Light truck frame fatigue simulation rapid analysis method

Abstract

A rapid fatigue simulation analysis method for light truck frames is disclosed. This method first determines the loading load and the ratio of bending to torsional loads in a bending-torsional combined load condition based on road spectrum data from one road cycle in a full-vehicle road durability test. The loading load of the bending-torsional combined load condition is then input into a constructed finite element model of the frame for finite element analysis. Based on the finite element analysis results, fatigue simulation analysis is performed by simulating the bending-torsional combined load condition using a combination of constant amplitude and cyclic loads. Finally, the fatigue life of the frame is calculated using the material's S-N curve. This invention not only effectively shortens the simulation modeling and iteration cycle but also has lower accuracy requirements for connector parameters.

Description

Technical Field

[0001] This invention belongs to the field of automotive system simulation testing, specifically relating to a rapid analysis method for fatigue simulation of light truck frames. Background Technology

[0002] As the base of a car chassis, the frame bears the weight of major assemblies, bending moments, and torsional angles caused by uneven road surfaces. Almost all automotive components are mounted on the frame via brackets. For certain structural components subjected to uneven stress, random road surface excitation can easily cause fatigue damage to the frame, thus affecting the overall vehicle safety performance. Therefore, fatigue durability analysis of the frame is particularly important.

[0003] Currently, the simulation analysis of vehicle frame fatigue durability performance typically employs a quasi-static simulation analysis method based on virtual iteration. This analysis process mainly includes inertial release to solve the finite element unit load stress-strain of the frame, acquisition of road spectrum data from the test track, iteration of the vehicle's multibody dynamics model, extraction of the load spectrum at frame connection points, and fatigue analysis using SN curves. This method can accurately analyze the fatigue durability performance of the vehicle during road durability tests, but the analysis cycle is long and requires high accuracy of the parameters of the elastic elements at the connection points. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned problems in the existing technology by providing a rapid analysis method for fatigue simulation of light truck frames with a short testing cycle and low requirements for parameter accuracy.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A rapid fatigue simulation analysis method for light truck frames includes the following steps:

[0007] Step A: Based on the road spectrum data from one road cycle in the vehicle road durability test, determine the loading load of the bending-torsional combined condition and the ratio coefficient of the bending condition to the torsional condition within the bending-torsional combined condition. Input the loading load of the bending-torsional combined condition into the constructed frame finite element model for frame finite element analysis. The loading load of the bending-torsional combined condition includes vertical impact load and torsional displacement. The method for determining the ratio coefficient of the bending condition to the torsional condition within the bending-torsional combined condition is as follows:

[0008] First, calculate the ratio P1 of the total damage of the Belgian section within a road cycle to the damage caused by the maximum vertical impact load, and the ratio P2 of the total damage of the tortuous section within a road cycle to the damage caused by a single torsional load. Then, use the ratio of P1 to P2 as the proportional coefficient between the bending condition and the torsional condition in the combined bending and torsional conditions.

[0009] Step B: Based on the finite element analysis results of the chassis, fatigue simulation analysis is performed by simulating bending and torsion combined conditions through a combination of constant amplitude load and cyclic load. The fatigue life of the chassis is then calculated using the material SN curve.

[0010] In step A, P1 is obtained by performing damage analysis on the strain of the Belgian road section.

[0011] In step A, P2 is obtained by performing damage analysis on the strain of the tortuous road section.

[0012] In step A, the vertical impact load is the maximum acceleration amplitude of the Belgian road section, and the torsional displacement is determined according to the standard for tortuous road sections.

[0013] In step A, the road spectrum data is the data after preprocessing the collected road spectrum signals, wherein the preprocessing includes signal cropping, filtering, sorting and combining.

[0014] The damage analysis and fatigue simulation analysis were both performed using nCode software.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] This invention discloses a rapid fatigue simulation analysis method for light truck frames. First, based on road spectrum data from a single road cycle in a full-vehicle road durability test, the loading load for the combined bending and torsional load condition and the ratio coefficient between the bending and torsional loads within this condition are determined. The loading load for the combined bending and torsional load condition is then input into a constructed finite element model of the frame for finite element analysis. Based on the finite element analysis results, fatigue simulation analysis is performed by simulating the combined bending and torsional load condition using a combination of constant amplitude and cyclic loading. The fatigue life of the frame is calculated using the material's SN curve. This method, based on road spectrum analysis from a single road cycle, maps bending and torsional load conditions to the frame finite element model. By replacing the virtual iterative process of multibody dynamics loads with fatigue simulation of the combined bending and torsional load condition, it effectively shortens the simulation modeling and iteration cycle, facilitating rapid assessment of the frame's durability performance. Furthermore, it has lower accuracy requirements for connector parameters. Therefore, this invention not only effectively shortens the simulation modeling and iteration cycle but also has lower accuracy requirements for connector parameters. Attached Figure Description

[0017] Figure 1 This is the overall flowchart of the present invention.

[0018] Figure 2 This is a diagram showing the total damage and the damage caused by the maximum vertical impact load on a Belgian road section within one road cycle in Example 1.

[0019] Figure 3This is a diagram showing the total damage of a tortuous road segment within a road cycle and the damage caused by a single torsional load in Example 1.

[0020] Figure 4 The image shows the fatigue damage cloud map of the chassis obtained in Example 1. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0022] See Figure 1 A rapid analysis method for fatigue simulation of light truck frames, comprising the following steps:

[0023] Step A: Based on the road spectrum data from one road cycle in the vehicle road durability test, determine the loading load of the bending-torsional combined condition and the ratio coefficient of the bending condition to the torsional condition within the bending-torsional combined condition. Input the loading load of the bending-torsional combined condition into the constructed frame finite element model for frame finite element analysis. The loading load of the bending-torsional combined condition includes vertical impact load and torsional displacement. The method for determining the ratio coefficient of the bending condition to the torsional condition within the bending-torsional combined condition is as follows:

[0024] First, calculate the ratio P1 of the total damage of the Belgian section within a road cycle to the damage caused by the maximum vertical impact load, and the ratio P2 of the total damage of the tortuous section within a road cycle to the damage caused by a single torsional load. Then, use the ratio of P1 to P2 as the proportional coefficient between the bending condition and the torsional condition in the combined bending and torsional conditions.

[0025] Step B: Based on the finite element analysis results of the chassis, fatigue simulation analysis is performed by simulating bending and torsion combined conditions through a combination of constant amplitude load and cyclic load. The fatigue life of the chassis is then calculated using the material SN curve.

[0026] In step A, P1 is obtained by performing damage analysis on the strain of the Belgian road section.

[0027] In step A, P2 is obtained by performing damage analysis on the strain of the tortuous road section.

[0028] In step A, the vertical impact load is the maximum acceleration amplitude of the Belgian road section, and the torsional displacement is determined according to the standard for tortuous road sections.

[0029] In step A, the road spectrum data is the data after preprocessing the collected road spectrum signals, wherein the preprocessing includes signal cropping, filtering, sorting and combining.

[0030] The damage analysis and fatigue simulation analysis were both performed using nCode software.

[0031] The principle of this invention is explained as follows:

[0032] This invention provides a rapid analysis method for fatigue simulation of light truck frames. This method uses a combination of bending and torsion conditions to simulate the fatigue durability of the frame, replacing the more cumbersome multibody dynamics model building and virtual iteration process. By measuring the strain signals of the Belgian road section and torsional road section in the test track that cause the main damage to the frame, and combining the damage equivalence principle, the ratio coefficient of the bending condition to the torsional condition in the combination of bending and torsion conditions is determined. It has the advantages of short test cycle and low requirements for connecting component parameters, and is suitable for rapid development and evaluation.

[0033] Normal vehicle durability testing requires approximately 25,000 km of mileage to complete, depending on the specific vehicle model and standards, with about 1,000 hours spent on half of that. This invention, however, only requires obtaining road spectrum data from the test track for one cycle (one cycle is 12.5 km) from road spectrum information, eliminating the need for multiple cycles to reach 25,000 km. Furthermore, after obtaining data from one cycle, the acquired data can be directly used for fatigue simulation analysis of other similar vehicle models, without requiring further full-vehicle road durability testing.

[0034] Example 1:

[0035] See Figure 1 A rapid fatigue simulation analysis method for light truck frames is proposed, which proceeds in the following steps:

[0036] 1. Construct a finite element model of the vehicle frame.

[0037] 2. According to the light truck durability test specifications, a full vehicle road durability test is conducted on different road surfaces. A road spectrum signal of one road cycle is collected and preprocessed as road spectrum data. The preprocessing includes signal trimming, resampling, filtering, channel selection, channel number sorting and combination.

[0038] 3. Pseudo-damage analysis was performed on the road spectrum data to determine that the Belgian section and the tortuous section caused the most damage to the chassis during the entire road test, accounting for more than 95%. Therefore, the working conditions of these two road sections were used as the working conditions for fatigue simulation analysis.

[0039] 4. Based on road spectrum data, using road spectrum data from one road cycle in the vehicle road durability test, determine the loading load of the bending-torsional combined condition and the ratio coefficient of the bending and torsional conditions within the bending-torsional combined condition. Input the loading load of the bending-torsional combined condition into the constructed finite element model of the chassis for finite element analysis of the chassis to determine the stress magnitude at various points on the chassis and the locations of potential risks. The loading load of the bending-torsional combined condition includes vertical impact load and torsional displacement. The vertical impact load is the maximum acceleration amplitude of the Belgian road section, and the torsional displacement is determined according to the standard for tortuous road section C. The calculation method for the ratio coefficient of the bending and torsional conditions within the bending-torsional combined condition is as follows:

[0040] First, damage analysis was performed on the strain of the Belgian road section and the tortuous road section using nCode software to obtain the ratio P1 of the total damage of the Belgian road section to the damage caused by the maximum vertical impact load within one pavement cycle, and the ratio P2 of the total damage of the tortuous road section to the damage caused by a single torsional load within one pavement cycle. Then, the ratio of P1 to P2 was used as the proportional coefficient between the bending condition and the torsional condition in the bending-torsional combined working condition.

[0041] In this embodiment, a comparison chart of the total damage to the Belgian road section within one road cycle and the damage caused by the maximum vertical impact load is provided. Figure 2 Comparative analysis determined that the total damage of the Belgian road section was 12.7 times that of the damage caused by the maximum vertical impact load, i.e., P1 = 12.7. A comparison chart of the total damage of a torsional section within one pavement cycle and the damage caused by a single torsional load can be found here. Figure 3 Through comparative analysis, it was determined that the total damage of the tortuous section is 12.7 times that of the damage caused by a single torsional load, i.e., P2=12.7. Therefore, the ratio of the bending condition to the torsional condition in the bending-torsional combined working condition is 1.

[0042] 5. Based on the finite element analysis results of the chassis, a combination of constant amplitude load and cyclic load was used to simulate bending and torsional conditions. Fatigue simulation analysis was performed using nCode software, and the results were as follows: Figure 4 The fatigue damage cloud map of the chassis shown is used to calculate the fatigue life of the chassis by combining the material SN curve, and to determine the equivalent fatigue endurance mileage of the chassis at the test track.

Claims

1. A rapid analysis method for fatigue simulation of light truck frames, characterized in that: The analytical method includes the following steps in sequence: Step A: Based on the road spectrum data from one road cycle in the vehicle road durability test, determine the loading load of the bending-torsional combined condition and the ratio coefficient of the bending condition to the torsional condition within the bending-torsional combined condition. Input the loading load of the bending-torsional combined condition into the constructed frame finite element model for frame finite element analysis. The loading load of the bending-torsional combined condition includes vertical impact load and torsional displacement. The method for determining the ratio coefficient of the bending condition to the torsional condition within the bending-torsional combined condition is as follows: First, calculate the ratio P1 of the total damage of the Belgian road section within a road cycle to the damage caused by the maximum vertical impact load, and the ratio P2 of the total damage of the tortuous road section within a road cycle to the damage caused by a single torsional load. Then, use the ratio of P1 to P2 as the proportional coefficient between the bending condition and the torsional condition in the bending-torsional combined working condition. Step B: Based on the finite element analysis results of the chassis, fatigue simulation analysis is performed by simulating bending and torsion combined conditions through a combination of constant amplitude load and cyclic load. The fatigue life of the chassis is then calculated using the material SN curve.

2. The rapid analysis method for fatigue simulation of a light truck frame according to claim 1, characterized in that: In step A, P1 is obtained by performing damage analysis on the strain of the Belgian road section.

3. A rapid analysis method for fatigue simulation of a light truck frame according to claim 1 or 2, characterized in that: In step A, P2 is obtained by performing damage analysis on the strain of the tortuous road section.

4. A rapid analysis method for fatigue simulation of a light truck frame according to claim 1 or 2, characterized in that: In step A, the vertical impact load is the maximum acceleration amplitude of the Belgian road section, and the torsional displacement is determined according to the standard for tortuous road sections.

5. A rapid analysis method for fatigue simulation of a light truck frame as described in claim 1 or 2, characterized in that: In step A, the road spectrum data is the data after preprocessing the collected road spectrum signals, wherein the preprocessing includes signal cropping, filtering, sorting and combining.

6. The rapid analysis method for fatigue simulation of a light truck frame according to claim 2, characterized in that: The damage analysis and fatigue simulation analysis were both performed using nCode software.

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