A computer experiment and surrogate model based method for ultra-long cargo transportation safety assurance

Abstract

The application provides a super-long goods transportation safety guarantee method based on computer experiment and alternative model, experiment scheme is determined; simulation experiment model is established; judgment basis is determined; the application adopts a large number of computer simulation to replace a large number of repeated real vehicle experiments, can effectively reduce the research cost, makes up for the shortage of the ideal assumption and statics analysis in the previous research, and the obtained theoretical simulation result can provide early screening reference for the real vehicle experiment scheme. In the face of the limitation of computer experiment in computing capacity and time, based on the simulation scheme, key factors and results, the alternative model of super-long goods allowable weight and goods protruding length is constructed, which not only makes up for the complexity of a large number of operations, but also compared with the discrete threshold value in the regulation, the flexibility is more convenient for the actual reference use of railway.

Description

Technical Field

[0001] The present invention relates to the field of traffic safety assessment, in particular to a method for ensuring the safety of ultra-long cargo transportation based on computer experiments and substitution models. Background Art

[0002] Railway freight cars have become a widely used freight transport tool in countries with extensive rail mileage. Given their safety and energy-efficiency, they have also become a potential solution for transporting unusually sized cargo in modern logistics. Typical unusually sized cargo, known as over-length cargo, is defined as a piece of cargo that exceeds the length of the vehicle it is loaded on, necessitating the use of traveling carriages or straddle-loading. These are commonly transported on railway flatcars. Common examples of over-length cargo include industrial construction equipment such as bridge components and large military wheeled equipment.

[0003] When transporting oversized cargo on railway flatcars, the allowable load weights for different protruding lengths are specified. This is because when a vehicle is loaded with a load protruding from the end of the vehicle, the vertical dynamic load on the vehicle increases during operation due to the vertical vibration of the protruding cargo, compared to conditions where the cargo does not protrude from the end of the vehicle. This increases the vehicle's centrifugal force, which in turn affects vehicle operational safety indicators such as the derailment coefficient and wheel load reduction rate. However, during vehicle design and testing, cargo is considered to not exceed the vehicle body length, and the loaded weight is the vehicle's marked load capacity. When loading cargo that exceeds the vehicle body length, if it is still loaded according to the vehicle's marked load capacity, the increased dynamic load will increase the total load acting on the vehicle body. This may cause the vehicle body's working stress to exceed the allowable stress of the material used, threatening the operational safety of railway freight cars.

[0004] To ensure operational safety, several countries and railway organizations have issued general rules regarding cargo loading. Only some of these rules explicitly limit the permissible weight of oversized cargo on railways. For example, restrictions are set for the permissible weight of cargo with varying protrusion lengths balanced on both ends of 60t and 61t rated flatcars. However, these restrictions do not cover all currently used models.

[0005] Although various railway organizations have issued general rules for cargo loading and allow for the long-duration, large-volume transport of oversized cargo by rail, there remains no consensus on the impact of cargo protruding from the vehicle body on the operational safety of railway freight cars, nor on the permissible weight limits for oversized cargo at varying protrusion lengths. With the increasing use of heavy-duty and containerized freight transport by rail, larger vehicle models have become increasingly dominant, and related management techniques have lagged far behind the latest developments in modern transportation equipment.

[0006] In addition, the allowable load weight value specified in the loading criterion is rough and empirical to some extent. Few literatures study the relationship between the allowable load weight of overlength cargo, the protruding length of cargo and the running safety of the freight train, and most of them are based on ideal assumptions (such as running on a straight line) and use mechanical calculation method (moment balance principle) for statics analysis, which lacks consideration of the following aspects: (1) nonlinear characteristics of the vehicle system such as track irregularities; (2) the influence of the vehicle passing through curves; (3) the influence of speed, curve radius and outer rail super-elevation on the vehicle system; (4) the object of study is not the main vehicle type.

[0007] Therefore, it is urgent to analyze the influence of the protruding length of overlength cargo and the allowable weight of cargo on the running safety of the freight train, and to develop technical specifications for transporting overlength cargo by railway freight vehicles represented by the main vehicle type, in order to ensure the safe operation of future larger load freight trains. However, it is not very feasible to conduct a large number of repeated real train tests in terms of time and funds. Since the literature on railway vehicle dynamics calculation method is very rich and mature, the results are very consistent with the results of physical experiments, so computer experiments are a reasonable choice to find these relationships. Although computer experiments allow to study systems in ways that would otherwise be difficult or impossible, they still have limitations, such as limited computing power and time as resources. SUMMARY

[0008] In view of the above problems, the present application proposes a comprehensive framework of computer experiments and surrogate models based on the idea of computer experiment design and analysis to discover and represent the relationship between the allowable load weight of overlength cargo and the running safety of the freight train under different protruding lengths, by conducting vehicle dynamics simulation research on the allowable weight of overlength cargo loaded by the freight train under different line conditions, different speeds and different curve radii, and constructing a surrogate model expressing the calculation of the allowable load weight of overlength cargo based on the screened factors, to provide theoretical calculation basis for future real train tests and for railway organizations to reach a consensus on overlength cargo loading specifications.

[0009] To achieve the above purpose, the technical scheme adopted by the present application is: an overlength cargo transportation safety guarantee method based on computer experiments and surrogate models, the method comprising,

[0010] determining the test scheme;

[0011] establishing a simulation test model;

[0012] determining the evaluation basis;

[0013] The test scheme determines, specifically includes, based on the actual transportation situation and constraint conditions, selecting two types of determining test elements and uncertain test elements, determining all computer test data in each selected vehicle test scheme; the determining test elements include the heavy vehicle gravity center height, the lateral deviation of the cargo gravity center from the truck center line, and the longitudinal deviation of the cargo gravity center from the truck center line; the uncertain test elements include the selected truck, the line condition, the line running speed, and the cargo protruding length;

[0014] The simulation test model is established, specifically including: constructing a truck simulation model according to a truck system random vibration model and a nonlinear force analysis in a bogie; constructing a track model according to a rail / sleeper model, a line geometry, and track irregularity;

[0015] The evaluation basis is determined, specifically including: taking the vertical force of the vehicle center disc as the main evaluation basis for determining the allowable weight of the cargo under different protruding lengths; comparing the vertical force of the center disc under the over-length cargo condition with the vertical force of the center disc under the non-over-length cargo full load condition to determine the allowable loading weight of the cargo; the vehicle derailment coefficient and the wheel load reduction rate are used to verify the vehicle operation safety.

[0016] Further, the simulation test model is established in SIMPACK; the construction step specifically includes,

[0017] According to the composition of the truck real vehicle system, stress analysis is performed on each component;

[0018] Wheel-rail contact relationship preprocessing;

[0019] Considering the stress relationship of the real vehicle system and each component, a truck system topology structure is established;

[0020] In the simulation platform, a super-long cargo transportation simulation model is established according to the truck system topology structure;

[0021] According to the rail or sleeper model, the line geometry, and the track irregularity, a track model is constructed in the simulation platform;

[0022] The final computer simulation test model is obtained;

[0023] The wheel-rail contact relationship preprocessing specifically includes the contact relationship between the wheel and the rail, and the contact relationship between the wheel and the rail includes the LM abrasion type tread and the R60 rail.

[0024] Further, the rail or sleeper model is a selected discrete equivalent rail or sleeper model.

[0025] Further, the elements of the track geometry, including the curvature variation along the length of the track, the superelevation of the outer rail, the lateral offset from the initial position; the element parameters determined in the test scheme are inputted to the SIMPACK preprocessor for calculation and analysis.

[0026] Further, the track irregularity is described by the power spectral density function as follows:

[0027] ;

[0028] ;

[0029] ;

[0030] wherein, the PSD functions of the lateral, vertical and gauge irregularities are described respectively, represents the spatial angular frequency, and represents the cut-off angular frequency, and is the roughness scalar, is the safety factor.

[0031] Further, the method further comprises introducing the numerical correlation between the research indicators and the factors by the GLM model with the research results determined by the judging basis as input as follows:

[0032] ;

[0033] wherein, the dummy variable is used to process the qualitative factors , then is used to describe the selected truck model, when or , or ; is used to describe the curve radius, thus represents the inverse of the curve radius; represents the allowable loading weight of the overlength goods, represents the protruding length of the overlength goods, represents the truck running speed.

[0034] Further, under the same truck model and track condition factors, the value of the center disc vertical force indicator can be regarded as a constant , as shown in equation (13):

[0035] ;

[0036] By equation transformation transfer, the formula (17) with the target item of cargo allowable weight can be derived:

[0037] ;

[0038] Therefore, the alternative model describing the relationship between the cargo allowable weight and the protruding length is

[0039] .

[0040] The beneficial effects of the present patent are:

[0041] 1. The present application adopts a large number of computer simulations to replace a large number of repeated real vehicle tests, which can effectively reduce the research cost, make up for the shortcomings of previous researches based on ideal assumptions and statics analysis, and provide early screening reference for real vehicle test schemes with the theoretical simulation results obtained.

[0042] 2. In the face of the limitations of computer tests in computing power and time, based on the simulation scheme, key factors and results, the alternative model of the allowable weight of the super-long cargo and the protruding length of the cargo is constructed, which not only makes up for the complexity of a large number of operations, but also has more flexibility than the discrete threshold values in the regulations, which is more convenient for the railway to refer to in practice. BRIEF DESCRIPTION OF DRAWINGS

[0043] The present application has the following drawings:

[0044] Figure 1 is a schematic diagram of the force of the flat car loaded with super-long cargo of the present application;

[0045] Figure 2 is a SIMPACK modeling flowchart of the present application;

[0046] Figure 3 is a freight car simulation model diagram of the present application;

[0047] Figure 4 is a discrete equivalent rail or sleeper model of the present application;

[0048] Figure 5 is the variation trend of the derailment coefficient (a), the wheel load reduction rate (b), and the vertical force of the center plate (c) with the protruding length of the cargo in the embodiment of the present application. DETAILED DESCRIPTION

[0049] The present application will be further described in detail below in combination with the drawings.

[0050] We analyze the force of the cargo and the freight car from the perspective of statics, such as Figure 1The main research is a four-axle flat car with three-piece bogie, so as to highlight the influence of the super-long cargo on the allowable weight of the cargo. The invention is analyzed with reference to the Chinese standard "Railway Freight Loading and Reinforcement Rules" (hereinafter referred to as "Loading and Reinforcement Rules").

[0051] ;

[0052] ;

[0053] ;

[0054] ;

[0055] ;

[0056] ;

[0057] When one end protruding loading, the maximum allowable loading can be calculated by the method of formula (1)-(4). First, according to the principle of moment balance, formula (1) and formula (2) can be obtained. Secondly, according to the distance relationship in the figure, formula (3) and formula (4) can be obtained. Then, according to the provisions of the reference standard related to the weight of the loaded goods, the total center of gravity of the loaded goods must be longitudinally offset after loading, and the weight of each vehicle bogie must not exceed half of the allowable load of the freight car, and the difference between the two bogies must not be greater than 10t, formula (5), formula (6) can be obtained respectively.

[0058] Therefore, by combining formula (1)-(6), the relationship between the maximum allowable weight of the goods and the protruding length of the goods shown in formula (7), formula (8) is derived.

[0059] ;

[0060] ;

[0061] Among them, the maximum allowable weight of the goods, the protruding length of the goods, the distance between the bogie B and the total center of gravity of the goods, the distance between the center pin of the bogie and the nearest floor end of the car, the center distance of the bogie of the car, the length of the floor of the car, and respectively represent the weight of the A and B bogies.

[0062] From formula (7) and formula (8), we can easily see that when the truck bogie center distance and truck marked load weight are constant, the maximum cargo allowable weight is inversely proportional to the cargo protruding length, the longer the cargo protruding length, the lower the cargo allowable weight. That is to say, in order to ensure the running safety of the super-long cargo after loading, it is necessary to restrict the cargo allowable weight according to the cargo protruding length.

[0063] The computer simulation test of the application comprises the following specific steps:

[0064] Step 1: Test scheme determination

[0065] Based on the actual transportation situation and related constraints, two types of test elements are selected, namely, certain and uncertain test elements.

[0066] The certain test elements include:

[0067] (1) Heavy vehicle center of gravity height: set to 2000mm;

[0068] (2) Lateral deviation of cargo center of gravity from the center line of the truck: set to 0mm;

[0069] (3) Longitudinal deviation of cargo center of gravity from the center line of the truck: set to 0mm.

[0070] For the uncertain test elements, the following is described:

[0071] (1) Selected wagons (W): we selected the 70t flat cars used for loading super-long cargo in Chinese railway freight transportation, including NX 70A , NX 70 and NX 70H three types of cars. The vehicle parameters are shown in Table 1.

[0072] Table 1 Vehicle parameters of NX 70 series flat car

[0073] Vehicle model Self weight (t) Vehicle length (mm) Vehicle width (mm) Empty vehicle center of gravity height (mm) Vehicle floor distance from rail surface height (mm) Bogie center distance (mm) Marked load (mm) Bogie model <![CDATA[NX 70H ]]> 23.8 15400 2960 738 1216 10920 70 Turn K5 type NX 70 ]] 23.8 15400 2960 738 1216 10920 70 Turn K6 type NX 70A ]] 23.8 2980 2980 727 1216 9000 70 Turn K6 type

[0074] (2) Line conditions (1 / r): in addition to the straight line condition, the line conditions of small radius curve and large radius curve with high outer rail should also be considered when the truck is running on the curve. At the same time, considering the line conditions of the existing railway network, in order to consider the most unfavorable working conditions, the line conditions in Table 2 are determined according to the "Code".

[0075] Table 2 Selected line condition parameters

[0076]

[0077] (3) The running speed (v) of the line: the running speed within the allowable range is obtained by referring to the constraints in the relevant provisions of the "Dynamics Performance Evaluation and Test Identification Specification for Rolling Stock":

[0078] The maximum running speed of the freight car Must be carried out in accordance with the requirements of the line level,

[0079] That is, on the III-grade line, Generally not more than 70km / h; on the I-grade line, with the speed-up of the main railway trunk line and the vehicle, Will reach 120km / h.

[0080] On the straight line, 1.1 times Or , take the larger value.

[0081] The test should be carried out at several speed levels under the maximum test speed, and the speed level increment is recommended to be 10km / h or 20km / h.

[0082] On the curve, 1.1 times , under difficult conditions, should not be less than . The test should be carried out at the maximum test speed.

[0083] (4) The protruding length of the cargo : The protruding length of the cargo in the "Addition Regulation" is set in the 0-5000mm interval, and changes at intervals of 500mm.

[0084] It is worth noting that the purpose of computer experiment is to find the allowable loading weight of flat car loading of different protruding lengths of over-length cargo, so in the setting of cargo loading conditions, in addition to the weight, length and other factors of the cargo, the two non-deterministic factors of whether the two ends are balanced protruding and whether the loading uses cross battens are also considered. These two non-deterministic factors have been converted to deterministic factors through pre-simulation test, that is, we believe that under the condition of consistent running conditions and speed conditions, the condition of balanced protruding at both ends and not using cross battens for loading is the adverse condition, so it is used as the basic condition of the loading condition in the test scheme.

[0085] Based on the above, it is determined that for each selected freight car type, all computer tests in Table 3 test scheme need to be carried out, a total of 1122 schemes of calculation are needed.

[0086] Table 3 Simulation test scheme

[0087]

[0088] Step 2: Simulation test model establishment

[0089] According to the above test plan, we use SIMPACK simulation software with the fastest solution speed, and NX 70H NX 70 and NX 70A Computer experiments were conducted on the freight car system as the analysis object. The random vibration of the freight car system will inevitably affect the vehicle's operating parameters. The random vibration of the freight car system is mainly affected by its own internal excitation factors and external excitation factors from the track. Therefore, a simulation model was constructed in the SIMPACK simulation platform, specifically including: (1) constructing a freight car simulation model (including cargo) based on the freight car system random vibration model and nonlinear force analysis in the bogie; (2) constructing a track model based on the rail or sleeper model, line geometry, and track irregularities.

[0090] The process of building a simulation model in SIMPACK is as follows Figure 2 shown.

[0091] The detailed modeling steps are as follows:

[0092] Step (1): Based on the structure of the actual truck system, perform stress analysis on each component.

[0093] Step (2): Pre-processing of the wheel-rail contact relationship. During vehicle operation, the wheel tread is in direct contact with the top surface of the rail. The contact relationship between the wheel and rail acts as a link, affecting the vehicle's operating characteristics to a certain extent. Railways in various countries determine the wheel tread shape and rail head shape based on their own practical experience. my country's railways use LM wear-type treads and R60 rails.

[0094] Step (3): Consider the actual vehicle system and the force relationships between its components to establish the topological structure of the truck system. The connections between the various objects in a multi-body system are called the system's topological configuration, or simply topology. The topological diagram is an important preliminary work for establishing the SIMPACK model. It is necessary to decompose the physical model into the basic elements of the MBS unit, including bodies, hinges, constraints, and force elements.

[0095] Step (4): Establish an ultra-long cargo transportation simulation model based on the truck system topology in the simulation platform. The cargo and the truck body are modeled as rigid bodies and connected by fixed articulations, so that they are regarded as a whole. Each type of truck has two bogies, and each bogie consists of a rocker, two wheels, and two side frames. These truck bodies are connected by forces, articulations, and constraints, including primary suspension forces, secondary suspension forces, etc. The wheelset adopts an LM wear-type tread profile that matches the R60 rail top surface profile. By processing the 3D shape, articulation relationship, and force elements, a simulation model is finally formed. Figure 3 shown.

[0096] Step (5): The basis of simulation model running is track model. Track model is built in simulation platform according to rail / sleeper model, track geometry and track irregularity. Specifically, rail / sleeper model, track geometry and realization of track irregularity excitation are included.

[0097] Rail / sleeper model

[0098] Through the research on rail / sleeper model, Figure 4 The discrete equivalent rail / sleeper model is selected as shown because it is closer to the actual track conditions. Among them, are the lateral and vertical stiffness coefficients of the track, respectively, are the lateral and vertical damping coefficients of the track, respectively.

[0099] Track geometry

[0100] Track geometry determines the change of wheelset position along the track direction in wheel-rail system, and further determines the dynamic change of each component of the freight car system. Track geometry includes the curvature change of the track along the length direction, the super-elevation of the outer rail, the lateral offset relative to the initial position and other elements. They are input with the parameters determined in the test scheme, and are calculated and analyzed by the SIMPACK pre-processing program.

[0101] Track irregularity excitation

[0102] The rail geometry is affected by factors such as rail wear, rail damage, uneven subgrade, sleeper spacing change and other factors to form track random irregularity. The vehicle is excited by track irregularity during operation to produce random vibration, which affects the safety of vehicle operation. Therefore, the random irregularity of the track is an essential track excitation input for computer simulation experiment. Generally, the track irregularity is described by the power spectral density (PSD) function as follows:

[0103] ;

[0104] ;

[0105] ;

[0106] Among them, describe the PSD functions of lateral, vertical and gauge irregularities, respectively, represent the spatial angular frequency, and represent the cut-off angular frequency, and is the roughness scalar, and It is worth noting that in order to obtain a line spectrum file suitable for SIMPACK in the simulation experiment, the track irregularity PSD density needs to be converted into a spectrum.

[0107] Step (6): Couple the models in steps (4) and (5) to obtain the final computer simulation test model.

[0108] Step 3: Determine the evaluation criteria

[0109] The varying length of cargo of the same weight and cross-sectional dimensions affects its moment of inertia. When oversized cargo is loaded protruding from the vehicle end, the vertical dynamic load on the vehicle increases compared to conditions where the cargo does not protrude due to vertical vibrations generated by various random excitations during operation. This increases the vehicle's centrifugal force, impacting operational safety indicators such as derailment coefficient and wheel load reduction ratio. During vehicle design and testing, cargo is assumed to not exceed the vehicle length, and the loaded weight is the vehicle's marked load capacity.

[0110] This step is to determine the basis for the subsequent simulation result evaluation, that is, to ensure that the operating conditions of a vehicle with over-length cargo are the same as those of cargo that does not exceed the vehicle body length. It is planned to use three common safety indicators, namely, the vertical force of the center plate, the derailment coefficient, and the wheel load reduction rate, to conduct a comparative analysis of cargo with the same operating conditions, the same weight, the same cross-sectional dimensions, and different lengths, and to find the indicators that vary more significantly with the cargo length. 70 This is explained by taking as an example a fully loaded freight car running at a speed of 100 km / h on a straight line of China's Class I railway with the cargo protruding evenly at both ends by 0, 1000, 2000, 3000 and 4000 mm.

[0111] Depend on Figure 5 Observing the trends in the derailment coefficient (a), wheel load reduction ratio (b), and center plate vertical force (c) as a function of cargo protrusion length shows that, under the same operating conditions, changes in the center plate vertical force are more sensitive to changes in cargo length. This is because the vertical dynamic load of the cargo is directly transmitted to the center plate via the carbody bolster and is less affected by other factors. The derailment coefficient and wheel load reduction ratio, on the other hand, are less sensitive to changes in cargo length. This is likely because they are significantly influenced by the bogie suspension and the wheel-rail relationship, which mitigates the impact of cargo length.

[0112] In general, the vertical force at the center of the vehicle is a more critical and sensitive indicator than the derailment coefficient in the present invention. Therefore, the vertical force at the center of the vehicle will serve as the primary criterion for determining the permissible cargo weight for different protrusion lengths. The permissible cargo load is determined by comparing the vertical force at the center of the vehicle with oversized cargo and the vertical force at the center of the vehicle with a full load of cargo (with a deviation of no more than 3%). Furthermore, the derailment coefficient and wheel load reduction ratio are used to verify vehicle operational safety.

[0113] The alternative model of the application takes into account that although computer simulation tests greatly reduce the cost of manpower and material resources, the uncontrollability of computer repeated tests on computing resources and computing time prompts the application to introduce an alternative model. On the one hand, the alternative model can reduce the amount of calculation under the research of the allowable load of super-long goods and the protruding length of goods in the future under the same conditions; on the other hand, it is beneficial to quantify the relationship between the allowable load of super-long goods and the protruding length of goods, and is more flexible to replace the single value table corresponding to the numerical value.

[0114] The alternative model in the application takes the research results of the foregoing simulation test as input, and introduces a GLM model to study the numerical correlation between the indicators and factors. Among them, the factors have been described in detail in step 1 of the computer simulation test. Based on the previous research, we believe that the heart disc vertical force as an indicator of the force transmission calculation element of the derailment coefficient and the wheel load reduction rate can be described by the GLM model as follows:

[0115] ;

[0116] Among them, is used as a dummy variable to process qualitative factors , then is used to describe the selected freight car type, when or , or ; is used to describe the curve radius, so represents the inverse of the curve radius; represents the allowable load of super-long goods, represents the protruding length of super-long goods, represents the running speed of the freight car.

[0117] And for the two main research objects of the application, the protruding length of goods and the allowable load of goods are usually constrained by one of the safety thresholds of the heart disc vertical force. That is, under the same car type, line condition factors, the value of the heart disc vertical force index can be regarded as a constant , as shown in equation (13).

[0118] ;

[0119] By equation transformation, the equation (17) with the allowable load of goods as the target item can be considered.

[0120] ;

[0121] Therefore, it is believed that there exists at least such a parameter term that satisfies equation (15), namely, an alternative model that describes the relationship between the allowable weight of cargo and the protruding length.

[0122] ;

[0123] Based on the above, the present invention will achieve two results based on the safety of railway freight car operation:

[0124] (1) Based on computer simulation tests, the minimum approximation method was used to obtain a table of maximum allowable cargo weights corresponding to different over-long cargo protrusion lengths under different flat car models, as well as a table of maximum allowable cargo weights corresponding to over-long cargo protrusion lengths under a certain type of rated load (e.g., 70t flat car).

[0125] (2) Based on the results of computer simulation tests as input, the relationship between the maximum allowable weight of overlength cargo under a certain type of rated load (e.g., 70t flat car) and variables such as the length of the cargo protruding from the car end, line conditions, and operating conditions is obtained.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although this patent is described in detail with reference to the embodiments, ordinary technicians in this field should understand that the technical solutions implemented by the present invention can be modified or replaced by equivalents without departing from the design spirit and scope of the present invention, which should be included in the scope of the claims of the present invention.

[0127] The contents not described in detail in this specification belong to the prior art known to those skilled in the art.

Claims

1. A computer experiment and surrogate model-based ultra-long cargo transportation safety assurance method, characterized in that, The method comprises, Test scheme determination; Simulation test model establishment; Evaluation basis determination; The test scheme determination specifically comprises selecting two types of determined test elements and uncertain test elements based on actual transportation conditions and constraint conditions, and determining all computer test data in the test scheme of each selected vehicle type; the determined test elements comprise a heavy vehicle gravity center height, a lateral deviation of a cargo gravity center from a truck center line, and a longitudinal deviation of the cargo gravity center from the truck center line; the uncertain test elements comprise a selected truck, a line condition, a line running speed, and a cargo protruding length; The simulation test model establishment specifically comprises constructing a truck simulation model according to a truck system random vibration model and a nonlinear force analysis in a bogie, and constructing a track model according to a rail / sleeper model, a line geometry, and track irregularity; The evaluation basis determination specifically comprises taking a vehicle center plate vertical force as a main evaluation basis for determining a cargo allowable weight under different protruding lengths, comparing the center plate vertical force under an overlong cargo condition with the center plate vertical force under a non-overlong cargo full load condition to determine the allowable loading weight of the cargo, and using a vehicle derailment coefficient and a wheel load reduction rate to verify vehicle running safety; The method further comprises introducing a GLM model to study a numerical correlation between indexes and factors by taking the research results determined according to the evaluation basis as input as follows: ; wherein, is used as a dummy variable to handle qualitative factors then is used to describe the selected truck model, when or then, or is used to describe the curve radius, thus represents the inverse of the curve radius; represents the allowable load weight of an overlength cargo, represents the overhang length of an overlength cargo, represents the truck running speed.

2. The computer experiment and surrogate model based ultra-long cargo transportation safety assurance method of claim 1, wherein, The simulation test model is established in SIMPACK; the establishment step specifically comprises, Performing stress analysis on each component according to a composition of a truck real vehicle system; Front processing of wheel / rail contact relationship; Comprehensively considering stress relationships of the real vehicle system and each component, and establishing a topological structure of the truck system; Establishing an overlong cargo transportation simulation model in a simulation platform according to the topological structure of the truck system; Constructing a track model in the simulation platform according to a rail or sleeper model, a line geometry, and track irregularity; Obtaining a final computer simulation test model; The front processing of the wheel / rail contact relationship specifically comprises a contact relationship between wheels and rails, and the contact relationship between the wheels and the rails comprises an LM abrasion type tread and an R60 rail.

3. The computer experiment and surrogate model based ultra-long cargo transportation safety assurance method of claim 2, wherein, The rail or sleeper model is a selected discrete equivalent rail or sleeper model.

4. The computer experiment and surrogate model based ultra-long goods transportation safety assurance method of claim 2, wherein, Elements of the line geometry comprise a curvature change in a length direction of the line, an outer rail super-elevation, and a lateral deviation from an initial position; Element parameters determined in the test scheme are taken as input, and calculation and analysis are performed by a SIMPACK front processing program.

5. The computer experiment and surrogate model based ultra-long cargo transportation safety assurance method of claim 2, wherein, The track irregularity is described by a power spectral density function as follows: ; ; ; where, The PSD functions for lateral, vertical and gauge irregularities are described respectively, represents the spatial angular frequency, and represents the cut-off angular frequency, and is the roughness scalar, is the safety factor.

6. The computer experiment and surrogate model based ultra-long cargo transportation safety assurance method of claim 5, wherein, Under the same vehicle type, line condition factors, the value of the vertical force index of the heart disc can be regarded as a constant value As shown in equation (13): ; By transformation and transfer of the formula, formula (17) with the cargo allowable weight as a target item can be derived: ; Therefore, a substitute model for describing a relationship between the cargo allowable weight and the protruding length is 。

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