bluuebunny/crossref_metadata_2025 huggingface dataset:
Clinical management and primary prevention of suspected coronary artery disease guided by computed tomography
Authors: Beyer Christoph , Birkl Katharina , Feuchtner Gudrun , Kofler Lisa-Maria , Friedrich Guy , Plank Fabian
Published: April 2021

Aims

Despite the well established role of coronary computed tomography angiography (CCTA) as a diagnostic gatekeeper, the yield of subsequent invasive coronary angiographies (ICA) remains low. We evaluated the adherence of CCTA integration in clinical management and primary prevention therapy.

Methods

We retrospectively analyzed patients referred for ICA after CCTA without known coronary artery disease (CAD) or structural cardiac pathologies. Based on computed tomography (CT) findings, patients were classified as appropriately or inappropriately referred to ICA, equaling Coronary Artery Disease – Reporting and Data System (CAD-RADS) categories 0–2 (<50% stenosis) and 3–5 (>50% stenosis), respectively. CT exams were compared regarding invasive findings and revascularizations. Integration of CT results into primary prevention measures was analyzed and compared to measures taken after ICA.

Results

Of 1005 patients referred for ICA, 81 (8.1%) had no obstructive CT findings and therefore no ICA indication. ICA inappropriate patients did not differ in symptom characteristics, but had a significantly lower revascularization rate (3.7% vs. 42.1%, P < 0.0001) compared with patients appropriately referred to ICA. In patients with indication for lipid-lowering therapy after the CCTA statin rate was 53.1% and significantly increased after ICA to 76.4% (P < 0.0001). In CCTA, obstructive findings in proximal-only lesions did not increase the revascularization rate (45.6% vs. 42.1%, P = 0.11) but missed nonproximal relevant stenoses (15.0% vs. 2.5%, P < 0.0001) compared with obstructive findings in all segments.

Conclusion

The overall rate of inappropriateness was low, but there is relevant statin underutilization in eligible patients due to a lack of CT findings integration. Both ICA referrals and primary preventive therapy could be improved by the implementation of CT results based on CAD-RADS recommendations.
Analysis of Activated Carbon Monolith Derived from Carrot Juice Waste for Supercapacitor Electrode Application
Authors: Ramayani Dewi , Hamzah Yanuar , Taer Erman , Yanti Novi , Apriwandi Afriwandi
Published: April 2021

Abstrak. Pengembangan sistem penyimpanan energi elektrokimia yang efektif dan efisien menjadi sangat penting pada era evolusi teknologi dan industri modern saat ini. Penelitian ini mengemukakan karbon aktif sebagai bahan dasar material elektroda untuk diaplikasikan pada piranti penyimpan energi, khsusunya superkapasitor melalui analisa densitas, X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) dan Cyclic Voltammetry (CV). Karbon aktif berbentuk monolit disiapkan dari ampas jus wortel melalui pendekatan pirolisis satu tahap terintegrasi dan aktivasi kimia KOH. Proses pirolisis satu tahap terintegrasi dilakukan melalui penggabungan karbonisasi dan aktivasi fisika dalam atmosfer gas N2/CO2. Berdasarkan analisis data, karbon aktif menunjukkan sifat amorf yang normal dan sifat porositas terkonfirmasi. Lebih lanjut, sifat elekrokimia dievaluasi menggunakan metode Cyclic Voltammetry (CV) pada sistem dua elektroda. Kapasitansi spesifik yang dihasilkan sebesar 155 F/g dalam elektrolit 1 M H2SO4 dengan energi spesifik dan daya spesifik adalah 21,52 Wh/kg dan 77,57 W/kg. Berdasarkan analisa ini maka ampas jus wortel terkonfirmasi berpotensi sebagai karbon aktif untuk elektroda yang diaplikasikan dalam piranti penyimpan energi superkapasitor.Abstract. The development of an effective and efficient electrochemical energy storage system is very important in today's era of technological evolution and the modern industry. This research suggests that activated carbon is the raw material for electrode materials to be applied to energy storage devices, especially supercapacitors through density analysis, X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), and Cyclic Voltammetry (CV). Activated carbon in the monolith form derived from carrot juice waste was prepared through a one-stage integrated pyrolysis approach and chemical activation of KOH. An integrated one-stage pyrolysis process was carried out by combining carbonization and physical activation in an N2/CO2 gas atmosphere. Based on data analysis, activated carbon performed normal amorphous behavior with confirmed porosity features. Furthermore, the electrochemical properties were evaluated using the Cyclic Voltammetry (CV) method at the two-electrode system. The specific capacitance was found as high as 155 F/g in the 1 M H2SO4 aqueous electrolyte with specific energy and specific power as high as 21.52 Wh/kg and 77.57 W/kg, respectively. Based on this analysis, the carrot juice waste has been confirmed to have the potential as activated carbon for the electrodes applied in supercapacitor energy storage technology.Keywords: Carrot Juice Waste, Activated Carbon, Electrode Materials, Supercapacitor
Preparation and characterization of ZnFe2O4 on the microstructures and magnetic properties
Authors: Simbolon Tua Raja , Sembiring Timbangan , Hamid Muhammadin , Hutajulu David Arianto , Rianna Martha , Sebayang Achmad Maulana Soehada , Tetuko Anggito P , Setiadi Eko Arief , Ginting Masno , Sebayang Perdamean
Published: April 2021

Abstrak. Telah berhasil dilakukan sintesis ZnFe2O4 menggunakan metode sol-gel. ZnO dan serbuk Fe3O4 dicampur dan dipanaskan menggunakan hotplate pada suhu 60oC selama satu jam. Efek dari doping ZnO pada mikrostruktur, morfologi dan sifat magnet dikarakterisasi menggunakan XRD, SEM dan VSM. Hasil dari XRD dan SEM mengkonfirmasi bahwa struktur ZnFe2O4 spinel ferit menunjukkan kristal rata-rata 1 μm. Kemudian sifat kemagnetan ZnFe2O4 yang dikonfirmasi bersifat paramagnetik dengan kondisi optimum dari sifat kemagnetan tersebut tercantum sebagai berikut: Ms 0.4 emu×g-1, Mr 0.2 emu×g-1, dan Hc 230 Oe.Abstract. ZnFe2O4 have been synthesized using sol-gel method. ZnO, and Fe3O4 powder was mixing with hotplate for one hour in 60oC. Effect of ZnO doped on microstructure, morphology and magnetic properties were investigated using XRD, SEM and VSM. The result of XRD and SEM confirmed that the ZnFe2O4 structure of spinel ferrite has average crystal of 1 μm. The magnetic properties of ZnFe2O4 confirmed paramagnetic with the optimum condition of the magnetic properties are listed in the following: Ms 0.4 emu×g-1, Mr 0.2 emu×g-1, and Hc 230 Oe.Keywords: ZnFe2O4, Sol-gel method, Microstructures, Magnetic Properties.
La modernización de la tradición. Algunos apuntes sobre la producción de mezcal
Authors: García-Garza Domingo
Published: April 2021

Objetivo: analizar algunas de las transformaciones productivas más significativas en la cadena mezcalera en México entre los siglos XX y XXI. Metodología: después de revisar la literatura especializada sobre el tema, se efectuó una investigación de campo de catorce meses repartidos en nueve años y se movilizaron diferentes métodos de investigación (entrevistas, observación participante y etnografía). Se realizaron alrededor de treinta y cinco entrevistas a productores in situ. En razón de la pandemia del COVID-19, estas se completaron con otras diez realizadas vía Zoom con universitarios responsables de los cursos de capacitación también llamados “asistencias técnicas”. Se realizaron asimismo alrededor de cuarenta entrevistas a personas que visitaron alguna microdestilería. Resultados: se identificó claramente el impacto de las asistencias técnicas en la producción tradicional. La implementación de las recomendaciones científicas explica en gran medida su éxito actual en el mercado global. Limitaciones: el estudio se limita a los universitarios que impartieron las capacitaciones, ya que los productores son reticentes, reservados o evasivos en la materia. Conclusiones: después de dos tentativas infructuosas, la tercera tentativa modernizadora arrojó resultados positivos. El seguimiento de las recomendaciones impactó favorablemente la calidad, tanto sanitaria, como organoléptica. Sin embargo, su adopción también produjo dos efectos colaterales: la disimulación de las contribuciones científicas y la modernización la tradición.
Evolution or Extinction: Might Zooplankton Adaptively Respond to the Novel Invasive Predator Bythotrephes longimanus?
Authors: Bloomfield Emma
Published: April 2021

Invasive predators are a large and growing threat to species diversity and human well-being. One of the reasons invasive predators have a negative impact is that native prey species do not possess appropriate anti-predator defenses. However, rapid evolution may allow prey species to respond adaptively to introduced predators. When this occurs the impacts of invasive predators are mitigated. An invasive predator that is of concern in North America is the spiny water flea, Bythotrephes longimanus. It disrupts freshwater ecosystems through voracious consumption of zooplankton. Declines in zooplankton abundance and richness reduce water quality and recreational fishing opportunities. However, a species of zooplankton, Daphnia mendotae has been found to adaptively respond to B. longimanus. This adaptation is diel vertical migration, the behavioral change of occupying a lower position in the water column during the day to reduce predation risk. Despite the ecological and economic implications of this behavior in response to B. longimanus, it has only been studied in a few lakes. This study investigated adaptive diel vertical migration in D. mendotae from multiple lakes. This was done by measuring the vertical position of D. mendotae in artificial water columns. It was hypothesized that D. mendotae from lakes that have been invaded by B. longimanus will exhibit diel vertical migration in the presence of B. longimanus. If this hypothesis is supported, rapid evolution of diel vertical migration can be established as a widespread response. This would strengthen understanding of rapid evolution and allow lakes more vulnerable to B.longimanus to be identified.
Ancestor Worship in Shanghai
Authors: Weston Harrison
Published: April 2021

This report examines different experiences of ancestor worship held by members of a younger and older generation living in Shanghai. The information used in this report has been gathered from Shanghainese and non-Shanghainese people interviewed in Shanghai. The participants were chosen based on what political era in China they grew up in. The goal of this research was to determine whether or not different generations of Chinese people held different beliefs towards ancestor worship or practiced ancestor worship differently in modern day Shanghai, and the extent of these possible differences. Over eighteen interviews, differences and disparities within ancestor worship practices became evident. Most notable were the distinct reasons as to why each generation viewed ancestor worship as valuable; while older people recognized the benefits of ancestor worship in promoting filial piety, the younger generation saw the practice as an expression of traditional Chinese culture. Results also showed that older participants mentioned a wider variety of types of offerings in comparison to those mentioned by the younger participants. There are many individual and generational disparities in the offerings and attitudes towards ancestor worship. What remains constant between generations is the participation in worship activities during significant Chinese festivals, the recognition of value of ancestor worship, the desire to teach ancestor worship to the next generation, the proportion of each generation that view ancestor worship as a superstition, the proportion that does not view ancestor worship as superstition, and the desire to make practices of ancestor worship less harmful to the environment.
The Use Case of the Sustainable Development Goals for Impact Investment Measurement
Authors: Schonewille Trevor
Published: April 2021

Investing private capital in projects designed to promote sustainable development is no new concept. Several models have been deployed such as social responsible investing, venture philanthropy and others. In 2007, a new system emerged called impact investing, which has three conditions to it. For-profit investments are made seeking financial returns. The ventures invested in must have positive impacts on society and/or the environment. These impacts need to be quantifiable and measurable. A framework to quantify the social and environmental impact created has yet to be developed. This paper will analyze how the United Nations Sustainable Development Goals (SDG) can be used as a resource to help develop an impact measurement system for impact investors. To examine the validity of the SDG indicators for impact investors, this project matches the SDG indicators with impact reports released by impact investment firms and associated businesses, as well as other impact measurement systems. The scope will cover a diversity of impact investment firms to test the flexibility of the SDGs. The current research surrounding impact investing focuses on defining impact investing, use cases, measurement strategies and implementation. For the SDGs, there is material that focuses on the validity and their practicality. This report will build on these theoretical frameworks for the specific case of using the SDGs to measure impact investing, and how a new framework can be developed out of the SDGs to create an effective impact measurement system for impact investors. This will help legitimize impact investing, bringing it to the forefront of sustainable development.
An Analysis of Orientation Bias: A Comparison Between Visual and Pictorial Space in Virtual Reality
Authors: Rosen Dean
Published: April 2021

If participants are asked to orient a face half way between frontal view and profile view, they typically choose an angle somewhere between 30 and 40 degrees. In this study, we demonstrate this phenomenon called orientation bias, and we test the hypothesis that it is directly related to presenting the face in the pictorial space of the flat screen rather than in the egocentric visual space of the observer.Participants were required to use a keyboard to rotate a 3D rendering of a human head to orient it at 45 degrees, that is, half way between frontal and profile view. Employing a repeated-measures design, participants completed two blocks in counterbalanced order. Both viewing conditions were implemented in virtual reality. In the first, participants saw a columnar pedestal with a head mounted on top of it in the visual space before them. In the second block, the very same scene was recorded with a fixed camera and projected on a virtual computer screen.The results indicated that the mean angle estimations in visual space (M = 43.01, SD = 5.96) and pictorial space (M = 37.40, SD = 6.99) differed significantly, t(15) = 5.13, p < .001.These differences could be a result of depth compression, which has been previously described in the context of distance perception. Given that interpretation, our results imply that depth compression might be a result of the flatness of the picture plane which is perceived in a “twofold” way alongside the depicted contents of the image.
Why we Act Irrationally
Authors: Ahmed Zohaib
Published: April 2021

Psychologists, cognitive experts, and philosophers alike have long been interested in why people go against their better judgement: why do people do y when they know all things considered x is better to do? Why does a student go out rather than working on his/her essay; the completion of which they know to be their top priority. The purpose of the presentation is twofold. First and foremost, it hopes to make digestible to the everyday thinker the philosophical research that has been conducted on this matter. Oftentimes when philosophers release ground-breaking work their paper is too dense and prose-filled to be comprehensible by non-philosophers. Secondly, this presentation hopes to locate not only the source of irrational action, which it finds to be the passions, but also present a solution to the problem of irrational action, which it argues is self-reflection. It is by having an honest and open conversation with oneself about 1) one's goals, aims, and ambitions and 2) one's values [what kind of person they want to be], that one is able to turn away from weakness and to act rationally. Moreover, this paper argues that acting rationally is an ongoing process, where the individual must continually assess their actions to ensure they are falling in line with their aims and values.
Pics or it Didn’t Happen: A Theatrical Examination of Definitions Truth, Reality and Authenticity in Twenty-First Century Post-Reality
Authors: Klassen Iliana
Published: April 2021

‘Pics or it didn’t happen’: if it’s not on social media, did it really happen? This colloquial phrase, which became popular in 2017 gives a helpful glimpse into concept of post-reality. Post- reality in this context refers to the idea that something is only considered true or real when it is affirmed by other people. Though post-reality is a recent phenomenon, an engagement with questions of the nature of truth and reality can be found throughout theatre theory. Theatre theorist and philosopher Plato defines truth and reality in The Republic (373 B.C.) while Denis Diderot reflects on truth on stage in Conversation on ‘The Natural Son’ (1757) and The Paradox of Acting (1773-1778), and Walter Benjamin reflects on the nature of authenticity in The Work of Art in the Age of Mechanical Reproduction (1935). While these theorists are by no means the only three theatre theorists examining truth, reality and authenticity, the way in which they define their terms has significant implications for how we live in a post-reality society in Canada in 2017. This paper places these three theorists in conversation with each other within the context of post-reality: a conversation which has significant implications for the theatre and world of post-reality in 2018.
AMS Panel discussion on Undergraduate Research
Authors: Chauhan Bianca , Laverty Cory , Marful Caroline
Published: April 2021

Speaker’s Corner, Stauffer Library
JUSTIFICATION OF CHOSEN VALUES OF THE WEIGHT COEFFICIENTS OF THE COMPACTION VALUE FOR CONTINUOUS COMPACTION CONTROL SYSTEMS FOR VIBRATION ROLLERS
Authors:   Yaroslavl state technical university, Yaroslavl, Russia, Tyuremnov I. S. , Morev A. S. ,   Yaroslavl state technical university, Yaroslavl, Russia, Krayushkin A. S. ,   Yaroslavl state technical university, Yaroslavl, Russia
Published: April 2021

Проблема контроля уплотнения дорожностроительных материалов при возведении строительных сооружений в настоящее время актуальна. Методы контроля качества уплотнения дорожностроительных материалов, использующиеся в настоящее время в РФ при приемке работ, позволяют оценивать не более 0,1% от общей площади уплотнения. На сегодняшний день существует большое разнообразие систем непрерывного контроля уплотнения дорожно-строительных материалов для вибрационных катков. Такие системы позволяют операторам вибрационных катков осуществлять мониторинг состояния уплотняемого материала при производстве работ в реальном времени, что значительно улучшает качество проводимых дорожно-строительных работ. Работа большинства систем контроля основана на расчете показателя уплотнения, получаемого при анализе спектра ускорений вибрационного вальца катка. На начальном этапе разработки отечественной системы контроля уплотнения грунта необходимо разработать и протестировать в полевых условиях новый, более совершенный показатель уплотнения, а также сравнить его с существующими показателями уплотнения...
JUSTIFICATION AND SELECTION OF RATIONAL PARAMETERS OF DRILLING PILES OF ENGINEERING STRUCTURES (ON THE EXAMPLE OF SOIL CONDITIONS OF THE CHAYANDINSKOYE OIL AND GAS CONDENSATE FIELD)
Authors:   Saken Seifullin Kazakh Agrotechnical University, Nur-Sultan, Kazakhstan, Gruzin V. V. , Gruzin A. V. ,   Omsk State Technical University, Omsk, Russia
Published: April 2021

Решение задачи рационального использования строительных материалов при обустройстве вновь осваиваемых месторождений позволяет минимизировать непроизводительный расход привлекаемых ресурсов. Целью выполненных исследований была разработка рекомендаций по выбору рациональных параметров буроопускных свай инженерных сооружений, возводимых на грунтах Чаяндинского нефтегазоконденсатного месторождения. С помощью существующих методик был выполнен расчёт несущей способности основания вертикально нагруженной висячей сваи. Выбор в качестве целевого параметра, характеризующего эффективность использования строительных материалов, удельной несущей способности позволил дать комплексную оценку влиянию как конструктивных параметров, так и природных факторов на несущую способность буронабивных свай по грунту основания. В ходе теоретических расчётов установлен сложный характер влияния как геометрических характеристик сваи, так и грунтовых условий на целевой параметр. Для инженерно-геологических условий Чаяндинского нефтегазоконденсатного месторождения было установлено, что рациональными являются использование свай увеличенного диаметра 0.4-0.5 м и длиной не более 6 м в грунтах с температурой не выше -2.0 ºC и с льдистостью не более 0.2...
EXPERIMENTAL RESEARCH OF DYNAMIC PARAMETERS OF AUTO-OSCILLATING HYDRAULIC DRIVE OF AN ASYMMETRIC ACTION
Authors:   Federal State Unitary Enterprise “Federal Research and Productive Center “Progress”, Omsk, Russia, Kilunin I. Yu. , Sorokin V. N. ,   Omsk state technical university, Omsk, Russia
Published: April 2021

В статье приводится описание автоколебательного гидравлического привода несимметричного действия и стенда для его экспериментальных исследований, позволяющего определить основные динамические параметры исследуемого привода. В работе представлены характеристики привода при работе под нагрузкой и на холостом ходу.
IMPROVEMENT OF OPERATOR VIBROPROTECTION SYSTEM IN THE ROAD ROLLER
Authors:   Siberian State Automobile and Highway University, KORCHAGIN P. A. , KORCHAGINA E. A. ,   Siberian State Automobile and Highway University, TETERINA I. A. ,   Siberian State Automobile and Highway University
Published: April 2021

В статье отражены результаты теоретических и экспериментальных исследований, цель которых заключалась в снижении динамических воздействий на рабочем месте оператора дорожного катка, за счет изменения конструктивных параметров динамической системы «опорная поверхность-каток-оператор». Представлены результаты экспериментальных исследований модернизированной конструкции шарнирных тяг. Определены коэффициенты жесткости упругих элементов наконечников шарнирных тяг. Графически представлена зависимость коэффициента жесткости от величины деформации наконечников шарнирных тяг. Представлен сравнительный анализ результатов экспериментальных исследований, направленных на определение величины динамических воздействий на рабочем месте оператора (полу кабины и кресле), проведенных на дорожном трехосном трехвальцовом катке, с заводскими и модернизированными шарнирными тягами. Получены коэффициенты передачи от двигателя внутреннего сгорания к полу кабины и креслу оператора при малых, средних и высоких оборотах двигателя, с включенным и выключенным вибровозбудителем. Сделаны выводы о правомерности использования модернизированной конструкции шарнирных тяг в качестве элемента системы выиброзащиты оператора дорожного катка.
MECHANISM FOR PUNCHING HOLES IN PLATES MADE OF BRITTLE MATERIAL
Authors:   Tula State University, Tula, Russia, Proskuriakov N. E. , Lopa I. V. ,   Tula State University, Tula, Russia
Published: April 2021

Рассматривается ударное нагружение пластины из хрупкого материала. Принимается гипотеза, что разрушение пластины может произойти за счет множественного откола ее тыльной части из-за действия отраженных растягивающих напряжений и одновременного среза лицевой части в виде пробки из-за действия касательных напряжений, генерируемых волной сжатия. Показано, что разрушение керамической пластины может произойти за счет множественного откола ее тыльной части из-за действия отраженных растягивающих напряжений и одновременного среза лицевой части в виде пробки из-за действия касательных напряжений, генерируемых волной сжатия. Сформулированы необходимые и достаточные условия пробития пластины и определены вероятные координаты ее сечений, в которых возникают разрушения типа откола. Представлены результаты численных расчетов. Полученные формулы могут помочь подобрать характеристики ударника, обеспечивающие пробитие отверстий нужного диаметра в пластинах из хрупкого наперед с наперед заданными свойствами.
Material Modelling of Fabric Deformation in Forming Simulation of Fiber-Metal Laminates – A Review on Modelling Fabric Coupling Mechanisms
Authors: Werner Henrik O. , Schäfer Florian , Henning Frank , Kärger Luise
Published: April 2021

During forming of complex fiber-metal laminates (FML), compressive stress zones occur. In pure textile forming, these compressive stresses typically lead to extensive wrinkling. In FML forming, however, wrinkling is partly hindered by the metal layers. Thus, combined stress states occur, where compression influences the deformation. In forming simulation, these compressive stresses can lead to erroneous formation of shear bands within the fabric layer, if the deformation behavior is not modelled correctly. Simple fabric models neither consider interactions between roving directions nor model interactions between membrane strains and shear strains. More advanced invariant-based hyperelastic material models are able to capture these interactions, but only consider tension and shear, while disregarding compression. A common assumption is to set the fabric compression stiffness close to zero. Experimentally, the in-plane fabric compression stiffness has not been determined so far. However, in FML forming, the compression stiffness and the combined compression-tension-shear behavior becomes relevant. In this article, the authors summarize and analyze the capacity of state-of-the-art fabric material models to predict the deformation behavior of fabrics under combined loading. Based on these findings, conclusions are drawn for a new macroscopic modeling approach for woven fabrics, including coupling of tension, compression and shear.
Contact pressure, sliding velocity and viscosity dependent friction behavior of lubricants used in tube hydroforming processes
Authors: Galdos Lander , Otegi Nagore , Mendiguren Joseba , Trinidad Javier , Saenz de Argandoña Eneko
Published: April 2021

The final quality of sheet and tube metal formed components strongly depends of the tribology and friction conditions between the tools and the material to be formed. Furthermore, it has been recently demonstrated that friction is the numerical input parameter that has the biggest effect in the numerical models used for feasibility studies and process design. Industrial dedicated software packages have introduced friction laws which are dependent on sliding velocity, contact pressure and sometimes strain suffered by the sheet and currently, temperature dependency is being implemented as it has also major effect on friction. This last dependency on temperature is attributed to the viscosity change of the lubricant with temperature. In this work, three lubricant having different viscosity have been characterized using the tube sliding test. The final aim of the study is to obtain friction laws that are contact pressure and sliding velocity dependent for their use in tube hydroforming modelling. The tests, performed at various contact pressures and velocities, demonstrate that viscosity has a major effect on friction. As shown in the literature, the friction coefficient is also varying with the contact pressure and sliding velocity.Abs
Waspaloy orthogonal hard machining simulation, a comparison among different rheological models
Authors: Rinaldi Sergio , Umbrello Domenico
Published: April 2021

Nickel based superalloys, such as Waspaloy, are extensively used to manufacture components that operate under high temperature cyclic loads, because of their superior chemical and thermo-mechanical properties. In particular, these artifacts are mainly produced by shaping and/or finishing machining operations. Despite of their huge properties, these alloys show an extremely poor workability, that makes them part of the group of the so called difficult-to-cut materials. Therefore, the proper selection of the machining conditions is always challenging for the designers. In this context, predictive models represent an extremely useful tool to numerically simulate the machining process, guaranteeing a good knowledge of the material behavior under machining conditions, and avoiding expansive and time consuming experimental campaigns. Besides, the proper selection of the material rheological model is of fundamental importance in order to obtain precise and affordable results from the numerical model. In this work a Johnson-Cook based viscoplastic flow behavior model was proposed. The model was obtained from Artificial Neural Network (ANN) based interpolation techniques and validated using orthogonal machining experimental tests. Moreover, the proposed model was compared with other rheological models available from literature to benchmark their affordability and assessing their performances.
Influence of the sheet metal Seebeck coefficient on wear detection based on thermoelectric measurement
Authors: Wu Yutian , Chen Chen , Wang Chengjun , Groche Peter
Published: April 2021

The measurement of thermoelectric current is a new and effective method for inline wear detection in sheet metal forming. The measuring principle is based on the Seebeck effect, whose characteristic value, the Seebeck coefficient depends on the material composition. In the previous research of the authors, a boundary value of the thermoelectric value that separates the mild and severe wear was identified. Due to the large deviation of the Seebeck coefficient of the material used in sheet metal forming, it is worth discussing the influence of the Seebeck coefficient of the sheet metal material on the effectiveness and boundary value of the thermoelectric current for wear detection. In this paper, the measuring principle is first illustrated using an equation based on thermoelectricity. The Seebeck coefficients of the tools and sheet metals are then determined by a specifically designed device. At the same time, the wear tests for different materials are used to determine the boundary values for different tribological systems. Finally, the obtained Seebeck coefficient and boundary values are compared. From the results it can be concluded that the value of the measured Seebeck coefficients have a discernible effect on the boundary values, which provides a useful insight for inline wear diagnosis for practical applications.
Silver and Copper nano-colloid generation via Pulsed Laser Ablation in Liquid: Recirculation nanoparticle production mode
Authors: Pavithran Sithara Sreenilayam , McCann Ronan , McCarthy Éanna , Freeland Brian , Fleischer Karsten , Goodnick Stephen , Bowden Stuart , Honsberg Christiana , Brabazon Dermot
Published: April 2021

Metal nanoparticles have unique chemical, physical, electrical, and optical properties that make them attractive for a wide range of applications in sensing, anti-fouling surfaces, medicine, and conductive inks. Pulsed Laser Ablation in Liquid (PLAL) is a green method of nanoparticle colloid production, capable of producing ligand-free nanoparticles in solution without the need for hazardous, environmentally unfriendly chemicals. Control of the process parameters can give control over the resulting colloid properties such as particle size distribution. In this work, silver (Ag) nanoparticles (NPs) with average particle size from 2.04 to 19.3 nm and copper (Cu) NPs with average particle size from 40 to 85.9 nm were produced by PLAL) technique.
Bonding between high-performance polymer processed by Fused Filament Fabrication and PEEK/carbon fiber laminate
Authors: Caprais Isciane , Joyot Pierre , Duc Emmanuel , Deseur Simon
Published: April 2021

Automated fiber placement processes could be combined with additive manufacturing to produce more functionally complex composite structures with more flexibility. The challenge is to add functions or reinforcements to PEEK/carbon composite parts manufactured by automated fiber placement process, with additive manufacturing by fused filament fabrication. This consists of extruding a molten polymer through a nozzle to create a 3D part. Bonding between polymer filaments is a thermally driven phenomenon and determines the integrity and the final mechanical strength of the printed part. 3d-printing high performance polymers is still very challenging because they involve high thermal gradients during the process. The purpose of this work is to find a process window where the bonding strength is maximized between the composite laminate and the first layer of printed polymer, and inside the printed function as well. Experimental measurements of the temperature profiles at the interface between a composite substrate and 3d-printed PEI under different processing conditions were carried out. The interface was observed using microscopic sections. The methodology for studying the impact of printing parameters on the cohesion and adhesion of printed parts with a composite laminate is described. This work provides insights about the influence of processing conditions on the bond formation between high-performance polymer surfaces. It highlights the importance of controlling the thermal history of the materials all along the process.
Parameters' Confidence Intervals Evaluation for Heterogeneous Strain Field Specimen Designs by Using Digital Image Correlation
Authors: Maček Andraž , Urevc Janez , Starman Bojan , Halilovič Miroslav
Published: April 2021

This paper aims to compare different heterogeneous test designs from the perspective of the confidence interval quantification of inversely identified parameters, where the influence of a DIC optical system systematic and random error are taken into account. Because the errors in optical measurement can arise from many reasons and sources, our methodology relies on the system's errors determined from initial sets of pictures acquired at the load-free state for hundreds of specimens (over 850 tests over the past three years). In this way, a prior probability distribution of systematic and random error, arisen from the system initial settings and testing procedures are determined. Further, by conducting an inverse identification procedure of linear orthotropic elastic material parameters, the influence of the error distributions is studied for different types of heterogeneous specimens. The presented methodology determines the DIC bias and random error propagation through the inverse identification procedure to individual parameters. For each specimen design, confidence intervals of identified material parameters were determined. The results show the appropriateness of a specimen design for the identification of particular material parameters.
Modeling of thin sheet forming processes by combining solid-shell finite element with isotropic elastoviscoplastic model. Application to magnetic pulse forming processes
Authors: Mahmoud Mohamed , Bay François , Mũnoz Daniel Pino
Published: April 2021

Sheet metal alloys are used in many industries to save material, reduce weight and improve the overall performance of products. For the last decades, many types of elements have been developed to resolve the locking problems encountered in the simulation of thin structures. Among these approaches, a family of assumed-strain solid-shell elements has proved to be very efficient and attractive in simulating thin 3D structures with various constitutive models. Furthermore, these elements are able to account for anisotropic behavior of thin structures since isotropic yield functions cannot capture the real physics of some forming processes. In this work, von Mises isotropic yield criterion with Johnson-cook hardening model are combined with a linear prismatic solid-shell element to simulate sheet metal forming processes. A new element assembly technique has been developed to permit the assembly of prismatic elements in a tetrahedral element-based software. This technique splits the prism into multiple tetrahedral elements in such a way that all the cross-terms are accounted for. Furthermore, a tetrahedral based partitioning code has been modified to account for the new prismatic element shape without changing the core structure of the code. More accurate results were obtained using low number of solid-shell elements compared to its counterpart tetrahedral element (MINI element). This reduction in the number of elements accelerated the simulation, especially in the coupled magnetic-structure simulation used for magnetic pulse forming process. The proposed element and criteria are implemented into FORGE (in-house code developed at CEMEF) for simulating magnetic pulse forming process.
Rapid Tooling for Impulse Forming
Authors: Langstädtler Lasse , Intemann Alex Peer , Herrmann Marius , Schenck Christian , Pegel Holger , Kuhfuss Bernd
Published: April 2021

Compared to cutting processes such as milling, forming processes like electrohydraulic forming offer advantages regarding resource as well as energy efficiency. Due to high tooling costs, forming technologies are nonetheless considered as economically inefficient for low production quantities. Using a combination of high-speed forming with 3D printing technologies for tool manufacturing, three variants to reduce tooling time and costs for processing sheet metals for small quantities were proposed. Since the dies have to withstand high dynamic loads, 3D-printed low-cost dies made of polylactide (PLA) are limited regarding their form stability, mainly depending on the forming energy and sheet thickness. To enlarge the scope of application for 3D-printed dies a method to reinforce these dies is presented and investigated. Armoring of the dies was achieved by electrohydraulic cladding of the dies with 0.5 mm thick aluminum sheet metals. To characterize and compare the properties of the unarmored and the armored polylactide dies, specific characteristics of the formed sheet metals concerning the die wear and the molding quality were investigated. Polylactide dies enabled embossing of fine structures in addition to the forming of the die shape. Armoring of the dies led to a reduction of the embossed layer structure. Therefore, the armoring can be used as a way to control the characteristics of the formed sheet metals. In a further step, the cladding sheets were produced with copper sheet metals and used as sinking electrode for electric discharge machining of steel dies.
Analysis for understanding and standardization of additive manufacturing processes
Authors: Matschinski Alexander , Osswald Tim , Drechsler Klaus
Published: April 2021

The market segment of additive manufacturing is showing an annual growth of more than ten percent, with extrusion-based processes being the larger segment of the market. The scope of use is limited to secondary structures. Equipment manufacturers try to guarantee constant material characteristics by closed systems. The characteristic values are up to 50% below the ones from injection molding. The processing of high-performance polymers with reinforcing fibers is an additional challenge. Further development requires an opening of the material and manufacturing systems. The guidelines and standardization for this are still missing. For this reason, a functional analysis (FA) according to TRIZ ("theory of the resolution of invention-related tasks") is performed within this study. This identifies the undesired functions and quantifies their coupling with process components and parameters. In the FA, the manufactured part is the target component in order to address its quality. This way the FA identifies five undesirable functions in the process. These are: deform, cool, weaken, swell and shape. For hightemperature thermoplastics, thermal shrinkage is the primary cause of geometric tolerance. Therefore, the deformation is largely dependent on the cooling mechanism. For a detailed analysis, the polymer melt is further disassembled. The results are six sub-components. The weakening is mainly due to the physical phase of the voids, which exists during the entire processing. The breakdown comprises physical fields such as stress, temperature and flow. These determine the output properties as well as the bonding between the layers. The associated functions are the swelling and shaping. In order to generate broadly applicable standardizations, research questions for further investigation are derived from this study.
Experimental Investigation of Process Forces and Part Quality for Fine Blanking of Stainless Steel with Inductive Heating
Authors: Weiser Ingo Felix , Mannens Robby , Feuerhack Andreas , Bergs Thomas
Published: April 2021

Fine blanking is a highly productive process of industrial mass production with which high quality components in particular but not exclusively for the automotive industry are produced. The manufacturing process faces its limits at elevated tensile strengths of the materials to be processed. Consequently, high-strength steels can currently only be fine blanked to a limited extent. This can be overcome by lowering the flow stress of high-strength steels by means of inductive heating. A steel of high importance especially for industries with high hygiene standards such as medical and nutrition production is the stainless steel X5CrNi18-10 (1.4301). As a metastable austenitic steel which can initiate cutting impact on the press through martensitization, fine blanking of stainless steel is a challenge. X5CrNi18-10 is not a high-strength steel per se but becomes difficult to process due to the high hardness of the martensite phase, known as transformation-induced plasticity (TRIP) effect. Thus, in order to combine the possible advantages of the fine blanking process with inductive heating and the important properties of stainless steel, fine blanking of this steel was investigated with inductive heating prior to the fine blanking. The process forces and product quality properties such as die roll were investigated and found to be advantageous in comparison to non-heated fine blanking specimens of the same steel. The process forces and the die roll height decreased due to the heating.
Development and identification of the cellular automata phase transformation model
Authors: Sitko Mateusz , Pietrzyk Maciej , Kuziak Roman , Szeliga Danuta , Chang Yuling , Bleck Wolfgang , Madej Lukasz
Published: April 2021

The development and identification of the complex microscale austenite to ferrite transformation model during continuous cooling based on the Cellular Automata method and DigiCore library is the main goal of the work. The model is designed to predict phase transformation from a fully austenitic range and involves nucleation of ferrite grains with their further growth. The major driving force for the CA grain growth is based on the carbon concentration differences across the microstructure. The model parameters are identified with the inverse analysis method with the goal function defined on the basis of the dilatometric investigation. The basic assumption of the developed model, experimental procedure, as well as subsequent identification stages, are presented within the work.
Prediction of the Impact Behavior of Bio-hybrid Composites Using Finite Element Method
Authors: Mocerino Davide , Boccarusso Luca , De Fazio Dario , Durante Massimo , Langella Antonio , Meo Michele , Pinto Fulvio , Rizzo Francesco
Published: April 2021

The use of composite hybridization using both synthetic and natural fibers, is one of the most established way to combine the advantages of each material that forms the composite system in order to obtain a composite with good in-plane and out-of-plane properties. For example, as pointed out in authors previous research works, considering carbon/hemp hybrid composites, it is possible to combine the ductile behavior and the capacity to absorb energy of hemp fibers with the higher strength and stiffness of carbon allowing the development of a hybrid system with enhanced energy absorption capability, reduced production cost and lower environmental impact respect to traditional carbon fibers composites. The aim of this work is to investigate both experimentally and numerically the mechanical behavior at impact of pure carbon, pure hemp and carbon/hemp hybrid composite laminate. Low velocity impact tests at 10 J and 20 J were carried and non-destructive analyses were performed for each impact energy to evaluate the internal damage extent. The same tests were numerically simulated with LS-DYNA software using shell elements and different material cards (i.e. MAT 54/55, MAT 24 depending on typology of fibers) and contact conditions in order to find the best configuration that matches the experimental results.
Simulation of the micro Single Point Incremental forming process of very thin sheets
Authors: Thuillet Stéphanie , Manach Pierre-Yves , Richard Fabrice , Thibaud Sébastien
Published: April 2021

The purpose of this paper is to simulate a complex forming process with parameters identified from tensile and shear tests. An elastic-plastic model is retained which combines a Hill’s 1948 anisotropic criterion and plastic potential using a non-associated flow rule. Firstly, a mechanical characterization is made with homogenous tests like tensile and shear tests [1]. On the other hand a process of micro Single Point Incremental forming is simulated [2]. It consists in deforming a clamped blank using a hemispherical punch which has a small diameter compared to the blank dimensions. From a small-size sheet of 0.2 mm thick, a square-based pyramid is obtained incrementally, with a define height path and advanced speed, by a tool instrumented to measure the forming force, which deforms locally the material. It is shown that the non-associated flow plasticity model leads to a good agreement between experimental and numerical results for the evolution of the punch force during the process.
A Comprehensive Assessment of Commercial Process Simulation Software for Compression Moulding of Sheet Moulding Compound
Authors: Qian Connie Cheng , Deshpande Abhaye , Jesri Mona , Groves Richard , Reynolds Neil , Kendall Ken
Published: April 2021

With a growing interest in the application of carbon fibre Sheet Moulding Compound (SMC), a number of commercial software packages have been developed for the simulation of compression moulding of SMC. While these packages adopt different algorithms and meshing strategies, the constitutive material model and processing control are usually adapted from injection moulding process simulation. Little has been done in the literature for assessing the capabilities of these software as design tools, and more importantly, validating the process simulation results using experimental data. This paper aims to provide an independent and comprehensive assessment of existing well-known process simulation software for SMC compression moulding. The selected software will be compared in terms of material models, and available processing settings in order to determine their robustness as a compression moulding design tool. The predictive accuracy of the software will also be assessed by comparing the compression force and filling patterns against the experimental data.