244 research outputs found
A computational framework for crack propagation along contact interfaces and surfaces under load
We present the first implicit computational framework for simulating crack propagation along contact interfaces and surfaces under load in three-dimensional bodies, which is distinct from modelling the contact interaction associated with crack closure. We restrict ourselves to brittle fracture and frictionless contact and focus on numerical challenges associated with the coupling of unilateral constraints emerging from the Griffith’s criterion and the contact conditions. The formulation is based on the configurational mechanics framework and is solved using the finite element method. The approach utilises a monolithic Arbitrary Lagrangian–Eulerian formulation permitting simultaneous resolution of crack propagation and unilateral contact constraints. Contact is embedded in the model using the well-known mortar contact formulation. Evolving cracks are explicitly modelled as displacement discontinuities within the mesh. Heterogeneous approximation of arbitrary order is used to discretise spatial displacements, enabling -adaptive refinement around the crack front and the contact interfaces traversed by the crack. The result is a holistic approach which handles issues associated with thermodynamic consistency, numerical accuracy and robustness of the computational scheme. Several numerical examples are presented to verify the model formulation and implementation; they also highlight how contact pressure and load applied on surfaces traversed by cracks influence their propagation. The robustness of the approach is validated by comparison of our simulations with existing numerical results and an industrial experiment involving cracks of complex morphologies propagating along contact interfaces between multiple deformable bodies
Edoardo Benvenuto Prize. Collection of papers
The promotion of studies and research on the science and art of building in their historical development constitutes the objective that the Edoardo Benvenuto Association has set itself, since its establishment, in order to honor the memory of Edoardo Benvenuto (1940-1998). The Association in recent years has achieved interesting results by developing various activities such as: organization of national and international meetings, conferences, study days; collaborations with national and foreign research institutions; promotion of the editorial series “Between Mechanics and Architecture"; activation of the portal Bibliotheca Mechanica Architectonica, first “open source” digitized library dedicated to historical research on mechanical and architectural texts. But perhaps the most qualifying initiative was the institution of the Edoardo Benvenuto Prize, arrived in 2019 in its twelfth edition, reserved for young researchers in the field of historical studies on science and the art of building. The awarding of the Prize takes place after an in-depth examination of the texts received by the Association by an international commission of experts. The purpose of this book is to collect and present the most recent studies and publications produced by the winners of the various editions of the Edoardo Benvenuto Prize
A Virtual Element Method for Contact Modeling and Dynamics
Decreasing resources and limited energy results in a greater demand for virtual development processes and efficient product development. This trend points out the importance of digitalization and the subsequent need for efficient and accurate numerical prediction methods for product development. Due to their flexibility, numerical methods are gradually and steadily replacing physical tests in industrial product developments.
The finite element method is perhaps the most well-known and widely used numerical method in industry and science. Increasing computer capabilities and further developments of these methods in recent years have increased the amount of application fields, including civil, automotive, naval, space and geo-technical engineering. However, along with complex geometries the spatial discretization of the domain emerges as a very time consuming step.
Due to the fact that the classical finite element method is restricted to basic regular shaped element topologies, a more general choice of element shapes would give more flexibility.
Within mesh-based methods, polygonal methods are a helpful alternative and showed great performance in engineering and science. However, most of these methods seem to need more computational effort and beside the aforementioned advantage of flexible element shapes, disadvantages appear as well. A relatively new method, the virtual element method, promises
great numerical properties and can be seen as a generalization of the classical finite element method. All new methods need to be investigated for different applications in engineering and science before they can be applied commercially.
This work deals with the application of the virtual element method to dynamic and elastoplastic material behavior. To deal with elastic and plastic incompressibility, a mixed virtual element formulation is presented as well. As a further development, the virtual element method is used to model three dimensional contact with different contact discretizations. A new projection algorithm is developed to manipulate the mesh at the contact interface, such that a very simple and efficient node-to-node contact formulation can be used.
Various numerical examples for all aforementioned applications are performed, including benchmark problems such as the classical patch test. For comparison purposes, different finite element formulations are also adopted. As a final example, all models, including plasticity, dynamics and contact, are coupled to model mechanical impact.Eine Verringerung von Ressourcen und die damit einhergehende Energieknappheit f ¨uhren
zu einem erh¨ohten Bedarf an virtuellen Entwicklungsprozessen und effizienter Produktentwicklung.
Dieser Trend verdeutlicht die Bedeutung der Digitalisierung und den daraus resultierenden
Bedarf an effizienten und hoch genauen numerischen Vorhersagemethoden f ¨ur
die Produktentwicklung. Aufgrund ihrer Flexibilit¨at und mit steigenden Rechnerkapazit¨aten
ersetzen numerische Methoden allm¨ahlich und stetig physikalische Tests in der industriellen
Produktentwicklung.
Die Finite Elemente Methode ist vielleicht die bekannteste und am weitesten verbreitete
numerische Methode in Industrie und Wissenschaft. Durch die zunehmenden Rechnerkapazit
¨aten und die Weiterentwicklung dieser Methoden in den letzten Jahren hat sich die
Zahl der Anwendungsbereiche vergr¨oßert. Numerische Methoden werden unter anderem
im Bauwesen, im Automobilbau, in der Schifffahrt, in der Luft- und Raumfahrt und in
der Geotechnik eingesetzt. Bei komplexen Geometrien erweist sich jedoch die r¨aumliche
Diskretisierung des Gebiets als ein sehr zeitaufw¨andiger Prozess. Da die klassische Finite
Elemente Methode auf einfache, regelm¨aßig geformte Elementgeometrien beschr¨ankt ist,
w¨urde eine allgemeinere Auswahl von Elementgeometrien mehr Flexibilit¨at bieten. Innerhalb
der netzbasierten Methoden sind polygonale Methoden eine hilfreiche Alternative und
haben sich bereits in Industrie und Wissenschaft bew¨ahrt. Allerdings scheinen die meisten
dieser Methoden einen h¨oheren Rechenaufwand zu erfordern, und neben dem bereits
erw¨ahnten Vorteil der flexiblen Elementgeometrien treten auch gewisse Nachteile auf. Eine
relativ neue Methode, die Virtuelle Elemente Methode, verspricht gute numerische Eigenschaften
und kann als eine Verallgemeinerung der klassischen Finite Elemente Methode
angesehen werden. Wie bei allen neuen Methoden m¨ussen auch hier verschiedene Anwendungen
in der Industrie und Wissenschaft untersucht werden, bevor die Methode kommerziell
eingesetzt werden kann.
Diese Arbeit befasst sich mit der Anwendung der Methode der virtuellen Elemente
auf dynamisches und elasto-plastisches Materialverhalten. Um elastische und plastische
Inkompressibilit¨at zu behandeln, wird auch eine gemischte virtuelle Elementformulierung
vorgestellt. In einem weiteren Schritt wird die Virtuelle Elemente Methode zur Modellierung
dreidimensionaler Kontaktprobleme mit verschiedenen Kontaktdiskretisierungen verwendet.
Es wird ein neuer Projektionsalgorithmus vorgestellt, welcher das Netz an der Kontaktschnittstelle
so manipuliert, dass eine sehr einfache und effiziente Knoten-zu-Knoten Kontaktformulierung
verwendet werden kann.
Es werden verschiedene numerische Beispiele f ¨ur alle oben genannten Anwendungen behandelt,
darunter auch Benchmark-Probleme wie der klassische Patch-Test. Um einen
geeigneten Vergleich durchzuf¨uhren, werden die entwickelten Formulierungen mit verschiedene
Finite Elemente Formulierungen verglichen. Als letztes Beispiel werden alle
Modelle, einschließlich Plastizit¨at, Dynamik und Kontakt, gekoppelt, um einen mechanischen
Stoß zu modellieren
Cyber-Human Systems, Space Technologies, and Threats
CYBER-HUMAN SYSTEMS, SPACE TECHNOLOGIES, AND THREATS is our eighth textbook in a series covering the world of UASs / CUAS/ UUVs / SPACE. Other textbooks in our series are Space Systems Emerging Technologies and Operations; Drone Delivery of CBNRECy – DEW Weapons: Emerging Threats of Mini-Weapons of Mass Destruction and Disruption (WMDD); Disruptive Technologies with applications in Airline, Marine, Defense Industries; Unmanned Vehicle Systems & Operations On Air, Sea, Land; Counter Unmanned Aircraft Systems Technologies and Operations; Unmanned Aircraft Systems in the Cyber Domain: Protecting USA’s Advanced Air Assets, 2nd edition; and Unmanned Aircraft Systems (UAS) in the Cyber Domain Protecting USA’s Advanced Air Assets, 1st edition. Our previous seven titles have received considerable global recognition in the field. (Nichols & Carter, 2022) (Nichols, et al., 2021) (Nichols R. K., et al., 2020) (Nichols R. , et al., 2020) (Nichols R. , et al., 2019) (Nichols R. K., 2018) (Nichols R. K., et al., 2022)https://newprairiepress.org/ebooks/1052/thumbnail.jp
Modelling, Monitoring, Control and Optimization for Complex Industrial Processes
This reprint includes 22 research papers and an editorial, collected from the Special Issue "Modelling, Monitoring, Control and Optimization for Complex Industrial Processes", highlighting recent research advances and emerging research directions in complex industrial processes. This reprint aims to promote the research field and benefit the readers from both academic communities and industrial sectors
A comparison of smooth basis constructions for isogeometric analysis
In order to perform isogeometric analysis with increased smoothness on
complex domains, trimming, variational coupling or unstructured spline methods
can be used. The latter two classes of methods require a multi-patch
segmentation of the domain, and provide continuous bases along patch
interfaces. In the context of shell modeling, variational methods are widely
used, whereas the application of unstructured spline methods on shell problems
is rather scarce. In this paper, we therefore provide a qualitative and a
quantitative comparison of a selection of unstructured spline constructions, in
particular the D-Patch, Almost-, Analysis-Suitable and the
Approximate constructions. Using this comparison, we aim to provide
insight into the selection of methods for practical problems, as well as
directions for future research. In the qualitative comparison, the properties
of each method are evaluated and compared. In the quantitative comparison, a
selection of numerical examples is used to highlight different advantages and
disadvantages of each method. In the latter, comparison with weak coupling
methods such as Nitsche's method or penalty methods is made as well. In brief,
it is concluded that the Approximate and Analysis-Suitable converge
optimally in the analysis of a bi-harmonic problem, without the need of special
refinement procedures. Furthermore, these methods provide accurate stress
fields. On the other hand, the Almost- and D-Patch provide relatively easy
construction on complex geometries. The Almost- method does not have
limitations on the valence of boundary vertices, unlike the D-Patch, but is
only applicable to biquadratic local bases. Following from these conclusions,
future research directions are proposed, for example towards making the
Approximate and Analysis-Suitable applicable to more complex
geometries
Semi-reduced order stochastic finite element methods for solving contact problems with uncertainties
This paper develops two-step methods for solving contact problems with uncertainties. In the first step, we propose stochastic Lagrangian multiplier/penalty methods to compute a set of reduced basis. In the stochastic Lagrangian multiplier method, the stochastic solution is represented as a sum of products of a set of random variables and deterministic vectors. In the stochastic penalty method, the problem is divided into the solutions of non-contact and possible contact nodes, which are represented as sums of the products of two different sets of random variables and deterministic vectors, respectively. The original problems are then transformed into deterministic finite element equations and one-dimensional (corresponding to stochastic Lagrangian multiplier method)/two-dimensional (corresponding to stochastic penalty method) stochastic algebraic equations. The deterministic finite element equations are solved by existing numerical techniques, and the one-/two-dimensional stochastic algebraic equations are solved by a sampling method. Since the computational cost for solving stochastic algebraic equations does not increase dramatically as the stochastic dimension increases, the proposed methods avoid the curse of dimensionality in high-dimensional problems. Based on the reduced basis, we propose semi-reduced order Lagrangian multiplier/penalty equations with two components in the second step. One component is a reduced order equation obtained by smooth solutions of the reduced basis and the other is the full order equation for the nonsmooth solutions. A significant amount of computational cost is saved since the sizes of the semi-reduced order equations are usually small. Numerical examples of up to 100 dimensions demonstrate the good performance of the proposed methods
Multi-field modeling and simulation of fiber-reinforced polymers
This work proposes a new numerical approach for analyzing the behavior of fiber-reinforced materials, which have gained popularity in various applications. The approach combines theories and methods to model the fracture behavior of the polymeric matrix and the embedded fibers separately, and includes a modified plasticity model that considers the temperature-dependent growth of voids. Tests are conducted to explore different types and sequences of failure in long fiber-reinforced polymers
Towards a circular economy: fabrication and characterization of biodegradable plates from sugarcane waste
Bagasse pulp is a promising material to produce biodegradable plates. Bagasse is the fibrous residue that remains after sugarcane stalks are crushed to extract their juice. It is a renewable resource and is widely available in many countries, making it an attractive alternative to traditional plastic plates. Recent research has shown that biodegradable plates made from Bagasse pulp have several advantages over traditional plastic plates. For example, they are more environmentally friendly because they are made from renewable resources and can be composted after use. Additionally, they are safer for human health because they do not contain harmful chemicals that can leach into food. The production process for Bagasse pulp plates is also relatively simple and cost-effective. Bagasse is first collected and then processed to remove impurities and extract the pulp. The pulp is then molded into the desired shape and dried to form a sturdy plate. Overall, biodegradable plates made from Bagasse pulp are a promising alternative to traditional plastic plates. They are environmentally friendly, safe for human health, and cost-effective to produce. As such, they have the potential to play an important role in reducing plastic waste and promoting sustainable practices. Over the years, the world was not paying strict attention to the impact of rapid growth in plastic use. As a result, uncontrollable volumes of plastic garbage have been released into the environment. Half of all plastic garbage generated worldwide is made up of packaging materials. The purpose of this article is to offer an alternative by creating bioplastic goods that can be produced in various shapes and sizes across various sectors, including food packaging, single-use tableware, and crafts. Products made from bagasse help address the issue of plastic pollution. To find the optimum option for creating bagasse-based biodegradable dinnerware in Egypt and throughout the world, researchers tested various scenarios. The findings show that bagasse pulp may replace plastics in biodegradable packaging. As a result of this value-added utilization of natural fibers, less waste and less of it ends up in landfills. The practical significance of this study is to help advance low-carbon economic solutions and to produce secure bioplastic materials that can replace Styrofoam in tableware and food packaging production
2007-2008, University of Memphis bulletin
University of Memphis bulletin containing the undergraduate catalog for 2007-2008.https://digitalcommons.memphis.edu/speccoll-ua-pub-bulletins/1448/thumbnail.jp
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