bluuebunny/crossref_metadata_2025 huggingface dataset:
Advanced image analysis of thermoplastic filaments’ viscous sintering kinetics: Contour fitting with a Lemniscate of Booth
Authors: Chaunier Laurent , Reguerre Anne-Laure , Leroy Eric
Published: April 2021

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.
A Versatile IoT-Approach to Process Data Acquisition
Authors: Behrens Bernd-Arno , Krimm Richard , Koß Jonas , Höber André
Published: April 2021

The acquisition and evaluation of process data in production engineering holds great potential. This allows detecting faulty processes at an early stage and processes to be optimized even more efficiently. However, the use of technologies for data acquisition in the manufacturing industry is far less widespread than the mentioned potential implies. This paper presents an Internet of Things approach by means of which production environments can be retrofitted easily and cost-effectively.
A Three-Dimensional Thermo-Chemical Characterization During the Whole Curing Cycle of a Carbon / Epoxy Prepreg
Authors: Sfar Zbed Rima , Sobotka Vincent , Le Corre Steven
Published: April 2021

Mitigation of cure-induced defects in thermoset composite parts has always been a challenging problem for manufacturers especially when it comes to high dimensional accuracy of components. Thus, it is crucial to understand the evolution of the thermo-chemical properties of these materials during the totality of the curing cycle. In this paper, a new methodology is presented to characterize the process-induced strains throughout the cure. The investigation is based on the development of an existing laboratory bench named as PvT-HADDOC. The tests were performed on an interlayer toughened aerospace carbon/epoxy prepreg. Unidirectional laminate samples (105x105 mm2) of almost 6 mm of thickness were manufactured by hand lay-up then debulked at room temperature under full vacuum. The PvT-HADDOC device allows a manufacturing process following the recommended cure cycle of epoxy composites under 7 bars pressure and a temperature up to 180°C. It enables the measurements of the process-induced strains, simultaneously, along two directions: through-thickness and in-plane. Results show a complex behavior of an assumed unidirectional composite. It exhibits a temperature and time dependent compaction behavior through the thickness only. The measured thermal expansion coefficients are proved to be higher in the thickness direction for the uncured as well as for the cured state of the material. Most of the chemical shrinkage occurs along the thickness direction. This unexpected complexity is mainly attributed to the presence of interleaf layers of resin in the laminate structure. Thus, the investigated M21/IMA material is considered fully orthotropic.
Effects of lubrication, specimen preparation and tool coating on the friction behavior of commercially pure titanium at elevated temperature
Authors: Roszak Jacob Aleksander , Rosochowski Andrzej , Rosochowska Malgorzata
Published: April 2021

Titanium forming processes are often limited by severe adhesive wear as a result of poor friction conditions. This can be partially remedied with careful selection of lubricant, billet preparation and tool coating, but the optimal combination of these factors is not known. A full factorial ring compression experiment, with grade 2 commercially pure titanium rings deformed at 300 °C, was conducted to study the effect of each of these factors over three levels. The change in internal diameter was compared to a set of calibration curves generated by an FEA simulation of the process in order to determine the friction coefficient during each trial. A robust statistical analysis methodology was used to isolate and evaluate the effect of varying each factor. The choice of lubricant was found to be the most statistically significant factor by a considerable margin, followed by the method of billet preparation, with tool coating found to be insignificant. Of the lubricants tested, the graphite-based lubricant resulted in the lowest friction, followed by the WS2- and MoS2-based lubricants. Sandblasted billet surfaces resulted in similar friction to as-machined surfaces, whereas those subjected to micro-arc oxidation performed notably worse. For reducing friction during warm forming of titanium, a graphite-based lubricant is therefore recommended, with tool coating and billet surface preparation unlikely to provide significant further improvement.
Development and experimental validation of a macroscopic analytical model aiming to generate metal-FRP stacks drilling cutting force and torque
Authors: Beuscart Thomas , Arrazola Pedro-José , Rivière-Lorphèvre Edouard , Ducobu François
Published: April 2021

Composites materials and especially FRP are increasingly employed in many fields of applications (transport, aerospace, …) due to the current trend of improving global energy performances of new designs notably by mass saving. However the use of metallic materials such as aluminum and titanium alloys is still necessary in many cases and a lot of structures are made of a dual technology called stacks (panels composed of different layers of FRP and metal bounded together). Combining the different properties of these materials offers many advantages regarding the mechanical and structural aspects. This is nevertheless for the same reason that machining and especially drilling stacks is a laborious task: the tools and cutting conditions are way too divergent to avoid vibrations, problems of dimensional tolerances and delamination of the composite. The knowledge and characterization of the drilling cutting forces is a first step to solve these issues. The purpose of this article is to provide an accurate macroscopic analytical model fitted for stacks and compare it quantitatively with experimental tests. The given model is divided in two parts (i.e. respectively adapted for the two materials) and is based on the discretization of the cutting edge. The proposed algorithm is able to predict accurately drilling force and torque along time in function of the cutting conditions, the tool and material configurations. A reverse least squared method is used to obtain the empirical input parameters, allowing to minimize the number of experimental drilling tests to obtain the empirical input parameters.
Influences of Cutting Speed and Material Constitutive Models on Chip Formation and their Effects on the Results of Ti6Al4V Orthogonal Cutting Simulation
Authors: Kugalur-Palanisamy Nithyaraaj , Rivière-Lorphèvre Edouard , Arrazola Pedro-José , Ducobu François
Published: April 2021

The highly used Ti6Al4V alloy is a well know hard-to-machine material. The modelling of orthogonal cutting process of Ti6Al4V attract the interest of many researchers as it often generates serrated chips. The purpose of this paper is to show the significant influence of cutting speed on chip formation during orthogonal cutting of Ti6Al4V along with different material constitutive models. Finite element analyses for chip formation are conducted for different cutting speeds and are investigated with well-known Johnson-Cook constitutive model, a modified Johnson–Cook model known as Hyperbolic Tangent (TANH) model that emphasizes the strain softening behavior and modified Johnson-Cook constitutive model that consider temperature dependent strain hardening factor. A 2D Lagrangian finite element model is adopted for the simulation of the orthogonal cutting process and the results from the simulations such as calculated forces, chip morphologies are analyzed and are compared with the experimental results to highlight the differences. The results analysis shows that, the temperature in the secondary deformation zone is directly proportional to the cutting speed.
Use of Laser Metal Deposition for launcher parts
Authors: Jimenez Mena Norberto , Dufour Philippe , Nutal Nicolas , Georges Cedric , Brandão Ana
Published: April 2021

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.
Experimental analysis on machining parameters and cooling conditions affecting surface integrity of Ti6Al4V
Authors: Saffioti Maria Rosaria , Sanguedolce Michela , Rotella Giovanna , Umbrello Domenico
Published: April 2021

Machining continues to dominate the market among manufacturing processes requiring in-depth investigation on how material removal processes influence the surface integrity of the products. In this paper, experimental studies were carried out to evaluate the influence of several process parameters on surface integrity changes of Ti6Al4V alloy and to improve the overall process/product performance. In particular, orthogonal cutting operations were conducted varying the process parameters as cutting speed, feed rate and cooling conditions (dry, MQL and cryogenic cooling). Product quality specifications have been monitored in terms of microstructure, hardness modification, phase changes, also including tool wear analysis. Indeed, a systematic study is necessary since various factors are simultaneously involved, as well as changes during processing. Thus, due to the complexity of the process and the number of factors involved, the analysis of variance (ANOVA) was performed to optimize the process through the identification of significant parameters to maximize the useful tool-life and minimize the time of production.
Estimation of track dimensions obtained in Laser Metal Deposition-powder thanks to a semi-analytical model coupled to an Eulerian thermal simulation
Authors: Leroy-Dubief Cécile , Poulhaon Fabien , Joyot Pierre
Published: April 2021

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.
Comparative life cycle assessment of carbon fiber reinforced compositecomponents for automotive industry
Authors: Forcellese Archimede , Mancia Tommaso , Simoncini Michela , Gentili Serena , Marconi Marco , Vita Alessio , Nardinocchi Alessia , Castorani Vincenzo
Published: April 2021

Advanced materials, especially carbon fiber reinforced composites (CFRP), have gained the attention of different industries whichproduce lightweight and high-performance components. The most used manufacturing processes to realize these kinds of products are Resin Transfer Molding (RTM) and vacuum bag molding with autoclave curing. RTM is based on dry fiber technology and it appears the most promising manufacturing process to realized high-quality carbon fiber parts reducing cost and manufacturing time, especially if high pressure variants are employed. On the other hand, vacuum bag molding with autoclave curing is a very consolidated process which is, however, associated with long manufacturing time and costs as well as to low repeatability of the process due to the high labor input. Out-of-autoclave methods, such as pressure bag molding (PBM) have been developed to overcome the issues of vacuum bag molding process. From the environmental point of view, the manufacturing of CFRP components is associated with high environmental loads due to the impacts related to both raw materials and manufacturing processes. For this reason, reducing the energy consumption of production phases can lead to the development of greener CFRP products. In this context, the main scope of the present research is to evaluate and compare the environmental loads of a component for the automotive industry realized exploiting the RTM, the PBM and the bag molding processes to determine which one is eco-friendlier. This analysis has been conducted following the standard Life Cycle Assessment methodology based on a “cradle to gate” approach. In this way, the use phase and the disposal of the CFRP component have not been included in the analysis. Results have been evaluated by comparing the equivalent CO2 related to each manufacturing process.
Evaluation of mechanical property predictions of refill Friction Stir Spot Welding joints via machine learning regression analyses on DoE data
Authors: Bock Frederic E. , Paulsen Tino , Brkovic Nikola , Rieckmann Lennart , Kroeger Dennis , Wolgast Dominik , Zander Philip , Suhuddin Uceu F. H. , dos Santos Jorge Fernandez , Klusemann Benjamin
Published: April 2021

The high-potential of lightweight components consisting of similar or dissimilar materials can be exploited by Solid-State Joining techniques. Whereas defects such as pores and hot cracking are often an issue in fusion-based joining processes, via solid-state joining processes they can be avoided to enable high-quality welds. To define an optimal process window for obtaining anticipated joint properties, numerous time and cost consuming experiments are usually required. Building a predictive model based on regression analysis enables the identification and quantification of process-property relationships. On the one hand, mechanical property and performance predictions based on specific process parameters are needed, on the other hand, inverse determination of required process parameters for reaching desired properties or performances are demanded. If these relations are obtained, optimized process parameter sets can be identified while vast numbers of required experiments can be reduced, as underlying physical mechanisms are utilized. In this study, different regression analysis algorithms, such as linear regression, decision trees and random forests, are applied to the refill Friction Stir Spot Welding process for establishing correlations between process parameters and joint properties. Experimental data sets used for training and testing are based on a Box-Behnken Design of Experiments (DoE) and additional test experiments, respectively. The machine-learning based regression analyses are benchmarked against linear regression and DoE statistics. The results illustrate a decryption of relationships along the process-property chain and its deployment to predict mechanical properties governed by process parameters.
Analysis of the extreme temperature's effect on the low-velocity impact behaviour and damage evolution in sandwich components
Authors: Papa Ilaria , Boccarusso Luca , Mocerino Davide , Langella Antonio
Published: April 2021

Literature reports several works concerning the impact response of composites reinforced with woven fibers and the mechanisms involved in impact energy dissipation. However, even if composites' structures are subjected to various environmental conditions during their service life, few papers are concerned about the impact behaviour at shallow temperatures. Very few discuss sandwich components. In this paper, sandwich composites' low-velocity impact behaviour constructed from carbon fibre reinforced face sheets surrounding a polyvinyl chloride core has been tested. Impact tests at penetration and indentation (U=5,7.5,12,10 and 15J) at room temperature and -55°C, +70 °C were carried out. After each impact test, indentation depth and ultrasound analysis measurements have been implemented to learn the damage modes of the tested samples. The results provided a useful indication on the extreme temperature's influence on both impact properties and damage evolution.
Evaluation of the crosslinking steps of an unsaturated polyester resin during the infusion process of polymer-matrix composites using embedded PZT transducer
Authors: Harizi Walid , Tuloup Corentin , Aboura Zoheir
Published: April 2021

The originality of this study lies in the real-time monitoring of the crosslinking steps of the polyester resin during the Liquid Resin Infusion (LRI) process of polymer-matrix composites (PMC) by a simple measurement of the electrical capacitance variation of a PZT (Lead Zirconate Titanate) transducer embedded into the heart of the fibrous stack. Three mass rates of a Methyl Ethyl Ketone Peroxide (MEKP) hardener were tested (1wt%, 1.5wt% and 2.5wt%). The electrical capacitance showed a very sensitivity to the crosslinking kinetics while identifying the key steps of the physicochemical transitions of the thermosetting matrix. To identify the promising potential of the PZT transducer as a real-time curing assessment tool of the thermosetting resins, and understand its capacitance signature, the LRI device was multi-instrumented by various non-destructive testing (NDT) techniques such as acoustic emission (AE) and infrared thermography (IRT). The obtained NDT results are confronted with the ones conducted using the oscillatory rheology tests. The agreement between the two types of results (NDT and rheological) allows determining the gelation and vitrification phases of the polyester resin impregnating six plies of 2/2 twill glass fabrics.
Experimental determination and numerical prediction of the dynamic forming limits of a press hardened steel
Authors: Weiß-Borkowski Nathalie , Lian Junhe , Schulz-Beenken Anne Suse , Tröster Thomas
Published: April 2021

Material characteristics such as yield strength, failure strain, strain hardening and strain rate sensitivity parameter are affected by loading speed. Therefore, the strain rate dependency of materials for plasticity and failure behavior is taken into account in crash simulations. Moreover, a possibility for consideration of instability at multi-axial dynamic loadings in crash simulations is the use of dynamic forming limit curves (FLC). In this study, the dynamic FLC of the press hardened automotive steel Usibor 1500 (AlSi coated 22MnB5) is investigated. The experimental results are obtained from a unique high-speed Nakajima setup. Two models are used for the numerical prediction. One is the numerical algorithm CRACH as part of the modular material and failure model MF GenYld+CrachFEM 4.2. Furthermore, the extended modified maximum force criterion considering the strain rate effect is also used to predict the dynamic FLC. The comparison of the experimental and numerical results are presented and discussed.
Analysis of Sub-processes Specific to Hybrid Non-conventional Machining Methods
Authors: Schulze Hans-Peter , Kröning Oliver
Published: April 2021

In principle, all non-conventional machining processes can be viewed as the sum of various sub-processes, the separate analysis of which influences the effectiveness of this machining process. The first question to answer is the criteria by which these sub-processes can analyzed. Since the non-conventional processes work exclusively based on electrical energy, voltage and current determine the character of the sub-process. The second focus is the time constant with which voltage and current influence the process, from which the measurement of the corresponding parameters result. The third group of influencing parameters is the working medium and its change due to the main removal process. In the summary, these three groups are consider with regard to a process model with which a process control (technology), a process regulation (process stability) and a safety control (limit value exceeded) are guide.
Clinching in In-situ CT – Experimental Study on Suitable Tool Materials
Authors: Köhler Daniel , Kupfer Robert , Troschitz Juliane , Gude Maik
Published: April 2021

In lightweight design, clinching is a cost-efficient solution as the joint is created through localized cold-forming of the joining parts. A clinch point’s quality is usually assessed using ex-situ destructive testing methods. These, however, are unable to detect phenomena immediately during the joining process. For instance, elastic deformations reverse and cracks close after unloading. In-situ methods such as the force-displacement evaluation are used to control a clinching process, though deviations in the clinch point geometry cannot be derived with this method. To overcome these limitations, the clinching process can be investigated using in-situ computed tomography (in-situ CT). However, a clinching tool made of steel would cause strong artefacts and a high attenuation in the CT measurement, reducing the significance of this method. Additionally, when joining parts of the same material, the sheet-sheet interface is hardly detectable. This work aims at identifying, firstly, tool materials that allow artefact-reduced CT measurements during clinching, and, secondly, radiopaque materials that can be applied between the joining parts to enhance the detectability of the sheet-sheet interface. Therefore, both CT-suitable tool materials and radiopaque materials are selected and experimentally investigated. In the clinching process, two aluminium sheets with radiopaque material in between are clinched in a single-step (rotationally symmetric joint without cut section). It is shown that e.g. silicon nitride is suited as tool material and a tin layer is suitable to enhance the detectability of the sheet-sheet interface.
On the multiscale analysis of a two phase material: crystal plasticity versus mean field
Authors: Mirhosseini Shahrzad , Perdahcioglu Semih , Atzema Eisso , Boogaard Ton van den
Published: April 2021

In this paper, a comparison is made between two multiscale methods, namely crystal plasticity finite element and mean field on a material composed of two phases. Both methods are used to homogenize a given microstructure. In order to obtain macroscopic behavior, in the mean field approach, a Self-Consistent scheme is used to evaluate stress and strain partitioning among the phases. In this method, an average of the fields is estimated and local distributions cannot be captured. In parallel, crystal plasticity simulations on Representative Volume Elements (RVEs) composed of hexagonal grains are performed. In these simulations, grain orientations are attributed randomly respecting Mackenzie's distribution function in order to achieve isotropic behavior and macroscopic hardening is extracted from the simulations. The results on macroscopic hardening of both methods are compared to distinguish the extents of validity of mean field homogenization. In addition to Self- Consistent, other mean field schemes such as Voigt, Reuss and Bound-Interpolation are compared in terms of efficiency and accuracy. The comparison manifests that Self-Consistent scheme is capable of predicting material behavior well.
Development of General data-based Process Models for Self-Pierce Riveting
Authors: Jäckel Mathias , Falk Tobias , Kropp Thomas , Drossel Welf-Guntram
Published: April 2021

The determination of ideal process parameters for mechanical joining processes such as self-pierce riveting currently requires a comprehensive understanding of the process, the availability of the materials to be joined and the corresponding system technology. General process models can simplify the use of these joining technologies, accelerate development cycles and thereby reduce the effort for implementation into production. In this paper, the development of general data-based process models for the mechanical joining method self-pierce riveting with semi-tubular rivet is described. Extensive experimental and numerical investigations with more than 2300 joint combinations for steel and aluminum sheets with tensile strengths between 240 - 1020 MPa were generated for the building of the models. Based on these results, different meta-models are fused into general data-based process models for the self-pierce riveting process in order to show the general relationships between material properties, process parameters and joining results. The paper discusses the acquisition of the experimental and numerical data, the statistical methods for evaluation and the application of the data-based process models.
Combined-cycle corrosion testing of steel/6000 series aluminum alloys joined by friction welding
Authors: Jin Jianchen , Iizuka Takashi
Published: April 2021

Tailored blanks, especially semi-finished parts formed by welding steel and aluminum alloys, are being employed in the automobile industry to reduce the weight of automobiles. However, when dissimilar metals are welded, galvanic corrosion due to differences in ionization tendency occurs, decreasing the reliability of such welded products. In addition, the heat input when aluminum alloys are welded causes an aging problem. In this study, combined-cycle corrosion testing was performed for S45C/6000 series steel/aluminum alloys joined by friction welding. First, S45C steel pipes were joined to A6061-T6 and A6063-T6 aluminum alloy pipes by friction welding. Then, after combined-cycle testing, changes in appearance and joint strength were investigated as the number of cycles increased. In the natural aging test, test pieces were placed in a desiccator whose temperature was adjusted to about 20 °C with a humidity from 0 to 10 %. One piece was removed at predetermined time intervals and used in tensile testing. After tensile testing, fracture surfaces were observed with an optical microscope. For the S45C/A6061 friction- welded material, a decrease in tensile strength was found at the 36th cycle. It was confirmed that the strength of the S45C/A6063 friction-welded material decreased clearly at the 27th cycle. Any obvious changes in strength were not seen in specimens after 540 hours of natural aging.
Investigation on tailored blanks in a full forward extrusion process of sheet-bulk metal forming
Authors: Reck Manuel , Merklein Marion
Published: April 2021

Due to the ongoing technological development, the demand for geometrically complicated high performance parts with great functional density is increasing. Often, the use of sheet metal is a beneficial approach in manufacturing technology to meet the requirements on components regarding material strength and lightweight construction goals. The forming of therefore required complex sheet metal part geometries with integrated functional elements cause the need for a three dimensional material flow. Sheet-bulk metal forming, characterized by the application of bulk forming operations on sheet metals, is a suitable approach to produce such components. A challenge is the material flow control, resulting in an insufficient die filling of the functional elements. The use of tailored blanks with a defined sheet thickness distribution is an auspicious approach to face this challenge in subsequent forming processes. In the presented work, semi-finished products with a continuous thickness profile manufactured by orbital forming are applied in a full forward extrusion process. By an additional implementation of a heat treatment, the tailored blanks undergo a recrystallization process that causes a softening of the strain hardened material. In this paper, the potential of a heat treatment in the process class of sheet-bulk metal forming is shown by characterizing the geometrical and mechanical properties of the functional components by applying the mild deep drawing steel DC04 with an initial sheet thickness of t0 = 2.0 mm.
Analysis and optimization of cooling channels performances for industrial extrusion dies
Authors: Pelacci Riccardo , Negozio Marco , Reggiani Barbara , Donati Lorenzo , Tomesani Luca
Published: April 2021

Liquid nitrogen cooling is widely used in the extrusion industrial practice in order to increase the production rate, to reduce the die temperature and to avoid defects on the profile exit surfaces resulting from an excessive heating. However, the efficiency of the cooling is deeply affected by position and design of the liquid nitrogen channel so that numerical modelling is gaining an increasing industrial interest in relation to the possibility offered to optimize the channel design without expensive and time-consuming experimental trials. In this work, a numerical FE model developed within COMSOL Multiphysics® is proposed and validated against experimental trials performed in industrial environment. The model combines the 3D simulation of the extrusion process with a 1D model of the cooling channel thus allowing the testing of a number of different solutions at the die design stage. The global aim of this work is the assessment of the liquid nitrogen cooling efficiency in the extrusion of an industrial aluminum profile and the proof of the potentials offered by numerical models to get an optimized channel design in terms of cooling efficiency, die thermal balancing and reduction of liquid nitrogen consumption.
Optimization of process-property relations of 3D printed ceramics using extrusion-based additive manufacturing
Authors: Farid Muhammad Asad , Strano Matteo , Rane Kedarnath
Published: April 2021

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.
Temperature induced friction increase in friction test and forming demonstrator for sheet metal forming
Authors: Filzek Jan , Keil Daniel , Schröder Holger
Published: April 2021

High process stability is needed in sheet metal forming industry. This can be achieved by predicting and controlling the transient process and temperature variation, especially at start of production. In this connection, the temperature induced friction changing plays a significant role because it leads to product failures. The handling of the transient friction effects is currently done reactively, based on the individual experience of the machine operators. In future, those transient effects need to be controlled. This paper shows initially an analysis of the temperature induced friction increase in a well-known and proven flat strip drawing test. Different tribological systems were tested at tool temperatures between 20 and 80 °C. The temperature increase results in a higher friction of up to 77 %. Several influences on friction increase will be presented. These friction influences were verified afterwards with a heated forming demonstrator under laboratory conditions.
Virtual parameter identification of the forming behaviour of discontinuous fibre reinforced thermoplastic composite sheets
Authors: Kabala Philipp , Ossowski Tim , Hürkamp André , Beuscher Jan , Dröder Klaus
Published: April 2021

Fibre-reinforced thermoplastics (FRTP), such as organo sheets or laminates, are increasingly being used in large-scale automotive production. The high weight-saving potential, high specific strengths and stiffnesses as well as processing times suitable for large-scale production are some of the reasons for using these materials. However, the formability of such semi-finished products is severely limited by the fibre reinforcement, which can lead to fibre breakage, fibre displacement or wrinkling in complex-shaped components. In order to increase the formability, an FRTP semi-finished product is developed, which consists of discontinuous tapes. Due to the local sliding of the tape sections, a pseudo-plastic material behaviour is achieved. Experimental uniaxial tensile tests at elevated temperatures are used to investigate the forming behaviour of the material for different tape lengths and overlap lengths. Subsequently, this tensile test is numerically modelled in order to fit the pseudo-plasticity to the experimental data by a virtual parameter identification. With the help of the parameters determined from the numerical tensile test, the sliding behaviour of the tape sections can be used for forming simulations in order to achieve a higher prediction quality.
A computational method for pass design of the four-roll rolling process for sizing of round sections
Authors: Overhagen Christian
Published: April 2021

The four-roll rolling process (4RP) enables the further evolution of sizing processes in rolling mills for round sections. The well-known advantages of the three-roll process over the two-roll process can be further improved using the 4RP. The participation of four rolls in the deformation zone instead of three or two leads to a significant increase in deformation efficiency. The present work shows a pass design method for pass sequences in the four-roll rolling process. Here, three basic types of roll groove geometries are discussed: the flat groove, the non-opened single-radius groove, and a tangentially opened type of a single radius groove. Based on a predefined cross-sectional evolution, grooves are found numerically to satisfy two conditions, i.e., the cross section of the rolled section and the groove filling criterion. The equations of the equivalent pass method, together with a suitable model for lateral spread and the geometric equations of the groove are solved by nonlinear optimization to minimize the sectional and filling errors of a specific pass. Combined for several rolling passes, a complete pass design can be carried out for the reduction of a specified initial section to a final section. The presented results show, how a pass design method for the four-roll rolling process can be constructed. The newly developed model is implemented in a software solution for pass design and analysis of full section rolling mills. An exemplified pass design is discussed to show the possibilities and limitations of the new model.
Fused Filament Fabrication of ONYX-Based Composites Coated with Aluminum Powders: a Preliminary Analysis on Feasibility and Characterization
Authors: Perna Alessia Serena , Astarita Antonello , Borrelli Domenico , Caraviello Antonio , Delloro Francesco , Della Gatta Roberta , Lomonaco Patrizio , Papa Ilaria , Sansone Raffaele , Viscusi Antonio
Published: April 2021

Polymer-based AM methods are the most mature additive technologies for their versatility and variety of products obtainable. The addition of fibre reinforcement can also confer to the manufactures produced good mechanical properties. Unfortunately, several applications are still precluded because polymers cannot guarantee appropriate electrical conductivity, erosion resistance and operating temperature. Aiming to overcome these issues, the metallization of the surfaces emerges as a possible solution. Unfortunately, thermoplastic polymers exhibit thermosensitive behaviour and run the risk of being damaged when traditional metallization techniques, which require the melting of metal powders which will act as a protective coating. For this reason, studies have focused on Cold Gas Dynamic Spray, an additive manufacturing technology, which exploits kinetic energy to favour the adhesion of metal particles rather than the increase in temperature. In this work, a first attempt is made to verify the feasibility of cold spray coatings on 3D printed composite substrates, produced by means of Fused Filament Fabrication (FFF) technique. FFF technology allows the deposition of two different types of filaments by using a double extruder. These composite fibres within 3D printed parts manage to give the object a resistance comparable to that of a metal part with lower production cost and a high degree of automation. These structures, made of ONYX, a Nylon matrix in which short carbon fibres are dispersed, and reinforced with long carbon fibres, are designed to better fit the CS deposition. Aluminium coatings have been produced and a characterization campaign has been carried on.
Efficient Prediction of Real-Time Forming Forces in Flexible Stretch Bending
Authors: Ma Jun , Welo Torgeir , Ringen Geir
Published: April 2021

Stretch bending is commonly used in the mass production of profile-like products in many industrial sectors due to its high dimensional accuracy and process capabilities. One of the challenges of conventional stretch bending is low flexibility, however, making it difficult to meet today’s requirements for mass customization. As a countermeasure, a novel flexible rotary stretch bending process was presented (Ma and Welo, 2021), which allows the forming of complex shapes with varying curvatures and angles. However, less knowledge is known about the most fundamental force requirements during forming, which in turn limits the design and development of product and process. In this research, an analytical model is developed for accurate and efficient prediction of real-time forming forces in flexible rotary stretch bending, aiming to enhance the understanding of applied force requirements throughout the process. In this model, the entire kinematically-controlled loading (strain) history is considered to realize real-time monitoring of force. In addition, the elastic-plastic properties of profile, the profile dimensions, the tooling geometries as well as the tool-workpiece friction are comprehensively taken into account to improve the analytical accuracy of forming force predictions. As an explicit solution can be achieved, the analytical model presents high efficiency for quick prediction, which can be used in attempts to adaptively control the process. Based on finite element simulation, the analytical model is validated in the forming of aluminium rectangular, hollow profiles, showing very high accuracy and efficiency for predicting real-time forming forces of both clamp unit and bending die for forming with different pre-stretching levels.
Investigation of The Anisotropic Behaviour of Laser Heat Treated Aluminium Blanks
Authors: Piccininni Antonio , Lattanzi Attilio , Rossi Marco , Palumbo Gianfranco
Published: April 2021

The continuous research for progressively lighter components moves the attention on the massive adoption of Al alloys. The achievement of such an ambitious goal passes through the definition of innovative manufacturing methodologies able to overcome some of the most hindering limitation of Al alloys, i.e. their poor formability at room temperature. A viable approach is based on the modification of the blank properties through a local heat treatment (to achieve an optimized spatial distribution of ductility/strength), so that the subsequent forming operation can be carried out at room temperature. The implementation of such approach relies on finite element simulations, where the use of a proper constitutive material model plays a fundamental role. In the present work an innovative methodology, already proposed by the authors in a previous research, is again adopted to enrich the characterization of a strain-hardenable Al alloy (AA5754), initially purchased in a pre-strained condition (H32), and locally annealed by means of a laser treatment: in particular, Thanks to the adoption of the DIC, the investigation of the anisotropy showed a strict correlation between the value of the Lankford parameter and the material condition reached at the end of the local treatment. The experimental data were fitted by a sigmoidal function and implemented in a modified Hill plasticity model for the simulation of the tensile test of a locally treated dogbone specimen, showing a good accordance with the experimental results.
Direct Laser Deposition for Tailored Structure
Authors: Silvestri Alessia Teresa , Amirabdollahian Sasan , Perini Matteo , Bosetti Paolo , Squillace Antonino
Published: April 2021

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.
Multi-scale characterization of material and surface integrity of Inconel 718 when milling by Abrasive Water Jet process: Context of repair application
Authors: Salinas Lorena Cano , Moussaoui Kamel , Hejjaji Akshay , Salem Mehdi , Hor Anis , Zitoune Redouane
Published: April 2021

Inconel 718 (IN718) is a precipitation hardened nickel-base super-alloy exhibiting poor machinability and used in the hot section of aircraft engines. These components are subjected to severe thermo-mechanical loads in a highly corrosive environment, limiting their service life due to cracks and wear. Due to their high added-value, repair of damaged IN718 components is an interesting alternative instead their replacement. Repair process involves material removal of the damaged zone and subsequent cavity refill. Nevertheless, material removal of IN718 by conventional methods is a challenging task. Abrasive Water Jet (AWJ), a non-conventional machining process, offers a potential alternative to mitigate IN718 machining problems. However, research on the impact of AWJ process parameters during IN718 milling on the surface and material integrity is limited in the literature. Furthermore, in repair context, no study proposes AWJ machining as material removal process. The present work focuses on a multi-scale characterization of the influence of AWJ process parameters (pressure, traverse speed, step-over distance and abrasive size) on surface roughness, depth of cut, abrasive embedment and residual stress, during milling of untreated IN718. Surface integrity characterization on the milled surfaces was conducted through 3D optical microscopy, profilometry and SEM techniques. Residual stress measurements were performed in longitudinal and transverse directions with respect to the machining path using XRD technique. The results showed that all milled surfaces presented abrasive embedment and a compressive residual stress state with similar values in both directions. Up to 15% of the area of a milled surface consisted of abrasive embedment. The tool path has not influenced the residual stresses. Furthermore, surface roughness is dependent on pressure and traverse speed; depth of cut is influenced by pressure, traverse speed and grit size; abrasive embedment depends on pressure, step-over distance and grit size; whilst, residual stresses are influenced by traverse speed and grit size.