CN114329773A - Carbon fiber composite material vehicle body structure and design method thereof - Google Patents
Carbon fiber composite material vehicle body structure and design method thereof Download PDFInfo
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Abstract
The invention discloses a carbon fiber composite material vehicle body structure and a design method thereof.A design space, a non-design space, a constraint condition, a calculation working condition and an optimization target are used as the input of simulation software to establish a vehicle body topology optimization structure model; and performing iterative calculation on the vehicle body topology optimization structure model by using a variable density method to obtain a force transmission path of the vehicle body structure under different material utilization degrees, which meets the requirements of constraint conditions and working conditions, and obtaining the optimal vehicle body structure configuration according to the force transmission path. The invention provides a design method of input parameters, which ensures that the required structure configuration can be obtained and improves the simulation efficiency and the simulation precision.
Description
Technical Field
The invention relates to the technical field of rail transit, in particular to a carbon fiber composite vehicle body structure and a design method thereof.
Background
For wheel rail formula train, maglev train passes through the electromagnetic force suspension on the track, and the automobile body does not have the contact with the track, does not produce the friction loss, and the operation is maintained simply and is a neotype traffic methods, and compares in the high-speed maglev train that is fit for long distance main line operation, and the economic nature of well low-speed maglev is better, and the construction degree of difficulty is low, and ambient noise is little, especially adapted intercity track traffic. Because the maglev train runs by means of levitation force, the maglev train puts higher requirements on the light weight of the train body compared with a wheel track type train which directly falls to the ground. The optimal design of a vehicle body structure and the application of a novel light material are necessary development directions for vehicle body light weight, but the application of the novel structure and the novel material often brings some new problems of vehicle body rigidity, noise, fire prevention and the like.
The carbon fiber composite material has light weight, high rigidity and high strength, is more and more widely applied to the field of rail transit, can be particularly used on a bearing structure, can obviously reduce the weight of a vehicle body while improving the rigidity of the vehicle body, and has wide application prospect. In the field of rail transit, there are a plurality of patent applications for preparing a car body structure by using a carbon fiber composite material, and patent application CN 105128876B "a carbon fiber composite material car body and a manufacturing method thereof" proposes that the car body is composed of an integrally formed car body and a bottom plate which are prepared by carbon fibers, the car body is composed of an outer skin, a sandwich layer, an inner skin and reinforcing ribs bonded on the inner skin, but the structure does not relate to the noise and fire prevention problems of the car body structure. Patent application CN 206187017U carbon fiber composite vehicle body structure for medium and low speed rail transit provides a carbon fiber composite vehicle body structure composed of a carbon fiber outer skin, a carbon fiber inner skin and a flame-retardant foam core material between the outer skin and the inner skin, and flame-retardant epoxy resin is added in the carbon fiber composite material of the inner skin and the outer skin. Patent CN 208325223U "a structure of low-cost carbon-fibre composite air-iron automobile body" has proposed a carbon-fibre composite air-iron automobile body structure for suspension type, its automobile body side wall and headwall include the strengthening rib skeleton, interior covering and outer covering, it is attached in the strengthening rib skeleton, on the outside surface, pack the core foam piece of pressing from both sides in the net of strengthening rib skeleton, but this automobile body structure does not relate to cab part, and there is the operating mode difference that is showing in the structural style of suspension type air-iron and the automobile body structure that falls on ground, also not specifically relate to structural strength and sound insulation, the comprehensive problem of fire prevention.
Patent application CN 110489907 a "method for optimizing design of digital prototype of vehicle body of rail transit vehicle" gives general steps of vehicle body topology optimization design, which is actually software logic for running topology optimization software itself, and the core key of vehicle body topology optimization design is not in the running logic and general operation steps of tool software, but in the design skill and thought of each specific parameter, which is the core key for obtaining the required structural configuration, and the scheme does not relate to parameter design content, so that it may not actually obtain the required structural configuration. The actual setting of the design space range, the specific constraint conditions and the calculation conditions is the key point and the difficulty of the topology optimization design, and whether the input parameter range is set is reasonable or not directly determines whether the optimization calculation is converged or not and the reliability of the simulation calculation.
The design parameter multi-objective optimization method provided in patent application CN 113033093 a, "a simulation model-based system design parameter multi-objective optimization method" is an optimization method limited to the same calculation model system, specifically, simulation calculation based on the strength of the spring system of the Mworks simulation platform, but for joint simulation among different-dimension calculation models, no feasible implementation scheme is provided.
At present, the train body with the cab structure prepared from the carbon fiber composite material adopts the hollow integral carbon fiber cab hood, the longitudinal impact force of 800KN cannot be borne at the cab, and the existing carbon fiber train body structure does not achieve coordination and unification in three aspects of structural bearing, sound insulation, noise reduction and fire prevention due to the disadvantages of the carbon fiber composite material in the aspects of sound insulation, noise reduction and fire prevention. In the field of maglev trains, no report on maglev train bodies made of carbon fiber composite materials exists at present.
Disclosure of Invention
The invention aims to solve the technical problem that the defects in the prior art are overcome, and the carbon fiber composite material vehicle body structure and the design method thereof are provided to ensure that the required structural configuration can be obtained and improve the reliability of simulation calculation.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a design method of a carbon fiber composite vehicle body structure comprises the following steps:
s1, taking a design space, a non-design space, a constraint condition, a calculation condition and an optimization target as the input of simulation software, and creating a vehicle body topology optimization structure model;
s2, carrying out iterative computation on the vehicle body topology optimization structure model by using a variable density method to obtain a vehicle body structure force transmission path under different material utilization degrees, which meets the requirements of constraint conditions and working conditions, and obtaining an optimal vehicle body structure configuration according to the force transmission path, wherein the configuration comprises a bearing framework and a bearing panel;
wherein the design space includes an outer interface of the design space and an inner interface of the design space; the outer interface of the design space is M times of the design size of the vehicle body, and does not exceed the running limit of the vehicle; the interior boundary surface of the design space is configured as a vehicle body design interior surface inward extension Kmm; in the invention, the inward extension is the extension from the outside of the vehicle to the center direction of the vehicle body;
the non-design space comprises interfaces of all equipment and components connected with the vehicle body;
the calculation working condition comprises all external loads and constraints for guaranteeing the safe operation of the vehicle;
the constraint conditions include: the weight reduction ratio of the vehicle body, the maximum displacement condition under the overload working condition of the whole vehicle and the modal frequency of the whole vehicle avoid the sinking and floating frequency of the suspension frame; the maximum displacement is selected as the longitudinal displacement of the car coupler and the vertical displacement of the middle part of the boundary beam of the car body; the finished automobile modal frequency avoiding the floating frequency of the suspension frame is defined as an optimized first-order vertical bending mode of the automobile body and simultaneously meets two conditions, namely the difference between the finished automobile modal frequency and the floating frequency of the suspension frame is not less than 2Hz and is more than N times of the floating frequency of the suspension frame; preferably, the maximum displacement and the vehicle body weight reduction ratio conform to the following formula: d ═ 0.8 × D/(1-s); wherein D is the maximum displacement allowed, D is the maximum displacement of the vehicle body structure, and s is the weight reduction ratio of the vehicle body;
the optimization target is set to be the maximum weighted rigidity of the vehicle body under all working conditions;
the bearing panel is a multi-layer structure panel.
In the invention, the optimal vehicle body structure configuration is obtained by manually reading the force transmission path.
The invention determines the design space, the non-design space, the constraint condition, the calculation condition and the optimization target as the input parameters of the simulation software, researches and analyzes each input parameter to obtain the setting method of each input parameter, and experiments prove that the method can ensure that the simulation software obtains the required structural configuration, improve the simulation efficiency and the reliability of the simulation calculation and ensure the convergence of the optimization calculation.
M is 1.1-1.2; k is 50-60; the weight reduction ratio of the vehicle body is set to be 20-40%; n is 1.32.
And in the parameter range, the outer interface and the inner interface of the vehicle body design are expanded, the appeared thin shell units can be swept, and more accurate force transmission path information can be obtained on the actual design section. The weight reduction ratio of the vehicle body is set according to the weight reduction target, and the value range is selected on the basis of considering the material density, so that the necessary weight reduction target can be achieved, and the material structure force transmission information distortion caused by the overlarge weight reduction ratio can be avoided. The range of the ratio of the overall vehicle modal frequency to the floating and sinking frequency of the suspension frame is set, so that the overall mode can fully avoid the floating and sinking frequency of the suspension frame, resonance is avoided, the requirement on the vehicle body modal frequency is not too high, and the orderly optimization of the vehicle body structure topology is facilitated.
The working conditions comprise a main working condition, a secondary working condition and a normal operation working condition, and the weighting coefficients of the working conditions are respectively set as: the main operating condition coefficient is 1, the secondary operating condition coefficient is 0.63, and the normal operating condition coefficient is 0.45.
The stress condition of the topological optimization process depends on the working condition conditions of calculation, but the important degrees of all the working conditions to the reliability of the car body structure are different, such as the pulling and pressing working conditions of a car body front-end car coupler, which are the main carrying working conditions of the car body structure, and the reason that the common stress exceeds, the coefficient of the main working condition is set to be 1 so as to completely meet the stress requirement of the main working condition to the car body, while the important degree of the secondary working condition is weaker than that of the main working condition, and the coefficient is reduced so as to be beneficial to the calculation of the whole stress structure, while the stress requirement of the car body structure under the normal operation working condition is not high, and under the working condition coefficient, the stress requirement of the car body under the operation can be met. The weight distribution of the main working condition, the secondary working condition and the normal working condition can better reflect the stress condition of the vehicle body under all required working conditions, and can more truly reflect the force transmission path of the vehicle body.
Further, the method of the present invention further comprises: s3, creating a vehicle body strength model, a vehicle body noise model and a vehicle body fire-proof simulation model; connecting a vehicle body strength model, a vehicle body noise model and a vehicle body fire-proof simulation model into a simulation calculation platform based on Isight software, selecting relevant parameters of strength, noise and fire-proof indexes, taking the thickness range of a beam rib plate of a bearing framework of an optimal vehicle body structure configuration and the thickness range of each layer of a bearing multilayer panel as input design variables of the simulation calculation platform, taking limiting conditions of the rigidity, the strength, the fatigue, the mode, the noise sound pressure level, the heat release rate and the smoke spreading rate of the whole vehicle as constraints, and taking weighted index values of the vehicle body weight, the sound insulation and the fire prevention as design targets, and establishing a strength, noise and fire-proof combined simulation model;
s4, taking the parameter combination of the input design variables as the input parameters of the optimal hyper-Latin method to obtain a characteristic sample space, carrying out sensitivity analysis on the characteristic sample space, reducing the dimension of the variable of the characteristic sample space, and obtaining the optimal sample space; establishing an optimized proxy model based on the optimal sample space;
and S5, calling a particle swarm algorithm, optimizing in the input and output combination of the optimization proxy model, and determining an optimal combination scheme.
According to the optimal sample space, the coupled simulation computing platform calculates the result of each data combination in the sample, and the data combination and the corresponding result are fitted by adopting a machine self-learning algorithm, so that an optimal proxy model is formed. And optimizing the input and the output of the agent model in the optimal agent model to obtain the final optimal solution.
Aiming at the defects and shortcomings of the existing carbon fiber composite material vehicle body structure in terms of structural bearing force, particularly longitudinal impact force of a cab, sound insulation, noise reduction, fire prevention safety and the like, the invention considers the disadvantages of the carbon fiber composite material in terms of sound insulation, noise reduction and fire prevention, ensures that the carbon fiber vehicle body structure achieves coordination and unification in three aspects of structural bearing force, sound insulation, noise reduction and fire prevention through the optimized design process, and can meet the performance requirements of good sound insulation, noise reduction, heat insulation, fire prevention and light weight on the premise of meeting the working condition of bearing strength of a maglev train.
In step S3, the creating process of the vehicle body strength model includes: and obtaining the vehicle body strength model by taking the thickness and material properties of the carbon fiber layer, the thickness and material properties of the foam layer, the damping layer and the rubber layer as input parameters of Optistruct software and taking the static strength, fatigue strength, rigidity and mode of the vehicle body structure as output parameters. The vehicle body strength model takes the material and thickness parameters of each layer of the panel into consideration, and ensures that the static strength, the fatigue strength, the rigidity and the mode of the vehicle body structure meet the design requirements.
In step S3, the thermophysical parameters of the material and the fire spreading parameters are input parameters of the FDS software, and the heat release rate, the temperature field distribution, and the smoke spreading characteristics of the vehicle body are output parameters to obtain the vehicle body fire-proof simulation model. The invention considers the fire-proof requirement of the vehicle body, creates a fire-proof simulation model of the vehicle body, and ensures that the vehicle body structure achieves coordination and unification in three aspects of structure bearing, sound insulation, noise reduction and fire prevention in the subsequent design optimization process.
In step S3, the association parameters include: the thickness of each layer of the multilayer force bearing panel and the thickness of the rib plate with an included angle of less than 60 degrees with the corresponding layer of the force bearing framework are both equal;
in step S3, the process of obtaining weighted index values of vehicle body weight, sound insulation, and fire resistance includes: normalizing the vehicle body weight, the sound insulation index and the fire prevention index, and weighting the normalized values to obtain weighted index values; the weighting coefficients are: the fire-proof coefficient is 0.4-0.6, the weight coefficient is 0.2-0.4, and the noise coefficient is 0.1-0.3. It should be noted that the weight index is in units of kilograms, the sound insulation index is in units of decibels, the fire prevention index is the heat release speed and the smoke spreading speed, and the indexes are different in units of millimeters/second and cannot be directly added together, so that the weight addition can be carried out without unit magnitude by only carrying out normalization processing on the numerical values of the indexes and neglecting the units.
In step S4, a parameter combination of design variables is input, an optimal hyper-latin algorithm is dispatched and transported, and a characteristic sample space capable of representing the entire sample information is obtained from a sample space composed of all the design variables based on the principle of the optimal hyper-latin algorithm.
In step S4, the contribution rates of the variables in the feature sample space to the model calculation result are different, and sensitivity analysis is performed on the feature sample space, where in the sensitivity analysis, a parameter with a sensitivity greater than 40% is selected, and the variable dimensions of the feature sample space are reduced to form an optimal sample space, so that the calculation rate of the joint simulation can be further increased.
In step S5, the input parameters of the optimal sample space and the output results obtained by the joint simulation are optimized by a machine self-learning method, so as to obtain an optimized proxy model.
And optimizing in a sample space formed by the input and the output of the optimization proxy model by adopting a self-adaptive particle swarm algorithm to determine an optimal combination scheme.
As an inventive concept, the invention also provides a carbon fiber composite vehicle body structure, which comprises a plurality of bearing panels and a plurality of bearing frameworks for supporting the bearing panels; the bearing panel comprises a damping layer; two sides of the damping layer are respectively attached to a foam layer, and one side of the foam layer, which is far away from the damping layer, is attached to the carbon fiber layer; the thicknesses of the damping layer, the foam layer and the carbon fiber layer and the thickness of the beam rib plate of the bearing framework are determined according to the design method of the invention.
(ii) a The adhesive layer is an epoxy resin adhesive added with an inorganic flame retardant, and the weight percentage of the added amount of the inorganic flame retardant is 40-50%.
In the invention, the foam layer is made of foam material with low shear modulus, and the low shear modulus means that the shear modulus is not more than 60 MPa.
In particular, in the present invention, the low shear modulus foam material may be selected from polyethylene foam materials.
The damping layer is made of styrene thermoplastic material.
The inner surfaces of the machine room arc-shaped panel, the middle U-shaped top side panel and the end wall panel of the vehicle body structure and the inner surface and the outer surface of the vehicle body underframe panel are sprayed with water system fireproof damping coatings, so that the fireproof performance of the vehicle body structure is further improved.
The bearing panels comprise a cab arc panel, a U-shaped top side panel in the middle of the vehicle body, an end wall panel and an underframe panel; the end part of the arc-shaped panel of the cab is fixedly connected with one end part of a U-shaped top side panel in the middle of the vehicle body; the other end of the U-shaped top side panel in the middle of the vehicle body is fixedly connected with the end wall panel; the bottom of the arc-shaped panel of the cab, the bottom of the U-shaped top side panel in the middle of the vehicle body and the bottom of the end frame panel are fixedly connected with the chassis panel.
The force bearing framework comprises cab end beam ribs arranged at the bottom of a cab arc-shaped panel, the force bearing framework is symmetrically arranged on cab arc-shaped forked support ribs at the left side and the right side of the top of the cab arc-shaped panel, a plurality of sealing type U-shaped support ribs are wrapped on a U-shaped top side panel and a bottom frame panel in the middle of a vehicle body, rib ribs are longitudinally extended along the vehicle body and arranged on a top cover side beam rib at the top of the middle U-shaped top side panel, bottom frame side beam ribs of all panels at the bottom of the vehicle body are connected, end wall transverse ribs arranged at the upper end and the lower end of an end wall panel, end wall vertical ribs arranged at the left side and the right side of the end wall panel, side wall transverse ribs arranged on the middle U-shaped top side panel and used for connecting two adjacent U-shaped support ribs and a plurality of vertical side wall vertical ribs arranged on the middle U-shaped top side panel.
As an inventive concept, the design parameters of the carbon fiber composite material vehicle body structure are determined by the design method.
Compared with the prior art, the invention has the beneficial effects that:
(1) the invention provides a design method of input parameters, which ensures that the required structure can be obtained, and improves the simulation efficiency and the simulation precision;
(2) according to the invention, the beam rib plate thickness of the carbon fiber integral bearing framework at different positions of the vehicle body and the thickness combination of the carbon fiber multi-layer panel plate matched with the beam rib plate thickness are obtained through the whole vehicle topology optimization and the multi-target collaborative optimization simulation calculation based on the digital prototype; experiments prove that the weight of the carbon fiber vehicle body prepared by the method is not more than 3 tons, the cab can bear the longitudinal compressive stress of 800kN, the noise in the vehicle is not more than 69 decibels, the fire-proof level reaches HL3 level, and the requirement of the magnetic suspension vehicle body on the carrying working condition is met
(3) The carbon fiber beam with the hollow cavity is adopted, integral forming or multi-component composite connection is carried out according to a force transmission path and a rib section configuration obtained by the topological optimization of the whole vehicle, an integral bearing framework of the magnetic levitation vehicle body is constructed, and the structural bearing requirement of the magnetic levitation vehicle body under the carrying working condition is met;
(4) according to the carbon fiber multilayer panel, the foam material with low shear modulus is used as the sandwich layer, and the damping layer is arranged between the foam sandwich layers, so that the disadvantage of poor sound insulation performance of the multilayer sandwich structure is overcome, and the sound insulation performance of the multilayer panel is effectively improved while the strength, rigidity and mode of the sandwich structure are met through the optimization of the thicknesses of the plates;
(5) according to the invention, the water-based fireproof damping coating is coated on the carbon fiber multi-layer panel, and the inorganic flame retardant with a specific weight percentage is added into the carbon fiber epoxy resin adhesive, so that the fireproof performance of the carbon fiber structural member is effectively improved.
Drawings
Fig. 1 is a flowchart of the topology optimization design of the integral force-bearing framework in embodiment 1 of the present invention.
Fig. 2 is a vehicle body structure model obtained in embodiment 1 of the present invention.
FIG. 3 is a structural diagram of an integral bearing skeleton of carbon fibers obtained after manual check in embodiment 1 of the present invention;
FIG. 4 is a structural diagram of a carbon fiber multi-layer panel obtained after manual checking in embodiment 1 of the present invention;
FIG. 5 is a flowchart of a method according to example 2 of the present invention;
fig. 6 is a schematic view of the structure of a carbon fiber multi-layer panel according to embodiment 3 of the present invention.
Detailed Description
The optimization design method of the carbon fiber maglev train body structure comprises topological optimization of the integral bearing framework of the body, manual shape modification and checking, beam rib plate thickness of the integral bearing framework of the body based on a digital prototype, thickness combination of each layer of the carbon fiber multilayer panel, and multi-target collaborative simulation optimization of strength, rigidity, mode, fatigue, sound insulation and fire prevention of the whole body structure.
As shown in fig. 1, in embodiment 1 of the present invention, topology optimization of an entire force-bearing skeleton of a vehicle body is performed by a variable density method based on OptiStruct software, an outer interface of a design space of the entire vehicle body is a vehicle operation limit, and an inner interface of the design space is a size of an inner space of the vehicle body; the non-design space is all equipment and component interfaces (vehicle doors, vehicle windows and the like) connected with the vehicle body; calculating all external loads and constraints for ensuring the safe operation of the vehicle under the working condition; constraint conditions of topology optimization are a vehicle body weight reduction ratio, a maximum displacement condition under the condition of vehicle overload, and a vehicle modal frequency fully avoided from the suspension frame sinking and floating frequency; the optimization target is that the weighted rigidity of the vehicle body is maximum under all working conditions.
A simulation model is created in Optistruct software, model parameters such as set internal and external design spaces, non-design spaces, constraint conditions, calculation conditions and optimization targets are input into the simulation model, the output of the simulation model is the vehicle body structure configuration under different material utilization degrees obtained through calculation, a designer can read the desired structure configuration under the material utilization degree, the configuration reflects the force transmission paths meeting the design requirements, and the final vehicle body model can be manually checked according to the force transmission paths.
The topological optimization of the integral bearing framework of the vehicle body is carried out by a variable density method based on OptiStruct software, and the specific input parameter range is as follows: (1) designing a space: a. designing an external interface of the space: the outer interface range of the design space of the whole vehicle body is 1.1 times of the design size of the vehicle body, and simultaneously, the outer interface range does not exceed the operation limit of the vehicle, and b, the inner interface of the design space: the inner surface of the designed vehicle body extends inwards by 50 mm; (2) non-design space: interfaces of all devices and components connected with the vehicle body (such as vehicle doors, vehicle windows, device installation areas and the like); (3) calculating the working condition: all external loads and constraints for ensuring the safe operation of the vehicle are determined according to the size and the position of loads or impact stress required by the actual operation of the vehicle body, such as the longitudinal compressive stress of 800KN borne by the front end of the cab; (4) constraint conditions are as follows: the weight reduction ratio of the vehicle body, the maximum displacement condition under the overload working condition of the whole vehicle and the modal frequency of the whole vehicle fully avoid the sinking and floating frequency of the suspension frame. The weight reduction ratio of the vehicle body is set according to the required weight reduction requirement, and the weight reduction ratio is 30% in the invention; the maximum displacement is selected as the longitudinal displacement of the car coupler and the vertical displacement of the middle part of the boundary beam of the car body, and the maximum displacement and the weight reduction ratio of the invention accord with the following formula: d is 0.8 × D/(1-s) (where D is the maximum displacement allowed by the present invention, D is the maximum displacement of the vehicle body structure, and s is the desired weight reduction ratio); the modal requirement of the invention is that the optimized first-order vertical bending mode of the vehicle body simultaneously meets two conditions, namely the sum of the whole vehicle modal frequency and the floating and sinking frequency of the suspension frame is more than 2Hz, and the division of the whole vehicle modal frequency by the floating and sinking frequency of the suspension frame is more than 1.32. (5) Optimizing the target: the invention takes the maximum weighted rigidity of the vehicle body under all working conditions as a target, and the specific weighted coefficient is as follows: the main operating condition coefficient is 1, the secondary operating condition coefficient is 0.63, and the normal operating condition coefficient is 0.45.
The vehicle body structure calculated by the above simulation is shown in fig. 2.
The manual shape correction and checking is based on the result of topology optimization, and the manual correction of the configuration of the integral bearing framework of the vehicle body is carried out according to the calculated force transmission path and topology configuration on the basis of considering the technological conditions of carbon fiber forming. The force-bearing framework and the car body outer cover after manual shape modification and checking are respectively shown in fig. 3 and fig. 4.
The flow chart of the embodiment 2 of the invention is shown in figure 5. The multi-target collaborative simulation based on the digital prototype is that after a vehicle body simulation model is established, the vehicle body simulation model is submitted to a developed digital prototype simulation platform, thickness combination of each layer of the carbon fiber multi-layer panel and optimization of the section size of the whole vehicle body bearing framework are developed based on the digital prototype, multi-target collaborative coupling of lightweight, sound insulation and fire resistance is comprehensively considered, the yield strength of materials used by the whole vehicle is taken as a stress constraint condition, the fatigue utilization degree of the materials is taken as a fatigue strength constraint condition, the vertical displacement of the middle part of a vehicle body variable is taken as a rigidity constraint condition, the first-order vertical bending frequency of the whole vehicle is taken as a modal constraint condition, the sound pressure level of noise in the vehicle is taken as a noise constraint condition, the heat conduction rate and the smoke spreading characteristic are taken as a fire resistance constraint condition, the thickness of each layer of the multi-layer bearing panel and the thickness of a rib plate with an included angle of less than 60 degrees with the multi-layer panel in the bearing framework are set as strength, noise, Correlation parameters of the fire-proof simulation model; and designing a multi-target weighting design target by using a fire protection coefficient of 0.5, a weight coefficient of 0.3 and a noise coefficient of 0.2.
The method comprises the steps of taking a parameter combination of design variables as input parameters of an optimal hyper-Latin method, obtaining a characteristic sample space, carrying out sensitivity analysis, selecting parameters with the sensitivity higher than 40%, reducing the variable dimension of the characteristic sample space, obtaining an optimal sample space, establishing an optimal proxy model by utilizing machine self-learning based on the optimal sample space, calling an adaptive particle swarm optimization algorithm, optimizing input and output parameters in the proxy model, realizing the multidisciplinary rapid engineering collaborative optimization simulation calculation of the carbon fiber vehicle body, and obtaining an optimal solution, namely a finally determined optimal design scheme.
Through multi-target collaborative optimization simulation calculation based on a digital prototype, the thickness of the rib plate of the carbon fiber integral bearing framework at different positions of the vehicle body and the thickness combination of the carbon fiber multi-layer panel matched with the rib plate are obtained.
Simulation experiments show that the weight of the carbon fiber vehicle body prepared by the method in the embodiment 2 of the invention is not more than 3 tons, the cab can bear the longitudinal compressive stress of 800kN, the noise in the vehicle is not more than 69 decibels, the fire-proof level reaches HL3 level, and the carrying working condition requirement of the magnetic suspension vehicle body is met.
Establishing a vehicle body strength model by adopting Optistruct software, inputting parameters by using the thickness and material properties (Poisson ratio, elastic modulus, tensile strength, compressive strength and shear strength in three directions of 0 degree, 90 degrees and layers) of a carbon fiber layer, the thickness and material properties (Poisson ratio, elastic modulus and tensile strength) of a foam layer, a damping layer and an adhesive layer, and outputting parameters by using static strength, fatigue strength, rigidity and mode of a vehicle body structure; adopting VA-one software to establish a vehicle body noise model, taking the sound insulation quantity of a material, the sound absorption coefficient of the material, the sound source frequency spectrum and the sound source position as input parameters, and taking the sound pressure level of noise inside and outside a vehicle as output parameters; a vehicle body fire-proof simulation model is created by utilizing FDS software, thermophysical parameters (density, specific heat capacity, heat transfer coefficient and the like) of materials and fire spreading parameters (combustion heat, reaction heat, Aloneius pre-finger factors and activation energy) are used as input parameters, and the heat release rate, the temperature field distribution and the smoke spreading characteristics (smoke spreading speed and smoke layer height) of a vehicle body are used as output parameters. The change of the plate thickness combination of the multilayer panel and the beam rib plate thickness of the bearing framework can cause the material thickness at different positions to generate relevant and interactive influence on the output of the vehicle body strength model, the noise model and the fire prevention model, for example, the rib plate in the vertical direction of the multilayer panel has obvious influence on the strength, but has very limited influence on the noise, and the parameter combination needs to be screened in a targeted manner.
Under the condition that design variables are changed, the input parameters of the three submodels generate huge input parameter combinations, the combination quantity required to be calculated is larger and far higher than the calculation combination quantity among the submodels, the huge calculation input and output parameter combinations are input of an optimal hyper-latin method, and the optimal hyper-latin method is to perform systematic comparison arrangement optimization on the combinations, so that the most reactive system characteristics are optimized, and the most significant sample space is influenced on the calculation result, so that the calculation quantity is reduced.
The Isight constraint condition is a limit limiting condition for output parameters in each submodel, namely a limit boundary condition which can be accepted by the submodel, and if the limit boundary condition is exceeded, the submodel is judged to be not in accordance with the optimization target.
Specifically, as shown in fig. 5, the implementation flow of embodiment 2 is as follows:
creating a vehicle body strength model, a vehicle body noise model and a vehicle body fire prevention simulation model; connecting a vehicle body strength model, a vehicle body noise model and a vehicle body fire-proof simulation model into a simulation calculation platform based on Isight software, selecting relevant parameters of strength, noise and fire-proof indexes, taking the thickness range of a beam rib plate of a bearing framework of an optimal vehicle body structure configuration and the thickness range of each layer of a bearing multilayer panel as input design variables of the simulation calculation platform, taking limiting conditions of the rigidity, the strength, the fatigue, the mode, the noise sound pressure level, the heat release rate and the smoke spreading rate of the whole vehicle as constraints, and taking weighted index values of the vehicle body weight, the sound insulation and the fire prevention as design targets, and establishing a strength, noise and fire-proof combined simulation model;
taking parameter combinations in the joint simulation model as input parameters of an optimal hyper-Latin method to obtain a characteristic sample space, carrying out sensitivity analysis on the characteristic sample space, selecting parameters with sensitivity higher than 40%, reducing variable dimensions of the characteristic sample space, and obtaining an optimal sample space; based on the optimal sample space, establishing an optimal proxy model by adopting a machine self-learning algorithm;
and calling a particle swarm algorithm, optimizing in the input and output combination of the optimization proxy model, and determining an optimal combination scheme.
The car body structure comprises a carbon fiber integral bearing framework, a carbon fiber multilayer panel and a water-based fireproof damping coating.
As shown in fig. 2, the whole bearing framework of carbon fiber comprises a cab end beam rib 1, bilateral symmetry's cab arc-shaped forked support rib 2, 4 sealing type U-shaped support ribs 3 consistent with the cross section of the vehicle body, a top cover side beam rib 4 along the longitudinal direction of the vehicle body, an underframe side beam rib 5, an end wall transverse rib 6, an end wall vertical rib 7, a side wall transverse rib 8 and a side wall vertical rib 9, the whole bearing framework of carbon fiber is formed by integrally molding the carbon fiber beam with a hollow cavity, and the hollow carbon fiber beam can be formed by gluing and riveting composite connection.
The integral bearing framework of the vehicle body obtained by adopting the complete vehicle topology optimization is a structure iteratively optimized according to the vehicle carrying working condition, and a force transmission path of the vehicle body under the actual working condition is embodied. And according to the force transmission path, integrally forming the carbon fiber beam with the hollow cavity inside according to the force transmission path to construct a force bearing framework of the vehicle body. According to the position and the stress of the vehicle body, the hollow cavity type section configuration and the wall thickness of the carbon fiber beam can be adjusted in an adaptive manner.
As shown in fig. 3 and 4, the carbon fiber multi-layer panel includes a cab arc panel 10, a middle U-shaped roof panel 11, an end wall panel 12, and an underframe panel 13; windows and car light openings of the cab are formed in the corresponding areas of the arc-shaped panel 10 of the cab; the corresponding area of the middle U-shaped top side panel 11 is provided with a vehicle door and a vehicle window opening; the end wall panel 13 is provided with a through passage opening; after the arc-shaped panel 10 of the cab, the middle U-shaped top side panel 11 and the end wall panel 12 are respectively and independently molded, the outer covers are covered on the corresponding carbon fiber integral bearing frameworks and are connected with the bearing frameworks in a composite connection mode of bonding and riveting, and the arc-shaped panel 10 of the cab, the middle U-shaped top side panel 11 and the end wall panel 12 are connected into a whole through bonding; the chassis panel 13 is laid on a plane formed by cab end beam ribs, carbon fiber chassis side beam ribs and sealed U-shaped supporting ribs, and is connected with the force-bearing framework in a bonding and riveting composite connection mode.
As shown in fig. 6, in embodiment 3 of the present invention, a cross section of a carbon fiber multilayer panel sequentially includes, from outside to inside, a carbon fiber outer panel, a foam sandwich layer i, a damping layer, a foam sandwich layer ii, and a carbon fiber inner panel, the carbon fiber outer panel and the carbon fiber inner panel are formed by laying carbon fiber woven cloth prepreg, the foam sandwich layer is made of a polyethylene foam material, the damping layer is made of a styrene-based thermoplastic material, and a carbon fiber adhesive is made by adding 40-50 wt% of an inorganic flame retardant to a carbon fiber epoxy resin adhesive; and water-based fireproof damping coatings are sprayed on the inner surfaces of the arc-shaped panel of the cab, the middle U-shaped top side panel and the end wall panel and the inner surface and the outer surface of the chassis panel of the vehicle body. The foam sandwich layer is made of foam material with low shear modulus (not higher than 60MPa), and the damping layer is made of thermoplastic elastic material.
To meet the vehicle body stiffness requirements, the sandwich layer filled with the carbon fiber sandwich structure is often a high modulus material, such as a PMI foam material. However, in the composite material multilayer structure, the high-modulus foam sandwich layer can cause the sound insulation performance of the sandwich structure to deviate from the sound insulation curve seriously, so that the sound insulation performance of the whole structure is reduced remarkably. The invention adopts the foam material with low shear modulus, and adds the thermoplastic elastic material damping layer between the foam materials, thereby further improving the sound insulation performance of the sandwich structure in the low frequency band. And obtaining the thicknesses of the carbon fiber inner and outer layer panels, the foam sandwich layer and the damping layer through coupled iterative calculation of structural strength, rigidity, mode, sound insulation performance and fire prevention performance. And the thickness of each layer of the carbon fiber multilayer panel is adaptively adjusted according to the strength of different positions of the vehicle body and different sound insulation requirements.
The arc-shaped panel of the cab, the middle U-shaped top side panel and the end wall panel are covered on the corresponding carbon fiber integral bearing framework and are connected with the bearing framework in a composite connection mode of bonding and riveting; the chassis panel is laid on a plane consisting of cab end beam ribs, carbon fiber chassis side beam ribs and sealed U-shaped supporting ribs and is connected with the force-bearing framework in a bonding and riveting composite connection mode.
The water system fireproof damping coating is sprayed on the inner surfaces of the arc-shaped panel of the cab, the middle U-shaped top side panel and the end wall panel and the inner and outer surfaces of the chassis panel of the vehicle body.
Compared with a metal material, the fireproof performance of the carbon fiber material is relatively low, and the bonding glue layer of the carbon fiber can cause high-temperature failure at high temperature, so that the fireproof performance of the carbon fiber material is remarkably reduced. According to the invention, 40-50 wt% of inorganic flame retardant is added into the epoxy resin adhesive of the carbon fiber, and water system fireproof damping coatings are sprayed on the inner surface of the car body and the inner and outer surfaces of the underframe panel, so that the fireproof safety performance of the car body structure is further improved.
Claims (10)
1. A design method of a carbon fiber composite material vehicle body structure is characterized by comprising the following steps:
s1, taking a design space, a non-design space, a constraint condition, a calculation condition and an optimization target as the input of simulation software, and creating a vehicle body topology optimization structure model;
s2, carrying out iterative computation on the vehicle body topology optimization structure model by using a variable density method to obtain a vehicle body structure force transmission path under different material utilization degrees, which meets the requirements of constraint conditions and working conditions, and obtaining an optimal vehicle body structure configuration according to the force transmission path, wherein the configuration comprises a bearing framework and a bearing panel;
wherein the design space includes an outer interface of the design space and an inner interface of the design space; the outer interface of the design space is M times of the design size of the vehicle body, and does not exceed the running limit of the vehicle; the interior boundary surface of the design space is configured as a vehicle body design interior surface inward extension Kmm;
the non-design space comprises interfaces of all equipment and components connected with the vehicle body;
the calculation working condition comprises all external loads and constraints for guaranteeing the safe operation of the vehicle;
the constraint conditions include: the weight reduction ratio of the vehicle body, the maximum displacement condition under the overload working condition of the whole vehicle and the modal frequency of the whole vehicle avoid the sinking and floating frequency of the suspension frame; the maximum displacement is selected as the longitudinal displacement of the car coupler and the vertical displacement of the middle part of the boundary beam of the car body; the finished automobile modal frequency avoiding the floating frequency of the suspension frame is defined as an optimized first-order vertical bending mode of the automobile body and simultaneously meets two conditions, namely the difference between the finished automobile modal frequency and the floating frequency of the suspension frame is not less than 2Hz, and the finished automobile modal frequency is more than N times of the floating frequency of the suspension frame; preferably, the maximum displacement and the vehicle body weight reduction ratio conform to the following formula: d ═ 0.8 × D/(1-s); wherein D is the maximum displacement allowed, D is the maximum displacement of the vehicle body structure, and s is the weight reduction ratio of the vehicle body;
the optimization target is set to be the maximum weighted rigidity of the vehicle body under all working conditions;
the bearing panel is a multi-layer structure panel.
2. The design method of the carbon fiber composite vehicle body structure according to claim 1, wherein M is 1.1-1.2; k is 50-60; the weight reduction ratio of the vehicle body is set to be 20-40%; n is 1.32.
3. The design method of the carbon fiber composite vehicle body structure according to claim 1, wherein the working conditions include a main working condition, a secondary working condition and a normal operation working condition, and the weighting coefficients of the working conditions are respectively set as: the main operating condition coefficient is 1, the secondary operating condition coefficient is 0.63, and the normal operating condition coefficient is 0.45.
4. The carbon fiber composite vehicle body structure design method according to claim 1, characterized by further comprising:
s3, creating a vehicle body strength model, a vehicle body noise model and a vehicle body fire-proof simulation model; connecting a vehicle body strength model, a vehicle body noise model and a vehicle body fire-proof simulation model into a simulation calculation platform based on Isight software, selecting relevant parameters of strength, noise and fire-proof indexes, taking the thickness range of a beam rib plate of a bearing framework of an optimal vehicle body structure configuration and the thickness range of each layer of a bearing multilayer panel as input design variables of the simulation calculation platform, taking limiting conditions of the rigidity, the strength, the fatigue, the mode, the noise sound pressure level, the heat release rate and the smoke spreading rate of the whole vehicle as constraints, and taking weighted index values of the vehicle body weight, the sound insulation and the fire prevention as design targets, and establishing a strength, noise and fire-proof combined simulation model;
s4, taking the parameter combination in the joint simulation model as an input parameter of an optimal hyper-Latin method to obtain a characteristic sample space, carrying out sensitivity analysis on the characteristic sample space, reducing the variable dimension of the characteristic sample space, and obtaining the optimal sample space; establishing an optimized proxy model based on the optimal sample space;
s5, calling a particle swarm algorithm, optimizing in the input and output combination of the optimization proxy model, and determining an optimal combination scheme;
preferably, the creating process of the vehicle body strength model in step S3 includes: the thickness and material properties of the carbon fiber layer, the thickness and material properties of the foam layer, the damping layer and the rubber layer are input parameters of Optistruct software, and the static strength, the fatigue strength, the rigidity and the mode of the vehicle body structure are output parameters to obtain a vehicle body strength model;
preferably, the sound insulation quantity of the material, the sound absorption coefficient of the material, the sound source frequency spectrum and the sound source position are input parameters of VA-one software, and the sound pressure levels of noise inside and outside the vehicle are output parameters to obtain the noise model of the vehicle body; preferably, the thermophysical parameters and the fire spreading parameters of the material are input parameters of FDS software, and the heat release rate, the temperature field distribution and the smoke spreading characteristics of the vehicle body are output parameters to obtain a vehicle body fire-proof simulation model;
preferably, in step S3, the association parameters include: the thickness of each layer of the multilayer force bearing panel and the thickness of the rib plate with an included angle of less than 60 degrees with the corresponding layer of the force bearing framework are both equal;
preferably, in step S3, the obtaining of the weighted index values of the vehicle body weight, the sound insulation, and the fire resistance includes: normalizing the vehicle body weight, the sound insulation index and the fire prevention index, and weighting the normalized values to obtain weighted index values; the weighting coefficients are: the fire-proof coefficient is 0.4-0.6, the weight coefficient is 0.2-0.4, and the noise coefficient is 0.1-0.3.
5. A carbon fiber composite material car body structure comprises a plurality of bearing panels and a plurality of bearing frameworks for supporting the bearing panels; the bearing panel is characterized by comprising a damping layer; two sides of the damping layer are respectively attached to a foam layer, and one side of the foam layer, which is far away from the damping layer, is attached to the carbon fiber layer; wherein the thicknesses of the damping layer, the foam layer and the carbon fiber layer and the thickness of the beam rib plate of the bearing framework are determined according to the method of one of claims 1 to 4.
6. The carbon fiber composite vehicle body structure according to claim 5, wherein the foam layer is made of a foam material having a shear modulus of not higher than 60 MPa; the damping layer is made of styrene thermoplastic material.
7. The carbon fiber composite vehicle body structure according to claim 5, wherein the plurality of multilayer force-bearing panels comprise a cab arc panel (10), a vehicle body middle U-shaped top side panel (11), an end wall panel (12) and an underframe panel (13); the end part of the arc-shaped panel (10) of the cab is fixedly connected with one end part of a U-shaped top side panel (11) in the middle of the vehicle body; the other end of the U-shaped top side panel (11) in the middle of the vehicle body is fixedly connected with an end wall panel (12); the bottom of the arc-shaped panel (10) of the cab, the bottom of the U-shaped top side panel (11) in the middle of the vehicle body and the bottom of the end wall panel (12) are fixedly connected with the chassis panel (13).
8. The carbon fiber composite vehicle body structure of claim 7, wherein the inner surfaces of the cab arc panel (10), the middle U-shaped top side panel (11), the end wall panel (12) and the inner and outer surfaces of the underframe panel (13) are sprayed with water-based fireproof damping coatings.
9. The vehicle body structure of carbon fiber composite material as claimed in claim 7, wherein the beam ribs of the load-bearing framework comprise cab end beam ribs (1) arranged at the bottom of the arc-shaped panel (10) of the cab, cab arc-shaped branched support ribs (2) symmetrically arranged at the left and right sides of the top of the arc-shaped panel (10) of the cab, a plurality of sealed U-shaped support ribs (3) surrounding the middle U-shaped top side panel (11) and the bottom frame panel (13) of the vehicle body, top cover side beam ribs (4) longitudinally extending along the vehicle body and arranged at the top of the middle U-shaped top side panel, bottom frame side beam ribs (5) connecting all panels at the bottom of the vehicle body, end wall transverse ribs (6) arranged at the upper and lower ends of the end wall panel (12), end wall vertical ribs (7) arranged at the left and right sides of the end wall panel (12), side wall transverse ribs (8) arranged on the middle U-shaped top side panel and connecting two adjacent U-shaped support ribs, and a plurality of vertical transverse ribs (8) arranged on the middle U-shaped top side panel The side wall vertical rib (9).
10. A carbon fiber composite vehicle body structure, characterized in that design parameters of the vehicle body structure are determined by the method of any one of claims 1 to 4.
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| CN115238387A (en) * | 2022-07-27 | 2022-10-25 | 中车成型科技(青岛)有限公司 | Topological lightweight method and system for mixed material of rail transit vehicle |
| CN115659711A (en) * | 2022-12-29 | 2023-01-31 | 北京云道智造科技有限公司 | Simulation method and device, electronic equipment and storage medium |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115238387A (en) * | 2022-07-27 | 2022-10-25 | 中车成型科技(青岛)有限公司 | Topological lightweight method and system for mixed material of rail transit vehicle |
| CN115659711A (en) * | 2022-12-29 | 2023-01-31 | 北京云道智造科技有限公司 | Simulation method and device, electronic equipment and storage medium |
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