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Reliability Considerations


Reliability, strictly speaking,  is the probability of performing specified functions under specified conditions for a specified period of time, and is denoted R(t).
Reliability is sometimes expressed as a mean time between (before) failure, or MTBF; as the percent that fail by time "x"; the number of failures expected to occur in a time interval; or the  probability of failing, F(t), which is the complement of the reliability, F(t) = 1 - R(t).
Assessing the reliability of your system is much more than a Mil-217 handbook prediction. The complexity of the system - in terms of definition of failure, redundancy and repair policy - can be overwhelming. What technique should be used? What tools are needed? Who understands the necessary underlying statistical assumptions well enough to create a good reliability model?
After your system model is created, where will you get the component and sub-system data to evaluate the model? Handbook predictions can be notoriously erroneous. Predecessor systems, tests and field experience offer the best sources of data.
Field data analysis is often misunderstood by reliability "experts". A constant failure rate should not be assumed, but should be proven. Data analyses must be performed to determine the characteristics of the probability density function (pdf). It is easy to assume failures follow an exponential distribution, and that assumption often simplifies many calculations; but, don't sacrifice accuracy for simplicity. Determine the pdf unless you know the simplifying assumptions are acceptable.
Regardless of the product, we all expect a certain level of reliability in everything we purchase and everything we use, from automobiles, to cell phones, to solar cells. I can provide exceptional expertise and value to your products and your company. Modeling and data analyses are two areas in which I have extensive experience; but, I also excel in applying the other common reliability tools. If your analysis requires a failure modes and effects analysis (FMEA) before setting up your system model, supplier audits, or reliability testing, I can plan and execute these activities as well.
Take some time to look around my website and you will see the nature of my education, the extent of my expertise, the industries in which I have worked and the detailed analyses presented in my papers. I am sure you will give me strong consideration for your next system reliability challenge. When you finish looking around, send me an email or give me a call.