CN111859756A

CN111859756A - Three-dimensional modeling-based alternative frame simulation method and system

Info

Publication number: CN111859756A
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: 2020-10-30
Anticipated expiration: 2040-07-20
Also published as: CN111859756B

Abstract

The invention belongs to the technical field of substitute frames, and discloses a substitute frame simulation method and a simulation system based on three-dimensional modeling.A three-dimensional modeling software is used for modeling a suitable substitute frame, carrying out a test experiment on an elastic constant of a carbon fiber composite laminate, analyzing a ply angle and ply thickness design by using ANSYS, and then analyzing under various working conditions to obtain a specific process flow of the carbon fiber composite material suitable for the substitute 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 process flow of the substituted frame is explained. The substitute frame in the invention is a sandwich structure shell which takes a high-rigidity light-weight carbon fiber/epoxy resin composite material as a panel and takes 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 alternative frame simulation method and system

Technical Field

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

Background

At present, replacement frame technology and composite material technology were originally introduced on ships and airplanes, such as boeing B787, and a large amount of composite material was used on airplane fuselages and airplane wings, and was used on automobiles since 1969. The development and use of new materials are imperative.

The first time that the F1 event appeared, it was widely known that LOTUS25 participated in the F1 event in 1962 adopted a light metal shell frame, and it was also known that the vehicle was a nose-crow suitable for replacing the frame now, and this attempt had been successful greatly, and this racing car had less weight, good field of vision, higher torsional rigidity, and more spacious cockpit space, and in the 1962 season, ten stations were spent in the whole course of the race, and seven stations were won.

To date, the utilization of monocoques has reached more than fifty percent in the international college student's equation race, especially in the field of electric racing.

In recent years, with the increasing interest of college schools on the college formula competition, various new technologies appear on the college formula competition, but the weight reduction is always the trend of automobile development and is one of the important points of attention of the college formula competition. Under the guidance of light weight, composite materials are also present in the college equation contest as racing car body-bearing materials. In China, due to the high cost of replacing the vehicle frames, the number of vehicle fleets adopting the replacing vehicle frames is not large, but the vehicle fleets are one of the important directions for the development of light weight of automobiles, and meanwhile, the improvement of the vehicle fleets and the participants is necessary for improving the strength of the vehicle fleets and the participants.

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

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

The manufacturing process is complicated. Many colleges and universities and cities in which the colleges and universities are located do not have equipment for manufacturing alternative frame manufacturing processes, the related process steps are multiple, and the process technical requirements are strict.

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

The fault tolerance rate is low. The replacement frame is often made wrongly or the frame runs in an accident, so that the maintenance difficulty is high, the cost is high, and the damage is irreversible in more times.

The difficulty in solving the above problems and defects is:

and 4, the cost is reduced. Domestic fleet expenses are almost derived from school financial fund withdrawal, and the ability of autonomous profitability is not provided, so that high-cost alternative frames are forbidden by many fleets for the tight expenses.

And (5) technical aspects. Compared with a steel pipe truss frame, the steel pipe truss frame has higher technical and technological requirements for replacing the frame, and many domestic fleets do not have the technical deposit in the aspect.

The enthusiasm of students. Many students know the advantages of alternative frames due to practical constraints, but can only be admirably limited because practical constraints know that alternative frames are not likely to be implemented and research on the aspect is lost over time.

School support strength. As many colleges and universities in China still use game scores as one of the reference indexes of the expenses, lots of fleets with insignificant scores are more stressed in the expenses. Instead, a plurality of motorcades with good performances use the substituted frame earlier, and the competition performances are further, the cycle is caused, and the two poles are differentiated.

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

and (3) on the aspect of students: the knowledge area of students is widened, the practical ability of students is improved, a hot aspect is pointed out for the knowledge expansion, and talents are cultivated for the happy national automobile industry.

In school aspect: the competition strength of school fleet events is enhanced, the school industry awareness and the school overall strength are improved, the competition level of the school fleet events is close to that of international famous colleges and universities, and the communication promotion is promoted.

In the aspect of events: the overall level of the event is improved, the good development of the event is promoted, and the popularity of the event and the participation enthusiasm of students are improved.

Disclosure of Invention

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

The invention is realized by the following steps:

1) carrying out design modeling suitable for replacing the frame by utilizing three-dimensional modeling software;

2) Carrying out design analysis on the layer laying angle and the layer laying thickness of the model by using ANSYS software;

3) verifying and analyzing the result of the test experiment of the elastic constant of the carbon fiber composite laminate;

4) performing theoretical analysis on the substituted frame under various limit working conditions by using ANSYS software;

5) and analyzing and enumerating the specific process flow of the carbon fiber composite material suitable for replacing the frame.

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

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

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

s2, holding the middle part of the sample with two hands, placing the upper end of the sample into the middle part of a clamp, holding the centering verticality of the sample with two hands, operating a mechanical testing machine with the right hand, slightly clamping the sample to prevent the sample from moving randomly, adjusting the vertical centering performance of the sample with a triangular plate, and clamping the sample;

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

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

s5, processing the collected data to obtain transverse, longitudinal and normal tensile moduli E₁、E₂、E₃Poisson ratio mu₁₂、μ₁₃、μ₂₃Shear modulus G₁₂、G₁₃、G₂₃，E₂＝E₃，G₁₂＝G₁₃，μ₁₂＝μ₁₃，μ₂₃And G₂₃Not independent.

Further, E₁And mu₁₂The calculation formula is shown below

In the formula: b is the width of the test piece; t is the thickness; p₁Is a 1-direction load;₁，₂strain in the 1,2 directions, respectively;

calculation of G₁₂The formula of (1) is as follows:

E₂the tensile modulus of the selected epoxy resin was obtained as the elastic constant of the 90 ° test piece by referring to the characteristic table after curing the resin, and was taken as the E of the 90 ° test piece₂；

Calculation of E₄₅The formula of (1) is as follows:

shear modulus G₂₃Can be calculated from the following formula

Wherein f is_GCan be obtained by quadratic equation

A＝3c₁c₂(1-V_f)²V_f+(c₂η₀-c₃V_f ³)(c₁η₀V_f-c₄)

μ₀-poisson's ratio of the matrix;

μ₁-the poisson's ratio of the fibres;

V_f-the volume fraction of the fibres;

G₀-shear modulus of the matrix;

G₁-the shear modulus of the fiber;

poisson ratio mu₂₃Obtained from the following equation:

further, the specific method for analyzing the ply angle by using ANSYS comprises the following steps:

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

S12, establishing a 150X50X2mm laminated plate in ANSYY, wherein the thickness of each layer is 0.5mm, and the layers are four layers in total, then fixing four sides of the laminated plate, and loading 1000N uniform loads on the surface;

s13, constructing the simulated displacement cloud pictures of the bending rigidity of the laminated plate with different stacking angles.

Further, when analyzing the thickness of the ply by using ANSYS, carrying out rigidity simulation of the thickness of the ply by adopting 0/90-degree interwoven fabric, which specifically comprises the following steps:

s21, establishing a 500-275 rectangular model, wherein the composite material panel adopts a T _700 unidirectional belt, the composite material panel is provided with layers, each layer is 0.4mm, 2 layers of T _700 are single and are 90 degrees, the sandwich layer adopts 15mm honeycomb aluminum, and the layer angle is 90 degrees;

s22, carrying out layering through the workbench _ ACP module, selecting the same layering angle, changing the layering number, and calculating the bending stiffness

And S23, setting the boundary condition to be 7000N force, and constraining the two 275mm sides according to the constraint mode of the simply supported beam.

Further, when analyzing under various working conditions, analyzing a static load working condition, a steering working condition, a braking working condition, bending rigidity, torsional rigidity and a six-order mode;

when a torsional rigidity test is carried out, firstly, all degrees of freedom of a front suspension hard point are restrained, opposite forced displacement of 1mm is applied to two sides of a rear suspension hard point in the vertical direction, degrees of freedom in the X direction and the Y direction are defined as Free, and a first torsional rigidity is obtained; then constraining all degrees of freedom of a hard point of the rear suspension, respectively applying opposite forced displacement for 1mm in the vertical direction on two sides of the hard point of the front suspension, and defining the degrees of freedom in the X direction and the Y direction as Free to obtain a 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 forced deformation torsion angle is theta, the torsional rigidity of the frame is as follows:

G＝FL/θ

θ -frame twist angle, °;

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

f is the bearing reaction force at the hard point of the vehicle suspension, N;

g-frame torsional stiffness, N.m/°;

when the bending rigidity working condition is simulated, all the displacement freedom degrees of the hard point of the front suspension are restrained, the displacement freedom degree of the rear suspension in the X direction is released, and a concentrated force is vertically and downwards applied to the cabin plate to bend the frame.

Further, the specific process flow of the carbon fiber composite material suitable for replacing the frame comprises a process method combining hand laying forming and an autoclave and a cutting and folding method;

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

(1) treating the surface of the mold, and brushing a release agent on the mold after the treatment;

(2) cutting the prepreg according to the designed laying structure, and then laying according to the required thickness and laying angle;

(3) after laying, adding auxiliary materials, packaging by using a vacuum bag, sticking the auxiliary materials on the vacuum bag by using a sealing adhesive tape while sticking the sealing adhesive tape on the sealing bag, and covering all the auxiliary materials by using the sealing adhesive tape;

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

(5) and (4) carrying out vacuum pumping and tightness inspection, heating and pressurizing for curing, and finally demoulding to obtain the alternative frame.

The cutting and folding method specifically comprises the following steps:

1) firstly, preparing a composite material sandwich structure panel with a whole block of honeycomb aluminum as a sandwich layer and carbon fibers as panels;

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

3) folding the composite material plate into the shape of a 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 cured;

4) in the aspect of suspension hard point accuracy, a mode of combining positioning, cutting and single shell manufacturing in a folding mode is adopted, positioning is carried out on suspension positioning through a manufacturing clamp, a distance is reserved between a suspension connecting point and a positioning point of a substitute frame, and an error generated by the substitute frame in the folding process is adjusted by adjusting the distance.

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

The width of the composite material removed where folding is desired is calculated using the following formula:

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

d is the thickness of the composite material panel;

theta is the folding angle.

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

the substitute frame modeling unit is used for modeling the applicable substitute frame by utilizing three-dimensional modeling software;

the carbon fiber composite laminate elastic constant testing unit is used for carrying out a carbon fiber composite laminate elastic constant testing experiment;

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

and (4) replacing the optimal parameter unit of the frame, and 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 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 applicable substitute vehicle frames by utilizing three-dimensional modeling software; carrying out an elastic constant test experiment on the carbon fiber composite laminate; determining the ply angle and the ply thickness by ANSYS analysis;

And 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 substitute frame in the invention is a sandwich structure shell which takes a high-rigidity light-weight carbon fiber/epoxy resin composite material as a panel and takes 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; the method comprises the steps of firstly designing a structure of a substitute frame based on a chassis of a certain three-cylinder engine, considering an assembly mode of the substitute frame and each component, obtaining 9 elastic constants of a composite single-layer plate through experiments, analyzing and summarizing rules of a layering angle and bending resistance of three-point bending through a workbench ACP module, carrying out simulation analysis on torsional rigidity and bending rigidity of the substitute frame, simulation analysis on static load, braking and sharp turning working conditions and analysis on modal analysis, and finally setting forth a process flow of the substitute frame.

Compared technical effects or experimental effects (data are derived from actual data of a certain motorcade in China):

substitute for each part mass of frame system

Quality of each part of steel pipe truss system

Stiffness to weight ratio of alternative frame system to steel pipe truss system

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

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used 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 it is obvious for those skilled in the art that other drawings can be obtained from the drawings without creative efforts.

FIG. 1 is a schematic view of an alternative frame model provided by an embodiment of the present invention.

Fig. 2 is an elevation view of an alternative vehicle frame provided by an embodiment of the present invention.

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

FIG. 4 is a top view of an alternative vehicle frame provided by an embodiment of the present invention.

Fig. 5 is a schematic structural diagram of twill carbon fiber cloth and unidirectional carbon fiber cloth provided by an embodiment of the invention.

Fig. 6 is a schematic structural diagram of a honeycomb aluminum provided by an embodiment of the present invention.

Fig. 7 is a schematic diagram of a material coordinate system provided by an embodiment of the invention.

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

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

Figure 10 is a force-displacement graph for a 45 sample 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.

Figure 13 is a schematic representation of a laminate model provided by 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 a first angular combination of plies and a material coordinate system provided by an embodiment of the present invention.

Fig. 16 is a displacement cloud diagram of the maximum deformation of the first angle combination according to the embodiment of the present invention.

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

Fig. 18 is a displacement cloud diagram of the maximum deformation of the second angle combination according to the embodiment of the present invention.

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

FIG. 20 is a displacement cloud of the maximum deformation for the third angle combination provided by the embodiment of the invention.

FIG. 21 is a schematic view of a fourth angle combination of plies and a material coordinate system provided by an embodiment of the present invention.

Fig. 22 is a displacement cloud diagram of the maximum deformation of the fourth angle combination according to the embodiment of the present invention.

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

Fig. 24 is a displacement cloud diagram of the maximum deformation of the fifth angle combination according to the embodiment of the present invention.

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

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

Fig. 27 is a schematic view of a simple beam model according to an embodiment of the present invention.

FIG. 28 is a schematic view of the direction of a 1-layer carbon fiber lay-up provided by an embodiment of the present invention.

FIG. 29 is a total displacement cloud of a 1-ply carbon fiber mat provided by an embodiment of the invention.

FIG. 30 is a schematic view of the direction of a 4-layer carbon fiber lay-up provided by an embodiment of the present invention.

FIG. 31 is a total displacement cloud of 4 carbon fiber plies provided by an embodiment of the invention.

FIG. 32 is a schematic view of the direction of a 3-layer carbon fiber lay-up provided by an embodiment of the invention.

FIG. 33 is a total displacement cloud of 3 carbon fiber plies provided by an embodiment of the invention.

Fig. 34 is a schematic diagram of meshing by using shell units according to an embodiment of the present invention.

FIG. 35 is a schematic representation of the torsional operating conditions boundary conditions provided by the embodiments of the present invention.

Fig. 36 is a schematic diagram of the right front suspension force provided by the embodiment of the invention.

Fig. 37 is a schematic diagram of the force applied to the left front suspension according to the embodiment of the present invention.

Fig. 38 shows specific values of the rear suspension force provided by the embodiment of the present invention.

FIG. 39 is a graphical representation of the boundary conditions for a bending mode provided by an embodiment of the present invention.

Fig. 40 is a schematic diagram of maximum deformation displacement under bending conditions according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

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

The three-dimensional modeling-based substitute frame simulation method provided by the embodiment of the invention utilizes three-dimensional modeling software to carry out modeling suitable for a substitute frame, carries out a test experiment on the elastic constant of the carbon fiber composite laminate, analyzes the ply angle and the ply thickness design by utilizing ANSYS, and then carries out analysis under various working conditions to obtain the process flow suitable for the substitute frame of the carbon fiber composite material.

The invention is further described below with reference to specific assays.

One, suitable for the design of the alternative frame

1.1 comparison of advantages and disadvantages of substitute vehicle frame and steel pipe truss vehicle frame

1.1.1 vehicle frame Mass

Generally, the excellent alternative frame includes a front ring, a main ring and an embedded part, and can be about 18 KG, but the excellent steel pipe truss frame includes all brackets (for example, the dongfeng HUAT fleet 2018 racing oil car frame, which does not include various lugs) with the weight of 26KG, and the weight difference between the two frames is large.

1.1.2 torsional stiffness

The substitution bicycle frame is also called a monomer shell in the formula competition of college students and can be regarded as a semi-closed box body in essence; 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 formula competition of college students can meet the requirement when the torsional rigidity is more than 1000N.M/°, the racing car replacing the frame basically has the torsional rigidity of about 4000N.M/°, and the steel pipe truss type frame (taking the eastern wind HUAT fleet 2018 racing season oil car frame as an example) is 2263N.M/°.

1.1.3 safety

For the formula car race of college students, the safety is the first, and many rules of the college race are based on the consideration of the safety, the substitute frame is contacted in a surface mode when collision occurs, and the sandwich material in the panel has better energy absorption capacity, so the substitute frame can better absorb impact force and better protect the personal safety of a driver.

1.1.4 cost

Firstly, the raw material carbon fiber for replacing the frame is expensive in material, secondly, a lot of auxiliary materials are needed, a mould is needed, the needed equipment is different due to different process choices, and many colleges and universities are not provided with equipment for producing the replacement frame, and domestic cities do not have the environment for processing the replacement frame at all. In terms of labor consumption, replacement of the frame requires a longer time period and more manpower. In capital, if a motorcade does not have a sponsor, the amount of substituted frames is at least more than 12 ten thousand yuan, which is far from the steel tube truss type frame, the cost of the substituted frames is much higher than that of the steel tube truss type frame, and under the condition that the domestic motorcade expenses are all relatively tight, 90% of college students in China plan to race the motorcade to select the steel tube truss type frame.

1.1.5 design and processing 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 vehicle frame is replaced by carbon fiber, and the characteristics of the carbon fiber are essentially different from those of a metal material. 4130 steel tube is isotropic, whereas carbon fiber is anisotropic. Isotropy is the property, such as poisson's ratio, strength, stiffness, etc., that is the same for any direction. The anisotropy is in different directions, the performance of the material is different, the carbon fiber is orthotropic, the performance is good in the fiber direction, and the other directions are poor. Therefore, based on the characteristics, the design of the substitute vehicle frame is complex, the design of the material layer needs to be studied, and a great deal of engineering experience is also needed for accumulation. For processing, a mould is needed to replace a frame, the requirement on the mould is high, the requirement on a layering is high, and reversibility is not available; the steel pipe truss frame basically depends on a clamp, hand-grinding steel pipes and welding, and has certain reversibility. If an accident occurs, the replacement vehicle frame is basically impossible to repair, but the steel pipe truss vehicle frame can be repaired within a certain range.

1.2 design of suitable replacement vehicle frame

The front cabin and the cabin part are designed according to the formula competition rule of the university students in 2019, the man-machine model of the east wind HUAT fleet 2019 competition season and the 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 applicable alternative frame mould and the convenience of the paving, and on the basis, the exquisite appearance and the shape are considered. The passing of the front cabin detection plate is fully considered in the front cabin, the passing of the cabin detection plate is fully considered in the cabin part, the space is fully utilized on the basis of passing, and the waste of the space is reduced.

The rear cabin part is designed in a way that the selection of the three-cylinder engine is fully considered, 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 according to the engine positioning parameters provided by the overall arrangement of the whole vehicle. Secondly, the rear cabin is contracted by utilizing the advantage of small volume of the three-cylinder engine, and becomes smaller, the left and right minimum distance is 496.4mm on the basis of the four-cylinder engine in the last year, the distance is 468mm in the year, and the length is shortened by 28.4 mm. 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 compared with the last year, and the height of the fixing point is higher.

Second, elastic constant test and ply design

2.1 brief introduction to composite materials

The composite material is a new material formed by two or more materials with different properties by a chemical or physical method, and the advanced resin composite material is prepared by taking epoxy resin as a matrix and high-performance continuous carbon fibers as a reinforcing material through a composite process, wherein the reinforcing performance of the advanced resin composite material comprises strength, rigidity, corrosion resistance, wear resistance and the like.

The embodiment of the invention uses a carbon fiber panel-aluminum honeycomb sandwich structure, and the structure is reasonable in design and can obtain higher strength and rigidity. One of 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 line carbon fiber cloth and the twill carbon fiber cloth are woven by transverse and longitudinal fiber yarns 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 made of honeycomb aluminum, is a sandwich material with better performance and wider application, and is shown in figure 6.

2.2 spring constant test experiment of carbon fiber composite plate

2.2.1 background of the experiment

The embodiment of the invention relates to design and process research of a certain three-cylinder engine suitable for replacing a frame based on FSCC (free space communication), wherein a front cabin and a cabin suitable for replacing the frame are formed by taking a carbon fiber composite material as a panel and taking honeycomb aluminum as a sandwich material in the middleThe rear cabin of the manufactured composite material plate is built by 4130 steel pipes. Before the analysis is performed, a material coordinate system needs to be established, as shown in fig. 7. The analysis by using simulation analysis software needs to carry out an elastic constant test experiment on the composite material plates of the front cabin and the cabin, and the aim is to obtain the tensile modulus E of the transverse direction, the longitudinal direction and the normal direction₁、E₂、E₃Poisson ratio v₁₂、ν₁₃、ν₂₃Shear modulus G₁₂、G₁₃、G₂₃。E₂＝E₃；G₁₂＝G₁₃；μ₁₂＝μ₁₃；μ₂₃And G₂₃Not independent.

2.2.2 testing the elastic constant and Poisson's ratio of the material in the principal axis and longitudinal directions by tensile test

2.2.2.1 protocol

The method comprises the steps of installing a rectangular sheet bar composite material plate in a chuck of a mechanical testing machine, applying monotonic tensile force, monitoring experimental strain by using a strain or displacement sensor, and determining the stress-strain according with the material plate. The execution standard of the experiment is GB/T32376-2015.

(1) Vernier caliper

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

(2) Strain gauge

According to the requirements of the experimental standard, the strain gauge can meet the requirements by adopting a resistance-type 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 over 350 ohms.

(3) Mechanics experiment machine

According to the provisions of the test standards, the mechanical testing machine selected for the test needs a fixed cross beam and a movable cross beam, the movable cross beam can move at a fixed relative speed which can be adjusted relative to the fixed cross beam, and the measurement error of the mechanical testing machine cannot exceed 1%. The test fixture is preferably selected to have a standard wedge-shaped slide that can move up and down within the fixture housing of the mechanical testing machine and provide sufficient lateral pressure to prevent relative sliding between the clamping surface and the test specimen, making the test data more accurate.

2.2.2.2 preparation before testing

1. Geometry of the test specimen

Firstly, when a sample is processed, the size design mainly comprises three important sample sizes of length, width and thickness, the selection of the length mainly meets three basic requirements, so that whether the effect of bending stress caused by clamping eccentricity on a gauge length section can be relieved, the gauge length section has enough distance with a clamping position, and most samples can be stressed. The main requirements for width and thickness are to ensure that the test fails within the gauge length and that the cross-section contains a sufficient number of fibres for the vast majority of composites represented statistically, the specific dimensions being given in table 1.

Table 1 Standard recommended tensile specimen dimensions

2. Control of test ambient temperature

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

3. Measurement of test dimensions

The actual width and thickness of each sample is measured before testing to derive the cross-sectional area of each sample. For the measurement of the width and the thickness, the number of the selected measuring points on the sample is not less than three, and the reading and the recording are carried out after the numerical value is stabilized during the reading.

2.2.2.3 Experimental procedures

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

1. The test fixture can be selected from a corresponding matched wedge-shaped fixture.

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 centering verticality of the sample is kept by the two hands, and the mechanical testing machine is operated by the right hand to slightly clamp the sample, so that the sample cannot move freely. And adjusting the vertical centering of the sample by using a triangular plate, and then clamping the sample.

3. And resetting the force display value of the mechanical testing machine and adjusting the position of the cross beam of the mechanical testing machine. Connect gradually foil gage wire and strain gauge wire, place its safety position after the connection is accomplished, can not receive external interference in the test process, guarantee to insulate.

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

2.2.2.4 data processing

1. The force-displacement and strain-time curves for the 0 ° sample are shown in fig. 8 and 9.

E₁And mu₁₂The calculation formula is shown below

In the formula: b is the width of the test piece; t is the thickness; p ₁Bit 1 directional loading;₁，₂strain in the 1 and 2 directions, respectively.

The exact data was read in an Excel table at the point 1/3 in the elastic deformation phase of the force-displacement versus strain-time curves of FIGS. 8 and 9 to obtain P₁And₁the value of (c).

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

P₁＝1.53KN；₁1274 mu; substituting into formula to obtain E₁＝106532MPa；

₂-215 μ; determination of V by the formula (2)₁₂＝0.165

2. Elastic constant of 90 degree sample piece

When loading is carried out in the direction vertical to the unidirectional composite material laminate, a person thinks that the composite material plate mainly depends on the cured epoxy resin to maintain the performance of the plate, and regards the plate as the cured epoxy resin under tension, so that the tensile modulus of the resin can be obtained by directly consulting the cured characteristic table of the selected epoxy resin and used as the E of a 90-degree test piece₂。

TABLE 2 epoxy resin curing characteristics Table

The tensile modulus of the cured epoxy resin is 2900-3000 MPa according to a table look-up. Get E₂＝3000Mpa。

2.2.3 determination of the in-plane shear Properties of the composites by the + -45 ° off-axis laminate tensile test

2.2.3.1 brief description of test methods

The uniaxial tensile test is carried out on the +/-45-degree laminated board, the theoretical derivation expression of the laminated board is utilized, the plane shear stress in a material coordinate system can be directly calculated from the load applied in the axial direction, the corresponding shear strain is derived from the positive strain in the longitudinal and transverse directions of the tensile, and an in-plane shear stress-shear strain curve is jointly established.

2.2.3.2 Experimental instruments and Experimental procedures

This test is similar to the previous tensile test, 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 the strain-time curve are shown in fig. 10 and fig. 11:

calculation of G₁₂The formula of (1) is as follows:

wherein E is₁、E₂、μ₁₂Has been derived from previous 0 DEG and 90 DEG tensile tests, however calculating E₄₅The formula of (1) is as follows:

then, the data points in the curves are selected in FIG. 10 and FIG. 11 and substituted into the above formula to obtain E₄₅＝2875Mpa、G₁₂＝1950Mpa。

The shear modulus G23 can be calculated from the following equation

Wherein f is_GCan be obtained by quadratic equation

A＝3c₁c₂(1-V_f)²V_f+(c₂η₀-c₃V_f ³)(c₁η₀V_f-c₄) (6)

μ₀-poisson's ratio of the matrix;

μ₁-the poisson's ratio of the fibres;

V_f-the volume fraction of the fibres;

G₀-shear modulus of the matrix;

G₁shear modulus of the fiber^[i]。

From the above formula, G is obtained₀＝1100MPa、G₁＝87.5GPa；G₂₃＝1213MPa

Poisson ratio v₂₃Obtained from the following equation:

E₂＝3000MPa；G₂₃1213 MPa; carry in to find mu₂₃All elastic constants are given in table 3, 0.23.

TABLE 3 elastic constants of composite laminates

2.3 simulation and optimization of ply lay direction of composite material sheet

2.3.1 composite Panel lay-up overview

The performance of the composite material plate is greatly influenced by the angle of the laying layer, the thickness of the laying layer and the number of the laying layers, the thickness of the laying layer in actual engineering is often a certain given thickness value, the number of the laying layers can be given due to the stress condition in design, therefore, the angle of the laying layer 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 principles:

(1) The lay-up of the composite laminate is symmetrical as a whole and follows the principle of equality, i.e. a positive angle lay-up is present, and correspondingly a negative angle lay-up is also present in the plane of symmetry, in order to prevent stretch-bending coupling and buckling during processing.

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

(3) The ply angle is set to some common values as much as possible, such as 45 °, -45 °, 0 °, and 90 °.

2.3.2 simulation of bending resistance of composite material laminate with different-angle laying layers

2.3.2.1 setting of ply angle coordinate system

Since the laying angle of each single layer in the composite material laminated plate is uncertain, in order to analyze and compare the mechanical properties of the laminated plates with different laying modes, marks for defining the laying direction and the laying sequence of the single layers of the laminated plate are needed, and the marks are also defined as the marks of the composite material laminated plate.

The composite laminates have an indeterminate principal direction of elasticity, and the composite laminate is typically selected with the principal direction of the structure as the reference coordinate system. If the rectangular plate is taken to be perpendicular to the two sides as a reference coordinate system, after the coordinates are selected, the composite laminated plate is labeled, and the included angle between the main axis of the composite material of the single-layer plate in the laminated plate and the reference coordinate axis is specified, as shown in fig. 12.

2.3.2.2 modeling of composite laminates and boundary conditions

As shown in fig. 13 and 14, a 150X50X2mm laminate was built in ANSYSY, each layer 0.5mm thick, for a total of four layers. The four sides of the laminate were then fixed and a uniform load of 1000N was applied to the faces.

2.3.3 simulated displacement cloud picture of bending rigidity of laminated plate with different ply angle

1、[0°、90°、0°、90°]

As shown in fig. 16, the maximum deformation amount is only 5.978 mm.

2、[0°、90°、30°、-60°]

As shown in fig. 18, the maximum deformation is 11.7 mm.

3、[0°、90°、45°、-45°]

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

4、[45°、-45°、45°、-45°]

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

5、[30°、-60°、30°、-60°]

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

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

2.4 three-point bending test simulation of composite material laminate

2.4.1 simulation of reference steel pipe in frame side anti-collision area

According to the stipulation of the equation of college students in 2019, namely the rule of competition for college equations 4.3, 7000N of load is pre-applied to the side anti-collision structure, and the load direction faces to a driver. A three-point bending performance test was performed on a 500X275mm composite laminate in place of the side impact region to demonstrate that the bending performance of the composite was equivalent to that of the baseline side impact steel pipe.

Therefore, the bending stiffness of the three reference side anti-collision steel pipes is firstly simulated according to the competition rule, and then the bending performance of the composite laminated plate is tested under the same boundary condition and used as the design lower limit of the composite laminated plate in the side anti-collision area.

2.4.2 bending performance simulation test of steel pipe in side anti-collision area

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

the frame structure is symmetrical about a vertical middle plane, the frame can be simplified and can be regarded as a simply supported beam, as shown in fig. 27, a fulcrum is a connecting point of a front suspension and a rear suspension and the frame, the maximum deflection value of the simply supported beam in the vertical direction can be obtained by applying concentrated force, and therefore the bending rigidity of the steel pipe in the side anti-collision area is calculated in the following mode.

The bending rigidity value is calculated according to the flexibility formula of the simply supported beam,

when x is less than or equal to b:

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

the above formula is compiled in table 4:

TABLE 4 parameter Table

And then the data is substituted into an editing result:

TABLE 5 calculation results Table

EI-bending stiffness, N²；

F-concentration, N;

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

a is the distance, m, from the force action point to the incomplete constraint;

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

l is the distance between two ends, m;

f-maximum deflection, m.

According to the rule of Dase, the bending stiffness of the composite plate is equal to that of the steel pipe, so the critical value is EI 6132N ·²。

2.4.3 simulation of bending performance of composite laminate with different layer thicknesses

After the preceding simulation of the ply angle, we know that the bending resistance is the best when the ply angle is 0 °/90 ° interweaving, so that when the ply is optimized, the expected stiffness removal simulation of the ply thickness is performed by using 0 °/90 ° interweaving cloth.

According to the rule of the formula racing car of college students in China, a 500 x 275 rectangular model is established, a composite material panel of the rectangular model is made of T _700 unidirectional tapes, layers are arranged, each layer is 0.4mm, 2 layers of T _700 single layers are 90 degrees, sandwich layers are made of honeycomb aluminum with the thickness of 15mm, and the layer angle is 90 degrees. And (3) layering is carried out through the workbench _ ACP module, the layering angles are selected to be the same, the layering number is changed, and the bending rigidity is calculated. The set boundary condition is 7000N force, and two 275mm sides are restrained according to the restraining mode of the simply supported beam.

1. 1-layer carbon fiber laying layer

TABLE 6 calculation of one layer of carbon fiber cloth

EI-bending stiffness, N²；

F-concentration, N;

a is the distance, m, from the force action point to the incomplete constraint;

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

l is the distance between two ends, m;

f-maximum deflection, m.

The EI is calculated to be 2399.524 N.m²Much less than the side impact zone equality requirement, so a 4-layer simulation is used.

2. 4-layer carbon fiber

Table 74 carbon fiber cloth calculation results

EI-bending stiffness, N²；

F-concentration, N;

a is the distance, m, from the force action point to the incomplete constraint;

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

l is the distance between two ends, m;

f-maximum deflection, m.

The bending stiffness was calculated to be 6747.677 N.m²>6132N·m²Meet the requirements, then test if one layer reduction meets the requirements.

3. 3-layer carbon fiber laying layer

Table 83 carbon fiber cloth calculation results

EI-bending rigidity, N.m ^ 2;

f-concentration, N;

a is the distance, m, from the force action point to the incomplete constraint;

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

L is the distance between two ends, m;

f-maximum deflection, m.

The bending stiffness was calculated to be 6098.37N m 2, which did not meet the equality requirements for the side impact zone 4130 steel tubing and was therefore not acceptable. Through the simulation, when the sandwich layer is made of honeycomb aluminum and the panel is made of 4 layers of unidirectional belts interwoven at 0 degrees and 90 degrees, the composite material structure meets the requirements of the rule of ' Chinese university student ' equation automobile tournament ', the basis is provided for filling in an upper cross structure equality form, and the road is laid for the subsequent overall laying design.

Triple-purpose alternative vehicle frame working condition analysis

According to the provisions in the national standard GB/T13043: the sample vehicle must travel a certain distance on the corresponding road at a specified speed, and typical road conditions are four conditions of high speed, strong torsion, curved road, and curve, torsion, emergency braking and sharp turning on the general road. These conditions are very challenging with respect to frame strength, stiffness and stability. In order to ensure the safety of the driver and give full play to the performance of the racing car, the frame has six considerations when performing finite element analysis: static load working condition, steering working condition, braking working condition, bending rigidity, torsional rigidity and six-order mode.

And (3) performing shell structure modeling on the applicable substitute vehicle frame by using the CATIA in combination with rules, human-machine engineering and arrangement forms of all assemblies. And (4) checking the strength, the rigidity and the natural frequency of the frame through the combined simulation of the Workbench and the ACP module to obtain feedback.

3.1 application to substitute vehicle frame Shell modeling, Unit partitioning, and ply design

3.2 vehicle frame stiffness calculation analysis

3.2.1 torsional stiffness analysis

The torsional rigidity of the frame determines the ability of the frame to resist deformation when the vehicle is on an uneven road or in a sharp turn, and has great influence on the accuracy of the vehicle suspension geometry. The operation stability and the driving safety of the racing car in the running process can be ensured only after the car frame has certain torsional rigidity. In the torsional rigidity test, one end of a front (rear) suspension of the racing car is fixedly restrained, and two sides of the other suspension are respectively forced to displace 1mm in opposite directions, so that the frame torsional angle theta can be obtained:

θ＝arctan(2/L)

G＝FL/θ

theta-angle of torsion of frame °

L-mean distance between hard points of suspension, m

F-reaction force of the suspension at hard point of the vehicle, N

G-frame torsional stiffness, N.m/°

Frame torsional stiffness calculation

The method for analyzing the torsional rigidity of the frame provided by the embodiment of the invention comprises the following two steps:

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

(2) All degrees of freedom of the rear suspension hard point are constrained, opposite forced displacements of 1mm are respectively applied to the two sides of the front suspension hard point in the vertical direction, and the degrees of freedom in the X and Y directions are defined as Free, so that a second torsional rigidity is obtained.

Boundary condition

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

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

The formula for torsional stiffness is compiled in the EXCLE table:

TABLE 7 torsional rigidity calculation results

Theta-angle of torsion of frame °

L-mean distance between hard points of suspension, m

F-reaction force of bearing at hard point of suspension, N

G-frame torsional stiffness, N.m/°

In the same way, the front suspension is fixed, and the vertical direction of the rear suspension is applied with opposite displacement of 1mm to obtain:

from FIG. 38, values are taken into the EXCLE table:

TABLE 8 torsional rigidity calculation results

θ -frame twist angle, °;

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

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

g is the torsional stiffness of the frame, N.m/°.

Therefore, the torsional rigidity of the whole automobile is G ═ 4663+2951.5)/2 ═ 3807N/°, from the view of autoclave molding to replace a frame, the torsional rigidity is generally 3000-.

3.2.2 frame bending stiffness calculation

The bending rigidity of the frame refers to the degree of flexural deformation of the frame when the frame bears vertical load, and the magnitude of the bending rigidity influences the wheelbase of the racing car, wheel positioning parameters of the vehicle and the steering stability of the whole racing car. The racing car frame structure is symmetrical about a longitudinal middle plane, the racing car frame can be regarded as a simply supported beam, a fulcrum is a connecting point of a front suspension and a rear suspension and the racing car 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 the bending stiffness working condition, restraining all the displacement freedom degrees of the hard point of the front suspension, and releasing the displacement freedom degree of the rear suspension in the X direction. A concentrated force is applied vertically downward on the deck plate to bend the frame.

Boundary condition

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 behavior suspension constraints

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 by the figure 40 is introduced into an EXCLE table:

TABLE 10 frame bending stiffness calculation results

The steel tube frame of the Dongfeng HUAT motorcade racing car is 99307 N.m²And other school alternative frames, with a bending stiffness of 523186N m²The requirements of formula racing of college students are met far more.

3.2.3 static load operating mode

When the vehicle is in a static state, the replacement frame mainly bears the gravity from a driver, an engine and other components, and the frame has enough strength and rigidity to resist the deformation of external force within the safe service life.

Simplifying the CAE model of the alternative frame, neglecting the smaller force existing on the alternative frame, and under the condition that the vehicle is static, the alternative frame mainly bears the gravity from people and a power system; when the racing car runs, the car frame bears the dead weight from a power system and a person, and is also stressed by a suspension system and a car body system, and the specific stress value refers to the following table:

TABLE 11 stress situation

Boundary condition

The CAE model is simplified, the weight of a person is 700N, the weight of a power system is 700N, uniformly distributed loads are applied to corresponding parts of the alternative frame, and the hard points of the alternative frame are constrained as follows:

TABLE 12 suspension constraints under static load conditions

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

3.2.4 brake Condition

Racing cars are required to accelerate and decelerate continuously during the race, and in some emergency situations it is necessary to be able to lock four wheels and only to participate in the race through a braking test. Therefore, during the braking process of the racing car, the alternative frame is subjected to the braking force of the braking system opposite to the driving direction, and the braking deceleration of 1.3G can be generated at most.

When the alternative vehicle frame carries people, the mass of the whole vehicle is about 300KG, and the coefficient of the dynamic load is 1.5, then

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 constrained, braking force is applied to the hard points on two sides of the rear suspension, the average braking force borne by each side of a rear shaft is 1576.6N, in addition, the human gravity 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 loads are applied to corresponding positions of the alternative frame, and the boundary conditions of the alternative frame are constrained as follows:

TABLE 13 brake Condition suspension constraints

From the results, the maximum deformation amount was 0.46 mm; the maximum principal stress still appears on the 4130 steel pipe according to the acquirable maximum principal stress, the maximum principal stress is 167MPa, which is less than the material yield limit 700MPa, and the requirement is met.

3.2.5 cornering conditions

When the racing car is used for racing, a lot of pile winding tests are carried out on the racing track, so that some acceleration and deceleration operations exist while steering is carried out, and the alternative frame is subjected to lateral force and longitudinal force. Because the racing car is in a racing race, the running speed is high, the fastest speed is also strived for in a curve, and the car can be subjected to a great centrifugal force, the lateral acceleration of the alternative frame is 1.3 gravity accelerations, the longitudinal deceleration of the alternative frame is 1.3 gravity accelerations, and the dynamic load coefficient is 1.5 in view of the road surface condition of the Xiangyang dream equation racing track.

Lateral force:

F＝kma1＝1.5*300*(1.3*9.8)＝5733N

the front axle load is 45% of the total mass, and the single-side lateral force of the front axle is as follows:

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, then the rear axle unilateral braking force is:

F＝5733*55％*0.5＝1576.6N

a lateral force 1289.9N is applied to the right front suspension, and a lateral force 1576.6N is applied to the right rear suspension, and a longitudinal force 1576.6N is applied to the right rear suspension. The human gravity is 700N, the power system gravity is 700N, the force of the front shock absorber is 1800N, and the force of the rear shock absorber is 2300N, and the loads are uniformly distributed and applied to the alternative frame. Hard point constraint of the frame is as follows

Meter 14 frame hard spot restraint

According to the result, the maximum stress value is 260MPa and is less than 4130 yield limit 700MPa, and the requirement is met.

3.2.6 Modal analysis

Vibration mode modal analysis is combined with structural strength and rigidity analysis; if the stress region with high strength analysis result 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 is considered to be dangerous. For this purpose, the frame is subjected to modal analysis by using ANSYS software, and the natural frequency of the frame is calculated to be staggered with the working frequency of a main vibration source of the racing car.

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

TABLE 15 sixth order modes

The modal 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 under the working state. In addition to the excitation from the load of the car itself, the car is subjected to various excitations from external sources while it is running. When the automobile runs on a normal road surface at the speed of less than 150km/h, the excitation frequency of the road surface to the automobile is less than 25 Hz; the excitation caused by wheel imbalance is mainly below 11 Hz. According to the modal analysis result, the modal natural frequency of each order of the frame is higher than the external main excitation frequency, so that the frame does not have a resonance phenomenon.

Fourthly, the method is suitable for the process research of replacing the vehicle frame

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

4.1.1 brief introduction to hand lay Process

The hand laying forming process is a process method for forming a composite material by laying a reinforcing material and resin on a mould manually or with the assistance of some machines and solidifying the resin, is the earliest and simplest process method in the field of composite materials, and still has a stable position in use due to unique technical characteristics. The raw materials of the hand-laying forming process mainly comprise a base 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 a product and improving the economic benefit.

4.1.2 preparation phase of hand lay Molding Process

The raw materials for hand lay forming mainly comprise reinforced materials, matrix materials and auxiliary materials, wherein glass fibers and carbon fibers are commonly used in the reinforced materials, and most of the reinforced materials are carbon fibers used in the alternative vehicle frame. The carbon fiber is divided into high performance and low performance, and the specific selection is determined according to the actual situation.

The prepreg is a semi-finished product which is stored for later use, is formed by impregnating resin with fibers under certain conditions, and is an intermediate product for manufacturing a composite material, but the storage requirement of the prepreg is high, and the prepreg needs to be stored at a low temperature because the chemical reaction speed is higher when the temperature of the resin is higher.

The auxiliary materials mainly comprise a curing agent, a release agent, an accelerator, a vacuum bag film, a sealing adhesive tape, an isolating film, an air-permeable felt, an adhesive absorption adhesive and the like, wherein the curing agent is a material for gelling or curing resin within a fixed time, and the release agent is generally used on the surface of a mould, so that the purpose is to better release the mould suitable for replacing a frame without damaging the replacing frame, but the existing motorcade adopts violent demoulding and adopts a disposable mould method.

4.1.3 introduction to the mold

The mold function is very huge in the manufacturing process of the alternative vehicle frame, the mold directly influences the quality of the alternative vehicle frame, the design of the mold is different for different alternative vehicle frames, and factors needing to be considered in the process are also many, such as cost, enough strength, rigidity, heat resistance, demolding mode and the like.

The die can be generally divided into a female die, a male die, a matched die 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 matched die is the combination of the female die and the male die, the combined die considers more factors, and the structure is more complex.

The die for replacing the frame is built by a density plate, the cost conditions of various motorcades are different, so that the materials of the die are different, and the processing mode of the die is mainly a milling machine.

4.1.4 course of the Process

1. The surface of the mould is first treated, including cleaning and surface flatness, and since the milled surface may not be particularly flat, special treatment is applied at this point, and after the mould has been treated, application of a release agent to the mould can begin with the lay-up of prepreg.

2. Cutting the prepreg according to the designed laying structure, laying according to the required thickness and laying angle, laying one layer by one layer in the process, if two protective films are arranged on the surface of the prepreg, removing one layer firstly, and then removing the next layer after laying. When the layers are laid, the layers are compacted as much as possible, and little air is generated between the layers to avoid wrinkles. The alternative frame is generally made of male molds, one male mold is made into two halves, carbon fiber dry cloth and resin are used as layers on the male mold, then the male mold enters a high-temperature curing furnace for curing, and then the male mold is demolded. Then, the manufactured part is made into a female die to manufacture the alternative frame. The female die is also an upper part and a lower part, and then the female die and the upper part and the lower part are combined together and then layered.

3. After the lay-up is complete, the auxiliary material is added and sealed with a vacuum bag. And a breathable felt is placed on the edge of the whole paving layer to ensure that an air inlet and exhaust channel is formed for the volatilization of the gas and the resin material in the breathable felt. A non-porous isolating film is laid on the surface of the part for separating the substitute frame from the auxiliary material, and the isolating film is longer at least to the middle position of the air-permeable felt. An air felt is also laid on top of the non-porous separator, and this air felt is laid to the bottom edge of the air felt, wrapping all the replacement vehicle frames and the auxiliary materials together.

4. And packaging the vacuum bag, wherein the sealing rubber strip is adhered to the sealing bag and the vacuum bag at the same time, all auxiliary materials are covered by the sealing rubber strip, and a gas channel cannot be left under the vacuum bag, so that the vacuum bag is as flat as possible.

5. After the vacuum bag is sealed, the vacuum nozzle is pressed and then vacuumized.

6. And finally, vacuumizing, checking the tightness, heating and pressurizing for curing, and finally demolding to obtain the required alternative frame, wherein the process is generally finished by professional personnel.

7. Characteristics of autoclave molding

Among many molding processes, autoclave molding is one of many fleet choices because of the wide application range, uniform pressure and temperature, simple mold, etc., but some of the disadvantages, such as high cost, etc.

4.2 cutting and folding method for making substitute vehicle frame

4.2.1 brief introduction

The method of hand lay-up and autoclave manufacturing for the replacement frame has been introduced, which requires high cost, great process difficulty, high requirements for configuration resources, and cutting and folding. This method has been used in the production of actual replacement frames in many fleets of vehicles in europe, for example the oxford brueckea fleet, known in the uk, to make replacement frames for their own fleets.

4.2.2 introduction to the cutting and folding method steps

1. Firstly, preparing a composite material sandwich structure panel with a whole block of honeycomb aluminum as a sandwich layer and carbon fiber as a panel.

2. Cutting off the carbon fiber composite material plates of the parts needing to be folded and other redundant carbon fiber composite material plates by using a numerical control machine, and then ensuring the integrity of the whole plates as much as possible when redundant exploration text composite material sandwich panels are removed

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 material panel;

theta is a folding angle;

3. the next step is the 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. At this time, the composite material plate needs to be folded into the shape of the designed alternative vehicle frame by manufacturing a bracket. The joints and the folds need to be fixed by adhesive, and the joints and the folds can be reinforced by aluminum plates or carbon fiber plates after the adhesive is cured. If a gap still exists, the gap is filled with adhesive and additional finishing or joining work may be required. The difficulty of folding the cut sheet into the designed alternative frame in this step is very high because the composite sheet is almost close to the composite sheet after folding, and the rigidity of the carbon fiber is very high, which greatly increases the difficulty of folding. .

At present, most of the alternative vehicle frames manufactured by cutting and folding are manufactured by adopting a structure that the front surface and the back surface of the plate are made of two layers of carbon fibers, and the middle sandwich layer is made of honeycomb aluminum, but the selection of the composite material plate depends on the mass of the carbon fibers and the torsional rigidity set by the design. In the process, the formula racer will invest a great deal of time, labor and materials to replace the frame manufacturing, but the manufacturing process seems to be a good choice for training the practical ability of the college students and matching the self with the development of the era. In the process, a person also knows that the motorcade alternative frame is provided with an aluminum skin on the outer part and a carbon fiber surface layer on the inner part, and thus the aluminum skin is also a good choice as a plate surface. For the process of manufacturing the alternative frame by using a cutting and folding method, the precision of the bracket determines the precision of the alternative frame, but the precision of the alternative frame indirectly determines the positioning precision of each part, and certainly, factors such as the ground clearance and the mass center position of the whole vehicle can be influenced. The design and production of the bracket holder is therefore also very important, in which respect much effort is required to repeat the measurements and corrections in order to ensure the accuracy of the alternative frame made by the cutting and folding method.

4. Finally, in the aspect of the accuracy of the hard points of the suspension, the mode of combining the existing positioning mode of the Dongfeng HUAT fleet with the monomer shell manufactured by the cutting and folding modes can be adopted, the suspension positioning is positioned by manufacturing a clamp, the corresponding distance is reserved between the connecting point of the suspension and the positioning point of the alternative frame, and the error generated by the alternative frame in the folding process is adjusted by adjusting the distance. In summary, the alternative frame manufactured by cutting and folding is more similar to the manufacturing mode of the existing frame of the east wind HUAT fleet, but the steel pipe truss is replaced by the composite material plate.

In the description of the present invention, "a plurality" means two or more unless otherwise specified; the terms "upper", "lower", "left", "right", "inner", "outer", "front", "rear", "head", "tail", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are only for convenience in describing and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, 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 above description is only for the purpose of illustrating the present invention and the appended claims are not to be construed as limiting the scope of the invention, which is intended to cover all modifications, equivalents and improvements that are within the spirit and scope of the invention as defined by the appended claims.

Claims

1. A three-dimensional modeling-based alternative vehicle frame simulation method is characterized by comprising the following steps:

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

2. The three-dimensional modeling based alternative frame simulation method according to claim 1, wherein the three-dimensional modeling based alternative frame simulation method specifically comprises:

modeling applicable substitute vehicle frames by utilizing three-dimensional modeling software;

carrying out design analysis on the layering angle and the layering thickness of the model by using software;

testing, verifying and analyzing the result of the elastic constant of the carbon fiber composite laminate;

Performing theoretical analysis on the substituted frame under various limit working conditions by using software;

the specific process of replacing the frame by the carbon fiber composite material is analyzed.

3. The three-dimensional modeling based alternative frame simulation method according to claim 1, wherein the carbon fiber composite laminate is formed by taking a carbon fiber composite material as a panel and taking a composite material plate made of honeycomb aluminum as a sandwich material in the middle;

the method for testing the elastic constant of the carbon fiber composite laminate 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 triangular plate, and clamping the sample tightly;

s3, adjusting the position of the cross beam of the mechanical testing machine, and sequentially connecting the strain gauge lead and the strain gauge;

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

s5, processing the collected data to obtain transverse, longitudinal and normal tensile moduli E₁、E₂、E₃Poisson ratio μ₁₂、μ₁₃、μ₂₃Shear modulus G₁₂、G₁₃、G₂₃，E₂＝E₃，G₁₂＝G₁₃，μ₁₂＝μ₁₃；

E₁And mu₁₂The calculation formula is as follows:

in the formula: b is the width of the test piece; t is the thickness; p₁Is a 1-direction load;₁，₂are respectively 1,2 A strain in a direction;

calculation of G₁₂The formula of (1) is as follows:

E₂is the elastic constant of a 90 DEG sample piece;

calculation of E₄₅The formula of (1) is as follows:

shear modulus G₂₃The following formula

Wherein f is_GObtained by quadratic equation

A＝3c₁c₂(1-V_f)²V_f+(c₂η₀-c₃V_f ³)(c₁η₀V_f-c₄)

C＝3c₁c₂(1-V_f)²V_f+(c₂+c₃V_f ³)(c₁V_f+c₄)

η₀＝3-4ν₀，η₁＝3-4ν₁

ν₀Poise of the substrateThe bulk ratio;

ν₁-the poisson's ratio of the fibres;

V_f-the volume fraction of the fibres;

G₀-shear modulus of the matrix;

G₁-the shear modulus of the fiber;

poisson ratio v₂₃Obtained from the following equation:

4. the three-dimensional modeling based alternative frame simulation method of claim 1, wherein the specific method for analyzing the ply angle by using ANSYS comprises the following steps:

s11, defining the laying direction and the laying sequence of the single layer of the laminated plate and the marks of the composite laminated plate, and selecting the main axis direction of the structure as a reference coordinate system;

s12, establishing a 150X50X2mm laminated plate in ANSYY, wherein the thickness of each layer is 0.5mm, the thickness of each layer is four layers, then fixing four sides of the laminated plate, and loading 1000N uniform loads on the surface;

s13, constructing bending rigidity simulation displacement cloud charts of the laminated plate with different stacking angles;

when the thickness of the layer is analyzed by ANSYS, the rigidity simulation of the thickness of the layer is carried out by adopting 0 degree/90 degree interwoven fabric, which specifically comprises the following steps:

s21, establishing a 500-275 rectangular model, selecting unidirectional tapes of T _700 as composite material panels, arranging layers, setting each layer to be 0.4mm, 2 layers of T _700 single layers and 90 degrees of each other, selecting honeycomb aluminum with the thickness of 15mm as sandwich layers, and setting the layer angle to be 90 degrees of each other;

S22, layering is carried out through the workbench _ ACP module, the layering angles are the same, the number of layering layers is changed, and bending rigidity is calculated;

5. The three-dimensional modeling based alternative frame simulation method according to claim 1, wherein during analysis under various working conditions, static load working conditions, steering working conditions, braking working conditions, bending stiffness, torsional stiffness and six-order modes are analyzed;

frame torsion angle θ:

θ＝arctan(2/L)；

G＝FL/θ；

Theta-frame torsion angle;

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

f is the bearing reaction force at the hard point of the vehicle suspension, N;

g-frame torsional stiffness, N.m/°;

6. The three-dimensional modeling based alternative frame simulation method according to claim 1, wherein the specific process flow of the carbon fiber composite material suitable for the alternative frame comprises a process method combining hand laying forming and autoclave and a cutting and folding method;

(3) after laying, adding auxiliary materials, packaging by using a vacuum bag, sticking the auxiliary materials to the vacuum bag by using a sealing adhesive tape while sticking the sealing adhesive tape to the sealing bag, and covering all the auxiliary materials by using the sealing adhesive tape;

(5) vacuumizing, checking the tightness, heating and pressurizing for curing, and finally demolding to obtain the alternative frame;

the cutting and folding method specifically comprises the following steps:

7. The three-dimensional modeling based alternative frame simulation method according to claim 6, wherein in the step 2) of the cutting and folding method,

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

d is the thickness of the composite material panel;

theta is the folding angle.

8. The three-dimensional modeling based surrogate frame simulation system for the three-dimensional modeling based surrogate frame simulation method according to any one of claims 1-7, wherein the three-dimensional modeling based surrogate frame simulation system comprises:

9. A computer device, characterized in that the computer device comprises a memory and a processor, the memory storing a computer program which, when executed by the processor, causes the processor to carry out the steps of:

10. A computer-readable storage medium storing a computer program which, when executed by a processor, causes the processor to perform the steps of: