Reliability HotWire: eMagazine for the Reliability Professional
Reliability HotWire

Issue 13, March 2002

Tool Tips

*How can I install Weibull++ Version 5.0 on my new PC that is running Windows 2000?

Weibull++ Version 5.0 was created before the release of Windows 2000. Consequently, if you attempt to re-install the product from the original CD-ROM (purchased before February 2000) on a Windows 2000 computer, you may encounter an error during the installation. To resolve this issue, you must install a Windows 2000 compatible release of the software. Contact ReliaSoft for information on how to download the required installation. A valid Weibull++ Version 5.0 license will be required to download and install the software. 

Note that a new version of the Weibull++ software, Weibull++ 6, is now available and the Weibull++ 5.0 software is no longer being updated. 

*What are the data requirements to perform an analysis in ALTA?

Certain minimum data requirements are needed to perform an accelerated life data analysis in ALTA. For example, it is impossible to perform a constant stress test at just one accelerated stress level and extrapolate back to a use stress; at least two accelerated stress levels are required to make the extrapolation. 

The requirements become more complex when dealing with more than one stress. When dealing with two or more stresses, a certain amount of "overlap" is required in the stresses. For example, consider a test with two different stresses. Stress 1 has two levels, A and B, and Stress 2 also has two levels, X and Y. Testing at low stress levels would have Stress 1 set at A and Stress 2 set at X. Testing at the high levels would have Stress 1 set at B and Stress 2 set at Y. However, in order for the effect of each stress to be calculated, there must be at least one data point where Stress 1 is set to A and Stress 2 is set to Y, or where Stress 1 is set to B and Stress 2 is set to X.

Note, however, that these requirements do not apply to the cumulative damage model, which is available only in ALTA PRO. The cumulative damage model uses stress profiles, which are time-dependent stress models. The cumulative damage model is capable of performing analyses based on only one stress profile.


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