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	Weibull++/ALTA Diagrams

Equation Viewer

In Weibull++/ALTA diagrams, the Equation Viewer shows the algebraic equation for the system reliability, pdf and failure rate as a function of the block reliabilities.

To open the Equation Viewer, click the Show Algebraic Solution (...) icon on the control panel.

There are two ways to view the system reliability equation: as a symbolic equation or as the complete equation. With either view, you can:

Select Show Legend to display the failure distribution for each block in the diagram.
Select Show Colors to use color-coding in the window to make the equations easier to view.

If you have made changes to these settings, click Refresh to update the contents of the window.

You can click Add Equation to Attachments to save the equation to the project attachments as an embedded *.rtf file.

Symbolic Equation View

The symbolic equation view uses tokens to represent portions of the equation. You can read the solution from the bottom up, replacing any occurrences of a particular token with its definition. For example, consider the RBD shown next.

When this diagram is analyzed, the symbolic reliability equation is:

This would be read as follows:

	(1)
	(2)
	(3)

We begin with Eqn. (3). This equation contains the token D₁, which is defined in Eqn. (2). This is then substituted into Eqn. (3), yielding:

(4)

Now Eqn. (4) contains the token I_D, which is defined in Eqn. (1). Substituting this into Eqn. (4) yields:

(5)

Complete Equation View

When you use the complete equation view, the software automatically performs all token substitutions. You should be aware that in some cases, the software may not be able to render the complete equation in the Equation Viewer even though it has internally computed it. This could happen if the memory available on your computer is insufficient and is therefore unable to construct the equation algebraically. This usually does not happen unless there are over one million terms.

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