Dependability Evaluation of a Vehicle System by Simulation Method

The vehicle system studied in this paper is a type of complex repairable system in which the subsystems follow various failure distributions and conform to arbitrary failure and repair distributions.The failure data of subsystems are sometimes lacking,and the reliability test sample sizes tend to be small.Monte-Carlo technique combined with Bayes method is used to evaluate its dependability（reliability and maintainability）.Following the ＂first-in,first-out＂ queuing rule,the logic relation of dependability is established by means of repairing priority and event lists.Simulation outputs the entire history of a mission,statistics of reliability and maintainability parameters and provides the basic data for system reliability design and maintainability management.     

Study on Design and Safety Evaluation Methods of Mechanical-Thermal Weak-Link

In an abnormal high-temperature fire environment,a structure with mechanical-thermal weak-link can be used to predict the permanent failure before the failure of some strong-links,such as explosive initiator,thus to protect the latter. An effective design can be defined as that the weak-link fails before the failure of the strong-link,and the system is safe; while an unsuccessful design means that the weak-link fails after the failure of the strong-link,and the system loses in safety. The probability of safety failure exists due to the uncertain failure temperatures of the weak-link and strong-link. In order to obtain the probability of safety failure,a statistical method was used to deal with the uncertainty of the failure temperatures. The integral method and stochastic simulation method were used in calculations. Finally,a sample was given to verify the consistence of the results given by two methods.     

On-line Measuring Method for. Shell Chamber Volume

Using the ideal gas state equation, an on-line measuring method for the shell chamber volume is studied in this paper. After analyzing how various measurement parameters affect the measurement accuracy, the system parameters are optimized in this method. Because the shape and volume of the tested items are similar, the method of using “tamping” to raise the accuracy and speed of the measurement is put forward. Based on the work above, a prototype of the testing instrument for shell chamber volume was developed, automatically testing and controlling. Compared with the method of “water weight”, this method is more accurate, quicker and more automotive, so it is adaptable for the use of on-line detection.     

An Estimation Method for Kill Probability Based on Random Residence Time Series

Relations between statistical residence time series and effective shooting are analyzed in accordance with the properties of the random residence time of maneuver targets crossing shot area in a given time. An estimation method for kill probability is proposed, which solves the probability of number of residence times satisfied effective shooting in given time. Some expressions and their approximate formulae of kill probability are derived, under known the distribution of residence time series. Theoretical analysis and simulation results show that this method is suitable for evaluating the hit ability of fire system for maneuver targets in random shooting.     

A Measuring Method on Moment of Inertia of Large-scale Ammunition

A compound pendulum based measurement method is put forward and the relevant equipment is designed. By using the variation of angle with the time acquired by an angular displacement sensor, the moment of inertia is obtained through the numerical solution of certain equations, which are deduced from the phase-plane analysis of compound pendulum. The influences of both friction and air resistance on the compound pendulum are already taken into consideration without estimating and measuring the resistances in advance. With this method, the to-be-measured object can be positioned and fixed easily and safely. Numerical simulations show a favorable precision of this method.     

An Object Threat Assessment Method Based on Indefinite Multiple Attribute Decision Making

On the basis of characteristics of threat assessment of aerial defense, a kind of MADM （multiple attribute decision making） method with unknown attribute weights and biased project on decision-maker is put forward. It can be used in dealing with the object threat assessment problem. A computing formula on project preference of decision-maker and one model of obtaining attribute optimization weight are set up. The method improves the veracity and reliability of computing object threat assessment, and the simulating result shows that this method is valid.     

The Research on Compressive Properties of Polytetrafluoroethylene at High Strain Rate

The mechanical behaviors of polytetrafluoroethylene （PTFE） in compressive test performed at different strain rates ranging from 10 2 s-1to 10 3 s-1 are studied. The experimental results show that the yield strength increases with the increase in strain rate and exhibits a bilinear dependence on the logarithms of the stain rates, but the yield strain decreases with the increase in strain rate. Based on the mathematical model proposed by Nunes and the bilinear relationship between yield strength and strain rate, a modified constitutive model which can describe its complex non-linear mechanical behavior is proposed. The experimental results are in a good agreement with the predicted results of model within 40% of strain.     

Numerical Research on The Nozzle Damping Effect by A Wave Attenuation Method

Nozzle damping is one of the most important factors in the suppression of combustion instability in solid rocket motors. For an engineering solid rocket motor that experiences combustion instability at the end of burning, a wave attenuation method is proposed to assess the nozzle damping characteristics numerically. In this method, a periodic pressure oscillation signal which frequency equals to the first acoustic mode is superimposed on a steady flow at the head end of the chamber. When the pressure oscillation is turned off, the decay rate of the pressure can be used to determine the nozzle attenuation constant. The damping characteristics of three other nozzle geometries are numerically studied with this method under the same operating condition. The results show that the convex nozzle provides ,tre damping than the conical nozzle which in turn provides more damping than the concave nozzle. All the three nozzles have better damping effect than that of basic nozzle geometry. At last, the phase difference in the chamber is analyzed, and the numerical pressure distribution satisfies well with theoretical distribution.     

Numerical Analysis of 3 mm Ferrite Dielectric Waveguide Through Galerkin＇s Method

With the development of long range missile early warning radar, MMW phased array antenna is strongly needed. The phase shifter （PS） with high power capability and low insertion loss is a key technology in this kind of radar. Ferrite dielectric waveguide is introduced in this paper to manufacture PS, the cross section can be enlarged to 4 times of that of the conventional PS, which facilitates the engineering realization with reduced insertion loss. A novel vector base function of Galerkin method is proposed in calculating the eigenvalue of ferrite dielectric waveguide. The field distribution of main mode, power density and efficiency of 94 GHz difference phase shifter are also given.     

Evaluation for Success Probability of Chaff Centroid Jamming

As the chaff centroid jamming can introduce the guiding error of the anti-warship missile＇s seeker and decrease its hitting probability,a new quantitative analysis method and a mathematic model are proposed in this paper to evaluate the success jamming probability.By using this method,the optimal decision scheme of chaff centroid jamming in different threat situations can be found,and also the success probability of this scheme can be calculated quantitatively.Thus,the operation rules of the centroid jamming and the tactical approach for increasing the success probability can be determined.     

基于仿真的某型号车辆底盘可信性评估

对某型号车辆底盘,在子系统服从任意失效和修复分布、失效数据不充分和可靠性试验小样本的情况下,采用Bayes与Monte- Carlo方法评估复杂可修系统的可信性（可靠性和维修性）。根据“先来先修”的队列原则,利用优先级和事件表建立了复杂可修系统的可信性仿真的逻辑关系,根据对运行特征的识别,得到复杂系统可信性的统计值,为可靠性设计和维修性管理提供依据。     

基于Weibull过程的可靠性增长试验Bayes分析

基于Weibull过程的可靠性增长试验Bayes分析,首先推导定时截尾情况下布形式.然后,在截尾时间内的期望故障数的验前分布服从Gamma分布情况下,导出简捷的验后分布形式.在利用该结果进行可靠性评定时,需采用矩相等的转换方法进行验前信息的转换和失效强度验后分布的估计.仿真表明,该方法精度较好,评估过程可靠.     

非恒定环境下基于载荷谱的导弹部件寿命预测

为了解决某导弹部件在非恒定贮存环境下的寿命预测问题,提出了一种基于环境载荷谱的预测方法。分别利用Normal、Gamma分布对温度、湿度载荷谱建模;采用三参数Weibull分布拟合产品的失效时间,进而通过加速因子不变原则推导与环境相关的模型参数,在此基础上利用简化的广义Eyring模型建立时变环境与寿命模型之间的联系。案例应用验证了所提方法的有效性,结果表明此方法比传统的基于环境平均值的预测方法降低了预测误差。     

无验前信息的成败型弹药产品可靠性评估

为有效评估成败型弹药的可靠性,介绍成败型部件可靠性经典评估方法和Bayes 评估方法。针对无验前 信息的弹药成败型部件可靠性评估问题,提出采用3 种常用共轭先验来求其可靠性下限,并通过数值仿真分析,得 到常用共轭先验分布对可靠度置信下限的影响规律以及每种共轭先验分布的适用情况。结果表明：3 种共轭先验分 布评估得到的结果较为合适,可为提高弹药可靠性评估的准确性提供支持。     

可修系统剩余寿命分析的广义发生函数法

系统剩余寿命是机电装备面向多生命周期设计、制造与服役的重要分析指标。基于更新过程理论,通过引入广义发生函数(UGF),提出一种针对元件及系统有限时间区间的剩余寿命概率分析的实用方法。当系统各元件承受具有整体不确定性的平稳载荷随机历程时,直接根据元件在各等效恒幅应力水平下的失效数据构建元件条件寿命发生函数,由自定义复合算子分别计算相应的系统条件剩余寿命发生函数,经统计平均得系统剩余寿命分布。运算过程中,可利用近似项合并技术大幅度提高分析效率。新方法适用于元件寿命为任意分布随机变量场合,并体现各元件因等效恒幅应力不确定而引发的失效相关性,可为装备系统剩余寿命精细化分析开辟新途径。     

基于多影响因子和重要度的故障样本优选

针对测试性试验故障样本选择时影响因子考虑不全面、抽样方法工程应用性不强、影响因子权值主观性较强等问题,提出基于故障模式多影响因子和重要度的故障样本优选方法。在分析基于多影响因子抽样必要性的基础上确定了故障模式影响因子,并提出了基于PageRank的传播强度计算方法;提出了基于信息熵的相似度和基于相对比较关系的支持度计算方法,采用博弈决策方法确定了影响因子权值,实现了基于相对重要度的故障样本优选。将该方法应用于某装备控制系统的测试性验证试验,结果表明：故障样本优选方法能降低单次试验评估结果的随机性;样本选取时综合考虑多种影响因子和既客观又满足试验双方要求的影响因子权值,更符合测试性试验需求,选取的故障样本更合理。     

基于Hopkinson杆试验技术的PA-GF50复合材料动态力学行为

为研究纤维含量50%短玻璃纤维增强聚酰胺复合材料PA-GF50的动态力学性能及其应变率效应,利用准静态液压试验机及分离式Hopkinson压杆、Hopkinson拉杆对标距段尺寸为6~10 mm的试样,进行了应变率范围0.000 5~1 600 s^-1的准静态压缩、准静态拉伸、动态压缩和动态拉伸试验。对试样的应力-应变曲线和最终破坏形态,材料在不同应变率下失效破坏过程的微结构力学机理进行了分析。研究结果表明：动态载荷下,材料强度明显高于准静态载荷（压缩载荷下材料在400 s^-1、900 s^-1和1 600 s^-1应变率下分别较准静态载荷下增强31%、25%和29%;拉伸载荷下材料在400 s^-1、800 s^-1和1 200 s^-1应变率下分别较准静态载荷下增强46%、47%和28%）,且失效应变有所降低;试样变形和最终破坏形态为压缩载荷下试样经历缺陷压实过程再进入弹性变形最终达到强度后失效,拉伸载荷下试样经历弹性变形达到强度后失效断裂;材料在不同应变率下的微结构机理为准静态载荷下微观裂纹扩展组合成为宏观裂纹,动态载荷下微裂纹分别扩展成为宏观裂纹;试样的宏观断口和扫描电子显微镜结果证实,材料在准静态压缩加载条件下断口较为平整,动态压缩载荷形成纤维拔出、纤维断裂等特征,准静态拉伸载荷下纤维拔出明显,而动态拉伸载荷下主要表现为纤维断裂。     

余度结构故障概率计算的一种方法

在一个余度结构中,有多种破坏模式,要精确计算结构的故障概率是复杂的。本文则根据限界准则和被删出的故障模式对结构故障概率最大贡献的公式,求得结构故障概率的上下限,简单地求得结构故障概率。为说明此方法的有效性,提出了数值例子。     

圆筒平盖封头压力管的应力数值分析

根据有关理论在某圆筒平盖封头压力管受内压作用时 ,对其两大组件 (平盖封头和内压圆筒 )中的应力分布进行了理论计算 ,也对整个结构 (包括焊接区 )进行了不同载荷下应力分布的数值计算。分析了各组件和焊接区的应力分布、可能的失效区域以及失效载荷。