Aeronautical Parts Research Articles

Applicability of Short Carbon Fiber technology to aeronautical structural parts of low responsibility

The development of structural parts optimized in weight and cost has always been a key aspect in the aeronautical industry. Nevertheless, these premises also appears in other industries. A specific study focused on the automative industry showed the possibility of re-studying a technology analyzed in the past: Short Carbon Fiber injection. The technology offered low recurring costs, high rate possibilities and reliable repetitivity of the processes. Based on these statements, aeronautical parts from the Horizontal Tail Plane (THS) with low structural responsibility were defined as target options. After defining the scope, different engineering and manufacturing studies were performed. The conclusions from both investigations, together with weight and cost estimations, confirmed the potential application of the technology for a present and future implementation. The previous project was included in the project FACTORIA, funded by the Ministerio de Economía y Competitividad, by means of the Centro Tecnológico Industrial (CDTI), in the Strategic Programme CIEN 2016.

Graphene for Anti-icing

Aeronautical sector, like many others, is trying to benefit from exceptional properties of graphene as soon as possible (low density, unique electrical, thermal, optical, mechanical properties…). In fact composite airframe enhancement by graphene related materials is part of the biggest European research project, the Graphene Flagship, which is trying to bring graphene from lab to society. Then, within this context, a first high potential application of graphene in aeronautical composite structure has been selected by Airbus: de- / anti-icing system. The graphene concept studied for anti-icing application is an electro-thermal system, where heat is generated by applying electrical voltage by Joule effect. Key work performed in this study was focused on following aspects: identification of use cases and requirements, selection of graphene based related material, integration concepts within carbon fiber reinforced polymers (CFRP), demonstration or proof of concept through manufacturing and functionality tests, and, finally, preliminary value and risk assessment of solution. As per work performed, it can be concluded that the potential of proposed innovative graphene based electro-thermal system for composite aeronautical part anti-icing function has been preliminary proven and demonstrated. However, there is still a long way to increase the maturity, scale-up the concept, demonstrate cost saving and benefits versus other solutions, as well as to overcome the identified risks.

In-situ measurement of machining part deflection with Digital Image Correlation

In the context of the aeronautics industry, aluminum alloy structural parts are manufactured in several stages, from forming processes and heat treatments to final machining. Some process steps may generate residual stresses. Thus, material removal during machining releases these residual stresses, which induces part deformation. Such deformations can lead to geometric nonconformity of the machined part. It is therefore essential to control this phenomenon. Due to the variability in residual stress distribution in each raw part, the modeling approaches must to be coupled with experimental measurements. This article thus aims to define a reliable experimental technique for measuring in-plane deformation of large aeronautical parts during their machining. The backbone of the technique relies on Digital Image Correlation (DIC), which enables the contactless measurement of part deformation during machining. Moreover, DIC provides a full-field measurement and a direct evaluation of part deformations. This work discusses more specifically problems related to the use of DIC during machining, the latter corresponding to a particularly harsh environment. Indeed, optical systems undergo undesirable movement and metal chips hide areas of the observed part. These unwanted events corrupt the results. In order to control these problems and consistently apply DIC part deformation measurement during machining, specific methods are proposed in this paper. Finally, DIC measurements are performed during the same machining sequence of two parts. The excellent agreement of the two measurements confirms the reliability of the technique. Finally, measurements are discussed, emphasizing the contribution they provide to the machining community.

Wire Arc Additive Manufacturing Process for Topologically Optimized Aeronautical Fixtures.

Additive manufacturing (AM) technologies in metallic materials have experienced significant growth over recent decades. Concepts such as design for additive manufacturing have gained great relevance, due to their flexibility and capacity to generate complex geometries with AM technologies. These new design paradigms make it possible to save on material costs oriented toward more sustainable and green manufacturing. On the one hand, the high deposition rates of wire arc additive manufacturing (WAAM) stand out among the AM technologies, but on the other hand, WAAM is not as flexible when it comes to generating complex geometries. A methodology is presented in this study for the topological optimization of an aeronautical part and its adaptation, by means of computer aided manufacturing, for WAAM manufacturing of aeronautical tooling with the objective of producing a lighter part in a more sustainable manner.

Modelling and analysis of the effect of nonlinear time-varying contact deformation on flexible precision grinding process

Belt grinding is gradually considered to be an effective method for precision machining those aeronautical parts with weak rigidity and complex surface. However, the characteristic of flexible grinding makes it difficult to precisely control the machining process and hinders its further development. In this paper, a series of detailed numerical studies are conducted to study the effect of complex contact deformation on the flexible precision grinding operation of titanium alloy. The flexible process of belt grinding was simulated numerically, and the spatial trajectory equation of abrasive grains in nonlinear time-varying contact state was obtained. Subsequently, the finite element simulation modelling and analysis of a single abrasive grain cutting titanium alloy workpiece under three different boundary conditions (no contact deformation, sinusoidal transformation contact deformation, nonlinear time-varying contact deformation) were performed. The characteristics of grinding morphology and the variation trends of grinding force obtained by simulation were almost consistent with the results of scratch experiments. On this basis, a series of orthogonal simulation studies were conducted to obtain the optimal processing parameters of belt grinding, in consideration of the changes in the spatial positions of abrasive grains caused by the time-varying contact deformation. The above research provides a theoretical framework for investigating the effect of nonlinear time-varying contact deformation, which is of great significance to reveal the mechanism of belt flexible grinding and expand its application in precision machining of aviation parts.

Example-based Reasoning for Deformation Design of Typical Aerospace Parts

To address the tedious process of modelling typical aviation parts, it is difficult to achieve rapid modelling phenomenon. Component Application Architecture, or CAA, is used to develop CATIA. It proposes a deformation design method for typical aeronautical parts based on example reasoning. A library of typical part models is first created, then similar models are retrieved by instance retrieval and matching, followed by retrieval of similar models. The next step is to analyze the target design model and the retrieved 3D model, and then make changes to its features to complete the deformation design. The results show that the deformation design method can quickly and accurately create 3D models, improve design efficiency and quality, and provide an effective guarantee for the processing and manufacturing of typical aeronautical parts.

Influence of cutting speed and tool geometry on form and machine tapping of carbon fibre-reinforced composites

Fibre-reinforced composites are widely applied in structural parts due to their high specific mechanical properties. The use of self-tapping screws in aerospace applications has been considered a controversial joining technique for years, owing to the risk of distortion and cracking of the composite material during fastening. The typical mechanical component used to assembly aeronautic parts is the rivet. Thus, the study of alternative components to produce joints and both their application and performance is necessary. This work investigates the threading processes by the forming and machining in carbon fibre-reinforced composites. Three taps were used in this work, the first one based on form tapping and the other two related to machine tapping. The results indicated that in the two tapping processes, the mechanisms involved consisted of a combination of plastic deformation, shearing, and bending failure. In general, the speed of 28 m/min provides minimum thrust force, 166.5% lower than the 10 m/min speed, in machining process, while the temperature is reduced by 53.9%. The speed/tool of 28 m/min and MH-tap (tapping process) reveals the most efficiently interaction. Filling rates of the thread profiles were acceptable for practical engineering applications, mainly when high speeds were applied. The results demonstrated that threaded workpieces could be applied to aeronautics components with limitations; nevertheless, additional studies should be carried out to determine the application range.

Wire arc additive manufacturing of an aeronautic fitting with different metal alloys: From the design to the part

• WAAM manufacturing steps from a CAD model to the final geometry of the part. • Optimal deposition parameters and mechanical properties for four metallic alloys. • The WAAM process reduces the component buy-to-fly ratio, rationalizing resource use. • A monitoring method is developed to obtain a unique fingerprint of each part. • A matrix manufacturing strategy is used to increase the productivity of the process. WAAM (Wire Arc Additive Manufacturing), an additive manufacturing technology with high deposition rates, can produce metallic components, layer by layer, from different alloys, yielding high mechanical performance. Customized AM machines with monitoring and control systems are necessary to facilitate automated manufacture of different types of components through WAAM technology. In this paper, a methodology for the validation of additive manufacturing is presented as an alternative to industrial machining, for the manufacture of medium-sized aeronautical parts. To begin with, the most appropriate welding technology and adequate parameters for four different metal alloys are selected. Successively, a characterization wall is manufactured with each of the four metal alloys, for metallographic and mechanical characterization, concluding that the material deposited utilizing the WAAM process is adequate for the fabrication of medium-sized aeronautical parts. Consecutively, machine paths are defined under conditions that consume the least possible amount of material for the manufacturing of the aeronautical part. Several aspects -manufacturing times, deposition rate, material efficiency ratio- of each component are then analyzed, relating them to the properties obtained in each alloy. The manufacturing process is supervised and controlled by online monitoring. The novelty of this paper consists in establishing unique dataset for each component that is defined as a unique additive manufacturing Fingerprint as baseline for in process defect detection. Finally, the unique contribution of stablishing a matrix-strategy for the manufacture of multiple parts with the same tooling to optimize the use of resources is presented.

Wire arc additive manufacturing Ti6Al4V aeronautical parts using plasma arc welding: Analysis of heat-treatment processes in different atmospheres

PAW (Plasma Arc Welding), a WAAM (Wire Arc Additive Manufacturing) technology with high deposition rates, can produce metallic components, layer by layer, of varied sizes, from different alloys, yielding high mechanical performance. Two Ti6Al4V walls are manufactured in an inert argon atmosphere using WAAM-PAW to analyze the deposition process in terms of growth in height per layer, deposition process temperature, and cooling times. The properties of the walls are compared with the values obtained from a thermo-mechanical simulation and both the microstructural and mechanical properties of the annealed WAAM-PAW wall are studied. Moreover, the effect of the media on the oxidation layer and on the mechanical properties are also analyzed throughout the heat treatment process, as well as the microstructure of Ti6Al4V. Stable deposition rates were achieved for a high deposition ratio of Ti6Al4V at 2 kg/h, restricting the oxygen levels to under 100 ppm. No significant differences were found in either the microstructural or the mechanical properties following heat treatments in a vacuum, in air or in argon. All the heat-treated samples met the AMS4928 standard for Yield Strength (YS) and Ultimate Tensile Strength (UTS).

Vibration signal-based chatter identification for milling of thin-walled structure

In high speed milling aeronautical part, tool condition monitoring (TCM) is very important, because it is prone to get a chatter owing to the low stiffness of thin-walled structures. And the TCM is key technology for automated machining. In this paper, aiming to chatter monitoring in thin-walled structure milling, a variational mode decomposition – energy distribution (VMD-ED) method is proposed to improve the identification accuracy. And a moving average root mean square – mean value (MARMS-MV) identification method and a variational mode decomposition – energy entropy (VMD-EE) identification method are also tested. Identification accuracy and computing time of the three methods are compared. The vibration signals collected from the spindle and worktable are also contrasted. The conducted experimental study shows that, the proposed VMD-ED method offers an identification method for chatter monitoring with greater sensitivity, better stability and less computing time, and mounting the vibration sensor on worktable is better than spindle for a chatter monitoring system.

A new method of design for additive manufacturing including machining constraints

Metal additive manufacturing is a major field of study and innovation. In almost every industry, a lot of effort goes into modelizing and optimizing designs in order to minimize global mass. In this context, despite all efforts, metal additive manufacturing, especially SLM, still produces parts generally considered as raw parts with some surfaces still needing to be machined in order to obtain the required geometrical quality. Despite sometimes, great complexity and cost, the machining stage is never taken into account in the design process, especially during the topological optimization approach. This paper proposes a new design for the additive manufacturing method in order to optimize the design stage and takes into account topological optimization machining as well as geometrical and mechanical constraints. The machining constraints are initially integrated as forces and functional surfaces, but also as the result of a topological optimization loop, in order to find the best possiblemounting solution for machining. It is shown on a typical aeronautic part that machining forcesmay be indeed the greatest forces during the part’s lifetime. Using two different topological optimization software, i.e. Inspire and Abaqus Tosca, the paper illustrates that it is possible to take into account most of the machining constraints to only slightly modify the initial design and thus simplify the machining stage and reduce cost and possible failure during machining.

Control and Mechanism Analysis of Serrated Chip Formation in High Speed Machining of Aluminum Alloy 7050-T7451

Aluminum alloy 7050-T7451 is widely used in aeronautical large structural parts, and high speed cutting is often used in machining. The serrated chip is a critical state for chip formation in high speed cutting, and its formation and control mechanism are of great significance for actual machining. To study the chip formation of high speed cutting aluminum alloy 7050-T7451, the chips at different cutting speeds are obtained by high speed cutting experiments. Combined with microscopic observation, the chip shape evolution, chip localization fracture process and mechanism of different cutting speeds are analyzed. The morphological evolution of chips and the mechanism of chip breaking during high speed cutting of aluminum alloy are revealed. According to the machined surface of the chip root and the angle of the chip, the formation mechanism of the curl radius formed by the chip is analyzed. The critical cutting speed of plastic-brittle transformation of aluminum alloy 7050-T7451 in high speed cutting is obtained by studying the critical condition for strip-to-serration transition of chip morphology.

Electromagnetic flanging: from elementary geometries to aeronautical components

Aeronautical companies are manufacturing many components of small (less than 200 mm) and medium (between 200 mm and 1000 mm) sizes by flexforming. In order to diversify the production facilities of these components, these companies are interested in evaluating the ability of electromagnetic forming processes to produce small parts. This paper describes the design of a set of experiments of electromagnetic flanging with some elementary geometries, whose purpose is to enlighten several geometrical defect issues encountered, and to propose some solutions. A particular attention is first paid to the straight flange, which allows to analyse, understand and then correct the main defect issues that can occur during the forming. The proposed solutions consist of some particular design of the inductors and the dies, in order to adjust the profile of the loading and the kinematics of bending of the flange to obtain the desired final geometry. Next, curved flanges are addressed, and finally the forming of a model aeronautical part combining several elementary geometries of flange is described. Promising results are obtained. In these experiments, sheets of 1, 2 and 1.6 mm thickness made of aluminium alloy 2024-T4 and sheets of 0.5 mm thickness made of aluminium alloy 1050 are used. The geometric dispersions and the material soundness of the parts have been controlled. Besides, a numerical model of the model aeronautical part has been developed in the LS-DYNA computing environment, whose final purpose is to facilitate the design of the coil. The results of the numerical simulations are shown to be qualitatively in accordance with experimental results.

Effect of cutting parameters and tool rake angle on the chip formation and adiabatic shear characteristics in machining Ti-6Al-4V titanium alloy

Ti-6Al-4V titanium alloy is widely used in aeronautical parts and the high-efficiency machining and manufacturing process is surely a challenging work. The cutting parameters’ proper selection and tool geometric angles’ adoption will affect the material removal process in terms of chip formation and machined surface formation processes. In this paper, Abaqus finite element software was utilized to model and simulate the Ti-6Al-4V titanium alloy cutting process. The setting and selection of the constitutive model, material failure criterion, friction attribute, and heat transfer model make sure that the simulation is more in line with the actual cutting process. The correctness of the simulation model is verified by comparing the cutting forces and chip morphological characteristics obtained by the simulation with the experiments. Then, the effect of cutting parameters and tool rake angle on the chip formation and analyses of the adiabatic shear banding process was investigated, by using the machining simulation tests with different tool rake angles and cutting speeds. Results illustrate that the chip segmentation degree increases with the increase of cutting speed and feed rate, while it decreases with the increase in rake angle. The adiabatic shear-banding chip formation mechanisms were revealed by analyzing the relationship between shear strain, shear stress, chip segmentation degree, and high-temperature shear zone in undeformed plot contours. The serrated chip formation process when machining titanium alloy accompanies with the dramatic changes of shear strain and stress in adiabatic shear banding.

Determination of wear resistance and wear mechanisms of HVAF coat-ings based on Ni-Al composition depending on the technological modes of their deposition

Presented studies are related to the spheres of aviation and machine-building. World aviation technology experience has accumulated a huge amount of statistical material on the failure airborne systems and ground equipment due to the increased level of parts wear. That is why the issue of research and improvement of anti-wear properties aeronautical parts is one the components when considering the priority directions of ensuring the reliability of operation motor vehicles and friction units. The Ni3Al coating has been deposited on the medium carbon steel using high velocity air fuel deposition. It has been established that it is very sensible for modes of coating deposition and different chemical phenomenon have been detected. The structure of the obtained coating has been thoroughly researched on the electronic microscope. The obtained coating has been tested on the friction bench modeling the fretting process that is taking place in the couple of locking devices of self-propelled passengers stairs. The coating has also corrosion protection. The friction surfaces have been investigated on the electronic microscope and the wear mechanisms have been established. The optimal modes of the HVAF coting deposition from the viewpoint of wear resistance have been detected

Comparison of AlSi7Mg0.6 alloy obtained by selective laser melting and investment casting processes: Microstructure and mechanical properties in as-built/as-cast and heat-treated conditions

AlSi7Mg0.6 alloy is widely used in the automotive and aeronautical industries, and metal additive manufacturing (AM) is a breakthrough technology that motivates foundry companies to explore its potential in these industries; however, there is no deep knowledge of the mechanical properties and their relationship to microstructure in parts obtained by selective laser melting (SLM), as there is for parts obtained by casting. In this work, a comparison of the microstructure and mechanical properties of AlSi7Mg0.6 alloy obtained by SLM and investment casting processes was made. The mechanical properties of tensile specimens processed by both technologies were evaluated by uniaxial tensile tests and microhardness measurements in as-built/as-cast and heat-treated conditions with different build orientations in the case of SLM. An advanced characterization of the microstructure by field emission scanning electron microscopy (FESEM) and x-ray diffraction (XRD) analysis was also performed. After analyzing the microstructure and mechanical properties obtained with different heat treatments, the strengthening mechanisms of the two processes were identified. It is possible to obtain improved mechanical properties with SLM processing, exceeding the typical values required for aeronautical parts obtained in investment casting heat-treated (T6), and the ductility is satisfactory. Direct aging after SLM processing can effectively strengthen the AlSi7Mg0.6 alloy and is the more effective way to improve the as-built mechanical properties.

Development Trend of NC Machining Accuracy Control Technology for Aeronautical Structural Parts

High-performance five-axis computer numerical control machine tools are widely used in the processing of Aeronautical Structural parts. With the increase of service life, the precision of CNC machine tools equipped by aeronautical manufacturing enterprises is declining day by day, while the new generation of aircraft structural parts are developing towards integration, large-scale, complexity, thin-walled and lightweight. It is very easy to produce dimension overshoot and surface quality defects due to unstable processing technology. The machining accuracy of aircraft structural parts is also affected by complex factors such as cutting load, cutting stability, tool error, workpiece deformation, fixture deformation, etc. Because of the complexity of structure and characteristics of Aeronautical Structural parts, the consistency and stability of cutting process are poor. It is easy to cause machining accuracy problems due to tool wear, breakage and cutting chatter. Relevant scholars have carried out a lot of basic research on NC machining accuracy control and achieved fruitful results, but the research on NC machining accuracy control of Aeronautical structural parts is still less. This paper elaborates from three aspects: error modeling method of NC machine tools, error compensation method, prediction and control of machining accuracy, and combines the characteristics of Aeronautical Structural parts, the development trend and demand of NC machining accuracy control technology are put forward.

From the fatigue properties of Ti6Al4V produced by ALM selective laser melting process to the mechanical design of an aeronautical part

Selective laser melting SLM is investigated through a study of redesign and characterization of an aeronautic part made of titanium Ti6Al4V. The part must ensure an excellent static and fatigue behaviour. The methodology developed hereby follows 3 main steps: First, the influence of laser power, laser speed and hatch distance on the amount/rate of porosity is performed to define optimized process parameters. Then, the influence of building process strategy, i.e. building direction or as-built surface roughness on the static and fatigue behaviour are studied and understood by following a vast experimental campaign. Obtained properties are finally used in a topology optimization study to find the best compromise between part weight and fatigue behavior . 3 prototypes of simulated part are produced and then characterized. Fatigue tests are conducted on the component and confirm the fatigue design proposed. Obtained results are encouraging and illustrate the fatigue design optimization of a complex Additive Manufacturing component.

Dynamic thermal behavior and thermal error prediction of spindle due to periodic jump motions in a large precision die-sinking EDM machine

Thermal error which has been widely studied in cutting machine tools, was ignored in the EDM machines in most cases, since there is usually no high-speed rotation for spindles. However, for large die-sinking EDM machines, due to heavy load of drive system and long processing cycle of large aeronautical parts, thermal error induced by jump motion has seriously impaired the machining accuracy and gradually been recognized. In this paper, the dynamic thermal behavior of spindle induced by periodic jump motions in large precision die-sinking EDM machine was studied for the first time. Noted that the Z-axis base and column show obvious temperature rise and the thermal error in Y direction is the largest, which is about 6.5 and 5 times compared with that in X and Z directions. Based on this, an efficient thermal error prediction model was presented. Thermal sensitive points were picked out through fuzzy clustering and correlation theory, taken as inputs of radial basis function (RBF) neural network to guarantee the accuracy. As a result, the prediction accuracy in X, Y and Z directions are 95.2 %, 92.5 % and 94.4 %, respectively. Finally, the effect of jump period on spindle thermal behavior was investigated, and suggestions for optimizing jump motion parameters were proposed to further improve the machining accuracy of large EDM machines.

Thermo-mechanical simulation of track development in the Laser Beam Melting process - Effect of laser-metal interaction

RésuméInterest has recently emerged for the manufacture of aeronautical parts by Laser Beam Melting (LBM) additive process. This energy efficient process can for instance be used to build complex geometries, which cannot be made with traditional processes. However, complex phenomena occur during powder melting and track development : vaporisation phenomena influence laser-matter interaction by creating metal vapours that are responsible for the reduction of absorbed energy. The recoil pressure generated by the vaporisation counteracts the surface tension between the melt pool and the inert gas, also inducing liquid instabilities. The study of laser-matter interaction and induced phenomena can help understand the origin of defects such as porosities or cracks. In this approach, a level-set modelling of the LBM process at a mesoscopic scale is proposed to follow melt pool evolution and track development during build. A volume heat source model is used for laser/powder interaction considering the material absorption coefficient. A surface heat source is used to take into account the high laser energy absorption by dense metal alloys. An energy solver is coupled with thermodynamic database and pre-determined solidification path. Shrinkage during consolidation from powder to liquid and compact medium is modelled by a compressible Newtonian constitutive law. An automatic remeshing adaptation is also used to save time and avoid high computational cost. In the future, the computation of multiple beads or the build of a wall in a context of lattice structures will have to be considered.