Papers by Author: C.J. Luis-Pérez

Abstract: ECAE process is a novel technology which allows us to obtain materials of sub-micrometric and/or nanometric grain size as a result of accumulating very high levels of plastic deformation in the presence of high hydrostatic pressure. This avoids the material being fractured and permits very high values of plastic deformation to be obtained (ε>>1). Therefore, these nanostructured materials can be used as starting materials for other manufacturing processes such as: extrusion, rolling and forging among others; with the advantage of providing nanostructure and hence improving the mechanical properties. In this present study, forging by finite element of materials that have been previously predeformed by ECAE is analysed. MSC.Marc^TM software will be employed with the aim of analysing the possibility of manufacturing mechanical components (spur gears) from materials nanostructured by ECAE.

Abstract: Over recent years, some severe plastic deformation processes have been developed with the aim of obtaining a material with sub-micrometric or even nanometric grain size, such as: ECAE (Equal channel angular extrusion) and HPT (High pressure torsion) among many others. The main aim of this present study is to analyse the upsetting of the 5083 Al-Mg-Mn alloy, which had been previously deformed by ECAE. Different processing temperatures will be used and the final properties of the resulting material will be determined.

Abstract: Recent studies have shown that Severe Plastic Deformation (SPD) processes improve the mechanical properties of the parts processed, through a reduction in the grain size. Equal Channel Angular Extrusion (ECAE) is one of the best -known SPD processes. A study was made of the force and the strain after two ECAE passages, as well as of the damage imparted to AA-6082, by means of experiments and Finite Element Simulations (FEM). The aim of this present research is to make a comparative study between experimental results and those obtained by FEM in order to verify the feasibility of these FEM simulations. In addition to this, it is intended to analyze the homogeneity obtained in the strain values after two ECAE passages made through route C.

Abstract: The aim of the work presented in this paper describes the development of a decision support system based on a discrete-event simulation model of an automobile assembly line. The model focuses at a very specific class of production lines with a four closed-loop network configuration. One key characteristic in the closed-loop system is that the number of pallets inside the first three loops has been made constant. The impact of the number of pallets circulating on the first three closed-loops and of the proportion of four-door car bodies on the performance of the production line has been thoroughly investigated. This has been translated into the number of cars produced per hour, in order to improve the availability of the entire manufacturing system.

Abstract: Recent studies have shown that severe plastic deformation processes (SPD) improve the mechanical properties of the processed parts. Some of the most outstanding SPD processes are as follows: High Pressure Torsion (HPT), Repetitive Corrugation and Straightening (RCS), Cyclic Extrusion Compression (CEC), Accumulative Roll Bonding (ARB), Conform and Continuous Combined Drawing and Rolling (CCDR), among others, but the most well-known is Equal Channel Angular Extrusion or Pressure (ECAE/ECAP). The aim of these processes is to introduce high values of deformation inside the parts in order to reduce the grain size and thus to improve the mechanical properties of the starting material. The study of the damage imparted to an AA-6082 alloy is made in the present work. This alloy is received as cast and it is quenched at a temperature of 530 °C during 4 hours in order to be processed by ECAE at room temperature using different geometries of the dies. The imparted damage is also studied by using FEM simulations.

Abstract: An experimental study of the variation of the mechanical properties of sheets of aluminium alloy 1050A due to heat treatment has been carried out. For this purpose, sheets and foils rolled from continuous casting strip (CCS) and from hot rolling strip (HRS) have been prepared in the laboratory. Initially, CCS and HRS had a thickness of 7,5 mm and 3,0 mm respectively. The final thickness achieved in both cases was 0,20 mm. In order to obtain hardening curves for CCS and HRS sheets and foils, specimens of different thickness were taken during the rolling process. Oven treatments were carried out for drawing softening curves of foils. Foil proceeding from CCS presents hardening due to the precipitation of Al3Fe particles at a temperature range of 160°C to 220 °C. HRS foil has a lower hardening in the same range of temperatures owing to its low supersaturation of Fe. Correlation between ultimate tensile strength Rm and Vickers hardness is studied. Micrographies of optical microscopy are offered at hard and recrystallized conditions.

Abstract: As is well-known, teaching of the computer-aided technologies is gaining more and more importance in the field of Manufacturing Processes Engineering. One such example is the growing tendency to employ computers in the simulation of material removal processes (CAM). In this study, a methodology proposed by the Manufacturing Processes Engineering Section in order to teach material removal processes is shown. This methodology is put into practice by employing one CAM software such as Surfcam® and is applied to the teaching subjects given by the previously-mentioned Section belonging to the Public University of Navarre. Due to the length of the practice manual developed for this purpose, which covers turning, milling and EDM processes, the present work has only been focused on the use of Surfcam® in the first case.

Abstract: Pure commercial Cu of 99,98 wt % purity was processed at room temperature by Equal- Channel Angular Pressing (ECAP) following route Bc. Heavy deformation was introduced in the samples after a considerable number of ECAP passes, namely 1, 4, 8, 12 and 16. A significant grain refinement was observed by transmission electron microscopy (TEM). Tensile and microhardness tests were also carried out on the deformed material in order to correlate microstructure and mechanical properties. Microhardness measurements displayed a quite homogeneous strain distribution. The most significative microstructural and mechanical changes were introduced in the first ECAP pass although a gradual increment in strength and a slight further grain refinement was noticed in the consecutive ECAP passes.

Abstract: A commercially pure niobium has been subjected to SPD at room temperature ( ~0.11 TM) via ECAP (90º, route BC) up to 16 passes and via HPT up to shear strains γ =1000. ECAP-ed samples show an equiaxed structure after 8 and 16 passes with a decreasing average grain size. The results show that both the microstructure and mechanical properties of ECAP-ed samples do not reach a steady state up to at least 16 passes. HPT samples show at outer region a finer structural size but similar hardness values at similar equivalent strains. The nanoindentation results show an evident indentation size-effect even for the most deformed samples. The hardness values at the nano level converge for the recrystallized, the ECAP-ed and the HPT samples. This implies that, at the nano level, when the geometrically necessary dislocation density overcomes significantly the (initial) statistically stored dislocation density, hardness depends mainly on the physical intrinsic properties of the material (Burgers modulus, bulk modulus...) and the contribution of bulk mechanical properties (i.e., bulk yield strength) to hardness is smoothed down. Strain-rate sensitivity (SRS) of plastic strength has been also measured by means of rate-jump nanoindentation tests. The SRS is proportional to the inverse of hardness.

Abstract: In this work, the strain field attained by using a severe plastic deformation (SPD) process called equal channel angular extrusion (ECAE) is studied by the finite element method (FEM). The three-dimensional model with circular section includes shear friction between the part and the die, the material strain hardening behaviour and a rigid-deformable contact between the billet and the die. In the ECAE process the part is extruded through two channels with similar diameter that intersect at an angle. When the extrusion process has been performed, the processed material remains it cross section, so there is not any geometric limitation to achieve the desired plastic strain. There are different ways of processing the material by using the ECAE process; those ways of processing are called routes. In this work two passages of route C have been simulated. Using route C means that the billet has been rotated 180º between each passage. Deformations imparted to the processed material have been calculated and a comparison with experimental results has been carried out.