8 Nondestructive Evaluation Techniques
There are times when we need to evaluate a product to determine is it assembled correctly or when looking for clues concerning a failure mechanism. Simple visual inspection may be sufficient and there are times when we need more information or detail.
A great first step is the use of an appropriate nondestructive evaluation (NDE) method. Done correctly we…
8 factors of design for maintainability
The first time I changed the oil filter of my car (first car in high school) I smashed my knuckles against an grimy block of metal. More than once. It may have been my lack of experience or improper tools. Or, it may have been a rather poor design
Watching the Indy 500, especially the pit stops, I quickly realized there has to be something different about…
Considerations for Reliability Testing
Reliability testing to determine what will fail or when will failures occur is expensive. Organizations invest in the development of a product and attempt through the design process to create a product that is reliable.
The design process has many unknowns though. This includes uncertainties about materials, design margins, use environments, loads, and aging…
Looking for failure data
Beyond understanding what will fail (failure mechanisms) we need to know when a system will fail. Both what and when information can be found in a variety of sources. Unlike the stock market where we are regularly warned that past performance does not indicate future performance, in reliability engineering past performance is the best predictor of future performance.
The other day a student said they are asking for failure dates, not failure rates. That is a marked improvement when requesting information for the many sources of reliability information. It is not sufficient though.
Also ask for the type of failures expected or encountered during the testing or observation. (more…)
Types of Reliability Data
We rely on data to make decisions, to reveal patterns or trends, to learn about our systems and world. Data has many forms and sources. Reliability data may provide what will fail and/or when a device will fail. (more…)
A non-parametric test to evaluate if a set of samples have the same variance. If the variances are equal they have homogeneity of variances.
Some statistical test assume equal variances across samples, such as analysis of variance and many types of hypothesis tests. It is also assumed for statistical process control purposes to determine stability (often done with range (r chart) or…
A contingency table, as in the chi-squared test of independence, reveals if two sets of data or groups are independent or not. It does not reveal the strength of the dependance. The contingency coefficient is a non-parametric measure of the association for cross-classification data.
After calculating the chi-squared value from the contingency table exercise, we can use…
I’ll be teaching the CRE prep course again for the ASQ Silicon Valley Section. We’re using Adobe Connect to provide the course online and recorded.
Join us for the discussions, practice and lectures to get you back put to speed and ready for the ASQ CRE exam in October 2014.