Composite molding process for four-bar linkage suspension subframe of commercial vehicle

Abstract

The invention provides a commercial vehicle four-bar linkage suspension subframe composite forming process, and belongs to the technical field of subframe production and manufacturing, and the commercial vehicle four-bar linkage suspension subframe composite forming process comprises the following steps: S1, determining subframe structure parameters based on CAE multi-objective collaborative optimization; s2, manufacturing a left longitudinal beam and a right longitudinal beam by adopting an extrusion forming process; s3, manufacturing the front cross beam by adopting a hydraulic forming process; s4, preparing a rear cross beam by adopting a composite structure; s5, all the components are positioned and clamped through a clamp, and structural adhesive is coated; and S6, machining a mounting point special for the four-connecting-rod suspension on the auxiliary frame. Through CAE multi-objective optimization driving multi-material composite forming and structural adhesive and rivet precise assembly, collaborative improvement of light weight and high torsional rigidity of the auxiliary frame can be achieved, the auxiliary frame is precisely matched with a four-bar linkage suspension, the NVH performance is improved, cost is reduced, efficiency is improved, the universalization degree is high, and long-term durability and reliability are guaranteed.

Description

Technical Field

[0001] This invention relates to the field of subframe production and manufacturing technology, and in particular to a composite molding process for a four-link suspension subframe for commercial vehicles. Background Technology

[0002] With the increasing demands for energy conservation, emission reduction, and driving comfort in commercial vehicles, subframes that combine lightweight design, high torsional rigidity, and vehicle adaptability have become a core industry requirement. The stringent requirements of four-link independent suspension on the precision of subframe mounting hard points and the force transmission path further highlight the limitations of existing molding processes.

[0003] In the prior art, for example, Chinese patent application CN116331355A discloses a lightweight sheet metal front subframe for electric vehicles, which adopts a double crossbeam and Z-shaped two-stage longitudinal beam structure welded from sheet metal. Weight reduction is achieved by eliminating the curved tube beam. However, this process relies solely on single sheet metal splicing and welding, without designing a dedicated mounting structure for four-link suspensions, and lacks systematic optimization methods, resulting in torsional stiffness and modal performance that are difficult to match the heavy-duty requirements of commercial vehicles. Another example is Chinese patent application CN116968813A, which discloses a three-beam front subframe for new energy electric vehicles. It adds a middle crossbeam and uses a tubular front crossbeam to improve load adaptability, but it still mainly relies on traditional welding processes and does not involve multi-material composite molding and precise parameter optimization, thus failing to meet the requirements of four-link suspensions for installation accuracy and stress distribution.

[0004] Furthermore, existing subframe molding processes generally suffer from the following drawbacks: First, low integration of materials and processes, often using single steel or ordinary aluminum alloys, lacking efficient molding solutions for carbon fiber composites and steel-aluminum composite structures; second, a disconnect between design and process, with molding parameters not guided by simulation optimization, leading to difficulties in balancing product weight and performance; and third, poor adaptability, unable to quickly respond to the modular installation requirements of four-link suspensions, resulting in long development cycles and high costs. Therefore, the industry urgently needs a simulation-optimized composite molding process to achieve a synergistic improvement in the lightweight, high rigidity, and versatility of commercial vehicle four-link suspension subframes, thereby addressing the technical deficiencies of existing technologies. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies, such as difficulty in adapting to four-link independent suspensions, poor synergy between lightweighting and high torsional stiffness, and lack of CAE multi-objective optimization drive design, and to provide a composite molding process for a four-link suspension subframe of commercial vehicles.

[0006] This invention is achieved through the following technical solution: a composite molding process for a four-link suspension subframe of a commercial vehicle, comprising the following steps: S1. The subframe structural parameters are determined based on CAE multi-objective collaborative optimization. The subframe has a butterfly-shaped layout, including a left longitudinal beam, a right longitudinal beam, a front crossbeam, and a rear crossbeam. The left and right longitudinal beams are symmetrically arranged and converge in the middle. The CAE multi-objective collaborative optimization includes topology optimization, static and stiffness analysis, dynamic and NVH analysis, and fatigue durability analysis. S2. High-strength aluminum alloy left and right longitudinal beams are manufactured using extrusion molding process. After molding, the left and right longitudinal beams have internal reinforcing rib grids and a variable thickness B-shaped cross-section. S3. The aluminum alloy front crossbeam is manufactured using a hydroforming process, and the entire front crossbeam is arched. S4. The rear crossbeam is made of high-strength steel HG785 and aluminum alloy composite structure. During the manufacturing process, an assembly groove is machined in the middle of the crossbeam, and the interior of the rear crossbeam is filled with microporous polyurethane damping material. S41. A crossbeam with a carbon fiber composite structure and adapted to an assembly groove, manufactured using an autoclave molding process; S5. Position and clamp each component using a fixture. Apply two-component epoxy resin structural adhesive to the overlapping areas of the left and right longitudinal beams with the front and rear cross beams, respectively. Embed the middle cross beam into the assembly slot and apply adhesive simultaneously. Before the structural adhesive initially sets, fix it by riveting. At the same time, reinforce the connection nodes with a connecting cap mechanism and a tower-shaped reinforcing plate, and assemble them into one unit. S6. Machining dedicated mounting points for the four-link suspension on the assembled subframe. The mounting points include the upper control arm mounting point, the lower control arm front mounting point, the lower control arm rear mounting point, and the stabilizer bar mounting point. Each mounting point is equipped with an adaptive bushing seat.

[0007] This process utilizes CAE-driven design to proactively mitigate performance defects, reduce the use of physical prototypes, shorten the development cycle by 40%, and lower development costs by 35%. Multiple processes are precisely adapted to the characteristics of various materials, and the combination of adhesive and riveting composite connections with double reinforcement enhances node reliability and prevents galvanic corrosion. The central crossbeam incorporates reinforced rear crossbeams, achieving overall lightweighting—37.5% lighter than equivalent steel subframes—and high torsional stiffness—≥4500N. m / deg, precisely adapted to the four-link independent suspension, significantly improving vehicle handling stability and NVH performance.

[0008] A further improvement of the present invention is that the high-strength aluminum alloy is 6082-T6, which is subjected to solution treatment and aging treatment in sequence after extrusion molding, and the solution treatment temperature is 530-550℃ and the aging treatment temperature is 160-180℃.

[0009] This process uses 6082-T6 aluminum alloy with precise heat treatment, combined with the uniform microstructure and stable mechanical properties of extrusion molding. While ensuring the high strength of the longitudinal beams—meeting the standards for tensile and yield strength—it further reduces the weight, meeting the requirements for lightweighting. The reinforcing grating and variable thickness structure work together after molding to significantly improve the deformation resistance of the longitudinal beams.

[0010] A further improvement of the present invention is that the connecting cap mechanism includes an upper cap body, a lower cap body, and a bolt group. The upper cap body and the lower cap body respectively wrap around all the connection points of the left longitudinal beam, the right longitudinal beam and the front crossbeam, the rear crossbeam, and the upper and lower ends of the assembly connection point of the middle crossbeam and the rear crossbeam. The bolt group passes through the flange and is fastened.

[0011] This process uses full-node coverage reinforcement to disperse stress concentration at connection points, preventing loosening or breakage. In conjunction with the adhesive riveting composite connection, it not only prevents galvanic corrosion at the aluminum-carbon fiber connection but also improves fatigue resistance under dynamic loads, extending the overall structural stability and fatigue life of the subframe and precisely adapting to the dynamic stress requirements of the four-link suspension.

[0012] Further improvements to this invention include: the number of topology optimization iterations is no less than 15, the objective function is to maximize static stiffness, the amount of constrained material does not exceed 30% of the design space, and the first-order natural frequency is ≥45Hz.

[0013] This process achieves precise material allocation through multiple iterations and optimizations, significantly improving the subframe stiffness while maintaining lightweight design. The first-order natural frequency avoids the engine's 20-35Hz excitation frequency range, effectively reducing the risk of resonance. At the same time, it shortens the development cycle by 40%, reduces development costs by 35%, further improves the overall vehicle NVH performance, and enhances the efficiency of design change transmission and evaluation.

[0014] A further improvement of the present invention is that the front crossbeam is made of 6061-T6 aluminum alloy tubing, which is hydraulically formed and then arched upwards in the middle, with the arch height meeting the space requirements for steering system clearance.

[0015] This process utilizes the hydroforming technology of 6061-T6 aluminum alloy tubing, which results in fewer parts and fewer welds compared to stamping and welding. While balancing the lightweight design of the front crossbeam with structural strength, it also improves overall rigidity and fatigue strength. The arched design ensures ground clearance, providing ample space for the steering system to avoid interference and enhance vehicle steering agility.

[0016] A further improvement of the present invention is that the middle crossbeam is interference-fitted with the assembly groove, and after being embedded, it is fixed with rivets by two-component epoxy resin structural adhesive, and rigidly connected to the rear crossbeam.

[0017] This process uses a triple fixing method of interference fit, adhesive bonding, and riveting to ensure a firm connection between the middle crossbeam and the rear crossbeam; the high strength characteristics of the carbon fiber middle crossbeam are fully utilized, significantly improving the bending and torsional strength of the rear crossbeam; the stress is evenly distributed during torsion, avoiding local stress concentration; and nonlinear buckling analysis has verified that the structure does not become unstable under 1.5 times the ultimate torque, extending the load-bearing life of the subframe.

[0018] A further improvement of the present invention is that the autoclave molding process parameters are: temperature 120-180℃, pressure 0.5-0.7MPa, carbon fiber composite material is T700 grade prepreg, and the layup sequence is [0° / 45° / 90° / -45°]s.

[0019] A further improvement of the present invention includes: two mounting points for the upper control arm, located at the front of the left and right longitudinal beams respectively; two mounting points for the lower control arm, located at the middle of the left and right longitudinal beams respectively; two mounting points for the lower control arm at the rear, located at the rear of the left and right longitudinal beams respectively; and two mounting points for the stabilizer bar, located at both ends of the rear crossbeam.

[0020] This process ensures the secure installation of all components of the four-link suspension through symmetrical layout and precise positioning of the mounting points, adapting to the kinematic characteristics of the suspension; motion envelope analysis and clearance optimization design avoid suspension motion interference and reduce oversteer or understeer; improve vehicle handling stability and ride comfort, and adapt to the force transmission requirements under different working conditions.

[0021] A further improvement of this invention is that a quality inspection is performed after assembly, and the inspection indicators include: torsional stiffness not less than 4500N. m / deg, first-order torsional mode frequency is 45-50Hz, maximum stress is lower than the material yield strength, and fatigue life coefficient ≥1.35 over 1 million kilometers.

[0022] This process uses quantitative testing indicators derived from multidisciplinary simulation verification to ensure that the subframe performance meets the standards; the torsional stiffness is increased by about 18% compared to traditional subframes, and the first-order modal frequency of 48.5Hz has a safety margin of 25% with respect to the engine excitation frequency, effectively avoiding resonance; the fatigue life coefficient for 1 million kilometers meets the requirements, and the life of the maximum damage area is increased by 2.5 times after optimization, avoiding driving risks, ensuring long-term reliability and safety, and reducing later maintenance costs.

[0023] A further improvement of the present invention is that the riveting is carried out using an automatic riveting device, the rivet spacing is 15-20mm, and the adhesive layer thickness is 0.5-1.0mm.

[0024] This process improves assembly accuracy and efficiency through automated riveting equipment. Reasonable rivet spacing and adhesive layer thickness balance connection strength and lightweight requirements. Adhesive bonding provides additional vibration damping and improves overall rigidity, while riveting provides initial strength before the adhesive cures. The two work together to achieve fatigue resistance, avoid weight increase caused by excessive adhesive layer or excessive rivet density, and prevent loosening of connections, thereby improving the stability and durability of the subframe structure.

[0025] As can be seen from the above technical solutions, the beneficial effects of the present invention are: 1. This process, through a butterfly-shaped convergent layout, dedicated mounting point design, and motion envelope analysis, ensures interference-free suspension throughout its entire travel, adapting to the suspension's kinematic characteristics. It simultaneously achieves a balance between lightweight design and high torsional stiffness, reducing weight by 37.5% compared to an equivalent steel subframe, increasing torsional stiffness by over 18%, achieving a first-order modal frequency of 48.5Hz, and maintaining a 25% safety margin with the engine excitation frequency, effectively avoiding resonance and significantly improving the vehicle's NVH performance and handling stability.

[0026] 2. This process integrates multiple techniques, including extrusion, hydraulics, and autoclaves, combined with adhesive riveting composite connection technology. This leverages the advantages of lightweight and high-strength materials while enhancing the fatigue resistance and corrosion resistance of joints. CAE multi-objective optimization-driven design reduces the use of physical prototypes, shortens the development cycle, lowers costs, and precisely optimizes structural parameters and stress distribution, avoiding the risk of localized failures.

[0027] 3. This process, through its parametric interface design, can be quickly adapted to different wheelbase models, reducing the investment in tooling and molds. The subframe has a fatigue life coefficient of ≥1.35 over 1 million kilometers and will not become unstable under 1.5 times the limit torque, ensuring high reliability over long-term use. The lightweight design also reduces overall vehicle energy consumption, combining economic and environmental benefits. Attached Figure Description

[0028] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a structural schematic diagram of the subframe according to a specific embodiment of the present invention.

[0030] Figure 2 This is a schematic diagram of the connecting cap mechanism according to a specific embodiment of the present invention.

[0031] In the diagram: 101, left longitudinal beam; 102, right longitudinal beam; 103, front crossbeam; 104, middle crossbeam; 105, rear crossbeam; 1051, assembly slot; 110, upper control arm mounting point; 111, lower control arm front mounting point; 112, lower control arm rear mounting point; 113, stabilizer bar mounting point; 301, upper cap; 302, lower cap; 303, bolt assembly. Detailed Implementation

[0032] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the specific embodiments. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this patent, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this patent.

[0033] Now refer to Figure 1-2 The following is a description of a composite molding process for a four-link suspension subframe for commercial vehicles according to the present invention, with reference to specific embodiments: The process includes the following steps: S1. The subframe structural parameters are determined based on CAE multi-objective collaborative optimization. The subframe has a butterfly-shaped layout, including a left longitudinal beam 101, a right longitudinal beam 102, a front crossbeam 103, and a rear crossbeam 105. The left longitudinal beam 101 and the right longitudinal beam 102 are symmetrically arranged and converge in the middle. The CAE multi-objective collaborative optimization includes topology optimization, static and stiffness analysis, dynamic and NVH analysis, and fatigue durability analysis. S2. High-strength aluminum alloy left longitudinal beam 101 and right longitudinal beam 102 are manufactured by extrusion molding process. After molding, the left longitudinal beam 101 and right longitudinal beam 102 have a reinforcing grid inside and the cross section is a variable thickness B-shaped structure. S3. The aluminum alloy front crossbeam 103 is manufactured using a hydroforming process, and the front crossbeam 103 is arched in shape. S4. The rear crossbeam 105 is made of high-strength steel HG785 and aluminum alloy composite structure. During the preparation, the assembly groove 1051 is machined in the middle and the interior of the rear crossbeam 105 is filled with microporous polyurethane damping material. S41. A crossbeam 104 with a carbon fiber composite structure manufactured using a hot autoclave molding process and adapted to the assembly groove 1051. S5. The components are positioned and clamped by the fixture. Two-component epoxy resin structural adhesive is applied to the overlapping areas of the left longitudinal beam 101 and the right longitudinal beam 102 with the front cross beam 103 and the rear cross beam 105, respectively. The middle cross beam 104 is embedded in the assembly groove 1051 and the adhesive is applied at the same time. Before the structural adhesive is initially cured, it is fixed by riveting. At the same time, the connection nodes are reinforced by the connecting cap mechanism and the tower-shaped reinforcing plate, and assembled into a whole. S6. Machine four-link suspension mounting points on the assembled subframe. The mounting points include upper control arm mounting point 110, lower control arm front mounting point 111, lower control arm rear mounting point 112, and stabilizer bar mounting point 113. Each mounting point is equipped with an adaptive bushing seat.

[0034] First, CAE multi-objective collaborative optimization—including topology optimization, static and stiffness analysis, dynamic and NVH analysis, and fatigue durability analysis—was used to optimize the structural parameters of the butterfly-shaped subframe (left longitudinal beam 101, right longitudinal beam 102, front crossbeam 103, and rear crossbeam 105) within a 1200mm×800mm×200mm design space for six key operating conditions, including vertical bumps, braking, and cornering. The force flow path was optimized through symmetrical convergence design of the left and right longitudinal beams 101 and 102. Then, a variable-thickness B-type subframe with reinforcing ribs was manufactured through extrusion molding. The longitudinal beams are formed by hydroforming an arched front crossbeam 103, and a composite structure is prepared for a rear crossbeam 105 with an assembly groove 1051 and filled with microporous polyurethane damping material. A carbon fiber middle crossbeam 104 adapted to the assembly groove 1051 is manufactured by autoclaving. Finally, the crossbeams are positioned and clamped by a special high-precision fixture. Two-component epoxy resin structural adhesive is applied to the overlapping area of ​​the longitudinal beams and crossbeams, and the assembly surface of the middle crossbeam 104 and the assembly groove 1051. Before the structural adhesive initially cures, it is fixed by an automatic riveting device. All connection nodes are reinforced by a connecting cap mechanism and a tower-shaped reinforcing plate. The special mounting points for the four-link suspension are processed and an adaptive bushing seat is assembled.

[0035] To avoid resonance with the engine excitation frequency, modal analysis under free state was performed. Shell elements were used for mesh generation, and the model contains 125,430 nodes and 138,556 shell elements, with the proportion of triangular elements controlled within 4.5%.

[0036] The material parameters are set as follows:

[0037] This process utilizes CAE-driven design to proactively mitigate performance defects, reduce the use of physical prototypes, shorten the development cycle by 40%, and lower development costs by 35%. Multiple processes are precisely adapted to the characteristics of various materials, and the combination of adhesive and riveting composite connections with double reinforcement enhances node reliability and prevents galvanic corrosion. The central crossbeam 104 is embedded with a reinforced rear crossbeam 105, achieving overall lightweighting—37.5% lighter than equivalent steel subframes—and high torsional stiffness—≥4500N. m / deg, precisely adapted to the four-link independent suspension, significantly improving vehicle handling stability and NVH performance.

[0038] Specifically, in step S2, the high-strength aluminum alloy is 6082-T6. After extrusion molding, it undergoes solution treatment and aging treatment in sequence. The solution treatment temperature is 530-550℃, and the aging treatment temperature is 160-180℃.

[0039] 6082-T6 high-strength aluminum alloy is selected. The aluminum alloy billet is heated to a plastic state through extrusion molding process, and then extruded under high pressure to form B-shaped left longitudinal beam 101 and right longitudinal beam 102 with internal reinforcing grating. After extrusion molding, the billet is subjected to solution treatment at 530-550℃ to improve plasticity and toughness, and aging treatment at 160-180℃ to enhance strength and hardness.

[0040] This process uses 6082-T6 aluminum alloy with precise heat treatment, combined with the uniform microstructure and stable mechanical properties of extrusion molding. While ensuring the high strength of the longitudinal beams—meeting the standards for tensile and yield strength—it further reduces the weight, meeting the requirements for lightweighting. The reinforcing grating and variable thickness structure work together after molding to significantly improve the deformation resistance of the longitudinal beams.

[0041] Specifically, refer to Figure 2 In step S5, the connecting cap mechanism includes an upper cap body 301, a lower cap body 302, and a bolt group 303. The upper cap body 301 and the lower cap body 302 respectively wrap around all the connection points between the left longitudinal beam 101, the right longitudinal beam 102 and the front cross beam 103, the rear cross beam 105, and the upper and lower ends of the assembly connection point between the middle cross beam 104 and the rear cross beam 105. The bolt group 303 passes through the flange and is fastened.

[0042] The connecting cap mechanism wraps all the connection points of the left longitudinal beam 101, right longitudinal beam 102 and front crossbeam 103, and rear crossbeam 105 through the upper cap body 301 and lower cap body 302, as well as the assembly connection point of the middle crossbeam 104 and rear crossbeam 105. The bolt group 303 passes through the flange for fastening, and forms a double reinforcement with the adhesive riveting composite connection. The adhesive layer makes the connection area form an overall increase in rigidity, and the riveting provides initial strength before the adhesive cures.

[0043] This process uses full-node coverage reinforcement to disperse stress concentration at connection points, preventing loosening or breakage. In conjunction with the adhesive riveting composite connection, it not only prevents galvanic corrosion at the aluminum-carbon fiber connection but also improves fatigue resistance under dynamic loads, extending the overall structural stability and fatigue life of the subframe and precisely adapting to the dynamic stress requirements of the four-link suspension.

[0044] Specifically, in step S1, the number of topology optimization iterations is no less than 15, the objective function is to maximize the static stiffness, the amount of constrained material usage does not exceed 30% of the design space, and the first-order natural frequency is ≥45Hz.

[0045] The CAE topology optimization iteration is no less than 15 times, with the goal of maximizing static stiffness. The material usage is constrained to not exceed 30% of the design space and the first-order natural frequency is ≥45Hz. Multiple iterations are carried out for 6 key working conditions to optimize the distribution of structural parameters and ensure efficient material utilization.

[0046] The calculated first five flexible modal frequencies of the subframe are shown in the table below:

[0047] This process achieves precise material allocation through multiple iterations and optimizations, significantly improving subframe stiffness while maintaining lightweight design. The first-order natural frequency avoids the engine's 20-35Hz excitation frequency range, effectively reducing resonance risk. At the same time, it shortens the development cycle by 40%, reduces development costs by 35%, further improves the overall vehicle NVH performance, and enhances the efficiency of design change transmission and evaluation.

[0048] Specifically, in step S3, the front crossbeam 103 is made of aluminum alloy 6061-T6 tubing, which is hydraulically formed and then arched upwards in the middle, with the arch height meeting the steering system's clearance space requirements.

[0049] 6061-T6 aluminum alloy tubing is selected. The pre-bent tubing is placed into a closed mold through a hydraulic forming process. High-pressure fluid is injected to make the tubing expand and fit tightly against the mold, forming a front crossbeam 103 with an upward arch in the middle. The arch height is precisely matched to the steering system's clearance space requirements.

[0050] This process utilizes the hydroforming technology of 6061-T6 aluminum alloy tubing, which results in fewer parts and fewer welds compared to stamping and welding. While maintaining the lightweight design of the front crossbeam 103 and structural strength, it also improves overall rigidity and fatigue strength. The arched design ensures ground clearance, providing ample space for the steering system to avoid interference and enhance vehicle steering agility.

[0051] Specifically, the middle crossbeam 104 is interference-fitted with the assembly groove 1051, and after being embedded, it is fixed with rivets using two-component epoxy resin structural adhesive, and rigidly connected to the rear crossbeam 105.

[0052] The assembly slots 1051 of the middle crossbeam 104 and the rear crossbeam 105 are initially fixed by interference fit. After being embedded, the gaps are filled and the stress is dispersed by two-component epoxy resin structural adhesive. Then, they are fixed for a second time by rivets to form a rigid connection. Together with the butterfly structure and the tubular closed section, a "space truss" force mechanism is constructed.

[0053] This process employs a triple fixing method—interference fit, adhesive bonding, and riveting—to ensure a firm connection between the middle crossbeam 104 and the rear crossbeam 105. The high strength of the carbon fiber middle crossbeam 104 is fully utilized, significantly improving the bending and torsional strength of the rear crossbeam 105. Stress is evenly distributed during torsion, avoiding localized stress concentration. Nonlinear buckling analysis verifies that the structure does not become unstable under 1.5 times the ultimate torque, extending the subframe's load-bearing life.

[0054] Specifically, the autoclave molding process parameters are: temperature 120-180℃, pressure 0.5-0.7MPa, carbon fiber composite material is T700 grade prepreg, and the layup sequence is [0° / 45° / 90° / -45°]s.

[0055] The central crossbeam 104 uses T700 grade carbon fiber prepreg, which is laid in the mold in the [0° / 45° / 90° / -45°] s layup sequence, sealed in a vacuum bag and placed in an autoclave, and cured in an environment of 120-180℃ and 0.5-0.7MPa. The micromechanics and macrostructure are optimized by multi-scale analysis using Digimat software.

[0056] This process ensures tight bonding between carbon fiber layers through precise autoclave molding parameters and layup design, combined with vacuum bag sealing technology. Multi-scale analysis and optimization enable the middle crossbeam 104 to reduce weight by 25% compared to the aluminum alloy solution while maintaining lateral stiffness. This fully leverages the advantages of carbon fiber composite materials, such as lightweight, high strength, and excellent fatigue resistance, and works in synergy with the rear crossbeam 105 to improve the overall performance of the subframe.

[0057] Specifically, refer to Figure 1 In step S6, there are two upper control arm mounting points 110, which are located at the front of the left longitudinal beam 101 and the right longitudinal beam 102, respectively; there are two lower control arm front mounting points 111, which are located at the middle of the left longitudinal beam 101 and the right longitudinal beam 102, respectively; there are two lower control arm rear mounting points 112, which are located at the rear of the left longitudinal beam 101 and the right longitudinal beam 102, respectively; and there are two stabilizer bar mounting points 113, which are located at both ends of the rear crossbeam 105.

[0058] Two upper control arm mounting points 110, a lower control arm front mounting point 111, and a lower control arm rear mounting point 112 are respectively set at the front, middle, and rear parts of the left longitudinal beam 101 and the right longitudinal beam 102. Two stabilizer bar mounting points 113 are set at both ends of the rear cross beam 105. Each mounting point is precisely positioned according to hard point coordinates. Motion envelope analysis is performed through the CATIA-DMU module to ensure that there is no interference between the suspension and the subframe throughout the entire travel range, and the minimum static clearance is ≥15mm.

[0059] This process ensures the secure installation of all components of the four-link suspension through symmetrical layout and precise positioning of the mounting points, adapting to the kinematic characteristics of the suspension; motion envelope analysis and clearance optimization design avoid suspension motion interference and reduce oversteer or understeer; improve vehicle handling stability and ride comfort, and adapt to the force transmission requirements under different working conditions.

[0060] Specifically, after assembly, quality inspection is carried out, and the inspection indicators include: torsional stiffness not less than 4500N. m / deg, first-order torsional mode frequency is 45-50Hz, maximum stress is lower than the material yield strength, and fatigue life coefficient ≥1.35 over 1 million kilometers.

[0061] After assembly, the torsional stiffness of the subframe was verified using testing equipment – ​​≥4500N. m / deg, first-order torsional modal frequency—45-50Hz, maximum stress—lower than the material yield strength, and fatigue life coefficient for 1 million kilometers—≥1.35. The test indicators are set based on the results of modal analysis, static stiffness analysis, and fatigue durability analysis to screen qualified products.

[0062] This process uses quantitative testing indicators derived from multidisciplinary simulation verification to ensure that the subframe performance meets the standards; the torsional stiffness is increased by about 18% compared to traditional subframes, and the first-order modal frequency of 48.5Hz has a safety margin of 25% with respect to the engine excitation frequency, effectively avoiding resonance; the fatigue life coefficient for 1 million kilometers meets the requirements, and the life of the maximum damage area is increased by 2.5 times after optimization, avoiding driving risks, ensuring long-term reliability and safety, and reducing later maintenance costs.

[0063] Specifically, in step S5, the riveting is done using an automatic riveting device, with a rivet spacing of 15-20mm and an adhesive layer thickness of 0.5-1.0mm.

[0064] In step S5, an automatic riveting device is used for riveting, controlling the rivet spacing to 15-20mm to ensure connection density, and the adhesive layer thickness to 0.5-1.0mm to ensure bonding strength and sealing. The riveting is completed before the structural adhesive initially sets, forming a composite connection with the adhesive, and achieving precise and uniform fixation of each component.

[0065] This process improves assembly accuracy and efficiency through automated riveting equipment. Reasonable rivet spacing and adhesive layer thickness balance connection strength and lightweight requirements. Adhesive bonding provides additional vibration damping and improves overall rigidity, while riveting provides initial strength before the adhesive cures. The two work together to achieve fatigue resistance, avoid weight increase caused by excessive adhesive layer or excessive rivet density, and prevent loosening of connections, thereby improving the stability and durability of the subframe structure.

[0066] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A composite molding process for a four-link suspension subframe of a commercial vehicle, characterized in that, Includes the following steps: S1. The subframe structural parameters are determined based on CAE multi-objective collaborative optimization. The subframe has a butterfly-shaped layout, including a left longitudinal beam (101), a right longitudinal beam (102), a front crossbeam (103), and a rear crossbeam (105). The left longitudinal beam (101) and the right longitudinal beam (102) are symmetrically arranged and converge in the middle. The CAE multi-objective collaborative optimization includes topology optimization, static and stiffness analysis, dynamic and NVH analysis, and fatigue durability analysis. S2. High-strength aluminum alloy left longitudinal beam (101) and right longitudinal beam (102) are manufactured by extrusion molding process. S3. The aluminum alloy front crossbeam (103) is manufactured using a hydroforming process, and the front crossbeam (103) is arched in shape. S4. The rear crossbeam (105) is made of a high-strength steel and aluminum alloy composite structure, and an assembly groove (1051) is machined in the middle during the manufacturing process. S41. A middle crossbeam (104) with a carbon fiber composite structure manufactured by autoclave molding process and adapted to the assembly groove (1051). S5. The components are positioned and clamped by the fixture. The overlapping areas of the left longitudinal beam (101) and right longitudinal beam (102) with the front cross beam (103) and rear cross beam (105) are coated with two-component epoxy resin structural adhesive. The middle cross beam (104) is embedded in the assembly groove (1051) and coated with adhesive at the same time. Before the structural adhesive is initially cured, it is fixed by riveting. At the same time, the connecting nodes are reinforced by the connecting cap mechanism and assembled into one piece. S6. Machining four-link suspension mounting points on the assembled subframe, including upper control arm mounting point (110), lower control arm front mounting point (111), lower control arm rear mounting point (112) and stabilizer bar mounting point (113).

2. The composite molding process for a commercial vehicle four-link suspension subframe according to claim 1, characterized in that, In step S2, the high-strength aluminum alloy is 6082-T6. After extrusion molding, it undergoes solution treatment and aging treatment in sequence. The solution treatment temperature is 530-550℃, and the aging treatment temperature is 160-180℃.

3. A composite molding process for a commercial vehicle four-link suspension subframe according to claim 1, characterized in that, In step S5, the connecting cap mechanism includes an upper cap body (301), a lower cap body (302), and a bolt group (303). The upper cap body (301) and the lower cap body (302) respectively wrap around all the connection points of the left longitudinal beam (101), the right longitudinal beam (102) and the front crossbeam (103), the rear crossbeam (105), and the upper and lower ends of the assembly connection point of the middle crossbeam (104) and the rear crossbeam (105). The bolt group (303) is fastened through the flange.

4. A composite molding process for a commercial vehicle four-link suspension subframe according to claim 1, characterized in that, In step S1, the number of topology optimization iterations is no less than 15, the objective function is to maximize the static stiffness, the amount of constrained material does not exceed 30% of the design space, and the first natural frequency is ≥45Hz.

5. A composite molding process for a commercial vehicle four-link suspension subframe according to claim 1, characterized in that, In step S3, the front crossbeam (103) is made of aluminum alloy 6061-T6 tubing. After hydraulic forming, the middle part is arched upwards, and the arch height meets the space requirements of the steering system.

6. A composite molding process for a commercial vehicle four-link suspension subframe according to claim 1, characterized in that, The middle crossbeam (104) is interference-fitted with the assembly groove (1051), and after being embedded, it is fixed with rivets by two-component epoxy resin structural adhesive and rigidly connected to the rear crossbeam (105).

7. A composite molding process for a commercial vehicle four-link suspension subframe according to claim 6, characterized in that, The autoclave molding process parameters are: temperature 120-180℃, pressure 0.5-0.7MPa, carbon fiber composite material is T700 grade prepreg, and the layup sequence is [0° / 45° / 90° / -45°]s.

8. A composite molding process for a commercial vehicle four-link suspension subframe according to claim 1, characterized in that, In step S6, there are two upper control arm mounting points (110), which are located at the front of the left longitudinal beam (101) and the right longitudinal beam (102), respectively; there are two lower control arm front mounting points (111), which are located at the middle of the left longitudinal beam (101) and the right longitudinal beam (102), respectively; there are two lower control arm rear mounting points (112), which are located at the rear of the left longitudinal beam (101) and the right longitudinal beam (102), respectively; and there are two stabilizer bar mounting points (113), which are located at both ends of the rear crossbeam (105).

9. A composite molding process for a commercial vehicle four-link suspension subframe according to claim 1, characterized in that, After assembly, quality inspection is carried out, and the inspection indicators include: torsional stiffness not less than 4500N. m / deg, first-order torsional mode frequency is 45-50Hz, maximum stress is lower than the material yield strength, and fatigue life coefficient ≥1.35 over 1 million kilometers.

10. A composite molding process for a commercial vehicle four-link suspension subframe according to claim 1, characterized in that, In step S5, the riveting is done using an automatic riveting device, with a rivet spacing of 15-20mm and an adhesive layer thickness of 0.5-1.0mm.

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