FMEA Class Add On
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Transcript of FMEA Class Add On
![Page 1: FMEA Class Add On](https://reader036.fdocuments.us/reader036/viewer/2022062401/577cca211a28aba711a570a7/html5/thumbnails/1.jpg)
Prof G.R.C.Nair
FMEA
Prof GRC Nair
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What is FMEA?
Prof G.R.C.Nair
• Failure • Modes• Effects• Analysis
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Prof G.R.C.Nair
Reasons to do FMEA• Define and guide a logical design
process • Identify, quantify, and reduce design
risk • Provide a traceable document for
design and development • Justify design activities • Provide a means for continuous
product improvement
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Prof G.R.C.Nair
Scope of FMEA• The FMEA is a team function
• All team members must participate• Multi-disciplinary expertise and input is beneficial • Input from all engineering fields is desirable
• Representatives from all areas (not just technical disciplines) are generally included as team members • The DFMEA will be refined and evolve with the
product • Numerous revisions are required to obtain the full
benefit of the DFMEA• The DFMEA should include all systems, sub-systems,
and components in the product design
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Availability
• Measure of Availability
MTRMTBFMTBFA
MTBF = mean time between failures
MTR = mean time to repair
MTTF = mean time to fail
MTBF or MTTF= (T1+T2+--+--+TN)/NMTR = (t1+t2+t3+---+---+tN)/ N
Prof G.R.C.Nair
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Availability is also called UTRUTR = Up time ratioDTR = down time ratioUTR + DTR = 1
System availability can be increased by • Increasing MTBF• Decreasing MTR• Or any favourable combination
Prof G.R.C.Nair
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Reliability• Generally defined as the ability of a product to perform as expected, over a period of time
• Formally defined as the probability that a product, piece of equipment, or system performs its intended function adequately for a stated period of time, under specified operating conditions.
Prof G.R.C.Nair
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Types of Reliability
• Inherent reliability – predicted by product design.
• Achieved reliability – observed during use.
Prof G.R.C.Nair
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Cumulative Failure Curve
Prof G.R.C.Nair
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Average Failure Rate
Prof G.R.C.Nair
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Bath Tub Curve
“Infant mortality period”/ Debug period
Prof G.R.C.Nair
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To take care of ‘Infant Mortality phase’, consider debugging team, Warrantee,free service, free replacement, pre testing for that period before release to market etc
Prof G.R.C.Nair
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Reliability Measurement • Failure rate () – number of
failures of break downs per unit time.
• Alternative measures•Mean time to fail (MTTF)•Mean time between failures(MTBF)MTBF orMTTF
Prof G.R.C.Nair
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Reliability Function
1
R(t)
R(t)
Time t
Prof G.R.C.Nair
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Reliability Function
• Reliability for a period of ‘t’ r(t) = e-t
• Probability of failure within time ‘t’
f(t) = 1 – e-t Prof G.R.C.Nair
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Exercises• MTBF = 500 hrs • Find Also find r (50, 400, 800,
1000,2000)
Prof G.R.C.Nair
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System Reliability
Depends on ,• Component Reliability• Number of Components• The Configuration
Prof G.R.C.Nair
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Series Configuration
R = r1 * r2 * r3 *... rn
1 2 n
Prof G.R.C.Nair
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Parallel Configuration
R = 1 – [(1 - r1) (1 - r2)…… (1 – rn)]
1
2
n
Prof G.R.C.Nair
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Optimum Reliability
Reliability
costProf G.R.C.Nair
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Prof G.R.C.Nair
Frequency Ranking
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Severity Rankings
Prof G.R.C.Nair
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• RPN (Risk Priority Number) 1 to 1000• Higher the number higher the risk• RPN= SxOxD each 1 to 10 increasing• S= Severity of failure - 1 to 10• O= Prob of Occurrence- 1 to 10• D= Difficulty in identifying 1 to 10
Prof G.R.C.Nair
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Prof G.R.C.Nair
Classification of “Risk”
PossibilityOf Occurrence
Severity of Outcome
High Risk
Moderate Risk
Low Risk