ALTA Life-Stress Folios Settings

The ALTA Life-Stress Folios page of Weibull++'s Application Setup contains default settings that will be applied when you create a new life-stress folio. Note that some of the configurable settings that are saved with the folio can still be modified from the control panel and others can now be modified via the Item Properties window.

• Data Sheet Options for ALTA
  • Show likelihood value (LK) displays the likelihood function value in the Analysis Summary area of the control panel. The LK value may be used to compare how well different models fit the same data set.
  • Show activation energy applies only to temperature-related models such as Arrhenius, Eyring, generalized Eyring, temperature-humidity, and temperature-nonthermal. It displays the activation energy (Ea) in the Analysis Summary area of the control panel. A large activation energy means temperature has a large effect on the life of the product. Click the Units drop-down list to specify which unit to use (Kelvin or Rankine).
  • Indicate stress columns used highlights the borders of the selected stress columns in the data sheet. Click the Color drop-down list to select the border color.
• Grouped Data Settings affect how individual median rank values are assigned to each data point (observation) within each group. Select the check box to plot all of the data points in each group on the MLE probability plot. If not selected, only the points with the highest median rank value within each group will be plotted. The line is independent of whether data points are treated as grouped or ungrouped.
• Other Options. Select the check box to allow the Use Stress Level window to remain open, while you have access to all life-stress folios. If not selected, you must close the Use Stress Level window to return to the folios.
• Default Life Distribution sets the default life distribution for life-stress folios. Note that if lognormal is selected as the default and you select a model for which the lognormal distribution is not available (i.e., Proportional Hazards or Cumulative Damage in Accelerated Life Testing PRO), the life distribution will automatically reset to Weibull.
• Cumulative Damage Model (ALTA PRO). These options apply to the cumulative damage life-stress model in Accelerated Life Testing PRO.
  • Time-dependent stress profiles specifies the time at which the stress will be applied to a time-to-failure data point that occurs at the both the End time of one segment and the Start time of another segment. Select Implement stress at end of step to apply the stress from the later segment, or Implement stress at beginning of step to apply the stress from the earlier segment.
    
    For example, suppose that the selected stress profile applies a stress of 300K to failure times between 0 and 100 hours and a stress of 350K to failure times between 100 and 200 hours. If the observed failure time is 100 hours, you must determine whether to apply the 300K or 350K stress to that data point.
  • Allow large Beta values displays beta values up to 250. If not selected, the default maximum beta value is 100.