C.J. Luis Pérez

Surface roughness prediction by factorial design of experiments in turning processes

Abstract Surface quality and dimensional precision will greatly affect parts during their useful life especially in cases in which the components will be in contact with other elements or materials during their useful life. Therefore, their study and characterisation is extremely important and, above all, those cases subjected to adverse environmental conditions and in contact with other elements or materials. Thus, measuring and characterising surface properties represents one of the most important aspects in manufacturing processes. In this paper, a development of models which permit to determine surface quality of parts obtained through turning processes is carried out using the response surface methodology. To achieve this, surface quality of several parts manufactured through a material removal process such as turning will be studied by means of using profile rugosimeters. Basically, this will be done by varying cut conditions.

Geometric roughness analysis in solid free-form manufacturing processes

Abstract Present day techniques of prototype manufacture based on computer-assisted design systems and material deposition processes have led to a considerable reduction in manufacturing time. However, numerous aspects of the use of these technologies have yet to be studied. One of these is characterisation of the surface roughness obtainable in layered manufacturing processes. To characterise effective roughness, a study of the roughness average (Ra) obtained through use of these manufacturing processes was carried out. This enabled us to establish two possible strategies for rapid prototype manufacture: manufacture at constant layer height, and manufacture with roughness confined within given limiting values. Prototype parts were manufactured using stereolithography technique and an experimental analysis of resulting surface roughness was carried out to enable us to compare the theoretical models proposed.

Upper Bound Analysis of the ECAE Process by Considering Strain Hardening Materials and Three-Dimensional Rectangular Dies

Equal channel angular extrusion (ECAE) or pressing is a process used to introduce severe plastic deformations to processed materials with the aim of improving their mechanical properties by reducing the grain size. At present, there are no analytical studies that have considered strain hardening materials in order to determine the required force to carry out the process. All the existing papers have only considered nonstrain hardening materials. Furthermore, all those studies have been done by considering plane strain conditions. In this work, an upper bound analysis of the required force for performing the ECAE process is made by considering a full three-dimensional geometry with a rectangular cross section. From this analysis, the influence of the geometric and the material parameters is studied by considering both friction and strain hardening materials. By using the upper bound method, an analytical formulation was obtained and the influence of all the parameters was determined. With this work, it is possible to have a wider knowledge of the influence of the main affecting parameters in the ECAE process and to optimize them.

Processing of aluminium alloys by equal channel angular drawing at room temperature

Abstract The equal channel angular drawing (ECAD) process is an innovative method that allows continuous processing of alloys. The material is drawn through two intersecting channels at an angle commonly between 90 and 135°. The equal channel angular extrusion (ECAE) process—in which the material is extruded instead of drawn—has been extensively studied in the literature in contrast with the ECAD process because of its novelty. In this work, the effect of different processing ways through the ECAD process and the heat treatment are analysed. This work shows the results obtained when the 1370 aluminium alloy is processed, at room temperature, with N=5 (N, number of passes), through two different routes. The experimental results confirm the refinement in final grain sizes in relation to the starting material.

Uncertainty analysis of multijet modelling processes for rapid prototyping of parts

Abstract The present study focuses on aspects of the surface qualities of prototypes obtained by multijet modelling (MJM) techniques. The surface finish and dimensional precision of parts obtained through these manufacturing processes are often highly important, especially in those cases where the manufactured prototypes are used as functional parts, as in the case of lost wax casting. Moreover, it is important to obtain an estimate of the average surface roughness in order to select the appropriate manufacturing parameters. Although there are many different techniques for evaluating surface roughness, one of the most commonly employed methods involves the assessment of the average surface roughness by means of stylus instruments. Prototypes were manufactured using two different MJM systems under different conditions for each prototype. After the parts were obtained, an experimental study of effective roughness was carried out. A comparative study using the same MJM systems with different accuracies was also performed in order to evaluate the capability of these rapid prototyping techniques to manufacture parts.

Upper Bound Analysis of the ECAE Process by Considering Circular Cross-Section and Strain Hardening Materials

Severe plastic deformation processes have a great deal of importance because of the improvement in mechanical properties of the processed parts as a consequence of the grain size reduction in the material due to the accumulation of deformation. One of the main severe plastic deformation (SPD) processes is called the equal channel angular extrusion (ECAE). Although a large amount of studies, which deal with experimental analysis of processed parts exist, few studies dealing with the force required to perform the process have been developed. In this study, an analytical modeling of the force required to perform the ECAE process has been developed using the upper bound method (UBM). The analytical equations developed take into account the material strain hardening and the ECAE dies with circular cross-section. Moreover, the experimental tests have been performed and the extrusion force has been measured. The UBM and experimental results have been compared showing a great deal of agreement.