Papers by Author: C.J. Luis-Pérez

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Authors: Daniel Salcedo, C.J. Luis-Pérez, Javier León, Rodrigo Luri, Ignacio Puertas
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.MarcTM software will be employed with the aim of analysing the possibility of manufacturing mechanical components (spur gears) from materials nanostructured by ECAE.
Authors: J. Pérez-Ilzarbe, J. Fernández Carrasquilla, C.J. Luis-Pérez
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.
Authors: Javier León, C.J. Luis-Pérez
Abstract: The equal channel angular drawing (ECAD) process is an innovative method to obtain materials with high plastic strain in a continuous way. This deformation is higher than the deformation achieved by a conventional wire drawing process, for the same reduction of the cross section, so if an adequate thermal treatment is employed later, it could be possible to obtain an initial material with high value that could be useful in conventional manufacturing processes. This process consists in drawing a material through a die where two circular channels intersect at an angle between 90º and 135º. In this work a study using finite element of the plastic strain and the stresses that appear for one aluminium alloy AA-1370 has been carried out. Two ECAD passes have been made, where for the second pass the billet has been rotated 180º along the longitudinal axis. Finally, a calibrated pass has been carried out in order to obtain the billet with homogeneous dimensions in all the cross section. All the simulations have been calculated at room temperature and by using good conditions of lubrication. In order to perform the FEM simulations, a three dimensional geometry has been used. To analyze by FEM the second ECAD pass and the calibration pass, the deformations and stresses achieved in the previous passes have been taken into consideration. This has been done with the aim of achieving higher accuracy. Moreover, a comparative analysis with experimental results has been carried out.
Authors: C.J. Luis-Pérez, Ignacio Puertas, Daniel Salcedo, Javier León, Ivan Pérez
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.
Authors: Javier León, C.J. Luis-Pérez, Daniel Salcedo, Ivan Pérez, Juan Pablo Fuertes, Ignacio Puertas, Rodrigo Luri
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.
Authors: Ignacio Puertas, C.J. Luis-Pérez, Rodrigo Luri, Javier León, Juan Pablo Fuertes
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.
Authors: Nayar Lugo, Jose María Cabrera, Núria Llorca-Isern, C.J. Luis-Pérez, Rodrigo Luri, Javier León, Ignacio Puertas
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.
Authors: C.J. Luis-Pérez, Ignacio Puertas, C. Remirez, Javier León, Rodrigo Luri
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.
Authors: Jon Alkorta, C.J. Luis-Pérez, E.N. Popova, Martin Hafok, Reinhard Pippan, J. Gil Sevillano
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.
Authors: Ignacio Puertas, C.J. Luis-Pérez
Abstract: In this work, a surface roughness study on the die-sinking electrical discharge machining (EDM) of siliconised silicon carbide (SiSiC) has been carried out. The selection of the abovementioned conductive ceramic was made taking into account its wide range of applications in the industrial field: high temperature gas turbines, bearings, seals and lining of industrial furnaces. This study was made only for the finish stages, due to the enormous importance that a good surface quality has over such important properties as, in the case of ceramic materials: corrosion, fatigue and wear resistance. The present study has been carried out on the influence of five design factors: intensity supplied by the generator of the EDM machine (I), pulse time (ti), duty cycle (η), opencircuit voltage (U) and dielectric flushing pressure (P), which are the most relevant parameters to be controlled by the EDM process machinists, over two roughness parameters such as Ra and Rq. The study of the behaviour of the two previously mentioned parameters has been done by means of the technique of design of experiments (DOE), which allows us to carry out the previous analysis performing a relatively small number of experiments. In this case, a 25-1 fractional factorial design, whose resolution is V, has been selected due to the number of factors considered in the study.
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