Statistics for Maintenance Modelling: Proportional Hazards and Accelerated Life Models

# Accelerated Life Model¤

The accelerated life model is another important class of regression models. Suppose we observe failure times for a system subject to a range of loads. One model that is easy to understand is that the failure time of the unit is the product of some function of the load. This is known as an accelerated life model because of the interpretation that increasing the load has the effect of accelerating the rate of failure by a deterministic constant.

More formally, the accelerated life model holds when the survival function S(t; y) = P(T t|y) is of the form:

S(t; y) = S0{t • g(y))}

where S0 is the baseline survival (reliability) function and g(y) is a positive function of y. The interpretation is that the life time is scaled down or up by a factor g(y).