Reliability HotWire

Reliability HotWire

Issue 126, August 2011

Tool Tips

*When my ALTA analysis considers more than one stress type, how do I choose which stress will be varied in the Life vs. Stress plot?

When you use a multi-stress model in ALTA (e.g., temperature-humidity or generalized Eyring), you consider more than one stress type in your analysis. However, only one stress can be varied in the following plot types:

  • Life vs. Stress: This plot shows the life characteristic of the selected life distribution (e.g., if Weibull is selected, the scale parameter eta) as a function of stress.

  • Standard Deviation vs. Stress (i.e., Std vs Stress): This plot shows the standard deviation of the life characteristic of the selected life distribution as a function of stress.

  • Acceleration Factor vs. Stress (i.e., AF vs Stress): This plot shows the acceleration factor as a function of stress. The acceleration factor is the factor by which life is shortened at a given stress level.

The stresses that are not varied are held constant at the specified use stress level for the purposes of generating the plot. To determine which stress is varied in these plots, or to change the displayed stress, click Set Use Stress in the control panel. The stress with the Vary option selected is the stress that is displayed in the plot.


*I’m new to reliability analysis. How can I get information on the basic concepts and what ReliaSoft’s software is for?

You will find many useful – and free! -- resources about reliability engineering and related fields on ReliaSoft’s website. For new practitioners, there are quick subject guides available on the following topics:

Also available are online textbooks, reliability software and tools, lists of recommended reading (both websites and books), discussion forums and numerous reference publications.