What will Advance Reliability Engineering?

August 15, 2012Engineeringanalysis, data, reliability, validityKirk Gray

Kirk Gray, Accelerated Reliability Solutions, L.L.C.

In all aspects of engineering we only make improvements and innovation in technology by building on previous knowledge. Yet in the field of reliability engineering (and in particular electronics assemblies and systems), sharing the knowledge about field failures of electronics hardware and the true root causes is extremely limited. Without the ability to share data and teach what we know about the real causes of “un-reliability” in the field, it is more easily understood why the belief in the ability able to model and predict the future of electronics life and MTBF continue to dominate the field of electronics reliability Continue reading What will Advance Reliability Engineering? →

Wrong Conclusions

August 12, 2012MTBFconclusions, MTBF, percentagesFred Schenkelberg

Here is a podcast by Chris Peterson of H and H Environmental Systems which includes her thoughts on the MTBF topic. She also explores how making even ‘obvious’ assumptions may lead to the wrong conclusions.

Chris records a podcast almost everyday and many are enjoyable, fun, and and provide something to think about as you go about your day. If you like the podcast above, check out her growing list of available podcasts.

Embedded podcast with permission of Chris.

For Maximum Test Value, Take it to the Limit!

August 8, 2012TestingHALT, limit, MTBF, testing, valueKirk Gray

When we go to an automobile race such as the Indianapolis 500, watching those cars circle the track can get fairly boring. What is secretly unspoken is that everyone observing the race is watching for a race car to find and sometimes exceed a limit, finding a discontinuity. The limit could be how fast he enters a curve before the acceleration forces exceed the tires coefficient of friction, or how close to the racetrack wall, he can be before he contacts it and spins out of control. Using the race analogy, Continue reading For Maximum Test Value, Take it to the Limit! →

Use Lognormal Distribution

August 5, 2012MTBFlognormalFred Schenkelberg

The lognormal distribution has two parameters, μ and σ. These are not the same as mean and standard deviation, which is the subject of another post, yet they do describe the distribution, including the reliability function.

$\displaystyle R(t)=1-\Phi \left( \frac{\ln (t)-\mu }{\sigma } \right)$

Where Φ is the standard normal cumulative distribution function, and t is time. Continue reading Use Lognormal Distribution →

Where does 0.7eV come from

August 1, 2012Predictions, TestingpopularFred Schenkelberg

This post is a conversation first held on the LinkedIn group No MTBF. I’m capturing a portion of the contributions here to continue the discussion or to widen the audience. Reminds me of always assuming 95% confidence is the right value when designing a test, or assuming constant failure rate. So, let the conversation continue, starting with the original post. Continue reading Where does 0.7eV come from →

Datasheet MTBF

July 22, 2012MTBFdatasheet, MTBF, reliabilityFred Schenkelberg

Some many years ago I ran across a data sheet for a cooling fan (used to cool a desktop computer, for example) that listed the fan’s life as 50,000 hours MTBF. The big bold lettering was on the data sheet and was the only use of bold on the entire data sheet. One couldn’t miss it. The computers we used these fans within had a one year warranty, plus were expected to operate for a home computer user for about 5 years. Thus, we would expect the fan to also operate for five years without failure. Continue reading Datasheet MTBF →

MTBF Eradication

July 17, 2012MTBFaction, MTBFFred Schenkelberg

After a discussion with a client this morning, and their motor vendor’s reliability engineer asked for a reference for a sample size calculation formula I recommended, I had a short email exchange with said reliability engineer. In my note with the references, I included an aside with a link to this site. He liked the site and agreed that MTBF was often Continue reading MTBF Eradication →

Pakistan budgets with MTBF

July 8, 2012MTBFMTBFFred Schenkelberg

Now for something completely different. Roaming the net looking for an interesting advertisement or data sheet with a ‘great’ (i.e. bad) example of the mis use of MTBF, ran across that MTBF is actually being used by at least one government for department budgeting.

This is bad. Continue reading Pakistan budgets with MTBF →

What’s All the Fuss about Bayesian Reliability Analysis?

July 6, 2012Predictionsbayesian reliability, bayesian reliability analysis, MCMC, reliability, Reliability predictions, reliability risk, statisticsMark Powell

The term Bayesian Reliability Analysis is popping up more and more frequently in the reliability and risk world. Most veteran reliability engineers just roll their eyes at the term. Most new reliability engineers dread the thought of having to learn something else new, just when they are getting settled in the job. Regardless, it is a really good idea for all reliability engineers to have a basic understanding of Bayesian Reliability Analysis.

This series explains Bayesian Reliability Analysis and justifies Continue reading What’s All the Fuss about Bayesian Reliability Analysis? →

The Worst Reliability Requirement

June 21, 2012MTBFMIL HNBK 217, MTBF, popular, reliabilityMark Powell

Most of us have seen reliability specified using a requirement like the following:

The Zeus 5000 SUV shall have an MTBF of 144,269.5 miles with a 90% confidence.

Some readers may not have seen reliability requirements specified in any other way. What they have always seen has read something like: The widget shall have an MTBF of X with a Y% confidence. This reliability requirement structure is rather ubiquitous Continue reading The Worst Reliability Requirement →

I must not MTBF. MTBF is the mind-killer. MTBF is the little-death that brings total obliteration. I will face my MTBF. I will permit it to pass over me and through me. And when it has gone past I will turn the inner eye to see its path. Where the MTBF has gone there will be nothing. Only Reliability will remain.

Bene Gesserit Litany Against Fear. (with apologies)

5 Reliability Training Options

June 7, 2012Uncategorizedbasics, consultants, education, reliability, statistics, universityFred Schenkelberg

Just answered a question on where to find reliability engineering training on basics and statistics. There are plenty of options and below I’m listing just where to find the many, many options available to you. Continue reading 5 Reliability Training Options →

Role of parts count prediction

June 1, 2012MTBF, Predictions, TestingFred Schenkelberg

Great note [response to comment on Drain in the Bathtub Curve on NoMTBF Linkedin Group] – yes, there is a place for parts count prediction — not to determine the mtbf, to encourage proper derating, thermal engineering, and parts reduction, etc. It’s a start and as you note only one part of the reliability program. Continue reading Role of parts count prediction →

Why The Drain in the Bathtub Curve Matters

May 23, 2012Predictions, UncategorizedBathtub curve, cost, failure prediction methodology, field failure correlations, popular, reliability, technology obsolescenceKirk Gray

Most reliability engineers are familiar with the life cycle bathtub curve, the shape of the hazard rate or risks of failure of a electronic product over time. A typical electronic’s life cycle bathtub curve is shown in figure 1. Continue reading Why The Drain in the Bathtub Curve Matters →

The Linkedin NoMTBF group is growing and while not very active does have an occasional interesting discussion. Join the discussion and maybe relate how you have raised awareness around the proper use of MTBF.

http://www.linkedin.com/groups/No-MTBF-1857182/about

No MTBF

A site devoted to the eradication of the misuse of MTBF : — ISSN 2168-4375

What will Advance Reliability Engineering?

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Wrong Conclusions

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For Maximum Test Value, Take it to the Limit!

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Use Lognormal Distribution

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Where does 0.7eV come from

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Datasheet MTBF

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MTBF Eradication

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Pakistan budgets with MTBF

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What’s All the Fuss about Bayesian Reliability Analysis?

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The Worst Reliability Requirement

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5 Reliability Training Options

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Role of parts count prediction

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Why The Drain in the Bathtub Curve Matters

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