Based on a review of the literature, a numerical model of the chip formation process in laminated rock formations has been developed. The model uses a finite element approach to simulate the anisotropic behavior of laminated rock formations. The finite element program has been developed with the assumption of two-dimensional plane strain. Anisotropic elements and dynamic loading are used to represent the actual penetration process of a bit tooth. An iteration method, using an incremental approach, has been applied for the continuous tooth penetration process. Displacements and axial loads have been modified after each iteration. The program provides quantitative information on stresses and displacements during the penetration process. Furthermore, bit deviations in laminated formations can be inferred.. Different rock strength characteristics have been employed on each side of the bit Bit tooth-rock interaction for various formation dips (from ()O to 9(0) of the Berea sandstone have been simulated and compared with experimental results. / Master of Science

This thesis presents a detailed analysis of the plane rake faced drill design, its grinding method and grinding wheel geometry. A fundamental geometrical analysis has then been carried out on the major cutting edges of the modified drills according to the national and international standards. It has been shown that this new drill design results in a significant increase in the normal rake angle at lips as well as point relieving at the chisel edge region. Geometrical models for the various drill point features have been established which uniquely define the drill point features of the modified drill design. A comprehensive experimental investigation has been carried out to study the drilling performance of the modified drills, when drilling a high tensile steel, ASSAB 4340, with TiN coated high speed steel drills over a wide range of drilling conditions. Comparing to the drilling performance with conventional twist drills under the corresponding conditions, it has been found that the modified drills can reduce the thrust force by as much as 46.9% with the average of 23.8%; the reduction of drilling torque is also significant at an average of 13.2% and the maximum of 24.9%. Similarly, the new drill design shows great superiorities over the conventional drills in terms of drill-life. In the drill-life tests, a few conventional drills were broken, but all plane rake faced drills performed very well. In order to estimate the cutting performance in process planning on a mathematical and quantitative basis when drilling with the modified drills, predictive cutting force models have been developed based on the unified-generalized mechanics of cutting approach. The models have been assessed qualitatively and quantitatively and showed good agreements with the experimental thrust, torque and power. Empirical-type force equations have also been developed to provide simple alternatives for practical applications.

This thesis presents a detailed analysis of the plane rake faced drill design, its grinding method and grinding wheel geometry. A fundamental geometrical analysis has then been carried out on the major cutting edges of the modified drills according to the national and international standards. It has been shown that this new drill design results in a significant increase in the normal rake angle at lips as well as point relieving at the chisel edge region. Geometrical models for the various drill point features have been established which uniquely define the drill point features of the modified drill design. A comprehensive experimental investigation has been carried out to study the drilling performance of the modified drills, when drilling a high tensile steel, ASSAB 4340, with TiN coated high speed steel drills over a wide range of drilling conditions. Comparing to the drilling performance with conventional twist drills under the corresponding conditions, it has been found that the modified drills can reduce the thrust force by as much as 46.9% with the average of 23.8%; the reduction of drilling torque is also significant at an average of 13.2% and the maximum of 24.9%. Similarly, the new drill design shows great superiorities over the conventional drills in terms of drill-life. In the drill-life tests, a few conventional drills were broken, but all plane rake faced drills performed very well. In order to estimate the cutting performance in process planning on a mathematical and quantitative basis when drilling with the modified drills, predictive cutting force models have been developed based on the unified-generalized mechanics of cutting approach. The models have been assessed qualitatively and quantitatively and showed good agreements with the experimental thrust, torque and power. Empirical-type force equations have also been developed to provide simple alternatives for practical applications.

The problem of this study was to determine the effect of short-duration high-speed drill on speed, accuracy and production rate development in the first year of typewriting.

Hearing test results of 23 dentists obtained before and after working hours are compared to determine if dentists experience any temporary hearing loss. The aim of the project is to determine whether dental drills cause hearing loss and to document the consequences of the loss. Hearing evaluations include pure-tone audiometry, middle-ear testing, and measurements of otoacoustic emissions. The results are expected to convince dentists of the danger of noise exposure and the need for hearing protection

The effects of fluency training on performance, maintenance, and generalization of parent training skills were examined within the context of a classroom and home setting. Three foster parents attended a 24-hour Parenting Tools for Positive Behavior Change (PBC) course. Participants completed timed fluency drills using flash cards to increase learning and performance of PBC tools. A non-concurrent multiple baseline design across participants was used to assess participant performance on flash card drills and PBC tools during in-class, pre-test, and post-test role plays, and in novel situations with children in the home before, during and after the course. Results showed that fluency training had little or no effect on increasing tool performance across all testing phases for all participants, nor were there any changes in frequency and accuracy of fluency trained tools in the home to indicate maintenance and generalization of treatment effects.

During the drilling process, sharp edges of material called burrs are produced and protrude from the original surface. When a through-hole is drilled, burrs form on both the entry and exit surfaces around the hole, requiring expensive deburring operations to be performed in order to meet part specifications. A common hole producing operation in aircraft assembly is drilling holes through multiple sheet metal layers in order to fasten them together. However, at the interface between two layers, burrs form on both the exit of the first layer (termed "skin") and entry of the second layer (termed "frame"). Consequently, the layers frequently need to be taken apart, deburred, and put back together again before being fastened, resulting in additional costs and increased assembly time. The goal of this thesis was to understand the role of key factors such as drill geometry, drill wear and clamping conditions on burr formation at the interface of two thin sheets of 2024-T3 aluminum so that interlayer burr formation could be minimized. This problem was approached from three different angles. First, an experimental study was performed to find the drill geometry parameters for minimization of interlayer burrs and to ascertain the relationship between the average burr size and drill wear. Next, a new kind of clamping system for holding sheet metal layers together during drilling was designed, prototyped, and tested for its effectiveness. Finally, a preliminary analytical model of interlayer burr formation was created in order to better understand the burr formation process in stacked layers of sheet metal and to better understand the effect that each drilling parameter has on the resulting burr size.

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No description available.

No description available.