Motor train unit train body service state detection method and system

Abstract

The invention discloses a motor train unit train body service state detection method and system, and belongs to the technical field of motor train unit detection. The method comprises the following steps: a corrosion state detection stage: positioning a corrosion area, recording a corrosion range and a maximum corrosion depth, and collecting a corrosion product sample; then component testing is conducted on the corrosion product sample, corrosion product components and corrosion types are analyzed, a corrosion mechanism is generated, and a corrosion detection result is obtained; a weld joint dual-detection stage: detecting structural defects or cracks of a target weld joint area through a dye penetrant inspection method, carrying out residual stress test by using ultrasonic waves, and evaluating the use performance of the vehicle to obtain a weld joint detection result; and a fatigue strength and residual life evaluation stage: establishing a vehicle body finite element model under different vehicle conditions according to a corrosion detection result and a welding seam detection result, evaluating the residual life of the vehicle body through static strength and fatigue strength simulation, and generating a vehicle body service state. According to the invention, high-efficiency and comprehensive monitoring and evaluation are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of EMU detection, and in particular to a method and system for detecting the service status of an EMU body. Background Art

[0002] The Harmony EMU's body load-bearing structure is constructed from large, hollow aluminum alloy profiles welded together along the entire length of the vehicle body, creating a cylindrical, integral load-bearing structure. This provides the vehicle with excellent vibration and sound insulation. The weldable aluminum alloy used ensures excellent corrosion resistance. According to design requirements, the Harmony EMU's body is scheduled to have a service life of 30 years (the same as the life of the entire vehicle). Since the body is a structural safety component, its lifespan directly affects the lifespan of the entire vehicle. Therefore, after a long period of online service, it is necessary to compare and analyze the Harmony EMU's original design documents and inspect and evaluate its service status to ensure safe operation throughout its life cycle.

[0003] The shortcomings of existing inspection technologies are as follows: 1. Vehicle corrosion status inspection: Existing corrosion inspections typically only record the presence or absence of corrosion, without detailing the specific extent and depth of the corrosion. This makes it difficult to accurately assess the severity of corrosion and fails to provide specific data to support subsequent repairs and anti-corrosion measures.

[0004] 2. Inspection of critical welds on vehicle bodies: Existing weld inspection methods primarily include radiographic testing, ultrasonic testing, magnetic particle testing, and penetrant testing. While radiographic and ultrasonic testing can detect internal defects, the former requires specialized equipment and protective measures, resulting in low efficiency and high costs. The latter has high surface requirements, while magnetic particle testing is limited to ferromagnetic materials and cannot detect internal defects. Therefore, neither is suitable for assembly line operations. Penetrant testing is simple to operate, low-cost, and suitable for detecting surface defects on a variety of materials, making it suitable for assembly line operations, but it cannot detect internal defects.

[0005] 3. Fatigue Life Assessment: Existing fatigue life assessment methods typically require fatigue testing of the material or the entire target. For large components such as EMU car bodies, this method is not only time-consuming and labor-intensive, but also costly and inefficient. Furthermore, the testing process is subject to numerous unstable factors, such as environmental changes and fluctuations in loading conditions, which can affect the accuracy and reliability of test results. Therefore, traditional fatigue testing methods face numerous challenges in practical application and struggle to meet the requirements for efficient and accurate assessments. Summary of the Invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a method and system for detecting the service status of a train body.

[0007] The object of the present invention is achieved through the following technical solutions: In a first aspect, the present invention provides: a method for detecting the service status of a motor vehicle body, comprising the following steps: During the corrosion status detection phase, the corrosion areas of the intermediate and lead car inspection areas are located, the corrosion range and maximum corrosion depth are recorded, and corrosion product samples are collected. The corrosion product samples are then tested for composition, and the corrosion product composition and corrosion type are analyzed to generate the corrosion mechanism and obtain the corrosion detection results. During the dual weld inspection phase, color flaw detection is used to detect structural defects or cracks in the target weld area, and ultrasonic residual stress testing is used to evaluate vehicle performance and obtain weld inspection results. During the fatigue strength and remaining life assessment phase, a finite element model of the vehicle body under different vehicle conditions is established based on the corrosion detection results and weld inspection results. The remaining life of the vehicle body is evaluated through static strength and fatigue strength simulation, and the vehicle body service status is generated.

[0008] Preferably, the inspection parts of the intermediate car include the door corners of the passenger compartment on the side wall of the intermediate car, the door corners of the end wall of the intermediate car, the coupler panel of the end wall of the intermediate car, the terminal box area at the end of the intermediate car chassis, the side beam equipment hoisting area of ​​the intermediate car chassis, the air duct partition wall of the intermediate car chassis and the opening area of ​​the intermediate car; the inspection parts of the leading car include the areas under the driver's cab, the door corners of the passenger compartment on the side wall of the leading car, the door corners of the end wall of the leading car, the coupler panel of the end wall of the leading car, the terminal box area at the end of the leading car chassis, the side beam equipment hoisting area, the air duct partition wall of the leading car chassis and the opening area of ​​the leading car.

[0009] Preferably, the corrosion state detection stage further includes the following steps: Use a stereo microscope to photograph the corrosion morphology of the corrosion areas at the inspection points of the intermediate and lead cars, use a depth micrometer to measure the depth of the corrosion pits in each corrosion area, and collect corrosion product samples; A variety of materials science testing methods are used to conduct qualitative and quantitative analysis of corrosion product samples to generate corrosion mechanisms.

[0010] Preferably, the material science detection method includes X-ray diffraction experiment, laser confocal Raman spectroscopy analysis and EDS composition test.

[0011] Preferably, the vehicle body finite element model includes a finite element model of a whole vehicle without corrosion, a finite element model of a whole vehicle with corrosion, and a finite element model of a whole vehicle with corrosion and taking into account the influence of residual stress.

[0012] Preferably, the fatigue strength and remaining life assessment stage further comprises the following steps: Apply static loads and fatigue loads to the car body finite element model under different train conditions according to the operating parameters during actual train operation, and calculate the static strength and fatigue strength of the car body finite element model under different train conditions to obtain static strength simulation results and fatigue strength simulation results; The remaining service life of the vehicle body is evaluated based on the static strength simulation results and fatigue strength simulation results, and the vehicle body service status is generated.

[0013] A second aspect of the present invention provides: a system for detecting the service status of an EMU vehicle body, for implementing any of the above-mentioned methods for detecting the service status of an EMU vehicle body, comprising: The corrosion status detection module is used to locate the corrosion area at the inspection points of the intermediate and lead cars, record the corrosion range and maximum corrosion depth, and collect corrosion product samples. The corrosion product samples are then tested for composition, analyzing the corrosion product composition and corrosion type to generate the corrosion mechanism and obtain the corrosion detection results. The weld dual inspection module is used to detect structural defects or cracks in the target weld area through color flaw detection and to perform residual stress testing using ultrasound to evaluate vehicle performance and obtain weld inspection results. The fatigue strength and remaining life assessment module is used to establish a finite element model of the vehicle body under different vehicle conditions based on the corrosion detection results and weld inspection results, evaluate the remaining life of the vehicle body through static strength and fatigue strength simulation, and generate the vehicle body service status.

[0014] The beneficial effects of the present invention are: 1) By carefully recording and analyzing the extent and depth of carbody corrosion and analyzing corrosion mechanisms through the integration of multiple materials science testing methods (such as X-ray diffraction, confocal laser Raman spectroscopy, and EDS composition testing), a comprehensive corrosion monitoring database was established, effectively improving the accuracy of corrosion status monitoring. Furthermore, comprehensive testing of key welds using penetrant testing and ultrasonic residual stress testing ensured weld quality. Based on line load data and industry standards, a simulation model was developed combining corrosion and weld inspection results to scientifically assess the remaining life of the carbody. This achieved highly efficient and comprehensive monitoring and assessment, significantly improving the safety and reliability of the EMU carbody. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Flow chart of the method of the present invention; Figure 2 This is a schematic diagram of the corrosion observation area of ​​the middle car; Figure 3 This is a schematic diagram of the corrosion observation area of ​​the lead vehicle; Figure 4 Schematic diagram of XRD test results; Figure 5 Schematic diagram of the electron microscope morphology of corrosion products; Figure 6 This is a conceptual diagram of the corrosion mechanism; Figure 7 Schematic diagram of the weld PT test area; Figure 8 Schematic diagram of PT test results for each weld test area; Figure 9 This is a schematic diagram of the ultrasonic test area; Figure 10 Schematic diagram of ultrasonic test points in each area; Figure 11 is the longitudinal and transverse distribution curve of residual stress; Figure 12 This is an overview of the residual stress amplitude in each area of ​​the intermediate car; Figure 13 This is an overview of the residual stress amplitude in each area of ​​the lead car; Figure 14 This is a schematic diagram of the vehicle mesh division of the finite element model of the vehicle body; Figure 15 Schematic diagram of prestressing method for vehicle body finite element model; Figure 16 This is a schematic diagram of the locations of defects in the vehicle body finite element model and their corresponding numbers. DETAILED DESCRIPTION

[0016] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work shall fall within the scope of protection of the present invention.

[0017] See Figures 1-16 The first aspect of the present invention provides: a method for detecting the service status of a motor vehicle body, comprising the following steps: During the corrosion status detection phase, the corrosion areas of the intermediate and lead car inspection areas are located, the corrosion range and maximum corrosion depth are recorded, and corrosion product samples are collected. The corrosion product samples are then tested for composition, and the corrosion product composition and corrosion type are analyzed to generate the corrosion mechanism and obtain the corrosion detection results. During the dual weld inspection phase, color flaw detection is used to detect structural defects or cracks in the target weld area, and ultrasonic residual stress testing is used to evaluate vehicle performance and obtain weld inspection results. During the fatigue strength and remaining life assessment phase, a finite element model of the vehicle body under different vehicle conditions is established based on the corrosion detection results and weld inspection results. The remaining life of the vehicle body is evaluated through static strength and fatigue strength simulation, and the vehicle body service status is generated.

[0018] In this embodiment, corrosion detection: The present invention inspects the corrosion status of the vehicle body by recording the corrosion range and depth in detail, pointing out the areas of severe corrosion on the vehicle body and strengthening monitoring. At the same time, a variety of material science detection methods are used to perform qualitative and quantitative analysis on the materials, including chemical analysis using methods such as X-ray diffraction experiments, laser confocal Raman spectroscopy analysis, and EDS component testing to analyze the corrosion mechanism, and these data are established into a database to effectively monitor the corrosion situation of the vehicle body during operation.

[0019] Inspection of key welds on vehicle bodies: This invention uses penetrant testing to inspect key welds for surface defects. Penetrant testing is simple to operate, low-cost, and suitable for detecting surface defects on a variety of materials. Furthermore, this invention uses ultrasonic residual stress testing to measure residual stress in key welds. By combining external inspection results with internal residual stress conditions, a comprehensive assessment of weld quality can be made.

[0020] Fatigue strength and remaining life assessment: Based on existing line load data and the requirements of TB / T 3451 "Design and Testing of EMU Carbody Structure Strength", according to the corrosion scope and corrosion depth results obtained from carbody structure corrosion inspection, and applying the residual stress test results of key carbody welds, a post-service carbody simulation model is established. Through simulation analysis of this model, the remaining life of the post-service carbody is scientifically assessed, achieving efficient and comprehensive monitoring and assessment.

[0021] In some embodiments, the inspection parts of the intermediate car include the door corners of the passenger compartment on the side wall of the intermediate car, the door corners of the end wall of the intermediate car, the coupler panel of the end wall of the intermediate car, the terminal box area at the end of the intermediate car chassis, the side beam equipment hoisting area of ​​the intermediate car chassis, the air duct partition wall of the intermediate car chassis and the opening area of ​​the intermediate car; the inspection parts of the leading car include the areas under the driver's cab, the door corners of the passenger compartment on the side wall of the leading car, the door corners of the end wall of the leading car, the coupler panel of the end wall of the leading car, the terminal box area at the end of the leading car chassis, the side beam equipment hoisting area of ​​the leading car chassis, the air duct partition wall of the leading car chassis and the opening area of ​​the leading car.

[0022] In some embodiments, the corrosion state detection stage further includes the following steps: Use a stereo microscope to photograph the corrosion morphology of the corrosion areas at the inspection points of the intermediate and lead cars, use a depth micrometer to measure the depth of the corrosion pits in each corrosion area, and collect corrosion product samples; A variety of materials science testing methods are used to conduct qualitative and quantitative analysis of corrosion product samples to generate corrosion mechanisms.

[0023] In this embodiment, the corrosion of key parts is checked, the degree of corrosion is recorded, and microscopic morphology of the corroded parts is photographed. After the photographing is completed, some corrosion products are scraped off for analysis. Figure 2As shown, it specifically includes the passenger compartment door corners of the middle car side wall (A1), the door corners of the middle car end wall (A2), the coupler panel of the middle car end wall (A3), the terminal box area at the end of the middle car chassis (A4, A5), the equipment hoisting area of ​​the side beam of the middle car chassis (A7, A8), the air duct partition wall of the middle car chassis and the opening area of ​​the middle car (A9, A10). Figure 3 The corrosion morphology is shown as follows: the driver's cab floor (B1), the passenger compartment door corners on the side walls (B2), the door corners on the lead car end wall (B3), the coupler panel on the lead car end wall (B4), the terminal box area at the end of the lead car underframe (B5 and B6), the equipment hoisting area for the lead car underframe side beams (B7 and B8), and the air duct partition wall and opening area on the lead car underframe (B9 and B10). An Olympus SZ61 stereo microscope was used to photograph the corrosion morphology of the corrosion areas, and a depth micrometer was used to measure the depth of the corrosion pits in each area (accuracy: 0.001 mm).

[0024] The corrosion condition of the vehicle was inspected and the corrosion results were shown in Tables 1 and 2. The corrosion was mainly concentrated in the underframe area of ​​the vehicle body, and no corrosion was found in other parts.

[0025] Table 1 Summary of corrosion conditions of intermediate cars Table 2 Summary of corrosion conditions of lead car Analysis of car body corrosion products: In order to determine the composition and content of corrosion products, a variety of material science testing methods are used to conduct qualitative and quantitative analysis of the materials, including X-ray diffraction experiments, laser confocal Raman spectroscopy analysis, EDS composition testing, etc. On-site corrosion products are collected, and a total of 3 parts are collected on the intermediate car: corrosion products in the cavity of the terminal box area of ​​the intermediate car, corrosion products in the side mounting plate of the terminal box area of ​​the intermediate car, and corrosion products in the hoisting area of ​​the side beam of the chassis of the intermediate car. The head car contains 2 parts: corrosion products in the cavity of the terminal box area of ​​the head car, and corrosion products in the hoisting area of ​​the side beam of the chassis of the head car. According to the corrosion detection results and the analysis of the composition test display, the concept of its corrosion mechanism is made as follows: Figure 6 shown.

[0026] Use dye penetrant testing (PT) to detect structural defects or cracks in key parts of the vehicle body structure and evaluate the vehicle's performance. Figure 7 shown.

[0027] The present invention uses ultrasonic waves to test residual stress. When ultrasonic waves propagate in an isotropic elastic medium, the change in ultrasonic wave velocity is linearly related to the change in residual stress. When the critical refracted longitudinal wave velocity increases, it indicates that compressive residual stress exists in the material, and vice versa, tensile residual stress exists. The ultrasonic residual stress testing technology is used to test the residual stress of key parts. The test parts are as follows: Figure 9 The measurement points are arranged according to the size of the paint stripping area, with a distance of 10 mm between each measurement point. The first row of measurement points is located at the weld, and the subsequent test lines are arranged with intervals of 10 mm away from the weld. The number of measurement points and test strips in each area is shown in the figure. Figure 10 The longitudinal and transverse distribution curves of residual stress are shown in Figure 11 As shown, in the figure, a is longitudinal and b is transverse.

[0028] The ultrasonic stress amplitudes of each area of ​​the intermediate car and the lead car are as follows: Figure 12 and Figure 13 The ultrasonic stress in each region meets the requirements and does not exceed the yield limit of the material of 200 MPa. The residual stress in each region is mostly tensile stress and is evenly distributed.

[0029] In some embodiments, the material science detection method includes X-ray diffraction experiments, laser confocal Raman spectroscopy analysis and EDS composition testing.

[0030] In some embodiments, the vehicle body finite element model includes a finite element model of the entire vehicle without corrosion, a finite element model of the entire vehicle with corrosion, and a finite element model of the entire vehicle with corrosion and taking into account the influence of residual stress.

[0031] In some embodiments, the fatigue strength and remaining life assessment stage further includes the following steps: Apply static loads and fatigue loads to the car body finite element model under different train conditions according to the operating parameters during actual train operation, and calculate the static strength and fatigue strength of the car body finite element model under different train conditions to obtain static strength simulation results and fatigue strength simulation results; The remaining service life of the vehicle body is evaluated based on the static strength simulation results and fatigue strength simulation results, and the vehicle body service status is generated.

[0032] In this embodiment, based on existing line load data and the requirements of TB / T 3451 "Design and Testing of EMU Carbody Structure Strength", according to the corrosion range and corrosion depth results obtained from the carbody structure corrosion inspection, and considering the residual stress test results of the key carbody welds, a post-service carbody simulation model is established to evaluate the remaining service life of the carbody after service.

[0033] During the corrosion process, the surface oxide film of aluminum alloys may be destroyed, allowing the corrosive medium to directly contact the aluminum substrate, triggering pitting or intergranular corrosion. However, this localized corrosion does not affect the material's elastic modulus or yield strength. Because vehicle structure corrosion testing revealed relatively small pit depths, with no significant impact on the material's mechanical properties, the calculations maintained the elastic modulus and yield strength constant, while thinning the cross section to simulate the pits. The area and depth of the thinned section were consistent with the results of field corrosion testing.

[0034] Considering the impact of residual stress after corrosion on the vehicle's service life, a prestress manager was used to apply prestress to the corresponding element locations in the model based on the test results to simulate residual stress. The magnitude of the prestress was consistent with the residual stress test results of the vehicle body.

[0035] According to the results of the vehicle body structure corrosion status inspection, the corrosion defects are mainly located at the vehicle body chassis side beam hoisting area (symbol "A"), the side bolt connection area of ​​the vehicle body chassis end terminal box area (symbol "B"), and the cavity cover plate of the vehicle body chassis end terminal box area (symbol "C"). In order to facilitate the evaluation and analysis of the subsequent results, each corrosion defect is numbered. The location and number of each corrosion defect are as follows Figure 16 shown.

[0036] Static strength verification condition: Static loads are applied based on the main parameters during the actual operation of the train. In order to compare and analyze the effects of corrosion and residual stress on the static strength of the car body, static strength calculations are performed on finite element models of three car conditions: the whole car is free of corrosion, the whole car is corroded, and the whole car is corroded and the influence of residual stress is considered.

[0037] The maximum vertical working load is shown in Table 3: Table 3 Maximum vertical working load conditions of vehicle body The longitudinal load conditions at the coupler connection are shown in Table 4: Table 4 Static strength verification conditions of coupler connection The compression load conditions of the end wall area are shown in Table 5: Table 5 Static strength verification conditions of end wall area The combined load conditions of airtightness strength load and vertical load are shown in Table 6: Table 6 Static strength verification conditions for combined airtightness strength and vertical load Static strength evaluation criteria: Calculate the von Mises stress values ​​for the vehicle's underframe and sidewalls, as well as the underframe side beam mounting area, the side bolt connections at the underframe end terminal box area, and the underframe terminal box area under three finite element models: no corrosion, corrosion, and corrosion after considering the effects of residual stress. If all stress values ​​do not exceed the yield strength of the corresponding material of 200 MPa, there is no significant impact on the vehicle's service life and the vehicle meets the requirements for continued service.

[0038] Tables 7 to 10 show the maximum von Mises stress value verification results under the most dangerous static strength condition. Tables 7 and 8 are the data measured under the maximum vertical working load condition, and Tables 9 and 10 are the data measured under the combined condition of a 1500 kN compressive load and a vertical load at the coupler connection. Table 7 Table 8 Table 9 Table 10 Static strength evaluation results: Compared with a finite element calculation model that did not consider the effects of residual stress and corrosion pitting, the static strength verification results under the two most critical operating conditions showed that under the maximum vertical working load, the combined effects of corrosion pitting and residual stress resulted in the maximum von Mises stress change at the bolted connections B-3 and B-4 on the side of the car body underframe terminal box area. The von Mises stress at these locations increased by 1.7 MPa to 3.1 MPa. Under a combined 1500 kN compressive load and vertical load at the coupler connection, the static strength verification results showed that under the combined effects of corrosion pitting and residual stress, the maximum von Mises stress change occurred at the bolted connections B-3 and B-4 on the side of the car body underframe terminal box area. The von Mises stress at these locations increased by 2.4 MPa to 18.6 MPa. All stress values ​​remained within the corresponding material's yield strength of 200 MPa. When considering the combined effects of residual stress and corrosion, the change in static strength results is more obvious than when only the effect of corrosion pits is considered, but it has no significant impact on the static strength stress distribution results of the entire vehicle, and meets the conditions for continued service.

[0039] Fatigue strength verification conditions: Based on the main parameters during actual train operation and in accordance with the car body fatigue strength calculation requirements of TB / T 3451-2016 "Design and Test of Car Body Structure Strength of EMUs", fatigue loads as shown in Table 11 are applied to the finite element models of three car conditions to perform fatigue strength calculations.

[0040] Table 11 Fatigue strength evaluation criteria: compare the von Mises equivalent stress range (Δσ eq ) with the fatigue limit 50 MPa in the S-N curve of the aluminum alloy corresponding to the fatigue number (100 million times), and evaluate the fatigue strength of the hoisting position. The three principal stresses σ 11 , σ 22 , σ 33 at the position of the maximum von Mises stress of each corrosion defect are extracted. Since shell elements are used in the calculation, the out-of-plane stress is 0, i.e. σ 33 is 0. To calculate the three-dimensional stress range Δσ 11 , Δσ 22 at the peak load and valley load, the von Mises equivalent stress range (Δσ eq ) at this position is obtained, which converts the multi-axial problem into a single-axial problem.

[0041] The maximum equivalent von Mises stress range check results under the most dangerous fatigue strength working conditions (working conditions 7 and 8 in Table 11) are shown in Tables 12-13: Table 12 Table 13 Fatigue evaluation results: compared with the finite element calculation model without considering the influence of residual stress and corrosion pits, the fatigue strength check results under the two most dangerous working conditions show that under the influence of the corrosion pit alone, the maximum change position of the equivalent von Mises stress range Δσ eq is the corrosion pit A-4 in the hoisting area of the side beam of the vehicle body chassis, and the equivalent von Mises stress range Δσ eq at this position is 7.9 MPa, an increase of 0.9 MPa; under the combined influence of corrosion pits and residual stress, the maximum change position of the equivalent von Mises stress range Δσ eq is the corrosion pit A-4 in the hoisting area of the side beam of the vehicle body chassis, and the equivalent von Mises stress range Δσ eq at this position is 7.9 MPa, an increase of 0.9 MPa. All equivalent von Mises stress ranges do not exceed the fatigue limit 50 MPa corresponding to the fatigue number. Under the two finite element models considering the combined action of residual stress and corrosion and the action of corrosion pits alone, the fatigue strength results do not change significantly, and have no great influence on the whole vehicle life, which meets the continue service condition.

[0042] The second aspect of the present application provides a train body service state detection system for realizing any of the above-mentioned train body service state detection methods, comprising: A corrosion state detection module is configured to locate corrosion areas of the intermediate car inspection part and the head car inspection part, record corrosion ranges and maximum corrosion depths, and collect corrosion product samples; then perform component testing on the corrosion product samples, analyze corrosion product components and corrosion types, generate corrosion mechanisms, and obtain corrosion detection results; A weld double detection module is configured to detect structural defects or cracks in the target weld area by using a coloring flaw detection method, perform residual stress testing using ultrasonic waves, and evaluate vehicle performance to obtain weld detection results; A fatigue strength and residual life evaluation module is configured to establish a train body finite element model under different vehicle conditions according to the corrosion detection results and the weld detection results, evaluate the residual life of the train body through static strength and fatigue strength simulation, and generate a train body service state.

[0043] The above-mentioned is only the preferred embodiment of the present application, and it should be understood that the present application is not limited to the form disclosed herein, and should not be considered as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein by using the above-mentioned teaching or related technical or knowledge. Any modification and change made by the person skilled in the art without departing from the spirit and scope of the present application shall be within the protection scope of the appended claims of the present application.

Claims

1. A method for detecting the service status of a motor vehicle body, characterized by: The following steps are involved: During the corrosion status detection phase, the corrosion areas of the intermediate and lead car inspection areas are located, the corrosion range and maximum corrosion depth are recorded, and corrosion product samples are collected. The corrosion product samples are then tested for composition, and the corrosion product composition and corrosion type are analyzed to generate the corrosion mechanism and obtain the corrosion detection results. During the dual weld inspection phase, color flaw detection is used to detect structural defects or cracks in the target weld area, and ultrasonic residual stress testing is used to evaluate vehicle performance and obtain weld inspection results. During the fatigue strength and remaining life assessment phase, a finite element model of the vehicle body under different vehicle conditions is established based on the corrosion detection results and weld inspection results. The remaining life of the vehicle body is evaluated through static strength and fatigue strength simulation, and the vehicle body service status is generated.

2. The method for detecting the service status of an EMU vehicle body according to claim 1, characterized in that: The inspection parts of the intermediate car include the door corners of the passenger compartment on the side wall of the intermediate car, the door corners of the end wall of the intermediate car, the coupler panel of the end wall of the intermediate car, the terminal box area at the end of the intermediate car chassis, the side beam equipment hoisting area of ​​the intermediate car chassis, the air duct partition wall of the intermediate car chassis and the opening area of ​​the intermediate car; the inspection parts of the leading car include the areas under the driver's cab, the door corners of the passenger compartment on the side wall of the leading car, the door corners of the end wall of the leading car, the coupler panel of the end wall of the leading car, the terminal box area at the end of the leading car chassis, the side beam equipment hoisting area, the air duct partition wall of the leading car chassis and the opening area of ​​the leading car.

3. The method for detecting the service status of an EMU vehicle body according to claim 1, characterized in that: The corrosion state detection stage further includes the following steps: Use a stereo microscope to photograph the corrosion morphology of the corrosion areas at the inspection points of the intermediate and lead cars, use a depth micrometer to measure the depth of the corrosion pits in each corrosion area, and collect corrosion product samples; A variety of materials science testing methods are used to conduct qualitative and quantitative analysis of corrosion product samples to generate corrosion mechanisms.

4. The method for detecting the service status of an EMU vehicle body according to claim 3, characterized in that: The material science detection method includes X-ray diffraction experiment, laser confocal Raman spectroscopy analysis and EDS composition test.

5. The method for detecting the service status of an EMU vehicle body according to claim 1, characterized in that: The vehicle body finite element model includes a finite element model of a vehicle without corrosion, a finite element model of a vehicle with corrosion, and a finite element model of a vehicle with corrosion and taking into account the influence of residual stress.

6. The method for detecting the service status of an EMU vehicle body according to claim 1, characterized in that: The fatigue strength and remaining life assessment stage further includes the following steps: Apply static loads and fatigue loads to the car body finite element model under different train conditions according to the operating parameters during actual train operation, and calculate the static strength and fatigue strength of the car body finite element model under different train conditions to obtain static strength simulation results and fatigue strength simulation results; The remaining service life of the vehicle body is evaluated based on the static strength simulation results and fatigue strength simulation results, and the vehicle body service status is generated.

7. A system for detecting the service status of an EMU vehicle body, characterized by: The method for detecting the service status of an EMU vehicle body according to any one of claims 1 to 6 comprises: The corrosion status detection module is used to locate the corrosion area at the inspection points of the intermediate and lead cars, record the corrosion range and maximum corrosion depth, and collect corrosion product samples. The corrosion product samples are then tested for composition, analyzing the corrosion product composition and corrosion type to generate the corrosion mechanism and obtain the corrosion detection results. The weld dual inspection module is used to detect structural defects or cracks in the target weld area through color flaw detection and to perform residual stress testing using ultrasound to evaluate vehicle performance and obtain weld inspection results. The fatigue strength and remaining life assessment module is used to establish a finite element model of the vehicle body under different vehicle conditions based on the corrosion detection results and weld inspection results, evaluate the remaining life of the vehicle body through static strength and fatigue strength simulation, and generate the vehicle body service status.

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