ABSTRACT
There are four factors that govern the permissible degree of acceleration: the sample size, the environment, the testing time, and the anticipated failure mode. Most accelerated tests involve an increase in intensity of a particular environmental stress, such as an increase in temperature or humidity. Samples of the test material are subjected to overstressing for relatively long periods of time. Plastic gears and gear trains have become the norm in light duty applications. Facsimile transmission machines, printers, enclosures for monitors, and the cases of personal computers are largely plastic. Because plastic has become such an important part of many products, the designer who intends to incorporate plastic parts into a product needs to know something about the way in which plastic ages. The aging of plastics is carried out by placing a sufficient number of specimens in each of a number of ovens operating continuously at different fixed temperatures.
