A strength analysis method for high rear door vehicles

Abstract

This paper discloses a strength analysis method for high-rear-door commercial vehicles. This method, specifically for rear-door commercial vehicles, uses fatigue testing to determine fatigue strain parameters by setting specific parameters. Based on the results, an optimized design solution is selected. This method can serve as a reference for strength analysis of rear-door commercial vehicles.

Description

Technical Field

[0001] The invention belongs to the technical field of vehicle body strength analysis, and in particular relates to a strength analysis method for a vehicle body with a high rear door. Background Art

[0002] In recent years, with the widespread adoption of commercial enclosed transport vehicles, the demand and requirements for these vehicles in the urban transportation industry have continued to increase. The frequent opening and closing of the rear doors during use can lead to cracking of the sheet metal or welds. Improving the door connection structure and adding reinforcements have become essential aspects of vehicle body design. Currently, there is no unified process or method for analyzing and processing door strength. Against this backdrop, major automakers conduct door strength analysis tests based on their specific vehicle models using specific test methods. After tens of thousands of repeated fatigue tests, these weak points are identified, allowing for optimized design and retesting to improve door strength and extend service life.

[0003] However, traditional testing is often focused on a single vehicle model or brand, lacking market standards and corresponding comparison parameters. The results obtained during testing cannot be compared, and there are no precise parameters for the overall door opening and closing frequency and strength. This inevitably leads to significant disparities in the service life and driving safety of rear doors produced by different manufacturers. Furthermore, rear doors are body components, and if they break or become damaged, they can easily damage the body frame, causing irreversible damage and impacting vehicle safety. While major manufacturers are doing their utmost to extend the service life of vehicle doors, a clear and accurate standard is still needed as a unified market entry inspection to ensure product quality.

[0004] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the Invention

[0005] The purpose of the present invention is to provide a unified vehicle body rear door detection method, determine the corresponding detection standard parameters, unify the market, facilitate the comparison of corresponding parameters of different models, and meet certain life standard requirements. The method of the present invention is aimed at high rear door vehicles, and a method for rear door strength analysis is designed, which can serve as a reference for the strength analysis of rear door commercial vehicles. This method is mainly aimed at rear door commercial vehicles. By setting certain parameters, fatigue tests are carried out to obtain corresponding fatigue strain parameters, and the corresponding optimization design scheme is selected according to the results.

[0006] The purpose of the present invention is to provide a new concept and approach to the strength testing of open and close vehicle doors, while accurately planning specific steps so that different vehicle models can be compared and referenced to a certain extent and certain normative standards can be established.

[0007] The slam door strength analysis method is a method performed on the rear door of the entire vehicle. Its main purpose is to detect stress concentration points and areas prone to plastic strain on the entire vehicle door. During the entire test process, the initial door angle and speed are controlled, and the door closing operation is repeated multiple times. After multiple cycles, an average value can be obtained, which serves as a guide for the optimization design of subsequent products.

[0008] The weld fatigue analysis method is a method for testing the strength of local welds and bolt holes on rear doors. Its main purpose is to detect the deformation of several important weld positions and bolt holes on the rear door at the moment of door slamming and during repeated door slamming. By repeating the test steps multiple times, the local plastic strain cloud map can be used to determine several holes or welds with large deformation, so as to make structural adjustments and welding improvements, thereby improving product quality and service life.

[0009] Furthermore, the key testing steps for the slam door strength analysis method and the weld fatigue analysis method are identical, differing only in the subsequent data processing and analysis. While the slam door strength analysis method can determine the plastic deformation of the entire vehicle door in just a few tests, the weld fatigue analysis method requires tens of thousands of test cycles to determine the plastic deformation of the welds.

[0010] Furthermore, the initial states in the tests of the slam door strength analysis method and the weld fatigue analysis method are both to limit the initial opening angle of the left door to 3° and the initial opening angle of the right door to 10°.

[0011] Furthermore, the initial conditions in the tests of the slam door strength analysis method and the weld fatigue analysis method are differentiated in the initial velocity. The slam door strength analysis method mainly focuses on the impact of strong impact on the door surface, while the weld fatigue analysis method focuses on the damage in the cycle. Therefore, the speed of the slam door strength analysis can be set generally higher than that of the weld fatigue analysis method. The slam door strength analysis can be set to 4m / s, and the weld fatigue analysis method can be set to 2m / s.

[0012] Furthermore, the initial conditions in the tests of the slam door strength analysis method and the weld fatigue analysis method are both set to 6 degrees of freedom for the degrees of freedom at the body-in-white cutoff.

[0013] Furthermore, in the extraction of analysis results from the slam door strength analysis method and the weld fatigue analysis method tests, the slam door strength analysis is to extract the dynamic change image of the entire door at the moment of closing the door and the plastic strain cloud map. In the weld fatigue analysis method, there are higher-level requirements for the extraction of results. First, the load history curves of the hinges and door locks during the slam door process must be extracted. Secondly, unit forces and moments in three directions must be applied to the same hinge and door lock. Finally, the number of cycles is also required to reach 100,000 cycles to obtain the plastic strain cloud maps of local welds and bolt holes.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1) This method is simple to operate, with fewer steps. It is easy for a robotic arm to operate the cyclic test, and the corresponding program can be set to quickly complete the test.

[0016] 2) This method is easy to extract data. If a physical operation test is used, accurate experimental results can be obtained in a relatively short time. If a simulation software test is used, accurate data parameters can be obtained, which can provide accurate guidance for subsequent optimization design.

[0017] 3) This method has a certain degree of universality and is applicable to both rear-door and large-door vans. Since the operation method is consistent, the data obtained can be compared and referenced.

[0018] 4) This method can be used as a reference for standardization. The relevant data obtained during the test can be standardized to a certain extent. For example, the vehicle door panel must not have any area with plastic deformation exceeding a certain value, or any welds or holes with plastic deformation exceeding a certain value. This can serve as a guide for regulating market conditions and can serve as a comparative reference for different vehicle manufacturers and models.

[0019] The above effects make the method of the present invention have long-term guiding and reference value in the fields of automobile design, research and development, optimization, equipment, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The initial state and boundary conditions for the slam door strength analysis method;

[0021] Figure 2 This is the plastic strain cloud diagram obtained by the slam-door strength analysis method;

[0022] Figure 3 This is the damage cloud diagram obtained by the weld fatigue analysis method. DETAILED DESCRIPTION

[0023] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0024] Unless expressly stated otherwise, throughout the specification and claims, the term "comprise" or variations such as "include" or "comprising", etc., will be understood to include the stated elements or components but not to exclude other elements or other components.

[0025] Figure 1 These are the finite element analysis boundary conditions for the embodiment of the strength analysis of the high rear door slamming shut described in the present invention. In order to analyze the strength characteristics of the rear door of the commercial vehicle, a finite element model including part of the body-in-white is established. During the strength analysis, the welding points, bolt connection holes, opening and closing connection parts of the vehicle model, and the positions prone to fatigue deformation are preliminarily determined. The initial state of the rear door is set to an initial opening angle of 3° for the left door and an initial opening angle of 10° for the right door. At zero time, the initial speed of the left and right doors is 4m / s. The operation cycle is repeated for a certain number of times or when obvious door damage occurs. Through the door closing simulation demonstration, the degree of deformation of the rear door during the entire door closing process is obtained, and then the result is obtained. Figure 2 The plastic strain contours at key locations on the vehicle door are shown. The figure shows that plastic deformation at some locations reaches 6.7%, exceeding the allowable deformation range and requiring structural optimization such as appropriate thickening. The door's failure-prone locations determined using this strength analysis method agree well with experimental data, demonstrating the reliability of this method.

[0026] The finite element analysis boundary conditions of the high rear door fatigue analysis embodiment of the present invention are consistent with the slam door strength analysis. In order to analyze the fatigue durability characteristics of the rear door of the commercial vehicle, a finite element model including part of the white body is established. During the fatigue analysis, the welding points, bolt connection holes, opening and closing connection parts and positions prone to fatigue deformation of the vehicle model are preliminarily determined. The initial state of the rear door is set to an initial opening angle of 3° for the left door and an initial opening angle of 10° for the right door. At time zero, the initial speed of the left and right doors is set to 2m / s. Determined by finite element analysis Figure 2 The plastic strain cloud and load history curve at the welding point and the lock position are shown in the figure. The fatigue durability analysis is carried out by applying unit force and moment in three directions to the same hinge and door lock to obtain the Figure 3The fatigue damage values ​​of the welds at the door hinges and door locks are shown, and the results are in good agreement with experimental results. For weld locations with significant damage, corresponding optimization design solutions are proposed to improve the strength of the connecting welds, thereby enhancing the overall strength of the door. After optimization and improvement, the fatigue analysis method is repeated to ultimately obtain the optimal results and solution. This technical solution was used to improve the strength and fatigue durability of the H2 high-rear-opening door of a certain vehicle model. Simulation results showed that the damage values ​​of the sheet metal and some welds at the upper hinge of the left rear door exceeded the design requirements, which is consistent with the actual vehicle test results. Further structural improvements were made by adding reinforcement plates and increasing the thickness of the sheet metal parts, and the simulation analysis method was used for verification. After the improvements, the fatigue damage values ​​at the critical points of the door were reduced by more than 60% after 100,000 cycles, showing a significant improvement. Compared with the original method based on experimental restoration, the door improvement method based on simulation analysis can improve the efficiency of door structure optimization design by more than 30% while ensuring the reliability of the results.

[0027] The foregoing descriptions of specific exemplary embodiments of the present invention are for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many variations and modifications are possible in light of the foregoing teachings. The exemplary embodiments have been selected and described for the purpose of explaining the specific principles of the invention and their practical application, thereby enabling those skilled in the art to realize and utilize a variety of exemplary embodiments of the invention and various options and modifications. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A strength analysis method for a high rear door vehicle, characterized in that: It includes a door slam strength analysis method and a solder joint fatigue analysis method, including the following steps: Step 1: Determine the model of vehicle to be selected, i.e., select the type of vehicle with high rear doors; Step 2: Create a finite element model that includes part of the body-in-white (BIW) to identify the vehicle's weld points, bolt connection holes, opening and closing joints, and locations prone to fatigue deformation. Based on the characteristics of each location, a preliminary optimization design solution is proposed. Step 3: Conduct a strength analysis test. First, define the degrees of freedom of the body-in-white (BIW). Then, open the rear doors to a certain angle and set a certain initial closing velocity for both doors (2m / s or 4m / s). Repeat the slamming door operation a certain number of times or until obvious door damage occurs. Step 4: For slam-door strength analysis, a door-closing simulation is performed to determine the door deformation during the entire closing process, and then a plastic strain cloud diagram is generated. For solder joint fatigue analysis, tens of thousands of opening and closing cycles are performed to determine the deformation of the relevant solder joints or holes in step 2, and then a plastic strain cloud diagram is generated. Step 5: Analyze the obtained plastic strain cloud map and determine the point or area where the strain is concentrated according to the color distribution change in the cloud map; Step 6: Based on these findings, propose optimized design solutions and conduct tests one by one; Step 7: Repeat steps 3 and 4 for the experiment in step 6 and compare the changes in the obtained cloud map. If the expected value or a certain range of values ​​can be reached, stop the experiment; otherwise, repeat the experiment until the optimal design improvement solution is obtained. The slam door strength analysis method is an operational step for adjusting the structure of the rear door of the entire vehicle. The strength analysis is performed by software analysis to obtain a cloud map corresponding to the overall plastic strain of the door. Locations with small plastic strain and several points or areas with large plastic strain are found in the cloud map. For the areas with large plastic strain, corresponding optimization design solutions are proposed to improve the overall strength of the door. After optimization and improvement, the strength analysis method is repeated to ultimately obtain the optimal result and solution. The weld fatigue analysis method is an operational step for structural adjustment of the hinge connection welds on the rear door. The strength analysis is to obtain a cloud map of the plastic strain of the welds at the corresponding connection locations through software analysis, accurately find welds with smaller plastic strains and welds with larger plastic strains in the cloud map, and propose corresponding optimization design solutions for the weld locations with larger plastic strains to improve the strength of the connection welds, thereby improving the strength of the entire door. After optimization and improvement, the strength analysis method is repeated to ultimately obtain the optimal result and solution.

2. The strength analysis method for a high rear door vehicle according to claim 1, characterized in that: The analysis method of the door slamming and weld fatigue analysis is as follows: the initial state is that the initial opening angle of the left door is 3°, and the initial opening angle of the right door is 10°.

3. The strength analysis method for a high rear door vehicle according to claim 1, characterized in that: The initial conditions defined by the door slamming and weld fatigue analysis method are: constraining 123456 degrees of freedom at the body cutoff, and giving the left and right doors a certain basic initial speed at time zero, including but not limited to 2m / s and 4m / s.

4. The strength analysis method for a high rear door vehicle according to claim 1, characterized in that: The analysis process of the slam door strength analysis method is as follows: the slam door strength analysis is to extract the dynamic change image of the entire door at the moment of closing and the plastic strain cloud map, and optimize the design for the position with larger plastic strain.

5. The strength analysis method for a high rear door vehicle according to claim 1, characterized in that: The analysis process of the weld fatigue analysis method is as follows: extracting the load history curves and plastic strain cloud diagrams of each hinge and door lock at the moment of slamming the door, and performing optimized design around the hinges with larger plastic strain.

6. The strength analysis method for a high rear door vehicle according to claim 1, characterized in that: The analysis requirement of the weld fatigue analysis method is to apply unit forces and moments in three directions to the same hinge and door lock.

7. The strength analysis method for a high rear door vehicle according to claim 1, characterized in that: The analysis requirement of the solder joint fatigue analysis method is 100,000 cycles.

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