基于FTA-FMMEA综合分析法的发动机曲柄连杆机构可靠性研究

为了提高发动机曲柄连杆机构的可靠度,采用FTA-FMMEA综合分析法对其进行分析。通过分析曲柄连杆机构各零件的故障,建立故障树模型,对其进行定性分析找出对系统影响较大的故障模式;对其中的活塞环磨损这一故障模式进行FMMEA分析,得到了其故障原因及故障机理,确定了其故障影响,并根据分析结果提出改进方案。改进前后的RPN值对比结果表明,FTA-FMMEA综合分析方法可以很好的分析系统故障并提高系统可靠性水平。     

基于航天系统的FPGA可靠性安全性分析方法研究

FPGA日益广泛地应用于航天系统的指挥与控制,实现较多关键功能,其产品必须具有高可靠性和安全性.目前,关于可靠性安全性分析方法的研究大部分是针对传统软件的,对FPGA不具有适用性.针对这一问题,通过研究软件的可靠性安全性分析方法,结合FPGA的应用特点,介绍了FPGA可靠性安全性分析方法,包括故障模式及影响分析(FME...     

用于低温氦及氮的双作用活塞泵运转情况

本文介绍了用于液氦、液氮的双作用活塞泵的设计、技术参数及其应用,并公布了已制造好的十五台活塞泵的运转时间和应用场合,其特点是可靠性很高,均无明显的热一声振荡和任何故障出现。图3。     

某型燃烧弹作用可靠率低的故障原因分析

采用故障树分析方法对某型燃烧弹故障问题进行了分析,建立了产品作用可靠率低的故障树,结合产品结构和试验故障现象进行故障树分析,指出引信体锥面角度过大和装药强度不足是故障产生的主要原因,通过采用减小引信体锥面角度、增加压药密度等措施,并经试验验证,对故障进行了有效归零;同时,提出了故障树分析方法在轻武器弹药故障分析领域应用的基本步骤和方法,对于故障树分析方法应用领域的拓展有一定借鉴作用.     

基于活塞杆轴心位置轨迹的往复压缩机故障诊断技术研究

提出了一种基于X方向、y方向的活塞杆轴心位置轨迹(Piston-Rod Axis Orbit)的故障诊断分析新方法,通过定义5种图形和6个特征参数来反映活塞杆的运行状态,解决了常规手段只能单一监测垂直方向位移的问题.通过仿真数据和故障数据分析,验证了活塞杆轴心位置图分析方法可以有效判断往复压缩机整个支承环的磨损方向和磨损程度,对于早期预警活塞组件、活塞杆运行状态十分有效.建立的理论方法可以早期、完整地发现往复压缩机活塞组件的潜在故障,定义的特征参数为早期预警和故障诊断专家系统规则量化提供了理论基础.     

单轴摆式加速度计输出异常的故障分析

针对某型单轴摆式加速度计在使用过程中出现的电压输出异常典型故障问题进行理论分析,利用故障树综合性分析方法,层层追踪分析,表达出输出电压出现异常故障内在联系,直观指出单元故障与整体故障之间的逻辑关系,切实归纳总结了工程运用中实际遇到的单轴摆式加速度计输出电压异常故障问题。而后对故障原因进行精确细致定位,提出振荡器电路中的D4二极管正极金丝断裂为此型号加速度计故障根本原因,融入电路金丝断裂机理分析法,并通过试验测试与改进措施方式验证了此故障分析的准确性,一定程度上提升了加速度计可靠性。研究成果可以为加速度计可靠性使用提供一定参考。     

基于图文法的产品族配置及其建模研究

根据产品族生成机理与图语言生成机理的相似性,提出了一种产品族的图文法表达方法,并根据产品族的图文法模型构建了基于图文法的产品族配置系统的体系结构.用UML对基于图文法的产品族配置系统进行用例建模、静态建模、动态建模以及编码与部署分析,从而为系统的具体开发做准备.     

机车故障数据分析系统设计与实现

随着机车设备制造业的快速发展,对于机电产品的可靠性要求大大增加了,本文在机车设备可靠性与故障诊断技术的基础上,着重分析了机车设备检测可靠性分析系统,基于机车检测的故障数据处理故障模式与故障原因分析系统,并且对可靠性数据分析系统设计功能进行相信的设计规划,在此基础上形成一个可靠实用的系统机车产品故障数据分析系统。     

柴油发电机组气缸活塞开裂分析

柴油发电机组气缸活塞裙部因开裂而导致早期失效.通过宏观和微观分析方法对开裂原因进行分析.认为活塞拉缸导致活塞裙部发生环境应力腐蚀疲劳,进而引起腐蚀疲劳断裂;活塞拉缸开裂的主要根源是活塞制造质量低劣.     

飞机真空泵故障模式分析

现代通用航空领域活塞发动机驱动的干式真空泵主要用于给姿态仪、航向仪等机载气动仪表提供真空源.简要介绍了现代通用航空领域活塞发动机驱动的干式真空泵的结构特点和工作原理,收集、整理了某飞行学校机队的真空泵故障数据,对真空泵故障模式进行了全面、系统的分类分析,并针对不同的故障模式研究对应的检查方法或预防措施,以延长真空泵寿命,提高真空泵的可靠性.     

Identification of Failure Mechanisms to Enhance Prognostic Outcomes

Predicting the reliability of a system in its actual life cycle conditions and estimating its time to failure is helpful in decision making to mitigate system risks. There are three approaches to prognostics: the physics-of-failure approach, the data-driven approach, and the fusion approach. A key requirement in all these approaches is the identification of the appropriate parameter(s) to monitor the collection of the data that can be employed to assess impending failure. This article presents the physics-of-failure approach, which uses failure modes, mechanisms, and effects analysis (FMMEA) to enhance prognostics planning and implementation. This article also presents the fusion approach to prognostics and the applicability of FMMEA to this approach. As an example, a case of generating FMMEA information, and using that to identify appropriate parameters to monitor, is presented.     

Accelerated Reliability Demonstration Testing Design Based on Reliability Allocation of Environmental Stresses

The traditional reliability demonstration testing based on statistical method requires a large number of samples and long testing time, failing to satisfy the demand for short cycle and low cost. This paper proposes a new accelerated approach for determining reliability target of each environment stress, accelerated test profile, and comprehensive acceleration factor for multi‐failure mode product to conduct assembly level accelerated demonstration testing under multiple stresses and levels. By decomposing the product from four levels, namely function, structure, mechanism, and stress, the products' weaknesses can be identified. The main failure modes and sensitive environmental stresses are determined based on environmental profile and FMMEA. In this design, the reliability is apportioned to each actual environmental stress by AHP. And the SSI model is used to establish accelerated stress profile. The overall acceleration factor can be derived from the model of assembly level accelerated testing. Combined with a statistical plan, the accelerated reliability demonstration testing plan and test profile is built. A case example is presented to illustrate the effectiveness of the proposed approach. Copyright © 2017 John Wiley & Sons, Ltd.     

Analysis of complex system reliability with correlated random vectors

The analysis of reliability of complex engineering systems remains a challenge in the field of reliability. It will be even more difficult if correlated random vectors are involved, which is generally the case as practical engineering systems invariably contain parameters that are mutually correlated. A new method for transforming correlated distributions, involving the Nataf transformation, is proposed that avoids the solution of integral equations; the method is based on the Taylor series expansion of the probability density function (PDF) of a bivariate normal distribution resulting in an explicit polynomial equation of the equivalent correlation coefficient. The required numerical results can be obtained efficiently and accurately.The proposed method for transformation of correlated random vectors is useful for developing a method for system reliability including complex systems with correlated random vectors. Based on the complete system failure process (originally defined as the development process of nonlinearity) and the fourth-moment method, the analysis of system reliability for elastic-plastic material avoids the identification of the potential failure modes of the system and their mutual correlations which are required in the traditional methods. Finally, four examples are presented – two examples to illustrate the potential of the new method for transformation of correlated random vectors, and two examples to illustrate the application of the proposed more effective method for system reliability.     

不完整结构系统同时考虑强度和刚度的可靠性分析

基于结构强度可靠性分析理论的基础之上,提出了不完整结构(结构系统中有部分元件已失效,但结构未变成机构仍具有一定的承载能力)强度、刚度可靠性的分析方法.该方法考虑了元件因强度失效对不完整结构系统强度、刚度可靠性的影响,同时导出了等效安全余量的形式,进而计算结构系统在失效各阶段的总体失效概率.并结合算例对结构系统在失效各阶段进行了强度、刚度的可靠性分析.算例表明,这样分析符合结构在使用各阶段可靠性的真实情况,从而为结构的合理利用起指导性作用.     

Geotechnical system reliability of slopes

In slope stability analysis it is customary to search for the critical slip surface considering the conventional factor of safety as an index of stability. With the development of reliability analysis approaches within a probabilistic framework, alternative definitions of the critical slip surface can be adopted. Thus one may define a critical slip surface as one with the lowest reliability index or one with the highest probability of failure. However, it is important to consider the slope stability problem in terms of a system of many potential slip surfaces. For such a system, the calculation of system reliability is appropriate and desirable. In this paper, system reliability bounds are calculated within a probabilistic framework. The ‘system reliability’ or the ‘system probability of failure’ must be estimated for comparison with the corresponding reliability or probability of failure with respect to a ‘critical’ slip surface. The general slope stability problem involving non-zero internal friction angle involves a non-linear performance function. Moreover, the expression for factor of safety is usually inexplicit except for the ordinary method of slices which is not accurate except when ‘ø = 0’. This paper addresses the system reliability for inexplicit and non-linear performance functions as well as for linear and explicit ones. Any version of the method of slices may be used although the proposed approach is presented on the basis of the Bishop simplified method. It is shown that the upper bound system failure probability is higher than the failure probability associated with a critical slip surface. The difference increases as the coefficient of variation of the shear strength parameters increases.     

岩质边坡稳定的体系可靠度分析及工程应用

对岩质边坡存在多个滑动面时的体系可靠度进行分析,可以对边坡的稳定性作出更加合理的评价。采用非线性有限单元法,通过降低岩体的强度参数,寻找边坡的潜在滑动面,并定义滑动面上所有单元同时破坏时,作为边坡的失稳模式;针对岩体破坏的特点,按Druker-Prager屈服准则和单轴抗拉强度准则构建失稳模式中单元的功能函数,再采用响应面法和蒙特卡罗法计算单元的可靠指标和相关系数;单一失稳模式是由滑动面上的单元组成的并联体系,为此,研究了一种逐步等效线性化求交法用于计算单一失稳模式的可靠指标;最后,用Ditlevsen窄界限公式估算由各失稳模式组成的串联体系的可靠指标。上述方法得到的可靠指标可用于边坡的稳定性评价。作为工程实例,对某水电站左岸坝肩边坡的体系可靠度进行了分析和评价,验证了本方法的合理性和可行性。     

土钉支护稳定性的机会约束规划方法

土钉支护稳定性所采用的极限平衡理论分析方法是根据"确定性"的土体、土钉强度参数搜索其潜在的滑动破坏面、计算稳定系数及其安全状态,但由于计算参数的随机性及其强度参数不能满足约束条件的随机性,使得稳定计算的可靠程度大为降低。因此采用机会约束规划理论(CCP)在应用概率理论控制其计算参数随机性的基础上,附加强度参数是否满足约束条件的随机性来分析土钉支护的可靠性,进而实现对土钉支护安全状态的判断。应用一工程实例来实现上述分析思想的安全判断结果。     

A reliability allocation method of mechanism considering system performance reliability

It is generally believed that the reliability of a mechanical system is determined by its composition. The system operates properly when all of its components do not fail. Based on this assumption, the reliability of the system can be represented by the reliability of its components. A problem arises when applying this hypothesis to a system containing motion mechanisms. There is a phenomenon in motion mechanism that the components do not happen structural failure (we call it “Type I failure”) and joint failure (we call it “Type II failure”), but the function of the mechanism cannot meet the requirements (we call it “Type III failure”). A reliability allocation method, which synthetically considers the composition and Type III failure modes of the motion mechanism, is proposed to solve this problem. A relative dispersion factor is introduced to describe the failure dependence of components and is proposed to calculate the complexity and criticality. A series system reliability allocation model considering three types of failure modes is established. Finally, using an airplane gear door lock mechanism as an example, a comparative analysis of the system reliability allocation results with and without considering Type III failure modes is made. The allocation results show the component reliability value without considering Type III failure modes is less than that when considering them, which will increase the system hazards. The result considering Type III failure modes is more reasonable than that from the traditional method.     

Sample regeneration algorithm for structural failure probability function estimation

An efficient strategy to approximate the failure probability function in structural reliability problems is proposed. The failure probability function (FPF) is defined as the failure probability of the structure expressed as a function of the design parameters, which in this study are considered to be distribution parameters of random variables representing uncertain model quantities. The task of determining the FPF is commonly numerically demanding since repeated reliability analyses are required. The proposed strategy is based on the concept of augmented reliability analysis, which only requires a single run of a simulation-based reliability method. This paper introduces a new sample regeneration algorithm that allows to generate the required failure samples of design parameters without any additional evaluation of the structural response. In this way, efficiency is further improved while ensuring high accuracy in the estimation of the FPF. To illustrate the efficiency and effectiveness of the method, case studies involving a turbine disk and an aircraft inner flap are included in this study.