Friction sensitivity test device under thermal coupling

Abstract

The application provides a friction sensitivity testing device under thermal coupling, and relates to the technical field of testing equipment. The testing device comprises a temperature control module, an electrostatic conducting workbench, a friction sensitivity device and a data acquisition and processing module. The temperature control module is used for controlling the sample temperature in real time in the friction sensitivity test, the electrostatic conducting workbench is used for quickly conducting away the static electricity accumulated on the surface of the sample and the static electricity on the operator, the friction sensitivity device is used for testing the friction sensitivity under the set condition, and the data acquisition and processing module is used for real-time monitoring of the rotating speed and transient power compensation. The application has the advantages of accurate data, high safety protection level, expandable temperature range, and obtainable friction sensitivity data under the coupling of heat and mechanical friction force. The application can be widely applied to the research, production, process optimization, storage and safe use of energetic materials, and is especially suitable for testing of the energetic materials sensitive to static electricity.

Description

Technical Field

[0001] This disclosure relates to the field of testing equipment technology, and in particular to a friction sensitivity testing device under thermal coupling. Background Technology

[0002] Energetic materials typically refer to gunpowder, explosives, and propellants. They are fundamental to national defense development and are essential components of various types of advanced aircraft and warheads. Friction sensitivity is a crucial parameter for the safety and susceptibility of energetic materials. For decades, friction sensitivity testing has been a common method for assessing the sensitivity of energetic materials to mechanical friction, and this testing method is widely found in numerous standards.

[0003] Traditional friction sensitivity tests are conducted at room temperature without specifying the temperature requirements for the sample. This method leads to biases and limitations in the data obtained. First, even within the same laboratory, room temperature varies at different times, resulting in discrepancies in results obtained from multiple tests of the same sample. Second, real-world operating conditions include high-temperature environments, where the friction sensitivity of the sample changes significantly, differing greatly from data obtained at room temperature.

[0004] There is a certain deviation between the preset motor power and the actual required power in traditional friction sensitivity testers, and this deviation will change to varying degrees with the change of counterweights, resulting in excessive error in the test results.

[0005] Furthermore, energetic materials are susceptible to explosions due to electrostatic discharge on the sample surface, electrostatic discharge generated during contact separation during sampling, and electrostatic discharge from the human body. Such electrostatic effects are difficult to identify and unavoidable, and once they occur, they can cause significant loss of life and property.

[0006] Therefore, there is an urgent need to develop a friction sensitivity testing device under thermo-mechanical coupling, which can be used to test friction sensitivity under different temperature conditions, eliminate errors in the traditional testing process, reduce the risks in the traditional testing process, and obtain friction sensitivity data under the coupling of heat and mechanical friction. Summary of the Invention

[0007] To address the above problems, this invention provides a friction sensitivity testing device under thermo-coupling, which can solve the problems of low test data accuracy, temperature limitation, and dangerous operation process, and can also obtain friction sensitivity data under the coupling effect of heat and mechanical friction.

[0008] The technical solution is as follows:

[0009] A friction sensitivity testing device under thermo-coupling effect is characterized by comprising a temperature control module, an electrostatic conductive worktable, a friction sensitivity device, and a data acquisition and processing module.

[0010] The temperature control module includes a heating plate, a heat insulation plate, a temperature measuring device, and a fixed bracket.

[0011] The heating plate is made of ceramic material, preferably MCH metal ceramic heating plate, which has high heat density and fast heating rate. Using this heating material, localized and rapid heating can be achieved.

[0012] The heat insulation plate is made of a polymer material with low thermal conductivity, preferably PEEK. The ceramic heating plate is placed on the friction device, which is made of metal. Without the PEEK heat insulation plate, a large amount of heat would be conducted away through the metal during the heating process, resulting in extremely low heating efficiency and making it impossible to conduct the experiment normally.

[0013] To further explain, the PEEK insulation board plays a crucial role in the experiment. Since the MCH ceramic heating plate is placed on the friction device, which is made of stainless steel, a significant amount of heat is conducted away through the friction device during heating. Without the PEEK insulation board, the maximum temperature during 20 minutes of full-power heating would not exceed 100°C, resulting in extremely low heating efficiency, making the experiment unusable. The use of the PEEK insulation board leverages its low thermal conductivity and high-temperature resistance. Furthermore, when heat is transferred between materials with different thermal conductivity, heat flow stagnation occurs. Utilizing this characteristic, we can not only reduce heat loss by approximately 80% but also ensure stable heat flow, resulting in minimal temperature curve fluctuations and excellent temperature control.

[0014] Furthermore, the ceramic heating plate uses 24VDC power, with a maximum current of 6A and a full-power energy consumption of less than 120W. Due to the high heat density of the ceramic heating plate and the insulation effect of the PEEK insulation board, it allows for heating using a low-voltage, low-power 24VDC power supply. Therefore, heating from room temperature to 200℃ takes only 2-3 minutes, with a stabilization process taking only 2 minutes and a fluctuation range of ≤±0.1℃. Traditional electric heating, on the other hand, requires at least 30 minutes or longer and 220VAC power. The friction device may cause leakage due to cable dragging or compression during operation; 24VDC is a safe voltage, preventing the hazards caused by leakage.

[0015] The temperature sensor is preferably a surface-mount platinum resistance temperature sensor, which has high testing accuracy and good stability.

[0016] The sensor heat flow suppression disk has two U-shaped slots with their tops intersecting vertically, into which a temperature sensor can be inserted for temperature measurement.

[0017] The sensor heat flow suppression disk is made of metal material and its inner surface is covered with a Teflon film layer, which can prevent heat loss through the surface of the sensor heat flow suppression disk, ensure the accuracy of temperature measurement, and reduce temperature fluctuations during the measurement process.

[0018] The sensor heat flow suppression disk is sandblasted with 30-50 mesh diamond abrasive to form regular particles on its inner surface, ensuring that the Teflon film layer is uniformly and firmly attached to its inner surface.

[0019] The sensor heat flow suppression plate is formed by melting Teflon material on the inner surface of a sandblasted metal material at 350°C, then extruding it using an aluminum alloy mold, and demolding it after cooling to form a Teflon film layer with a thickness of 0.5 mm.

[0020] To further explain, if the heat flow suppression disk of the sensor is made of non-metallic material, it will deform after prolonged heating, causing the temperature control sensor to be unable to make stable and sufficient contact with the heating plate, and the sample sensor to be unable to make stable and sufficient contact with the surface of the ceramic plate used in the experiment, resulting in errors in temperature control and measurement results.

[0021] If the inner wall of the sensor's heat flow suppression disk does not have a Teflon film layer for heat flow suppression, a large amount of heat will be lost from the metal surface of the sensor's heat flow suppression disk, causing large fluctuations in the experimental temperature and affecting the test results.

[0022] The temperature measuring device includes a non-contact infrared temperature sensor with its probe facing the sample position, which can perform auxiliary measurement of the sample temperature in real time. Combined with the test data of the patch-type platinum resistance temperature sensor, multiple temperature measurement methods are used to reduce the deviation of temperature measurement.

[0023] The fixed bracket can fix the temperature measuring device, heating plate and heat insulation plate in sequence. During the test, the tray moves back and forth quickly under the drive of the stepper motor and eccentric wheel. The fixed bracket needs to fix the relevant components firmly and tightly to ensure that the two temperature sensors are in full and close contact with the heating plate and friction ceramic plate, so as to avoid temperature fluctuations caused by unstable contact.

[0024] The rubber layer on the surface of the electrostatic conductive workbench is embedded with copper contacts and grounding posts. The copper contacts are copper hemispheres embedded in the surface of the rubber layer with a diameter of 4mm. The grounding posts are connected to the copper hemispheres, with a length of 45mm and a diameter of 2mm. This combination structure is distributed at 100mm intervals on the workbench surface. All grounding posts are connected to the grounding plate to form a grounding network.

[0025] To further explain, the copper hemisphere exhibits excellent conductivity, rapidly dissipating static electricity accumulated on the sample surface, from the operator, and from the surrounding environment through the connected grounding post, with a grounding resistance of less than 4Ω. In contrast, while the rubber layer undergoes electrostatic discharge treatment and incorporates conductive materials during manufacturing, its high resistance, reaching the GΩ level, limits its electrostatic discharge effectiveness.

[0026] The data acquisition and processing module adds a real-time speed monitoring unit and a power transient compensation unit to the traditional motor drive. The monitoring interval is once every 5ms, and the compensation interval is once every 10ms. Upon detecting a deviation of the motor speed from the set value, the module immediately uses power transient compensation technology to perform pulse-to-point power correction, ensuring that the motor operates at its set speed during testing.

[0027] To further explain, during the friction test, the stepper motor drives the tray to reciprocate. The friction device starts to move, and the speed rises from 0 to a peak value, then drops to 0. The speed then increases in the opposite direction to reach a peak value, then drops to 0 and stops. This type of movement is reciprocating motion, and its trajectory is a sine curve.

[0028] To ensure the repeatability and accuracy of the test results, the width and height of the sine curve must remain consistent. However, during the experiment, it was found that when using weights exceeding 5 kg, the tray's moving speed slowed down, resulting in a wider sine curve and a lower height. Conversely, when using weights below 0.5 kg, the tray's moving speed increased, leading to a narrower sine curve and a wider height. These changes in the trajectory curve resulted in significant deviations in the test results and poorer repeatability of the experimental data, because the dynamic friction and compression effects acting on the sample changed significantly.

[0029] To address the aforementioned issues and ensure consistency between the real-time movement speed and trajectory curve of the pallet, the data acquisition and processing module incorporates a real-time rotation speed monitoring unit and a transient power compensation unit. This unit monitors the dynamic speed and uses transient power compensation technology to ensure that the width and height of the sinusoidal curve of the pallet's movement trajectory remain consistent.

[0030] Because the real-time speed monitoring unit and the power transient compensation unit have high monitoring accuracy, the compensation function can be activated at the same time as the power deviation is detected. The similarity between the corrected speed curve and the target curve can reach more than 95%.

[0031] The beneficial effects of the technical solution provided in this disclosure include at least the following:

[0032] 1. This invention couples heat and mechanical friction to act on the sample under test, enabling the acquisition of friction sensitivity data at any temperature from room temperature to 200°C. This significantly improves the repeatability and reproducibility of the test results. The output data is used to ensure the correct use and storage of energetic materials, prevent explosions, and ensure safe management. By coupling heat and mechanical friction to act on the sample under test, the test results can more accurately and comprehensively simulate real-world operating conditions, providing more important guidance for the performance characterization, formulation optimization, quality control, transportation, storage, and classification of energetic materials.

[0033] 2. This invention uses a temperature control module to control the temperature of the sample loaded between the ceramic plate and the ceramic rod. The temperature range can be arbitrarily set from room temperature to 200℃. By testing the friction sensitivity of the sample at different temperatures, the influence of varying room temperature conditions on the test results is eliminated, resulting in highly repeatable and representative experimental data. By testing the changes in the friction sensitivity of the same sample at different temperatures, the influence of temperature on friction sensitivity can be studied. The data can be used for research on the heat resistance and sensitivity of energetic materials, better serving the safe production and process aspects of chemical plants.

[0034] 3. This invention adds an electrostatic elimination module. The electrostatic conductive worktable in the module can quickly conduct away static electricity, avoiding explosion accidents caused by static accumulation from the sample surface, contact separation during the sampling process, and electrostatic discharge from the human body. It is particularly suitable for testing energetic materials that are sensitive to static electricity.

[0035] 4. This invention adds a real-time speed monitoring system and a power transient compensation system to the traditional motor drive, eliminating the influence of motor speed deviation on friction sensitivity testing. The similarity between the corrected speed curve and the target curve can reach over 95%. This significantly improves the repeatability and reproducibility of sample test results, enhances the reliability of the test results, and allows the test results to be directly used for safety assessment and product optimization.

[0036] 5. The temperature control device of this invention provides localized heating only to the ceramic plate and sample, requiring only 2-3 minutes to heat from room temperature to 200°C, and only 2 minutes for stabilization, with a fluctuation range of ≤±0.1°C. Traditional electric heating methods, on the other hand, require at least 30 minutes or longer. This invention significantly reduces the initial heating time during testing, thus shortening the testing cycle.

[0037] 6. The temperature control module in this invention uses a safe 24VDC voltage and a maximum current of 6A, ensuring safety. Since the friction-sensitive tray and friction parts are made of metal, and the heating element's connectors and cables are connected, safety issues can easily arise during tray movement. The use of 24VDC completely eliminates the risk of electric shock during testing. Attached Figure Description

[0038] Figure 1 This is the front view of the present invention;

[0039] Figure 2 This is a rear view of the present invention;

[0040] Figure 3 This is a structural diagram of the temperature control module;

[0041] Figure 4 A comparison diagram of the rotational speed and motion trajectory of the device of the present invention and a conventional device under extremely heavy test weights;

[0042] Figure 5 This is a comparison diagram of the rotational speed and motion trajectory of the device of the present invention and a conventional device when the test weights are extremely light.

[0043] The components include: 1. Temperature control module; 1-1 Heating plate; 1-2 Heat insulation plate; 1-3 Temperature measuring device; 1-31 Temperature sensor; 1-32 Sensor heat flow suppression plate; 1-33 Non-contact infrared temperature sensor; 1-4 Fixed bracket; 1-5 Ceramic plate; 2. Electrostatic discharge workbench; 2-1 Copper contact; 2-2 Grounding post; 3. Friction sensitivity device; 3-1 Load arm; 3-2 Ceramic rod; 3-3 Weight; 4. Data acquisition and processing module. Detailed Implementation

[0044] This invention can be embodied in many different embodiments, and the scope of protection of this invention is not limited to the embodiments mentioned herein.

[0045] The friction sensitivity testing device under thermal coupling as shown in the attached figure includes a temperature control module (1), a static electricity conductive workbench (2), a friction sensitivity device (3), and a data acquisition and processing module (4); the temperature control module (1) and the friction sensitivity device (3) are respectively connected to the data acquisition and processing module (4); the static electricity conductive workbench (2) is connected to the friction sensitivity device (3).

[0046] The temperature control module (1) shown in the attached figure includes a heating plate (1-1), a heat insulation plate (1-2), a temperature measuring device (1-3), and a fixing bracket (1-4). The fixing bracket (1-4) fixes the temperature measuring device (1-3), the heating plate (1-1), and the heat insulation plate (1-2) together in order from top to bottom. The non-contact infrared temperature sensor (1-33) is placed horizontally with the probe facing the sample position.

[0047] The rubber layer of the electrostatic conductive workbench (2) is embedded with copper contacts (2-1) and grounding posts (2-2); the copper contacts (2-1) are copper hemispheres embedded in the surface of the rubber layer, and the copper contacts (2-1) and grounding posts (2-2) are distributed at equal intervals of 100mm on the rubber layer. All grounding posts (2-2) are connected to the ground wire to form a grounding network.

[0048] The data acquisition and processing module (4) has a built-in real-time speed monitoring unit and a power transient compensation unit. The monitoring interval is once every 5ms and the compensation interval is once every 10ms. During the test, the motor speed is monitored and recorded in real time. Once the motor speed is found to deviate from the set value, the power transient compensation technology is immediately used to perform pulse point-to-point power correction to ensure that the motor runs at its set speed and to ensure the consistency of its motion trajectory sine curve.

[0049] To further demonstrate the accuracy of the test data from the device of the present invention, the following comparative experiment was designed:

[0050] Extreme weight test. Using the friction sensitivity testing device of this invention and its matching real-time speed monitoring unit and power transient compensation unit, a no-load test was conducted. A 10.08 kg test weight (3-3) was loaded onto the corresponding slot position of the load arm (3-1), the friction test was started, the speed data was recorded, and the motion trajectory curve was plotted. A conventional friction sensitivity device (without a real-time speed monitoring unit and power transient compensation unit) was used to conduct a no-load test at 10.08 kg, and an external real-time speed monitoring unit was used to record the speed data and plot the motion trajectory curve.

[0051] The test weight is extremely light. Using the friction sensitivity testing device of this invention and its matching real-time speed monitoring unit and power transient compensation unit, an unloaded test was conducted. A 0.28 kg test weight (3-3) was loaded onto the corresponding slot position of the load arm (3-1), the friction test was started, the speed data was recorded, and the motion trajectory curve was plotted. Alternatively, a conventional friction sensitivity device (without a real-time speed monitoring unit and power transient compensation unit) was used to conduct an unloaded test at 0.28 kg. An external real-time speed monitoring unit was used to record the speed data and plot the motion trajectory curve.

[0052] The test results show that:

[0053] like Figure 4 As shown, the "○ line" represents the motor speed curve of the friction sensitivity device of the present invention, after using the power transient compensation technology of the present invention and a test with a 10.08kg weight, which is slightly wider and slightly lower than the target speed curve, but is basically the same overall; the "▲ line" represents the traditional friction sensitivity device, after using a 10.08kg weight and a test with a speed curve, which is significantly wider and significantly lower than the target curve.

[0054] like Figure 5 As shown, the "○ line" represents the motor speed curve of the friction sensitivity device of the present invention, when tested with a 0.28kg weight, after using the power transient compensation technology of the present invention, which has a slightly larger amplitude and a slightly lower amplitude compared to the target speed curve, but is basically the same overall; the "▲ line" represents the traditional friction sensitivity device, when tested with a 0.28kg weight, whose speed curve has a significantly smaller amplitude and a significantly larger amplitude compared to the target curve.

[0055] In summary, the motor speed curve after adopting the invented power transient compensation technology is close to the target speed curve, while the motor speed curve without this technology differs significantly from the target speed curve. The friction sensitivity data after power compensation has a smaller deviation and higher repeatability.

[0056] The friction sensitivity testing device under thermo-coupling provided in this invention is mainly used for testing the friction sensitivity of energetic materials. Taking trinitroazacyclobutane as an example, the specific operating steps are as follows:

[0057] 1. Sample loading. Place the sample to be tested (usually 5-50 mg) on ​​the designated position on the surface of the ceramic plate.

[0058] 2. Load the weights. First, lower the load arm (3-1) and gently touch the sample with the tip of the ceramic rod (3-2). Do not forcefully impact the sample to avoid an explosion. Select the weight (3-3) and suspend it on the corresponding slot on the load arm (3-1).

[0059] 3. Turn on the friction generator. Turn on the power supply to the friction generator, set the test parameters, and start the remote control.

[0060] 4. Power on the temperature control module. Turn on the power supply to the temperature control unit. Mount the temperature measuring device (1-3), heating plate (1-1), and heat insulation plate (1-2) onto the friction device using the fixing bracket (1-4). Install the non-contact infrared temperature sensor (1-33). Connect the cables of the temperature sensor (1-31) and the heating plate (1-1) to the corresponding interfaces on the temperature control module.

[0061] 5. Start sample heating. Set the test temperature via the main unit's touchscreen, for example: 160℃. Wait 2-3 minutes for the ceramic plate surface temperature to reach approximately 160℃, then stabilize for another 2 minutes to ensure the sample temperature on the ceramic plate remains stable at around 160℃.

[0062] 6. Start friction. The operator uses the remote control function of the data acquisition and processing module (4) to start friction remotely. The stepper motor drives the tray to reciprocate to rub the sample. The camera observes whether the sample reacts. Reactions include: explosion or fire, smoke, color change, etc.

[0063] 7. Repeat the experiment. Select different weights (3-3) to conduct a series of experiments until the minimum frictional load value at which the sample reacts under the preset temperature conditions is determined. This value is taken as the frictional sensitivity value of the sample and expressed as N.

[0064] 8. Tests under different temperature conditions. Repeatedly conduct tests at different temperatures to determine the minimum frictional load value at which the sample reacts under different temperature conditions, and plot the relationship curve between temperature and frictional load value.

[0065] 9. End of test. After the friction sensitivity test is completed, first turn off the temperature control module (4), wait for the surface temperature of the ceramic plate to drop to room temperature, then remove the test weights (3-3), lift the load arm (3-1), clean the test residue on the surface of the friction device, and turn off the power of the equipment after the test is completed.

Claims

1. A friction sensitivity testing device under thermo-coupling, characterized in that, The friction sensitivity testing device under thermal coupling includes: a temperature control module (1), an electrostatic conductive workbench (2), a friction sensitivity device (3), and a data acquisition and processing module (4). The temperature control module (1) is used to locally heat the ceramic plate (1-5) carrying the sample in the friction sensitivity test, thereby controlling the sample temperature to any set value within the range of room temperature to 200°C. The electrostatic discharge workbench (2) is used to quickly discharge static electricity accumulated on the sample surface and static electricity from the operator. The friction sensitivity device (3) is used to perform friction sensitivity tests under set conditions; The data acquisition and processing module (4) is used for real-time speed monitoring and power transient compensation. The rubber layer on the surface of the electrostatic discharge workbench (2) is embedded with copper contacts (2-1) and grounding posts (2-2). The copper contacts (2-1) are copper hemispheres embedded in the surface of the rubber layer. The copper contacts (2-1) and grounding posts (2-2) are connected and equidistantly distributed on the rubber layer. All grounding posts (2-2) are connected to the ground wire to form a grounding network. The data acquisition and processing module (4) contains a real-time speed monitoring unit and a power transient compensation unit. The detection time interval of the real-time speed monitoring system is 5ms, and the compensation time interval of the power compensation system is 10ms. Once the motor speed is found to deviate from the set value, the power transient compensation technology is immediately used to increase or decrease the motor power to ensure that it is tested according to the set speed.

2. The friction sensitivity testing device under thermo-coupling effect according to claim 1, characterized in that, The temperature control module (1) includes a heating plate (1-1), a heat insulation plate (1-2), a temperature measuring device (1-3), and a fixing bracket (1-4). The fixing bracket (1-4) fixes the heat insulation plate (1-2), the heating plate (1-1), and the temperature measuring device (1-3) in sequence.

3. The friction sensitivity testing device under thermo-coupling effect according to claim 2, characterized in that, The heating plate (1-1) is made of ceramic material, and the heat insulation plate (1-2) is made of polymer material with low thermal conductivity.

4. The friction sensitivity testing device under thermo-coupling effect according to claim 2, characterized in that, The temperature measuring device (1-3) includes a temperature sensor (1-31), a sensor heat flow suppression disk (1-32), and a non-contact infrared temperature sensor (1-33).

5. The friction sensitivity testing device under thermo-coupling effect according to claim 4, characterized in that, The sensor heat flow suppression disk (1-32) is a metal disk with a sandblasted surface and a Teflon film coating.

6. The friction sensitivity testing device under thermo-coupling effect according to claim 4, characterized in that, The sensor heat flow suppression plate (1-32) has two U-shaped slots with their tops intersecting vertically, which can be used to insert a temperature sensor (1-31) for temperature measurement.

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