Quanterion publishes an electronic version of “Reliability Ques” periodically as a means of keeping its customers and other interested parties up-to-date on effective tools, techniques, and approaches to improving the reliability, maintainability, and quality of products and systems.
Pieces of Pi
Pieces of Pi
Welcome to a new reliability engineering tech brief series written by one of our in-house engineers!
“Pieces of Pi” is a new article series that explores the unique aspects of Reliability, Maintainability and Quality of certain forms of design. It is the author’s opinion that reliability and design practices are closely related. The inherent… Read More
GalleryCalculating an Average Infant Mortality Factor Over a Given Service Life Using the 217Plus™ Methodology
Calculating an Average Infant Mortality Factor Over a Given Service Life Using the 217Plus™ Methodology
Infant mortality is a term that is often used to describe early-life failures – that is, failures that occur due to premature excitation of failure mechanisms. Such failures are typically due to inferior material (e.g., parts used in the manufacturing process… Read More
Confidence Bounds on the Mean Time Between Failure (MTBF) for a Time-Truncated Test
There is a long standing discussion on how best to calculate the lower and upper confidence bounds on the Mean Time Between Failure (MTBF) for a time-truncated test (Type I Censoring) assuming that the times between failure are exponentially distributed (constant failure rate). Read More
Maintenance Planning with Wearout Failure Modes
This Reliability Que will discuss how Weibull analysis qualitative results showing a wearout failure mode can be utilized to quantitatively drive the decision making process in Reliability Centered Maintenance (RCM) programs. Read More
Maintenance Planning with a Constant Failure Rate
This Reliability Que will discuss an example of how Weibull analysis qualitative results showing a constant failure rate affect the maintenance planning process. The qualitative results can be utilized to quantitatively drive the decision-making process in Reliability Centered Maintenance (RCM) programs. Read More
Maintenance Planning with Early Failures
This Reliability Que will discuss an example of how Weibull analysis qualitative results showing early failures (Infant Mortality) can be utilized to quantitatively drive the decision making process in Reliability Centered Maintenance (RCM) programs. Read More
Interference Stress/Strength Analysis
Interference Stress/Strength Analysis
In simplest terms, an item fails when a stress to which it is subjected exceeds the corresponding strength. In this sense, strength can be viewed as “resistance to failure.” Good design practice is such that the strength is always greater than the expected stress. The safety factor “η” can be defined in terms… Read More
Derating
Derating
Introduction
A brief overview of the importance of derating has been provided here, along with a sample determination of requirements calculations using Quanterion’s QuART-ER derating calculator and a description of the Stress-Derating Spreadsheet Calculator – SD-18. This topic is also covered in the Quanterion-authored Reliability Information Analysis Center (RIAC) publication “System Reliability Toolkit” and is included… Read More
GalleryModels Commonly Used to Measure Reliability Growth
Models Commonly Used to Measure Reliability Growth
Reliability growth is the intentional positive improvement that is made in the reliability of a product or system as defects are detected, analyzed for root cause, and removed. The process of defect removal can be ad hoc, as they are discovered during design and development, a function of an… Read More
How Good Is Your Reliability Approach?
How Good Is Your Reliability Approach?
Product reliability is an important discriminator in today’s global marketplace but does your organization know how it’s doing compared to competitors in terms of designing and building reliability into its products? Could/should you be doing more “upfront” reliability activities to improve customer satisfaction, to reduce warranty costs, and to reduce… Read More