Ideally, in every design of every component, the stress – strength relationship looks like this figure. The stress is well below the strength. [Read more…]
Stress Strength Normal Assumption
CRE Preparation Notes
Prep notes for ASQ Certified Reliability Engineer exam ISSN 2165-8633
The idea of the CRE Preparation Notes series is to provide you short practical tutorials on all the elements that make up the ASQ CRE body of knowledge. The articles provide introductionary material, basics, how-to’s, examples, and practical use guidance for the full range of reliability engineering concepts, terms, tools, and practices.
Keep your knowledge fresh with regular review of topics and tools that make up reliability engineering.
Sign up for the CRE Preparation Notes email list to receive weekly reliability engineering short tutorials.
- Improve your reliability engineering skills
- Learn about the wide range of tools available
- Enhance your resume with the ASQ CRE
You will find the most recent tutorials in reverse chronological order below. Below each article is the section and specific clause of the CRE Body of Knowledge that tutorial addresses. Click on those tags to find other articles on the same topic. To the right on the sidebar, there is a listing of the 7 major categories in the body of knowledge - it's a quick way to find groups of articles on each specific area. You can also use the search function to locate articles, podcasts, or tutorials on specific topics.
Mann Reverse Arrangement Test
In the analysis of repairable equipment, one may need to make the assumption of constant failure rate. In my opinion, anytime one wants to make the assumption of constant failure rate, it should be validated. [Read more…]
Statistical Confidence
An error that I see on occasion is the use of statistical confidence with a goal or target value. For example, we want 95% reliability at five years with 90% confidence. What does that mean? [Read more…]
Hypothesis Test Sample Size
Hypothesis testing permits us to compare two groups of items and determine if there is a significant difference or not. There are many types of hypothesis tests depending on the specific question, type of data, and what is or is not known when designing the test. [Read more…]
Reliability Centered Maintenance
The document by Nowlan and Heap
Part of keeping equipment operational is affecting repairs appropriately. Sometimes it makes sense to replace an element of some equipment before it fails, i.e. automobile tires as the tread wears. Sometimes is doesn’t make sense to repair a functioning unit as the result would be a system that is less reliable then before. [Read more…]
2012 in Review
The WordPress.com stats helper monkeys prepared a 2012 annual report for this blog.
Here’s an excerpt:
600 people reached the top of Mt. Everest in 2012. This blog got about 11,000 views in 2012. If every person who reached the top of Mt. Everest viewed this blog, it would have taken 18 years to get that many views.
2012 ASQ Salary Survey is out
Once again those with a CRE are at or near the top of the salaries reported in this survey. See more at http://www.qualityprogress.com/salarysurvey
CRE Exam Preparation
I never did like taking final exams in college as I viewed them as four hours I would rather spend doing something (anything) else. An exam is a check of what you know about a topic or subject. We prepared for those exams by reading, studying, practicing working problems (doing homework) and trying to understand the key concepts, trends, themes, etc. Some of my classmates thought it was about how much they could stuff into short term memory, others though sleep deprivation had something to do with preparing for an exam. [Read more…]
M and A Sample Questions
Just a couple of sample questions from deep in the body of knowledge this week.
Which of the following can be evaluated with dye penetrant methods? [Read more…]
Question a Day Idea
Hi all,
I’m asking for feedback here. I’m thinking about building a subscription service that sends the subscriber a CRE preparation question a day (maybe adjustable by subscriber … not sure how to do this yet). [Read more…]
Sample Size Problem
Let’s work a sample size problem.
A random sample size, n, is to be taken from a large population having a standard deviation of 1″. The sample size is to be determined so that there well be a 0.05 risk probability of exceeding a 0.1″ tolerance error in using the sample mean to estimate μ. Which of the following values is nearest the required sample size?
a. 42
b. 106
c. 203
d. 384 [Read more…]
Sample size
I recently received a question concerning what sample size to use when assessing call center calls. Not a lot of information in the request, so my answer was rather general. And, thought it might provide some insight to others facing sample size questions of their own. [Read more…]
Websites for Reliability
note: if you know of a great online resource that isn’t on this list, please add a comments and we’ll add it to the list for all to share.
Shon Isenhour recently posted on Linkedin a question about online resources helpful for reliability engineers. I added my list and hadn’t seen any other links added. There must be more than the few I know about – what can you add to this list? [Read more…]
Dependability
Ran across an interesting graphic in a new book recently. It single-handedly placed dependability in its proper context. It is an umbrella term that includes most of what we commonly think of as reliability and the other ‘ilities.’ It encompasses the various connotations of dependable and reliable that are conveyed during common use. And, the term dependability permits the overarching context for defining very clearly the various [Read more…]
Root Cause Knowledge and Models
Two short questions to evaluate your knowledge of failure mechanisms (root causes) and common reliability models. The answers will be posted in a comment, later.
Which of the following failure root causes is most likely NOT due to power line variation (electronic-based product)?
A. Circuit design margin exceeded
B. Power dissipation
C. In-rush current response
D. Mechanical fatigue [Read more…]
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