Abstract
M.Tech.
This dissertation details the research performed into the development of a smart material for roofbolt application in the mining industry. It describes the methodology and research done to design a smartbolt using a metastable austenitic stainless steel. A number of measuring devices were used to study the properties and structure of this smartbolt alloy. These devices include a Ferritescope and a Krautkramer USM 25 DAC ultrasonic sound velocity measuring instruments. The dissertation details the development, processing, laboratory and field testing of the smartbolt alloy. The designed alloy was found to have much stronger workhardening effect, causing it to have a relatively low ductility. Therefore, the threads on the roofbolts produced from this alloy were machined instead of thread rolled. It was also found that the incubation strain of the smartbolt alloy to be <5% and that the microstructural transformation rate is high, thus enabling effective monitoring.
Magnetic and ultrasonic techniques were used to monitor the progress of the y->a' transformation in the smartbolt alloy loaded in uniaxial and biaxial tension. It was found that the von Mises effective strain criterion gives a reasonable correlation of transformation kinetics. Using the modelling method, it was found that the failure strains for the rock are not the same as those for the smartbolt alloy. All the smartbolts installed in the haulage tunnel (level 94 of mineshaft) showed a pattern of increasing longitudinal ultrasonic velocity (load) with time. This was due to the fact that mining was taking place above the area (in level 93 of the mineshaft).