可靠性及設(shè)備維護-緒論

1、可靠性與設(shè)備維護-1可靠性與維修性工程 一門相對較新的工程學科 發(fā)展因由： 系統(tǒng)越來越復雜； 產(chǎn)品帶來的后果越來越嚴重； 公眾對產(chǎn)品質(zhì)量的意識和執(zhí)著； 產(chǎn)品質(zhì)量責任的法律和法規(guī)越來越完善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.磨合期有用壽命期磨損期Maintainability 維修性 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維修的種類 Renewal：as good as new,修舊如新 Minim

6、al repair：最小維修，通過維修部分組件或零件，使系統(tǒng)可靠性延續(xù)其在故障時刻的狀況。 Partial repair：部分維修機車維修：法國 AGV日本 E2-1000德國德國 ICEICE 法國法國 TGVTGV日本 700系我國機車的維修按照修程里程和維修范圍實行等級分類，分為大修、中修、小修和輔修四類，相互關(guān)系如圖2所示。其中根據(jù)實施維修地點的區(qū)別又劃分為廠修和段修，大修一般在機車制造工廠進行，稱為廠修；中、小和輔修在機務(wù)段進行，則稱為段修。中國中國 和諧號和諧號工程中的維修工程中的維修大修：大修是對機車進行全面檢查修理，恢復機車基本性能。大修屬于機車全面恢復性維修，即全面解體、更換

7、或修復所有不符合技術(shù)標準和要求的零部件，使機車達到或者接近新造機車標準或者達到規(guī)定的技術(shù)性能指標。 中修：中修是對機車主要部件檢查修理，恢復機車主要功能。中修的性質(zhì)屬于機車的平衡性修理，即恢復機車某些部分，使其與其他未修理部分能配套繼續(xù)使用。 小修：小修是對機車關(guān)鍵部件進行檢查，更換達到使用限度的易耗性零部件，有針對性地恢復機車運行可靠性。有診斷技術(shù)條件的，可按照其狀態(tài)進行修理。性質(zhì)屬于機車運行性維修。 輔修：輔修是對機車進行一般性檢查，做故障診斷，狀態(tài)修理。輔修的性質(zhì)屬于機車的臨時性維修和養(yǎng)護。 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表示系統(tǒng)狀態(tài)，X1（系統(tǒng)正常），X0，系統(tǒng)故障 可用度A=PX=1 可用度，就是設(shè)備被有效利用的時間。Example 1.3 一條連續(xù)生產(chǎn)線，產(chǎn)品需要在線上由10臺不同機器串行加工，一臺機器故障則整個生產(chǎn)線必須停下等待維修； 該生產(chǎn)線的平均停機時間（以后會詳細解釋這一在維修中的重要概念）為12小時； 機器在8小時工作時間內(nèi)的可靠性為0.99； 整

9、個生產(chǎn)線的可靠性為0.9910=0.9； 如果失效分布規(guī)律為指數(shù)分布，則MTBF（mean time between failure）為75.9工作小時； 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 為了完成生產(chǎn)量要求，必須保證可用度為0.92，即有足夠的生產(chǎn)時間； 為了提高A，有不同途徑， 但是，目前看來要繼續(xù)提高機器本身的可靠性相當困難； 因此企業(yè)決定，通過改進維修性來提高可用度； 75.9/(75.9+x)=0.92, x=6.6小時； 可以使用更多維修人員

10、，更熟練的維修人員，增加機器的零部件庫存，將零件放置得離現(xiàn)場更近，改善診斷程序，從而減低維修時間，提高可用度。Example 1.3可靠性，維修性，可用度 從定義可以看到，可靠性、維修性和可用度都是一種概率。后面的課程中我們會看到，用某個隨機變量而不是概率本身更方便一點。比如用某種壽命指標來代表可靠性。 如一種數(shù)碼相機，標稱快門壽命為30萬次，我們說它的快門壽命為30萬次的可靠性為0.99和0.9是不一樣的。而如果30萬次是平均壽命的話差別就更大了。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