Polygonal Tubes Research Articles

Study on energy absorption of paper honeycomb sandwich tube filled by polyethylene foam under axial loading

This work proposed an approach to multi-component non-metallic materials, namely regular polygonal paper honeycomb sandwich tubes filled with polyethylene (PE) foam, and focused on the influence of drop impact parameters and structural parameters on the deformation characteristics and energy absorption of the filled tubes. Axial drop impact tests were employed to exert drop impact loading on cross-sections of the specimens with a square drop weight. The results showed that the X-direction filled tube (X-DFT) had a higher crushing strength and yield strength than that of the Y-direction filled tube (Y-DFT). As the tubular cross-section edge number of the filled tube increased, the specific energy absorption (SEA) and specific total efficiency (STE) decreased. Under the same axial drop impact loading conditions, the SEA and STE of the X-DFT were superior to those of the Y-DFT. As the edge number of the tubular cross-section or the tubular length ratio increased, the SEA and STE of the filled honeycomb tube decreased significantly. While the impact energy increased, the SEA and STE of the filled tubes increased approximately linearly. This work investigated the influence of drop-impact and structural parameters on deformation characteristics and energy absorption. It is expected to provide supplementary documentation for the advancement of cushion protection technology and the optimization of product structure.

Crashworthiness design for novel polygonal asymmetric origami tubes

Origami tubes have attracted widespread attention because it is inclined to deform in the complete diamond mode (DM) with a low initial peak force Fmax and high average crushing force Fave. Although conventional origami tubes can improve crashworthiness, there are still many areas that fail to generate traveling plastic hinge lines, and the crashworthiness can be further improved. This paper presents a novel polygonal asymmetric origami tube (PAT) with origami patterns that can trigger more traveling plastic hinge lines compared to those of conventional origami patterns. The theoretical analysis of the deformation mechanism suggests that the PAT can realize hierarchical deformation and avoid stress concentration at sharp corners. The quasi-static experiments and numerical simulations reveal that the novel origami pattern can successfully trigger up to four times more traveling plastic hinge lines than the conventional square box (CSB) under the premise that each plastic hinge line is similar in length. Compared with the CSB, the PAT can deform in DM with a 56.0 % reduction of Fmax and a 59.1 % increase of Fave. Notably, the stableness of load-carrying capacity SLC is 90.2 %, which is 260.8 % higher than the CSB. A series of parametric studies reveal that the dihedral angle ratio α / β and the width-to-thickness ratio c / t of the PAT have a significant effect on crashworthiness. A smaller ratio of α / β and c / t provides the PAT with superior crashworthiness. Comparing the PAT with other types of origami tubes and multi-cell tubes indicates that the PAT also exhibits outstanding crashworthiness. The impact experiments also unveil a significantly enhanced crashworthiness of the PAT. Compared with the CSB, the Fmax decreases by approximately 46.4 %, while the Fave increases by around 92.7 %. The SLC and SEA values for the PAT surpass those of the CSB by about 260.8 % and 93.1 %, respectively. Furthermore, the theoretical analysis for predicting the Fave of the PAT is developed, with a maximum error not exceeding 8.5 %.

Folding Auxetic Polygonal Kirigami Tubes

Abstract Tubular auxetic structures have wide-ranging applications including medical stents, collapsible energy absorbers, and novel fasteners. To accelerate the development in these areas, and open up new application directions, an expanded range of design and construction methods for auxetic tubes is required. In this study, we propose a new method to construct polygonal cross-sectional auxetic tubes using the principles of origami and kirigami. These tubes exhibit useful global auxetic behavior under axial extension, despite the individual polygon faces not being auxetic themselves. In general, a flat kirigami sheet cannot be simply folded into a polygonal tube since this creates kinematic incompatibilities along the polygon edges. We resolve this issue by replacing the edge folds with an origami mechanism consisting of a pair of triangular facets. This approach eliminates the incompatibilities at the edges while maintaining a connection between faces. The proposed edge connection also introduces additional control parameters for the tube kinematics: for example, introducing a kinematic limit on tube extension and enabling non-uniform behavior along the length of the tube. The rich kinematic behavior possible with polygonal cross-sectional kirigami tubes has potential applications ranging from soft robotics to energy-dissipating devices.

Transient Thermal Spreading From a Circular Heat Source in Polygonal Flux Tubes

Abstract This study develops a numerical simulation to assess transient constriction resistance in various semi-infinite flux channel geometries, including circle on circle, triangle, square, pentagon, and hexagon, which are derived from various heat source arrangements in a large domain. Using both isothermal and isoflux circular heat sources in polygonal flux channels, and employing a finite volume method, the study evaluates transient constriction resistance. The research confirms that for different geometries, similar nondimensionalized constriction resistance results are obtained, particularly when using the square root of the source area as the characteristic length and the square root of the constriction area ratio. The study reveals that flux tube shape has a minimal impact on thermal spreading resistance, with the circle-on-triangle configuration displaying the largest deviation from a simple circle-on-circle model. These insights advance our understanding of thermal spreading resistance in polygonal flux channels and their applications in thermal engineering, especially in contact heat transfer problems.

Designer pseudopeptides: autofluorescent polygonal tubes via Phe-zipper and triple helix.

Chemists are increasingly turning to biology for inspiration to develop novel and superior synthetic materials. Here, we present an innovative peptide design strategy for tubular assembly. In this simple design, a phenylene urea unit is introduced as an aglet at the N-terminus of the peptide. When α-amino isobutyric acid (Aib) is the first residue and phenylalanine (Phe) is the second residue from the phenylene urea entity, it induces an edge-to-face π-π interaction resulting in a turn conformation. The peptides with a unique reverse turn conformation associate to form polygonal peptide tubes via a Phe-zipper arrangement, as evidenced by microscopic and single crystal X-ray studies. Ultra-microscopic imaging revealed that the tubular assembly is hexagonal, square, and triangular in shape. This hierarchical assembly reveals the interplay between π-π interactions and hydrogen bonding. In another design, pseudopeptide 5, wherein a Phe-Phe (FF) unit is linked to phenylene urea, formed polygonal tubes via a triple helical arrangement. Interestingly, the extension of this design to the bis-urea core resulted in vesicular assembly. These supramolecular polygonal tubes and vesicles showed autofluorescence, which allowed confocal imaging. The observed fluorescence is an additional advantage for applications in biological and medical sciences.

Crushing behavior of polygonal multicellular structures with a novel pattern of design for their cross-section under multiple crushing angles

This paper evaluated the crushing performance of multicellular structures with a novel cross-sectional design pattern under impact loads. These structures included polygonal external tubes with identical internal tubes placed at their corners with various ratio of l/L. Crashworthiness indices including SEA, F max, CFE and ULC were found to be dependent on the l/L and shape of the cross-section. TOPSIS method was then applied to the structures, taking into account 16 criteria. Accordingly, the Tr-3, Sq-3, Pen-1, Hex-1 and Oct-4 outperform their corresponding cross-sectional shapes. Among the investigated structures, the Hex-1 and Sq-3 were ultimately chosen as the top-performing structures.

Energy absorption and topology optimization of self-similar inspired multi-cell square tubes

Due to their low cost and lightweight properties, multi-cell square tubes have been widely used in impact protection as energy absorbers. In this study, two kinds of multi-cell square tubes were constructed according to the local self-similar and global self-similar layout strategies. The experiments and numerical simulations were conducted to investigate their quasi-static compression deformation and energy absorption. The results demonstrated that self-similar layout strategies can significantly enhance the crashworthiness of multi-cell square tubes, and the global self-similar layout appears to be more effective at energy absorption. A simplified theoretical model for the mean crushing force (MCF) was developed for its constituent elements of the proposed square tubes. Furthermore, the COPRAS method and the non-dominated sorting genetic algorithm II (NSGA-II) were employed for optimal structure selection and multi-objective optimization. The results showed that the 2nd-order global self-similar multi-cell square tube (MSTG1-2) had prominent crashworthiness compared with some typical self-similar square tubes. The current optimization and topology design strategies can be used in other polygonal multi-cell tubes, which provides an effective guide for enhancing the crashworthiness of these multi-cell tubes.

Crushing performances and crashworthiness optimization of polygonal double tubes under multiple angle loadings

Crushing performances and crashworthiness optimization of polygonal double tubes under multiple angle loadings

United composite strength calculation method for special-shaped CFST columns with multiple cavities

The present study investigates the method of calculating the composite strength of special-shaped concrete-filled steel tube (CFST) members with multiple cavities. Based on the research findings of CFST unified theory and some tests, a quantitative method to evaluate the concrete constraint effect is proposed for cross-sectional shapes ranging from regular triangles, squares…regular octagons to circles. The cross-sectional composite strength of regular polygonal CFST members is determined by the way dividing the concrete into effective and ineffective constraint regions, discounting constraint coefficients, and applying unified formulas. Additionally, a regression analysis is conducted to establish the relationship between interior angles and constraint effects. Subsequently, using quadrangle CFSTs as an example, this study investigates the relationship between cross-sectional regularity and constraint effect, and proposes a composite strength calculation method related to it. Finally, the special-shaped multi cavity cross section is separated into several simple polygonal cross sections, taking into account shape efficiency and regularity, to calculate the composite strength of each cavity CFST member and summarize them for determining the total axial compressive bearing capacity. The research findings indicate that a linear relationship exists between the interior angle of the cross section and the initial tangent line angle of the second-degree curve, which serves as the boundary between effective and ineffective constraint regions in regular polygonal steel tube confined concrete. The proposed unified composite strength calculation method, specifically designed for special-shaped CFST columns with multiple cavities, can accurately predict their actual strength.

Partially curved-wall polygonal tube with multi-phase plateau force under quasi-static loads

The plateau force is an important factor affecting the performance of energy absorber. In this paper, a partially curved-wall polygonal tube (PCPT) is proposed by studying the relationship between the section shape and the force–displacement response of hexagonal and circular tubes. According to the different contact modes in the deformation process, PCPT can be divided into curved wall phase and straight wall phase. The stiffness, plateau force and the transition position of the curved wall phases can be regulated by the ovality h and the straight wall angle β. The multi-straight wall design makes the straight wall phase of PCPT have stepped plateau force, which improves the energy absorption. The desired plateau force characteristics can be obtained through parameter adjustment, such as stable plateau force. As an energy absorber, PCPT has excellent designability.

Static behavior of TOBs bolted endplate connection to strengthened HSST with fixed thread length

Five thread-anchored one-side bolts connected endplate connections to Hollow Square Steel Tube (TOBEC-HSSTs) with various strengthening measures were tested to investigate the structural performance under monotonic loads. The thread anchored length was 1.2 times the bolt diameter for all specimens. The connection behaviour were influenced by the endplate thicknesses and the strengthening measures (i.e. the internal polygonal tube, the internal polygonal tube with infilled concrete, and the cross-H section stiffener with infilled concrete). The failure patterns, moment-rotation curves, and strain response of joints were obtained through tests. It was found that (1) 1.2 times the bolt diameter was taken as the safe thread assembled length, which can avoid the premature failure of hole threads not before the fracture of other components under monotonic loads. (2) The presence of the infilled concrete can improve the rigidity and strength of the connection by 84% and 23%, respectively, compared to the reference joint without the infilled concrete, and the thickness of the column wall can be reduced when the concrete was infilled into hollow steel tube. (3) For the connections with thin endplates, the cross-H section stiffener exhibited 8.8% and 3.5% higher preliminary stiffness and yield bending moment than the inner polygonal tube, but the cross-H section stiffener had 14.3% lower rotation capacity. (4) Thickening endplates can change the failure modes of the connections to beam plastic hinge formation, enhance the preliminary stiffness and yield bending moment of joints by 2.4% ∼11%, but decrease the rotation capacity of joints by 54% compared to thin endplates. Based on experimental results, the calculation methods of the bending moment bearing capacity for TOBEC-HSSTs considering the strengthening effect of internal stiffeners and infilled concrete under different failure patterns were proposed with errors no greater than 15%.

A new species of the mysterious genus Spirodiscus (Annelida: Serpulidae) of the eastern Australian abyss

In May–June 2017 an expedition on board RV Investigator sampled benthic communities along the lower slope and abyss of Australia’s eastern margin from off mid-Tasmania to the Coral Sea. Over 200 annelids of the family Serpulidae collected during the voyage were collected and deposited in the Australian Museum in Sydney. Among them there was a new species of the poorly known abyssal (3754–4378 m) genus Spirodiscus. Serpulids typically build cylindrical calcareous tubes attached to hard substrates. Until now, only three serpulid species inhabiting free-lying polygonal tubes were reported from the deep sea: Spirodiscus grimaldii Fauvel, 1909 with quadrangular spirally coiled tubes, Bathyditrupa hovei Kupriyanova, 1993 with quadrangular tusk-shaped tubes, and Spirodiscus groenlandicus (McIntosh, 1877) with octagonal tusk-shaped tubes. The new species, S. ottofinamusi sp. nov. has very characteristic thin tusk-shaped unattached fluted tubes similar to those found in S. groenlandicus, but it differs by the details of collar, thoracic tori and abdominal chaetae. Morphologically, it has a pinnulated opercular peduncle and flat geniculate abdominal chaetae like filogranin serpulids but lacks thoracic Apomatus chaetae like serpulins. The first DNA sequences of this mysterious taxon places the new species within the filogranins in sister group relationship with Chitinopoma serrula.

Study and optimization of energy absorption characteristics of a new concave polygon tube

To improve the energy absorption characteristics of the traditional convex polygonal tube and the existing concave polygonal tube, a new evolutionary scheme for the concave polygonal tube was proposed. The energy absorption characteristics of different concave tubes evolved from the common scheme (Scheme-I) and the new evolution scheme (Scheme-II) were studied through quasi-static compression experiments and numerical simulations. The results show that under the same mass, the concave polygonal tube evolved by Scheme-II has better energy absorption characteristics. The folded half-wavelength is smaller at the same compression distance, and compared with the traditional pentagon tube, the energy absorption (EA) of the pentagon concave of Scheme-II (N5E-CT) is improved by 218%, and the crushing force efficiency (CFE) is improved by 69%. Secondly, the mean crushing force of convex and concave tubes is derived and verified by the folded element theory. The mode of deformation of concave tubes under different structural sizes was investigated, and the size range within which the concave tube can remain stable was obtained. In addition, the evolution of the specific energy absorption (SEA) of the concave tubes was explored, and the SEA and the number of structural sides (N) show a trend of first increasing and then decreasing. Finally, the multi-objective optimization of the pentagon concave tube with excellent energy absorption characteristics was conducted, and the initial peak crushing force of the optimized structure was reduced by 19.92%.

Experimental and numerical studies of concrete-filled corrugated steel tubular column under axial compression

This paper proposed a novel composite structure of concrete-filled corrugated steel tubular column with polygonal steel tubes (CFCST-PST), which consisted of concrete and multi-cell steel tubular column, includingpolygonalsteeltubesandcorrugatedsteelplates. This new column enables the confinement of multi-cell steel tubular column to the core concrete in addition to preventing local buckling of the tubes. To investigate the axial compression mechanical properties of the column and the capabilities of polygonal steel tubes, a concrete-filled corrugated steel tubular column with square steel tubes (CFCST-ST) was designed and fabricated as a comparative specimen. Axial compression experiments and finite element studies (FEM) were carried out on both CFCST-PST and CFCST-ST specimens. Through the previous research, it was found that CFCST-ST has better ductility and higher bearing capacity, while the corrugated plate with higher lateral stiffness, so that concrete is well restrained. In this paper, research had revealed that CFCST-PST effectively expands the strongly confined area of core concrete, as compared to CFCST-ST. A detailed discussion of the strain development of the corrugated plates was presented in order to demonstrate the confinement effect. Finally, the method of confining stress homogenization was used to establish formulas for calculating the axial compression load capacity of CFCST-PST for engineering purposes.

Numerical Investigation on the Axial Load Behaviour of Polygonal Steel Tube Columns

Hollow steel tubes members with different properties are being increasingly used for structural applications, such as columns in frame structures, roof structures, truss columns, and other applications. These structural members are primarily subjected to compressive and flexural loading. Due to the insufficient studies regarding the influence of the cross-section’s shapes on the axial load behaviour of hollow steel columns, this study has presented eight different cross-sections shapes and has indicated their effect on the axial load behaviour of the polygonal hollow steel columns. Eighty different FE models have been designed and analysed to find the effect of the cross-section shape, thickness, length, and materials on the axial load behaviour of the polygonal hollow steel columns. The FE results have proved that the cross-sectional shapes affect the ultimate axial load behaviour of the hollow steel tubes by 14%. The highest ultimate axial load resistance recorded by Rec. model has been followed by Squ. unlike Cir. model, which has presented the lowest ultimate axial load resistance followed by Ova. model. This study also demonstrates that when the cross-sectional shape of the hollow steel tubes is near to a rectangular shape, the ultimate axial load resistance will be higher, while, if it is near to a circular shape then low ultimate axial load has been registered. Moreover, there is a small effect of the steel tube thickness, length and material on the axial load behaviour of the hollow steel tubes with different cross-sectional shapes, with almost -2% to -14%.

Experimental study on cyclic behavior of thread-fixed one-side bolts bolted endplate connection to strengthened concrete filled square steel tube with fixed thread length

This paper presented the experimental results of the Endplate Connection to Concrete Filled square Steel Tube (ECCFST) with fixed thread length via Thread-fixed One-side Bolts (TOBs) under cyclic loading. Two stiffening strategies, namely the internal polygonal tube stiffener and the cross-H section stiffener, with two stiffener flange thicknesses (18 mm and 14 mm) corresponding to two column wall thicknesses (6 mm and 10 mm), respectively, were proposed to strengthen the panel zone of the connections. Failure modes occurring for the connections were mainly affected by the weakest component of the joint region. Besides, the moment-rotation hysteretic curves and seismic performance of the joints were compared and analyzed. For all cases with fixed thread anchored length, the TOBs performed well and no thread failure occurred under the repeated reversal loading. Test results revealed that the mechanical performance of the joints can be ameliorated by adopting the strengthening components especially the cross-H section stiffener, which effectively limited the tube wall deformation from transferring the force to the opposite tube wall through the web of the stiffener. The rotation capacity and ductility of ECCFSTs were satisfactory and can meet the ductility limitation with regard to FEMA-350, demonstrating a potential for ECCFSTs in practical application.

Seismic behavior of TOBs bolted endplate connection to strengthened CFST column

When using the Thread-anchored One-side Bolts (TOBs) which are a type of one-side bolts anchored through the tube wall hole threads instead of the nuts, the conventional Concrete Filled square Steel Tube (CFST) with the limited wall thickness fails to provide the sufficient thread anchored length to resist the tensile force of TOBs. Meanwhile, the joint region of the relatively thin tube wall is prone to deform outward to a large degree, which is crucial to the safety of the whole structure. To solve the above issues, in this work an experimental investigation on TOBs bolted Endplate Connection to strengthened CFST (TOBEC-CFST) under cyclic loads is conducted by putting a stiffener inside the CFST. Six specimens were designed to study the effects of following parameters: (a) stiffener type (the inner polygonal tube stiffener or the cross-H section stiffener); (b) thread anchored length (18 mm and 24 mm); and (c) bolt diameter (M16, M20 and M22). The experimental results revealed that the hole thread fracture can be avoided by increasing the stiffener flange thickness to extend the hole thread length and the inner stiffener can improve the behavior of the panel zone of the connection. Compared to the inner polygonal tube stiffener, the cross-H section stiffener can effectively enhance the overall integrity of the connection because of the presence of the web transferring force directly to the opposite tube wall, contributing to a higher bearing capacity and energy dissipation capacity of the joints. Increasing the bolt diameter can improve the bearing capacity and energy dissipation capacity of TOBEC-CFSTs, but the degree of the improvement does not increase linearly with bolt diameter. Based on test results, to enhance the overall mechanical behavior of TOBEC-CFSTs in seismic zones, the cross-H section stiffener is recommended provided for sufficient thread length.

Binding of curvature-inducing proteins onto biomembranes

In this paper, we review the theoretical analyses and simulations of the interactions between curvature-inducing proteins and biomembranes. Laterally isotropic proteins induce spherical budding, whereas anisotropic proteins such as Bin/Amphiphysin/Rvs (BAR) superfamily proteins, induce tubulation. Both types of proteins can sense the membrane curvature. We describe the theoretical analyzes of various transitions of protein binding accompanied by a change in various properties, such as the number of buds, the radius of membrane tubes, and the nematic order of anisotropic proteins. Moreover, we explain the membrane-mediated interactions and protein assembly. Many types of membrane shape transformations (spontaneous tubulation, formation of polyhedral vesicles, polygonal tubes, periodic bumps, network structures, etc.) have been demonstrated by coarse-grained simulations. Furthermore, traveling waves and turing patterns under the coupling of reaction-diffusion dynamics and membrane deformation are described.

Improving the crashworthiness of bio-inspired multi-cell thin-walled tubes under axial loading: Experimental, numerical, and theoretical studies

Bio-inspired thin-walled structures are widely applied in the engineering field to improve energy-absorption performance. In this study, the axial crushing resistances with large plastic deformation of polygonal single-cell (PSC) and novel bio-inspired polygonal multi-cell (BPMC) thin-walled tubes were investigated using comprehensive experimental, numerical, and theoretical methods. Combining the biological characteristics of plant stems and the mechanical properties of thin-walled structures, BPMC tubes were introduced based on the structural characteristics of horsetails formed from two straight polygonal tubes with the same cross-sectional shapes, which were connected by several ribs at the corners. A total of 108 design conditions were considered, including nine cross-sectional shapes with different scales and two different thicknesses. Quasi-static experiments were performed to study the energy-absorption characteristics of thin-walled tubes with different multi-cell and multi-corner configurations. Nonlinear explicit finite element analysis (EFEA) was employed to simulate the crushing behavior. Theoretical models were established to analyze the large deformation mechanism, and expressions were derived to predict the mean crushing force (Fm), special energy absorption (SEA), crushing force efficiency (CFE), and corresponding normalized parameters. The results of the theoretical models were highly consistent with the experimental and numerical results. Finally, using the optimization function fmincon, a BPMC-20 tube with a scale number of 0.35 was selected as the better energy absorber. The normalized mean crushing force (NFm) of the optimal BPMC-20 tube was 1.64 and 8.30 times larger than that of the BPMC-10 and PSC-10 tubes, respectively. In conclusion, the energy-absorption characteristics of the structure could be significantly improved by adding ribs at the corners. Furthermore, the introduction of the novel BPMC tube could effectively improve the crashworthiness of the structure, thereby serving as a potential candidate for future crashworthiness applications.

Ultrastructure of setae of a planktonic diatom, Chaetoceros coarctatus

Silica frustules of most planktonic diatoms have many shallow holes in which the length (L) is smaller than the width (W). The present study focuses on a silica ultrastructure of setae of a planktonic diatom having deep (L/W > 1) holes. Here, we characterized microscopically patterned nanoholes on the silica walls of thick, robust, and hollow setae of a colony of Chaetoceros coarctatus. Basically, tetragonal poroid arrangements with and without a costa pattern are observed on the inner and outer surfaces, respectively, for three kinds of curving hollow setae attached to the anterior, intercalary, and posterior parts of the colony. The seta structures including specific poroid arrangements and continuity of deep nanoholes depend on the location. The deep nanoholes ∼90 nm wide are elongated from 150 to 1500 nm (L/W ∼17) with an increase in the wall thickness of the polygonal tubes of the setae. The inside poroid array, with a period of 190 nm in the extension direction of setae, is lined by parallel plates of the costae. However, the poroid arrangement on the outer surface is disordered, with several holes obstructed with increasing wall thickness of the posterior terminal setae. According to the movement of a colony in a fluid microchannel, the thick curving terminal setae is suggested to involve attitude control and mechanical protection. Using an optical simulation, the patterned deep through-holes on the intercalary setae were suggested to contribute anti-reflection of blue light in the wavelength range of 400 to 500 nm for the promotion of photosynthesis in seawater.