Analysis Of The Thermal Stress And Fracture Mechanics Of Micro-Optical-Thermal Actuator

Micro-optical-thermal actuator can output the micro/nano-size diaplacement because of thermal expansion effect of material. Many researchers focus on it benefiting by its advantages including easy control, compact structure, heavy force and easy integration. And the problems of defects between layers and it's fatigue life become an important research topic.The defect model always be called crack in fracture mechanics. To study the strength of object or cracks, many researchers focus on the strength rule of crack and crack propagation. In this sense, mechanics of fracture can be called mechanics of crack. Micro-optical-thermal actuator is made up of two different materials. Because of the different physical and mechanical properties, cracks may easy occurs in the interface. So the interface crack model is common. When actuator works, its performance is up to the performance of materials and the defects. So the material parameters and structure sizes can be important influence facors to the performance of cracks, which has been an important research.The main research work and results of this paper can be summarized as following aspects:(1)According to the classical theory of elastic mechanics, the expression of stress intensity factors and T stress are deduced assuming the material is linear elastic, isotropic and homogeneous. The calculation principle of stress intensity factor and T stress in finite element program Abaqus is introduced.(2)Analyse the crack angle and stress intensity factors at crack tip because of T stress based on the maximum circumferential stress criterion and strain energy density factor criterion.(3)Establish three crack model including type I, type II and the interlaminar crack model, and calculate the values of stress intensity factors and T stress at different sizes. To the interlaminar crack among different materials, the effect of elastic modulus ratios is discussed further.(4)Simplify the mode of micro-optical-thermal actuator as double cantilever beams model, and further divided into two kinds of models according to the location of cracks. Analyses the change of parameters including stress intensity factors, T stress and crack angle under a laser pulse. And discuss the effect of different tips of crack, different sizes and different materials to the parameters.