Study of Residual Stresses from Two Machining Protocols Using an Indentation Method

Although high-speed machining offers a number of advantages over conventional machining, it is possible that the residual stress distributions generated by the former can affect the service life of the processed components. In this paper, a newly developed micro-indent method is used to evaluate different residual stress states, which were introduced in samples of AA 7075-T6 aluminum alloy milled at low and high-speed. Different surfaces were generated by varying the cutting speed in one order of magnitude, from 100 m/min to 1000 m/min. Two machining protocols, which consist of using different machine tools, were evaluated. The results show that it is possible to generate and to evaluate very small residual stresses. Finally, the values and levels obtained for normal components were analyzed in function of mechanical and thermal effects that generated the residual stresses.Fil: Diaz, Felipe Victor. Universidad Catolica de Santiago del Estero. Departamento Academico de Rafaela; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Santa Fe; ArgentinaFil: Mammana, Claudio A.. Universidad Catolica de Santiago del Estero. Departamento Academico de Rafaela; ArgentinaFil: Guidobono, Armando P.. Instituto Nacional de Tecnologia Industrial; Argentin

Method to obtain nonuniformity information from field emission behavior

Copyright © 2010 American Vacuum Society / American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Journal of Vacuum Science and Technology Part B: Microelectronics and Nanometer Structures, 28(3), Article number 441 and may be found at http://scitation.aip.org/content/avs/journal/jvstb/28/3/10.1116/1.3327928.This article describes the characterization of field emission from a planar cathode to a spherical anode with the approach curve method (ACM). In such a diode configuration the electric field strength at the cathode surface is nonuniform. This nonuniformity gives an extra degree of freedom and it allows the interpretation of the current-voltage and voltage-distance (V×d) curves in terms of nonuniformity. The authors apply the ACM to Cu emitters to explain the nonlinearity of the V×d curve in ACM measurements. This analysis provides a good insight into field emission phenomena, supporting a method for nonuniformity characterization based on field emission behavior

The approach curve method for large anode-cathode distances

An important technique used to characterize field emission is the measurement of the emitted current against electric field (IxE). In this work we discuss a procedure for obtaining IxE data based on multiple approach curves. We show that the simulated features obtained for an idealized uniform surface matches available experimental data for small anode-cathode distances, while for large distances the simulation predicts a departure from the linear regime. We also discuss the shape of the approach curves for large anode-cathode distances for a cathode made of carbon nanotubes

The approach curve method for large anode-cathode distances

An important technique used to characterize field emission is the measurement of the emitted current against electric field (IxE). In this work we discuss a procedure for obtaining IxE data based on multiple approach curves. We show that the simulated features obtained for an idealized uniform surface matches available experimental data for small anode-cathode distances, while for large distances the simulation predicts a departure from the linear regime. We also discuss the shape of the approach curves for large anode-cathode distances for a cathode made of carbon nanotubes

Study of Residual Stress Relaxation Mechanics Using a Micro-indent Method

The aim of this study is to show the feasibility and accuracy of a micro-indent method to comprehensively evaluate the relaxation mechanics of residual stress in specimens of rolled aluminium alloy. This micro-indent method was adapted to implement four annealing treatments. The residual displacements were measured using a high-accuracy measuring machine, which enables to decrease the absolute error down to ± 300 nm. This work presents an innovative data analysis using Mohr´s circles, which allowed to study all directions of the in-plane residual stress for different relaxation times. The results revealed that the relaxation process finishes when the residual stress relief is completed in some preferential directions, and then, a brief stress recovery phase begins. Fil: Diaz, Felipe Victor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Tecnológica Nacional. Facultad Regional Rafaela; ArgentinaFil: Mammana, C. A.. Universidad Tecnológica Nacional. Facultad Regional Rafaela; ArgentinaFil: Guidobono, A. P. M.. Instituto Nacional de Tecnología Industrial; Argentin

Analysis of Residual Stresses in High Speed Milled Aluminum Alloys

The purpose of this study is to evaluate, from high speed machining tests, the behavior of the residual stresses induced in samples of AA 6082-T6 and AA 7075-T6 aluminum alloys. This study includes an exhaustive analysis of residual stress anisotropy from diameters of Mohr´s circles. The combination of process parameters was modified in order to evaluate the stress changes introduced in different zones of the surfaces generated. A method of micro-indents, which includes the adaptation of a universal measuring machine, was used to determine, with high accuracy, the normal components of residual stress in several directions. The obtained results reveal that although, in the alloy 7075-T6, the normal components are lower, in the alloy 6082-T6, these normal components tend to be grouped into smaller intervals and also, to show a more homogeneous directional behavior when the cutting conditions are more severe.Fil: Vottero, S.. Universidad Tecnológica Nacional. Facultad Regional Rafaela; ArgentinaFil: Diaz, Felipe Victor. Universidad Tecnológica Nacional. Facultad Regional Rafaela; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Mammana, C. A.. Universidad Tecnológica Nacional. Facultad Regional Rafaela; ArgentinaFil: Guidobono, A. P. M.. Instituto Nacional de Tecnología Industrial; Argentin

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