可靠度的计算方式讲解
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• Customer request
– Design goal – Hard Requirement
Stress Analysis
• Establishes the presence of a safety margin
– Good engineering practice – Enhances system life – Provides input data for Reliability Prediction
• Common Standards
– MIL-HDBK-217
• Generally associated with military systems
– Models are very detailed – Provides for many environments – Provides multiple quality levels
Electronic Components Consulting Services Inc.
Reliability Calculations
What, Why, When &
How do we benefit from them?
Who am I?
• Harvey Altstadter
– 34 years experience in Component Engineering and Reliability
• Military • Commercial • Commercial Space
• HR EleEcletrcotrnoincicCCoommppoonnenetns tCsonCsounltisnuglStienrgvicSeserInvcic. es Inc • Consultant to Industry
– Stress Analysis – Reliability Predictions – FMEA (Failure Mode and Effects Analysis) or – FMECA (Failure Mode Effects and Criticality Analysis)
• Yardstick for comparison of design approaches
– Example: for a system with a predicted MTBF of 1000 hours, on average the system experiences one failure in 1000 hours of operation or a Failure Rate of 1000 per 106 hours
If you don’t like the numbers... ...give me five minutes, I will make up a better one
Reliability Predictions (MTBF)
• Form the basis of Reliability Analyses
– Compute predicted system failure rate or Mean Time Between Failures
• Failure Rate is usually expressed in Failures per 106 or 109 hours • MTBF is usually expressed in terms of hours
• 631 928-2847
Wha百度文库 are Reliability Calculations?
• Methodology for analyzing the expected or actual reliability of a product, process or service, and identifying actions to reduce failures or mitigate their effect.
– Cost-Benefit Trade
Why Do Reliability Calculations?
• Make the product more reliable
– Selling feature – Reduce returns – Lower costs – Enhance or maintain company reputation – Comparisons with competition
• Describes operating condition as a percentage of rating
– Customer requirement – Validates compliance with Derating Criteria
Reliability Predictions (MTBF)
– Methodology
• Use accepted standards
– Model failure rates of components – Analyze system – Calculate the system predicted failure rate or MTBF
• Evaluate prediction vs target or required MTBF
– Evaluate stress or temperature reduction design changes – Evaluate practicality of design change especially when MTBF is self imposed
Reliability Predictions (Continued)
– Bellcore (Telcordia)
• Telecommunications Industry standard
– Seems to have supplanted French CNET and British Telcom standards – Models patterned after MIL-HDBK-217, but simplified – Provides multiple quality levels – Can incorporate current laboratory test data – Can incorporate current field performance data
– Design goal – Hard Requirement
Stress Analysis
• Establishes the presence of a safety margin
– Good engineering practice – Enhances system life – Provides input data for Reliability Prediction
• Common Standards
– MIL-HDBK-217
• Generally associated with military systems
– Models are very detailed – Provides for many environments – Provides multiple quality levels
Electronic Components Consulting Services Inc.
Reliability Calculations
What, Why, When &
How do we benefit from them?
Who am I?
• Harvey Altstadter
– 34 years experience in Component Engineering and Reliability
• Military • Commercial • Commercial Space
• HR EleEcletrcotrnoincicCCoommppoonnenetns tCsonCsounltisnuglStienrgvicSeserInvcic. es Inc • Consultant to Industry
– Stress Analysis – Reliability Predictions – FMEA (Failure Mode and Effects Analysis) or – FMECA (Failure Mode Effects and Criticality Analysis)
• Yardstick for comparison of design approaches
– Example: for a system with a predicted MTBF of 1000 hours, on average the system experiences one failure in 1000 hours of operation or a Failure Rate of 1000 per 106 hours
If you don’t like the numbers... ...give me five minutes, I will make up a better one
Reliability Predictions (MTBF)
• Form the basis of Reliability Analyses
– Compute predicted system failure rate or Mean Time Between Failures
• Failure Rate is usually expressed in Failures per 106 or 109 hours • MTBF is usually expressed in terms of hours
• 631 928-2847
Wha百度文库 are Reliability Calculations?
• Methodology for analyzing the expected or actual reliability of a product, process or service, and identifying actions to reduce failures or mitigate their effect.
– Cost-Benefit Trade
Why Do Reliability Calculations?
• Make the product more reliable
– Selling feature – Reduce returns – Lower costs – Enhance or maintain company reputation – Comparisons with competition
• Describes operating condition as a percentage of rating
– Customer requirement – Validates compliance with Derating Criteria
Reliability Predictions (MTBF)
– Methodology
• Use accepted standards
– Model failure rates of components – Analyze system – Calculate the system predicted failure rate or MTBF
• Evaluate prediction vs target or required MTBF
– Evaluate stress or temperature reduction design changes – Evaluate practicality of design change especially when MTBF is self imposed
Reliability Predictions (Continued)
– Bellcore (Telcordia)
• Telecommunications Industry standard
– Seems to have supplanted French CNET and British Telcom standards – Models patterned after MIL-HDBK-217, but simplified – Provides multiple quality levels – Can incorporate current laboratory test data – Can incorporate current field performance data