Fatigue analysis of U‐shaped flexural electro‐thermal micro‐actuators

Abstract

A simple fatigue experiment procedure is developed for U‐shaped flexural electric‐ thermal micro‐actuators. Long‐term fatigue test data of the actuators is acquired from the experiment. ANSYS™ finite element code is employed herein to establish a 3‐D model for static verification and then for developing the fatigue mathematical models of the actuators. The actuators, with scaled dimensions are studied for size effects on structural fatigue behavior. Furthermore, the effects of input electrical power and operation frequency on lifetime of the actuators are investigated. It is found that the traditionally adopted S‐N curve (NSm =A) is reasonably applicable to the assessment of fatgiue life for the actuator. The derived S‐N models show that the fatigue strength exponent, m, ranging from 2.37 to 4.03, has an average of 3.1. Results also show that fatigue life of the actuator becomes shorter when greater electrical power is input. At fixed operating frequency, decreasing the power from 80mW to 40mW increases the fatigue life (by a factor of ten). On the other hand, actuators of larger size tend to have shorter fatigue life. This could be accounted for by “size effect.” At fixed input voltage of 7V, the fatigue life of the actuator is positively correlated with operating frequency; the data falls in a nearly linear trend.