bluuebunny/crossref_metadata_2025 huggingface dataset:
ESSENTIAL METHODS OF MATH ANXIETY REGULATION
Authors: Мацепуро Дарья Михайловна , Есипенко Елена Александровна , Терехина Ольга Владимировна
Published: April 2021

Представлен феномен математической тревожности и рассмотрены методы, позволяющие регулировать данный вид тревожности, способы их реализации, а также потенциальное применение с точки зрения их эффективности и надежности. Описанные методы практически не проверялись на российских выборках, в связи с этим требуется их дальнейшее изучение и экспериментальная верификация, а также апробация в условиях образовательного процесса. Новая реальность смешанного и онлайн-обучения может способствовать развитию математической тревожности и привести к увеличению количества школьников, испытывающих дискомфорт при работе с числовой информацией. Это требует переосмысления и усовершенствования методов ее регуляции.

Math anxiety (MA) is a feeling of fear, worry and discomfort when working with numerical information. Students with a high level of math anxiety tend to avoid mathematics and further study in areas where mathematical knowledge is required. This leads to a shortage of applicants for technical and natural sciences. The development of MA can be caused by: poor mathematical skills, genetic predisposition, socio-environmental factors. In fact, some of the same genetic and environmental reasons affect both math ability and math anxiety. This paper discusses such methods of MA regulation as: expressive writing, reappraisal, relaxation, meditation, mindfulness, art therapy, bibliography, music therapy, and psychophysiological methods (i.e. transcranial stimulation). The effects obtained by these methods, its implementation, as well as potential applications in terms of their effectiveness and reliability have been covered. The studied methods have practically not been tested on Russian samples. Therefore, their further study and experimental verification are required. Regulation methods also require testing in real conditions of the educational process. The new reality of blended and online learning could trigger math and academic anxiety. It is important that some of the proposed methods can be indirectly applied to other types of “academic anxiety” (anxiety caused and experienced by students for other specific discipline).
INCLUSION OF DISTANCE LEARNING TECHNOLOGIES IN THE PROCESS OF TRAINING FUTURE PRIMARY SCHOOL TEACHERS
Authors: Лебедева Ксения Сергеевна , Рыбина Олеся Евгеньевна
Published: April 2021

Рассматриваются вопросы применения дистанционных образовательных технологий (ДОТ) при организации профессиональной подготовки будущих учителей начальных классов. Анализ основных тенденций подготовки студентов педагогического направления в вузе и результаты проведенного анкетирования обучающихся позволили выявить необходимость использования новых ДОТ. В качестве примера эффективного использования ДОТ приводится описание работы по созданию студентами электронного журнала, позволившего вовлечь обучающихся в образовательную деятельность и приобрести опыт применения дистанционных технологий. Практическая значимость применения дистанционной формы работы проявилась в возможности для будущих учителей начальных классов попробовать сначала самим то, что в процессе профессиональной деятельности они будут реализовывать вместе с детьми; инициировать через пробные действия и организовать пространство собственной подготовки.

The article deals with the application of distance learning technologies in the organization of professional training of future primary school teachers. The authors analyze the main trends in the preparation of students of the pedagogical direction in the university. One of the main trends is the formation of the ability to use and creatively process educational technologies in the course of their professional activities. Taking into account this trend and the results of the survey of students allowed the authors to identify the need to use new distance learning technologies. As an example of the effective use of distance learning technologies, the authors describe the work on the creation of an electronic journal by students. This type of work made it possible to involve students in educational activities. In addition, students have gained experience in the use of distance learning technologies. The researchers think that participation of students in this work takes on a new meaning in their professional training, acting not only as a means of evaluating the acquired knowledge, skills, but also as a resource for developing their subject-methodical competencies and educational actions. The article is of interest to teachers of colleges and higher educational institutions and also students of pedagogical specialties.
Impact of Social Networks on the Labor Market Inequalities and School-to-Work Transitions
Authors: Özer Mahmut , Perc Matjaz
Published: April 2021

Countries invest in education systems in order to increase the quality of their human capital. In this context, it is seen that especially after the expansion of the higher education systems, countries try to increase higher education graduation rates in order to improve the quality of human resources in the labor market. The ultimate goal of these efforts is to facilitate the transitions from school-to-work, and to increase social welfare by meeting the human resources needs of the labor market. The facilitation of school-to-work transitions has a direct impact on youth unemployment. School-to-work transitions are influenced not only by the quality of education from primary to higher education but also by the dynamics of the labor market. Social network analysis can provide important insights into this dynamics, and in doing so reveal that there are indeed many factors that play a key role in determining who gets a job and why, including, first and foremost, social contacts. An analysis of job search channels reveals that partners, friends, and relatives are those social contacts that are most decisive for employment outcomes. Research reveals that employers use social-contact-based reference channels much more frequently than formal channels for recruitment. Thus, employers frequently use such reference channels in recruitment. It has also been shown that the use of social-contact channels reduces employers' costs of finding suitable employees and increases productivity since employees hired through these channels also stay longer in their firms. We here explore the full potential of social network analysis to better our understanding of school-to-work transitions, to reveal in no uncertain terms the importance of social contacts, and to show how these insights can be leveraged to level the labor market for all involved. An important take-home message is that the labor market dynamics is strongly affected by the Matthew effect, such that the inequalities and the gaps between opportunities only grow and widen as the underlying social networks evolve. It is therefore important to mitigate these effects well before school-to-work transitions come into play, namely during the education. In particular, we assert that minimizing the inequalities during education should effectively mitigate the uneven impact of social networks on school-to-work transitions.
Main financial instruments used by petroleum companies
Authors: Serookiy V. G.
Published: April 2021

In this article the author considers the key financial instruments used by fuel multinational corporations, which are necessary for financing corporate needs. The structure and dynamics of the share capital of the main players in the domestic oil business market are analyzed. Derivatives are characterized as an essential part of oil trading.
Trends in the film showcase market of the Russian Federation
Authors: Poluyanov V. P.
Published: April 2021

The institutional characteristics of the 10 largest enterprises in terms of revenue and value of assets on the balance sheet to perform movies functions in the Russian Federation are considered. The conclusion is made about market concentration processes through the creation of a network of cinemas.

For the period 2015-2019, a quantitative seasonal wave was identified and estimated in the dynamics of the change in the RBEI attendance index. Quantitative increase of seasonality assessment by the end of the study period was revealed. At the same time, for other movies of the Russian Federation that are not included in the RBEI index, a seasonal wave of changes in the attendance index with a seasonality coefficient for 2015-2017 - 19.6%, for 2016-2018. - 21.3% and 2017-2019. - 26.2%.
Ethical issues on tax evasion from the students’ perception
Authors: Ida suriya ismail  , Siti Aida Suman  , Puteri Adlina Noor Hasnizam  , Nurul Najihah Shaharin  , Hanis Aqilah Rusnipa
Published: April 2021

Paying taxes is not a favorable choice; even it is a compulsory financial obligation to each taxpayer towards its government. However, the evasion of tax is immoral since it is illegal and unethical. This paper examines university students’ perception in Malaysia on the ethics of tax evasion. A survey method consisting of 18 statements was distributed to 120 students from Diploma to Postgraduate students in three higher learning institutions. This study used descriptive analysis to examine the overall mean responses and followed by additional analysis to compare the mean responses according to the respondent’s age and level of educations. The results of this study indicated that respondents agreed that tax evasion was unethical. However, tax evasion becomes ethical under some circumstances when the tax system is unfair and the government or political party is involved in corruption. In terms of age, the youngest group (18 – 25 years old) tends to believe that tax evasion was ethical compared to medium age and older age groups. Besides, the diploma students felt that tax evasion was ethical when they had the highest score than students with degree and masters level. The findings show an early indicator of future taxpayers who believe that tax evasion is ethical depending on the government’s governance, taxpayer’s experience, and the level of tax knowledge. Therefore, this study recommends universities to educate their students on tax evasion areas through the formal syllabus or informal programs in ensuring their students to become good taxpayers.
Transfer Pricing: The Role of Tax Income and Tunneling Incentive
Authors: Husnizam Hosin  , Vidiyanna Rizal Putri
Published: April 2021

The purpose for this investigation is to examine the impact of income tax, bonus mechanism, motivating force burrowing to tunneling incentive. The sample choice utilizing purposive examining technique and examined 23 manufacturing companies recorded in Indonesian Stock Exchange (IDX). The samples are chosen by using purposive sampling method and the companies chosen are the among top 30 companies LQ 30 Index in Indonesia Stock Exchange. The information are obtained from optional information of yearly report of fundamental and manufacturing companies recorded in Indonesia Stock Exchange from 2012-2016. The investigation method utilized in this exploration is binary logistic regression analysis. The result of this investigation demonstrates that the income tax is significant and noteworthy to the transfer pricing, tunneling incentives powerful and critical to transfer pricing, while the bonus mechanism does not influence the transfer pricing.
TUNNELING IONIZATION STUDY OF LINEAR MOLECULES IN STRONG-FIELD LASER PULSES
Authors: PETROVIĆ V. , DELIBAŠIĆ H. , PETROVIĆ I.
Published: April 2021

We theoretically studied photoionization of atoms and molecules in the frame of Perelomov-Popov-Terent’ev (PPT) and Ammosov-Delone-Krainov (ADK) theories. Strong-field single ionization of two diatomic molecules, N2 and O2, are studied and compared to Ar and Xe atoms, using an 800 nm Ti:sapphire laser in the 3×1013 to 1×1015 Wcm-2 intensity range. To eliminate disagreement between theoretical and experimental findings in a low intensity fields (~6×1013 Wcm-2), we considered the influence of shifted ionization potential. Including these effects in the ionization rates, we numerically solved rate equations in order to determine an expression for the ionization yields. The use of modiﬁed ionization potential showed that the ionization yields will actually decrease below values predicted by original (uncorrected) formulas. This paper will discuss the causes of this discrepancy.
"El Gran Viaje": Muerte y Espacio-Luz en los textos de Eugenio Trías. Contestación a Heidegger.
Authors: MARTINEZ PULET JOSE MANUEL
Published: April 2021

Este artículo se propone acompañar a Eugenio Trías en su tarea de articular una concepción de la muerte y de la condición mortal radicalmente critica con el marco nihilista de la analítica existencial heideggeriana, que, como se sabe, hace del Dasein un ser-para-la-muerte. Para Trías, se trataría de replantear la analíticaexistencial desde el marco ontológico de una tradición, oculta y ocultada, (y que él mismo se esfuerza en teorizar), que vincula a Nietzsche y a Platón, así como de hacerla fecunda para la propuesta de una ontología trágica que identifique ser y tiempo, de manera que pueda llevarse a culminación el proyecto fallido deHeidegger. Asimismo, se completa esta exposición con la teorización de la temporalidad del fronterizo, llevada a cabo en sus últimos textos, dilucidada a través de la experiencia musical.
The impact of periprocedural myocardial infarction on mortality in older adults with non-ST-segment elevation acute coronary syndrome: a pooled analysis of the FRASER and HULK studies
Authors: Erriquez Andrea , Pavasini Rita , Biscaglia Simone , Tebaldi Matteo , Tonet Elisabetta , Maietti Elisa , Cimaglia Paolo , Grazzi Giovanni , Scoccia Alessandra , Cardelli Laura S. , Verardi Filippo M. , Morelli Cristina , Campana Roberta , Rubboli Andrea , Mazzoni Gianni , Volpato Stefano , Ferrari Roberto , Campo Gianluca
Published: April 2021

Aims

The prognostic implication of periprocedural myocardial infarction (MI) in older patients has been less investigated. The aim of this study is to assess the relationship between large periprocedural MI and long-term mortality in older patients with non-ST-segment elevation acute coronary syndrome (NSTEACS) undergoing percutaneous coronary intervention (PCI).

Methods

This is a pooled analysis of older NSTEACS patients who were included in the FRASER and HULK studies. Periprocedural MI was defined in agreement with the Society for Cardiovascular Angiography and Interventions definition. The primary outcome was all-cause mortality. The secondary outcome was cardiovascular mortality. The predictors of periprocedural MI and the relationship with scales of physical performance, namely Short Physical Performance Battery and grip strength, were also investigated.

Results

The study included 586 patients. Overall, periprocedural MI occurred in 24 (4.1%) patients. After a median follow-up of 1023 (740–1446) days, the primary endpoint occurred in 94 (16%) patients. After multivariable analysis, periprocedural MI emerged as an independent predictor of all-cause mortality (hazard risk 4.30, 95% confidence interval 2.27–8.12). This finding was consistent for cardiovascular mortality (hazard risk 7.45, 95% confidence interval 3.56–15.67). SYNTAX score, multivessel PCI and total stent length were independent predictors of large periprocedural MI. At hospital discharge, patients suffering from periprocedural MI showed poor values of Short Physical Performance Battery and grip strength as compared with others.

Conclusion

In a cohort of older NSTEACS patients undergoing PCI, large periprocedural MI occurred in around 4% of patients and was associated with long-term occurrence of all-cause and cardiovascular mortality.

Clinical trial registration

ClinicalTrials.gov: NCT02324660 and NCT03021044.
There’s Just No Place for a Street Fighting Man!: Understanding the Influences of Race, Gender and Sexual Orientation in Britain’s Counterculture Between 1964-1971
Authors: Hurley Elizabeth
Published: April 2021

During the 1960s, young Britons began to challenge the restrictive social norms, roles and responsibilities that governed their culture and asserted their voices to promote individual expression and freedom. At the core of this youth rebellion were the Rolling Stones. Within their music, performance, appearance and fashion, the Stones epitomized the anti-establishment attitudes harboured by Britain’s young people and made the cultural shifts that were taking place in the country tangible. In this research paper, I will investigate how Blackness, sexual orientation and gender identification challenged and reshaped the Rolling Stones’s message of rebellion, nonconformity and decadence. By reviewing a diverse range of archival footage, including the Stones’s performances on Ready Steady Go!, Jean-Luc Godard’s short film One-Plus-One and The Stones in the Park, as well as contemporary literary sources, music periodicals, Parliamentary legislation and British feminist, queer and Black Panther activism, I will evaluate the complicated, and often obscurantist, ways in which Britain’s youth rebellion fortified the subordination of traditionally marginalized communities while simultaneously making racial, queer and gender-based injustice visible to the British public. In sum, by placing the Stones’ racial, gendered and queer imagination within a complex political culture, I believe that my research will provide a unique perspective to the complexities and nuances of the social upheaval that occurred in Britain during the 1960s.
Relative Movement: Investigating the Entanglement of Women's Physical and Political Emancipation
Authors: Gallagher Allison , Gao Xiaoyue , MacDonald Kaitlyn , Radisic Gregory , Yuan Elaine
Published: April 2021

This joint research project stems from our seminar "Contemporary Germany through Media and News". 2018 marks 100 years since women gained the right to vote in Germany and Austria and 47 years post-suffrage in Switzerland. To celebrate and assess this milestone, our course is focusing on women's suffrage now and then.

What does universal suffrage mean now, in a Germany with a female Chancellor and a Parliament containing a right-wing party; in a Europe that is regionalizing; in a world in which governments are in deficit while the richest avoid taxation and finance their chosen interests?

What did the vote mean then, during the heat of the struggles; when activists risked lives for more self-determination; when societies were organized around working-class women's double burdens and bourgeois women's matrimonial hearths?

Our materials of study include the following: two feature films that frame the period, Asta Nielsen's die Suffragette (1913), a perhaps ironic love story about the voting struggle in Germany, and Petra Volpe's die göttliche Ordnung (2017), a tale of a small Swiss town's decision for universal suffrage. These films are augmented by contemporary essays by women active in today's public landscape in Europe and texts that thematize women and movement.

We are each writing on aspects of women's physical and political mobility and aim to publish in the Anthology on Social Justice and Intersectional Feminism. By presenting at Inquiry@Queen's we hope both to share results and improve our work ahead of submission to this peer-reviewed e-journal in early April 2018.
DEVS OS (Discrete Even Visualization and Simulation Operating System)
Authors: Hajar Adnan
Published: April 2021

The use of traditional approaches to teach Operating Systems usually lacks the visual aspect. The following research investigates the novel use of DEVS (Discrete Even Visualization and Simulation) in simulating the operation of an operating system. Cd boost++ was the framework of choice for this project. The simulation successfully mimicked the work of an operating system by simulating multiple cycles of program requests. This simulation is capable of further enhance the explanation of how an operating system works. The cases studied in this work include: 1- two processes running concurrently doing multiple IO’s, 2-four processes running concurrently based on a first come first serve scheduling algorithm, and 3- 20 processes running concurrently using highest priority scheduling algorithm. Output observation of the last case show promising results of successful use of DEVS and cd boost++ as a framework to build an operating system.
Onset of intermittent flow: Visualization of flow structures
Authors: Arabi Abderraouf , Salhi Yacine , Bouderbal Amina , Zenati Youcef , Si-Ahmed El-Khider , Legrand Jack
Published: April 2021

The transition from stratified to intermittent air-water two-phase flow was investigated experimentally, by flow visualization and pressure drop signals analyses, in a 30 mm ID pipe. The intermittent flow’s onset was found to be mainly dependent on the liquid superficial velocity and the pipe diameter. Plug flow, Less Aerated Slug (LAS) or Highly Aerated Slug (HAS) flows could be obtained on the gas superficial velocity grounds. The available models, compared to experiments, could not predict adequately the intermittent flow onset. The appearance of liquid slugs was revealed by peaks in the pressure drop signal. Furthermore, it was shown that the available slug frequency correlations were not valid in the zone of the onset of intermittent flow.
THE INERTIAL COMPENSATION OF THE VIBROACTIVE FORCE IN THE OSCILLATING SYSTEM
Authors:   Omsk State Technical University, Omsk, Russia, Burian Yu. A. , Sitnikov D. V. ,   Omsk state technical university, Omsk, Russia, Silkov M. V. ,   Omsk state technical university, Omsk, Russia
Published: April 2021

Рименяемые в активных системах виброизоляции различного типа актуаторы либо устанавливаются между колеблющейся массой и основанием, либо рядом с упруго-диссипативными элементами пассивной системы. Управление актуатором обычно производится по информации от силоизмерительных устройств, что значительно усложняет реализацию таких систем. В работе рассмотренаактивная система, в которой для компенсации виброактивных сил, передающихся на основание, использован электродинамический привод (актуатор), устанавливаемый на основание и управляемый от акселерометров на подвижных массах пассивной системы и актуатора. Прямолинейные управляемые колебания подвижной массы актуатора обеспечивают инерционную компенсацию виброактивных усилий на основании.
ANALYTICAL DESCRIPTION OF THE INTERACTION OF A RIGID ROLLER WITH A COMPACTED SURFACE USING THE GENERAL DYNAMICS EQUATION
Authors:   Siberian State Automobile and Highway University (SibADI), Omsk, Russian Federation, Tarasov V. N. , Boyarkina I. V. ,   Siberian State Automobile and Highway University (SibADI), Omsk, Russian Federation, Boyarkin G. N. ,   Omsk state technical university, Omsk, Russia
Published: April 2021

В данном исследовании решена задача создания теории уплотнения грунта жестким вальцом, основанная на использовании общего уравнения динамики. Валец при качении по деформируемому грунту выполняет операцию уплотнения и представляет собой механическую систему, на которую действуют стационарные динамические силы. Создана расчетная схема для рассмотрения динамических процессов взаимодействия вальца с уплотняемым грунтом, в которой главными параметрами являются: угол α взаимодействия вальца с грунтом, угол β наклонной плоскости, моделирующей сопротивление перекатывания вальца при уплотнении грунта и геометрические параметры вальца. Общее уравнение динамики позволяет получить аналитическое решение задачи взаимодействия вальца с грунтом в виде суммы элементарных работ силы тяги Т, нагрузки Q на оси колеса, сил реакций грунта на валец, сил сопротивления качению. Решение представлено в виде уравнения суммы элементарных работ всех указанных сил, которая равна нулю. Получены аналитические зависимости момента качения вальца, силы сопротивления качению и коэффициента сопротивления качению вальца по деформируемому грунту в привязке к строительным грунтам I-IV категории прочности. Полученные результаты могут быть использованы при проектировании виброкатков для уплотнения деформируемых сред.
Numerical study of the square cup stamping process: a stochastic analysis
Authors: Pereira André Filipe Gomes , Ruivo Miguel Fernandes , Oliveira Marta Cristina , Fernandes José Valdemar , Prates Pedro André
Published: April 2021

The industrial demand for products with better quality and lower production costs have encouraged the widespread application of the finite element analysis (FEA) in the development and optimization of sheet metal forming processes. To ensure that the FEA solutions are reliable and robust it is important to take into account the uncertainties that inevitably arise in a real industrial environment. In this context, a numerical study on the influence of the material and process uncertainty in the stamping results of a square cup is presented. In this analysis, it is assumed uncertainty in the elasticity properties, hardening law parameters, anisotropy coefficients, blank thickness, friction coefficient and in the blank holder force. The effect of the uncertainty in these input parameters is evaluated in the punch force, equivalent plastic strain, thickness and cup geometry. Firstly, quasi-Monte Carlo method was used to evaluate the variability in the simulation outputs, considering the uncertainty of the input parameters. This analysis shows that the geometry is the output most sensitive to the uncertainty of the input parameters. Afterwards, a variance-based sensitivity analysis was carried out to identify the input parameters that most influence the output variability. It was concluded that the hardening law parameters and the anisotropy coefficients have the most influence in the stamping results variability of a square cup.
Design of heterogeneous interior notched specimens for material mechanical characterization
Authors: Conde Mariana , Andrade-Campos António , Oliveira Miguel Guimarães , Martins João Miguel Peixoto
Published: April 2021

Nowadays, virtual predictions are essential in the design and development of new engineering parts. A critical aspect for virtual predictions is the accuracy of the constitutive model to simulate the material behavior. A state-of-the-art constitutive model generally involves a large number of parameters, and according to classical procedures, this requires many mechanical experiments for its accurate identification. Fortunately, this large number of mechanical experiments can be reduced using heterogeneous mechanical tests, which provide richer mechanical information than classical homogeneous tests. However, the test’s richness is much dependent on the specimen's geometry and can be improved with the development of new specimens. Therefore, this work aims to design a uniaxial tensile load test that presents heterogeneous strain fields using a shape optimization methodology, by controlling the specimen's interior notch shape. The optimization problem is driven by a cost function composed by several indicators of the heterogeneity present in the specimen. Results show that the specimen's heterogeneity is increased with a non-circular interior notch. The achieved virtual mechanical test originates both uniaxial tension and shear strain states in the plastic region, being the uniaxial tension strain state predominant.
Investigation of the formability behaviour of optimized tufted and un-tufted multi-layer carbon preforms during the stamping process
Authors: Gnaba Imen , Soulat Damien , Legrand Xavier , Wang Peng
Published: April 2021

The originality of this work consists of studying the stamping behaviour of tufted and un-tufted multi-layer carbon preforms. Several tufted preforms with different stratifications have been manufactured. The stamping test was carried out using a hemispherical punch and conducted at two blank-holder pressures (0.05 and 0.2 MPa). The experimental data show that the addition of tufting yarn, the number of layers and the blank-holder pressure significantly affected the forming behaviour: the tufted preform presents a higher punch force, lower material drawin and shear angles with significant structural defects than the un-tufted preform. The increase of the blank-holder pressure increases all these characteristics and emphasizes the structural defects on the fibrous reinforcements. Similarly, the transition from two layers to four layers lamination at the same blank-holder pressure is followed by an increase of the punch force, reducing the material draw-in and the shear angles especially those measured at the transient zone, and causes more structural defects on all stamped preforms. Therefore, two localized tufting configurations, Right Localized Tufted and Inclined Localized Tufted, at the stamping transition area have been proposed. The results show that these two configurations present a minimum punch force and a maximum material draw-in similar to those measured on the un-tufted structure. The shear angles are much greater than those recorded on the conventionally (fully) tufted preform. Thus, the localized tufting in the most stressed areas proves to be the most suitable solution for the stamped preforms.
Residual stresses developed in thermoplastic composites during laser-assisted tape laying
Authors: El Bayssari Anna Maria , Jacquemin Frédéric , Péron Mael , Barasinski Anaïs , Daghia Fédérica , Guillon Damien
Published: April 2021

The main focus of the study is the determination of residual stresses developed in thermoplastic composites during tape placement. An experimental characterization of the residual stresses is carried out and based on the measurement of the curvature variation with temperature for unsymmetrical laminates. The tested plates are made of APC-2 and processed on the SPIDE-TP, a filament winding machine based in Cetim, France. A thermo-mechanical model based on the modified laminate theory is used in this work. Heat transfer and crystallization are taken into account in the model, allowing the description of the evolution of the mechanical properties of the composite during the whole process. The model is able to predict the residual stresses present at the end of the process. The results showed stress gradients through the thickness of the laminates where the transverse residual stresses can reach up to 20 MPa. In addition, the results showed that increasing the mandrel temperature reduces the crystallization and thermal gradients in the laminate thickness.
Forming of metastable austenitic stainless steel tubes with axially graded martensite content by flow-forming
Authors: Arian Bahman , Homberg Werner , Vasquez Julian Rozo , Walther Frank , Riepold Markus , Trächtler Ansgar
Published: April 2021

One of the main objectives of production engineering is to reproducibly manufacture (complex) defect-free parts. To achieve this, it is necessary to employ an appropriate process or tool design. While this will generally prove successful, it cannot, however, offset stochastic defects with local variations in material properties. Closed-loop process control represents a promising approach for a solution in this context. The state of the art involves using this approach to control geometric parameters such as a length. So far, no research or applications have been conducted with closed-loop control for microstructure and product properties. In the project on which this paper is based, the local martensite content of parts is to be adjusted in a highly precise and reproducible manner. The forming process employed is a special, property-controlled flow-forming process. A model-based controller is thus to generate corresponding correction values for the tool-path geometry and tool-path velocity on the basis of online martensite content measurements. For the controller model, it is planned to use a special process or microstructure (correlation) model. The planned paper not only describes the experimental setup but also presents results of initial experimental investigations for subsequent use in the closed-loop control of α’-martensite content during flow-forming.
Draping modelization of stitched composite reinforcements
Authors: Huang Jin , Hamila Nahiène , Boisse Philippe
Published: April 2021

In the aeronautic industry, thicker and more complex composite parts are required. Multi-layered reinforcements are widely used to achieve a certain thickness for the composite part. The tufting technology has become one of the most effective three-dimensional (3D) reinforcement technologies to improve the through-the-thickness mechanical properties of multi-layered reinforcements. A finite element model is proposed for the simulation of tufted reinforcements preforming. The textile reinforcement is modelled by shell elements, and the tufting thread is modelled by bar elements. A specific contact algorithm is developed to manage the interaction between reinforcements and tufting threads. This meso-macroscopic approach reduces the number of finite elements and saves calculation time compared to a mesoscopic model. The model shows a good prediction of deformations during the forming on a hemispherical shape.
Cryogenic machining to enhance surface finish of a biomedical grade ultra-high-molecular weight polyethylene
Authors: Bertolini Rachele , Ghiotti Andrea , Bruschi Stefania
Published: April 2021

In recent years, polymeric materials are being used at an increasing rate in the biomedical industry. In particular, Ultra-High-Molecular Weight Polyethylene (UHMWPE), a thermoplastic polymer characterized by high toughness, good chemical stability and self-lubricating properties, is an ideal candidate for the manufacture of bearing implants used in hip or knee replacements. Nevertheless, it is difficult to achieve a good level of surface finish when turning it, because of its high instability at increasing temperature. In the present study, cryogenic machining was applied instead of dry cutting to machine a biomedical grade UHMWPE at different cutting speeds. The surface finish was assessed in terms of surface roughness, crystallinity degree and hardness in correspondence of the surface. To correlate machinability results with the UHMWPE mechanical behaviour, uniaxial tensile tests were performed in a wide range of temperatures. The obtained results showed that the application of cryogenic machining was an efficient mean to increase the surface finish: in fact, smoother and harder surfaces were obtained regardless of the adopted cutting parameters.
Evaluation of material behavior of wire strips under cyclic bending load and preparation of an experimental test method
Authors: Biallas Alina , Merklein Marion
Published: April 2021

Steel fibers as concrete reinforcement improve the building material’s mechanical properties and enlarges its field of application. The production of steel fibers by the process chain notch rolling and cyclic bending promises energetic improvement compared to the conventional manufacturing process wire drawing. The innovative procedure is not yet researched extensively and modelling of the material behavior brings with it many challenges. Different stress states of both process steps require various material models and material failure must be considered. The study brings an appropriate modelling of the test sheet metal DP600 with a thickness of t0=0.8 mm for the second process step into focus. The wire strip’s notches are exposed to a cyclic tension-compression load for which high strength steel exhibits early yielding and a distinct transient region of the stress-strain curve after load reversal. For this reason, the isotropic-kinematic hardening model by Chaboche and Rousselier determined in tension-compression tests is validated by cyclic bending tests. For considering crack initiation, an appropriate ductile damage model for depicting material fatigue is identified. To allow practical realization of the process and validation of the material model, an experimental test method for manufacturing wire strip samples by notch stamping is introduced.
Experimental investigation of shear cutting techniques for fiber-reinforced-plastics-metal-laminates
Authors: Reichel Vicky , Beuscher Jan , Hürkamp André , Dröder Klaus
Published: April 2021

Hybrid structures made of fiber-reinforced plastics (FRP) and metals are currently in focus of research and industry to develop weight reduced and functional optimized components for lightweight solutions. Manufacturing processes were adapted and developed to produce components based on hybrid materials with high economic efficiency. The cutting process is used to pre-assemble the semi-finished products or to post-process the edges of consolidated parts. The mechanisms of damage edge behavior and possible cutting qualities on these parts are not investigated jet. To close this knowledge gap and to support the future application of hybrid FRP-Metal-Laminates different cutting procedures were studied. This paper shows the process related dependences on the failure behavior of two dimensional specimens. The failure modes are described via quality characteristics like surface roughness, trueness and precision of the cut as well as influences of aging processes. In the end optimized parameter for each process are shown and compared under technical and economic criteria for large scale production. In the scope of this work an experimental study of piercing of glass and carbon fiber reinforced thermoplastic with different steel and bonding agents at different cutting sequences were performed. It was shown that the cutting edge geometry significantly differs. Possible mechanical explanations of the dependencies were formulated. Also the accuracy of the cuts was evaluated which showed a higher accuracy for the steel component. The measurements on the surface roughness could not show any dependencies and relations.
A computer vision-based, in-situ springback monitoring technique for bending of large profiles
Authors: Ha Taekwang , Ma Jun , Blindheim Jørgen , Welo Torgeir , Ringen Geir , Wang Jyhwen
Published: April 2021

Bending processes have various advantages, such as less processing time, lower number of tooling parts, and cost compared to other manufacturing processes. However, one of the disadvantages of a bending process is the inevitable springback problem, which entails geometrical inaccuracy. Many researchers have made attempts to effectively measure springback in-line to control product quality and compensate for variability. While measurement tools and machines are available to measure springback, they might not be able to accommodate large products due to the size limit of measurement devices. Nevertheless, sensor-based monitoring is becoming critical to control product quality and to move towards Industry 4.0. In this paper, an in-situ springback monitoring technique for bending of large-size profiles is proposed to overcome the measurement restrictions for such profiles. A computer vision technique with the circular Hough transform was used to evaluate springback. The marked points on a profile were used to track the deformation of the workpiece. However, a weakness with image processing is to recognize the points from the complex background. Instead of employing global search for the points in an image frame, the marked points were detected by locally setting regions based on forming parameters such as a bending angle and stretching level. Springback was calculated by the change of position of those points. The results of springback monitoring were validated with the physically measured data from experiments. Based on this measurement technique, the feasibility of a computer vision-based springback monitoring in large-size profile bending is discussed in detail.
Corrugated Structure Reinforcing Aluminum Foam
Authors: Durante Massimo , Boccarusso Luca , Formisano Antonio , De Fazio Dario , Viscusi Antonio , Carrino Luigi
Published: April 2021

Metal foams have a number of established niche market and potential applications under investigation due to their peculiarities including thermal, acoustic and mechanical properties at low weight. In order to produce structures resistant at high temperature and acting as barrier to the fire, metals with closed cells are often required, and one of the most consolidate manufacturing process for their production is the gas releasing particles decomposition in semisolids, by means of which a foam is created by a foaming agent dispersed into a precursor. In previous researches, the authors have investigated the possibility of foaming the aluminum starting by a precursor, placed between two skins consisting of steel grids, in order to obtain a sandwich structure at the same time of the foaming step. In line to continue on this topic and to improve the compression strength of the aluminum-foamed core, in this work the steel grid was used both as skins and as a corrugated skeleton inside the core. Different types of sandwich structures were manufactured, following some experimental tests executed to determine the optimal value of temperature and time to foam the precursor. Then, compression tests were carried out, in order to investigate the effectiveness of the proposed solution on the improvement of this mechanical behavior. The mechanical tests highlighted the increase of mechanical properties using this type of corrugated core.
Recyclability Process of Gypsum Reinforced with Hemp Fabrics: Impact and Flexural Behaviour
Authors: Boccarusso Luca , Mocerino Davide , Durante Massimo , Iucolano Fabio , Minutolo Fabrizio Memola Capece , Langella Antonio
Published: April 2021

Gypsum is an ancient material, still widely used and suitable for many applications in the constructions due to its low cost, availability, lightweight, good thermal and sound isolating behaviour, fire resistance and low energy consumption. One of the most established application is its use as building walls and as pointed out in authors previous research works, it can be very useful and interesting to reinforce the gypsum with vegetable fibres like hemp. This aspect is in line with the current world situation where every industrial company needs to decrease the materials waste, increase recyclability and use more eco-friendly materials. Therefore, this work aims at designing, manufacturing, and testing of both commercial and recycled gypsum specimens reinforced with hemp fabrics, in order to improve impact and flexural resistance of traditional gypsum boards. The recycling process was carefully studied to detect the best grinding time, temperature and time of the heat treatment required to allow the reutilization of gypsum powders. Three point bending and impact tests at different energy levels were carried out in order to understand how the presence of the hemp fabrics within the gypsum matrix and how the recycling process affect the mechanical response of reinforced gypsum.
Thermal analysis of Wire Arc Additive Manufacturing process
Authors: Belhadj Mohamed , Werda Sana , Belhadj Asma , Kromer Robin , Darnis Philippe
Published: April 2021

Wire arc additive manufacturing process (WAAM) is an innovative technology that offers freedom in terms of designing functional parts, due to its ability to manufacture large and complex workpieces with a high rate of deposition. This technology is a metal AM process using an electric arc heat source. The parts manufactured are affected by thermal residual stresses due to high-energy input between wire and workpiece despite numerous advantages with this technology. It could cause severe deformation and change the global mechanical response. A 3D transient thermal model was created to evaluate the thermal gradients and fields during metal deposition. The material used in this study is a steel alloy (S355JR-AR). This numerical model takes into account the heat dissipation through the external environment and the heat loss through the cooling system under the base plate. Birth-element activation strategy was used to generate warm solid part following the movement of the heat source. The metal deposition is defined with constant welding speed. Goldak model was used to simulate the heat source in order to have a realistic heat flow distribution. Results were in concordance for thermal cycles at different points comparing with experimental results issued from bibliography in terms of: (1) Temperature maximum, (2) Thermal cycles and (3) Cooling gradient phase. This study enabled to check the numerical model and used as a predictive tool
Flow curve prediction of cold forging steel by artificial neural network model
Authors: Kocatürk Fatih , Toparli M. Burak , Tanrıkulu Barış , Yurtdaş Sezgin , Zeren Doğuş , Kılıçaslan Cenk
Published: April 2021

A limited number of material models or flow curves are available in commercial finite element softwares at varying temperature and strain rate ranges for plasticity analysis. To obtain more realistic finite element results, flow curves at wide temperature and strain rate ranges are required. For this purpose, a material model for a medium carbon alloy steel material which is used for fastener production was prepared. Firstly, flow curves of the material were obtained at 4 temperatures (20, 100, 200, 400 °C) and 3 strain rates (1, 10, 50 s-1). Then, experimental data was used to construct an artificial neural networks model (ANN) for the material. 75% of the experimental data was used to train the model and the rest was employed for validation and verification. ANN model used in flow curve prediction was developed using the scikit-learn library on Python. Temperature, strain rate and strain were employed as input parameters and flow stress as output parameter in ANN model. In order to increase the accuracy of the ANN model, the number of hidden layers and the number of neurons were also optimized by mean squared error approach. As a result of studies, an ANN-based material model that can be used for wide range of temperature and strain rate values were developed based on the experimental data.
Rapid tooling for injection molding inserts
Authors: Farioli Daniele , Strano Matteo , Vangosa Francesco Briatico , Zaragoza Veronica Geraldine , Aicardi Andrea
Published: April 2021

Injection molding is a widespread manufacturing technology for mass production of polymeric parts. Conventionally, fused polymers are injected at high pressure in a metallic mold. This tool is typically characterized by high manufacturing costs and times, making the injection molding process not affordable for small batches or prototypal applications. Additive Manufacturing represents a practical solution to cut down tooling costs and times of molds and inserts. In this work, FDM (Fused Deposition Technology) has been considered as candidate technology to produce polymeric inserts for injection molding. Considering the commercially available filaments for FDM, a PEI (Polyetherimide) grade has been selected as tooling material for the injection of a part made of Polypropylene. The PEI grade represents a good compromise between manufacturing costs and thermo-mechanical properties required for the application. The PEI grade has been characterized with DSC (Differential Scanning Calorimetry), DMA (Dynamical Mechanical Analysis) and compression tests. The data gathered were used to set up 2D simplified thermo-mechanical finite element analyses, simulating the response of the PEI inserts subjected to repeated injection molding cycles. The simulations confirmed that the PEI grade is a good candidate tooling material but the progressive tool heating could lead to prolonged cooling time of the Polypropylene part. Finally, some PEI inserts were 3D printed with FDM and tested in a real injection molding machine injecting POM. In total, 20 POM parts have been injected correctly without relevant damaging of the PEI inserts.