Device and method for measuring ablation thickness of thermal protection layer of metal cabin of aircraft

Abstract

The invention relates to a device and a method for measuring the ablation thickness of a thermal protection layer of a metal cabin of an aircraft, belongs to the technical field of aerospace special parameter measurement, and solves the problems that an existing method for measuring the ablation amount of a dimensional ablative material needs to damage the structure and the integrity of a cabin wall surface, and the synchronism of a sensor and a measured thermal protection layer is poor. The invention discloses a device for measuring the ablation thickness of a heat-proof layer of an aircraft. The device comprises an ultrasonic transducer, a temperature sensor, an ultrasonic signal transceiver, a data acquisition device, a power supply, a data processing and display device, a special fixture and a screw, according to the invention, only the threaded hole fixing device needs to be arranged on the metal layer, the measurement can be completed without damaging the wall surface structure, the integrity of the metal cabin and any damage to the metal cabin of the aircraft, and the installation is convenient; according to the invention, the thermal protection layer of the metal cabin is directly measured, the limitation of a traditional trepanning measurement mode on the measurement position is broken through, and the synchronism is good.

Description

Technical Field

[0001] The invention relates to the technical field of special parameter measurement of aerospace, and in particular to a device and method for measuring the ablation thickness of a heat protection layer of a metal cabin of an aircraft. Background Art

[0002] When the aircraft is flying at high speed, the outer surface of the aircraft body is subjected to severe aerodynamic heating, and its surface temperature is very high. As an important part of the thermal protection structure, the ablative thermal protection layer must control the ablation rate and ablation amount of the thermal protection layer. If the ablative thermal protection layer is burned through during flight, aerodynamic heating will cause the surface temperature of the spacecraft to be too high, resulting in damage to the spacecraft or causing the internal temperature of the spacecraft to be too high, and the instruments cannot work properly.

[0003] Spacecraft with high maneuverability requirements need to maintain their aerodynamic shape during flight, and the ablative material needs to maintain its shape and strength during the ablation phase change process. This type of ablative material is called a dimensional ablative material. Dimensional ablative materials are different from ordinary ablative materials that rely on chemical reactions and mechanical stripping. They are essentially a reinforced phenolic resin material. The ablation process is actually the process of carbonization of the material. The shape and strength of the material hardly change during the ablation and carbonization process and after complete carbonization. Therefore, the traditional wire-laying detection technology relies on the method of measuring the ablation amount by the ablative material scouring and destroying the embedded sensitive element, and the method of measuring the ablation amount by the embedded resistance wire fusing the resistance wire, both of which cannot measure the ablation amount of dimensional ablative materials.

[0004] At present, the commonly used method for measuring the ablation amount of dimensional ablative materials in the industry is to use an embedded ablation sensor. This method of embedded ablation sensors requires designing installation holes on the metal cabin and non-metallic wall in advance, destroying the original wall structure. Therefore, it is urgent to propose a method for measuring the ablation amount without destroying the cabin and the ablation layer structure. Summary of the invention

[0005] In view of the above analysis, the present invention aims to provide a device and method for measuring the ablation thickness of the thermal protection layer of the metal cabin of an aircraft, so as to solve at least one of the following problems: 1. The existing method for measuring the ablation amount of dimensional ablative materials requires destroying the cabin wall and the ablation layer structure; 2. The existing method for measuring the ablation amount of dimensional ablative materials has poor synchronization between the sensor and the thermal protection layer being measured.

[0006] The purpose of the present invention is mainly achieved through the following technical solutions:

[0007] The present invention provides a device for measuring the ablation thickness of a heat-resistant layer of a metal cabin of an aircraft, comprising: an ultrasonic transducer, a temperature sensor, an ultrasonic signal transceiver, a data acquisition device, a power supply, a data processing and display device, a fixture, and screws;

[0008] The ultrasonic transducer is fixed to the metal bulkhead of the aircraft through a fixture, and the fixture is bolted to the metal bulkhead of the aircraft through screws;

[0009] The gap between the ultrasonic transducer and the metal bulkhead of the aircraft is filled with a high temperature resistant coupling agent;

[0010] The ultrasonic transducer and the ultrasonic signal transceiver are connected via a cable;

[0011] The temperature sensor is crimped onto the metal bulkhead of the aircraft;

[0012] The temperature sensor is connected to the data acquisition device for communication, and the ultrasonic signal transceiver is connected to the data acquisition device for communication, and is connected to the power supply through a cable;

[0013] The data processing and display device is communicatively connected with the data acquisition device.

[0014] Furthermore, the ultrasonic transducer is used to output and receive ultrasonic signals, the temperature sensor is used to measure the inner surface temperature of the metal layer of the aircraft's metal cabin, the ultrasonic signal transceiver is used to output and receive alternating voltage, the data acquisition device is used to obtain the time difference between wave peaks in the ultrasonic echo signal, and the data processing and display device is used to calculate and output the ablation thickness of the thermal protection layer in real time.

[0015] Furthermore, a spring is included between the fixture and the screw to adjust the pressure between the ultrasonic transducer and the metal cabin wall surface of the aircraft.

[0016] The present invention also provides a method for measuring the ablation thickness of a heat protection layer of a metal cabin of an aircraft, comprising the following steps:

[0017] S1: establishing a first interpolation function between the propagation speed of the ultrasonic signal in the metal layer material of the aircraft metal cabin and the average temperature of the metal layer and importing it into a data processing and display device;

[0018] S2: establishing a second interpolation function between the propagation speed of the ultrasonic signal in the heat protection layer material of the aircraft metal cabin and the average temperature of the unablated layer and importing it into the data processing and display device;

[0019] S3: Establishing the measurement program and temperature-sound velocity correction program and importing them into the data processing and display device;

[0020] S4: The ultrasonic signal transmitting and receiving device outputs an alternating voltage with a fixed transmitting frequency and period according to the settings, transmits ultrasonic signals to the metal cabin of the aircraft through the ultrasonic transducer and receives echo signals, and the data acquisition device extracts the "metal layer transition time" and "unablated layer transition time" of the echo of the metal cabin material of the aircraft from the echo signals and inputs them into the data processing and display device, which completes data processing in real time according to the measurement program and the temperature-sound velocity correction program and outputs the thickness of the unablated layer.

[0021] Furthermore, in step S3, the measurement program is established based on the principle that:

[0022]

[0023] Where, X—ablation thickness, mm;

[0024] X′—unablated layer thickness, mm;

[0025] X0—total thickness of heat protection layer, mm;

[0026] V(T)—the sound velocity of the ultrasonic signal in the unablated layer of the aircraft metal cabin, m / s;

[0027] t Δ —Transit time of the unablated layer, μs.

[0028] Furthermore, in step S3, the principle of establishing the temperature-sound velocity correction program includes: according to the metal layer thickness L of the aircraft metal cabin and the metal layer transition time t 12 , calculate the average speed of ultrasonic signal propagation in the metal layer of the aircraft metal cabin:

[0029]

[0030] Wherein, L is the thickness of the metal layer of the aircraft metal cabin, mm;

[0031] t 12 —Metal layer transition time, μs;

[0032] V 金属 —The average speed at which ultrasonic signals propagate in the metal layer of the aircraft’s metal cabin, m / s.

[0033] Furthermore, in step S3, the principle of establishing the temperature-sound velocity correction program also includes: using a first interpolation function, according to the average speed V of the ultrasonic signal propagating in the metal layer of the aircraft metal cabin 金属 , get the average temperature of the metal layer of the aircraft metal cabin corresponding to the average speed

[0034] Furthermore, in step S3, the principle of establishing the temperature-sound velocity correction program also includes: obtaining the inner surface temperature Tc of the metal layer of the aircraft metal cabin by measuring with a temperature sensor in the measuring device, and Tc to calculate the temperature T of the interface between the metal layer of the aircraft metal cabin and the heat protection layer J :

[0035]

[0036] in, —Average temperature of the metal layer of the aircraft metal cabin, °C;

[0037] Tc—the inner surface temperature of the metal layer of the aircraft metal cabin, °C;

[0038] T J —The temperature of the interface between the metal layer and the thermal protection layer of the aircraft's metal cabin, ℃.

[0039] Furthermore, in step S3, the temperature-sound velocity correction program establishment principle also includes: J and the carbonization temperature T of the aircraft metal cabin heat protection layer material s Calculate the average temperature of the unablated layer of the aircraft metal cabin

[0040]

[0041] Among them, T J —Temperature of the interface between the metal layer of the aircraft metal cabin and the heat protection layer, °C;

[0042] T s —Carbonization temperature of the heat protection layer material of the aircraft metal cabin, °C;

[0043] —The average temperature of the unablated layer of the aircraft metal cabin;

[0044] Through the second interpolation function, according to the average temperature of the unablated layer of the aircraft metal cabin The propagation velocity V(T) of the ultrasonic signal in the unablated layer of the aircraft metal cabin at the average temperature is obtained.

[0045] Further, in step S4, the fixed transmission frequency is 1-10 Hz, and the fixed period is 0.1s-1s.

[0046] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0047] 1. The existing method of measuring the ablation thickness of the thermal protection layer of the aircraft metal cabin by embedding the ablation sensor requires designing installation holes on the metal cabin and the non-metallic wall (thermal protection layer) in advance, which penetrates the entire cabin and destroys the original wall structure and integrity of the metal cabin. The measuring device and the measuring method of the present invention only need to set threaded holes and fixing devices on the metal layer, without destroying the wall structure, without destroying the integrity of the metal cabin, and without causing any damage to the metal cabin of the aircraft. The measurement can be completed, and the installation is convenient.

[0048] 2. In the existing method of measuring the ablation thickness of the thermal protection layer of the aircraft metal cabin through an embedded ablation sensor, there is a gap between the sensor and the cabin opening, the outer wall surface is mostly a curved surface that is difficult to completely correspond to the sensor, and the ablation of the sensor and the thermal protection layer is not synchronized, resulting in poor synchronization between the sensor and the measured thermal protection layer. The method of the present invention directly measures the thermal protection layer of the metal cabin, breaking through the limitations of the traditional opening measurement method on the measurement position and having good synchronization.

[0049] 3. The existing method of measuring the ablation thickness of the aircraft metal cabin thermal protection layer by embedding the ablation sensor. The embedded metal sensitive line affects the one-dimensional heat transfer. The method of the present invention does not perform any processing on the metal cabin thermal protection layer and directly measures it, which does not affect the heat transfer of the material.

[0050] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0052] Figure 1 It is a schematic diagram of the structure of the measuring device of the present invention;

[0053] Figure 2 This is a schematic diagram of the echo signal collected during the measurement of the present invention;

[0054] Figure 3 It is a schematic diagram of the principle of the measurement method of the present invention;

[0055] Figure 4 It is an interpolation curve diagram of the first interpolation function and the second interpolation function according to an embodiment of the present invention.

[0056] Reference numerals:

[0057] 1-aircraft metal cabin wall; 2-threaded hole; 3-spring; 4-screw; 5-special fixture; 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-heat protection layer; 14-ablation layer; 15-unablated layer. DETAILED DESCRIPTION

[0058] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a 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 used to limit the scope of the present invention.

[0059] Dimensional ablative materials are different from ordinary ablative materials that rely on chemical reactions and mechanical stripping. They have the following characteristics: 1. Dimensional ablative materials are essentially a reinforced phenolic resin material. The ablation process is essentially the carbonization process of the material. The material can begin to carbonize when the temperature is greater than its carbonization temperature, and the carbonization rate is related to the temperature; 2. The material's external dimensions and strength hardly change during and after the material is completely carbonized. Therefore, the traditional wire-laying detection technology relies on the method of measuring the ablation amount by the ablative material eroding and destroying the embedded sensitive element, and the method of measuring the ablation amount by the embedded resistance wire fusing the resistance wire, which cannot measure the ablation amount of dimensional ablative materials. At present, the commonly used method for measuring the ablation amount of dimensional ablative materials in the industry is to use an embedded ablation sensor. This method of embedded ablation sensor requires the design of installation holes on the metal cabin and non-metallic wall in advance, destroying the original wall structure. It should be noted that, usually, the dimensional ablative material heat shield is bonded to the metal cabin wall of the aircraft through a colloid to form a thinner adhesive layer, and the properties of the colloid are similar to those of the dimensional ablative material heat shield.

[0060] The present invention provides a device for measuring the ablation thickness of the heat protection layer of the metal cabin of an aircraft, such as Figure 1 As shown, it includes an ultrasonic transducer 6, a temperature sensor 8, a special fixture 5, an ultrasonic signal transceiver 9, a data acquisition device 10, a power supply 11, a data processing and display device 12, and a screw 4;

[0061] The ultrasonic transducer 6 is fixed to the metal bulkhead 1 of the aircraft through a special fixture 5, and the special fixture 5 is bolted to the metal bulkhead 1 of the aircraft through screws 4; a spring 3 can be added between the special fixture 5 and the screws 4 to adjust the pressure between the ultrasonic transducer 6 and the metal bulkhead surface of the aircraft;

[0062] The temperature sensor 8 is crimped onto the aircraft metal cabin wall 1 and is used to measure the inner surface temperature of the metal layer of the aircraft metal cabin;

[0063] The gap between the ultrasonic transducer 6 and the aircraft metal bulkhead 1 is filled by a high temperature resistant coupling agent 7;

[0064] The ultrasonic transducer 6 and the ultrasonic signal transceiver 9 are connected via a cable to realize the output and reception of ultrasonic signals;

[0065] The temperature sensor 8 is connected to the data acquisition device 10 for communication, and the ultrasonic signal transceiver 9 is connected to the data acquisition device 10 for communication, and is connected to the power source 11 through a cable;

[0066] The data acquisition device 10 includes a signal amplifier, an oscilloscope and a filter, and is used to obtain the time difference between the peaks in the ultrasonic echo signal;

[0067] The data processing and display device 12 is connected to the data acquisition device 10 for real-time calculation and output of the ablation thickness of the heat protection layer.

[0068] It should be noted that the ultrasonic transducer 6 includes a piezoelectric element, which is excited by a short electrical pulse to generate an ultrasonic pulse; the ultrasonic transducer 6 and the ultrasonic signal transceiver 9 are connected by a cable to realize the output and reception of ultrasonic signals. The output of ultrasonic signals refers to the ultrasonic signal transceiver 9 exciting the ultrasonic signal through the ultrasonic transducer 6 according to the setting output of the alternating voltage of a fixed period, and the reception of ultrasonic signals refers to the ultrasonic transducer 6 converting the structural vibration generated by the pressure or deformation of the piezoelectric element into an electrical signal and inputting it into the ultrasonic signal transceiver 9 for storage or outputting it to the data acquisition device 10 to obtain the time difference between the peaks in the ultrasonic echo signal; ultrasonic waves in the megahertz range cannot be effectively transmitted through the air, so a high temperature resistant coupling agent 7 is used between the ultrasonic transducer 6 and the metal bulkhead 1 of the aircraft to achieve good ultrasonic transmission; the threaded hole 2 is pre-processed on the metal bulkhead 1 of the aircraft for the special fixture 5 to be bolted to the metal bulkhead 1 of the aircraft through the screw 4; the ultrasonic signal transceiver 9 is connected to the power supply 11 through a cable, and the power supply 11 can be a power supply on the aircraft or an external power supply on the ground.

[0069] When the above-mentioned measuring device is used to measure the ablation amount of the aircraft thermal protection layer, the ultrasonic signal transmitting and receiving device 9 excites the ultrasonic signal (i.e., the transmitting signal) through the ultrasonic transducer 6 according to the setting output of the alternating voltage of the fixed period, and the ultrasonic signal passes through the high temperature resistant coupling agent-aircraft metal cabin wall-glue layer-unablated layer-transition layer-completely ablated layer (carbonized layer)-air layer in sequence. Each time the ultrasonic wave passes through the boundary of the two layers, transmission and reflection will occur. The transmission wave continues to propagate, and the reflected wave propagates back to the ultrasonic transducer 6. The ultrasonic transducer 6 converts the acoustic energy into electrical energy, which is then stored or output by the ultrasonic signal transceiver 9 to the data acquisition device 10 to obtain the time difference between the peaks in the ultrasonic echo signal; based on the echo signal of the transmitting signal received by the ultrasonic transducer 6, the data acquisition device 10 extracts the time difference between the peaks from the echo signal and inputs it to the data processing and display device 12 through the communication connection. The data processing and display device 12 calculates the ablation degree according to the time domain of each period echo signal and outputs the ablation thickness of the thermal protection layer in real time.

[0070] Specifically, the present invention also provides a method for measuring the ablation thickness of the heat protection layer of the metal cabin of an aircraft, and the measurement is completed by the above-mentioned measuring device, comprising the following steps:

[0071] S1: establishing a first interpolation function between the propagation speed of the ultrasonic signal in the metal layer material of the aircraft metal cabin and the average temperature of the metal layer and importing it into a data processing and display device;

[0072] S2: establishing a second interpolation function between the propagation speed of the ultrasonic signal in the heat protection layer material of the aircraft metal cabin and the average temperature of the unablated layer and importing it into the data processing and display device;

[0073] S3: Establishing the measurement program and temperature-sound velocity correction program and importing them into the data processing and display device;

[0074] S4: The ultrasonic signal transmitting and receiving device outputs an alternating voltage with a fixed transmitting frequency and period according to the settings, transmits ultrasonic signals to the metal cabin of the aircraft through the ultrasonic transducer and receives echo signals, and the data acquisition device extracts the "metal layer transition time" and "unablated layer transition time" of the echo of the metal cabin material of the aircraft from the echo signals and inputs them into the data processing and display device, which completes data processing in real time according to the measurement program and the temperature-sound velocity correction program and outputs the thickness of the unablated layer.

[0075] It should be noted that a complete ultrasonic signal cycle typically has a time interval of only a few microseconds, but it will contain multiple peaks, such as Figure 2As shown, during the measurement process, multiple wave peaks of the ultrasonic signal are filtered and displayed by the data acquisition device; the signal amplifier in the data acquisition device amplifies the ultrasonic signal, the filter filters out the signal that is less than 80% of the transmission signal frequency and higher than 120% of the transmission signal frequency, and the oscilloscope displays each wave peak (the horizontal axis represents time, and the vertical axis represents voltage); Figure 2 Among them, the first peak is generated when the ultrasonic transducer excites the ultrasonic signal, the second peak is the reflected wave generated when the ultrasonic signal passes through the metal cabin of the aircraft and enters the glue layer and the unablated layer, and the time difference between the first peak and the second peak is the "metal layer transition time". Since the glue layer between the metal cabin wall of the aircraft and the unablated layer is very thin, and there is no obvious boundary between the glue layer and the unablated layer and the properties of the materials are similar, there will be a small 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, and the time difference between the second peak and the third peak 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. There are many clutters after the third peak, and the fourth and fifth peaks are easily submerged by clutters. The transition layer is in a state of being ablated. Therefore, when measuring the ablation thickness of the aircraft metal cabin thermal protection layer, the ablation thickness of the aircraft metal cabin thermal protection layer can be obtained by subtracting the un-ablated thickness of the ablation layer from the total thickness of the ablation layer.

[0076] Specifically, before the measurement begins, a first interpolation function between the propagation speed of the ultrasonic signal in the metal layer material of the aircraft metal cabin and the average temperature of the metal layer, a second interpolation function between the propagation speed of the ultrasonic signal in the heat protection layer material of the aircraft metal cabin and the average temperature of the unablated layer, a measurement program and a temperature-sound speed correction program are first established and imported into a data processing and display system;

[0077] It should be noted that in step S1, the average temperature of the metal layer of the metal cabin is generally lower than 400°C. Therefore, according to GB / T23900-2009 "Method for measuring ultrasonic velocity of non-destructive inspection materials", a high and low temperature test chamber is used to provide the required temperature environment, and a database is established between the propagation velocity of the ultrasonic signal in the metal layer material of the aircraft metal cabin and the average temperature of the metal layer. Then, the first interpolation function is obtained by fitting according to the least squares method. In step S2, since the temperature resistance of the high-temperature resistant coupling agent in the measuring device is 800°C and the carbonization temperature of the aircraft metal cabin thermal protection layer material is greater than 400°C, it is necessary to first produce a standard sample and use a tubular furnace to provide the required temperature environment. The standard sample test section is placed in the constant temperature zone of the tubular furnace. The standard sample waveguide section is used to guide the ultrasonic probe to transmit and receive ultrasonic waves in a lower temperature area. After intercepting the echo signal of the test section, the sound velocity of the ultrasonic signal at the current temperature is obtained according to GB / T23900-2009 "Ultrasonic Velocity Measurement Method for Non-destructive Inspection Materials", and a database between the propagation velocity of the ultrasonic signal in the aircraft metal cabin thermal protection layer material and the average temperature of the unablated layer is established. Then, the second interpolation function is obtained by fitting according to the least squares method.

[0078] Specifically, in step S3, the measurement program is established based on the principle that:

[0079]

[0080] Where, X—ablation thickness, mm;

[0081] X′—unablated layer thickness, mm;

[0082] X0—total thickness of heat protection layer, mm;

[0083] V(T)—the sound velocity of the ultrasonic signal in the unablated layer of the aircraft metal cabin, m / s;

[0084] t Δ —Unablated layer transition time, (i.e., the time difference between the second and third wave peaks), μs.

[0085] According to formula 1, edit through C language, matlab or labview, establish the measurement program and import it into the data processing and display device.

[0086] It should be noted that V(T) is the sound velocity of the ultrasonic signal in the thermal protection layer material of the aircraft metal cabin. It changes with the temperature of the thermal protection layer. Therefore, proper temperature correction can greatly improve the measurement accuracy. Therefore, before the measurement begins, a temperature-sound velocity correction program is established. The establishment principle is:

[0087] The first step is to calculate the thickness of the metal layer L of the aircraft metal cabin and the metal layer transition time t according to formula 2. 12, calculate the average speed of ultrasonic signal propagation in the metal layer of the aircraft metal cabin:

[0088]

[0089] Wherein, L is the thickness of the metal layer of the aircraft metal cabin, mm;

[0090] t 12 —Metal layer transition time, μs;

[0091] V 金属 —The average speed at which ultrasonic signals propagate in the metal layer of the aircraft’s metal cabin, m / s.

[0092] In the second step, the first interpolation function is used to calculate the average velocity V of the ultrasonic signal propagating in the metal layer of the aircraft metal cabin. 金属 , get the average temperature of the metal layer of the aircraft metal cabin corresponding to the average speed

[0093] The third step is to measure the inner surface temperature Tc of the metal layer of the aircraft metal cabin by the temperature sensor in the measuring device. According to formula 3, and Tc to calculate the temperature T of the interface between the metal layer of the aircraft metal cabin and the heat protection layer J :

[0094]

[0095] in, —Average temperature of the metal layer of the aircraft metal cabin, °C;

[0096] Tc—the inner surface temperature of the metal layer of the aircraft metal cabin, °C;

[0097] T J —The temperature of the interface between the metal layer of the spacecraft's metal cabin and the thermal protection layer, ℃.

[0098] Step 4: According to formula 4, through T J and the carbonization temperature T of the aircraft metal cabin heat protection layer material s Calculate the average temperature of the unablated layer of the aircraft metal cabin

[0099]

[0100] Among them, T J —Temperature of the interface between the metal layer of the aircraft metal cabin and the heat protection layer, °C;

[0101] T s —Carbonization temperature of the heat protection layer material of the aircraft metal cabin, °C;

[0102] —Average temperature of the unablated layer of the aircraft metal cabin, ℃.

[0103] It should be noted that, usually when taking measurements, the material used for the thermal protection layer of the aircraft's metal cabin is known, and its carbonization temperature can be known based on the type of thermal protection layer material. When the thermal protection layer material is determined, the carbonization temperature of the material (i.e., the temperature at which ablation begins) is known and fixed.

[0104] The fifth step is to use the second interpolation function to calculate the average temperature of the unablated layer of the aircraft metal cabin. Obtaining the propagation velocity V(T) of the ultrasonic signal in the unablated layer of the aircraft metal cabin at the average temperature;

[0105] According to the above principles, the editing is completed through C language, matlab or labview, the temperature-sound velocity correction program is established and imported into the data processing and display device.

[0106] Specifically, in step S4, the ultrasonic signal transmitting and receiving device outputs an alternating voltage with a fixed transmitting frequency and period according to the settings, transmits an ultrasonic signal to the metal cabin of the aircraft through the ultrasonic transducer and receives an echo signal, and the data acquisition device extracts the "metal layer transition time t" of the echo of the metal cabin material of the aircraft from the echo signal. 12 ” and “transit time of unablated layer t Δ " and input into the data processing and display device, which completes data processing in real time according to the measurement program and the temperature-sound velocity correction program and outputs the thickness of the unablated layer, including the following stages:

[0107] In the first stage, at room temperature, the ultrasonic signal transmitting and receiving device outputs an alternating voltage with a fixed transmitting frequency and period according to the settings, transmits ultrasonic signals to the metal cabin of the aircraft through the ultrasonic transducer and receives echo signals. The fixed transmitting frequency is 1-10Hz, and the fixed period is 0.1s-1s; the vibration frequency of the ultrasonic transmitting signal is 0.5-3MHz. For example, the vibration frequency of the ultrasonic transmitting signal is 0.8MHz, 1MHz, 1.5MHz, 2MHz, and 2.5MHz. The higher the measurement accuracy requirement, the higher the ultrasonic transmitting signal vibration frequency of the transmitting and receiving device is used. At this time, the metal cabin of the aircraft has not yet begun to heat up, and the ultrasonic signal passes through the high temperature resistant coupling agent-aircraft metal cabin wall-glue layer-unablated layer-air layer in sequence, generating the first peak and the second peak; the data acquisition device extracts the "metal layer transition time t of the aircraft metal cabin material echo from the echo signal 12 " and the total thickness of the heat protection layer X0, as the initial value of the measurement;

[0108] In the second stage, the aircraft metal cabin begins to be heated, and the temperature of the aircraft metal cabin gradually increases. The ultrasonic signal transmitting and receiving device outputs an alternating voltage at the same fixed frequency and period as in the first stage, transmits ultrasonic signals to the aircraft metal cabin through the ultrasonic transducer and receives echo signals, and begins to heat until the aircraft metal cabin thermal protection layer begins to ablate. The ultrasonic signal passes through the high temperature resistant coupling agent-aircraft metal cabin wall-glue layer-unablated layer-transition layer-air layer in sequence, generating the first wave peak, the second wave peak, and the third wave peak. However, the time difference between the second wave peak and the third wave peak in this stage is t Δ It is very small and infinitely close to 0. Therefore, at this stage, the temperature-sound velocity correction program does not intervene in the measurement. The thickness of the unablated layer X′ is approximately equal to the total thickness of the heat protection layer X0, and the ablated thickness X is 0.

[0109] In the third stage, the outer surface temperature of the aircraft's metal cabin reaches the carbonization temperature of the heat protection layer, and the heat protection layer begins to ablate. The ultrasonic signal transmitting and receiving device outputs an alternating voltage at the same fixed frequency and period as in the first stage, and transmits ultrasonic signals to the aircraft's metal cabin through the ultrasonic transducer and receives echo signals. The ultrasonic signal passes through the high-temperature resistant coupling agent-aircraft metal cabin wall-glue layer-unablated layer-transition layer-completely ablated layer (carbonized layer)-air layer in sequence, generating the first peak, the second peak, the third peak, the fourth peak and the fifth peak. The data acquisition device extracts the "metal layer transition time t" of the aircraft's metal cabin material echo from the echo signal. 12 ” and “transit time of unablated layer t Δ " and input it into the data processing and display device. When the measuring device observes the generation of the fourth wave peak, it means that the heat protection layer begins to ablate. The temperature-sound velocity correction program starts and the measurement is intervened. The data processing and display device completes the data processing in real time according to the measurement program and outputs the thickness of the unablated layer. At this time, the thickness of the unablated layer is X'. As the measurement proceeds, the data processing and display device displays in real time and ablation thickness X.

[0110] Example

[0111] In this embodiment, it is known that the metal layer material of a certain aircraft metal cabin is aluminum alloy, and the thickness L is 20 mm; the heat protection layer material is phenolic resin, and the thickness X0 is 20 mm. The carbonization temperature of the heat protection layer is T s It is 650℃.

[0112] The device and method for measuring the ablation thickness of the heat-resistant layer of the aircraft metal cabin body proposed by the present invention are used to measure the ablation thickness of the heat-resistant layer of the aircraft metal cabin body after the heat-resistant layer of the aircraft metal cabin body is heated, comprising the following steps:

[0113] Step 1: Follow the measurement device diagram (such as Figure 1 As shown), arrange the components of the measuring device;

[0114] Step 2: Before the measurement begins, a first interpolation function between the propagation speed of the ultrasonic signal in the aluminum alloy layer of the aircraft metal cabin and the average temperature of the aluminum alloy layer and a second interpolation function between the propagation speed of the ultrasonic signal in the heat protection layer material of the aircraft metal cabin and the average temperature of the unablated layer are established and imported into the data processing and display device 12 in the measuring device;

[0115] The interpolation curve diagram of the first interpolation function and the second interpolation function is as follows: Figure 4 shown.

[0116] Step 3: Before the measurement begins, a measurement program and a temperature-sound velocity correction program are established and imported into the data processing and display device 12 in the measurement device. The principle of establishing the measurement program and the temperature-sound velocity correction program is as described in the specification;

[0117] Step 4: Measurement starts, the aircraft metal cabin starts to be heated, the ultrasonic signal transmitting and receiving device 9 outputs an alternating voltage with a fixed frequency and period according to the setting, transmits an ultrasonic signal to the aircraft metal cabin through the ultrasonic transducer 6 and receives an echo signal, wherein the fixed transmitting frequency is 10 Hz, the fixed transmitting period is 0.1 s, and the vibration frequency of the ultrasonic transmitting signal is 2.5 MHz;

[0118] The echo signal waveform displayed by the data acquisition device 10 is manually observed or automatically checked by a measuring device. At the beginning, the echo signal shows 2-3 peaks, indicating that the heat protection layer material has not yet reached the carbonization temperature and has not started to ablate. The temperature-sound velocity correction program is not started, and the data processing and display device 12 shows that the ablation thickness is 0mm.

[0119] When the echo signal displayed by the data acquisition device 10 shows the fourth peak through manual observation or automatic inspection by the measuring device, it indicates that the heat protection layer begins to ablate, and the temperature-sound velocity correction program is started and the measurement is intervened. Take a certain moment as an example:

[0120] At this moment, the data acquisition device 10 displays the first peak, the second peak, the third peak, the fourth peak, and the fifth peak. Figure 2 As shown; it can be seen that the time difference between the first peak and the second peak, that is, the metal layer transition time t 12 =8.08μs; the time difference between the second and third peaks, i.e. the unablated layer transit time t Δ =11.76μs. The data acquisition device 10 measures the metal layer transition time t 12 and the unablated layer transit time t Δ Transmitted to the data processing and display device 12.

[0121] At this moment, the temperature sensor 8 measures and obtains that the inner surface temperature Tc of the aluminum alloy layer of the aircraft metal cabin is 50°C.

[0122] The internal calculations of the measurement program and the temperature-sound velocity correction program of the data processing and display device 12 are as follows:

[0123] The average speed of ultrasonic signal propagation in the aluminum alloy layer of the aircraft metal cabin:

[0124]

[0125] Through the first interpolation function, according to the average speed V of the ultrasonic signal propagating in the aluminum alloy layer of the aircraft metal cabin, 铝 , obtain the average temperature of the aluminum alloy layer of the aircraft metal cabin corresponding to the average speed

[0126] pass and Tc to calculate the temperature T of the interface between the metal layer of the aircraft metal cabin and the heat protection layer J :

[0127]

[0128] By T J The carbonization temperature of the aircraft metal cabin heat protection layer material is 650℃. Calculate the average temperature of the unburned layer of the aircraft metal cabin

[0129]

[0130] Through the second interpolation function, according to the average temperature of the unablated layer of the aircraft metal cabin Obtain the propagation velocity of the ultrasonic signal in the unablated layer of the aircraft metal cabin at the average temperature V(T) = 2586 m / s;

[0131] Thickness of unablated layer of heat protection layer

[0132] The ablation thickness of the heat protection layer is X=X0-X'=4.8mm.

[0133] When the heat protection layer reaches the ablation temperature, each time the data acquisition device 10 receives an echo signal, the measuring device performs the above calculations according to the measurement program and the temperature-sound velocity correction program, and the data processing and display device 12 displays the output ablation thickness.

[0134] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A device for measuring the ablation thickness of a heat-resistant layer of a metal cabin of an aircraft, characterized in that: include: Ultrasonic transducer, temperature sensor, ultrasonic signal transceiver, data acquisition device, power supply, data processing and display device, fixture, screws; The ultrasonic transducer is fixed to the metal bulkhead of the aircraft through a fixture, and the fixture is bolted to the metal bulkhead of the aircraft through screws; The gap between the ultrasonic transducer and the metal bulkhead of the aircraft is filled with a high temperature resistant coupling agent; The ultrasonic transducer and the ultrasonic signal transceiver are connected via a cable; The temperature sensor is crimped onto the metal bulkhead of the aircraft; The temperature sensor is connected to the data acquisition device for communication, and the ultrasonic signal transceiver is connected to the data acquisition device for communication, and is connected to the power supply through a cable; The data processing and display device is communicatively connected with the data acquisition device.

2. The measuring device according to claim 1, characterized in that The ultrasonic transducer is used to output and receive ultrasonic signals, the temperature sensor is used to measure the inner surface temperature of the metal layer of the aircraft's metal cabin, the ultrasonic signal transceiver is used to output and receive alternating voltage, the data acquisition device is used to obtain the time difference between wave peaks in the ultrasonic echo signal, and the data processing and display device is used to calculate and output the ablation thickness of the thermal protection layer in real time.

3. The measuring device according to claim 1, characterized in that A spring is included between the clamp and the screw, which is used to adjust the pressure between the ultrasonic transducer and the metal cabin wall surface of the aircraft.

4. A method for measuring the ablation thickness of a heat-resistant layer of a metal cabin of an aircraft, which is accomplished by the measuring device according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1: establishing a first interpolation function between the propagation speed of the ultrasonic signal in the metal layer material of the aircraft metal cabin and the average temperature of the metal layer and importing it into a data processing and display device; S2: establishing a second interpolation function between the propagation speed of the ultrasonic signal in the heat protection layer material of the aircraft metal cabin and the average temperature of the unablated layer and importing it into the data processing and display device; S3: Establishing the measurement program and temperature-sound velocity correction program and importing them into the data processing and display device; S4: The ultrasonic signal transmitting and receiving device outputs an alternating voltage with a fixed transmitting frequency and period according to the settings, transmits ultrasonic signals to the metal cabin of the aircraft through the ultrasonic transducer and receives echo signals, and the data acquisition device extracts the "metal layer transition time" and "unablated layer transition time" of the echo of the metal cabin material of the aircraft from the echo signal and inputs them into the data processing and display device, and the data processing and display device completes data processing in real time according to the measurement program and the temperature-sound velocity correction program and outputs the thickness of the unablated layer.

5. The measuring method according to claim 4, characterized in that: In step S3, the measurement procedure is established based on the principle that: Where, X—ablation thickness, mm; X0—total thickness of heat protection layer, mm; V(T)—the sound velocity of the ultrasonic signal in the unablated layer of the aircraft metal cabin, m / s; t Δ —Transit time of the unablated layer, μs.

6. The measuring method according to claim 5, characterized in that: In step S3, the principle of establishing the temperature-sound velocity correction program includes: according to the metal layer thickness L of the aircraft metal cabin and the metal layer transition time t 12 , calculate the average speed of ultrasonic signal propagation in the metal layer of the aircraft metal cabin: Wherein, L is the thickness of the metal layer of the aircraft metal cabin, mm; t 12 —Metal layer transition time, μs; V 金属 —The average speed at which ultrasonic signals propagate in the metal layer of the aircraft’s metal cabin, m / s.

7. The measuring method according to claim 6, characterized in that: In step S3, the principle of establishing the temperature-sound velocity correction program also includes: using a first interpolation function, according to the average speed V of the ultrasonic signal propagating in the metal layer of the aircraft metal cabin 金属 , get the average temperature of the metal layer of the aircraft metal cabin corresponding to the average speed 8. The measuring method according to claim 7, characterized in that: In step S3, the principle of establishing the temperature-sound velocity correction program also includes: obtaining the inner surface temperature Tc of the metal layer of the aircraft metal cabin through the temperature sensor in the measuring device, and obtaining the inner surface temperature Tc of the metal layer of the aircraft metal cabin through the temperature sensor in the measuring device. and Tc to calculate the temperature T of the interface between the metal layer of the aircraft metal cabin and the heat protection layer J : in, —Average temperature of the metal layer of the aircraft metal cabin, °C; Tc—the inner surface temperature of the metal layer of the aircraft metal cabin, °C; T J —The temperature of the interface between the metal layer and the thermal protection layer of the aircraft's metal cabin, ℃.

9. The measuring method according to claim 8, characterized in that: In step S3, the principle of establishing the temperature-sound velocity correction program also includes: J and the carbonization temperature T of the aircraft metal cabin heat protection layer material s Calculate the average temperature of the unablated layer of the aircraft metal cabin Among them, T J —Temperature of the interface between the metal layer of the aircraft metal cabin and the heat protection layer, °C; T s —Carbonization temperature of the heat protection layer material of the aircraft metal cabin, °C; —The average temperature of the unablated layer of the aircraft metal cabin; Through the second interpolation function, according to the average temperature of the unablated layer of the aircraft metal cabin The propagation velocity V(T) of the ultrasonic signal in the unablated layer of the aircraft metal cabin at the average temperature is obtained.

10. The measuring method according to claim 4, characterized in that: In step S4, the fixed transmission frequency is 1-10 Hz, and the fixed period is 0.1 s-1 s.

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