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

Issue 2, April 2001

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

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Hot Topics  
Determining the Reliability of Complex Systems
Part 1 - Analytical Techniques
A complex system is one that cannot be broken down to groups of series and parallel components. Due to this, it can sometimes be difficult to determine the reliability of the system as a function of the component reliabilities.  There are two general strategies when solving for system reliability: analytical techniques and simulation. In this article, we will look at some of the analytical techniques that can be employed to determine system reliability. With component-level reliability information available, it then becomes necessary to determine how these component values are combined to determine the reliability for the overall system. This article discusses the decomposition, event space, and path tracing methods of analyzing complex systems.

In next month's issue, we will look at using simulation to determine system reliability.

To read more, see 

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

Specifications and Product Failure Definitions
Before life data can be analyzed or even collected, the definition of failure must be established. While this may seem like a simplistically obvious piece of advice, lack of generally accepted definitions for performance-related failures can result in misunderstandings over validation and reliability specifications, wasted test time, and squandered resources. The process of characterizing the reliability and defining the failures for a product is directly related to the product's mission. Essentially, reliability can be defined as the ability of the product to perform its intended mission without failing. The definition of reliability springs directly from the product mission, in that product failure is the inability of the product to perform its defined mission.

To read more, see 

Tool Tips  

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

  • Can I speed up the data entry process in Weibull++ and ALTA?

  • What do I need to know before analyzing data from an Accelerated Life Test with two types of stresses?

  • How do I get the latest software updates?

  • When reinstalling older versions of software on a PC that is running Windows 2000, I get an error message saying that I need a service pack for Windows NT. What can I do to fix this?

To read more, see

Hot News

*Free Simulation Tool Available - ReliaSoft is pleased to offer a new free simulation tool to our customers. SimuMatic allows you to automatically perform large numbers of Monte Carlo simulations, analyze the resulting data sets, and tabulate results of interest. This tool is perfect for calculating bootstrap confidence intervals, evaluating potential test designs, and other simulation-based analyses. See for downloading instructions. (NOTE: SimuMatic requires Weibull++ 6 to be installed on the user's PC. To download an evaluation copy for use with SimuMatic, see

*Next Seminar in Tucson, June 4-8  - The next ReliaSoft "Master the Subject, Master the Tools" seminar will be held in Tucson from June 4-8, 2001 at the Sheraton Tucson Hotel and Suites. Topics for this five-day seminar include Life Data Analysis, Accelerated Life Testing, and System Reliability, Maintainability and Availability. For more information on course content and how to register, see
*ReliaSoft at the SAE Show - ReliaSoft attended the 2001 Society of Automotive Engineers (SAE) World Congress March 5-8, 2001. We want to thank everyone who came by our booth!
  *ReliaSoft's BlockSim and RAC's PRISM tool integration - The latest service release of BlockSim includes the integration of the Reliability Analysis Center's (RAC) PRISM software, thus allowing access to RAC's extensive electronic failure rate database (included in PRISM) as an integrated add-on to the BlockSim application. To use this functionality, you must have both PRISM and BlockSim installed on your computer.  Both products are available as a bundle from ReliaSoft.

*ReliaSoft Announces the Beta  Release of ALTA-PRO - It has been said that development of a software package capable of analyzing accelerated test data from tests conducted using time varying stress levels would be a major undertaking requiring a team of engineers, statisticians and programmers. It was, and it did! After years of R&D, ReliaSoft officially announced the Beta release of ALTA-PRO, the first commercial software package capable of analyzing accelerated data form specimens subjected to time varying stresses. ReliaSoft's first version of ALTA enabled engineers to get estimates for the population cdf, confidence intervals, and other quantities of interest (such as the MTTF) at use level from data obtained through an accelerated test, and where the stresses applied to the units were not a function of time. ALTA-PRO expands this ability, allowing engineers to perform the same analysis utilizing data gathered from accelerated tests where the stress profile is varying with time (i.e., step-stress, ramp-stress or with any other quantifiable stress profile).

*Reliability consulting now available through ReliaSoft Professional Services - ReliaSoft Professional Services now offers expert consulting help. For more information, 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:

  • Exploring Reliability Analysis Using Simulation - This article uses simulation to explore reliability analysis methods and theory. ReliaSoft's new SimuMatic utility, which allows users to automatically perform a large number of reliability analyses on data sets created using Monte Carlo simulation, is used to demonstrate the concepts. See
  • A High Value of Beta is Not Necessarily a Cause for Concern - Although often viewed with fear and loathing by reliability engineers, this article demonstrates that a high value of the shape parameter for the Weibull distribution (beta) is not necessarily a cause for concern if the value of the scale parameter (eta) is high enough to meet the reliability specification. See
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.
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