Gripping Prospective of Non-Shear Flows under High-Pressure Torsion

The article presents a theoretical study of the regimes of high-pressure torsion (HPT) for which slippage of the deforming material on the interfaces with anvils is possible. The approach taken is a generalisation of the currently accepted view of the HPT process. It enables a rational explanation of its salient features and the effects observed experimentally. These include a lag in the rotation angle of the specimen behind that of the anvils, an outflow of the material from the deformation zone, enhancement in gripping the specimen with anvils with increasing axial pressure, etc. A generalised condition for gripping the specimen with anvils, providing a basis for an analytical investigation of the HPT deformation at a qualitative level, is established. The results of the analytical modelling are supported by finite-element calculations. It is shown that for friction stress below the shear stress of the specimen material (i.e., for the friction factor m < 1), plastic deformation is furnished by non-shear flows, which expands the range of possible process regimes. The potential of these flow modes is impressive, which is reflected in the second meaning of the word “gripping” in the title of the article. Non-shear flows manifest themselves in the spreading of the material over the anvil surfaces whose cessation signifies the end of deformation and the beginning of slippage of the specimen as a whole. The model shows that for m < 1 such a finale is inevitable at any axial pressure. It predicts, however, that the highest achievable strain is increased when the axial pressure is raised in the course of the HPT process. Unlimited deformation of the specimen is only possible for m = 1, when slippage of the deforming material relative to the anvils is suppressed

The Earth\u27s Lithosphere Inspires Materials Design

Structural patterns found in living organisms have long been inspiring biomimetic materials design. Here, it is suggested that a rich palette of patterns occurring in inanimate Nature, and especially in the Earth\u27s lithosphere, could be not less inspirational for design of novel architectured materials. This materials design paradigm is referred to as lithomimetics and it is demonstrated that some of the patterns found in the lithosphere can be emulated by established processes of severe plastic deformation. This opens up interesting avenues for materials design in which potentially promising structural patterns are borrowed from the lithosphere\u27s repository. The key aim here is to promulgate the “lithomimetics” paradigm as a promising approach to developing novel architectured materials

Совершенствование технологического процесса изготовления корпуса фрезы торцевой 3844

Выпускная квалификационная работа – 88 страниц, 6 рисунков, 16 таблиц, 15 использованных источников. Ключевые слова: торцевая фреза, технологический процесс, размерный анализ, конструкторский раздел. Тема выпускной квалификационной работы: совершенствование технологического процесса изготовления фрезы торцевой Ø125мм. В технологическом разделе был разработан технологический процесс изготовления фрезы, выполнен размерный анализ технологического процесса, в который входят расчёт припусков и технологических размеров, проверка конструкторских размеров. Также был произведён расчёт режимов резания и норм времени и выбор оборудования и технологической оснастки. В конструкторском разделе спроектировано приспособление – кондуктор с откидной плитой для сверления семи технологических отверстий. ПредFinal qualifying work - 88 pages 6 pictures, 16 tables, 15 sources used. Keywords: end mill, the technological process. Theme of qualifying work: improving the technological process of milling end Ø125mm. In the technology section was developed technological process of manufacturing mills, dimensional analysis is made of the process, which includes the calculation of allowances and technological dimensions, checking of design sizes. Also it was made calculation of cutting conditions and norms of the time and the choice of equipment and tooling. In the design section, designed tool - the conductor of the hinge plate drilling seven holes technology. Presented calculations actuator device, the selection is made of springs, describes the design and operation of the device. Economically, the definitions section of the calculation processing of the cost cutters, acting under the conditions of medium series and developed for small-scale process. The economic efficiency of the proposed variant of the process with respect to the current annual volume of 600 shares issue. It is also considered the economic effect of the use of devices in the drilling operation. In the ecology and livelihoods bezoposnost discussed issues related to the presence of dangerous and harmful factors of production, labor protection, safety and industrial hygiene, cast lighting calculation

Architecturing materials at mesoscale: some current trends

This article overviews several areas of research into architectured materials which, in the opinion of the authors, are most topical and promising. The classes of materials considered are based on meso scale designs inspired by animate and inanimate Nature, but also on those born in the minds of scientists and engineers, without any inspiration from Nature. We present the principles governing the design of the emerging materials architectures, discuss their explored and anticipated properties, and provide an outlook on their future developments and applications

Lattice Metamaterials with Mesoscale Motifs: Exploration of Property Charts by Bayesian Optimization

Through the current work, the usefulness of the concept of architectured rod lattices based on unit cell motifs designed at mesoscale is demonstrated. Specifically, 2D triangular lattices with unit cells containing different numbers of rods are considered. Combinations of rods of two different types provide the lattices explored with a greater complexity and versatility. For mesocells with a large number of variable parameters, it is virtually impossible to calculate the entire set of the points mapping the material onto its property space, as the volume of calculations would be gigantic. The number of possible motifs increases exponentially with the number of rods. Herein, the lattice metamaterials with mesoscale motifs are investigated with the focus on their elastic properties by combining machine learning techniques (specifically, Bayesian optimization) with finite element computations. The proposed approach made it possible to construct property charts illustrating the evolution of the boundary of the elastic compliance tensor of lattice metamaterials with an increase in the number of rods of the mesocell when a full-factor experiment would not be possible

Deformation mechanisms in an ultra-fine grained Al alloy

This work focuses on the deformation behavior of an ultra-fine grained Al-Mg-Si alloy processed by equal channel angular pressing over a wide range of temperatures and strain rates. The effect of temperature and strain rate on the homogeneity of plastic deformation, the evolution of microstructure, the strain rate sensitivity and the underlying deformation mechanisms are investigated. It is demonstrated that the localization of plastic deformation at the micro scale is triggered by grain boundary sliding due to grain boundary sliding due to grain boundary diffusion. The contributions of different deformation mechanisms during the plastic deformation of the material are discussed. <br /

A Mathematical Model of Deformation under High Pressure Torsion Extrusion

High pressure torsion extrusion (HPTE) is a promising new mechanism for severe plastic deformation of metals and alloys. It enables the manufacture of long products with a radial gradient ultrafine-grained structure and of composite materials with a helical inner architecture at the meso and the macro scale. HPTE is very promising as a technique enabling light weighting, especially with magnesium, aluminium and titanium alloys. For the first time, this article presents an analytical model of the HPTE process that makes it possible to investigate the role of the various process parameters and calculate the distribution of the equivalent strain over the entire sample length. To verify the model, its predictions were compared with the numerical simulations by employing the finite element software QForm. It was shown that potential negative effects associated with the slippage of a sample relative to the container walls can be suppressed through appropriate die design and an efficient use of the friction forces