| Summary: | 碩士 === 國立臺北科技大學 === 土木與防災研究所 === 95 === Nowadays, extensive uses of full-faced mechanical boring method in recent years. But the relationship between mechanical indenter and rocks in cutting process is still not clear, so, this study set up normal wedge indentation fracture test combines with electronic speckle pattern interferometry (ESPI) and acoustic emission (AE) for nondestructive test to monitor the contact fracture characteristics of rock material, in order to get some data for in situ.
To control the post-peak stability to obtain a complete loading curve, and to investigate nondestructive techniques data, the crack opening displacement (COD) is used to be a close-loop control unconfinement case. This study can divide three parts: (a) By varying wedge angle of cutter and grain size of rock-like materials, experimental observation of intrinsic flaw length was made. Furthermore, the intrinsic flaw length of fractured material was monitored by optical interferometry and then compared with the analytical solution based upon the opening mode of linear elastic fracture model (LEFM). We found that the blunter wedge angle of indenter, the larger the maximum indentation force. In addition, the indentation pressure and the critical indentation depth would decrease as increasing wedge angle. Because, intrinsic flaw length is treated as a material property in fracture mechanics. (b) Follow previous paper about single indenter, in order to understand double indenters behavior, we do double indenters and analysis the relation between micro and macro crack behavior. Testing results indicate the distance of indenters decreases with direction of crack initiation deviate from original vertica line, deviate angle increases with the distance of indenters decreases. So, proper indenter distance contribute to machinery excavate has help about the improvement of cutting efficiency. (c) Synchronize electronic speckle pattern interferometry and acoustic emission to investigate fracture characteristics of indentation test, first, monitor the radius of elasto-plastic interfacial to prove coupled nondestructive techniques is fine to work in displace-continuity, second, monitor the process zone about fitting and proper in displace-discontinuity.
We get rather unanimous trend in experiment achievement compared with corresponding theory.
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