Methodology for implementing accelerated life stress on stepper motors

In the industrial world the need to guarantee a long-life product becomes imperative. Life testing of electromechanical parts under nominal operating conditions may be time- and resource-consuming, making sometimes, such procedures expensive and impractical. As a result, technologies for accelerated life testing have been developed, to design high level stress tests (e.g. temperature, voltage, pressure, corrosive media, load, vibration, etc.). However, not all industries have access to the expensive equipment, such as thermal chambers and shakers, usually used for accelerated life tests. Hence, in this research, a methodology for implementing accelerated test by varying internal system variables is proposed and applied to a stepper motor. The issue of prediction accuracy associated with extrapolating data outside the range of testing, or even to a singularity level (no stress), has not yet been fully addressed. An increasing mechanical and thermal solicitation is evaluated in order to introduce an acceleration factor and to induce motor failure. The aim of this work is to estimate an ageing model to evaluate the life distribution in terms of time and stresses. The methodology is applied to stepper motors as a case study, some relevant experimental results are reported and commented.