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

Issue 7, September 2001

*Hot Topics
*Reliability Basics
*Tool Tips
*Hot News
*From The Edge
*Contribute to HotWire

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Hot Topics  

Using Accelerated Life Testing Analysis to Characterize "Shelf Life"
In this case study, we take a look at how ReliaSoft's ALTA software can be utilized to characterize the "shelf life" of certain chemicals. Most life data or accelerated testing analyses have time as the dependent variable and other inputs as stress factors. However, in this case, time will be considered to be the stress factor, while the dependent variable is a particular characteristic of the chemical, such as concentration. Through this type of analysis, one can determine the probability that the chemical's characteristic will be outside an acceptable range of values based on test readings taken at various time intervals.

To read more, see 

Reliability Basics  

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

The Reliability Function
The most frequently used function in life data analysis and reliability engineering is the reliability function. This function gives the probability of an item operating for a certain amount of time without failure. As such, the reliability function is a function of time, in that every reliability value has an associated time value. In other words, one must specify a time value with the desired reliability value, i.e. 95% reliability at 100 hours. This degree of flexibility makes the reliability function a much better reliability specification than the MTTF, which represents only one point along the entire reliability function. In this article, we will take a look at the reliability function, how it is derived, and an elementary statistical background.

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Tool Tips  

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

  • How do I remove the Program ID from the plots in Weibull++ and ALTA?

  • Is there a quick way to specify stress profiles in ALTA 6 PRO?

  • Can I have circular references in my RBD in BlockSim?

To read more, see

Hot News

Sold Out Reliability Seminar  - We want to express our appreciation to everyone who attended the sold out "Master the Subject, Master the Tools" reliability training seminar in San Diego, California last week. Thanks for your participation!

BlockSim MT for the Machine Tool Industry - ReliaSoft has been working closely with Ford Motor Company and their machine tool suppliers to develop a customized version of BlockSim. BlockSim MT, which was released earlier this month, was designed to provide an easily understandable standardized R&M report, including an Operational Availability Tree for machine tool equipment.


Next Seminar in Tucson, October 15 - 19  - The next ReliaSoft "Master the Subject, Master the Tools" reliability training seminar will be held October 15 - 19, 2001 in Tucson, Arizona at the Sheraton Hotel and Suites. Topics for this five-day seminar include life data analysis, accelerated life testing data analysis, and system reliability, maintainability and availability. For more information on course content and how to register, see


QALT Boot Camp - ReliaSoft will begin offering an intensive three-day course on advanced topics, concepts and applications of quantitative accelerated life testing (QALT) with its "QALT Boot Camp." This is a three-day seminar that covers advanced topics in accelerated life test data analysis such as time-varying stresses and multiple stress testing. The next QALT Boot Camp will be held in Tucson, Arizona on November 14 - 16, 2001 (New dates!). For more information on course content and how to register, see

From the Edge  

Every quarter, 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:

  • Using Degradation Data for Life Data Analysis - One of the obstacles to performing a complete life data test is the amount of time it may incur. Given reduced development cycle time and increased product reliability, it may be unrealistic to run test units to failure in a timely fashion. The analysis of degradation data is one way to overcome this obstacle. Degradation analysis involves the measurement of the degradation of a product, where the degradation can be directly related to the expected failure of the product. This information is then used to estimate the eventual failure time for the product. See
  • Classic Case Studies in Reliability Analysis: The Weibull Distribution - It has been exactly 50 years since Professor Walloddi Weibull published his groundbreaking paper, "A Statistical Distribution Function of Wide Applicability," in the Journal of Applied Mechanics. The 1951 paper contained seven case studies. This article revisits the first of these examples using modern computer tools. See
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Contributions Welcome
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.

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