Equation Fit Solver

The Equation Fit Solver is a tool that allows you to estimate the parameters of any user-defined non-linear equation. This gives you the flexibility to perform simple parameter estimation on statistical models other than the life distributions available in Weibull++.

To add an Equation Fit Solver folio to a project, choose Insert > Tools > Equation Fit Solver or right-click the Tools folder in the current project explorer and choose Add Equation Fit Solver on the shortcut menu.

This topic provides an example on how to use the Equation Fit Solver. For a description of the control panel settings, see Equation Fit Solver Control Panel.

Example

Consider a product that has the following mean life for each stress level:

Table 1: Stress vs. Mean Life
Stress Level (Temperature K) Mean Life (Hours)
393 6685.111904
408 5730.096004
423 4775.08002

 

The relationship between the stress level and mean life can be described by the Eyring acceleration model:

where:

In order to estimate the mean life at any given temperature, parameters A and B must be determined. To solve for these parameters, follow the steps outlined below:

For this example, use the following values:

The parameter values are found to be A = -11.1465 and B = 1430.2558, as shown next. By obtaining the parameters, we can now estimate the mean life (y) for any given stress level (x) by using the Calculate Y given X tool. For example, in the figure shown next, the estimated mean life for a temperature of 430 K is 4486.81 hours.

 

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