A three-dimensional acoustic emission based microcrack source localization method and its biomechanical application.

摘要

In this dissertation, a 3D Acoustic emission (AE) based microcrack source localization method for the detection of the microcracks in complex structures was presented. The major component of the method was the development of a variable velocity model algorithm. This algorithm had the advantage of smaller computational residuals, faster convergence, and relatively reliable results over current widely used constant velocity model algorithm. In this work, the variable velocity model algorithm was validated through theoretical and experimental approaches. To illustrate the proposed technique, a biomechanical application was presented using cemented total hip arthroplasty (THA) models. This application investigated the influence of the stem surface texture on microcrack activities.; In the variable velocity model algorithm, the velocity model was achieved in two steps. The first step was assigning each sensor an initial signal velocity based on its coordinates relative to an estimated microcrack. The second step was adjusting the initial velocity based on the computational residual.; The theoretical validation of the variable velocity model algorithm showed that the variable velocity model can achieve an event residual RES that is smaller than the constant velocity model. The variable velocity model algorithm was also validated through a series of pencil lead break tests and fatigue tests performed on a cemented THA specimen. The results indicated that the variable velocity model algorithm locates the fatigue microcracks more accurately than the constant velocity model algorithm.; In the biomechanical application of the 3D AE based microcrack source localization method, the AE results demonstrated that stem surface roughness is an important parameter to determine the fatigue performances of the cemented THA specimens.; The main contribution of this dissertation was the development of the 3D AE based microcrack source localization method. Compared to current widely used constant velocity model algorithm, the variable velocity model algorithm was capable of improving the microcrack localization accuracy when the specimen is a complex structure. This method showed the potential for broader applications that are difficult to study using current AE techniques.