| Summary: | 博士 === 國立成功大學 === 資源工程學系碩博士班 === 98 === This study presents crack velocity measurement and crack strain gage systems. A series of investigations on crack initiation and propagation were conducted. The results are stated as follows:
(1)With respect to crack measurement technique research and development: A crack detection sensor was used as the sensing material in this study because it is the best choice for monitoring crack propagation velocity.
(2)With respect to crack propagation fractal characteristics: The faster the loading rate is, the higher the average crack velocity. The fractal crack velocity rises with the increase in fractal dimensions.
(3)In terms of subcritical crack propagation observations: The initiation load, subcritical load, subcritical crack propagation length and crack propagation velocity under stable and unstable conditions in the vicinity of the crack tip were measured and defined.
(4)With regard to crack propagation velocity observations in the notched disc edge test: Using the crack velocity measurement system and crack strain gage system, the crack propagation velocity was measured at both sides of A and B in the same specimen. The average crack velocities obtained for both sides were close to each other.
(5)With regard to uniaxial compression tests on the single inclination flaw specimen: Using the relevant fracture criteria, we can learn that wing crack emergence at the crack tip of the PMMA specimen is due to tensile failure. The anti-wing crack at the crack tip of the sandstone specimen is due to shear failure. Crack initiation, propagation, crack propagation velocity and strain energy density are all affected by the crack inclination angle.
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