Thesis (M.S.)--University of Wisconsin--Madison, 1968. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

O estudo das forças de corte em usinagem tem várias aplicações, tais como definir a melhor geometria da ferramenta e sua interação com a peça. Este trabalho apresenta os resultados de simulações do processo de torneamento utilizando o método dos elementos finitos no corte ortogonal em aço AISI 4340 usando insertos de metal duro, comparando-os com resultados experimentais. As simulações foram realizadas no programa comercial Abaqus/Explicit TM considerando os efeitos térmicos do processo oriundos tanto da deformação do material quanto dos atritos nas interface peça-ferramenta-cavaco. As variáveis do processo estudadas foram a velocidade de corte e o avanço. Os resultados da força de corte simulada mostraram-se bem próximos daqueles obtidos experimentalmente, com erro médio em torno de 5%, enquanto que os da força de avanço apresentaram erro médio de cerca de 27%. / Cutting force is a very important parameter, which can be used to determine tool geometry and its interaction with the workpiece. This work presents some orthogonal cutting simulations using Abaqus/Explicit TM finite element methods code with carbide tool on an AISI 4340 hardened steel workpiece. Comparison with experimental results are also carried out. The simulation considers the thermal effect caused by material deforming and friction between tool, workpiece and chips. The main parameters changed during the simulations are the cutting speed and the feed rate. As results, the simulated cutting forces showed an error around 5% and the simulated feed forces about 27% when compared to the experimental values.

Thesis (M.App.Sc.) - Carleton University, 2006. / Includes bibliographical references (p. 88-96). Also available in electronic format on the Internet.

O estudo das forças de corte em usinagem tem várias aplicações, tais como definir a melhor geometria da ferramenta e sua interação com a peça. Este trabalho apresenta os resultados de simulações do processo de torneamento utilizando o método dos elementos finitos no corte ortogonal em aço AISI 4340 usando insertos de metal duro, comparando-os com resultados experimentais. As simulações foram realizadas no programa comercial Abaqus/Explicit TM considerando os efeitos térmicos do processo oriundos tanto da deformação do material quanto dos atritos nas interface peça-ferramenta-cavaco. As variáveis do processo estudadas foram a velocidade de corte e o avanço. Os resultados da força de corte simulada mostraram-se bem próximos daqueles obtidos experimentalmente, com erro médio em torno de 5%, enquanto que os da força de avanço apresentaram erro médio de cerca de 27%. / Cutting force is a very important parameter, which can be used to determine tool geometry and its interaction with the workpiece. This work presents some orthogonal cutting simulations using Abaqus/Explicit TM finite element methods code with carbide tool on an AISI 4340 hardened steel workpiece. Comparison with experimental results are also carried out. The simulation considers the thermal effect caused by material deforming and friction between tool, workpiece and chips. The main parameters changed during the simulations are the cutting speed and the feed rate. As results, the simulated cutting forces showed an error around 5% and the simulated feed forces about 27% when compared to the experimental values.

This study focuses on developing explicit analytical and numerical process models for mechanical micro-machining of heterogeneous materials. These models are used to select suitable process parameters for preparing and micro-machining of these advanced materials. The material system studied in this research is Magnesium Metal Matrix Composites (Mg-MMCs) reinforced with nano-sized and micro-sized silicon carbide (SiC) particles. This research is motivated by increasing demands of miniaturized components with high mechanical performance in various industries. Mg-MMCs become one of the best candidates due to its light weight, high strength, and high creep/wear resistance. However, the improved strength and abrasive nature of the reinforcements bring great challenges for the subsequent micro-machining process. Systematic experimental investigations on the machinability of Mg-MMCs reinforced with SiC nano-particles have been conducted. The nanocomposites containing 5 Vol.%, 10 Vol.% and 15 Vol.% reinforcements, as well as pure magnesium, are studied by using the Design of Experiment (DOE) method. Cutting forces, surface morphology and surface roughness are characterized to understand the machinability of the four materials. Based on response surface methodology (RSM) design, experimental models and related contour plots have been developed to build a connection between different materials properties and cutting parameters. Those models can be used to predict the cutting force, the surface roughness, and then optimize the machining process. An analytical cutting force model has been developed to predict cutting forces of MgMMCs reinforced with nano-sized SiC particles in the micro-milling process. This model is iv different from previous ones by encompassing the behaviors of reinforcement nanoparticles in three cutting scenarios, i.e., shearing, ploughing and elastic recovery. By using the enhanced yield strength in the cutting force model, three major strengthening factors are incorporated, including load-bearing effect, enhanced dislocation density strengthening effect and Orowan strengthening effect. In this way, the particle size and volume fraction, as significant factors affecting the cutting forces, are explicitly considered. In order to validate the model, various cutting conditions using different size end mills (100 µm and 1 mm dia.) have been conducted on Mg-MMCs with volume fraction from 0 (pure magnesium) to 15 Vol.%. The simulated cutting forces show a good agreement with the experimental data. The proposed model can predict the major force amplitude variations and force profile changes as functions of the nanoparticles’ volume fraction. Next, a systematic evaluation of six ductile fracture models has been conducted to identify the most suitable fracture criterion for micro-scale cutting simulations. The evaluated fracture models include constant fracture strain, Johnson-Cook, Johnson-Cook coupling criterion, Wilkins, modified Cockcroft-Latham, and Bao-Wierzbicki fracture criterion. By means of a user material subroutine (VUMAT), these fracture models are implemented into a Finite Element (FE) orthogonal cutting model in ABAQUS/Explicit platform. The local parameters (stress, strain, fracture factor, velocity fields) and global variables (chip morphology, cutting forces, temperature, shear angle, and machined surface integrity) are evaluated. Results indicate that by coupling with the damage evolution, the capability of Johnson-Cook and Bao-Wierzbicki can be further extended to predict accurate chip morphology. Bao-Wierzbiki-based coupling model provides the best simulation results in this study. v The micro-cutting performance of MMCs materials has also been studied by using FE modeling method. A 2-D FE micro-cutting model has been constructed. Firstly, homogenized material properties are employed to evaluate the effect of particles’ volume fraction. Secondly, micro-structures of the two-phase material are modeled in FE cutting models. The effects of the existing micro-sized and nano-sized ceramic particles on micro-cutting performance are carefully evaluated in two case studies. Results show that by using the homogenized material properties based on Johnson-Cook plasticity and fracture model with damage evolution, the micro-cutting performance of nano-reinforced Mg-MMCs can be predicted. Crack generation for SiC particle reinforced MMCs is different from their homogeneous counterparts; the effect of micro-sized particles is different from the one of nano-sized particles. In summary, through this research, a better understanding of the unique cutting mechanism for particle reinforced heterogeneous materials has been obtained. The effect of reinforcements on micro-cutting performance is obtained, which will help material engineers tailor suitable material properties for special mechanical design, associated manufacturing method and application needs. Moreover, the proposed analytical and numerical models provide a guideline to optimize process parameters for preparing and micro-machining of heterogeneous MMCs materials. This will eventually facilitate the automation of MMCs’ machining process and realize high-efficiency, high-quality, and low-cost manufacturing of composite materials.