Reliability HotWire: eMagazine for the Reliability Professional
Reliability HotWire

Issue 20, October 2002

Tool Tips


*What are the differences between ALTA 6 Standard and ALTA 6 PRO?

A full features comparison between the two versions of ALTA 6 can be found at However, the main difference between the two versions is in the available life-stress relationships. ALTA 6 Standard includes life-stress relationships that allow you to conduct analysis with up to two stresses. ALTA 6 PRO includes all of the models in ALTA 6 Standard, as well as two life-stress relationships with the ability to analyze data with up to eight stresses. In addition, ALTA 6 PRO can analyze data with a time-varying stress profiles (e.g. step stress) using the Cumulative Damage model.

Examples using ALTA 6 Standard and ALTA 6 PRO can be found at

*Where can I find resources on life data analysis, accelerated life testing analysis and system reliability analysis?

The Web site provides resources for the professional in reliability engineering and related fields. Among these are the available eTextbooks; Life Data Analysis Reference, Accelerated Life Testing Reference and System Reliability Reference. Whether you are simply looking for a quick reference guide or for detailed information, these reference guides will get you going in the right direction. And if that still is not enough, our list of recommended books cover a variety of reliability topics. contains an extensive set of resources. Free reliability resources include online textbooks, reliability software and tools, discussion forums and numerous reference publications for life data analysis (Weibull) analysis and related fields.

*How do I specify which time-varying profile(s) to use in calculations when implementing the Cumulative Damage model in ALTA 6 PRO?

Once you have defined your profiles using the Stress Profile Explorer and have associated the appropriate library with the Folio, there are a couple of ways to assign a profile to a specific analysis. The first method, and most obvious, is to simply type in the name of the profile in the stress column for each data point. In this case, be sure that you enter the name of the profile correctly. The profile name is case sensitive. If you have entered the name incorrectly, or if the profile does not exist in the active Stress Profile Library, then a message will appear indicating that the entered profile name does not exist or that you have entered it incorrectly. 

The second method, discussed next, alleviates the problem of having to remember the name of each profile. First be sure that Cumulative Damage has been selected as the life-stress relationship. Next, select a cell within the stress column for which you would like to specify a profile. Right-click within the stress column and a list of the available profiles within the associated stress library will be displayed. Sample data and a list of available profiles is shown in Figure 1.

Display of available profiles within associated stress library

Figure 1: Display of available profiles within associated stress library

So now all you have to do is to select the profile you would like to enter. Once you have the one you want, double-click it or select the name and click Add. The name of the profile will be added to the spreadsheet, as shown in Figure 2.

Selected profile has been entered into spreadsheet

Figure 2: Selected profile has been entered into the spreadsheet



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