1. Reliability A. A. Elimam

2. Reliability: Definition The ability of a product to perform its intended function over a period of time and under prescribed environmental conditions

3. Factors Impacting Reliability n n Initial design n n Complexity of design n n Manufacturing process n n Handling during shipping n n Environment of use n n Its end user

4. Product Life Cycle n n Early Failure (infant Mortality) : Exponential n n Chance Failure n n Wear-out: As the product ages

5. Measures of Reliability n n Failure-terminated tests When a predetermined number of failures occur in sample n n Time-terminated tests when an established number of hours is reached.

6. Time-Dependent Performance n n Mean Life n n Mean Time between Failures n n Mean Time to Failures (non- repairable systems) n n Availability = mean time to failure (MTTF) MTTF + mean time to repair

7. Time-Dependent Performance n n Failure rates = # of Failures observed sum of test times or cycles n n Average Life = sum of test times or cycles # of Failures observed

8. System Reliability n n System in series exists only if its functioning depends on that of ALL its parts n n R s = r 1. r 2. r 3.....r n R s = reliability of series system r i = reliability of component i n = number of parts in system

9. System Reliability n n Parallel System in able to function if at least one of its components is functioning n n R p = 1- (1-r 1 ). (1-r 2 )....(1- r n ) R p = reliability of parallel system

10. Redundant Systems Reliability n n Backup/spare components used if primary comp. fails n n R b = r 1 + r b (1- r 1 ) R b =reliability of backup system r 1 =reliability of primary comp. r b =reliability of backup comp.

11. Reliability Programs n n The entire system n n The humans in the system n n Maintenance of the system n n Simplicity n n Redundant & fail-safe features

12. Reliability Programs n n Manufacturing methods and purchasing requirements n n Maintenance of complete product or system performance records n n Communication