GEORGE P. HANSEN, PH.D. August 9, 2016 INTRODUCTION TO RELIABILITY Distribution Statement A: Approved for public release; distribution is unlimited. UNCLASSIFIED DSIAC is a DoD Information Analysis Center (IAC) sponsored by the Defense Technical Information Center (DTIC) with policy oversight provided by the Office of the Under Secretary of Defense (OUSD) for Research and Engineering (R&E). DSIAC is operated by the SURVICE Engineering Company
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GEORGE P. HANSEN, PH.D.
August 9, 2016
INTRODUCTION
TO RELIABILITYDistribution Statement A: Approved for public release; distribution is unlimited.
UNCLASSIFIED
DSIAC is a DoD Information Analysis Center (IAC)
sponsored by the Defense Technical Information
Center (DTIC) with policy oversight provided by the
Office of the Under Secretary of Defense (OUSD)
for Research and Engineering (R&E). DSIAC is
operated by the SURVICE Engineering Company
UNCLASSIFIED | Distribution Statement A: Approved for public release; distribution is unlimited.
The main question is, when?
How long can we count on it?
How does it happen?
Can we aid or design it to last longer?
EVERYTHING EVENTUALLY FAILS
UNCLASSIFIED | Distribution Statement A: Approved for public release; distribution is unlimited.
What is Reliability?
Probability that a thing will perform its intended function for a
specified time under defined conditions without failure or
performance degradation.
Consider performance life times the way an insurance actuary
looks at human populations.
• We don’t know exactly when an individual will fail.
• Given that it has survived till now, we can estimate its chance of continued
survival.
End users define intended function, time and use conditions.
Design engineers ensure it meets these requirements.
UNCLASSIFIED | Distribution Statement A: Approved for public release; distribution is unlimited.
Reliability is always comprised of four key factors:
What is Reliability?
• Often multiple.
• Rank and pick most
important.
• Consider use frequency.
Function
• Often multiple and
complex.
• Rank and pick most
important.
• Consider unexpected or
infrequent devastating
events.
• Consider usage
conditions, habits,
random accidents.
Environment
• Duration, cycles, duty
cycles, hours, miles.
• Can be several points,
depending on strategy.
Function
Probability of Success (or Failure)
UNCLASSIFIED | Distribution Statement A: Approved for public release; distribution is unlimited.
What is Reliability?
• Judicious material selections
• De-rating materials, components and
subsystems
• Innovative use of redundancy or backup
• Designing maintenance requirements
• Other strategies…
Reliability engineering involves
improving reliability by:
• Identifying all potential design failure
modes and mechanisms.
• Testing a “large number” of items to failure
and measuring failure times for each failure
mode.
• Quantifying probability of failure for a given
time in the product usage life.
Reliability assessment involves:
UNCLASSIFIED | Distribution Statement A: Approved for public release; distribution is unlimited.
What is Reliability?
Quantified risk of product, component or material failure
Known warranty and legal liabilities
Known maintenance and repair liabilities
• Reduced spare parts inventory & cost
• Reduced maintenance labor cost
• Reduced unscheduled downtime
• Increased production stability & efficiency
Customers perceive reliability as product quality
• Longer equipment life
• More consistent performance
Reliability techniques can be applied to assessing performance of products, production processes, infrastructure, services…
UNCLASSIFIED | Distribution Statement A: Approved for public release; distribution is unlimited.