Double Circular Tube Research Articles

Design of hierarchical multi-cell double circular tubes thin-walled structures for energy absorption

This study aims to investigate the crashworthiness performance of a novel hierarchical multi-cell double circular tubes (HMDC) structure under axial impact. Various dual-tube structures of different cross-sections were designed. The effects of hierarchical order, peak number of the core column, and inner circle diameter on the structure were analyzed using Abaqus finite element analysis. The results indicate that in dual-tube structures, replacing the traditional multi-cell structure with a hierarchical multi-cell structure in the interlayer significantly improves energy absorption (EA) characteristics. With the inner circle diameter of the HMDC fixed at 20 mm, the ratio of mean crushing force (MCF) to peak crushing force at the third order increased by 70.70% and 35.68% compared to the first and second orders, respectively. Experimental results and finite element results show that the initial peak value differed by 1.47%, indicating a close match between the experimental and simulation results. The parametric study shows that the inner circle diameter and the peak number of the core column significantly affect EA. The findings of this study provide effective guidance for designing multi-cell dual circular tubes with high EA efficiency.

Energy absorption investigation of SFRFC-filled double circular tubes under quasi-static compression and low velocity impact loading

The filled thin-walled tube (FTT) is a common energy absorption device, which consists of two important parts: filled materials and thin-walled tubes. According to existing researches, the filled materials significantly influence the mechanical properties of FTTs, especially the energy absorption capacity. In this study, a novel design of FTTs is proposed and studied, which adopts the double aluminum (Al) pipe and is filled with the steel fiber reinforced foamed concrete (SFRFC). Firstly, specimens with different steel fiber contents of 0, 0.5, 1, 1.5, and 2% are prepared and tested under quasi-static compression, and the influence of dynamic velocity (4.4, 6.2and 7.6 m/s) are investigated; then, the numerical modeling is conducted to study the influence of structural parameters on the energy absorption properties of the proposed SFRFC FTTs under quasi-static compression loadings. Results show that an appropriate content of steel fiber can prolong the stress platform under quasi-static compression loadings, and stabilize the fluctuation during dynamic plastic buckling. The thickness、diameter、aspect ratio of SFRFC FTTS have a significant effect on the SEA and CFE, especially the thickness of the inner tubes, which means the geometry parameters obviously affect the crashworthiness characteristics of SFRFC FTTs. According to the results of this research, it can be concluded that SFRFC is an excellent and potential energy adsorption filled material for FTTs, which can obviously improve the mechanical properties of filled thin-walled tubes under quasi-static and low velocity impact loadings.

Optimization of Foam Filled Door Sill for Pure Electric Vehicle

In this work, the optimization values for several double circular tubes filled with foam under dynamic bending loading are compared. The thin-walled tube is frequently used in vehicle construction, especially on the door sill, to reduce impact. Double circular tubes made of the aluminum alloy AA6063 T6 were filled with foam for this numerical study. Structures are modeled and analyzed using the ABAQUS algorithm. Optimization of tubes determined using Non-Dominated Sorting Genetic Algorithm version II (NSGA II). Excellent agreement between the results of the simulation and the empirically validated FE model has been attained. Also, It was found that a double circular tube filled with foam absorbs more energy than one that is empty of foam. Hence, it can be recommended that this structure be used as an energyabsorbing part, such as a door sill, for pure electric vehicles (PEV).

Research on Heat Transfer Enhancement of Vortex-Induced Vibration of Side-by-Side Double Tubes

The fluid-induced vibration heat transfer enhancement technology has great potential, because it can effectively improve the heat transfer efficiency without consuming additional energy. A reasonable design of the elastic heat exchange tube bundle structure is the key to the engineering application of this technology. In this paper, the effects of flow velocity and the center distance on the characteristics of vortex- induced vibration heat transfer in side-by-side double circular tubes are studied. We demonstrate that, when the center distance is no more than (outer diameter), the interference effect of the flowfield around the two tubes is greater, and the amplitude of the double tube is small. However, with the increase of , the flowfield interference decreases. Within the scope of this paper, two modes of vibration are obtained: in-phase vibration and out-of-phase vibration. When and , the fluid vortex-induced elastic supported side-by-side double circular tubes’ vibration can enhance heat transfer. Especially, when , the heat transfer enhancement effect is the strongest, reaching 14.5%. However, when , the heat transfer enhancement effect is not obvious. The research on the heat transfer characteristics of fluid flowing around the static double tube shows that when the distance is small, the flow velocity around the static tubes is larger, resulting in a higher surface average heat transfer coefficient, and as the distance increases, the heat transfer coefficient decreases.

Experimental studies on quasi-static axial crushing of additively-manufactured PLA random honeycomb-filled double circular tubes

The Voronoi-based random honeycomb cylindrical shell with specific mesostructures was constructed programmatically and additively manufactured on material of polylactide (PLA). Then, a new PLA random honeycomb-filled double circular tube (PLA-RHFDCT) was proposed. The mechanical performance of the PLA-RHFDCTs in terms of deformation mode, crushing response and energy absorption was studied experimentally by carrying out the quasi-static axial compression loading. A parametric study was performed to evaluate the influence of tube sizes and the mesostructures of honeycomb cores on the crushing resistance and energy absorption capacity of the PLA-RHFDCTs. Results indicate that the cell configuration dominates the deformation modes of PLA honeycomb cylindrical structure. For the PLA-RHFDCTs, the deformation and the bearing capacity are mainly determined by the wall thicknesses of tubes. The introduction of PLA honeycomb core enhances the mechanical performance and affects the localized buckling of the PLA-RHFDCTs due to both the in-plane and out-of-plane crushing resistance of honeycomb core structures. Compared with the parameter of cell irregularity, the relative density of honeycomb cylindrical cores exhibits a higher influence on the energy absorption performance of the PLA-RHFDCTs, though the relatively low crushing strength of PLA honeycomb cylindrical structures.

Optimisation and validation of full and half foam filled double circular tube under multiple load cases

In this study, numerical results are conducted to determine the deformation mode of foam filled double circular tubes, namely; half foam filled double circular tube (FD), and full foam filled double circular tube (DD) under oblique loading. To validate the simulation and experimental results, two-parameter Weibull probability distribution was used. The proposed function of the multi-objective optimisation design (MOD) process was based on the Finite Element Analysis results. The metamodels in were constructed to predict the crashworthiness criteria of specific energy absorption and peak crushing force under oblique impact loading. Also examined in the study were the MOD problems of the two structure types under multiple impact angles using the NSGA II algorithm. The findings from the study determined that the optimal full foam filled double circular tube had better crashworthiness under pure axial loading. While the optimal half foam filled, double circular tube had more space to enhance the crashworthiness under an oblique impact.

Energy absorption characteristic of double circular tube filled with liquid

Energy absorption characteristic of double circular tube filled with liquid

Comparative analysis of crashworthiness of empty and foam-filled thin-walled tubes

Quasi-static axial compression tests were conducted on two types of empty aluminum alloy tubes (circular and square) and five types of aluminum ex-situ foam filled tube structures (foam-filled single circular and square tubes, foam-filled double circular and square tubes, and corner-foam-filled square tube). The load-deformation characteristics, deformation mode and energy absorption ability of these structures were investigated. Several parameters related to their crashworthiness were compared, including the specific energy absorption, the energy-absorbing effectiveness factor, etc. The influence of physical dimension on the crashworthiness of these structures was explored. Dimensions of the inner tube were found to have significant influence on the structural crashworthiness of foam-filled double tubes. The averaged crush force, specific energy absorption, energy absorption per stroke and energy-absorbing effectiveness factor of thin-walled circular structures are higher than those of thin-walled square structures, respectively. Foam-filled single and double circular tube structures are recommended as crashworthy structures due to their high crush force efficiency and energy-absorbing efficiency.

Study on Axial Compressive Behaviors and Bearing Capacity Formulas of the Composite CFST Columns

Introduction: With stronger confinement effects, the composite CFST column exhibits higher ultimate bearing capacity and better seismic performance than ordinary CFST column, so it has a broad application prospect in the field of structural engineering. Methods: This paper summarized recent researches on the axial compressive behavior of two typical composite CFST columns including the section of outer square tube-inner circular tube and the section of double circular tubes. Parameter analysis on axial compressive behavior was presented in detail according to all the experimental and theoretical results of the composite CFST columns. Result and Conclusion: The different axial compression ultimate bearing capacity formulas were compared based on the experimental results. Simultaneously, the insufficiencies of present work were pointed out. Lastly, suggestions for further study in this field were put forward.

Finite Element Analysis and Crashworthiness Optimization of Foam-filled Double Circular under Oblique Loading

Finite element analysis and optimization design carry out for the quasi static responses of foam-filled double circular tube is presented in this paper. In the investigation of the crashworthiness capability, some aspects were considered for variations in geometry parameters of tubes and the loading condition to investigate the crashworthiness capability. Empty, foam-filled, and full foam-filled double tubes of thin walled structures were observed subjected to oblique impact (0˚ - 40˚). The numerical solution was used to determine the crashworthiness parameters. In addition, NSGA II and Radial Basis Function were used to optimize the crashworthiness capability of tubes. In conclution, the crash performaces of foam-filled double tube is better than the other structures in this work. The outcome that expected is the new design information of various kinds of cylindrical tubes for energy absorber application.

Experiences on treatment of lacrimal canaliculus laceration with hidden ends of both upper and lower rupture site

Objective To investigate the surgical methods and clinical efficacy for both ruptured upper and lower lacrimal canaliculi with the hidden broken ends. Methods For 12 eyes of 12 cases with both ruptured upper and lower lacrimal canaliculi after trauma, the nasal broken ends were not found by using various methods. The lacrimal sac was incised, retrograde seeking upper and lower canalicular nasal ends was done respectively, and then the upper and lower lacrimal canaliculus anastomosis was applied with dual ring method using a double probe silicone tube.The long-term curative effect after operation was observed. Results Before extubation after surgery, the patients had mild epiphora, foreign body sensation, inner canthus hyperemia, slight shift of silicone tube. There was no dropout of tube. The patients were followed up for 3 months to 1 year after extubation, 10 eyes were cured without tearing, lacrimal duct was unobstructed, and the cure rate was 83.3%. Two eyes were treated effectively with occasional epiphora, stenosis of lacrimal passage with part reflux of washing liquid, and the relative cure rate was 16.7%. Conclusion Lacrimal sac incision combined with double circular tube method in the treatment of both upper and lower lacrimal canaliculi ruptured with hidden nasal broken ends is intuitive and reliable. The concealed supporting tube which does not affect the postoperative appearance, and it avoid the lower eyelid and lower punctum ectropion. Key words: Laceration, upper and lower lacrimal canaliculi; dacryocyst incision; Intubction, dual annular stent

Non-linear finite element analysis of bitubal circular tubes for progressive and bending collapses

This paper presents non-linear finite element analysis to carry out the dynamic response of foam-filled double circular tubes for axial progressive and global bending collapse modes. Some aspects were considered to investigate the crashworthiness capability of cylindrical tube for instance geometry, material and loading parameters. In addition, three types of structures namely empty double tubes (ED), foam-filled double tubes (FD), and foam-filled single tubes (FS) were observed under oblique impact. Crashworthiness parameters were determined in the numerical solution after validated with experiment and theoretical results in relevant references. Moreover, it is evident that the crash ability of the foam-filled double tube is better than the other structures. Finally, the main outcome of this study is the new design information of different tube configurations as energy absorber where two collapse modes are expected.

Optimization of foam-filled double circular tubes under axial and oblique impact loading conditions

This paper presents the multi objective optimization of foam-filled tubular tubes under pure axial and oblique impact loadings. In this work, the double circular tubes, whose bottom is the boundary condition, while at the top, is the impacted rigid wall; with respect to the axis of the tubes. The optimal crash parameter solutions, namely the minimum peak crushing force and the maximum specific energy absorption, are constructed by the Non-dominated Sorting Genetic Algorithm-II and the Radial Basis Function. Different configurations of structures, such as empty empty double tube (EET), foam filled empty double tube (FET), and foam filled foam filled double tube (FFT), are identified for their crashworthiness performance indicators. The results show that the optimal foam filled foam filled tube (FFT) had better crashworthiness than the others under pure axial loading. However, the foam filled empty tube (FET) was the best choice for structures under an oblique loading.

Multi-Objective Optimization of Aluminum Foam Double Tube Subjected to Oblique Impact Loading for Automobile Bumper Beam

This paper presents the multi-objective optimization of aluminum foam double circular tube under oblique load for various load angle and geometry parameters. Thin-walled metallic tubes are used in vehicle structures to absorb impact energy, such as in bumper beams. In this research, aluminum alloy AA6063 T6 foam filled tube which both end were clamped, at bottom as boundary condition and at the top of tube applied quasi-static force of load angle of 0o to 30o with respect to longitudinal direction of tubes. The finite element analysis using ABAQUS code was validated according to the relevant experimental data, and the deformation modes of the tubes were studied. Multi-objective optimization design of crush parameters such as minimum peak crushing force and maximum specific energy absorption were performed using particle swarm optimization algorithm. Different optimal designs for different angles of loading and geometries of double circular tubes was identified.

Crashworthiness of foam-filled thin-walled circular tubes under dynamic bending

The bending crashworthiness of empty and foam-filled thin-walled circular tubes was investigated through dynamic three-point bending experiments. Three types of tubular structures with different configurations, including empty tubes, foam-filled single tubes and foam-filled double tubes, were tested. The load-deformation characteristics, failure modes and energy absorption capacity of different structures under dynamic loading were investigated and compared with the results of quasi-static tests. Several key parameters related to their crashworthiness were evaluated, including the specific energy absorption and the energy-absorbing effectiveness factor, thus the bending crashworthiness merits of foam-filled double tubes are identified. Due to their high dynamic bending resistance and energy-absorbing effectiveness, foam-filled double circular tube structures are recommended as crashworthy structures.

Pressure-flow relationships for steady flow through an eccentric double circular tube**Translated from Nagare, Journal of Japan Society of Fluid Mechanics 5 (1986) 158–166.

Pressure-flow relationships are derived for the steady flow through an eccentric double circular tube whose cross section takes the form of an annulus bounded by two circles which are in general not concentric. The velocity distribution can be obtained by solving a two-dimensional Poisson equation with the use of conformal mapping. In a case when the two circles touch, a mapping function of different type is required to solve the equation. The relationships thus derived are reduced to the well-known formula for the limit of concentric circles. It is found that when the region between touching circles becomes sufficiently thin, the tube conductance behaves like the cube of the difference of radii of the two circles.