Reliability HotWire

Reliability HotWire

Issue 129, November 2011

Tool Tips

*Are there any basic tips for using the Function Wizard to build custom analyses and reports?

Many of ReliaSoft’s standard software tools offer the ability to use built-in spreadsheets for custom analysis and reporting. When you use the Function Wizard to build functions in these spreadsheet reports, here are a few basic tips to keep in mind. (Note: Although the pictures shown are from Weibull++, similar functionality is available in ALTA and RGA.)

  • If your regional settings use a comma as the decimal separator, the software will use a semicolon to separate function arguments. For example:
    • =RELIABILITY(Default;250;;0,95)
      returns the 95% 1-sided confidence bound on the reliability at 250, based on the default data sheet.
  • If you want the function results to vary depending on what has been entered into another cell in the spreadsheet, you can enter a spreadsheet cell reference as the function input. For example:

    Function Wizard: Spreadsheet cell reference as function input

    Note that you can click the icon at the right side of the input box to automatically enter the reference for the cell that is currently selected in the spreadsheet. If you press CTRL when you click the icon, the reference will be absolute (e.g., $B$1).
  • Although spreadsheet cells are referenced by a letter for the column and a number for the row, if the function requires you to specify a cell in the data source, you must use numbers to identify both the row and the column, and these coordinates are entered as separate inputs. For example:
    • =DATAENTRY(Default,2,1)
      returns the value that was entered into row 2 of column 1 (a.k.a. cell “A2”) in the standard folio that is the data source for this function.
  • If the required input is text, it must be enclosed in quotation marks. This includes the name of a specific data sheet when the function is not using the default data source. It also includes dates/times when they’re entered in a text format rather than a serial number. For the data source, the software will apply the quotes when you insert the function into the spreadsheet. For other inputs, you must include the quotation marks in the text that you type into the Function Wizard input field. For example:

Select Derating Standard window

*How can I apply a derating standard to one of my reliability prediction analyses in Lambda Predict?

In Lambda Predict 3 predictions you can select a derating standard at the System level that applies to all components and blocks within that system. To select a derating standard, click the system in the System Hierarchy panel and then choose Tools > Apply Derating Standard.

Select Derating Standard window

In the Available Standards field, select any published or user-defined derating standard, and then click OK.

In the System Hierarchy panel, the status of each component in the system with regards to derating is indicated by the component’s icon:

  • A green icon indicates that the component meets the derating requirements defined in the standard (i.e., the stress level and temperature fall within the nominal case curve).
  • A light blue icon indicates that the component does not meet the derating requirements, but it is not overstressed (i.e., the stress level and temperature fall outside the nominal case curve, but within the worst case curve).
  • A red icon indicates that the component is overstressed according to the derating standard (i.e., the stress level and temperature fall outside the worst case curve).
  • A dark blue icon indicates that the component is not included in the derating standard and therefore derating has not been applied to the component.

To view detailed derating information for a component, select it and choose Tools > View Component Derating Information.

Component Derating window

All of the information on the Derating tab applies to the stress that is selected in the Stress field.

The values used to create the nominal case curve and the worst case curve are displayed on the left. The plot area on the right translates these points into the derating curves. By default, the nominal case curve is displayed in green and the worst case curve is displayed in red. The blue dot on the plot shows where the component stands with respect to the requirements of the derating standard. You can point to elements in the plot to view their description and, in the case of points, their coordinates.