bluuebunny/crossref_metadata_2025 huggingface dataset:
An Efficient Workflow for Background Masking in Small-Object Photogrammetry
Authors: Gleason Mitchell
Published: April 2021

Modern photogrammetry software offers a relatively inexpensive and very high quality technique to produce textured 3D models of museum objects. The efficacy of this technique has already been demonstrated by Queen’s students in digitizing Greco-Roman vessels from the Department of Classics’ Diniacopoulos Collection, terra-cotta figurines from National Institution Stobi in the Republic of Macedonia, and wood fragments from The White Coffin held in the Art Conservation Program at Queen’s. A significant bottleneck, however, in the workflow remains the removal of the background from each of the input photos when using a rotary table and tripod-mounted camera; with the object moving on the rotary and the background remaining fixed, the software becomes confused in its reconstruction of the scene and no full-3D model can be created. The process to remove the background by hand can take upwards of 10 hours for a single object. Proposed is a new, efficient workflow that uses intelligent edge-detection algorithms to automatically separate in-focus from out-focus areas in the scene. With only a small modification to the photographic parameters to reduce depth-of-field, the out-of-focus background can be removed for large datasets (>150 images) in less than 30 minutes with minimal human intervention. Further, recently released AI-based subject selection algorithms as part Adobe Photoshop promise to speed this process even further and to radically simplify the use of photogrammetry in creating interactive virtual exhibits, and 3D-printable data. Much work still needs to be done in evaluating the robustness of this AI "black-box" from Adobe in photogrammetry applications.
Blood Economy: The Failure of the Developed World to End Conflict Minerals in the Congo
Authors: Guest James Andrew
Published: April 2021

Conflict minerals have long been among the leading causes of violence in part of the Global South. For many years there was little attention to the issue despite an enormous dependence on conflict minerals by advanced and emerging economies. In recent years however it seems that countries of the Global North have finally begun to take notice. Despite this attention efforts rarely equal success and the attempts by the developed world to end or reduce the trade in conflict minerals are no exception. The Kimberley Process, arguably the most successful effort so far, has generally been decried as ineffective and unproductive by several NGOs and some governments. This paper examines the issue of conflict minerals, their relationship with war and violence, and their role in the global economy in order to explain the failure of the developed world to end the trade of conflict minerals. The paper seeks to understand the lack of international attention to some of the worst atrocities since the holocaust and explores recently attempted solutions and the obstacles therein. The Democratic Republic of the Congo is used as a case study as the Second Congo War and the continuing violence in the country illuminate the murky complexities of the conflict mineral trade, from raw minerals to finished products.
The Political and Revolutionary Implications of the Mysterious History of Parquet Flooring
Authors: McCoy Katharine
Published: April 2021

This presentation seeks to ask about the potential political implications of the history of parquet flooring. This is to prove that while politics indeed shape art, art also has a hand in shaping politics; and it is more symbiotic than generally assumed. Using empirical quantitative and qualitative research, I traced the origins of parquet flooring to the Palace at Versailles. This is where wood and the techniques of marquetry were first used to replace a marble floor in the King’s bedroom. The marble was too cold, and as the King’s Bedroom had a number of issues with drafts, it added to the health risk to keep the marble floor. Changing the marble to wood, but keeping the pattern of a marble floor allowed for the aesthetics of marble without the hazard.This presentation will look at the history of parquet flooring and apply it to the political climate of pre-revolutionary France. It will first address the research required to find the origins of the flooring. It will then argue the necessity of parquet flooring, along with other later features of the palace, as symbolic of the flaws of absolutism. Finally, the presentation will how this symbolic art fits into the complicated relationship between politics and art.
Comfort while Dying: a Transnational History of Pediatric End of Life Care
Authors: Hill-Smith Emilie
Published: April 2021

Through an in-depth analysis of current and historical literature, this thesis explores the question: what is hospice and end of life care for children? I will dissect the various dimensions of children’s hospice care and how it has evolved over time. Also in my thesis, I will draw from my personal experiences in volunteering at a children’s hospice to discuss the support and care that volunteers receive. Through this literature review I hope to bring to light to a subject that is often overlooked or too difficult for people to discuss. I will propose plans to better the care for children and families who are facing the end of life. My thesis will summarize the current literature available about the type of care that children receive worldwide and how this care affects families and children’s well-being. There has been minimal research done on children in end of life due to the topic’s sensitive nature. My goals is to inform the public of an under discussed but important topic in paediatric medicine.
Children of the Revolution: Looking Towards a Future of Altruistic and Prosocial Media
Authors: Clark Rory
Published: April 2021

The first generation of social media natives, those who grew up with smartphones and social media, are now coming of age. It may not be incidental that questions probing the broader, weightier, possibly detrimental implications of social media, are beginning to be asked—not just by academics, not just by the public at large, but even by the architects of the phenomenon themselves. New mediums—TV, radio, the Internet—have generally taken approximately a decade from wide-spread availability to mass adoption for the full breadth of their influence, for better or for worse, to come to fruition. We are now at that juncture with social media. This research intends to examine this phenomenon and the disruptions currently taking place, how social media natives fit into this narrative, and what a path towards a more prosocial media might look like. Keeping in mind social media was originally intended to simply digitize social connections, communities and communications, not incite policy change, sway elections, or topple regimes, this research will examine the potential of a technology designed for the former to facilitate the latter, as well as social capital and bonding. Ultimately, this research aims to frame the entry of social media natives into the adult world as part of a paradigm shift and envision how social media with a more intentional, built-in functionality to facilitate altruistic and prosocial actions, in a more tangible fashion, as well as mitigating its capacity to foment malice, might operate.
The Wandering Eye: An Eye Tracking Approach to Mind Wandering
Authors: Schnabel Jessica
Published: April 2021

Mind wandering, or “daydreaming,” is a shift in the contents of a thought away from a task and/or event in the external environment, to self-generated thoughts and feelings. This research seeks to test the reliability of eye tracking as an objective of measure mind wandering using the Wandering Eye Paradigm, as well as examine the relationships between mind wandering and individual characteristics. Fifty participants will be recruited for two appointments a day apart, on each day on each day completing two eye tracking sessions following a moving target. In this task, participants will be instructed to press the space bar if they feel they are mind wandering, and then answer three questions about their episode content. Questionnaires measuring mind wandering, procrastination, mindfulness, creativity and personality (in particular conscientiousness) will be completed between eye tracking sessions. By comparing the eye tracking data in the period prior to the spacebar press we can determine quantifiable indicators of the onset and duration of mind wandering episodes by analyzing gaze location in relation to the target location. It has been hypothesized that severity of task performance failures (losing track of the target) should correlate with the “depth” of the mind wandering episode content. Additionally, we expect the frequency of mind wandering episodes to correlate with individual characteristics, and that these measures will be consistent across trials. This research would provide a novel objective way to identify and measure mind wandering, and would help further advance the understanding of its behavioral and subjective dimensions.
Halogenation for improvement of seed yield and quality in chilli (Capsicum annuum L.)
Authors: Herbert Milu , Bastian Dijee , Francies Rose Mary , Cherian K. Anita , Prameela P. , Mathew Riya Mary
Published: April 2021

Freshly harvested seeds of chilli variety Anugraha were treated with halogens namely Calcium oxy chloride (CaOCl2) and Iodine crystal (I2) indirectly through a carrier Calcium carbonate (CaCO3). The treatments included Control (Untreated), CaOCl2 + CaCO3 (2g each/kg seed), CaOCl2 + CaCO3 (4g each/kg seed), Iodine crystal + CaCO3 (50mg each/kg seed) and Iodine crystal + CaCO3 (100mg each/kg seed).  Seed treatment with CaOCl2 + CaCO3 @2g each/kg seed registered significantly higher values for fruits per plant, fruit weight, seed yield per plant and hundred seed weight followed by CaOCl2 + CaCO3 @4g each/kg seed. The treatments, CaOCl2 + CaCO3 @2 g each/kg seed and Iodine crystal + CaCO3 @100mg each/kg seed performed superior in seed quality with higher seedling vigour and lower electrical conductivity of seed leachates over other treatments, while untreated control recorded least seedling vigour indices and highest electrical conductivity.
Hierarchical simultaneous upscaling of porosity and permeability features using the bandwidth of kernel function and wavelet transformation in two dimensions: Application to the SPE-10 model
Authors: Azad Mohammad-Reza , Kamkar-Rouhani Abolghasem , Tokhmechi Behzad , Arashi Mohammad
Published: April 2021

In this paper, two methods of kernel bandwidth and wavelet transform are used for simultaneous upscaling of two features of hydrocarbon reservoir. In the bandwidth method, the criterion for upscaling is the cell variability, and by calculating the optimal bandwidth and determining the distance matrix, the upscaling process is performed in a completely non-uniform and unregularly manner. In areas with extreme variability, the bandwidth is considered small enough to maintain the fine scale characteristics of model. Conversely in homogenous areas, with the choice of large bandwidth, the maximum rate of upscaling will occur. The bandwidth upscaling algorithm is an iterative and hierarchical algorithm. The bandwidth method, unlike conventional scale-up methods, focuses on how to upgrid cells and, by determining the optimal averaging window, we will have the least loss information for the fine scale model. Upscaling is a pre-processing to building a simulator model with lower cell number, and thus, reducing volume and computational cost, while maintaining and retaining the basic information of the fine model. Due to the various variability of the reservoir features, the attribute upscaling pattern differs, and in order to show the variability of two features in the upscaling model simultaneously, it is suggested in this paper to upscale two features simultaneously. For simultaneous upscaling, we applied two different approaches; minimum and maximum bandwidth. Moreover, wavelet transformation is applied to upscaling the model. Then, as a result, the variance of the scale-up models based on wavelet is about one-third of the variance of the bandwidth method. Simulation results show that the bandwidth method is a good approach for upscaling the heterogeneous reservoirs.
INVESTIGATION OF THE EFFECT OF A DENT ON THE STRESS STATE OF THE WHEEL IN THE "WHEEL-RAIL" CONTACT
Authors:   Peterburg state University of Railways of Emperor Alexander I, Saint Petersburg, Russia, Vorobyev A. A. , Krutko A. A. ,   Omsk state technical University, Omsk, Russia, Sedykh D. A. ,   Omsk state technical University, Omsk, Russia
Published: April 2021

Целью работы является определение влияния выщербины на напряженное состояние колеса различной толщины обода. В статье используются численные методы решения дифференциальных уравнений отдельных производных (метод конечных элементов) для определения напряженного положения на стыке «колесо-рельс» при различной толщине обода с выщербиной и без выщербины. На основе проведенных исследований были выработаны рекомендации по изменению норм брака колес с тонкими кромками при наличии выщербины на поверхности скольжения. Изменение норм брака с тонкой кромкой колес позволит увеличить ресурс колес при наличии выщербины на поверхности скольжения и тем самым снизить потребность новых колес.
ESTIMATION OF DYNAMIC CHARACTERISTICS FOR LOAD-BEARING STRUCTURES OF WORKING EQUIPMENT OF MINING EXCAVATOR
Authors:   Siberian Federal University, Krasnoyarsk, Russia, ALSHANSKAYA A. А. , DORONIN S. V. ,   Federal Research Center for Information and Computational Technologies, Krasnoyarsk, Russia
Published: April 2021

Эксплуатация карьерных экскаваторов сопровождается систематическим трещино-образованием в элементах силовых конструкций. Понимание причин трещинообразования актуально для предотвращения разрушений и повышения надежности экскаваторов. Цель исследования заключается в изучении взаимосвязи случаев фактического трещинообразования и динамических характеристик конструкций рабочего оборудования для понимания опасности динамических эффектов различного происхождения и их возможного вклада в трещинообразование и снижение надежности металлоконструкций. Методы исследования - обобщение статистических данных о фактических случаях трещинообразования, численный анализ собственных частот и форм свободных колебаний. Установлена необходимость построения и анализа моделей динамических процессов вследствие нештатных условий динамического нагружения.
LAW ENFORCEMENT OF ILLEGAL BUSINESS TRANSACTION ON THE BORDER AREA BETWEEN INDONESIA AND TIMOR LESTE IN A DILEMMA
Authors: Mahendrawati NLM , Pandit I Gde Suranaya , Sujana IN , Nahak S , Soares C.A. , Telman A. M.
Published: April 2021

This study is a type of empirical legal study conducted based on the discrepancy between the existing provisions and theories and the legal facts occurring among the society, that is, the transaction of goods carried out by crossing the border between two countries.Any hindering obstacles and barricades to the law enforcement over illegal businesses can be settled through social and cultural, economic, political, and security approaches. Alternative solutions that should be applied in dealing with such legal issues can be establishing buildings in the border area, which are specifically directed to help accelerate the handling of three fundamental problems faced in the scope of the development of the border area in question, one of which is delimitation and delineation aspects of the state's boundaries, the aspect of affirming national borders on watershed areas between Indonesia and Timor Leste, the aspect of development discrepancy in the form of fulfilling infrastructure needs in the economic field to foster opportunities for the border areas to participate and compete amid both global and regional markets.
Artificial Intelligence Based Space Reduction of Structural Models
Authors: Ghnatios Chady , El Haber George , Duval Jean-Louis , Ziane Mustapha , Chinesta Francisco
Published: April 2021

The need of solving industrial problems using faster and less computationally expensive techniques is becoming a requirement to cope with the present digital transformation of most industries. Recently, data is conquering the domain of engineering with different purposes: (i) defining data-driven models of materials, processes, structures and systems, whose physics-based models, when they exists, remain too inaccurate; (ii) enriching the existing physics-based models within the so-called hybrid paradigm; and (iii) using advanced machine learning and artificial intelligence techniques for scales bridging (upscaling), that is, for creating models that operating at the coarse-grained scale (cheaper in what respect the computational resources) enables integrating the fine-scale richness. The present work addresses the last item, aiming at enhancing standard structural models (defined in 2D shell geometries) for accounting all the fine-scale details (3D with rich through-the-thickness behaviors). For this purpose, two main strategies will be combined: (i) the in-plane-out-of-plane proper generalized decomposition -PGD- serving to provide the fine-scale richness; and (ii) advance machine learning techniques able to learn and extract the regression relating the input parameters with those high-resolution detailed descriptions.
Hybrid Twins - a highway towards a performance-based engineering. Part I: Advanced Model Order Reduction enabling Real-Time Physics
Authors: Champaney Victor , Sancarlos Abel , Chinesta Francisco , Cueto Elías , González David , Alfaro Iciar , Guevelou Simon , Duval Jean Louis , Chambard Anne , Mourgue Philippe
Published: April 2021

This work retraces the main recent advances in the so-called non-intrusive model order reduction, and more concretely, the construction of parametric solutions related to parametric models, with special emphasis on the technologies enabling allying accuracy, frugality and robustness. Thus, different technologies will be revisited beyond the usual metamodeling techniques making use of polynomial basis or kriging, for addressing multi-parametric models, with sometimes several tens of parameters, while keeping the complexity (DoE size) scaling with the number of parameters. Moreover, sparsity can be profitable for increasing accuracy while avoiding overfitting, and when combined with ANOVA-based decompositions the benefits are potentially huge.
Hybrid Twins. Part II. Real-time, data-driven modeling
Authors: Cueto Elías , González David , Badías Alberto , Chinesta Francisco , Hascoet Nicolas , Duval Jean-Louis
Published: April 2021

We have seen in Part I of this paper that model order reduction allows the involvement of physics-based models in design, as in the past, but now also in online decision-making, without requiring unreasonable computing resources. On the other hand, machine learning techniques were not ready to cope with the processing speed and the lack of data. It was therefore necessary to adapt a number of techniques, and to create others, capable of operating online and even in the presence of a very small amount of data: the so-called "physics-informed artificial intelligence" techniques. For that purpose, we have adapted and proposed a number of techniques, which have proven and are proving every day in many industrial applications their capabilities and performances. Six major uses of AI in engineering concern: (i) visualization of multidimensional data; (ii) classification and clustering, supervised and unsupervised, where it is assumed that members of the same cluster have similar behaviors; (iii) model extraction, that is, discovering the quantitative relationship between inputs (actions) and outputs (reactions) in a consistent manner with respect to the physical laws. When addressing knowledge extraction, item (iv) above, as well as the need of explaining for certifying, item (v), advances are much limited and both items need for major progresses, as the one enabling discarding useless parameters, or discovering latent variables whose consideration becomes compulsory for explaining experimental findings, or combining parameters that act in a combined manner. Discovering equations is a very timely topic because it finally enables transforming data into knowledge.
Numerical design of load response in magneto-rheological actuators for sheet metal stamping
Authors: Brun Michele , Ghiotti Andrea , Simonetto Enrico , Bruschi Stefania
Published: April 2021

Auxiliary systems for sheet forming processes are widely used to improve products accuracy and increase tools life. As example, in blanking hydraulic dampers are widely used to reduce shocks and vibrations; nitrogen springs are often integrated in deep drawing tools to correct the ram tilt or to locally increase the blank-holder force, obtaining geometrical features on the stamped blank with one press pass. In this paper, a Magneto-Rheological (MR) semi-active actuator is developed for sheet forming operations and the interaction between MR fluid and electromagnetic field is investigated by Finite Element (FE) analysis. To overcome the limitations of gas springs and hydraulic actuator, the static electromagnetic circuits is reconfigured with respect of conventional MR actuators known in the state-of-the-art. The novel MR actuator has an inner bore where the electric windings are placed, while the narrow gap, in which the active MR fluid flows, is obtained between the inner bore and the cylinder internal surface. The resulting magnetic fields H and induction fields B, as well as the selection of components materials, are studied through the magneto-static FE model. The results from FE simulations show a longer activation length along the gap resulting in higher controllable forces values, without increasing the overall dimensions of the proposed prototype.
In-situ study of strain and texture evolution during continuous strain path change
Authors: Dhara Sisir , Taylor Scott , Figiel Łukasz , Hughes Darren , Shollock Barbara , Hazra Sumit
Published: April 2021

Automotive stamping is a multi-stage process where a sheet material is drawn in first stage and then redrawn, flanged and pierced in subsequent stages. In the first draw stage, continuous strain path change is induced in the material while a discontinuous strain path change occurs when the material is processed in the subsequent stages of a multi-stage stamping operation. The strain path transition can potentially alter the forming limit of the material. Previous research has investigated the effect of the discontinuous mode of strain path change by loading the sample in one strain path, unloading it, then reloading it in a second path. Thus, discontinuous strain path change was obtained. In this work, the effect of continuous strain path change was investigated with a novel experimental design that allowed cruciform samples to change strain path continuously without unloading. The work was carried out in two stages. In the first stage, the design of the cruciform sample was verified with finite element modelling to ensure the occurrence of continuous strain path change and this was validated experimentally using DX54 material by capturing full-field strain measurements data using digital image correlation technique. The size of the experimental apparatus permitted it to be placed inside a scanning electron microscope chamber. In the second stage, the validated test method was used to evaluate microstructural changes during the deformation including full-field strain and texture evolution. The micro-strain evolution showed rotation of strain bands while the texture evolution conveyed grain rotation during continuous strain path change.
Advanced computational modelling of metallic wire-arc additive manufacturing
Authors: Kovšca Dejan , Starman Bojan , Ščetinec Aljaž , Klobčar Damjan , Mole Nikolaj
Published: April 2021

Wire-arc welding-based additive manufacturing (WAAM) is a 3D printing technology for production of near-net-shape parts with complex geometry. This printing technology enables to build up a required shape layer by layer with a deposition of a consumable welding wire, where the welding arc is a source of heat. Welding is usually performed by CNC-controlled robotic manipulator, which provides a controlled location of material layer adding. Because the process itself involves thermo-mechanically complex phenomena, Finite Element-based virtual models are commonly employed to optimize the process parameters. This paper presents advanced computational modelling of the WAAM of a tube. A thermo-mechanical numerical model of the process is calibrated against experimental data, measured as temperature variation at the acquisition point. The virtual modelling starts with a preparation of the tube geometry in CAD software, where the geometry of the single-layer cross-section is assumed. The geometry is then exported to a G-code format data file and used to control robotic manipulator motion. On the other side, the code serves as an input to in-house developed code for automatic FEs activation in the simulation of the material layer-adding process. The time of activation of the finite elements (FEs) is directly related to the material deposition rate. The activation of the FEs is followed by a heat source, modeled with a double ellipsoidal power density distribution. The thermo-mechanical problem was solved as uncoupled to speed-up computation.
Towards a dislocation-based model for strain path effects in bainitic pipeline steels
Authors: Bönisch Matthias , Seefeldt Marc , Van Bael Albert , Sanchez Nuria , Cooreman Steven
Published: April 2021

Modern pipeline steels exhibit complex microstructures that cause mechanical anisotropy in various respects. For instance, strain path effects under non-monotonic loadings are exceptionally pronounced in these steels. Crystallographic texture and morphological anisotropy are the main contributors to strength and hardening directionality in pipeline steels under monotonic loading. In contrast, the dislocation substructure is seen as the primary source for Bauschinger and cross effects during complex non-monotonic loading, e.g. during pipe forming. The Bauschinger effect for example may arise from pile-ups formed at obstacles such as intragranular shear bands, and homo- or heterophase boundaries. The dislocation-based model by Peeters et al. [Acta Mater., 49 (2001), pp. 1607-1619] developed for coarse-grained ferritic steel allows for complex strain path effects through the accumulation of dislocations at micro-shear bands. However, it struggles to reproduce the large Bauschinger effect of ~250MPa in fine-grained bainitic pipeline steel [Bönisch et al., Procedia Manuf., 47 (2020), pp. 1434-1441]. Considering the microstructural differences between the two steel varieties, a promising way to improve the model predictions - especially for the Bauschinger effect - is to incorporate dislocation interactions with phase and/or grain boundaries. In the present work, we introduce this approach and demonstrate the basic capabilities of such a grain boundary-extended Peeters model. By accounting for the formation of pile-ups at grain boundaries the Bauschinger effect is enlarged. Furthermore, by explicitly considering the grain boundary spacing, the model can deliver grain size (Hall-Petch) strengthening.
Powder bed fusion modelling based on Discontinuous Galerkin formulation
Authors: Arbaoui Larbi , Schrooyen Pierre , Poletz Nicolas , Hillewaert Koen
Published: April 2021

Microscopic defects may occur during powder-bed fusion processes which originate from molten pool instabilities. To investigate this issue, a numerical model focusing on the interaction between laser and powder, melt pool formation and thermodynamics effects is on development. The approach used in the model assumes an incompressible Newtonian flow based on an enthalpy-porosity method for solid/liquid metal transition. The jump conditions at the liquid-solid interface for the energy equation are included through the modification of the enthalpy which incorporates the latent heat of fusion. A Carman-Kozeny porosity method is implemented in the momentum equation to penalize the flow in the solid phase. Molten flows are driven by natural and thermocapillary convection which are modelled using Boussinesq approximation and Marangoni free-surface stresses respectively. This numerical model is implemented within a Discontinuous Galerkin (DG) finite element formulation which ensures high order convergence on unstructured mesh [1]. In this work, a sharp interface method is integrated into the three dimensional high-order DG code Argo [2] to capture the free surface of the melt pool. This method allows to keep the high-order of convergence of the DG scheme even near the interface not conforming with the mesh. This is essential to capture the thermo-hydrodynamics phenomena during powder-bed fusion with accuracy. Current effort is dedicated to improve the model accounting for physical phenomena such as surface tension and vaporization. The main purpose is to investigate the occurrence of discontinuities in fused powder tracks depending on material properties and process parameters.
Identification of AlSi10Mg matrix behavior by nanoindentation
Authors: Dedry Olivier , Bouffioux Chantal , Tran Hoang Son , Macías Juan Guillermo Santos , Habraken Anne Marie , Mertens Anne
Published: April 2021

Laser powder bed fusion (LPBF) is an additive manufacturing technique that is widely used to produce AlSi10Mg parts with a good strength-to-weight ratio and a very fine microstructure thanks to high cooling rates. However, to obtain better mechanical properties, a good ductility and higher fatigue resistance, post-treatments have to be performed. In this work, friction stir processing, a thermomechanical post-treatment, is applied on an as-built plate of 5 mm of thickness. This post-treatment leads to a decrease of the percentage of porosities and to modification of the microstructure: globularized Si-rich particles are surrounded by the α-Al phase. The method presented uses nanoindentation to determine the behavior of the different phases present in the material for future numerical simulations and a better understanding of the relation between microstructure and fatigue strength. The Bucaille method [1] is used to determine the links between indentation curves and elastoplastic parameters. Three different pyramidal indenters are used: Berkovich, cube corner and an indenter with a centerline-to-face angle of 50 degrees. From the loading / unloading curves and after post-processing, the Young's modulus, the representative strain and the associated stress are determined. With the three different indenters and their three true stress/true strain points, a good description of the elastoplastic behavior can be defined.
Strain distribution during air bending of ultra-high strength steels
Authors: Pokka Aki-Petteri , Arola Anna-Maija , Kaijalainen Antti , Kesti Vili , Larkiola Jari
Published: April 2021

Air bending is a widely used method for forming ultra-high strength steels (UHSS). However, the limited formability of UHSS poses some challenges for the bending process in the form of strain localisation, surface defects, punch detachment (multi-breakage) and pseudo-polygonal “nut-like” shape of the bend. In this study, the bendability of three UHSS grades (700, 900 and 1100 MPa) is investigated with 3-point bending tests, utilising Digital Image Correlation (DIC) for measuring the strain distributions on the outer curvature. The differences in the extent of multi-breakage and the bend shapes are also studied, and these observations are correlated with the findings from the bending force and strain measurements. The differences between the investigated UHSS grades are significant. The 900 MPa grade produces more localised strain distributions and pronounced multi-breakage compared to the other grades, along with a more polygonal “nut-like” geometry. The reasons and effects of the multi-breakage phenomenon, as well as the causes for the observed differences in the behaviour of the materials are discussed in this paper. The presented results and the measurement data provide more information about the behaviour of the investigated materials in bending, and can be used for improving bending simulation, numerical models, and workshop instructions.
Numerical prediction of the stress state in CFRP induced by installing a blind rivet nut
Authors: Van de Velde Arne , Coppieters Sam , Debruyne Dimitri
Published: April 2021

The present paper offers a FE modeling strategy to predict the stress state in carbon fiber reinforced plastic (CFRP) plate material after installing a Blind Rivet Nut (BRN). In industry, a BRN is a permanent mechanical fastener used to equip plate material with a threaded part. Analogue to the installing process of the more common blind rivet, the BRN deforms plastically in such a way a counter head is formed on the underside of the plate. Simultaneously, the upper side of the deformation chamber expands in the radial direction creating an interference fit. The interference fit together with the counter head units the nut to the plate. However, the high contact forces between the BRN and the plate often cause damage in the CFRP material compromising the integrity of the joint. The latter observation implies that while setting a BRN in CFRP, the detrimental contact forces must be controlled to guarantee a qualitative joint. The necessary understanding of the stress distribution in the plate material is numerically investigated in two steps. In the first step, a computational efficient axisymmetric model is used to reveal the contract pressure between the BRN and the plate during the setting process. In the second step, the contact pressures are transferred to a 3D model of the plate. In this stage, the orthotropic properties of the composite are assigned to the plate material and an adequate failure criterion is adopted. The result is compared to a full 3D model using the Tsai – Wu failure criterion.
Independent Validation of Generic Specimen Design for Inverse Identification of Plastic Anisotropy
Authors: Zhang Yi , Coppieters Sam , Gothivarekar Sanjay , Van de Velde Arne , Debruyne Dimitri
Published: April 2021

Advanced inverse material identification procedures rely on the richness of strain fields generated in a complex specimen. Currently, the design of a complex specimen is mainly based on engineering judgement and experience that are often user-specific. This intuitive approach forms the crux of the problem, addressed in the current research. To this end, the paper embarks on devising a generic and automated method to design mechanical heterogeneous experiments. A notched tensile specimen is optimized to maximize a previously proposed heterogeneity indicator-IT. The effectiveness of this procedure for identifying the anisotropic parameters of the Hill48 yield criterion is validated using two independent methodologies, namely the identifiability method and the Finite Element Model Updating (FEMU) approach to assess the parameter identification quality. The latter approach is based on carefully generated synthetic experiments including the metrological aspects of Digital Image Correlation (DIC) while having access to the ground truth material behavior. For the plane stress Hill48 anisotropic yield criterion, it is shown that the IT-based design procedure correlates with both the identifiability method and the identification accuracy obtained through FEMU.
Multi-scale Design, Prototyping and Validation Testing of a Composite Anti Roll Bar
Authors: Eyckens Philip , Boulay Emilie , Cavaliere Giulio Pietro , Stroobants Jan , Kot Adam
Published: April 2021

Lightweighting in automotive has already been a key research area for decades, and more recently this research driver has been augmented with electrification and sustainability of new mobility solutions. This contribution focuses on the redesign of a passenger vehicle anti-roll bar from the traditional steel design into a braided glass fiber reinforced composite solution. This work focuses on the functional, central part of the anti-roll bar, targeting a significant weight reduction and sustainability improvement. In terms of design and engineering using finite element methods, a multiscale approach of the composite design has been considered. At microscale the braid unit cell and at macro scale a component were modelled. For the microscale of the braided structure, a selection of design variables has been scrutinized, notably the effect of the braiding angle on the shear stiffness. On the macro scale, finite element modelling is adopted to relate the overall performance to the composite structure and part dimensioning. Additionally, high-potential designs have been prototyped by overbraiding and Vacuum-Assisted Resin Infusion processes. Functional performance testing on the prototypes evaluates the adopted simulation strategies and validates the design.
The effect of reinforcement, fibre, and matrix on the forming behaviour of continuous fibre reinforced thermoplastic composites
Authors: Veenstra Simon , Wijskamp Sebastiaan , Rosic Bojana , Akkerman Remko
Published: April 2021

Forming simulations are a cost-effective solution to mitigate process-induced defects. The models developed to simulate the forming process require material property data for the dominant deformation mechanisms: intra-ply shear, bending, and inter-ply friction. These mechanisms are considered independent, and material property data has to be derived from experimental data for each mechanism separately. However, it is known that the material response to the deformation mechanisms is correlated, as the choice of matrix, fibre, and reinforcement influences the response to all mechanisms. Over the past years a large variety of thermoplastic composites have been characterised, covering a broad field of applications in automotive and aerospace industry. This makes it possible to start correlating the forming behaviour of thermoplastic composites. In this study, the effect of the constituents of a composite on the forming behaviour is analysed. To this end, a Bayesian cross-classified multilevel model with varying intercepts was applied, and the effects found by the model were analysed. Correlations were found between the effect of the constituents and their properties. The study confirms that the matrix material is an important indicator for the forming behaviour.
Analysis of laser cut slots on different thickness steel plates
Authors: Olaru Sergiu Constantin , Coteaţă Margareta , Nagîţ Gheorghe , Hriţuc Adelina , Dodun Oana , Slătineanu Laurenţiu
Published: April 2021

One of the processes used to separate parts from plate-type workpiece is laser beam cutting. The evaluation of the quality of the machined surfaces can be performed by taking into account the influence exerted by some input factors in the cutting process on the width of the slot and on the roughness of the surfaces generated by the laser beam cutting process. The paper presents the results of experimental research performed on a steel plate type workpiece. The objective pursued was to reveal the influence exerted by several input factors of the laser beam cutting process on some output parameters of this process. Empirical mathematical models corresponding to the output parameters taken into account were established. It was possible to order the input factors in the process by taking into consideration their weight in the values of the output parameters.
Self-consistent, polycrystal rate-independent crystal plasticity modeling for yield surface determination
Authors: Perdahcioglu Semih , Mirhosseini Shahrzad , Boogaard Ton van den
Published: April 2021

The evolution of the macroscopically observed yield surface has been the subject of many studies due to its significant effect on the numerical simulation of metal forming processes. Although macroscopic models exist that aim to define this evolution accurate data for calibration as well as validation of these models are difficult to obtain. One common approach is to use crystal plasticity simulations for analyzing the mesoscopic behavior followed by a homogenization scheme for gathering the aggregate behavior. In this study a similar approach is followed the difference being the choice of the crystal plasticity and homogenization methods. A rate-independent crystal plasticity framework where all slip system activities are solved implicitly using a backward Euler approach in combination with an interior point method for constrained optimization is used for single crystal behavior. The aggregate behavior is obtained using a self-consistent analytical homogenization scheme. The results of the homogenization scheme are compared against full-field crystal plasticity finite element simulations. The determination of the yield surface is done by considering the macroscopic behavior where the strain rate direction and magnitude changes over a threshold during stress-based loading.
Intra-ply shear characterization of unidirectional fiber reinforced thermoplastic tape using the bias extension method
Authors: Brands Dennis , Grouve Wouter , Wijskamp Sebastiaan , Akkerman Remko
Published: April 2021

Press forming of thermoplastic unidirectional (UD) carbon fiber reinforced laminates is an attractive production method in the aerospace industry for cost-effective manufacturing of high-performance parts. The possible formation of wrinkling defects in the formed parts has led to the development of predictive, finite element based, process simulation tools. The material behavior during the forming process is described based on the governing deformation mechanisms, being intra-ply shear, inter-ply and tool-ply slippage and bending. Intra-ply shear is especially important when forming parts having double curvature. The intra-ply shear behavior of fabric-based composite materials is often characterized using the bias extension method but has not successfully been applied to thermoplastic UD tapes yet. This work describes the application of bias extension experiments on cross-ply UD laminates at forming conditions to characterize the intra-ply shear material behavior. The test procedure was designed to prevent deconsolidation and improve load introduction, promoting specimen integrity and reduce shear buckling during testing. Preliminary results show that the material exhibits rate-dependent behavior. A video extensometer was used to measure the shear deformation in the center of the specimen. Additionally, a deformation analysis was performed using a grid of lines on the specimen, where the theoretical areas of constant shear according to a pin-jointed net can be recognized but are not fully uniform. In particular, shear banding parallel to the fiber direction is observed on the outer ply at a length scale below the grid size used for the deformation analysis suggesting a yield point and softening behavior on the meso scale which is not directly evident from the macroscopic response.
Tool geometry analysis for plunge milling of lead-free CuZn-alloys
Authors: Baier Stefan , Kokozinski Lukas , Schraknepper Daniel , Bergs Thomas
Published: April 2021

Plunge milling is a critical process step in mass manufacturing of rectangular shapes in electrical connector components. These shapes are manufactured by drilling a pilot hole and subsequent plunge milling with a radial offset (pitch) one or more times. The plunged cavity serves as guidance for the final broaching cut. In light of new legislative initiatives, the electronics industry is forced to use lead-free Cu-Zn-Alloys for mass manufacturing of these connectors. The plunging tool is deflected due to the higher cutting forces experienced in machining of lead-free CuZn-alloys in comparison to alloys with lead. This results in an offset of the milled cavity and negatively impacts tool guidance in the subsequent broaching process. Therefore, the geometric tolerances cannot be met. In this paper, the effect of tool geometry and cutting parameters on the workpiece geometry in plunge milling is investigated. The effect of the microstructure of the work-piece materials CuZn37, CuZn42 and CuZn21Si3P on the tool deflection and cutting force components is examined. The tools used vary regarding the design of the corner in terms of the corner chamfer and the inner shaft thickness. Friction between chips in the tools inner flutes and the cavity walls reduced workpiece accuracy. Improvements were achieved by reducing the width of the cutting corner chamfers, using large inner flutes and applying low cutting parameters.
Generation and homogenization of foamed polymer RVEs: microstructure-mechanical properties relationship
Authors: Bouvard Jean-Luc , Feng Shaoheng , Alexis Florent , Bernacki Marc , Pino-Munoz Daniel , Agazzi Alban , Goff Ronan Le , Drouel Guillaume
Published: April 2021

The main purpose of this study is to better understand the relationship between the microstructure of foamed polymer and mechanical properties. X-Ray tomography was performed on polypropylene foam specimens machined from injected plates. These plates were obtained for different thicknesses and exhibit different microstructure morphologies. The tomography scans were first digitalized and meshed. Then, numerical simulations were performed on representative volume elements (RVEs) to get homogeneous mechanical property of the material using a parallel C++ library Cimlib developed at CEMEF. Numerical methods described in this study focused on immerged or body-fitted strategy (FE context - level set framework - meshing adaptation) for exact and statistical RVEs generation. The numerical results were compared to experimental testing performed under tension and compression at different strain rates using image correlation. Good agreement was observed between simulations performed at the mesoscale and experimental tests carried out at the macroscale for both real and statistical RVEs. This methodology opens a way for the development of digital materials designed for specific mechanical properties.
Robot-assisted surface treatment strategies of AA6014 sheet metal for accumulative roll bonding
Authors: Zettl Bastian , Merklein Marion
Published: April 2021

The application of high strength aluminum sheet metal components in automotive and aviation products effectively saves material and thus weight. Material strengthening can be realized by accumulative roll bonding (ARB), which belongs to the severe plastic deformation processes. Through repeated rolling steps a multilayered sheet metal is produced, which possesses increased strength due to its ultra-fine grained microstructure. Prior to each rolling step a surface treatment via wire brushing is mandatory for removing the oxide layer and roughening the sheet surface, which enables the bonding between the unique layers during rolling. The necessary surface treatment of the sheets is not fully understood by the current state of the art. In the past, it was not possible to achieve a defined and stable surface finish, because the brushing operation was done manually. The improvement of the process stability is essential to determine the relationship between the input parameters for brushing and the resulting bond strength of multilayered ARB sheets. For this reason, a robot-controlled surface treatment is introduced. The investigated material is the precipitation-hardened aluminum AA6014 with a sheet thickness of 1 mm. A suitable brushing kinematic under constant load is implemented and its effects on the surface properties are investigated by roughness measurements. The investigation shows, that the parameter combination leads to comparable or even higher roughness values than through manual brushing. Through 16 consecutive brushing paths a homogeneous and sufficient high surface roughness is realized, which enables material bonding in the rolling step. Thus, the research results indicate, that the robot-assisted surface treatment of ARB sheet metal is a promising method for a better automation and reproducibility of the brushing and the overall ARB process.