Aeronautical Parts Research Articles

Subcutaneous coding via laser directed energy deposition (DED-LB) for unalterable component identification

Part identification has become a priority in manufacturing, especially when it comes to the additive manufacturing (AM) industry, where the counterfeit printing of almost any digitalized component is possible. As a means of avoiding forgery, the development of non-detectable labels, or digital passports is necessary. In the present work, a novel methodology for printing subcutaneous coding on aeronautical parts is proposed thanks to the multimaterial capabilities of the laser based directed energy deposition (DED-LB). The coding is based on embedding a dot pattern of a high-density alloy on a small area of a lower density component, which once covered and finished generates a pattern only visible by X-ray imagining. The viability of the proposed methodology is proven by embedding WC particles on a Ti6Al4V substrate. Firstly, the most relevant process parameters are optimized to ensure a sharp and a readable code, and their geometry is analysed by means of industrial Computed Tomography (CT). Also, the metallurgical quality and chemical composition of the generated dots is evaluated by Scanning Electron Microscope (SEM). Finally, a demonstrator part is fabricated with a hidden code. The code readability and the mechanical properties are tested to ensure the feasibility of the developed methodology.

Novel sensorized additive manufacturing-based enlighted tooling concepts for aeronautical parts

This paper presents lightweight tooling concepts based on additive manufacturing, with the aim of developing advanced tooling systems as well as installing sensors for real-time monitoring and control during the anchoring and manufacturing of aeronautical parts. Leveraging additive manufacturing techniques in the production of tooling yields benefits in manufacturing flexibility and material usage. These concepts transform traditional tooling systems into active, intelligent tools, improving the manufacturing process and part quality. Integrated sensors measure variables such as displacement, humidity and temperature allowing data analysis and correlation with process quality variables such as accuracy errors, tolerances achieved and surface finish. In addition to sensor integration, additive manufacturing by directed energy arc and wire deposition (DED-arc) has been selected for part manufacturing. The research includes the mechanical characterisation of the material and the microstructure of the material once manufactured by DED-arc. Design for additive manufacturing" principles guide the design process to effectively exploit the capabilities of DED-arc. These turrets, equipped with sensors, allow real-time monitoring and control of turret deformation during clamping and manufacturing of aeronautical parts. As a first step, deformation monitoring is carried out within the defined tolerance of ± 0.15, which allows a control point to be established in the turret. Future analysis of the sensor data will allow correlations with process quality variables to be established. Remarkably, the optimised version of the turret after applying DED technology weighed only 2.2 kg, significantly lighter than the original 6 kg version. Additive manufacturing and the use of lightweight structures for fixture fabrication, followed by the addition of sensors, provide valuable information and control, improving process efficiency and part quality. This research contributes to the development of intelligent and efficient tool systems for aeronautical applications.

A self-adaptive agent for flexible posture planning in robotic milling system

In recent years, industrial robots are widely used in the milling processes of the fundamental components such as aeronautic parts, aerospace cabins and blades on the marine propellers of the worships, because of their flexible structure, large operating space, and robust capacity of rapid reconfiguration. Along with the robotic machining process, multiple types of geometrical and physical constraints display the time-varying characteristics, which are difficult to be considered simultaneously by the traditional static planning methods on the robotic milling posture. Therefore, a deep reinforcement learning (DRL) enhanced virtual repulsive potential field flexible model is proposed for the robotic milling posture dynamic planning. The preliminary planning of static milling posture is realized based on the fixed setting of the virtual modal parameters in the posture planning model, which is treated as a theory preparation for training the deep reinforcement learning agent. To develop the static planning model, multiple constraints are established by considering the performances of geometric, kinematic and machining precision simultaneously. Furthermore, a reward function is constructed for the dynamic agent, comprehensively combining the long and short reward benefits in nonlinear correlation with virtual repulsive forces. By taking the virtual modal parameters as the action space of the dynamic agent, a DRL enhanced agent VRPF-SAC is created and trained under the dynamic milling environment from virtual repulsive planning field. Four tasks of large size robotic milling simulations and experiments are designed and developed to validate the effectiveness of the flexible planning model. In comparison with the static model, the flexible planning model displays the excellent global effects covering the kinematic, and precision performance, with 65.78 %, 72.04 %, and 70.25 % reduction in velocity, acceleration, and jerk of robotic joints, and ensuring the effective precision performance from −0.365 to 0.283 mm of large size workpiece with large curvature changes. The proposed flexible posture planning architecture can provide a basic for robotic dynamic milling of core parts with large size, narrow space and sharp curvatures of the aeronautic parts, aerospace cabins and worship propellers.

Multi-sensor-based process monitoring and quality assessment during laser forming of novel titanium foam to prevent cellular structure damage

Titanium foam finds its application in different fields like battery electrodes, heat exchangers, biological prosthetics, and lightweight structures for aeronautical parts. However, the inherent property of the foam to fail during mechanical loading conditions poses a challenge in providing final shape to these materials for practical applications. The present work investigates forming of Titanium foam (Ti Foam) using inline process monitoring for achieving controlled foam deformation while maintaining its quality without failure. Infrared (IR) pyrometer and laser-based displacement sensor were used to monitor the foam deformation behavior and thermal signature. The monitoring data were used to understand the process mechanism of laser forming. The bending mechanism within the foam was analysed with respect to solid sheet bending process. The correlation of the achieved bending angles, was attempted with the process parameters for surface, microstructural, elemental, and phase transformation. A critical analysis of Ti foam behavior, like surface melting, in situ oxidation, phase transformation, and formation of nano-structures on foam surface was addressed based on process parameter combinations. Micro-computed tomography (μCT) was carried out to investigate the pore deformation mechanism. Metallurgical characterisations for foam surface and phase analysis were carried out using X-ray photoelectron spectroscopy (XPS) and tunneling electron microscopy (TEM) to determine the chemical and crystallographic states of the laser-formed surface.

Experimental investigation of tool feed rate and machining strategy on surface roughness in flat end milling of Nickel-Iron alloy Supra50

The Nickel-Iron alloy Supra50 is one of the commonly used materials for manufacturing aeronautical parts and is resistant to excessive thermal stress. Due to its low coefficient of expansion, this material can guarantee dimensional stability at high temperatures while also offering mechanical characteristics like those of stainless steel. However, several works in the literature demonstrate that the Nickel-Iron alloy Supra50 has low machinability due to low thermal conductivity and work hardening. These main qualities, with its magnetic characteristics, qualified it for the manufacture of components for solenoid valves in aircraft. Despite its performance, obtaining Supra50 parts by machining presents difficulties. Indeed, faced with tight dimensional and geometric tolerances, manufacturers must invest in means and methods that converge to an agreement between cost and quality that ensures the efficiency of the machining process. This research work aims to analyze the effect of machining strategies and the tool feed rate on surface roughness by using an experimental approach in a Fe-Ni-based alloy-Supra50 surfacing operation with a flat end-mill tool. This study addresses a gap in the literature, focusing on the unique challenges posed by Supra 50 machining. It was demonstrated that the feed rate strongly affects surface roughness. In other hand, it was demonstrated that the machining strategy sweep gives the minimum of arithmetic mean height of the surface (Sa), compared to other analyzed machining strategies, such as mono-directional sweep and spiral sweep. All experimental results were demonstrated in sequence with other literature works on Fe-Ni-based alloy machining.

Improving accuracy reconstruction of parts through a capability study: A methodology for X-ray Computed Tomography Robotic Cell

Aeronautical performance is enhanced by increasingly complex and lightweight composite parts. The improvement of their manufacturing must ensure the quality measured by Non-Destructive Testing. To evaluate the health of aeronautical parts that are a few meters long, we built a high dimensional robotic cell including two industrial robots positioned on 5-meter-tracks equipped with X-ray Computed Tomography devices. Our main objective is to reconstruct the interior of the parts and detect any anomaly that may have occurred during life cycle or manufacturing (such as porosity or inclusions). In this way, the objective is to present a methodology, firstly, to evaluate the raw process capability and secondly, to assess the improved process capability. The raw process capability uses geometrical identification and we demonstrate that without proper identification, some defects can remain hidden. Three strategies are then developed. The first one involves improving the robot behavior model, which takes into account a thermo-geometrical model, including backlash compensation. Due to possible repositioning problems and to ensure the correct knowledge of the source with respect to the detector, the second strategy involves a real-time test phantom located on the detector named the comb prototype. Finally, a large-sized steel balls phantom is designed to allow a calibration in the full workspace of the robots. This phantom is also used to accurately determine the axis of the rotary horizontal-axis support on which the large parts to be controlled are fixed. We demonstrate that such an architecture, for reconstructing a perfect sphere, leads to an initial mean radius error of 0.05 mm which we improve to 0.016-0.017 mm with our methodology.

About the high temperature fatigue performance of thermoplastic-based composite laminates for aeronautical applications

The use of thermoplastic-based composites for applications in high temperature aeronautical parts is often considered contradictory with respect to the softening of the matrix and the subsequent degradation of their mechanical properties, especially when service temperature T exceeds glass transition temperature. This paper examines the fatigue performance of unidirectional (UD) carbon fibers reinforced PolyArylEtherKetone (PAEK) laminates subjected to tension-tension fatigue at different testing temperatures (Room Temperature, 120°C and 170°C). Laminates consisting of different portions of plies in 0°/+45°/−45°/90° orientations have been investigated to evaluate the contribution of each ply orientation to the fatigue performance in terms of S-N diagrams. From the evolution of life span as a function of applied stress, it appears that the influence of temperature on fatigue behaviour of C/PAEK composites depends on the temperature conditions. 0° plies behaviour is known to be temperature-independent as is dominated by the mechanical behaviour of UD carbon fibers. It is expected to reflect on the fatigue behaviour at high temperature. From the obtained results, one may conclude that the 0° plies primarily bear the tensile load in fatigue (47-67-91% in SOFT, QI and HARD laminates, respectively) and therefore dominate the fatigue behaviour. The deformation mechanisms in +/−45° plies (localized plastic-viscoplastic dissipative behaviors) favoured at temperatures higher than Tg (e.g. 143°C) are limited by the low deformation of 0° plies. SOFT (12% of 0° plies) and QI (25% of 0° plies) laminates have similar relative fatigue performance. Unexpectedly, the fatigue performance of HARD laminates (about 62% of 0° plies) is improved at T>Tg at high stress levels. A simple temperature-dependent analytical model was used to successfully predict the fatigue life of C/PAEK laminates with different stacking sequences.

Experimental optimization of cutting conditions to improve surface roughness of aeronautic parts made of Fe-Ni alloys

Fe-Ni alloys present excellent heat resistance properties while preserving their rigidity, strength, toughness, and dimensional stability at high temperatures. As a result, they are widely used in manufacturing aerospace or aeronautic parts where the operating temperature is very close to their melting temperature. Supra50 (named in the Unified Numbering System UNS as K94800) is a Fe-Ni alloy currently used in space and aviation industries, which confirmed its efficiency. However, improving the surface roughness of this high-precision part is challenging to overcome in manufacturing. The main objective of this study is to carry out an experiment based on a factorial plan and aims to predict the surface roughness of Supra50 parts as a function of cutting parameters in a milling process. Results show that the best combination of cutting parameters, giving the best surface roughness, is obtained at the lowest value of feed per tooth. Results also show that cutting speed and radial depth have little effect on roughness quality.

INFLUENCIA DEL ÁNGULO DE POSICIÓN EN EL DISEÑO DEL ROMPEVIRUTAS: ESTUDIO DE HERRAMIENTAS DE TORNEADO DINÁMICO Y DE ALTO AVANCE EN INCONEL® 718

Dynamic turning is a recent technology that allows inserts with different cutting edges to be used and the side cutting edge angle to be modified by controlled spindle rotation and synchronised variation of the cutting parameters. This makes it possible to eliminate downtime by reducing tool changes. Chip breaking is a relevant fact in the turning of aeronautical parts, as it allows a higher heat dissipation performance when working with heat-resistant superalloys, materials that degrade inserts rapidly. An initial study has been carried out, using different fixed side cutting edge angles, to test the chipbreaker performance of an experimental dynamic turning insert in order to adapt its design to the machining of aeronautical components, obtaining that, although the cutting performance is good, the chipbreaker does not perform correctly in finishing conditions, and therefore it must be redesigned by reducing its distance to the cutting edge. Keywords: dynamic turning; high feed; aerospace superalloy; chipbreaker, side cutting edge angle.

Manufacturing time estimator based on kinematic and thermal considerations: application to WAAM process

Metal additive manufacturing has been pointed as the answer to reduce manufacturing time and cost for aeronautic parts with a high buy to fly ratio. The manufacturability of a part by additive manufacturing depends on important indicators that would allow it to be cost effective. One key indicator is the manufacturing time, which is highly dependent on an important factor: the interlayer time. The interlayer time is the time needed by the material to cool down to a chosen temperature, called interlayer temperature, that allows a new deposition of molten material. The interlayer temperature is defined by using time–temperature-transformation (TTT) diagrams, the final goal being to avoid the appearance of detrimental phases that could lead to a decrease in the material’s mechanical properties. The interlayer temperature is intimately correlated with the cooling curve. The difficulty of predicting the cooling time is due to the influence of the part geometry, the deposition strategy, and the dimensions of the substrate. Their correlation needs to be understood in order to minimize the travel time (ttravel) while ensuring an acceptable material quality. This paper presents a methodology to estimate manufacturing time that combines kinematic and thermal criteria for Wire and Arc Additive Manufacturing (WAAM) process. Application is performed for stainless steel 316L. In this first step toward an advanced manufacturing time estimator, only the first layer attached to the building plate is analyzed from a thermal point of view. The thermal analysis is based on an analytical model enabling the evaluation of the preheating temperature (PhT) in a first approach and providing an adequate framework for the evaluation of cooling curves in a second time. The model includes an accurate description of robot kinematics through the consideration of a realistic travel speed variation along the toolpath. It is used to evaluate an indicator that quantifies the thermal influence of a given deposition strategy. The results show the dependency relationship between manufacturing strategy and inherent thermal gradient and its implications on part production time.

A novel hybrid approach GREG-fuzzy-GA for minimizing work piece temperature during 2.5D milling of Inconel625 super alloy

PurposeMilling is a flexible creation process for the manufacturing of dies and aeronautical parts. While machining thin-walled parts, heat generation during machining essentially affects the accuracy. The workpiece temperature (WT), as well as the responses like material removal rate (MRR) and surface roughness (SR) for input parameters like cutting speed (CS), feed rate (F), depth-of-cut (DOC), step over (SO) and tool diameter (TD), becomes critical for sustaining the accuracy of the thin walls.Design/methodology/approachResponse surface methodology was used to make 46 tests. To convert the multi-character problem into a single-character problem, the weightage was assessed using the entropy approach and the grey relational coefficient (GRC) was determined. To investigate the connection among input parameters and single-objective (GRC), a fuzzy mathematical modelling technique was used. The optimal performance of process parameters was estimated by grey relational entropy grade (GREG)-fuzzy and genetic algorithm (GA) optimization.FindingsSR was found to be a significant process parameter, with CS, feed and DOC, respectively. Similarly, F, DOC and TD were found to be significant process parameters with MRR, respectively, and F, DOC, SO and TD were found to be significant process parameters with WT, respectively. GREG-fuzzy-GA found more suitable for minimizing the WT with the constraint s of SR and MRR and provide maximum desirability of 0.665. The projected and experimental values have a good agreement, with a standard error of 5.85%, and so the responses predicted by the suggested method are better optimized.Originality/valueThe GREG-fuzzy-GA is a new hybrid technique for analysing Inconel625 behaviour during machining in a 2.5D milling process.

Modeling of the shot peening of a nickel alloy with the consideration of both residual stresses and work hardening

Shot peening of turbine disk engines is performed in the aerospace industry in order to enhance fatigue life. This surface enhancement method generates beneficial modifications like superficial compressive residual stresses that are known to delay crack initiation and propagation. In the same way, work hardening is also introduced at the surface of the part during shot peening and can have a significant influence on fatigue crack initiation. Taking this parameter into account in the fatigue design of parts, in addition to the residual stresses, is a real challenge to be the most predictive. One possibility for this is to be able to predict it during the modeling of the shot peening process. In the present work, various peening conditions are considered in order to be able to propose a model able to account for the influence of coverage and Almen intensity on residual stresses and work hardening. The studied material is Inconel 718, commonly used for aeronautical parts. The X-ray diffraction method is used to obtain the in-depth residual stress and work hardening profiles. A three-dimensional numerical model is proposed to predict these quantities. Efforts are made to consider all recent advances in three-dimensional simulation of the process, in terms of coverage assessment, shot and treated part modeling. The numerical results are compared to the experimentally measured residual stresses and work hardening.

Analyses of Key Variables to Industrialize a Multi-Camera System to Guide Robotic Arms

Robotic arms are widely used in sectors such as automotive or assembly logistics due to their flexibility and cost. Other manufacturing sectors would like to take advantage of this technology, however, higher accuracy is required for their purposes. This paper integrated a multi-camera system to achieve the requirements for milling and drilling tasks in aeronautic parts. A closed-loop framework allows the position of the robot’s end-effector to be corrected with respect to a static reference. This is due to the multi-camera system tracking the position of both elements due to the passive targets on their surface. The challenge is to find an auxiliary system to measure these targets with an uncertainty that allows the desired accuracy to be achieved in high volumes (>3 m3). Firstly, in a reduced scenario, a coordinate measuring machine (CMM), a laser tracker (LT), and portable photogrammetry (PP) have been compared following the guidelines from VDI/VDE 2634-part 1. The conclusions allowed us to jump into an industrial scenario and run a similar test with a higher payload than in the laboratory. The article ends with an application example demonstrating the suitability of the solution.

On the effect of coatings and pre-corrosion during fatigue tests of 7075-T6 aluminum alloy monitored with acoustic emission (AE)

Strength hardened aluminum alloys as 7075-T6 al are widely used in aeronautical industry due to their low density and high mechanical properties. Their specific microstructural composition makes them sensitive to corrosion damage at intermetallic particles. Aeronautical parts are often submitted to corrosive environments and fatigue loadings. For safety and economic matters, it is important to be able to monitor the development of damages during application. In this context, Acoustic Emission (AE) is a useful tool to monitor the state of material damage and predict its remaining useful lifetime. This work, which is part of a larger European project (Early detection and progress monitoring and prediction of corrosion in aeronautic Al alloys through calibrated Ultrasonic-CorROSion Sensor application), has for main objective to understand, identify and quantify, via AE, how corrosion defects impact the fatigue behaviour of aluminum alloy 7075-T6 specimens and covered with different types of coatings (top coat, primer and a conversion coating obtained by anodizing process). Therefore, tensile-tensile fatigue tests (R? = 0.1) monitored with AE are performed at room temperature on non-corroded samples and on corroded samples. Precorrosion defects are generated by the complete immersion of the samples in an NaCl bath (3.5% wt). Pre-corrosion defects tend to decrease the fatigue lifetime of the material tested and create damage in the substrate and coatings generating new AE sources. For all types of coated specimens, damage indicators based on the AE activity are studied in order to find characteristic damage times giving information on the remaining useful lifetime of the material during fatigue tests. Characteristic times linked to damage initiation in the substrate and propagation the main fatigue crack in the material are defined.

AEROPLAS – Desarrollo de componentes para la industria aeronáutica mediante tecnologías de bajo coste

The future of the aeronautical sector is oriented towards manufacturing lighter and more profitable structures and components, using more ecological materials and technologies, that allow reducing costs, weight and fuel consumption, with shorter manufacturing cycles, while increasing energy efficiency manufacturing. AEROPLAS project arises in this context, with the aim of contributing to the advanced manufacturing process of thermoplastic composites using low-cost technologies for the aeronautical industry. This study focuses on the replacement of aeronautical parts currently manufactured in thermosetting composite by thermoplastic ones, in two real components: cover panel and access door of the ventral fairing of A350, using two materials of different quality: LM-PAEK/CF semipreg (TenCate Cetex® TC1225) and PC/CF prepreg (ePreg245CHT/PC40). Through design and calculation, the stacking and part thicknesses necessary to cover the structural requirements of both components have been obtained, based on the data acquired from the characterization of the base materials. Two manufacturing processes have been studied and compared to obtain the new parts, selecting thermoforming and stamping as the most promising. Finally, the characterization of the pieces obtained has been carried out by means of non-destructive tests (visual inspection, ultrasonic verification, dimensional inspection using laser tracker) and destructive tests (pull-out strength on riveted joints [AITM1-0066], bearing strength [AITM1-0009], laminate tensile strength [AITM1-0007], fastened joints strength [AITM1-0067]).

Thermal expansion behaviour of Invar 36 alloy parts fabricated by wire-arc additive manufacturing

Invar 36 alloy is of high interest in various industrial sectors, due to its reduced thermal expansion properties. This study aims to validate Wire-Arc Additive Manufacturing (WAAM) technology as a valid method for manufacturing aerospace tooling in Invar 36. The main novelty and the objective of this work is to study the properties of Invar deposited by WAAM technology and to provide guidelines for the manufacture of parts using this technology. To do so, the thermal expansion behaviour of Invar specimens manufactured using Gas Metal Arc Welding (GMAW)-based WAAM technology and Plasma Arc Welding (PAW)-based WAAM technology is analyzed for subsequent comparison with the values obtained from the laminated Invar sample used as the reference specimen. A wall is manufactured with each technology, for comparative purposes, from which specimens were extracted for the dilatometry test and metallographic analysis. The results of these analyses show the advantages of GMAW technology for the manufacture of Invar alloy parts, as it presents the same thermal expansion behaviour as the laminated reference material with less presence of precipitates and no macrostructural failures such as pores, cracks and lacks of fusion. Furthermore, to conclude, an aeronautical tooling that has been manufactured within this work demonstrated the potential of this technology to manufacture specialized aeronautical parts.

Validation of the Mechanical Behavior of an Aeronautical Fixing Turret Produced by a Design for Additive Manufacturing (DfAM).

The design of parts in such critical sectors as the manufacturing of aeronautical parts is awaiting a paradigm shift due to the introduction of additive manufacturing technologies. The manufacture of parts designed by means of the design-oriented additive manufacturing methodology (DfAM) has acquired great relevance in recent years. One of the major gaps in the application of these technologies is the lack of studies on the mechanical behavior of parts manufactured using this methodology. This paper focuses on the manufacture of a turret for the clamping of parts for the aeronautical industry. The design of the lightened turret by means of geometry optimization, the manufacture of the turret in polylactic acid (PLA) and 5XXX series aluminum alloy by means of Wire Arc Additive Manufacturing (WAAM) technology and the analysis by means of finite element analysis (FEA) with its validation by means of a tensile test are presented. The behavior of the part manufactured with both materials is compared. The conclusion allows to establish which are the limitations of the part manufactured in PLA for its orientation to the final application, whose advantages are its lower weight and cost. This paper is novel as it presents a holistic view that covers the process in an integrated way from the design and manufacture to the behaviour of the component in use.

INVESTIGATION OF MACHINABILITY PERFORMANCE IN TURNING OF Ti–6Al–4V ELI ALLOY USING FIREFLY ALGORITHM AND GRNN APPROACHES

Ti–6Al–4V ELI alloy is one of the most familiar materials for orthopedic implants, aeronautical parts, marine components, oil and gas production equipment, and cryogenic vessel applications. Therefore, its appropriate quality of finishing is highly essential for these applications. But the characteristics like lower modulus of elasticity, lesser thermal conductivity, and high chemical sensitivity placed it in the categories of difficult-to-cut metal alloys. Also, tooling cost is one of the prime issues in the machining of this alloy. Therefore, this research is more inclined to use a low-budget uncoated carbide tool in turning the Ti–6Al–4V ELI alloy. Also, the selection of suitable levels of machining parameters is highly indispensable to get the appropriate surface finish with a low tooling cost. So, the [Formula: see text] experimental design is utilized to check the performances of the uncoated carbide tool in the turning tests. The performance indexes like surface roughness (Ra), flank wear of tool (VBc), and material removal rate (MRR) are measured and studied with the help of surface plots and interaction plots. Further, the Firefly Algorithm optimization is employed to find the optimal cutting parameters and cutting response values. The local optimal values of the input parameters a, f, and Vc are estimated as 0.3241[Formula: see text]mm, 0.0893[Formula: see text]mm/rev, and 82.41[Formula: see text]m/min, respectively. Similarly, the global optimal values for the responses Ra, VBc, and MRR are reported as 0.6321[Formula: see text]μm, 0.09253[Formula: see text]mm, and 24.61[Formula: see text]g/min, individually. Additionally, to predict the responses, Generalized Regression Neural Network (GRNN) modeling is employed and the average absolute error for each response is noticed to be less than 1%. Therefore, the GRNN modeling tool is strongly recommended for various machining applications.

Comparison of visual servoing technologies for robotized aerospace structural assembly and inspection

This work presents a novel approach for visual servoing of robotized aerospace manufacturing cells, based on the combined use of a camera and a 2D-beam scanner and a 1-D beam distance sensor attached to the end-effector of a collaborative robot. The proposed system can detect features associated with mechanical bounds over the aircraft structure, making possible the robot automatic online trajectory/path generation when the robot performs a target task over an aeronautical part. The effectiveness of this method is demonstrated by means of experimental evaluations carried out in unstructured environments without illumination and temperature control (simulating real shop floor conditions), evincing that the proposed approach is more robust. We also show that it is able to automatically generate and follow a target path with an accuracy of 0.40 mm and repeatability of 0.59 mm, which is roughly 2 times more accurate than the classical computer vision servoing used in the experiments. The proposed solution is suitable to applications in modern collaborative robotized aerospace assembly cells.

In situ tomographic study of a 3D-woven SiC/SiC composite part subjected to severe thermo-mechanical loads

A high-temperature multi-axial test is carried out to characterize the thermo-mechanical behaviour of a 3D-woven SiC/SiC composite aeronautical part under loads representative of operating conditions. The sample is L-shaped and cut out from the part. It is subjected to severe thermal gradients and a superimposed mechanical load that progressively increases up to the first damage. The sample shape and its associated microstructure, the heterogeneity of the stress field and the limited accessibility to regions susceptible to damage require non-contact imaging modalities. An in situ experiment, conducted with a dedicated testing machine at the SOLEIL synchrotron facility, provides the sample microstructure from computed micro-tomographic imaging and thermal loads from infrared thermography. Experimental constraints lead to non-ideal acquisition conditions for both measurement modalities. This article details the procedure of correcting artefacts to use the volumes for quantitative exploitation (i.e. full-field measurement, model validation and identification). After proper processing, despite its complexity, the in situ experiment provides high-quality data about a part under realistic operating conditions. The influence of the mesostructure on fracture phenomena can be inferred from the tomography in the damaged state. Experiments show that the localization of damage initiation is driven by the geometry, while the woven structure moderates the crack propagation. This study widens the scope of in situ thermo-mechanical experiments to more complex loading states, closer to in-service conditions.