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Reliability Analysis Pat Hammett
Reliability Analysis
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Reliability
n Reliability Defined: Reliability is the probability
that a system or product will perform in a
satisfactory manner for a given period of time
when operated under specified conditions.
n Reliability Analysis: Analysis of system failures
and repairs to:
n increase the design life of a product.
n reduce the likelihood of failures.
n reduce manufacturing process downtime.
n eliminate safety concerns.
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Total Quality Management - University of Michigan
Reliability Analysis Pat Hammett
Reliability and Six Sigma Projects
n Consider the following defects:
n High warranty costs due to excessive
replacement of certain ponents.
n Late delivery of products due to excessive
machine downtime.
n An effective method to examine the effects
of these defects is Reliability Analysis.
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Product Types / Failure Conditions
-repairable items {replace} (., light bulb)
n interested in probability of first and only failure
(hazard rate)
n Analyze MTTF (mean-time-to-failure)
items (., copy machine)
n interested in probability that a failure will occur over
some time period
n Analyze MTBF (mean-time-between-failures)
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Total Quality Management - University of Michigan
Reliability Analysis Pat Hammett
Reliability Assessment
n To describe failure patterns in order to predict
future issues, we need statistical distributions.
mon distributions for non-repairable devices:
n Weibull
n Exponential* is special case where failure rate is constant.
n Log-normal
n Normal*
mon distributions for repairable devices:
n Poisson
n Nonhomogenous Poisson Process (NHPP)
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Failure Pattern for Product Life
Cycle - Bathtub Curve
l,
(failure
rate or
hazard rate)
Bathtub Curve 6
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Total Quality Managemen