Reliability HotWire

Issue 76, June 2007

Tool Tips

* What are the options for associating degradation analyses and/or non-parametric life data analyses with the standard analysis folios in Weibull++ 7 and ALTA 7?
Both Weibull++ 7 and ALTA 7 offer the ability to create associations within a particular project file between Standard Folios, where the typical life data analysis or accelerated life data analysis is performed, and Specialized Folios, where related analyses such as degradation analysis are performed. From a Standard Folio Data Sheet, to associate a Specialized Folio or remove an association, select Associate Specialized Folio from the Data menu or click the Associate Specialized Folio icon.

A window listing the available Specialized Folios in the project will appear (in Weibull++, Degradation Analysis Folios and Non-Parametric LDA Folios; in ALTA, Degradation Analysis Folios). You can select one Folio and click OK to associate it with the current Data Sheet. If a Specialized Folio is already associated with the data sheet, you can select it and click Remove to remove the association.

Note that associations can be created/removed from within Specialized Folios as well, using the Transfer Life Data to and Remove Folio Association icons.

There are two levels of association. By default, associated Folios have the Auto Transfer Link option enabled. At this level, the Data Sheet in the Standard Folio is locked so that data must be entered via the associated Specialized Folio, not the Data Sheet. Whenever the Specialized Folio is calculated, the results are transferred to the Data Sheet automatically. If desired, you can turn off the Auto Transfer Link option by de-selecting Auto Transfer Link in the Data menu or by de-selecting the Auto Transfer Link icon. At this level of association, you can enter data in the Data Sheet. Calculating the Specialized Folio will not automatically transfer results to the Data Sheet, but if you select Transfer Life Data to Selected Folio(s) from the Data menu or click its icon on the Control Panel, the Data Sheet that the Specialized Folio is associated with is automatically selected. You can select additional Data Sheets or a different Data Sheet, if desired.

* How does degradation analysis in ALTA 7 differ from that in ALTA 6?
In ALTA 7, degradation analysis is no longer performed using a separate utility. Instead, ALTA 7 uses the Degradation Analysis Folio, which works in much the same way as the Standard Folio. This means that degradation analysis can be performed without an associated standard accelerated life testing data analysis, if desired.

You will see that the Data Sheet used in the Degradation Analysis Folio is very similar to the one used in ALTA 6.

[Click to Enlarge]

Note that all command icons are now located in the Control Panel on the right side of the window. In version 7, the Degradation Model Wizard is available to help you select the degradation model that best fits your data set. Simply click the Degradation Model Wizard icon and in the window that appears, select the models to be considered and click Analyze. The models are ranked based on the Mean Square Error (MSE) between the observations and the fitted model.

Once you have selected a model, clicking Calculate calculates the model parameters and extrapolates failure/suspension times for each unit based on the settings you specify in the Control Panel. These results are no longer added as new pages; instead, they can be viewed in ALTA's Results Panel by clicking the Show Fit Parameters and Show Extrapolated Values buttons, respectively.

Once the parameters and extrapolated failure/suspension times have been calculated, you now have the option to transfer the extrapolated life data to an existing or new Standard Folio. Using either command creates an association between the Degradation Analysis Folio and the Standard Folio. You can create as many of these associations as you wish. There are two levels of association: with or without the Auto Transfer Link option enabled. To remove one or more of the associations, you can click the Remove Folio Association button. You will see a window displaying all Standard Folios currently associated with the Degradation Analysis Folio. You can clear the checkbox beside the Folio/Data Sheet name to remove the association.

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