S.R. Fernández-Vidal

Tribological Wear Analysis of Laser Surface Treated Ti6Al4V Based on Volume Lost Evaluation

Surface modification of materials through thermal or chemical treatments and coatings development can be used to obtain improved behavior under abrasive and adhesive wear. A great variety of surface structures with different properties can be adapted to the most demanding requirements. This is due to the high number of parameters that can be controlled in each treatment, such as the technique used, the atmosphere, the use of additive elements to the base material, the thickness of the modified layers, etc., In order to monitoring more accurately the wear conditions on the alloy, tribological tests were carried out that enable to control anytime the application parameters of a process, thus generating very accurate, reliable and easier to evaluate data, than industrial machining processes. One of the most significant wear variables in the study is the change in volume of material experienced by the sample after the sliding process. This contribution aims at assessing the volume of worn material, analyzing the tribological behavior of surface treated by laser Ti6Al4V samples.

Processing and Quality Evaluation of Additive Manufacturing Monolayer Specimens

Although its importance has increased significantly, Additive Manufacturing is not yet a fully accepted industrial manufacturing process for load-carrying parts. The future success of the process group depends on its standardization. This work proposes a methodology for the design, manufacturing, and quality evaluation of specimens manufactured by Fused Layer Modeling that are composed of only one layer (so-called monolayers). The processing methodology and properties of monolayers have not been studied systematically yet. A first systematic design of monolayers for mechanical testing is presented. Rectangular and circular monolayers adapted to the loads of tensile and compression testing are manufactured using different trajectory strategies. Frequently occurring macro- and microgeometrical defects are evaluated and categorized in order to optimize the part quality. This work also studies the effect of some manufacturing parameters such as the gap between print head and machine bed, trajectory strategy, bed leveling, and temperatures on part quality. The most suitable specimens are tested mechanically in tensile or compression tests. In the case of study, tensile strength values are only 8.6% lower than the values for reference tests on the unextruded filament. However, the properties deviate more strongly for compression tests which may be due to the selected specimen geometry.

Tool Wear Mechanism in Cutting of Stack CFRP/UNS A97075

The aeronautics industry’s competitiveness has led to the need to increase productivity with one shot drilling (OSD) systems capable of drilling stacks of dissimilar materials (fibre/metal laminates, FML) in order to reduce riveting times. Among the materials that constitute the current aeronautical models, composite materials and aluminium (Al) and titanium (Ti) alloys stand out. These one-pass machining techniques produce high-quality holes, especially when all the elements that have to be joined are made of the same material. This work has followed a conventional OSD strategy and the same cutting conditions applied to CFRP (carbo-fibre-reinforced polymer), Al and CFRP/Al stacked sheets to know the wear mechanisms produced. With this purpose, results were obtained by using current specific techniques, such as microstructural analysis, monitoring of the shear forces and analysis of macrogeometric deviations. It has been determined that when these drilling techniques are applied under the same cutting conditions to stacks of materials of a different nature, the results of the wear mechanisms acting on the tool differ from those obtained when machining each material separately. This article presents a comparison between the effects of tool wear during dry drilling of CFRP and UNS A97075 plates separately and when machined as stacks.

Experimental Parametric Model for Adhesion Wear Measurements in the Dry Turning of an AA2024 Alloy

Adhesion wear is the main wear mechanism in the dry turning of aluminium alloys. This type of wear produces an adhesion of the machining material on the cutting tool, decreasing the final surface quality of the machining parts and making it more difficult to maintain industrial tolerances. This work studies the influence of the cutting parameters on the volume of material adhered to the cutting tool surface for dry machining of AA2024 (Al-Cu). For that purpose, a specific methodology based on the automatic image processing method that can obtain the area and the thickness of the adhered material has been designed. This methodology has been verified with the results obtained through 3D analysis techniques and compared with the adhered volume. The results provided experimental parametric models for this wear mechanism. These models are analytic approximations of experimental data. The feed rate mainly results in low cutting speed, while low depths of cut presents a different behaviour due to the low contact pressure. The unstable behaviour of aluminium adhesion on the cutting tool produces a high variability of results. This continuous change introduces variation in the process caused by the continuous change of the cutting tool geometry.

A Single Students' Experience for Visualizing Completely a Semester Subject

Manufacturing Engineering Processes Knowledge Area has developed an innovative teaching experience in order to give, only in one session, a complete view of a basic subject, Manufacturing Engineering. This experience has been developed on the basis of making a cube constructed in card by groups of students. Starting from this, the different steps of a manufacturing process have been identified, as well as the necessity of establishing a quality control for any of them. Moreover, the different material processing technology types have been distinguished, the concept of process performance has been introduced and the different possibilities for sequential and/or parallel processing have been analyzed. On the basis of this, the students have built the topics program of the subject, justifying its competences distribution. In the same way, the students have defined the related basic concepts. At the end of the course, a questionnaire containing the basic cognitive concepts was answered by them, 100% successfully.

Comparison of Diameter and Area Change Based Methods for Evaluating Break-IN and Break-OUT Damages in Dry Drilled Holes of Aeronautical Carbon Fiber Composites

Currently, Carbon Fiber Reinforced Non-Metal Composites (CFRC) are commonly applied in structural components of aircrafts. Frequently, these elements need to be drilled for their assembly in the final product. Chips close to powder are formed when this kind of material is machined. Because of this, drilling processes are mostly performed in absence of cutting fluids. High quality requirements are demanded for holes due to the fact than those elements are placed in key components of the aircrafts. The most relevant defects that can be produced in the dry drilling of CFRC are located in the both tool input and tool output. These defects are known as Break-IN (B-IN) and Break-OUT (B-OUT). This paper reports on the results of a comparative study of different methodologies for evaluating those defects. First of them is based on the analysis of the diameter deviation. Second procedure is based on the damaged area. Both parameters have been measured making use of image analysis techniques. Obtained results have revealed that damaged area based method is more sensitive to hole changes.

Cutting Speed and Feedrate Based Analysis of Cutting Forces in the One Shot Drilling (OSD) of CFRC/Al Hybrid Stacks

Hybrid stacks structures Composite/Metallic Alloy are commonly applied for manufacturing of structural components in different industrial sectors. Particularly, they are increasingly widely used in the aerospace industry because of these materials combine light weight with a high mechanical resistance. This fact helps to increase the load without needing to increment — even diminishing — the energetic consumption. Carbon Fiber Reinforced Composites (CFRC) and light alloys, such as Aluminium or Titanium based alloys, are usually combined for performing those stacks.CFRC/Alloy stacks based airship structural elements commonly require drilling operations for the posterior assembly tasks. However, the machining processes of Non-Metal Matrix Composites (NMMC), and particularly CFRC, show significant differences with the machining processes of metallic materials. Because of this, it is very difficult to find a joint only one of cutting parameters for drilling these structures using One Shot Drilling (OSD) techniques.In this work, a study of the cutting forces developed in the dry-OSD of CFRC/UNS A92024 stacks has been achieved as a function of the cutting speed and feedrate parameters. Dry drilling tests have been performed using different parameters for drilling CFRC and alloy. A change of the parameters in the interface between CFRC and the alloy has been programmed through a CAM software.Higher cutting force values have been observed in the case of the Aluminium alloys. For both materials, obtained results have shown a strong increase of the cutting force with the increase of feedrate. However, only a slight increase with cutting speed has been observed.The evolution of the cutting force as a function of the holes number has shown a trend to increase only for highest feedrates when CFRC/Alloy is drilled. From the obtained results a F(f,v) model has been proposed.Copyright