可靠性及设备维护-绪论

1、可靠性与设备维护-1可靠性与维修性工程 一门相对较新的工程学科 发展因由： 系统越来越复杂； 产品带来的后果越来越严重； 公众对产品质量的意识和执着； 产品质量责任的法律和法规越来越完善Reliability 可靠性Reliability is the probability that a component or system will perform its intended (or required) function for a specified interval of time when used under stated conditions. Probability Requi

2、red function Specified time Stated conditionsMTTFformer300=7545/2=3773.5MTTFlast200=4328/12=360.7Example 1.1Example 1.2 The time to failure of a VCR made by XYZ company. F(t)=1-e-t/8750 Assuming that a typical consumer uses his VCR 3 hrs. daily. Totally 1095 hours will be observed for the first year

3、. F(1095)=1-e-1095/8750 =0.1176It means that over 10 percent of the products sold expected to fail during the first year. It will be a large amount of money for warranty cost.Reliability TrendsMost product will begin their life with a higher failure rate and then exhibit a decreasing failure rate up

4、 to a point.The failure rate then usually stabilizes to a constant failure rate during the useful life of the produce.As time goes on and the product ages, or reaches the wear out life, the failure rate increase rapidly with time.磨合期有用寿命期磨损期Maintainability 维修性 The probability that a failed component

5、 or system will be restored or repaired to a specified condition within a period of time when maintenance is performed in accordance with prescribed procedures. Probability Repaired (replaced), restored Specified condition A period of time Prescribed procedures维修的种类 Renewal：as good as new,修旧如新 Minim

6、al repair：最小维修，通过维修部分组件或零件，使系统可靠性延续其在故障时刻的状况。 Partial repair：部分维修机车维修：法国 AGV日本 E2-1000德国德国 ICEICE 法国法国 TGVTGV日本 700系我国机车的维修按照修程里程和维修范围实行等级分类，分为大修、中修、小修和辅修四类，相互关系如图2所示。其中根据实施维修地点的区别又划分为厂修和段修，大修一般在机车制造工厂进行，称为厂修；中、小和辅修在机务段进行，则称为段修。中国中国 和谐号和谐号工程中的维修工程中的维修大修：大修是对机车进行全面检查修理，恢复机车基本性能。大修属于机车全面恢复性维修，即全面解体、更换

7、或修复所有不符合技术标准和要求的零部件，使机车达到或者接近新造机车标准或者达到规定的技术性能指标。 中修：中修是对机车主要部件检查修理，恢复机车主要功能。中修的性质属于机车的平衡性修理，即恢复机车某些部分，使其与其他未修理部分能配套继续使用。 小修：小修是对机车关键部件进行检查，更换达到使用限度的易耗性零部件，有针对性地恢复机车运行可靠性。有诊断技术条件的，可按照其状态进行修理。性质属于机车运行性维修。 辅修：辅修是对机车进行一般性检查，做故障诊断，状态修理。辅修的性质属于机车的临时性维修和养护。 Availability（可用性，可用度） The probability that a com

8、ponent or system is performing its required function at a given point in time when used under stated operating conditions. 如果X表示系统状态，X1（系统正常），X0，系统故障 可用度A=PX=1 可用度，就是设备被有效利用的时间。Example 1.3 一条连续生产线，产品需要在线上由10台不同机器串行加工，一台机器故障则整个生产线必须停下等待维修； 该生产线的平均停机时间（以后会详细解释这一在维修中的重要概念）为12小时； 机器在8小时工作时间内的可靠性为0.99； 整

9、个生产线的可靠性为0.9910=0.9； 如果失效分布规律为指数分布，则MTBF（mean time between failure）为75.9工作小时； R(8)=e-8/MTBF=0.9 A=MTBF/(MTBF+MTTR) MTTR: Mean time to repair 所以，A=75.9/(75.9+12)=0.86 为了完成生产量要求，必须保证可用度为0.92，即有足够的生产时间； 为了提高A，有不同途径， 但是，目前看来要继续提高机器本身的可靠性相当困难； 因此企业决定，通过改进维修性来提高可用度； 75.9/(75.9+x)=0.92, x=6.6小时； 可以使用更多维修人员

10、，更熟练的维修人员，增加机器的零部件库存，将零件放置得离现场更近，改善诊断程序，从而减低维修时间，提高可用度。Example 1.3可靠性，维修性，可用度 从定义可以看到，可靠性、维修性和可用度都是一种概率。后面的课程中我们会看到，用某个随机变量而不是概率本身更方便一点。比如用某种寿命指标来代表可靠性。 如一种数码相机，标称快门寿命为30万次，我们说它的快门寿命为30万次的可靠性为0.99和0.9是不一样的。而如果30万次是平均寿命的话差别就更大了。Why reliability ?Product cost VS. reliability Reliability engineering pro

11、vides the theoretical and practical tools whereby the probability and capability of parts, components, equipment products, and systems to perform their required functions for desired periods of time without failure, in specified environments, and with a desired confidence, can be specified, designed

12、 in, predicted, tested, and demonstrated.Reliability engineeringHistory of reliability engineering1940s-V-1 rocket, V-2 rocket1952-AGREE1960s-Miciroelectronics reliability1969-Apollo 111986-The space shuttle challenger WeibullBazovsky1961Barlow and Proschan1967Smith 1976Kapur 1977Early project incep

13、tion- parts-level reliability testingMiddle development phase- system-level testing of model-shop unitsFinal development phase- pre-release reliability demonstration testingEarly manufacturing phase- determine effect of manufacturing variation of reliabilityFull manufacturing phase- determine reliab

14、ility effects of design or process changesOngoing testing- determine long-term reliability for use with future projects.When should reliability engineering be appliedPublicationIEEE Transaction on ReliabilityMicroelectronics and ReliabilityReliability Engineering and System SafetyManagement Science Probability in Engineering and Inform