The Reliability Engineering Glossary
Reliability engineering and related fields use a vocabulary unique to our field of endeavor. For example, the term ‘reliability’ has the meaning of ‘trustworthy’ in everyday English use. For us, ‘reliability’ has a precise engineering definition.
Glossary description and plans
This glossary is meant to help us learn the language of reliability engineering. The category of ‘Terms’ is like a dictionary, including terms and their definitions as used by engineers. The category of ‘Methods’ is a listing of the techniques, tools, approaches, or concepts that may be found within a reliability plan. In the near future, we expect to expand the ‘Methods’ pages to include guidelines on use or application, examples, and additional references.
We also plan to expand the glossary to include formulas and failure mechanisms. Please let us know if there is another list of terms that should be added if you do not find a term that should be included or if you would like to recommend a change to an existing entry.
Method Categories
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- Automatic test equipment (ATE)Equipment that is designed to automatically conduct analysis of functional or static parameters and to evaluate the degree of UUT (Unit Under Test) performance degradation; and may be used to perform fault isolation of UUT malfunctions. The decision making, control, or evaluative functions are(...) Read More
- AutonomationDescribes a feature of machine design to effect the principle of jidoka (自働化) used in the Toyota Production System (TPS) and Lean manufacturing. It may be described as "intelligent automation" or "automation with a human touch." Read More
- Autonomous maintenanceMaintenance performance by equipment operators, primarily for deterioration prevention. Read More
- Autonomous work groupA production or interdepartmental team that operates within some constraints or schedule, yet has little external reporting or supervision. Read More
- AvailabilityA measure of the degree to which an item is in an operable and committable state at the start of a mission when the mission is called for at an unknown (random) time. The ability of an item to perform its designated function when required for use. Read More
- Availability, achievedThe probability that an item will operate satisfactorily at a given point in time when used under stated conditions in an ideal support environment (i.e., that personnel, tools, spares, etc. are instantaneously available). It excludes logistics time and waiting or administrative downtime. It(...) Read More
- Availability, inherentThe probability that an item will operate satisfactorily at a given point in time when used under stated conditions in an ideal support environment. It excludes logistics time, waiting or administrative downtime, and preventive maintenance downtime. It includes corrective maintenance downtime. Read More
- Availability, instantaneous or pointThe probability that an item will be up and running (functional) at a specific time. Read More
- Availability, mean or average uptimeThe proportion of time during a time period (mission duration) that the item is available for use. It is the mean of the instantaneous availability or the duration of interest. Read More
- Availability, operationalThe probability that an item will operate satisfactorily at a given point in time when used in an actual or realistic operating and support environment. It includes logistics time, ready time, and waiting or administrative downtime, and both preventive and corrective maintenance downtime. Read More
- Availability, steady state, long run or asymptoticThe mathematical limit as time tends to infinity for the availability function. Read More
- AverageA measure of central tendency determined by the sum of the values divided by the number of values. When calculated on a sample of items it is an estimate of the population mean. Read More
- Average amount of inspectionIn acceptance sampling, the expected number of items to be inspected per lot for a given acceptance sampling scheme with a goal to reach a decision for a certain average lot quality level. Read More
- Average junction temperatureThe average value of a specific semiconductor device virtual junction temperature over an operating cycle. Read More
- Average outgoing quality (AOQ)The expected average quality level for a given incoming quality level experiencing an acceptance sampling scheme. Read More
- Average outgoing quality level (AOQL)The maximum AOQ given the full range of possible incoming product quality level values experiencing a specific acceptance quality plan. Read More
- Average quality protectionA stated value of product average percent defective after inspection (AOQL) to not exceed in the long run without regard of the submitted product’s level of percent defective. Read More
- Average run length (ARL)In sampling it is the average number of times a process is sampled and evaluated before a observing a shift in a process characteristic level. In item-to-item production it is the number of items produced before observing a shift in a characteristic level. Read More
- Average sample sizeThe average number of units in samples drawn per lot used to determine lot acceptance or rejection for a specific acceptance sample plan. Read More
- Average standard deviationThe arithmetic average of sample standard deviations. Read More
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