Reliability Ques (Tech Briefs)

We publish electronic versions of “Reliability Ques” periodically as a means of keeping our community up-to-date on effective tools, techniques, and approaches to improving the reliability, maintainability, and quality of products and systems.

Design of Experiments for Reliability Improvement

July 26th, 2007
Many times we want to improve Reliability (or other Quality characteristics) by way of increasing positive and reducing negative factor effects that influence performance.   Read More

Test Samples: How Many Are Needed?

April 26th, 2007

For demonstrating product reliability the question of how many test samples are needed to be “X” percent confident of having met a reliability objective often comes up. Let’s say that manufacturer is going to produce 5,000 rooftop car carriers and is willing to tolerate roughly 100 returns over the next five years. How can this…  Read More

Need Technical Help? Try an IAC

September 26th, 2005

Last month we introduced you to the Department of Defense (DoD) Reliability Information Analysis Center (RIAC), formerly known as the Reliability Analysis Center (RAC), as a valuable resource for expertise and data/information in reliability, maintainability, quality, supportability, and interoperability.Now we want to tell you more about the technologies covered by all twenty-one Centers of Excellence…  Read More

Reliability Certification

May 26th, 2005

Starting salaries for engineers graduating from college this spring will be in the $50K neighborhood and even higher for the top students, as well as those with specialized experience. The degrees are typically electrical, electronics, mechanical, materials, civil, industrial, computer, and so on. Seldom is there a “reliability engineering” graduate. There are a few exceptions…  Read More

Mission Reliability and Logistics Reliability: A Design Paradox

April 26th, 2005
The goal of improving system reliability often presents a design paradox; “mission” reliability cannot be increased without simultaneously decreasing “logistics” reliability. When faced with the challenge of a system that has inadequate reliability to meet specification requirements, hardware redundancy is often implemented, leading to   Read More

Probability and Statistics for Reliability: An Introduction

March 26th, 2005
Painful as it is to many of us, the generally desirable product characteristicReliability is heavily dependent on Probability and Statistics for measuring and describing its characteristics. This edition of Reliability Ques will only be the tip of the iceberg in this regard. Let’s start with a few basics:   Read More

Better Reliability Predictions Using Experience Data

February 26th, 2005

There are many approaches that can be used to predict the reliability of an item. Sometimes when asked to provide a “quick estimate” of an item’s reliability, the use of field experience is overlooked, or if no failures have occurred, overly conservative estimates are made by assuming one failure. This article describes a simple approach…  Read More

Reliability: Costly, or Cost Effective?

October 26th, 2004

There are those who would argue that the costs of reliability activities associated with developing new products have little payoff. Whether we’re talking about commercial products or military systems, we don’t agree. Concepts like Life Cycle Costs, Total Ownership Costs, Reliability-based Maintenance, Performance-Based Logistics, and others clearly recognize the contribution of reliability activities in reducing…  Read More

Reliability Predictions: Parts Count, Part Stress, Pseudo Stress and Dormant

September 26th, 2004
Reliability predictions are an important tool for making design trade-off decisions and estimating future system reliability. They are often used for making initial product support decisions such as how many spares are required to support fielded systems. Inaccurate predictions can lead to overly conservative designs and/or excessive   Read More

Warranty Cost: An Introduction

April 26th, 2004
Whether your company is marketing commercial products or selling to the Government, warranties are an important ingredient to competitive success. Effective warranty planning can ensure success, but lack of attention to cost analyses can spell disaster. This article is intended to introduce the basics of warranties and to identify sources for more information.   Read More