Method for measuring ablation amount of heat protection layer of aircraft metal cabin body

Abstract

This invention relates to a method for measuring the ablation amount of the heat-resistant layer of an aircraft's metal cabin, belonging to the field of aerospace special parameter measurement technology. The method includes: simulating a temperature environment; transmitting ultrasonic signals to the aircraft's metal cabin at a fixed frequency and period; establishing a first interpolation function and a second interpolation function; heating the metal cabin; transmitting ultrasonic signals to the cabin; acquiring ultrasonic echo signal maps to obtain the metal layer transit time; calculating the average speed of the ultrasonic signal propagation in the metal layer; obtaining the corresponding average temperature of the metal layer based on the first interpolation function and the average speed of the ultrasonic signal propagation in the metal layer; measuring the inner surface temperature of the metal layer; calculating the interface temperature between the metal layer and the heat-resistant layer; calculating the average temperature of the unablated layer; obtaining the corresponding ultrasonic signal propagation speed in the unablated layer based on the second interpolation function and the average temperature of the unablated layer; continuously acquiring ultrasonic echo signal maps to obtain the unablated layer transit time; and calculating the ablation amount of the heat-resistant layer.

Description

Technical Field

[0001] This invention relates to the field of aerospace special parameter measurement technology, and in particular to a method for measuring the ablation amount of the heat-resistant layer of a metal cabin of an aircraft. Background Technology

[0002] When a spacecraft re-enters the atmosphere, its outer surface is subjected to the high temperatures generated by high-speed flight, exceeding 2000°C. Ordinary metal structures cannot withstand such temperatures, therefore a high-temperature resistant composite material layer, known as a heat shield, is typically applied over the metal structure. When a spacecraft flies at high Mach numbers for extended periods, aerodynamic heating becomes a significant issue. The materials in the airframe can ablate and deform under these high temperatures, seriously endangering the lives of the pilots. Therefore, it is necessary to evaluate the heat shield performance of materials experimentally, and the ablation rate is one of the key criteria for this evaluation.

[0003] Spacecraft requiring high maneuverability need to maintain their aerodynamic shape during flight. This necessitates that ablative materials retain their shape and strength during the ablation phase transition; such materials are called dimensional ablation materials. Unlike ordinary ablation materials that rely on chemical reactions and mechanical stripping, dimensional ablation materials are essentially reinforced phenolic resin materials. The ablation process is essentially a carbonization process, during which the material's dimensions and strength remain almost unchanged. Therefore, traditional wire-laying detection techniques, which rely on the ablation material eroding and destroying embedded sensitive elements to measure the ablation amount, and methods that measure the ablation amount by melting embedded resistance wires, are both ineffective in measuring the ablation amount of dimensional ablation materials.

[0004] Currently, the commonly used method in the industry for measuring the ablation amount of dimensional ablation materials is to use an embedded ablation sensor. This method requires pre-designing mounting holes on the metal cabin and non-metallic walls, which compromises the integrity of the aircraft cabin structure. Furthermore, gaps exist between the sensor and the cabin openings, and the curved surfaces of the outer walls make it difficult to perfectly align with the sensor. This leads to asynchronous ablation between the sensor and the heat protection layer, resulting in poor synchronization between the sensor and the measured heat protection layer. Therefore, there is an urgent need to propose a method for measuring the ablation amount of the heat protection layer of an aircraft's metal cabin that does not damage the cabin and ablation layer structure. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a method for measuring the ablation amount of the heat protection layer of an aircraft metal cabin, and at least solves one of the following problems: 1. Existing methods for measuring the ablation amount of dimensional ablation materials damage the structural integrity of the aircraft metal cabin; 2. Existing methods for measuring the ablation amount of dimensional ablation materials have poor synchronization between the sensor and the heat protection layer being measured.

[0006] The objective of this invention is mainly achieved through the following technical solutions:

[0007] This invention provides a method for measuring the ablation amount of the heat-resistant layer of an aircraft's metal hull, comprising the following steps:

[0008] S1: Simulate the temperature environment, transmit ultrasonic signals to the metal cabin of the aircraft at a fixed frequency and period, and establish a first interpolation function between the propagation speed of the ultrasonic signal in the metal layer material of the aircraft's metal cabin and the average temperature of the metal layer, and a second interpolation function between the propagation speed of the ultrasonic signal in the heat-insulating layer material of the aircraft's metal cabin and the average temperature of the unablated layer.

[0009] S2: Heat the metal hull of the aircraft, and emit ultrasonic signals to the metal hull of the aircraft according to the fixed frequency and period in step S1. Collect the ultrasonic signal echo signal map to obtain the metal layer transition time t. 12 ;

[0010] S3: Calculate the average velocity V of the ultrasonic signal propagating in the metal layer of the aircraft's metal cabin based on the metal layer transition time and the thickness of the metal layer. 金属 ;

[0011] S4: Based on the first interpolation function and the average velocity V of the ultrasonic signal propagating in the metal layer of the aircraft's metal cabin. 金属 Obtain the average temperature of the metal layer of the aircraft's metal cabin, corresponding to the average propagation speed within the metal layer.

[0012] S5: Measure and obtain the inner surface temperature Tc of the metal layer of the aircraft's metal cabin;

[0013] S6: Based on the average temperature of the metal layers in the aircraft's metal cabin. Based on the inner surface temperature Tc of the metal layer of the aircraft's metal cabin, the temperature T at the interface between the metal layer and the heat shield layer of the aircraft's metal cabin is calculated. J ;

[0014] S7: Based on the temperature T at the interface between the metal layer and the heat shield layer of the aircraft's metal cabin. J Carbonization temperature T of heat shield material for aircraft metal hull s The average temperature of the unablated layer of the aircraft's metal hull was calculated.

[0015] S8: Based on the second interpolation function and the average temperature of the unablated layer of the aircraft metal cabin, obtain the propagation speed V(T) of the ultrasonic signal in the unablated layer of the aircraft metal cabin corresponding to the average temperature of the unablated layer of the aircraft metal cabin.

[0016] S9: Continuously acquire ultrasonic signal echo image to obtain the transition time t of the unablated layer. ΔBased on the total thickness X0 of the aircraft's heat shield, the propagation velocity V(T) in the unablated layer of the aircraft's metal hull, and the transit time t of the unablated layer... Δ The amount of heat-resistant layer ablation X of the aircraft's metal cabin is calculated.

[0017] Furthermore, in step S1, the fixed transmission frequency is 1-10Hz.

[0018] Furthermore, in step S1, the fixed period is 0.1s-1s.

[0019] Furthermore, in step S1, the transmission vibration frequency of the ultrasonic signal is 0.5-3MHz.

[0020] Further, in step S3, the average speed of the ultrasonic signal propagating in the metal layer of the aircraft's metal cabin is calculated using the following formula:

[0021]

[0022] Wherein, L represents the thickness of the metal layer of the aircraft's metal cabin, in mm;

[0023] t 12 — Metal layer transition time, μs;

[0024] V 金属 —The average speed of ultrasonic signals propagating through the metal layers of the aircraft's metal cabin, in m / s.

[0025] Furthermore, in step S6, the temperature at the interface between the metal layer of the aircraft's metal cabin and the heat-resistant layer is calculated using the following formula:

[0026]

[0027] in, —The average temperature of the metal layer of the aircraft's metal cabin, in °C;

[0028] Tc—Inner surface temperature of the metal layer in the metal hull of the aircraft, in °C;

[0029] T J —Temperature at the interface between the metal layer and the heat shield of the aircraft's metal cabin, in °C.

[0030] Further, in step S7, the average temperature of the unablated layer of the aircraft's metal hull is calculated using the following formula:

[0031]

[0032] Among them, T J —Temperature at the interface between the metal layer and the heat shield layer of the aircraft's metal cabin, in °C;

[0033] T s —Carbonization temperature of the heat-resistant layer material of the aircraft's metal hull, °C;

[0034] —The average temperature of the unablated layer of the aircraft's metal hull.

[0035] Further, in step S9, the ablation amount of the heat-resistant layer of the aircraft's metal cabin is calculated using the following formula:

[0036]

[0037] Where X is the ablation thickness, in mm;

[0038] X0—Total thickness of the heat insulation layer, mm;

[0039] V(T) — the propagation speed of ultrasonic signals in the unablated layer of the metal hull of an aircraft, m / s;

[0040] t Δ —Transition time of the unablated layer, μs.

[0041] Furthermore, in step S1, the simulated temperature environment is achieved through a high and low temperature test chamber or a tube furnace.

[0042] Furthermore, in step S5, the temperature of the inner surface of the metal layer of the aircraft's metal cabin is measured by a temperature sensor.

[0043] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0044] 1. The measurement method of the present invention can complete the measurement without damaging the wall structure, without compromising the integrity of the metal cabin, and without causing any damage to the metal cabin of the aircraft, which is convenient and quick.

[0045] 2. The method of the present invention directly measures the heat insulation layer of the metal cabin. Compared with the existing open-hole measurement method, it breaks through the limitations of the traditional open-hole measurement method on the measurement position, has good synchronization, and does not affect the heat transfer of the material.

[0046] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0047] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0048] Figure 1 This is a flowchart of the measurement method of the present invention;

[0049] Figure 2 This is a schematic diagram of the echo signal collected during the measurement process of this invention;

[0050] Figure 3 This is an interpolation curve diagram of the first interpolation function and the second interpolation function according to an embodiment of the present invention;

[0051] Figure 4 This is a schematic diagram of the specific structure of the measurement system in Embodiment 2 of the present invention;

[0052] Figure 5 A schematic diagram illustrating the measurement principle when using the measurement system of Embodiment 2 of the present invention.

[0053] Figure label:

[0054] 1-Aircraft metal bulkhead; 2-Threaded hole; 3-Spring; 4-Screw; 5-Special clamp; 6-Ultrasonic transducer; 7-High temperature resistant coupling agent; 8-Temperature sensor; 9-Ultrasonic signal transceiver; 10-Data acquisition device; 11-Power supply; 12-Data processing and display device; 13-Heatproof layer; 14-Ablation layer; 15-Unablation layer. Detailed Implementation

[0055] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0056] Ablation materials possess advantages such as high thermal protection efficiency, reliable operation, and strong adaptability to changes in flow fields. They are widely used in aviation, aerospace, missile, nuclear industry, furnace manufacturing, and other industries with extremely demanding operating conditions. The performance of ablation materials directly affects the operating status, reliability, and signal characteristics of aircraft, and the ablation rate is one of the important criteria for evaluating their performance. Rapid, accurate, and complete testing of the ablation rate is of great significance for the research and application of ablation materials.

[0057] Unlike ordinary ablation materials that rely on chemical reactions and mechanical peeling, dimensionally reinforced phenolic resin materials are essentially a type of material whose dimensions and strength remain almost unchanged during and after carbonization. Typically, the heat-resistant layer of dimensionally ablation material is bonded to the metal bulkhead of an aircraft via an adhesive, forming a thin adhesive layer. The properties of the adhesive are similar to those of the heat-resistant layer. Traditional wire-laying detection techniques, which rely on the ablation material eroding and destroying embedded sensitive elements to measure the ablation amount, or on embedded resistance wires melting and measuring the ablation amount, are both ineffective for measuring the ablation amount of dimensionally ablation materials. Currently, the most commonly used method in the industry for measuring the ablation amount of dimensionally ablation materials is to use embedded ablation sensors. This method requires pre-designing mounting holes on both the metal bulkhead and non-metallic walls, thus disrupting the original wall structure. The measurement method of the present invention does not require damage to the wall structure or the integrity of the metal cabin. It directly measures the heat protection layer of the metal cabin without causing any damage to the metal cabin of the aircraft. It breaks through the limitations of traditional hole measurement methods in terms of measurement location and has good synchronization.

[0058] Specifically, the present invention provides a method for measuring the ablation amount of the heat shield layer of an aircraft, comprising the following steps:

[0059] S1: Simulate the temperature environment, transmit ultrasonic signals to the metal cabin of the aircraft at a fixed frequency and period, and establish a first interpolation function between the propagation speed of the ultrasonic signal in the metal layer material of the aircraft's metal cabin and the average temperature of the metal layer, and a second interpolation function between the propagation speed of the ultrasonic signal in the heat-insulating layer material of the aircraft's metal cabin and the average temperature of the unablated layer.

[0060] S2: Heat the metal hull of the aircraft, and emit ultrasonic signals to the metal hull of the aircraft according to the fixed frequency and period in step S1. Collect the ultrasonic signal echo signal map to obtain the metal layer transition time t. 12 ;

[0061] S3: Calculate the average velocity V of the ultrasonic signal propagating in the metal layer of the aircraft's metal cabin based on the metal layer transition time and the thickness of the metal layer. 金属 ;

[0062] S4: Based on the first interpolation function and the average velocity V of the ultrasonic signal propagating in the metal layer of the aircraft's metal cabin. 金属 Obtain the average temperature of the metal layer of the aircraft's metal cabin, corresponding to the average propagation speed within the metal layer.

[0063] S5: Measure and obtain the inner surface temperature Tc of the metal layer of the aircraft's metal cabin;

[0064] S6: Based on the average temperature of the metal layers in the aircraft's metal cabin. Based on the inner surface temperature Tc of the metal layer of the aircraft's metal cabin, the temperature T at the interface between the metal layer and the heat shield layer of the aircraft's metal cabin is calculated. J ;

[0065] S7: Based on the temperature T at the interface between the metal layer and the heat shield layer of the aircraft's metal cabin. J Carbonization temperature T of heat shield material for aircraft metal hull s The average temperature of the unablated layer of the aircraft's metal hull was calculated.

[0066] S8: Based on the second interpolation function and the average temperature of the unablated layer of the aircraft metal cabin, obtain the propagation speed V(T) of the ultrasonic signal in the unablated layer of the aircraft metal cabin corresponding to the average temperature of the unablated layer of the aircraft metal cabin.

[0067] S9: Continuously acquire ultrasonic signal echo image to obtain the transition time t of the unablated layer. Δ Based on the total thickness X0 of the aircraft's heat shield, the propagation velocity V(T) in the unablated layer of the aircraft's metal hull, and the transit time t of the unablated layer... Δ The amount of heat-resistant layer ablation X of the aircraft's metal cabin is calculated.

[0068] Specifically, in step S1, before the high-temperature heating of the aircraft's metal cabin for ablation, the temperature environment is first simulated and measured to establish a first interpolation function between the propagation speed of the ultrasonic signal in the metal layer material of the aircraft's metal cabin and the average temperature of the metal layer, and a second interpolation function between the propagation speed of the ultrasonic signal in the heat-resistant layer material of the aircraft's metal cabin and the average temperature of the unablated layer.

[0069] It should be noted that in step S1, the average temperature of the metal layer of the metal cabin is generally below 400℃. Therefore, according to GB / T23900—2009 "Method for Measurement of Ultrasonic Velocity of Materials for Non-destructive Testing", a high and low temperature test chamber is used to provide the required temperature environment, and a database is established between the propagation speed of ultrasonic signals in the metal layer material of the aircraft's metal cabin and the average temperature of the metal layer. Then, the first interpolation function is obtained by fitting using the least squares method. Since the carbonization temperature of the heat-resistant layer material of the aircraft's metal cabin is >400℃, it is necessary to first make a standard sample and use a tube furnace to provide the required temperature environment. The test section of the standard sample is placed in the constant temperature zone of the tube furnace, and the waveguide section of the standard sample is used to guide the ultrasonic probe to emit and receive ultrasonic waves in a lower temperature area. After intercepting the echo signal of the test section, the speed of sound of the ultrasonic signal at the current temperature is obtained according to GB / T23900—2009 "Method for Measurement of Ultrasonic Velocity of Materials for Non-destructive Testing". A database is established between the propagation speed of the ultrasonic signal in the heat-resistant layer material of the aircraft's metal cabin and the average temperature of the unablated layer. Then, the second interpolation function is obtained by fitting using the least squares method.

[0070] Specifically, in step S1, the fixed transmission frequency is 1-10Hz, and the fixed period is 0.1s-1s; the vibration frequency of the ultrasonic transmission signal is 0.5-3MHz. For example, the vibration frequency of the ultrasonic transmission signal is 0.8MHz, 1MHz, 1.5MHz, 2MHz, or 2.5MHz. The higher the measurement accuracy requirement, the higher the vibration frequency of the ultrasonic transmission signal is used in the transmitting and receiving device.

[0071] It should be noted that a typical complete ultrasound signal cycle takes only a few microseconds, but it contains multiple peaks, such as... Figure 2 As shown, the first peak is the wave generated when the ultrasonic signal is emitted; the second peak is the reflected wave generated when the ultrasonic signal passes through the metal cabin of the aircraft and enters the adhesive layer and the unablated layer. The time difference between the first and second peaks is the "metal layer transition time". Since the adhesive layer between the metal cabin wall of the aircraft and the unablated layer is very thin, and there is no obvious boundary between the adhesive layer and the unablated layer and the properties of the materials are similar, there will be a slight fluctuation after the second peak; the third peak is the reflected wave generated when the ultrasonic signal enters the transition layer from the unablated layer. The time difference between the second and third peaks is the "unablated layer transition time"; the fourth peak is the reflected wave generated when the ultrasonic signal enters the carbonized layer from the transition layer; and the fifth peak is the reflected wave when the ultrasonic signal enters the air interface from the carbonized layer. Among them, there are more clutter waves after the third peak, and the fourth and fifth peaks are easily submerged by clutter waves. The transition layer is in a state of ablation. Therefore, when measuring the ablation amount of the heat protection layer of the aircraft metal cabin, the total thickness of the ablated layer of the aircraft metal cabin can be subtracted from the thickness of the unablated layer to obtain the ablation amount of the heat protection layer of the aircraft metal cabin.

[0072] Specifically, in step S2, the metal hull of the aircraft is heated, and the temperature of the metal hull gradually increases. Ultrasonic signals are emitted into the metal hull according to the fixed frequency and period specified in step S1, and the echo signal diagram of the ultrasonic signals is collected. The transition time t of the metal layer can be obtained from the echo signal diagram. 12 (i.e., the time difference between the first and second peaks); it should be noted that at the beginning of heating, the heating temperature has not yet reached the carbonization temperature of the heat shield layer of the aircraft's metal cabin. Therefore, the ultrasonic signal echo diagram shows the first, second, and third peaks. However, at this stage, the time difference between the second and third peaks is very small, almost zero. At this point, ablation has not yet begun, and the thickness of the unabsorbed layer is approximately equal to the total thickness of the heat shield layer; the ablation amount of the heat shield layer is almost zero. As heating continues, the outer surface temperature of the aircraft's metal cabin reaches the carbonization temperature of the heat shield layer, and the heat shield layer begins to ablate. Then, the ultrasonic signal echo diagram shows the first, second, third, fourth, and fifth peaks, allowing the calculation of the "metal layer transition time t" of the aircraft's metal cabin material echo. 12 "and "transition time t of the unablated layer" Δ ".

[0073] Specifically, in step S3, the metal layer transition time t 12 The thickness L of the metal layer in the aircraft's metal cabin is known, obtained from the ultrasonic signal echo image in step S2. The average velocity V of the ultrasonic signal propagating within the metal layer of the aircraft's metal cabin is calculated using Formula 1. 金属 :

[0074]

[0075] Wherein, L represents the thickness of the metal layer of the aircraft's metal cabin, in mm;

[0076] t 12 — Metal layer transition time, μs;

[0077] V 金属 —The average speed of ultrasonic signals propagating through the metal layers of the aircraft's metal cabin, in m / s.

[0078] Specifically, in step S4, the average velocity V of the ultrasonic signal propagating in the metal layer of the aircraft's metal cabin is obtained through the first interpolation function and step S3. 金属 Obtain the average temperature of the metal layer of the aircraft's metal cabin at that average speed.

[0079] Specifically, in step S5, a temperature sensor can be used to directly measure the inner surface temperature Tc of the metal layer of the aircraft's metal cabin.

[0080] Specifically, in step S6, based on the average temperature of the metal layer of the aircraft's metal cabin obtained in step S4... The temperature Tc of the inner surface of the metal layer of the aircraft metal cabin, measured in step S5, is used to calculate the temperature T at the interface between the metal layer and the heat shield layer of the aircraft metal cabin using formula 2. J :

[0081]

[0082] in, —The average temperature of the metal layer of the aircraft's metal cabin, in °C;

[0083] Tc—Inner surface temperature of the metal layer in the metal hull of the aircraft, in °C;

[0084] T J —Temperature at the interface between the metal layer and the heat-insulating layer of the spacecraft's metal cabin, °C.

[0085] Specifically, in step S7, based on the temperature T at the interface between the metal layer and the heat shield layer of the aircraft's metal cabin obtained in step S6... J Carbonization temperature T of heat shield material for aircraft metal hull s Formula 3 was used to calculate the average temperature of the unablated layer of the metal hull of the spacecraft.

[0086]

[0087] Among them, T J —Temperature at the interface between the metal layer and the heat shield layer of the aircraft's metal cabin, in °C;

[0088] T s —Carbonization temperature of the heat-resistant layer material of the aircraft's metal hull, °C;

[0089] —The average temperature of the unablated layer of the aircraft's metal hull, in °C.

[0090] It should be noted that, usually when making measurements, the material used in the heat shield of the aircraft's metal cabin is known. The carbonization temperature can be known based on the type of heat shield material. When the heat shield material is determined, the carbonization temperature of the material (i.e. the temperature at which ablation begins) is known and fixed.

[0091] Specifically, in step S8, the average temperature of the unablated layer of the aircraft's metal cabin, obtained in step S7, is used as the basis for the second interpolation function. Obtain the propagation speed V(T) of the ultrasonic signal in the unablated layer of the aircraft's metal cabin at the given average temperature.

[0092] Specifically, in step S9, the transition time t of the unablated layer is obtained by acquiring the ultrasonic signal echo signal map. Δ Based on the total thickness X0 of the aircraft's heat shield, the propagation velocity V(T) in the unablated layer of the aircraft's metal hull obtained in step S8, and the transit time t of the unablated layer... Δ Using Formula 4, the ablation amount X of the heat-resistant layer of the aircraft's metal cabin is calculated:

[0093]

[0094] Where X is the ablation thickness, in mm;

[0095] X′—Thickness of the unablated layer, mm;

[0096] X0—Total thickness of the heat insulation layer, mm;

[0097] V(T) — the speed of sound of ultrasonic signals in the unablated layer of the metal hull of an aircraft, m / s;

[0098] t Δ —Transition time of the unablated layer (i.e., the time difference between the second and third peaks), μs. Figure 1 The diagram shown is a flowchart of the measurement method of the present invention.

[0099] The measurement method of the present invention can be accomplished by a measurement system for the ablation amount of the heat-resistant layer of an aircraft metal cabin. The measurement system includes: a temperature simulation unit, an ultrasonic transducer unit, a temperature measurement unit, an ultrasonic signal transceiver unit, and a data acquisition and analysis unit.

[0100] Specifically, the temperature simulation unit includes a high and low temperature test chamber and a tube furnace, which are used to provide different temperature environments to simulate the temperature when the metal cabin of an aircraft is actually heated; it is also connected to the data acquisition and analysis unit.

[0101] The ultrasonic transducer unit includes an ultrasonic transducer, which can be fixed to the metal bulkhead of the aircraft using a special clamp. The special clamp can be bolted to the metal bulkhead of the aircraft using screws. A spring can be added between the special clamp and the screw to adjust the pressure between the ultrasonic transducer and the metal bulkhead of the aircraft. The gap between the ultrasonic transducer and the metal bulkhead of the aircraft can be filled with a high-temperature resistant coupling agent. The ultrasonic transducer and the ultrasonic signal transceiver unit are connected by a cable to realize the output and reception of ultrasonic signals.

[0102] The temperature measurement unit includes a temperature sensor, which is pressed against the metal bulkhead of the aircraft to measure the inner surface temperature of the metal layer of the aircraft's metal bulkhead.

[0103] The ultrasonic signal transceiver unit includes an ultrasonic signal transceiver device for outputting and receiving alternating voltage.

[0104] The data acquisition and analysis unit includes a data acquisition device and a data analysis module. The data acquisition device includes a signal amplifier, an oscilloscope, and a filter, which are used to obtain the time difference between the peaks in the ultrasonic echo signal. The data analysis module includes a first interpolation function, a second interpolation function, a measurement program, and a temperature-correction program, which are used to calculate and output the amount of heat protection layer ablation in real time.

[0105] It should be noted that the temperature sensor, ultrasonic signal transceiver, and data analysis module are all connected to the data acquisition device.

[0106] It should be noted that the ultrasonic transducer includes a piezoelectric element, which is excited by short electrical pulses to generate ultrasonic pulses. The ultrasonic transducer and the ultrasonic signal transceiver are connected by a cable to realize the output and reception of ultrasonic signals. The output of ultrasonic signals refers to the ultrasonic signal being generated by the ultrasonic transceiver through the ultrasonic transducer by the ultrasonic signal transceiver outputting an alternating voltage with a fixed cycle according to the settings. The reception of ultrasonic signals refers to the ultrasonic transducer converting the structural vibration caused by the pressure or deformation of the piezoelectric element into an electrical signal, which is input to the ultrasonic signal transceiver for storage or output to the data acquisition device. The signal amplifier in the data acquisition device amplifies the ultrasonic signal, and the filter filters out signals that are less than 80% of the transmitted signal frequency and more than 120% of the transmitted signal frequency. The oscilloscope displays each peak (the horizontal axis represents time, and the vertical axis represents voltage). The schematic diagram of the ultrasonic echo signal acquired by the data acquisition device can be used to determine the "metal layer transition time t". 12 "and "transition time t of the unablated layer" Δ Ultrasonic waves in the megahertz range cannot propagate effectively through the air. Therefore, a high-temperature resistant coupling agent is used between the ultrasonic transducer and the metal bulkhead of the aircraft to achieve good ultrasonic transmission. Threaded holes can be pre-machined on the metal bulkhead of the aircraft for special clamps to be bolted to the metal bulkhead of the aircraft with screws. The ultrasonic signal transmitting and receiving device is connected to a power source via a cable. The power source can be an onboard power source or an external ground power source.

[0107] It should be noted that the data analysis module includes a first interpolation function, a second interpolation function, and a temperature correction program. The first and second interpolation functions are established according to the method described in step S1 above, simulating the temperature of a real aircraft's metal cabin through a temperature simulation unit. The measurement program is formula 4 described in step S9 above, and is edited using C language, MATLAB, or LabVIEW. The temperature correction program is established according to formulas 1-3 in steps S2-S8 above, and is edited using C language, MATLAB, or LabVIEW.

[0108] During measurement, the ultrasonic signal transmitting and receiving device outputs an alternating voltage with a fixed cycle according to the settings, which excites an ultrasonic signal (i.e., the transmitted signal) through the ultrasonic transducer. The ultrasonic signal passes sequentially through the high-temperature resistant coupling agent, the aircraft's metal bulkhead, the adhesive layer, the unablated layer, the transition layer, the fully ablated layer (carbonized layer), and the air layer. Each time the ultrasonic wave passes through the boundary between two layers, it undergoes transmission and reflection. The transmitted wave continues to propagate, while the reflected wave propagates back to the ultrasonic transducer. The ultrasonic transducer converts the acoustic energy into electrical energy, which is then stored by the ultrasonic signal transceiver or output to the data acquisition device to obtain the time difference between the peaks in the ultrasonic echo signal. Based on the echo signal of the transmitted signal received by the ultrasonic transducer, the data acquisition device extracts the time difference between the peaks from the echo signal and inputs it to the data analysis module through the communication connection. The data analysis module calculates the degree of ablation based on the time domain of the echo signal for each cycle and outputs the ablation amount of the heat-resistant layer in real time.

[0109] The measurement method of the present invention does not require damage to the wall structure or the integrity of the metal cabin. It directly measures the heat-insulating layer of the metal cabin without affecting the heat transfer of the material or causing any damage to the metal cabin of the aircraft. It breaks through the limitations of traditional hole measurement methods in terms of measurement location and has good synchronization.

[0110] Example 1

[0111] In this embodiment, it is known that the metal layer material of a certain aircraft's metal cabin is aluminum alloy with a thickness L of 20mm; the heat-insulating layer material is phenolic resin with a thickness X0 of 20mm, and the carbonization temperature T of the heat-insulating layer is... s The temperature is 650℃.

[0112] The method for measuring the ablation amount of the heat protection layer of an aircraft, as proposed in this invention, measures the ablation amount of the heat protection layer of the aforementioned aircraft metal cabin after it has been subjected to heating. The method includes the following steps:

[0113] S1: Simulate the temperature environment and transmit ultrasonic signals to the aircraft's metal cabin at a fixed frequency and period. Establish a first interpolation function between the propagation speed of the ultrasonic signal in the metal layer material of the aircraft's metal cabin and the average temperature of the metal layer, and a second interpolation function between the propagation speed of the ultrasonic signal in the heat-resistant layer material of the aircraft's metal cabin and the average temperature of the unablated layer; for example... Figure 3 As shown.

[0114] The fixed transmission frequency is 10Hz, the fixed transmission period is 0.1s, and the vibration frequency of the ultrasonic transmission signal is 2.5MHz.

[0115] S2: Heat the metal cabin of the aircraft, and emit ultrasonic signals to the metal cabin of the aircraft according to the fixed frequency and period in step S1. Collect the ultrasonic signal echo signal map to obtain the metal layer transition time.

[0116] The ultrasonic signal echo graph shows that the echo signal initially has 2-3 peaks, indicating that the heat shield material has not yet reached the carbonization temperature and has not yet started to ablate, with an ablation amount of 0 mm.

[0117] When the echo signal in the ultrasonic signal echo graph shows the fourth peak, it indicates that the heat-resistant layer has begun to ablate. Taking a certain moment as an example:

[0118] At that moment, the data acquisition device 10 displays the first peak, the second peak, the third peak, the fourth peak, and the fifth peak, as shown below. Figure 2 As shown, the time difference between the first and second peaks, i.e., the metal layer transition time t, can be determined. 12 = 8.08 μs; the time difference between the second and third peaks, i.e., the transition time t of the unablated layer. Δ =11.76μs.

[0119] S3: Calculate the average speed of the ultrasonic signal propagating in the metal layer of the aircraft's metal cabin based on the metal layer transition time and the thickness of the metal layer:

[0120]

[0121] S4: Using the first interpolation function, based on the average velocity V of the ultrasonic signal propagating in the aluminum alloy layer of the aircraft's metal cabin. 铝 Obtain the average temperature of the aluminum alloy layer of the aircraft's metal cabin at that average speed.

[0122] S5: The temperature Tc of the inner surface of the aluminum alloy layer of the aircraft's metal cabin is measured to be 50℃ by a temperature sensor.

[0123] S6: Based on the average temperature of the metal layer of the aircraft's metal cabin and the inner surface temperature of the metal layer of the aircraft's metal cabin, the temperature at the interface between the metal layer of the aircraft's metal cabin and the heat protection layer is calculated:

[0124]

[0125] S7: via T J Given that the carbonization temperature of the heat-insulating layer material of the aircraft's metal hull is 650℃, calculate the average temperature of the unablated layer of the aircraft's metal hull.

[0126]

[0127] S8: Using the second interpolation function, based on the average temperature of the unablated layer of the aircraft's metal cabin... The propagation speed of the ultrasonic signal in the unablated layer of the aircraft's metal hull at this average temperature was obtained as V(T) = 2586 m / s;

[0128] S9: The ablation amount of the heat shield layer of the aircraft is calculated based on the total thickness of the aircraft's heat shield layer, the propagation velocity in the unablated layer of the aircraft's metal hull, and the transit time of the unablated layer.

[0129] Thickness of the heat-resistant layer without ablation ;

[0130] The heat shield ablation amount X = X0 - X' = 4.8 mm.

[0131] Once the heat shield reaches its ablation temperature, ultrasonic signal echo maps are continuously collected to obtain the transit time of the unablated layer. Based on the total thickness of the heat shield, the propagation velocity in the unablated layer of the aircraft's metal cabin, and the transit time of the unablated layer, the ablation amount of the heat shield of the aircraft's metal cabin is calculated.

[0132] Example 2

[0133] This embodiment provides a specific implementation device for a system for measuring the ablation amount of the heat-resistant layer of an aircraft's metal hull, such as... Figure 4 As shown.

[0134] The measurement system includes: a temperature simulation unit, an ultrasonic transducer unit, a temperature measurement unit, an ultrasonic signal transceiver unit, and a data acquisition and analysis unit;

[0135] The temperature simulation unit includes a high and low temperature test chamber and a tube furnace, which are used to provide different temperature environments to simulate the temperature when the metal cabin of an aircraft is actually heated.

[0136] The ultrasonic transducer unit includes an ultrasonic transducer 6 for outputting and receiving ultrasonic signals. The ultrasonic transducer 6 is fixed to the metal bulkhead 1 of the aircraft by a special clamp 5. The special clamp 5 can be bolted to the metal bulkhead 1 of the aircraft by screws 4. A spring 3 can be added between the special clamp 5 and the screws 4 to adjust the pressure between the ultrasonic transducer and the metal bulkhead of the aircraft. The gap between the ultrasonic transducer 6 and the metal bulkhead 1 of the aircraft can be filled by a high-temperature resistant coupling agent 7. Threaded holes 2 are pre-machined on the metal bulkhead 1 of the aircraft for the special clamp 5 to be bolted to the metal bulkhead 1 of the aircraft by screws 4.

[0137] The temperature measurement unit includes a temperature sensor 8, which is communicatively connected to the data acquisition device 10 in the data acquisition and analysis unit, and is used to measure the inner surface temperature of the metal layer of the aircraft's metal cabin.

[0138] The ultrasonic signal transceiver unit includes an ultrasonic signal transceiver 9, which is connected to an ultrasonic transceiver 6 via a cable. The ultrasonic signal transceiver 9 outputs an alternating voltage with a fixed cycle according to a set setting, which excites an ultrasonic signal through the ultrasonic transceiver 6. The ultrasonic transceiver 6 converts the structural vibration of the piezoelectric element caused by pressure or deformation into an electrical signal, which is input to the ultrasonic signal transceiver 9 for storage or output to the data acquisition device 10. The ultrasonic signal transmitting and receiving device 9 is connected to a power supply 11 via a cable.

[0139] The data acquisition and analysis unit includes a data acquisition device 10 and a data analysis module 12. The data acquisition device 10 includes a signal amplifier, an oscilloscope, and a filter, used to acquire the time difference between wave peaks in the ultrasonic echo signal. The data analysis module 12 includes a first interpolation function, a second interpolation function, a measurement program, and a temperature correction program, used to calculate and output the ablation thickness of the heat-resistant layer in real time. The data acquisition device 10 and the data analysis module 12 are communicatively connected.

[0140] A schematic diagram illustrating the measurement of ablation of the heat-resistant layer of an aircraft's metal cabin using the measurement system of this embodiment is shown below. Figure 5 As shown.

[0141] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method of measuring the ablation of a heat shield of a metallic cabin of an aircraft, characterized in that, The method comprises the following steps: S1: simulate a measuring temperature environment, emit ultrasonic signals to the metal cabin of the aircraft at a fixed frequency and period, and establish a first interpolation function between the propagation speed of the ultrasonic signals in the metal layer material of the metal cabin of the aircraft and the average temperature of the metal layer and a second interpolation function between the propagation speed of the ultrasonic signals in the heatproof layer material of the metal cabin of the aircraft and the average temperature of the un-ablated layer; S2: heating the aircraft metal cabin, transmitting ultrasonic signals to the aircraft metal cabin according to the fixed frequency and period in step S1, collecting ultrasonic signal echo signal diagrams, and obtaining a metal layer crossing time t 12 ; S3: Calculate the average velocity V of the ultrasonic signal propagating in the metal layer of the aircraft metal cabin according to the metal layer crossing time and the thickness of the metal layer of the aircraft metal cabin 金属 ; S4: obtaining an average temperature of the aircraft metal cabin metal layer corresponding to the average speed of propagation in the aircraft metal cabin metal layer 金属 , obtaining an average temperature of the aircraft metal cabin metal layer corresponding to the average speed of propagation in the aircraft metal cabin metal layer S5: measure and obtain the inner surface temperature Tc of the metal layer of the metal cabin of the aircraft; S6: calculating the temperature T of the interface between the metal layer of the metal cabin of the aircraft and the thermal protection layer from the average temperature of the metal layer of the metal cabin of the aircraft and the inner surface temperature Tc of the metal layer of the metal cabin of the aircraft and the inner surface temperature Tc of the metal layer of the metal cabin of the aircraft J ; S7: calculating the average temperature of the non-eroded layer of the metal cabin of the aircraft based on the temperature T of the interface between the metal layer and the heat protection layer of the metal cabin of the aircraft J and the carbonization temperature T of the heat protection layer material of the metal cabin of the aircraft s , calculating the average temperature of the non-eroded layer of the metal cabin of the aircraft based on the temperature T of the interface between the metal layer and the heat protection layer of the metal cabin of the aircraft S8: according to the second interpolation function and the average temperature of the un-ablated layer of the metal cabin of the aircraft, obtain the propagation speed V(T) of the ultrasonic signals in the un-ablated layer of the metal cabin of the aircraft corresponding to the average temperature of the un-ablated layer of the metal cabin of the aircraft; S9: continuously collect the ultrasonic signal echo signal diagram to obtain the un-ablated layer crossing time t Δ According to the total thickness X0 of the aircraft heat protection layer, the propagation speed V(T) in the un-ablated layer of the aircraft metal cabin, and the un-ablated layer crossing time t Δ The ablation amount X of the aircraft metal cabin heat protection layer is calculated and obtained.

2. The measurement method according to claim 1, characterized in that, In step S1, the fixed emission frequency is 1-10 Hz.

3. The measurement method according to claim 2, characterized in that, In step S1, the fixed period is 0.1 s-1 s.

4. The measurement method according to claim 3, characterized in that, In step S1, the emission vibration frequency of the ultrasonic signals is 0.5-3 MHz.

5. The measurement method according to claim 1, characterized by, In step S3, the average speed of the ultrasonic signals propagating in the metal layer of the metal cabin of the aircraft is obtained by calculation according to the following formula: Wherein, L is the thickness of the metal layer of the metal cabin of the aircraft, mm; t 12 — metal layer crossing time, μs; V 金属 - average speed of ultrasound signal propagation in the metal layer of the aircraft metal cabin, m / s.

6. The measurement method according to claim 1, characterized by, In step S6, the temperature of the interface between the metal layer and the heatproof layer of the metal cabin of the aircraft is obtained by calculation according to the following formula: wherein, - average temperature of the metal layer of the aircraft metal cabin, °C; Tc is the inner surface temperature of the metal layer of the metal cabin of the aircraft, ℃; T J — Temperature of the interface between the metal layer and the heat shield of the metal cabin of the aircraft, °C.

7. The measurement method according to claim 1, characterized by, In step S7, the average temperature of the un-ablated layer of the metal cabin of the aircraft is obtained by calculation according to the following formula: Wherein, T J Temperature of the interface between the metal layer and the thermal protection layer of the metal cabin of the aircraft, ℃ T s — Carbonization temperature of heat shield material for metal cabin of aircraft, °C - Average temperature of the non-eroded layer of the metallic cabin of the aircraft.

8. The measurement method of claim 1, wherein, In step S9, the ablation amount of the heatproof layer of the metal cabin of the aircraft is obtained by calculation according to the following formula: Wherein, X is the ablation thickness, mm; X0 is the total thickness of the heatproof layer, mm; V(T) is the propagation speed of the ultrasonic signals in the un-ablated layer of the metal cabin of the aircraft, m / s; t Δ —Unablated layer crossing time, μs.

9. The measuring method according to any one of claims 1 to 8, characterized in that, In step S1, the simulated measuring temperature environment is realized by a high-low temperature test box or a tube furnace.

10. The measuring method according to any one of claims 1 to 9, characterized in that, In step S5, the inner surface temperature of the metal layer of the metal cabin of the aircraft is measured by a temperature sensor.

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