bluuebunny/crossref_metadata_2025 huggingface dataset:
PENGARUH ADVERSITY QUOTIENT TERHADAP MOTIVASI BELAJAR SISWA PADA MATA PELAJARAN EKONIMO DI SEKOLAH MENENGAH ATAS NEGERI 2 SIAK HULU
Authors: Salmiah Mia
Published: April 2021

This research aims to get information about how big the effect adversity quotient toward Student’s Learning Motivation in Economics at the Sttate Senior High School of 2 Siak Hulu. The background of the research were some student cheated in doing their tasks, they did not submit their assignment on time, they did not bring their economics textbooks, and they did not study seriously. This was a quantitative research. The subject of this research was the eleventh grade students whose major were sosial science. The object of this research was the effect adversity quotient to word students’s learning motivation. The number of sample of this research were 127 students. The research used random sampling technique. The data collection technique used was questionares and documentations. This technique of analysis used to examine the hypothesis was simple linier regression. Based on the result of the research and data analysis, it was found that ro (observasi) 0,688 bigger than rt (tabel) with the level of sifnificance 5% (0,1743) and 1% (0,2278) at (0,1743<0,688>0,2278) or that there is a significant effect of adversity quotient toword students’ learning motivation in economics at the State Senior High School of 2 Siak Hulu. The percentage of adversity quotient effect toward students’ learning motivation was 47,3% while the rest 52,7% was influenced by other variables which were not included in this research.
Surface finish of Additively Manufactured Metals: biofilm formation and cellular attachment
Authors: Ginestra Paola , Riva Leonardo , Ceretti Elisabetta , Lobo David , Mountcastle Sophie , Villapun Victor , Cox Sophie , Grover Liam , Attallah Moataz , Addison Owen , Shepherd Duncan , Webber Mark
Published: April 2021

Powder bed fusion techniques enable the production of customized and complex devices that meet the requirements of the end user and target application. The medical industry relies on these additive manufacturing technologies for the advantages that these methods offer to accurately fit the patients’ needs. Besides the recent improvements, the production process of 3D printed bespoke implants still requires optimization to achieve the optimal properties that can mimic both the chemical and mechanical characteristics of the anatomical region of interest. In particular, the surface properties of an implant device are crucial to obtain a strong interface and connection with the physiological environment. The layer by layer manufacturing processes lead to the production of complex and high-performance substrates but always require surface treatments during post-processing to improve the implant interaction with the natural tissues and promote a shorter assimilation for the fast recovery and wellness of the patient. Although the surface finishing can be tailored to enhance cells adhesion, proliferation and differentiation in contact with a metal implant, the same surface properties can have a different outcome when dealing with bacteria. This work aims to provide a preliminary analysis on how different post-processing techniques have distinct effects on cells and bacteria colonization of 3D printed titanium implants. The goal of the paper is to highlight the importance of the identification of an optimized methodology for the surface treatment of Ti6Al4V samples produced by Selective Laser Melting (SLM) that improves the implant antimicrobial properties and promotes the osseointegration in a long-term period.
Surface modification of additively manufactured parts by forming
Authors: Hafenecker Jan , Kuball Clara-Maria , Rothfelder Richard , Schmidt Michael , Merklein Marion
Published: April 2021

Additive manufacturing (AM) has many advantages compared to conventional processes. Of particular interest is the tool-less manufacturing of components, which allows one component to differ from the next completely and has the possibility of producing complex geometries. At the same time, however, AM has deficits such as long production times, low production tolerances and low surface qualities compared to conventional processes. Therefore, a finishing process using machining is often necessary, which extends the manufacturing time and produces waste. Thus, the avoidance of machining rework is of high interest, especially with expensive materials such as stainless steel or titanium. One approach to avoid machining processes is to use forming technology. By applying a forming operation, surfaces can be smoothened and geometrical aspects can be defined more sharply. Especially for functional surfaces, this procedure is favorable because of the work hardening, which in turn increases the strength of the material. Using the example of laser-based powder bed fusion (PBF-LB) followed by a cup backward extrusion process, two materials, which are frequently used in AM are investigated. On the one hand, the titanium alloy Ti-6Al-4V, as a material with low machinability and low formability at room temperature, and the stainless steel 316 L. Compared to Ti-6Al-4V, 316 L has a higher formability. Cylinders are built using PBF-LB and then formed to smoothen the surface and achieve a higher geometrical accuracy concerning edges. Formed, additively made parts have a more defined geometry, namely sharp edges and a surface roughness reduced by up to 90 %.
Analysis of the Tool Stick-Out Influence on Machining Chatter
Authors: Albizu Asier Barbeito , Arrazola Pedro-José , Ørskov Klaus Bonde
Published: April 2021

Increased stability in machining processes is highly desired by all machining industries when vibrations and specially chatter occur. This phenomenon is defined as a self-excited vibration that occurs due to the regeneration of waviness of the workpiece surface. In machining industry, the trend is to rely on the trial and error method or mere experience when deciding the machining spindle speeds, depths of cut and tool stick-outs, all of which are parameters directly related to chatter occurrence. Currently, the shortest possible tool stick-out is chosen by default, but literature has proven that longer stick-outs may bring some advantages when it comes to material removal rates. Aiming to prove this theory, this paper will discuss the influence of the tool stick-out on machining chatter occurrence. To that end, the effect of the tool stick-out on the modal parameters of the system, on the Stability Lobe Diagram (SLD) and on productivity will be analysed. Therefore, a number of Tap-Tests to different tool/tool-holder/stick-out combinations have been performed, in order to gather the data (FRFs and SLDs) where the analysis is based on. Last but not least, some machining tests have been conducted aiming to compare the theoretical chatter occurrence conditions, provided by the SLD, with the experimental ones. For that, two Al5083 workpieces have been slot milled under different cutting conditions, facilitating the unexpected results wherein the conclusions have been based upon.
Challenges in modelling the forming of unidirectional HiTape® reinforcements
Authors: Durif Bastien , Moulin Nicolas , Drapier Sylvain , Bouquerel Laure , Blais Maxime
Published: April 2021

Recent years have seen the development and democratization of continuous fibre composite materials for the manufacture of primary aeronautical structures. Composite materials exhibit excellent specific properties compared to aluminium alloys historically used for these applications. The need in cadence improvement leads the aeronautic industry to consider new processes for primary aeronautical structures manufacturing. Therefore, new dry reinforcements are developed, such as the HiTape® reinforcement designed by Hexcel Reinforcements. HiTape® plies are designed for automated laying in order to build dry stacks that can be formed and infused/injected by a liquid resin afterwards to greatly increase the production rates. To understand and predict results from the forming stage, numerical models are considered as a useful tool. In this work, we propose a new computational approach to model the forming stage of dry HiTape® stacks. The HiTape® ply is a slender structure, exhibiting a transversely isotropic behaviour in large deformations as well as a non-linear bending behaviour. Another particularity is that the bending stiffness of the ply is not directly related its membrane stiffness. When stacks are considered, inter-ply phenomena (opening and sliding) appear and greatly influence the bending stiffness of the structure. To model every of these specificities, diverse techniques are used: solid-shell elements are considered to answer the ply slenderness, embedded elements approach helps to model the membrane/bending behaviours decoupling, frictional cohesive zone model stands for inter-ply phenomena and the particular behaviour of the ply is described using a non-linear physical-invariant based hyperelastic constitutive. The finite element (FE) software Abaqus will be used in this work.
Effect of input variables uncertainty in free tube hydroforming process
Authors: Khalfallah Ali , Prates Pedro André , Fernandes José Valdemar
Published: April 2021

Tube hydroforming (THF) is a plastic forming process that uses tubes with an initial circular cross section, in which pressurized fluid and axial feeds are applied for producing parts with various cross-sectional shapes. Despite of the complexity of THF process, a great progress in the automotive and aerospace industry has been made due to its advantages, such as, consolidation and weight reduction over conventional stamped and welded parts. The analysis of THF process is typically based on deterministic approaches, excluding scattering effects that influence the process reliability. Thus, robust design of tube hydroforming aims to vanish noise factors effects on process responses by considering the influence of process parameters variability. If this fluctuation is not monitored, then the fluctuation of the hydroformed parts quality may contribute to high scrap rates. In this work, the influence of variability in the THF material and process parameters (e.g. yield stress, strength coefficient, strain hardening exponent, plastic anisotropy, initial tube thickness and bulged length) on the bursting pressure is analyzed resorting to a response surface model. The statistically significant variables, which mostly influence the free bulge hydroforming process, are identified through an analysis of variance. Assuming that the input parameters variability follows the normal distribution, the probability distribution of the bursting pressure is evaluated by involving random process variables into the built response surface model. It was shown that the initial tube thickness is the most statistically significant variable, whereas the strain hardening exponent is the least statistically significant variable.
Innovative Measurement Of Stress Superposed Steel Strip For Straightening Machines
Authors: Bader Fabian , Bathelt Lukas , Djakow Eugen , Homberg Werner , Henke Christian , Trächtler Ansgar
Published: April 2021

Higher quality requirements by customers demand higher precision and accuracy from manufacturing processes. Application oriented preparation of semi-finished materials is key for subsequent forming operations, therefore, straightening machines are employed. Straightening strengthens the material by increasing plastic deformation by means of strain hardening, resulting in undesirable reduction in formability when processing high strength materials, in particular. Conventional roll-type straightening machines process either bars or strips. This is achieved upon passing material between rolls arranged in two staggered rows. However, conventional straightening processes do not adapt to the local varying distortion of coiled strips. Innovative, self-correcting process control techniques, which adapt to the initial geometric characteristics of the strip, present a promising approach to fix this issue through optimization of the leveling process. Here, an innovative strategy to improve straightening of high strength steel materials (1.4310) is presented. This implements optimized leveling, adding minimal plastic deformation and, thus, strain hardening. To operate an intelligent straightening machine, a reliable online measurement of the surface defects is fundamentally essential. The MagnaTest, which is developed for material testing, is made feasible for such purposes after calibrating for curvature measurement. Preliminary results are promising in regards to measuring the curvature online, so that the following straightening process can be close loop controlled. The bending measurement is linked to open/closed loop control, therefore providing an optimal straightening result in regards to formability, leveling, and reduced strain hardening.
Spreading of Powders in Powder Bed Additive Manufacturing: an Experimental Approach
Authors: Lampitella Valerio , Trofa Marco , Astarita Antonello , D’Avino Gaetano
Published: April 2021

Powder bed additive manufacturing allows for the production of fully customizable parts and is of great interest for industrial applications. However, the repeatability of the parts and the uniformity of the mechanical properties are still an issue. More specifically, the physical mechanism of the spreading process of the powders, which significantly affects the characteristics of the final part, is not completely understood. In powder bed fusion technologies, the spreading is performed by a device, typically a roller or a blade, that collects the powders from the feedstock and successively deposits them in a layer of several dozens of microns that is then processed with a laser beam. In this work, an experimental approach is developed and employed to study the powder spreading process and analyze in detail the motion of the powders from the accumulation zone to the deposition stage. The presented experiments are carried out on a home-made device that reproduces the spreading process and enables the measurement of the characteristics of the powder bed. Furthermore, the correlation with the process parameters, e.g., the speed of the spreading device, is also investigated. These results can be used to obtain useful insights on the optimal window for the process parameters.
Data-driven Prediction of Temperature Evolution in Metallic Additive Manufacturing Process
Authors: Pham Quy Duc Thinh , Hoang Truong Vinh , Pham Quoc Tuan , Huynh Than Phuc , Tran Van Xuan , Fetni Seifallah , Duchêne Laurent , Tran Hoang Son , Habraken Anne Marie
Published: April 2021

In this study, a data-driven deep learning model for fast and accurate prediction of temperature evolution and melting pool size of metallic additive manufacturing processes are developed. The study focuses on bulk experiments of the M4 high-speed steel material powder manufactured by Direct Energy Deposition. Under non-optimized process parameters, many deposited layers (above 30) generate large changes of microstructure through the sample depth caused by the high sensitivity of the cladding material on the thermal history. A 2D finite element analysis (FEA) of the bulk sample, validated in a previous study by experimental measurements, is able to achieve numerical data defining the temperature field evolution under different process settings. A Feed-forward neural networks (FFNN) approach is trained to reproduce the temperature fields generated from FEA. Hence, the trained FFNN is used to predict the history of the temperature fields for new process parameter sets not included in the initial dataset. Besides the input energy, nodal coordinates, and time, five additional features relating layer number, laser location, and distance from the laser to sampling point are considered to enhance prediction accuracy. The results indicate that the temperature evolution is predicted well by the FFNN with an accuracy of 99% within 12 seconds.
Adjusting Mechanical Properties of Forging Dies Produced by Ausforming
Authors: Behrens Bernd-Arno , Brunotte Kai , Petersen Tom , Ostermeyer Corvin , Till Michael
Published: April 2021

Due to high thermo-mechanical loads, tools used in hot forming operations need a high resistance to different damage phenomena, such as deformation, cracking and abrasion. They are exposed to cyclic thermo-mechanical stress conditions, which leads to tool failure and subsequent tool replacement during cost-intensive production interruptions. To increase wear resistance, forging tools can be produced in the metastable austenite area. Forming of steel below the recrystallisation temperature, also known as “ausforming”, offers the possibility to increase strength without affecting ductile properties. This is due to grain refinement during forming. In this study, the thermo-mechanical treatment ausforming will be used to form the final contour of forging dies. For this purpose, an analogy study was performed where a cup-preform is ausformed, which represents the inner contour of a highly mechanically loaded forging die. It is investigated to what extent a fine-grained microstructure generated in the last forming stage can be achieved and how it influences the tool’s performance. The hot-working tool steel X37CrMoV5-1 (AISI H11) was used as workpiece material. To achieve optimal properties, process routes with tempering temperatures from 300 °C to 500 °C and global true plastic strains of φ = 0.25 and φ = 0.45 were examined. The results were evaluated by pulsation tests, metallographic analysis and hardness measurements of the formed parts. Optimal ausforming parameters were derived to produce a high performance forging die.
Manufacturing and metallization of hybrid thermoplastic-thermoset matrix composites
Authors: Parmar Hetal , Gambardella Antonio , Perna Alessia Serena , Viscusi Antonio , Della Gatta Roberta , Tucci Fausto , Astarita Antonello , Carlone Pierpaolo
Published: April 2021

Metallization is a common strategy employed to enhance the electrical and thermal conductivity of polymer matrix composite materials. Nevertheless, metallic deposition on polymer-based materials is challenging due to the inherent limitations related to high temperature exposure of the substrate. In this article, a new technique for the manufacturing of composite laminates and the subsequent metallization by cold spraying of metallic powder is presented. The composite manufacturing route is based on the production of thermoplastic-thermoset hybrid substrates and consisted of two main stages: in the first stage the partial impregnation of a reinforcement textile by a thermoplastic film was promoted by hot pressing compaction. Afterwards, the prepared lamina was vacuum bagged with other reinforcing layers and impregnated by the thermoset catalyzed resin by a vacuum infusion process. Finally, the thermoset and thermoplastic layers were co-cured to increase the adhesion of the substrate with the thermoplastic film. The metallization of composite laminate was obtained through the cold spraying technique, depositing powders on the thermoplastic surface layer. The effect of processing parameters on the coating deposition, quality and microstructure was reported and discussed.
Design of a fuzzy controller to prevent wrinkling during rotary draw bending
Authors: Borchmann Linda , Schneider Dominique , Engel Bernd
Published: April 2021

Rotary draw bending (RDB) is a forming process that is commonly used to bend tubes with small wall thicknesses and small bending radii. One of the limitations of this process is the formation of wrinkles caused by compressive stress on the inner bend. In order to design the bending process without wrinkles and to determine the necessary process parameters, adjustment tests are required. Within this work, a fuzzy controller is to be developed which automatically prevents the formation of wrinkles and thus eliminates the need for time-consuming set-up tests to determine the necessary process parameters. The fuzzy controller is based on fuzzy set theory and fuzzy logic. In connection with a rule base it is possible to simulate the human decision process. A fuzzy controller is programmed based on a max-min controller, with the required rules resulting from previous bending tests. After the fuzzy controller has been implemented, it must be connected to the bending machine by suitable interfaces. The input values, which indicate wrinkles, are measured by sensors during the bending process and provide the controller with data. The fuzzy controller then uses the control base to specify the required control variables. After programming has been completed, practical validation tests were carried out. In the validation tests using different tube wall thicknesses and materials, a significant reduction of wrinkles is achieved. Bending of completely wrinkle-free tubes is also possible due to the automated finding of optimal tool settings. Using the fuzzy controller eliminates the need for costly adjustment bends, resulting in significant time and cost savings.
Anisogrid lattice cylinders made of thermoplastic composite under buckling loading
Authors: Iorio Leandro , Bellisario Denise , Gallo Nicola , Papa Claudia , Regi Marco , Santoro Daniele , Quadrini Fabrizio , Santo Loredana
Published: April 2021

Anisogrid lattice cylinders have been produced by means of an innovative out-of-autoclave (OOA) process by using thermoplastic prepreg. Unidirectional thermoplastic tapes with polypropylene matrix and glass fibers were wound on cylindrical mandrels at room temperature. Composite consolidation was achieved by using the compression of a heat-shrink tube during its shape recovery in oven. A cylindrical anisogrid lattice structure was manufactured and mechanically tested under vertical loading. Results from the buckling test revealed the optimal adhesion between prepreg layers after the out-of-autoclave molding. Numerical modelling of buckling has been performed to correlate the structural behavior of the anisogrid lattice cylinder with composite material properties and geometrical features. A parametric model of the lattice structure has been defined for this aim. The proposed manufacturing technology combines the advantages of thermoplastic composites (reparability, easy handling, easy storage, long prepreg life, productivity) with the designing potential of anisogrid lattice structures in terms of lightness and stiffness.
Thermal design methodology to hybrid manufacturing process of high performance thermoplastics composites
Authors: Rodriguez Enrique Reyes , Tardif Xavier , Bailleul Jean-Luc , Allanic Nadine , Sobotka Vincent
Published: April 2021

Thermal analysis plays a key role in the design of hybrid manufacturing processes of High-Performance Thermoplastic Composites (HP-TPC) parts. Indeed, an inadequate temperature distribution, during the transformation of these materials, could not only lead to mechanical and surface defects but also to inefficient energy consumption. These problems become difficult to avoid with the interaction of different materials within the part, and also with the influence of subsequent stages on the process. To overcome this challenge, the methodology proposed in this work aims to determine the spatial and temporal distribution of the heat sources that must be applied at each sequential stage of a process to reach a thermal objective within the part. The methodology is based on the concept of conformal cooling [1]. A surface enveloping the part is created [2]. Once a computational model is set up, the optimization problem is treated as an inverse problem subjected to constraints that depend on the process response in terms of temperature cycles. Thus, it requires the calculation of the direct problem, the adjoint-state solution, and the development of the sensitivity equations to implement a first-order gradient-based algorithm. As an application example, a thermo-stamping of HP-TPC with a metal insert followed by an over-molding process has been chosen because of the different stages and materials involved. The first results show a reduction of temperature gradients on the part surface at each stage while arriving at the established temperature level. Further analysis will include a constraint problem taking into account adhesion and/or energy criteria.
On the origin of start-up effects in ply-ply friction for UD fiber-reinforced thermoplastics in melt
Authors: Pierik Rens , Grouve Wouter , Wijskamp Sebastiaan , Akkerman Remko
Published: April 2021

Hot press forming is an attractive production technology to fulfil the increasing demand for complex fiber-reinforced thermoplastic parts. Over the years, process simulation tools on press forming have shown to be very helpful in facilitating the design stage for defect free parts production. One of the important deformation mechanisms considered in process simulations is the relative slip of successive plies or ply-ply friction, of which the underlying principles need to be better understood in order to improve the overall predictive simulation quality. In particular the use of steady-state friction values, neglecting the transient response, is questionable as experiments showed that shear stress overshoots can be as high as three times the long-time value. The phenomenon of the overshoot at start-up shear is analyzed. Possible explanations include nonlinear viscoelasticity and a slip relaxation effect giving rise to wall slip, which are discussed using relevant ply-ply friction measurements carried out on a dedicated friction test set-up. Experimental results on UD C/PEEK show that the shear stress build up and subsequent relaxation comply with nonlinear viscoelasticity. However, the long-time shear stress fails to match the matrix material’s viscosity, possibly due to a yield stress. The flow curve corrected for a yield stress resembles the effects of wall slip. A transient model according to these findings will enhance the accuracy of press forming simulation software.
Experimental studies for the additive manufacturing of continuous fiber reinforced composites using UV-curing thermosets
Authors: Kunze Eckart , Müller-Pabel Michael , Weißenborn Oliver , Luft Ron , Faust Johann , Geller Sirko , Gude Maik
Published: April 2021

The economical production of lightweight structures with tailor-made properties and load-adapted geometry is limited using conventional technologies. Additive manufacturing processes offer a high potential to meet these requirements, where the established solutions are based primarily on thermoplastics matrix systems. From a process-technological point of view, thermoplastics enable simplified processing, but only a limited range of applications for high-performance components. These limitations are due to their comparatively low heat resistance, low melting temperatures and limited adhesion to embedded reinforcing fibers. In contrast, thermosets show high potential for realization of high- performance lightweight structures with adaptable properties. The present work employs a UV-curing thermoset resin for the impregnation of a continuous filament strand for 3D printing. The main challenge is to reconcile the crosslinking reaction of the thermoset and the process velocity during impregnation and cure. The liquid polymer must provide low initial viscosity to impregnate the filaments and a sufficiently high cure rate and dimensional stability after discharge from the print head to ensure sufficient bonding strength to the substrate. To demonstrate feasibility, a prototypic print head with UV-LED activation was designed and implemented. With a robot-guided printing platform, the 3D-deposition of continuous fiber-reinforcements without additional supporting structures can be realized. To derive initial process parameters, reaction and thermos-mechanical properties are determined by rheometer measurements. Impregnation and cure behavior of the glass fiber reinforced resin is investigated. The presented results provide a reliable process window and a straightforward process monitoring method for further enhancement of the conceived 3D printing process.
The effect of kinematic hardening on the fatigue behaviour of bent high strength steel
Authors: Gothivarekar Sanjay , Coppieters Sam , Talemi Reza , Debruyne Dimitri
Published: April 2021

The integration of forming in the fatigue modelling of cold-formed components significantly improves the predictive accuracy of the estimated life. The current study investigated the fatigue behaviour of a bent specimen made from a 5 mm thick, S900MC high strength steel plate. Because of its superior static and dynamic strength, this grade is progressively used for hollow cold-formed sections in mobile applications. However, it exhibits a strong stress saturation as well as limited formability. In this regard, a finite element modelling framework was adopted from previous research and further developed to integrate bending in the fatigue modelling and life estimation procedure. However, this framework currently ignores the possible influence of kinematic hardening and associated Bauschinger effect. For this reason, a numerical study was performed that compares isotropic with kinematic hardening for this specific application. First, the characteristic behaviour of these models was verified in a virtual tension-compression test. Subsequently, they were implemented in forming simulation followed by fatigue loading. Herein, the stress-strain evolution was investigated and a multi-axial fatigue criteria was used to map the sensitivity of the estimated life to the type of hardening. In general, the stress that entered the fatigue calculation was at least 21% lower for the kinematic model. As a result, a significant increase of 65% was observed for the estimated fatigue life, yielding a better comparison with experimental data.
Friction Stir Welding of dissimilar aluminum-steel joints for the shipbuilding industry
Authors: Campanella Davide , Buffa Gianluca , Fratini Livan
Published: April 2021

In recent years, the development of innovative joining methods has increased significantly due to the demands of several industries, such as the naval one, for lightweight structures. In fact, the safeguarding of the sea takes place through the reduction of climate-altering gas emissions, which is induced by energy savings. The latter can be achieved by the adoption of innovative technological solutions inherent to both the manufacturing processes and the increase in the use of light alloys. These solutions can reduce the environmental impact of vessels both in refitting operations and in new buildings. Although its potential in producing effective joints of different materials, the Friction Stir Welding process is still poorly used in the naval field due to difficulties in welding dissimilar joints of thick plates. In this paper, Friction Stir Welding was used to produce joints, in lap configuration, out of two very different, yet widely used in the naval sector, materials. This research work focuses on the engineering of the process, in terms of identification of welding parameters aimed at welding AA5083 H321 aluminum alloy and naval steel grade DH 36 plates with a thickness of 6mm. The results obtained indicate that sound joints can be obtained with a reasonably wide process parameters window when the aluminum plate is placed on top of the steel one.
Methods for online measurement and control of section deviations during hot rolling of wire rod and bars
Authors: Overhagen Christian , Braun Rolf , Deike Rüdiger
Published: April 2021

In the joint project PIREF, the metal forming group of the University of Duisburg-Essen has collaborated with the University of Applied Sciences Ruhr-West Mülheim (Ruhr), the University of Siegen, EMG Automation GmbH and SMS group GmbH to develop sensors, for an online measurement of material velocity and cross section as well as control models for the rolling process of wire rod and bars. The University of Duisburg-Essen provided a metal forming process model for the rolling process to assess the influencing parameters on the rolled section precision. A technique was found to segregate height- from width- influencing parameters from a measured cross-sectional area and actual roll gap. With this measuring technology and with help of the process model, rules for control of the rolling process to achieve close tolerances were obtained. The modelling was accompanied by rolling trials on a laboratory rolling mill at the University of Duisburg-Essen, where a typical Round-OvalRound pass sequence was used for validation of the rolling model concerning lateral spread, inlet and outlet velocity as well as rolling force and torque calculation. The present paper shows how the material flow and the distribution of the velocity in the roll gap can be described. In subsequent rolling of bar and rod in a continuous rolling mill the dimensions can be influenced by application of longitudinal stresses and screwdown. The application of stress can be achieved by an inter-stand velocity mismatch. With the developed models the necessary velocity mismatch can be calculated.
Analytic Model for Multi-point Large-Radius Bending of Steel Sheets
Authors: Thielen Cedric , Decroos Koen , Shore Diarmuid , Crevecoeur Guillaume , De Belie Frederik
Published: April 2021

While the majority of industrial sheet bending processes consist of conventional air bending, more complex bending processes such as multi-point bending are also utilized. Multi-point bending involves forming several bends simultaneously with changing contact conditions. Of the various models that may be employed to simulate such processes, analytic models are most attractive for industrial applications as they are time-efficient, strongly theoretically supported and easily extended to a wide range of dies layouts without the need of additional experimental data. In this paper a new analytic model is presented to predict the forming forces, the deformation of the sheet and the springback. The model is based on the literature around large-radius air bending. The geometry of the sheet is determined at each moment as a function of the tool’s positions. The reaction forces are calculated based on the equilibrium of forces and moments and the springback is calculated based on the elastic unloading of the internal bending forces. The model has been compared with a more time consuming finite element (FE) model and the geometry of the sheet has been experimentally verified by means of digital processing of video images. The proposed analytic model shows good agreement with the computational FE model and it is demonstrated to be a robust tool for calculation of the bending characteristics.
Anisotropic Plastic Behavior of Additively Manufactured PH1 Steel
Authors: Liu Wenqi , Li Zinan , Bossuyt Sven , Forsström Antti , Que Zaiqing , Björkstrand Roy , Salmi Mika , Partanen Jouni , Lian Junhe
Published: April 2021

Metals made by additive manufacturing (AM) have intensely augmented over the past decade for customizing complex structured products in the aerospace industry, automotive, and biomedical engineering. However, for AM fabricated steels, the correlation between the microstructure and mechanical properties is yet a challenging task with limited reports. To realize optimization and material design during the AM process, it is imperative to understand the influence of the microstructural features on the mechanical properties of AM fabricated steels. In the present study, three material blocks with 120×25×15 mm3 dimensions are produced from PH1 steel powder using powder bed fusion (PBF) technology to investigate the anisotropic plastic deformation behavior arising from the manufacturing process. Despite being identical in geometrical shape, the manufactured blocks are designed distinguishingly with various coordinate transformations, i.e. alternating the orientation of the block in the building direction (z) and the substrate plate (x, y). Uniaxial tensile tests are performed along the length direction of each specimen to characterize the anisotropic plastic deformation behavior. The distinctly anisotropic plasticity behavior in terms of strength and ductility are observed in the AM PH1 steel, which is explained by their varied microstructure affected by the thermal history of blocks. It could also be revealed that the thermal history in the AM blocks is influenced by the block geometry even though the same process parameters are employed.
Understanding formability and geometrical accuracy of SPIF process used as Reshaping approach
Authors: Zaheer Omer , Ingarao Giuseppe , Lorenzo Rosa Di , Fratini Livan
Published: April 2021

Putting in place Circular Economy strategies is an urgent action to be undertaken. Manufacturing processes play a relevant role as efficient material reuse enabler. Scientists have to make an effort either to find new process or to rethink old process to reprocess End-of-life (EoL) components to recover both material and functions. In this paper, Single Point Incremental Forming (SPIF) process is used for reshaping sheet metal EoL components. Deep drawing process as well as uniaxial pre-straining (to imitate the End-of-Life component) followed by SPIF operations (to obtain the reshaped components) are set- up and implemented to form and reform aluminum sheet metal components. As the authors have already proved the technical feasibility of such an approach, the present paper aims at a better understanding of the formability and geometrical accuracy performance of SPIF process as used to reform components. Specifically, an experimental campaign varying kind and extent of restraining is developed and the formability and geometrical accuracy of the subsequent SIPF operations is analyzed. Results proves that SPIF process is a promising approach for reshaping purpose.
Numerical analysis of plastic die deformation during high temperature copper extrusion
Authors: Lechner Stefan , Nitschke Renè , Müller Sören
Published: April 2021

In copper extrusion, billet temperatures of 600°C or more are very common and the dies are therefore exposed to high thermo-mechanical stress. This causes deflection and wear of the dies and thus reduced quality of the extruded profile. In the present study, die deflection and residual deformation after several extrusion cycles was investigated by means of extrusion trials and numerical analyses. Material models of four tool materials (hot-work tool steels 1.2367 and CS1, nickel-based alloy 718, cobalt-based alloy Stellite 1) and the copper alloy CW024A were provided by hot compression tests. Extrusion trials were carried out applying four different dies, each made of another tool material. Using the FEM based software DEFORM 2D, the extrusion trials were modeled and decoupled die stress analyses were performed, which simulated three consecutive load cycles. The focus of the data interpretation was in die deflection in proximity of the die land due to the thermo-mechanical load and residual plastic deformation after relief of the mechanical load. Larger values of deflection close to the die land were observed for the hot-work tool steels, while the deflection of nickel- and cobalt-based alloys was negligibly small. Also, remarkable plastic deformation was only determined for the hot-work tool steels, with increasing values for every simulated load cycle. This analysis characterizes the performance limits of hot-work tool steels and the benefits of nickel- and cobalt-based alloys regarding contour accuracy during high temperature copper extrusion.
The Indian Ocean as Diasporic Space: A conceptual introduction
Authors: Walker Iain , Slama Martin
Published: April 2021

Over the past two decades there has been a growing interest in Indian Ocean networks within diaspora studies, and within migration studies more generally. In this introduction we develop the idea of the Indian Ocean as a space within which diasporas come into being, endure, and sustain relationships. Taking this Indian Ocean perspective, we suggest that the concept of the diaspora as currently employed in scholarship could be strengthened and we outline some suggestions for a reframing of the concept. Through an emphasis on its enduring character, as a community, and through a decentring of the homeland, we propose to understand a diaspora as a community that is diffuse but coherent, both spatially and temporally, and that has agency, facilitating the activities of its members. This provides a framework for the variety of approaches to the concept in the articles in the collection that follows.
Preserving and Transmitting the Teachings of the Thariqah 'Alawiyyah: Diasporic Ba 'Alawi female preachers in contemporary Indonesia
Authors: Husein Fatimah
Published: April 2021

Within academic discussions of Indonesia’s Hadhrami diaspora, women’s voices have often escaped scholarly attention. This paper focuses on the changing roles of three contemporary Indonesian Ba ‘Alawi female preachers, in Jakarta, Surabaya and Solo, with regard to their endeavors in preserving and transmitting the teachings of the Thariqah ‘Alawiyyah, a Sufi path that is traditionally reserved for men and which was established by the founding ancestor of the Ba ‘Alawi, a descendant of the Prophet Muhammad named Muhammad b. ‘Ali ‘Alawi (d. 1255). While many important studies focus on the Hadhrami diaspora in Southeast Asia, and particularly on the role of male religious authorities, there is a dearth of research that takes the role of female actors seriously. This article presents a more complex picture of female Ba ‘Alawi religious teachers, highlighting similarities between them, but also the differences. It argues that the intellectual legacies, spiritual engagements and genealogical connections that these female preachers enjoy have enabled them also to assume the roles of preservers and transmitters of the teachings of the thariqah. In doing so, they inform the dynamics of religious transmission spearheaded by Hadhramis in Indonesia today.
White Women Poets: The Fight Towards the Abolition of the Slave Trade in Eighteenth-Century Britain
Authors: Pelletier Miria
Published: April 2021

The British Parliament passed the act to abolish the slave trade in 1807. Many historians focus on the powerful men that challenged Parliament such as Thomas Clarkson and William Wilberforce, but rarely do they acknowledge the active role that British white women played in the abolition campaign. Women raised awareness of the slave trade by supporting abolition societies, promoting the boycott of slave-grown sugar, and creating anti-slavery writing. Poetry, in particular, was the most common type of anti-slavery writing done by white women. This paper explores the use of poetry as a tool to promote the abolition of the slave trade by examining Mary Birkett Card’s A Poem on the African Slave Trade, Hannah More’s Slavery, A Poem and Sorrows of Yamba, and Ann Yearsley’s A Poem on the Inhumanity of the Slave Trade. These poems highlight three key themes including the separation of family, Christianity, and the luxuries the British possessed at the expense of the Africans suffering.
Use of online applications in maintaining MSMEs performance during the COVID-19 pandemic
Authors:   Politeknik Negeri Medan, Nurlinda Nurlinda , Sinuraya Junus ,   Politeknik Negeri Medan, Asmalidar Asmalidar ,   Politeknik Negeri Medan, Hassan Rahayu ,   Politeknik Port Dickson, Supriyanto Supriyanto ,   Politeknik LP3i Medan
Published: April 2021

This study aims to see whether there are differences in sales made by offline/conventional and online MSMEs to discover alternative media transactions to survive and increase sales during the COVID-19 period. This research is an exploratory study on MSMEs players who sell Rujak Sentir at Simpang Jodoh, Percut Sei Tuan, Deli Serdang District, Indonesia. The data source in this research is primary data by collecting data using a questionnaire on 50 samples of Rujak Sentir MSMEs merchants. Data were analyzed using statistical descriptive analysis of the Wilcoxon Signed Rank Test. The final analysis of data shows that the apply of online applications can be an alternative for MSMEs in maintaining and improving performance throughout the COVID-19 pandemic. The usage of this research practice is to give input to related parties regarding other options that can be utilized by enterprises throughout the Coronavirus widespread so that in the future, MSMEs are ready to face uncertainties that arise due to external factors. In addition to this, this research will be a recommendation regarding technical guidance that can be carried out by the local government in fostering MSMEs.
Effects of rhizome extracts from invasive knotweed species Fallopia japonica and F. ×bohemica on radish seed germination and root growth of seedlings
Authors: Šoln K. , Likar M. , Dolenc Koce J.
Published: April 2021

Japanese knotweed (Fallopia japonica) (Houtt.) Ronse Decr. and Bohemian knotweed (F. ×bohemica) (Chrtek and Chrtková) J. P. Bailey are invasive plants in Slovenia. We studied the effects of aqueous extracts [0.5 %, 1 %, 2 %, 5 % and 10 % (w/v)] from rhizomes of F. japonica and F. ×bohemica on the seeds of radish (Raphanus sativus) and examined the morphological and biochemical changes during germination and early growth of seedlings. Germination and early growth of radish were monitored 3, 5 and 7 days after treatment. Extracts of these two knotweed taxa delayed seed germination and strongly reduced the length of the primary root, but had less effect on shoot growth. These extracts triggered stress-induced morphogenic responses in the treated radish seedlings, stimulating the formation of lateral roots at low concentrations and causing inhibition at high concentrations. The extract concentration and not the knotweed taxon influenced the biochemical markers of oxidative stress in the radish. Total antioxidative capacity was increased in treated radish seedlings. The extract of F. japonica had a greater impact on the radish morphology than that of F. ×bohemica, with similar influences on the biochemical parameters. High pressure liquid chromatography identified emodin, resveratrol, catechin and epicatechin in the rhizomes of both knotweed species. Their contents were species dependent.
Effects of potato-onion intercropping on root morphology of tomato through volatile organic compounds
Authors: Shi J.B. , Gong X.Y. , Khashi u Rahman M. , Yua T. , Zhou X.G. , Wu F.Z.
Published: April 2021

Facilitative interactions occur between the plants in intercropping systems, however, the underlying allelopathy mechanisms are poorly understood. We determined the effects of potato-onion (Allium cepa var. agrogatum Don.) intercrop on root morphology of tomato (Lycopersicon esculenum L.) through volatile organic compounds (VOCs). There were four treatments as (i) Tomato/tomato without VOCs interaction (-TT), (ii) Tomato/tomato with VOCs interaction (+TT, control), (iii) Potato-onion/tomato without VOCs interaction (-OT) and (iv) Potato-onion/tomato with VOCs interaction +(OT) in glasshouses. As compared to tomato, VOCs from potato-onion significantly increased the number of root tips total length but decreased the root diameter of tomato, however significantly the increase the tomato root length (0-0.5 mm mean diameter). These results indicated that the tomato root morphology has influenced by aboveground secreted VOCs from neighboring plants in potato-onion intercropping system.