Transcript Reliability Chapter Ten Reliability Definitions    Reliability: The ability of a product, part, or system to perform its intended function under a prescribed set of conditions Failure:

Reliability
Chapter Ten
Reliability
Definitions



Reliability: The ability of a product, part,
or system to perform its intended function
under a prescribed set of conditions
Failure: Situation in which a product, part,
or system does not perform as intended
Normal operating conditions: The set of
conditions under which an item’s
reliability is specified
Reliability
Reliability Example
Determine the reliability of the system shown
.98
.90
.92
.90
.95
Reliability
Solution
The system can be reduced to a series of three components
.98
.90+.90(1-.90)
.95+.92(1-.95)
.98 x .99 x .996 = .966
Reliability
Failure Rate Curve
Infant
mortality
Failures due
Few (random) failures
to wear-out
Time, T
Reliability
Failure Rate as an
Exponential Function
Reliability = e -T/MTBF
1- e -T/MTBF
T
Reliability
Time
Normal Approximation
Reliability
0
Reliability
z
Availability

The fraction of time a piece of equipment
is expected to be available for operation
MTBF
Availability 
MTBF  MTR
MTBF = mean time between failures
MTR = mean time to repair
Reliability
Improving Reliability
Component design
 Production/assembly techniques
 Testing
 Redundancy
 Preventive maintenance procedures
 User education
 System design
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Reliability