bluuebunny/crossref_metadata_2025 huggingface dataset:
The use of MOOCs as additional tools for teaching NoSQL in blended and distance learning mode
Authors: Zinovieva I S , Artemchuk V O , Iatsyshyn Anna V , Romanenko Y O , Popov O O , Kovach V O , Taraduda D V , Iatsyshyn Andrii V
Published: June 2021

Today there is a significant demand for improving the quality of the educational process in higher education institutions, in particular, through the improvement of principles and methods of teaching various sciences by enhancing the practical skills of students and graduate students. The implementation of this task is particularly difficult in the context of distance learning (for full-time and part-time) and blended learning. This study corresponds to the current direction, as it concerns the study of the possibilities and feasibility of using additional tools for teaching disciplines within NoSQL. Paper’s focus is on the justification of the use as an additional tool of a number of massive open online courses (MOOC) distance learning platforms, a comparative analysis of a number of platforms for their compliance with the established criteria. Examples of using MOOC MongoDB University within the discipline “Organization of NoSQL databases” are given. To confirm the facts of the expediency of using MOOC as an additional tool in blended learning and distance learning mode, the data of the survey of students are presented.
Teaching robotics to future teachers as part of education activities
Authors: Valko N V , Osadchyi V V
Published: June 2021

One of the most effective ways to implement STEM education in full secondary education is through research activities. It is implemented by performing certain projects. Professional activity of teachers of natural and mathematical disciplines in STEM education is aimed at the students’ mental, cognitive, and personal qualities formation and development. Their level determines the possibility of further mastering by students of a promising specialty STEM industry. It also involves the formation of the ability and willingness to solve complex problems, which is possible with the appropriate level of critical thinking, creativity, cognitive flexibility, teamwork, as well as the ability to implement research activities. In article determines the nature of the relationship between disciplines and the degree of integration. The place of project activity on robotics in school training is considered, describes the competencies that are formed as a result of such project activities. the possibility of teaching robotics to future teachers within the framework of existing curricula is also considered. The concept of STEM education has a broad interpretation: from a simple list of “exact” or “engineering” disciplines to inventive activity. In Ukraine, this area has become synonymous with scientific and research work: research and experiments. From this point of view, robotics is an effective means of developing STEM education. But this is a new tool and schools have a low level of interest in its study. Therefore, our article focuses on finding opportunities to implement the basics of robotics in education. The article formulated course requirements in accordance with the educational needs of the future teachers of science, mathematics and the level of technology development. The paper presents an example of project implementation in robotics, describes the stages of its implementation and achieved educational results.
Specific features of the use of augmented reality technologies in the process of the development of cognitive component of future professionals’ mental capacity
Authors: Osadchyi V V , Osadcha K P , Varina H B , Shevchenko S V , Bulakh I S
Published: June 2021

Ways of development and modernization of modern higher education are largely determined by the scientific and technological progress. The article is devoted to the current issue of the augmented reality technology use in professional education. The paper analyzes foreign and domestic experience of the use of augmented reality technologies as a means educational, research and project activities implementation. The author also describes the benefits of the augmented reality technologies use for the curricula design. Taking into account the reorganization of the educational process due to pandemic isolation, caused by COVID-19, the issue of the identification of AR technologies impact on the development of cognitive component of future specialists’ mental capacity is becoming extremely relevant especially in the conditions of adaptive and blended learning. The paper, in a structured way, describes the experience of introducing the augmented reality elements in the process of developing cognitive component of future professionals’ mental capacity. The ascertaining and formative stages of the empirical research were carried out during 2020 on the basis of Bogdan Khmelnytsky Melitopol State Pedagogical University. Relevant interdisciplinary research is a logical construct of cooperation between leading scientists of the Department of Psychology and the Department of Informatics and Cybernetics of Bogdan Khmelnytsky Melitopol State Pedagogical University. The structure of the study includes the main scientific developments in the context of the research work, performed at the expense of the General Fund of the state budget: “Adaptive system for individualization and personalization of professional training of future specialists in blended learning”. Based on certain psychological and pedagogical determinants of the AR technologies use for the development of cognitive component of the future specialists’ mental capacity, we have proposed the implementation of interactive technologies at three levels: competence-oriented, structural-cognitive, emotional-reflexive, on the example of doing the course “Introduction to Specialty (Psychology)” in the conditions of distance learning. According to the results of an interdisciplinary research, it was found out that students gained skills which are necessary for their adaptation to a new intellectual and educational environment. Due to positive qualitative and quantitative changes in the cognitive structure of personality there was an increase in the first-year students’ mental capacity in its main components (the level of attention stability and selectivity, short-term memory span and analytical thinking, level of development of special qualities necessary for mental capacity, formation of mental capacity culture).
Using interactive semantic networks as an augmented reality element in autonomous learning
Authors: Tarasenko R O , Amelina S M , Semerikov S O , Shynkaruk V D
Published: June 2021

This paper focuses on the using augmented reality elements in the educational process, in particular in autonomous learning. The possibility of using interactive semantic networks in learning foreign languages is considered. The technology of selection and structuring of specialised terminology on the basis of interactive semantic networks for their further use in the study of foreign languages and mastering automated translation systems has been developed and proposed. The criteria for creating and supplementing terminological databases with appropriate structuring of the domain terminology selected on the basis of interactive semantic networks have been defined, namely universality, structurability, convertibility, extensibility. The possibility of further use of terminology bases for foreign language learning using mobile applications, mastering Computer Aided Translation (CAT) systems, mastering Computer Aided Interpretation (CAI) are outlined. Based on the practical use of the developed technology in the process of autonomous training of translators, positive results have been concretised and areas for further activities in their technological training have been identified.
The cryogenics and xenon handling system for the PandaX-4T experiment
Authors: Zhao L. , Cui X. , Ma W. , Fan Y. , Giboni K. , Zhang T. , Liu J. , Ji X.
Published: June 2021

PandaX-4T, the new generation of the PandaX detector, is a xenon dual-phase detector with about six tons of liquid xenon as target for dark matter search. A cryogenics and xenon handling system is designed to liquify and purify this large detector. In this paper, the results on the commission of the cryogenics and gas handling system are reported. The maximum cooling power of ∼ 580 W at 178 K with three cooperating coldheads has been achieved. The filling rate with an assisted liquid nitrogen cooling can reach ∼ 700 kg/day. The average rate of recuperation by liquid nitrogen is around 440 kg/day. The maximum total purification speed of two circulation loops is up to ∼ 155 slpm. Each loop is using a large heat exchanger with a measured heat exchange efficiency of ∼ 97.5±0.5%.
Manufacturing, assembling and plasma cleaning of new SANAEM RFQ
Authors: Cosgun E. , Yasatekin B. , Kilic I. , Bolukdemir A.S. , Olgac Y. , Cicek E. , Yesilbag B. , Alacakir A.
Published: June 2021

A new 1.2 m radio frequency quadrupole (RFQ) accelerator cavity, made of oxygen-free copper (OFC) and capable of accelerating protons up to 1.3 MeV energy, is recently manufactured for the Turkish Atomic Energy Authority (TAEA), based on the motivation of establishing a proton beamline with indigenous capabilities. In the present article, the manufacturing and assembling procedures related to the new RFQ copper vanes, especially the novelties applied to a vane type RFQ accelerator cavity, namely plasma cleaning of vane surfaces and utilization of indium wire in vacuum sealing, will be described. The preliminary results, the vacuum level and quality factor, suggest that these applications indicate promising options for future accelerator cavity production.
Individual Selection Soybean (Glycine max L.) The Genotype of Cross Argomulyo and Tanggamus Based on Character of Yield Component
Authors: Sihaloho Arvita Netti , Sitinjak Wahyunita , Purba Tioner
Published: June 2021

Selection is one of plant breeding techniques to obtain a desired character. The objective of this research was to determine information about the trait variance in F3 lines in terms of yield and yield components, knowing character could be improved through selection to obtain high yield lines. This study was conducted on june until august 2020 in the village Karang Bangun Rambung Merah Kecamatan Pematangsiantar, kabupaten Simalungun 500-550 with an elevation place, use augmented design. 20 × 30 cm plant distance, data observed for each individual plant, and done to find genetic variance, environment variance, phenotif variance, GCV, broad-sense heritability and Coefficient correlation. The result show that the value of heritability all character was moderate until high except the days of harvest was low. The value of GCV was narrow to the days to flowering and harvest, while other character value of the GCV was moderate until broad. Coefficient correlation indicated that Seed weight per plant was positively and significantly correlated with all studied traits except the days to flowering was negative and non-significant. Based on high heritability and broad GCV, selection process on seed weight per plant so 10 selected lines with highest seed weight.
Mapping Climate Classification of Oldeman in Agricultural Resources Management in South Tapanuli District
Authors: Harahap Imelda Sari , Matondang Irwan Zulfikri , Suryanto  , Indah Erti Kumala , Fitri Irmalia
Published: June 2021

The Oldeman classification system is very useful in the classification of agricultural land for food crops in Indonesia using the element of rainfall. The criteria are based on the calculation of wet months (BB) and dry months (BK), respectively, with the limits taking into account the chance of rain, effective rain and water requirements for plants. With the Oldeman climate classification, a cropping pattern system can be determined in an area. Based on the research results obtained 4 types of climate in the South Tapanuli region, namely: D1, D2, E1, and E2. The wettest climate type in the Sipirok region is climate type D1 with 4-5 wet months and ,2 dry months. And those that are suitable for planting short-lived rice are 3 (three) harvests or short-lived rice is 2 (two) harvests and secondary crops 1 (sastu) harvests. The driest climate types in the East Angkola region are climate types E1 and E2 with the number of wet months ,3 and the number of dry months 6-7. What is suitable for planting short-lived lowland rice is 1 (one) harvest and secondary crops 2 (two) times, the second special harvest falls in the dry season. The topographical condition of an area greatly influences the climatic conditions of the area. With a good climate classification and suitable for rice plants without irrigation assistance, the climate types are D1 and D2, namely in Sipirok District, West Angkola District and a Small Part of Saipar Dolok Hole and Batang Angkola Districts. Meanwhile, the East Angkola sub-district can be planted with rice with the help of irrigation, especially in the dry season.
Dormancy Breaking of Kimalaka Seeds (Phyllanthus emblica L.) at Various Concentrations of Sulfuric Acid
Authors: Adelina Rasmita , Hanafiah Nasution Muhammad Nizar , Harahap Darmadi Erwin , Nasution Jihadul Fadhli
Published: June 2021

The kimalaka plant (Phyllanthus emblica L.), known as „balakka”, by the people of North Sumatra, with the English translation is called indian gooseberry [1] and is called “popok melaka” in Malaysia [2]. The kimalaka plant is a commodity with great potential to be developed, one of which is due to the high content of vitamin C so that the kimalaka plant has many health benefits. Especially in the Padangsidimpuan area and its surroundings, this kimalaka plant is more widely known as a mixture of traditional cooking spices, with the name of the food being called „holat”.The widespread conversion of land into smallholder plantations with commodities such as rubber and oil palm is one of the threats to the extinction of the kimalaka plant. Lack of information about the kimalaka plant is also the cause of the underdevelopment of this kimalaka cultivation. Kimalaka seed with a very hard seed coat is a factor causing kimalaka seed dormancy. So before planting, there must be a treatment to break dormancy. This study aims to see and observe the effect of various sulfuric acid concentrations to break the dormancy of kimalaka seeds. This study used a non-factorial randomized block design (RBD) with one factor, namely the concentration of sulfuric acid with 4 levels, namely: A0 = Control, A1 = 4%, A2 = 6%, A3 = 8%. The observation variables were the percentage of germination (%), plant height (cm), and the number of leaves. Based on the results of this study, it was found that the treatment of sulfuric acid concentration was significantly different in all observation variables. The treatment that gave the best effect on all observation parameters was sulfuric acid at a concentration of 8%. In future research, it is suggested to increase the sulfuric acid concentration.
The Development of a Software Tool for Improvement Tracking System Using Dynamic Systems Development Methodology
Authors: Imamuddin Ashari , Sobarnas Mohamand Anas , Iskandar
Published: June 2021

The present study aims to develop a software tool for improvement tracking system for a waste management company in Indonesia. The tool was built as a system to track the improvement process of following up findings of the validation and verification process in the management system of the company. The company also obtains a few audits by the authorities, certification bodies, and its customers. The company applied several management systems in assuring all persons in charges are responsible for following up on the improvement findings. The outcome of the study is a proven software tool that has supported the top management in making decisions in terms of the improvement processes. The system automatically reports to the top management when the findings of each individual responsible person have not been executed yet as well as the top management can take direct decisions and actions to the current status of their improvements processes.
Experimental analysis of the influence of the embossing and upsetting process on joint strength in resistance element welding with upset auxiliary joining elements
Authors: Meinhardt M , Lechner M , Merklein M
Published: June 2021

The use of conventional resistance spot welding in the car body shop for joining an aluminium part to a steel part is possible with the process-invention of the resistance element welding (REW) with upset auxiliary joining elements. Within this process, the challenges arise from the novel approach of combining forming process steps in the insertion of the auxiliary joining elements. Thus, the process understanding is to be compiled to the combination of the individual process steps. For this reason, the study deals with the influence of the forming process steps on joint strength of REW with upset auxiliary joining elements. The focus is set to the improvement of the positive locking and force fit considering the results of previous strength analysis. As the key result, the initial relative position of the carrier sheet and the auxiliary joining element is highlighted as the most significant factor on joint strength. The material flow, illustrated in metallographic microsections, is used to explain this effect. Based on the elaborated cause-and-effect-chains, a geometrical model is derived and validated to produce high-quality joints with high joint strength.
Joining with Friction Spun Joint Connectors – Manufacturing and Analysis
Authors: Wischer C , Steinfelder C , Homberg W , Brosius A
Published: June 2021

Nowadays, the production of modern lightweight structures, like a body in white structure requires a wide variety of mechanical joining processes. To fulfill the various demands, mechanical joining processes and joining elements (JE) are used. Very often, they are adapted to the application, which leads in turn to a numerous of different variants, high costs, and loss of the process chain versatility. To overcome this drawback, an innovative approach is the usage of individually produced and task-adapted JE, the so-called friction spun joint connectors (FSJC). These connectors can be modified in shape as well as in material properties. This flexibility offers high potential for lightweight design but also increases the necessary analytical effort regarding the forming process as well as the manufactured joint’s properties. Therefore, a new analysis strategy based on the Finite-Element-Method (FEM) is proposed, which numerically determines the local load bearing capacity within a given joint in order to identify the critical regions for load transfer. The process of joining element manufacturing and the analysis strategy will be described in detail and optimization results of the joints are shown. Numerical results are discussed and possible recommendations for joint manufacturing are derived.
Effect of heat treatment conditions on the fatigue resistance of press hardened 22MnB5 steel evaluated through rapid testing technique
Authors: Parareda S. , Casellas D. , Frómeta D. , Garcia-Llamas E. , Lara A. , Pujante J. , Mateo A.
Published: June 2021

Fatigue strength is considered as a crucial parameter for automotive applications subjected to cyclic loads during their long service life, as chassis parts. The high yield stress of press hardened steels poses them as good candidates for lightweight solutions with improved fatigue resistance. However, their high strength leads to an increase in notch sensitivity which can ruin the whole part’s integrity. This behaviour was observed in previous works on press hardened steels, where their high fatigue strength was significantly affected by the surface conditions and by heat treatment conditions. Nevertheless, press hardening steels are still good candidates to manufacture complex geometry parts reaching high performance.

Aiming at increasing the existing knowledge on the fatigue behaviour of press hardened steels, this paper analyses the fatigue performance of boron steel (22MnB5) under different time austenitizing times. Fatigue resistance is evaluated using a novel rapid fatigue testing technique based on the stiffness evolution. The method permits a fast and reliable determination of the fatigue limit. Based on results obtained with this rapid testing method, the most suitable heat treatment to mitigate fatigue notch sensitivity and then achieving the best fatigue performance for chassis applications is discussed.
Effect of strain rate on formability of 22MnB5 steel during hot stamping process
Authors: Singh Amarjeet Kumar , Narasimhan K
Published: June 2021

Hot stamping is a high temperature and high strain rate deformation process, which is widely used in automotive industries because of the advantages associated with the process like higher formability, no spring back, higher specific strength to weight ratio etc. When strain rate increases, the formability of materials decreases but in some conditions reversal behavior was also observed, therefore in this work, the focus is to find the effect of strain rate on thickness distribution, thickness gradient evolution and formability of 22MnB5 Steel. To capture the effect of strain rate, a wide range of high-temperature tensile tests were conducted in the thermomechanical simulator (Gleeble-3800) for different strain rates (0.01, 0.1, 1/s) under uniaxial and plain strain conditions. It is found that formability of 22MnB5 steel increases with increase in strain rate in the drawing region.
New sheet metal forming process for springback reduction by continuous stress superposition
Authors: Briesenick D , Liewald M , Riedmueller K R
Published: June 2021

The use of ultra-high-strength steels (UHSS) enables a lightweight and resistant design of sheet metal parts in modern car body structures. In terms of manufacturing such dedicated materials, intense springback phenomena reduce the process stability and dimensional quality. In this context, new developments in springback compensation show promising results when superimposing stresses. Therefore, this paper deals with a new approach, which modifies conventional deep drawing of open profiles by substituting the blankholder by L-shaped sliders. This allows an additional application of horizontally acting forces along the edge of the flange and leads to advantageous free buckling and rolling of the material onto lateral punch surfaces. A numerical feasibility study of this new forming method was performed in this work, showing that compressive stresses and alternate bending through buckling in fact does reduce the amount of springback remarkably compared to conventional deep drawing.
Dimensionally accurate parts made of high-strength steels - compressive stress superposition instead of tool compensation
Authors: Linnepe M , Sieczkarek P , Kibben M , Botz F
Published: June 2021

As a result of the increasing use of high-strength and ultra-high-strength steels as part of the automobile lightweight construction strategies, the issue of dimensional accuracy of component structures is increasingly becoming the focus of toolmakers, pressed part suppliers and automobile manufacturers. In particular, the modern dual-phase steels with strengths of over 800 MPa possess-depending on the respective component geometry and the forming process employed-a pronounced springback behaviour. The compensation measures commonly used so far are more and more reaching their limits, which in turn impairs the process ability of these grades in the cold forming process. The smartform® process developed by thyssenkrupp Steel Europe AG allows the cold forming of high-strength steels with high repeatable accuracy, which significantly expands their areas of application. In this process, the tensile stresses from the forming operation causing the springback of the part are eliminated by compressive stress-superposition, which leads to high dimensional stability. There is almost no need to adapt the tool surfaces to achieve a dimensionally accurate part. How close the formed component comes to the dimensional tolerances specified by the end user is usually determined within the framework of numerical method development. In this context, the result of a springback simulation depends on various parameters. The description of the material behaviour is of major importance. Moreover, the use of extended material models can have an influence on the predictive accuracy and reduce the deviations between simulation and real material behaviour. It remains to be identified to what extent the increase in accuracy is proportional to the modelling effort.
Springback and compensation in sheet metal forming reconsidered as an ill-posed problem
Authors: Hartmann Christoph , Maier Lorenz , Volk Wolfram
Published: June 2021

Springback is a fundamental challenge in sheet metal forming and a critical issue with respect to part quality and dimensional accuracy. To overcome the problem, different strategies for springback compensation have emerged in recent years. In this paper, we give a review on fundamental strategies of compensation for deviations in sheet metal forming and embed them, for the first time, in a general description framework rooted in the solution of ill-posed problems. On this basis, we conclude by briefly comparing different approaches and elaborate on future challenges and chances that naturally arise from the presented problem formulation.
Comparison of different forming methods on deep drawing and springback behavior of high-strength aluminum alloys
Authors: Rigas N , Schmid H , Merklein M
Published: June 2021

High-strength aluminum alloys of the 7XXX series have a high potential for safety and crash-relevant components due to their advantageous density-to-strength ratio. Currently, the use of these alloys is limited because of the low formability at room temperature. By using thermal supported forming strategies, failure-free deep drawing is possible for these materials. At present, several thermal-assisted forming processes exist, but so far there is no comparison between these forming operations. For this purpose, this study compares the deep drawing behavior of the alloy AA7075 by using different thermally-assisted forming operations. Aim of this work is to enhance the understanding and comparability between different thermally-assisted forming processes for high-strength aluminum alloys. First, a thermal simulator is used to investigate the mechanical material behavior according to different temperature-time curves by using uniaxial tensile tests. Subsequently, the formability and springback behavior is determined numerically and experimentally in a model test. Finally, for one thermally assisted forming method, the experiments are scaled up to a real size process with drawbeads to validate the transferability. This study can help to improve the scientific knowledge for the use of these materials in future.
Equivalence between Localization Criteria and Fracture Criteria as Forming Limit in Failure Evaluation for 7xxx Series Aluminum Alloy Sheets
Authors: Hong J-H , Kim D
Published: June 2021

The equivalence between the localization criteria and the fracture criteria was validated as a forming limit for the proper prediction of failure induced by severe strain localization in the two-step hybrid forming process of 7xxx series aluminum alloy sheets at the elevated temperature. In the previous researches, an extensive and systematic method combined with sophisticated material characterization had been revisited as the localization criterion to estimate the onset of the failure without any fracture criteria. As for the fracture criteria, a deformation path and effective strain-rate sensitive fracture criterion was utilized. In the event of failure occurrence with abrupt strain localization, which has been traditionally known as the localization criteria dominant case, the fracture criteria can replace the localization criteria as a forming limit.
Simplified measurement of the strain to fracture for plane strain tension: On the use of 2D DIC for dual hole plane strain tension mini Nakazima specimens with dihedral punch
Authors: Adlafi M. , Galpin B. , Mahéo L. , Roth C. C. , Mohr D. , Grolleau V.
Published: June 2021

A plane-strain-tension stress state leads to a minimum in ductility in most micro-mechanical and phenomenological fracture models as well as Forming Limit Curves. Hence, this stress state plays a crucial role in many applications and a reliable measurement of the strain to fracture under plane strain tension is of particular importance when calibrating modern fracture initiation models. Recently, a new experimental technique has been proposed for measuring the strain to fracture for sheet metal after proportional loading under plane strain conditions. The basic configuration of the novel setup includes a dihedral punch applying out-of-plane loading onto a Nakazima-type disc-shaped specimen with two symmetric circular cut-outs. 3D Digital Image Correlation (DIC) is used to measure the surface strains of the specimen up to fracture. In contrast to the widely used V-Bending test, the maximum obtainable strain is not limited when using this set up, and fracture will always initiate after proportional loading in a plane strain tension stress state. In the present study, a major simplification of the testing methodology is proposed, reducing from 3D DIC to a simple 2D DIC method for measuring the fracture strain. Comparisons are presented on three metals, a 1.5 mm thick DP600 steel, a 0.8 mm thick DP450 steel and a 1.2 mm thick AA2024 aluminum alloy.
Performance Evaluation of Planar Anisotropy Yield Criteria for Aluminum Sheet Forming Analysis
Authors: Ghoo B , Ichijo N , Selig M , Manopulo N , Carleer B , Suzuki W , Takizawa H
Published: June 2021

The present work aims making a step by identifying a set of standardized accuracy measures based on laboratory experiments. Uniaxial tension, plane strain tension, hemispherical dome, and square cup tests were conducted for a 6000 series aluminum sheet used as automotive panels. Principal strain distribution, punch height at fracture, draw-in, and wrinkling were measured and compared with numerical simulation predictions. The performance of the five yield criteria, Barlat89, BBC2005, Hill48, Vegter2017, and YSD6 (Yoshida 6th order polynomial function) was measured and evaluated using the conventional accuracy index and the proposed accuracy indexes that represent manufacturing defects encountered in practice. It is found that state of the art material models such as BBC2005, Vegter2017 and YSD6 are fully able of representing standardized material test results, which is also well reflected in the predictive accuracy of simulated hemispherical dome and square cup tests. Because earlier models such as Hill48 and Barlat89 lack in capturing a high number of experimentally determined data points, they should be used with caution even Barlat89 shows good performance in the hemispherical dome tests.
Potential use of machine learning to determine yield locus parameters
Authors: Karadogan C , Cyron P , Liewald M
Published: June 2021

The determination and validation of material parameters required for the finite element simulation of sheet metal forming processes can be realized by a full-field optical measurement of the deformation of a test specimen in combination with a simulation-based inverse approach. Development of such an inverse approach can be quite time consuming and requires programming skills and also expertise in FEM analysis and optimization. Emerging machine learning techniques offer a practical alternative to optimization and inverse approaches provided that the ground truth is completely known and generalized by the machine learning model. To be more precise, a machine learning model can directly compute the material parameters from the experimental measurements if the hypothetical mapping function between material parameters and deformation behavior is learned as ground truth. This paper presents such a machine learning based approach for the determination of validated yield locus parameters.
Effects of initial microstructure before cold rolling on microstructure evolution and mechanical behaviour of CGLcompatible Q&P steel
Authors: Wang Yu , Xu Yunbo , Zhang Tianyu
Published: June 2021

Quenching and partitioning (Q&P) steels offer impressive combination of strength and ductility that can reduce the mass and improve the crash worthiness. In order to be able to meet consumer’s durability expectations, corrosion protection and galvanizability become crucial. In this paper, based on a cold-rolled high strength steel (0.225C-0.85Si-2.02Mn-0.91Al, in wt.%) and continuous galvanizing line (CGL) compatible Q&P treatment, the effects of the initial microstructure before cold-rolling were systematically investigated by means of SEM, EPMA, TEM, EBSD and XRD. It is shown that the resulting microstructure and mechanical properties after Q&P treatment are influenced by the initial microstructure. About 10.2-16.1vol.% RA are obtained, which is potential to gain the desired mechanical stability. Compared with “Q&P sample with initial microstructure prepared by quenching and austempering (i.e., Q&P(QAT))”, “Q&P sample with initial microstructure prepared by quenching and austempering followed by tempering (i.e., Q&P(QAT&T))” obtained a higher fraction of retained austenite (16.1%RA) and relatively low carbon content, thus resulted in an excellent ductility because of better mechanical stability and consequently more effective and sustained TRIP effect at high strain. With increasing the tempering time, the tempering degree of martensite increases markedly, while it does not have strong effects on the microstructures, leading to the similar fractions of RA and properties in “Q&P sample with initial microstructure prepared by quenching and tempering for 4min (i.e., Q&P(Q&T-1))” and “Q&P sample with initial microstructure prepared by quenching and tempering for 10min (i.e., Q&P(Q&T-2))”.
Virtual design of formability for Zircaloy-4 sheet through texture control
Authors: Liu H , Deng S , Chen S , Song H , Zhang S
Published: June 2021

Zircaloy-4 (Zr-4) sheet is commonly used in fuel assembly structural parts as spacer grids which are subjected to high temperature and stresses, corrosive and radiation environment. The knowledge regarding the properties and the formability with respect to initial texture of Zr-4 sheet is not enough. In this paper, finite element method was used to simulate the forming process of Zr-4 sheet, and effect of different initial hardening exponent (n value) on the formability of sheet is studied. The results show formability of sheet reveals better with larger n value. However, the hardening exponent (n value) is closely related to the features of initial texture of sheet. Thus, the well-established polycrystal plasticity method, visco plastic self-consistent (VPSC) model, was used to predict the effect of different initial textures on the hardening exponent of Zr-4 sheet, and plastic deformation mechanism of different initial textures in stamping process was analyzed. The results show that a larger the hardening exponent is obtained under a smaller normal Kearn factor (Fn) of the initial texture, and the activation of prismatic slip decreases with increasing the Fn.
A novel approach for characterising the cause of disc formation by the shear cutting process in a punching machine
Authors: Niessner S , Liewald M
Published: June 2021

The objective of this paper is to validate a method for identifying the cause of disc formation by numerical and experimental investigations for a single-stage shear cutting process in a tool-bound punching machine. To this end, first a 2D simulation model for the deep-drawing steel DC01 is developed, which enables the sophisticated requirement of tracking the material flow behaviour in the cutting process to be met by using the FEM Software DEFORM. Furthermore, the plastic flow behaviour is measured in an equivalent experiment with strain gauges near the cutting process. Then, the measurement results from the experimental investigation are contrasted with those from the simulation and compared for reliability at the measuring position of the strain gauges. The main contribution of this paper is a numerically and experimentally performed comparative study, in which the verified results of the first investigation near the shearing process are transferred into the cutting area and are validated subsequently.
Zero-error-production through inline-quality control of presshardened automotive parts by multi-camera systems
Authors: Pierer A , Wiener T , Gjakova L , Koziorek J
Published: June 2021

Visual inspection often represents a bottleneck in the production chain due to limited receptivity and human fatigue. Depending on the inspection task, human classification error decisions greater than 10% are not uncommon. In order to make the manufacturing process more robust and sustainable, this paper presents innovative automated inline monitoring to realize a zero-error strategy in the field of industrial manufacturing. The central idea is to detect surface defects in the running production process by data fusion of a multi-camera system. Due to the required data analysis in conjunction with the targeted high throughput rates in production, this generates large amounts of data to process. Massively parallel hardware structures are used to enable defect detection within the production cycle. The paper especially addresses how to tackle boundary conditions in productive press-lines like the software-based mitigation of placement tolerances of parts and real-time capabilities. As a result, benefits could be achieved in terms of minimum detectable failure sizes and inspection speed, enabling 100% inline inspection of produced parts. The feasibility of the presented approach is demonstrated on realistic press-hardened deep-drawn automotive parts.
New press deflection measuring methods for the creation of substitutive models for efficient die cambering
Authors: Pilthammar J. , Skâre T. , Galdos L. , Frojdh K. , Ottosson P. , Wiklund D. , Carlholmer J. , Sigvant M. , Ohlsson M. , Argandoña E. Sáenz de , Abbasi F. , Sarasua O. , Garro A. , Rutgersson W.
Published: June 2021

Cost and time for die tryout are significant within the car industry, and elastic deflections of dies and presses are most commonly not considered during the virtual die design and forming simulation phase. Because of this, active surfaces of stamping dies are only cambered based on previous experiences of tool types and presses. However, almost all stamping dies and presses are unique, and available experiences are not valid for new materials. Partners within the Eureka SMART Advanced Manufacturing research project CAMBER have developed advanced deflection measuring devices to quantify the elastic deformations of presses. Using these measurements, cambering methodologies can be utilized in sheet metal forming simulations. Important breakthroughs in recent years enabling the cambering methodology consists of efficient simulation strategies for full scale simulations with elastic dies and optimization techniques for creating substitutive press structures based on measurements. Furthermore, modern press deflection measurement methods are beneficial in applications such as Industry 4.0, predictive maintenance, product quality control, etc. through a more advanced understanding and live monitoring of the press system.
Process data based estimation of tool wear on punching machines using TCN-Autoencoder from raw time-series information
Authors: Asahi Shota , Karadogan Celalettin , Tamura Satoshi , Hayamizu Satoru , Liewald Mathias
Published: June 2021

Tracking the wear states of tools on punching machines is necessary to reduce scrap rates. In this paper, we propose a method to estimate wear state of punches using Temporal Convolutional Network Autoencoder (TCN-Autoencoder), one of the deep learning techniques for learning time-series information with convolutional architecture. Approach involves inputting raw time-series information, such as sensor, vibration and audio data, into TCN-Autoencoder, and calculating the reconstruction error between the output and the input data. The reconstruction error is used as “anomaly score” and indicates the distance from the normal state. By training TCN-Autoencoder only with data annotated as “normal” state, the reconstruction error becomes larger when inputting abnormal state data, which corresponds the wear state of the punch. Performance is evaluated on experimental measurement data that spans various wear states of the punch. The results showed our model can estimate anomalies faster than the conventional machine-learning-based anomaly estimation method, while maintaining the high estimation accuracy. This is due to TCN-Autoencoder being able to learn from both frequency and time domain.
Variance based sensitivity analysis of deep drawing processes based on neural networks using Sobol indices
Authors: Kott M , Kraft M , Emrich A , Groche P
Published: June 2021

Today’s deep drawing of car body parts is operated increasingly closer to the process limits, making it more challenging to ensure a high robustness of the process. Disturbances like varying material properties or changing tribological conditions may negatively affect the process, leading to deteriorated product properties and a loss of productivity. In the past, several approaches using different combinations of sensors and actuators to build up a control system have been investigated to fulfil the need of a more robust process. Hence, a thorough process analysis comes to be beneficial to evaluate the expediency of a control system and to make a reasonable preselection of sensors in order to avoid unnecessary costs. This paper presents a method using variant simulations to evaluate the expediency of a control system, including the necessary sensors. The influence of disturbances in the process is evaluated by a numerical sensitivity analysis under consideration of interaction effects. These higher order effects are calculated by Monte Carlo integration. Potential measurands are determined by the maximum achievable observability of not directly measurable quality criteria of a part. For this purpose, different modelling approaches of the observability are considered and compared with regard to their goodness-of-fit.
Approaches to analysing scatter in forming simulations: from fundamental to pragmatic
Authors: Atzema E. H. , Scholting M.E. , Abspoel M.
Published: June 2021

Including scatter in material properties has received attention in the last decades but, it is not fully mature yet. Industry has cooperated with academia to progress the topic, but at the same time devised simpler ways to start analysis anyway. Robustness analysis is a pre-requisite for process optimisation. Tata Steel has been in material modelling for Sheet Metal Forming for many years and has developed its own yield locus model to enable better customer support. The accuracy of this Vegter model comes at a price, however: more parameters to be measured. Wiebenga devised a robustness analysis but it requires more input than is usually available. At the same time leading software vendors introduced options to evaluate statistical behaviour. Obviously, process optimisation is only useful when accurate models can be employed, so in this paper we will focus on how the scatter in material properties translates in scatter in yield locus for the BBC2005 model vs. Vegter 2017. Automated statistical analysis was not available for Vegter 2017. So, finally, to enable estimation of scatter in forming processes in the short term with Vegter individual simulations were done on a selected number of input datasets. This is shown to give markedly different results to BBC2005.
Corrigendum: Tribological characteristics of natural fiber composite - Review (IOP Conf. Ser.: Mater. Sci. Eng. 954 (2020) 012048)
Authors: Mohan K. , Rajmohan T.
Published: June 2021

Please see Article PDF for corrigendum text.
Microbial bioelectrochemical cells for hydrogen generation based on irradiated semiconductor photoelectrodes
Authors: Morgante Michele , Vlachopoulos Nick , Hagfeldt Anders , Fischer Fabian
Published: June 2021

In recent years, one of the most important challenges of the 21st century is to satisfy the ever-increasing world’s energy demand. Many efforts are being undertaken to find alternative renewable energy sources, which ideally should outcompete fossil fuel use in all its aspects. In this respect, photo-assisted microbial bioelectrochemical cells (MBECs) in which the reduction of water to hydrogen takes place have been of considerable interest in recent years. Two categories of such systems have been investigated: MBECs with a semiconductor photocathode or photoanode, and hybrid systems, in which an MBEC cell with dark electrodes is coupled to an electrochemical photovoltaic cell. A common denominator of all these systems is the need of microorganisms at the anode, the action of which results in the generation of an electron flow by organic matter oxidation. The aim of this review is to describe the general working principles, with respect to both biochemical and electrochemical aspects, and the performance of various categories of hydrogen-generating photo-assisted MBECs.
All-electron full-potential implementation of real-time TDDFT in exciting
Authors: Rodrigues Pela Ronaldo , Draxl Claudia
Published: June 2021

Linearized augmented planewaves combined with local-orbitals (LAPW + lo) are arguably the most precise basis set to represent Kohn–Sham states. When employed within real-time time-dependent density functional theory (RT-TDDFT), they promise ultimate precision achievable for exploring the evolution of electronic excitations. In this work, we present an implementation of RT-TDDFT in the full-potential LAPW + lo code exciting. We benchmark our results against those obtained by linear-response TDDFT with exciting and by RT-TDDFT calculations with the Octopus code, finding a satisfactory level of agreement. To illustrate possible applications of our implementation, we have chosen three examples: the dynamic behavior of excitations in MoS2 induced by a laser pulse, the third harmonic generation in silicon, and a pump–probe experiment in diamond. Besides, we provide further benchmark results.
Hand-Arm Vibration Exposure in Rock Drill Workers: A Comparison between Measurements with Hand-Attached and Tool-Attached Accelerometers
Authors: Clemm Thomas , Nordby Karl-Christian , Lunde Lars-Kristian , Ulvestad Bente , Bråtveit Magne
Published: June 2021

Objectives

To assess the hazard of tool vibrations, we need valid exposure measurements. The use of hand-attached accelerometers (vibration sensors) to measure hand-arm vibrations (HAVs) has become a popular approach. However, according to International Standard ISO 5349-2, the preferred attachment of accelerometers is at the tool handle. We compared measures of HAV between hand- and tool-attached accelerometers in rock drilling.

Methods

We measured HAV in five rock drillers using jackleg drills in normal working operations with simultaneous measures of both hand-attached and tool-attached accelerometers. Five to seven measurement cycles of 15 s were executed on each worker, resulting in a total of 29 measurement cycles. To identify possible differences in working technique, we recorded videos of tool handle handgrips during drilling.

Results

There was a significant difference (9.5 m s−2; P ≤ 0.05) in vibration magnitudes measured by the tool-attached accelerometers compared with the hand-attached accelerometers. The hand-attached accelerometer showed a lower vibration magnitude for all workers (range of difference: 2.3–14.6). The variation between the two accelerometer attachments was larger between workers than within workers (ICC = 0.68).

Conclusions

For measurements of HAV from jackleg drills, the use of hand-attached accelerometers may cause a lower recorded vibration level compared with tool-attached accelerometers. This difference is likely to vary depending on how workers grip the tool handle, and a misclassification of exposure will occur if workers grip the tool handle in a way that makes the accelerometer lose contact with the vibrating surface. Individual differences in how workers grip the tool handles should be considered when assessing HAV.