Flat Strip Research Articles

Sedimentation dynamics of triply twisted Möbius bands: Geometry versus topology

We explore the sedimentation dynamics of triply twisted Möbius bands, each characterized by threefold rotational symmetry but distinguished by its construction and intrinsic geometrical properties. Three types of bands are considered: one with vanishing Gaussian curvature, constructed by isometrically deforming flat rectangular strips through bending without stretching; and two with negative Gaussian curvature, one being constructed by isometrically deforming helicoids. Experiment on these three types of bands, with a focus on varying aspect ratios, reveals a singular phenomenon: while the spin directions of bands not derived from helicoids spin in directions consistent with their inherent chirality, bands derived from helicoids exhibit an aspect-ratio-dependent spin, pointing to the existence of a critical aspect ratio at which geometric factors dominate over chiral influences. Supported by numerical simulations and a detailed analysis of the resistance tensors, we propose the unique response of bands derived from helicoids originates from a complex interaction among geometry, topology, and hydrodynamics. Two explanations are offered for the chiral transition observed in bands derived from helicoid. First, this transition may parallel the dynamics of superhelices, for which competing chiralities influence rotational behavior. Second, the unique geometrical properties of bands derived from helicoids, coupled with deviations between the rotation axis and the local symmetry axis, may underlie the observed aspect-ratio-dependent chiral transition. Our study underscores the significant role of geometrical and topological nuances in determining the behavior of chiral objects suspended in fluids. In addition to offering transformative potential across diverse fields, it promises advancements in mixing, separation processes, and innovative passive swimmers. Published by the American Physical Society 2024

Dyakonov surface waves in dielectric crystals with negative anisotropy

Abstract Since the initial discovery of Dyakonov surface waves at a flat infinite interface of two dielectrics, at least one of which is positively anisotropic, extensive research has been conducted towards their theoretical and experimental studies in materials with positive anisotropy. The potential applications of these waves were initially limited due to the stringent conditions for their existence and the requirement for position anisotropy. In our study, we present the theoretical prediction and experimental observation of a novel type of Dyakonov surface waves that propagate along the flat strip of the interface between two dielectrics with negative anisotropy. We demonstrate that the conditions for surface waves are satisfied for negatively anisotropic dielectrics owing to the specific boundaries of the strip waveguide confined between two metallic plates. We study such modes theoretically by using the perturbation theory in the approximation of weak anisotropy and demonstrate that the electromagnetic field distribution in these modes is chiral. Experimental verification of theoretical predictions is made in the microwave range using 3D-printed negatively anisotropic water-dielectric metamaterial slabs. The existence of Dyakonov surface waves in negative crystals prompts a reassessment of the list of materials suitable for practical realization of these waves in the visible and infrared ranges. Due to the ability of the considered modes to transmit chiral light, they have potential in the sensing of chiral organic molecules.

EnZolv delignification of cotton spinning mill waste and optimization of process parameters using response surface methodology (RSM)

BackgroundEnZolv is a novel enzyme-based, eco-friendly biomass pretreatment process that has shown great potential in the field of textile engineering and biotechnology. It employs laccase from Hexagonia hirta MSF2 and 2% ethanol in the process of delignification. The process is designed to evaluate optimal conditions to remove lignin and other impurities from cotton spinning mill waste (CSMW), without compromising the quality and strength of the fibers. CSMW is a low-cost and readily available source of cellulose, making it an ideal candidate for delignification using EnZolv. By optimizing the pretreatment conditions and harnessing the potential of enzymatic delignification, this research aims to contribute to more sustainable and efficient ways of utilizing lignocellulosic biomass in various industries for the production of biochemical and bioproducts.ResultsThe present study emphasizes the EnZolv pretreatment in the delignification of cotton spinning mill wastes irrespective of the cellulose content. EnZolv process parameters such as, moisture content, enzyme load, incubation time, incubation temperature, and shaking speed were optimized. Under pre-optimized conditions, the percent lignin reduction was 61.34%, 61.64%, 41.85%, 35.34%, and 35.83% in blowroom droppings (BD), flat strips (FS), lickerin fly (LF), microdust (MD) and comber noils (CN), respectively. Using response surface methodology (RSM), the statistically optimized EnZolv pretreatment conditions showed lignin reduction of 59.16%, 62.88%, 48.26%, 34.64%, and 45.99% in BD, FS, LF, MD, and CN, respectively.ConclusionTraditional chemical-based pretreatment methods often involve harsh chemicals and high energy consumption, which can have detrimental effects on the environment. In contrast, EnZolv offers a greener approach by utilizing enzymes that are biodegradable and more environmentally friendly. The resulting fibers from EnZolv treatment exhibit improved properties that make them suitable for various applications. Some of the key properties include enhanced cellulose recovery, reduced lignin content, and improved biophysical and structural characteristics. These improvements can contribute to the fiber's performance and processability in different industries and future thrust for the production of cellulose-derived and lignin-derived bioproducts.Graphical

Stability and decay estimates of the 2D incompressible magneto-micropolar fluid system with partial viscosity on a flat strip

Stability and decay estimates of the 2D incompressible magneto-micropolar fluid system with partial viscosity on a flat strip

Development and characterization of thin iron-based shape memory alloy prestressing wire

Iron-based shape memory alloys (Fe-SMA) have been used successfully in the previous years as prestressing reinforcement in the form of rebars, rods and flat strips, for various types of structural elements and loading scenarios. This paper introduces a new application of this material in the form of thin wire. An experimental characterization study is presented herein for Fe-SMA wire that was drawn to a diameter of 0.5 mm, regarding its tensile stress-strain response and recovery stress development upon heating, for different activation temperatures and prestraining levels. Furthermore, an investigation is presented regarding the effects of heat treatment conditions on the mechanical response and prestressing performance of the wire. For the optimum heat treatment conditions and activation temperature range considered in this study, the measured tensile strength and recovery stress of the Fe-SMA wire was 1117 MPa and up to 390 MPa, respectively. The results indicate a strong potential of Fe-SMA as a candidate prestressing material where flexible wire cross-sections of small diameter are desired instead of larger, solid cross-section tendons (e.g., multi-strand wire ropes or concrete confinement spirals), or as novel short fiber reinforcement for concrete with prestressing capabilities.

Elastic/viscoelastic polymer bilayers: a model-based approach to stretch-responsive constructs.

The use of polymers in the fabrication of bilayers for stimuli-responsive systems is well-known, yet viscoelasticity and viscoelastic models representing bilayer behavior have received surprisingly little attention. Of particular recent interest to us are simple polymeric bilayers in which one material, such as styrene-ethylene-propylene-styrene (SEPS) or styrene-isobutylene-styrene (SIBS), shows typical rubbery elastic response upon extension and retraction, and the other, an unvulcanized, low-Tg polymer such as butyl rubber (butyl), exhibits a viscoelastic response. When such a bilayer strip is extended to a fixed strain and held for several seconds followed by sudden release of this strain, rapid curling is observed, achieving a maximum curvature within 1 second, with a gradual uncurling, typically taking 300-600 seconds to eventually return to a flat strip. Attention has been directed to modeling the observed bilayer behavior. We compare predicted curvature and relaxation time constants from finite element analysis (FEA) simulations using Maxwell, Zener, Generalized Maxwell, and Parallel Rheological Framework (PRF) viscoelastic models to the experimentally measured values. We find that the Generalized Maxwell model predicts curvature over time with the lowest overall mean absolute scaled error (MASE) of 0.519, corresponding to a 4.9% difference from the second lowest error model and a 76.8% difference from the highest error model. Building upon an understanding of the material mechanics in simple bilayer strips, more complex bilayer systems can be designed. Samples of cross and weave geometries were fabricated from bilayer films and initial testing demonstrates how these materials can be used in potential applications.

Rectifying Strip Patterns

Straight flat strips of inextensible material can be bent into curved strips aligned with arbitrary space curves. The large shape variety of these so-called rectifying strips makes them candidates for shape modeling, especially in applications such as architecture where simple elements are preferred for the fabrication of complex shapes. In this paper, we provide computational tools for the design of shapes from rectifying strips. They can form various patterns and fulfill constraints which are required for specific applications such as gridshells or shading systems. The methodology is based on discrete models of rectifying strips, a discrete level-set formulation and optimization-based constrained mesh design and editing. We also analyse the geometry at nodes and present remarkable quadrilateral arrangements of rectifying strips with torsion-free nodes.

Восстановление пространственной функции распределения неоднородностей покрытия по функции распределения на шлифе

In the experimental studies of the structure of the special coating layer overlaid on metal applying gas-thermal spraying technique, one of the main methods is the study of polished specimen micrography. According to the computer analysis of microphotographs, it is possible to obtain the distribution function of inhomogeneities in the sample. However, since micrography is a flat image, the resulting function will be two-dimensional, whereas in a real sample, the distribution of defects is described by a three-dimensional function. In this paper, the problem of the space function recovery for the distribution of defects in a gas-thermal coating is viewed on the basis of the analysis of polished specimen micrography. The actual inclusion of an irregular shape is replaced by an effective three-axis ellipsoid. The problem is solved in the general form of reduction of the space function f of inhomogeneities distribution according to their distribution function f P on the cross - sectional plane P, which includes some integral transformation I. It is shown that in the special case of spherical particles, the inversion I^(-1) exists and is an integral transformation of the same type as I. The space distribution of spherical particles is also viewed, which does not depend on the longitudinal coordinate z, where particle sizes are limited at each point by a function R(x,y), depending on the coordinates. This distribution is suitable in its essense to the stationary spraying technology, when in deep layers near the substrate, the coating material melts completely and forms a single melt, while closer to the surface and edges, the parts that are not completely melted form inclusions of noticeable sizes. The reduction of the Fuller distribution law, used to optimize the granulometric composition of powder materials, is viewed as a second example. It is found that the reduction of the density of the ellipsoid distribution function to the section of a flat strip transfers the density of the distribution of centers as original, and the product of Fuller distributions times independent parameters is transformed into the product of distributions times the opposite degree parameters and also the previous values of the parameters of the ellipsoid

Fabrications of electrically small hemispherical antenna

AbstractA hemispherical‐shaped folded electrically small antenna (ESA) is a well‐known antenna where the radiating conductor is a wire or flat strip of variable width. This work analyzed the performance of strip‐based ESA for a constant strip width and focused on the fabrication procedure which utilizes the low‐cost dielectric material and ubiquitous 3‐D printer. The impact of additional dielectric support on the performance of ESA was investigated. This work also introduced conductive paint for the radiating part, along with metallic wire and strip. There is a good agreement between simulated and measured results. The 3‐D printing technique offers design flexibility, eases fabrication difficulty, reduces material cost, and improves the mechanical stability of the antenna.

Effect of triangular perforated flat cone-shaped inserts on performance of double-tube heat exchanger

This study investigated the effect of triangular perforations with flat conical inserts in a double-tube heat exchanger. Triangular perforations with flat cone-shaped inserts were placed inside the inner tube to enhance the heat transfer coefficient. The experiments were conducted for a number of flat conical strips (m) and pitch ratios (P = p/di) for flows varying from Re = 3000 to 9000 at a constant attack angle (α = 20°). The results showed that a triangular perforation with flat cone-shaped inserts remarkably increases the heat transfer factor, in contrast to flat conical inserts. The rise in the coefficient of heat was attributed to the creation of turbulence and disturbance of the boundary layer caused by perforated inserts. Furthermore, it was observed that the heat transfer coefficient increased with the Reynolds number, indicating that the effect of the inserts was more significant at higher fluid velocities. Correlations were developed to compare and analyze the results of the Nusselt number and friction factor. The developed correlation results are in good agreement with the experimental results. The findings obtained from this study can be implemented to enhance the performance and optimize the design parameters of industrial heat exchangers.

The Effect of Soaking Time on Mechanical Properties of Roll-Bonded AA3003 and AA4045 Used for Heat Exchangers

Due to the rising need for energy saving, high-performing automotive heat exchangers, demand has significantly grown in recent years. As a result, effective fin-tube heat exchangers are becoming more popular. These tubes are typically made by rolling flat strips of AA3003 aluminum alloys that have either one or both sides coated with AA4xxx alloys. The AA3003 type of alloy is typically used as the core, which is then covered in either AA4045 or AA4343, which melts during the brazing process to adhere the fins to the tubes. To maintain the optimal size and distribution of manganese (Mn)-containing precipitates, preheating parameters are carefully controlled. Then, longer soaking times or higher soaking temperatures result in larger precipitates, which cause the final product to exhibit poor mechanical properties. Therefore, it is crucial to optimize the different manufacturing steps, such as homogenization, soaking time, and brazing in order to achieve a high quality product. Studies on the impact of homogenization temperature and time on the microstructure of AA3xxx aluminum alloys have been conducted. However, there has been little research on the impact of soaking (reheating) time on AA3003 cladded alloys. Hence, the effects of isothermal soaking time on the microstructure and mechanical properties of AA3003 cladded with AA4045 alloy were investigated in this work. Optical microscopy (OM) and scanning electron microscopy (SEM) were used to characterize the microstructure and identify intermetallic phases. The final microstructure in terms of grain structure at various homogenization times was characterized by electron backscattered diffraction (EBSD). After the hot-rolling and cold-rolling of the as-received material, large particles of intermetallic (mainly in the form of Chinese script morphology consisting of Fe-Mn-Si) were broken into smaller particles with an increased Fe, Mn, and Si content, indicating the formation of an α-Al(Fe,Mn)Si phase. The α-Al(Mn,Fe)Si was found to be a dominant dispersoid precipitate in the modified AA3003 core. Coarsening of the Al(Mn,Fe)Si dispersoids at 505 °C was only observed at a 45 h homogenization time. The hardness trend with homogenization time was found to be similar to that after homogenization, cold working, and annealing, with exception of an increase in hardness in the latter possibly due to strain hardening (from cold-rolling).

Stripped and layered fabrication of minimal surface tectonics using parametric algorithms

Abstract This article describes a parametric design and fabrication workflow influenced by Frei Otto’s form-finding experiments on soap films. The research investigates minimal surface geometry by combining physical and digital experiments in a computational framework. Operating on mesh topology, various parametric design tools and plug-ins in Rhinoceros/Grasshopper are presented to discuss the translation of minimal surfaces to flat strips suitable for planar fabrication using flexible materials. These tools are tested on a case study to show the automated design and manufacture of double-curved surfaces as double-layered strips running in perpendicular directions that can be affixed at point connections for structural stability. The development of the parametric workflow, material constraints, and stripped fabrication of layers are discussed.

Experimental Investigation and Characterization of Friction Stir Spot-Welded Dissimilar Aluminum Copper Metallic Lap Joints.

Due to their contrasting physical properties, joining materials like copper and aluminum has always proven difficult. The disadvantages of traditional joining methods include additional weight, solidification problems, and energy waste. Friction stir spot-welding (FSSW) was utilized for joining copper and aluminum in order to get around these difficulties. This study illustrates that friction stir spot-welding (FSSW) produces joints between incompatible copper and aluminum alloys with better mechanical and electrical properties. The numerous FSSW parameters play an important role in deciding how well the welded joint performs. Tool rotational speed (TRS), plunge rate (PR), and dwell duration (DT) are the study parameters. During manufacture, a case-hardened H13 tool was used to lap-joint AA 6061 T6 hot-rolled aluminum flat strips with C11000 copper strips while operating at three different levels of TRS, PR and DT. SEM analysis was utilized to investigate the interface region and bimetallic interface of the joints. In order to demonstrate modifications in the grain-related characteristics, the joints were examined for electrical conductivity, mechanical strength (lap shear, bending, and microhardness test), and analysis of the microstructure at the weld zones. The outcome demonstrates that other factors, such as plunge rate, dwell time, and tool rotation speed, had the greatest impact on the joints' electrical conductivity, mechanical strength, and microstructure.

A bistable helical structure based on composite tape-springs

Conventional twistable structures use discrete parts articulated around a number of linkages. These allow only a limited degree of twisting angle, are low in storage ratio, heavy and complex in morphing mechanisms. Double-helix structures are commonly applied to induce twistable shape-changing capability for deployable structures, these being capable of large axial deformations where prestressed thin-shell composite flanges or strips are employed; however, their structural stabilities are susceptible to thermal effects, and suffer from non-zero Gaussian curvature deformation induced by prestressing of the precured flat strips. Here, we propose a novel bistable helical structure, where zero Gaussian curvature deformation applies, and shows more stable and reliable morphing mechanics for a twistable structure to be engineered. This is achieved by exploiting bistable composite tape-spring (CTS) structures, where two CTS samples are pin-joined through spokes to formulate a helical structure. It is capable of large axial morphing, and stable in both the fully extended and twisted configurations, with adjustable storage ratio. A theoretical model was established to predict its bistability and a bespoke axial displacement rig was developed to investigate its non-linear morphing mechanisms in order to reveal the underlying fundamentals. These will facilitate torsional structural design for aerospace deployable structures.

Structural buckling analysis of pre-twisted strips

This article focuses on the buckling response of columns formed by pre-twisting a flat, narrow and straight material strip of a rectangular cross section. The experimental analysis accomplished for birch plywood strips covers twisting up to 90 degrees. The corresponding computational analysis covers the twisting process (geometrically nonlinear analysis) and the subsequent compression (linear buckling analysis, including the residual stresses from the twisting process) and includes comparisons for 3D solid and 2D shell finite elements within orthotropic linear elasticity. A further finite element analysis provides findings up to twisting angles of 400 degrees and includes nonlinear post-buckling analyses for the compression subsequent to twisting, in addition to the linear buckling analyses. These sets of analyses reveal some new findings regarding this classical problem. Most importantly, there are four characteristic twisting angles which are associated to mode jumps in buckling, to a plateau in the curve relating the critical load and the twisting angle and, finally, to a loss of stability during the twisting process. The influence of the twisting-induced stresses on the buckling response is investigated as well.

Deployable strip structures

We introduce the new concept of C-mesh to capture kinetic structures that can be deployed from a collapsed state. Quadrilateral C-meshes enjoy rich geometry and surprising relations with differential geometry: A structure that collapses onto a flat and straight strip corresponds to a Chebyshev net of curves on a surface of constant Gaussian curvature, while structures collapsing onto a circular strip follow surfaces which enjoy the linear-Weingarten property. Interestingly, allowing more general collapses actually leads to a smaller class of shapes. Hexagonal C-meshes have more degrees of freedom, but a local analysis suggests that there is no such direct relation to smooth surfaces. Besides theory, this paper provides tools for exploring the shape space of C-meshes and for their design. We also present an application for freeform architectural skins, namely paneling with spherical panels of constant radius, which is an important fabrication-related constraint.

Reinforcement Learning With Model-Based Assistance for Shape Control in Sendzimir Rolling Mills

As one of the most popular tandem cold rolling mills, the Sendzimir rolling mill (ZRM) aims to obtain a flat steel strip shape by properly allocating the rolling pressure. To improve the performance of the ZRM, it is meaningful to adopt recently emerging deep reinforcement learning (DRL) that is powerful for difficult-to-solve and challenging problems. However, the direct application of DRL techniques may be impractical because of a serious singularity, partial observability, and even safety issues inherent in mill systems. In this brief, we propose an effective hybridization approach that integrates a model-based assistant into model-free DRL to resolve such practical issues. For the model-based assistant, a model-based optimization problem is first constructed and solved for the static part of the mill model. Then, the obtained static model-based coarse assistant, or controller, is improved by the proposed reinforcement learning, considering the remaining dynamic part of the mill model. The serious singularity can be resolved using the model-based approach, and the issue of partial observability is addressed by the long short-term memory (LSTM) state estimator in the proposed method. In simulation results, the proposed method successfully learns a highly performing policy for the ZRM, achieving a higher reward than pure model-free DRL. It is also observed that the proposed method can safely improve the shape controller of the mill system. The demonstration results strongly confirm the high applicability of DRL to other cold multiroll mills, such as four-high, six-high, and cluster mills.

Dynamic Evolution of Cracks in Slag-Modified Soil under Uniaxial Loading Using Real-Time X-Ray Computed Tomography

The cracking behavior of subgrade filling is crucial for the stability of road embankments. Slag-modified soil (SMS), which is commonly used as a reinforcing material for construction in highway and railway engineering, has special mechanical and microstructural characteristics that are easily altered under external disturbances. Although the macroscopic deformation of SMS has been widely examined, research on its cracking behavior at the mesoscale under an external load has received insufficient attention thus far. This study uses real-time X-ray computed tomography (X-CT) as a nondestructive tool for characterizing the microstructure of a SMS specimen subjected to uniaxial compression. Rules for the dynamic propagation of cracks in the specimen during deformation are identified based on two-dimensional (2D) and three-dimensional (3D) visualization and quantitative characterization. The results showed that the SMS can be divided into three components—cracks, soil, and steel slag—based on the density gradients from X-ray CT images. The preprocessed X-ray CT images and reconstructed crack models dynamically demonstrated the expanding and connecting patterns of internal cracks during the entire process of deformation. Values of the crack ratio and the degree of connectivity were positively correlated with the axial strain as expressed by a cubic spline function and a linear function, respectively. Curves of the distribution of the volumes of the cracks suggest that cracks in SMS can be divided into four groups: minicracks, mesocracks, medium cracks, and macroscopic cracks. From quantitative and visual perspectives, a large number of original cracks with small volume and low connectivity were gradually transformed into a main fracture under uniaxial loading. The localized shear band, which existed in the zone adjacent to the main fracture, was generated and obliquely distributed in an irregular, flat strip shape in the middle of the SMS specimen. This study suggests that the real-time X-ray CT scanning technique has broad application prospects for detecting the mesostructure in subgrade filling.

The Regularization Technique in Modeling of the Plane E-Polarized EM Wave Scattering by Coplanar System of Electrically Conducting Flat Strips

The integral equations technique has been successfully modified for studying the plane E-polarized electromagnetic wave scattering by multilevel coplanar systems of zero-thickness impedance strips. Reformulation of the scattering problem in the form of the second-kind regular integral equations has been realized on the base of the Carleman regularization technique. Two novel and original classes of specific Cantor functions have been presented and analyzed. Using new Cantor functions, it is easy to create a lot of non-classical orderings for specific multilevel coplanar strips systems. That sort of system can be useful for modeling irregular natural processes and zones in the future. Considerable attention was focused on the plane E-polarized electromagnetic wave scattering by sparsely filled coplanar systems of electrically narrow impedance strips. An explicit solution of the scattering problem has been obtained for such case of strips system.

Contribution of Landsat imagery to map vulnerable areas to seawater intrusion along the Mt.-Cameroon coastal area using lineaments pattern

Large overpopulated coastal areas are, nowadays, affected by seawater intrusion, and the contamination of the groundwater is a real threat. This paper aims to identify the zones along which seawater spreads in the Mt. Cameroon coastal region of Cameroon, and to map the most vulnerable areas to this threat. The results are based on the location of the contaminated boreholes, statistical analysis of automatic and manual lineaments, topographic and slope maps. The elaborated thematic maps allow identification of the fractured zones along which seawater can spread and the areas where the impact of this phenomenon could be more severe. The presence of a large number of contaminated coastal boreholes suggests that elevation (<100 masl), slope (<3°) and fractures are the factors promoting the seawater intrusion along the narrow and flat coastal strip of study areas. The network of closely spaced and intersecting fractures along the gentle slope (<8°) of the Mt. Cameroon, favour the boreholes contamination up to 4 km from the shoreline. Between the Mt. Cameroon and Limbe-Mabeta Massif, a wide NE-SW-oriented system of long and intersecting fractures, promote the inland seawater intrusion up to 10 km inland. The closely spaced and intersecting fractures along which seawater can easily spread has been reconstructed based on orientation, density and length of manual lineaments and the lineaments intersection map. Landsat 7 ETM + image is the one which provides the most reliable vulnerable zone with respect to lineament pattern in this region than both Landsat 8 OLI and Sentinel 1-A images.