Thin-walled Tubular Structures Research Articles

Novel thermo-mechanical triggers processed by friction stir to enhance the crashworthiness of an automobile crash-box

Thin-walled tubular structures, also known as crash-boxes, are found to be efficient in dissipating kinetic energy of external impact. It is observed that the conventional aluminium square crash-boxes are characterized by higher initial peak crushing force and low crush force efficiency. In this work, a novel concept of inducing “Thermo-Mechanical Triggers” (TMTs) at discrete locations in a conventional aluminium square crash-box to enhance its crashworthiness behaviour is studied. TMTs are induced with the help of “Friction Stir Processing” (FSP), which is a localized heat treatment. The material properties of a crash-box are modified wherever TMTs are induced using FSP. The effect of changes in the location and the number of TMTs along the length of an aluminium crash-box is examined. By triggering a conventional square crash-box with TMTs, significant improvement is observed in its crashworthiness performance. The improvements are: (1) a 24% reduction in the initial peak force and (2) a 23% increase in the crush force efficiency. Therefore, TMTed crash-boxes will prove to be effective in enhancing passenger safety, which is a major concern in the automobile industry. The crashworthiness performance of a TMTed crash-box can be improved further by optimizing both the location and the number of TMTs.

Polar-coordinate line-projection light-curing continuous 3D printing for tubular structures

3D printing techniques offer an effective method in fabricating complex radially multi-material structures. However, it is challenging for complex and delicate radially multi-material model geometries without supporting structures, such as tissue vessels and tubular graft, among others. In this work, we tackle these challenges by developing a polar digital light processing technique which uses a rod as the printing platform. The 3D model fabrication is accomplished through line projection. The rotation and translation of the rod are synchronized to project and illuminate the photosensitive material volume. By controlling the distance between the rod and the printing window, we achieved the printing of tubular structures with a minimum wall thickness as thin as 50 micrometers. By controlling the width of fine slits at the printing window, we achieved the printing of structures with a minimum feature size of 10 micrometers. Our process accomplished the fabrication of thin-walled tubular graft structure with a thickness of only 100 micrometers and lengths of several centimeters within a timeframe of just 100 s. Additionally, it enables the printing of axial multi-material structures, thereby achieving adjustable mechanical strength. This method is conducive to rapid customization of tubular grafts and the manufacturing of tubular components in fields such as dentistry, aerospace, and more.

Crashworthiness in preliminary design: Mean crushing force prediction for closed-section thin-walled metallic structures

To design crash structures for disruptive aircraft designs, it is required to have fast and accurate methods that can predict crashworthiness of aircraft structures early in the design phase. Axial crushing is one of the key energy absorbing mechanisms during a crash event. In this study, various analytical models proposed for calculation of mean crushing force for thin-walled tubular structures are compared with a database of numerical and experimental values to ascertain their accuracy. Improvements to some of the models have also been proposed. Finally a generalized model based on the studied and improved analytical models for prediction of mean crushing force for closed section thin-walled tubular structures is introduced. The generalized model demonstrates high accuracy when compared against experimental/numerical dataset as evidenced by a high coefficient of determination (R2) value of 0.97 and can therefore be used to estimate the mean crushing force for closed-section thin-walled metallic tubular structures with various cross-sectional shapes and crushing modes early in the design phase.

Welding of P355NH steel for the construction of a medium-pressure gas pipeline

AbstractThere is an increasing demand for welding of steel pipes meant for pressure purposes. P355NH (1.0473) steel became an important construction material used for structuring and restructuring of a medium-pressure gas pipeline due to its properties, such as significant tensile strength at the level of 600 MPa and increased yield point. These properties ensure appropriate service life of the principal pipeline structures. When welding P355NH steel, processes that enable high-quality welds without significant changes in the chemical composition of the base material, are applied. It is recommended to use the TIG welding process to produce joints, although P355NH steel joints are considered as difficult to weld. During welding, various welding defects might appear, which mainly include sticking and lack of fusion. Creation of joints with the desired properties, including those used in the construction of medium pressure gas pipelines, with the required class B quality, requires selection of appropriate parameters and compliance with the welding process practice. This is very important for the service life of the structure. Therefore, the article aims to select the most appropriate parameters and thermodynamic conditions for welding P355NH steel in order to obtain the best mechanical properties. The most important of the tested welding parameters of P355NH steel is welding speed, welding current, preheating temperature, interpass temperature and, above all, the role of various shielding gases. (Three different shielding gases containing argon and helium additives were tested.) The obtained joints were tested by: non-destructive tests, such as VT—visual examination; MT—magnetic particle testing, PT—penetration tests, UT—ultrasonic testing and by the destructive methods, such as tensile strength, impact toughness, bending test, light microscopy and scanning electron microscopy. The cause-and-effect relationships between the obtained joint structure and its mechanical properties were determined. The considerations were supported by the nucleation model and the mechanisms of formation of the acicular ferrite phase in the joint material. The chosen parameters of TIG process allow to obtain joint with adequate strength for the production of the gases pipeline, without welding defects. The results have a practical implication, the developed production technology for the obtaining the joints. The presented solution gives the possibility of producing correct welded joints, which can be used in the responsible steel construction. The originality of manuscript is the presentation the newly, uncomplicated solution of obtaining joint with good mechanical properties included the thin-walled tubular structure with a thickness of 3.6 mm. A novelty in the article is a clear indication of the importance of detailed thermodynamic welding conditions and obtained weld structure on the mechanical properties of the P355NH steel joint, which lead to the formation of various non-metallic titanium inclusions, which have a decisive impact on the mechanical properties of the joint, especially its strength and impact strength.

Carbon chains modulate carrier transport in tubular graphitic carbon nitride for efficient photocatalytic degradation

In recent years, environmental wastewater has become an increasingly prominent problem, and photocatalytic degradation is one of the effective means to treat waste pollutants. In this study, glycine was embedded in a tubular carbon nitride material with melamine as the parent by a supramolecular self-assembly strategy to prepare carbon chains implanted tubular graphitic carbon nitride (CTCN). The introduction of carbon chains can reduce the formation of hydrogen bonds, which is beneficial to improve the carrier transport efficiency. It can also adjust the valence band position and has better reduction performance. The thin-walled tubular structure formed by supramolecular self-assembly exposes more active sites and shortens the carrier transport distance due to the size effect, which further improves the carrier separation efficiency. The synergistic effect of the two greatly contributes to the photocatalytic performance of the material. The degradation rate of 0.3% CTCN is 8.1 times higher than that of Bulk CN, and 0.3% CTCN exhibits good stability. This solution is beneficial to optimize some existing wastewater treatment methods and has a role in environmental protection.

Control of the Deformation Mode of Aluminum Foam-Filled Tubes as a Function of Foam Porosity

This paper focuses on the computational modeling of the crashworthiness performance of designed foam-filled thin-walled tubular structures under quasi-static compression loading. The studied foam sample is designed in SolidWorks using the ‘sphere subtraction method’ and implemented as a filler material in the thin-walled tube. The quasi-static compression was simulated by Abaqus software. The foam porosity is manipulated to enhance the crashworthiness performance of empty tubes. The deformation mode and energy absorption capability of the analyzed structures are introduced in detail. The numerical results showed that foam-filler material could change the deformation mode and improve stability during the compression process of thin-walled tubular structures. The number of lobes significantly increases when introducing the foam filler to the tube. These folds are affected by the foam porosity. Results also indicate that the total crushing load of the foam-filled tube is also a function of foam porosity, the mechanical response of the foam-filled tubes tended towards the response of the empty tube for a high porosity (P >85%), while for low porosity (P<85%) the mechanical response of the foam-filled tubes exhibits the three universal deformation characteristics of foams, namely, initial linear stage, extended plateau stage, and final densification stage. The main mechanical properties: collapse stress, plateau stress, and densification strain were obtained via the energy-efficient method for different configurations. The calculated mechanical properties exhibited a strong dependence on foam porosity. To give a quantitative description of the obtained quasi-static compressive properties, these properties are expressed as a function of foam porosity. The proposed formulas can easily recover the quasi-static compressive properties of the empty tube in the case of the absence of foam. The control of the compressive performance of foam-filled tubes as a function of porosity allows for finding an optimum geometry with a predefined foam porosity value adjusted for a given application.

A hybrid shell-beam element for straight thin-walled tubular structures

A novel beam model is proposed in order to consider deformations of its cross-section in the context of straight thin-walled tubes. For this purpose, the straight beam kinematics is enriched by addition of orthogonal shell-type displacement field of the tube section. Linear strain in terms of displacement is considered in conjunction with the non-linear coupling between local deformation of the section and its global rotation. Both Euler–Bernoulli and Love-Kirchhoff hypotheses for beam and shell kinematics, respectively, are adopted as well as the thin-walled assumption. First-order shear deformation for the radial variable and Fourier expansion in terms of the circumferential variable are also considered for the mid-surface displacement field. Then, the stress tensor is obtained under plane stress conditions. The virtual power principle is finally used to obtain the equations of motion satisfied by the corresponding generalized forces. Afterwards, an explicit updated Lagrangian Finite-Element approach using a lumped mass matrix is proposed for solving the tube governing equations and the stability condition of the time integration is given. Test-cases are then chosen to assess the present tube finite-element. Both static and dynamic problems are considered. First, the proposed model is compared to analytical solutions. Finally, a tube subjected to a distributed patch loading is studied. The influence of the number of Fourier modes, of warping and coupling terms is examined. The proposed model makes it possible to retrieve classical shell solution of the cross-section deformation with significant computational savings.

Study of effect of provision of cut-outs on axial collapse behaviour of circular aluminium tubes

Geometrical modification of thin-walled tubular structure is one of the innovative ways in the development for vehicle safety design. This research is developed in accordance with the need of investigation on behaviour of tubular structures with geometrical modifications like cut-outs under dynamic loading technique. Diamond and elliptical cut-out shapes are provided in multiple number arranged circumferentially in a single row on a tube surface. Tubes with cut-outs are loaded axially at three different velocities, corresponding to three different strain rates. Energy absorption characteristics like energy efficiency, specific energy absorption, peak collapse force, mean collapse force and efficiency of peak force reduction at the initiation of tube deformation are calculated and compared using finite element (FE) based ABAQUS/Explicit® software. Split-Hopkinson Pressure Bar (SHPB) is modelled in the FE software to understand the material behaviour under high strain dynamic loading. Johnson-Cook material model parameters are incorporated in the study to understand the strain rate sensitive behaviour of aluminium alloy material. Results revealed that providing diamond and elliptical cut-outs on tube is much efficient than providing circular cut-outs on tube, in terms of percentage peak load reduction as well as energy efficiency of structure. It was observed that number of cut-outs influences the polygonal deformation pattern of tube with cut-outs. Overall study significantly helps to achieve the aim of improving vehicle crashworthiness characteristics by implementing cut-outs in a crash frame.

Electric field-driven microscale 3D printing of flexible thin-walled tubular mesh structures of molten polymers

Thin-walled tubular mesh structures are the basic form of tubular scaffolds, such as vascular and nerve conduit stents, in tissue engineering. A novel electric field-driven microscale three-dimensional printing (EFD μ-3D printing) was proposed for manufacturing these structures of molten polymers with high resolution. For printing on curved substrates, the distributions of electric field force on substrates with different curvature radii in the self-excited electrostatic field were revealed via numerical simulations. The optimal process parameters for EFD μ-3D printing on curved substrates were determined. To improve printing accuracy, a micro-area preset eccentricity strategy was proposed by reducing the vertical angle of printing jets. A number of printing cases have been carried out. It is shown that the proposed method is effective for the micro-nano scale printing of 3D structures. The printed structures have good flexibility; they can be restored to their original state after 8.9 % axial compression, with an original length of 67 mm. Moreover, a conformal printing variable stiffness thin-wall tubular mesh structure has been achieved with a length of 28 mm, a line diameter of 80 μm, a big end diameter of 8 mm, and a small end diameter of 4 mm.

Structural and Behaviour Optimization of Tubular Structures Made of Tailor Welded Blanks by Applying Taguchi and Genetic Algorithms Methods

Even though they initially appeared as a method of using waste from other production processes, tailored welded blanks (TWB) presented several advantages by combining materials with different characteristics. On the one hand, this study focuses on minimizing the adverse effects caused by the springback of TWB parts. The proposed method is based on the Taguchi technique using orthogonal type 23 networks. On the other hand, genetic algorithms were applied to obtain maximum performance parameters within the dynamic loadings of tubular structures made of TWB by advantageous positioning of the weld line. The obtained data were compared and evaluated through software platforms such as MATLAB, Design Expert, and Dynaform, and experimental validation. By generating an objective function, the construction of thin-walled tubular structures can be controlled for a predetermined deformation and maximum energy absorption. The data obtained has an error rate of less than 3%, thus considering that this method can be used successfully in the qualitative and quantitative estimation of dynamically loaded TWB tubular structures.

Manufacture of braided-textile reinforced multi-walled tubular structures and axial compression behaviors

Carbon fiber reinforced polymer (CFRP) thin-walled tubular structures have been widely used in lightweight energy absorbing components. In this paper, CFRP tubular braided-textiles, foam-filling technique, and sandwich structure were applied to make low-cost multi-walled sandwich tubular structures. Through axial compression tests, the compression behaviors, crushing modes and energy absorption performance of the braided-textile reinforced multi-walled sandwich tubes were contrastively analyzed. Experimental results show that the foam-filling technique and the sandwich structure are both effective in modifying the crushing patterns and improving the energy absorption efficiency. Especially for the multi-walled sandwich structure, it can increase the specific energy absorption (SEA) by at least 66% and change the crushing mode from local bucking to progressive diamond folding.

Lateral Crushing of Square Aluminium Tubes Filled with Different Cores

Thin-walled tubular structures are widely used in industries such as automotive, aerospace and military because of their lightweight and excellent performance under different loading conditions. This study aimed to investigate the lateral crushing performance of square aluminium tubes filled with different cores (honeycomb, polyurethane foam and mixed of these two fillers). Different failure modes of tested structures have been observed and they are progressive failure with plastic hinges formed in the middle of the tube wall, cracks at the corners of some tested tubes and fractures in the mixed foam and honeycomb core. Results show that the lateral crushing performance of aluminium tubes was significantly improved when using mixed filler (honeycomb and foam). The average load, energy dissipation and specific energy absorption of mixed core filled tubes increased up to 638%, 451% and 177% respectively when compared to those for hollow tubes.

OBTAINING NEW THIN WALLED TUBULAR STRUCTURES THROUGH MATRIX MORPHOLOGICAL RESEARCH

New products based on a structure that represents a combination of known elements in a higher quality set, as well as products that refer to new shapes, new curves, new surfaces can be obtained logically - analytically - deductively or by methods specific to the optimal calculation. The present paper focuses on the method of analyzing tridimensional morphology, some possible solutions being evaluated on value criteria. Of course, these methods can be applied in the field of engineering with very good results. The focus of this study is to obtain new thin walled tubular structures - such as car crash members - which in the case of axial shock loads have a higher predictable behavior compared to those already used in various technical fields. Following the study, it can be said that depending on the amount of absorbed energy in the case of axial collisions and the absorption of kinetic energy developed at the time of impact, the optimal crashworthiness solution could be tubular structures with a circular support base and rectangular deformable area for impact.

Crushing analysis under multiple impact loading cases for novel tailored-property multi-wall tubes

Multi-wall profile as one of the most widely approaches can enhance the crashworthiness properties in thin-walled tubular structures. In actual application process as energy absorbers, there may be a variety of circumstances including axial crushing and lateral crushing. However, the crashworthiness in the multi-wall tubular structure considering both axial crushing and lateral crushing circumstances has rarely been evaluated in the existing literature. In the study, a new tailored-property multi-wall thin-walled structure (TMTS) is put forward to increase the ultimate strength of this material in the region of corner to accommodate two conditions including lateral and axial crushing conditions. Finite element models verified from experiments were established in PAM-CRASH to analyse the crashworthiness performance for this structure. Under lateral and axial crushing, it was revealed that TMTSs exhibited obvious superiority to the corresponding traditional structures. It was concluded that wall thickness, tailoring length and other geometry parameters could effectively influence the crushing performance of the TMTSs. In addition, the progressive deformation mode could be exhibited by the well-designed TMTSs under axial impact. Furthermore, the theoretical model of the TMTS was proposed according to the Super-folding Element Theory. Theoretical analysis is consistent with simulation results, which proves that the deformation formula and the analytical model are all correct. Finally, according to the multi-objective optimisation method, the thicknesses of tailored and non-tailored regions of the TMTS were reasonably configured to further enhance crashworthiness. The research results provide good guidance and theoretical support for the development of novel lightweight energy-absorbing structures under various loading circumstances.

Crashworthy characteristics of sustainable thin-walled tubes: A study on recycled beverage cans

Thin-walled tubular structures are widely employed in applications. The current study proposes an innovative cost-saving and eco-friendly thin-walled cylinder concept using recycled beverage cans. Axial compression experiments are conducted to characterize the crushing performance under quasi-static and dynamic loading. Besides, the polyurethane foam (PUF)-filled beverage cans are fabricated to improve the compression resistance and energy absorption capacity. Experimental results show that empty beverage cans behave as a typical Type-II absorber and fail by local buckling of the cylinder belly. The initial peak force increases with deformation rates while the highest mean crushing force is obtained at compressive velocity of 50 mm/min. In contrast, PUF-filled beverage cans collapse with a progressive folding process and present significant improvement in crashworthiness. Experimental results are compared with theoretical analysis and conventional energy absorbers to clarify the crashworthiness. In addition, the interaction effect between the PUF fillings and the recycled beverage cans is discussed comprehensively.

A simplified approach to estimate the fatigue life of full-scale welded cast steel thin-walled tubular structures

Cast steel joints (CSJ) are widely used in complex tubular structures to connect different parts of structures. This paper presents a simplified approach for efficient fatigue life estimation of full-scale welded cast steel structures. The proposed approach is applied to analyze a set of fatigue data of a full-scale CSJ thin-walled tubular truss structure. The results indicate that the fatigue lives estimated based on the simplified approach compare well with the experimental data. It is also shown that the simplified approach is much more efficient than the classical three-dimensional finite element-based method.

Lateral crushing behavior of novel carbon fiber/epoxy composite bidirectional self-locked thin-walled tubular structure and system

Bidirectional self-locked structure has important significance in energy absorption protection, especially complex loading absorbing energy. This paper reports on the lateral crushing behavior of novel carbon fiber/epoxy composite bidirectional self-locked thin-walled tubular structure (BST) and system (BSTS), as well as some improved bidirectional self-locked thin-walled tubular structures and systems. The lateral crushing behaviors of BST and BSTS were investigated by experiment and finite element analysis. It was found that the specific energy absorption (SEA) of BSTS was inferior to BST, which indicated the assembling system weakened energy absorption. The simulated results indicated that changing stacking sequence of carbon fiber/epoxy prepreg had not significantly effect on crushing performance of BST. Finally, the improved bidirectional self-locked thin-walled tubular structures and systems were designed and tested. The improved design enabled to enhance 139.9% in the crushing force efficiency (CFE) (specifically from 33.3% to 79.9%) and 27.5% in the SEA (from 4.0 J/g to 5.1 J/g). It was worth mentioning that the bidirectional self-locked system with PMI foam-filled enhanced 20.8% than bidirectional self-locked thin-walled tubular structure with PMI foam-filled in the SEA (from 5.3 J/g to 6.4 J/g).

Simulation of expansion a branch-pipe with «blinds» by the pressure of magnetic field

Thin-walled tubular structures that are used to connect units and supply gas or liquid are widely used in aircraft devices. Aircraft pipelines have a complex cross-sectional profile, large differences in size, the presence of different holes, shape changes, stiffeners, etc. Often, such parts have insufficient indicators of durability during the process of maintenance. The main reason is the use of traditional technological processes in the production of such parts. This paper presents an analysis of electrodynamic processes during magnetic - pulse «expansion» of thin-walled tubular parts. To carry out the technological process, separation operations plus calibration, a branch-pipe was chosen, which serves to mix the flows of hot and cold air in the aircraft air conditioning system. A prerequisite for the achievement of this goal is high demands on the quality of the internal and external surfaces, shape retention, minimal thinning of the walls.

АНАЛИЗ ФАКТОРОВ ПОВЫШЕНИЯ ПРОЧНОСТИ НЕАВТОКЛАВНОГО ГАЗОБЕТОНА

non-autoclaved aerated concrete is the only real alternative to gas silicate in the organization of its release on the basis of regional production of small and medium capacity. This will help improve the competitive environment in the building materials market and optimize the cost of construction. Of particular interest is the possibility of expanding the field of application of this material due to a significant increase in strength characteristics, while maintaining its average density in acceptable, in terms of thermal insulation properties, limits - not more than 1000 ... 1100 kg/m3. At a strength level of 10 MPa and above, in combination with dispersed reinforcement or the use of traditional non-metallic reinforcing elements, such aerated concrete can be used as a lightweight structural material for creating power elements of low-rise buildings, including in promising construction printing technologies; devices distributing the load belts; non-removable formwork; porous, stiffening, filling thin-walled tubular structures. The paper presents an assessment of the effectiveness of traditional ways to increase the strength of non-autoclaved aerated concrete. New solutions for the purposeful formation of the pore space structure are proposed and tested due to the creation and use of a gas generator with normalized gas evolution, which allows the creation of pores of a given volume. The key to the economic effectiveness of the proposed solutions is the transition from traditional portland cement to composite binders based on it. The substantiated choice of the amount and composition of the mineral additive makes it possible to optimize the properties of the binder under the particularity of the problem being solved, and to minimize the consumption of cement and chemical modifiers, increase the speed of durability and the final indices of non-autoclaved aerated concrete.

Review of the crushing response of collapsible tubular structures

Studies on determining and analyzing the crushing response of tubular structures are of significant interest, primarily due to their relation to safety. Several aspects of tubular structures, such as geometry, material, configuration, and hybrid structure, have been used as criteria for evaluation. In this review, a comprehensive analysis of the important findings of extensive research on understanding the crushing response of thin-walled tubular structures is presented. Advancements in thin-walled structures, including multi-cell tube, honeycomb and foam-filled, multi wall, and functionally graded thickness tubes, are also discussed, focusing on their energy absorption ability. An extensive review of experimentation and numerical analysis used to extract the deformation behavior of materials, such as aluminum and steel, against static and dynamic loadings are also provided. Several tube shapes, such as tubes of uniform and nonuniform (tapered) cross sections of circular, square, and rectangular shapes, have been used in different studies to identify their efficacy. Apart from geometric and loading parameters, the effects of fabrication process, heat treatment, and triggering mechanism on initiating plastic deformation, such as cutouts and grooves, on the surface of tubular structures are discussed.