bluuebunny/crossref_metadata_2025 huggingface dataset:
Computational Modelling of Closed-Cell Aluminium Foams to Investigate Structural Deformation under Quasi-Static Loading
Authors: Kader Md Abdul , Islam Md Ashraful , Hazell Paul Jonathan , Escobedo Juan Pablo , Saadatfar Mohammad , Brown Andrew
Published: July 2016

Computational modelling has been performed to understand the deformation mechanisms of closed-cell aluminium foams under quasi-static compression. A micro-computed tomography-based 3D foam geometry was developed that described the interior of the foam. The FE software ABAQUS/Explicit has been used for the present meso-scale modelling. A good correlation of load-strain response was found between the simulations and experimental results. A sectional view was observed during deformation to explore the internal deformation mechanisms. It was revealed that localized cell collapse occurs due to complex movements of the cell-walls with thin/weaker cells being deformed faster than thick/stronger cells.
Simulation of Multipass Hot Rolling for 7050 Aluminum Alloys
Authors: An Yang , Hodgson Peter , Yang Chun Hui
Published: July 2016

To determine the relations between rolling passes, mechanical behaviours and microstructure evolution of AA7050 aluminum alloys, finite element modeling of a multipass hot rolling process is developed and employed to investigate thermo-mechanical evolution during this processing. Through parametric studies, the distribution of local strain and temperature across thickness during the hot rolling process are numerically determined. These results are used to determine the subgrain size and thus the microstructure evolution during the hot rolling process are estimated.
Modelling of Auxetic Foam Embedded Brittle Materials and Structures
Authors: Dhanasekar Manicka , Zahra Tatheer , Jelvehpour Ali , Noor-E-Khuda Sarkar , Thambiratnam David P.
Published: July 2016

Building structures use brittle materials extensively. Under impact or blast loads these structures perform poorly due to tensile strains caused by Poisson’s effect normal to the direction of such loadings. Auxetic materials exhibit negative Poisson’s ratio – a property which can be exploited to eliminate those tensile strains. In this study, Auxetic layers embedded masonry is modelled using a representative volume element (RVE) with periodic boundary conditions and an explicit finite element (EFE) modelling method for a boundary value problem of a masonry wall with an Auxetic foam rendered face is subject to out-of-plane load. The RVE is limited to in-plane loads only and hence subjected to in-plane shear and compression and the EFE was used to assess the performance under out-of-plane loading. The results show significant post-yield strain hardening under axial compression and in-plane shear and high increase in capacity for walls under out of plane flexure.
Development of a Fluid-Structure Model for Gas-Lubricated Bump-Type Foil Thrust Bearings
Authors: Qin Kan , Jahn Ingo , Jacobs Peter
Published: July 2016

In the present study, a computational model for the coupled fluid-structure simulation of bump-type foil thrust bearings is developed. A three-dimensional compressible Navier-Stokes solver is extended to model the fluid flow within the thin gap. In addition, a new solver is developed to model the bump and top foils within the foil thrust bearings. These two solvers are linked with a coupling algorithm that maps pressure and deflection at the fluid-structure interface. The theory and verification of this coupling algorithm are detailed as the focus of this paper. Finally, this coupled fluid-structure simulation for the foil thrust bearings is validated with experiment results from the literature. The resulting fluid-structure model can be used to assist the design of bump-type foil thrust bearings for various applications.
Atomistic Study for the Vibrational Properties on Σ5 Symmetric Tilt Bicrystal Copper Nanowires
Authors: Xing Bo Bin , Yan Shao Hua , Jiang Wu Gui , Qin Qing Hua
Published: July 2016

In this study, an atomistic simulation was performed to investigate intrinsic resonance propensity of clamped-clamped copper nanowires with Σ5 (310)/[001] symmetric tilt grain boundary. Grain boundary energy γGB for bicrystal structure was calculated based on an iterative approach. The stable atomic configuration was then doubly clamped and excited via flexural oscillation under varied temperatures. From the result, the appearance of grain boundary significantly alters the resonance properties of Cu nanowires. Greater attenuation in kinetic energy can be observed with increased temperature. Quality factors attains Q ~ 1/T0.7144 and 1/T0.7249 with temperatures from kinetic energy and centroid root mean square spectrum, respectively, where the former seems more reliable to employ at elevated temperatures.
Numerical Simulation of Aluminum Honeycomb Subjected to Combined Compression-Shear Loads
Authors: Ashab Asm Ayman , Ruan Dong , Lu Guo Xing
Published: July 2016

A full scale finite element (FE) analysis has been conducted on aluminum hexagonal honeycomb to investigate its deformation mechanism and mechanical performance under combined compression-shear loads. ANSYS LS/DYNA software has been employed in this numerical study. The honeycomb FE model has the same dimensions (cell size and cell wall thickness) as those used in the previous experimental study. The FE model has been verified by the experimental results. A good agreement between the experimental and numerical results has been reached. This numerical analysis facilitates the measurement of the vertical and horizontal forces applied to honeycomb specimens. The effects of strain rate, plane orientation of cell walls and loading angle on the plateau stress and energy absorption of honeycomb specimens under combined compression-shear loads were investigated.
Simulating Post Punching Behaviour of RC Slab-Column Connections Using a Micro Model
Authors: Xue Hui Zhong , Guan Hong , Lu Xin Zheng , Li Yi
Published: July 2016

Punching shear is a common failure mode occurring at the slab-column connection region of a reinforced concrete (RC) flat plate. Progressive collapse of RC flat plates poses a significant scientific question on the post punching behaviour of such a structural system. The challenge lies in the complex interactions amongst various internal actions including large unbalanced moments and shear forces. Existing numerical models are unable to differentiate the influence of each individual action within the connection region after punching occurs. Therefore, a new numerical model is required to model these actions individually as well as to evaluate their interrelationships. This paper thus aims to propose a numerical method to investigate the structural response of RC slab-column connections by using a micro model, based on a representative post punching failure experiment. In the micro model, concrete is simulated using solid elements whilst the reinforcement is modelled with truss elements. In this micro model, the constitutive laws and failure criteria of materials play a crucial role in describing the model’s structural behaviour. A typical structural response is discussed and a calibration method is established. Ultimately this study is expected to facilitate the development of an effective, yet simplified numerical model for future progressive collapse simulation of slab-column connections.
Numerical Investigation of Hammer Erosive Wear due to Particle Impact
Authors: Hasan Md Shahanur , de Pellegrin Dennis V. , Hargreaves Douglas , Clegg Richard
Published: July 2016

Hammers are the key machine element of high-speed hammer mills which lead to the coal pulverisation process. Progressive material loss from the hammer occurs due to the mechanical interactions between the coal particles and the hammer surface. Coal pulveriser industries implement extensive efforts to combat against premature material loss from the hammer surface due to coal particle impact which may result in premature failure. This work investigates the erosion wear mechanism through computational simulation. A numerical model is developed using Abaqus® to simulate the solid coal particle impacting onto the hammer (target).The Abaqus/Explicit® dynamic simulation solver is used for this analysis. The interactions between the solid coal particles and the target are modelled using the Abaqus/Explicit® element deletion method. The Johnson and Cook plasticity model is employed to analyse the flow stress behaviour of ductile materials during impact. The developed stress and plastic strain are analysed through simulation on the impact surface. This model is applied to different ductile alloys to determine the best erosion wear resistance hammer material for extending the operating life of hammers in the coal pulverisation process.
On Application of the Third Medium Contact Method in Analysis of Geotechnical Problems
Authors: Khishvand Mohammad , Nazem Majidreza
Published: July 2016

In computational contact mechanics, the contact constraints are usually applied using the Lagrange multiplier method, the penalty method, or alternative variants. Traditional contact approaches discretise the contact constraints in a weak sense, providing a stable interpolation scheme. However, they demand complicated search algorithms for contact detection at the interface between the intersecting bodies, and they usually lead to formulations that yield highly nonlinear tangent matrices, particularly for cases with realistic soil models and frictional contact. Recently, a new contact method based on the concept of a third medium has been developed, which overcomes the drawbacks of the conventional contact mechanics techniques. This new scheme is based on a space filling mesh in which the contacting bodies can move and interact. Contact constraints are enforced by changing the mechanical properties of medium with respect to the movements of the bodies. This new method has been developed for contact bodies undergoing large deformations using a hyper-elastic material law. In this study, the method is further extended to solve geomechanics problems in which the material behaviour is elastoplastic and the soil is subjected to large deformations. Potential merits of the third medium contact concept for analysing the geotechnical problems by the finite element method will also be addressed.
Finite-Temperature Multiscale Simulations for 3D Nanoscale Contacts
Authors: Zhang Jie , Zhang Liang , Tieu Ahn Kiet , Michal Guillaume , Zhu Hong Tao , Deng Guan Yu
Published: July 2016

A finite-temperature analysis of a multiscale model, which couples finite element and molecular dynamics, is presented in this paper. The model is evaluated by the patch test and demonstrates its capacity. Then, the multiscale scheme is used to study 3D nanoscale contacts. The linear relationship between the contact area ratio and load is observed at small loads, but the temperature effect is small. However, the change in the root mean square (RMS) of heights depends on the temperature at high loads.
A Multigrid Accelerated Code for Simulating Unsteady Conjugate Natural Convection Boundary Layers
Authors: Khatamifar Mehdi , Wood Emma Lee , Lin Wen Xian , Holmes David , Armfield Steven W. , Kirkpatrick Michael P.
Published: July 2016

This paper presents a numerical study on the flow dynamics and heat transfer behaviour of unsteady conjugate natural convection boundary layers (CNCBLs) in a partitioned, air filled square cavity. An unsteady two-dimensional multigrid-assisted solver is developed in the C#.NET programming language on stretched Cartesian meshes. The finite volume method is used to discretise the governing equations. To solve the coupled pressure and velocity, the SIMPLE algorithm is used, and to increase simulation accuracy the Adam-Bashforth, QUICK and central difference schemes are employed for time, convection, and diffusion terms respectively. The Poisson pressure equation is solved through the use of the multigrid method. The developed code is used to model CNCBLs which typically require a large amount of simulation time. The numerical results provide detailed descriptions of unsteady CNCBLs and associated heat transfer behaviour over a wide range of Ra, such as the thermal and viscous boundary layer thicknesses, temperature and velocity distributions, and maximum velocities within the CNCBLs.
Hertz Contact at the Nanoscale with a 3D Multiscale Model
Authors: Zhang Jie , Michal Guillaume , Tieu Ahn Kiet , Zhu Hong Tao , Deng Guan Yu
Published: July 2016

This paper presents a three-dimensional multiscale computational model, which is proposed to combine the simplicity of FEM model and the atomistic interactions between two solids. A significant advantage of the model is that atoms are populated in the contact regions, which saves significant computation time compared to fully MD simulations. The model is used in the case of asperity contact. The normal displacement, contact radius and pressure distribution are compared with those from Hertz’s solution and atomistic simulations in the literature. Some important features of nanoscale contacts obtained by MD simulations can be caught by the model with acceptable accuracy and low computational cost.
Effect of Ground Mineralogy on Energy Pile Performance in Dense Sand
Authors: Kazzaz Abraham , Einav Itai , Proust Gwénaëlle , Gan Yi Xiang
Published: July 2016

Geothermal energy piles have emerged as a cost effective and efficient solution for heating and cooling buildings through renewable energy. Although significant research effort has been dedicated to investigating the performance of these systems, the effect of ground mineralogy has received little attention. This study examines the likely performance of energy piles in dense sand with varying mineralogy. A 3D thermal discrete element model is used to determine the dry thermal conductivity of quartz, feldspar and mica rich sand. This is then used in a 2D finite element analysis to estimate the dissipation/extraction capacity of the soil surrounding a typical energy pile. A 35% increase in quartz content is predicted to result in 51% improvement in the thermal performance of a pile.
Investigation of Point Load Index Using Novel Discrete Based Model
Authors: Behraftar Somayeh , Heslin Joshua , Galindo Torres S. , Scheuermann Alexander
Published: July 2016

In this study, a micro-mechanical model is developed to study the correlation of the point load index in rocks with uniaxial compressive strength (UCS) tests. The model is represented by an array of bonded particles simulated by a novel discrete based model, which was introduced by the authors previously. The point load test (PLT) is performed in the field on rock samples to classify and estimate the UCS of a rock type via the index-to-strength correlation factor k. Numerical analyses, such as the one presented in this work, will serve to close the knowledge gap concerning the correlation between k, UCS and other material properties of rocks.
Exergy Analysis of Data Centres-Effect of the Rack Location and Airflow Direction on the Thermal Performance
Authors: Fakhim Babak , Behnia Masud , Armfield Steven W.
Published: July 2016

In this paper, a numerical analysis of flow and temperature distribution of a small raised-floor data centre is conducted in order to evaluate the thermal performance of the data centre. The flow patterns and temperature profiles established leads to a detailed exergy analysis of the data centre, which results in better understanding of irreversibilities in room airspace. The impact of the rack location in the data centre room and the airflow direction through perforated tiles on the thermal performance of the data centre is investigated using first-law and second-law of thermodynamics.
A Fractional Generalised Finite Difference Method to Linear Porous Media Dynamics
Authors: Zhang Y.P. , Pedroso D.M. , Li L.
Published: July 2016

The generalised finite difference method (GFDM) is a mesh-free method for solving partial differential equations (PDEs) in non-structured grids. Due to its strong theoretical background and simplicity, hence efficiency, it has been introduced to handle interesting and sophisticate engineering problems. However, the GFDM has not been applied to problems associated to dynamics of porous media yet. In these problems, the strong coupling between solid displacements and liquid pressures may cause large numerical oscillations if equal order interpolation functions are used for both variables. Nevertheless, some fractional steps techniques can be introduced in order to minimise these problems. In this contribution, a fractional steps scheme is developed and applied to the GFDM in order to model fully saturated porous media dynamics. Simulations of 1D and 2D wave propagation are performed in order to reveal the advantages, drawbacks and capabilities of the proposed method.
Meshfree Method Analysis of Biot's Consolidation Using Cell-Based Smoothed Point Interpolation Method
Authors: Tootoonchi Arash , Khoshghalb Arman , Khalili Nasser
Published: July 2016

A set of cell-based smoothed point interpolation methods are proposed for the numerical analysis of Biot’s formulation. In the proposed methods, the problem domain is discretized using a triangular background mesh. Shape functions are constructed using either polynomial or radial point interpolation method (PIM), leading to the delta function property of shape functions and consequently, easy implementation of essential boundary conditions. The Biot’s equations are discretised in space and time. A variety of support domain selection schemes (T-schemes) are investigated. The accuracy and convergence rate of the proposed methods are examined by comparing the numerical results with the analytical solution for the benchmark problem of one dimensional consolidation.
Alternative Mesh Refinement Methods for Analysing Soil Penetration Problems
Authors: Moavenian M.H. , Nazem Majidreza , Carter John Phillip
Published: July 2016

Despite recent advances in the finite element method, mesh distortion due to large deformations may still occur in some problems such as footings subjected to deep penetration or objects penetrating into a soil layer. In order to overcome mesh distortion, robust remeshing techniques are required. In this paper the performance of four remeshing methods is studied by analysing a free falling penetrometer penetrating into an undrained layer of soil. These techniques are implemented within the framework of the Arbitrary Lagrangian-Eulerian method and include the refinement based on an elastic relocation, a technique based on the Radial Basis Functions, the Spring Analogy method, and the Elastic Hardening method. Since one of the challenging problems in a large deformation analysis is dealing with complex boundary shapes, a scheme based on the B-Splines used in isogeometric analysis is also presented here.
Micro-Scale Flow Simulations and Permeability Estimation of Cleat Networks in Coal
Authors: Busse J. , Galindo Torres S. , Scheuermann Alexander , Li L. , Bringemeier D.
Published: July 2016

Coal mining raises a number of environmental and operational challenges, including the impact of changing groundwater levels and flow patterns on adjacent aquifer and surface water systems. Therefore it is of paramount importance to fully understand the flow of water and gases in the geological system on all scales. Flow in coal seams takes place on a wide range of scales from large faults and fractures to the micro-structure of a porous matrix intersected by a characteristic cleat network. On the micro-scale these cleats provide the principal source of permeability for fluid and gas flow. Description of the behaviour of the flow within the network is challenging due to the variations in number, sizing, orientation, aperture and connectivity at a given site. This paper presents a methodology to simulate flow and investigate the permeability of fractured media. A profound characterization of the geometry of the cleat network in micrometer resolution can be derived by CT-scans. The structural information is fed into a Lattice Boltzmann Method (LBM) based model that allows the implementation of virtual flow experiments. With the application of suitable hydraulic boundary conditions the full permeability tensor can be calculated in 3D.
Assessment of the Mechanical Behaviour of Granular Media by DEM-Based True Triaxial Tests
Authors: Cabrejos-Hurtado J. , Galindo Torres S. , Pedroso D.M.
Published: July 2016

This study presents the numerical simulation of a true triaxial test by means of the discrete element method (DEM). Experimental results performed on Toyoura sand are employed as reference and the calibration methodology is explained. Physical aspects of the real soil, such as the grain size distribution and the relative density, are considered during the generation of the virtual sample. It is shown that the main aspects of the macro-mechanical behaviour of granular soils during compression loading can be fairly represented by the idealised simulations with particles.
Numerical Investigation of a Hybrid FRP-Geopolymer Concrete Beam
Authors: Li Zong Jun , Khennane Amar , Hazell Paul Jonathan
Published: July 2016

Over the past years, numerical investigations have gained more attention and success in analysing the overall performance of hybrid FRP-concrete structures in civil engineering applications. In this study, a hybrid FRP-geopolymer concrete beam, which consists of high-strength geopolymer concrete filled into a rectangular hollow section pultruded GFRP profile, has been investigated numerically using the commercial software ABAQUS. A non-linear finite element model has been developed to simulate the flexural behavior of this hybrid beam under four-point static loading. Different material models were employed to describe the materials used for the hybrid beam members. The numerical results including the flexural capacity and load deflection curves are compared and verified with published experimental data from literature. The determination of dilation angle of geopolymer concrete and the effect of mesh dimensions are also compared and reported in this study. A reasonable agreement between experimental data and the numerical result is obtained, which indicates the finite element model developed in this numerical investigation is able to predict the non-linear behavior of this hybrid beam.
Influence of Architecture and Orientation in 2-Layers Fabric Structures
Authors: Yang Cheng Chou , Imbalzano Gabriele , Tran Phuong , Ngo Tuan D.
Published: July 2016

In this work, ballistic resistance of single and 2-layers aramid fabric structures with different weaving architectures and orientations were investigated via the impact tests carried out using a gas gun setup. To analyse the influence of each structural factors and their significance, a statistical study was performed using Taguchi method with a L9 matrix, which indicated the optimum structural arrangements for the 2-layer fabrics. The reduction of the velocity, the consequently absorbed energy, and the post-mortem failure modes were analysed to understand the ballistic resistance of the fabric structures studied. To investigate the damage mechanisms of different weaving structures, mesoscale Finite Element models were developed to observe the resultant velocity of the projectile, the deformation of the woven yarns, as well as the evolution of the energy components. The final model was then constructed in resembling the optimum structural arrangement derived from the Taguchi statistical study, which revealed the significance of yarn-yarn and yarn-projectile friction properties towards the ballistic resistance of the fabrics.
Influences of Material and Geometry in the Performance of Auxetic Composite Structure under Blast Loading
Authors: Imbalzano Gabriele , Tran Phuong , Lee Peter V.S. , Gunasegaram Dayalan , Ngo Tuan D.
Published: July 2016

This paper aims at investigating the deformation and damage mechanisms of auxetic sandwich panels subjected to localised blast. The ability of self-densifying and adjusting to the loads, typical of auxetic structures, has been evaluated. A numerical model of the auxetic cellular composite panel has been developed to conduct statistical studies on different parameters (core geometry and material) using Taguchi design of experiment (DOE) method combined with general linear model (GLM) for analysis of variance (ANOVA). The optimisation has been conducted evaluating different parameters: energy absorption of the entire panel and deformation of the back facet were measured. The analysis of the numerical model of the core suggests the importance of the self-adapting mechanism of the auxetic structure under blast loading.
The Effect of Non-Local Approach in Simulating Cross-Weld Tensile Test Specimen
Authors: Alisibramulisi A. , Lademo Odd Geir , Myhr Ole Runar , Larsen Per Kristian
Published: July 2016

This paper is part of ‘through process modelling of welded aluminium’ project. It describes experimental and numerical investigation on butt-welded specimens of aluminium alloy AA6060. In the experiments, tensile test was used with Digital image correlation (DIC) technique to obtain full field strain measurement on the transversely loaded specimens. The tensile properties of these specimens are presented in terms of response curves. A user defined material was implemented in the explicit finite element code for the numerical calculations. The concept of non-local approach for plane stress analyses and the Cockroft Latham fracture criterion were used respectively to reduce mesh dependence of strain localization and to predict ductile fracture. The numerical results were compared to the experimental data and the measured and predicted response was evaluated.
SIMP for Complex Structures
Authors: Munk David J. , Boyd David W. , Vio Gareth A.
Published: July 2016

Designing structures with frequency constraints is an important task in aerospace engineering. Aerodynamic loading, gust loading, and engine vibrations all impart dynamic loads upon an airframe. To avoid structural resonance and excessive vibration, the natural frequencies of the structure must be shifted away from the frequency range of any dynamic loads. Care must also be taken to ensure that the modal frequencies of a structure do not coalesce, which can lead to dramatic structural failure. So far in industry, no aircraft lifting surfaces are designed from the ground up with frequency optimisation as the primary goal. This paper will explore computational methods for achieving this task.This paper will present a topology optimisation algorithm employing the Solid Isotropic Microstructure with Penalisation (SIMP) method for the design of an optimal aircraft wing structure for rejection of frequency excitation.
Geometric Bounds for Buckling-Induced Auxetic Metamaterials Undergoing Large Deformation
Authors: Ghaedizadeh Arash , Shen Jian Hu , Ren Xin , Xie Mike
Published: July 2016

The performance of a metamaterial is dominated by the geometric features and deformation mechanisms of its microstructure. For a certain mechanism, the geometric features have bounds in which the performance of a metamaterial such as negative Poisson’s ratio (NPR) can be designed. Previous investigation on buckling-induced auxetic metamaterial revealed that there is a geometric limit for its microstructure to exhibit auxetic behaviour in infinitesimal deformation. However, the limit for auxetic metamaterials undergoing large deformation is different from that under small deformation and has not been reported yet. In this paper, the geometric limit was investigated in an elastic and infinitesimal deformation range using linear buckling analysis. Furthermore, experimentally validated finite element models were used to identify the geometric limits for auxetic metamaterials undergoing large deformation. Depending on the control parameters of the topology, the bounds were represented by a line strip for one control parameter, an area for two control parameters and spatial domain surrounded by a 3D surface for three parameters. The limit was determined by the shape and size of the void of the metamaterials and it was identified through the large deformation analysis as well as the linear buckling analysis. We found that there was a significant difference in the geometric bounds obtained through those two methods. The results from this study can be used to design an auxetic metamaterial for different applications and to control the auxetic performance.
Identification of Nonlinearities Using Computational Approaches
Authors: Critchley-Marrows Joshua , Karambhe Samanvay , Khan Denzil , Vasilikas Elias , Vio Gareth A.
Published: July 2016

This paper presents an analysis into the computational results for modelling of a two degree-of-freedom nonlinear vibrating structure. Fast Fourier Transformations, Short Time Fourier Transformations, Hilbert Transformations and wavelets are used to model this system. These techniques aim to locate and quantify the nonlinear behaviour of the system. Coulomb friction was detected with a number of these techniques, however other nonlinearities could not be detected. From the analysis conducted, improved computational methods are necessary for the detection of nonlinearities.
Design and Fabrication of Structural Connections Using Bi-Directional Evolutionary Structural Optimization and Additive Manufacturing
Authors: Seifi Hamed , Xie Mike , O’Donnell James , Williams Nicholas
Published: July 2016

The need to simplify the construction issues of complex structures leads to definition of SmartNodes project as a research which aims to confine the complexity of structure to a limited area (nodes) in order to decrease processing steps and labor intensity by application of additive manufacturing (AM) techniques. Bi-Directional Evolutionary Structural Optimization (BESO) is used to design efficient and elegant nodal connections of large scale spatial structures and minimise the volume of nodes to be printed and to ultimately replace welded, forged and cast connections by 3D printed connections. The prototypes discussed in this paper demonstrate BESO design process through two generic cases.
RANS Modelling of Shock-Wave Boundary Layer Interaction in a Mixed Compression Axisymmetric Hypersonic Intake
Authors: Kumar Abhijeet , Thornber Ben
Published: July 2016

This work focuses on developing a design methodology for a mixed compression axisymmetric hypersonic intake and numerically computing flow around the designed intake using RANS methods to study shock/shock and shock wave/boundary layer interaction. The focus of the computational study is on the effect of increasing the blunt radius of the cowl lip on the resulting shock/shock interaction between the oblique shock emanating from the cone compression apex and the bow shock on the cowl lip; as well the resulting reflected oblique shock boundary layer interaction from the cowl tip onto the cone compression surface. Three (3) radii are tested: 2mm, 16mm and 32mm at Mach 2 and the study is extended to a nominal 16mm condition at Mach 5. It is found that with increasing cowl-lip radius the magnitude of the shock-wave/boundary layer interaction increases significantly. Separation on the cone compression surface is observed at the 16mm and 32mm case at the Mach 2 position and in the 16mm case at the Mach 5 position. In addition in the 16mm and 32mm cases at the Mach 2 position, a Mach stem is observed. The shock/shock interactions, however, are found to be less dramatic. Type III and IV phenomena are observed, however, there is limited interference with the bow shock.
Natural Convection of Air through an Asymmetrically Heated Vertical Channel with a Baffle
Authors: Lei Cheng Wang , Wang Tuo Tian
Published: July 2016

The buoyancy-induced air flow through a two-dimensional vertical ventilation channel is calculated. One of the channel walls is heated uniformly, and the other wall is adiabatic. A thin baffle is placed on the heated wall to manipulate the air flow through the channel. Numerical results are obtained for baffles of different lengths and placed at various heights along the heated wall. It is found that the baffle is effective in weakening a reverse flow at the exit of the channel, and significant enhancement of ventilation performance may be achieved with the presence of the baffle.
CFD Simulation of CO2 Dispersion in a Real Terrain
Authors: Liu Bin , Liu Xiong , Lu Cheng , Tieu Ahn Kiet , Godbole Ajit , Michal Guillaume
Published: July 2016

A deeper understanding of CO2 dispersion resulting from accidental releases is essential to evaluate the risk associated with the Carbon Capture and Storage (CCS) technology. The dispersion patterns of CO2, which is a heave gas, may vary according to local conditions. In this study the possibility of simulating the dispersion of CO2 clouds over a real topographically complex area in Australia by a general purpose Computational Fluid Dynamics (CFD) code is investigated. The study may offer a viable method for assessment of risks associated with CCS.
Analysis of ZDDP Films on Sticking Defects by FEM during Hot Rolling of Ferritic Stainless Steel Strips
Authors: Hao Liang , Jiang Zheng Yi , Gong Dian Yao , Wei Dong Bin , Cheng Xia Wei , Zhao Jing Wei , Luo Su Zhen , Jiang Lei Zhu
Published: July 2016

The aim of this study is to understand the effect of zinc dialkyl dithio phosphate (ZDDP) films on sticking defects during the hot rolling of ferritic stainless steel strips. The surface characterisation and crack propagation are very important for the sticking defects of ferritic stainless steel strip. A finite element method (FEM) model is constructed with different crack size ratios, in which the profile of the strip roughness and ZDDP films are taken into consideration. Simulation results show that the widths of cracks tend to be reduced with the introduction of ZDDP films, improving the sticking defects, which is confirmed by the hot rolling trials.
Microplane Model for Concrete: Part II - Applications on CFRP Confined Concrete Elements
Authors: Gambarelli Serena , Nisticò Nicola , Ožbolt Joško
Published: July 2016

In the paper the main results of numerical study presented in Gambarelli et al. [1] on concrete elements confined by carbon fiber reinforced polymer (CFRP), are overviewed. Furthermore, preliminary results of numerical simulations performed at mesoscale are presented.The numerical study is based on a extensively experimental campaign conducted by Wang and Wu [2] on small CFRP-confined concrete columns loaded in uni-axial compression. The specimens are characterized by constant size but different cross-section corner radius (from square to circular cross section). The experimental results clearly demonstrate that CFRP confinement is much less effective in square then in circular cross-section.Several numerical models have been performed at macro-scale and meso-scale to confirm the predictability of the used numerical approach, based on the microplane constitutive law for concrete [3]. In the finite element model carbon fibers (truss FE) are embedded into matrix (solid 3D FE). The same as for concrete, the constitutive law for matrix is also based on the microplane model.It is demonstrated that the numerical model is able to predict behavior of confined concrete columns from the experimental investigations. Therefore, the results of the study confirm the predictability of the used numerical approach.
Cyclic Behaviors of Steel Braces in Concentrically Braced Frames
Authors: Zhou Zhi Hao , Nuti Camillo , Lavorato Davide , Bergami Alessandro Vittorio
Published: July 2016

In this paper, a new model named as “brace01” for steel brace is presented on the basis of experimental data on different types of steel struts. This model shows a peasant capability in the structural analysis of Concentrically Braced Frames. A brace is idealized as a pin-ended member with a plastic hinge located at its midspan. This expression of the model is proposed by combining the mechanical properties and the phenomenological characters. The model for steel brace is implemented in an effective way in OpenSees. The calibration of the material model is done by comparing the numerical curves generated by the numerical model with the experimental curves of pin-ended steel braces. The new model is proved applicable to practical Concentrically Braced Frame.
Finite Element Calculation for the Tensile Elastic Modulus of Honeycomb Materials with Different Pore Shape
Authors: Su Shu Lan
Published: July 2016

The square and hexagonal honeycomb materials were studied by finite element simulation of tensile test in order to calculate the elastic modulus in tension under different porosity and to analyze tensile properties affected by the pore shape of honeycomb materials. Research results show that the tensile elastic modulus of the square honeycomb is larger than the hexagonal honeycomb. The reason is that the square structure has a larger stiffness than hexagonal structure. Also, the equivalent elastic moduli of calculated values are higher than the theoretical values, because the finite element model is based on solid elements while the theoretical model is based on the Euler beam.
Modified Monti-Nuti Model for Different Types of Reinforcing Bars Including Inelastic Buckling
Authors: Zhou Zhi Hao , Nuti Camillo , Lavorato Davide
Published: July 2016

The material model for reinforcing bar takes a very important role in the seismic analysis of reinforced concrete structures. The seismic performance of the structural elements such as column will be overestimated if the inelastic buckling is not incorporated in the material model. The Monti-Nuti Model could consider the buckling effect properly. The critical slenderness and anisotropy were discussed which has an important effect on the seismic behaviors of the reinforcement. Then this paper proposed a modified Monti-Nuti Model for different types of reinforcing bars, such as carbon steel reinforcement and stainless steel reinforcement including inelastic buckling. Subsequently, the implementation of the modified Mont-Nuti Model in OpenSees was introduced. Through validating with the experimental curves, the numerical curves generated by the modified model verified its capability.
Rapid Repair Technique to Improve Plastic Dissipation of Existing Chinese RC Bridges
Authors: Lavorato Davide , Nuti Camillo , Briseghella Bruno , Santini Silvia , Xue Jun Qing
Published: July 2016

A rapid repair and retrofitting technique for reinforced concrete (rc) Chinese existing bridges damaged by a strong earthquake, is proposed and tested. These bridges were designed according to Chinese codes [1] [2] [3] but with insufficient transversal steel reinforcement. The damaged rebar and concrete parts were replaced by new bar systems and concrete cast respectively. Finally, a C-FRP wrapping was applied to increase the insufficient shear strength and to guarantee the necessary ductility in plastic hinge. This repair technique is an upgrade of the one tested with very good results during a previous experimental research [4] on bridge designed according to old Italian code [5] without proper seismic details. A new bar system assures that plastic dissipation is distributed in plastic hinge only. Some pier specimens (in scale 1:6) were built with and without the new bar systems. These specimens were tested by cyclic tests at Fuzhou University lab (China) to evaluate the effectiveness of the intervention.
Amplified Seismic Loads in Steel Moment Frames
Authors: Aksar Bora , Dogru Selcuk , Akbas Bulent , Shen Jay , Seker Onur , Wen Rou
Published: July 2016

This study focuses on exploring the seismic axial loads for columns in steel moment resisting frames (SMRFs) under strong ground motions. For this purpose, the increases in axial loads are investigated at the maximum lateral load level and the corresponding lateral displacement. The results are presented in terms of maximum amplification factors (Ω0) of all frame columns under the selected ground motions and axial load-moment levels in columns. four typical steel moment resisting frames representing typical low, medium and high rise steel buildings are designed based on the seismic design requirement in ASCE 7-10 and AISC 341-10 . An ensemble of ground motions range from moderate to severe are selected to identify the seismic response of each frames. Two sets of ground motions corresponding to 10% and 2% probability of exceedance are used in nonlinear dynamic time history analyses.
A Direct Five-Step Procedure for the Dimensioning of Viscous Dampers to Be Inserted in Frame Structures
Authors: Palermo Michele , Silvestri Stefano , Gasparini Giada , Trombetti Tomaso
Published: July 2016

Many design methods for the design of viscous dampers to be inserted in building structures are available in the scientific literature and building codes. Among others, the authors proposed a five-step procedure guiding the practioner from the choice of a target reduction in the seismic response of the structural system (with respect to the response of a structure without any additional damping devices), to the identification of the corresponding damping ratio and the mechanical characteristics of the commercially available viscous dampers. The original procedure required the development of numerical simulations for the evaluations of the peak inter-storey velocity profiles, necessary for the evaluation of the non-linear damping coefficient. More recently, a fully analytical version of the 5-step procedure (direct) has been also introduced. In the present work, an application of the direct procedure for a three-storey school building is presented.
M-N Interaction Effect on the Frames Failure Mechanisms
Authors: Buonocore Giuseppe , Gesualdo Antonio , Iannuzzo Antonino , Modano Mariano , Monaco Michela , Savino Maria Teresa
Published: July 2016

The collapse factor is a significant parameter in the framework of the safety assessment and economical design of ductile structures. This fact draws attention to the necessity of a careful assessment of the limit analysis approaches. The kinematics in these structures arises in fact from the actual rotation of the plastic hinges under axial force and bending moment. It can be shown that it is possible to obtain a reliable tool capable of competing with computationally expensive methodologies. The application of the methods of limit analysis involves a simplified and idealised model of the structure and, notwithstanding the fact that hundreds of papers have been devoted to the topic, some consequences of apparently unimportant simplifications still seem to have not been properly and firmly highlighted. This paper investigates the ultimate load and collapse modes of steel frames under combined vertical and horizontal forces through limit analysis.
Fatigue Behavior of Cement Asphalt Emulsion Mortar
Authors: Tian Dong Mei , Yin Jian
Published: July 2016

As one of the key components of non-ballast slab track in high speed railway, cement asphalt emulsion mortar (CAM) has low compressive strength and low elastic modulus. This makes CAM possible to be served as supporting, height-adjusting, vibration-dissipating and deformation-fitting sandwich-layer between pre-stress slab and concrete roadbed. To study the fatigue behavior of the CAM, fatigue tests were conducted at room temperature and negative temperature, respectively. The permanent strain, elastic modulus and yield strength of fatigue-tested specimens were compared to the reference one. The results showed that the small permanent deformation lead to very little displacement differences among the slab track system. Secondly, the elastic modulus and yield strength of fatigue test specimens were both higher than that of reference one. Because the fatigue process might strengthen the CAM by compacting micro-cracks. Additionally, arising from the temperature sensitivity of asphalt, viscosity behavior of asphalt mortar at room temperature is changed to brittleness behavior at negative temperature.
Ductility Enhancement in Reinforced Concrete Structure with Buckling Restrained Braced Frames
Authors: Senol Erkan , Kose Ismail , Doran Bilge , Mezrea Pelin Elif , Akbas Bulent
Published: July 2016

Adding braces to moment frames is considered to be quite an efficient technique for increasing the global stiffness and strength of the structure. It has not only been used in steel moment frames, but also in reinforced concrete (RC) moment frames in recent years. It certainly can increase the energy absorption capacity of structures and also decrease the demand imposed by seismic ground motions. Steel braces are anchored firmly to boundary beams and columns. They are modeled as truss elements and increase earthquake resistance of the building. Buckling restrained braced frames (BRBFs) in which members yield under both tension and compression without significant buckling have been used in recent years in order to ensure the desired seismic performance of special concentrically braced frames. BRBFs are similar to the special concentrically braced frames in that seismic accelerations are resisted by a building-frame members and diagonal braces whereas the design procedure is different. BRBs should be designed to permit ductile yielding both in compression and tension. In this paper, flat-slab RC building with two different configurations of buckling restraint braces (BRBs) is studied. The buildings have 4-storey with 5 bays in both X-and Y-directions and have been designed according to Turkish Specification of Reinforced Concrete Design (TS 500). In order to explore overall behavior up to failure and lateral load resisting capacities for these buildings, nonlinear static analyses have then been performed using SAP 2000-V14.1. Pushover analysis under constant gravity loads and monotonically increasing lateral forces during an earthquake until a target displacement is reached is generally carried out as an effective tool for performance based design. The major outcome of a pushover analysis is the capacity curve which shows the base shear vs. the roof displacement relationship and represents the overall performance of the building. The results of the analyses are presented in terms of capacity curve and energy dissipation.
Optimization Analysis of Seismic Damage Evaluation Model Based on Fuzzy Analytical Hierarchy Process
Authors: Sun Ying , Chen Tian Hai , Zhuo Wei Dong , Gu Yin , Ping Shang Guan
Published: July 2016

The establishment of fuzzy judgement matrix plays an important role in the accuracy of seismic damage assessment using Fuzzy Analytic Hierarchy Process (FAHP). The optimization analysis is mainly focus on the fuzzy judgement matrix because the important value of each two influencing factors is given by the seismic damage experience and seismic design theory subjectively. In this paper, the initial fuzzy judgement matrix has been set up and the assessment results are given by them. Optimization analysis of single factor is carried out in the adjustment of fuzzy judgement matrix to obtain the best assessment results under the assumption of keeping the fuzzy evaluation matrix of index layer unchangeable. The result shows that accuracy of assessment calculated by the optimal fuzzy judgement matrix has been improved by 1.48%.
Experimental Study on the Size Effect on Flexural Behavior of Larch Glulam Beams
Authors: Zhou Xian Yan , Cao Lei , Zeng Dan
Published: July 2016

At present, design values in codes and regulations are mainly based on test results of small size specimens, which are different from large-scale members used in practical engineering, therefore size adjustment coefficients are needed to be established. The four-point bending test method was adopted to investigate four groups of different sizes of Larch Glulam beams in their flexural behavior. Experiment data such as ultimate bearing capacity, deflection, strains and others are obtained, and the failure pattern and failure mechanism of bending members are analyzed. The research results indicate that the bending modulus of elasticity of Larch Glulam beam is not affected by the size. Bending strength of the Larch Glulam beam show a declining trend as the size of specimens increases, however, the ultimate bending moment increases. In addition, by means of a two-parameter Weibull model, a so-called size effect coefficient has been calculated by the slope method, thus providing a basis for the design and application of Larch Glulam beams.