bluuebunny/crossref_metadata_2025 huggingface dataset:
Yeni dünya ekonomik düzeni: G-11 ülkeleri
Authors: CİNEL Emek Aslı
Published: April 2021

2005 yılında Goldman Sachs, nüfusu oldukça yüksek düzeyde olan on bir ülkeyi aynı sınıflandırmaya dâhil ederek “Gelecek 11 (Next 11)” ya da N-11 biçiminde ifade etmiştir. Bu sınıflandırmaya dâhil olan ülkeler Bangladeş, Mısır, Endonezya, İran, Güney Kore, Meksika, Nijerya, Pakistan, Filipinler, Türkiye ve Vietnam olarak belirlenmiştir. Bu ülkelerin hepsinde nüfusun oldukça yüksek düzeyde olduğu dikkat çekmektedir. 2000-2010 döneminde yenidünya ekonomik düzeni oluşmaya başlamıştır. 2000’li yılların ortalarına gelirken dünya devi olarak ifade edilen Amerika gibi ülkelerin yaşamış olduğu ekonomik durgunluk sonrasında özellikle gelecek on bir (G-11) ülkelerinin dikkat çekmeye başladığı, yükselen piyasalar olarak nitelendirildiği gözlenmiştir. Çalışmanın amacını Türkiye’nin de içinde yer aldığıyeni yükselmeye başlayan ve (G-11) olarak ifade edilen ülke ekonomilerini incelemek ve karşılaştırmak oluşturmaktadır. Bu amaç doğrultusunda çalışmada bu ülke ekonomilerine ait ekonomik, finansal ve demografik veriler kullanılarak ülke piyasaları değerlendirilmiştir. G-11 ülkeleri yenidünya ekonomik düzeninin bir yansımasıdır. Bu ülkelerin birçoğu geleceği yönlendirebilecek olan ülkelerdir. Güney Kore, teknolojiyi üretmede ve kullanmada gösterdiği üstün başarı ve hızlı büyüme ile bunu tüm dünyaya ispat etmiştir. Bu anlamda, Güney Kore’nin ekonomik başarısını ve uyguladığı ekonomi politikalarınıdiğer G-11 ülkeleri de örnek almalı ve aynı başarıyı gösterebilmelidir. Türkiye ekonomisinin geleceğini şekillendirecek olan ekonomik ve sosyal reformların hızla uygulanması, yükselen piyasalarla rekabet gücünün artırılması gerekmektedir.
On the optimisation efficiency for the inverse identification of constitutive model parameters
Authors: Oliveira Miguel Guimarães , Martins João Miguel Peixoto , Coelho Bernardete , Thuillier Sandrine , Andrade-Campos António
Published: April 2021

The development of full-field measurement techniques paved the way for the design of new mechanical tests. However, because these mechanical tests provide heterogeneous strain fields, no closed-form solution exists between the measured deformation fields and the constitutive parameters. Therefore, inverse identification techniques should be used to calibrate constitutive models, such as the widely known finite element model updating (FEMU) and the virtual fields method (VFM). Although these inverse identification techniques follow distinct approaches to explore full-field measurements, they all require using an optimisation technique to find the optimum set of material parameters. Nonetheless, the choice of a suitable optimisation technique lacks attention and proper research. Most studies tend to use a least-squares gradient-based optimisation technique, such as the Levenberg-Marquardt algorithm. This work analyses optimisation algorithms, gradient-based and -free algorithms, for the inverse identification of constitutive model parameters. To avoid needless implementation and take advantage of highly developed programming languages, the optimisation algorithms available in optimisation libraries are used. A FEMU based approach is considered in the calibration of a thermoelastoviscoplastic model. The material parameters governing strain hardening, temperature and strain rate are identified. Results are discussed in terms of efficiency and the robustness of the optimisation processes.
Numerical prediction of process-dependent properties of high-performance Ti6Al4 in LS-DYNA
Authors: Buhl Johannes , Klöppel Thomas , Merten Mathias , Haufe Andre , Rameez Israr , Bambach Markus
Published: April 2021

In modern manufacturing processes such as hot forming or additive manufacturing, the workpiece material undergoes very complex thermomechanical load cycles. The local mechanical properties in the component are process-dependent and the result of the different micro-structure evolution mechanisms in the material. Numerical process simulation tools aim to include more and more of these mechanisms in order to improve the accuracy of the simulations. The mechanical strength of high-performance materials such as Ti-6Al-4V depends on microstructural parameters, which are influenced by the temperature and strain histories. This contribution puts forward an implementation of a new generalized internal variables material model *MAT_GENERALIZED_PHASECHANGE in LS-DYNA. The evolution of internal variables such as phase fractions, grain size and dislocation densities can be predicted by evolution equations, and combined with yield stress models taking the contribution of the phases, grain sizes (Hall-Petch effect), and the dislocation density into account to predict the resulting mechanical properties of the processed material. The benefits of the implementation in the commercial software LS-DYNA is the possibility to solve complex coupled problems. For example, the new material law can be used to simulate hybrid manufacturing processes like forging and an additional additive manufacturing process, where changes in microstructure are highly coupled and important for the part properties.
Forming defects prediction in cup drawing and embossing of a thick steel sheet
Authors: Oliveira Marta Cristina , Neto Diogo M. , Barros Pedro D. , Alves José L. , Menezes Luis F.
Published: April 2021

The accurate prediction of forming defects is fundamental for the virtual try-out of metallic sheet components. However, the constitutive model can have a strong impact on the numerical predictions, namely the cup earing, the occurrence of wrinkles and the tearing failure. The process conditions considered in this work are the ones established for the “Benchmark 2 – Cup Drawing of Anisotropic Thick Steel Sheet”, proposed under the Numisheet 2018 international conference. The axisymmetric cups are obtained from a steel sheet with 2.8 mm of thickness, resorting to different process conditions to induce different defects. The advanced yield criterion proposed by Cazacu and Barlat is used to define the anisotropic behavior of the blank. The calibration of the material parameters is carried out by fitting the following experimental data from: (i) uniaxial tensile tests performed in every 15º to the rolling direction; (ii) biaxial tension tests to evaluate the directions of the plastic strain rates in the first quadrant of the yield loci. The numerical predictions are compared with the experimental measurements, allowing to assess the accuracy of the finite element model to predict each type of forming defect. The cup earing and the strain localization are accurately predicted, while the wrinkles amplitude is clearly underestimated.
Influence of the Laser Heat Treatment on the AA5754-H32 strain path during hydraulic bulge tests
Authors: Cusanno Angela , Moturu Shanmukha , Carty David , Palumbo Gianfranco
Published: April 2021

The hydraulic bulge test represents an effective experimental method to characterise sheet metals since the equivalent strains before failure are much larger than those measured during tensile testing and there is nearly no frictional effect on the results. Recently this test has been proposed not only for extracting data concerning the equi-biaxial strain condition, but to determine the forming limit diagram (FLD) in the range of positive minor strains. In the proposed methodology, different strain paths can be obtained by merely using a test blank having two holes with a suitable geometry and position to be tested, without the need of dies with elliptical apertures. However, a carrier sheet is necessary, thus implying results may be affected by friction effects. This paper proposes a new methodology for the determination of the right side of the Forming Limit Curve (FLC), based on the adoption of local heat treatments aimed at determining different strain paths on the blank to be tested while using the classical circular die for bulge tests. In particular, the formability of the alloy AA5754-H32 was investigated; 3D Finite Element simulations were conducted setting different laser strategies and monitoring the resulting strain path. Results revealed that the proposed methodology supports obtaining many additional points in the right side of the FLC, thus being effective and friction free.
Revisiting flangeability in hole-flanging by single-stage incremental forming and conventional process
Authors: Borrego Marcos , Morales-Palma Domingo , Lopez-Fernandez José Andrés , Martinez-Donaire Andrés J. , Centeno Gabriel , Vallellano Carpóforo
Published: April 2021

Recently, hole-flanging by single-stage incremental forming (SPIF) has been proposed as a suitable process to perform hole flanges for small- and medium-sized batches with high flexibility in shape. However, this incremental forming has many differences compared with the conventional press working operation in terms of strain and thickness distributions, failure mechanisms and flangeability measures. In fact, regarding the evaluation of the formability of the flanges, the classical Forming Limit Ratio (LFR) should be used with care to quantify this property in hole-flanging by SPIF. Additionally, the FLC (Forming Limit Curve for necking) and FFL (Fracture Forming Limit) curves, powerful tools for analysing sheet failure in practice, may also yield erroneous prediction of necking in conventional press working or fracture in SPIF. The aim of this work is to present a comparison and analysis of the formability of hole flanges performed by SPIF and press working in AA7075-O sheets. Two complementary parameters to the LFR to compare the flangebility in both operations are discussed, along with the influence of bending induced by the forming tool and the stress triaxiality in the evolution of the principal strains during the forming process. The results point out the limitations in the current practice.
A non-intrusive model order reduction approach for multi-physics parametrized problems - Application to induction heating process
Authors: Derouiche Khouloud , Chinesta Francisco , Daoud Monzer , Traidi Khalil
Published: April 2021

Finite element modeling (FEM) has recently become the most attractive computational tool to predict and optimize many industrial problems. However, the FEM becomes ineffective as far as complex multi-physics parameterized problems, such as induction heating process, are concerned because of high computational cost. This work aims at studying the possibility of applying a new approach based on the reduced order modeling (ROM) to obtain approximate solutions of a parametric problem. Basically, the effect of induction heating process parameters on some physical quantities of interest (QoI) will be analyzed under the real-time constraint. To achieve this dimensionality reduction, a set of precomputed solutions is first collected, at some sparse points in the space domain and for a properly selected process parameters, by solving the full-order models implemented in the commercial finite element software FORGE®. A Proper Orthogonal Decomposition (POD) based reducedorder model is then applied to the collected data to find a low dimensional space onto which the solution manifold could be projected and an approximated solution for new process parameters could be efficiently computed in real time. Besides, the POD is applied to build a reduced basis and to compute their corresponding modal coefficients. It is then followed by artificial intelligence techniques for regression purpose, such as sparse Proper Generalized Decomposition, to fit the low dimensional POD modal coefficients. Hence, the problem can be solved with a much lower dimension compared to the initial one. It was shown that a good approximation of the QoI was provided, in low-data limit, using a single POD modal coefficient as a response for the regression methods. However, the obtained approximation accuracy needs to be enhanced.
Investigation of the forming behavior of carbon fiber yarns on microscopic scale with detailed statistical volume elements
Authors: Engelfried Mathias , Middendorf Peter
Published: April 2021

Simulations at microscopic scale are subject of research in many fields of continuous fiber reinforced materials. They allow the virtual characterization with clearly defined boundary conditions and the investigation of effects that cannot easily be observed in experimental tests, such as crack initiation. While the influence of differently detailed modeling, such as variable fiber radii, is well investigated for consolidated composite materials, that influence is not well investigated for dry yarns. The effect of different modeling aspects on the shearing of statistical volume elements (SVE) is object of this study. Those aspects are in particular the SVE’s size and side ratio, the deformation velocity, the friction coefficient and the initial stress of the elements. The investigations have shown that the deformation of the SVEs is very sensitive to changes of the named parameters. Especially parameters that influence the number of fiber contacts or the friction forces have a noticeable effect on the shear stress. In addition, changes in the velocity have a significant impact on the deformation. Therefore, it is necessary to characterize the fiber and yarn parameters precisely and transfer them into the simulation model to obtain a realistic deformation behavior.
Effect of Single Crystal Orientation on Forming
Authors: Chandola Nitin , Cazacu Oana , Revil-Baudard Benoit
Published: April 2021

Among processes involving plastic deformation, sheet metal forming requires a most accurate description of plastic anisotropy. One of the main sources of mechanical anisotropy is the intrinsic anisotropy of the constituent crystals. In this paper, we present the single-crystal yield criterion recently developed by Cazacu et al. [1] and its application to the prediction of anisotropy in uniaxial tension of strongly textured polycrystalline sheets. Namely, it is shown that using this single crystal yield criterion the Lankford coefficients exist and have finite values for all loading orientations. Moreover, the variation of both the yield stress and Lankford coefficients with the crystallographic direction can be expressed analytically. An application of this criterion to forming a cylindrical cup from a single crystal of (100) orientation is presented. Finally, we show that using this single-crystal model, one can describe well the effect of the spread around an ideal texture component on the anisotropy in uniaxial tensile properties of a polycrystal.
Expansion of oval tubes: prediction and experiment
Authors: Clausmeyer Till , Gutknecht Florian , Hassan Hamad ul , Kaya Deniz , Stiglmair Manfred , Tadeu Francisco , Stennei Markus
Published: April 2021

The manufacturing of oval tubes for automotive components from sheets consists of several steps, from the flat sheet to a tube with expanded ends. It involves roll-bending of tubes, welding and several expansion processes with segmented tools. Forming steps in this process are subject to springback after the release of tools. Finite-element-simulations offer an efficient method to predict the springback behavior. For the industrial application it is important to identify the processes which contribute significantly to springback. At first glance one might expect that the consideration of the whole process chain is required to predict the final shape of such tubes. It turns out, that springback is related to the later stages of the process. The difference in springback behavior of circular and oval tubes is investigated. A simulation model is validated on the basis of experiments for circular tubes and applied to predict the final shape of oval tubes. This offers the perspective to adjust the tooling design at an earlier design stage to respect all the influences in the process on the final geometry and therefore meet tighter tolerances.
Influencing the forming zone by altering the contact pressure in a bending process
Authors: Frohn-Sörensen Peter , Reuter Jonas , Engel Bernd
Published: April 2021

In a modern production environment, flexible manufacturing methods are important because an overall trend towards mass customization and on-demand production is observed. Kinematic and incremental forming methods with generic tools can provide a large product variation but a deeper understanding of the forming mechanisms is required for process modelling, e.g. Incremental Swivel Bending (ISB). Particularly crucial is to identify the influences on the forming zone in order to purposefully control the material flow of a forming process. For a bending process where the bending moment is transmitted by clamping tools, this paper presents a method to alter the contact pressure distribution in order to affect the angular size and strain gradient of the forming zone. In the light of these results, the presented method can be deployed for a tooling with adaptive contact pressure to directly influence material flow, in particular using generic tools to overall provide a better control of flexible forming methods.
Numerical and experimental simulation of shrinkage porosity closure during hot rolling of bars
Authors: Pondaven Corentin , Langlois Laurent , Erzar Benjamin , Bigot Régis
Published: April 2021

Hot rolling of bars issued from continuous-casting aims at refining the material structure and guaranteeing the central soundness of the metallurgical product. The rolling route must be designed to achieve the complete closure of the shrinkage porosity inherent in the continuous casting process. To predict the void evolution, many models exist that can be implemented in the finite element simulation of the process. Nevertheless, these models need parameter adjustments to be adapted to the forming process, the formed material, and the real geometry of the void. Real scale tests being very expensive in the long product rolling mill, an improved representativeness experimental configuration was designed to reproduce at the laboratory scale the key characteristics of the thermomechanical path driving the void closure phenomenon. This testing consists of successive forming stages with shaped anvils applied to samples containing a shrinkage cavity. The shaped anvils and the forming conditions are calibrated to reproduce the levels of strain and the stress triaxiality of rolling stands, and the alternation of the forming direction of the industrial process. The geometry of the voids before and after the forming paths are measured by tomography. The simulation of the test with an explicit modelling of the void is developed parallel to the experiments. The simulation/experiment comparison allows the validation of the numerical model. The obtained model will be used in future works to perform a more extended design of experiments to characterise void closure during hot rolling of bars.
Contribution to process digitisation of cold forging processes using additive manufactured tools
Authors: Deliktas Tahsin , Liewald Mathias , Nezic Nikola
Published: April 2021

Cold forging tools become increasingly complex and require enhanced functionality, especially in the context of digitisation. Conventional subtractive manufacturing processes often reach their limits when the geometric complexity of the workpiece increases, hence additive manufacturing processes have become increasingly important in the last decades. Additive manufacturing processes have already been used in many fields of manufacturing technology to produce tool components with promising results, but the potentials of additive manufacturing processes have not yet been applied to cold forging tools. Therefore, the Institute for Metal Forming Technology (IFU) of the University of Stuttgart has developed an additive manufactured cold extrusion tool with integrated functional features. As functional features in the additive manufactured extrusion tool, a close contour glass fiber sensor for temperature measurement, a cooling system and a lubrication system for the controlled injection of minimal lubricant amounts during the forming process were integrated. Due to the integrated functional features, structural degradation appears in the tool, therefore the structural-mechanical tool properties were analyzed numerically with the FE-Software DEFORM 3D™ in this report as well. Furthermore, the additive manufactured cold extrusion tool was experimentally evaluated in sequentially executed extrusion operations. Thereby the integrated functional features were used and gathered data were recorded. As a result of the experimental forming tests, near-contour temperature measurements in the extrusion tool with and without the use of the integrated cooling system as well as the modification of the maximum punch forces by an inline lubricant application were obtained. In addition, the experimentally determined temperature fields in the extrusion die are validated with numerically calculated results.
Prediction of forming effects in UD-NCF by macroscopic forming simulation – Capabilities and limitations
Authors: Kärger Luise , Galkin Siegfried , Kunze Eckart , Gude Maik , Schäfer Bastian
Published: April 2021

Unidirectional non-crimp fabrics (UD-NCF) provide the highest lightweight potential among dry textile materials. Compared to multiaxial NCF, the fabric layers in UD-NCF enable a more targeted tailoring. Compared to woven fabrics, the fibres of UD-NCF are straight without weakening undulations. However, the formability of UD-NCF is more challenging compared to woven fabrics. The yarns are bonded by a stitching and the deformation behaviour highly depends on this stitching and on the slippage between the stitching and the fibre yarns. Moreover, distinct local draping effects occur, like gapping and fibre waviness, which can have a considerable impact on the mechanical performance. Such local effects are particularly challenging or even impossible to be predicted by macroscopic forming simulation. The present work applies a previously published macroscopic UD-NCF modelling approach to perform numerical forming analyses and evaluate the prediction accuracy of forming effects. In addition to fibre orientations and shear angles, as investigated in previous work, the present work also provides indication for fibre area ratios, gapping, transverse compaction and fibre waviness. Moreover, the prediction accuracy is validated by comparison with experimental tests, where full-field strains of inner plies are captured by prior application of dots onto the fibre yarns, by measuring them via radiography and applying a photogrammetry software. The modelling approach provides good prediction accuracy for fibre orientations, shear strains and fibre area ratio. Conversely, normal fibre strains, indicating fibre waviness, and transverse strains, indicating gapping, show some deviations due to the multiscale nature of UD-NCF that cannot be captured entirely on macroscopic scale.
Influence of Automated Fiber Placement Parameters on Thermoplastic Composite Blanks Used on Stamp Forming Process
Authors: Vernejoux Camille , Fischer Xavier , Deseur Simon , Duc Emmanuel
Published: April 2021

In recent years, advanced manufacturing processes have been developed to increase the speed of production in order to reduce production costs. At the scale of thermoplastic composites, the translation is the combination of advanced manufacturing processes. The focus in this study is more specifically on the coupling of automated lay-up (AFP) and stamp forming processes. To date, a consolidation process, such as press-consolidation of thermoplastic composites, obtained blanks. Several trials have begun using an automated fiber placement consolidation to reduce manufacturing time and use unidirectional material. However, the combination of AFP and stamp forming is useful if it optimizes this process without the blank’s full consolidation, which by resulting reduces the manufacturing time. This study estimates blank characteristics through thermal history imposed by a more rapid manufacturing process. A set of blanks with varying process parameters is produced to investigate the influence at the microscopic scale. The interface behaviour is observed with optical microscope and image processing. A statistical study applied to the process is carried out in order to relate the material observations to the input parameters. The results of this study are used for the study of the next process of the combination: the stamp forming.
A Sequential Approach for Simulation of Thermoforming and Squeeze Flow of Glass Mat Thermoplastics
Authors: Dörr Dominik , Ivanov Stanislav , Gergely Ryan , Meyer Nils , Henning Frank , Straatman Anthony G. , Hrymak Andrew
Published: April 2021

In this study, a sequential thermoforming and squeeze flow simulation approach for Glass Mat Thermoplastic (GMT) material is proposed and applied to a hat section geometry using input properties based upon Tepex flowcore, a long glass fiber reinforced polyamide (PA/GF) mat manufactured by Lanxess. First, a fully-coupled thermomechanical simulation is conducted based on a purely Lagrangian description, to efficiently capture thermoforming. Subsequently, relevant state variables are mapped and initialized for a Coupled-Eulerian-Lagrangian (CEL) approach. The CEL approach is adopted to accurately capture squeeze flow, which is not possible by a purely Lagrangian description. While numerical techniques differ, both approaches use the same three-dimensional and thermomechanical constitutive equations including an equation of state, a nonlinear viscosity model, and crystallization kinetics, implemented through a material user-subroutine (VUMAT) for the commercially available simulation software package ABAQUS/Explicit.
Punching with a slant angle - cutting surface quality
Authors: Schenek Adrian , Liewald Mathias
Published: April 2021

For economic or process-related reasons, punching of structural sheet metal components often has to be used for car bodies. The difference in angle of attack between punch and sheet metal component is referred to as “slant angle”. However, at the current state of the art, no precise information is available on the characteristics of cutting surfaces in relation to the slant angles. For this reason, cost-intensive slider units are used for comparatively small slant angles of around 10° in order to ensure series suitability of corresponding punching processes. In this respect, recent studies performed by the authors have shown that good cutting surface qualities can also be achieved for slant angles distinctly beyond 10°. This contribution presents an empirical test series for the characterization of cutting surface parameters when punching with a slant angle. Here, the experimental cutting surface analysis showed an asymmetric characteristic of the cutting surface along the hole circumference. Furthermore, the investigated sheet metal materials HC340LA, DP600 and DP800 revealed recurring tendencies regarding the parameters “edge draw-in”, “clean cut”, “fracture surface” and “burr height”, which had been combined to corresponding three-dimensional regression models. With these regression models, cutting simulations could be calibrated, allowing a quality prognosis of cutting surfaces achievable when punching at specific slant angles.
Modeling and Simulation of the Robotic Layup of Fibrous Preforms for Liquid Composite Molding
Authors: Esperto Vitantonio , Gambardella Antonio , Pasquino Germana , Tucci Fausto , Durante Massimo , Carlone Pierpaolo
Published: April 2021

In recent years, the concepts of industry 4.0 are widely spreading in many different sectors, from agriculture to home automation, from transportation systems to manufacturing processes. One of the pillars of this concept is related to the use of robotic cells. The focus of the present work is the robotic automated layup of dry fibrous preforms to be employed in liquid composite molding (LCM) processes. In particular, the article describes a software tool developed to simulate the automated placement and layup of fiber fabrics and tissues on complex shape molds by means of a robotic system. The tool has been coded in Matlab language. An end-effector has been appositely designed for the fiber layup and it has been included in the model. The simulation provides as output the path generation and the configuration of the robotic arm and of end effector along the entire layup process. The implemented code has been compared with the commercial software RoboDK.
A Numerical Investigation about Temperature Influence on Thermoplastic Hot-Formed Reinforced Composites Under Low-Velocity Impact
Authors: Bruno Matteo , Carrino Luigi , Esposito Luca , Lopresto Valentina , Papa Ilaria , Russo Pietro , Viscusi Antonio
Published: April 2021

In the field of impact response of thermoplastic reinforced composites, several investigations about material behaviour in terms of delamination, indentation and fracture mechanism were conducted. Although a significant influence of the polymer temperature on the overall material impact response is expected, a limited number of studies are available in this regard. Most of the available scientific evidence concerns thermosetting composites and thermoplastic composites response only at room temperature. In particular, the purpose of this contribution is to better understand the dissipation mechanisms involved in thermoplastic reinforced composite under impact conditions for different temperatures. Starting from the few available literature data about the modelling of the problem, the aim of the present work is the development of a numerical approach able to reproduce the experimentally tested conditions. An experimental campaign on hot pressed polyamide 6 /basalt plain fabric laminates impact was selected as the benchmark for the numerical approach. The laminates impact response at increasing values of impact energy between 5J and 30J were simulated under three temperature conditions set around the polymer transition temperature (40°C, 80°C and 100°C). By validating the overall numerical model response on the room temperature experiment, considerations about the magnitude of viscous dissipation and its influence, for the different tested temperatures and in function of the adopted lamination technology, were made.
Rheology and tribology: investigating the migration of small molecules in recycled agricultural waste multilayer films
Authors: Cabrera Géraldine , Pichon Gérard , Maazouz Abderrahim , Lamnawar Khalid
Published: April 2021

This paper deals with polyisobutylene (PIB) migration through post-consumer agricultural waste multilayer films based on four linear low-density polyethylene (LLDPE) matrices. Connections between shear, elongational rheology and tack surface properties were revealed for both model and recycled blends. The effects of aging time and temperature were investigated and rationalized, depending on the short- and long-chain branching in LLDPE matrices as well their polyethylene (PE) crystallization. Linear and nonlinear viscoelastic properties were influenced by even small amounts of PIB. This migration also influenced slippage in the steady-flow regime. Transient uniaxial extensional properties were shown to be very sensitive to the presence of PIB, which seems to hold back the PE strain hardening properties. Therefore, the axial force and the surface friction coefficient were determined and discussed in correlation with bulk rheological findings. These results help unveil new insights about the physical mechanisms governing PIB migration with or without fillers inhibiting this migration in recycled films.
Manufacturing Of Aluminum Coating On 3D-Printed Onyx With Cold Spray Technology
Authors: Della Gatta Roberta , Astarita Antonello , Borrelli Domenico , Caraviello Antonio , Delloro Francesco , Lomonaco Patrizio , Papa Ilaria , Perna Alessia Serena , Sansone Raffaele , Viscusi Antonio
Published: April 2021

Composite materials are widely used as main parts and structural components in different fields, especially for automotive and military applications. Although these materials supply different advantages comparing to the metals, their implementation in engineering applications is limited due to low electrical and thermal properties and low resistance to erosion. To enhance these above-mentioned properties, the metallization of composite materials by creating a thin metal film on their surface can be achieved. Among different coating deposition techniques, Cold Spray appears to be the most suitable one for the metallization of temperature-sensitive materials such as polymers and composites with a thermoplastic matrix. This process relies on kinetic energy for the formation of the coating rather than on thermal energy and consequent erosion and degradation of the polymer-based composite can be avoided. In the last years, a new method to produce composite materials, as known as Fused Filament Fabrication (FFF), has been developed for industrial applications. This technique consists of a 3D printing process that involves the thermal extrusion of thermoplastic polymer and fibers in the form of filaments from a heated mobile nozzle. The implementation of this new technique is leading to the manufacturing of customized composite materials for the cold spray application. In the presented experimental campaign, Onyx material is used as a substrate. This material is made of Nylon, a thermoplastic matrix, and chopped carbon fibers randomly dispersed in it. Aluminum powders were cold sprayed on the Onyx substrate with a low-pressure cold spray (LPCS) system. This study aims to investigate the possibility of the metalizing 3D-printed composite material by cold spray technology. For this purpose, optical and microscopical analyses are carried out. Based on the results, the feasibility of the process and the influence of the morphology of the substrate are discussed, and optimal spraying conditions are proposed.
Potential and challenges of a solid-shell element for the macroscopic forming simulation of engineering textiles
Authors: Schäfer Bastian , Dörr Dominik , Kärger Luise
Published: April 2021

Finite element (FE) forming simulation offers the possibility of a detailed analysis of the deformation behaviour of engineering textiles during forming processes, to predict possible manufacturing effects such as wrinkling or local changes in fibre volume content. The majority of macroscopic simulations are based on conventional two-dimensional shell elements with large aspect ratios to model the membrane and bending behaviour of thin fabrics efficiently. However, a three-dimensional element approach is necessary to account for stresses and strains in thickness direction accurately, which is required for processes with a significant influence of the fabric’s compaction behaviour, e.g. wet compression moulding. Conventional linear 3D-solid elements that would be commercially available for this purpose are rarely suitable for high aspect ratio forming simulations. They are often subjected to several locking phenomena under bending deformation, which leads to a strong dependence of the element formulation on the forming behaviour [1]. Therefore, in the present work a 3D hexahedral solid-shell element, based on the initial work of Schwarze and Reese [2,3], which has shown promising results for the forming of thin isotropic materials [1], is extended for highly anisotropic materials. The advantages of a locking-free element formulation are shown through a comparison to commercially available solid and shell elements in forming simulations of a generic geometry. Additionally, first ideas for an approach of a membrane-bending-decoupling based on a Taylor approximation of the strain are discussed, which is necessary for an accurate description of the deformation behaviour of thin fabrics.
Initiation of Dynamic Recrystallization of As-Cast N08028 Alloy
Authors: Mora Elena , Navarro Aitor , Silveira Elena , Poletti Cecilia , Mendiguren Joseba , Hurtado Iñaki
Published: April 2021

The use of high nickel content austenitic stainless steels (SASS) has significantly increased in the last decade. The corrosion and high fatigue resistance of these materials make them suitable for manufacturing oil country tubular goods (OCTG). SASS are processing by forging from casting conditions. Dynamic recovery (DRV) and recrystallization (DRX) of as-cast super austenitic stainless steel, N08028 Alloy, is investigated to study the refining effect from the as-cast grain structure to fully recrystallized austenite due to hot deformation. Both the critical stress and strain for the initiation of DRX are determined using the flow curves. To perform this analysis, hot compression tests are performed at temperatures between 900°C and 1250°C, and strain rates between 0.1 s-1 and 10 s-1, up to 0,8 final strain using a Gleeble®3800 thermomechanical simulator. Subsequently, the Johnson-Avrami-Mehl-Kolmogorow (JMAK) model is used to numerically fit the flow curves and consequently determine the critical strain. No critical points are seen for temperatures under 1100°C. Above this temperature, the JMAK model proves to be valid in all studied strain rates.
Analysis of the mechanical composite properties of ii-chamber variations in the closed injection pultrusion process
Authors: Strauß Sebastian , Boysen Simon , Senz Andreas , Wilhelm Frederik , Rilli Niko
Published: April 2021

Pultrusion is an established and efficient process for producing continuous fiber-reinforced composites. The resin systems that are currently most frequently used are unsaturated polyesters and vinylesters. These have a long pot life, are well known, and have good processing properties. Highly reactive resins such as polyurethane (PU) and amine hardening epoxy have been in use for a few years. These resin classes are remarkable for their extended range of properties. This opens up new application fields for pultrusion technology but poses challenges for the processing technology. Short pot lives of just a few minutes require a modified process: closed injection pultrusion (CIP). Various approaches about the design and layout of the internal geometry of the injection and impregnation chambers (ii-chamber) are the subject of ongoing research. Numerous parameters influence the impregnation process in the ii-chamber and the quality of the resulting composite. In this study, two innovative, highly reactive resins for use in the pultrusion process were analyzed, both resins based on aliphatic polyurethanes. In phase 1 of the experiments, a commercial aliphatic polyurethane-system for pultrusion applications was used. In Phase 2, the recently developed bio-based aliphatic polyurethane-system for pultrusion applications was used for the study's main experiments. The aim of the study was to analyze the material and processing properties with various modifications of the impregnation setup. Therefore, a newly developed ii-chamber and die were tested. The ii-chamber was designed to enable easy adjustment of some of the main influencing parameters during the pultrusion process. A test strategy was developed to evaluate the properties of the composites. An assessment of the influence of the process- and die-based parameters should enable an evaluation of the optimal processing settings by analysis of the material characteristics. The most significant effect of variations in the pultrusion process was found in the interlaminar shear strength (ILSS). ILSS was analyzed for all process variations for both resin systems.
Stirring Peptide Synthesis to a New Level of Efficiency
Authors: Naoum Johnny N , Alshanski Israel , Mayer Guy , Strauss Poriah , Hurevich Mattan
Published: April 2021

In this work, a new setup that relies on fast stirring and heating was used to increase the diffusion of both reagents and solid support. we show that the combination of fast mixing and elevated temperature enables the acceleration of solid-phase peptide synthesis without using a large excess of reagents, providing a greener and accessible alternative to the state-of-the-art.
Первично — множественные опухоли
Authors: Торба А. В. , Рябцева О. Д. , Перцова Ю. Г. , Казьмин А. П. , Болдырева В. А. , Андрияш Е. В.
Published: April 2021

В последние годы отмечено увеличение частоты множественных новообразований. Факторами, влияющими на рост заболеваемости первично — множественными злокачественными новообразованиями, являются: увеличение средней продолжительности жизни как в целом, так и после успешного лечения онкологических заболеваний; возрастание интенсивности канцерогенных воздействий, урбанизация, накопление наследственной отягощенности, улучшение диагностики онкологических заболеваний. Зачастую недостаточная информированность врачей о возможности множественного опухолевого поражения является причиной того, что после выявления одной злокачественной опухоли не принимается во внимание возможность существования других опухолей и поэтому в некоторых случаях не производится не только целенаправленное исследование других отделов органа, в котором развилась опухоль, но и других органов. В этом случае на первый план выходят врачи — диагносты, и именно знание данной патологии, ее особенностей позволит оказать пациенту своевременную и квалифицированную помощь.
Патогенетические аспекты тромбоцитарно-опосредованного метастазирования опухолевых клеток
Authors: Греков И. С. , Кондратюк Р. Б. , Ярков А. М.
Published: April 2021

Проблема взаимодействия опухолевых клеток и тромбоцитов обсуждается в клинической и экспериментальной онкологии уже на протяжении многих лет. Тромбоциты являются важнейшим компонентом системы гемостаза, однако наряду с этим их функции не ограничиваются одним лишь участием в реакциях тромбообразования. Также известно, что тромбоциты всячески способствуют формированию специфического микроокружения опухолевых клеток, изменяя фенотипические и некоторые иммуногистохимичекие свойства последних. Подобное «клеточное сотрудничество» дает целый ряд преимуществ опухолевым клеткам, что в свою очередь приводит к прогрессированию и метастазированию самих опухолей. Несмотря на достигнутые результаты в изучении различных путей реализации таких взаимодействий, многие вопросы остаются невыясненными до настоящего времени. Понимание сущности тромбоцит-опосредованного метастазирования и прогрессирования рака позволит разработать абсолютные новые стратегии лечения и ведения пациентов с онкологической патологией, что значительно улучшит прогноз и выживаемость таких больных.
Гастропластическая онкохирургия
Authors: Ладур А. И. , Попович А. Ю. , Заика А. Н. , Глотов А. В. , Кубышковский А. Л. , Ладур К. А. , Аль Баргути Р. А.
Published: April 2021

В данной работе приведены литературные данные об эволюции гастрохирургии, изучена роль двенадцатиперстной кишки в хирургических аспектах, изучены функциональные результаты и качество жизни больных после гастрэктомии с формированием «искусственного желудка» по Г. В. Бондарю.
Approach to: Amenorrhea
Authors: Baril Sophie
Published: April 2021

This article provides an approach to amenorrhea and is intended for pre-clinical and clerkship medical students. Primary amenorrhea refers to the absence of menarche by 15 years or 3 years post thelarche while secondary amenorrhea is the cessation of menses for 3 months in women with a previously regular cycle or for 6 months in women with previously irregular menses. While amenorrhea can be physiological it can also reflect an anatomical or more complex hormonal problem that students must learn to identify and investigate.
Exploring the Impact of COVID-19 on Greeting Behaviours in Education Through a Lens of Relational Engagement
Authors: Smith Aaron
Published: April 2021

Various impacts of COVID-19 have been explored throughout the literature; however, no research has yet considered the impact of COVID-19 on greetings in education. This paper represents an attempt to address this gap.

Using a lens of Relational Engagement, this paper explores the findings of a recent survey (n = 67) that asked how teachers have historically greeted students and how they will go about doing so upon return to a physical classroom space. Findings suggest that COVID-19 has significantly impacted teachers’ beliefs about greetings in the context of education, that teachers’ greeting behaviours are likely to change, and that it is possible if not likely that many teachers may experience various intra- and interpersonal conflicts when they next encounter students face-to-face.
The overview and role of heat shock proteins (HSP) especially HSP 60 and 70 in reproduction and other pathologies (a literature review)
Authors: Berestoviy V.O. , Mahmood Ahmad , Venckivska I.B. , Ginzburg V.G. , Sokol I.V. , Berestoviy O.O. , Govsieiev D.O.
Published: April 2021

A search of peer-reviewed articles regarding heat shock proteins (HSP’s) especially HSP 60 and 70 was conducted in this review to understand its role in the development of various complications like miscarriage, preterm birth, tubal infertility and spontaneous abortion associated with chlamydial HSP 60 in IVF, male infertility, preeclampsia, cancer, immune system activation, autoimmune diseases, coronary heart disease, dysregulation of steroidal hormone from the endometrium and its up-regulation in stress response. ELISA, western blotting, immunofluorescence, and affinity chromatography were the most common methods researchers used to determine and separate HSP 60 and antibodies related to it. Heat shock proteins are responsible for normal folding of other proteins and prevent its abnormal folding and cause degradation of abnormally folded proteins, mitochondrial protein transport, DNA metabolism, regulation of apoptosis are their significant functions. HSP 60 is a homologue of bacterial HSP 60 (GroEL) and needs co-chaperonin HSP 10 for its proper functioning. Gynaecological and obstetrical complications were more prevalent in most studies. Pregnant women were mostly affected subjects. Abnormal HSP 60 leads to a high level of unfolded or misfolded proteins, which in turn activate other body systems to produce the clinical outcome. Some researchers stated that there is no association between preterm birth and HSP 60 & 70, chlamydial HSP 60 antibodies trigger tubal infertility, preeclamptic pregnancies has detectable HSP60 as compared to control, GroEL leads to tubal infertility and IVF failure, chlamydial (CHSP 60) activates autoimmunity. HSP60 seropositivity reduces the opportunities of ectopic pregnancy, levels of HSP 60 does not stay constant throughout the menstrual cycle in reference to control, while other opposed these conclusions in their research works. According to some researchers, HSP 60 is a risk factor for pregnancy-related pathologies development, and some other opposed this theory and considered HSP 60 as a safety factor for normal pregnancy outcome, according to this review harmful effect of HSP 60 dominate, in future further high-quality studies need to be done for better understanding.