Papers by Author: Xiao Dong Wang

Abstract: A two-dimensional electroelastic model of embedded piezoelectric actuators was proposed to study the coupled electromechanical behaviour of a thin piezoceramic actuator embedded in an elastic host structure under applied stresses. Interfacial normal and shear stresses for both plane stress and plane strain deformations were calculated to evaluate the actuation effects transferred from the actuator to the host structure. Three dimensional analyses were also conducted using the finite element method to validate the present model by comparing the two results for specific examples. It was observed that the current model provided reasonable prediction of the load transfer by the actuator.

Abstract: The ultrasonic time-of-flight-diffraction (TOFD) detection method has been widely used in crack size assessment. The key issue in TOFD is to determine the arrival time of crack tip diffracted signal. In the traditional cross correlation method, the resulting maximum peak of cross correlation function between two signals indicates the time of flight between them. In practical ultrasonic measurement, the transmission wave may be distorted and phase shift may be introduced. This paper presents a method using cross correlation and phase shift correction to improve the accuracy of crack sizing in the TOFD framework. The resulting maximum peak of the cross correlation function between two signals combining with time delay introduced by phase shift determine the arrival time of diffracted signal. Experimental results are used to demonstrate the advantage of the proposed method.

Abstract: A computational model is proposed to analyze the nanoscale self-assembling phenomenon of monolayers on heterogeneous surfaces. Morse potential is used to describe the pairpotential between molecules or atoms. Minimization of free energy is used to regulate different phases and lattices to form optimized heterogeneous structures of different sizes with periodical patterns. A representative volume element (RVE) is first defined and an optimization algorithm is developed to adjust the positions of particles in it to reduce its potential until global equilibrium is reached. The pair-potential distribution in the monolayer and the substrate layers are studied. It is interesting to observe that the pair-potential distribution in the substrate layers resumes uniformity just a few layers away from the interfacial boundary.