Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Analysis of the metal cutting process using the shear plane model(Montana State University - Bozeman, College of Engineering, 2010) Chen, Cameron Kai-Ming; Chairperson, Graduate Committee: David A. MillerThe objective of the metal cutting process is to reshape a piece of metal, or workpiece, of initial geometry into a new geometry of desired shape. Although there are a variety of ways to cut metal, this study focuses on the type of cutting where metal is sheared away from the workpiece as is commonly done with machine tools such as the lathe or mill. Typically, the correct machine settings can be found from reference guides that summarize a great amount of empirical data on metal cutting. Trial and error when combined with experience, often suffices to select the proper process parameters. The aim of this study is to predict the outcome of a metal cutting process given the properties of the workpiece, feed and cutting speed in order to understand the cutting process and predict optimum conditions. The shear plane model is well known, having been developed in the early and mid-20th century. However the empirical nature of the model and approximations made in making predictions of the metal cutting process serve to limit the usefulness of this model. A calculation routine devised by P.L.B Oxley to predict how to cut steel was created with modifications allowing predictions of the metal cutting process with any metal. A comparative study was done with 1006 steel, 6Al-4V titanium, 2024-T3 aluminum and OFE copper regarding the differences in tool forces and temperatures that would result if each metal was cut with the same process. A quantitative prediction of the metal cutting process was made for the four metals under study. Although there is no experimental data with which to evaluate these predictions, a number of case studies were performed. These case studies involved the prediction of experimental data presented in literature from other laboratories. The metal cutting model presented here has great promise as a guide to predict the best machine tool parameters.Item Tool geometry effects in metal shearing using FEM(Montana State University - Bozeman, College of Engineering, 2011) Barkan, Eric David; Chairperson, Graduate Committee: David A. MillerIn manufacturing industry cutting of sheet metals is an everyday occurrence. With this in mind hand tool design is limited by empirical conventions for tool clearance, in the range of 4.5% to 8%. Conventional cutting force calculations and tool clearance calculations exist in reference material and can easily be calculated. These conventions are based on shear theory for force and experimental data for tool clearance. By applying these conventions to an FEM model for common engineering alloys of thicknesses between .020" and .080", and analyzing it the resulting stress fields and tool displacements trends in the increase of tool displacement required for the same stress state for all tool clearances. Cohesive zone placement based on first analysis leads to describing the failure of the material cutting process. Traction separation laws describing cohesive elements can accurately describe the cutting of sheet metals. For the 6061-T6 aluminum, 1020 steel, 4340 steel, and 302 stainless the optimum tool clearance discovered through the cohesive zone FEM model is shown to be 3.8% to 8.3%. This information can be used for extrapolating the optimum clearances for other thicknesses of the materials, and the model can be expanded to encompass a larger material set.