Reliability HotWire: eMagazine for the Reliability Professional
In this issue:

Issue 21, November 2002

*Hot Topics
*Reliability Basics
*Tool Tips
*Latest Software Updates
*Hot News
*From the Edge
*Contribute to HotWire

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Hot Topics  
The Bathtub Curve and Product Failure Behavior
Part One - The Bathtub Curve, Infant Mortality and Burn-in

Reliability specialists often describe the lifetime of a population of products using a graphical representation called the bathtub curve. The bathtub curve consists of three periods: an infant mortality period with a decreasing failure rate followed by a normal life period (also known as "useful life") with a low, relatively constant failure rate and concluding with a wear-out period that exhibits an increasing failure rate. This article provides an overview of how infant mortality, normal life failures and wear-out modes combine to create the overall product failure distributions. It describes methods to reduce failures at each stage of product life and shows how burn-in, when appropriate, can significantly reduce operational failure rate by screening out infant mortality failures. The material will be presented in two parts. Part One (presented in this issue) introduces the bathtub curve and covers infant mortality and burn-in. Part Two (presented in next month's HotWire) will address the remaining two periods of the bathtub curve: normal life failures and end of life wear-out.

To read more, see 

Reliability Basics  
The purpose of this section is to offer background and advice to the novice reliability engineer.

Determining the Reliability of a System with Standby Redundancy
In the last issue of the HotWire, we discussed the case of a system with load sharing components. Load sharing is a form of redundancy with dependent components, i.e. the failure of one component affects the likelihood of failure for the other component(s). In this issue, we will discuss another form of redundancy, namely standby. This article describes the three types of standby configurations (hot, warm and cold) and presents an example analysis for a system with one active and one standby component.

To read more, see 

Tool Tips  

The Tool Tips section addresses helpful hints and frequently asked questions about ReliaSoft software products.

  • Can I use Weibull++ to calculate the optimum replacement time for a component?

  • Can I perform QCP calculations in Weibull++ for multiple Data Folios without having to open and close the QCP each time?

  • How can I create a Web-friendly graphic file (such as a *.gif) of a plot in RS Draw?

To read more, see 

Latest Software Updates
New service packs have been released for Weibull++ 6 (SP 4), Weibull++ MT (SP 4) and Weibull++ DE (SP 1). To determine the compile revision of the application on your computer, select About from the Help menu.


Application Date Created Version
Weibull++ 6 10/24/02 6.0.9
Weibull++ 6 Service Pack 10/24/02 SP4 CRV 9
Weibull++ MT    
Weibull++ 6 MT 10/24/02 Weibull ++ 6.0.9 - MT 6.1.6
Weibull++ 6 MT Service Pack 10/24/02 SP4 CRV 9 - 6
Weibull++ DE    
Weibull++ DE 11/1/02 1.0.2 (RSW6API.OCX) and 1.0.5 (RSW6I.DLL)
Weibull++ DE Service Pack 11/1/02 SP 1 CRV 2 - 5
Hot News
* Reliability Training Seminars - Upcoming ReliaSoft public reliability training seminars include:
- Master the Subject, Master the Tools training seminar for life data analysis, accelerated life data analysis and system reliability analysis: November 18 - 22, 2002 in Tucson, Arizona and December 9 - 13, 2002 in Singapore. For more information, see BlockSim will be used for the system reliability analysis course!
* ReliaSoft at the IEEE ICC Meeting - Pantelis Vassiliou, ReliaSoft's President and CEO, was a presenter at the IEEE ICC Meeting held in St. Petersburg, Florida October 27 - 30, 2002. ReliaSoft would like to thank those of you who attended the presentation. We hope that we helped to make this a productive and interesting meeting for you.
* ReliaSoft to Co-Sponsor the 40th Annual Reliability Engineering and Management Institute  - Along with Siemens, Boeing, Dell, Eaton, General Electric, Honeywell, Raytheon, Intel, and SMSC, ReliaSoft will once again be co-sponsoring the Annual Reliability and Maintainability Management Institute. The institute will be held November 18-21 in Tucson, Arizona. If you will be attending, we would love to meet you at the ReliaSoft corporate headquarters, conveniently located nearby. Call +1.520.886.0410 if you would like to arrange a meeting to discuss your reliability needs. Also, be sure to attend the overview of ReliaSoft's reliability engineering software tools, given by ReliaSoft's President and CEO Pantelis Vassiliou on Thursday, November 21.
* Reliability Training Schedule for Delphi Automotive - We are pleased to announce that ReliaSoft will provide reliability training for Delphi Automotive personnel on the subject of life data analysis and the use of ReliaSoft's Weibull++. The schedule for upcoming seminars is presented below. Delphi personnel can contact the corporate training office for more information.


November 11 - 13, 2002 Delphi Saginaw - Saginaw, MI


December 9 - 11, 2002 Delphi Interior - Troy, MI
- January 13 - 15, 2003 Delphi Harrison - Lockport, NY
- January 22 - 24, 2003 Delphi Delco - Kokomo, IN
- February 3 - 5, 2003 Delphi Packard - Warren, OH
- February 17 - 19, 2003 Delphi E & C - Troy, MI
From the Edge
In addition to the monthly Reliability HotWire, ReliaSoft publishes Reliability Edge, a printed journal that includes articles and information related to the field of reliability engineering. Articles of interest in the current edition:
  • Critical Examination of a Common Assumption in System Availability Computations: This article provides a critical examination of the common assumption that the method used to compute system reliability based on component data can also be used for system availability calculations. With a series system, for example, the system reliability can be computed by multiplying the reliabilities of the components and there is a common assumption that the availability for a series system can be computed by simply multiplying the availabilities. As the article demonstrates, this assumption is only justified under certain conditions and, in most cases, another factor must be taken into account when computing system availability from component data.
  • Failure Modes, Effects and Criticality Analysis: Failure Modes and Effects Analysis (FMEA) and Failure Modes, Effects and Criticality Analysis (FMECA) are methodologies designed to identify potential failure modes for a product or process before the problems occur, to assess the risk associated with those failure modes and to identify and carry out measures to address the most serious concerns. This article presents a brief general overview of FMEA and FMECA analysis techniques and applications.
Contribute to HotWire
Contributions Welcomed
As always, your feedback and contributions are appreciated. ReliaSoft is able to provide the most user-friendly reliability software packages and support because we listen to our customers. This applies to our newsletters and publications as well. We welcome any suggestions or contributions you may have for Reliability HotWire. If you have a topic or article that you think would be useful to the readers of Reliability HotWire, feel free to contact us.

Copyright 2002 ReliaSoft Corporation, ALL RIGHTS RESERVED