In this issue: Issue 110, April 2010
 Hot Topics Reliability Basics Tool Tips Latest Software Updates Hot News Contribute to HotWire

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Hot Topics
Another Look at the Shape Parameter of the Weibull Distribution (Beta)
It is well known that the shape parameter of the Weibull distribution, beta, represents the failure rate behavior. If beta is less than 1, then the failure rate decreases with time; if beta is greater than 1, then the failure rate increases with time. When beta is equal to 1, the failure rate is constant. Assume that we have two failure data sets. From one data set, the estimated beta is 5; from another data set, the estimated beta is 3. Both have increasing failure rates. If the two data sets were combined together, would the estimated beta for the overall data set be a value between 3 and 5, or would it be a value outside of this range? Could it be less than 1, which would imply that the combined data set has a failure rate that is decreasing with time? In this article, we will use examples to show the relationship between these betas.

Reliability Basics
Degradation analysis involves the measurement and extrapolation of degradation or performance data that can be directly related to the failures of a product. Many failure mechanisms can be directly linked to the degradation of the parts of a product, and degradation analysis allows the user to extrapolate to an expected failure time based on the measurements of degradation or performance over time. When accelerated testing techniques are used to reduce testing time, the analysis of the degradation measurements obtained at the accelerated stress levels can be extrapolated to normal use conditions. In this article, we will give an example that uses the accelerated degradation analysis tool in ALTA 7.

Tool Tips
• How can I use ALTA to make warranty predictions based on data from a quantitative accelerated life test?
• How can I quickly apply the same changes to the subordinate items of a block in Lambda Predict 3?

New service releases are now available for RGA (SR 7.0.3), BlockSim (SR 7.0.11) and Lambda Predict (SR 3.0.4). To determine the compile revision of the application on your computer, select About from the Help menu. More Software Downloads...
 Application Date Created Version RGA RGA 7 3/2/10 7.0.3 BlockSim BlockSim 7 3/10/10 7.0.11 Lambda Predict Lambda Predict 3 3/30/10 3.0.4
Hot News

Advance Registration Deadline - The 2010 ARS North America will be held at the Grand Sierra Resort in Reno, Nevada from June 15 - 17, 2010 and the Early Registration Deadline is April 23, 2010. Visit http://www.ARSymposium.org/register.htm and register now in order to save \$200. Detailed information about ARS, including the program matrix and venue, are available online at http://www.ARSymposium.org.

ASQ CRE Exam - Once again, the ARS Committee has partnered with ASQ to bring the Certified Reliability Engineer Exam to the 2010 ARS North America conference in Reno, Nevada, in June. The exam will be offered on June 14, 2010 and the application deadline for the CRE exam is April 30, 2010. Please register with ASQ at their website.