Automobile exhaust system hook position arrangement analysis method

Abstract

The application discloses a kind of automobile exhaust system lifting hook position arrangement analysis methods, comprising the following steps: S1, model establishment and finite element pre-processing;S2, exhaust system free mode analysis;S3, average driving freedom degree displacement ADDOFD quantitative calculation;S4, based on ADDOFD cloud atlas determines optimal lifting hook arrangement point position: traditional experience design is converted into quantitative analysis, utilizes ADDOFD (average driving freedom degree displacement) index accurately identifies the vibration node of exhaust system under dynamic excitation, reduces the dynamic stiffness to car body from the root;It can intervene in the early project scheme stage, avoids mold modification and project delay due to NVH problem in later period, and greatly saves research and development cost;Lifting hook is arranged on the node where vibration energy is weakest, effectively prevents lug from falling off due to excessive fatigue, and improves the structural reliability of exhaust system.

Description

Technical Field

[0001] This invention relates to the field of automotive exhaust system technology, and in particular to a method for analyzing the position arrangement of hooks in automotive exhaust systems. Background Technology

[0002] A car's exhaust system typically consists of components such as an exhaust manifold, catalytic converter, bellows, mufflers (front and rear), and connecting pipes. It connects to the engine exhaust end via flanges and is suspended from the vehicle floor by multiple hooks and rubber hangers. As one of the vehicle's key vibration and sound sources, the exhaust system is subjected to the dual effects of engine vibration and internal airflow pulsation. If the hook suspension points are improperly positioned, the exhaust system's vibration energy will be directly transmitted to the vehicle floor via the hangers, exciting local floor vibrations and radiating noise into the cabin, severely impacting the passenger comfort (NVH performance), as illustrated by a verification method for improving exhaust system vibration transmission disclosed in patent CN119043734A. Furthermore, an unreasonable suspension position can cause the hangers to bear excessive dynamic loads over long periods, accelerating fatigue and aging, and even leading to reliability risks such as hanger detachment.

[0003] In the current automotive R&D process, there are significant technical limitations in determining the location of exhaust system hangers: Currently, most automakers rely primarily on the experience of design engineers or reverse engineering of competing models to determine the hanger location. As the development cycle of automotive platforms continues to shorten and the overall vehicle layout becomes increasingly compact (e.g., limited by space constraints such as fuel tanks, rear suspension, and spare tire wells), it is frequently found in the later prototype stages that the hanger location cannot meet NVH performance requirements.

[0004] If design changes are made at this point, not only will the surrounding environment be difficult to adjust, but it will also bring high costs and time delays due to mold modifications. The traditional "trial and error method" lacks quantitative prediction methods for vibration transmission paths in the early design stage, and cannot scientifically guide the placement of hooks at nodes or low-sensitivity areas of exhaust system vibration, thus failing to block the transmission of vibration to the vehicle body at the source. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for analyzing the position arrangement of hooks in automotive exhaust systems, aiming to place the hooks in the area with the weakest vibration energy.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] This application provides a method for analyzing the position arrangement of hooks in an automotive exhaust system, including the following steps:

[0008] S1. Model Establishment and Finite Element Preprocessing:

[0009] Collect complete geometric data models of the exhaust system of the target vehicle model, and use Hypermesh preprocessing software to build a refined finite element model of the exhaust system. The complete finite element model of the exhaust system includes all structural components such as the exhaust manifold, catalytic converter, bellows, front muffler, rear muffler and connecting pipes.

[0010] S2. Free modal analysis of the exhaust system:

[0011] The standard modal analysis module of the solver is called to perform modal calculations on the finite element model of the exhaust system in an unconstrained free state. The modal analysis frequency range is set to 20Hz to 200Hz. The natural frequencies, mode displacement vectors and element strain energy data of each mode of the exhaust system in this frequency range are solved and output.

[0012] S3, Average Driven Degrees of Freedom Displacement ADDOFD Quantization Calculation:

[0013] Based on the theory of modal superposition, using white noise / full-band sweep frequency as the equivalent excitation source of the system, under the preset conditions of modal mass normalization and approximately equal damping of each modality, the average driving degree of freedom displacement ADDOFD value corresponding to each degree of freedom of each node of the exhaust system is calculated by weighted superposition.

[0014] S4. Determine the optimal hook placement point based on ADDOFD cloud map:

[0015] Based on the ADDOFD calculation results of the full model nodes, an ADDOFD numerical distribution cloud map of the exhaust system is generated. The vibration node region corresponding to the local minimum value of ADDOFD in the cloud map is identified, and the vibration node region is used as the priority layout coordinate of the hook. Then, the feasibility of the layout point is verified by combining the space layout constraints around the vehicle fuel tank, rear suspension, and spare tire pit. After the verification is passed, the hook layout analysis report is output, and the optimized layout of the exhaust system hook position is completed.

[0016] Further or preferred:

[0017] The analysis method described herein is applicable to the early NVH forward design of the exhaust system at the P1 scheme node, P2 digital model refinement node, and P3 engineering freeze node in the initial data stage of the vehicle, and is also applicable to the optimization and improvement of the exhaust system hook arrangement in the facelift model.

[0018] The 20Hz to 200Hz analysis frequency range matches the vibration frequency range corresponding to the dual excitation of exhaust system airflow pulsation and engine body vibration under engine idling conditions to medium and high speed conditions.

[0019] The minimum value region of the ADDOFD value is the vibration stationary node with the lowest vibration amplitude under wideband excitation of the exhaust system. Placing the hook in this region can cut off the path of the exhaust system vibration energy transmitted to the vehicle floor through the rubber hanger, reduce the radiated noise in the vehicle, and at the same time reduce the dynamic alternating load of the hanger.

[0020] In the aforementioned analysis method, the unidirectional ADDOFD distribution cloud map is solved for the X, Y, and Z unidirectional degrees of freedom, or the total ADDOFD distribution cloud map is synthesized by superimposing the three unidirectional degrees of freedom, which is used to distinguish the vibration-sensitive areas of the exhaust system in different directions.

[0021] In the analysis method, if the vibration node with the minimum ADDOFD value has spatial interference with the surrounding components of the vehicle, the next lower ADDOFD value area near the interference boundary is selected as the alternative hook placement point, and multiple sets of NVH simulation comparison data of the alternative points are output simultaneously.

[0022] In step S2, after the free modal analysis is completed, the strain energy of each modal element is extracted simultaneously. The strain energy distribution results are then jointly verified with the ADDOFD cloud map to eliminate high stress areas with concentrated strain energy and further screen for hook placement points with better structural durability.

[0023] In step S3, the quantization calculation formula is as follows:

[0024]

[0025] in,

[0026] N is the total number of modes in the 20-200Hz analysis frequency band; φjr is the modal participation factor or mode shape component of the j-th node degree of freedom in the r-th mode; ωr is the natural circular frequency of the r-th mode.

[0027] The analytical method is applied in the development of NVH performance of automobiles and the optimization of the structural durability and reliability of exhaust systems.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] The proposed method for analyzing the placement of the exhaust system hooks is rationally designed, transforming traditional experience-based design into quantitative analysis. By utilizing the ADDOFD (Average Driven Degrees of Freedom Displacement) index, it accurately identifies vibration nodes in the exhaust system under dynamic excitation, thereby reducing the dynamic stiffness transmitted to the vehicle body from the root. This approach allows for intervention in the early stages of the project, avoiding mold modifications and project delays caused by NVH issues later on, significantly saving R&D costs. Placing the hooks at the nodes with the weakest vibration energy effectively prevents the lifting lugs from falling off due to excessive fatigue, thus improving the structural reliability of the exhaust system. Attached Figure Description

[0030] The following is a brief explanation of the contents of each of the accompanying drawings and the markings in the drawings:

[0031] Figure 1 This is a schematic diagram of the analysis process for this invention. Detailed Implementation

[0032] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and through the description of the examples.

[0033] Although the invention has been shown and described herein with reference to specific embodiments, it is not intended to be limited to the details shown. Rather, various modifications in detail may be made within the equivalent scope and scope of the claims without departing from the invention. In the drawings, the same item numbers refer to the same elements.

[0034] Throughout this disclosure, various terms are used to describe the physical shape or arrangement of features. Many of these terms are used to describe features conforming to a cylindrical or generally cylindrical geometry with the feature as its radius and a central axis perpendicular to that radius. Unless otherwise specified, the terms are given the following meanings: The terms “longitudinal,” “longitudinal,” “axial,” and “axial” refer to a direction, dimension, or orientation parallel to the central axis. The terms “radial” and “radially” refer to a direction, dimension, or orientation perpendicular to the central axis. The terms “inward” and “inner” refer to a direction, dimension, or orientation extending radially toward the central axis. The terms “outward” and “outer” refer to a direction, dimension, or orientation extending radially away from the central axis.

[0035] In this specification, relative terms such as “horizontal,” “vertical,” “upward,” “downward,” “top,” and “bottom,” and their derivatives (e.g., “horizontal,” “downward,” “upward,” etc.) should be interpreted as referring to the direction described or the direction shown in the accompanying drawings. These relative terms are for ease of description and are not generally intended to require a specific direction.

[0036] like Figure 1 As shown, this application provides a method for analyzing the position arrangement of a car exhaust system hook, including the following steps:

[0037] S1. Model Establishment and Finite Element Preprocessing:

[0038] Collect complete geometric data models of the exhaust system of the target vehicle model, and use Hypermesh preprocessing software to build a refined finite element model of the exhaust system. The complete finite element model of the exhaust system includes all structural components such as the exhaust manifold, catalytic converter, bellows, front muffler, rear muffler and connecting pipes.

[0039] S2. Free modal analysis of the exhaust system:

[0040] The standard modal analysis module of the solver is called to perform modal calculations on the finite element model of the exhaust system in an unconstrained free state. The modal analysis frequency range is set to 20Hz to 200Hz. The natural frequencies, mode displacement vectors and element strain energy data of each mode of the exhaust system in this frequency range are solved and output.

[0041] S3, Average Driven Degrees of Freedom Displacement ADDOFD Quantization Calculation:

[0042] Based on the theory of modal superposition, using white noise / full-band sweep frequency as the equivalent excitation source of the system, under the preset conditions of modal mass normalization and approximately equal damping of each modality, the average driving degree of freedom displacement ADDOFD value corresponding to each degree of freedom of each node of the exhaust system is calculated by weighted superposition.

[0043] The quantitative calculation formula is as follows:

[0044]

[0045] in,

[0046] N represents the total number of modes in the 20-200Hz analysis frequency band; φjr represents the modal participation factor or mode shape component of the j-th node degree of freedom in the r-th mode; ωr represents the natural circular frequency of the r-th mode.

[0047] In Patran or HyperView post-processing software, PCL functions are called to execute... The calculation involves performing modal weighted superposition on the three translational degrees of freedom or the one-way target vibration degrees of freedom of the nodes, and finally obtaining the ADDOFD values ​​of each node after full-band weighting.

[0048] Solve the unidirectional ADDOFD distribution cloud map for each of the X, Y, and Z degrees of freedom, or combine the three degrees of freedom to synthesize the total ADDOFD distribution cloud map, which is used to distinguish the vibration-sensitive areas of the exhaust system in different directions;

[0049] S4. Determine the optimal hook placement point based on ADDOFD cloud map:

[0050] Based on the ADDOFD calculation results of the full model nodes, an ADDOFD numerical distribution cloud map of the exhaust system is generated. The vibration node region corresponding to the local minimum value of ADDOFD in the cloud map is identified, and the vibration node region is used as the priority layout coordinate of the hook. Then, the feasibility of the layout point is verified by combining the space layout constraints around the vehicle fuel tank, rear suspension, and spare tire pit. After the verification is passed, the hook layout analysis report is output, and the optimized layout of the exhaust system hook position is completed.

[0051] This invention relates to the application of the method for analyzing the position arrangement of exhaust system hooks in automobiles in the development of NVH performance and the optimization of exhaust system structure durability and reliability. Specifically, it is applicable to the early NVH design of the exhaust system at the P1 scheme node, P2 digital model refinement node, and P3 engineering freeze node in the initial data stage of the vehicle. It is also applicable to the optimization and improvement of the exhaust system hook arrangement in modified models.

[0052] In step S2, after the free modal analysis is completed, the strain energy of each modal element is extracted simultaneously. The strain energy distribution results are then checked together with the ADDOFD cloud map to eliminate high stress areas with concentrated strain energy and further screen for hook placement points with better structural durability.

[0053] The analysis frequency range of 20Hz to 200Hz matches the vibration frequency range corresponding to the dual excitation of exhaust system airflow pulsation and engine body vibration under engine idling conditions to medium and high speed conditions.

[0054] In the method for analyzing the position arrangement of the automotive exhaust system hook in this invention:

[0055] The minimum value region of ADDOFD is the vibration stationary node with the lowest vibration amplitude under wideband excitation of the exhaust system. Placing the hook in this region can cut off the path of the exhaust system vibration energy transmitted to the vehicle floor through the rubber hanger, reduce the radiated noise in the vehicle, and at the same time reduce the dynamic alternating load of the hanger.

[0056] If the minimum ADDOFD vibration node interferes with the surrounding components of the vehicle, the next lower ADDOFD low value area near the interference boundary is selected as the alternative hook placement point, and multiple sets of NVH simulation comparison data of the alternative points are output simultaneously.

[0057] This method for analyzing the placement of the exhaust system hooks is rationally designed, transforming traditional experience-based design into quantitative analysis. By utilizing the ADDOFD (Average Driven Degrees of Freedom Displacement) index, it accurately identifies vibration nodes in the exhaust system under dynamic excitation, fundamentally reducing the dynamic stiffness transmitted to the vehicle body. It can be intervened in the early stages of the project, avoiding mold modifications and project delays caused by NVH issues later on, significantly saving R&D costs. Placing the hooks at the nodes with the weakest vibration energy effectively prevents the lifting lugs from falling off due to excessive fatigue, improving the structural reliability of the exhaust system.

[0058] This solution changes the traditional development model of exhaust hooks, which relies on experience benchmarking and prototype trial and error. It transforms the exhaust system hook layout from qualitative experience-based design to quantitative simulation analysis. The solution uses the average drive degree of freedom displacement (ADDOFD) as a unified quantitative evaluation index. Based on modal simulation of 20Hz to 200Hz, which closely matches the actual excitation frequency band of the engine, it accurately identifies the stationary nodes under broadband vibration of the exhaust system through a standardized finite element calculation process. This can block the transmission of vibration to the vehicle body through the hook at the design source, fundamentally optimizing the NVH performance of the entire vehicle, effectively suppressing floor vibration and in-vehicle radiated noise, and significantly improving driving comfort.

[0059] This analytical method can be embedded into the entire development process of a vehicle project, from the early M0 model to the P3 engineering freeze stage. It allows for the optimization of hook placement without waiting for physical prototype manufacturing, avoiding the high costs and project delays incurred by modifying structures and adjusting molds due to spatial interference after NVH defects are discovered later in the process, as is common with traditional solutions. The entire analysis process is standardized, relying on visual ADDOFD distribution cloud maps to intuitively display the vibration intensity in each area. It also facilitates collaboration and communication between CAE simulation engineers and structural layout engineers, reducing cross-disciplinary design communication costs.

[0060] This application simultaneously considers the overall vehicle NVH performance and the structural durability and reliability of the exhaust system. By placing the hook at the ADDOFD low-value vibration node, the dynamic alternating load on the rubber hanger can be significantly reduced, mitigating reliability risks such as hanger fatigue aging and detachment. At the same time, the solution supports joint verification of modal strain energy and ADDOFD cloud map, and comparison and screening of multiple sets of low-value alternative points. Even when spatial interference from surrounding components occurs, a feasible solution that balances NVH and structural strength can still be quickly selected, adapting to various development scenarios such as new platform models and facelifted models.

[0061] The main concepts behind the analysis method for the location arrangement of the automotive exhaust system hook are as follows:

[0062] The protection utilizes the average driven degrees of freedom displacement (ADDOFD) as a quantitative evaluation criterion for the quality of the exhaust system hook position, and its specific calculation formula is used for weighted summation. The protection sets a specific analysis frequency range for the exhaust system NVH performance, namely 20Hz to 200Hz, which is highly consistent with the exhaust excitation frequency band from engine idle speed to mid-to-high frequency. The complete operation process includes obtaining the geometric model, establishing the finite element model, performing SOL 103 free modal analysis, data post-processing and weighted solution of ADRDOFD cloud map, and determining the hook position based on the local minimum principle.

[0063] This invention aims to solve the technical problem that existing exhaust system hook placement relies on experience and cannot effectively predict vibration transmission paths in the early stages. Its key point lies in transforming "passive testing" into "active design": by constructing the system's modal space using finite element method and simulating the system's potential displacement response under broadband excitation using the average driving degree of freedom displacement method, the invention identifies the stationary point on the exhaust system with the minimum forced vibration before physical prototype manufacturing, serving as the breakpoint for force transmission. This decouples the vibration excitation source from the vehicle body, ultimately improving NVH performance.

[0064] The above description is merely an illustration of preferred embodiments of the present invention, and the above technical features can be arbitrarily combined to form multiple embodiments of the present invention.

[0065] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the concept and technical solution of the present invention, or the direct application of the concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A method for analyzing the position arrangement of hooks in an automotive exhaust system, characterized in that: Includes the following steps: S1. Model Establishment and Finite Element Preprocessing: Collect complete geometric data models of the exhaust system of the target vehicle model, and use Hypermesh preprocessing software to build a refined finite element model of the exhaust system. The complete finite element model of the exhaust system includes all structural components such as the exhaust manifold, catalytic converter, bellows, front muffler, rear muffler and connecting pipes. S2. Free modal analysis of the exhaust system: The standard modal analysis module of the solver is called to perform modal calculations on the finite element model of the exhaust system in an unconstrained free state. The modal analysis frequency range is set to 20Hz to 200Hz. The natural frequencies, mode displacement vectors and element strain energy data of each mode of the exhaust system in this frequency range are solved and output. S3, Average Driven Degrees of Freedom Displacement ADDOFD Quantization Calculation: Based on the theory of modal superposition, using white noise / full-band sweep frequency as the equivalent excitation source of the system, under the preset conditions of modal mass normalization and approximately equal damping of each modality, the average driving degree of freedom displacement ADDOFD value corresponding to each degree of freedom of each node of the exhaust system is calculated by weighted superposition. S4. Determine the optimal hook placement point based on ADDOFD cloud map: Based on the ADDOFD calculation results of the full model nodes, an ADDOFD numerical distribution cloud map of the exhaust system is generated. The vibration node region corresponding to the local minimum value of ADDOFD in the cloud map is identified, and the vibration node region is used as the priority layout coordinate of the hook. Then, the feasibility of the layout point is verified by combining the space layout constraints around the vehicle fuel tank, rear suspension, and spare tire pit. After the verification is passed, the hook layout analysis report is output, and the optimized layout of the exhaust system hook position is completed.

2. The method for analyzing the position arrangement of the automotive exhaust system hook as described in claim 1, characterized in that: The analysis method described herein is applicable to the early NVH forward design of the exhaust system at the P1 scheme node, P2 digital model refinement node, and P3 engineering freeze node in the initial data stage of the vehicle, and is also applicable to the optimization and improvement of the exhaust system hook arrangement in the facelift model.

3. The method for analyzing the position arrangement of the automotive exhaust system hook as described in claim 1, characterized in that: The 20Hz~200Hz analysis frequency range matches the vibration frequency range corresponding to the dual excitation of exhaust system airflow pulsation and engine body vibration under engine idling conditions to medium and high speed conditions.

4. The method for analyzing the position arrangement of the automotive exhaust system hook as described in claim 1, characterized in that: The minimum value region of the ADDOFD value is the vibration stationary node with the lowest vibration amplitude under wideband excitation of the exhaust system. Placing the hook in this region can cut off the path of the exhaust system vibration energy transmitted to the vehicle floor through the rubber hanger, reduce the radiated noise in the vehicle, and at the same time reduce the dynamic alternating load of the hanger.

5. The method for analyzing the position arrangement of the automotive exhaust system hook as described in claim 1, characterized in that: In the aforementioned analysis method, the unidirectional ADDOFD distribution cloud map is solved for the X, Y, and Z unidirectional degrees of freedom, or the total ADDOFD distribution cloud map is synthesized by superimposing the three unidirectional degrees of freedom, which is used to distinguish the vibration-sensitive areas of the exhaust system in different directions.

6. The method for analyzing the position arrangement of the automotive exhaust system hook as described in claim 1, characterized in that: In the analysis method, if the vibration node with the minimum ADDOFD value has spatial interference with the surrounding components of the vehicle, the next lower ADDOFD value area near the interference boundary is selected as the alternative hook placement point, and multiple sets of NVH simulation comparison data of the alternative points are output simultaneously.

7. The method for analyzing the position arrangement of the automotive exhaust system hook as described in claim 1, characterized in that: In step S2, after the free modal analysis is completed, the strain energy of each modal element is extracted simultaneously. The strain energy distribution results are then jointly verified with the ADDOFD cloud map to eliminate high stress areas with concentrated strain energy and further screen for hook placement points with better structural durability.

8. The method for analyzing the position arrangement of the automotive exhaust system hook as described in claim 1, characterized in that: In step S3, the quantization calculation formula is as follows: ； in, N is the total number of modes in the 20-200Hz analysis frequency band; φjr is the modal participation factor or mode shape component of the j-th node degree of freedom in the r-th mode; ωr is the natural circular frequency of the r-th mode.

9. The method for analyzing the position arrangement of the automotive exhaust system hook as described in any one of claims 1-8, characterized in that: The analytical method is applied in the development of NVH performance of automobiles and the optimization of the structural durability and reliability of exhaust systems.

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