scholarly journals Numerical Modelling and Design of Aluminium Alloy Angles under Uniform Compression

CivilEng ◽  
2021 ◽  
Vol 2 (3) ◽  
pp. 632-651
Author(s):  
Evangelia Georgantzia ◽  
Michaela Gkantou ◽  
George S. Kamaris
Keyword(s):  
Aluminium Alloy ◽  
Cross Sections ◽  
Numerical Study ◽  
Local Buckling ◽  
Design Standards ◽  
Uniform Compression ◽  
Cross Sectional ◽  
Modified Method ◽  
Aspect Ratios ◽  
Modelling Assumptions

Research studies have been reported on aluminium alloy tubular and doubly symmetric open cross-sections, whilst studies on angle cross-sections remain limited. This paper presents a comprehensive numerical study on the response of aluminium alloy angle stub columns. Finite element models are developed following a series of modelling assumptions. Geometrically and materially nonlinear analyses with imperfections included are executed, and the obtained results are validated against experimental data available in the literature. Subsequently, a parametric study is carried out to investigate the local buckling behaviour of aluminium alloy angles. For this purpose, a broad range of cross-sectional aspect ratios, slenderness and two types of structural aluminium alloys are considered. Their effect on the cross-sectional behaviour and strength is discussed. Moreover, the numerically obtained ultimate strengths together with literature test data are utilised to assess the applicability of the European design standards, the American Aluminium Design Manual and the Continuous Strength Method to aluminium alloy angles. The suitability of the Direct Strength Method is also evaluated and a modified method is proposed to improve the accuracy of the strength predictions.

scholarly journals Aluminium alloy cross-sections under uniaxial bending and compression: A numerical study

2021 ◽  
Vol 1058 (1) ◽  
pp. 012011
Author(s):  
Evangelia Georgantzia ◽  
Michaela Gkantou ◽  
George S. Kamaris ◽  
Kunal Kansara ◽  
Khalid Hashim
Keyword(s):  
Aluminium Alloy ◽  
Cross Sections ◽  
Numerical Study

scholarly journals Numerical and Experimental Study of Cross-Sectional Effects on the Mixing Performance of the Spiral Microfluidics

Micromachines ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1470
Author(s):  
Omid Rouhi ◽  
Sajad Razavi Bazaz ◽  
Hamid Niazmand ◽  
Fateme Mirakhorli ◽  
Sima Mas-hafi ◽  
...  
Keyword(s):  
Cross Sections ◽  
Numerical Study ◽  
Large Angle ◽  
Element Model ◽  
Channel Length ◽  
Cross Sectional ◽  
Flow Rates ◽  
Lab On Chip ◽  
Mixing Performance ◽  
Dean Flow

Mixing at the microscale is of great importance for various applications ranging from biological and chemical synthesis to drug delivery. Among the numerous types of micromixers that have been developed, planar passive spiral micromixers have gained considerable interest due to their ease of fabrication and integration into complex miniaturized systems. However, less attention has been paid to non-planar spiral micromixers with various cross-sections and the effects of these cross-sections on the total performance of the micromixer. Here, mixing performance in a spiral micromixer with different channel cross-sections is evaluated experimentally and numerically in the Re range of 0.001 to 50. The accuracy of the 3D-finite element model was first verified at different flow rates by tracking the mixing index across the loops, which were directly proportional to the spiral radius and were hence also proportional to the Dean flow. It is shown that higher flow rates induce stronger vortices compared to lower flow rates; thus, fewer loops are required for efficient mixing. The numerical study revealed that a large-angle outward trapezoidal cross-section provides the highest mixing performance, reaching efficiencies of up to 95%. Moreover, the velocity/vorticity along the channel length was analyzed and discussed to evaluate channel mixing performance. A relatively low pressure drop (<130 kPa) makes these passive spiral micromixers ideal candidates for various lab-on-chip applications.

Local buckling of rectangular concrete-filled steel tubular columns with binding bars under eccentric compression

2020 ◽  
Vol 23 (10) ◽  
pp. 2204-2219
Author(s):  
Jun Wan ◽  
Jian Cai ◽  
Yue-Ling Long ◽  
Qing-Jun Chen
Keyword(s):  
Stress Gradient ◽  
Local Buckling ◽  
Steel Plates ◽  
Cross Sectional ◽  
Tubular Columns ◽  
Buckling Stress ◽  
Aspect Ratios ◽  
Eccentric Compression ◽  
Buckling Behavior ◽  
Elastically Restrained

Based on the energy method, this article presents a theoretical study on the elastic local buckling of steel plates in rectangular concrete-filled steel tubular columns with binding bars subjected to eccentric compression. The formulas for elastic local buckling strength of the steel plates in eccentrically loaded rectangular concrete-filled steel tubular columns with binding bars are derived, assuming that the loaded edges are clamped and the unloaded edges of the steel plate are elastically restrained against rotation. Then, the experimental results are compared with these formulas, which exhibits good agreement. Subsequently, the formulas are used to study the elastic local buckling behavior of steel plates in rectangular concrete-filled steel tubular columns with binding bars under eccentric compression. It is found that the local buckling stress of steel plates in eccentrically loaded rectangular concrete-filled steel tubular columns with binding bars is significantly influenced by the stress gradient coefficient, width-to-thickness ratio, and the longitudinal spacing of binding bars. With the decrease of width–thickness ratios or the longitudinal spacing of binding bars or with the increase of the stress gradient coefficient, the local buckling stress increases. Furthermore, the influence of the longitudinal spacing of binding bar is more significant than the stress gradient coefficients. Finally, appropriate limitation for depth-to-thickness ratios ( D/ t), width-to-thickness ratios ( B/ t), and binding bar longitudinal spacing at various stress gradient coefficients ( α0) corresponding to different cross-sectional aspect ratios ( D/ B) are suggested for the design of rectangular concrete-filled steel tubular columns with binding bars under eccentric compression.

scholarly journals Effect of structural interaction on the aerodynamic properties

2020 ◽  
Vol 17 (3) ◽  
pp. 79-86
Author(s):  
R. N. Guzeev ◽  
◽  
E. S. Goloviznina ◽  
Keyword(s):  
Cross Sections ◽  
Mutual Influence ◽  
Numerical Study ◽  
Vortex Method ◽  
Discrete Vortex ◽  
Discrete Vortex Method ◽  
Structural Interaction ◽  
Cable Stayed Bridge ◽  
Aspect Ratios ◽  
Aerodynamic Properties

Effect of structural interaction on drag coefficient is considered. Numerical study is performed using discrete vortex method. There have been obtained dependences of the mutual influence of rectangular cross sections with different aspect ratios depending on the reduced distance between the cross sections, on their aerodynamics. The effect of structural interaction of cable-stayed bridge pylon legs is investigated on the examples of Golden Bridge and Russian Bridge in Vladivostok.

Effect of Deterministic Asperity Geometry on Hydrodynamic Lubrication

2004 ◽  
Vol 126 (3) ◽  
pp. 527-534 ◽  
Author(s):  
Ravinder B. Siripuram ◽  
Lyndon S. Stephens
Keyword(s):  
Friction Coefficient ◽  
Cross Sections ◽  
Numerical Study ◽  
Hydrodynamic Lubrication ◽  
Leakage Rate ◽  
Area Fraction ◽  
Cross Sectional ◽  
Constant Height ◽  
Sectional Shape ◽  
The Impact

This paper presents a numerical study of the effects of different shapes of deterministic microasperities in sliding surface lubrication when hydrodynamic films are found. Positive (protruding) and negative (recessed) asperities of constant height (depth) are considered with circular, square, diamond, hexagonal and triangular cross-sections. Of particular interest is the impact of asperity/cavity cross-sectional geometry on friction and leakage, which has importance in sealing applications. The results indicate that the friction coefficient is insensitive to asperity/cavity shape, but quite sensitive to the size of the cross-section. By contrast, leakage rates are found to be quite sensitive to both cross-sectional shape and size, with triangular asperities giving the smallest leakage rate and square asperities giving a largest leakage rate. The minimum coefficient of friction for all shapes is found to occur at an asperity area fraction of 0.2 for positive asperities and 0.7 for negative asperities. Finally, the results indicate the existence of a critical asperity area fraction where the performance curves for positive and negative asperities cross over. These cross-over points are identified for friction coefficient and leakage rate.

Buckling of High-Strength Steel Cylinders Under Cyclic Bending in the Inelastic Range1

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
George E. Varelis ◽  
Spyros A. Karamanos
Keyword(s):  
Finite Element ◽  
High Strength Steel ◽  
Numerical Study ◽  
Local Buckling ◽  
High Strength ◽  
Element Model ◽  
Cyclic Plasticity ◽  
Repeated Loading ◽  
Cross Sectional ◽  
Cyclic Bending

The present paper examines the structural behavior of elongated steel hollow cylinders, referred to as tubes or pipes, subjected to large cyclic bending, through a rigorous finite element simulation. The bent cylinders exhibit cross-sectional distortion, in the form of ovalization, combined with excessive plastic deformations. Those deformations grow under repeated loading and may lead to structural instability in the form of local buckling (wrinkling) and, eventually, failure of the loaded member. The study focuses on relatively thick-walled seamless cylindrical members made of high-strength steel, which exhibit local buckling in the plastic range of the steel material. The analysis is conducted using advanced nonlinear finite element models capable of describing both geometrical and material nonlinearities. A cyclic plasticity model that adopts the “bounding surface” concept is employed. The material model is calibrated through special-purpose material testing, and implemented within ABAQUS, using a user-subroutine. The finite element model is validated by comparison with two experiments on high-strength steel tubular members. Special emphasis is given on the increase of ovalization and the gradual development of small-amplitude initial wrinkles with repeated loading cycles. A parametric numerical study is conducted, aimed at determining the effects of initial wrinkles on plastic buckling performance.

Numerical Study of External Flow over Ducts with Various Cross-Sections

2016 ◽  
Vol 366 ◽  
pp. 10-16 ◽  
Author(s):  
Erfan Maleki ◽  
Hani Sadrhosseini
Keyword(s):  
Cross Sections ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
External Flow ◽  
Two Dimensions ◽  
Wake Region ◽  
Reattachment Point ◽  
Cross Sectional ◽  
Low Reynolds Numbers ◽  
Stagnation Points

In this article a comprehensive numerical study is performed to compare the effect of fluid flow across a duct with various cross sectional shapes and with different velocities of the flow. Circular, elliptical and rectangular cross sections have been chosen for the ducts and air flows across them with four values of low Reynolds numbers in the range of Re = 1 to Re = 1000. Continuity and momentum equations with proper boundary conditions are solved in two dimensions. Streamlines, pressure distribution and Velocity profiles are obtained and creation of vortices, boundary layers, separation region, wake region, reattachment point and stagnation points are studied in detail and the results are compared for various cases. The value of the Reynolds number which the flow transits from steady to unsteady has been compared for the different cross sectional shapes.

Cyclic Performance Evaluation of Hollow Structural Section (HSS) and Concrete-Filled Tube (CFT) Braces

2019 ◽  
Vol 19 (11) ◽  
pp. 1950140 ◽  
Author(s):  
Samira Ebrahimi ◽  
Seyed Mehdi Zahrai ◽  
Seyed Rasoul Mirghaderi
Keyword(s):  
Compressive Strength ◽  
Energy Dissipation ◽  
Cross Sections ◽  
Numerical Study ◽  
Local Buckling ◽  
Diameter Ratio ◽  
Thickness Ratio ◽  
Cyclic Response ◽  
Concrete Filled Tubes ◽  
Energy Dissipation Capacity

Hollow structural sections (HSS) are widely used as braces because they have inherent axial, flexural, and torsional capacities. Delaying or preventing local buckling is accomplished by concrete infill in HSS braces to improve their cyclic response heavily relying upon three key parameters: (1) presence of concrete infill, (2) width (diameter)-to-thickness ratio, and (3) length-to-width (diameter) ratio impress the cyclic response of HSS braces. Nevertheless, it is not clear that based on which parameter, concrete infill can significantly enhance the peak compressive strength and energy dissipation capacity of HSS braces. This paper aims to investigate this concern while presenting a numerical study on the cyclic response of 120 HSS and Concrete-Filled Tubes (CFT) braces with various geometric characteristics. Square and circular cross-sections, 10, 12, 13.33, 20, 30, 33.33, and 50 width (diameter)-to-thickness ratios and 10, 15, 20, 25, 30, 37.5, 45, 50, 75, and 112.5 length-to-width (diameter) ratios are selected for the numerical investigation. Obtained results indicated that concrete infill can increase peak compressive and post-buckling strengths and energy dissipation capacity of HSS braces around 81%, 43%, and 73%, respectively. It was found that concrete infill and parameters of width (diameter)-to-thickness ratio and length-to-width (diameter) ratio influence the cyclic response of HSS braces differently. On the other hand, concrete infill noticeably enhances the peak compressive strength of HSS braces with larger values of width (diameter)-to-thickness ratio and energy dissipation capacity of such braces with lower values of length-to-width (diameter) ratio.

Wall proximity effects on flow over cylinders with different cross sections

2014 ◽  
Vol 92 (10) ◽  
pp. 1141-1148 ◽  
Author(s):  
Seyfettin Bayraktar ◽  
Sedat Yayla ◽  
Alparslan Oztekin ◽  
Haolin Ma
Keyword(s):  
Cross Sections ◽  
Stokes Equations ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Proximity Effects ◽  
Navier Stokes ◽  
Cross Sectional ◽  
Navier Stokes Equations ◽  
Finite Volume Discretization ◽  
Wall Proximity

This paper presents the results of a numerical study on flow characteristics over circular, square, and diamond cross-sectional cylinders. Investigations are performed in a two-dimensional domain using the finite volume discretization method solver for Reynolds number, Re = 20 000. Unsteady Reynolds averaged Navier–Stokes equations with Spalart–Allmaras turbulence model have been used as a turbulence closure. After the validation of the simulations with the available experimental data from the open literature, global characteristics of the flow field around different shaped cylinders near the wall have been presented. Effects of wall proximity on cylinders are investigated for four different gap width (G) to cylinder width (D) ratios.

scholarly journals Numerical Application of Effective Thickness Approach to Box Aluminium Sections

2021 ◽  
Vol 5 (11) ◽  
pp. 291
Author(s):  
Elide Nastri ◽  
Vincenzo Piluso ◽  
Alessandro Pisapia
Keyword(s):  
Cross Sections ◽  
Local Buckling ◽  
Experimental Tests ◽  
Effective Thickness ◽  
Numerical Application ◽  
Uniform Compression ◽  
Plate Elements ◽  
Ultimate Resistance ◽  
Theoretical Results ◽  
Recent Extension

The ultimate behaviour of aluminium members subjected to uniform compression or bending is strongly influenced by local buckling effects which occur in the portions of the section during compression. In the current codes, the effective thickness method (ETM) is applied to evaluate the ultimate resistance of slender cross-sections affected by elastic local buckling. In this paper, a recent extension of ETM is presented to consider the local buckling effects in the elastic-plastic range and the interaction between the plate elements constituting the cross-section. The theoretical results obtained with this approach, applied to box-shaped aluminium members during compression or in bending, are compared with the experimental tests provided in the scientific literature. It is observed that the ETM is a valid and accurate tool for predicting the maximum resistance of box-shaped aluminium members during compression or in bending.

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