bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Experience, Expectation, and University Readiness on Learning Satisfaction in the Pandemic
Authors: El Hafiz Subhan , Meinarno Eko A. , Purba Ridhoi Meilona , Hadziq M. Fuad
Published: July 2022

Aims from the present study are to analyze the effect of students’ experience, expectation, and campus readiness on students’ e-learning satisfaction during the Covid-19 pandemic. The present studies explore the three variables’ effect on learning satisfaction in two phases, i.e., examining learning satisfaction between a distance learning campus and traditional campuses and comparing learning satisfaction between two conditions with a one-semester time lag. The results show that students enrolled in distance learning campuses have higher learning satisfaction, and students’ experience incorporates systems readiness affecting e-learning satisfaction. Further, the longitudinal study shows that fulfilling the learning mode’s expectations will increase e-learning satisfaction. The study also found that no effect from learning application which was used on e-learning satisfaction. The implication was discussed.
Didactic Model Aiming at the Use of Digital Information and Communication Technologies in Science Education
Authors: Gil Vanessa Arias , Moreira Marco Antonio , Villagrá Jesús Ángel Meneses
Published: July 2022

The scope of academic processes in which Information and Communication Technologies are incorporated (ICT) has increased in recent decades, same as the number of concerns about its contributions to learning itself. A predominantly instrumental sense of these technologies becomes evident as far as scientific education in Colombia is concerned. This work seeks the construction of a teaching model that may guide natural science teachers around the design of proposals for implementing Digital Information and Communication Technologies (DICT), based on science education challenges (Hodson, 2003; 2010) and the Critical Meaningful Learning Theory (Moreira, 2005; 2010). Thus, Design-Based Research (DBR) is regarded as a methodological standpoint, which, based in turn on a systemic and iterative process, allows the development of a model and validate the potential these technologies have to meet the challenges science teaching entails when their foray into the classroom is based on didactic, pedagogical and epistemological foundations.
Antecedents of Instructor Intention to Continue Using E-Learning Systems in Higher Learning Institutions in Tanzania
Authors: Lashayo Deogratius Mathew , Mhina Julius Raphael Athman
Published: July 2022

Over the years, higher learning institutions (HLIs) have been deploying e-learning systems to complement traditional learning systems in Tanzania. This initiative has consumed many resources including institutions' money, human resources, and time to mention the least. However limited studies have been conducted to investigate long-term intention to use e-learning systems by instructors who are important for initiating, facilitating, and administrating e-learning systems. The current study adopted the information system continuance model (ISCM) and integrated it with two factors (i.e., service quality [SEQ] and system quality [SQ]) from the IS success model to examine their influence on the continuance intention to use e-learning systems. The sample for the study involved 131 instructors drawn from six public-owned HLIs in Tanzania (i.e., IFM, IAA, CBE, DIT, TPSC, and NIT). The study found that the integrated factors (i.e., SEQ and SQ) significantly enhanced the predicting ability of the underlying ISCM in explaining the continuance of intentions to use e-learning systems among instructors.
Experimental Analysis of Circular Milling for Material Identification in Aerospace Industry
Authors: Deshpande Sughosh , Araujo Anna Carla , Lagarrigue Pierre , Landon Yann
Published: July 2022

In the airplane design, thousand holes should be manufactured by machining leading this process in the first place for process optimization. Recently, the stack materials used in this application are sheet layers of Titanium alloy, Aluminum alloy and CFRP, which normally are machined under different cutting conditions. There are two main solutions when drilling stacks: using the more conservative ones or changing the parameters for each layer. In orbital drilling the forces are lower, with better quality but with longer machining time, compared to drilling, allowing the measurement and control of the process. Smart machining techniques can be applied for recognising and adapting the cutting parameters in real time, depending on a database for decision-making. In this paper, a technique is proposed to identify the cutting material based on the cutting and feed components of the machining force in a circular milling process. Experiments consist of machining separately Titanium and Aluminium alloy workpieces in a similar range of cutting speed and feed, measuring forces and the position of the cutting tool (X,Y, SP) using the machine-tool data. The results show that it is possible to identify the materials using the calculated tangential and radial force components in the tool referential frame because the values of specific cutting and feed force are significantly different for each material. An specific force map is used as a signature to distinguish the materials in real time machining which can be used for orbital drilling in the next step of the research.
Near-Net Forging of Titanium and Titanium Alloys by the Plasma Carburized SKD11 Dies
Authors: Aizawa Tatsuhiko , Ishiguro Shunsuke , Shiratori Tomomi , Yoshino Tomoaki
Published: July 2022

The carbon supersaturated SKD11 punch and core-die were prepared by the plasma carburizing at 673 K for 14.4 ks. The upsetting experiment was performed by using this punch to describe the plastic flow of pure titanium and β-titanium works in higher reduction of thickness than 50%. The measured load – stroke relationship was utilized to describe the frictional behavior on the contact interface of punch to work materials and their work hardening process. The contact interface of carbon supersaturated punch to work was analyzed to investigate the formation of isolated carbon tribofilms from punch material and to describe the in situ solid lubrication on the contact interface. The micro-hardness mapping technique was also utilized to investigate how to suppress the work-hardening behavior by this in-situ solid lubrication. Free near-net forging experiments were performed to shape the circular β-titanium alloy wires to triangular bars.
Numerical Investigation of Al-Reinforced CFRP Composite under Low-Velocity Impact
Authors: Falaschetti Maria Pia , Zavatta Nicola , Rondina Francesco , Troiani Enrico , Donati Lorenzo
Published: July 2022

Fibre-reinforced composite materials are widespread in lightweight, high-performance applications. However, polymeric composites generally exhibit a brittle behaviour, which makes them susceptible to impact damage. Even low-velocity impacts can produce delaminations, which cause a substantial reduction of the compressive mechanical properties. Metallic layers have been embedded in composite laminates with the aim to improve their fracture behaviour: aluminium plies can be employed to increase the indentation resistance of Carbon Fibre Reinforced Polymers (CFRP) specimens. For this reason, hybrid fibre-metal laminates are expected to be a viable solution to reduce the damage caused by low-velocity impacts. In this work, CFRP specimens reinforced with aluminium plies were modelled using the finite element method and a cohesive zone model. Cohesive elements based on a traction-separation formulation were embedded at each ply-to-ply interface to enforce delamination damage. Different configurations of the Al reinforcements were studied by varying the position of the aluminium layers between the CFRP plies.
Effect of the Geometries on the Fabric’s Formability
Authors: Azzouz Rym , Allaoui Samir
Published: July 2022

The composite materials are high on demand in various applications, because of the wide range of properties that they offer, for that, they need to adapt into complex shapes to serve as a functional part. So, the forming process must be mastered and studied to benefit from what composites offer. The most used manufacturing process for composite materials are the resin transfer molding (RTM), which require a preforming of the dry fabric into the desired shape. During the pre-forming process yarns networks orientation change and different defects can be generated due to a variety of factors that have a role in their appearance, such as the process settings, type of the reinforcement, the characteristics of the shapes’ geometry. In this study, we concentrate on the effect of the geometries’ characteristics on the appearance of the different defects and the induced shear on the fabric. Different geometries have been selected based on a benchmark of the shapes studied in the literature [1–3]. The pre-forming was conducted on 3 types of dry fabrics. Woven and non-woven, balanced, and unbalanced fabrics have been intentionally selected as fabrics with completely different structures (type of material, weaves, balance...) to observe the change in the fabric’s behavior and he induceddefects, in terms of profil, location and amplitude.
Analysis of Thickness Distributions Calculated from Surface Strains Obtained through Digital Image Correlation for Incremental Sheet Forming
Authors: Vanhulst Marthe , Vanhove Hans , Carette Yannick , Waumans Stijn , Duflou Joost R.
Published: July 2022

This paper discusses the thickness distributions calculated from surface strain measurements using stereo Digital Image Correlations (DIC) for parts produced with Single Point Incremental Forming (SPIF). The research is carried out on six benchmark cones and pyramids with each convex, straight and concave walls. The accuracy of the thickness calculations, under the assumption of material incompressibility and using the formula for the Green-Lagrange strains, is compared to the thickness distributions measured with a fringe projection scanner. The thickness estimations based on the measured strains proved to be representative for the measured thickness distributions with a mean error of 0.0182 mm, which corresponds to a relative error of 1.47 % of the mean measured thickness. However, errors of up to 0.1688 mm were found in areas of high wall angles and curvatures, corresponding to a relative maximal error of 13.69 % of the mean measured thickness. Hence, the DIC measurements are well suited for characterizing the thickness. Using the thicknesses calculated from the DIC measurements to find the minimal thickness as an indicator of part failure, is possible with relative errors that have an average overestimation of 2.87% of the minimal measured thickness.
A Crystallization Kinetic Model for Long Fiber-Based Composite with Thermoplastic Semicrystalline Polymer Matrix
Authors: Bigot Nicolas , Boutaous M'hamed , Xin Shi He , Hamila Nahiene
Published: July 2022

A numerical model is presented to simulate the crystallization kinetics in fiber-based composite with thermoplastic semicrystalline matrix. The proposed model, based on Schneider's formalism, considers the specificity of crystalline entities growing in confined medium such as fibrous composite. Indeed, transcrystallization has been experimentally observed many times and its effects on both kinetics and mechanical properties have been largely demonstrated. As an application, this paper aims at illustrating this former effect with a finite element (FE) simulation of the cooling down of a plate. The simulated materials are polypropylene alone and a fiber-based composite with a polypropylene matrix. Information on the temperature, the rate of transformation and the microstructure are obtained from both materials and compared to emphasize the contribution of transcrystallization.
Further Development of an Adaptive Joining Technique Based on Friction Spinning to Produce Pre-Hole-Free Joints
Authors: Wischer Christian , Homberg Werner
Published: July 2022

Mechanical joining processes are an essential part of modern lightweight construction. They permit materials of different types to be joined in a way that is suitable for the loads involved. These processes reach their limits, however, as soon as the boundary conditions change. In most cases, these elements are specially adapted to the joining point and cannot be used universally. Changes require cost-intensive adaptation of both the element and the process control, thus making production more complex. This results in high costs due to the increased number of auxiliary joining element variants required and reduces the economic efficiency of mechanical joining. One approach to overcoming this issue is the use of adaptive auxiliary joining elements formed by friction spinning. This article presents the current state of research on pre-hole-free joining with adaptive joining elements. The overall process chain is illustrated, explained and analyzed. Special attention is paid to demonstrating the feasibility of pre-hole-free joining with adaptive joining elements. The chosen mechanical parameters are subsequently listed. Finally, a comprehensive outlook of the future development potential is derived.
Rapid Heat Control for Thermoplastic Injection Tooling Using Lattice Structures as Heat Exchanger
Authors: Lepoivre Arthur , Edelin Denis , Baudin Nicolas , Soto Jérôme , Villière Maxime , Redais Benoît , Delaunay Didier , Sobotka Vincent
Published: July 2022

Since conventional cooling systems with channels are not adequate to achieve a high aspect quality with a short cycle time, a better concept has to be used to control the fast variation of temperature in the mold, close to the injected part. Recently, with advanced manufacturing technologies like 3D-printing, rapid heat cycle molding are developing, using for example lattice structures as heat exchanger inside the mold. Our work proposes an experimental study to analyze the influence of four lattice structures that were specifically designed for this industrial application. An instrumented bench was developed at the laboratory scale, to test the thermal efficiency of the lattice. The material and geometry of the lattice structures were selected based on their thermomechanical properties and their efficiency as a heat-exchanger. The instrumentation of the bench consists in measuring the flow rate and the pressures in the fluid, and also the temperatures at various locations. This allows us to determine the performances of the lattice structure. The results show that the denser the lattice structure, the better, whether considering the mechanical resistance or the thermohydraulic performances. The key element to understand this phenomenon is the average velocity of the fluid flowing inside the lattice structure, accelerating when the porosity decreases and thus bringing a more intense heat exchange.
Investigation of the Membrane Behavior of UD-NCF in Macroscopic Forming Simulations
Authors: Schäfer Bastian , Haas Stefan , Boisse Philippe , Kärger Luise
Published: July 2022

Unidirectional non-crimp fabrics (UD-NCF) provide an exceptionally high lightweight potentialcompared to other dry fabrics. However, their defect-free formability is limited compared towoven or biaxial fabrics due to their susceptibility to draping effects like wrinkling, gapping andfiber waviness. To predict these local effects and the global forming behavior efficiently, macroscopicmodelling approaches require the consideration of the mesoscopic material structure. A very detailedmacroscopic approach was proposed by Schirmaier et al. [1] and its prediction accuracy validatedwith qualitative and quantitative comparisons to component forming results. However, the approachcouples several deformation modes and therefore requires a very high number of inversely determinedmaterial parameters. In the present work a new macroscopic forming model for the membrane behaviorof UD-NCF is introduced based on superimposed shear, transverse tensile and perpendicular to thecarbon fiber tows oriented compressive strains. The model is parametrized with experimental resultsof different off-axis-tension-tests (OATs) (30°, 45° and 60°) and compared to the model proposed bySchirmaier et al. [1]. The results of the new membrane model agree well with the experimental andsimulative results in large areas, while utilizing a significantly reduced number of material parameters.However, some limitations are identified due to the reduced complexity of the model.
Calibration of the Elasto-Plastic Properties of Friction Stir Welded Blanks in Aluminum Alloy AA6082
Authors: Tucci Fausto , Andrade-Campos António , Thuillier Sandrine , Carlone Pierpaolo
Published: July 2022

In recent years remarkable efforts have been devoted to the study of the formability of tailored blanks processed by friction stir welding (FSW) by means of numerical and experimental approaches. This study aims to perform an inverse analysis to calibrate the constitutive law of FSW blanks produced with different parameters. The evaluated mechanical behavior will be employed in future studies to investigate the formability of such elements by single point incremental forming. This study analyzes friction stir welded blanks in aluminum alloy AA6082-T6 produced with different advancing velocities and tool rotational speeds. Coupons for tensile testing have been cut and collected from the FSW blanks. The longitudinal dimension of the coupons was perpendicular to the tool advancing direction, with the welding centerline located at the middle point of the coupon. From the same welded blanks further coupons have been collected to conduct microhardness testing of the cross-section in the welding zone. Data from digital image correlation (DIC) have been adopted to detect the zones of local variation of the mechanical properties related to the peculiar microstructure determined by friction stir welding. In particular, the data were used as input to feed an iterative numerical routine to calibrate the constitutive law variable as a function of the distance from the welding centerline.
Estimation of the Effective Magnetic Properties of Two-Phase Steels
Authors: Soyarslan Celal , Havinga Jos , Abelmann Leon , van den Boogaard Ton
Published: July 2022

We investigate the predictive performance of specific analytical and numerical methods to determine the effective magnetic properties of two-phase steels at the macroscale. We utilize various mixture rules reported in the literature for the former, some of which correspond to rigorous bounds, e.g., Voigt (arithmetic) and Reuss (harmonic) averages. For the latter, we employ asymptotic homogenization together with the finite element method (FEM) and periodic boundary conditions (PBC). The voxel-based discretization of the representative volume element is conducted with digital image processing on the existing micrographs of DP600-grade steel. We show that unlike the considered isotropic mixture rules, which use only the phase volume fraction as the statistical microstructural descriptor, finite element method-based first-order asymptotic homogenization allows prediction of both phase content and directional dependence in the magnetic permeability by permitting an accurate consideration of the underlying phase geometry.
On the Suitability of Induction Heating for the Manufacture of Reinforced Aluminum Foam Structures
Authors: Formisano Antonio , Boccarusso Luca , Durante Massimo , Galise Francesco , Langella Antonio , Palmieri Barbara , Viscusi Antonio
Published: July 2022

Thanks to an intriguing combination of properties, aluminum foams are becoming materials useful for applications in several industrial fields and can be of great interest as core of reinforced structures. Starting from previous studies of the authors, this research work investigates the feasibility of using the induction heating, a fast, clean, and localized source of energy, to produce structures on aluminum foam, also reinforced; in the last case, by means of an innovative single-step process based on the powder compact melting technique, which considers a steel wire mesh-grid as reinforcement and as a mold. In particular, the aim of the work is a screen of the potential of the induction heating to manufacture plain and reinforced aluminum foam structures.
Influence of Conformal Cooling Channel Parameters on Hot Stamping Tool and Press-Hardening Process
Authors: Palmieri Maria Emanuela , Tricarico Luigi
Published: July 2022

Press hardening is a technology increasingly used in the automotive industries to produce high-strength structural parts in boron steel. The part strengthening is due to a martensitic microstructure, which is obtained during the quenching phase of the process by imposing cooling rates typically higher than 27 K/s. To improve cooling efficiency, conformal cooling channels (CCC) are increasingly adopting thanks to opportunities offered by additive manufacturing (AM) technologies in combination with the development of powders with high thermal conductivity.In this work a methodology for the design of CCC inside hot stamping tools is presented and the press hardening of an automotive B-Pillar in 22MnB5 has been used as case study. The proposed methodology provides for an optimization of the distance between the cooling channels (p) and distance between the tool surface and the cooling channel center (d).
Bond Strength of Co-Bonded Thermoplastic Leading Edge Protection (LEP): The Effect of Processing-Driven Interphase Morphology
Authors: Erartsin Ozan , Zanjani Jamal , Baran Ismet
Published: July 2022

Integrated leading edge protection (InLEP) is a novel LEP method that involves co-bonding a tough thermoplastic to the blade shell of the wind turbine made of fiber-reinforced thermoset polymer. In the co-bonding process, as a result of the interdiffusion of the bonded thermoplastic and thermoset polymers, an interphase is formed between them. An important factor affecting the level of interdiffusion is the cure temperature. In this work, we investigate the influence of cure temperature on the interphase morphology and bond strength of ABS-polyester/glass and PC-polyester/glass hybrid composites. The hybrid composites are manufactured via vacuum-assisted resin transfer molding. Interphase morphology is observed and the interphase thickness is measured via optical microscopy. Bond strength is tested via climbing drum peel testing and subsequently, fractography analysis is carried out on the fractured samples. It was found that both the interphase thickness and bond strength decrease with an increase of cure temperature. The decrease in bond strength at high temperatures was accompanied by an increase in the extent of interfacial failure, while interphase failure at low temperatures promoted higher bond strength.
Numerical Simulation of Recycled PET Preforms Infrared Heating Including Force Convection Effect in the Industrial ISBM Ovens
Authors: Le Anh Duc , Gilblas Rémi , Le Maoult Yannick , Schmidt Fabrice
Published: July 2022

Nowadays, injection stretch blow molding (ISBM) process represents the most employed technology to produce plastic bottles. An important step of this process is the heat conditioning stage which is performed within infrared ovens by the use of powerful halogen lamps. Homogenizing the temperature distribution along and inside the preform at the end of this conditioning stage is one of the key parameters to determine the final quality of the bottle (thickness, mechanical properties, transparency...). In this research work, a numerical software has been developed to simulate recycled PET (rPET) preforms infrared heating inside the industrial ISBM ovens, where both rotation and translation of the preform across different heating modules occur. In addition, the presence of a fan system involving a forced convective condition inside the ovens is also considered using a Computational Fluid Dynamics (CFD) approach instead of using a conventional heat transfer coefficient.
Effect of Temperature on Surface Cracking Defects in AA7075 Hot Extrusion
Authors: Funazuka Tatsuya , Dohda Kuniaki , Takatsuji Norio , Takano Kaito , Sukunthakan Ngernbamrung
Published: July 2022

Aluminum alloys in the 7000 series are high-strength alloys that are used in a wide variety of products in the transportation equipment and aerospace fields to reduce weight. In particular, the A7075 alloy has the highest strength and is expected to find further applications in a wide range of fields such as aircraft parts and sporting goods. However, low productivity is a problem due to its high deformation resistance, tendency to produce surface defects called tearing on the product surface, and short tool life. Tearing tends to occur under high temperature and high speed conditions, and is thought to be caused by local melting of Zn, an additive element, due to heat generation in processing. In this study, to improve the productivity of A7075 alloy, the profile was cooled during extrusion to prevent recrystallization of extrudate surface grains due to processing heat and to prevent processing heat during forming. In order to investigate the cooling effect, hot extrusion simulation was conducted. The cooling effect successfully suppressed the occurrence of tearing. These results indicate that cooling the extrudate during forming reduces the effect of heat generation during forming and prevents recrystallization of the extrudate surface grains and local melting of Zn.
Efficient Build-Up of High-Strength Aluminum Structures Using Friction Stir Additive Manufacturing
Authors: Sigl Martina Elisabeth , Danninger Paula , Bernauer Christian , Hartl Roman , Zaeh Michael F.
Published: July 2022

Friction Stir Additive Manufacturing (FSAM) is a novel process with which large-scale aluminum structures can be produced from high-strength alloys such as the 7xxx series. Due to the prevalence of these alloys in airplanes and rockets, the process offers high application potential, for example in fabricating stringers and stiffeners. The building process in FSAM is characterized by sequentially stacking and friction stir lap welding (FSLW) metal sheets. Before adding the next layer, the surface is machined (i.e., by milling). So far, this is a necessary step to enable gap-free welding of the layers, which results in increased costs and reduced layer heights. The investigations described in this paper were aimed at improving the weld surface quality to enable defect-free FSAM without the additional machining step. For this, FSLW was conducted using different welding tools. The resulting welds were evaluated based on superficial and internal characteristics as well as the mechanical properties (shear strength). With a welding tool in which both a rotating and a stationary shoulder were combined, defect-free weld seams with a mean underfill and a mean flash height of 0.07 mm were produced. In a subsequent study, it was proven that defect-free FSAM without surface machining is possible up to the fifth layer using the combined welding tool.
Comparative Study of the Drilling Operation in Duplex Stainless Steels with Drills of Two and Three Cutting Edges
Authors: Marouvo João , Ferreira Pedro , Simões Fernando
Published: July 2022

The three cutting edge drills are not the most common drills, nevertheless, are characterized by superior stability, excellent precision and finishing, due to the intersection of three cutting edges at one point. In general, stainless steels are considered as difficult to machine materials due to their tendency to work harden, their toughness and relatively low conductivity, leading to poor surface finish, poor chip breaking and built-up-edge formation. In the case of duplex stainless grades, the high strength, and the very good corrosion resistance, only compared with austenitic steels, make these materials as an alternative to the austenitic stainless steels, with superior mechanical properties. In this study, the performance of the drills with two and three cutting edges were evaluated in the drilling of duplex stainless steels, when low-pressure external cooling or high-pressure internal cooling were applied. Whether used drills of two or three cutting edges, the most important factor to increase the number of holes made, is the use of high-pressure internal cooling, in detriment of external low-pressure external cooling. The drills of three cutting edges have better results in roughness and dimensional tolerance of the holes. However, these drills proved to be more fragile and more sensitive to the cutting parameters. The use of three cutting edges drills is recommended for situations where hole quality is more important, while two cutting edges drills is recommended for situations where productivity is the main objective.
Evaluating the Corrosion Resistance of Inconel 625 Coatings, Processed by Compact Plasma Spray, for Applications in Concentrating Solar Power Plants
Authors: Rubino Felice , Merino David , Munez Claudio , Poza Pedro
Published: July 2022

Thermal energy storage (TES) systems have paramount importance in the design of Concentrating Solar Power (CSP) plants. TES systems allow storing the energy collected from solar radiation as heat energy in a thermal fluid and, in that way, extending the energy duration period of the plant and making the produced electricity dispatchable, depending on the actual demand and not only on the availability of the sun. The thermal fluids, synthetic oils, or molten salts, usually operate at temperatures from 500°C up to 800°C. The harsh operative conditions bring out issues related to the compatibility with the construction materials of CSP components, i.e., carbon and stainless steel. Coating of low-alloy structural steel with high-resistant materials has been addressed as a promising solution for mitigating the corrosion in TES system components. Compact plasma spray process was used to deposit Inconel 625 alloy onto T22 carbon steel coupons. Nitrate salts mixture, 60%NaNO3-40KNO3, commonly employed in CSP systems as operative and thermal storage fluid was used as corrosion medium. The tests were conducted by immersing coated and uncoated samples in molten salts at 500°C for 1, 3 7, and 14 days to assess the corrosion behavior of the In625 coatings. After 24 hours of exposition to molten nitrate salts, the T22 surface showed a pronounced oxidized layer having a thickness of approximately 20 µm. This layer is mainly composed of oxygen, iron, and chromium, which are the main constituents of carbon steel, with a few traces of sodium and potassium derived from the reaction of salts with the steel. Inconel 625, on the other hand, showed the formation of very thin scales of corrosion products localized only on the surface of the sample. Longer exposition is expected to produce a more pronounced degradation of uncoated steel, but barely affect the Inconel 625 coating
Flexible and High-Precision Integration of Inserts by Combining Subtractive and Non-Planar Additive Manufacturing of Polymers
Authors: Springmann Marlies , Matkovic Nikolas , Schäfer Adrian , Waldhof Marcel , Schlotthauer Tristan , Friedmann Marco , Middendorf Peter , Fleischer Jürgen , Parspour Nejila
Published: July 2022

Additive manufacturing of polymers offers great potential for the production of complex structures. In particular, Fused Filament Fabrication (FFF) processes can be used to create functionally integrated components, in addition to easy handling, tool-free production and large material options. By combining a FFF system with a robot, inserts of different types can be integrated automatically during the printing process [1]. The low dimensional accuracy of FFF induces great difficulties during the insertion operation. Furthermore, with FFF, a planar layer structure leads to a stair-step effect when overprinting inserts with curved outer contours and reduces the adhesion to the insert. Further, the adhesion of FFF-filaments to the insert depends on the surface treatment of the insert [1]. A FFF system was combined with a robot [2] and has now been expanded to include a subtractive finishing unit and an inline process control based on a machine vision system, which enables the dimensional accuracy of the FFF components to be checked during the printing process. To be able to produce functionally integrated components, a flexible control architecture is being developed that enables the execution of additive and subtractive process steps. Optimal integration of inserts with complex geometries is facilitated by using non-planar layers in the FFF path planning. For this purpose, the filament layers of the FFF components follow the tilted or curved contours of the inserts. The modified process is demonstrated by manufacturing an integrated stator for an electric motor. A system for an additive-subtractive process for the integration of functional inserts was developed. In addition, a concept for the implementation of an improved connection of the inserts through non-planar FFF layers was created. First steps for the integration of the various system-modules and optical analysis of the dimensional accuracy and the development of a printing strategy for non-planar overprinting of the inserts have been realized.
Analysis, Prediction and Reduction of Emissions in an Industrial Hot Forming Process Chain for the Manufacture of Sheet Metal Components
Authors: Ghattamaneni Manish Chowdary , Wernicke Sebastian , Hainmann T.S. , Sulaiman H. , Tekkaya A. Erman
Published: July 2022

Increasing demands for reducing greenhouse gases drive the metal processing industries to a CO2-neutral production. A thorough understanding of CO2 emission sources from the stage of material acquisition up to the final component is thus necessary to improve the CO2 footprint of sheet metal hot forming process chains. To emphasize on this, an exemplary hot forming process chain is assessed to identify the impact of each sub-process step on total CO2 emissions and the savings potential of individual measures is evaluated. Moreover, a mathematical model is proposed that enables for the prediction of the product specific CO2 emissions as early as in the product design stage. This model is tested to calculate the CO2 emissions resulted during the production of an exemplary hot stamped sheet component. The results point out that the heating stage is responsible for the second highest percentage of CO2 emissions in the process chain next to the material acquisition. Thus, as one of the most suitable measures, a concept to recover process heat from hot formed components to the cold initial blanks is proposed and evaluated analytically.
The Virtual Fields Method to Indirectly Train Artificial Neural Networks for Implicit Constitutive Modelling
Authors: Lourenço Rúben , Andrade-Campos António , Georgieva Pétia
Published: July 2022

Artificial Neural Networks (ANNs) have the potential to provide a different approach to constitutive modelling, with the main advantage that these do not require to postulate a mathematical formulation or identify empirical parameters. Currently, the training of an ANN for implicit constitutive modelling mostly relies on paired data, usually stress-strain however, stress cannot be directly measured in a real experiment. As such, the training should be carried out indirectly using measurable variables from the experimental setting, such as displacements and the applied force. In the current work, displacements and global force data are used to indirectly train an ANN to predict the stress state of a material. An experimental test is recreated numerically in order to obtain displacement and global force data for different load distributions, i.e. obtaining synthetic data using a virtual experiment. The strain from the current and previous time increments are obtained from the corresponding displacements and used as inputs for the ANN to predict the current state of stress. Training is carried out without stress labels to compute the loss. Instead, the local and global equilibrium conditions, corresponding to the application of the Virtual Fields Method (VFM) to the physical model, are employed to compute the loss and update the network parameters, until the predicted stress state is accurate.
Analysis of Machine-Sided Influences during Clinching
Authors: Grimm Thomas , Drossel Welf Guntram
Published: July 2022

Mechanical joining techniques like clinching are standard joining techniques for processing aluminum and steel alloys in the automotive car body manufacturing. When using conventional methods, joints will have a high quality after a finally tool check on a specific joining press system. However, if the press system during manufacturing will changed, it can occur that joints get other quality values e.g. smaller interlock. The reason for that has multiple influences,this paper considers especially the press-sided ones. With optical measurements of press deformation and punch speed during real joining processes, new 3D-halfsymmetric simulation models were built up, which take into account of press-side behavior such as joining velocity and angular as well as lateral misalignment of the joining tools during clinching process. Sensitivity analyses identifies significant influencing variables. On the base of this, equations of quality changes can be determined. Finally, this allows better prediction of the modification about joint quality after a press change from system A to B or C during manufacturing.
Selected Aspects of Surface Integrity of Inconel 625 Alloy after Dry-EDM in Carbon Dioxide
Authors: Żyra Agnieszka , Skoczypiec Sebastian , Bogucki Rafał
Published: July 2022

The dry-EDM process is environmentally neutral and enables to obtain good machining accuracy and relatively good surface quality. On the other hand, the application of dry-EDM is limited due to problems with the effective dissipation of heat from the machining zone and instability of material removal. The machining of Inconel 625 alloy was carried out in the carbon dioxide as a dielectric supplied to the machining gap through the channel in the working electrode, in the milling kinematics. In one of the investigated variants, the workpiece was submerged additionally in the deionized water during machining. The main aim of this research was to determine an influence of EDM milling in carbon dioxide with and without external workpiece cooling on the workpiece technological surface integrity ie. roughness, morphology and microhardness. The pulse time, current amplitude and gas pressure were selected as investigated parameters. Obtained results indicate significant differences in surface layer properties for both investigated machining variants.
Laser Metal Deposition with Coaxial Wire Feeding for the Automated and Reliable Build-Up of Solid Metal Parts
Authors: Bernauer Christian , Merk Thomas , Zapata Avelino , Zaeh Michael F.
Published: July 2022

Due to their outstanding characteristics, additive manufacturing processes are attracting increasing industrial interest. Among these processes, laser metal deposition (LMD) is an innovative technology for the production of metal components. In order to create three-dimensional parts, wire or powder is deposited layer-wise onto a substrate. When wire is used as feedstock, major drawbacks of the powder-based process, such as the low material usage, contamination of the process cell with metal powder, and health or safety issues, can be overcome or even avoided. In addition, recent developments in laser optics allow for a coaxial wire feeding in the center of an annular laser beam. This eliminates the strong directional dependence of the process when feeding the wire laterally. However, wire-based LMD is highly sensitive to process disturbances, which impedes its broader industrial application. Since it is necessary to completely melt the fed wire to achieve a stable process, self-regulating effects such as overspray in powder-based LMD are not present. In contrast to the widely investigated thin walls, the build-up of multi-track solid structures poses a particular challenge. Therefore, process strategies for producing such solid structures are presented in this paper. The experiments were carried out using a laser processing head that enables coaxial wire feeding (CoaxPrinter, Precitec). By systematically varying the lateral overlap between adjacent weld beads, it was shown that an optimum exists at which minimum surface waviness is achieved. Based on this, defect-free multi-layer solid components could be generated in a reproducible manner. During the process, the melt pool temperature was evaluated using a pyrometer. Furthermore, a microscopic examination of the resulting parts was conducted. The results obtained show the need for process monitoring and control, for which a novel and holistic approach has been developed.
Performance Analysis of Work-Roll Wear Models on Hot Rolling
Authors: Souto Nelson , Marchand Elise , Gay Antonin , Koont Zafer , Legrand Nicolas
Published: July 2022

The purpose of this work is to evaluate the performance of several wear models, either with different mathematical formulation or different definition of the unknown wear coefficients, on the prediction of the work-roll wear amplitude in Hot Strip Mills (HSM). To achieve this goal, a classical model calibration approach based on inverse optimization has been developed to calibrate these several wear models. A large industrial hot rolling database composed by roll wear amplitude measurements for both later finishing mill stands (F6 and F7) from ArcelorMittal Dofasco HSM was considered and a least-square cost function was applied to minimize the differences between both numerical and experimental results during the optimization process. The averaged roll wear gap between measurements and optimized numerical predictions was then used as a quantitative indicator to compare the performance between the wear models and identify the most suitable one for roll wear prediction. In addition, an Artificial Neural Network (ANN) approach was developed based on the most suitable wear model. Thus, roll wear predictions obtained using the ANN were compared with the ones obtained using Classical calibration to evaluate the performance of both approaches.
Analysis of the Part Quality and Process Stability when Producing Metallic Micro Parts by Multi-Stage Bulk Forming from Sheet Metal
Authors: Kraus Martin , Merklein Marion
Published: July 2022

Miniaturization of parts for technical products is an ongoing trend across all industries over the past decades. Due to the large number of possible applications, several billion micro parts are produced every year. In mass production, cold forming offers technological, economical and ecological benefits in comparison to other manufacturing methods. Unfortunately, due to size effects that negatively influence the part geometry, the process stability, the handling and the tool stress, this manufacturing technology is currently barely used. Previous research results have shown that bulk microforming from sheet metal has the potential to reduce the aforementioned restrictions decisively. Within this paper, a three-stage bulk microforming process from sheet metal is experimentally analysed to form a demonstrator geometry with dimensions in the sub-millimetre range in all spatial directions. In the first stage, material is provided in form of a pin for subsequent forming stages. During the second stage, a cup geometry is formed on the pin. Finally, the micro part is separated from the sheet metal by shear cutting. To ensure a wide range of applications, the investigations are carried out with copper, steel and aluminium material. This study is focused on the evaluation of the achievable part quality and the process stability. For the evaluation of the geometry and the surface quality, the micro parts are optically measured with a three-dimensional surface measuring system. The standard deviation of the part dimensions and the process forces are used to investigate the influence of size effects in relation to the material and the grain structure.
A Comprehensive Analysis of AISI 316L Samples Printed via FDM: Structural and Mechanical Characterization
Authors: Carminati Mattia , Quarto Mariangela , D'Urso Gianluca Danilo , Giardini Claudio , Borriello Carmela
Published: July 2022

Metal Fused Deposition Modelling is a promising multi-step process able to manufacture metal parts by means of a low-cost additive technique. In this study, a metal-polymer composite filament characterized by homogenous mixture of AISI 316L sinterable metal powders and a multi-component polymeric matrix was used to fabricate samples by means of a FDM printer. A 24 full factorial design of experiments was elaborated to define the possible influence of the relevant printing parameters on dimensional shrinkage, bulk density and overall porosity of printed samples. In addition, the mechanical properties of printed AISI 316L samples were investigated by performing tensile tests, compression tests, Charpy impact tests, Rockwell B and Vickers hardness tests. An X-ray diffraction analysis was conducted to assess the crystallographic structure of the FDM AISI 316L samples.
Metal Forming-Induced Residual Stresses and Rule of Mixtures’ Prediction of Tensile Behavior of Bimetallic Wires
Authors: Dashti Alireza , Guillet Alain , Keller Clément , Vieille Benoit
Published: July 2022

The present study investigates the tensile behavior of the two bimetallic composite wires Cu-Al and Fe-Al. The purpose is to understand the deviation their tensile strengths show from the Rule of Mixtures’ prediction. To that end, an experimental-numerical approach was adopted. Following tensile testing of the above cold-drawn composite wires, the manufacturing process (wire drawing) was simulated via finite element analysis. The prominent role of processing-induced residual stresses on the yield strength of cold-drawn products is known. Therefore, a discussion based on the axial tensile residual stress profile was developed. It was concluded that the higher-magnitude-near-surface tensile residual stresses in the Fe-Al wire causes its tensile curve to show a negative deviation from the Rule of Mixtures (RoM). The Cu-Al wire, on the contrary, exhibits a slight positive deviation.
Slider on Sheet Tester Development for Characterizing Galling
Authors: Venema Jenny , Korver Frank , Chezan Toni
Published: July 2022

The overwhelming majority of automotive part manufacturing processes successfully process hot dip galvanized sheet metal. However, there were reported situations were abrasive wear (galling), visible as narrow and long scratches, was observed on the surface of the formed parts. Investigations using a Slider On Sheet Tester (SOST) were performed in order to determine the conditions that lead to scratch forming on the galvanized sheet metal surface and to identify parameters that would guarantee a scratch free situation. The tests identified the tool roughness and the contact pressure as important parameters governing the coating wear phenomena. The tests proved that the coating resists relative high contact conditions in case of smooth tool surface, explaining why in the large majority of the industrial applications coated materials can be used without issues.