Method for detecting a composite head cover of a rail vehicle using analog pressure

Abstract

The application discloses a method for detecting a rail vehicle composite material head cover by using analog pressure, and comprises the following steps: S1, installing three sound sensors on fixed positions on the surface of the head cover, and filling the space between the sound sensors and the surface of the head cover with coupling agent; S2, installing three calibration sound sources on the fixed positions on the surface of the head cover, and filling the space between the calibration sound sources and the surface of the head cover with coupling agent; the application uses the sound signals generated by the rail vehicle composite material head cover when the microstructure inside the product is damaged in the process of being subjected to the analog pressure provided by the detection equipment as the basis to make the first judgment, and uses strain gauges to locally measure strain data for the second judgment in the key areas. The application solves the problems in the prior art detection technology, such as the detection result analysis being easily affected by the difference in product manufacturing level, the detection content being limited, the detection period being long, and the detection cost being high.

Description

Technical Field

[0001] This invention relates to the field of vehicle composite material front cover testing technology, specifically to a method for testing composite material front covers of rail vehicles using simulated pressure. Background Technology

[0002] In recent years, high-speed rail vehicles, represented by high-speed trains, have developed rapidly, with the number of operating vehicles and operating mileage repeatedly reaching new highs. However, as the operating time of these vehicles continues to accumulate, ensuring the safety and stability of vehicle components has become a top priority for the rail transit industry. The composite material front cover, as an essential component of high-speed rail vehicles, is installed at the very front of the vehicle and bears the highest aerodynamic load among all the vehicle's outer shell components. Damage to it, and its detachment, can easily cause the vehicle to derail.

[0003] During vehicle mechanics, composite material hoods need to be removed from the vehicle and transported to a designated manufacturer for non-destructive testing and repair. Non-destructive testing is the foundation of repair, and its importance is self-evident.

[0004] The existing non-destructive testing methods applicable to composite material parts include the following:

[0005] Ultrasonic testing, penetrant testing, infrared thermography testing, X-ray testing, acoustic impedance and acoustic resonance testing, stress and strain testing.

[0006] While the above testing methods are applicable to conventional composite material parts, they are not suitable for products such as composite material head covers for rail vehicles.

[0007] First, the manufacturing process for composite material front covers of rail vehicles is not standardized. The overall manufacturing specifications for front covers are rather vague, requiring each supplier to determine its own production parameters, such as layup, processes, and materials. This results in significant differences between front cover products from different suppliers in terms of overall strength, service life, types and distribution of internal defects, and weather resistance.

[0008] Secondly, existing non-destructive testing methods for composite materials also have their own limitations.

[0009] Ultrasonic testing is a commonly used non-destructive testing technology for composite materials, and it has been widely applied in the inspection of various aircraft composite material parts. This testing method can accurately describe the type, size, and location of damage in a product. Inspectors can then comprehensively determine whether the product needs repair and, if so, which parts require repair, based on the damage and the manufacturing process parameters. However, this method is an indirect assessment method that requires comprehensive consideration to determine whether a product needs repair. Furthermore, this method requires a high degree of consistency in product manufacturing quality; the internal damage should be identical to pre-existing defects in a defect sample. However, due to significant differences between manufacturers producing composite material front covers, the inherent defects are diverse, which can severely interfere with the high-precision ultrasonic testing technology, resulting in a large amount of difficult-to-analyze noise in practical applications. Additionally, the numerous and overlapping types of inherent defects make it difficult for inspectors to develop a standardized set of judgment criteria, leading to low efficiency and a high risk of missed or incorrect assessments.

[0010] Because damage to composite materials may occur internally while the outer skin remains intact, penetrant testing, a method that requires surface cracks, is subject to significant limitations in its application.

[0011] X-ray inspection is difficult to detect serious defects such as delamination and debonding, which greatly limits its application.

[0012] Infrared thermal imaging, acoustic impedance, and acoustic resonance are suitable for detecting the bonding between the honeycomb core and the skin, but they are not applicable to composite material hoods that use foam as the core material.

[0013] Stress-strain testing offers a relatively intuitive way to observe a product's current performance and strength without being affected by manufacturing processes, making it a reliable and straightforward testing method. However, this method requires attaching strain gauges to the product surface and can only be performed manually. Attaching strain gauges to every area of ​​the composite material front end requires significant time and manpower. Due to the large surface strain of the composite material front end, only high-strain-limit special strain gauges can be used, resulting in high costs. Furthermore, reusing the gauges requires additional manpower to remove them after they have been attached. This method can only provide a comprehensive and complete assessment of the product, not a rapid preliminary evaluation. Therefore, it is typically used to assess the performance indicators of product prototypes. Applying it to the testing of every single product would not meet the inspection schedule requirements during peak maintenance periods, and its high cost makes it unsuitable for widespread use.

[0014] Based on this, the present invention provides a method for testing composite material front covers of rail vehicles using simulated pressure. Summary of the Invention

[0015] The purpose of this invention is to provide a method for testing composite material front covers of rail vehicles using simulated pressure, in order to solve the problems mentioned in the background art.

[0016] To achieve the above objectives, the present invention provides the following technical solution:

[0017] A method for testing composite material front covers of rail vehicles using simulated pressure includes the following steps:

[0018] S1: Install three sound sensors at fixed positions on the surface of the hood, and fill the gap between the sound sensors and the surface of the hood with coupling agent;

[0019] S2: Install three calibration sound sources at fixed positions on the surface of the hood, and fill the gap between the calibration sound sources and the surface of the hood with coupling agent;

[0020] S3: Start the calibration procedure. The host computer controls the calibration sound source to emit calibration sound waves in the frequency range of 0~450kHz. After the sound sensor receives the sound wave signal, the calibration module calculates the calibration parameters of the hood based on the time difference and attenuation of the received signal. This allows the entire equipment to accurately measure the location information when damage occurs on the surface of the hood and the value of the accumulated acoustic emission energy. After calibration, the calibration sound source is removed.

[0021] S4: Insert the composite material front cover into the strength testing device and apply a load of 100% to 120% of the maximum pressure load during operation to the front surface using the strength testing device;

[0022] S5: If the acoustic emission accumulated energy in a certain area of ​​the composite material hood exceeds the calibrated threshold, it indicates that the area has been damaged. However, the extent of the damage needs to be verified. If the acoustic emission accumulated energy in all areas of the composite material hood does not exceed the calibrated threshold, it indicates that the current strength index of the hood fully meets the strength requirements for safe operation until the next disassembly and return to the factory for maintenance.

[0023] S6: Push the composite material front cover out of the strength testing device, attach strain gauges to the parts where the degree of damage needs to be verified, and after attaching and connecting the strain gauges, insert the composite material front cover back into the strength testing device.

[0024] S7: Execute the verification procedure. The strength testing device applies local pressure to the part that needs to be verified. The pressure sensor in the strength testing device and the strain gauge on the surface of the hood transmit the pressure data and strain data to the strength verification module. The strength verification module calculates and determines whether the current strength of the part that needs to be verified meets the strength requirements for safe operation until the next disassembly and return to the factory for maintenance.

[0025] S8: If the requirements are not met, it is determined that repair is required. After repair, the inspection from step S1 to step S7 will be carried out again. After the inspection is passed, the product can be shipped out and continue to operate.

[0026] Preferably, in step S4, if the interior of the composite material hood is damaged or the strength of part or all of the hood material is insufficient due to aging, the interior of the composite material hood will be damaged under pressure. Common damage modes include: cracking of the resin matrix, breakage of the reinforcing fibers, internal delamination, and separation of the fibers from the resin matrix.

[0027] Preferably, the interior of the composite material hood will break under pressure, emitting a sound signal. Since the breakage occurs inside the composite material hood and the sound signal can easily propagate within the composite material, the sound signal emitted when the composite material breaks can be received by three sound sensors installed on the surface of the hood. After receiving the signal, the sound sensors transmit the signal to a preamplifier for signal amplification and gain. The amplified signal then enters the data acquisition card, converts the analog signal into a digital signal, and transmits it to the host computer for data processing.

[0028] Preferably, during the compression process of the composite material hood, if the hood is damaged at a certain point, the sound signal emitted at the time of damage can be received by three sound sensors. After knowing the parameters of the sound signal propagation inside the hood, the specific location where the sound signal is emitted, i.e. the location of damage, is determined by calculating the time difference between the sound signals received by the three sound sensors.

[0029] Preferably, due to the high manufacturing variability of composite material hoods, using fixed parameters to calculate the specific location of the emitted sound signal is prone to error. Therefore, the method in steps S1 to S3 is adopted. Before the actual testing of each composite material hood, a specific sound source is used to emit a specific sound signal at a specific location on the surface of the hood. After the sound signal propagates in the composite material hood, it is received by three sound sensors. By using the positional relationship between the sound source and the sound sensors, as well as the time difference between the emission and reception of the sound signal, the propagation parameters of the sound signal inside each composite material hood can be obtained. Using these parameters, which are customized and calibrated for each hood, the accurate location of the sound signal at any point on the hood can be accurately calculated. At the same time, by comparing and calculating the energy of the calibration sound signal when it is emitted, the energy of the calibration sound signal when it is received, and its propagation distance, the loss parameters of the sound signal propagating in the composite material of each hood can be obtained. Using these parameters, the energy of each sound signal emitted when the composite material of the hood is damaged can be detected and calculated by the test device during actual testing.

[0030] Preferably, during the entire pressure test of the composite material hood, the testing equipment receives and analyzes all sound signals of the composite material used in the hood being damaged. Each sound signal is located and its energy is recorded. If a certain part of the hood is damaged multiple times, that part will emit multiple sound signals. The cumulative energy of the sound signals of that part can be obtained by accumulating and superimposing the energy of these sound signals. Since the severity of the damage corresponds to the energy of the sound signals emitted when the damage occurs, analyzing the cumulative energy of the sound signals of a certain part of the hood can clearly indicate the severity of the damage to that part.

[0031] Preferably, if the composite material hood does not emit any sound signal during the entire pressure test, it is understood that the hood has not suffered any damage, and its strength fully meets the test requirements and also fully meets the requirements for operation.

[0032] Preferably, in step S6, considering that the parts to be checked may have large strain values, it is necessary to use special strain gauges with a strain limit of 10%.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1) This invention uses the sound signal generated when the internal microstructure of a composite material front cover of a rail vehicle is damaged under simulated pressure provided by testing equipment as the basis for initial judgment. A secondary judgment is then made by using strain gauges to locally measure strain data in key areas. This invention solves the problems of existing testing technologies, such as the susceptibility of test results analysis to variations in product manufacturing levels, limited testing content, long testing cycles, and high testing costs.

[0035] 2) This testing method uses a maximum of two testing steps and only tests four pieces of information on the composite material hood product: whether it is damaged, the location of the damage, the severity of the damage, and the remaining rigidity after damage. Of these four pieces of information: whether it is damaged and the remaining rigidity after damage can be directly measured; the location of the damage and the severity of the damage can be calibrated for each hood product. Furthermore, this testing method requires relatively low precision, which gives these four pieces of information high reliability and the advantage of not being affected by manufacturing differences or various manufacturing defects in hoods. Using these four pieces of information, it is clear whether the tested composite material hood product needs repair and the parts that need repair, without needing information such as the specific form, depth, and precise boundaries of the damage, which are difficult to calibrate and easily interfered with.

[0036] 3) Before sound signal testing, a standardized semi-automatic calibration procedure is performed on each composite material hood. This ensures high reliability of the detected information and prevents interference from manufacturing differences and various manufacturing defects in the hood. The semi-automatic calibration procedure requires only manual installation of three calibration sound sources; the rest of the work is completed automatically by the calibration module.

[0037] 4) Leveraging the ease with which sound signals propagate through solids, only three sound sensors installed at fixed positions on the surface of the hood are needed to pinpoint the location and extent of damage to the composite material hood. Because the number of sensors is small and their positions are fixed, the installation and debugging time can be significantly reduced. As a preliminary screening method, it offers advantages such as high efficiency, low cost, and low false alarm rate. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to specific examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] This embodiment of a method for testing composite material front cover of a rail vehicle using simulated pressure includes the following steps:

[0040] S1: Install three sound sensors at fixed positions on the surface of the hood, and fill the gap between the sound sensors and the surface of the hood with coupling agent;

[0041] S2: Install three calibration sound sources at fixed positions on the surface of the hood, and fill the gap between the calibration sound sources and the surface of the hood with coupling agent;

[0042] S3: Start the calibration procedure. The host computer controls the calibration sound source to emit calibration sound waves in the frequency range of 0~450kHz. After the sound sensor receives the sound wave signal, the calibration module calculates the calibration parameters of the hood based on the time difference and attenuation of the received signal. This allows the entire equipment to accurately measure the location information when damage occurs on the surface of the hood and the value of the accumulated acoustic emission energy. After calibration, the calibration sound source is removed.

[0043] S4: Insert the composite material front cover into the strength testing device and apply a load of 100% to 120% of the maximum pressure load during operation to the front surface using the strength testing device;

[0044] S5: If the acoustic emission accumulated energy in a certain area of ​​the composite material hood exceeds the calibrated threshold, it indicates that the area has been damaged. However, the extent of the damage needs to be verified. If the acoustic emission accumulated energy in all areas of the composite material hood does not exceed the calibrated threshold, it indicates that the current strength index of the hood fully meets the strength requirements for safe operation until the next disassembly and return to the factory for maintenance.

[0045] S6: Push the composite material front cover out of the strength testing device, attach strain gauges to the parts where the degree of damage needs to be verified, and after attaching and connecting the strain gauges, insert the composite material front cover back into the strength testing device.

[0046] S7: Execute the verification procedure. The strength testing device applies local pressure to the part that needs to be verified. The pressure sensor in the strength testing device and the strain gauge on the surface of the hood transmit the pressure data and strain data to the strength verification module. The strength verification module calculates and determines whether the current strength of the part that needs to be verified meets the strength requirements for safe operation until the next disassembly and return to the factory for maintenance.

[0047] S8: If the requirements are not met, it is determined that repair is required. After repair, the inspection from step S1 to step S7 will be carried out again. After the inspection is passed, the product can be shipped out and continue to operate.

[0048] In step S4 of this embodiment, if the interior of the composite material hood is damaged or the strength of part or all of the hood material is insufficient due to aging, the interior of the composite material hood will be damaged under pressure. Common damage modes include: cracking of the resin matrix, breakage of the reinforcing fiber, internal delamination, and separation of the fiber from the resin matrix.

[0049] In this embodiment, the interior of the composite material hood will break under pressure, emitting a sound signal. Since the breakage occurs inside the composite material hood and the sound signal can easily propagate within the composite material, the sound signal emitted when the composite material breaks can be received by three sound sensors installed on the surface of the hood. After receiving the signal, the sound sensors transmit the signal to a preamplifier for signal amplification and gain. The amplified signal then enters the data acquisition card, converts the analog signal into a digital signal, and transmits it to the host computer for data processing.

[0050] In this embodiment, if the composite material hood is damaged at a certain point during the compression process, the sound signal emitted at the time of damage can be received by three sound sensors. After knowing the parameters of the sound signal propagation inside the hood, the specific location where the sound signal is emitted, i.e. the location of the damage, is determined by calculating the time difference between the sound signals received by the three sound sensors.

[0051] Due to the high degree of variation in the manufacturing of composite material hoods in this embodiment, using fixed parameters to calculate the specific location of the emitted sound signal is prone to errors. Therefore, the method in steps S1 to S3 is adopted. Before the actual testing of each composite material hood, a specific sound source emits a specific sound signal at a specific location on the surface of the hood. After the sound signal propagates in the composite material hood, it is received by three sound sensors. By analyzing the positional relationship between the sound source and the sound sensors, as well as the time difference between the emission and reception of the sound signal, the propagation parameters of the sound signal inside each composite material hood can be obtained. Using these parameters, which are customized and calibrated for each hood, the accurate location of the sound signal at any point on the hood can be calculated. At the same time, by comparing and calculating the energy of the calibration sound signal when it is emitted, the energy of the calibration sound signal when it is received, and its propagation distance, the loss parameters of the sound signal propagating in the composite material of each hood can be obtained. Using these parameters, the energy of each sound signal emitted when the composite material of the hood is damaged can be detected and calculated by the testing device during actual testing.

[0052] Throughout the compression test of the composite material hood in this embodiment, the testing equipment receives and analyzes all sound signals indicating damage to the composite material used in the hood. Each sound signal is located and its energy is recorded. If a certain part of the hood is damaged multiple times, that part will emit multiple sound signals. By accumulating and superimposing the energy of these sound signals, the cumulative energy of the sound signals at that part can be obtained. Since the severity of the damage corresponds to the energy of the sound signals emitted when the damage occurs, analyzing the cumulative energy of the sound signals at a certain part of the hood can clearly indicate the severity of the damage at that part.

[0053] In this embodiment, if the composite material hood does not emit any sound signal during the entire pressure test, it is understood that the hood has not suffered any damage, and its strength fully meets the test requirements and also fully meets the requirements for operational use.

[0054] In step S6 of this embodiment, considering that the part that needs to be checked may have a large strain value, it is necessary to use a special strain gauge with a strain limit of 10%.

[0055] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0056] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for testing composite material front covers of rail vehicles using simulated pressure, characterized in that, Includes the following steps: S1: Install three sound sensors at fixed positions on the surface of the hood, and fill the gap between the sound sensors and the surface of the hood with coupling agent; S2: Install three calibration sound sources at fixed positions on the surface of the hood, and fill the gap between the calibration sound sources and the surface of the hood with coupling agent; S3: Start the calibration procedure. The host computer controls the calibration sound source to emit calibration sound waves in the frequency range of 0~450kHz. After the sound sensor receives the sound wave signal, the calibration module calculates the calibration parameters of the hood based on the time difference and attenuation of the received signal. This allows the entire equipment to accurately measure the location information when damage occurs on the surface of the hood and the value of the accumulated acoustic emission energy. After calibration, the calibration sound source is removed. S4: Insert the composite material front cover into the strength testing device and apply a load of 100% to 120% of the maximum pressure load during operation to the front surface using the strength testing device; S5: If the acoustic emission accumulated energy in a certain area of ​​the composite material hood exceeds the calibrated threshold, it indicates that the area has been damaged. However, the extent of the damage needs to be verified. If the acoustic emission accumulated energy in all areas of the composite material hood does not exceed the calibrated threshold, it indicates that the current strength index of the hood fully meets the strength requirements for safe operation until the next disassembly and return to the factory for maintenance. S6: Push the composite material front cover out of the strength testing device, attach strain gauges to the parts where the degree of damage needs to be verified, and after attaching and connecting the strain gauges, insert the composite material front cover back into the strength testing device. S7: Execute the verification procedure. The strength testing device applies local pressure to the part that needs to be verified. The pressure sensor in the strength testing device and the strain gauge on the surface of the hood transmit the pressure data and strain data to the strength verification module. The strength verification module calculates and determines whether the current strength of the part that needs to be verified meets the strength requirements for safe operation until the next disassembly and return to the factory for maintenance. S8: If the requirements are not met, it is determined that repair is required. After repair, the inspection from step S1 to step S7 will be carried out again. After the inspection is passed, the product can be shipped out and continue to operate.

2. The method for testing composite material front cover of a rail vehicle using simulated pressure according to claim 1, characterized in that, In step S4, if the interior of the composite material hood is damaged or the strength of part or all of the hood material is insufficient due to aging, the interior of the composite material hood will be damaged under pressure. Common damage modes include: cracking of the resin matrix, breakage of the reinforcing fibers, internal delamination, and separation of the fibers from the resin matrix.

3. The method for testing composite material front cover of a rail vehicle using simulated pressure according to claim 2, characterized in that, The interior of the composite material hood will break under pressure, emitting a sound signal. Since the breakage occurs inside the composite material hood and the sound signal can easily propagate within the composite material, the sound signal emitted when the composite material breaks can be received by three sound sensors installed on the surface of the hood. After receiving the signal, the sound sensors transmit the signal to a preamplifier for signal amplification and gain. The amplified signal then enters the data acquisition card, converts the analog signal into a digital signal, and transmits it to the host computer for data processing.

4. The method for testing composite material front cover of a rail vehicle using simulated pressure according to claim 2, characterized in that, During the compression process of the composite material hood, if a certain part of the hood is damaged, the sound signal emitted at the time of damage can be received by three sound sensors. After knowing the parameters of the sound signal propagation inside the hood, the specific location of the sound signal emitted by the hood, i.e. the location of the damage, can be determined by calculating the time difference between the sound signals received by the three sound sensors.

5. A method for testing composite material front cover of a rail vehicle using simulated pressure according to claim 4, characterized in that, Due to the high degree of variability in the manufacturing of composite material hoods, using fixed parameters to calculate the exact location of the emitted sound signal is prone to errors. Therefore, the method described in steps S1 to S3 is adopted. Before actual testing of each composite material hood, a specific sound source emits a specific sound signal at a specific location on the hood surface. After the sound signal propagates within the hood, it is received by three sound sensors. By analyzing the positional relationship between the sound source and the sound sensors, as well as the time difference between the emission and reception of the sound signal, the propagation parameters of the sound signal inside each composite material hood can be obtained. Using these parameters, which are customized and calibrated for each hood, the precise location of the sound signal at any point on the hood can be accurately calculated. Simultaneously, by comparing and calculating the energy of the calibration sound signal when it is emitted, the energy of the calibration sound signal when it is received, and its propagation distance, the loss parameters of the sound signal propagating in the composite material of each hood can be obtained. Using these parameters, the energy of each sound signal emitted at each point of failure in the composite material used in the hood can be detected and calculated using a testing device during actual testing.

6. A method for testing composite material front covers of rail vehicles using simulated pressure according to claim 2, characterized in that, Throughout the entire pressure test of the composite material hood, the testing equipment receives and analyzes all sound signals indicating damage to the composite material used in the hood. Each sound signal is located and its energy is recorded. If a certain part of the hood is damaged multiple times, that part will emit multiple sound signals. By accumulating and superimposing the energy of these sound signals, the cumulative energy of the sound signals at that part can be obtained. Since the severity of the damage corresponds to the energy of the sound signals emitted when the damage occurs, analyzing the cumulative energy of the sound signals at a certain part of the hood can clearly indicate the severity of the damage at that part.

7. A method for testing composite material front covers of rail vehicles using simulated pressure according to claim 2, characterized in that, If the composite material hood does not emit any sound signal during the entire pressure test, it is understood that the hood has not suffered any damage, and its strength fully meets the test requirements and also fully meets the requirements for operational use.

8. The method for testing composite material front cover of a rail vehicle using simulated pressure according to claim 1, characterized in that, In step S6, considering that the parts to be checked may have large strain values, it is necessary to use special strain gauges with a strain limit of 10%.