Papers by Author: J.C. Outeiro

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Authors: J.C. Outeiro, Domenico Umbrello, Rachid M'Saoubi
Abstract: The reliability of a mechanical component depends to a large extent on the physical state of its surface layers. This state includes the distribution of residual stresses induced by machining. Residual stresses in the machined surface and subsurface are affected by the cutting tool, work material, contact conditions on the interfaces, cutting regime parameters (cutting speed, feed and depth of cut), but also depends on the cutting procedure. In this paper, the effects of cutting sequence on the residual stress distribution in the machined surface of AISI 316L steel are experimentally and numerically investigated. In the former case, the X-ray diffraction technique is applied, while in the latter an elastic-viscoplastic FEM formulation is implemented. The results show that sequential cut tends to increase superficial residual stresses. A greater variation in residual stresses is observed between the first and the second cut. Moreover, an increase in the thickness of the tensile layer is also observed with the number of cuts, this difference also being greater between the first and the second cut. Based on these results, the residual stress distribution on the affected machined layers can be controlled by optimizing the cutting sequence.
Authors: J.C. Outeiro, A. Morão Dias
Abstract: Machining residual stresses are considered as part of surface integrity and a consequence of the machining process. Theses stresses are closely correlated with the corresponding process parameters, including the work material properties. As it is well known, not only the mechanical but also the physical properties of the work materials have great influence on machining residual stress. This was demonstrated in the present work through studying the residual stress and work hardening induced by the turning of AISI 316L and AISI 1045 steels. The residual stresses were determined at the workpiece surface and in-depth using the X-ray diffraction technique. To understand the influence of the work material properties on the residual stress and work hardening distributions, the mechanical and thermal phenomena occurring during the cutting process were studied, using a t developed experimental procedure. The experimental setup included a piezoelectric dynamometer to determine the cutting forces, and thermal imaging equipment developed to assess the temperature distribution in the deformation zone in turning. The results showed that the cutting forces and temperatures in the machining of 316L steel are much higher than those in the machining of 1045 steel. Thus, machining 316L steel, when compared to 1045 steel, results in higher superficial residual stresses and stronger in-depth residual stress gradients, higher superficial work-hardening and greater thickness of the work hardened layer.
Authors: Maria José Marques, J.C. Outeiro, A. Morão Dias, Rachid M'Saoubi, Hariharan Chandrasekaran
Abstract: The quality of a mechanical component such as its geometrical accuracy stability and fatigue life are significantly affected by the surface integrity generated by machining process. Residual stresses are a major part of the mechanical state of a machined layer and they can be beneficial or detrimental depending of their nature and magnitude. This study concerns phase analysis and residual stress profile characterization by X-ray diffraction (XRD) technique and microhardness profile of AISI H13 ESR mould steel, milled using carbide and CBN tools. Analysis of the cross-section of the AISI H13 ESR samples, milled using both tools, reveal a martensitic microstructure, with a very thin layer heavily deformed due to the machining process. However, no phase transformation was detected by XRD. Concerning the residual stresses, the results show that they are predominantly compressive at the samples surface. However, depending of the cutting tools, the in-depth residual stresses profiles present different evolutions. This difference in the in-depth residual stresses profiles between the two kind of cutting tools is attributed to the different cutting tool parameters, including the tool geometry.
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