Research On AE Sensor Made By Orthotropic Piezoelectric Composite Materials

Acoustic emission (AE) is stress wave produced when the materials are distorted, or under the outside load. It can provide important information for structural health monitoring. AE test process includes: stress wave emitted from the source and sensed by the transducers, and then converted into electricity signals, from which we could locate the damage and estimate its type. Since the frequency range of AE signals is wide from hypo- audio frequency up to 50MHz, the AE sensors must have the characteristics of wide frequency band and high sensitiveness.PZT sensor has the characteristics of high sensitive, wide band, high measure precision, and stabilization when used to sense stress wave, so it has been widely used in structural damage test.OPCM (Orthotropic Piezoelectric Composite Materials) not only has good flexibility ,high intensity, large strain, light weight as common Piezoelectric Composite Materials, but also is orthotropic to stress wave and can distinguish stress wave of different components on the same surface . So it is more effective in AE test than PZT. In this paper, OPCM was fabricated for AE test research. The numerical method, FEM is used to design and optimize the configuration, size, characteristics of OPCM, include: (1) Electrode simulation method of PZT, discuss the feasibility and superiority of the method of reading the volt degrees of nodes;(2) simulation of AE sources in the structure with a certain method to evaluate the sensor's characteristics. (3) Analyzing signals outputted from simulation and experiment based on the signal process tools of MATLAB.In order to verifying the simulation results, experiments are designed to test the Orthotropic characteristics of the sensor, and influential factors are studied by comparing the results of experimental and simulations; In addition, the fabrication techniques of OPCM is discussed. A series of theoretic methods based on FEM in the research of AE sensor and the discipline of structure parameters of OPCM influencing the sensor characteristics have been presented. The theoretic method is correct and useful for the future AE sensor design. In the end, also discuss the applications foreground of the sensor.