Deformation of Surfaces in Lie Sphere Geometry

The theory of surfaces in Euclidean space can be naturally formulated in the more general context of Legendre surfaces into the space of contact elements. We address the question of deformability of Legendre surfaces with respect to the symmetry group of Lie sphere contact transformations from the point of view of the deformation theory of submanifolds in homogeneous spaces. Necessary and sufficient conditions are provided for a Legendre surface to admit non-trivial deformations, and the corresponding existence problem is discusse

Verification and application of the Iosipescu shear test method

Finite element models were used to study the effects of notch angle variations on the stress state within an Iosipescu shear test speciment. These analytical results were also studied to determine the feasibility of using strain gage rosettes and a modified extensometer to measure shear strains in this test specimen. Analytical results indicate that notch angle variations produced only small differences in simulated shear properties. Both strain gage rosettes and the modified extensometer were shown to be feasible shear strain transducers for the test method. The Iosipoescu shear test fixture was redesigned to incorporate several improvements. These improvements include accommodation of a 50 percent larger specimen for easier measurement of shear train, a clamping mechanism to relax strict tolerances on specimen width, and a self contained alignment tool for use during specimen installation. A set of in-plane and interlaminar shear properties were measured for three graphite fabric/epoxy composites of T300/934 composite material. The three weave patterns were Oxford, 5-harness satin, and 8-harness satin

Global rheological approach to the quality of the rollers pumping of dough

An analysis was made of the model approximations of three-phase medium and its behavior under deformation impacts in the rollers bulk feed, the lack of reliability of their operation was noticed and regularities and reasonable geometric parameters was determined. The influence of engineering rheology on the medium was considered and on its basis was derived an analytical mechanical model for determining the optimum value of shift deformation in order to ensure reliable operation of the rollers injection mechanism. A new design and method of determining the geometrical parameters of the pumping unit rollers were proposed and the yeast dough state was examined after cyclic action of the rollers

Исследование характера механического взаимодействия рабочих поверхностей сильноточных разрывных контактов

Характер взаимодействие рабочих поверхностей сильноточных электрических контактов однозначно влияют на их работоспособность. К отказу в работе контактов в основном приводят процессы, возникающие в результате комплекса факторов деструктивно влияющих на их работоспособность. При этом не все процессы подробно изучены и поддаются моделированию. Одним из существенных факторов, влияющим на работу контактной пары, служит усилие сжатия контактных поверхностей. Сжатие разрывных контактов напрямую связано с процессами упругой и пластической деформации контактных материалов, что особенно наглядно проявляются на контакт-деталях из порошковых или композиционных материалов. В статье основное внимание уделяется пластической деформации поверхностных слоев разрывных контактов в процессе замыкания, поскольку считается, что она напрямую связана с механизмом проводимостью контактов. Как показано, существенное влияние на деформацию контактных поверхностей оказывает и рабочая среда, в частности трансформаторное масло. Оценка влияния усилия сжатия на деформацию контактной поверхности проводилась экспериментально с использованием метода голографической интерферометрии. Приведены результаты исследования, в которых указывалось, что для компактных и порошковых материалов пластическая деформация внутри и вокруг зоны микроконтактов указывается упрощенно, что требует экспериментального уточнения.Характер взаємодії робочих поверхонь сильнострумних електричних контактів однозначно впливає на їх працездатність. До відмови в роботі контактів в основному приводять процеси, що виникають в результаті комплексу факторів деструктивно впливаючи на їх працездатність. При цьому не всі процеси докладно вивчені і піддаються моделюванню. Одним з істотних чинників, що впливає на роботу контактної пари, служить зусилля стискання контактних поверхонь. Стискання розривних контактів прямо пов'язане з процесами пружної і пластичної деформації контактних матеріалів, що наочно виявляються на контакт-деталях з порошкових або композиційних матеріалів. У статті основна увага приділяється пластичній деформації поверхневих шарів розривних контактів у процесі замикання, оскільки вважається, що вона прямо пов'язана з механізмом провідності контактів. Як показано, істотний вплив на деформацію контактних поверхонь має і робоче середовище, зокрема трансформаторне масло. Оцінка впливу зусилля стиснення на деформацію контактної поверхні проводилася експериментально з використанням методу голографічної інтерферометрії. Наведено результати експериментальних досліджень, в яких вказується, що для компактних і порошкових матеріалах пластична деформація всередині і навколо зони мікроконтактів наводиться спрощено, що вимагає експериментального уточнення.Introduction. The nature of the interaction of high-working surfaces of the electrical contact uniquely affects their performance. By the failure of the contacts in the main drive processes resulting from complex destructive factors affecting their performance. However, not all processes are studied in detail and give in modeling. The purpose of the paper is to show the possibility of using the method of holographic interferometry to estimate the plastic deformation in the zone of contact interaction. One of the significant factors affecting the work of the contact pair is the compressive force of the contact surfaces. Compression discontinuous contact is directly connected with the processes of elastic and plastic deformation of the contact material, which is particularly evident in the contact details of the powder or composite materials. The paper focuses on the plastic deformation of the surface layers of discontinuous contact in circuit, it is believed that it is directly related to the mechanism of conductivity of contacts. As shown, a significant effect on the deformation of the contact surfaces and renders the working environment, in particular transformer oil. Methodology. Assessing the impact of compression forces on the deformation of the contact surface was conducted experimentally using the method of holographic interferometry. Results. Experimental studies, which indicated that the compact and powder materials plastic deformation in and around the area microcontacts simplistically stated that requires experimental verification. A method for evaluating the state of stress, which affects the formation and destruction of the local contact spots. Practical value. Using the experimental method of determining the movement of the contact region allows you to optimize discontinuous contacts from composite and powder materials

DEVELOPMENT, PARAMETERIZATION AND VALIDATION OF DYNAMIC MATERIAL MODELS FOR SOIL AND TRANSPARENT ARMOR GLASS

Despite the signing of several mine ban treaties in the 1990\u27s, it is widely recognized that there is a landmine crisis. The following are some of the main aspects of this crisis: (a) Millions of unexploded landmines remain deployed all over the world; (b) Thousands of civilians are killed or maimed every year by unintended detonations of the mines; (c) The cost of medical treatment of landmine injuries runs into the millions; (d) the ability of the international community to provide the humanitarian relief in terms of medical services, safe drinking water and food, etc., is greatly hampered by landmine contamination of the infrastructure in mine affected countries; and so on. To address the aforementioned landmine crisis, the research community around the world has taken upon itself the challenge of helping better understand the key phenomena associated with landmine detonation and interaction between detonation products, mine fragments and soil ejecta with the targets (people, structures and vehicles). Such improved understanding will help automotive manufacturers to design and fabricate personnel carriers with higher landmine-detonation survivability characteristics and a larger level of protection for the onboard personnel. In addition, the manufacturer of demining equipment and personnel protection gear used in landmine clearing are expected to benefit from a better understanding of the landmine detonation-related phenomena. The landmine detonation-related research activity can be broadly divided into three main categories: (a) shock and blast wave mechanics and dynamics including landmine detonation phenomena and large-deformation/high-deformation rate constitutive models for the attendant materials (high explosive, air, soil, etc.); (b) the kinematic and structural response of the target to blast loading including the role of target design and use of blast attenuation materials; and (c) vulnerability of human beings to post-detonation phenomena such as high blast pressures, spall fragments and large vertical and lateral accelerations. The present work falls primarily into the category (a) of the research listed above since it emphasizes the development of a large-deformation/high-deformation rate material model for soil. It is generally recognized that the properties of soil, into which a landmine is buried, play an important role in the overall effectiveness/lethality of the landmine regardless of the nature of its deployment (fully-buried, flush-buried or ground-laid). Therefore, in the present work, a series of continuum-level material models for soil of different types has been derived (using available public-domain data and various basic engineering concepts/principles), parameterized and validated against experimental results obtained from standard mine-blast testing techniques. Special attention is paid to improving the understanding of the effects of moisture, clay and gravel content on the different aspects of soil material behavior under blast loading conditions. Specifically, the effect of these soil constituents/conditions on the equation of state, strength and failure modes of the material response is investigated. The results obtained clearly revealed that: (a) the moisture clay and gravel contents of soil can substantially affect the response of soil under blast loading conditions as well as the extent of detonation-induced impulse transferred to the target structure/personnel; (b) over all, the models developed in the present work, when used in transient non-linear dynamics analysis of landmine detonation and detonation product/mine-fragment/ soil-ejecta interaction with the target structures/personnel, yielded results which are in reasonably good agreement with their experimental counterparts