qm zg528-l4.pptx
TRANSCRIPT
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QM ZG528 L-4
Reliability EngineeringGajanand Gupta
Department of Mechanical Engineering
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Consider the case of two independent and
redundant components each having same
constant failure rate .
!stem failure will occur when "oth componentsfails "! time t, for this case pro"a"ilit! is
!stem relia"ilit! is
Redundancy and CR !"del
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$he ha%ard rate in this case is&
'! inspection is clearl! not a constant ha%ard ratehowever as
(ence redundant s!stem failure rate as!mptoticall!
approaches the constant failure rate
Redundancy and CR !"del
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$he s!stem M$$* can "e determined from&
+n other words two component redundant s!stem will
increase M$$* "! factor 1.over the single component
M$$*.
Redundancy and CR !"del
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microwave transmitter has e/hi"ited a constant failure
rate of 0.000)- failure per operating hour. second
redundant transmitter is added. *ind out the relia"ilit!
over a )0 da! continuous operating period.
lso find the M$$*.
E#a!$le
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Ti!e-%e$endent ailure M"del&Chapter & -
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Models useful in descri"ing failure process
&E/ponential
& 2ei"ull
&3ormal &4ognormal
Constant ha%ard rate& E/ponential
+f ha%ard rate is not constant over time& 2ei"ull, 3ormal,
4ognormal
Intr"ducti"n
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6ne of the most pro"a"ilit! distri"ution in relia"ilit!
engineering is 2ei"ull.
+t is characteri%ed "! ha%ard rate function of the form
*or mathematical convenience is e/pressed as&
T'e (eibull %i&tributi"n
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hape Parameter
+f 81 9 hape of PD* is similar to e/ponential
+f :;) e normal distri"ution
+f 9 PD* shape is s>ewed +f ;1, =constant & PD* is identical to e/ponential with(
;1?
& cale Parameter
+nfluences mean and spread of distri"ution@@@@@@@@@@@@.
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Given a desired relia"ilit! B,
$hen design life @@@.
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T'an+&
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