Physical acceleration means that operating a unit at some higher stress level(s) (i.e, higher temperature, voltage, humidity or duty cycle, etc…) should produce similar failures as would occur at typical-use stresses, except that they are expected to occur much sooner.
Failures may be due to mechanical fatigue, corrosion, chemical reaction, diffusion, migration, etc. These are the same cause of failures under normal stress condition; the only difference is the time scale (the time to failure).
When there is true acceleration, changing stress is equivalent to transforming the time scale used to record when failures occur. The transformations commonly used are linear, which means that time-to-fail at high stress just has to be multiplied by a constant (the Acceleration Factor or AF) to obtain the equivalent time-to-fail at use stress.
For many engineers, this is where they encounter the biggest challenges: what is the preferred model? How do I fit the model to the condition, materiel and physical attributes of the UUT?
Too many knowledgeable users employ the Arrhenuis equation, but this is not always the preferred method, and care must be taken to apply the proper model.
What are the experiences with other models?
What are the success stories?