Circular Hollow Tubes Research Articles

Otimização topológica de treliças mistas considerando a emissão de CO2 por meio de algoritmos meta-heurísticos

Abstract In order to provide more sustainable solutions to the design of composite truss beams, the present work proposes a formulation to optimize dimensional, geometric and topologic parameters aiming to minimize CO2 emissions. Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) are used to solve the optimization problem considering the choice of steel profiles, characteristic strength of concrete, formwork, number of panels and truss total height. The methodology is applied to three problems where three different types of profile geometry and three models of truss are considered in order to compare and analyze its results. The program considers double angles, circular hollow tubes and circular concrete-filled tubes, as well as Pratt, Howe and Warren models. The three problems are identical, with the exception of the span size, varying between 8, 24 and 40 meters. In conclusion, results show the algorithms provide equal or similar solutions, with the Warren model and circular concrete-filled tube being the best solutions in all cases, especially for larger spans, reaching an emission reduction of up to 40% in relation to the Howe model using double angles. The critical criterion in the sizing of all cases attained a design-resistant effort relation greater than 90% in all cases, confirming the effectiveness of the optimization, being the combined criterion the critical in most of them.

Sheet-Metal Formability Study on a Circular Tube with a Folding Bottom Feature

The formability of sheet-metal with a folding-bottom circular hollow tube has been studied both by numerical simulation and experiment. A mesh-convergence analysis has been carried out to determine an optimum element size for purposes of numerical simulation. The geometry and dimension of the dies and of the punch are designed to simulate the multi-stage deep drawing operation to take place. During the deep drawing operation, the strains of the sheet blank are always located in the second quadrant of the forming limit diagrams, and it continuously moves in a linear state to the left side of the diagram. At the final stage, the tube is drawn to a certain height without evidence of fracture. In order to obtain a quality product, an optimization of input parameters for the deep drawing operation is conducted using Taguchi method. Finally, a validation test is also employed to demonstrate the accuracy of forming processes. The result reveals sufficient agreement in both geometry and dimension between simulated and actual tubes to meet a good quality standard.

Drying of green veneer hollow tubes monitored using stereo digital images correlation

The present study is based on the patent FR3052379A1, which consists of rolling and gluing green veneers to form structural size hollow tubes. The objective was to study the drying behavior of circular hollow tubes and investigate the method of crack detection using image correlation from green conditions to equilibrium moisture content. The manufactured tubes are composed of six plies. Three different configurations of global grain angle orientations with respect to the tube longitudinal axis are used: {0, 0, 0}°, {10, 0, 10}°, and {− 10, 0, 10}°. Each grain angle was made up of two plies. The tubes deformation and crack formation due to drying shrinkage were measured using a stereo digital image correlation system. The stereo correlation is suitable for measuring tangential shrinkage and studying the opening and/or closing of cracks on the surface of the tubes subjected to internal moisture variations and blocked deformations. The influence of grain angle was discussed in this paper; however, due to the very few numbers of samples, no conclusive findings can be made.

Bioinspiration of the vein structure of dragonfly wings on its flight characteristics.

Dragonflies have excellent flight characteristics, which are inextricably related to the characteristics of their wings. Their wings not only support a variety of loads during flight but also maintain high-efficiency flight characteristics. In this study, the forewing of a dragonfly (Pantala flavescens (Fabricius)) was used as a research object to explore the microstructure of the surface, cross section, and the vein distribution. Three-dimensional models of three different structures of the forewing vein, including an oval-shaped hollow tube, a circular hollow tube, and a circular solid tube, were established. Fluid dynamics analysis of these three forewing models under different angles of attack during gliding was carried out by FLUENT software, and subsequently, the influence of the dragonfly forewing vein structure on its flight characteristics was analyzed. The numerical simulation results indicated that the vein structure has a considerable influence on the lift, drag, and lift-drag ratio of the P. flavescens forewing. It was indicated that among the tested models, the forewing model with oval-shaped hollow tubular veins has better flight efficiency and aerodynamic characteristics. The results of this study may provide the basis for a novel bionic concept of flapping wing microaircraft design.

Circular steel tubes filled with rubberised concrete under combined loading

The research on rubberised concrete (RuC) could promote the recycling of end-of-life tyres and reduce natural resource extraction. To mitigate the greatly reduced compressive strength and fully utilise the desirable characteristics such as improved ductility and energy absorption of RuC, confinement through a steel outer tube could be adopted. This paper investigated the effect of using circular steel tube as confinement of the RuC under axial, flexural and combined loading conditions. A total of 4 circular hollow tube sections with d/t (depth/thickness) ranging from 18 to 36 was used in this study. Three rubber replacement ratios (0%, 15%, 30%) by mass of the total aggregates were examined, along with 4 load eccentricities (0, 0.25d, 0.5d and bending) used to construct the interaction diagrams. As a result of the steel confinement, the difference in load capacity between RuC and normal concrete significantly reduced compared to the plain concretes. Additionally, RuC filled steel tube (RuCFST) members were more ductile than their normal concrete counterparts. The circular cross-section showed superior load carrying capacities compared to the square sections, due to a relatively uniform stress distribution in the cross-section. The interaction diagrams of RuCFST members could be reasonably predicted in terms of accuracy and safety of design. The tested moment capacity of RuCFST also greatly exceed the predicted values. This study has demonstrated the possibility of using RuCFST in applications where high energy absorption and ductility capacities were sought, for example, the structural members in seismic regions and flexible roadside barriers.

Fatigue behavior of circular hollow tube and wood filled circular hollow steel tube

This paper presents the experimental work on fatigue life and specific fatigue strength of circular hollow sectioned steel tube and wood filled circular hollow section steel tube. Burning effect was observed in the case of circular hollow sectioned steel tube when it is subjected to Maximum bending moment of 19613.30 N-mm at 4200 rpm, but this did not happen in the case of wood filled hollow section. Statistical analysis was done based on the experimental data and relations have been built to predict the number of cycles for the applied stress or vice versa. The relations built in this paper can safely be applied for design of the fatigue life or fatigue strength of circular hollow sections and wood filled hollow sections. Results were validated by static specific bending strengths determined by ANSYS using a known applied load.

Experimental investigation of FRP-strengthened tubular T-joints under axial compressive loads

This paper describes an experimental program conducted on steel welded tubular T-joints fabricated from circular hollow tube brace and chord members. In order to gain an understanding of the effect of the fiber reinforced polymers on the ultimate capacity, an experimental study has been conducted into the static behavior of axially loaded T-joints in compression and reinforced with FRP composites. The tests were performed by supporting the chord member of the specimen along its entire length with a compression force applied to the chord face by the brace member. Two tests were performed. The first test which served as the reference for comparison was an un-strengthened joint and the second test was an identical joint with FRP reinforcement. A typical glass/vinyl ester composite was used for wrapping the joint. The general test arrangement, specimen details, and most relevant results are presented. The experiments revealed a significant strength enhancement and improved joint behavior for the reinforced T-joint in comparison with the ultimate capacity of the corresponding unreinforced joint. A finite element analysis was also employed to validate the analytical results which in turn showed to have a good correlation and consequently the perfect bond numerical model was justified.

SB2등급 연성베리어의 충돌지점(CIP)에 대한 연구

PURPOSES : The impact performance of flexible barrier system such as structural response, vehicular motion and occupant safety vary depending on the impact point. Thus, to properly evaluate the performance of a flexible barrier system, impact should be made to a point which will lead to the worst possible results. This point is called the Critical Impact Point (CIP). This paper presents the way to determine the CIP for a SB2 class flexible barrier system which is consisted of Thrie-Beam rail and circular hollow tube post of 2m span. METHODS: Barrier VII simulations were made for impact points; Case 1 at a post, Case 2 at 1/3 span downstream from a post, Case 3 at middle of the span, Case 4 at 2/3 span downstream from a post. For the structural performance (deflections), impact simulation of 8000kg-65km/h-15degree was used, and for vehicle motion and occupant safety, simulation of 1300kg-80km/h-20degree impact was made and analysed. RESULTS: Case 1 gave the largest dynamic deflection of 75.72cm and also gave the largest snag value of 44.3cm. Occupant safety and exit angle of the vehicle after the impact were not sensitive to the impact point and were all below the allowable limit. CONCLUSIONS : For the SB2 class flexible barrier system's CIP can be regarded as a post which is sufficiently away from the end of Length of Need in order to avoid the end-effect of the barrier system. It can be more economic in the long run because the normal concrete pavement material is likely to cost more due to higher probability of maintenance and repair and higher social cost due to traffic accident, etc.

Collapse mechanism maps for a hollow pyramidal lattice

Cellular materials with hollow lattice truss topologies exhibit higher compressive strengths than equivalent structures with solid trusses owing to their greater resistance to plastic buckling. Consequently, hollow trusses have attracted interest as the cores for sandwich panels. Finite-element calculations are used to investigate the elastic–plastic compressive collapse of a metallic sandwich core made from vertical or inclined circular tubes, made from annealed AISI 304 stainless steel. First, the dependence of the axial compressive collapse mode upon tube geometry is determined for vertical tubes with built-in ends and is displayed in the form of a collapse mechanism map. Second, the approach is extended to inclined circular hollow tubes arranged as a pyramidal lattice core; the collapse modes are identified and the peak compressive strength is determined as a function of geometry. For a given relative density of hollow pyramidal core, the inclined tube geometry that maximizes peak strength is identified. The predicted collapse modes and loads for the pyramidal core are in excellent agreement with measurements for the limited set of experimentally investigated geometries.

Welded‐Tee end Connections for Circular Hollow Tubes

The paper investigates, theoretically aand experimentally, the behavior of welded‐tee end connections for circular hollow tubes in tension. Elastic stress distributions around the tube walls below the cap plate are derived. The results show that maximum stresses in the tube below the cleat‐plate corners may be reduced if thicker or narrower cleat plates are used. A total of 21 end connections having various combinations of 8 mm and 12 mm cap and cleat‐plate thicknesses on three tube sizes are tested. The observed first‐yield load, the ultimate load, and the mode of failure are reported for each test specimen. It was found that apart from possible weld defects failure of the end connections is either by local fracture in the tube below the cleat‐plate corners, or by tube yielding if thick enough cap and cleat plates are used. Results reveal that considerable stress redistribution occurs in the test specimens before failure. A simple design approach based on a 60° spread of load through the cap plate is proposed.