Electromagnetic Gage Techniques for Dynamic Tensile Fracture

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YOUNG Excavation of hard rock is controlled by dynamic tensile fracture which is a process that is poorly understood. Available data on the dynamic tensile strength of brittle materials such as rocks and ceramics is extremely limited, and the data available is open to question because it is obtained by surface measurements where surface flws may have an influence on the fracture properties. This research program involves the measurement of dynamic tensile strength with an embedded gage placed in the interior of the test specimen. Specifically, the research program entails the development of an electromagnetic gage of small dimension which will sense particle velocities which can be related to the imposed dynamic stresses. Gage placment techniques in the specimen will be an important part of the project. The data will be recorded digitally and processed automaticallly to give velocity, displacement and stress as a function of time during the dynamic fracture process. The method will be demonstrated and dynamic tensile strength and/or toughness will be determined for several brittle rocks, plastics, composites and ceramics. Sunburst Recovery is a small company with an excellent laboratory for conducting this experimental program. The principal investigator has an excellent background in rock mechanics and has shown the feasibility of using electromagnetic transducers in measuring properties of geo- materials. An award is recommended.