可靠度的计算方式.ppt

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 Electronic Components Consulting Services Inc Consultant to Industry 631 928-2847 What 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. Stress Analysis Reliability Predictions FMEA (Failure Mode and Effects Analysis) or FMECA (Failure Mode Effects and Criticality Analysis) Yardstick for comparison of design approaches 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 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 Describes operating condition as a percentage of rating Customer requirement Validates compliance with Derating Criteria Reliability Predictions (MTBF) 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 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 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