Reliability HotWire: eMagazine for the Reliability Professional
Reliability HotWire

Issue 12, February 2002

Tool Tips

How can I get analytical values such as failure rates for the system analysis in BlockSim?

In addition to standard simulation results, the BlockSim software can also provide analytical metrics based on the analysis of the system RBD. One of the ways that BlockSim provides these values is through the Quick Calculation Pad (QCP), which returns single values for common reliability metrics such as reliability, failure rate, mean time, etc.

BlockSim QCP with Reliability Results.

Another way to provide more extensive analytical results is through the Function Wizard. In order to use the Function Wizard, however, there must be a spreadsheet in the project. In order to insert a spreadsheet, select Add New File then Add New Spreadsheet from the File menu or the Project Explorer shortcut menu (accessible by right-clicking inside the Project Explorer window). With the spreadsheet open, select the cell where you want the information to go and select Function Wizard from the Tools menu, click the icon or press F8. This will activate the Function Wizard window, which allows you to put a variety of reliability metrics, tables and statistical values directly into the spreadsheet.

BlockSim's Function Wizard 

How can I calculate Weibull MLE parameter estimates for data sets with very small variance in Weibull++?

In data sets that have small variances (i.e. the data values are very closely grouped), the value for beta - the Weibull slope - tends to be very large. By default, the Weibull++ software will produce an error message for data sets that have a beta value greater than 20 when using the MLE analysis method. However, this can be bypassed by increasing the numerical precision of the calculations. In order to do this, select User Setup from the File menu. Go to the Calculations tab and select the Use Higher Numerical Precision on Calculations option. This will allow Weibull++ to return MLE Weibull parameter estimates for data sets with closely grouped values.

Calculations page of the Weibull++ 6 User Setup window

 

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