Surface Quality and Free Energy Evaluation of s275 Steel by Shot Blasting, Abrasive Water Jet Texturing and Laser Surface Texturing

Surface modification by different technologies prior to joining operations or improving tribological properties is a point of great interest. Improving surface activation by increasing the roughness of the metal is a relationship that is becoming more defined. In turn, an increase in surface wettability by evaluating contact angles indicates surface activation by obtaining a high surface free energy. Technologies such as shot blasting and laser surface texturing (LST) have generated several scientific studies where they have identified the influence of parameters on the formation of rough surfaces with defined patterns. However, the application of abrasive water jet texturing (AWJT) has been little studied as an alternative. This article compares these technologies in the texturing of a carbon steel s275 in order to identify the relationship between surface quality and surface activation. It has been determined that AWJT produces the highest Rt values close to 64 mu m with a cross feed of 0.45 mm and a traverse speed of 5000 mm/min. Furthermore, LST obtains the best values of free surface energy by combining a power of 20 W with a frequency of 20 kHz and a sweeping speed of 10 mm/s. Finally, contour diagrams have been obtained which relate these variables to the texturing parameter

Evaluation of geometrical defects in AWJM process of a hybrid CFRTP/Steel structure

The bonding of Carbon Fibre Reinforced ThermoPlastic composites (CFRTP) and steel is of great interest nowadays. Nevertheless, the difference in machinability between dissimilar materials requires a specific machining process. Abrasive water jet machining is a flexible and environmentally friendly technology that can machine dissimilar materials at the same time with good results. However, due to the characteristics of the process and materials, geometrical defects such as taper angle can be caused by the loss of kinetic energy. In this research, the study of the final geometry in abrasive waterjet machining of a hybrid CFRTP/Steel structure. A new methodology for the evaluation of taper angle with high accuracy has been developed through image processing. In addition, the surface quality in terms of Ra and Rz has been assessed. A potential-type trend between taper and hydraulic pressure has been established for both materials. Minimum taper values between 1.5° and 5° have been obtained for both materials and stacking configurations with a combination of a hydraulic pressure of 420 MPa, an abrasive mass flow of 225 g/min and a traverse speed of 50 mm/min. © 2021 The Author(s

On the Surface Quality of CFRTP/Steel Hybrid Structures Machined by AWJM

The joining of dissimilar materials in a hybrid structure is a line of research of great interest at present. Nevertheless, the machining of materials with different machinability requires specific processes capable of minimizing defectology in both materials and achieving a correct surface finish in terms of functional performance. In this article, abrasive water jet machining of a hybrid carbon fiber-reinforced thermoplastics (CFRTP)/Steel structure and the generated surface finish are studied. A parametric study in two stacking configurations (CFRTP/Steel and Steel/CFRTP) has been established in order to determine the range of cutting parameters that generates the lowest values in terms of arithmetic mean roughness (Ra) and maximum profile height (Rz). The percentage contribution of each cutting parameter has been identified through an ANOVA analysis for each material and stacking configuration. A combination of 420 MPa hydraulic pressure with an abrasive mass flow of 385 g/min and a travel speed of 50 mm/min offers the lowestRaandRzvalues in the CFRTP/Steel configuration. The stacking order is a determining factor, obtaining a better surface quality in a CFRTP/Steel stack. Finally, a series of contour diagrams relating surface quality to machining conditions have been obtained

Compraventa de vivienda (Jurisdicción Civil). Robo con fuerza (Jurisdicción Penal)

[Abstract not available

El posgrado en el marco del Espacio Europeo de Educación

La adaptación de la oferta académica de postgrado al Espacio Europeo de Educación Superior en España no ha seguido el desarrollo que la lógica de la nueva ordenación de enseñanzas exigía, dando como resultado una adaptación con evidentes carencias que, aún pasando el umbral de 2010, serán temas de agenda pendiente por resolver en la reforma universitaria. El proceso para la definición del marco normativo ha seguido causes más políticos que estratégicos en el diseño de los nuevos estudios oficiales, dotando al proceso de convergencia elementos de confusión de cara a la comunidad universitaria. El marco para el desarrollo de las competencias de los estudios de postgrado y el sistema de garantía de la calidad en el mismo son dos de los temas que destacan por su deficiente desarrollo, y a los cuáles habrá que hacer frente inexcusablemente. AbstractThe adaptation of the post grade curricula to the European Higher Education Area has not followed a logic way based on the new studies structure approved. The results obtained shows several lacks that, once passed the 2010 goal, will be schedule issues to resolve for the higher education reform. The legislative process has followed a political way instead of a strategic in the new official studies, giving to the university community more confusion elements about the convergence. The frame for the development of the competences in the post grade studies and also the quality assessment system for these studies are two of the themes that arise for its deficient design, that universities and government must face on