cavity. The controller is signal-connected to the electric heater, the speed-regulating fan, and the temperature measuring element for measuring the temperature of the test sample, and is used to adjust the heating power of the electric heater and the speed of the speed-regulating fan according to the collected temperature of the test sample.

2. The heating device for high-temperature Hopkinson bar experiments according to claim 1, characterized in that, The inner walls of the preheating chamber and the mixing chamber are provided with thermal insulation material.

3. The heating device for high-temperature Hopkinson's rod experiments according to claim 1, characterized in that, The electric heater is an electric heating wire.

4. The heating device for high-temperature Hopkinson's rod experiments according to claim 1, characterized in that, The temperature sensing element is a thermocouple.

5. A heating device for high-temperature Hopkinson's rod experiments according to claim 1, characterized in that, It also includes an incident rod bracket and a transmission rod bracket disposed outside the housing to support the incident rod and the transmission rod.

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