CN111859756B

CN111859756B - Three-dimensional modeling-based alternate vehicle frame simulation method and simulation system

Info

Publication number: CN111859756B
Application number: CN202010701700.9A
Authority: CN
Inventors: 石振; 付文福; 郭建伟
Original assignee: Hubei University of Automotive Technology
Current assignee: Hubei University of Automotive Technology
Priority date: 2020-07-20
Filing date: 2020-07-20
Publication date: 2023-12-01
Anticipated expiration: 2040-07-20
Also published as: CN111859756A

Abstract

The invention belongs to the technical field of a substituted frame, and discloses a substituted frame simulation method and a simulation system based on three-dimensional modeling, wherein three-dimensional modeling software is utilized to perform modeling suitable for a substituted frame, a carbon fiber composite laminate elastic constant test experiment is performed, ANSYS is utilized to analyze a layering angle and a layering thickness design, and analysis under various working conditions is performed to obtain a specific process flow of a carbon fiber composite material suitable for a substituted frame; the simulation analysis of torsional rigidity and bending rigidity, the simulation analysis of static load, braking and sharp turning working conditions and the analysis of modal analysis are carried out on the substituted frame, and finally the technological process of the substituted frame is explained. The replacement frame is a sandwich structure shell taking a high-rigidity light-weight carbon fiber/epoxy resin composite material as a panel and a low-density low-strength aluminum honeycomb as a core material, and has the advantages of high torsional rigidity, light weight, accurate and convenient assembly and positioning, free and attractive appearance and the like.

Description

Three-dimensional modeling-based alternate vehicle frame simulation method and simulation system

Technical Field

The invention belongs to the technical field of alternative frames, and particularly relates to an alternative frame simulation method and system based on three-dimensional modeling.

Background

Currently, alternative frame and composite technologies originated at the earliest on board ships and aircraft, such as boeing B787, using a large number of composites on the aircraft fuselage and wings, beginning in 1969 on automobiles. The development and use of new materials are imperative.

The first appearance of an F1 event is that a suitable alternative frame is adopted, and widely known is that a light metal shell frame is adopted in a LOTUS25 for participating in the F1 event in 1962, meanwhile, the current attempt is successful greatly, the racing car has less weight, good visual field, larger torsional rigidity and wider cockpit space, ten stations are adopted in the whole racing season in 1962, and the winning of seven stations is achieved.

To date, the use of single shells has reached over fifty percent in the racing of foreign university student's equation, particularly in the field of electric racing.

In recent years, with the increase of attention of each college student equation class, various new technologies are more developed on college student equation car, but the weight reduction is always a trend of car development, and is also one of the important points of attention of college student equation class. Under the guidance of light weight, composite materials are also found in college student equation runs as racing car carrying body materials. In the domestic aspect, due to the high cost of the alternative frame, the fleet adopting the alternative frame is not more, but is one of the important directions of the light weight development of the automobile, and the improvement of the fleet and the players is necessary for improving the strength of the fleet.

Through the above analysis, the problems and defects existing in the prior art are as follows:

the cost is high. The materials used for replacing the vehicle frame in the prior art are high in price, and the manufacturing process equipment is high in use cost

The manufacturing process is complex. Many universities and cities thereof are not provided with equipment for manufacturing alternative frame manufacturing processes, the related process steps are more, and the process technology requirements are strict.

The manufacturing period is long. Compared with a steel pipe truss frame, the manufacturing time of the replacement frame is longer, and more manpower is needed.

The fault tolerance is low. The replacement frame is often manufactured in error or after the frame runs unexpectedly, the maintenance difficulty is high, the cost is high, and more time damage is irreversible.

The difficulty of solving the problems and the defects is as follows:

and the cost aspect. Domestic fleet finance almost always comes from school financial money, and no autonomous profit is available, so for intense expenses, high cost replacement frames have made many fleet prohibitive.

Technical aspects. Compared with the steel pipe truss frame, the steel pipe truss frame has higher technical and technological requirements for replacing the frame, and many domestic motorcades do not have the technical accumulation.

The enthusiasm of students. Many students know the advantages of the alternative frame due to the restriction of reality, but only have a little delight, because the restriction of reality indicates that the possibility of implementing the alternative frame is not great, and the study on the aspect is lost in the past.

School support force. Since many universities in China still use the competition results as one of the reference indexes of the expenses, many motorcades with insignificant results have more intense expenses. Instead, a plurality of motorcades with good results use the alternative frames earlier, and the event results are further, causal circulation and bipolar differentiation.

The meaning of solving the problems and the defects is as follows:

the aspect of students: the knowledge surface of students is widened, the practical capability of the students is improved, a popular aspect is indicated for knowledge expansion, and talents are cultivated for the national automobile industry.

School aspect: the competitive power of the school motorcade is enhanced, the popularity of the school industry and the overall strength of the school are improved, the school motorcade is horizontally close to the international famous college and university, and the promotion of communication is promoted.

Aspect of the event: the overall level of the event is improved, the good development of the event is promoted, and the popularity of the event and the enthusiasm of the students to participate are improved.

Disclosure of Invention

Aiming at the problems existing in the prior art, the invention provides a three-dimensional modeling-based alternate vehicle frame simulation method and a three-dimensional modeling-based alternate vehicle frame simulation system.

The invention is realized by the following steps:

1) Performing design modeling applicable to the substitute frame by utilizing three-dimensional modeling software;

2) Performing design analysis on the layering angle and layering thickness of the model by using ANSYS software;

3) Performing an elasticity constant test experiment of the carbon fiber composite laminate to verify and analyze the result;

4) Carrying out theoretical analysis on the substituted frame under various limit working conditions by utilizing ANSYS software;

5) And analyzing and listing a specific process flow of the carbon fiber composite material suitable for replacing the vehicle frame.

The carbon fiber composite laminate is a composite material plate made of carbon fiber composite materials serving as a panel and honeycomb aluminum serving as a sandwich material in the middle.

Further, when the carbon fiber composite laminate elastic constant test experiment is carried out, the following steps are adopted:

s1, turning on a power supply of a mechanical experiment machine and a strain gauge, checking the temperature of an experiment environment, and selecting a corresponding matched wedge-shaped clamp as an experiment clamp;

s2, holding the middle part of the sample by two hands, placing the upper end of the sample into the middle part of a clamp, keeping the centering verticality of the sample by the two hands, slightly clamping the sample by using a right-hand operation mechanical testing machine, enabling the sample not to move at will, adjusting the vertical centering of the sample by using a triangular plate, and then clamping the sample;

s3, resetting a force display value of the mechanical testing machine, adjusting the position of a beam of the mechanical testing machine, sequentially connecting a strain gauge wire with a strain gauge wire, placing the strain gauge wire at a safe position after connection is completed, and ensuring insulation when external interference cannot be received in the testing process;

S4, opening testing machine control software on a computer matched with the mechanical testing machine, setting parameters according to the specific testing machine, then starting loading, recording and collecting data, and obtaining force-displacement and strain-time graphs of different angles;

s5, processing the collected data to obtain transverse, longitudinal and normal tensile modulus E ₁ 、E ₂ 、E ₃ Poisson's ratio mu ₁₂ 、μ ₁₃ 、μ ₂₃ Shear modulus G ₁₂ 、G ₁₃ 、G ₂₃ ，E ₂ ＝E ₃ ，G ₁₂ ＝G ₁₃ ，μ ₁₂ ＝μ ₁₃ ，μ ₂₃ And G ₂₃ Not independent.

Further, E ₁ Sum mu ₁₂ The calculation formula is shown as follows

Wherein: b is the width of the test piece; t is the thickness; p (P) ₁ Is a 1-direction load; epsilon ₁ ，ε ₂ Strain in 1,2 direction respectively;

calculation G ₁₂ The formula of (2) is as follows:

E ₂ the tensile modulus of the epoxy resin is obtained by referring to the characteristic table of the cured epoxy resin for 90 degrees of elastic constant of the test piece, and is used as E of the 90 degrees of test piece ₂ ；

Calculation E ₄₅ The formula of (2) is as follows:

shear modulus G ₂₃ This can be calculated by the following formula

Wherein f _G Can be obtained by a quadratic equation

A＝3c ₁ c ₂ (1-V _f ) ² V _f +(c ₂ η ₀ -c ₃ V _f ³ )(c ₁ η ₀ V _f -c ₄ )

μ ₀ Poisson's ratio of the matrix;

μ ₁ poisson's ratio of the fibres;

V _f -the volume fraction of the fibres;

G ₀ -shear modulus of the matrix;

G ₁ -shear modulus of the fiber;

poisson's ratio mu ₂₃ The method is obtained by the following formula:

further, the specific method for analyzing the layering angle by utilizing ANSYS comprises the following steps:

s11, defining marks of a laying direction and a laying sequence of the single layers of the laminated plates, also defining the marks of the laminated plates made of the composite material, and selecting a main axis direction of the structure as a reference coordinate system;

S12, building a laminated plate with the thickness of 0.5mm for each layer of 150X50X2mm in ANSYSYS, fixing four sides of the laminated plate, and loading 1000N uniform load on the surface;

s13, constructing bending stiffness simulation displacement cloud charts of laminated plates with different layering angles.

Further, when analyzing the ply thickness by ANSYS, the stiffness simulation of the ply thickness is performed by using 0 °/90 ° woven cloth, specifically including:

s21, establishing a 500 x 275 rectangular model, wherein a composite material panel adopts a T_700 unidirectional tape, layering is arranged, each layer of 0.4mm, 2 layers of T_700 single layers are 90 degrees, a sandwich layer adopts 15mm honeycomb aluminum, and layering angles are 90 degrees;

s22, layering through a workbench_ACP module, wherein the layering angles are the same, the layering layers are changed, and the bending rigidity is calculated

S23, restraining the two sides of 275mm according to the restraint mode of the simple beam by setting the boundary condition to 7000N.

Further, when analysis is performed under various working conditions, analysis is performed on static load working conditions, steering working conditions, braking working conditions, bending stiffness, torsional stiffness and six-order modes;

when torsional rigidity test is carried out, all degrees of freedom of a front suspension hard point are restrained firstly, opposite forced displacement is applied to two sides of a rear suspension hard point respectively in the vertical direction by 1mm, and degrees of freedom in the X direction and the Y direction are defined as Free, so that first torsional rigidity is obtained; then restraining all degrees of freedom of the rear suspension hard point, respectively giving opposite forced displacement for 1mm in the vertical direction on two sides of the front suspension hard point, and defining the degrees of freedom in the X and Y directions as Free to obtain second torsional rigidity;

Frame torsion angle θ:

θ＝arctan(2/L)

if the average distance between the suspension hard points of the frame is L and the deformation torsion angle which is forcedly generated is theta, the torsional rigidity of the frame is:

G＝FL/θ

θ—the torsion angle of the frame, °;

l is the average distance between hard points of the suspension, m;

f, supporting reaction force at a hard point of a vehicle suspension, N;

g, torsional rigidity of the frame, N.m/°;

when the bending stiffness working condition is simulated, all the displacement degrees of freedom of the hard points of the front suspension are restrained, the displacement degrees of freedom of the rear suspension in the X direction are released, and a concentrated force is applied vertically downwards to the cabin plate, so that the frame is bent.

Further, the concrete process flow of the carbon fiber composite material applicable to replacing the frame comprises a process method combining hand lay forming and an autoclave and a cutting and folding method;

the process method for combining hand lay forming and autoclave specifically comprises the following steps:

(1) The surface of the mould is treated, and after the treatment, a release agent is brushed on the mould;

(2) Cutting the prepreg according to the designed layering structure, and layering according to the required thickness and layering angle;

(3) After the layering is finished, adding auxiliary materials, packaging by using a vacuum bag, and adhering the auxiliary materials on the vacuum bag by using a sealing adhesive tape while adhering the auxiliary materials on the sealing bag, wherein the sealing adhesive tape covers all the auxiliary materials;

(4) After the vacuum bag is packaged, a vacuum nozzle is arranged, and then vacuum pumping is carried out;

(5) And (3) vacuumizing, checking tightness, heating and pressurizing for solidification, and finally demolding to obtain the alternative frame.

The cutting and folding method specifically comprises the following steps:

1) Firstly, preparing a composite sandwich structure panel with a whole honeycomb aluminum layer as a sandwich layer and carbon fibers as a panel;

2) Cutting off the carbon fiber composite material plate of the part to be folded and other redundant parts by using a numerical control machine tool;

3) Folding the composite material plate into the shape of the designed alternative frame by manufacturing a bracket, fixing the joint and the folding position by using an adhesive, and reinforcing the joint and the folding position by using an aluminum plate or a carbon fiber plate after the adhesive is solidified;

4) In the aspect of the accuracy of the hard points of the suspension, a mode of combining positioning, cutting and folding is adopted, the suspension is positioned by manufacturing a clamp, a space is reserved between a suspension connecting point and a positioning point of the alternative frame, and the error generated by the alternative frame in the folding process is adjusted by adjusting the space.

Further, in the step 2 of the cutting and folding method,

The width of the composite material removed where folding is desired is calculated as follows:

a is the width of the composite panel to be removed;

d is the thickness of the composite panel;

θ is the folding angle.

Another object of the present invention is to provide an alternate frame simulation system based on three-dimensional modeling, comprising:

the vehicle frame replacing modeling unit is used for modeling the vehicle frame replacing by utilizing three-dimensional modeling software;

the carbon fiber composite laminate elastic constant testing unit is used for performing an experiment of testing the carbon fiber composite laminate elastic constant;

the pavement angle and pavement thickness analysis unit is used for determining the pavement angle and pavement thickness by ANSYS analysis;

and (3) replacing the optimal parameter unit of the frame, and then analyzing under various working conditions to obtain the optimal parameter of the carbon fiber composite material suitable for replacing the frame.

It is a further object of the present invention to provide a computer device comprising a memory and a processor, the memory storing a computer program which, when executed by the processor, causes the processor to perform the steps of:

modeling the applicable alternative frame by using three-dimensional modeling software; performing an elasticity constant test experiment of the carbon fiber composite laminate; determining a ply angle and a ply thickness using ANSYS analysis;

And then analyzing under various working conditions to obtain the optimal parameters of the carbon fiber composite material suitable for replacing the frame. .

It is another object of the present invention to provide a computer readable storage medium storing a computer program which, when executed by a processor, causes the processor to perform the steps of:

By combining all the technical schemes, the invention has the advantages and positive effects that:

the replacement frame is a sandwich structure shell taking a high-rigidity light-weight carbon fiber/epoxy resin composite material as a panel and a low-density low-strength aluminum honeycomb as a core material, and has the advantages of high torsional rigidity, light weight, accurate and convenient assembly and positioning, free and attractive appearance and the like; firstly, a structure of a substituted frame is designed based on a chassis of a certain three-cylinder engine, in addition, the assembly mode of the substituted frame and each part is considered, then 9 elastic constants of a composite material single-layer plate are obtained through experiments, the rule of a layering angle and the bending resistance of three-point bending are summarized through analysis of a workbench ACP module, simulation analysis of torsional rigidity and bending rigidity, simulation analysis of static load, braking and sharp turning working conditions and analysis of modal analysis are carried out on the substituted frame, and finally, the technological process of the substituted frame is explained.

Compared technical effect or experimental effect (data are derived from actual data of a certain vehicle team in China):

mass of each part of the replacement frame system

Mass of each part of steel pipe truss system

Rigidity-weight ratio of substituted frame system to steel pipe truss system

The mass is reduced by 6.94kg, and the rigidity-weight ratio is improved by 6.16%.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic diagram of an alternative frame model according to an embodiment of the present application.

Fig. 2 is a front view of an alternative frame provided by an embodiment of the present application.

Fig. 3 is a left side view of an alternative vehicle frame provided by an embodiment of the present application.

Fig. 4 is a top view of an alternative frame provided by an embodiment of the present application.

Fig. 5 is a schematic structural diagram of a diagonal carbon fiber cloth and a unidirectional carbon fiber cloth according to an embodiment of the present application.

Fig. 6 is a schematic view of a honeycomb aluminum structure according to an embodiment of the present application.

Fig. 7 is a schematic diagram of a material coordinate system according to an embodiment of the present invention.

FIG. 8 is a graph of 0℃sample force versus displacement provided by an embodiment of the present invention.

Fig. 9 is a graph of 0 ° sample strain versus time provided by an embodiment of the present invention.

Fig. 10 is a graph of 45 ° sample force versus displacement provided by an embodiment of the present invention.

Fig. 11 is a graph of strain versus time for a 45 ° sample provided by an embodiment of the present invention.

Fig. 12 is a schematic diagram of a model coordinate system according to an embodiment of the present invention.

FIG. 13 is a schematic view of a laminate model provided in an embodiment of the present invention.

Fig. 14 is a schematic diagram of boundary conditions provided by an embodiment of the present invention.

FIG. 15 is a schematic view of the various ply and material coordinate systems of a first angular combination provided by an embodiment of the present invention.

Fig. 16 is a maximum deflection displacement cloud for a first angular combination provided by an embodiment of the present invention.

FIG. 17 is a schematic view of the ply and material coordinate system of a second angular combination provided by an embodiment of the present invention.

Fig. 18 is a maximum deflection displacement cloud for a second angular combination provided by an embodiment of the present invention.

FIG. 19 is a schematic view of the ply and material coordinate system of a third angular combination provided by an embodiment of the present invention.

Fig. 20 is a maximum deflection displacement cloud for a third angular combination provided by an embodiment of the present invention.

FIG. 21 is a schematic view of the fourth angular combination of ply and material coordinate systems provided by embodiments of the present invention.

Fig. 22 is a maximum deflection displacement cloud for a fourth angular combination provided by an embodiment of the present invention.

FIG. 23 is a schematic view of the ply and material coordinate system of a fifth angular combination provided by an embodiment of the present invention.

Fig. 24 is a maximum deflection displacement cloud for a fifth angular combination provided by an embodiment of the present invention.

Fig. 25 is a schematic diagram of boundary conditions of a steel pipe according to an embodiment of the present invention.

Fig. 26 is a schematic diagram of boundary conditions of a steel pipe according to an embodiment of the present invention.

Fig. 27 is a schematic diagram of a simply supported beam according to an embodiment of the present invention.

Fig. 28 is a schematic view of a layering direction of 1 layer of carbon fibers according to an embodiment of the present invention.

Fig. 29 is a graph showing the total displacement cloud of 1-layer carbon fiber laminates provided by an embodiment of the present invention.

Fig. 30 is a schematic view of a layering direction of 4 layers of carbon fibers according to an embodiment of the present invention.

Fig. 31 is a cloud image of total displacement of 4 carbon fiber laminates provided by an embodiment of the present invention.

Fig. 32 is a schematic view of a 3-layer carbon fiber lay-up direction according to an embodiment of the present invention.

Fig. 33 is a cloud image of total displacement of 3 carbon fiber laminates provided by an embodiment of the present invention.

Fig. 34 is a schematic diagram of meshing with a shell unit according to an embodiment of the present invention.

FIG. 35 is a schematic diagram of a torsional mode boundary condition provided by an embodiment of the present invention.

Fig. 36 is a schematic view of the stress of the front right suspension according to the embodiment of the present invention.

Fig. 37 is a schematic view of a front left suspension according to an embodiment of the present invention.

Fig. 38 is a graph showing specific values of rear suspension stress provided by an embodiment of the present invention.

FIG. 39 is a schematic diagram of a boundary condition of a bending operation provided by an embodiment of the present invention.

FIG. 40 is a graph showing the maximum deflection displacement for a bending mode according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the following examples in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.

Aiming at the problems existing in the prior art, the invention provides a three-dimensional modeling-based alternate vehicle frame simulation method and a three-dimensional modeling-based alternate vehicle frame simulation system, and the invention is described in detail below with reference to the accompanying drawings.

The three-dimensional modeling-based alternate vehicle frame simulation method provided by the embodiment of the invention utilizes three-dimensional modeling software to perform modeling applicable to an alternate vehicle frame, performs a carbon fiber composite laminate elastic constant test experiment, analyzes a layering angle and a layering thickness design by utilizing ANSYS, and performs analysis under various working conditions to obtain a technological process of the carbon fiber composite material applicable to the alternate vehicle frame.

The invention is further described in connection with specific analysis.

First, design suitable for replacing frame

1.1 comparison of the advantages and disadvantages of the applicable substitution frame and the steel pipe truss frame

1.1.1 frame Mass

Generally, the excellent alternative frame comprises a front ring, a main ring and an embedded part, which can achieve about 18 KG, however, the excellent steel pipe truss frame comprises 26KG of all brackets (for example, the Dongfeng HUAT car team 2018 racing car oil car frame, excluding various lugs), and the weight difference of the two is larger.

1.1.2 torsional stiffness

The alternative frame is also called a single shell in the college student equation competition, and can be essentially regarded as a semi-closed box body; the steel pipe truss frame is a space truss structure, and steel pipes on the frame can be regarded as lines. The torsional rigidity of the frame in the equation competition of universities is more than 1000N.M/°, the torsional rigidity of the racing car which replaces the frame basically has about 4000N.M/°, and the steel pipe truss type frame (taking the Dongfeng HUAT motorcade 2018 racing season oil car frame as an example) is 2263N.M/°.

1.1.3 Security

For the competition of the formula car for universities, the safety is the first, many rules of the competition are for the safety, the replacement car frame is contacted in a face mode when collision occurs, and the energy absorbing capacity of the sandwich material in the panel is better, so that the replacement car frame can absorb the impact force better, and the personal safety of a driver can be better protected.

1.1.4 cost

Firstly, the raw material carbon fiber of the replacing frame is expensive in terms of materials, the auxiliary materials needed are too much, the die is needed, the needed equipment is different due to different process selections, and many universities are not provided with equipment for producing the replacing frame, so that the domestic cities do not have the environment for processing the replacing frame at all. In the aspect of consuming manpower, the time period required for replacing the frame is longer, and more manpower is required. In terms of funds, if a motorcade does not have sponsors, the amount of money for making the replacement frame is at least more than 12 ten thousand yuan, which is far from the steel pipe truss frame, the cost of the replacement frame is much higher than that of the steel pipe truss frame, and under the condition that the cost of the domestic motorcade is relatively high, the domestic 90% college student equation racing motorcade selects the steel pipe truss frame.

1.1.5 design and machining requirements

From the design point of view, the steel pipe truss frame is made of 4130 steel pipes, and various performances of the steel pipe truss frame are stable. However, the material of the alternative frame is carbon fiber, and the characteristics of the alternative frame are essentially different from those of the metal material. 4130 steel pipe isotropic material, however carbon fiber is an anisotropic material. Isotropy is the same for any one direction as in poisson's ratio, strength, stiffness, etc. The anisotropy is different directions, the performance of the material is different, the carbon fiber is orthotropic, and the performance of the material is good in the fiber direction and poor in other directions. Based on this characteristic, the design of the replacement frame is therefore complex, and the design of the material ply is to be studied, which also requires a great deal of engineering experience to accumulate. For processing, a mold is needed for replacing the frame, the mold requirement is high, the layering requirement is high, and the reversibility is not realized; the steel pipe truss frame basically depends on a clamp, a hand-ground steel pipe and welding, and has certain reversibility. In the event of an accident, the replacement frame is basically impossible to repair, however, the steel pipe truss frame can be repaired within a certain range.

1.2 design of applicable substitute frame

First, the front cabin and the cabin part are designed according to the rules of the equation of university students in 2019, the man-machine model of the Dongfeng HUAT motorcade 2019 racing season and hard point parameters of a suspension steering system. The design of the front cabin and the cabin part fully considers the design simplicity of the die suitable for replacing the frame and the convenience of layering, and the design is exquisite in appearance. The front cabin detection plate is fully considered to pass through the front cabin, the cabin detection plate is fully considered to pass through the cabin part, space is fully utilized on the basis of passing through, and space waste is reduced.

The design of the rear cabin fully considers the selection of the three-cylinder engine, and according to the engine positioning parameters provided by the total arrangement of the whole vehicle, the ground clearance of the small chain wheel is 225mm, and the center distance of the large chain wheel and the small chain wheel is 183mm. And secondly, the advantage of small volume of the three-cylinder engine is utilized, the rear cabin is contracted, the rear cabin is smaller, the left and right minimum distance of the rear cabin is 496.4mm on the basis of the four-cylinder engine in the last year, the left and right minimum distance of the rear cabin is 468mm in the next year, and the rear cabin is shortened by 28.4mm. Finally, since the six fixing points of the engine are different, the position of the fixing point on the engine is greatly changed in the frame design than the last year, and the height of the fixing point is higher.

Secondly, spring constant test and ply design

2.1 composite introduction

In terms of definition, composite materials are new materials composed of two or more materials with different properties by chemical or physical methods, and advanced resin composite materials are used herein, which are prepared by using epoxy resin as a matrix and high-performance continuous carbon fibers as reinforcing materials through a composite process, wherein the reinforcing properties of the composite materials are strength, rigidity, corrosion resistance, abrasion resistance and the like.

The embodiment of the invention uses a carbon fiber panel-aluminum honeycomb sandwich structure, and the structural design is reasonable, so that higher strength and rigidity can be obtained. One of the raw materials of the carbon fiber panel is carbon fiber cloth, the carbon fiber cloth can be divided into straight lines, twill lines and the like according to lines, and the straight lines carbon fiber cloth and the twill lines carbon fiber cloth are formed by weaving transverse and longitudinal fiber filaments according to a certain weaving mode; the carbon fiber cloth composed of unidirectional or longitudinal carbon fiber filaments is called unidirectional cloth, and as shown in fig. 5A and 5B, the carbon fiber cloth becomes a carbon fiber plate after the matrix is cured. The honeycomb aluminum sandwich layer is composed of honeycomb aluminum, and is a sandwich material with better performance and wider application, as shown in fig. 6.

2.2 spring constant test experiments of carbon fiber composite plates

2.2.1 Experimental background

The embodiment of the invention is based on the design and process research of a certain three-cylinder engine applicable to a substituted frame, a front cabin and a cabin applicable to the substituted frame are made of carbon fiber composite materials as panels, honeycomb aluminum is used as a sandwich material in the middle of the composite materials, and a rear cabin is built of 4130 steel pipes. Before analysis can be performed, a material coordinate system needs to be established, as shown in FIG. 7. The analysis by using the simulation analysis software is to perform an elasticity constant test experiment on the composite material plates of the front cabin and the cabin, so as to obtain a transverse, longitudinal and normal stretching dieQuantity E ₁ 、E ₂ 、E ₃ Poisson's ratio v ₁₂ 、ν ₁₃ 、ν ₂₃ Shear modulus G ₁₂ 、G ₁₃ 、G ₂₃ 。E ₂ ＝E ₃ ；G ₁₂ ＝G ₁₃ ；μ ₁₂ ＝μ ₁₃ ；μ ₂₃ And G ₂₃ Not independent.

2.2.2 testing the elastic constants and Poisson's ratio of the principal axes and longitudinal directions of the materials by tensile test

2.2.2.1 Experimental protocols

A sheet bar composite material plate with a rectangular shape is arranged in a chuck of a mechanical testing machine, a monotone tensile force is applied, and a strain or displacement sensor is used for monitoring the experimental strain to determine the stress-strain of the material layer plate. The standard for the performance of this experiment was GB/T32376-2015.

(1) Vernier callipers

According to the requirement of the experimental standard, the precision of the experimental instrument needs to be within one percent of the minimum reading in the measuring direction of the sample, and the minimum precision of the experimental instrument is +/-0.25 um.

(2) Strain gauge

According to the experimental standard requirement, the strain gauge can meet the requirement by adopting a resistance strain gauge with the effective length of 6 mm. The minimum effective length of the strain gauge cannot be less than 3 mm, and the resistance value is preferably above 350 ohms.

(3) Mechanical experiment machine

According to the rules of the test standard, the mechanical testing machine selected for the test requires a fixed beam and a movable beam, the movable beam can move relative to the fixed beam at a fixed relative speed, and the measured value error of the mechanical testing machine cannot exceed 1%. The test fixture is preferably selected to be a standard wedge-shaped slide that moves up and down within the fixture housing of the mechanical testing machine and provides sufficient lateral pressure to prevent relative sliding between the clamping surface and the test specimen, resulting in more accurate test data.

2.2.2.2 preparation before test

1. Geometry of the sample

Firstly, when a sample is processed, the dimension design mainly comprises three important sample dimensions of length, width and thickness, the selection of the length mainly meets three basic requirements, so that the effect of bending stress brought by the eccentric clamping on a gauge length section can be slowed down, the gauge length section and the clamping position have enough distances, and the rest is that most of the sample can be stressed. The main assurance for width and thickness is that the test breaks in the gauge length and that the cross section contains a sufficient number of fibers to statistically represent the vast majority of the composite, the specific dimensions are shown in table 1.

Table 1 Standard recommended tensile sample size

2. Control of test ambient temperature

The temperature and humidity of the test environment have a great influence on the mechanical test performance of the composite material, so that the temperature and humidity of the environment where the test sample is located must be required when the test is carried out, and the relative humidity cannot exceed fifty percent for the room temperature environment temperature given by the standard between 20 and 28 ℃.

3. Measurement of test dimensions

The actual width and thickness of each sample needs to be measured before the test is performed in order to derive the cross-sectional area of each sample. For the measurement of the width and the thickness, the number of the selected measurement points on the sample is not less than three, and the reading and the recording are carried out after the numerical value is stable during the reading.

2.2.2.3 Experimental procedure

After the preparation work is completed, the power supply of the mechanical experiment machine and the strain gauge is turned on, and the experimental environment temperature is checked again.

1. And the test fixture is selected from the corresponding matched wedge fixtures.

2. The middle part of the sample is held by two hands, the upper end of the sample is placed in the middle part of the clamp, the two hands keep the centering verticality of the sample, and the mechanical testing machine is operated by the right hand to slightly clamp the sample, so that the sample cannot move at will. And then adjusting the vertical centering of the sample by using a triangle, and then clamping the sample.

3. And (3) resetting the force display value of the mechanical testing machine and adjusting the position of the cross beam of the mechanical testing machine. The strain gauge wires and the strain gauge wires are connected in sequence, and placed at a safe position after connection is completed, so that external interference cannot be received in the test process, and insulation is ensured.

4. And opening tester control software on a computer matched with the mechanical tester, setting parameters according to the specific tester, and then starting loading, recording and collecting data.

2.2.2.4 data processing

1. Force-displacement and strain-time curves for the 0 deg. test piece are shown in fig. 8 and 9.

E ₁ Sum mu ₁₂ The calculation formula is shown as follows

Wherein: b is the width of the test piece; t is the thickness; p (P) ₁ Bit 1 directional loading; epsilon ₁ ，ε ₂ Strain in the 1,2 direction, respectively.

The data points at 1/3 of the elastic deformation stage in the force-displacement curve and strain-time curve in FIGS. 8 and 9 are read in an Excel table to obtain P ₁ And epsilon ₁ Is a value of (2).

Test piece size: b=25 mm; t=0.4 mm

P ₁ ＝1.53KN；ε ₁ =1274 μ; carrying out formula to find E ₁ ＝106532MPa；

ε ₂ -215 μ; carrying in (2) to obtain V ₁₂ ＝0.165

2. Spring constant of 90 degree test piece

When loading in the direction perpendicular to the unidirectional composite laminate, the pencil worker considers that the composite laminate is mainly dependent on the cured epoxy resin to maintain the performance of the laminate, and regards the cured epoxy resin as the tensile force, so that the tensile modulus of the epoxy resin can be directly obtained by consulting the characteristic table of the cured epoxy resin, and the tensile modulus is used as E of a 90-degree test piece ₂ 。

TABLE 2 epoxy resin curing Property Table

The tensile modulus of the cured epoxy resin is 2900-3000 MPa as shown in table lookup. Taking E ₂ ＝3000Mpa。

2.2.3 determination of in-plane shear Properties of composite by tensile test of + -45 degree off-axis laminates

2.2.3.1 brief description of the test method

And carrying out uniaxial tensile test on the laminate with the angle of +/-45 degrees, and utilizing a theoretical derivation expression of the laminate, wherein plane shear stress in a material coordinate system can be directly calculated by applying axial load, corresponding shear strain is derived by positive strain in the longitudinal and transverse directions of stretching, and a curve of the shear stress-shear strain in the plane is jointly built.

2.2.3.2 Experimental apparatus and Experimental procedure

The test is similar to the previous tensile test, and the test method has been described above and will not be described here.

2.2.3.3 test data processing

The force-displacement curve and strain-time curve are shown in fig. 10 and 11:

calculation G ₁₂ The formula of (2) is as follows:

wherein E is ₁ 、E ₂ 、μ ₁₂ Has been derived from previous 0 ° and 90 ° tensile tests, however, calculate E ₄₅ The formula of (2) is as follows:

then, the data points in the curves are selected in the figures 10 and 11 and are brought into the formula to calculate, thus obtaining E ₄₅ ＝2875Mpa、G ₁₂ ＝1950Mpa。

The shear modulus G23 can be calculated from the following formula

Wherein f _G Can be obtained by a quadratic equation

A＝3c ₁ c ₂ (1-V _f ) ² V _f +(c ₂ η ₀ -c ₃ V _f ³ )(c ₁ η ₀ V _f -c ₄ ) (6)

μ ₀ Poisson's ratio of the matrix;

μ ₁ poisson's ratio of the fibres;

V _f -the volume fraction of the fibres;

G ₀ -shear modulus of the matrix;

G ₁ shear modulus of the fibers ^[i] 。

From the above formula, G is obtained ₀ ＝1100MPa、G ₁ ＝87.5GPa；G ₂₃ ＝1213MPa

Poisson ratio v ₂₃ The method is obtained by the following formula:

E ₂ ＝3000MPa；G ₂₃ =1213 MPa; carry-in to obtain mu ₂₃ =0.23, all elastic constants are shown in table 3.

TABLE 3 elastic constants of composite laminates

2.3 simulation and optimization of the layering direction of composite boards

2.3.1 overview of composite Material Panel layering

The performance of the composite material plate is greatly affected by the angle of the layers, the thickness of the layers and the number of the layers, the thickness of the layers is always a given thickness value in actual engineering, and the number of the layers can be given due to the stress condition during design, so that the angle of the layers can be optimally designed according to the actual condition, and the performance of the whole composite material plate can reach the optimal state. The layering of the composite material plate has the following point principles:

(1) The composite laminate ply has symmetry as a whole and also follows the principle of equilibrium, i.e. a ply with a positive angle is present and a ply with a negative angle is present on the corresponding symmetry plane, in order to prevent stretch-bending coupling and buckling deformation during processing.

(2) The layers with different angles are uniformly distributed in the thickness of the layers as far as possible, so that continuous layers with the same angle are avoided, and the aim of preventing stress concentration and internal microcracks is achieved.

(3) Setting the angle of the layer, wherein the angle of the layer is set to be a common value as much as possible, such as 45 degrees, 0 degrees, 90 degrees and the like.

2.3.2 simulation of the bending resistance of composite laminates laid at different angles

2.3.2.1 setting of the layering Angle coordinate System

Since the laying angle of each individual layer in the composite laminate is uncertain, in order to facilitate analysis and comparison of the mechanical properties of the laminate in different laying modes, it is necessary to define the indicia of the laying direction and the laying order of the individual layers of the laminate, also the indicia of the composite laminate.

The composite laminate has an indeterminate principal direction of elasticity and the composite laminate generally selects the principal axis direction of the structure as the reference coordinate system. If the rectangular plate takes the direction vertical to two sides as a reference coordinate system, after the coordinates are selected, the composite material laminated plate is marked, and the included angle between the main shaft of the single-layer composite material in the laminated plate and the reference coordinate axis is defined, as shown in fig. 12.

Modeling and boundary conditions for 2.3.2.2 composite laminates

As shown in fig. 13 and 14, a 150X50X2mm laminate was built up in ANSYSY, each layer having a thickness of 0.5mm for a total of four layers. Then fixing four sides of the laminated plate, and loading 1000N uniform load on the surface.

2.3.3 simulation Displacement cloud image of bending stiffness of laminated plates with different layering angles

1、[0°、90°、0°、90°]

As shown in FIG. 16, the maximum deformation amount thereof was only 5.978mm.

2、[0°、90°、30°、-60°]

As shown in FIG. 18, the maximum deformation was 11.7mm.

3、[0°、90°、45°、-45°]

As shown in fig. 20, the maximum deformation amount was 15.06mm.

4、[45°、-45°、45°、-45°]

As shown in fig. 22, the maximum displacement amount was 40.004mm.

5、[30°、-60°、30°、-60°]

As shown in FIG. 24, the maximum displacement is 37.711mm

From the displacement cloud presented above, it can be seen that the displacement variation is minimal when the ply angle is a combination of 90 ° and 0 °, i.e. this is the best bending resistance of such a composite laminate when the ply is one layer coincident with the stress direction and one layer perpendicular to the stress direction.

2.4 simulation of three-point bending test of composite laminates

2.4.1 Standard Steel pipe simulation of the frame side Collision avoidance zone

According to the rules of the equation of the university of China, and the rules of the racing, 4.3, a load of 7000N is pre-applied to the opposite side anti-collision structure, and the load direction is opposite to a rider. A 500X275mm composite laminate was used in place of the side impact area, and a three-point bending performance test was performed on the composite laminate to demonstrate that the bending performance of the composite was equivalent to the baseline side impact steel tube.

Therefore, the bending rigidity of three reference side anti-collision steel pipes is firstly simulated according to the large-scale rules, and then the bending performance of the composite material layer plate is tested under the same boundary condition and is used as the design lower limit of the side anti-collision area composite layer plate.

2.4.2 simulation test of bending properties of Steel pipes in side anti-collision areas

1. According to the rule requirements, the length of the steel pipe is 500mm, the specification is 25.4X1.6, the two ends of the steel pipe are restrained, a load of 7000N is given, and the steel pipe is solved, as shown in FIG. 25:

the frame structure is symmetrical about a vertical middle plane, the frame can be simplified to be regarded as a simply supported beam, as shown in fig. 27, the supporting points are the connection points of the front suspension and the rear suspension with the frame, and the maximum deflection value of the simply supported beam in the vertical direction can be obtained by applying concentrated force, so that the bending rigidity of the steel tube in the side anti-collision area is calculated in the following manner.

Calculating a bending stiffness value according to a deflection formula of the learned middle simply supported beam,

when x is less than or equal to b:

when b is less than or equal to x is less than or equal to L:

the above formula is compiled in table 4:

table 4 parameter table

And then brings it into the editing result:

table 5 calculation results table

EI-bending stiffness, N ² ；

F, concentrating force and N;

x is the distance from the maximum deformation point to the incomplete constraint point, m;

a, a distance from a force acting point to an unconstrained point, m;

b-distance from the force application point to the full constraint, m;

l-distance bounded at both ends, m;

f-maximum deflection, m.

According to the rules of large-scale racing, the bending rigidity of the composite layer plate is equal to that of a steel pipe, so that the design critical value is EI=6132N DEG ² 。

2.4.3 simulation of bending Properties of composite laminates with different ply thicknesses

After the previous simulation of the angle of the layer, we know that the bending resistance is best when the angle of the layer is 0 degree/90 degree interweaving, so that when the layer is optimized, the simulation of the collapse stiffness of the layer thickness is carried out by adopting 0 degree/90 degree interweaving cloth.

According to the rule of the formula car of university of China, a 500 x 275 rectangular model is established, wherein a composite material panel adopts T_700 unidirectional belts, layering layers are arranged, each layer of 0.4mm, 2 layers of T_700 single layers are 90 degrees, a sandwich layer adopts 15mm honeycomb aluminum, and layering angles are 90 degrees. Layering is carried out through the workbench_ACP module, the layering angles are the same, the layering layers are changed, and the bending rigidity is calculated. The boundary condition is 7000N force, and two sides of 275mm are restrained according to the restraint mode of the simple beam.

1. 1 carbon fiber layer

TABLE 6 calculation results of a layer of carbon fiber cloth

EI-bending stiffness, N ² ；

F, concentrating force and N;

a, a distance from a force acting point to an unconstrained point, m;

b-distance from the force application point to the full constraint, m;

l-distance bounded at both ends, m;

f-maximum deflection, m.

Calculated ei= 2399.524n·m ² Far less than the side impact zone equivalence requirement, and therefore a 4-layer simulation was employed.

2. 4-layer carbon fiber

Table 74 calculation results of carbon fiber cloth

EI-bending stiffness, N ² ；

F, concentrating force and N;

a, a distance from a force acting point to an unconstrained point, m;

b-distance from the force application point to the full constraint, m;

l-distance bounded at both ends, m;

f-maximum deflection, m.

Calculated to have a bending stiffness of 6747.677 N.m ² >6132N·m ² The requirements are met and then a test is made to determine if one layer less meets the requirements.

3. 3 carbon fiber laminates

Table 8 3 calculation results of carbon fiber cloth

EI-bending stiffness, N.m.times.2;

f, concentrating force and N;

a, a distance from a force acting point to an unconstrained point, m;

b-distance from the force application point to the full constraint, m;

L-distance bounded at both ends, m;

f-maximum deflection, m.

The bending stiffness is 6098.37 N.m. times.2, which is calculated, does not meet the requirement of the side anti-collision area 4130 for the equality of the steel pipe, and therefore does not meet. Through the simulation, when the sandwich layer is honeycomb aluminum and the panel is 4 layers of 0-90-degree interwoven unidirectional tapes, the composite material structure meets the requirement of the rule of 'Chinese university equation automobile large racing', which provides a basis for filling up the up-to-date structural equivalence form, and lays a road for the subsequent overall layering design.

Three-application-based alternative vehicle frame working condition analysis

According to the national standard GB/T13043: the sample vehicle must travel a distance on the corresponding road at a prescribed speed, typical road conditions being four conditions of high speed, strong torsion, curved road and bending, torsion, emergency braking, and tight cornering on a general road. These conditions are very strong tests of the strength, rigidity and stability of the frame. In order to ensure the safety of the driver and fully exert the performance of the racing car, six considerations exist in the finite element analysis of the frame: static load conditions, steering conditions, braking conditions, bending stiffness, torsional stiffness and sixth order modes.

The shell structure modeling of the applicable alternate vehicle frame is performed by CATIA in combination with rules, ergonomics and various assembly arrangements. And checking the strength, the rigidity and the natural frequency of the frame through the joint simulation of the Workbench and the ACP module, and obtaining feedback.

3.1 applicable surrogate frame shell modeling, unit division, and ply design

3.2 analysis of the frame stiffness calculation

3.2.1 torsional stiffness analysis

The torsional stiffness of the frame determines the ability of the frame to resist deformation when the vehicle is on uneven road or cornering sharply, and has a significant impact on the accuracy of the vehicle suspension geometry. Only after the frame has certain torsional rigidity, the steering stability and driving safety of the racing car in the driving process can be ensured. When torsional rigidity test is carried out, one end of a front (rear) suspension of a racing car is restrained fixedly, forced displacement in opposite directions is applied to two sides of the other suspension respectively for 1mm, and therefore a torsion angle theta of the frame can be obtained:

θ＝arctan(2/L)

G＝FL/θ

theta-frame twist angle, °

Average distance between hard points of L-suspension, m

F-reaction force of support at hard point of suspension of vehicle N

G-torsional rigidity of vehicle frame, N.m/°

Frame torsional stiffness calculation

The method for analyzing the torsional rigidity of the frame comprises the following two steps:

(1) All degrees of freedom of the front suspension hard point are restrained, opposite forced displacement is applied to two sides of the rear suspension hard point in the vertical direction by 1mm respectively, and degrees of freedom in the X direction and the Y direction are defined as Free, so that first torsional rigidity is obtained.

(2) And constraining all degrees of freedom of the rear suspension hard point, respectively giving opposite forced displacement for 1mm in the vertical direction on two sides of the front suspension hard point, and defining the degrees of freedom in the X and Y directions as Free to obtain second torsional rigidity.

Boundary conditions

As shown in fig. 35 and 36, the rear left and right suspensions were fixed, and opposite forcible displacement of 1mm was applied to the front left and right suspensions.

The average distance between the front suspension hard points is 0.405, and the average distance between the rear suspension hard points is 0.480.

The torsional rigidity formula is obtained by programming the torsional rigidity formula into an EXCLE table:

TABLE 7 calculation of torsional stiffness

Theta-frame twist angle, °

Average distance between hard points of L-suspension, m

F-reaction force at hard point of suspension N

G-torsional rigidity of vehicle frame, N.m/°

And in the same way, fixing the front suspension, and applying opposite displacement to the vertical direction of the rear suspension by 1mm to obtain:

as can be taken from fig. 38, the values are brought into the EXCLE table:

Table 8 torsional stiffness calculation results

θ—the torsion angle of the frame, °;

l is the average distance between hard points of the suspension, m;

f, supporting reaction force at the hard point of the suspension, N;

g-torsional rigidity of the frame, N.m/°.

Therefore, the torsional rigidity of the whole automobile is G= (4663+2951.5)/2=3807N/°, and the torsional rigidity of the automobile participating in the formula car of university of China is larger than 1000N/° generally at 3000-4000N/° according to the condition that the automobile is manufactured to replace a frame by autoclave molding, so that the design target value is reasonable.

3.2.2 frame bending stiffness calculation

The bending rigidity of the frame refers to the degree of deflection of the frame when bearing vertical load, and the magnitude of the bending rigidity can influence the wheelbase of a racing car and the wheel positioning parameters of the vehicle, and influence the steering stability of the whole racing car. The racing car frame structure is symmetrical about a longitudinal middle plane, the frame can be regarded as a simply supported beam, the supporting point is a connecting point of the front suspension and the rear suspension with the frame, and the maximum deflection value of the simply supported beam in the vertical direction can be obtained by applying concentrated force. And (3) simulating bending stiffness working conditions, restraining all displacement degrees of freedom of the hard points of the front suspension, and releasing the displacement degrees of freedom of the rear suspension in the X direction. A concentrated force is applied vertically downward to the cabin floor to bend the frame.

Boundary conditions

A concentrated force F of 3000N is applied vertically downwards on the cabin. Suspension hard point constraints are shown in table 11:

table 9 alternative frame bending condition suspension restraint conditions

The frame bending stiffness solving method refers to the calculation of the bending stiffness of the front side anti-collision area, and the numerical value obtained in the graph 40 is taken into an EXCLE table:

table 10 calculation results of frame bending stiffness

The steel pipe frame of the racing car of the HUAT motorcade of Dongfeng is 99307 N.m ² And other school-replacement frames with a bending stiffness of 523186 N.m ² The requirements of formula car for college students have been met far.

3.2.3 static load conditions

When the vehicle is in a stationary state, the alternative vehicle frame mainly bears the gravity from a driver, an engine and other parts, and the vehicle frame has enough strength and rigidity to resist deformation caused by external force in a safe service life.

Simplifying the CAE model of the alternative frame, neglecting the smaller forces present on the alternative frame, which is mainly subjected to gravity from the human and power system when the vehicle is stationary; when racing, the frame receives the force of the suspension system and the car body system besides the dead weight of the power system and the person, and the specific stress value is referred to the following table:

TABLE 11 stress conditions

Boundary conditions

Simplifying CAE model, weight 700N, power system weight 700N, applying the uniform load to the corresponding part of the alternative frame, and constraining the hard points of the alternative frame as follows:

table 12 static suspension constraints

According to the replacement frame of the Harbin industrial university of the reference object, the deformation amount can meet the requirement below 0.5mm, and according to the result, the maximum stress appears on the steel pipe of the rear frame 4130, and the maximum main stress is 85.69Mpa and is far less than the material yield strength of 700Mpa, so that the requirement is met.

3.2.4 braking Condition

Racing cars need to be continuously accelerated and decelerated during racing, and in certain emergency situations, it is required that four-wheel locking be enabled, and only a brake test is passed to participate in racing. Thus, during racing braking, the replacement frame is subjected to braking forces of the braking system opposite to the direction of travel, which can produce a maximum braking deceleration of 1.3G.

When the alternative frame carries a person, the whole vehicle has a mass of about 300KG, and the moving load coefficient is 1.5

F＝k*ma＝1.5*300*(1.3*9.8)＝5733N

The rear axle load is 55% of the total mass, and the rear axle braking force is:

F＝5733*55％＝3153.2N

the hard points of the front suspension are restrained, braking force is applied to the hard points on two sides of the rear suspension, the average braking force born by each side of the rear axle is 1576.6N, in addition, the gravity of a person is 700N, the gravity of a power system is 700N, the downward pressure of a front wing is 550N, the downward pressure of a tail wing is 400N, uniform load is applied to the corresponding position of a substituted frame, and the boundary conditions of the substituted frame are restrained as follows:

Table 13 brake operating mode suspension constraints

From the results, the maximum deformation amount was 0.46mm; according to the maximum main stress which can be obtained, the maximum main stress still appears on the 4130 steel pipe, the maximum main stress is 167Mpa, and the maximum main stress is less than 700Mpa which is the yield limit of the material, thereby meeting the requirements.

3.2.5 turning condition

While racing, there are many pile-winding tests on the track, so there are some acceleration and deceleration operations while steering, the alternate frame is subjected to lateral forces, and also longitudinal forces. Because the running speed is higher during racing, the highest speed is also sought in a curve and the centrifugal force is high, the lateral acceleration received by the alternative frame is 1.3 gravity accelerations, the longitudinal deceleration received by the alternative frame is 1.3 gravity accelerations, and the dynamic load coefficient is 1.5 in view of the road conditions of the Xiangyang dream equation racing field racing of the annual racing.

Lateral force:

F＝kma1＝1.5*300*(1.3*9.8)＝5733N

front axle load is 45% of total mass, then front axle unilateral lateral force is:

F＝5733*45％*0.5＝1289.9N

the rear axle load is 55% of the total mass, then the rear axle unilateral lateral force is:

F＝5733*55％*0.5＝1576.6N

longitudinal force:

F＝kma2＝1.5*300*(1.3*9.8)＝5733N

the rear axle load is 55% of the total mass, and the rear axle unilateral braking force is:

F＝5733*55％*0.5＝1576.6N

lateral force 1289.9N is applied to the right front suspension and lateral force 1576.6N is applied to the right rear suspension and longitudinal force 1576.6N is applied to the right rear suspension. The human gravity is 700N, the power system gravity is 700N, the force 1800N of the front shock absorber and the force 2300N of the rear shock absorber are all uniformly distributed and loaded on the alternative frame. Frame hard point constraints are as follows

Table 14 frame hard spot constraints

According to the result, the maximum stress value is 260Mpa, which is less than 4130 yield limit 700Mpa, and meets the requirement.

3.2.6 Modal analysis

The mode analysis is combined with the structural strength and rigidity analysis; if a stress region with high strength analysis results is overlapped with a region with larger displacement of a certain order mode shape (whether the order mode can occur or not needs to be judged), the structure can be considered to be dangerous. Therefore, the model analysis is carried out on the frame by using ANSYS software, and the natural frequency of the frame is calculated to be staggered from the working frequency of the main vibration source of the racing car.

The racing car uses a three-cylinder gasoline engine, the idling speed n=3000 r/min, and the idling frequency f= (n/60) ×2=100 Hz is calculated according to a formula; the road surface excitation frequency of the track does not exceed 25Hz; and calculating to obtain the first sixth-order mode of the frame.

Table 15 sixth order modality

The mode natural frequency of the analyzed frame structure is higher than the frame load excitation frequency (20-35 Hz), and the resonance phenomenon can not occur in the working state. In addition to excitation from the load of the racing car itself, the racing car is subjected to various excitation from external excitation sources during running. When the automobile runs on a normal road surface at a speed lower than 150km/h, the excitation frequency of the road surface to the automobile is lower than 25Hz; excitation due to wheel imbalance is mainly below 11 Hz. According to the mode analysis result, the natural frequency of each mode of the frame is higher than the main excitation frequency of the outside, so that the frame cannot generate resonance phenomenon.

Fourth, is suitable for replacing the technological study of the frame

4.1 Process method for manufacturing applicable alternative frame by combining hand lay forming and autoclave

4.1.1 brief introduction of hand lay technique

The hand lay forming process is a process method for forming a composite material by laying reinforcing materials and resin on a mould manually or with the aid of certain machines and curing the resin, and is the earliest process method in the field of composite materials and the simplest process method. The raw materials of the hand lay forming process mainly comprise a matrix material, a reinforcing material and an auxiliary material, and the selection of the materials is a key link for ensuring the quality requirement and the cost requirement of the product and improving the economic benefit.

4.1.2 preparation stage of hand lay-up Forming Process

The raw materials for hand lay-up mainly include reinforcing materials, matrix materials, and auxiliary materials, glass fibers and carbon fibers are commonly used in reinforcing materials, however, carbon fibers are the most used in alternative frames. Carbon fibers are classified into high-performance and low-performance, and the specific choice depends on the actual situation.

Among the matrix materials, we use resin materials, commonly used epoxy resins as matrix materials, and many fleets now use prepregs as alternative frame manufacturing raw materials, wherein the prepregs are semi-finished products for storage, are formed by impregnating fibers with resins under certain conditions, and are intermediate products for manufacturing composite materials, but the prepregs have high storage requirements, and the prepregs need to be stored at low temperature because the higher the temperature is, the faster the chemical reaction speed is.

Auxiliary materials mainly comprise curing agents, release agents, accelerators, vacuum bag films, sealing tapes, isolating films, airfelt, adhesive absorption and the like, wherein the curing agents are materials for enabling resin to gel or solidify in fixed time, the release agents are generally used on the surface of a mold, so that the mold is suitable for better demolding of a substituted frame without damaging the substituted frame, but the existing motorcade adopts a violent demolding method by adopting a disposable mold.

4.1.3 introduction of the die

The mold has a very great effect in the manufacturing process of the alternative frame, and directly influences the quality of the alternative frame, and the molds designed for different alternative frames are different, so that a plurality of factors such as cost, enough strength, rigidity, heat resistance, demolding mode and the like need to be considered.

The die can be generally divided into four types, namely a female die, a male die, a pair of dies and a combined die, wherein the female die is concave on the working surface of the die, the male die is convex on the working surface, the pair of dies is a combination of the female die and the male die, and the combined die has more considered factors and more complex structure.

The mould of the alternative frame is built by a density board more, and because the cost conditions of various motorcades are different, the materials of the selected moulds are different, and the processing mode of the mould is mainly milling machine.

4.1.4 Process

1. The surface of the mould is firstly treated, the treatment comprises cleaning of the surface and surface evenness, and the milled surface is not particularly even, so that the special treatment is carried out at the moment, and after the mould is treated, the mould is brushed with a release agent, and then the prepreg can be used for paving.

2. Cutting the prepreg according to the designed layering structure, then layering according to the required thickness and layering angle, paving one layer by one layer in the process, if two layers of protective films are arranged on the surface of the prepreg, firstly removing one layer, and then removing the next layer. When laying, also let layer by layer compaction as far as possible, little air appears between layer, avoids appearing the fold. The alternative frame is generally made of a male die, one male die is made into two halves, carbon fiber dry cloth and resin are used as a layer on the male die, and then the carbon fiber dry cloth and the resin enter a high-temperature curing furnace for curing, and then the mold is removed. The manufactured piece is then used as a female mold to manufacture an alternative frame. The female mould is also an upper part and a lower part, and then is combined together and is paved.

3. After the lay-up is completed, additional material is added and sealed with a vacuum bag. And an air-felt is placed at the edge of the whole layer, so that the volatilization of gas and resin materials in the air-felt is ensured to have an air inlet and exhaust channel. A first layer of non-porous isolating film is laid on the surface of the part for separating the alternative frame from the auxiliary material, and the isolating film should be longer at least to the middle position of the airfelt. The airfelt is also laid on top of the non-porous barrier film, and the airfelt is the airfelt at the bottom edge, and all the alternative frames and auxiliary materials are wrapped together.

4. The vacuum bag is packaged, the sealing rubber strip is adhered to the vacuum bag at one side of the vacuum bag, the sealing rubber strip covers all auxiliary materials, and a gas channel cannot be reserved below the vacuum bag, so that the vacuum bag is as smooth as possible.

5. After the vacuum bag is packaged, the vacuum nozzle is pressed, and then vacuum is pumped.

6. Finally, vacuumizing and airtight checking are carried out, heating and pressurizing are carried out for curing, and finally, demoulding is carried out, so that the needed alternative frame is obtained, and the process is generally completed by professionals.

7. Molding characteristics of autoclave

Among the molding processes, autoclave molding is one of the choices of many fleets because the process is very widely applicable, including pressure and temperature uniformity, simple mold, etc., but there are some sections, such as very high cost, etc.

4.2 cutting and folding method for making substituted carriage

4.2.1 brief description

The method for manufacturing the alternative frame by using the manual pasting and the autoclave is introduced, and the method has the advantages of high cost, high process difficulty, high requirement on configuration resources and high cutting and folding requirements. This approach has been applied to practical replacement frame production by many fleets in europe, such as the well-known oxforus flea in uk, which has been used to make replacement frames for flea of home vehicles.

4.2.2 description of the cutting and folding method steps

1. Firstly, preparing a composite sandwich structure panel with a whole honeycomb aluminum layer as a sandwich layer and carbon fibers as a panel.

2. Cutting off the carbon fiber composite material plate needing to be folded and other redundant carbon fiber composite material plates by using a numerical control machine tool, and then ensuring the integrity of the whole plate as much as possible when removing redundant quest composite material sandwich panels

The width of the composite material removed where folding is desired can be calculated using the following equation:

a is the width of the composite panel to be removed;

d is the thickness of the composite panel;

θ is the folding angle;

3. the following is a critical step. The quality of the step is related to the precision of the manufactured alternative frame, and the step is the most difficult step in the whole process. It is now necessary to fold the composite sheet into the shape of the designed alternate frame by making the brackets. The joints and the folding parts need to be fixed by an adhesive, and the joints and the folding parts can be reinforced by aluminum plates or carbon fiber plates after the adhesive is cured. If gaps still exist, the gaps are also filled with adhesive and additional finishing or joining work may be required. The difficulty in folding the cut sheet into the designed replacement frame is very high in this step, because the composite sheet is almost close to the composite sheet after folding, and the stiffness of the carbon fibers is great, which also greatly increases the difficulty in folding. .

Most of the prior art alternative frames manufactured by cutting and folding adopt a structure that the plates are of a front carbon fiber layer and a back carbon fiber layer, and the middle sandwich layer is of honeycomb aluminum, but the selection of the composite material plates is more dependent on the quality of the carbon fibers and the torsional rigidity of the design set target. In this process, the equation racing motorcade will invest a lot of time, manpower and material resources for the manufacture of the alternative carriages, but the manufacture process seems to be a good choice for training the practical ability of college students and fitting their own talents to the context of the age development. The pencil owner also knows in this process that the outer part of the replacement frame of the motorcade is made of aluminum skin, and the inner part is made of carbon fiber, so that the aluminum skin is a good choice as a plate surface. For the process of manufacturing the alternative vehicle frame by using the cutting and folding method, the accuracy of the bracket determines the accuracy of the alternative vehicle frame, but the accuracy of the alternative vehicle frame indirectly determines the accuracy of positioning each part, and the factors such as the ground clearance, the mass center position of the whole vehicle and the like can be influenced. The design and production of the bracket clamps is also important, and in this respect, a lot of effort is required to make repeated measurements and corrections to ensure the accuracy of the alternative carriage made by the cutting and folding method.

4. Finally, in terms of accuracy of hard points of the suspension, a mode of combining the existing positioning mode of the Dongfeng HUAT motorcade with the single shell manufactured by cutting and folding modes can be adopted, the suspension is positioned by manufacturing a clamp, a corresponding distance is reserved between a suspension connecting point and a positioning point of the substituted frame, and errors generated by the substituted frame in the folding process are adjusted by adjusting the distance. In summary, the alternative frame made by cutting and folding is more similar to the current frame of the eastern style HUAT fleet except that the steel tube truss is replaced with a composite plate.

In the description of the present invention, unless otherwise indicated, the meaning of "a plurality" is two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front," "rear," "head," "tail," and the like are used as an orientation or positional relationship based on that shown in the drawings, merely to facilitate description of the invention and to simplify the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the invention. Furthermore, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. .

The foregoing is merely illustrative of specific embodiments of the present invention, and the scope of the invention is not limited thereto, but any modifications, equivalents, improvements and alternatives falling within the spirit and principles of the present invention will be apparent to those skilled in the art within the scope of the present invention.

Claims

1. The three-dimensional modeling-based alternate vehicle frame simulation method is characterized by comprising the following steps of:

then analyzing under various working conditions to obtain the optimal parameters of the carbon fiber composite material applicable to the replacement frame;

the carbon fiber composite laminate is a composite sandwich structure panel made of carbon fiber composite materials serving as panels and honeycomb aluminum serving as a sandwich material in the middle;

the carbon fiber composite laminate elastic constant test comprises the following steps:

s1, selecting a corresponding matched wedge-shaped clamp as a test clamp;

s2, adjusting the vertical centering of the sample by using a triangle, and clamping the sample;

S3, adjusting the position of a cross beam of the mechanical testing machine, and sequentially connecting a strain gauge wire and a strain gauge;

s4, setting parameters according to a specific testing machine by computer control software matched with the mechanical testing machine, and recording and collecting data to obtain force-displacement and strain-time graphs of different angles;

s5, processing the collected data to obtain transverse, longitudinal and normal tensile modulus E ₁ 、E ₂ 、E ₃ Poisson's ratio v 12, v ₁₃ 、ν ₂₃ Shear modulus G ₁₂ 、G ₁₃ 、G ₂₃ ，E ₂ ＝E ₃ ，G ₁₂ ＝G ₁₃ ，v ₁₂ ＝v ₁₃ ；

E ₁ And v ₁₂ The calculation formula is as follows:

calculation G ₁₂ The formula of (2) is as follows:

E ₂ the elastic constant of the sample piece is 90 degrees;

calculation E ₄₅ The formula of (2) is as follows:

shear modulus G ₂₃ From the following formula

Wherein f _G Obtained by quadratic equation

C＝3c ₁ c ₂ (1-V _f ) ² V _f +(c ₂ +c ₃ V _f ³ )(c ₁ V _f +c ₄ )

η ₀ ＝3-4ν ₀ ，η ₁ ＝3-4ν ₁

ν ₀ Poisson's ratio of the matrix;

ν ₁ poisson's ratio of the fibres;

V _f -the volume fraction of the fibres;

G ₀ -shear modulus of the matrix;

G ₁ -shear modulus of the fiber;

poisson ratio v ₂₃ The method is obtained by the following formula:

；

the specific method for analyzing the layering angle by utilizing ANSYS comprises the following steps:

s11, defining a laying direction and a laying sequence mark of a single layer of the laminated board and a mark of the composite material laminated board, and selecting a main shaft direction of a structure as a reference coordinate system;

S12, building a laminated plate with the thickness of 150X50X2mm in ANSYS, wherein the thickness of each layer is 0.5mm, and the laminated plate is four layers in total, then fixing four sides of the laminated plate, and loading 1000N uniform load on the surface;

s13, constructing bending stiffness simulation displacement cloud charts of laminated plates with different layering angles;

when the ANSYS is used for analyzing the thickness of the layer, 0 degree/90 degree interweaved cloth is adopted for carrying out rigidity simulation of the thickness of the layer, and the method specifically comprises the following steps:

s21, a rectangular model with 500 x 275mm is established, a T_700 unidirectional tape is selected as a composite sandwich structure panel, layering is arranged, each layer of 0.4mm, 2 layers of T_700 single layers are 90 degrees each other, 15mm honeycomb aluminum is selected as a sandwich layer, and layering angles are 90 degrees each other;

s22, layering is carried out through a workbench_ACP module, the layering angles are selected to be the same, the layering layers are changed, and the bending rigidity is calculated;

s23, restraining two sides of 275mm according to a constraint mode of a simply supported beam by setting a boundary condition of 7000N;

when analysis under various working conditions is carried out, the static load working condition, the steering working condition, the braking working condition, the bending rigidity, the torsional rigidity and the six-order mode are analyzed;

Frame torsion angle θ:

θ＝arctan(2/L)；

G＝FL/θ；

θ—the torsion angle of the frame;

l is the average distance between hard points of the suspension, m;

f, supporting reaction force at a hard point of a vehicle suspension, N;

g, torsional rigidity of the frame, N.m/°;

when the bending stiffness working condition is simulated, all the displacement degrees of freedom of the hard points of the front suspension are restrained, the displacement degrees of freedom of the rear suspension in the X direction are released, and a concentrated force is vertically downwards applied to the cabin plate, so that the frame is bent;

the specific process flow of the carbon fiber composite material applicable to replacing the frame comprises a process method combining hand lay forming and an autoclave and a cutting and folding method;

(3) After the layering is completed, adding auxiliary materials, packaging by using a vacuum bag, and adhering the auxiliary materials on the vacuum bag by using a sealing adhesive tape while adhering the auxiliary materials on the sealing bag, wherein the sealing adhesive tape covers all the auxiliary materials;

(5) Vacuumizing, checking tightness, heating and pressurizing for solidification, and finally demolding to obtain the substituted frame;

the cutting and folding method specifically comprises the following steps:

2) Cutting off the carbon fiber composite sandwich structure panel of the part needing folding and the carbon fiber composite sandwich structure panel of other redundant parts by using a numerical control machine tool;

3) Folding the composite sandwich structure panel into the designed shape of a substitute frame by manufacturing a bracket, fixing the joint and the folding position by using an adhesive, and reinforcing the joint and the folding position by using an aluminum plate or a carbon fiber plate after the adhesive is solidified;

4) In the aspect of the accuracy of hard points of the suspension, a mode of combining positioning, cutting and folding is adopted, the suspension is positioned by manufacturing a clamp, a space is reserved between a suspension connecting point and a positioning point of a substituted frame, and errors generated by the substituted frame in the folding process are adjusted by adjusting the space.

2. The method for three-dimensional modeling based on alternate vehicle frame simulation according to claim 1, wherein in the step 2) of the cutting and folding method,

；

a is the width of the composite sandwich structure panel to be removed;

d is the thickness of the composite sandwich structure panel;

θ is the folding angle.

3. A three-dimensional modeling-based alternate frame simulation system of an alternate frame simulation method according to any one of claims 1-2, wherein the alternate frame simulation system comprises:

4. A computer device, characterized in that it comprises a memory and a processor, the memory storing a computer program which, when executed by the processor, causes the processor to perform the three-dimensional modeling-based alternate vehicle frame simulation method according to any of claims 1-2.

5. A computer readable storage medium storing a computer program which, when executed by a processor, causes the processor to perform the three-dimensional modeling-based alternate vehicle frame simulation method according to any one of claims 1-2.