A fuze slow cook-off test output pressure testing system and method

Abstract

The application relates to the technical field of fuze safety evaluation, and discloses a fuze slow-baking test output pressure test system which is composed of a slow-baking test device and an ultrahigh-speed dynamic strain test system. The ultrahigh-speed dynamic strain test system comprises a high-temperature strain type pressure rod sensor and a signal collection system, and the high-temperature strain type pressure rod sensor and the signal collection system are connected through high-temperature-resistant shielding wires. The high-temperature strain type pressure rod sensor comprises a copper pad, a pressure rod (an elongated cylindrical elastic rod), a shell, a base, a buffer pad block and a high-temperature strain gauge. The signal collection system comprises a bridge box, shielding wires, an ultrahigh-speed dynamic strain gauge and an oscilloscope. The fuze slow-baking test output pressure test system can achieve accurate effects in the response output pressure test of fuzes under a baking environment.

Description

Technical Field

[0001] This invention relates to the field of fuze safety assessment technology, and in particular to a fuze slow-burn test output pressure testing system and method for studying fuze safety assessment. Background Technology

[0002] A fuze is a detonation device attached to shells, bombs, landmines, etc., which uses target and environmental information to detonate or ignite the warhead charge of the munition under predetermined conditions. When assessing the thermal safety of a fuze, the combustion test is the primary evaluation method. Among these, the slow combustion safety test is the most direct and effective means of assessing the thermal safety of the fuze and its propellant, and it is also one of the most difficult items to pass in fuze vulnerability assessment. NATO international standard AOP-39 defines the reaction levels of munitions under various external stimuli as no reaction, combustion, deflagration, explosion, partial detonation, and detonation. The slow combustion test requires that the munition's response level cannot exceed that of an explosive reaction. The reaction level of the fuze combustion test is comprehensively judged through qualitative descriptions such as indentations on the witness plate, prototype fragments, and consumption of energetic materials, neglecting the quantitative determination of the reaction level during the combustion process, which greatly reduces the accuracy of the fuze combustion test results. However, the evaluation standards for slow-burn tests on fuses and warheads differ significantly. Currently, the Navy requires shipboard ammunition to be in a combined fuse and warhead configuration. Although separate fuses and warheads can both pass the slow-burn test, if the fuse output pressure is sufficient to detonate the warhead when the fuse and warhead are combined, it will cause enormous damage. Therefore, obtaining the fuse output pressure in slow-burn tests is crucial, as it determines whether the fuse will detonate the warhead under unexpected stimuli.

[0003] Currently, the most common method for testing shock wave loads is using piezoelectric or piezoresistive pressure sensors. However, the high-frequency pressure and high temperature generated by near-field free-field explosions can overload and even damage the sensors, making testing impossible. Traditional piezoelectric pressure sensors have too low a response frequency, leading to waveform distortion. Piezoresistive pressure sensors have a small range and cannot effectively measure high pressures. Manganese-copper pressure sensors with the appropriate range cannot measure pressures in high-temperature environments. Therefore, there is a lack of an effective method for testing the output pressure field of the fuze in slow-heat tests.

[0004] Therefore, it is necessary to provide a fuze slow-burn test output pressure testing system and method to solve the above-mentioned technical problems. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a system and method for testing the output pressure of a fuze in a slow-burning test. Based on the propagation characteristics of stress waves in a slender rod, this invention designs a strain gauge pressure bar sensor to measure the magnitude of the fuze response output pressure during the burning test. When the shock wave generated by the fuze response acts on one end of the pressure bar, a stress wave is formed within the rod because the shock wave is pressing against the cross-section of the rod end. According to the elementary theory of one-dimensional stress waves, the magnitude of the shock wave at the pressure bar end can be inferred by measuring the stress wave within the rod. This testing system can be used to measure the output pressure value during a slow-burning test of a fuze.

[0006] The fuze slow-heat test output pressure testing system provided by this invention consists of two parts: a slow-heat test device and an ultra-high-speed dynamic strain test system.

[0007] The slow-baking test apparatus includes a slow-baking oven, a temperature controller, and a temperature acquisition instrument; the ultra-high-speed dynamic strain testing system includes a high-temperature strain gauge bar sensor and a signal acquisition system.

[0008] The high-temperature strain gauge pressure bar sensor includes a housing, a pressure bar, a base, a buffer pad, a copper pad, and a high-temperature strain gauge; the signal acquisition system includes a bridge box, a shielded wire, an ultra-dynamic strain gauge, and an oscilloscope.

[0009] The signal acquisition system uses a 1 / 4 bridge box to connect the high-temperature strain gauge, the ultra-dynamic strain gauge, and the oscilloscope in sequence via shielded wires.

[0010] Preferably, the outer shell is a cylindrical structure with a groove in the middle to lead out the test line; the outer shell and the pressure rod are fitted with a clearance fit and rubber rings are installed at local positions to give it good acoustic insulation properties, ensure that the free radial movement of the pressure rod is not hindered, and avoid waveform distortion.

[0011] Preferably, the compression bar material is 18Ni steel, which is maraging steel C350 with a yield strength of 2300MPa, a tensile strength of 2400MPa, and a Young's modulus of 192GPa.

[0012] Preferably, the base is made of metal, which ensures that the end face of the pressure rod is parallel to the end face of the fuse detonation casing during the arrangement process. The base has a reserved mounting groove for the buffer pad, and the reflective pad is made of polytetrafluoroethylene, which can reflect the shock wave without loss, making it convenient to verify the accuracy of the test results by means of the reflected wave signal.

[0013] Preferably, the diameter of the pressure bar is 6mm. Since the diameter of the pressure bar is much smaller than the wavelength, the propagation speed of each sinusoidal component is the same, so the superimposed waveform will not be distorted, the shape of any stress wave will not change during the propagation process, and the stress will be evenly distributed on the cross-section of the bar, which conforms to the elementary theory of elastic wave propagation along a slender bar and will not produce a dispersion effect.

[0014] Preferably, the length of the pressure bar is 400mm. This is mainly to ensure that the stress wave output during the test will not superimpose with the reflected stress wave. The length of the pressure bar is selected by referring to the magnitude of the elastic wave velocity in the pressure bar and the pulse width of the stress wave in the pressure bar during the slow baking test.

[0015] Preferably, the copper pad is used to prevent the pressure bar from undergoing plastic deformation, which would affect the test accuracy. The shock wave generated by the fuze response first acts on the copper pad, and then the shock wave gradually decays and enters the interior of the pressure bar, but its strength is always less than the yield strength of the pressure bar. The copper pad has a diameter of 6 mm, a length of 6 mm, and a compressive strength of 260 MPa.

[0016] Preferably, the high-temperature strain gauge is BAB120-3AA250(11)-G500, with a working temperature range of -269 to 250°C. The high-temperature strain gauge is tightly bonded to the pre-reserved opening in the outer shell using a high-temperature adhesive. The high-temperature adhesive is a single-component medium-high temperature adhesive made by copolymerizing phenolic resin and epoxy resin and adding fillers. It has the advantages of strong adhesion, outstanding insulation performance, high temperature resistance, good stability, and wide working temperature range. It is mainly used for bonding resistance strain gauges used in medium-high temperature applications.

[0017] Preferably, the slow-heating oven mainly performs the heating function, the temperature controller controls the heating rate during the combustion test, and the temperature acquisition instrument can test the temperature field size at the fuse detonator during the combustion test.

[0018] This invention also proposes a test method for a fuze slow-burn test output pressure test system, applied to the aforementioned fuze slow-burn test output pressure test system, the method comprising the following steps:

[0019] (1) Design and processing

[0020] The length and diameter of the pressure bar are determined by combining the response frequency and wave velocity;

[0021] (2) Assembly

[0022] Assemble the base, outer shell, buffer pad, pressure rod, and copper pad in sequence;

[0023] (3) Screening of high-temperature strain gauges

[0024] Including appearance and resistance checks:

[0025] Visual inspection is performed using a magnifying glass. The high-temperature resistance strain gauge should be free of bubbles, mold, and rust spots, and the grid should be straight, neat, and uniform.

[0026] To check the resistance value, use a multimeter to measure the resistance value, ensuring there is no short circuit or open circuit.

[0027] (4) Processing test points

[0028] Check the surface condition at the test point; the test point should be flat, without defects or cracks.

[0029] Use sandpaper or a grinder to polish the surface of the test points to make the surface smooth, free of rust and laitance;

[0030] Clean the test points with acetone or alcohol to ensure there are no contaminants.

[0031] (5) Attach high-temperature strain gauges

[0032] Apply a thin layer of high-temperature adhesive to the test point using a special adhesive applicator, ensuring the application is done in one stroke to avoid overlapping. Use special tweezers to attach the high-temperature strain gauge to the test point, cover it with a polytetrafluoroethylene film, and squeeze out air bubbles and excess adhesive along the axis of the high-temperature strain gauge with your fingers. After covering it with a silicone rubber sheet, place it in a fixture, apply pressure of 0.1~0.3MPa and keep it stable, then put it in an oven.

[0033] (6) Curing treatment

[0034] Heat to 135℃ at 2℃ / min, hold for 2 hours, and then release the pressure after cooling to room temperature in the oven; heat to 165℃ again at 2℃ / min, hold for 2 hours, and then cool to room temperature in the oven.

[0035] (7) Quality inspection of pasting

[0036] This includes visual inspection, resistance inspection, and insulation inspection;

[0037] Visual inspection should be performed with the naked eye using a magnifying glass to ensure that the high-temperature strain gauge is free of bubbles, firmly attached, and accurately positioned; resistance should be checked with a multimeter to measure the resistance value, requiring no short circuits or open circuits, and the resistance value should be basically the same as before attachment; insulation should be checked with a megohmmeter to check the insulation between the pressure rod and the strain gauge, which should be greater than 50 megohms.

[0038] (8) Wire connection

[0039] Apply adhesive tape or paper to the bottom of the high-temperature strain gauge lead wires to ensure that the lead wires do not form a short circuit with the pressure bar;

[0040] Fixing point setup: Secure the terminals with adhesive or use tape to secure the connecting wire between the strain gauge and the bridge box, ensuring that the lead wire does not break when the wire is slightly pulled;

[0041] Wire soldering: Use a soldering iron to solder the lead wire to the shield wire. The solder joint should be smooth, full and free of cold solder joints.

[0042] (9) Installation

[0043] The fuze 2 and the high-temperature strain gauge pressure bar sensor 3 are coaxially mounted and fixed together using four screws with a length of 700mm~800mm.

[0044] (10) Wiring

[0045] The high-temperature strain gauge, bridge box, ultra-dynamic strain gauge, and oscilloscope are connected in sequence using high-temperature shielded wires.

[0046] (11) Test parameter settings

[0047] After completing the wiring, adjust the sampling depth, delay, trigger source, trigger mode, trigger level, and sampling method of the signal acquisition system to meet the test requirements;

[0048] (12) Verification

[0049] The high-temperature strain gauge was calibrated using an ultra-dynamic strain gauge, and the signal acquisition system obtained the expected waveform.

[0050] (13) Installation of slow oven

[0051] The fuse and high-temperature strain gauge pressure bar sensor are placed in the slow-burning oven. The oven wall is heated by electricity. The wires of the temperature controller are connected to the nickel-chromium / nickel-silicon thermocouple fixed on the outer wall of the slow-burning oven. The temperature of the outer wall is fed back to the temperature controller. The temperature controller then adjusts the heating rate of the slow-burning oven by controlling the output power. A measuring point is set at the position of the fuse and the explosive casing. A K-type armored miniature thermocouple is installed and connected to the temperature acquisition instrument to obtain the temperature-time data of the measuring point during the combustion process.

[0052] (14) Data Acquisition

[0053] Use an oscilloscope to acquire the voltage signal on the pressure rod when the fuze responds;

[0054] (15) Data processing

[0055] The equation for converting a voltage-time signal into a pressure-time signal is:

[0056]

[0057] In the formula, U 0 represents the instrument's output voltage. K Represents the sensitivity coefficient of a high-temperature strain gauge. G Represents the instrument's magnification. U 1 represents the bridge input voltage. E Represents the elastic modulus of the compression bar;

[0058] The attenuation law of shock waves in copper is derived from the following equation:

[0059]

[0060] in, x The thickness of the copper pad, P 0 represents the output pressure of the fuze reaction. P x This is a stress wave in the compression bar. The compressive yield strength of copper is given by the pressure at the top of the rod, which is the peak stress within the rod. Therefore, substituting the experimentally measured data into the copper attenuation law equation yields the fuze's response output pressure. P 0.

[0061] Compared with related technologies, the fuze slow-heating test output pressure testing system and method provided by the present invention have the following beneficial effects:

[0062] This system incorporates a pressure bar and one-dimensional stress theory to achieve high-temperature, wide-area stress wave measurement.

[0063] A reflective pad was installed to avoid the diffusion effect and to solve the shortcomings of the overpressure formula.

[0064] High-temperature strain gauges were installed, enabling the measurement of high pressure in high-temperature environments;

[0065] A buffer pad was installed so that the high-temperature strain gauge could collect reflected waves normally to verify the response pattern.

[0066] A base is provided to facilitate the placement of strain gauge pressure bar sensors.

[0067] A strain gauge pressure sensor measurement system capable of measuring high pressure in high-temperature environments was established, reducing the impact of high-temperature environments on experimental testing and providing an effective testing technique for measuring output pressure in fuze slow-heating tests. Attached Figure Description

[0068] Figure 1 This is a schematic diagram of the high-temperature strain gauge pressure bar sensor in this invention;

[0069] Figure 2 This is a schematic diagram of an ultra-high-speed dynamic strain testing system;

[0070] Figure 3 This is a schematic diagram of the overall structure of the present invention.

[0071] Reference numerals in the attached diagram: 1. Fixing plate one; 2. Fuze; 3. High-temperature strain gauge pressure bar sensor; 4. Slow oven; 5. Fixing plate two; 6. Nut; 7. Screw; 9. Signal acquisition system; 8. Base; 10. Temperature acquisition instrument; 11. Thermocouple; 12. Temperature controller; 13. Wire; 31. Copper pad; 32. Housing; 33. Pressure bar; 34. High-temperature strain gauge; 35. Buffer pad; 36. Base; 41. Shielded wire; 42. Bridge box; 43. Ultra-dynamic strain gauge; 44. Oscilloscope. Detailed Implementation

[0072] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0073] The present invention proposes a fuze slow-heating test output pressure testing system, which consists of two parts: a slow-heating test device and an ultra-high-speed dynamic strain testing system.

[0074] The slow-baking test device includes a slow-baking oven 4, a temperature controller 12, and a temperature acquisition instrument 10; the ultra-high-speed dynamic strain testing system includes a high-temperature strain gauge bar sensor 3 and a signal acquisition system 9.

[0075] The high-temperature strain gauge pressure bar sensor 3 includes a housing 32, a pressure bar 33, a base 36, a buffer block 35, a copper pad 31, and a high-temperature strain gauge 34. The signal acquisition system 9 includes a bridge box 42, a shielded wire 41, an ultra-dynamic strain gauge 43, and an oscilloscope 44.

[0076] The signal acquisition system 9 connects the high-temperature strain gauge 34, the ultra-dynamic strain gauge 43, and the oscilloscope 44 in sequence via a shielded cable through a 1 / 4 bridge box 42.

[0077] In a further preferred embodiment of the present invention, the outer shell 32 is a cylindrical structure, and a groove is provided in the middle part of the outer shell 32 to lead out the test line; the outer shell 32 and the pressure rod 33 are fitted with a clearance and a rubber ring is installed in a local position to give it good acoustic insulation properties, ensure that the free radial movement of the pressure rod 33 is not hindered, and avoid waveform distortion.

[0078] In a further preferred embodiment of the present invention, the pressure bar 33 is made of 18Ni steel, which is maraging steel C350 with a yield strength of 2300MPa, a tensile strength of 2400MPa, and a Young's modulus of 192GPa.

[0079] In a further preferred embodiment of the present invention, the base 36 is made of metal, which can ensure that the end face of the pressure rod 33 is parallel to the end face of the fuse detonation shell during the arrangement process. The base 36 has a reserved mounting groove for the buffer pad, and the reflective pad is made of polytetrafluoroethylene, which can reflect the shock wave without loss, making it convenient to verify the accuracy of the test results by means of the reflected wave signal.

[0080] In a further preferred embodiment of the present invention, the diameter of the pressure rod 33 is 6mm. Since the diameter of the pressure rod 33 is much smaller than the wavelength, the propagation speed of each sinusoidal component is the same, so the superimposed waveform will not be distorted, the shape of any stress wave will not change during the propagation process, and the stress will be evenly distributed on the cross-section of the rod, which conforms to the elementary theory of elastic wave propagation along a slender rod and will not produce a dispersion effect.

[0081] In a further preferred embodiment of the present invention, the length of the pressure bar 33 is 400mm. This is mainly to ensure that the stress wave output during testing will not superimpose with the reflected stress wave. The length of the pressure bar 33 is selected by referring to the magnitude of the elastic wave velocity in the pressure bar and the pulse width of the stress wave in the pressure bar during the slow baking test.

[0082] In a further preferred embodiment of the present invention, the copper pad 31 is used to prevent the pressure rod 33 from undergoing plastic deformation and affecting the test accuracy; the shock wave generated by the fuze 2 first acts on the copper pad 31, and then the shock wave gradually attenuates and enters the interior of the pressure rod 33, but its strength is always less than the yield strength of the pressure rod 33; the copper pad 31 has a diameter of 6 mm, a length of 6 mm, and a compressive strength of 260 MPa.

[0083] In a further preferred embodiment of the present invention, the high-temperature strain gauge 34 is BAB120-3AA250(11)-G500, with a working temperature range of -269 to 250°C. The high-temperature strain gauge 34 is tightly bonded to the pre-reserved opening of the outer shell 32 using a high-temperature adhesive. The high-temperature adhesive is a single-component medium-high temperature adhesive made by copolymerizing phenolic resin and epoxy resin and adding fillers. It has the advantages of strong adhesion, outstanding insulation performance, high temperature resistance, good stability, and wide working temperature range. It is mainly used for bonding resistance strain gauges used in medium-high temperature applications.

[0084] In a further preferred embodiment of the present invention, the slow oven 4 mainly realizes the heating function, the temperature controller 12 controls the heating rate in the combustion test, and the temperature acquisition instrument 10 can test the temperature field size at the fuse detonator in the combustion test.

[0085] This invention also proposes a test method for a fuze slow-burn test output pressure test system, applied to the aforementioned fuze slow-burn test output pressure test system, the method comprising the following steps:

[0086] (1) Design and processing

[0087] The length and diameter of the pressure bar are determined by combining the response frequency and wave velocity.

[0088] (2) Assembly

[0089] Assemble the base 36, outer shell 32, buffer pad 35, pressure rod 33, and copper pad 31 in sequence, as follows: Figure 1 As shown;

[0090] (3) Screening of high-temperature strain gauges 34

[0091] Including appearance and resistance checks:

[0092] Visual inspection is performed using a magnifying glass. The high-temperature strain gauge 34 should be free of bubbles, mold spots, and rust spots, and the grid should be straight, neat, and uniform.

[0093] To check the resistance value, use a multimeter to measure the resistance value, ensuring there is no short circuit or open circuit.

[0094] (4) Processing test points

[0095] Check the surface condition at the test point; the test point should be flat, without defects or cracks.

[0096] Use sandpaper or a grinder to polish the surface of the test points to make the surface smooth, free of rust and laitance;

[0097] Clean the test points with acetone or alcohol to ensure there are no contaminants.

[0098] (5) Attach high-temperature strain gauges 34

[0099] Apply a thin layer of high-temperature adhesive to the test point using a special adhesive applicator, ensuring the application is done in one stroke to avoid overlapping. Use special tweezers to attach the high-temperature strain gauge 34 to the test point, cover it with a polytetrafluoroethylene film, and squeeze out air bubbles and excess adhesive along the axis of the high-temperature strain gauge 34 with your fingers. After covering it with a silicone rubber sheet, place it in a fixture, apply pressure of 0.1~0.3MPa and keep it stable, then put it in an oven.

[0100] (6) Curing treatment

[0101] Heat to 135℃ at 2℃ / min, hold for 2 hours, and then release the pressure after cooling to room temperature in the oven; heat to 165℃ again at 2℃ / min, hold for 2 hours, and then cool to room temperature in the oven.

[0102] (7) Quality inspection of pasting

[0103] This includes visual inspection, resistance inspection, and insulation inspection;

[0104] Visual inspection should be performed with the naked eye using a magnifying glass to ensure that the high-temperature strain gauge 34 is free of air bubbles, firmly attached, and accurately positioned; resistance should be checked with a multimeter to measure the resistance value, requiring no short circuits or open circuits, and the resistance value should be basically the same as before attachment; insulation should be checked with a megohmmeter to check the insulation between the pressure rod 33 and the high-temperature strain gauge 34, which should be greater than 50 megohms.

[0105] (8) Wire connection

[0106] Apply adhesive tape or adhesive paper under the lead wire of the high-temperature strain gauge 34 to ensure that the lead wire does not form a short circuit with the pressure bar 33;

[0107] Fixing point setup: Secure the terminals with adhesive or secure the connecting wire between the high-temperature strain gauge 34 and the bridge box 42 with tape to ensure that the lead wire does not break when the wire is slightly pulled.

[0108] Wire soldering: Use a soldering iron to solder the lead wire to the shield wire 41. The solder joint should be smooth, full and free of cold solder joints.

[0109] (9) Installation

[0110] The fuze 2 and the high-temperature strain gauge pressure bar sensor 3 are coaxially mounted and secured together using four screws with a length of 700mm~800mm. Figure 3 As shown;

[0111] (10) Wiring

[0112] The high-temperature strain gauge 34, bridge box 42, ultra-dynamic strain gauge 43, and oscilloscope 44 are connected sequentially via high-temperature shielded wire 41, as follows: Figure 2 As shown;

[0113] (11) Test parameter settings

[0114] After completing the wiring, adjust the sampling depth, delay, trigger source, trigger mode, trigger level, and sampling method of the signal acquisition system 9 to meet the test requirements;

[0115] (12) Verification

[0116] The high-temperature strain gauge was calibrated using an ultra-dynamic strain gauge, and the expected waveform was obtained by the signal acquisition system 9.

[0117] (13) Installation of slow oven

[0118] The fuse 2 and the high-temperature strain gauge pressure bar sensor 3 are placed in the slow-burning oven 4. The oven wall is heated by electricity. The wires of the temperature controller 12 are connected to the nickel-chromium / nickel-silicon thermocouple fixed on the outer wall of the slow-burning oven 4. The temperature of the outer wall is fed back to the temperature controller 12. The temperature controller 12 then adjusts the heating rate of the slow-burning oven by controlling the output power. A measuring point is set at the position of the fuse and the explosive casing. A K-type armored miniature thermocouple is installed and connected to the temperature acquisition instrument 10 to obtain the temperature-time data of the measuring point during the burning process.

[0119] (14) Data Acquisition

[0120] Use oscilloscope 44 to acquire the voltage signal on pressure rod 33 when fuze 2 responds;

[0121] (15) Data processing

[0122] The equation for converting a voltage-time signal into a pressure-time signal is:

[0123]

[0124] In the formula, U 0 represents the instrument's output voltage. K Represents the sensitivity coefficient of a high-temperature strain gauge. G Represents the instrument's magnification.U 1 represents the bridge input voltage. E Represents the elastic modulus of the compression bar;

[0125] The attenuation law of shock waves in copper is derived from the following equation:

[0126]

[0127] in, x The thickness of the copper pad, P 0 represents the output pressure of the fuze reaction. P x This is a stress wave in the compression bar. The compressive yield strength of copper is given by the pressure at the top of the rod, which is the peak stress within the rod. Therefore, substituting the experimentally measured data into the copper attenuation law equation yields the fuze's response output pressure. P 0.

[0128] The fuze slow-burn test output pressure testing system proposed in this invention, combined with the attached... Figure 3 A common operating condition diagram is provided. A temperature testing system is added, with fuse 2 and high-temperature strain gauge pressure bar sensor 3 placed in a slow-heating oven 4. The oven wall is heated by electricity. Temperature controller 12 is connected to a nickel-chromium / nickel-silicon thermocouple fixed to the outer wall of the slow-heating oven 4. The outer wall temperature is fed back to temperature controller 12, which then adjusts the heating rate of the slow-heating oven by controlling the output power. The ultra-high-speed dynamic strain testing system includes a high-temperature strain gauge pressure bar sensor and signal acquisition. A high-temperature strain gauge with a grid length of 3mm and an operating temperature range of -269 to 250℃ is used. Its sensitivity coefficient is 1.8, and it can measure frequencies up to 167kHz. This high-temperature strain gauge has built-in temperature compensation. Each set of high-temperature strain gauges only needs to be pasted on one side of the pressure bar, and the high-temperature strain gauge is connected to the ultra-dynamic strain gauge through a 1 / 4-inch bridge box.

[0129] The principle of the high-temperature strain gauge pressure bar sensor in this invention is as follows:

[0130] In the slow-heating test, after the fuse responds, a shock wave is generated and enters the copper pad 31. The copper pad 31 undergoes plastic deformation, and the shock wave attenuates to below the compressive yield strength of the pressure rod 33, propagating into the pressure rod 33 as a stress wave. The high-temperature strain gauge pressure rod sensor 3 is correctly positioned so that the copper pad 31 and the axis of the pressure rod 33 coincide. When the stress wave acts on the front end of the pressure rod 33, it will excite an elastic stress wave composed of longitudinal waves that propagates along the rod. If this wave is measured and its change over time is recorded at a certain point in the rod, the change in pressure acting on the end of the rod over time can be calculated based on the propagation law of elastic waves in the rod.

[0131] The high-temperature strain gauge bar sensor 3 is designed based on one-dimensional stress theory. The wave equation for the longitudinal wave in the slender bar is:

[0132]

[0133] In the formula x The horizontal axis represents the cross-sectional micro-element. u It is a displacement infinitesimal element; For the speed of wave propagation, E The elastic modulus of the compression bar. ρ This represents the density of the compression bar.

[0134] According to the theory of partial differential equations, solving this equation yields...

[0135]

[0136] The strain, stress, and particle velocity within the slender rod are as follows:

[0137]

[0138]

[0139]

[0140] As can be seen from the above equation, strain, stress, and velocity all propagate along the rod at wave speed.

[0141] According to Fourier analysis, waves of any shape can be represented by the superposition of their sinusoidal components.

[0142]

[0143] When the diameter of the rod is much smaller than the wavelength, the propagation speed of each sinusoidal component is the same, the waveform will not be distorted, and the stress will be evenly distributed on the rod. At this time, the pressure signal can be obtained by collecting the strain on the surface of the rod through a high-temperature strain gauge.

[0144] To minimize the effects of dispersion, the diameter of the pressure bar should be minimized, requiring the selection of the pressure bar radius for the pressure bar sensor. a When, the inequality should be satisfied. ,in It is the shortest wavelength contained in the stress pulse to be measured. If the rod dimensions are fixed, it can be calculated using the formula:

[0145]

[0146] The upper limit of the frequency that the compression bar can accurately measure was estimated. Combined with the experimental use of a 3mm long high-temperature strain gauge, its highest measurable frequency is 167kHz. The stress wave velocity in the compression bar is 5200m / s. Therefore, the radius of the compression bar is... aIt should be less than 3mm. To ensure the response rise time of the high-temperature strain gauge, the distance from the strain gauge mounting position to the front end of the pressure bar should be greater than 220mm. To ensure that the measured waveform does not superimpose reflected waves, the distance from the high-temperature strain gauge to the tail end should be... L 2≥ Column wave velocity C 0 = 5200 m / s, and the duration of the fuze response shock wave is approximately 30~50 μs. The distance from the high-temperature strain gauge to the tail end is greater than 130 mm, ensuring that the waveforms do not overlap.

[0147] Considering the difficulty in ensuring the straightness of slender rods during machining, the rod length was minimized while still meeting testing requirements. Taking into account the bonding and maintenance of the high-temperature strain gauges, the final rod length was determined to be [length to be specified]. L =400mm.

[0148] In shock wave measurement, the compressive yield strength of the pressure bar is an important indicator of its performance. The maximum pressure that can be measured depends on the yield limit of the material. If the shock wave exceeds the yield strength of the pressure bar, the pressure bar will fail and cannot be measured. Therefore, a copper pad is added between the pressure bar and the fuse to attenuate the shock wave, mainly because the shock wave attenuation law of copper is known, so that the pressure wave entering the pressure bar is less than the output limit of the pressure bar material.

[0149] During use, the outer shell 32 is tightly connected to the base 36 by threads, and the reflective pad, pressure rod 33, and copper pad 31 are installed in sequence. The high-temperature strain gauge 34 is tightly glued to the reserved opening of the outer shell 32 using a high-temperature adhesive.

[0150] The screw 7 is fixed to the base 8 by the nut 6. The fuse seat 5 is installed at the designated position on the screw 7 using the nut 6. The simulated projectile is arranged and fixed by the nut 6 through the fixing plate 1 and the fixing plate 2. The base 36 is adjusted so that the end face of the buffer pad 35 is tangent to the stress wave.

[0151] The high-temperature strain gauge 34, bridge box 42, ultra-dynamic strain gauge 43, and oscilloscope 44 are connected in sequence via shielded cable 41.

[0152] Will K =1.8, G =1000, U 1 = 2V, E =210000N / m 2 Substitute into the formula This allows the voltage-time signal acquired by the oscilloscope to be converted into a pressure-time signal, from which the stress wave inside the pressure bar can be obtained. The peak value of the stress wave can then be substituted into the attenuation law equation of copper to obtain the magnitude of the fuze output pressure.

[0153] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A fuze slow-heat test output pressure testing system, characterized in that, It consists of two parts: a slow-baking test device and an ultra-high-speed dynamic strain testing system. The slow-baking test device includes a slow-baking oven (4), a temperature controller (12), and a temperature acquisition instrument (10); the ultra-high-speed dynamic strain testing system includes a high-temperature strain gauge bar sensor (3) and a signal acquisition system (9). The high-temperature strain gauge pressure bar sensor (3) includes a housing (32), a pressure bar (33), a base (36), a buffer pad (35), a copper pad (31), and a high-temperature strain gauge (34). The housing (32) and the base (36) are tightly connected by threads. The buffer pad (35), the pressure bar (33), and the copper pad (31) are sequentially installed in the housing (32). The high-temperature strain gauge (34) is tightly glued to the reserved opening in the housing (32) using a high-temperature adhesive. The signal acquisition system (9) includes a bridge box (42), a shielded wire (41), an ultra-dynamic strain gauge (43), and an oscilloscope (44). The fuze (2) and the high-temperature strain gauge pressure bar sensor (3) are placed in a slow oven (4). The fuze (2) and the high-temperature strain gauge pressure bar sensor (3) are coaxially installed and set at the other end of the copper pad (31) relative to the pressure bar (33). The signal acquisition system (9) connects the high-temperature strain gauge (34), the ultra-dynamic strain gauge (43), and the oscilloscope (44) in sequence via a shielded wire (41) through a 1 / 4 bridge box (42); The outer shell (32) is a cylindrical structure, and a groove is provided in the middle part of the outer shell (32) to lead out the test line; the outer shell (32) and the pressure rod (33) are fitted with a clearance and a rubber ring is installed in a local position to give it good acoustic insulation properties, ensure that the free radial movement of the pressure rod (33) is not hindered, and avoid waveform distortion; The compression bar (33) is made of 18Ni steel, which is maraging steel C350 with a yield strength of 2300MPa, a tensile strength of 2400MPa, and a Young's modulus of 192GPa. The base (36) is made of metal, which can ensure that the end face of the pressure rod (33) is parallel to the end face of the fuse detonation shell during the arrangement process. The base (36) has a reserved mounting groove for the buffer pad (35). The buffer pad (35) is made of polytetrafluoroethylene, which can reflect the shock wave without loss, making it easy to verify the accuracy of the test results by means of the reflected wave signal. The diameter of the pressure bar (33) is 6mm. The diameter of the pressure bar (33) is much smaller than the wavelength. The propagation speed of each sinusoidal component is the same, so the superimposed waveform will not be distorted. The shape of any stress wave will not change during the propagation process. At the same time, the stress will be evenly distributed on the cross-section of the bar, which is in line with the elementary theory of elastic wave propagation along a slender bar and will not produce a dispersion effect. The length of the pressure bar (33) is 400mm. This is mainly to ensure that the stress wave output during the test will not be superimposed with the reflected stress wave. The length of the pressure bar (33) is selected by referring to the magnitude of the elastic wave velocity in the pressure bar and the pulse width of the stress wave in the pressure bar during the slow baking test.

2. The fuze slow-heat test output pressure testing system as described in claim 1, characterized in that, The function of the copper pad (31) is to prevent the pressure rod (33) from undergoing plastic deformation and affecting the test accuracy; the fuze (2) generates a shock wave that first acts on the copper pad (31), and then the shock wave gradually decays and enters the interior of the pressure rod (33), but its strength is always less than the yield strength of the pressure rod (33); the copper pad (31) has a diameter of 6 mm, a length of 6 mm, and a compressive strength of 260 MPa.

3. The fuze slow-heat test output pressure testing system as described in claim 1, characterized in that, The high-temperature adhesive is a single-component medium-high temperature adhesive made by copolymerizing phenolic resin and epoxy resin and adding fillers.

4. The fuze slow-heat test output pressure testing system as described in claim 1, characterized in that, The slow oven (4) is used to achieve the heating function, the temperature controller (12) controls the heating rate in the baking test, and the temperature acquisition instrument (10) can test the temperature field size at the fuse detonator in the baking test.

5. A test method for a fuze slow-heat test output pressure test system, characterized in that, The method is applied to the fuze slow-burn test output pressure testing system according to any one of claims 1-4, and the method includes the following steps: S1, Design and Manufacturing The length and diameter of the pressure bar are determined by combining the response frequency and wave velocity; S2, Assembly Assemble the base (36), outer shell (32), buffer pad (35), pressure rod (33), and copper pad (31) in sequence; S3. Screening high-temperature strain gauges (34) Including appearance and resistance checks: Visual inspection is performed using a magnifying glass. The high-temperature strain gauge (34) should be free of bubbles, mold spots, and rust spots, and the grid should be straight, neat, and uniform. To check the resistance value, use a multimeter to measure the resistance value, ensuring there is no short circuit or open circuit. S4, Processing test points Check the surface condition at the test point; the test point should be flat, without defects or cracks. Use sandpaper or a grinder to polish the surface of the test points to make the surface smooth, free of rust and laitance; Clean the test points with acetone or alcohol to ensure there are no contaminants. S5. Attach high-temperature strain gauges (34) Apply a thin layer of high-temperature adhesive to the adhesive area of ​​the test point using a special adhesive pen. Apply the adhesive in one go to avoid overlapping the application. Use special tweezers to attach the high-temperature strain gauge (34) to the test point, cover it with a polytetrafluoroethylene film, and squeeze out air bubbles and excess adhesive along the axis of the high-temperature strain gauge (34) with your fingers. After covering it with a silicone rubber plate, place it in a fixture, apply pressure of 0.1~0.3MPa and keep it stable, and put it in an oven. S6, Curing treatment Heat to 135℃ at 2℃ / min, hold for 2 hours, and then release the pressure after cooling to room temperature in the oven; heat to 165℃ again at 2℃ / min, hold for 2 hours, and then cool to room temperature in the oven. S7. Adhesion Quality Inspection This includes visual inspection, resistance inspection, and insulation inspection; Visual inspection should be performed with the naked eye using a magnifying glass to ensure that the high-temperature strain gauge (34) is free of bubbles, firmly attached, and accurately positioned; resistance inspection should be performed by measuring the resistance value with a multimeter, requiring no short circuit or open circuit, and the resistance value should be basically the same as before attachment; insulation inspection should be performed by checking the insulation between the pressure rod (33) and the high-temperature strain gauge (34) with a megohmmeter, which should be greater than 50 megohms; S8, Wire Connection Apply adhesive tape or adhesive paper under the lead wire of the high temperature strain gauge (34) to ensure that the lead wire does not form a short circuit with the pressure bar (33); Fixing point setting: Fix the terminals with glue or fix the connecting wire between the high temperature strain gauge (34) and the bridge box (42) with tape to ensure that the lead wire does not break when the wire is slightly pulled; Wire soldering: Use a soldering iron to solder the lead wire to the shield wire (41). The solder joint should be smooth, full and without any cold solder joints. S9, Installation The fuze (2) and the high-temperature strain gauge pressure bar sensor (3) are coaxially mounted and fixed together by four screws with a length of 700mm~800mm. S10, Wiring The high-temperature strain gauge (34), bridge box (42), ultra-dynamic strain gauge (43), and oscilloscope (44) are connected in sequence through a high-temperature shielded wire (41); S11, Test Parameter Settings After completing the wiring, adjust the sampling depth, delay, trigger source, trigger mode, trigger level, and sampling method of the signal acquisition system (9) to meet the test requirements; S12, Verification The high-temperature strain gauge (34) is checked by the ultra-dynamic strain gauge (43), and the expected waveform is obtained by the signal acquisition system (9). S13, Slow Cooker Installation The fuse (2) and the high-temperature strain gauge pressure bar sensor (3) are placed in the slow oven (4). The oven wall is heated by electricity. The wire of the temperature controller (12) is connected to the nickel-chromium / nickel-silicon thermocouple fixed on the outer wall of the slow oven (4) to feed back the temperature of the outer wall to the temperature controller (12). The temperature controller (12) then adjusts the heating rate of the slow oven by controlling the output power. A measuring point is set at the position of the fuse explosive shell. A K-type armored miniature thermocouple is installed and connected to the temperature acquisition instrument (10) to obtain the temperature-time data of the measuring point during the baking process. S14, Data Acquisition Use an oscilloscope (44) to acquire the voltage signal on the pressure rod (33) when the fuse (2) responds; S15, Data Processing The equation for converting a voltage-time signal into a pressure-time signal is: ， In the formula, U 0 represents the instrument's output voltage. K Represents the sensitivity coefficient of a high-temperature strain gauge. G Represents the instrument's magnification. U 1 represents the bridge input voltage. E Represents the elastic modulus of the compression bar; The attenuation law of shock waves in copper is derived from the following equation: ， in, x The thickness of the copper pad (31) is... P 0 represents the output pressure of the fuze reaction. P x This is a stress wave in the compression bar. The compressive yield strength of copper is given by the pressure value at the top of the pressure bar (33), which is the peak value of the internal stress of the pressure bar. Therefore, by substituting the experimentally measured data into the copper attenuation law equation, the reaction output pressure of the fuze can be obtained. P 0.

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