Single-layer Tube Research Articles

Crashworthiness analysis of bio-inspired hierarchical multi-cell circular tubes under axial crushing

Drawing inspiration from nature’s hierarchical organization, we propose a novel bio-inspired hierarchical multi-cellular circular tubes (BHMC) with a fractal structure. Using an experimentally validated LS-DYNA finite element model, we investigated the impact resistance of this structure under axial loading. Numerical analysis was conducted to explore the energy absorption performance of BHMC tubes with varying numbers of branches, fractal orders, and tube masses. The numerical findings indicate that specific energy absorption (SEA) increases with higher numbers of fractal orders. Specifically, the SEA of 2nd order BHMC tubes surpasses that of conventional multicellular circular and single-layer tubes by approximately 35.07% and 17.10%, respectively. Optimal performance is achieved with the proposed structure featuring tree branching (N = 6) and 2nd order fractal characteristics, yielding the highest specific absorption energy across different parameters. These results offer valuable insights for designing multicellular bilayer tubes with superior energy absorption efficiency, providing an effective guideline for structural optimization.

Critical Velocities of Single-layer and Two-layer Composite Tubes of Transversely Isotropic Materials Based on a Potential Function Method in 3-D Elasticity

Abstract Critical velocities of a single-layer tube of a transversely isotropic material and a two-layer composite tube consisting of two perfectly-bonded cylindrical layers of dissimilar transversely isotropic materials are analytically determined using the potential function method of Elliott in three-dimensional (3-D) elasticity. The displacement and stress components in each transversely isotropic layer of the tube subjected to a uniform internal pressure moving at a constant velocity are derived in integral forms by applying the Fourier transform method. The solution includes those for a tube composed of two dissimilar cubic or isotropic materials as special cases. In addition, it is shown that the model for the two-layer composite tube can be reduced to that for the single-layer tube. Closed-form expressions for four critical velocities are derived for the single-layer tube. The lowest critical velocity is obtained from plotting the velocity curve and finding the inflection point for both the single-layer and two-layer composite tubes. To illustrate the newly developed models, two cases are studied as examples – one for a single-layer isotropic steel tube and the other for a two-layer composite tube consisting of an isotropic steel inner layer and a transversely isotropic glass-epoxy outer layer. The numerical values of the lowest critical velocity predicted by the new 3-D elasticity-based models are obtained and compared with those given by existing models based on thin- and thick-shell theories.

Design and mechanical properties analysis of a cellular Waterbomb origami structure

Cellular structures are commonly used to design energy-absorbing structures, and origami structures are becoming a prevalent method of cellular structure design. This paper proposes a foldable cellular structure based on the Waterbomb origami pattern. The geometrical configuration of this structure is described. Quasi-static compression tests of the origami tube cell of this cellular structure are conducted, and load-displacement relationship curves are obtained. Numerical simulations are carried out to analyze the effects of aspect ratio, folding angle, thickness and number of layers of origami tubes on initial peak force and specific energy absorption (SEA). Calculation formulas for initial peak force and SEA are obtained by the multiple linear regression method. The degree of influence of each parameter on the mechanical properties of the single-layer tube cell is compared. The results show that the cellular structure exhibits negative stiffness and periodic load-bearing capacity, as well as folding angle has the most significant effect on the load-bearing and energy-absorbing capacity. By adjusting the design parameters, the stiffness, load-bearing capacity and energy absorption capacity of this cellular structure can be adjusted, which shows the programmable mechanical properties of this cellular structure. The foldability and the smooth periodic load-bearing capacity give the structure potential for application as an energy-absorbing structure.

A comparative analysis of the performance of backfill heat exchangers in deep mine geological environments

With the increase of mineral mining depth, the technologies of constructing heat exchanger in stopes to exploit geothermal resources from deep mines have received great attention. The heat extraction capacities of heat exchangers are closely related to the geological environments of deep mines, especially backfill mines. Therefore, a three-dimensional unsteady heat transfer and seepage coupling model of backfill heat exchangers (BFHEs) is created and verified in this work using COMSOL simulation software. Then, the influences of geological environments, involving groundwater seepage, initial temperature and thermal conductivity of surrounding rock etc., on the ability of five BFHEs with the equal buried tube length to extract heat in different configurations are investigated by this model. The findings indicate that groundwater flow can significantly improve the performance of BFHEs. Double-layer tube BFHEs have the best overall performance in the studied seepage velocity range. Only when there is no or little seepage is the performance of single-layer tube BFHEs equivalent to that of double-layer tube BFHEs. The heat extraction capacity of BFHEs is greatly improved under seepage conditions with the increase in the initial temperature of surrounding rock, although the impact is low in the absence of groundwater seepage. The benefit of backfill body's thermal conductivity on BFHEs' ability to transport heat is significantly greater than that of surrounding rock, but the effect becomes smaller as the value increases. Further increasing the thermal conductivity of the backfill body will not considerably increase the heat extraction capability of BFHEs after it reaches 2.5 (W·m−1·K−1). Therefore, if the cost is too high, continued enhancement is not recommended. The findings offer theoretical recommendations for optimizing BFHEs’ setup to better adapt to deep mine geological environments and increase geothermal extraction capability.

Digital twins for the rapid startup of manufacturing processes: a case study in PVC tube extrusion

In this work, a soft sensor–based digital twin (DT) was developed to reduce the startup time in manufacturing plastic tubes and enable real-time product quality monitoring, i.e., the weight per unit length and the inner and outer diameters of the tube. An experimental campaign was conducted on a real tube extrusion line using three polyvinyl chloride (PVC) compounds and different process conditions, and machine learning regression algorithms were trained and tested to create the models of the extruder and the extrusion die the DT is based on. The characterization of the considered material, whose properties were given as input to the digital models, was carried out according to a procedure based only on the data collected by the production line. The DT was tested for the startup of the production of a single-layer tube and allowed to achieve the specified customer requirements (thickness and weight) in a few minutes. The proposed solution thus proved to be a valuable tool for reducing the setup time, thus increasing the efficiency of the process.

Limit and shakedown analysis of double-layer tube considering different material properties

This paper is devoted to the maximum bearing capacity of double-layer tubes subjected to monotonic and cyclic loading, within the framework of static limit and shakedown analysis. The double-layer tube comprises inner and outer layers made of different materials, both obeying the von Mises criterion. The effects of different geometric dimensions (thickness and volume fraction) and material properties (elastic modulus, Poisson’s ratio, and yield stress) on the effective mechanical behavior are studied analytically and numerically. The results indicate that the bearing capacity of the double-layer tube under monotonic load reaches its maximum value when both inner and outer layers reach their elastic or plastic limits simultaneously. The computation of plastic and shakedown limits are presented, divided into different cases by considering the volume fraction of the inner and outer layers. The double-layer structure under cyclic loads may fail due to fatigue and excessive deformation mechanisms of the inner or outer layers at the first cycle. Only when both layers fail due to fatigue simultaneously, the shakedown limit of the structure reaches its maximum value. Compared to a single-layer tube, the long-term strength of the double-layer tube can be significantly improved by applying appropriate geometric dimensions and materials in fabrication.

Paper-folding-based terahertz anti-resonant cavity.

Recently, the concept of core-anti-resonant reflection (CARR) has been proposed, greatly expanding the options of cladding materials and morphologies for Fabry-Perot-type (F-P) cavities. For instance, a single-layer tube made of A4 paper can be a precision resonator in the terahertz (THz) band, which seemed counterintuitive before. More importantly, thanks to the involvement of paper-like materials as the cavity plates, it is possible to equip the CARR cavity with the currently popular origami functionality. Following this clue, in this work we combined a simple octagonal paper tube with different origami patterns and realized the programmable adjustment for the distance between two parallel surfaces of the tubular cavity. Accordingly, the combination of the CARR cavity and the origami property offers a new degree of freedom and flexibility to vary the cavity distance, tune the resonant frequency, and explore related applications. For applied examples, we carried out pressure sensing with this foldable structure and achieved a high sensitivity (S = 57.9 kPa-1). Meanwhile, the origami cavity could also act as a THz polarization converter, and the output polarization state of the cavity mode was easily modulated from the original linear to circular polarizations with different chiralities. In future works, besides the pressure-driven method used here, heat and magnetism, etc., can further be employed to tune the CARR cavity, benefiting from four dimensional (4D) or soft-magneto origami materials as the cavity wall.

Design optimization of lightweight structures inspired by the rostrum in Cyrtotrachelus buqueti Guer (Coleoptera: Curculionidae)

The rostrum of Cyrtotrachelus buqueti Guer has excellent mechanical properties, such as high-specific strength and high-specific stiffness, and it is an example of successful evolution in nature. In this paper, based on the biological structural characteristics of the rostrum, bionic variable-density lightweight structures of varying layer number are designed, and their mechanical properties are analyzed under different helix angles. The results show that when the helix angle is greater than or equal to 40°, the maximum compressive load borne by the three-layer tube is 30.75 N, which is 1.89 times that of the single-layer tube. Through calculation, at a helix angle of 15°, the torsion lightweight coefficient of the single-layer, double-layer, and three-layer structures is 0.99 ± 0.03 N·M g−1, 1.75 ± 0.05 N·M g−1, and 2.32 ± 0.06 N·M g−1, respectively, where that of the three-layer structure was approximately 2.34 times that of the single-layer structure. Further calculations show that the bending lightweight factor of the single-layer, double-layer, and three-layer tubes is 17.89 ± 0.20 N g−1, 33.16 ± 0.45 N g−1, 41.33 ± 0.55 N g−1, respectively, where that of the three-layer tube is 2.31 times that of the single-layer tube. In addition, this paper also investigates the cushioning energy absorption characteristics of the bionic lightweight tubes by using an impact testing machine. The results show that under the same conditions, as the number of layers of the lightweight tube increases, the buffering energy absorption also increases. The total energy absorption and specific energy absorption of the three-layer lightweight tube are approximately 10 times those of the single-layer tube. Finally, a response surface-based optimization method is proposed to optimize the bionic structures under a combined compression-torsion load. The results lay the foundation for the lightweight design of thin-walled tube structures.

Machine learning prediction of mechanical properties of braided-textile reinforced tubular structures

Braided-textile composites have been applied in various engineering fields and used for high-efficiency energy absorbers to meet different loading requirements. However, it’s difficult to accurately forecast the mechanical properties of these braided-textile composites based on theoretical method, which is a big obstacle to the precise design of the energy-absorbing structure. In this research, carbon fiber reinforced composite (CFRC) tubular structures were fabricated by two-dimensional braided textiles, and 160 groups of orthogonal axial compression experiments were carried out.Axial compression behaviors of CFRC tubular structures, including peak force, mean crushing force, energy absorption, specific energy absorption, elastic modulus and other relevant parameters, were tested and collected in a database. The feed forward back propagation (FFBP) algorithm based on artificial neural network (ANN), as an algorithm with high convergence accuracy in machine learning (ML), was adapted to build a prediction model to forecast the overall axial compression properties of those CFRC tubular structures uncollected in the database. By a series of error analyses, the ML method was proven to have high accuracy in predicting the relevant mechanical properties within the range of orthogonal design groups. Although the relative error of marginal sample data (especially single-layer tubes) is large, the mean absolute error (MAE) of training set and test set is only about 5% and 10%, respectively. Our work demonstrates the potential of machine learning methods in predicting the overall mechanical properties and guiding the design of composite materials.

Multi-layer hollow-core PMMA grating tube waveguides for THz sensing applications

Multi-layer hollow-core PMMA tube waveguides with varying grating structures were theoretically and experimentally investigated for the terahertz (THz) chemical material sensor applications. Compared with single-layer tube, the multi-layer cases can produce a delayed response in the time domain with an improved extinction ratio. A double tube combination consisted of a thick double-groove chirped grating tube and a thin single-groove chirped grating one can realize an improved detection sensitivity. With different extinction ratio of the measured THz spectra, ethanol and vinegar can be distinguished with a sensitivity of about 18 dB/mL. The proposed multi-layer hollow-core grating waveguide can be further applied for the THz gas sensing applications.

Prevention of localized bulging in an inflated bilayer tube

This paper studies the bifurcation behavior in an inflated bilayer tube of arbitrary thickness under inflation and uni-axial extension. It is assumed that both layers are composed of the Gent material with each layer having its own Jm, where Jm is a material parameter in the Gent model that signifies the maximum extensibility. First, we determine several critical parametrical regions where localized bulging disappears for a single-layer tube. Then we investigate localized bulging in an inflated bilayer tube, where one layer (layer I) of the tube cannot bulge whereas the other part (layer II) can. Surprisingly, we find that such a composite tube is still susceptible to localized bulging and localized bulging can be prevented only if the proportion of layer I exceeds a critical value, no matter whether layer I occupies the inner side or the outer side. Even for a very thin bilayer tube, the same feature holds. The cases of fixed axial force and fixed axial stretch are both studied, and the critical geometrical parameters marking the transition between bulging and no bulging are determined. Moreover, we carry out a numerical analysis by use of the finite element method to verify the applicability of an explicit bifurcation condition and the predicted bifurcation behavior. This paper offers a possible way to avoid bulging formation in a cylindrical tube while retaining moderate extensibility.

Analysis of multilayer electro-active tubes under different constraints

Dielectric elastomers are an emerging class of highly deformable electro-active materials employed for electromechanical transduction technology. For practical applications, the design of such transducers requires a model accounting for insulation of the active membrane, non-perfectly compliant behavior of the electrodes, or interaction of the transducer with a soft actuated body. To this end, a three-layer model, in which the active membrane is embedded between two soft passive layers, can be formulated. In this article, the theory of non-linear electro-elasticity for heterogeneous soft dielectrics is used to investigate the electromechanical response of multilayer electro-active tubes—formed either by the active membrane only ( single-layer tube) or by the coated active membrane ( multilayer tube). Numerical results showing the influence of the mechanical and the geometrical properties of the soft coating layers on the electromechanical response of the active membrane are presented for different constraint conditions.

A Novel Steerable Single Layer Tubes of Surgcial Manipulator Based on Ni-Ti Alloy

Objective Minimally Invasive Surgery (MIS) requires armamentarium with high positioning accuracy and maneuverability. At the same time, the equipment need have more functions and smaller size, it can reduce patient’s operative incision and pain perception when in operating can still keep steerability and stability. Method. Traditional design with multi-tubes assemabled, we designed a new stucture which just have single layer tube Results Finite element method can analysis this model which designed by another 3D drawing software in different size, varied exteral force can conclude that the angle of end deformation. 3D model adopted the isometric atom with nickel titanium alloy we take advantage of Ni-Ti alloy’s superelasticity which can recover to orignal shape in recoverable deformation interval, realise proximal end control distal end.

Experimental and numerical analysis on bilayer tube forming

Moving deeper into the twenty-first century, lightweight construction has become a central principle in component design in industry-wide efforts towards increasing vehicle fuel economy to maintain adherence to tighter government environmental standards. To achieve new levels of weight reduction in components, simplistic materials are being replaced with compound materials and composites such as tailored blanks and multi-layered materials or ‘hybrid’ components when dissimilar materials are used together (metal and plastic polymer, for example). Usage of these new composite materials has been observed to yield lower component weights as well as the same or higher performance as conventional materials. To investigate this further, conical flaring of a hybrid, bilayer tube comprising an interior metal tube surrounded by an exterior polymer tube is considered. For experimentation, a steel inner tube was used with a PVC exterior tube. In testing, the formability of the steel tube was observed to have increased with the implementation of the exterior PVC layer in comparison to single layer tubes comprised of steel alone. Observation and analysis of this behavior pointed towards the contact stress of the two materials increasing the formability and delaying the failure. Beyond the scope of observing the flare, another property of the bilayer tube was that the addition of the PVC layer reduced the collapse of the steel tube adjacent to the flared region, which remained undeformed. The results of experimentation confirm that the hybrid component outperforms its conventional counterpart by exhibiting higher formability, lower stress in the flared region, and better overall structural integrity of the specimens after being flared.

The vertebrate heart: an evolutionary perspective.

Convergence is the tendency of independent species to evolve similarly when subjected to the same environmental conditions. The primitive blueprint for the circulatory system emerged around 700-600 Mya and exhibits diverse physiological adaptations across the radiations of vertebrates (Subphylum Vertebrata, Phylum Chordata). It has evolved from the early chordate circulatory system with a single layered tube in the tunicate (Subphylum Urchordata) or an amphioxus (Subphylum Cephalochordata), to a vertebrate circulatory system with a two-chambered heart made up of one atrium and one ventricle in gnathostome fish (Infraphylum Gnathostomata), to a system with a three-chambered heart made up of two atria which maybe partially divided or completely separated in amphibian tetrapods (Class Amphibia). Subsequent tetrapods, including crocodiles and alligators (Order Crocodylia, Subclass Crocodylomorpha, Class Reptilia), birds (Subclass Aves, Class Reptilia) and mammals (Class Mammalia) evolved a four-chambered heart. The structure and function of the circulatory system of each individual holds a vital role which benefits each species specifically. The special characteristics of the four-chamber mammalian heart are highlighted by the peculiar structure of the myocardial muscle.

In vitro assembly of the Rous Sarcoma Virus capsid protein into hexamer tubes at physiological temperature

During a proteolytically-driven maturation process, the orthoretroviral capsid protein (CA) assembles to form the convex shell that surrounds the viral genome. In some orthoretroviruses, including Rous Sarcoma Virus (RSV), CA carries a short and hydrophobic spacer peptide (SP) at its C-terminus early in the maturation process, which is progressively removed as maturation proceeds. In this work, we show that RSV CA assembles in vitro at near-physiological temperatures, forming hexamer tubes that effectively model the mature capsid surface. Tube assembly is strongly influenced by electrostatic effects, and is a nucleated process that remains thermodynamically favored at lower temperatures, but is effectively arrested by the large Gibbs energy barrier associated with nucleation. RSV CA tubes are multi-layered, being formed by nested and concentric tubes of capsid hexamers. However the spacer peptide acts as a layering determinant during tube assembly. If only a minor fraction of CA-SP is present, multi-layered tube formation is blocked, and single-layered tubes predominate. This likely prevents formation of biologically aberrant multi-layered capsids in the virion. The generation of single-layered hexamer tubes facilitated 3D helical image reconstruction from cryo-electron microscopy data, revealing the basic tube architecture.

Design and analysis on fume exhaust system of blackbody cavity sensor for continuously measuring molten steel temperature

Fume exhaust system is the main component of the novel blackbody cavity sensor with a single layer tube, which removes the fume by gas flow along the exhaust pipe to keep the light path clean. However, the gas flow may break the conditions of blackbody cavity and results in the poor measurement accuracy. In this paper, we analyzed the influence of the gas flow on the temperature distribution of the measuring cavity, and then calculated the integrated effective emissivity of the non-isothermal cavity based on Monte-Carlo method, accordingly evaluated the sensor measurement accuracy, finally obtained the maximum allowable flow rate for various length of the exhaust pipe to meet the measurement accuracy. These results will help optimize the novel blackbody cavity sensor design and use it better for measuring the temperature of molten steel.

Electrical, structural and thermal studies of carbon nanotubes from natural legume seeds: kala chana

ABSTRACTCarbon nanotubes (CNTs) are the carbon materials measured at nanoscale level and they are defined in two types according to the number of concentric layers, i.e. single-layer tube is single-walled nanotubes, while multi-layer tube structure is called multi-walled nanotubes. The green method synthesis for the preparation of CNTs begins with the smashing of legume seeds kala chana, and then they form complex with cobalt salt. Desiccation of the complex compound forms cobalt salt and seed protein. The complex is then decomposed at 625 ºC in muffle furnace for 20 min. Purification of the decomposed sample is done through acid wash treatment and dried in vacuum oven. The confirmations of CNTs are done by nuclear magnetic resonance and Fourier transform infrared, which analyzes the denatured protein, reacted to the metal salt. X-Ray diffraction determines the MWNTs with transmission electron microscope (TEM) reports the network structure of CNTs. thermal gravimetric analysis (TGA)–differential thermal analysis (DTA)–thermogravimetric analysis (DTG) tests the amount of sample under thermal treatment. Vibrating sample magnetometer determines the paramagnetic nature of CNTs. CNTs thus prepared can be used in mechanical fields, in solar cells, in electronics fields, etc. because of their multidisciplinary properties. The synthesized CNTs are eco-friendly in nature, prepared by the legume seed natural precursor.

Optimization of the rheology and sintering behavior of electrolyte and anode pastes to be used in co-extrusion of solid oxide fuel cells

Typical electrolyte paste including Yittria Stabilized Zirconia (YSZ) and anode paste containing YSZ, NiO, starch/activated carbon (pore former) were prepared. In order to perform co-extrusion process the pastes must have nearly same rheological properties. So, the prepared pastes unified in order to have same rheological characteristics using the Benbow–Bridgwater model. The unification results showed a linear relationship between the required liquid content for paste preparation and weight percentage of NiO powder in unified pastes. Such a linear relationship can be used to predict the required liquid content of the intermediate anode pastes. The unified pastes were extruded as single layer tubes and sintered at various experimental conditions. Micro-structural features of the sintered tubes were investigated using Scanning Electron Microscope (SEM) and optimum sintering temperature and time were found as 1450 °C and 2 h, respectively for full electrolyte densification. Moreover, 30 wt% of carbon may be regarded as the optimum carbon content for creating enough porosity in the anode layers.

중공품 성형시 삼중관의 액압성형성에 미치는 압력경로의 영향

Tube hydroforming is a technology that utilizes hydraulic pressure to form a tube into desired shapes inside die cavities. Due to its advantages, such as weight reduction, increased strength, improved quality, and reduced tooling cost, single-layered tube hydroforming is widely used in industry. However in some special applications, it is necessary to produce multi-layered tubular components which have corrosion resistance, thermal resistance, conductivity, and abrasion resistance. In this study, a hollow forming process to fabricate a part from multi-layered tubes for structural purposes is proposed. To accomplish a successful hydroforming process, an analytical model that predicts optimal load path for various parameters such as tube material properties, thickness of tubes, diameter of holes and the number of holes was developed. Tubular hydroforming experiments to fabricate a hollow part were performed and the optimal loading path developed by the analytical model was successfully verified. The results show that the proposed hydroforming process can effectively produce hollow parts with multi-layered tube without defects such as wrinkling or fracture.