MECH 4401 - Design for Reliability

  1. Name four distinct items that would be on a system life-cycle reliability review checklist
    • Are reliability requirements properly defined?
    • Are the reliability requirements realistic and compatible with other requirements?
    • Has the complexity been minimized?
    • Have the failure modes and effects been identified?

    • Rest of them
    • System life-cycle reliability review checklist:
    • 1. Were the reliability requirements properly defined at the beginning of
    • the project in the conceptual design phase?
    • 2. Have the requirements established in the conceptual design phase been
    • properly allocated down to the sub-system level?
    • 3. Are the reliability requirements realistic and compatible with other
    • system requirements?
    • 4. Has system design complexity been minimized?
    • 5. Have system failure modes and effects been identified?
    • 6. Are system, subsystem, unit, and component-part failure rates known?
    • 7. Are the failure characteristics (i.e. physics of failure) known for each
    • applicable component part?
    • 8. Has the system or product wear-out period been identified?
    • 9. Have the component parts with excessive failure rates been identified?
    • 10. Have fail safe characteristics been incorporated where applicable
  2. What is reliability?
    • – the probability that the system will perform in a
    • the satisfactory manner for a given period when used under specified operating conditions

    • Elements of reliability include:
    • • Probability of failure
    • • Satisfactory performance
    • • Time
    • • Specified operating conditions
  3. Name the two reliability methods analyzed. Briefly describe
    • FMECA
    • Reliability prediction
  4. Name the four reliability prediction techniques
    • Prediction may be based on the analysis of similar equipment
    • New equipment reliability similar to one used


    • Prediction may be based on an estimate of active element groups (AEG)
    • An AEG is the smallest functional building block that controls or converts energy.
    • An AEG includes one active element (transducer, transistor, pump, etc…) and a number of passive elements.
    • By counting the number of AEGs and considering their complexity one can predict the reliability of a system


    • Prediction may be accomplished from an equipment parts count
    • Design parts are listed and categorized according to their tendency to fail
    • Failure rates are assigned and combined to predict the MTBF for the system


    • Prediction may be based on a stress analysis
    • Stresses on components can be analyzes
Card Set
MECH 4401 - Design for Reliability