Your Reliability Engineering Professional Development Site
A listing in reverse chronological order of articles by:
Can you identify the effect of the door latch-pin failure in this case study? The loss of the aft cargo door on the American Airlines DC-10 aircraft will be the focus of this Problems and Solutions article. This real-life case study is being used to practice identifying FMEA elements.
Why do you think FMEA procedure requires effects to be taken to the system or end user? Why not describe the consequence only at the local level. If a bolt in a complex system fails, the parts that the bolt was clamping together may come apart. Isn’t that enough?
“Wisdom consists of the anticipation of consequences.”
Norman Cousins
Frequently, data collection is the most time consuming and expensive part of a project. Consequently, people work with small sample data. There is too little data to plot a histogram, so the analysis assumes the underlying population is normally distributed.
A frequent error is to assume the sample average and standard deviation are the population normal mean and standard deviation. When small sample sizes are being analyzed, these assumptions lead to estimation errors.
Methods to make better estimates are discussed in this article. [Read more…]
In this Q and A article, a reader asks an interesting question about whether or not to update a System FMEA, when making subsequent changes to lower-level items. This is an excellent question, and shows the reader has good insight into the application of FMEA.
“Judge a man by his questions, not his answers.”
Voltaire
Whether you are new to FMEA or more experienced, these problems will challenge your skills. The intermediate/advanced problem uses an actual airline disaster to challenge readers with an FMEA problem, and practice identifying the elements of an FMEA.
The most common types of engineering data are measurements. There can be a few, thousands, or millions of data points to analyze. Without analytic tools, one can get lost in the data.
This article presents
To reduce schedules, prototype cycles are often randomly slashed. Eventually the time and resources are needed and create cost and schedule over runs. We need to recognize that prototypes exist to help us learn about our product. If we use a risk based test strategy approach, we can test at lower levels to gain the required understanding. Then, we can confirm our learning with the higher level, system prototypes.
Just 4 minutes and 19 second long. To me, a prototype does include bench testing at lower levels as long as it includes the relevant functionality to represent the area for learning. [Read more…]
Do you know why we ask for the “mode” of failure when performing FMEAs? This article will provide theory and practical examples of defining failure modes, and highlight an application tip that can improve your FMEA effectiveness.
“I haven’t failed, I’ve just found ten thousand ways that don’t work”
Thomas Edison
If a tree falls in a forest with no one around to hear it, does it still make a sound?
If a fault occurs in a combinational circuit but its masked at the outputs is it still a fault?
If you can’t excite a fault from the circuit inputs does it really exist?
If you can’t propagate a fault to an output pin, does it matter?
In assessing an integrated circuit’s testability engineers consider the concepts of controllability and observability. In these specific characteristics of testability came up often the academic test literature of the 1970’s and 1980’s. The challenge back then was automatic test generation and fault simulation. [Read more…]
Model Building is a key theme for several advanced techniques. It boils down to creating an equation. Done well, one can predict and forecast how things will behave. Creating understanding reduces product risk and increases the chances for success.
Just 3 minutes and 9 second long, lets get the basics of model building to improve your understanding of how a system works. [Read more…]
In this question, a reader asks how to define system-level functions, and how they are different from subsystem and component functions.
“A prudent question is one-half of wisdom.”
Francis Bacon
Our white paper regarding t-test calculations has been very popular. Those that use the t-test tool regularly have commented “I finally understand what it is all about.”
The natural question they ask me next is “have you done anything with the F-test?” It is another common tool and one that is equally misunderstood.
Due to popular request, here is our attempt at explaining the F-test tool, in the two possible methods of use. [Read more…]
Do you consider yourself an FMEA beginner or are you more experienced? Challenge yourself with these problems about FMEA functions, and see how you do. One of the best ways to learn is by pondering application problems and seeing of you can solve them.
If you haven’t yet read last week’s article Understanding FMEA Functions – Part 1, it would be a good idea to read it now, as the questions are based on that article.
In honor of Labor Day, I thought I would jump over to the Built-In Self-Test (BIST) wing of the DFT Castle.
I will provide you with a quick tour. Then when you hear the term in a meeting you can follow along and ask a few questions.
BIST saves labor for the Automatic Test Equipment (ATE).
Though there’s no free lunch. BIST does require an engineer to labor—someone has to design it specific to the device under test (DUT). [Read more…]
This is an example of a practical DOE that was used in the development of a manual window mechanism for a truck application. A similar process can be used for current mechanical and electrical design and development projects. In this article, you will see that the DOE method: