基于加速寿命试验的引信贮存寿命预测

引信的贮存寿命预测对提高弹药装备可靠性指标具有重要的意义。在分析某引信在自然贮存环境下的失效模式和失效机理的的基础上,建立其贮存可靠性模型,确定贮存加速模型和加速寿命试验方案,利用恒湿恒温箱进行试验,对某引信试验数据进行处理,利用威布尔分布和极大似然估计预测其贮存寿命为10.50年,该方法的采用有效提高了引信后勤保障的费效比。     

内燃机铝合金活塞疲劳寿命预测研究

以内燃机铝合金活塞弹塑性有限元计算为基础，研究了高温蠕变影响下铝合金活塞寿命的预测方法，给出了寿命宏观预测公式。针对一具体的高强化柴油机铝合金活塞，计算预测了其寿命，并将计算结果与活塞台架试验及发动机整机可靠性试验数据进行了比较，证明了预测公式及预测方法的可靠性。     

基于退化量分布的电主轴可靠性评估

针对在较短的时间内难以评估高可靠度、长寿命电主轴可靠度的问题,利用基于退化量分布的方法对其可靠性进行评估。首先对电主轴的失效机理进行了分析;然后结合退化量分布的基本原理和退化试验数据对电主轴的可靠性进行评估,分别求出电主轴的4个常用可靠性指标,同时绘制可靠度曲线、失效概率密度曲线以及失效率曲线;最后估计出电主轴的平均寿命和特征寿命。该方法缩短了试验时间,提高了评估精度,对长寿命产品的可靠性研究具有一定的意义。     

泥浆泵活塞偏磨分析

泥浆泵是石油钻井的重要设备之一。活塞是泥浆泵运转过程中的易损件,是比较容易失效的部件,活塞偏磨是引起其失效的主要原因。活塞偏磨后容易造成缸套拉伤,一旦拉伤严重,就需要成套更换,无形中增加了钻井成本。本文通过对泥浆泵活塞偏磨的原因进行了分析,可以采取预防性措施,提高活塞的使用寿命,从而提高钻井效率,降低钻井成本。     

高速磨削电主轴可靠性加速寿命试验分析

为在短时间内获得高速磨削电主轴的寿命信息,通过加大载荷应力的方式建立起加速寿命试验模型,进行了两组恒定应力加速寿命试验。采用威布尔分布对电主轴寿命进行描述,并借助于最小二乘法对威布尔分布函数的两个参数进行估算,确定出电主轴可靠性寿命的相关指标,最终计算出基准载荷下电主轴的可靠性寿命。数据统计结果表明,电主轴的寿命服从威布尔分布,其加速模型符合逆幂律关系,从而验证了在不改变失效机理的前提下对高速磨削电主轴进行载荷应力加速寿命试验的可行性,极大地提高了产品寿命的预测效率,对电主轴生产厂商和用户均有很强的指导意义。     

基于Weibull分布的小型气缸可靠性分析

在气动系统应用中,气缸作为最多的一种执行机构,其可靠性是实现整个系统安全、可靠的前提。以某小型高速气缸的常规寿命试验为基础,通过对气缸的失效机理分析,确定其失效模型。根据可靠性统计方法确定气缸寿命的具体分布形式。利用中位秩法对失效数据进行预处理,提出利用计算机实现可靠性特征参数的最小二乘估计的方法,并在此基础上建立了气缸可靠性分析模型。应用此模型可以得到气缸的可靠度分布,为气缸的可靠性定量分析提供了一种可行的方法。     

无失效数据的可靠性评估和寿命预测

提出一种无失效数据可靠性评估和寿命预测方法 ,给出其可靠度和使用寿命的置信下限。该方法在Weibull分布形状参数下限已知的情况下 ,能将所有无失效寿命数据进行累加 ,大大提高可靠性分析的精度 ;而在对数正态分布标准差上限已知的情况下 ,可以充分发挥对数正态分布的可靠度和使用寿命置信下限较高的优点。此外 ,还建立对数寿命标准差和Weibull分布形状参数之间的关系式 ,从而能够根据工程上积累的大量对数正态分布标准差上限的数据求得Weibull分布形状参数下限 ,反之亦然。本文方法易于计算 ,便于工程应用     

无失效数据的可靠-I生评估和寿命预测

提出一种无失效数据可靠性评估和寿命预测方法，给出其可靠度和使用寿命的置信下限。该方法在weibull分布形状参数下限已知的情况下，能将所有无失效寿命数据进行累加，大大提高可靠性分析的精度；而在对数正态分布标准差上限已知的情况下，可以充分发挥对数正态分布的可靠度和使用寿命置信下限较高的优点。此外，还建立对数寿命标准差和weibull分布形状参数之间的关系式，从而能够根据工程上积累的大量对数正态分布标准差上限的数据求得weibull分布形状参数下限，反之亦然。本文方法易于计算，便于工程应用。     

探针电连接件的退化失效及寿命分析

从一款探针电连接器使用时的快速退化失效现象出发,提出了基于失效原因的可靠性建模方法.通过分析指出其失效原因是负载电流过大导致工作温升过大,从而导致加速失效,仿真验证时通过设置合理的仿真参数保证了仿真结果的可靠性.进行了温度应力下的寿命建模,数据上结合了仿真给出的温度-电流关系和使用时的寿命次数-电流关系.方法上采用了Arrhenius温度应力退化模型和退化速率线性假定,综合考虑了失效阈值的动态影响,给出了寿命次数-温度模型,建模结果与实际寿命数据有着较好的拟合效果,并利用模型给出探针使用和改良指导.该过程与一般的基于加速退化实验的建模方法比较,数据依赖度小,可行度高,可为工程人员提供一种实用的连接器失效分析方法.     

高频轻载自润滑关节轴承加速寿命试验方法

为在短时间内获得高频轻载自润滑关节轴承的寿命信息,通过增大载荷的方式建立了加速寿命试验模型,进行了2组恒定应力加速寿命试验。采用韦布尔分布对关节轴承寿命进行描述,并借助最小二乘法对韦布尔分布函数的2个参数进行估算,确定出关节轴承可靠性寿命的相关指标,最终计算出基准载荷下关节轴承的可靠性寿命。数据统计结果表明,关节轴承的寿命服从韦布尔分布,其加速模型符合逆幂律关系,从而验证了在不改变失效机理的前提下对高频轻载自润滑关节轴承进行载荷应力加速寿命试验的可行性,极大地提高了产品寿命的预测效率。     

表面形貌对活塞环密封及摩擦性能的影响

综合考虑活塞环表面形貌、弹性变形、运动面型线影响,建立柴油机活塞环-缸套摩擦副的弹性流体动压润滑计算模型,分析活塞环表面纹理方向及粗糙度大小对活塞环窜气及摩擦功耗的影响。研究发现,随着转速的提升,活塞的窜气量及摩擦功耗会加剧,导致发动机效率降低;活塞环-缸套摩擦副的表面纹理方向影响窜气量和摩擦功耗,采用活塞环横向纹理和缸套纵向纹理配合时,对活塞环窜气量及摩擦功耗的改善效果较好;活塞环和缸套的表面粗糙度对密封和润滑特性有较大影响,当缸套表面粗糙度增大时,窜气量先减小后增大,摩擦功耗先增大后减小,而在一定范围内,当活塞环表面粗糙度增大时,窜气量和摩擦功耗都减小。     

激光淬火在高压空气压缩机气缸套中的应用

通过对高压空气压缩机气缸套内表面激光淬火与传统热处理对比, 结果表明经过激光淬火大大提高了缸套的耐磨性、抗疲劳、耐腐蚀、抗氧化等性能,且改善了摩擦副间的润滑状况,从而很好地延长了气缸套和活塞环的使用寿命.     

Frictional evaluation of thermally sprayed coatings applied on the cylinder liner of a heavy duty diesel engine: Pilot tribometer analysis and full scale engine test

The piston system accounts for roughly half of the mechanical friction of an internal combustion engine, thus it is important to optimize. Different thermally sprayed cylinder liners were investigated in order to optimize the frictional impact of the contact between cylinder liner and piston ring/piston. A novel tribometer test setup was used to scan through different materials at different running conditions. Two cylinder liner materials showed significantly lower friction than the other tested materials, CrC–NiCr and MMC. All the thermally sprayed cylinder liners were worn significantly less than the reference material. Based on these results a full-scale single cylinder test was performed to validate the results from the rig. Comparing the thermally sprayed cylinder liner MMC with reference cylinder liner the test showed higher friction torque for the MMC cylinder liner except in one case; at low speed and high pressure. An analysis of the results between the tribometer and the engine points at the importance of the ratio between viscous and mechanical friction losses. The most probable cause of higher friction torque for the thermally sprayed coating (MMC) is that the functional surface of the cylinder liner promotes an increase in viscous friction.     

船舶柴油机气缸套拉缸机理的试验研究

根据模拟试验的相似准则设计磨损试验,研究对船舶航行安全构成严重威胁的异常磨损现象,例如拉缸和咬缸。试验结果表明硬化相的性能和含量与试验所选用的材料耐磨性相一致,且随着载荷的增加,材料发生拉毛的时间呈指数关系下降,本文根据摩擦副三滑磨面接触模型,进而提出摩擦界面温度升高导致粘着以及摩擦副表面的强烈摩擦导致硬化相的碎裂甚至折断等因素是气缸套异常磨损的根本原因,为预防气缸套拉缸或者咬缸提供了理论依据。     

Investigation on the radial micro-motion about piston of axial piston pump

The limit working parameters and service life of axial piston pump are determined by the carrying ability and lubrication characteristic of its key friction pairs. Therefore, the design and optimization of the key friction pairs are always a key and difficult problem in the research on axial piston pump. In the traditional research on piston/cylinder pair, the assembly relationship of piston and cylinder bore is simplified into ideal cylindrical pair, which can not be used to analyze the influences of radial micro-motion of piston on the distribution characteristics of oil-film thickness and pressure in details. In this paper, based on the lubrication theory of the oil film, a numerical simulation model is built, taking the influences of roughness, elastic deformation of piston and pressure-viscosity effect into consideration. With the simulation model, the dynamic characteristics of the radial micro-motion and pressure distribution are analyzed, and the relationships between radial micro-motion and carrying ability, lubrication condition, and abrasion are discussed. Furthermore, a model pump for pressure distribution measurement of oil film between piston and cylinder bore is designed. The comparison of simulation and experimental results of pressure distribution shows that the simulation model has high accuracy. The experiment and simulation results demonstrate that the pressure distribution has peak values that are much higher than the boundary pressure in the piston chamber due to the radial micro-motion, and the abrasion of piston takes place mainly on the hand close to piston ball. In addition, improvement of manufacturing roundness and straightness of piston and cylinder bore is helpful to improve the carrying ability of piston/cylinder pair. The proposed research provides references for designing piston/cylinder pair, and helps to prolong the service life of axial piston pump.     

润滑油中加入纳米氧化铝对缸套-活塞环摩擦副摩擦磨损特性的影响

在普通CD40润滑油中加入纳米氧化铝，研究了在不同载荷条件下对缸套活塞环摩擦副摩擦磨损特性的影响；用铁谱仪对试验油样进行了磨粒分析；用原子力显微镜对缸套试样表面的微观形貌进行了测试；用LAS-3000型表面分析系统对磨损表面进行了成分分析。结果表明：缸套活塞环摩擦副在含纳米氧化铝的润滑油作用下，表现出优越的抗摩减磨性能，其效果随栽荷的增大而增强；在高载荷作用下缸套试样表面形貌有了明显的改观，减小了摩擦阻力，降低了摩擦因数。     

润滑油粘度对缸套/活塞环摩擦学性能的影响

在内燃机实际运行中,润滑油的粘度直接影响到润滑油膜的状态,因而活塞环在缸套中不同位置时的摩擦、润滑状态各不相同。文中以缸套活塞环为研究对象,建立了润滑计算模型,并运用该模型对缸内压力、温度、油膜厚度和摩擦系数进行了分析。结果表明,润滑油膜厚度和摩擦系数随转速改变而发生变化,而剪切稀化导致润滑油粘度减小是引起该变化的主要原因。最后,通过对计算结果的分析,提出了适用于缸套活塞环的润滑油粘度指标。     

Frictional modes of barrel shaped piston rings under flooded lubrication

A friction force measurement system using the floating liner method was developed to study the frictional behavior of piston rings. The measurement system was designed to control the effect of the secondary piston motion and to control temperatures of the cylinder wall and oil. The friction force between the barrel shaped piston ring and the cylinder liner was measured under flooded oil supply conditions. The measured friction forces were classified into five frictional modes with regard to the combination of predominant lubrication regimes (boundary, mixed and hydrodynamic lubrication) and stroke regions (mid-stroke and dead centers). The modes were identified on a Stribeck diagram, where the friction coefficients were evaluated both at mid-stroke and at the dead centers.     

Effect of Bio-Lubricant and Biodiesel-Contaminated Lubricant on Tribological Behavior of Cylinder Liner–Piston Ring Combination

This article addresses the issue of friction and wear characteristics of diesel engine cylinder liner–piston ring combinations under different lubricating conditions using a pin-on-disc wear tribometer. The discs were made out of actual engine cylinder liner material using a casting process. Pins were made out of top compression ring material. The tests were conducted on a pin-on-disc tribometer for wear and friction characteristics of the cylinder liner and piston ring combination with diesel-contaminated rapeseed oil–based bio-lubricant, diesel-contaminated commercial synthetic lubrication oil (SAE 20W40), biodiesel-contaminated commercial synthetic lubrication oil (SAE 20W40), and used (150 h) commercial synthetic lubrication oil (SAE 20W40). Experimental results demonstrated that the rapeseed oil–based bio-lubricant and biodiesel-contaminated synthetic lubricant exhibited better performance in terms of wear, friction, and frictional force under similar operating conditions. Thus, usage of newly formulated bio-lubricant and biodiesel in the long run may have a positive impact on engine life.     

发动机缸套-活塞环摩擦磨损特性试验研究

利用缸套-活塞环摩擦磨损试验台研究了速度，温度，载荷，供油等因素对缸套-活塞环系统摩擦磨损特性的影响。试验结果表明，缸套-活塞环摩擦副在发动机工作循环中润滑状态不断发生变化。在试验条件下，温度对摩擦磨损有显著影响，载荷和速度对摩擦力的影响较小。