【作者】 李鹏；

【导师】 李杰；

【作者基本信息】 吉林大学 ， 车辆工程， 2007， 硕士

【摘要】 汽车可靠性试验是汽车产品定型和质量考核过程中的重要环节之一,随着我国汽车工业的发展,国内几大汽车试验场已相继建成并陆续投入使用,国产汽车产品开发的可靠性试验工作已经由公路行驶试验转变为试验场试验。通过试验场强化试验认识与提高汽车产品的可靠性,是当今国内外汽车生产企业加快产品开发速度以及提高质量的主要手段之一。按照强化试验规范进行的汽车可靠性试验,试验周期大为缩短,试验费用也大大降低,对汽车产品的开发具有十分重要的意义。汽车试验场道路强化系数的研究和估算是制定强化试验规范的重要依据,也是制定规范的基础工作之一。本文以某载货汽车为研究对象,以其关键部件汽车车桥在普通公路与强化道路的试验数据为基础,从疲劳寿命和失效概率两个角度讨论强化系数的计算方法,以便为汽车试验场可靠性强化试验规范的制定提供重要依据。对采集到的时域试验数据进行包括剔除异常点、消除趋势项、平稳性及正态性检验等数据预处理与检验工作。采用国内外目前认为最为符合疲劳损伤规律的雨流计数法,对试验数据进行分析处理工作,得到载荷的应力均幅值和频次的关系。利用Goodman疲劳经验公式,对应力频次关系进行非零平均应力的等效转换。通过计算得到汽车车桥的疲劳特性曲线及等效应力幅值的双参数威布尔分布函数,将实测载荷扩展后得到车桥的八级程序载荷谱。根据Miner线性疲劳累积损伤理论,从零部件疲劳寿命的角度建立强化系数的数学模型,利用这一数学模型通过计算可以得到试验场的道路强化系数,通过推导得到组合道路的综合强化系数的数学模型。采用参数估计的方法得到了汽车车桥疲劳极限的正态分布函数,根据应力—强度干涉理论建立强化系数的数学模型,从而可以通过计算得到失效概率指标下的道路强化系数。基于疲劳寿命和失效概率两个指标建立的强化系数数学模型,开发了一套完整的汽车试验场道路强化系数的计算软件,根据试验数据对两种模型得到的计算结果进行了对比与评价,对课题下一阶段的研究工作提出了一些有意义的参考意见。更多还原

【Abstract】 The automobile reliability test is one of the important links in the process of finalizing and evaluating the automobile products. Along with the development of automobile industry in China, major domestic automobile proving ground have been built and gradually put into use. The reliability test for exploitation of automobile products has shifted from road test on to proving ground test. Most of the automobile proving grounds have more stringent testing road conditions. When vehicles drive on these roads, their vibration will be stronger than on actual ones, that is to say the stress load and the frequency of the components will increase. Compared to the actual roads, automobile reliability test on proving ground are also named the enhanced test or the accelerated life test. Nowadays, more and more auto manufacturers accelerate the pace of developing and improving the reliability of automobile products by testing on proving grounds. According to proving ground running standards, the automobile reliability test can significantly shorten the test cycle. As the test cost will be greatly reduced, there will be great significance for the development of vehicle products. With these reasons, the research on automobile enhancement test has been an important subject .Based on China’s current road conditions, vehicle structure, the use of the environment and working conditions features, there are such practical problems as researches on the rules and methods of enhancement test, designing the proving ground road and establishing enhancement test norms. The various road mileages, the test speed distribution and the composite patterns must be stipulated, particularly in enhancement test norms. It is one of the important contents and the significant basis in drawing up automobile proving ground enhancement test norms, which studies and estimates the enhancement coefficient. The enhancement coefficient is the ratio of injury equivalent in practical road condition and proving condition.This paper takes the model truck as the object, which is researched by the method of calculating enhancement coefficient of motor vehicle reliability on proving ground, according to the equal damage fatigue life principle.By measuring one of the key components, the trucks axles fatigue capability, the fatigue life and the failure probability parameters have been discussed as the method of calculation and the theoretical proof of enhancement coefficient. So this paper could provide an important foundation for constituting the automobile reliability test norms of proving grounds.The research of this thesis can be summarized in the following aspects:(1) In this paper, the author uses an improved PaйTa rule to remove the anomalies of test data, which is followed by the use of the least squares method to eliminate the trend data component, and the inspection of the smooth and normality relations of test data by using rounds test andχ2 method. The results also prove that the test data are consistent with the smooth and normality indicators.(2) The test data are load-time histories, which have been pretreated. In order to analyze the fatigue damage of automobile parts, they must be simplified to a series of the entire circle or semi-circle process, so that we could analysis fatigue life and calculate the enhancement coefficient. In this paper, we have acquired the relationship of the frequency of the mean and amplitude load by using rainflow method. Then we obtain the zero mean equivalent loads by using Goodman experiential fatigue equation.(3) In this paper, we use Basquin relationship to acquire the fatigue characteristic curve of the automobile axles material. Then we employ the least-squares method to acquire the Weibull distributing function of equivalent loads of the rear axle and used the K-S method to inspect the assumption of the distribution function. The results have proved that the equivalent stress amplitude obeys the hypothetical distribution function. We also calculate the max loads by expanded sample method, and acquire eight routine loads spectrum of rear axle by Conover classification method. Meanwhile the author calculates the enhancement coefficient in principle of Miner linear accumulated fatigue damage rule and educes the mathematical model of calculating enhancement coefficient of synthesized roads.(4) We outline the reliability function of automotive products and acquire materials fatigue characteristic indicators of rear axle, and obtain the normal distribution function of the automobile rear axle fatigue limit by parameter estimation method. Then we have educed the failure probability indicators mathematical model of calculating enhancement coefficient by using the stress-strength interference theory and the Weibull distributing function and calculated the enhancement coefficient.In this paper, we have researched the complete determination and calculation method of the enhancement coefficient. Through the fatigue life and the failure probability acquired mathematical model of the enhancement coefficient, this paper compares and evaluates calculated results. Eventually, we give a summary to the research content of this paper, and provide some meaningful suggestions to the next stage research work.更多还原