8.
Assessing Product Reliability
8.1. Introduction 8.1.7. What are some basic repair rate models used for repairable systems?


The Exponential Law is another flexible NHPP model 
An NHPP
with ROCOF or intensity function given by
$$ m(t) = \mbox{exp} \left(\alpha + \beta t \right) \,\, , $$
is said to follow an Exponential Law. This is also called the
loglinear model or the CoxLewis model.
A system whose repair rate follows this flexible model is improving if \(\beta\) < 0 and deteriorating if \(\beta\) > 0. When \(\beta\) = 0, the Exponential Law reduces to the HPP constant repair rate model 