Non-Invasive Acoustic Emission Testing of Compressed Trabecular Bone and Porous Ceramics using Seismic Analysis Techniques
Hollis, Gaylon C.
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Acoustic emission(AE) is one of the most sensitive techniques to non invasively monitor deformation, fatigue, and fracture of many materials. The purpose of this study was to evaluate the potential to use AE to detect local failure events within porous ceramic materials. The primary material of interest was mineralized trabecular bone. A better understanding of the failure of trabecular bone is highly relevant to skeletal fragility diseases such as osteoporosis. This study sought to develop a post processing technique that could strengthen the relation between the events detected and the phenomena occurring as a specimen is loaded. The deficiency in other techniques is that they did not fully make a quantitative correlation between acoustic emission event characteristics and the physical occurrence of damage events. The study evaluated the use of seismic power laws because these laws were able to attach a quantitative model to an earthquake and its successive aftershocks. Earthquake transmission has similar propagation attributes when compared to acoustic emission; seismic waves radiate from the epicenter of an earthquake. Acoustic waves radiate from the source of energy release in an acoustic emission event. The study measured the acoustic emission response of trabecular bone and highly oriented ceramics. The bone and ceramics were extracted in two perpendicular directions so that the structural orientation was different. The study sought to evaluate if the power-laws could differentiate the acoustic emission response based on varying the material and varying the structural orientation. The samples were quasi-statically compressed; the mechanical and acoustic emission data were simultaneously recorded. The study found that using the seismic power-law did not statistically differentiate the directional orientation for trabecular bone or ceramic specimens. Acoustic emission did indicate that event detection was different for each type of the of material. Correlations were established with the acoustic emission response and the mechanical testing data. These relationships were explainable because of the mechanical properties of the material.