【作者】 于海波；

【导师】 李幼德；

【作者基本信息】 吉林大学 ， 车辆工程， 2008， 博士

【摘要】 针对传统汽车试验场可靠性试验技术规范存在的问题,提出一种与用户用途关联的汽车可靠性试验方法,与现行的试验方法相比,该方法能把用户对车辆的实际使用工况与试验场强化试验结合起来,真正考虑了用户的真实用法,避免了试验盲目性。根据威布尔分布参数估计值及Miner线性累积损伤法则,计算出了用户平坦、中等不平和极端不平三种典型路面汽车承载系构件的B₁₀疲劳寿命里程,通过Monte-Carlo仿真获得了承载系构件的90%用户目标里程。应用修正的Neuber公式及Manson-Coffin应变寿命曲线方程绘制了承载系构件的双对数应变-疲劳寿命曲线。在研究车辆用户用途关联可靠性试验技术原理的基础上,应用Visual C++语言编写了汽车承载系试验场可靠性试验寿命仿真计算软件,结果表明仿真计算的寿命里程与试验场和用户使用试验结果基本吻合。利用试验场与用户的关联数学模型,优化计算出90%用户和试验场数据雨流矩阵载荷谱相同条件下的试验场强化路循环次数,制订了与用户用途关联的汽车承载系可靠性试验规范,新规范与现行的试验方法相比能快速预报承载系构件的潜在故障,缩短试验周期、降低试验成本及新产品开发费用。更多还原

【Abstract】 Modern vehicle design must take market as guidance, the product of design life excessive or insufficient is usually uneconomical and lacks market competition. So no matter in process of the vehicle design, development or test stage, should consider customer field usage. The vehicle reliability test is one important method, which inspects and evaluates whether the vehicles are durable or not. The traditional test basis is partial to the strength test, but not the life test. They are all in order to guarantee vehicle components haven’t fracture under the worst operating condition, and also can satisfy the general project requirement. Obviously, these tests basically rely on the experience or custom, mainly depend on the extrapolation, but not base on the scientific principle. The domestic present reliability test specifications of automotive proving grounds are partial to simple, and the testing eligible products on proving ground can not guarantee satisfaction to customers, and neglected the influence of the operating order of the road categories on the structural fatigue life, so as to the failure regularity difference is obvious between the test results of proving ground and customer actual usage, separately fits the different probability distribution.In view of the above questions,the customer correlation reliability test technique was proposed, the technique considered real world customer field usage, compared with the traditional test method. Through the optimization and calculation of the correlation model between the customer and proving ground, can establish the reliability test specifications, which reflected the customer actual operating conditions, and provide a new method for vehicle reliability test.Combined with the Formulating Method of the Customer’s Relevant Test Specifications of the Motor Truck Load Carrying Proving Ground and Formulation of the Reliability Test Specifications of the Main Automotive Assemblies in Nong’an Automotive Proving Ground, the key research projects of the Technological Center of China FAW Group Corporation, the research is carried out in the paper. A new method for customer correlation reliability test was proposed based on automotive proving ground, and the method can combine the real customer field usage to the vehicle with the enhancement test on proving ground, and avoid the test blindness. Aiming at the data that were tested on the typical road surfaces of the customer and enhancement roads of proving ground, the rain-flow counting method was used to obtain the load distribution matrixes , according to the correlation equation, the cumulative fatigue damage and loading spectrums of the 90% customer and proving ground were optimized and calculated. Through the correlation analysis of the test data, the road surface enhancement coefficient and the reliability test specifications of proving ground were obtained. The test results indicate that the new specifications can predict the potential failures of the load carrying structures quickly, shorten the test cycles, and reduce the test cost and new product development expense, compared with the existing test method.1. Research of the Customers Target Mileage CorrelationIn order to make the formulated test specifications able to truly reflect the customer’s use, the on-site investigation of the actual use of the national relevant vehicles. According to the customer’s data investigated, the MLE technique is applied to evaluate the Weibull parameters of the three typical road surfaces. The determined Weibull parameters and Miner cumulative damage rule are used to calculate the customer’s total fatigue failure mileage of the load carrying structures of the even, moderately uneven and extremely uneven road surfaces. With the Monte-Carlo simulation, 90% of the customer’s target mileage of the load carrying structures is available.2. Research of the Customer Correlation Reliability Test ProjectWith the analysis of the model stress and limit elements of the load carrying structures and experience, the critical dangerous positions of the structures. ADAMS and limit element fatigue software are used to carry out the fatigue analysis of the weigh beam and determine its weak position. According to the stress centralization principle of the electric resistance strain gage, stress, displacement and acceleration sensors of the loading structures are laid out. Considering the demand of the measuring precision, the engine suspension is designed and modified again to make it play the roles of suspension and sensor simultaneously.3. Research of the Correlation Test Model of Automotive Load Carrying System between Proving Ground and Customers UsageIn application of the least square method and combination with the fatigue cumulative damage and Basquin relation, the linear fitting of the fatigue life discrete data is made and the mathematical model of the S-N curve is obtained. The Goodman experience fatigue formula is used to equivalently transform the non-zero average stress to the zero average stress. The modified Neuber method and Manson-Coffin strain life curve equation are used to transform the nominal strain-time course to the local strain-time course and draw the double-log strain-fatigue life curve of the load carrying structures.4. Analysis and Disposal of the Customer Correlation Reliability test Data between Proving Ground and Customers UsageAccording to the principle of the customer’s use correlation reliability test technology, the rain-flow matrix equivalent loading spectrum method is used to build the customer’s use and proving ground correlation mathematical model, treat the test data of the customer and the proving ground and optimally calculate the proving ground strengthened road cycle indexes of the rain-flow matrix loading spectrum of 90% of the customer’s and proving ground data. In line with the problems existing in the technical specifications of the traditional reliability test, according to the road loading spectrum correlation mathematical model of the customer and proving ground, the automotive load carrying reliability test specifications related to the customer’s use are scientifically formulated, which provides the new test method for the determination of the new automotive products and reliability test.5. Simulation Analysis and Test Validation of the Customer Correlation Reliability Test MethodThe special test clamp is used to carry out the loading calibration of the key examined load carrying structures (front and rear axles, front and rear suspensions and weigh beams of the cabin). According to the equivalent life method of the fatigue test, the mathematical model of the acceleration coefficient of the key structures. The calculating procedure of the acceleration coefficient is used and the S-N curve is combined to calculate all the strengthened roads and the acceleration coefficient of the combined comprehensive road. The Visual C++ language is applied to formulate the automotive load carrying proving ground reliability life mileage evaluation software. The life evaluation software is used to evaluate the actual used life mileage of the automotive proving ground and the customer. The results show that the life mileage evaluated by the simulation evaluation software is basically consistent with the test results of use of the proving ground and the customer.更多还原