Acceleration Factor Plots

The acceleration factor is a unitless number that relates a product's life at an accelerated stress level to the life at the use stress level. It is defined by:

(1)

where:

Lu is the life at use stress level.

LA is the life at the accelerated level.

As it can be seen in Eqn. (1), the acceleration factor depends on the life-stress relationship (i.e. Arrhenius, Eyring, etc.) and is thus a function of stress.

The acceleration factor vs. stress plot is generated using Eqn. (1) at a constant use stress level and at a varying accelerated stress. In Figure 9, the acceleration factor vs. stress was plotted for a constant use level of 300K. Since LA = Lu, the value of the acceleration factor at 300K is equal to 1. The acceleration factor for a temperature of 450K is approximately 8. This means that the life at the use level of 300K is eight times higher than the life at 450K.

Fig. 9: Acceleration Factor vs. Stress Plot