Mean Time to Failure MTTF

1
Mean Time to Failure (MTTF)

• The MTTF is the expected time that a system will
  operate before the first failure occurs.
• The MTTF can be calculated by finding the
  expected value of the time of failure
• f(x) is the probability density function

2
Mean Time to Failure (MTTF)

• f(t) failure density function

3
Mean Time to Failure (MTTF)

• If reliability obeys the exponential failure law
• Note At t MTTF

4
Mean Time to Repair (MTTR)

• Repair rate average number of repairs per hour

5
Mean Time Between Failure (MTBF)

• The MTBF is the average time between failures of
  a system
• The average number of failures
• N number of systems
• ni the number of failures encountered by unit i

6
Mean Time Between Failure (MTBF)

• Assuming that all repairs to a system makes the
  system perfect once again