Steel-aluminum heterogeneous connection system with constant force characteristic displacement compensation and its calibration method

Abstract

This invention discloses a steel-aluminum heterogeneous connection system with constant force characteristic displacement compensation and its calibration method, relating to the fields of vehicle engineering and structural strength technology. The system includes bolts, an elastic compensation core, and a rigid limiting element. The elastic compensation core forms a constant force characteristic platform area through specific geometric parameter ratios, and the platform width can completely cover the thermal expansion mismatch displacement of the steel and aluminum caused by temperature differences. The rigid limiting element has an axial limiting part, achieving temperature difference displacement compensation under normal conditions and quickly switching to rigid force transmission under collision conditions. The calibration method uses a room temperature mid-position anchoring method, initially compressing the elastic compensation core to the midpoint of the constant force platform to achieve bidirectional displacement compensation. This invention effectively solves the problems of drastic changes in preload, loosening and abnormal noise, stress failure, and unreliable force transmission in steel-aluminum connections under extreme temperature differences, improving structural durability, NVH performance, and simulation accuracy. It is applicable to various vehicle steel-aluminum composite bolt connection scenarios.

Description

Technical Field

[0001] This invention relates to the fields of vehicle engineering and structural strength technology, specifically to a steel-aluminum heterogeneous connection system with constant force characteristic displacement compensation and its calibration method. Background Technology

[0002] Under the trend of lightweight automotive design, composite structures of aluminum alloy beams and steel beams have become the mainstream application form for key body components (such as anti-collision beams and frames) because they balance lightweighting and structural strength. However, there is a significant difference in the coefficients of linear expansion between steel and aluminum; the coefficient of linear expansion of aluminum alloy is approximately 23 × 10⁻⁶. -6 At / ℃, the coefficient of linear expansion of steel bolts and steel beams is approximately 12×10⁻⁶. -6 / ℃, under extreme temperature differences, the two will experience severe thermal expansion mismatch, directly leading to the risk of failure of the connection structure: Under high-temperature conditions, such as car body painting baking and extreme summer temperatures, excessive expansion of aluminum alloy beams can cause a sharp increase in bolt preload, which can easily crush the insulating gaskets at the connection points or cause thread yielding and structural plastic deformation. In low-temperature conditions, such as the low temperatures of winter in cold regions, the severe contraction of aluminum alloy beams can lead to the complete loss of bolt preload, causing abnormal NVH noises and loose connections in the vehicle, while also posing a serious collision safety hazard. Existing steel-aluminum connection compensation technology has obvious limitations. Traditional rigid gaskets have no elastic compensation capability and cannot absorb axial displacement caused by temperature difference. Ordinary linear springs are limited by installation space and cannot withstand the large load required by high-grade bolts such as 10.9 grade. Moreover, the load changes linearly with displacement and cannot adapt to the temperature difference displacement compensation requirements, making it difficult to achieve stable control of preload in the entire temperature range. Therefore, the industry urgently needs a connection compensation solution that can adapt to limited installation space, withstand high bolt loads, and maintain constant preload under temperature and displacement fluctuations. Summary of the Invention

[0003] In view of this, the present invention aims to provide a steel-aluminum heterogeneous connection system with constant force characteristic displacement compensation, to solve the technical problem in the prior art of large fluctuations in preload caused by thermal expansion mismatch under extreme temperature differences due to the lack of a steel-aluminum connection structure, and the lack of a reliable elastic compensation system. The specific technical solution is as follows: A steel-aluminum heterogeneous connection structure with constant force characteristic displacement compensation is applied to the bolted connection parts of steel-aluminum composite structures in vehicles, including: bolt; Elastic compensation core, the elastic compensation core is sleeved on the outer periphery of the bolt; A rigid limiting element is coaxially sleeved on the outer periphery of the bolt and forms a rigid positioning fit with the elastic compensation core, and the two maintain a relatively fixed overall relationship. The elastic compensating core is a disc spring or an elastic pad constructed as a single conical piece, and the elastic compensating core has a height defined as the inner cone height. With single-piece thickness The parameters, inner cone height With single-piece thickness The ratio satisfies ; Compressive displacement of the elastic compensating core in the bolt axial direction A constant force characteristic plateau region is formed with a load fluctuation range of ≤±10%, and the width of the constant force characteristic plateau region is... Satisfying formula (1): (1); in, The equivalent clamping length for the bolted connection system; The highest ambient temperature encountered by the steel-aluminum composite structure throughout the vehicle's entire life cycle; The lowest ambient temperature at which the steel-aluminum composite structure is subjected to throughout the entire life cycle of the vehicle; Due to extremely large temperature differences in the environment; is the coefficient of linear expansion of aluminum alloy; is the coefficient of linear expansion of steel; The rigid limiting element and the elastic compensation core are fitted together in the bolt preload path, and the rigid limiting element is provided with an axial limiting part extending along the bolt axis; The stepped surface of the axial limiting part maintains a preset axial gap with the insulating hole cover surface of the steel-aluminum composite structure, and the axial stiffness of the rigid limiting element is at least one order of magnitude higher than the equivalent stiffness of the elastic compensation core in the constant force characteristic plateau region.

[0004] Furthermore, the elastic compensation core is a disc spring; Disc springs are used to absorb axial displacement caused by the difference in thermal expansion coefficients in steel-aluminum composite structures, so as to maintain the preload fluctuation range of bolts ≤ ±10%.

[0005] Furthermore, the axial limiting part is used to limit the maximum axial compression stroke of the disc spring, and abuts against the insulating hole cover when the vehicle encounters a transient high collision load, so that the rigid limiting element forms a rigid force transmission path and realizes the rigid transmission of collision load.

[0006] Furthermore, the inner cone height of the disc spring With single-piece thickness The preferred ratio is 1.5 to 1.6.

[0007] Furthermore, the disc spring is a single-piece conical disc spring structure conforming to DIN2093 standard; or It is a slotted disc spring.

[0008] Furthermore, the rigid limiting element is a sleeve; or It consists of multiple rigid bodies arranged in a radial circumference along the bolt.

[0009] A calibration method for a steel-aluminum heterogeneous connection system with constant force characteristic displacement compensation, used for calibrating the connection system, includes: In a normal temperature assembly environment, by controlling the tightening torque or tightening angle, the initial compression displacement of the elastic compensation core is positioned at the midpoint of the span of the constant force characteristic plateau region of the load and deformation curve. Midpoint of the span, i.e., compressive displacement Place.

[0010] Furthermore, before calibration, the maximum axial displacement difference and compressive displacement of the steel-aluminum composite structure due to temperature difference are calculated. This makes the constant force characteristic plateau width of the disc spring... This is to achieve bidirectional displacement compensation at both high and low temperatures.

[0011] Furthermore, after calibration, the displacement fluctuation of the steel-aluminum heterogeneous connection system with constant force characteristic displacement compensation under extreme temperature differences is limited to the range of the constant force characteristic plateau region, and the bolt preload fluctuation range is ≤±10%.

[0012] Furthermore, the range of the constant force characteristic plateau region is the axial compressive displacement range. At that time, the fluctuation range of bolt preload within this range is ≤±5%.

[0013] Compared with the prior art, the present invention can achieve the following beneficial effects: Firstly, this solution can achieve connection stability across the entire temperature range, reducing the fluctuation range of bolt preload from ±40% in the traditional solution to within ±10%, which greatly extends the fatigue life of the connection point. Secondly, the structural durability of this solution is as follows: it effectively alleviates the stress concentration in the aluminum alloy holes and PA insulation medium under high temperature conditions, avoids permanent plastic thinning of the material, and extends fatigue life. Thirdly, it solves the problem of boundary condition failure caused by temperature load in CAE simulation, making the collision model more accurate in comparison with the measured values.

[0014] Fourthly, by maintaining a constant preload, the present invention effectively avoids structural local modal frequency drift caused by loose connections, ensuring the robustness of the vehicle's NVH performance throughout its entire life cycle and temperature range. Attached Figure Description

[0015] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention.

[0016] In the attached diagram: Figure 1 A cross-sectional view of the elastic compensation core and rigid limiting element of Embodiment 1 of the present invention; Figure 2 An enlarged schematic diagram of the elastic compensation core and axial limiting part in Embodiment 1 of the present invention; Figure 3 A cross-sectional view of the elastic compensation core and rigid limiting element of Embodiment 2 of the present invention; Figure 4 An enlarged schematic diagram of the elastic compensation core and axial limiting part in Embodiment 2 of the present invention; Figure 5 A schematic diagram of the connection positions of the steel-aluminum heterogeneous connection system according to an embodiment of the present invention; Figure 6 Another schematic diagram of the connection position of the steel-aluminum heterogeneous connection system according to an embodiment of the present invention; Figure 7 A schematic diagram illustrating an embodiment of the present invention using a DIN2093 standard disc spring as an example; Figure 8 A schematic diagram illustrating the characteristics of the disc spring in the constant force plateau region according to an embodiment of the present invention.

[0017] Explanation of reference numerals in the attached figures: 10. Bolt; 20. Elastic compensation core; 30. Rigid limiting element; 40. Axial limiting part; 100. PA coated insulating hole cover; 200. PA coated insulating pad. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0019] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0020] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0021] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] The present invention aims to provide a steel-aluminum heterogeneous connection system with constant force characteristic displacement compensation, in order to solve the technical problem in the prior art that the lack of a steel-aluminum connection structure leads to large fluctuations in preload due to thermal expansion mismatch under extreme temperature differences, and the lack of a reliable elastic compensation system. Specific explanation of the above technical issues: In the full temperature range of the vehicle steel-aluminum heterogeneous composite connection structure, the preload is unstable, the connection reliability is poor, and the force transmission failure due to the mismatch of the thermal expansion coefficients of steel and aluminum is caused by the inherent defects of traditional compensation elements, such as insufficient load adaptability and limited displacement compensation capability. As a result, the steel-aluminum connection is difficult to maintain constant force and stable clamping and durable and safe service under extreme temperature difference and dynamic load. The core of this invention lies in utilizing the quasi-static or zero stiffness characteristics of a disc spring (or a component with similar disc spring properties, such as a single conical elastic pad with disc spring characteristics) under specific geometric parameters to construct a displacement adaptive system. Obviously, the component with similar disc spring properties mentioned in this application does not exclude multi-conical elastic pads. The technical principle of this scheme is based on the relationship between the load P and deformation of the displacement adaptive system. The nonlinear functional relationship follows the Almen-Laszlo equation: ; in, For elastic modulus, Poisson's ratio, outer diameter, For thickness, The height of the inner cone. The diameter ratio is a related calculation constant (defined as the first ratio value). ); The principle behind the calibration logic based on the above content is as follows: This invention sets a dimensionless parameter lock by limiting the height of the inner cone. With single-piece thickness The ratio is 1.4 1.7 range (preferably 1.5) 1.6), making the curve (attached) Figure 8 (Schematic diagram of the stiffness characteristics of a disc spring) During compression displacement (deformation) A "constant force plateau area" with a very small slope appears nearby, as shown in the attached figure. Figure 8 As shown; Using the displacement matching equation, the design criteria for this system must satisfy the following equation: The elastic compensating core 20 is a disc spring or an elastic pad constructed as a single cone shape, and the elastic compensating core 20 has a height defined as the inner cone height. With single-piece thickness The parameters, inner cone height With single-piece thickness The ratio satisfies ; The compressive displacement of the elastic compensating core 20 in the axial direction of the bolt 10 A constant force characteristic plateau region is formed with a load fluctuation range of ≤±10%, and the width of the constant force characteristic plateau region is... Satisfying formula (1): (1); in, The equivalent clamping length for the bolted connection system; The highest ambient temperature encountered by the steel-aluminum composite structure throughout the vehicle's entire life cycle; The lowest ambient temperature at which the steel-aluminum composite structure is subjected to throughout the entire life cycle of the vehicle; Due to extremely large temperature differences in the environment; is the coefficient of linear expansion of aluminum alloy; is the coefficient of linear expansion of steel; Therefore, this invention first proposes a steel-aluminum heterogeneous connection system with constant force characteristic displacement compensation, applied to the bolted connection parts of a vehicle's steel-aluminum composite structure, comprising: Bolt 10, elastic compensation core 20 is sleeved on the outer periphery of bolt 10; The rigid limiting element 30 is coaxially sleeved on the outer periphery of the bolt 10 and forms a rigid positioning fit with the elastic compensation core (20). The two maintain a relatively fixed overall relationship, as shown in the attached figure. Figure 1 Appendix Figure 2 Appendix Figure 3 Appendix Figure 4 Two sets of embodiments are shown; Example 1 and Example 2 are two disc springs with different shapes, and the structural form of Example 2 is equivalent to a single conical elastic pad with an inner cone height. With single-piece thickness Parameter design definition; In terms of connection method, Example 1 is as shown in the attached diagram. Figure 1 Appendix Figure 2 As shown, the rigid limiting element 30 and the elastic compensation core 20 form a snap-fit ​​engagement, and the two maintain a relatively fixed overall relationship. In terms of connection method, Example 2 is as shown in the attached diagram. Figure 3 Appendix Figure 4 As shown, the rigid limiting element 30 and the elastic compensation core 20 form an abutment, but the rigid limiting element 30 is fixed by using the cooperation with the bolt 10. Similarly, the rigid limiting element 30 and the elastic compensation core 20 maintain a relatively fixed overall relationship. The elastic compensating core 20 is a disc spring or an elastic pad constructed as a single cone shape, and the elastic compensating core 20 has a height defined as the inner cone height. With single-piece thickness The parameters, inner cone height With single-piece thickness The ratio satisfies ; The compressive displacement of the elastic compensating core 20 in the axial direction of the bolt 10 A constant force characteristic plateau region is formed with a load fluctuation range of ≤±10%, and the width of the constant force characteristic plateau region is... Satisfying formula (1): (1); in, The equivalent clamping length for the bolted connection system; The highest ambient temperature encountered by the steel-aluminum composite structure throughout the vehicle's entire life cycle; The lowest ambient temperature at which the steel-aluminum composite structure is subjected to throughout the entire life cycle of the vehicle; Due to extremely large temperature differences in the environment; is the coefficient of linear expansion of aluminum alloy; is the coefficient of linear expansion of steel; The rigid limiting element 30 and the elastic compensation core 20 are fitted together in the pre-tightening path of the bolt 10. The rigid limiting element 30 is provided with an axial limiting part 40 extending along the axial direction of the bolt 10. The stepped surface of the axial limiting part 40 maintains a preset axial gap with the insulating hole cover surface of the steel-aluminum composite structure, and the axial stiffness of the rigid limiting element 30 is at least one order of magnitude higher than the equivalent stiffness of the elastic compensation core 20 in the constant force characteristic plateau region. Regarding the insulating hole cover, see attached. Figure 1 , 3 As shown, the system also includes a PA-coated insulating hole cover 100 and a PA-coated insulating pad 200. A steel-aluminum heterogeneous connection system with constant force characteristic displacement compensation, including those based on Nonlinear compensation of eigenvalues ​​is achieved by integrating an elastic compensation core 20 with a specific geometric ratio in the preload path of bolt 10, which is achieved by setting the inner cone height. With single-piece thickness The ratio (most preferred embodiment) This enables it to maintain a constant load within a range of temperature variations; Compared to linear springs ( ), flip spring ( This solution can maintain a nearly constant bolt load when displacement fluctuations are within a certain range, avoiding bolt stress spikes or loosening. The elastic element of this invention preferably adopts a single-piece conical disc spring structure conforming to DIN2093 standards. To obtain a wider constant force compensation range, a slotted disc spring can also be used; alternatively, a single-piece conical elastic pad can be used, and it can still be defined as a non-standard structure of the disc spring category. In summary, the selection of certain structures with elastic properties has been ruled out, such as: The first exclusion option is linear / incremental type ( This is excluded from the present invention because even as deformation increases, the load continues to rise; exhibiting the most common spring characteristics, it is not suitable for thermal compensation because even a small expansion of the aluminum beam will cause the preload to spike dramatically.

[0024] The second type is negative stiffness and flipping type ( ), curve (attached) Figure 8(Diagram of disc spring stiffness characteristics) After reaching its peak, the stiffness will decrease, and there may even be a situation where the load decreases as the deformation increases. Although it has unique characteristics, it is extremely unstable for structural connections and is prone to "jumping", so it should be excluded.

[0025] Therefore, a constant force platform type is preferred. (≈1.5), the most preferred embodiment of the present invention, the constant force platform region characteristic display curve, attached. Figure 8 The schematic diagram of the disc spring's stiffness characteristics shows an increase in the initial stage of loading, but... The area nearby becomes extremely flat; within this range, This means that the displacement difference caused by the environmental temperature difference As long as it falls within this range, the preload P on the bolt remains almost constant; Based on the above, this solution needs to complete the dynamic calibration of precompression based on the "median anchoring method"; Unlike conventional springs with arbitrary installation positions, this invention provides a calibration method: under normal temperature assembly conditions, by controlling the tightening angle or torque, the elastic element is initially compressed to the midpoint of the constant force platform span of its load-deformation curve (approximately 0.5). (place); From a mechanical perspective, if the displacement difference caused by the temperature difference is... The selected constant force platform width Must meet By anchoring the initial working point at 0.5 Nearby, this gives the system a symmetrical bidirectional compensation capability: that is, sufficient displacement compensation to prevent overload under extreme high temperatures, and an equal amount of rebound compensation to maintain preload under extreme low temperatures, ensuring that displacement fluctuations remain within a constant force platform regardless of whether the ambient temperature rises or falls. Specifically: A calibration method for a steel-aluminum heterogeneous connection system with constant force characteristic displacement compensation, used for calibrating the steel-aluminum heterogeneous connection system, includes the following steps: In a normal temperature assembly environment, by controlling the tightening torque or tightening angle, the initial compression displacement of the elastic compensation core 20 is positioned at the midpoint of the span of the constant force characteristic plateau region of the load and deformation curve. Midpoint of the span, i.e., compressive displacement Place.

[0026] In addition, regarding the rigid-flexible graded limit protection design, the present invention provides an axial limit part 40 with axial travel through the elastic compensation core 20, which maintains a preset gap with the locking end face. In terms of graded force transmission logic, the elastic compensation core 20 is responsible for compensating for daily temperature difference deformation; when a high-speed collision and high-load transient occurs, the axial limiting part 40 quickly stops and turns into rigid force transmission, ensuring that the collision energy can be effectively transferred to the energy absorption box and not be excessively absorbed by the elastic compensation core 20.

[0027] A rigid limiting element 30 is coaxially sleeved on the outer periphery of the bolt 10 and forms a rigid positioning fit with the elastic compensation core 20, and the two maintain a relatively fixed overall relationship. The rigid limiting element 30 is provided with an axial limiting portion 40 extending along the bolt axis, and the axial limiting portion 40 and the insulating hole cover surface maintain a preset gap in the axial direction. The rigid limiting element 30 is a sleeve; or it is a plurality of rigid bodies arranged in a radial circumferential array along the bolt.

[0028] Regardless of the form used, the axial stiffness of the rigid limiting element 30 should be at least one order of magnitude higher than the equivalent stiffness of the elastic element 20 in the plateau region to ensure a rigid force transmission path under dynamic collision loads. In one specific embodiment, please refer to the appendix. Figure 5 , 6 As shown, the elastic compensation core 20 is a disc spring, and the elastic compensation core 20 is fixedly limited to a disc spring. Disc springs are used to absorb axial displacement caused by the difference in thermal expansion coefficients in steel-aluminum composite structures, so as to maintain the preload fluctuation range of bolt 10 ≤ ±10%.

[0029] In one specific embodiment, please refer to the appendix. Figure 1-4 As shown, the axial limiting part 40 is used to limit the maximum axial compression stroke of the disc spring, and abuts against the insulating hole cover when the vehicle encounters a transient high collision load, so that the rigid limiting element forms a rigid force transmission path and realizes the rigid transmission of the collision load.

[0030] In one specific embodiment, the inner cone height of the disc spring With single-piece thickness The preferred ratio is 1.5 to 1.6.

[0031] In one specific embodiment, please refer to the appendix. Figure 1 As shown, the disc spring is a single-piece conical disc spring structure conforming to the DIN2093 standard; or; It is a slotted disc spring.

[0032] In one specific implementation method, before calibration, the maximum axial displacement difference and compressive displacement of the steel-aluminum composite structure due to temperature difference are calculated. This makes the constant force characteristic plateau width of the disc spring... This is to achieve bidirectional displacement compensation at both high and low temperatures.

[0033] In a specific implementation method, after calibration, the displacement fluctuation of the steel-aluminum heterogeneous connection system with constant force characteristic displacement compensation under extreme temperature difference is limited to the range of constant force characteristic plateau area, and the bolt preload fluctuation range is ≤±10%.

[0034] For a specific implementation method, please refer to the appendix. Figure 1-7 As shown, the range of the constant force characteristic plateau region is the axial compressive displacement range. At that time, the fluctuation range of bolt preload within this range is ≤±5%.

[0035] Example (Failure Scenario) This invention provides an embodiment under a failure scenario, which can be understood as: the system is in a situation where there is no constant force platform area, no rigid limit, and the stiffness is less than an order of magnitude, and the fluctuation exceeds 10%; in the prior art, if the connection system is not equipped with an elastic element with constant force characteristics, when the relative displacement is caused by temperature change or structural deformation, the connection preload will change significantly with the displacement, making it difficult to maintain a stable contact state. Without a rigid limiting structure, when the displacement exceeds the effective working range of the elastic element, the system will enter an uncontrolled deformation state, which may lead to a decrease in preload or structural instability. Furthermore, when the stiffness of the limiting structure and the stiffness of the elastic element are not effectively distinguished, the system cannot effectively transition from constant force response to rigid bearing after entering the limiting state. At the same time, when the force fluctuation within the so-called constant force range exceeds the preset range, it will weaken its ability to compensate for displacement changes, thereby affecting the overall performance of the connection system.

[0036] Example (Computational Verification Scenario) The disc spring has a stiffness of 30 N / mm, the rigid limiting element (i.e., the limiting sleeve) has a stiffness of 360 N / mm, and the single-piece thickness is... 2mm, inner cone height It is 3.2mm, calculated The ratio is 1.6, falling on Within the numerical range; In a preferred embodiment, the equivalent stiffness of the disc spring is 10-50 N / mm, and in this embodiment it is 30 N / mm; the equivalent stiffness of the limiting structure is significantly higher than that of the disc spring, preferably by an order of magnitude, for example, 300-800 N / mm, to ensure that the system enters a near-rigid load-bearing state after the limit is reached.

[0037] Inner cone height of disc spring With single-piece thickness The ratio is preferably 1.4 to 1.7. Within this range, the disc spring exhibits an approximately constant force plateau characteristic during compression. The corresponding constant force platform has a displacement range of 1 to 5 mm, which is used to compensate for the relative displacement of the connection system under temperature change conditions.

[0038] Within the constant force platform range, the fluctuation of the connection preload is preferably controlled within the range of ±5% to ±10%, which is approximately ±8% in this embodiment, thereby ensuring the stability of the connection system under thermal cycling and load variation conditions.

[0039] Example (Constant Force Platform Area) As attached Figure 8 As shown, the connection system exhibits segmented force and displacement response characteristics during assembly and compression.

[0040] During the initial assembly stage, the disc spring gradually transitions from a free state to a compressed state, and the system stiffness gradually increases with the compression displacement. Once the preset assembly position is reached, the disc spring enters a constant force operating range, within which the overall system stiffness is relatively low (first ratio). (as shown in the position), and the output load changes little with displacement, thus absorbing the relative displacement caused by temperature changes or material expansion differences, and achieving stable maintenance of preload; When the displacement exceeds the constant force working range, the limiting structure begins to participate in the force, the system stiffness gradually increases, and it enters the transition stage. As attached Figure 8 When the system reaches the limit contact state, its stiffness rapidly increases to the second ratio. The position, and the second ratio The position is significantly higher than the first ratio The position of the load is preferably an order of magnitude higher than that of the load-bearing system, so that the system can enter a near-rigid load-bearing state to meet the structural load-bearing requirements under extreme conditions.

[0041] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0042] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A steel-aluminum heterogeneous connection structure with constant force characteristic displacement compensation, applied to the bolted connection parts of a vehicle steel-aluminum composite structure, characterized in that... include: Bolt (10); An elastic compensation core (20) is sleeved on the outer periphery of the bolt (10); A rigid limiting element (30) is coaxially sleeved on the outer periphery of the bolt (10) and forms a rigid positioning fit with the elastic compensation core (20), and the two maintain a relatively fixed overall relationship. The elastic compensation core (20) is a disc spring or an elastic pad constructed as a single cone, and the elastic compensation core (20) has a height defined as the inner cone height. With single-piece thickness The parameter, the inner cone height With the thickness of the single piece The ratio satisfies ; The elastic compressive core (20) is compressed in the axial direction of the bolt (10). A constant force characteristic plateau region is formed with a load fluctuation range of ≤±10%, and the width of the constant force characteristic plateau region is... Satisfying formula (1): （1）； in, The equivalent clamping length for the bolted connection system; The highest ambient temperature encountered by the steel-aluminum composite structure throughout the vehicle's entire life cycle; The lowest ambient temperature at which the steel-aluminum composite structure is subjected to throughout the entire life cycle of the vehicle; Due to extremely large temperature differences in the environment; is the coefficient of linear expansion of aluminum alloy; is the coefficient of linear expansion of steel; The rigid limiting element (30) is configured in conjunction with the elastic compensation core (20) in the pre-tightening path of the bolt (10), and the rigid limiting element (30) is provided with an axial limiting part (40) extending along the axial direction of the bolt (10). The stepped surface of the axial limiting part (40) maintains a preset axial gap with the insulating hole cover surface of the steel-aluminum composite structure, and the axial stiffness of the rigid limiting element (30) is at least one order of magnitude higher than the equivalent stiffness of the elastic compensation core (20) in the constant force characteristic plateau region.

2. The steel-aluminum heterogeneous connection system with constant force characteristic displacement compensation according to claim 1, characterized in that, The elastic compensation core (20) is a disc spring; The disc spring is used to absorb the axial displacement caused by the difference in thermal expansion coefficients of the steel-aluminum composite structure, so as to maintain the preload fluctuation range of the bolt (10) ≤ ±10%.

3. The steel-aluminum heterogeneous connection system with constant force characteristic displacement compensation according to claim 2, characterized in that, The axial limiting part (40) is used to limit the maximum axial compression stroke of the disc spring and abuts against the insulating hole cover when the vehicle encounters a transient high collision load, so that the rigid limiting element forms a rigid force transmission path and realizes the rigid transmission of the collision load.

4. The steel-aluminum heterogeneous connection system with constant force characteristic displacement compensation according to claim 2, characterized in that, The inner cone height of the disc spring With single-piece thickness The preferred ratio is 1.5 to 1.

6.

5. The steel-aluminum heterogeneous connection system with constant force characteristic displacement compensation according to claim 2, characterized in that, The disc spring is a single-piece conical disc spring structure conforming to DIN2093 standard; or It is a slotted disc spring.

6. The steel-aluminum heterogeneous connection system with constant force characteristic displacement compensation according to claim 1, characterized in that, The rigid limiting element (30) is a sleeve; or It consists of multiple rigid bodies arranged in a radial circumferential array along the bolt.

7. A calibration method for a steel-aluminum heterogeneous connection system with constant force characteristic displacement compensation, used to calibrate the connection system according to any one of claims 1 to 6, characterized in that, include: In a normal temperature assembly environment, by controlling the tightening torque or tightening angle, the initial compression displacement of the elastic compensation core (20) is positioned at the midpoint of the span of the constant force characteristic plateau region of the load and deformation curve; The midpoint of the span, i.e., the compression displacement Place.

8. The steel-aluminum heterogeneous connection system with constant force characteristic displacement compensation according to claim 7, characterized in that, Before calibration, calculate the maximum axial displacement difference and compressive displacement of the steel-aluminum composite structure caused by temperature difference. The width of the constant force characteristic plateau of the disc spring is thus increased. This is to achieve bidirectional displacement compensation at both high and low temperatures.

9. The steel-aluminum heterogeneous connection system with constant force characteristic displacement compensation according to claim 8, characterized in that, After calibration, the displacement fluctuation of the steel-aluminum heterogeneous connection system with constant force characteristic displacement compensation under extreme temperature difference is limited to the range of the constant force characteristic platform area, and the bolt preload fluctuation range is ≤±10%.

10. The steel-aluminum heterogeneous connection system with constant force characteristic displacement compensation according to claim 9, characterized in that, The range of the constant force characteristic platform region is the axial compressive displacement range. At that time, the fluctuation range of the bolt preload within this interval is ≤ ±5%.

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