Longitudinal Surfaces Research Articles

Longitudinally consistent registration and parcellation of cortical surfaces using semi-supervised learning

Temporally consistent and accurate registration and parcellation of longitudinal cortical surfaces is of great importance in studying longitudinal morphological and functional changes of human brains. However, most existing methods are developed for registration or parcellation of a single cortical surface. When applying to longitudinal studies, these methods independently register/parcellate each surface from longitudinal scans, thus often generating longitudinally inconsistent and inaccurate results, especially in small or ambiguous cortical regions. Essentially, longitudinal cortical surface registration and parcellation are highly correlated tasks with inherently shared constraints on both spatial and temporal feature representations, which are unfortunately ignored in existing methods. To this end, we unprecedentedly propose a novel semi-supervised learning framework to exploit these inherent relationships from limited labeled data and extensive unlabeled data for more robust and consistent registration and parcellation of longitudinal cortical surfaces. Our method utilizes the spherical topology characteristic of cortical surfaces. It employs a spherical network to function as an encoder, which extracts high-level cortical features. Subsequently, we build two specialized decoders dedicated to the tasks of registration and parcellation, respectively. To extract more meaningful spatial features, we design a novel parcellation map similarity loss to utilize the relationship between registration and parcellation tasks, i.e., the parcellation map warped by the deformation field in registration should match the atlas parcellation map, thereby providing extra supervision for the registration task and augmented data for parcellation task by warping the atlas parcellation map to unlabeled surfaces. To enable temporally more consistent feature representation, we additionally enforce longitudinal consistency among longitudinal surfaces after registering them together using their concatenated features. Experiments on two longitudinal datasets of infants and adults have shown that our method achieves significant improvements on both registration/parcellation accuracy and longitudinal consistency compared to existing methods, especially in small and challenging cortical regions.

Structure, properties, and fabric applicability of sustainable paper yarn with high washing stability

This research provides an in-depth assessment of two paper yarn variants, examining their structural, functional, and performance characteristics. These yarns demonstrated favorable properties, including suitable linear density, twist, typical cellulosic functional groups as confirmed by Infrared spectroscopy, minimal hairiness, moisture transfer, and creditable mechanical strength. These yarns have flat layered cross-sections and grooved longitudinal surfaces. In addition, a low hairiness index (1.3–1.33) further acknowledged their smooth surface. Their remarkable evenness (15.86% and 7.08%) supported their effective wicking properties. Despite average breaking strength (0.77 cN/dTex and 1.05 cN/dTex) and moderate elongation, these yarns exhibited exceptional water-washing resistance and retained over 89% breaking strength after 15 washes. This study ranks these paper yarns as highly suitable for durable clothing fabrics, providing promising sustainable alternatives in the textile industry.

Surface texture characterisation of longitudinal and latitudinal external and internal surfaces of laser powder bed fusion processed bespoke ball artefact

This research aims to study the diverse surface topographical features that emerge on both longitudinal and latitudinal facets' external and internal surfaces of a bespoke ball artefact. The focus variation measurement technique is employed to visually inspect the surface quality derived from a plethora of surface topographical defects and asperities namely balling, staircase effect, spatters, and un-melted/partially melted particles. These diverse defects, asperities and associated surface quality are characterised and correlated with an array of suitable areal surface texture height and hybrid parameters, and quantified with newly developed feature-based particle analysis mentioned in ISO 25178-2. The longitudinal facet external surfaces measurement range is selected from 15° to 135°, while internal surfaces measurement is performed between 15° to 165°. Similarly, the latitudinal facet external and internal surfaces are examined by full-turn at the equator. A comprehensive statistical analysis of variance (ANOVA) is employed to examine the statistical significance of inclinations angles, build orientations, and types of surfaces. The experimental results and ANOVA analysis showed that a strong interrelationship exists between the different build inclination angles and the distinct surface topographical features that emerge on longitudinal facet external and internal surfaces, while the latitudinal facet external and internal surfaces presented minimal difference in surface quality.

Differential Etching of Rays at Wood Surfaces Exposed to an Oxygen Glow Discharge Plasma.

Basswood samples were exposed to oxygen glow-discharge plasmas for 30 min, and etching of radial and tangential longitudinal surfaces was measured. It was hypothesized that there would be a positive correlation between etching and plasma energy, and differential etching of wood surfaces because of variation in the microstructure and chemical composition of different woody tissues. Etching at the surface of basswood samples was examined using profilometry. Light and scanning electron microscopy were used to examine the microstructure of samples exposed to plasma. There was a large effect of plasma energy on etching of basswood surfaces, and radial surfaces were etched to a greater extent than tangential surfaces. However, rays at radial surfaces were more resistant to etching than fibers, resulting in greater variation in the etching of radial versus tangential surfaces. The same phenomenon occurred at radial surfaces of balsa wood, jelutong and New Zealand white pine subjected to plasma etching. The possible reasons for the greater resistance of rays to plasma etching are explored, and it is suggested that such differential etching of wood surfaces may impose a limitation on the use of plasma to precisely etch functional patterns at wood surfaces (raised pillars, grooves), as has been done with other materials.

Drag reduction on micro-trench and micro-post superhydrophobic surfaces underneath a motorboat on the sea

Superhydrophobic (SHPo) surfaces can capture a thin layer of air called a plastron under water to reduce skin friction. Although a ~30 % drag reduction has been recently reported with longitudinal micro-trench SHPo surfaces under a boat and in a towing tank, the results lacked the consistency to establish a clear trend. Designed based on Yu et al. (J. Fluid Mech, vol. 962, 2023, A9), this work develops and tests a series of high-performance SHPo surface coupons that can sustain a pinned plastron underneath a passenger motorboat revamped to reach 14 knots. Importantly, plastrons in a pinned state, not just their existence, are confirmed during flow experiments for the first time. All the drag-reduction data measured on different longitudinal micro-trenches are found to collapse if plotted against slip length in wall units. In comparison, aligned posts and transverse trenches show less and little drag reduction, respectively, confirming the adverse effect of the spanwise slip in turbulent flows. This report not only verifies SHPo surfaces can provide a consistent drag reduction at high speeds in open sea but also shows that one may predict the amount of drag reduction in turbulent flows using the physical slip length obtained for Stokes flows.

NbSbO4 Kristalinin Yapısal, Elastik ve Piezoelektrik Özelliklerinin İncelenmesi

The structural, elastic, and piezoelectric properties of the NbSbO4 crystal were calculated based on the density functional theory. These properties were calculated using the ABINIT package program under both the generalized gradient approximation and the local density approximation. The elastic stiffness tensor and the elastic compliance tensor for the NbSbO4 crystal were calculated in the ground state. Voigt Bulk Modulus, Reuss Bulk Modulus, Hill Bulk Modulus, Voigt Shear Modulus, Reuss Shear Modulus, Hill Shear Modulus, Young Modulus, Poisson Ratio, Flexibility Coefficient, Debye temperature, Longitudinal sound wave velocity for NbSbO4 crystal using elastic stiffness and elastic compliance tensor, Transverse sound wave velocity and Average speed of sound were calculated. Then, the ground state piezoelectric tensor of the NbSbO4 crystal was calculated. Accordingly, 2D longitudinal surfaces and 3D representation surfaces of the piezoelectric tensor were obtained using MTEX software. The properties obtained with both the generalized gradient approximation and the local density approximation are compared. As a result of the calculations, it was understood that the material was a flexible and formable material in both approximations.

Selected Mechanical and Physical Properties of Thermally Modified Wood after Field Exposure Tests

This study aimed to evaluate the impact of thermal modification on the physical and mechanical properties of three different wood species from Bosnia and Herzegovina, namely beech wood (Fagus sylvatica L.), linden wood (Tilia cordata), and silver fir wood (Abies alba). The samples underwent thermal modification at five different temperatures (170 °C, 180 °C, 195 °C, 210 °C, and 220 °C) for varying durations (ranging from 78 to 276 min). After treatment, they were exposed to outdoor conditions for twelve months. The study examined the four-point bending strength, tensile force, color change, and surface quality of the modified and unmodified samples. The results showed that outdoor exposure negatively impacted the mechanical properties of the unmodified samples, especially in the linden wood which was 41% and the beech wood which was 42%. Additionally, outdoor exposure caused significant surface cracks in the thermally modified linden and beech wood. The study also found prominent color changes in the modified and unmodified samples during twelve months of exposure. The roughness of the samples was determined with a confocal laser scanning microscope, which showed that the roughness increased on both the axial and the longitudinal surfaces after weathering. The highest roughness for the fir wood was determined to be 15.6 µm. Overall, this study demonstrates the importance of wood modification and its impact on the use-value of wood products.

Laboratory Investigations of Mold Growth on Transverse and Longitudinal Wood Surfaces

The possible influence of anatomical sections of wood on mold growth was investigated by means of a laboratory experiment. The selected fungi, Aspergillus sp., Penicillium sp., and Alternaria sp. were inoculated by spraying on the surface of wood specimens prepared from pine (Pinus sylvestris) and spruce (Picea abies). The incubation was carried out under stable environmental conditions (temperature of 22 °C, relative humidity of 75, 87, and 95%) over three months. Mold growth was evaluated based on regular microscopic and macroscopic observations. The recorded mold coverage fractions and the qualitative indicators of mold development were later expressed by a dimensionless mold index. The differences in mold growth in the anatomical sections of wood were found to be relatively insignificant. In contrast, comparison of measured data with other experimental studies showed large differences, especially in the initial growth phase. The discrepancy is probably related to differences among the experimental protocols. It is concluded that laboratory mold growth studies would be improved if a common standardized methodology was developed and followed.

Research on welding-induced inhomogeneous stress in thick plate EH40 butt joint considering phase transformation

In this work, the inhomogeneous residual stress distribution and evolution of thick plate in single-pass full penetration laser welding are systematically investigated using phase transformation model. The material constitutive model considering solid-state phase transformation according to the actual weld microstructure is proposed to predict the inhomogeneous stress distribution of the welded joint. The inhomogeneous stress distributions along the longitudinal, transverse and thickness direction surfaces of the welded joint are systematically analyzed and deeply discussed, respectively. The results show that there is an obvious inhomogeneous distribution of the temperature field between the start-welding, middle section and end-welding position of the weld. It is obviously observed that the top and bottom surfaces of welded joint produce remarkably high stress areas and high stress gradients. The maximum longitudinal and transverse stress gradient values in the top surface are up to 1240.1 MPa and 1175.7 MPa, respectively. It is found that martensitic transformation is the main reason for the inhomogeneous stress distribution including high stress areas and high stress gradients in thick plate welded joint. The current research is beneficial to reduce the detrimental effects of welding-induced inhomogeneous residual stress on thick plate welded joints.

Modeling and analysis of sliding wear based on fractal surface reconstruction in line contact mixed lubrication

In mixed lubrication, the direct rough contact between the two contact surfaces causes material wear and lead to the variation of the surface micro-topography. In turn, the variation of the micro-topography affects the lubrication state between the two contacting surfaces. For the better comprehension of the interaction of lubrication and wear on rough surfaces in mixed lubrication, in this paper, a coupled model of fluid flow, rough contact, and surface wear was established, with fractal theory being applied to predict the changes in surface microtopography. Furthermore, the effects of fractal dimension, roughness direction, contact load and slide-roll ratio on the surface contact area ratio, accumulated wear, film thickness and friction coefficient are analyzed. The results demonstrated that surfaces with large fractal dimension have denser roughness peaks, resulting in larger contact areas and more severe wear. Transverse roughness surfaces exhibit better lubrication and wear performance compared to longitudinal and isotropic surfaces. In addition, increasing the contact load and slip-roll ratio increases the contact area ratio, resulting in lower lubricating performance and increased wear.

Effect of Graphene Coating of Carbon Fibers on the Fracture of Uni-directional Laminates

High specific strength and stiffness of carbon fiber reinforced polymer (CFRP) composites make them the preferred structural materials for a wide range of applications. The interfacial region between the matrix and reinforcing phases plays a critical role in determining the performance of CFRPs under mechanical loading. Hence, enhancing the interfacial bonding between the epoxy and the fibers is expected to improve the strength of the resulting composites. In the current study, a coating of graphene nano-platelets (GNPs) on unidirectional carbon-fibers has been made with the aim to strengthen the interface/interphase between the fiber and the matrix. Vacuum assisted resin transfer molding technique was used to manufacture the laminates after the solvent spray coating of the GNPs onto carbon fiber. The uncoated and GNPs coated CFRPs have been subjected to tensile tests followed by detailed fractographic analysis. Uniaxial tensile strength and Young’s modulus of the laminates have been found to improve with GNP addition. The fractographs reveal debonding gaps between fiber and epoxy in cross-sectional fracture surfaces and adherence of the epoxy with fibers in longitudinal fracture surfaces. Laminates made with fibers with a coating of GNPs showed smaller debonding gaps and larger epoxy adherence on the fibers than the pristine laminates. A larger interphase for the former laminate was found using carbon linear elemental mapping with the help of SEM equipped with energy dispersive X-ray spectroscopy.

Spherical Transformer on Cortical Surfaces.

Motivated by the recent great success of attention modeling in computer vision, it is highly desired to extend the Transformer architecture from the conventional Euclidean space to non-Euclidean spaces. Given the intrinsic spherical topology of brain cortical surfaces in neuroimaging, in this study, we propose a novel Spherical Transformer, an effective general-purpose backbone using the self-attention mechanism for analysis of cortical surface data represented by triangular meshes. By mapping the cortical surface onto a sphere and splitting it uniformly into overlapping spherical surface patches, we encode the long-range dependency within each patch by the self-attention operation and formulate the cross-patch feature transmission via overlapping regions. By limiting the self-attention computation to local patches, our proposed Spherical Transformer preserves detailed contextual information and enjoys great efficiency with linear computational complexity with respect to the patch size. Moreover, to better process longitudinal cortical surfaces, which are increasingly popular in neuroimaging studies, we unprecedentedly propose the spatiotemporal self-attention operation to jointly extract the spatial context and dynamic developmental patterns within a single layer, thus further enlarging the expressive power of the generated representation. To comprehensively evaluate the performance of our Spherical Transformer, we validate it on a surface-level prediction task and a vertex-level dense prediction task, respectively, i.e., the cognition prediction and cortical thickness map development prediction, which are important in early brain development mapping. Both applications demonstrate the competitive performance of our Spherical Transformer in comparison with the state-of-the-art methods.

Loose Material Filling in the Loading Trough Profile of the Belt Conveyor

The paper presents a mathematical expression of the sizes of the transverse and longitudinal cross-section surfaces and of the volume of the loose material spread on the surface of the conveyor belt before the transverse partition of the belt conveyor, inclination angle of which exceeds the limit transport angle permitted for the belt conveyor of a classic design. Volume and geometric shape of the lose material; transported in the trough (two-roller bench) loading profile; are impacted by the mechanical characteristics of the transported material, width of the conveyor belt, inclination angle of the side rollers, height of the transverse ribs and especially inclination angle of the conveyor. The maximal cross-section surface of the lose material filling at the conveyor with a smooth belt can be (for conveyor belts modified based on the shape of the trough) expressed as the sum of the cap cross-section surface and the surface of the bottom part of the belt filling. The paper describes the jacket curve of the of the cap cross-section using a parabola equation, and the surface curve of the bottom part of the belt filling using a line equation. The size of the cross-section surface of the belt filling along the longitudinal plane of the conveyor belt is defined as the difference between the inclination angle of the conveyor and the discharge angle of the transported material.

Design of vertical members in large-span steel structures: Can relevance of seismic actions be exceeded on account of indirect fire actions?

Effect of lateral actions evolving from restrained thermal expansions of horizontal structural elements (beams, slabs) on stability of vertical elements (columns, walls) of fire-engulfed buildings remains unaddressed sometimes in engineering practice. Discussion with engineers has revealed that two reasons may contribute most to such design inconsistency. The first is premature assumptions that the effects of these actions can not be sufficient to exceed the effects of other lateral design actions, especially if for the same building considerable seismic influences are also expected. The second reason is the fact that, according to the present version of Eurocodes, these actions need not be addressed specifically if the design is carried out under standard fire curve. This curve, however, is still applied often in practice. For certain vertical members, such as the ones positioned somewhere within the middle of fire compartments, indirect lateral fire actions may indeed be negligible, e.g., due to partial or complete balancation of these actions in fire evolving simultaneously at two opposite sides. However, more pronounced effect might be observed for vertical members at the boundary between a fire-engulfed and a neighbouring cold-side compartment, especially in steel or RC buildings with larger horizontal spans prone to striking lateral thermal elongations. While such structures represent a fair share of existing building stock (they are common, e.g., in prefabricated industrial and commercial buildings), this problem deserves a special attention. In this paper two real one-storey large-span halls are analysed for confirmation of the above hypothesis. Each of them comprises two structurally connected units, i.e. one RC- and the other steel-framed, where fire is assumed to engulf the steel-framed unit. Stability of the ’cold-side’ RC columns at the boundary between both sectors is discussed and for the latter indirect fire actions from the connecting fire-engulfed steel members are found to be of a comparable or a greater size to effect of moderate-size seismic actions. The greatest effects of the observed fire actions are found at average steel temperatures below 400 °C. This is a rather low temperature expected to be achieved (sooner or later) in most fire-affected steel elements with or without fire protection. At the same time, as in this paper also proven by results of exact visco-plastic structural computations, this is also a temperature at which no pronounced creep strains yet evolve in steel within time frames relevant for common structural fire analyses. In addition, the paper also shows that these conclusions would not change for other variations of the discussed two buildings where other possible kinematic boundary conditions were applied at the ends of the steel members or other possible thermal boundary conditions were assumed along their longitudinal surfaces. At most, the observed indirect fire effects would only increase further in these cases. Thus, at least for structures of a similar type (i.e. one-storey frame structures of horizontal spans of similar size and materials), the authors propose that the discussed lateral indirect fire actions are not dismissed from any design procedure regardless of the expected fire scenario as long as steel is allowed to heat to moderate temperatures (around 400 °C). In the last part of the paper the authors also discuss possible change of these findings for multi-storey frame structures and/or frame structures of other spans. However, for these (and other possible) structural types, a more detailed further investigation is proposed.

Characterization of wood popularly known as “Louros” in the Brazilian amazon by visible spectroscopy and CIELAB parameters

Aim of study: The objective of this work was to evaluate the potential of colorimetry to discriminate wood from the “louros” group, in particular to contribute to a database of Brazilian native species for future application in logging control actions.Area of study: The wooden discs were collected in a Sustainable Forest Management Area (AMFS) belonging to two extractivist communities, Paraiso and Arimum, both in the “Green Forever” Extractivist Reserve, in the municipality of Porto de Moz, Pará state, Brazil.Material and methods: Colorimetric evaluation was carried out based on data from the CIEL*a*b* system, analyzed using PCA and ANOVA in a completely randomized design in a two-factor scheme.Main results: PCA produced some evidence of color patterns and some parameters may be more useful in caracterization. Longitudinal surfaces were more indicated for this group caracterization. The data from CIEL*a*b* system produce helpful information for distinction of wood from “louros” group, and so, the colorimetric technique can be an auxiliary tool for separation of this group, complementary to other techniques as wood anatomy.Research highlights: Correct discrimination of wood from “louros” group in commerce control; Brazilian native species.Keywords: Species distinction; Lauraceae; Proteaceae; color parameters.Abbreviations used: Comission International de L’Eclairage: CIE, Sustainable Forest Management Area: AMFS, Ministry of the Environment: MMA, Chico Mendes Institute: ICMBio, Authorization and Biodiversity Information System: SISBIO, National System for Genetic Heritage Management: SisGen, Analysis of variance: ANOVA, Principal Component Analysis: PCA, Aniba sp.: PR, Euplassa sp.: LB, Roupala sp.: LV, Ocotea sp.: LR, Ocotea sp.: LPI, Mezilaurus sp.: IT, Mezilaurus sp.: ITA.

Influence of weathering on surface roughness of thermally modified wood

Wood is one of the most important building materials. Thermally modified wood is entering the market and replacing wood preservatives and tropical wood species in some applications. Thermally modified wood is exposed to weathering similarly as other wood-based building materials. It has been reported that if thermally modified wood is exposed to weathering, its moisture performance might decrease fairly fast. Moisture performance reflects the material’s ability to remain dry and dry out fast when wet. The aim of this study was to determine whether this phenomenon is associated with crack formation or roughness. Norway spruce, thermally modified spruce, wax-treated thermally modified spruce, and European larch heartwood samples were exposed to artificial accelerated weathering and natural weathering for 9, 18, and 27 months. Samples were subsequently isolated, and their roughness was determined with a confocal laser scanning microscope on axial and longitudinal surfaces at 10× and 50× magnification. After weathering, roughness increased on both axial and longitudinal surfaces. This was evident from the profile 2D measurements (Ra) and surface 3D measurements (Sa). The effect of natural weathering on roughness was higher than artificial accelerated weathering, presumably due to synergistic effects of abiotic and biotic factors. This may be associated with Wenzel’s theory on the influence of roughness on the contact angles of water on the surface; namely, increased roughness will decrease the contact angle on hydrophilic surfaces.

Indocyanine Green Fluorescence Angiography of the Transverse Cervical Arterial Supply to Clavicle Flaps: An Anatomical Study.

To describe the anatomy of the transverse cervical artery and to prove its perfusion to the clavicle using indocyanine green fluorescence angiography as an alternative vascularized bone for head and neck reconstruction. Cadaveric dissection. Anatomy lab. Twenty-two necks and shoulders from 11 fresh-frozen cadavers were dissected. The transverse cervical artery diameter, length, emerging point, and the length of clavicle segment harvested were described. Photographic and near-infrared video recordings of the bone's medial and longitudinal cut surfaces were taken prior to, during, and after indocyanine green injection. The transverse cervical artery originated from the thyrocervical trunk and emerged at the level of the medial one-third of the clavicle in 22 of 22 (100%) specimens. The average length of the pedicle was 3.6 cm (range, 2.2-4.4 cm), and the mean diameter was 2.5 mm (range, 1.8-3.4 mm). The harvested bone had a mean length of 5.1 cm (range, 4.3-5.8 cm). After injecting the indocyanine green, 22 of 22 (100%) specimens showed enhancement in the periosteum, bony cortex, and medulla. The middle third of the clavicle can be reliably harvested as a vascularized bone with its perfusion solely from the transverse cervical artery pedicle, as shown by the near-infrared fluorescence imaging. The pedicle was sizable and constant in origin.

Colorimetry of Acacia mangium wood from plantations in northeast Brazil

Abstract The aim of this study was to evaluate color characteristics in wood samples from Acacia mangium from a homogeneous plantation in Bahia state, northeast Brazil, and also analyze the influence of anatomical section and radial position in the trunk on color response to contribute to information for the best use of the wood, such as, for example, the optimization of the performance of the pieces in sawmill through the most acceptable aesthetic form by the final consumer. Six trees with age of 14 years were cut. The species was identified by anatomical analysis at the Laboratory of Wood Anatomy of the Federal University of Paraná, comparing the sample collected with the authenticated material. A disc from the base of each tree was divided into six samples oriented in anatomical sections (transversal, radial and tangential), with dimensions of 20 × 20 × 30mm, named near pith, intermediate and near bark. A total of 36 samples were evaluated, 12 from each position. The colorimetric evaluation was performed with a CM-5 spectrophotometer. Data on lightness, green-red and blue-yellow chromatic coordinates were obtained, and values of saturation and hue angle were calculated. Acacia wood from planted forest is classified as olive color. Color parameters were influenced by anatomical section and radial position in the trunk, being found 44 for the transversal section, 55 for the tangential section and 57 in the radial for luminosity. Transversal sections had lower values in comparison to longitudinal surfaces and radial sections had higher luminosity than tangential sections. The near bark region presented lower values in most colorimetric parameters, except hue angle, in comparison with the intermediate and near pith regions, which was around 70 in the different positions of the wood.

Analytical Solution to the Plane Bending Task of the Multilayer Beam with a Circular Axis under Normal Uniform Loading

Circular bars are widespread elements in building and mechanical engineering. They allow one to enhance the strength of the multilayer composite materials along with their weight reduction. However, their analytical modeling is developed rather poorly, which creates additional obstacles in their efficient design. The paper presents the results of the exact analytical solution to the plane bending task of elasticity theory for the multilayer beam with a circular axis under normal uniform loading on its longitudinal surfaces considering the cylindrical orthotropy of its layers’ materials. The problem has been solved using the methods of linear elasticity theory based on the continual approach where the circular bar is considered as a solid with the elastic characteristics varying in the radial direction. The solution for the shear stresses is assumed using the known distribution in the cross section. Therefore, the solution to the problem is reduced to the determination of two unknown functions of stress distribution throughout the section height. The system of linear differential equations has been obtained for the determination of the sought functions and unknown functions of integration in the process of the solution to the equations of plane theory considering the variable elastic characteristics. General analytical solutions for uniform and discontinuous-nonuniform layers from cylindrically orthotropic and isotropic materials have been developed. The influence of transverse shear deformation and compression on the characteristics of the stress-strain state of a cantilever three-layer beam with a semicircular axis is theoretically investigated. The obtained relations allow us to predict the stress-strain state of circular multilayer beams, as well as to build applied methods for solving problems of strength, rigidity, and optimal design of such structural elements.

Severe plastic deformation of AA 5083 and copper bimetallic metal

The purpose of the present study is to investigate the effect of Cu casing and wall thickness of the drilled copper bars on uniform distribution of imposed stain in terms of structural homogeneity and distribution of micro-hardness in the severely deformed AA 5083 after equal channel angular extrusion (ECAE). In this study, AA 5083 cylindrical inserts of 6 mm, 8 mm and 10 mm diameter with 100 mm length are tightly inserted in the 16 mm square copper bars having the respective diameter holes. The square cross sectioned AA 5083 billets of 16 mm × 16 mm and 100 mm length are also considered as feedstock. The longitudinal surfaces of the bimetallic metals are polished and annealed at 530 °C for 1 h and then processed by ECAE up to four passes in route A (same sense after every pass without any rotation) at room temperature using a die with square cross-sectioned channels having channel intersection angle (ϕ) 105° and outer corner angle (Ψ) 30°. The initial grain size of 60 µm has been greatly refined and the ultrafine grains of the sizes in the range of 400–700 nm are formed in the extruded AA 5083 inserts after the four passes. The microhardness of extruded AA 5083 significantly increased from 69 to 134 VHN, 132, 176 and 157 respectively for the square billets without Cu casing and cylindrical inserts with the diameters of 6, 8 and 10 mm covered with Cu casing after the four passes. The variations in the microhardness measurements at different regions on the sectioned surfaces are also investigated in this study. The requirement of pressing force is very significantly reduced by using copper casing which is having more ductile nature and the frictional forces between the copper and steel die are very less as compared to the Aluminium and steel. The chances of formation of dead metal zone are avoided by filling the corner gap by cooper metal during the ECAE process. The uniform distribution of strain imposed on the severely deformed billets develops the homogeneous ultrafine grain structure and significantly improves the micro-hardness of the processed material.