摘 要

汽车转向节作为汽车悬架中至关重要的部件，有着极其恶劣的工作环境，所以对其有着较高的刚强度要求。随着汽车铝合金转向节的应用，使其较之以前的铸铁件有了大大提升，能够顺应汽车轻量化发展的要求，同时对于复杂工况与安全要求能够很好地满足。当然为了解决铝合金材料不如铸铁件刚强度问题，所以对于铝合金转向节进行结构优化，以保证在尽量少的材料使用上满足工作需求。由于要考虑不确定载荷的影响，本文整体设计思路是稳健性优化设计，即在追求应力最小地情况得到最优的减重效果。在为此本文以奥迪某款车型铝合金转向节为目标通过有限元分析对得到应力条件，再进行拓扑优化，根据拓扑优化结果刚强度分析结果进行对比，再对改进后的模型进行形状优化，进一步降低最大应力值。论文最终结果达到了减重9%的效果，同时整体思考上采用稳健性优化设计思路，符合安全性、可靠性和实用性的要求。

关键词:铝合金转向节，有限元分析，拓扑优化，稳健性

Abstract

As an important part of automobile suspension, the steering knuckle has extremely bad working environment, so it has high rigid strength requirement. With the application of aluminum alloy steering knuckle, it can be greatly improved compared with the previous cast iron parts, which can meet the requirements of automobile lightweight development, and can meet the requirements of complex working conditions and safety. Of course, in order to solve the aluminum alloy material is not as strong as cast iron, so the aluminum alloy steering knuckle structure optimization to ensure that the use of as few materials as possible to meet the work needs. Considering the influence of uncertain load, the whole design idea of this paper is robust and excellent。

Keywords: aluminum alloy steering knuckle, finite element analysis, topology optimization, robustness

Record

Chapter 1 Introduction 1

Chapter 2 Finite Element Analysis 5

2.1 Method for determining the load of the steering knuckle 5

2.2 Establishment of a suspension multi-dynamic model to solve the load 6

2.3 Finite element analysis 7

2.3.1. Finite element analysis and software introduction 7

2.3.2 Finite Element Analysis 9

2.4 Summary of the chapter 11

Chapter 3 Topology Optimization 12

3.1 Topology Optimization Introduction 12

3.2 Topology Optimization Model 13

3.3 Topology Optimization Process and Results 15

3.4 Rigid Strength Analysis 17

3.4.1 Over rough roads 18

3.4.2 Emergency Brake Conditions 19

3.4.3 Steering slip 20

Chapter 4 Shape Optimization 23

4.1 Optimized pre-processing 23

4.2 Optimization process 25

4.3 Summary 26

Chapter 5 Summary and Prospect 27

5.1 Conclusions 27

5.2 Outlook 27

References 29

Chapter 1 Introduction

With the rapid development of social economy, the automobile industry is changing with each passing day and vigorous forward^[1]. The output of automobile increases year by year, and the quantity of automobile ownership also increases greatly. However, the advantages and disadvantages depend on each other, which brings more serious challenges to environmental resources, and environmental protection is becoming more and more stringent. First of all, the huge increase in cars brings about increased energy consumption of oil resources and a sharp rise in vehicle emissions. At present, our country's automobile oil accounts for 5% of the total amount of oil used, oil dependence degree of 55.5%, has exceeded the United States. At present, facing the great pressure of energy environmental protection, it seriously restricts the development of our country's automobile industry. This requires the automotive industry in energy conservation and emission reduction has this better performance -- automotive lightweight technology came into being, is favored.

Automotive lightweight technology can ensure the quality of the vehicle to reduce, promote the development of the vehicle towards miniaturization, lightweight and small row quantification. This is of great significance to environmental protection, first of all reflected in the reduction of oil, which is the most direct aspect of environmental pollution, lightweight applications naturally have a unique advantage on it^[2] .Of course, lightweight technology is not just fuel-saving, but it also has a qualitative improvement in the traditional performance requirements of cars. In fact, the lightening of the body is of great benefit to the fuel economy, vehicle control stability and collision safety of the whole vehicle, and has the advantages of high output power, low noise, low vibration and good maneuverability and high reliability^[3]. These advantages have led many domestic car companies to start the reform of automotive lightweight. A year later, car companies at the Shanghai International Auto Show showed off their lightweight results. Automobile manufacturers are constantly looking for stronger and lighter raw materials to meet the requirements of consumers for environmental protection and safety performance of automobiles. Automobile lightweight technology should be linked with innovative demand, take the core technology of automobile lightweight as the long-term strategic goal, strengthen the cooperation between industry, university and research, and vigorously develop new materials, new technology, new technology and new products. Breaking through the bottleneck of the development of automobile lightweight technology and bringing it into the modern automobile manufacturing industry is of great significance for saving energy and reducing emissions. From the connotation of lightweight technology, it is necessary to integrate structural optimization design, multi-material and multi-manufacturing technology to achieve product weight loss under the condition of satisfying product function requirements and cost control. Lightweight isn't just a jerry-building, it's not just a lightweight for a simple body or a car component. In its report on "the significance of automobile lightweight ", the china auto association has pointed out that: the overall structure of automobile is analyzed and optimized to realize the simplification, integration and lightweight of automobile parts^[4]; engine lightweight; transmission lightweight; suspension lightweight; body lightweight; transmission lightweight; suspension lightweight; suspension lightweight; body lightweight and accessories lightweight are six aspects of the current realization of integrated lightweight. Automotive lightweight technology can be divided into three main aspects: structural optimization design, lightweight material application and the adoption of advanced manufacturing technology^[5,6]. Among them, structural optimization design aspects include size optimization, shape optimization, topology optimization and multidisciplinary design optimization of automotive structures; lightweight materials include high strength steel, aluminum alloy, magnesium alloy, titanium alloy, carbon fiber, plastic and composite materials; advanced manufacturing processes include, hydraulic forming and laser welding, et^[7]c. Of course, at present for the application of automotive lightweight materials, aluminum alloy materials are the first. For the steering knuckle using cast iron, it is easy to meet the strength requirements, but the disadvantage is that the quality is large, its structure has been quite compact, so it is not easy to further lightweight in the structure. Lightweight design of steering knuckle can not only reduce the weight of vehicle, promote energy saving and emission reduction, but also reduce the under-spring quality and improve the control stability of vehicle. However, directly changing the original cast iron steering knuckle to the steering knuckle of aluminum alloy material, it is easy to appear that the rigid strength is insufficient, which affects the reliability of the parts. The usual practice is to add more materials to the original structure. Although this practice can meet the strength requirements, blindly increasing the material can not make more efficient use of the material, resulting in the effect of the final weight loss is not obvious^[8]. Therefore in the aluminum alloy steering knuckle design and manufacture process, should carry on the sufficient structure optimization design.

At present, in the research of domestic and foreign scholars, we focus on the strength or fatigue analysis of the steering knuckle, and some scholars have designed the knuckle based on topology optimization^[9].Ⅴ. Sivananth studied the properties of aluminum matrix composites with TiC strengthening, aluminum alloy without strengthening and ball-milled cast iron applied to steering knuckle. Including its maximum damage test, impact resistance and fatigue test,at the same time, the aluminum alloy with TiC material is applied to the steering knuckle, with superior strength performance. Yuan Dan et al studied the modeling method of finite element model of steering knuckle. The modeling methods at part level, subsystem level and system level are analyzed respectively. The accuracy and advantages and disadvantages of various modeling methods are obtained. Jiang Yingchun and others established the rigid-flexible coupling dynamic model of suspension system^[10]. The load of the steering knuckle under three limit conditions is obtained and the finite element statics analysis is carried out. Using combined matlab and Adams software to obtain the load spectrum of the steering knuckle under the uneven degree of B pavement, The multi-axis fatigue life of steering knuckle is analyzed. The results show that the steering knuckle meets the design requirements of strength and fatigue life. Bai Tingting studies modal analysis theory,a modal analysis of the aluminum alloy steering knuckle is carried out using the ANSYS structural dynamics analysis module^[11]. Calculate and extract the vibration characteristics of the steering knuckle, The vibration characteristics of the steering knuckle are calculated and extracted. the first ten order intrinsic modes and frequencies of the steering knuckle are obtained^[12]. The steering knuckles of TiC reinforced aluminum matrix composites are simulated and optimized by S.Vijayarangan. Compared to the knuckles of ball-milled cast iron, It can lose about 55%.Sussumu Nohara et al. analyzed the finite element modeling method of the steering knuckles. at the same time, the evaluation criteria of the steering knuckles stiffness, stress-strain and fatigue analysis under different types of working conditions were also expounded, and the shape optimization of the steering knuckles was carried out with the simulation results as a reference, which was nearly 9% relative to the original model to reduce vibration^[13]. By simplifying the geometric model of a steering knuckle and using the ANSYS to model it, Yuan Dan sets the geometric dimensions and coordinates of the parameterized model as the design variables. Based on the lightweight development project of SUV automobile steering knuckles ,11% zeng wenhao studied the structural lightweight design method based on topology optimization, and used finite element analysis and fatigue simulation analysis to predict the static strength and fatigue performance of steering knuckles.

Therefore, this paper is based on the light weight optimization design of the steering knuckle of an Audi vehicle. There are many uncertain factors such as material density, load and so on in the process of steering knuckle manufacture and work. The influence of such factors should be fully considered in the optimization design of steering knuckle, and the fluctuation of optimization target caused by the change of uncertain factors should be considered in the optimization process. So the optimization process of aluminum alloy steering knuckle is as follows, first the stress cloud diagram is obtained by finite element analysis, and then the topology optimization is carried out according to the above results, and some materials are subtracted. The removal of the material inevitably brings the stress worth rising. The results are analyzed by the analysis of the rigid strength and the displacement diagram. In order to reduce the maximum stress value and achieve the requirements of lightweight, reliability and robustness, the shape control parameters are optimized.

Chapter 2 Finite Element Analysis

2.1 Method for determining the load of the steering knuckle