Development of software for easy prediction of process parameters in air bending with local heating

This paper presents a new software tool for sheet metal forming, based on an analytical model of the process. The advantages of this kind of tool, compared with numerical models based on finite element codes, are described. The analysis is focused on sheet metal bending at high temperature that is a promising method for metal forming, improving sheet formability and machines range of use.Publicad

Analysis of tool wear patterns in finishing turning of Inconel 718

This paper focuses on the analysis of tool wear mechanisms in finishing turning of Inconel 718, one of the most used Ni alloys, both in wet and dry cutting. Cemented carbides, ceramics and CBN tools are suitable for machining Ni alloys; coated carbide tools are competitive for machining operations of Ni alloys and widely used in industry. Commercial coated carbide tools (multilayer coating TiAl/TiAlN recommended for machining Ni alloys) were studied in this work. The feasibility of two inserts tested for dry cutting of Inconel 718 has been shown in the work. Experimental test were performed in order to analyze wear patterns evolution. It was found great influence of side cutting edge angle in tool wear mode.The financial support of this work to the Ministry of Economy and Competitiveness of Spain (under project DPI2008–06746).Publicad

Tool wear and induced damage in CFRP drilling with step and double point angle drill bits

Drilling operations on Carbon Fiber Reinforced Plastics (CFRP) have become crucial for the manufacturing process of multiple components on the aerospace industry. The main objective of this research is to develop a comparative analysis between a step geometry drill bit, currently used in the aerospace industry for drilling processes in CFRP with a hole diameter of 9.54 mm, and the double point angle geometry. The tool material is tungsten carbide with a diamond coating. The performance of each cutting geometry is assessed based on the type of tool wear, the evolution of the thrust force and cutting torque and the onset of machining induced damage on the test specimens. Although the main wear mechanism suffered by both tools was very similar, it was observed a remarkable influence of the cutting geometry on the tool wear evolution and the associated thrust force. This different performance also affected the onset of the machining induced damage.The authors acknowledge the financial support of Airbus Defense and Space through the project Drilling Processes Improvement for Multi Material CFRP-Al-Ti Stacks, and the Ministry of Economy and Competitiveness of Spain through a grant with reference PTA2015-10741-I and project DPI2017-89197-C2-1-R

Theoretical analysis of air bending at high temperature

This paper is focused on the theoretical analysis of air bending at high temperature. A thermo-mechanical model able to predict temperature distribution and main bending parameters is developed. Thermal model assumes local heating of the sheet along bend length and is based in previous numerical model. The influence of temperature in mechanical properties of the sheet is taken into account with temperature dependent parameters of constitutive equation. Mechanical model is formulated in order to satisfy industrial requirements. Desired geometry of the piece fixes final bending angle after unloading, so this parameter is the input of the model. An iterative calculation process is used to solve presented equations obtaining curvature, sheet shape, contact force and springback. These parameters are very important in industrial processes, allowing establishment of punch displacement and maximum force to make the desired workpiece. Other results may be obtained from this model: moment distribution, maximum stress and strain. These results are related to important features of the actual process, like tools design and formability limits of the sheet.Publicad

Numerical analysis of the tool wear effect in the machining induced residual stresses

Machining is a dynamic process involving coupled phenomena: high strain and strain rate and high temperature. Prediction of machining induced residual stresses is an interesting objective at the manufacturing processes modelling field. Tool wear results in a change of tool geometry affecting thermo-mechanical phenomena and thus has a significant effect on residual stresses. The experimental study of the tool wear influence in residual stresses is difficult due to the need of controlling wear evolution during cutting. Also the involved phenomena make the analysis extremely difficult. On the other hand, Finite Element Analysis (FEA) is a powerful tool used to simulate cutting processes, allowing the analysis of different parameters influent on machining induced residual stresses. The aim of this work is to develop and to validate a numerical model to analyse the tool wear effect in machining induced residual stresses. Main advantages of the model presented in this work are, reduced mesh distortion, the possibility to simulate long length machined surface and time-efficiency. The model was validated with experimental tests carried out with controlled worn geometry generated by electro-discharge machining (EDM). The model was applied to predict machining induced residual stresses in AISI 316 L and reasonable agreement with experimental results were found.The authors are indebted for the financial support of this work, to the Ministry of Science and Education of Spain (under Project DPI2008-06746). The authors also acknowledge to the CAM-UC3M for the financial support obtained for this work with the Project CCG08-UC3M/DPI-4494.Publicad

Hybrid Composite-Metal Stack Drilling with Different Minimum Quantity Lubrication Levels

Hybrid stack drilling is a very common operation used in the assembly of high-added-value components, which combines the use of composite materials and metallic alloys. This process entails the complexity of machining very dissimilar materials, simultaneously, on account of the interactions that are produced between them, during machining. This study analyzed the influence of Minimum Quantity Lubrication (MQL) on the performance of diamond-coated carbide tools when drilling Ti/carbon fiber reinforced plastics (CFRP)/Ti stacks. The main wear mechanism observed was diamond-coating detachment, followed by fragile breaks in the main cutting-edge. The tests done with the lower lubrication levels have shown an important adhesion of titanium (mainly on the secondary cutting-edge) and a higher friction between the tool and the workpiece, producing higher temperatures on the cutting region and a thermal softening effect on the workpiece. These phenomena affect the evolution of cutting power consumption with tool wear in the titanium layer. Regarding the quality of the test specimen, no significant differences were observed between the lubrication levels tested.The authors acknowledge the financial support of Airbus Defense and Space, through the project Drilling Processes Improvement for Multi Material CFRP-Al-Ti Stacks, and the Ministry of Economy and Competitiveness of Spain through the grant PTA2015-10741-I and the project DPI2017-89197-C2-1-

Sustainable high-speed finishing turning of haynes 282 using carbide tools in dry conditions

Nickel-based superalloys exhibit an exceptional combination of corrosion resistance, enhanced mechanical properties at high temperatures, and thermal stability. The mechanical behavior of nickel-based superalloys depends on the grain size and the precipitation state after aging. Haynes 282 was developed in order to improve the creep behavior, formability, and strain-age cracking of the other commonly used nickel-based superalloys. Nevertheless, taking into account the interest of the industry in the machinability of Haynes 282 because of its great mechanical properties, which is not found in other superalloys like Inconel 718 or Waspaloy, more research on this alloy is necessary. Cutting tools suffer extreme thermomechanical loading because of the high pressure and temperature localized in the cutting zone. The consequence is material adhesion during machining and strong abrasion due to the hard carbides included in the material. The main recommendations for finishing turning in Haynes 282 include the use of carbide tools, low cutting speeds, low depth of pass, and the use of cutting fluids. However, because of the growing interest in sustainable processes and cost reduction, dry machining is considered to be one of the best techniques for material removal. During the machining of Haynes 282, at both the finishing and roughing turning, cemented carbide inserts are most commonly used and are recommended all over the industry. This paper deals with the machining of Haynes 282 by means of coated carbide tools cutting fluids (dry condition). Different cutting speeds and feeds were tested to quantify the cutting forces, quality of surface, wear progression, and end of tool life. Tool life values similar to those obtained with a lubricant under similar conditions in other studies have been obtained for the most favorable conditions in dry environments.This research was funded by the Ministry of Economy, Industry, and Competitiveness, and the FEDER program, grant number DPI2017-89197-C2-1-R

Influence of cutting parameters on tool wear and hole quality in composite aerospace components drilling

Composite Fiber Reinforced Plastics (CFRP) are characterized by their outstanding mechanical properties combined with reduced density and good resistance to corrosion and fatigue which make them suitable for aerospace components. During assembly procedures, one shoot drilling operations, usually including countersinking cycle, are required to minimize positional errors, enhance tight tolerances and reduce process time. Countersink drill bits were tested on CFRP test specimens, representative of aircraft components. Along testing, tool wear was monitored with an optical microscope to track its evolution and determine the dominant wear mechanism. On the other hand, hole quality was evaluated since tool life criterion is based on the assessment of machined surface quality. The influence of cutting speed and feed was analyzed with the objective of looking for extended tool life and more productive cutting parameters. The information gathered from monitoring tool wear and inspecting hole quality can be used for the enhancement of CFRP drilling and the improvement of the manufacturing process competitiveness, in terms of production cost and time.The authors acknowledge the financial support to AIRBUS DEFENCE AND SPACE through the project DRILLING PROCESSES IMPROVEMENT FOR MULTI MATERIAL CFRP-AL-TI STACKS and to the Ministry of Economy and Competitiveness of Spain through the grant with reference PTA2015-10741-I

Analysis of orthogonal cutting of biocomposites

The use of 100% biodegradable composites in the industry is increasing significantly over the years, mainly due to their excellent properties as well as to the growing ecologic concern. However, after their manufacture, the composite pieces do not always have the final shape, requiring subsequent processing operations, usually drilling and trimming. The performance of cutting processes on fully biodegradable composites are often limited by induced damage as fraying and delamination. This type of phenomena is related, among others, with the cutting parameters and geometries of the tool. Orthogonal cutting is a simplified process that could help in the understanding of damage mechanisms, it is a well-known technique in traditional composites but its use in biocomposites is an almost unexplored field. This work focuses on flax/PLA 100% biodegradable woven composites. The specimens have been manufactured with different angles of orientation, ranging from 0° to 60°, being subjected to orthogonal cutting in a special machine developed for that purpose that allows to develop cutting tests with linear displacement at high speeds. Damage extension, failure modes, and cutting forces are analyzed allowing the extraction of important experimental information.Authors gratefully acknowledges the financial support to the Ministry of Economy and Competitiveness of Spain and FEDER program through the project DPI2017-89197-C2-1-R

Influence of special tool geometry in drilling woven CFRPs materials

Machining processes of Carbon Fiber Reinforced Polymer (CFRP) are commonly required in order to achieve final assembly specifications. Despite the good mechanical properties of this kind of materials, they are hard to be machined due to the presence of hard particles; delamination, fiber pull-out and matrix thermal degradation are usually observed during its machining. Drilling operations are required before mechanical joining of the CFRP components. The actual interest in reducing delamination rests in the fact that it is the most serious damage found during drilling. In this work, a comparative study of three special geometries under different cutting conditions is presented. Thrust force and torque were monitoring during drilling tests and delamination extension was quantified. Results showed that a good drill tip geometry and feed rate selection is fundamental to reduce delamination damages.The funding received from the Ministry of Economy and Competitiveness of Spain under the project DPI2011-25999 and FPI subprogram with the reference BES-2012-055162 is highly appreciated