The reliability estimation of pipeline using FORM, SORM and Monte Carlo Simulation with FAD

In this paper, the reliability estimation of pipelines is performed by employing the probabilistic method, which accounts for the uncertainties in the load and resistance parameters of the limit state function. The FORM (first order reliability method) and the SORM (second order reliability method) are carried out to estimate the failure probability of pipeline utilizing the FAD (failure assessment diagram). And the reliability of pipeline is assessed by using this failure probability and analyzed in accordance with a target safety level. Furthermore, the MCS (Monte Carlo Simulation) is used to verify the results of the FORM and the SORM. It is noted that the failure probability increases with the increase of dent depth, gouge depth, operating pressure, outside radius, and the decrease of wall thickness. It is found that the FORM utilizing the FAD is a useful and is an efficient method to estimate the failure probability in the reliability assessment of a pipeline. Furthermore, the pipeline safety assessment technique with the deterministic procedure utilizing the FAD only is turned out more conservative than those obtained by using the probability theory together with the FAD. The probabilistic method such as the FORM, the SORM and the MCS can be used by most plant designers regarding the operating condition and design parameters.     

Reliability calculation under seasonally varying failure rate

This paper treats of the analytical solution of reliability problems in the special case when the failure rate acting on an object is a periodic piecewise constant function of time. It is proposed that the nonstationary failure rate be substituted by a stationary one. The formula intended for calculation of this fictitious equivalent stationary failure rate is derived. This makes possible the finding of approximate solutions of reliability problems in an analytical form convenient for applications in the sphere of engineering and for the following analysis. A simplistic example is used to demonstrate the proposed approach.     

Effects of crack geometries on reliabilities using probability theories

The methodologies to estimate the reliability of cracked structures using the fracture toughness and the SIF are developed. The probability theories such as the FORM and the SORM are utilized to calculate the failure probability. It is found that the failure probability increases with the increase of the crack size and the applied stress, and the decrease of the fracture toughness. It is also found that the failure probabilities obtained by the FORM and the SORM are similar each other for the through crack,the edge crack, and the single and the double crack emanated from a hole, and turn out different for the elliptical and semi-elliptical surface cracks. It is noted that the tensile stress affects significantly on the failure probability among the other random variables on the various crack geometries.     

Reliability estimation of solder joints under thermal fatigue with varying parameters by using FORM and MCS

One of major reasons for the failure of solder joints is thermal fatigue. Also, the failure of solder joints under thermal fatigue loading is influenced by varying boundary conditions such as the material of the solder joint, the materials of substrates(related to the difference in CTE), the height of solder, the distance of the solder joint from the neutral point (DNP), the temperature variation and the dwell time. In this paper, first, the experimental results obtained from thermal fatigue test are compared to the outcomes from theoretical thermal fatigue life equations. Second, the effects of varying boundary conditions on the failure probability of the solder joint are studied by using probabilistic methods such as the first order reliability method (FORM) and Monte Carlo simulation (MCS).     

用嵌入系统对大功率UPS的loo2D冗余——从整机降到部件以提高可靠性降低成本

本文用概率论证明了，对UPS的loo2D冗余，以嵌八系统，从整机降到部件，在相同数量的UPS部件下，可提高可靠性降低成本。     

管道类连续系统可靠性建模与应用

以管道-典型的连续系统失效概率估计为背景,通过最小次序统计量推导出Weibull尺寸效应,建立了考虑尺寸效应的管道类连续系统可靠性模型,同时能反映共因失效的影响,并分析了尺寸效应对连续系统可靠度的影响,最后对大连续系统的失效概率进行了估算.建立的模型可以应用于管道、钢缆等连续系统的可靠性设计与可靠性计算.     

利用故障迫切度对数控车床进行可靠性分析

采用了故障迫切度的方法来分析数控车床整机可靠性,该方法综合考虑了数控车床各子系统故障对整机可靠性提升的重要程度,可以快捷、准确地确定数控车床产品可靠性改进的重点方向.以某型号的数控车床整机为例,对故障数据进行了统计分析,指出其可靠性薄弱环节为刀架系统、主轴系统和电气系统,分析了薄弱环节产生故障的原因,并提出了相应的改进措施.结果证明该方法合理、实用.     

基于网络的腐蚀失效模式和原因识别诊断系统及其应用

建立了基于网络的腐蚀失效模式和原因识别诊断系统,该系统综合了产生式和框架式两种知识表示方法表 示案例知识,推理机采用基于案例的推理方法。系统案例知识库中存储有压力容器压力管道相关的腐蚀失效案例, 失效模式包括应力腐蚀、腐蚀疲劳及晶间腐蚀等。该系统根据输入的腐蚀失效特征信息识别出腐蚀失效模式,以 相似度作为诊断结果的评价参数,解释发生腐蚀失效的原因。     

数控系统软件故障可靠性分析

对某系列数控系统的软件部分进行了故障部位、故障模式及故障原因分析，指出此系列数控系统软件的可靠性薄弱环节，为探寻数控系统的可靠性设计提供依据。     

以载荷作用次数为寿命指标的失效相关系统可靠性建模

提出以随机载荷作用次数为寿命度量指标框架下的失效相关系统可靠性建模方法。考虑系统中各零部件之间存在的失效相关性,通过引入条件可靠度建立失效相关系统可靠性模型。分别以静强度失效和疲劳失效的可靠性分析为背景,给出强度不退化和强度退化时随机载荷多次作用下的系统可靠度与失效率计算模型,并研究系统可靠度与失效率随载荷作用次数的变化规律。研究表明,即使强度不退化,系统的可靠度和失效率也会随着随机载荷作用次数的增加而逐渐减小,失效率曲线具有浴盆曲线"早期失效期"和"偶然失效期"的特征。强度随载荷作用次数退化时,随着载荷作用次数的增加,系统的可靠度降低较为明显;失效率先减小后增大,具有"浴盆曲线"的特征。所建立的模型可用于指导系统的可靠性设计、可靠性试验和全生命周期管理。     

Uncertainty modeling and predicting the probability of stability and performance in the manufacture of dynamic systems

In this work, a method for determining the reliability of dynamic systems is discussed. Using statistical information on system parameters, the goal is to determine the probability of a dynamic system achieving or not achieving frequency domain performance specifications such as low frequency tracking error, and bandwidth. An example system is considered with closed loop control. A performance specification is given and converted into a performance weight transfer function. The example system is found to have a 20% chance of not achieving the given performance specification. An example of a realistic higher order system model of an electro hydraulic valve with spring feedback and position measurement feedback is also considered. The spring rate and viscous friction are considered as random variables with normal distributions. It was found that nearly 6% of valve systems would not achieve the given frequency domain performance requirement. Uncertainty modeling is also considered. An uncertainty model for the hydraulic valve systems is presented with the same uncertain parameters as in the previous example. However, the uncertainty model was designed such that only 95% of plants would be covered by the uncertainty model. This uncertainty model was applied to the valve control system example in a robust performance test.     

Ni薄膜热敏电阻失效机理研究

通过对Ni薄膜热敏电阻进行可靠性试验得出其失效模式,并对失效机理进行了分析。     

静态应力—强度模型中概率设计的不可靠度范围

静态应力-强度模型中,零件失效的概率仅与随机变量应力和强度的干涉区有关。本文介绍一种计算零件不可靠度的方法,即在不知道应力和强度分布特征,而仅了解应力强度干涉区中有关信息时,建立求解零件不可靠度的数学模型,利用优化技术,求出不可靠度值的范围,并给出这一优化问题的解答。本文还提出一新的求解零件不可靠度的数学模型,可求出更精确的不可靠度范围。     

基于Copula失效相关结构系统的失效概率计算

针对具有相关失效模式的结构系统可靠性分析问题,提出利用Copula计算结构系统的失效概率。Copula函数可以采用多种边缘分布函数来推求联合分布函数,构造随机变量间的相关结构。该方法分别以各失效模式的功能函数值为Copula分析变量,利用MATLAB软件和Monte Carlo模拟法产生的随机抽样数据估计Copula参数,实现各功能函数间的联合概率分布函数的Copula建模,从而可以利用Copula计算结构系统的失效概率。最后用工程算例验证该理论方法的可行性,为具有相关失效模式的结构系统可靠性分析提供新途径。     

采用电化学交流阻抗等测试方法研究无机富锌与有机富锌涂层在海水腐蚀环境中的失效机理

本文采用M398交流阻抗系统对无机富锌和有机富锌涂层进行电化学交流阻抗谱测定,采用截面电镜照片分析不同浸泡时间涂层微观形貌变化,采用EDAX分析涂层浸泡前后腐蚀产物。通过以上3种手段比较分析特定的无机富锌和有机富锌涂层在3.5%NaCl水溶液中的失效机理。     

Modeling of probability distribution functions for automatic threshold calculation in condition monitoring systems

A suitable setting of threshold levels has been a dilemma for engineers in a number of science and industrial fields. It is a common problem in monitoring, where deviation from a correct state needs to be detected. As the number of monitored values in modern systems reaches thousands, threshold calculations became a significant yet frequently underestimated concern. Due to a prohibitive cost of manual threshold setting, many systems generate thousands of false alarms consequent upon running on default threshold levels. In the paper, the authors illustrate a methodology for automatic threshold calculations in a large monitoring system. The paper is mainly addressed to engineers and machine monitoring systems developers, therefore selected statistical topics were treated briefly with main focus on practical solutions. Two fundamental data types are considered; namely, vibration signal measures, which can be extended to any nonnegative data, and symmetrical process values. As it is shown, these data types have significantly different probability distributions. Since real data seldom fits the Gaussian model, an investigation of several distributions and their comparison is presented. The proposed approach is validated on four datasets including process values from a gas compressor and vibration signal measures from a wind turbine.     

An evaluation method of probability of elastic-plastic fracture by 2-parameter criterion

Many researchers have made a lot of progress in studying the evaluation of fracture probability of brittle materials. However, studies of fracture probability for elastic-plasticity have not been made yet. An evaluation method for fracture probability which is grafted onto a 2-parameter criterion and statistical probability analysis is not only introduced in this study, but also applied to the simple 2-dimensional model and carbon steel piping to vealuate the effect of statistical variables.     

建立油气管道设备失效率数据库的技术探讨

随着现代管道技术的突飞猛进,与过去相比站场设施的可靠性已经得到了极大改善,但是可靠性较差的设备仍会造成管线停产和产生过高的维修费用,所以清晰地认识设备失效事件的本质原因,对合理预测、安排和实施维修活动都具有关键的意义.通过建立油气管道设备失效率数据库,可以合理的预测、安排和实施维修和维护活动,同时对站场整体可靠性产生持续性的改进,更有效的改善安全性和经济效益.通过对失效率数据的分析可以产生广泛的收益,如：可以优化安排设备检修和大修时间、维护保养项目;除此之外,还可以在较大范围内对设备全生命周期中的备品备件和升级计划进行优化制定.     

SIS冗余结构可靠性影响参数分析

可靠性是衡量安全仪表系统性能（SIS）优劣的重要指标之一。本文基于故障树模型的SIS可靠性公式,对安全仪表系统常用5种冗余结构5个参数进行Matlab程序仿真,直观的分析各参数对SIS常用冗余结构可靠性的影响,分析冗余结构可靠性性能关系,分析结果对安全仪表系统的设计和整改具有重要意义。     

柱塞往复泵填料寿命周期及失效模式分析

为了延长泵设备中填料的使用寿命,减少泵的被迫停机次数,运用RCM方法中的可靠性技术对填料的寿命周期及失效模式进行研究分析。整理某厂填料的维修记录,统计出其有效运行时间,通过K-S检查法进行拟合优度检验,知道填料的有效运行时间服从威布尔分布。然后利用三参数威布尔分布得出填料寿命时间概率密度函数、可靠性趋势及失效率函数等。通过分析可知:现阶段泵填料的维修大多集中于2000h左右;在可靠度0.9下,填料的寿命周期为982.2h;磨损和表面拉毛是引起填料故障的主要原因。