1、Designation: E3159 18 An American National StandardStandard Guide forGeneral Reliability1This standard is issued under the fixed designation E3159; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number
2、 in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide covers fundamental concepts, applications,and mathematical relationships associated with reliability asused in industrial areas an
3、d as applied to simple components,processes, and systems or complex final products.1.2 The system of units for this guide is not specified.Quantities in the guide are presented only as illustrations of themethod or of a calculation. Any examples used are not bindingon any particular product or indus
4、try.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to
5、 use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarrie
6、rs to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E456 Terminology Relating to Quality and StatisticsE2334 Practice for Setting an Upper Confidence Bound Fora Fraction or Number of Non-Conforming items, or a Rateof Occurrence for Non-conformities, Using AttributeData, When There
7、 is a Zero Response in the SampleE2555 Practice for Factors and Procedures for Applying theMIL-STD-105 Plans in Life and Reliability InspectionE2696 Practice for Life and Reliability Testing Based on theExponential Distribution2.2 ISO Standards:3ISO 3534-1 StatisticsVocabulary and Symbols, Part 1:Pr
8、obability and General Statistical TermsISO Guide 73 Risk Management Vocabulary3. Terminology3.1 Definitions:3.1.1 Unless otherwise noted, terms relating to quality andstatistics are as defined in Terminology E456. Other generalstatistical terms and terms related to risk are defined in ISO3534-1 and
9、ISO Guide 73.3.1.2 Bplife, nfor continuous variables, the life at whichthere is a probability (expressed as a percentage) of failure ator less than this value.3.1.2.1 DiscussionExample: The B10life is a value of life,t, such that cumulative distribution function, F(t) = 0.1 or 10 %.3.1.3 hazard rate
10、, ndifferential fraction of items failing attime t among those surviving up to time t, symbolized by h(t).E25553.1.3.1 Discussionh(t) is also referred to as the instanta-neous failure rate at time t and called a hazard function. It isrelated to the probability density (pdf) and cumulative distri-but
11、ion function (cdf)byh(t) = f(t)/(l F(t), where f(t) is thepdf and F(t) the cdf.3.1.4 mean time between failures (MTBF), nthe averagetime to failure for a repairable item.3.1.4.1 DiscussionA repairable system is one that can berepaired and returned to service following a failure. When anitem is repai
12、red, it may not necessarily be returned to service inas good as new condition. There may be a reduction in life ina repaired item making the item not as robust as a new item.Any failure-repair sequence may continue for several cycles,further reducing longevity of service following each repairtime. O
13、ften the more times the item is repaired, the smaller willbe the expected remaining life until the next repair. However,some repairable systems (for example, electronic) may justhave some components replaced from time to time renderingthe unit as good as new.1This guide is under the jurisdiction of
14、ASTM Committee E11 on Quality andStatistics and is the direct responsibility of Subcommittee E11.40 on Reliability.Current edition approved April 1, 2018. Published May 2018. DOI: 10.1520/E3159-18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service a
15、t serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.Copyright ASTM International, 100 Bar
16、r Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recomm
17、endations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.13.1.5 mean time to failure (MTTF), nin life testing, theaverage length of life of items in a lot. E26963.1.6 reliability, nthe probability that a component,device, product, process or system will function o
18、r fulfill afunction after a specified duration of time or usage underspecified conditions.3.2 Definitions of Terms Specific to This Standard:3.2.1 failure mode, nthe way in which a device, process orsystem has failed.3.2.1.1 DiscussionUnder some set of conditions, anydevice, process or system may be
19、 vulnerable to several failuremodes. For example, a tire may fail in the course of time dueto a puncture by a sharp object, from the tire simply wearingout, or from a tire manufacturing anomaly. Each of thesedescribe different failure modes. These three failure modes aresaid to be competing with res
20、pect to the failure event.3.2.2 non-repairable system, na system that is intendedfor a single use and discarded/replaced following its firstfailure.3.2.3 repairable system, na system that is intended to beused through multiple failure-repair cycles.4. Significance and Use4.1 The theory of reliabilit
21、y is used for estimating anddemonstrating the probability of survival at specific times orfor specific usage cycles for simple components, devices,assemblies, processes, and systems. As reliability is one keydimension of quality, it may be more generally used as ameasure of quality over time or over
22、 a usage or demandsequence.4.1.1 Many industries require performance metrics andrequirements that are reliability-centered. Reliability assess-ments may be needed for the determination of maintenancerequirements, for spare parts allocation, for life cycle costanalysis and for warranty purposes. This
23、 guide summarizesselected concepts, terminology, formulas, and methods associ-ated with reliability and its application to products and pro-cesses. Many mathematical relationships and methods arefound in the annexes. For general statistical terms not found inSection 3, Terminology E456 and ISO 3534-
24、1 can be used fordefinitional purposes and ISO Guide 73 for general terminol-ogy regarding risk analysis.4.2 The term “system” implies a configuration of interactingcomponents, sub-assemblies, materials, and possibly processesall acting together to make the system work as a whole. Partsof the system
25、 may be linked in combinations of series andparallel configuration and redundancy used in some parts toimprove reliability.Additional conditions of complex engineer-ing may have to be considered.4.3 Process reliability concerns the assessment of any typeof well-defined process. This can include manu
26、facturingprocesses, business processes, and dispatch/demand type pro-cesses. Assessment typically measures the extent to which theprocess can continually perform its intended function without“upset” as well as process robustness.4.4 A number of reliability metrics are in use. For example,mean time t
27、o failure (MTTF) is a common measure of averagelife or average time to the first time a unit fails. For this reasonit is said to apply to non-repairable systems. Other lifepercentiles (or quantiles) are in use such as for example a Bplife or that life at which there is p % expected failure. Thus, th
28、eB50or median life is the life at which 50 % of items would beexpected to fail as well as survive; The B0.1life is the life atwhich would be expecteda1in1000 failure probability 0.1 %failure) and a 99.9 % reliability.4.4.1 Failure rate and average failure rate are also commonmetrics in reliability.
29、With failure rates, it is important tounderstand that a rate may be changing with time and this maybe increasing, decreasing or some combination of these overthe life of a product or service. The failure rate may also beconstant.4.5 Bench testing of a device is used to obtain earlyreliability assess
30、ment or to demonstrate a specific reliabilityrequirement or a related metric. There are a number of keymethodologies that are used for this purpose. Demonstrationtesting may be dependent on the assumption of a distribution offailure time or may be carried out using nonparametricmethods.4.6 When a sy
31、stem is repaired following failure and placedback into service, we refer to the object as a repairable system.Akey metric for this is the mean time between failure (MTBF);and this is not to be confused with MTTF. When a system isrepaired, it may not be the case that its expected remaining lifeis as
32、good as a new one. There may be a reduction in expectedlife following a repair and this may continue with continuingrepair cycles. The MTBF metric applies to all such sequencesof repair and restoration cycles over a service life period. Thisincludes the first time to failure, the 2nd time, the 3rd t
33、ime, etc.5. Life Concepts5.1 Before reliability can be assessed, the measure of lifemust be selected. Table 1 shows a sample of units that arecommonly used as a measure of life.5.1.1 Variations of these units can be found as for examplethe difference between an aircraft total engine operating time(E
34、OT) and its time/hours in flight or engine flight hours (EFH).Cycles are dependent on ordinary time in that any cycle maylast for any length of time. In another case, continued life maybe driven more by calendar time.5.1.2 A dispatch of a product or service can be used tocompute the products dispatc
35、h reliability (for example, rela-tive frequency of failure free dispatches without a change to aschedule). Demand cycle is different than ordinary cycles inthat a product may only be demanded infrequently but must bein serviceable condition when called on (for example, fireextinguishers, ambulance v
36、ehicles). Calendar time may beapplicable in situations where a product is exposed to field orTABLE 1 Common Measures of Product LifeLife Unit Exampleoperating time hrs., minutes, dayscycles of usage flights, dispatchescalendar time days since new; shelf lifedemand cycles unit is demanded occasionall
37、yE3159 182environmental conditions during most of its life and would besubject to chemical, thermal or other actions causing perfor-mance degradation over time. Shelf life is applied to manychemical and biological products and is a prime example of themore general “service life” concept.5.1.3 A prod
38、ucts service life is a duration of life (in theappropriate life units) over which the manufacturer believes theproduct is serviceable or useful. The term useful life is alsoused synonymously. In some industries, the concept of “mis-sion” is used interchangeably. A duty cycle is often used todescribe
39、 the fraction of the time and under what conditions thata product is called on for its intended use relative to somearbitrary time period. For example jet engines operate at alower level of stress during the cruise portion of any flight,whereas during the takeoff and landing portion of the flight, t
40、heduty requirements are greater. In a duty cycle profile, a productmay be exposed to a distribution of stress during a typicalusage cycle.5.1.4 In many types of products, components or subsystems,the unit may be subject to life limiting. The unit must bereplaced with a new one immediately upon reach
41、ing the lifelimit, if not failed. Such units have increasing failure rates withage and the life limit is judiciously selected at a point prior toreaching the unacceptable failure rate. Life limiting is differentthan service life in that the former applies to non-repairableitems (for example, one use
42、 only, then dispose and replace). Aconcept related to life limiting is a replacement or preventativemaintenance interval. Replacement intervals are commonlyfound in electro-mechanical applications such as in machinehardware, automotive or aerospace applications.5.2 Maintenance Schedules or Intervals
43、The continueduseful life of many types of products is dependent on appro-priate maintenance. Such maintenance is often specified con-tractually or as part of a warrantee stipulation. Inappropriateproduct use or operation of the product outside of an intendedusage range may retard or negate the desir
44、able effect of amaintenance interval.5.3 Failure Modes and Failure RateIn using reliabilitycalculations consideration should be given to the type of failuremode that is expected for the specific product and its intendedapplication. Three broad classes of failure modes are incommon use. Table 2 descr
45、ibes these. See (1)4and (2) forfurther detail around the failure mode concept.5.3.1 The term “infant mortality,” borrowed from the bio-logical science, is now common in engineering. Each of thesethree classes may contain numerous more specific failuremodes depending on the type of product considered
46、. Asso-ciated with each of the three broad classes of failure mode arethe three types of failure rate.5.3.2 A failure rate (also called force of mortality)isameasure of the rate of failure of currently surviving units at aspecific time. For infant mortality cases, the failure ratedecreases with time
47、. The explanation is that the presence ofspecial causes will cause failure, typically early in the lifecycle; the longer a unit survives, the less likely it is infectedwith the said special cause and hence the failure rate decreasesas the unit ages.5.3.3 Infant mortality is the reason for conducting
48、 a “burn-in” application where products are exposed to usage prior tofield introduction in order to identify potential early failuresprior to field use by a customer. For example, this practice iscommon for personal computer (PC) manufacturers who wantto ensure their machines do not have special cau
49、se type defectsand will function immediately upon a customers use.5.3.4 A random failure mode is one that may occur at anytime over a service life period but generally may be a rareevent. The frequency of such failures is not age-dependent andis only a function of duration time or size of the observationregion (that is, how long the unit is observed for). Randomfailures occur at a constant failure rate throughout a servicelife. Examples include errors of operation; installation andmaintenance mistakes; foreign object damage (including hardobjects, liquids, or b
