Thesis (Ph.D.)--Tennessee Technological University, 2007. / Bibliography: leaves 184-187.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: chip breaking chart; insert groove; critical feed rate. Includes bibliographical references (p. 77-86).

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references.

Thesis (Ph. D.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains v, 91 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 53-56).

No description available.

The work reported in this thesis has been developed to predict and measure the cutting forces in the gear hobbing process. A review of past research in this area has highlighted the need to adopt a different approach to modelling the process in order to predict the cutting forces. The hobbing process has been described using six different co-ordinate systems and the kinematic relationships between these systems established. A single rack profile has been used to represent the profile of a single cutting tooth from the hob which was then extended to simulate the hob itself. When the hob gashes pass through the cutting region surfaces are generated which, if mapped on a regular grid can give the basis to estimate the depth of cut, i.e. the instantaneous chip thickness produced by that particular tooth. The instantaneous cutting forces generated by that tooth then can be estimated by using the concept of a specific cutting force of the workpiece material. The estimation of cutting forces acting on a single tooth space was used to predict the cutting forces produced during machining of a full gear, by assuming that the forces acting in a particular tooth space are equal to those acting on the adjacent tooth space at an equivalent instant in the cutting cycle. In order to validate predicted results, a Churchill PH1612 hobbing machine was retrofitted with a CNC control system at Newcastle University, utilising a programmable multi axis controller (PMAC). A specially made single toothed gear, and a full gear were machined, and cut on this machine, and the cutting forces measured in real time using a 3-axis dynamometer. The force signals produced by the dynamometer were measured utilising a 12-bit ADC card. Code, written in C, was developed to perform the many functions needed for the overall control of the machine, but additionally was used to capture both the cutting forces and axis position data. The results of the simulation and modelling have shown very good agreement with those obtained experimentally.

To further the research done in machining complex surfaces, Jensen [1993] developed an algorithm that matches the normal curvature at a point along the surface with the resultant radius formed by tilting a standard flat end mill. The algorithm called Curvature Matched Machining (CM2) is faster and more efficient than conventional three-axis machining [Jensen 1993, Simpson 1995 & Kitchen 1996]. Despite the successes of CM2 there are still many areas available for research. Consider the machining of a mold or die. The complex nature of a mold requires at least 20-30 weeks of lead time. Of those 20-30 weeks 50% is spent in machining. Of that time 50-65% is spent in rough machining. For a mold or die that amounts to 7 to 8 weeks of rough machining. If one could achieve as much as a 10-15% reduction in machining time that would amount to almost one week worth of time savings. As can be seen, small improvements in time and efficiency for rough machining can yield significant results [Fallbohmer 1996]. This research developed an algorithm that focused on reducing the overall machining time for parts and surfaces. Particularly, the focus of this research was within rough machining. The algorithm incorporated principles of three-axis rough cutting with five-axis CM2, hence Rough Curvature Matched Machining (RCM2). In doing so, the algorithm ‘morphed‘ planar machining slices to the semi-roughed surface allowing the finish pass to be complete in one pass. This roughing algorithm has significant time-savings over current roughing techniques.

In the study, a self-developed electrolytic micro-machining tester is employed to investigate the effects of the supply voltage and the highest position of the workpiece relative to the tool on the geometry of the tungsten rod. The peripheral surface of the iron needle (tool) is insulated by an insulator and its tip with a diameter of 50£gm is exposed to the electrolyte as a cathode. The tungsten rod (workpiece) with 200£gm in diameter reciprocates as an anode. Both the cathode and the anode are dipped into an aqueous electrolyte of 2wt % sodium hydroxide to proceed electrochemical machining. Experimental results show that since the length and the diameter of the workpiece are varied during the machining process, it is necessary to manually adjust the highest position and the gap between the workpiece and the tool in each reciprocating motion to achieve a uniform tungsten rod. Moreover, because of the higher removal rate of the workpiece at the higher supply voltage, it is hard to control the geometry of the workpiece. On the contrary, the geometry of the workpiece can be controlled at the lower supply voltage. Finally, the workpiece is first machined at the higher supply voltage, and then the supply voltage is switched to the lower one to achieve a uniform tungsten rod with 2£gm in diameter and 200£gm in length, or 100 in aspect ratio.

No description available.

The influence of different microstructural attributes on the material properties such strength, hardness, residual stress or other physical properties are very well understood. During the manufacturing of mechanical parts utilized in important industries such as energy, aerospace or biomedical, the effect of the processing in term of thermal and mechanical loading is very important as it is directly influencing the microstructure evolution and the properties. The understanding of how the manufacturing process such as high precision machining will affect first the microstructure and therefore the part properties. In this work, we propose the Materials-Affected Manufacturing (MAM). It is a new paradigm helping to understand the interaction between the manufacturing process parameters, materials microstructure attributes and the properties. This is solved using a computational approach using an iterative blending to relate different models. Residual stresses are also studied. An enhanced analytical model is proposed. The model is capable for the first time to predict analytically the residual stress regeneration in the multi-step machining problem. An enhancement of the existing model is proposed. The (MAM) method was applied to the case of turning process of Aluminum 7075. The average grain size and the crystallographic texture were predicted and validated experimentally. The residual stress regeneration was computed for the case of milling of Aluminum 2024. Experimental validations using X-ray technique were performed for validations.