A method and system for evaluating the bolt loosening life of a vehicle

Abstract

The present invention provides a method and system for evaluating the loosening life of vehicle bolts, which relates to the technical field of detecting bolt loosening in rail transit. The method includes conducting a lateral vibration test on vehicle bolts, collecting the clamping force-time history of vehicle bolts, and recording the number of vibrations in the loosening state when the clamping force decays to three remaining clamping forces; obtaining the lateral displacement-loosening life curve of vehicle bolts in three loosening states; constructing a first equivalent relationship and obtaining a second equivalent relationship according to the first equivalent relationship; based on the first and second equivalent relationships, equivalently converting the lateral displacement-loosening life curve of vehicle bolts into a stress-loosening life curve for evaluating loosening by stress cumulative damage; and obtaining the loosening life of vehicle bolts according to the Miner linear cumulative fatigue damage criterion and the stress-loosening life curve. The beneficial effect of the present invention is that it can monitor and evaluate in real time, which has important scientific value and engineering significance for optimizing structural design and preventing bolt loosening.

Description

Technical Field

[0001] The present invention relates to the technical field of rail transit bolt loosening detection, and in particular, to a method and system for evaluating the loosening life of vehicle bolts. Background Art

[0002] Due to the advantages of simple structure, convenient disassembly and assembly, and high reliability, bolt connections are widely used in the fields of rail vehicles, automobiles, ships, and aerospace. Although bolt connection structures are strictly checked and evaluated at the initial design stage, they are still prone to bolt loosening and fatigue failure in the complex environment of long-term vibration, shock, and alternating loads. Generally, bolts become loose before fatigue fracture, so bolt loosening is the most common failure form. In addition, due to the characteristics of suddenness, concealment, and difficulty in prevention of bolt loosening, once loosening failure occurs, very serious consequences will be caused.

[0003] Furthermore, bolt loosening is a process of clamping force decay affected by multiple factors and having strong non-linear coupling characteristics. The bolt loosening mechanism is extremely complex. There are certain limitations in preventing bolt loosening based on the theoretical critical loosening load or loosening monitoring methods. Moreover, the formation and evolution mechanism of bolt loosening is complex and there are many influencing factors, which makes bolt loosening difficult to monitor, prevent, and evaluate, seriously threatening the safety and reliability of mechanical equipment. Therefore, it is crucial to study the method for evaluating the loosening life of bolts. Summary of the Invention

[0004] The purpose of the present invention is to provide a method and system for evaluating the loosening life of vehicle bolts to improve the above problems. To achieve the above purpose, the technical solutions adopted by the present invention are as follows:

[0005] In a first aspect, the present application provides a method for evaluating the loosening life of vehicle bolts, including:

[0006] Conduct a lateral vibration test on vehicle bolts, collect the clamping force-time history of vehicle bolts, and record the number of vibrations in the loosening state when the clamping force decays to three remaining clamping forces, where the three remaining clamping forces are the clamping forces when the initial preload decays to 90%, 80%, and 70%;

[0007] Take the average value of the number of vibrations as the horizontal coordinate of the vehicle bolt loosening curve, and take the lateral displacement amplitude as the vertical coordinate to obtain the lateral displacement-loosening life curve of vehicle bolts in three loosening states;

[0008] Construct a first equivalent relationship, and obtain a second equivalent relationship according to the first equivalent relationship, where the first equivalent relationship is the equivalent relationship between the external load of the bolt connection and the load on the screw rod, and the second equivalent relationship is the equivalent relationship between the load on the screw rod and the stress at the root of the thread;

[0009] Based on the fatigue life calculation method, the lateral displacement-loosening life curve is combined with the first and second equivalent relationships to obtain a stress-loosening life curve for evaluating the loosening of vehicle bolts by stress cumulative damage;

[0010] The loosening life of vehicle bolts is obtained according to Miner's fatigue damage linear cumulative criterion and the stress-loosening life curve.

[0011] Preferably, the lateral vibration test of vehicle bolts is carried out, the clamping force-time history of vehicle bolts is collected, and the number of vibrations in the loosening state when the clamping force decays to three remaining clamping forces is recorded, including:

[0012] The bolts of the rail vehicle and a single-lap T-shaped fixture are used to clamp and assemble the bolts, and monitoring is carried out through a pressure sensor, and the assembly conditions are the same for each test;

[0013] A sinusoidal lateral displacement load is applied, and its calculation formula is as follows:

[0014]

[0015] In the formula, is the lateral displacement amplitude, is the vibration frequency, is the test vibration time, is the lateral displacement load;

[0016] Five displacement amplitude value levels are set, and the pre-tightening force of the bolts is obtained according to the preset standard of mechanical design, and its calculation formula is as follows:

[0017]

[0018] In the formula, is the pre-tightening force, and are the yield strength of the bolt material and the effective area of the bolt cross-section respectively.

[0019] Preferably, after using the bolts of the rail vehicle and a single-lap T-shaped fixture to clamp and assemble the bolts, it includes:

[0020] Applying a lateral displacement load to carry out the vehicle bolt loosening test;

[0021] Judgment is made according to the first basis and the second basis, where the first basis is whether the remaining clamping force of the vehicle bolt decays below 70% of the initial pre-tightening force, and the second basis is whether the vehicle bolt breaks;

[0022] If the judgment result is yes, stop the test, then change the lateral displacement amplitude, and continue to apply the lateral displacement load to carry out the vehicle bolt loosening test; if the judgment result is no, repeat the same test until three effective specimens are satisfied and the test ends.

[0023] Preferably, constructing the first equivalent relationship and obtaining the second equivalent relationship according to the first equivalent relationship, including:

[0024] Analyze the force on the vehicle bolt connection, and establish the bending moment equation for each section of the vehicle bolt connection;

[0025] Based on Castigliano's second theorem of material mechanics and the bending moment equation, obtain the first equivalent relationship;

[0026] Based on the first equivalent relationship, taking the thread material as an elastic body, obtain the force on the thread under the lateral external load by taking an infinitesimal element on the thread surface, and establish the second equivalent relationship.

[0027] Preferably, obtaining the vehicle bolt loosening life according to Miner's fatigue damage linear cumulative criterion and the stress-loosening life curve, including:

[0028] Based on the time-correlated damage editing method, count the stress-time history in the second equivalent relationship to obtain the number of cycles at different stress levels;

[0029] Based on Miner's fatigue damage linear cumulative criterion and the number of cycles, establish a vehicle bolt loosening damage accumulation model, and obtain the vehicle bolt loosening cumulative damage value;

[0030] Judge whether the vehicle bolt loosening cumulative damage value meets the preset threshold. If it meets, perform optimized connection of the vehicle bolt and re-test for verification; if it does not meet, it means the vehicle bolt has not loosened, then predict the life of the vehicle bolt.

[0031] In a second aspect, the present application also provides a vehicle bolt loosening life evaluation system, including a test module, a first acquisition module, a construction module, a second acquisition module, and a calculation module, where:

[0032] The test module: is used to carry out the lateral vibration test of the vehicle bolt, collect the clamping force-time history of the vehicle bolt, and record the number of vibrations in the loosening state when the clamping force decays to three remaining clamping forces, where the three remaining clamping forces are the clamping forces when the initial pre-tightening force decays to 90%, 80%, and 70%;

[0033] The first acquisition module: is used to take the average value of the number of vibrations as the horizontal coordinate of the vehicle bolt loosening curve, and take the lateral displacement amplitude as the vertical coordinate to obtain the lateral displacement-loosening life curve of the vehicle bolt in three loosening states;

[0034] Building module: used to build the first equivalent relationship and obtain the second equivalent relationship according to the first equivalent relationship, where the first equivalent relationship is the equivalent relationship between the external load of the bolt connection and the load of the screw rod, and the second equivalent relationship is the equivalent relationship between the load of the screw rod and the stress at the root of the thread;

[0035] Second acquisition module: used to combine the lateral displacement-loosening life curve with the first and second equivalent relationships based on the first and second equivalent relationships to obtain a stress-loosening life curve for evaluating vehicle bolt loosening by stress cumulative damage;

[0036] Calculation module: used to obtain the vehicle bolt loosening life according to the Miner fatigue damage linear cumulative criterion and the stress-loosening life curve.

[0037] In a third aspect, the present application also provides a vehicle bolt loosening life evaluation device, including:

[0038] A memory for storing a computer program;

[0039] A processor for implementing the steps of the vehicle bolt loosening life evaluation method when executing the computer program.

[0040] In a fourth aspect, the present application also provides a readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the above-mentioned vehicle bolt loosening life evaluation method are implemented.

[0041] The beneficial effects of the present invention are:

[0042] The present invention measures the axial force-time history and bending moment-time history of the screw rod under random vehicle loads through a force-measuring bolt. Then, the load-time history (bending moment-time history and axial force-time history) of the bolt is converted into the stress-time history at the root of the thread through the equivalent relationship between the load of the screw rod and the stress at the root of the thread. After that, the stress-time history is counted based on the time-correlated damage editing method to obtain the number of cycles at different stress levels; finally, the bolt loosening deterioration cumulative value and loosening life are obtained with reference to the Miner fatigue damage linear cumulative criterion. The present invention establishes a bolt loosening life evaluation method that is oriented to engineering applications, can be monitored / evaluated in real time, has high reliability and strong applicability, and has important scientific value and engineering significance for optimizing structural design and preventing bolt loosening.

[0043] The present invention is a method for evaluating the loosening life of bolts for engineering applications, which can be monitored / evaluated in real time. By this method, the bolt load can be collected in real time and equivalent to the stress at the root of the thread to evaluate the loosening life of the bolt, effectively preventing and controlling the occurrence of bolt failure accidents, and having important scientific value and engineering significance for optimizing the structural design and ensuring the safe operation of vehicles.

[0044] For bolt connections with simple external loads and easy-to-monitor relative displacements, the present invention can use D – N the curve to evaluate the loosening life of the bolt. However, in the actual random vibration service environment, the external loads on the bolt connection are complex, and it is difficult to obtain its displacement load, so it is difficult to accurately evaluate the loosening life of the bolt. In this case, the method for evaluating the loosening life of vehicle bolts based on the bolt load relationship proposed by the invention can make up for the above deficiencies and achieve an accurate evaluation of the loosening life of bolts under random lateral loads, which is of great significance for ensuring the service safety of vehicle bolt connection equipment and the safety of the lives and property of drivers and passengers.

[0045] Other features and advantages of the present invention will be described in the subsequent specification, and, in part, will become apparent from the specification or can be understood by implementing the embodiments of the present invention. The objectives and other advantages of the present invention can be realized and obtained by the structures specifically pointed out in the written specification, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0047] Figure 1 It is a schematic flow chart of the method for evaluating the loosening life of vehicle bolts described in the embodiments of the present invention;

[0048] Figure 2 It is a schematic structural diagram of the system for evaluating the loosening life of vehicle bolts described in the embodiments of the present invention;

[0049] Figure 3 It is a schematic structural diagram of the equipment for evaluating the loosening life of vehicle bolts described in the embodiments of the present invention;

[0050] Figure 4 It is a schematic flow chart of the bolt lateral vibration test of the method for evaluating the loosening life of vehicle bolts described in the embodiments of the present invention;

[0051] Figure 5Schematic diagram of the force on the bolt connection for the vehicle bolt loosening life evaluation method described in the embodiments of the present invention;

[0052] Figure 6 Mechanical equivalent model of the bolt connection thread for the vehicle bolt loosening life evaluation method described in the embodiments of the present invention;

[0053] Figure 7 For the bolts in three loosening states of the vehicle bolt loosening life evaluation method described in the embodiments of the present invention S – N curve.

[0054] In the figure: 701, test module; 7011, monitoring unit; 70111, second application unit; 70112, first judgment unit; 70113, selection unit; 7012, first application unit; 7013, first calculation unit; 702, first acquisition module; 703, construction module; 7031, first establishment unit; 7032, second calculation unit; 7033, second establishment unit; 704, second acquisition module; 705, calculation module; 7051, acquisition unit; 7052, third establishment unit; 7053, second judgment unit; 800, vehicle bolt loosening life evaluation device; 801, processor; 802, memory; 803, multimedia component; 804, I / O interface; 805, communication component. Detailed implementation manners

[0055] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and illustrated herein can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0056] It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. At the same time, in the description of the present invention, the terms "first", "second", etc. are only used for differential description and cannot be construed as indicating or implying relative importance.

[0057] Embodiment 1:

[0058] At present, there are many mature monitoring methods for bolt loosening, but the methods for evaluating the bolt loosening life are relatively lacking. Among them, a bolt loosening life prediction method disclosed in the invention patent application with the application (patent) number CN201810578081.1 establishes a displacement-loosening life curve of the bolt through bolt loosening tests under different lateral displacement amplitudes ( D – N curve) to evaluate the bolt loosening life. This method is completely feasible in the laboratory environment, but it is difficult to obtain the displacement load of bolt connections in the line environment, so it is impossible to online evaluate the loosening life of in-service bolts. Moreover, a transmission tower bolt life evaluation method disclosed in the invention patent application with the application (patent) number CN202310340847.3 obtains the weak positions through finite element simulation, and then obtains the load-displacement curve and D – N curve through tests. Finally, the loosening life of the transmission tower bolts is obtained based on the rain flow counting method. This method also evaluates the bolt loosening life in the laboratory environment and cannot evaluate the bolt loosening life in real time online. Therefore, the present invention establishes a bolt loosening life evaluation method for engineering applications, which can be monitored / evaluated in real time, has high reliability and strong applicability, and has important scientific value and engineering significance for optimizing structural design and preventing bolt loosening. See the following embodiments for details:

[0059] This embodiment provides a method for evaluating the loosening life of vehicle bolts.

[0060] See Figure 1 . The figure shows that this method includes step S100, step S200, step S300, step S400 and step S500.

[0061] S100. Conduct a lateral vibration test on vehicle bolts, collect the clamping force-time history of the vehicle bolts, and record the number of vibrations in the loosening state when the clamping force decays to three remaining clamping forces, where the three remaining clamping forces are the clamping forces when the initial preload decays to 90%, 80% and 70%.

[0062] It can be understood that in this step S100, it includes S101, S102 and S103, where:

[0063] S101. Use the bolts of the rail vehicle and a single-lap T-shaped fixture to clamp and assemble the bolts, and monitor through a pressure sensor, where the assembly conditions are the same for each test;

[0064] S102. Apply a sinusoidal lateral displacement load, and its calculation formula is as follows:

[0065]

[0066] In the formula, is the lateral displacement amplitude, is the vibration frequency, is the test vibration time, is the lateral displacement load;

[0067] S103. Set five levels of displacement amplitude values, and obtain the pre-tightening force of the bolt according to the preset standard of mechanical design. The calculation formula is as follows:

[0068]

[0069] In the formula, is the pre-tightening force, and are the yield strength of the bolt material and the effective area of the bolt cross-section, respectively.

[0070] It should be noted that the test piece uses a high-strength bolt of 8.8 grade M10×1.5×70 commonly used on rail vehicles. The bolt is clamped and assembled with a single-lap T-shaped fixture on an electro-hydraulic servo fatigue testing machine. The pre-tightening force of each test is controlled by a torque wrench and monitored by an EVT-14T3-10T pressure sensor to ensure that the assembly conditions of each test are the same. The testing machine applies a sinusoidal lateral displacement load, and the displacement amplitudes are set at five levels of 0.3 mm, 0.4 mm, 0.6 mm, 0.8 mm, and 1 mm, and the test frequency is 5 Hz. The EVT-14T3-10T pressure sensor is used to collect the clamping force-time history of the bolt in real time, and the vibration times in the three loosening states when the clamping force decays to 90%, 80%, and 70% of the initial pre-tightening force are recorded. The test process is as Figure 4 shown.

[0071] It should be noted that after step S101, it includes S1011, S1012, and S1013, where:

[0072] S1011. Apply a lateral displacement load to conduct the vehicle bolt loosening test;

[0073] S1012. Make a judgment according to the first basis and the second basis, where the first basis is whether the remaining clamping force of the vehicle bolt decays below 70% of the initial pre-tightening force, and the second basis is whether the vehicle bolt breaks;

[0074] S1013. If the judgment result is yes, stop the test, then change the lateral displacement amplitude, and continue to apply the lateral displacement load to conduct the vehicle bolt loosening test; if the judgment result is no, repeat the same test until three valid specimens are satisfied and the test ends.

[0075] S200. Take the average value of the number of vibrations as the horizontal coordinate of the vehicle bolt loosening curve, and take the lateral displacement amplitude as the vertical coordinate to obtain the lateral displacement-loosening life curve of the vehicle bolt under three loosening states.

[0076] It can be understood that in this step, the average number of vibrations when the clamping force in the bolt clamping force curve decays to 90%, 80%, and 70% of the initial pre-tightening force is used as the horizontal coordinate, and the lateral displacement amplitude is used as the vertical coordinate to obtain the lateral displacement-loosening life curve of the bolt under three loosening states, that is D – N Curve.

[0077] S300. Construct a first equivalent relationship, and obtain a second equivalent relationship according to the first equivalent relationship, where the first equivalent relationship is the equivalent relationship between the external load of the bolt connection and the load on the screw rod, and the second equivalent relationship is the equivalent relationship between the load on the screw rod and the stress at the root of the thread.

[0078] It can be understood that this S300 step includes S301, S302, and S303, where:

[0079] S301. Analyze the force on the vehicle bolt connection and establish the bending moment equations for each section of the vehicle bolt connection;

[0080] S302. Obtain the first equivalent relationship based on Castigliano's second theorem of material mechanics and the bending moment equations;

[0081] S303. Based on the first equivalent relationship, take the thread material as an elastic body, obtain the force on the thread under the lateral external load by taking a micro-element on the thread surface, and establish a second equivalent relationship.

[0082] It should be noted that when a lateral external load is applied to the pre-tightened bolt connection, the screw rod will be subjected to axial force and bending moment. As Figure 5 shown, when the bolt connection is only subjected to the pre-tightening force , no slip occurs on each contact surface, and it is in the clamped state at this time. If a lateral displacement external load is applied to the A plate, the contact surface between the A plate and the bolt head will be subjected to friction , forcing the bolt head to also move laterally. Due to the relative constraint of the thread pair of the nut, this causes the screw rod to be subjected to a bending moment and produce bending deformation. In order to solve the bending moment , analyze the force on the bolt connection. First, establish the bending moment equations for each section of the bolt connection,

[0083]

[0084] In the formula, is the clearance of the bolt hole, is the clamping length, and is the supporting force borne when the bolt head contacts the A plate, is the distance from any position of the mating pore to the support point, is the distance from any position of the screw rod to the bolt head.

[0085] Based on the second Castigliano's theorem of material mechanics, the lateral displacement of the bolt connection D and the lateral external load of the equivalent relationship and the equivalent relationship between the bolt lateral external load and the screw rod bending moment.

[0086] Based on the first equivalent relationship, a second equivalent relationship is obtained. Considering the thread material as an elastic body, as Figure 6 shown, by taking an infinitesimal element on the thread surface to derive the acting force on the thread under the lateral external load. Among them, is the pre-tightening force and the bending moment M the acting force on the infinitesimal element and the sum of, the direction is perpendicular to the thread inclined plane. is the lateral external load the acting force on the infinitesimal element, and the direction is the same as . Taking the O point of the contact surface between the nut and the lower plate as the origin, calculating the acting force of each meshing thread infinitesimal element along the nut thickness direction, and obtaining the load at the z position of the screw rod axis of the thread and the acting force on the thread infinitesimal element.

[0087] It should be noted that after obtaining the equivalent method, a simplified finite element model of the bolt connection is constructed for verification, which is used to simulate the load state of the screw rod under the action of the external load. This model simplifies the thread pair structure and regards the bolt and the nut as a whole. This is because the screw rod is the main research object of the load analysis of the bolt, and has little relationship with the thread pair. Simplifying the thread can greatly improve the calculation efficiency. All meshes are C3D8R elements, the mesh size is 0.5 mm, and a surface-to-surface contact pair is applied to the contact area of each component. The lower plate is defined as a rigid body and all degrees of freedom are constrained. The bolt pre-tightening force is applied by the temperature load method. The longitudinal thermal expansion coefficient of the upper plate is 1.5×10−5 / °C, and the other directions are set to 0. A lateral displacement is applied to the upper plate to simulate the load process of the screw rod, and the simulation result outputs the bending moment of the screw rod to verify the equivalent relationship between the bolt connection external load and the screw rod load.

[0088] Specifically, a refined finite element model of bolt connection is constructed to simulate the load state on the thread teeth. Since the contact relationship between the thread pairs is relatively complex during the lateral vibration process, a refined model with threads needs to be established strictly according to the structural parameters to ensure the accuracy of the simulation results. All meshes are C3D8R elements. The mesh of the thread is denser, with a size of 0.0375 mm, and the size of other meshes is 0.5 mm. A surface-to-surface contact pair is applied to the contact area of each component. The lower plate is defined as a rigid body and all degrees of freedom are constrained. The bolt pre-tightening force is applied by the temperature load method. The longitudinal thermal expansion coefficient of the upper plate is 1.5×10−5 / °C, and the other directions are set to 0. A lateral displacement is applied to the upper plate to simulate the load process on the thread teeth, and the thread tooth stress is output from the simulation results to verify the equivalent relationship between the screw load and the stress at the root of the thread tooth.

[0089] S400. Based on the first and second equivalent relationships, combine the lateral displacement-loosening life curve with the first and second equivalent relationships to obtain a stress-loosening life curve for evaluating vehicle bolt loosening by stress cumulative damage.

[0090] It can be understood that in this step, referring to the fatigue life calculation method, combine the lateral displacement-loosening life curve and the first and second equivalent relationships, and the curve for evaluating loosening by macroscopic load D – N is equivalently converted into a bolt stress-loosening life curve for evaluating loosening by stress damage accumulation, that is S – N the curve is used to calculate the loosening life of the bolt. D – N After the lateral displacement external load of the curve is equivalently converted into the stress range at the root of the first working thread tooth, the obtained S – N curve is as shown in Figure 7 – D – N Similar to the S – N curve, this curve also has the characteristics of bilinearity and high-low cycle demarcation. Referring to the Basquin formula, establish the

[0091] Table 1 Curve equations of bolts in three loosening states S–N curve equations of bolts in three loosening states as shown in Table 1.

[0092]

[0093] S500. Obtain the vehicle bolt loosening life according to the Miner fatigue damage linear cumulative criterion and the stress-loosening life curve.

[0094] It is understandable that in this step S500, it includes S501, S502, and S503, where:

[0095] S501. Count the stress-time history in the second equivalent relationship based on the time-correlated damage editing method to obtain the number of cycles at different stress levels;

[0096] S502. Establish a vehicle bolt loosening damage accumulation model based on the Miner fatigue damage linear cumulative criterion and the number of cycles, and obtain the vehicle bolt loosening cumulative damage value;

[0097] S503. Judge whether the vehicle bolt loosening cumulative damage value meets the preset threshold. If it meets, perform optimized connection of the vehicle bolt and re-verify through tests; if it does not meet, it means the vehicle bolt has not loosened, and then perform life prediction on the vehicle bolt.

[0098] It should be noted that first, measure the axial force-time history and bending moment-time history of the screw rod under the random load of the vehicle through a force-measuring bolt. Then, convert the load-time history (bending moment-time history and axial force-time history) received by the bolt into the stress-time history of the thread root based on the equivalent relationship between the screw rod load and the stress at the thread root. After that, count the stress-time history based on the time-correlated damage editing method to obtain the number of cycles at different stress levels. Finally, obtain the bolt loosening deterioration cumulative value and loosening life with reference to the Miner fatigue damage linear cumulative criterion.

[0099] Embodiment 2:

[0100] As Figure 2 shown, this embodiment provides a vehicle bolt loosening life evaluation system. Refer to Figure 2 The system includes a test module 701, a first acquisition module 702, a construction module 703, a second acquisition module 704, and a calculation module 705, where:

[0101] The test module 701: is used to carry out the lateral vibration test of the vehicle bolt, collect the clamping force-time history of the vehicle bolt, and record the number of vibrations in the loosening state when the clamping force decays to three remaining clamping forces, where the three remaining clamping forces are the clamping forces when the initial pre-tightening force decays to 90%, 80%, and 70%;

[0102] The first acquisition module 702: is used to take the average value of the number of vibrations as the horizontal coordinate of the vehicle bolt loosening curve and the lateral displacement amplitude as the vertical coordinate to obtain the lateral displacement-loosening life curve of the vehicle bolt in three loosening states;

[0103] Building module 703: used to build the first equivalent relationship and obtain the second equivalent relationship according to the first equivalent relationship, where the first equivalent relationship is the equivalent relationship between the external load of the bolt connection and the load on the screw rod, and the second equivalent relationship is the equivalent relationship between the load on the screw rod and the stress at the root of the screw thread;

[0104] Second acquisition module 704: used to combine the lateral displacement-loosening life curve with the first and second equivalent relationships based on the fatigue life calculation method to obtain a stress-loosening life curve for evaluating the loosening of vehicle bolts by stress cumulative damage;

[0105] Calculation module 705: used to obtain the loosening life of vehicle bolts according to the Miner linear cumulative fatigue damage criterion and the stress-loosening life curve.

[0106] Specifically, the test module 701, which includes a monitoring unit 7011, a first application unit 7012, and a first calculation unit 7013, where:

[0107] Monitoring unit 7011: used to clamp and assemble bolts using the bolts of the rail vehicle and a single-lap T-shaped fixture, and monitor through a pressure sensor, where the assembly conditions are the same for each test;

[0108] First application unit 7012: used to apply a sinusoidal lateral displacement load, and its calculation formula is as follows:

[0109]

[0110] In the formula, is the lateral displacement amplitude, is the vibration frequency, is the test vibration time, is the lateral displacement load;

[0111] First calculation unit 7013: used to set five levels of displacement amplitude values and obtain the pre-tightening force of the bolt according to the preset standard of mechanical design, and its calculation formula is as follows:

[0112]

[0113] In the formula, is the pre-tightening force, and are the yield strength of the bolt material and the effective area of the bolt cross-section respectively.

[0114] Specifically, the monitoring unit 7011 then includes: a second application unit 70111, a first judgment unit 70112, and a selection unit 70113, where:

[0115] The second application unit 70111: used to apply lateral displacement loads to conduct vehicle bolt loosening tests;

[0116] The first judgment unit 70112: used to make judgments based on the first basis and the second basis, where the first basis is whether the remaining clamping force of the vehicle bolt decays below 70% of the initial pre-tightening force, and the second basis is whether the vehicle bolt breaks;

[0117] The selection unit 70113: used to stop the test if the judgment result is yes, and then change the lateral displacement amplitude and continue to apply lateral displacement loads to conduct vehicle bolt loosening tests; if the judgment result is no, repeat the same test until three valid specimens are satisfied and the test ends.

[0118] Specifically, the construction module 703, which includes a first establishment unit 7031, a second calculation unit 7032, and a second establishment unit 7033, where:

[0119] The first establishment unit 7031: used to analyze the forces on the vehicle bolt connection and establish the bending moment equations for each section of the vehicle bolt connection;

[0120] The second calculation unit 7032: used to obtain the first equivalent relationship based on Castigliano's second theorem of mechanics of materials and the bending moment equation;

[0121] The second establishment unit 7033: used to, based on the first equivalent relationship, take the thread material as an elastic body, obtain the forces on the threads under the lateral external load by taking an infinitesimal element on the thread surface, and establish the second equivalent relationship.

[0122] Specifically, the calculation module 705, which includes an acquisition unit 7051, a third establishment unit 7052, and a second judgment unit 7053, where:

[0123] The acquisition unit 7051: used to count the stress-time history in the second equivalent relationship based on the time-correlated damage editing method to obtain the number of cycles at different stress levels;

[0124] The third establishment unit 7052: used to establish a vehicle bolt loosening damage accumulation model based on Miner's fatigue damage linear cumulative criterion and the number of cycles, and obtain the vehicle bolt loosening cumulative damage value;

[0125] The second judgment unit 7053: used to judge whether the vehicle bolt loosening cumulative damage value meets a preset threshold. If it meets, optimize the connection of the vehicle bolt and re-verify through tests; if it does not meet, it means the vehicle bolt has not loosened, and then conduct a life prediction for the vehicle bolt.

[0126] It should be noted that regarding the system in the above embodiments, the specific manners in which each module performs operations have been described in detail in the embodiments of the method, and will not be elaborated herein.

[0127] Embodiment 3:

[0128] Corresponding to the above method embodiment, in this embodiment, a vehicle bolt loosening life evaluation device is also provided. A vehicle bolt loosening life evaluation device described below can be correspondingly referred to with a vehicle bolt loosening life evaluation method described above.

[0129] Figure 3 is a block diagram of a vehicle bolt loosening life evaluation device 800 shown according to an exemplary embodiment. As Figure 3 shown, the vehicle bolt loosening life evaluation device 800 includes: a processor 801 and a memory 802. The vehicle bolt loosening life evaluation device 800 further includes one or more of a multimedia component 803, an I / O interface 804, and a communication component 805.

[0130] Among them, the processor 801 is used to control the overall operation of the vehicle bolt loosening life evaluation device 800 to complete all or part of the steps in the above-mentioned vehicle bolt loosening life evaluation method. The memory 802 is used to store various types of data to support the operation of the vehicle bolt loosening life evaluation device 800. These data may include, for example, instructions for any application or method operating on the vehicle bolt loosening life evaluation device 800, as well as application-related data, such as contact data, sent and received messages, pictures, audio, video, and so on. The memory 802 can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, magnetic disk or optical disc. The multimedia component 803 may include a screen and an audio component. The screen can be, for example, a touch screen, and the audio component is used to output and / or input audio signals. For example, the audio component may include a microphone for receiving external audio signals. The received audio signals can be further stored in the memory 802 or sent through the communication component 805. The audio component also includes at least one speaker for outputting audio signals. The I / O interface 804 provides an interface between the processor 801 and other interface modules, and the above-mentioned other interface modules can be a keyboard, a mouse or buttons, etc. These buttons can be virtual buttons or physical buttons. The communication component 805 is used for wired or wireless communication between the vehicle bolt loosening life evaluation device 800 and other devices. Wireless communication, such as Wi-Fi, Bluetooth, near field communication (NFC), 2G, 3G or 4G, or a combination of one or more of them. Accordingly, the communication component 805 may include: a Wi-Fi module, a Bluetooth module or an NFC module.

[0131] In an exemplary embodiment, the vehicle bolt loosening life evaluation device 800 can be implemented by one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), controllers, microcontrollers, microprocessors or other electronic components, and is used to execute the above-mentioned vehicle bolt loosening life evaluation method.

[0132] In another exemplary embodiment, a computer-readable storage medium including program instructions is further provided. When the program instructions are executed by a processor, the steps of the above-mentioned vehicle bolt loosening life evaluation method are implemented. For example, the computer-readable storage medium can be the above-mentioned memory 802 including program instructions, and the above-mentioned program instructions can be executed by the processor 801 of the vehicle bolt loosening life evaluation device 800 to complete the above-mentioned vehicle bolt loosening life evaluation method.

[0133] Embodiment 4:

[0134] Corresponding to the above method embodiment, a readable storage medium is further provided in this embodiment. A readable storage medium described below can be correspondingly referred to with a vehicle bolt loosening life evaluation method described above.

[0135] A computer program is stored on the readable storage medium. When the computer program is executed by a processor, the steps of the vehicle bolt loosening life evaluation method in the above method embodiment are implemented.

[0136] Specifically, the readable storage medium can be various readable storage media such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disc that can store program codes.

[0137] In summary, the present invention establishes a bolt loosening life evaluation method based on load relationship, oriented to engineering applications, with high reliability, strong applicability and real-time monitoring / evaluation, which has important scientific value and engineering significance for optimizing structural design and preventing bolt loosening. D – NThe curve evaluates the loosening life of the bolt. However, in the actual random vibration service environment, the external loads acting on the bolt connection are complex, and it is difficult to obtain its displacement load. Therefore, it is difficult to accurately evaluate the loosening life of the bolt. In this case, the vehicle bolt loosening life evaluation method based on the bolt load relationship proposed by the invention can make up for the above deficiencies and achieve an accurate evaluation of the bolt loosening life under random lateral loads, which is of great significance for ensuring the service safety of vehicle bolt connection equipment and the life and property safety of drivers and passengers.

[0138] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0139] As described above, this is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or replacements, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for evaluating the loosening life of vehicle bolts, characterized in that, Including: Conduct a lateral vibration test on vehicle bolts, collect the clamping force-time history of the vehicle bolts, and record the number of vibrations in the loosening state when the clamping force decays to three remaining clamping forces, where the three remaining clamping forces are the clamping forces when the initial preload decays to 90%, 80%, and 70%; Take the average value of the number of vibrations as the horizontal coordinate of the vehicle bolt loosening curve, and take the lateral displacement amplitude as the vertical coordinate to obtain the lateral displacement-loosening life curve of the vehicle bolts in three loosening states; Construct a first equivalent relationship, and obtain a second equivalent relationship according to the first equivalent relationship, where the first equivalent relationship is the equivalent relationship between the external load of the bolt connection and the load on the screw, and the second equivalent relationship is the equivalent relationship between the load on the screw and the stress at the root of the thread; Based on the fatigue life calculation method, combine the lateral displacement-loosening life curve, the first equivalent relationship, and the second equivalent relationship to obtain a stress-loosening life curve for evaluating the loosening of vehicle bolts by stress cumulative damage; Obtain the loosening life of vehicle bolts according to Miner's linear cumulative fatigue damage criterion and the stress-loosening life curve; The constructing of the first equivalent relationship and obtaining the second equivalent relationship according to the first equivalent relationship includes: Analyze the force on the vehicle bolt connection and establish the bending moment equations for each section of the vehicle bolt connection; Based on Castigliano's second theorem of mechanics of materials and the bending moment equations, obtain the first equivalent relationship; Based on the first equivalent relationship, take the thread material as an elastic body, obtain the force on the thread under the lateral external load by taking an infinitesimal element on the thread surface, and establish the second equivalent relationship.

2. The vehicle bolt loosening life evaluation method according to claim 1, wherein, The conducting of the lateral vibration test on vehicle bolts, collecting the clamping force-time history of the vehicle bolts, and recording the number of vibrations in the loosening state when the clamping force decays to three remaining clamping forces includes: Use the bolts of the rail vehicle and a single-lap T-shaped fixture to clamp and assemble the bolts, and monitor through a pressure sensor, where the assembly conditions are the same for each test; Apply a sinusoidal lateral displacement load, and its calculation formula is as follows: In the formula, is the lateral displacement amplitude, is the vibration frequency, is the test vibration time, is the lateral displacement load; Set five levels of displacement amplitude values, and obtain the preload of the bolts according to the preset standards of mechanical design, and its calculation formula is as follows: In the formula, is the pre-tightening force, and are respectively the yield strength of the bolt material and the effective area of the bolt cross-section.

3. The vehicle bolt loosening life evaluation method according to claim 2, wherein After using the bolts of the rail vehicle and a single-lap T-shaped fixture to clamp and assemble the bolts, it includes: Apply a lateral displacement load to conduct a vehicle bolt loosening test; Make a judgment according to the first basis and the second basis, where the first basis is whether the remaining clamping force of the vehicle bolt decays below 70% of the initial preload, and the second basis is whether the vehicle bolt breaks; If the judgment result is yes, stop the test, then change the lateral displacement amplitude, and continue to apply the lateral displacement load to conduct a vehicle bolt loosening test; if the judgment result is no, repeat the same test until three valid specimens are satisfied and the test ends.

4. The vehicle bolt loosening life evaluation method according to claim 1, characterized in that The obtaining of the loosening life of vehicle bolts according to Miner's linear cumulative fatigue damage criterion and the stress-loosening life curve includes: Based on the time-correlated damage editing method, count the stress-time history in the second equivalent relationship to obtain the number of cycles at different stress levels; Based on the Miner linear cumulative fatigue damage criterion and the number of cycles, a vehicle bolt loosening damage accumulation model is established, and the vehicle bolt loosening cumulative damage value is obtained; Judge whether the vehicle bolt loosening cumulative damage value meets a preset threshold. If it meets, optimize the connection of the vehicle bolt and re-verify through tests; if it does not meet, it means the vehicle bolt has not loosened, and then predict the life of the vehicle bolt.

5. A vehicle bolt loosening life evaluation system, characterized in that, It includes: Test module: used to conduct the lateral vibration test of vehicle bolts, collect the clamping force-time history of vehicle bolts, and record the number of vibrations in the loosening state when the clamping force decays to three remaining clamping forces, where the three remaining clamping forces are the clamping forces when the initial preload decays to 90%, 80%, and 70%; First acquisition module: used to take the average value of the number of vibrations as the horizontal coordinate of the vehicle bolt loosening curve and the lateral displacement amplitude as the vertical coordinate to obtain the lateral displacement-loosening life curve of the vehicle bolt in three loosening states; Construction module: used to construct the first equivalent relationship and obtain the second equivalent relationship according to the first equivalent relationship, where the first equivalent relationship is the equivalent relationship between the external load of the bolt connection and the load on the screw rod, and the second equivalent relationship is the equivalent relationship between the load on the screw rod and the stress at the root of the thread; Second acquisition module: used to combine the lateral displacement-loosening life curve, the first and the second equivalent relationships based on the first equivalent relationship and the second equivalent relationship to obtain the stress-loosening life curve for evaluating the loosening of vehicle bolts with stress cumulative damage; Calculation module: used to obtain the vehicle bolt loosening life according to the Miner linear cumulative fatigue damage criterion and the stress-loosening life curve; The construction module, which includes: First establishment unit: used to analyze the force on the vehicle bolt connection and establish the bending moment equations for each section of the vehicle bolt connection; Second calculation unit: used to obtain the first equivalent relationship based on Castigliano's second theorem of mechanics of materials and the bending moment equations; Second establishment unit: used to based on the first equivalent relationship, take the thread material as an elastic body, obtain the force on the thread under the lateral external load by taking a microelement on the thread surface, and establish the second equivalent relationship.

6. The vehicle bolt loosening life evaluation system according to claim 5, wherein The test module, which includes: Monitoring unit: used to clamp and assemble bolts using the bolts of the rail vehicle and a single-lap T-shaped fixture, and monitor through a pressure sensor, where the assembly conditions are the same for each test; First application unit: used to apply a sinusoidal lateral displacement load, and its calculation formula is as follows: In the formula, is the lateral displacement amplitude, is the vibration frequency, is the test vibration time, is the lateral displacement load; First calculation unit: used to set five levels of displacement amplitude values and obtain the preload of the bolt according to the preset standard of mechanical design, and its calculation formula is as follows: In the formula, is the pre-tightening force, and are respectively the yield strength of the bolt material and the effective area of the bolt cross-section.

7. The vehicle bolt loosening life evaluation system according to claim 6, wherein, The monitoring unit, which then includes: Second application unit: used to apply a lateral displacement load to conduct the vehicle bolt loosening test; First judgment unit: used to judge according to the first basis and the second basis, where the first basis is whether the remaining clamping force of the vehicle bolt decays below 70% of the initial preload, and the second basis is whether the vehicle bolt breaks; Selection unit: used to stop the test if the judgment result is yes, and then change the lateral displacement amplitude, and continue to apply the lateral displacement load to carry out the vehicle bolt loosening test; if the judgment result is no, repeat the same test until three effective specimens are satisfied and the test ends.

8. The vehicle bolt loosening life evaluation system according to claim 5, wherein The calculation module, which includes: Obtaining unit: used to count the stress-time history in the second equivalent relationship based on the time-correlated damage editing method to obtain the number of cycles at different stress levels; Third establishment unit: used to establish a vehicle bolt loosening damage accumulation model based on the Miner fatigue damage linear cumulative criterion and the number of cycles, and obtain the vehicle bolt loosening cumulative damage value; Second judgment unit: used to judge whether the vehicle bolt loosening cumulative damage value meets the preset threshold. If it is satisfied, optimize the connection of the vehicle bolt and verify it by retesting; if it is not satisfied, it means that the vehicle bolt has not loosened, and then predict the life of the vehicle bolt.

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