Remaining useful life estimation for deteriorating systems with time-varying operational conditions and condition-specific failure zones

Dynamic time-varying operational conditions pose great challenge to the estimation of system remaining useful life (RUL) for the deteriorating systems. This paper presents a method based on probabilistic and stochastic approaches to estimate system RUL for periodically moni-tored degradation processes with dynamic time-varying operational conditions and condition-specific failure zones. The method assumes that the degradation rate is influenced by specific oper-ational condition and moreover, the transition between different operational conditions plays the most important role in affecting the degradation process. These operational conditions are assumed to evolve as a discrete-time Markov chain (DTMC). The failure thresholds are also determined by specific operational conditions and described as different failure zones. The 2008 PHM Conference Challenge Data is utilized to illustrate our method, which contains mass sensory signals related to the degradation process of a commercial turbofan engine. The RUL estimation method using the sensor measurements of a single sensor was first developed, and then multiple vital sensors were selected through a particular optimization procedure in order to increase the prediction accuracy. The effectiveness and advantages of the proposed method are presented in a comparison with exist-ing methods for the same dataset.     

导弹密封皮碗的可靠寿命试验与评估

对某型号导弹密封系统所用的橡胶材料进行了加速老化试验,通过分析给出贮存可靠及可靠寿命等性能指标随时间、温度的变化规律。并引进随温度变化的失效率与加速系数,来研究材料对贮存温度的敏感性,从而为确定最佳贮存温度提供依据。     

一种新的应变疲劳材质参数估算方法

本文根据金属材料的循环硬化/软化特性和由能量—寿命关系导出的有关应变疲劳材质参数的估算表达式,讨论并提出了一种用材料的静力参数估算其应变疲劳材质参数的新方法,文中称之为混合法。该方法简单、明了,与目前已有的通用斜率法、四点关联法及改进的四点关联法比较具有更好的应变疲劳材质参数估算精度。     

涂层硬质合金刀具加工镍基合金的应用

本文在对镍基合金进行系统车削实验基础上,研究了多种先进硬质合金刀片的切削性能。并对涂层硬质合金刀片独特的优良性能进行了论述。文中从抗磨料磨损、抗扩散磨损及抗氧化磨损几方面,对涂层刀具的切削机理进行了分析研究。     

机械加工切削用量的优化

本文探讨了机械加工中,切削用量优化目标函数,优化数学模型,优化方法步骤。以期用该模式取代凭经验选定切削用量的方法,从而提高经济效益。     

新型铜合金衬套的研制

铝青铜合金衬套主要用在飞机起落架部位,衬套的质量问题也会影响飞行的安全。和国内现有的同种材料的铜合金衬套相比,新型铜合金衬套提高了自身的强度及耐磨性能,可减少起落架装置的故障,满足了军机的使用需求。本文介绍了这种衬套的结构特点、材质分析、制造工艺和摩擦系数测量及规定寿命试验的试验过程。     

基于神经网络与果蝇优化算法的涡轮叶片低循环疲劳寿命健壮性设计

在对涡轮叶片低循环疲劳寿命概率分析的基础上,将广义回归型神经网络(generalized regression neural network,GRNN)与果蝇优化算法(fruit fly optimization algorithm,FFOA)结合,利用果蝇优化算法的多点全局的快速搜索能力来优化影响疲劳寿命的随机变量,进行涡轮叶片低循环疲劳寿命健壮性优化设计.优化结果表明:疲劳寿命的概率区间减小17.9%,对随机变量的敏感度降低,从而可以更精确地对疲劳寿命进行估计.计算结果验证了该方法在工程应用中的可行性.      

多轴随机载荷下的疲劳寿命估算方法

提出了一种多轴随机载荷下的疲劳寿命预测方法.通过雨流计数法对各平面上的剪应变进行循环计数,以统计出的剪应变循环作为多轴疲劳损伤的主要控制参数,将各剪应变循环历程内对应的最大正应力和正应变变程作为多轴疲劳损伤的第二控制参数.根据多轴疲劳寿命模型计算出各平面上的损伤,以最大损伤平面作为多轴随机疲劳的临界平面,通过该临界平面上的损伤计算出多轴随机载荷下的疲劳寿命.采用SNCM630钢,304不锈钢和S45C钢3种金属材料的多轴随机疲劳试验数据对提出的寿命预测方法进行评估和验证.结果表明:疲劳寿命预测结果大都分布在试验结果的2倍分散带之内.     

飞机机体使用寿命定义

 <正> The maximum service period reached safely and economically by frames of an airplane is defined as service life. This definition is different from \"safe life\" or \"economic life\" specified in MILA-008866A or MIL-A-87221, respectively.It is explicated that service life is related to the overall process of production activity from material to operation management. The paper has also pointed out the way of obtaining the service life.     

涡轮叶片疲劳-蠕变寿命稳健性优化方法

为了清晰地反映涡轮叶片的疲劳-蠕变交互作用,提高寿命预测结果的准确性及可靠性,并改善涡轮叶片疲劳寿命对随机变量的敏感程度,分别采用Manson-Coffin公式和Larson-Miller方程计算了涡轮叶片的低循环疲劳寿命和蠕变持久寿命,利用修正的时间-寿命分数法计算了涡轮叶片疲劳-蠕变损伤,在此基础上,将响应面法(RSM)与果蝇优化算法(FFOA)相结合,考虑载荷、材料参数、疲劳-蠕变交互程度的不确定性,对涡轮叶片疲劳寿命进行了稳健性优化设计。优化结果表明:涡轮叶片疲劳-蠕变小时寿命的概率区间减小了8.48%,验证了该优化方法的工程可行性。