CN107215394B - Front-mounted rear-drive truss type sports car frame and car body structure design method - Google Patents
Front-mounted rear-drive truss type sports car frame and car body structure design method Download PDFInfo
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- CN107215394B CN107215394B CN201710250772.4A CN201710250772A CN107215394B CN 107215394 B CN107215394 B CN 107215394B CN 201710250772 A CN201710250772 A CN 201710250772A CN 107215394 B CN107215394 B CN 107215394B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D21/00—Understructures, i.e. chassis frame on which a vehicle body may be mounted
- B62D21/08—Understructures, i.e. chassis frame on which a vehicle body may be mounted built up with interlaced cross members
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/10—Geometric CAD
- G06F30/15—Vehicle, aircraft or watercraft design
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/40—Engine management systems
Abstract
The invention relates to a front-mounted rear-drive truss type sports car frame and a car body structure design method. In the structural design process, a local structure is obtained through analysis of three single working conditions of bending, torsion and turning, a main structure is obtained according to multi-working condition analysis, the main structure is complementary with the local structure, a main bearing path of the structure is obtained, and a vehicle body structure is designed based on the main bearing path. The whole body of the vehicle forms a space frame structure which is balanced to bear, the comprehensive utilization rate of materials is greatly improved, and meanwhile, the thickness of the structure is more reasonable through a size optimization analysis technology, and the structure quality is further reduced.
Description
Technical Field
The invention relates to a front-mounted rear-drive truss type sports car frame and a car body structure design method, in particular to a truss type sports car body structure design method suitable for front-mounted rear-drive of an engine; structural optimization is a main mode for improving the overall performance of the frame, and the aim of balanced bearing of the truss type vehicle body is achieved through a reasonable design of a load transmission path.
Background
The frame is an assembly and bearing matrix of the whole vehicle, and the function of the frame is to support and connect various assemblies and parts of the frame and bear various forces and moments transmitted to the frame, so that the frame structure needs to have enough rigidity and strength to ensure good smoothness and enough reliability, and the frame with good balanced bearing capacity can ensure that the whole frame cannot lose normal working capacity under complex working conditions, and cannot deform and crack during use;
the traditional frame structure design has a certain blindness, and a designer generally designs the product structure by experience and imagination, so that the performance, reliability, manufacturability and the like of the product are difficult to accurately consider. After the design of the vehicle body frame structure is initially completed, finite element analysis is carried out on the vehicle body structure, whether the parameters of the vehicle body structure meet the requirements of the overall performance of the whole vehicle is verified, and meanwhile, weak links found in the analysis are improved. However, only the improvement adjustments to the local area can be made by the designer. The method is completely dependent on the experience of engineers, and a large amount of experiments are needed, so that the period is long and the cost is high;
meanwhile, most truss frames have the problems of overlarge overall quality due to unreasonable design and overlarge or undersize local rigidity of the frames and uneven deformation due to excessive and excessive design units, so that the load born by the vehicles under various working conditions cannot be uniformly transferred to the structures of other parts of the frames in the running process of the vehicles, and the performance of the whole vehicle is affected;
disclosure of Invention
The invention provides a front-mounted rear-drive truss type sports car frame and a car body structure design method. According to the method, the structure is optimally designed, the weight ratios of different analysis loads are distributed according to the importance degree of working conditions, and the optimal structure under the combined working conditions of bending, torsion and turning is determined, so that the side wall structure is complementary with the bottom frame structure, the whole structure of the vehicle body is complementary with the partial structure of the vehicle body, the bending load bearing structural member, the torsion load bearing member and the lateral load bearing member are complementary, and the truss type vehicle frame with reasonable structure and balanced bearing is obtained. The method can effectively solve the problems of overlarge overall mass and uneven frame rigidity caused by empirical idea in the design process of the existing truss type vehicle body structure.
The invention is realized by the following technical scheme, and the following description is taken in conjunction with the accompanying drawings:
the utility model provides a leading rear-drive truss type sports car frame, includes four girders 1, four main crossbeams 2, many sloping 3, roll-proof frame 4, roll-proof frame bracing 5 and preceding baffle 6 welding form, four girders 1 are two-to-two symmetrical along the frame longitudinal center line, and every girder 1 is the curved beam structure that has certain radian, goes up girder 1a and buckles downwards at the frame rear portion, and lower girder 1b is upwards buckled at the rear portion, welds together at the frame rear portion, the front end of going up girder 1a and lower girder 1b passes through preceding baffle 6 and connects, roll-proof frame 4 is fixed on last girder 1a, and through roll-proof frame bracing 5 support is fixed, girder 1 constitutes the wide form in front of front portion and back with main crossbeam 2.
The oblique beams 3 are connected with the main beams 1 at the same side in a butt joint way to form a plurality of triangular structures, and the triangular structures are arranged from the front part of the frame to the rear part of the frame in a dense-sparse-dense way according to the arrangement mode of the engine, the seat and the person.
The front partition plate 6 is composed of four closed steel pipes including a front lower cross beam 2a and two reinforcing beams 7, the four closed steel pipes form a plane rectangular structure, the reinforcing beams 7 form three triangular structures, the two reinforcing beams 7 are equal in size, and the lower ends of the two reinforcing beams are welded in the middle of the front lower cross beam 2a in a butt joint mode.
The middle and rear part of the frame also comprises two seat mounting beams 8 and two second auxiliary main beams 9 above the two seat mounting beams, and the two beams on the same side are connected through a plurality of triangle structures formed by butt joint of a plurality of inclined beams 3.
A front-mounted rear-drive truss type sports car body structure design method mainly comprises the following steps:
(1) Determining a design space according to the arrangement form and the overall size of each assembly of the vehicle, simplifying an actual model, obtaining the overall appearance characteristic of the vehicle frame, taking the overall appearance characteristic as a main analysis object, and determining the load distribution condition under three single working conditions of bending, torsion and turning;
(2) Respectively carrying out structural optimization analysis on the frame model established in the step (1) under three single working conditions of bending, torsion and turning to obtain main bearing structures under the three single working conditions;
(3) The method of pairing comparison is adopted to compare three single working conditions pairwise to obtain the importance ratio of each working condition, and the optimal weight ratio of the three single working conditions of bending, torsion and turning and the deformation condition of the three single working conditions are respectively obtained;
(4) According to the weight ratio of the three single working conditions obtained in the step (3), carrying out multi-working-condition structural optimization on the frame model, and analyzing to obtain the main structure of the truss type frame;
(5) And (3) according to the optimal main structure under the multiple working conditions obtained in the step (4), locally improving the result obtained in the step (2), namely obtaining the main structure according to the multiple working conditions analysis, obtaining the local structure according to the single working condition analysis, and obtaining the initial frame model by complementing the main structure and the local structure.
(6) And (3) comprehensively considering the processing manufacturability on the basis of the improved result in the step (5), adding and subtracting the number of the rod pieces properly while ensuring enough bearing capacity to form an improved model of the vehicle frame, carrying out strength analysis on the vehicle body structure after structure optimization, carrying out necessary modification on the local structure according to the analysis result, judging whether the strength condition is met or not according to dangerous stress, and defining the dangerous stress of each point of the structure as a full-load bending working condition, a left front wheel suspension working condition and a turning working condition. Repeating the steps (2) - (6) until the structure meets the requirement of strength and rigidity;
the implementation of the simplified model in the step (1) is as follows: extracting main parameters of the appearance of the vehicle, including the length, width, height, wheelbase, track width and the like of the vehicle as design parameters, reducing the rounded corner transition of the curved surface of the vehicle body, adopting a simple plane to replace the curved surface, and ensuring that the truss type vehicle frame does not form a closed space, so that no design surface is closed above the passengers;
the implementation of the load distribution conditions under three single conditions of bending, torsion and turning in the step (1) is specifically shown as follows: in the running process of the vehicle, the static load and the dynamic load are mainly borne, in the optimizing process, the static load such as an engine, a seat, a person, a steering system and the like is loaded on a vehicle body model in a mode of centralizing or uniformly distributing the load according to specific mass parameters and mass center position coordinates of the static load, under a bending working condition, the deformation of the vehicle frame is mainly in a vertical direction, the borne load needs to be multiplied by a certain dynamic load coefficient, and the dynamic load coefficient is taken to be 2.0; in the torsion working condition, the load born by the frame is basically consistent with the bending working condition in the plumb direction, and the vertical forces with the same magnitude and opposite directions are loaded at the left and right front suspension supports; in a turning working condition, the load born by the frame is basically consistent with a bending working condition in the vertical direction, and a transverse acceleration is applied to the mass center of the vehicle body framework to simulate the transverse load, wherein the size of the transverse acceleration is 1g;
the implementation of the main bearing structure obtained in the step (2) is as follows: applying load boundary conditions under three single working conditions determined according to the step (1) to a vehicle body structure model, and obtaining a clear structure by adjusting penalty factors, namely a main bearing structure respectively obtained under the action of the three working conditions;
the determination of the reasonable weight ratio in the step (3) is realized and is embodied as follows: according to decision theory, adopting a pairing comparison method for three working conditions of bending, torsion and turning, distributing different weight ratios a1, a2 and a3. according to the importance degree of the working conditions, wherein the importance ratio between the working conditions is compared in pairs, namely, the importance ratio of the working condition 1 is a1, the importance ratio of the working condition 2 is a2, the importance ratio of the working condition 1 to the working condition 2 is a1/a2, if n single working conditions exist, n (n-1)/2 ratios are obtained, and the pairing comparison matrix is given according to the importance ratio only by selecting the three most classical working conditions
CR＝CI/RI
CI＝(λmax-n)/(n-1)
Wherein N is the number of working conditions and is 3, CI is a consistency index, RI is the maximum eigenvalue of a random generation matrix, lambda max is N, a consistency ratio CR is derived according to a consistency judgment criterion of a pairing comparison matrix, and if CR is smaller than 0.1, the consistency of the matrix can be judged to be acceptable; otherwise, the calculation should be re-assumed to be analyzed again until satisfied. The corresponding feature vector is the corresponding weight ratio of 3 working conditions;
the multi-working condition structure optimization in the step (4) is realized, and the main structure of the frame is obtained by the following concrete steps: according to the three single-working-condition weight ratios obtained in the step (2), the topological optimization condition under multiple working conditions is converted into a single-target optimization problem, the weighted flexibility of the objective function being 3 working conditions is minimum, and symmetrical constraint is needed when the vehicle body is subjected to topological optimization, so that the optimization structure is bilaterally symmetrical. And the definition of the frame structure is changed by adjusting the magnitude of the punishment factors, so that the main bearing structure of the frame is obtained. And finally converting the structure into an IGES curved surface, leading the IGES curved surface into CATIA software, and drawing a frame model.
The implementation of the local improvement of the optimal main structure under multiple working conditions in the step (5) is specifically shown as follows: the frame main structure is obtained by carrying out multi-working condition analysis on the frame model, the frame of the main structure at the moment has the problem of unclear boundary, and the single-working condition bearing structure obtained in the step (2) can help understand the structural performance of the frame, so that the obtained structure is clearer, and the defect of unclear local boundary of the main structure can be overcome. The distribution mode of the rod pieces is reasonably adjusted by comprehensively comparing the main structure with the single-working-condition structure, and finally, a space frame structure with good uniform bearing capacity is formed;
the invention has the beneficial effects that:
according to the method, a main structure is obtained through multi-working condition analysis, a local structure is obtained through single working condition analysis, the main structure and the local structure are complementary to form a space frame structure with complementary performances, the bending rigidity and the torsional rigidity of the frame are enhanced, the overall stress condition is improved, and the load born by the vehicle body can be uniformly transmitted to the main structure, so that the truss type frame with reasonable structure, few design units and easy processing and balanced bearing is obtained;
drawings
FIG. 1 is a top view of the bottom skeleton of the vehicle body skeleton of the present invention;
FIG. 2 is a front view of a left side frame of the body frame of the present invention;
FIG. 3 is a front view of the present invention;
FIG. 4 is a top view of the present invention;
FIG. 5 is an axial view of the present invention;
FIG. 6 is a side view of the present invention;
in the figure: 1. the main beams 1a, the upper main beam 1b, the lower main beam 2, the main beam 2a, the front main lower beam 3, the inclined beam 4, the anti-rolling frame 5, the anti-rolling frame inclined strut 6, the front partition 7, the reinforcement beam 8, the second auxiliary main beam 9 and the seat mounting beam
Detailed Description
Referring to fig. 1, the running car frame of the invention adopts a main beam 1 and a main beam 2 as bearing structures. The main beam 1 is of a bent beam structure with a certain radian, the main beam 1 and the main beam 2 form a front narrow rear wide form in top view, the upper main beam 1a is bent downwards at the rear part of the frame in side view, the lower main beam 1b is bent upwards at the rear part of the frame, the upper main beam 1a and the lower main beam 1b are welded together at the rear part of the frame, and the structure is simple and compact, has better integrity and is beneficial to modeling of the frame. The main beam 1, the main beam 2 and the main bearing structure are round steel pipes with larger diameters, so that the bearing capacity is improved.
In this embodiment, the oblique beams 3 form a plurality of triangular structures by butt joint between the main beams 1 on the same side, and the triangular structures are arranged from the front part of the frame to the rear part of the frame according to the arrangement mode of the engine, the seat and the person. The triangle structure has better stability, large rigidity and difficult deformation, and can uniformly transmit the impact force born by the frame to other parts of the frame, thereby improving the uniform bearing capacity and solving the problem of overlarge local rigidity.
In this embodiment, the front bulkhead 6 is composed of four closed steel pipes and two reinforcing beams 7. The four closed steel pipes form a plane rectangular structure, the two reinforcing beams 7 form three triangular structures, the two reinforcing beams 7 are equal in size, the lower ends of the two reinforcing beams are welded in the middle of the front main lower cross beam 2a in a butt joint mode, the four closed steel pipes are longitudinally symmetrically arranged, and the bearing capacity transmission and distribution are more reasonable.
In this embodiment, the seat mounting beam 8 at the rear part of the frame and the second auxiliary main beam 9 above the seat mounting beam have the function of isolating the transmission shaft besides being used for seat mounting, and a plurality of triangular structures formed by butt joint of the inclined beams 3 exist between the two beams at the same side, so that the load is balanced in cooperation with the stress.
In this embodiment, all structures of the frame have longitudinal symmetrical arrangement, and the design unit is few, and the triangle structure is many, has structural strength good, and bearing capacity is strong, and the appearance is pleasing to the eye.
In combination with the attached drawings, the design scheme of the front-mounted rear-drive truss type sports car body structure is taken as an example, and the design process comprises the following steps:
(1) And determining a design space according to the arrangement form and the overall size of each assembly of the vehicle, extracting main parameters of the appearance of the vehicle, and obtaining the appearance characteristics of the whole frame. The front-mounted rear-drive truss type sports car body with the two seats has the total car length of 3050mm, the cabin width of 1150mm, the engine cabin width of 610mm, the car height of 485mm and the wheelbase of 2430mm. In order to simplify an actual model, a complex curved surface is converted into a plane so as to reduce curved surface transition, and a closed space is not formed on the truss type frame, so that a closed design surface is not needed above a passenger, and the vehicle body model is taken as a main analysis object to determine the load distribution condition under three single conditions of bending, torsion and turning. In the running process of the vehicle, the static load and the dynamic load are mainly borne, in the optimizing process, the static load of an engine, a seat, a person, a steering system and the like is loaded on a vehicle body model in a centralized or uniformly distributed load mode according to specific mass parameters and mass center position coordinates of the static load, and the seat, the person, an oil tank, a steering gear and the like are directly connected with a vehicle frame, so that the vertical load of the parts is directly acted on the corresponding position of the vehicle frame to meet the actual situation, and the vertical load is distributed to the simulation of corresponding nodes for each working condition in a small-area uniformly distributed load mode; in the case of an engine, the drive shaft and the like should be loaded on the vehicle body in a concentrated load manner because of the relatively concentrated points of action. The gravity of the engine is 3000N, the gravity of the transmission shaft is 1500N, the gravity of the seat and the gravity of the person 6000N, the oil tank 650N and the steering gear 240N; the bending working condition is simulated, the four wheels are grounded at a constant speed and linearly run when the vehicle is fully loaded, under the working condition, the deformation of the vehicle frame is mainly in the vertical direction, the born load needs to be multiplied by a certain dynamic load coefficient, and the prior study shows that the maximum dynamic load coefficient is not more than 2.5 when the vehicle frame is simulated under the bending working condition, so that the dynamic load coefficient is taken to be 2.0; the torsion working condition is used for simulating the situation that the front wheels are deformed due to the action of different torsion forces transmitted by the ground during the running process of the vehicle, and in the torsion working condition, the load born by the vehicle frame is basically consistent with the bending working condition in the vertical direction, and the vertical forces with the same magnitude and opposite directions are loaded at the supporting positions of the left and right front suspensions; the turning working condition is the response condition of the vehicle body framework under the comprehensive action of the transverse inertia force and the vertical load when the vehicle turns, the load born by the vehicle frame is basically consistent with the bending working condition in the vertical direction, the transverse acceleration is applied to the center of mass of the vehicle body framework to simulate the transverse load, and the transverse acceleration at the moment is determined to be 1g according to the maximum lateral load of a steady-state turning test in consideration of the fierce driving of the racing vehicle;
(2) Applying load boundary conditions under three single working conditions determined according to the step (1) to a vehicle body structure model, and obtaining a clear structure by adjusting penalty factors, namely a main bearing structure respectively obtained under the action of the three working conditions; through analysis of the three structures, load transmission paths of the frame under three working conditions of bending, torsion and turning are respectively obtained, and modification of the unclear local boundary of the main structure in the later period is facilitated;
(3) According to the importance degree of working condition, different weight ratios are distributed, a pairing comparison method is adopted, the importance degree ratio between two working conditions is compared, namely, the importance degree weight ratio of the working condition 1 is a1, the importance degree weight ratio of the working condition 2 is a2, the importance ratio of the working condition 1 to the working condition 2 is a1/a2, if n single working conditions exist, n (n-1)/2 ratios are obtained, the method only selects the three most classical working conditions, namely, bending, torsion and turning, the importance degree weight ratios of the three working conditions are a1, a2 and a3 respectively, the importance ratio a1/a2 is assumed to be 3, a1/a3 is assumed to be 7, a2/a3 is assumed to be 5, and the following pairing comparison matrix is given
CR＝CI/RI CI＝(λmax-n)/(n-1)
CI is a consistency index, each judgment matrix can derive a consistency ratio CR, and if the value is smaller than 0.1, the consistency of the matrix can be judged to be acceptable; otherwise, the calculation should be re-assumed to be analyzed again until satisfied. RI is the consistency index of the random generation matrix, and the corresponding feature vector is the corresponding weight ratio of 3 working conditions. In the embodiment, λmax= 3.0649, cr=0.0559 <0.1, so that the consistency is acceptable, and the weight ratio of the three working conditions of bending, torsion and turning is 0.9140, 0.3928 and 0.1013;
according to the weight ratio of the three single working conditions obtained in the step (3), carrying out multi-working-condition structural optimization on the frame model, and analyzing to obtain the main structure of the truss type frame; the topological optimization condition under multiple working conditions is converted into a single-objective optimization problem, the weighted flexibility of an objective function is minimum for 3 working conditions, and symmetrical constraint is needed when the topological optimization is carried out on the vehicle body, so that the final optimization structure is bilaterally symmetrical. And the definition of the frame structure is changed by adjusting the magnitude of the punishment factors, so that the main bearing structure of the frame is obtained.
(5) The main frame structure is obtained through analyzing the combined working condition determined by the optimal weight ratio, the frame structure obtained through analysis under the multi-working condition is locally improved according to the result obtained in the step (2), the comprehensive comparison is carried out, the distribution mode of the rods is reasonably adjusted, a triangular structure with alternate densities between the main beams is adopted, so that the strong side at the bottom of the frame is complemented with the side wall (front side wall) with weaker bearing capacity, the weak side is complemented with the side wall (rear side wall) with stronger bearing capacity, and a uniformly-bearing 'dense-sparse-dense' space frame structure is formed at the side wall part; the bottom framework is shown in figure 1, and the side wall framework is shown in figure 2; the main structure is obtained according to multi-working condition analysis, the local structure is obtained according to single working condition analysis, the main structure and the local structure are converted into IGES curved surfaces and are led into CATIA software, and an optimized frame model with the main structure and the local structure being complementary is formed.
(6) Considering the processing manufacturability of the results obtained after optimization in step (5), it is noted in terms of functionality that: 1) The load application position and the actual stress condition of the vehicle body have certain difference during topology optimization, so that key connection points of the vehicle body are consistent with design parameters as much as possible; 2) The CATIA model of the frame must not interfere with moving parts of the vehicle, such as jumping of front and rear tires, steering of front wheels, and movement of steering links. Attention is paid to the manufacturability: 1) The trend of the steel pipe of the truss frame should adopt a plane curve as much as possible and ensure smooth transition, so as to avoid small-radius circular arcs or excessive fold lines, otherwise, the steel pipe is excessively stretched or wrinkled, and the phenomena of stress concentration, cracks and the like are easy to occur; 2) On the premise of meeting the rigidity of the vehicle body structure, the number of the steel pipes and the thickness of the steel pipes are reduced as much as possible; 3) Welding inconvenience caused by welding a plurality of steel pipes at the same position should be avoided.
(6) And (3) carrying out strength analysis on the vehicle body structure after structure optimization, carrying out necessary modification on the local structure according to an analysis result, and judging whether the strength condition is met or not according to dangerous stress, wherein the dangerous stress of each point in the structure is defined as a full-load bending working condition, a left front wheel suspension working condition and a turning working condition. Repeating the steps (2) - (6) until the structure meets the requirement of strength and rigidity; the truss type vehicle body structure design method can improve the overall stress condition of the vehicle body, avoid the problem of uneven local rigidity, and lead the vehicle body structure to form an even bearing whole body through reasonable rigidity matching;
according to the design flow of the invention, the applicant designs a front-mounted rear-drive truss type sports car body structure scheme of a two-person seat with the total car length of 3050mm, the cabin width of 1150mm, the engine cabin width of 610mm, the car height of 485mm and the wheelbase of 2430mm, and the car body structure of the car is shown in figures 1 to 6. Checking the strength and rigidity of the designed frame, wherein the maximum stress of the designed frame is smaller than the yield limit of the material, namely the designed frame is reasonable in design;
the analysis results of the vehicle body structure properties are as follows:
the maximum stress of the full-load bending working condition of the vehicle body is as follows: 165MPa;
the maximum stress of the suspension working condition of the left wheel of the automobile body is as follows: 145MPa;
the maximum stress of the turning working condition of the vehicle body is as follows: 158.6MPa;
material (Q235) yield limit: 235 MPa.
Claims (8)
1. A front-end rear-drive truss type sports car body structure design method based on a front-end rear-drive truss type sports car frame, the frame comprising: four main beams (1), four main beams (2), a plurality of oblique beams (3), an anti-rolling frame (4), an anti-rolling frame oblique support (5) and a front partition plate (6) are welded together, the four main beams (1) are symmetrical in pairs along the longitudinal center line of a frame, each main beam (1) is of a bent beam structure with a certain radian, an upper main beam (1 a) is bent downwards at the rear part of the frame, a lower main beam (1 b) is bent upwards at the rear part of the frame, the rear parts of the frames are welded together, the front ends of the upper main beam (1 a) and the lower main beam (1 b) are connected through the front partition plate (6), the anti-rolling frame (4) is fixed on the upper main beam (1 a) and is supported and fixed through the anti-rolling frame oblique support (5), and the main beam (1) and the main beam (2) form a front narrow rear wide structure; the design method mainly comprises the following steps:
(1) Determining a design space according to the arrangement form and the overall size of each assembly of the vehicle, simplifying an actual model, obtaining the overall appearance characteristic of the vehicle frame, taking the overall appearance characteristic as a main analysis object, and determining the load distribution condition under three single working conditions of bending, torsion and turning;
(2) Respectively carrying out structural optimization analysis on the frame model established in the step (1) under three single working conditions of bending, torsion and turning to obtain main bearing structures under the three single working conditions;
(3) The importance ratio of each working condition is obtained by comparing the three single working conditions in pairs by adopting a pairing comparison method, and the reasonable weight ratio of the three single working conditions of bending, torsion and turning and the deformation condition of the three single working conditions are respectively obtained;
the determination of the reasonable weight ratio is specifically embodied as follows: according to the decision theory, a pairing comparison method is adopted for three working conditions of bending, torsion and turning, corresponding weight ratios a1, a2 and a3. are distributed according to different importance degrees of the working conditions, the importance of the working conditions is compared in pairs, namely the importance ratio of the working condition 1 to the working condition 2 is a1/a2, if n single working conditions exist, n (n-1)/2 ratios are obtained, and the pairing comparison matrix is given according to the importance ratio only by selecting the three most classical working conditions
CR＝CI/RI
CI＝(λmax-n)/(n-1)
Wherein N is the number of working conditions and is 3, CI is a consistency index, RI is the maximum eigenvalue of a random generation matrix, lambda max is N, a consistency ratio CR is derived according to a consistency judgment criterion of a pairing comparison matrix, and if CR is smaller than 0.1, the consistency of the matrix can be judged to be acceptable; otherwise, re-supposing the re-analysis calculation until the condition is met, wherein the corresponding feature vector is the weight ratio corresponding to 3 working conditions;
(4) According to the reasonable weight ratio of the three single working conditions obtained in the step (3), carrying out multi-working-condition structural optimization on the frame model, and analyzing to obtain the main structure of the truss type frame;
(5) According to the optimal main structure under the multiple working conditions obtained in the step (4), locally improving the result obtained in the step (2), namely obtaining the main structure according to multiple working conditions analysis, obtaining the local structure according to single working conditions analysis, and obtaining an initial frame model by complementing the main structure and the local structure;
(6) Comprehensively considering the processing manufacturability on the basis of the improved result in the step (5), adding and subtracting the number of rod pieces properly while ensuring enough bearing capacity to form an improved model of the frame, carrying out strength analysis on the structure-optimized vehicle body structure, carrying out necessary modification on the local structure according to the analysis result, judging whether the strength condition is met or not according to the dangerous stress, wherein the dangerous stress of each point of the structure is defined as the yield stress under the full-load bending working condition, the left front wheel suspension working condition and the turning working condition; repeating the steps (2) - (6) until the structure meets the requirement of strength and rigidity.
2. The front-end rear-drive truss type sports car body structure design method according to claim 1, wherein the method comprises the following steps:
the simplified actual model in step (1): the main parameters of the appearance of the vehicle are extracted, including the length, width, height, wheelbase, track width and the like of the vehicle are taken as design parameters, the transition of curved corners of the vehicle body is reduced, a simple plane is adopted to replace a curved surface, and a truss type frame does not form a closed space, so that no design surface is needed above the passengers to be closed.
3. The front-end rear-drive truss type sports car body structure design method according to claim 1, wherein the method comprises the following steps:
the specific expression of the load distribution conditions under three single conditions of bending, torsion and turning in the step (1) is as follows: in the running process of the vehicle, the vehicle mainly bears static load and dynamic load, and in the optimizing process, the seats, the person, the oil tank, the steering gear and the like are directly connected with the vehicle frame, so that the vertical loads of the parts directly act on the corresponding positions of the vehicle frame to meet the actual conditions, and the vertical loads are distributed to the simulation of the corresponding nodes to each working condition in a small-area uniform load distribution mode; for the engine, the transmission shaft and the like are concentrated due to the action points and are loaded on the vehicle body in a concentrated load mode; under the bending working condition, the deformation of the frame is mainly in the vertical direction, and the born load needs to be multiplied by a certain dynamic load coefficient, wherein the dynamic load coefficient is taken as 2.0; in the torsion working condition, the load born by the frame is basically consistent with the bending working condition in the plumb direction, and the vertical forces with the same magnitude and opposite directions are loaded at the left and right front suspension supports; in the turning working condition, the load born by the frame is basically consistent with the bending working condition in the vertical direction, and the transverse acceleration is applied to the mass center of the vehicle body framework to simulate the transverse load, wherein the size is 1g.
4. The front-end rear-drive truss type sports car body structure design method according to claim 1, wherein the method comprises the following steps:
the main bearing structure obtained in the step (2) is specifically expressed as follows: and (3) applying load boundary conditions under three single working conditions determined according to the step (1) to the vehicle body structure model, and obtaining a structure with clear boundary, namely a main bearing structure obtained under the action of the three working conditions respectively by adjusting penalty factors.
5. The front-end rear-drive truss type sports car body structure design method according to claim 1, wherein the method comprises the following steps:
and (3) optimizing the multi-working condition structure in the step (4), wherein the obtained frame main structure is specifically expressed as follows: according to the three single-working-condition weight ratios obtained in the step (2), converting the topological optimization condition under multiple working conditions into a single-target optimization problem, wherein the objective function is that the weighted flexibility of 3 working conditions is minimum, and symmetrical constraint is needed when the vehicle body is subjected to topological optimization, so that the optimized structure is bilaterally symmetrical; the definition of the frame structure is changed by adjusting the magnitude of the punishment factors, so that a main bearing structure of the frame is obtained; and finally converting the structure into an IGES curved surface, leading the IGES curved surface into CATIA software, and drawing a frame model.
6. The front-end rear-drive truss type sports car body structure design method according to claim 1, wherein the method comprises the following steps:
the specific expression of the local improvement of the optimal main structure under the multiple working conditions in the step (5) is as follows: the frame main structure is obtained by multi-working condition analysis of the frame model, the frame of the main structure has the problem of unclear boundary, and the single-working condition bearing structure obtained in the step (2) can help understand the structural performance of the frame, and the obtained structure is clearer so as to make up the defect of unclear local boundary of the main structure; by comprehensively comparing the main structure with the single-working-condition structure, the distribution mode of the rod pieces is reasonably adjusted, and finally, a space frame structure with good uniform bearing capacity is formed.
7. The front-end rear-drive truss type sports car body structure design method according to claim 1, wherein the method comprises the following steps: the inclined beams (3) are connected with the main beams (1) at the same side to form a plurality of triangular structures, and the triangular structures are arranged from the front part of the frame to the rear part of the frame in a dense-sparse-dense manner according to the arrangement mode of an engine, a seat and a person;
the front partition plate (6) is composed of four closed steel pipes including a front lower cross beam (2 a) and two reinforcing beams (7), the four closed steel pipes form a plane rectangular structure, the reinforcing beams (7) form three triangular structures, the two reinforcing beams (7) are equal in size, and the lower ends of the two reinforcing beams are welded in the middle of the front lower cross beam (2 a) in a butt joint mode.
8. The front-end rear-drive truss type sports car body structure design method according to claim 1, wherein the method comprises the following steps: the rear part in the frame also comprises two seat mounting beams (9) and two second auxiliary main beams (8) below the seat mounting beams, and the seat mounting beams (9) and the second auxiliary main beams (8) on the same side are connected through a plurality of triangular structures formed by butt joint of a plurality of inclined beams (3).
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| CN111222264B (en) * | 2019-11-01 | 2023-03-03 | 长春英利汽车工业股份有限公司 | Manufacturing method of composite continuous glass fiber reinforced front-end module |
| CN115092257B (en) * | 2022-06-29 | 2023-08-11 | 清华大学苏州汽车研究院（吴江） | Truss type vehicle body frame and vehicle |
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