https://popups.uliege.be/esaform21/index.php?id=87 Coordinator: Prof. Dermot Brabazon Co-organisers: Prof. Antonello Astarita, Dr Christian Grandfils, Dr. Sumsun Naher, Dr. Anne Mertens Description: The aim if this min-symposium is to discuss the optimisation, capabilities and development within Additive Manufacturing. The pre-process, in-situ process, and post process aspects of additive manufacturing are important to characterise and understand well how these impact on the final produced part properties. Experimental, fundamental modelling and data analytic developments in relation to additive manufacturing are considered within this mini-symposium. Charactreisation of aspects of additive manufacturing production quality will be discussed within this mini-symposium. Mini Symposia fr Wed, 03 Mar 2021 09:37:10 +0100 Wed, 14 Apr 2021 09:57:47 +0200 https://popups.uliege.be/esaform21/index.php?id=87 0 https://popups.uliege.be/esaform21/index.php?id=403 In recent years, recycling the powder leftover within the additive manufacturing process has been attractive for both research, development and industry production. Powder recycling can significantly enhance the sustainability of the manufacturing process, reduce the cost and avoid producing metallic waste as a potential environmental hazard. The first step in reusing the recycled powders in the 3D printing process is to characterize the microstructure and surface quality of the powder for oxidation and impurity analysis. Here, scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy (XPS) have been used for the morphology and surface composition analysis of the 316L powders within the Aconity 3D printer. A new powder collection strategy has been introduced to collect powders from different locations in the powder bed: from the top most and surface of the parts and powder bed after the print terminated, from between the printed parts at different heights. The XPS measurements revealed that oxidation is a common in all the powders compared to virgin powder and more oxidation was detected from the powders collected on the very top of the leftover powder and from surface of the bed. The size of the particles does not change much but larger particles remained at the topmost surface. This finding would help in designing a protocol for collecting the recycled powder from the powder bed and it is suggested to follow a a procedure of collecting powders from the different sections of the powder bed in order to avoid mixing the most and least affected particles. Fri, 19 Mar 2021 18:38:11 +0100 https://popups.uliege.be/esaform21/index.php?id=403 https://popups.uliege.be/esaform21/index.php?id=459 The additive manufacturing technique represents a way to realize components or prototypes without the use of conventional tools.The research presented aims at proposing a methodology based on the use of three different techniques that are the poly-jet 3D using UV photo-polymerization, the FDM of polyamide materials and the FDM of PLA materials. The original data were used at the beginning with the first technique in order to detect the shape and the geometry by a 3D SCANNER. The objective was the re-building of a model shape made using a procedure in which the input file characteristics were updated starting from those got by the scanning device in order to respect the original requirements defined in the computer aided environment. It was found that the physical re-building of an object is depending the characteristics of the input file that needs to be digitally processed in order to get the desired shape and geometry. In that way also FDM using PLA and polyamide materials can be utilized to get components or prototypes from scanned digital data. The results are reported in details. Fri, 19 Mar 2021 22:00:04 +0100 https://popups.uliege.be/esaform21/index.php?id=459 https://popups.uliege.be/esaform21/index.php?id=486 Ti-6Al-4V is the most prominent titanium alloy widely used e.g. for aerospace applications. Conventionally, many Ti-6Al-4V aerospace components are produced by a multi-stage hot forging process followed by subsequent machining which often generates a high amount of scrap. Additive manufacturing (AM), such as powder-based laser material deposition (p-LMD), enables parts to be made with geometric freedom and near-net-shape, but so far lacks high deposition rates. The present study proposes high-deposition-rate laser material deposition manufacturing using a large laser beam diameter and increased scanning speed to achieve deposition rates up to 5 kg/h. As Ti-6Al-4V is prone to oxygen pick-up, the process was performed in an inert atmosphere. We determined suitable process windows for tracks without fusion defects and low porosity and investigated microstructure and hardness. Fri, 19 Mar 2021 23:49:49 +0100 https://popups.uliege.be/esaform21/index.php?id=486 https://popups.uliege.be/esaform21/index.php?id=756 Additive manufacturing has proven to be a very beneficial production technology in the medical and healthcare industries. While existing for over four decades, recent work has seen great improvements in the quality of products; particularly in medical devices such as implants. Improved customization reduced operating time and increased cost-effectiveness associated with Metal AM for these products offers a new value proposition.  This paper investigates and evaluates modelling methods for the zygoma bone (human jawbone) and explores the most suitable material and optimum design for this critical biomedical implant. This paper proposes an innovative and efficient pre-process methodology that includes modelling, design validation, topological optimization, and numerical analysis. The method includes the generation of the model using reverse engineering of CT scan data and a topology optimization technique which makes the implant lightweight without causing excessive stress concentration. Static structural Finite Element Analysis was conducted to test three different biocompatible materials (Ti6Al4V, stainless steel 316L and CoCr alloys) which are commonly available for metal additive manufacturing. The stresses and conditions in the analysis were that of the human mastication process and all the implant design were tested with the three material types. The Taguchi method was used to determine the optimum design which was found to result in the highest mass reduction of 25% with Ti6Al4V as the implant material. Sun, 21 Mar 2021 13:01:12 +0100 https://popups.uliege.be/esaform21/index.php?id=756 https://popups.uliege.be/esaform21/index.php?id=858 Composite materials are widely used as main parts and structural components in different fields, especially for automotive and military applications. Although these materials supply different advantages comparing to the metals, their implementation in engineering applications is limited due to low electrical and thermal properties and low resistance to erosion. To enhance these above-mentioned properties, the metallization of composite materials by creating a thin metal film on their surface can be achieved. Among different coating deposition techniques, Cold Spray appears to be the most suitable one for the metallization of temperature-sensitive materials such as polymers and composites with a thermoplastic matrix. This process relies on kinetic energy for the formation of the coating rather than on thermal energy and consequent erosion and degradation of the polymer-based composite can be avoided. In the last years, a new method to produce composite materials, as known as Fused Filament Fabrication (FFF), has been developed for industrial applications. This technique consists of a 3D printing process that involves the thermal extrusion of thermoplastic polymer and fibers in the form of filaments from a heated mobile nozzle. The implementation of this new technique is leading to the manufacturing of customized composite materials for the cold spray application. In the presented experimental campaign, Onyx material is used as a substrate. This material is made of Nylon, a thermoplastic matrix, and chopped carbon fibers randomly dispersed in it. Aluminum powders were cold sprayed on the Onyx substrate with a low-pressure cold spray (LPCS) system. This study aims to investigate the possibility of the metalizing 3D-printed composite material by cold spray technology. For this purpose, optical and microscopical analyses are carried out. Based on the results, the feasibility of the process and the influence of the morphology of the substrate are discussed, and optimal spraying conditions are proposed. Sun, 21 Mar 2021 22:20:35 +0100 https://popups.uliege.be/esaform21/index.php?id=858 https://popups.uliege.be/esaform21/index.php?id=1563 Despite the attractive capabilities of additive manufacturing (AM) technology, the industrialization of these processes remains very low. This is attributed to the complexes physical phenomena involved in the AM process and the layered structure of the produced parts. Intense research work is still needed for the prediction and optimization of AM parts mechanical properties. In this study, the influence of particle size distribution (PSD) of stainless steel 316L (SS 316L) powders on AM parts properties was investigated. Four PSD were used to produce test parts and compare the resulting porosity, surface roughness and macro-hardness. The SS 316L specimens were fabricated by Laser Powder Bed Fusion process (LPBF) on a SLM 125HL machine using variations in laser power and scan velocity. Computed scan tomography (CT) was used to characterize the defects. Lack of fusion and keyhole defects were detected. Defects were detected even in nearly dense parts. The powder size distribution was found to affect the porosity. Results from CT tests were used to identify the minimum achievable porosities for each powder, through the appropriate selection of process parameters. The macro-hardness and surface roughness were found to vary with the powder properties. Mon, 22 Mar 2021 20:12:13 +0100 https://popups.uliege.be/esaform21/index.php?id=1563 https://popups.uliege.be/esaform21/index.php?id=1931 Cold forging tools become increasingly complex and require enhanced functionality, especially in the context of digitisation. Conventional subtractive manufacturing processes often reach their limits when the geometric complexity of the workpiece increases, hence additive manufacturing processes have become increasingly important in the last decades. Additive manufacturing processes have already been used in many fields of manufacturing technology to produce tool components with promising results, but the potentials of additive manufacturing processes have not yet been applied to cold forging tools. Therefore, the Institute for Metal Forming Technology (IFU) of the University of Stuttgart has developed an additive manufactured cold extrusion tool with integrated functional features. As functional features in the additive manufactured extrusion tool, a close contour glass fiber sensor for temperature measurement, a cooling system and a lubrication system for the controlled injection of minimal lubricant amounts during the forming process were integrated. Due to the integrated functional features, structural degradation appears in the tool, therefore the structural-mechanical tool properties were analyzed numerically with the FE-Software DEFORM 3D™ in this report as well. Furthermore, the additive manufactured cold extrusion tool was experimentally evaluated in sequentially executed extrusion operations. Thereby the integrated functional features were used and gathered data were recorded. As a result of the experimental forming tests, near-contour temperature measurements in the extrusion tool with and without the use of the integrated cooling system as well as the modification of the maximum punch forces by an inline lubricant application were obtained. In addition, the experimentally determined temperature fields in the extrusion die are validated with numerically calculated results. Tue, 23 Mar 2021 10:41:38 +0100 https://popups.uliege.be/esaform21/index.php?id=1931 https://popups.uliege.be/esaform21/index.php?id=2034 Viscous sintering kinetics of thermoplastic polymers has been studied for powders using models refining the Frenkel-Eshelby approach. It is usually based on the measurement of the bonding neck between two molten particles submitted to thermo-microscopy trials. Recently, specific experimental setups have been described for studying the viscous sintering of filaments used in additive manufacturing by FDM. The description of their coalescence by models developed for particles is a rough approximation. However, the evolution of the shape of their section can be modelled by lemniscate curves. In the present work, we present an advanced image analysis approach allowing the fitting of the contour of the filaments by a Lemniscate of Booth. It is based on the automatic assessment of the coordinates of their edge pixels and the adjustment of lemniscates to match their evolving shape as a succession of inverse ellipses. We apply this procedure to a model-biopolymer recently shown as 3D-printable, the plasticized zein, a corn protein extruded as cylindrical filaments. Their sintering is recorded at 120°C as 8-bits coded raw images. After segmentation, a numerical mask is applied to follow the filaments outline. Using Matlab® as computer algebra system, the adjustment and the identification of lemniscates parameters leads to determine the viscous sintering characteristic time, similar to those of standard polymers. Then, the full monitoring of sintering kinetics is achievable and makes possible a better modelling of such experimental trials and their application to enhance the control of the welding between layers in additive manufacturing. Tue, 23 Mar 2021 12:30:41 +0100 https://popups.uliege.be/esaform21/index.php?id=2034 https://popups.uliege.be/esaform21/index.php?id=2089 Powder bed fusion techniques enable the production of customized and complex devices that meet the requirements of the end user and target application. The medical industry relies on these additive manufacturing technologies for the advantages that these methods offer to accurately fit the patients’ needs. Besides the recent improvements, the production process of 3D printed bespoke implants still requires optimization to achieve the optimal properties that can mimic both the chemical and mechanical characteristics of the anatomical region of interest. In particular, the surface properties of an implant device are crucial to obtain a strong interface and connection with the physiological environment. The layer by layer manufacturing processes lead to the production of complex and high-performance substrates but always require surface treatments during post-processing to improve the implant interaction with the natural tissues and promote a shorter assimilation for the fast recovery and wellness of the patient. Although the surface finishing can be tailored to enhance cells adhesion, proliferation and differentiation in contact with a metal implant, the same surface properties can have a different outcome when dealing with bacteria. This work aims to provide a preliminary analysis on how different post-processing techniques have distinct effects on cells and bacteria colonization of 3D printed titanium implants. The goal of the paper is to highlight the importance of the identification of an optimized methodology for the surface treatment of Ti6Al4V samples produced by Selective Laser Melting (SLM) that improves the implant antimicrobial properties and promotes the osseointegration in a long-term period. Tue, 23 Mar 2021 12:46:45 +0100 https://popups.uliege.be/esaform21/index.php?id=2089 https://popups.uliege.be/esaform21/index.php?id=2114 FDM is one of the simplest and cheapest available additive technologies, mostly limited to polymeric materials. Metal-FDM process may overcome this limit using a metal filament bounded with polymer, which is removed through debinding and sintering treatments. Producing metal components using an economic machine would make it possible to produce non-critical components with complex geometry at an industrial level and at low-cost. This work aims to investigate whether a low-cost commercial 3D printer may be able to print a metal filament and what are the achievable density and the shrinkage on the final part. An experimental campaign (24 factorial plan) was performed, considering as variable factors the nozzle temperature, the infill pattern, the print speed and the layer thickness. Statistical tools as the boxplot for determining outliers and the analysis of variance (ANOVA) were used to evaluate the results, identifying which process parameters ad their interactions affect the selected indicators (density and shrinkage). The results show that the conversion of a low-cost FDM machine from polymer to metal filament is possible, generating repeatable and stable results. The process is faster and less expensive than the existing powder-bed-fusion based metal AM technology. The best combination of printing parameters was identified considering as target point the density of the “traditional” AISI 316L steel. Different behaviors in terms of shrinkage were identified: trends are stable and very similar for X and Y directions, independently from the printing parameters, while the interaction between temperature and other parameters causes higher variability along the Z-axis. Tue, 23 Mar 2021 12:52:28 +0100 https://popups.uliege.be/esaform21/index.php?id=2114 https://popups.uliege.be/esaform21/index.php?id=2124 Additive manufacturing (AM) has many advantages compared to conventional processes. Of particular interest is the tool-less manufacturing of components, which allows one component to differ from the next completely and has the possibility of producing complex geometries. At the same time, however, AM has deficits such as long production times, low production tolerances and low surface qualities compared to conventional processes. Therefore, a finishing process using machining is often necessary, which extends the manufacturing time and produces waste. Thus, the avoidance of machining rework is of high interest, especially with expensive materials such as stainless steel or titanium. One approach to avoid machining processes is to use forming technology. By applying a forming operation, surfaces can be smoothened and geometrical aspects can be defined more sharply. Especially for functional surfaces, this procedure is favorable because of the work hardening, which in turn increases the strength of the material. Using the example of laser-based powder bed fusion (PBF-LB) followed by a cup backward extrusion process, two materials, which are frequently used in AM are investigated. On the one hand, the titanium alloy Ti-6Al-4V, as a material with low machinability and low formability at room temperature, and the stainless steel 316 L. Compared to Ti-6Al-4V, 316 L has a higher formability. Cylinders are built using PBF-LB and then formed to smoothen the surface and achieve a higher geometrical accuracy concerning edges. Formed, additively made parts have a more defined geometry, namely sharp edges and a surface roughness reduced by up to 90 %. Tue, 23 Mar 2021 12:56:32 +0100 https://popups.uliege.be/esaform21/index.php?id=2124 https://popups.uliege.be/esaform21/index.php?id=2239 Metal nanoparticles have unique chemical, physical, electrical, and optical properties that make them attractive for a wide range of applications in sensing, anti-fouling surfaces, medicine, and conductive inks. Pulsed Laser Ablation in Liquid (PLAL) is a green method of nanoparticle colloid production, capable of producing ligand-free nanoparticles in solution without the need for hazardous, environmentally unfriendly chemicals. Control of the process parameters can give control over the resulting colloid properties such as particle size distribution. In this work, silver (Ag) nanoparticles (NPs) with average particle size from 2.04 to 19.3 nm and copper (Cu) NPs with average particle size from 40 to 85.9 nm were produced by PLAL) technique. Tue, 23 Mar 2021 14:54:53 +0100 https://popups.uliege.be/esaform21/index.php?id=2239 https://popups.uliege.be/esaform21/index.php?id=2320 Modeling of Additive Manufacturing (AM) at the part scale involves non-linear thermo-mechanical simulations. Such a process also imposes a very fine discretization and requires altering the geometry of the models during the simulations to model the addition of matter, which is a computational challenge by itself. The first focus of this work is the addition of an additive manufacturing module in the fully implicit in-house Finite Element code Metafor [1] which is developed at the University of Liège. The implemented method to activate elements and to activate and deactivate boundary conditions during a simulation is adapted from the element deletion algorithm implemented in Metafor in the scope of crack propagation [2]. This algorithm is modified to allow the activation of elements based on a user-specified criterion (e.g. geometrical criterion, thermal criterion, etc.). The second objective of this work is to improve the efficiency of the AM simulations, in particular by using a dynamic remeshing strategy to reduce the computational cost of the simulations. This remeshing is done using non-conformal meshes, where hanging nodes are handled via the use of Lagrange multiplier constraints. The mesh data transfer used after remeshing is based on projection methods involving finite volumes [3]. The presented model is then compared against a 2D numerical simulation of Direct Energy Deposition of a High-Speed Steel thick deposit from the literature [4]. Tue, 23 Mar 2021 16:47:40 +0100 https://popups.uliege.be/esaform21/index.php?id=2320 https://popups.uliege.be/esaform21/index.php?id=2335 Automated fiber placement processes could be combined with additive manufacturing to produce more functionally complex composite structures with more flexibility. The challenge is to add functions or reinforcements to PEEK/carbon composite parts manufactured by automated fiber placement process, with additive manufacturing by fused filament fabrication. This consists of extruding a molten polymer through a nozzle to create a 3D part. Bonding between polymer filaments is a thermally driven phenomenon and determines the integrity and the final mechanical strength of the printed part. 3d-printing high performance polymers is still very challenging because they involve high thermal gradients during the process. The purpose of this work is to find a process window where the bonding strength is maximized between the composite laminate and the first layer of printed polymer, and inside the printed function as well. Experimental measurements of the temperature profiles at the interface between a composite substrate and 3d-printed PEI under different processing conditions were carried out. The interface was observed using microscopic sections. The methodology for studying the impact of printing parameters on the cohesion and adhesion of printed parts with a composite laminate is described. This work provides insights about the influence of processing conditions on the bond formation between high-performance polymer surfaces. It highlights the importance of controlling the thermal history of the materials all along the process. Tue, 23 Mar 2021 16:58:33 +0100 https://popups.uliege.be/esaform21/index.php?id=2335 https://popups.uliege.be/esaform21/index.php?id=2340 Wire-arc welding-based additive manufacturing (WAAM) is a 3D printing technology for production of near-net-shape parts with complex geometry. This printing technology enables to build up a required shape layer by layer with a deposition of a consumable welding wire, where the welding arc is a source of heat. Welding is usually performed by CNC-controlled robotic manipulator, which provides a controlled location of material layer adding. Because the process itself involves thermo-mechanically complex phenomena, Finite Element-based virtual models are commonly employed to optimize the process parameters. This paper presents advanced computational modelling of the WAAM of a tube. A thermo-mechanical numerical model of the process is calibrated against experimental data, measured as temperature variation at the acquisition point. The virtual modelling starts with a preparation of the tube geometry in CAD software, where the geometry of the single-layer cross-section is assumed. The geometry is then exported to a G-code format data file and used to control robotic manipulator motion. On the other side, the code serves as an input to in-house developed code for automatic FEs activation in the simulation of the material layer-adding process. The time of activation of the finite elements (FEs) is directly related to the material deposition rate. The activation of the FEs is followed by a heat source, modeled with a double ellipsoidal power density distribution. The thermo-mechanical problem was solved as uncoupled to speed-up computation. Tue, 23 Mar 2021 17:02:11 +0100 https://popups.uliege.be/esaform21/index.php?id=2340 https://popups.uliege.be/esaform21/index.php?id=2433 Powder bed additive manufacturing allows for the production of fully customizable parts and is of great interest for industrial applications. However, the repeatability of the parts and the uniformity of the mechanical properties are still an issue. More specifically, the physical mechanism of the spreading process of the powders, which significantly affects the characteristics of the final part, is not completely understood. In powder bed fusion technologies, the spreading is performed by a device, typically a roller or a blade, that collects the powders from the feedstock and successively deposits them in a layer of several dozens of microns that is then processed with a laser beam. In this work, an experimental approach is developed and employed to study the powder spreading process and analyze in detail the motion of the powders from the accumulation zone to the deposition stage. The presented experiments are carried out on a home-made device that reproduces the spreading process and enables the measurement of the characteristics of the powder bed. Furthermore, the correlation with the process parameters, e.g., the speed of the spreading device, is also investigated. These results can be used to obtain useful insights on the optimal window for the process parameters. Tue, 23 Mar 2021 19:02:41 +0100 https://popups.uliege.be/esaform21/index.php?id=2433 https://popups.uliege.be/esaform21/index.php?id=2441 Microscopic defects may occur during powder-bed fusion processes which originate from molten pool instabilities. To investigate this issue, a numerical model focusing on the interaction between laser and powder, melt pool formation and thermodynamics effects is on development. The approach used in the model assumes an incompressible Newtonian flow based on an enthalpy-porosity method for solid/liquid metal transition. The jump conditions at the liquid-solid interface for the energy equation are included through the modification of the enthalpy which incorporates the latent heat of fusion. A Carman-Kozeny porosity method is implemented in the momentum equation to penalize the flow in the solid phase. Molten flows are driven by natural and thermocapillary convection which are modelled using Boussinesq approximation and Marangoni free-surface stresses respectively. This numerical model is implemented within a Discontinuous Galerkin (DG) finite element formulation which ensures high order convergence on unstructured mesh [1]. In this work, a sharp interface method is integrated into the three dimensional high-order DG code Argo [2] to capture the free surface of the melt pool. This method allows to keep the high-order of convergence of the DG scheme even near the interface not conforming with the mesh. This is essential to capture the thermo-hydrodynamics phenomena during powder-bed fusion with accuracy. Current effort is dedicated to improve the model accounting for physical phenomena such as surface tension and vaporization. The main purpose is to investigate the occurrence of discontinuities in fused powder tracks depending on material properties and process parameters. Tue, 23 Mar 2021 19:08:09 +0100 https://popups.uliege.be/esaform21/index.php?id=2441 https://popups.uliege.be/esaform21/index.php?id=2451 In this study, we focus on additive manufacturing using Laser Metal Deposition (LMD) to produce a large space aluminum component that is expensive to manufacture with conventional methods and requests a long lead time. Two main objectives are aimed at: the setup of the process with the determination of process parameters that lead to healthy parts and the demonstration that the component size and geometry is largely compatible with LMD. Two materials are considered for this component. AlSi10Mg and Scalmalloy®. Processing parameters have been optimized to obtain a density on both materials over 99.5%. The final material is chosen with regard to the mechanical performance. Scalmalloy provides both better strength and ductility and is chosen to print a demonstrator. The demonstrator printed in this study is a section of a large (1 m diameter) ring-shaped component that has been topologically optimized. Some modifications are made on the original design in order to make it compatible with LMD printing. The printing strategy is then established. The results of the (non-) destructive testing reveal that the demonstrator is healthy and the mechanical properties are as expected. Tue, 23 Mar 2021 19:11:35 +0100 https://popups.uliege.be/esaform21/index.php?id=2451 https://popups.uliege.be/esaform21/index.php?id=2464 Laser powder bed fusion (LPBF) is an additive manufacturing technique that is widely used to produce AlSi10Mg parts with a good strength-to-weight ratio and a very fine microstructure thanks to high cooling rates. However, to obtain better mechanical properties, a good ductility and higher fatigue resistance, post-treatments have to be performed. In this work, friction stir processing, a thermomechanical post-treatment, is applied on an as-built plate of 5 mm of thickness. This post-treatment leads to a decrease of the percentage of porosities and to modification of the microstructure: globularized Si-rich particles are surrounded by the α-Al phase. The method presented uses nanoindentation to determine the behavior of the different phases present in the material for future numerical simulations and a better understanding of the relation between microstructure and fatigue strength. The Bucaille method [1] is used to determine the links between indentation curves and elastoplastic parameters. Three different pyramidal indenters are used: Berkovich, cube corner and an indenter with a centerline-to-face angle of 50 degrees. From the loading / unloading curves and after post-processing, the Young's modulus, the representative strain and the associated stress are determined. With the three different indenters and their three true stress/true strain points, a good description of the elastoplastic behavior can be defined. Tue, 23 Mar 2021 19:28:40 +0100 https://popups.uliege.be/esaform21/index.php?id=2464 https://popups.uliege.be/esaform21/index.php?id=2488 Originally issued from cladding, the LMD-p process widens the field of possibilities in terms of manufacturing. Depending on the targeted application, the needs regarding the track geometry are different and the ability to adapt it is a key challenge. In LMD-p, the laser beam attenuation as well as the powder particles preheating are both determined by laser-powder interactions before the powder reaches the substrate. The track dimensions are directly correlated to the melt pool size: a larger pool will tend to capture more powder resulting in a higher deposition rate. The model presented here intends to determine, for a given working distance, the partition of energy, and to estimate the area of the generated melt pool and finally the dimensions of the deposited track. It is first based on a semi-analytical approach that models the powder distribution and calculates the transmitted power to both substrate and powder particles. The attenuated power density is then an input for a light Eulerian thermal simulation from which the contour of the molten zone is extracted. Several iterations are carried out to account for the energy loss caused by the heating and melting of the powder entering the pool. Lastly, the track dimensions are estimated from the stabilized melt pool configuration. Track geometries obtained with a BeAM® machine are compared to the model predictions. Such an approach opens very interesting perspectives in studying the influence of the working distance and its optimization for a given material and/or a given application. Tue, 23 Mar 2021 20:31:42 +0100 https://popups.uliege.be/esaform21/index.php?id=2488 https://popups.uliege.be/esaform21/index.php?id=2495 The market segment of additive manufacturing is showing an annual growth of more than ten percent, with extrusion-based processes being the larger segment of the market. The scope of use is limited to secondary structures. Equipment manufacturers try to guarantee constant material characteristics by closed systems. The characteristic values are up to 50% below the ones from injection molding. The processing of high-performance polymers with reinforcing fibers is an additional challenge. Further development requires an opening of the material and manufacturing systems. The guidelines and standardization for this are still missing. For this reason, a functional analysis (FA) according to TRIZ ("theory of the resolution of invention-related tasks") is performed within this study. This identifies the undesired functions and quantifies their coupling with process components and parameters. In the FA, the manufactured part is the target component in order to address its quality. This way the FA identifies five undesirable functions in the process. These are: deform, cool, weaken, swell and shape. For hightemperature thermoplastics, thermal shrinkage is the primary cause of geometric tolerance. Therefore, the deformation is largely dependent on the cooling mechanism. For a detailed analysis, the polymer melt is further disassembled. The results are six sub-components. The weakening is mainly due to the physical phase of the voids, which exists during the entire processing. The breakdown comprises physical fields such as stress, temperature and flow. These determine the output properties as well as the bonding between the layers. The associated functions are the swelling and shaping. In order to generate broadly applicable standardizations, research questions for further investigation are derived from this study. Tue, 23 Mar 2021 20:43:30 +0100 https://popups.uliege.be/esaform21/index.php?id=2495 https://popups.uliege.be/esaform21/index.php?id=2599 In this study, a data-driven deep learning model for fast and accurate prediction of temperature evolution and melting pool size of metallic additive manufacturing processes are developed. The study focuses on bulk experiments of the M4 high-speed steel material powder manufactured by Direct Energy Deposition. Under non-optimized process parameters, many deposited layers (above 30) generate large changes of microstructure through the sample depth caused by the high sensitivity of the cladding material on the thermal history. A 2D finite element analysis (FEA) of the bulk sample, validated in a previous study by experimental measurements, is able to achieve numerical data defining the temperature field evolution under different process settings. A Feed-forward neural networks (FFNN) approach is trained to reproduce the temperature fields generated from FEA. Hence, the trained FFNN is used to predict the history of the temperature fields for new process parameter sets not included in the initial dataset. Besides the input energy, nodal coordinates, and time, five additional features relating layer number, laser location, and distance from the laser to sampling point are considered to enhance prediction accuracy. The results indicate that the temperature evolution is predicted well by the FFNN with an accuracy of 99% within 12 seconds. Wed, 24 Mar 2021 18:28:20 +0100 https://popups.uliege.be/esaform21/index.php?id=2599 https://popups.uliege.be/esaform21/index.php?id=2812 In the last decade, machine learning is increasingly attracting researchers in several scientific areas and, in particular, in the additive manufacturing field. Meanwhile, this technique remains as a black box technique for many researchers. Indeed, it allows obtaining novel insights to overcome the limitation of classical methods, such as the finite element method, and to take into account multi-physical complex phenomena occurring during the manufacturing process. This work presents a comprehensive study for implementing a machine learning technique (artificial neural network) to predict the thermal field evolution during the direct energy deposition of 316L stainless steel and tungsten carbides. The framework consists of a finite element thermal model and a neural network. The influence of the number of hidden layers and the number of nodes in each layer was also investigated. The results showed that an architecture based on 3 or 4 hidden layers and the rectified linear unit as the activation function lead to obtaining a high fidelity prediction with an accuracy exceeding 99%. The impact of the chosen architecture on the model accuracy and CPU usage was also highlighted. The proposed framework can be used to predict the thermal field when simulating multi-layer deposition. Wed, 24 Mar 2021 19:04:24 +0100 https://popups.uliege.be/esaform21/index.php?id=2812 https://popups.uliege.be/esaform21/index.php?id=3003 PMCs are anisotropic and heterogeneous structures with excellent performances in terms of mechanical strength and stiffness, coupled with reduced weight, widely used in engineering sectors. The use of PMCs can be further extended by improving their surface properties such as electrical conductivity, erosion, radiation and lightning protection. In this context, the surface metallization seems to be best solution. In particular, the cold spray (CS) technique candidates as a potential method for the manufacturing of a metal coating on PMCs’ surface. However, the design and the manufacturing methods of PMCs can play a crucial role for an effective metallization through CS. The additive manufacturing technologies for composite materials can be used to manufacture customized reinforced polymer-based panels, like PMCs; the most common method for printing them is the Fused Filament Fabrication (FFF) technique which relies on the thermal extrusion of a thermoplastic feedstock from a mobile heated nozzle. Therefore, this research activity aims to manufacture customized PMCs panels by using FFF technology for the substrate and the cold spray technique for the metallization in order to study the influence of the substrate manufacturing strategy on CS deposition process. For this purpose, three kind of 3D-printed PMCs were manufactured through the FFF technology by varying the percentage fill of the Onyx polymeric matrix and aluminum powders were sprayed on the substrates with a low-pressure cold spray (LPCS) system; both FFF and CS process parameters were varied to study the process in its wholeness. Microscope analyses were carried out to analyze the influence of the manufacturing strategy on the coating quality. Fri, 26 Mar 2021 15:15:18 +0100 https://popups.uliege.be/esaform21/index.php?id=3003 https://popups.uliege.be/esaform21/index.php?id=3627 The additive manufacturing has initially gained popularity for production of non-loadbearing parts and components or in the fields where the material strength and ductility are less important such as modelling and rapid prototyping. But as the technology develops, availability of metal additive manufacturing naturally dictates the desire to use the produced components in load-bearing parts. This requires not-only a thorough documentation on the mechanical properties but also additional and independent research to learn the expected level of variation of the mechanical properties and what factors affect them. The presented paper investigates strength, ductility, hardness, and microstructure of the AlSi10Mg alloy produced by the selective laser melting (SLM). The mechanical properties were determined through a series of uniaxial tension tests and supplementary hardness tests and rationalized with the microstructure evolution with regard to printing direction and heat treatment. The paper also addresses the effect of surface roughness on the mechanical properties of the material, by comparing the machined and net shape tension samples. As expected, the as-manufactured AlSi10Mg-alloy appears to be a semi-brittle alloy, but its microstructure can be altered, and ductility increased by a proper heat-treatment. The effect of surface layer removal on the measured mechanical properties is of particular interest. Mon, 29 Mar 2021 13:43:07 +0200 https://popups.uliege.be/esaform21/index.php?id=3627 https://popups.uliege.be/esaform21/index.php?id=3723 The capability and applicability of additive manufacturing have mesmerized the entire manufacturing world. One major technique of additive manufacturing is extrusion-based additive manufacturing (EAM), which has been recently employed for the rapid production of ceramic components, among other applications. This study focused on establishing the process-property relations for extrusion-based additively manufactured ceramics, namely Alumina (Al2O3) and Zirconia (ZrO2), and then optimization of the relations to get the desired mechanical properties for applicability. Extrusion-based additive manufacturing was used to obtain the ceramic sample parts from ceramic-binder mixtures and by subsequent post-processing. The process parameters chosen for the study were extrusion velocity and part orientation whereas the mechanical properties selected were hardness and flexural strength. Extrusion velocity was varied at three levels i.e. 7.5 mm/s, 12.5 mm/s and 17.5 mm/s. Two levels selected for part orientation were horizontal and vertical. The design of experiments technique was used to establish the process-property relations by highlighting the most significant process parameters affecting the selected mechanical properties. Optimization was achieved by highlighting those levels of significant process parameters that provided the desired values of mechanical properties. Part orientation came out to be a significant factor affecting both the hardness and flexural strength of the two ceramics whereas extrusion velocity was found to be insignificant for both mechanical properties. Among the two levels of part orientation, vertical orientation samples showed higher values of hardness while horizontal samples showed higher flexural strength thus, aiding in the optimization of the process-property relations. Mon, 29 Mar 2021 14:20:30 +0200 https://popups.uliege.be/esaform21/index.php?id=3723 https://popups.uliege.be/esaform21/index.php?id=3763 A study of mechanical and optical properties of samples of transparent plastic Polyethylene terephthalate glycol (PETG) manufactured by additive technology Fused Filament Fabrication (FFF) was carried out. PETG plastic is used in medicine, particularly in dentistry due to its unique set of properties: strength, elasticity, resistance to aggressive environments, transparency. Preserving the complex of properties of PETG plastic, including transparency, during 3D-printing is an important technical task. In order to solve this task a set of studies of PETG laboratory samples was carried out. The optimum modes of 3D printing were determined to provide PETG samples with increased strength properties, preservation of elastic properties and optical transparency of the material. The increase in the optical transparency of the material is provided by an additional post-treatment of the printed samples surface with a chemical reagent. The influence of technological parameters of the post- treatment mode on the mechanical and optical properties of the printed samples has been investigated. The novelty of the work consists in a comprehensive study of the modes of manufacturing products from PETG by technology FFF with subsequent post-treatment, allowing to preserve the transparency of the polymeric material. Mon, 29 Mar 2021 14:27:46 +0200 https://popups.uliege.be/esaform21/index.php?id=3763 https://popups.uliege.be/esaform21/index.php?id=3807 The economical production of lightweight structures with tailor-made properties and load-adapted geometry is limited using conventional technologies. Additive manufacturing processes offer a high potential to meet these requirements, where the established solutions are based primarily on thermoplastics matrix systems. From a process-technological point of view, thermoplastics enable simplified processing, but only a limited range of applications for high-performance components. These limitations are due to their comparatively low heat resistance, low melting temperatures and limited adhesion to embedded reinforcing fibers. In contrast, thermosets show high potential for realization of high- performance lightweight structures with adaptable properties. The present work employs a UV-curing thermoset resin for the impregnation of a continuous filament strand for 3D printing. The main challenge is to reconcile the crosslinking reaction of the thermoset and the process velocity during impregnation and cure. The liquid polymer must provide low initial viscosity to impregnate the filaments and a sufficiently high cure rate and dimensional stability after discharge from the print head to ensure sufficient bonding strength to the substrate. To demonstrate feasibility, a prototypic print head with UV-LED activation was designed and implemented. With a robot-guided printing platform, the 3D-deposition of continuous fiber-reinforcements without additional supporting structures can be realized. To derive initial process parameters, reaction and thermos-mechanical properties are determined by rheometer measurements. Impregnation and cure behavior of the glass fiber reinforced resin is investigated. The presented results provide a reliable process window and a straightforward process monitoring method for further enhancement of the conceived 3D printing process. Mon, 29 Mar 2021 14:43:22 +0200 https://popups.uliege.be/esaform21/index.php?id=3807 https://popups.uliege.be/esaform21/index.php?id=3861 The particle finite element method (PFEM) is used to simulate a simple phase change problem. This is a first step towards the simulation of additive manufacturing (AM) processes at the meso-scale, where the liquid melt pool interacts with the surrounding solid material and undergoes phase change. The focus of this paper lies on strategies to deal with the release or absorption of latent heat in the PFEM, especially with regard to mesh refinement. We briefly describe how mesh refinement in PFEM works and how it can be chosen specifically to achieve convergence despite the highly non-linear latent heat term. It is found that good agreement with the literature can be achieved on a simple 1D phase change test case, while using an automatic local mesh refinement. Mon, 29 Mar 2021 14:51:38 +0200 https://popups.uliege.be/esaform21/index.php?id=3861 https://popups.uliege.be/esaform21/index.php?id=3894 With the advent of 3D printing, it is now possible to produce any part or system with an approach than makes design much deeply interlaced with production. In this scenario, CAE has gained power thanks to the possibility of thinking and then manufacture ideas that go well beyond what was possible in the past. This design approach is perfectly suitable to push forward mould conformal cooling performance. In this work, a coupling of CAD, CFD and 3D printing supported by experimental tests was applied to define a design procedure for conformal cooling channels. In particular, cooling channels for a mould were engineered via CAD, then tested via CFD and, after an initial optimization procedure, the chosen design was 3D printed in specimens suitable to be mounted on a heat exchanger (HX) experimental test rig that was especially adapted for the scope. Fluids temperature, volume flow rates and heat transfer performance were measured. A feedback loop was considered to link measurements and channels redesign. Results together with design and testing procedures are reported and commented. Mon, 29 Mar 2021 14:56:38 +0200 https://popups.uliege.be/esaform21/index.php?id=3894 https://popups.uliege.be/esaform21/index.php?id=3972 In milling operations, the weight of the milling tool greatly affects the motion speed of the mandrel, especially when a complex tool path must be performed. Thus, it is essential to realize more lightweight tools, without a significant decrease in the mechanical and production performance. Traditionally, due to the limitation of the conventional manufacturing processes, the design of a new milling tool cannot be too much complex and thus cannot fully satisfy the mentioned goals. Nowadays, thanks to the topology optimization technique and the additive manufacturing (AM) technologies, such as the selective laser melting (SLM), it is possible to realize more complex part geometries to obtain more lightweight and high-performance tools. In this paper, a new design of a milling tool with a weight reduced by 30% is presented; SLM process has been selected to realize the milling tool. In order to minimize the use of support structures, required by the SLM process to correctly realize the desired part, the new geometry has been little modified. A more lightweight milling tool has been produced and every support structure has been successfully removed from the component. Tue, 30 Mar 2021 09:22:16 +0200 https://popups.uliege.be/esaform21/index.php?id=3972 https://popups.uliege.be/esaform21/index.php?id=4095 Wire arc additive manufacturing process (WAAM) is an innovative technology that offers freedom in terms of designing functional parts, due to its ability to manufacture large and complex workpieces with a high rate of deposition. This technology is a metal AM process using an electric arc heat source. The parts manufactured are affected by thermal residual stresses due to high-energy input between wire and workpiece despite numerous advantages with this technology. It could cause severe deformation and change the global mechanical response. A 3D transient thermal model was created to evaluate the thermal gradients and fields during metal deposition. The material used in this study is a steel alloy (S355JR-AR). This numerical model takes into account the heat dissipation through the external environment and the heat loss through the cooling system under the base plate. Birth-element activation strategy was used to generate warm solid part following the movement of the heat source. The metal deposition is defined with constant welding speed. Goldak model was used to simulate the heat source in order to have a realistic heat flow distribution. Results were in concordance for thermal cycles at different points comparing with experimental results issued from bibliography in terms of: (1) Temperature maximum, (2) Thermal cycles and (3) Cooling gradient phase. This study enabled to check the numerical model and used as a predictive tool Tue, 30 Mar 2021 15:17:25 +0200 https://popups.uliege.be/esaform21/index.php?id=4095 https://popups.uliege.be/esaform21/index.php?id=4124 In the context of Industry 4.0, interest is increasing towards Additive Manufacturing processes due to their several advantages. Among these, the Direct Laser Deposition (DLD) is an innovative technology for additive metal part fabrication, and it is currently demonstrating its ability to revolutionize the manufacturing industry. It is particularly interesting for industrial applications in terms of reduction of waste materials by starting with fewer feedstocks, reduction of machining time by only have material where it is needed but, above all, it is interesting to extend the life of parts. Indeed, with the DLD, it is possible to repair an item or coat parts via cladding, making it more wear-resistant. It is also possible to give "another life" to broken or waste components, for example, by replacing the damaged area using new material. Moreover, particularly intriguing is the possibility to create hybrid or graded parts by varying material/alloy concentrations. This paper aims to combine the abovementioned advantages to develop tailored structures in order to accomplish complex and functional products. For this purpose, a specific case study was investigated, starting with the study of the appropriate powders to use and ending with the printing process using the DMG Mori Lasertec65. Microstructural and mechanical analyses were carried out to evaluate the products and to validate the process. The final results show the properties and performances of products obtained using this technology. Tue, 30 Mar 2021 17:47:53 +0200 https://popups.uliege.be/esaform21/index.php?id=4124 https://popups.uliege.be/esaform21/index.php?id=4172 Identified in the European strategy as a key enabling technology, Additive Manufacturing (AM) has a great potential for industries to reshape, improve and optimize product life cycle, with reduced environmental footprint such as material waste in production. Allowing to meet structural and multi-disciplinary requirements with complex freeform design at a much lower weight than high constrained conventional manufacturing, AM can benefit to numerous space applications. Beside manufacturing process development, software and process control are becoming absolutely necessary to support digitalization of industrial workflow. Dedicated tools such as Computer Aided Design (CAD), Computer Aided Engineering (CAE) and Computer Aided Manufacturing (CAM) were introduced in the digital manufacturing chain; however, their development was driven by standard manufacturing processes. Therefore, appropriate design methods for AM must emerge in a fully integrated end-to-end solution to foster and support the growth and competitiveness of AM. In order to support industrialization of AM, the European Space Agency has selected the Design4AM project, based on a strong partnership between Siemens and Sonaca, for “Development of Design Methods for AM including CAD Design, Optimization, FEM Analysis and Manufacturing features”. On one hand, the project aims at combining within a comprehensive end-to-end process, topology optimization, seamless CAD data flows and predictive process simulation in the Siemens’ NX™ and Simcenter™ environments. On the other hand, the integration of dedicated industrial design workflow within the enhanced Siemens Digital Innovation Platform is validated on a relevant ESA space application provided by Sonaca. Thu, 01 Apr 2021 13:47:22 +0200 https://popups.uliege.be/esaform21/index.php?id=4172 https://popups.uliege.be/esaform21/index.php?id=4236 Metals made by additive manufacturing (AM) have intensely augmented over the past decade for customizing complex structured products in the aerospace industry, automotive, and biomedical engineering. However, for AM fabricated steels, the correlation between the microstructure and mechanical properties is yet a challenging task with limited reports. To realize optimization and material design during the AM process, it is imperative to understand the influence of the microstructural features on the mechanical properties of AM fabricated steels. In the present study, three material blocks with 120×25×15 mm3 dimensions are produced from PH1 steel powder using powder bed fusion (PBF) technology to investigate the anisotropic plastic deformation behavior arising from the manufacturing process. Despite being identical in geometrical shape, the manufactured blocks are designed distinguishingly with various coordinate transformations, i.e. alternating the orientation of the block in the building direction (z) and the substrate plate (x, y). Uniaxial tensile tests are performed along the length direction of each specimen to characterize the anisotropic plastic deformation behavior. The distinctly anisotropic plasticity behavior in terms of strength and ductility are observed in the AM PH1 steel, which is explained by their varied microstructure affected by the thermal history of blocks. It could also be revealed that the thermal history in the AM blocks is influenced by the block geometry even though the same process parameters are employed. Thu, 01 Apr 2021 16:56:29 +0200 https://popups.uliege.be/esaform21/index.php?id=4236 https://popups.uliege.be/esaform21/index.php?id=4350 Square pole implant models of Ti-6Al-4V were fabricated by selective laser melting (SLM) and osteoconductivity was investigated on their surface. The models have 3 types of surfaces; top surface, side surface, and polished surface. The surfaces have each different surface roughness and the influence of the roughness on the osteoconductivity was observed in-vivo experiment. The models were implanted in rat femurs and observed after 2 and 8 weeks. We observed the amount of hard tissue produced on the surfaces in the cut-off cross section of the femurs with the model by means of an optical microscope and bone-implant contact ratio (RB-I) was evaluated. As the result, in the case of 2 weeks-raised rats, the RB-I of the polished surface was the highest of all surfaces. The RB-I of the surface was however the lowest and that of the top surface was the highest in the case of 8 weeks-raised rats. Thu, 01 Apr 2021 21:40:46 +0200 https://popups.uliege.be/esaform21/index.php?id=4350 https://popups.uliege.be/esaform21/index.php?id=4641 The objective of the present work is to study the raster generation to realize Fused Filament Fabrication parts. The research in this paper focused on the evaluation of the deposition of a simple geometry with a FFF machine, supported by an analytical model to compute the build time, also evaluating the geometrical variations caused by changes in process parameters. The main parameters were the print temperature and speed as a function of the thermal and rheological properties of the PLA filament. The study identified essential correlations between process parameters, raster dimensions, and filament properties. An experimental procedure, supported by an analytical model, was implemented for computing raster time and material dimensions. Wed, 07 Apr 2021 18:37:25 +0200 https://popups.uliege.be/esaform21/index.php?id=4641