bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Seismic Ground Response in Makassar Using Geotechnical In Situ Tests
Authors: arsyad ardy , Muhiddin Akhmad Bakri , Rante Ryan , Djamaluddin Abdul Rahman , Suprapti Ariningsih
Published: July 2016

This paper presents the analysis of seismic ground response of Makassar, the capital city of South Sulawesi Province in Indonesia, by employing an equivalent linear approximation of non-linear response technique. In this way, in-situ geotechnical tests were undertaken to obtain soil mechanics properties and establish shear wave velocity profiles by using CPT and SPT based empirical correlation formulas. Acceleration time histories model, which is considered to be able to propagate similar maximum credible earthquake, was used for input motion in computing seismic ground response of typical deep sediment in Makassar. Our findings suggested that seismic wave travels from bedrock to surface would be amplified at range of 0.124g to 0.349g with amplification factor of 1.14 to 5.54. Response spectral acceleration is found at range of 0.315g to 1.501g with the frequency of 7.69 Hz to 20 Hz. The southern areas of the city would propagate a high seismic amplification, while the eastern areas would yield low amplification. This is due to typical deep sediment seated on the southern areas is a thick clay overlying stiff sand. This would create impedance contrast, leading to reverberating a trapped seismic wave in between those two layers, and then producing high resonance at surface level. Deep sediment with interbedded clay and sand or interbedded sand and clay above bedrock would yield a larger seismic amplification than deep sediment with only clay dominated or sand dominated soil.
Axial Pile Capacity Prediction Obtained from Environmental Friendly Jack-In Piling Test on Clayey Soil
Authors: Muslih Purwana Yusep , Silmi Surjandari Niken , Wahyu Haryanto
Published: July 2016

Jack-in piling is environmental friendly system enabling placement of the pile into soil layer with minimum disturbance. It works with very low noise, low vibration, allows piling in confined area, relatively very fast in term of installation rate, better quality control and very fast in mobility. The main issue regarding the pile is bearing capacity; the ability of the pile to withstand axial load without failure. This study attempts to find the correlation between jack-in force and ultimate pile bearing capacity. The result of 5 piling record on clayey layer soil indicates that there is a good correlation between jack-in force and empirical ultimate pile bearing capacity.
A Numerical Procedure for Modelling the Thermal Performance of Ventilated Hollow Core Slabs
Authors: Faheem Ahmed , Ranzi Gianluca , Fiorito Francesco , Lei Cheng Wang
Published: July 2016

This paper presents a numerical procedure for modelling the thermal performance of ventilated hollow core slabs (VHCS). A turbulence model suitable for this purpose is identified first by considering a smooth horizontal pipe subjected to turbulent mixed convention conditions typical of VHCSs. Comparison of the fully-developed dimensionless velocity (u+) and temperature (T+) profiles as well as the Nusselt numbers (Nu) predicted by five different turbulence models against empirical expressions available in the literature shows that the Standard and Realisable k-ε models provide the best overall predictions of u+, T+ and Nu. Since the Standard k-ε model gives slightly better estimates of the Nu values, it is adopted to model the thermal performance of a VHCS geometry for which experimental thermal responses are reported in the literature. The numerical predictions of local temperatures within the VHCS agree well with the experimental measurements, and hence the Standard k-ε model is recommended here for the modeling of VHCSs.
Numerical Modelling of Degradation of Cement Paste under External Sulfate Attack
Authors: Yu Yu Guo , Khennane Amar , Zhang Yi Xia
Published: July 2016

In this study, a numerical method is developed to simulate the degradation of cement paste when subjected to sodium sulfate solutions. The proposed numerical method accounts for ionic diffusion, chemical reactions and the damage propagations, which are three main phenomena accompanied with degradation. A modified Poisson-Nernst-Planck model is developed to model the diffusion of multiple ions in a gradually degraded material. The cracking suction effect is introduced to consider the suction action caused by the newly-formed unsaturated cracks, which would accelerate the diffusion process within the cracking area. The proposed model is applied to model the experiments reported in the literature. The numerical results obtained agree very well with those from experiments.
Numerical Modelling of Mechanical Behaviour of Fibre Reinforced Cementitious Composites
Authors: Tian He , Zhang Yi Xia , Yang Chun Hui
Published: July 2016

In this paper, a new numerical model is developed to model the tensile behavior of the cementitious composites reinforced with hybrid bagasse fibres and steel fibres based on the extended finite element method. The numerical model considers random fibre distribution, which is generated automatically, and the cohesive behavior, which represents the bonding between fibres and the matrix. The cementitious matrix is modeled using extended finite element method. The developed numerical model is implemented in commercial software ABAQUS and the computed results are compared with the corresponding experimental results for numerical validation. It is found that the tensile behavior of the composites predicted from the new numerical model is consistent with that obtained from experimental study, and that the developed numerical model can accurately predict the uniaxial tensile behavior, including the post-cracking behavior of fibre reinforced cementitious composites.
Thermal Buckling and Postbuckling Analysis of Functionally Graded Carbon Nanotube-Reinforced Composite Beams
Authors: Wu He Long , Kitipornchai Sritawat , Yang Jie
Published: July 2016

Thermal buckling and postbuckling of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) beams are investigated in this paper based on Timoshenko beam theory within the framework of von Kármán geometric nonlinearity. The material properties of FG-CNTRCs are assumed to be temperature-dependent and vary in the beam thickness direction. The governing equations are derived by employing Hamilton’s principle then discretized by using differential quadrature (DQ) method. An iterative scheme is used to obtain the critical buckling temperature and nonlinear thermal postbuckling equilibrium path of the FG-CNTRC beam. Numerical results are presented for FG-CNTRC beams hinged or clamped at both ends, with particular focuses on the effects of the volume fraction of carbon nanotubes (CNTs), slenderness ratio, and end supports on the thermal buckling and postbuckling characteristics.
Nonlinear Vibration Analysis of a Dielectric Elastomer Based Microbeam Resonator
Authors: Feng Chuang , Yang Jie , Ke Liao Liang
Published: July 2016

Dynamic characteristics of a dielectric elastomer based micro beam resonator are investigated by taking into consideration of squeeze-film damping, large deformation and electrical voltage. The analysis shows that the resonant frequency of the resonator can be tuned through changing applied electrical voltage. It is observed that the natural frequency of the resonator increases with the increase of the vibration amplitude. In addition, the ambient pressure can significantly alter the resonant frequency of the resonator. The analysis is envisaged to provide qualitative predictions and guidelines for design and application of DE-based micro resonators.
Rotor Vibration under the Coupled Effects of Mass Unbalance and Asymmetric Bearings
Authors: Spagnol Joseph Patrick , Wu Helen
Published: July 2016

Large unbalance in rotor-dynamic systems is typically responsible for high energy vibrations and the consequent decrease in machine life. This paper presents an analytical model developed using Lagrangian mechanics and partial differential equations (PDEs) for the purpose of early fault-detection in rotor-bearing systems. The model was validated through a Fortran based program, RDA99 developed by Adams (2010), by successfully quantifying the single-peak unbalance response of the simple 8 DOF and 12 DOF rotor-bearing mass stations over two cases. Case I uses bearings with symmetric stiffness and damping matrix. The critical speed for Case I occurred at 1690 rpm and orbital shapes of each mass station was found to be circular with forward-whirl orbits. In Case II asymmetrical bearing stiffness and damping coefficient matrices demonstrate an anisotropic system. Critical speed occurred at 1655 rpm and rotor, bearing and pedestal orbits were seen to be elliptical and changing with shaft speed. Both cases demonstrated a significant shaft bending contribution to the disk displacement.
Numerical Investigation on the Failure Behavior of Brittle Granular Chain under Impact
Authors: Liu Dong Xin , Shen Lu Ming , Einav Itai , Guillard Francois
Published: July 2016

In brittle granular materials, the fragmentation waves have received far less attention due to their complexity despite of their significant role in mineral processes, earthquake hazards control, etc. In this research, the Material Point Method (MPM) is used to analyze how fragmentation waves propagate in a 3-dimensional 10 brittle beads chain with a rate-dependent elasto-damage model. The simulations show that generally, the second bead will become the most severely damaged one, followed by the third bead. Most failure points will appear near the contact surface between the brittle spheres and extend to interior conically. An interesting phenomenon is that with a lower damage threshold or fracture energy, despite of the increase of total damage in the whole chain, less damage is developed in some beads after a period of time. This is mainly because more damage in the beginning dissipates excessive stress wave energy to the extent such that the reflected wave will not be able to cause more damage in the local system.
Coupling Effects of Chloride Penetrating and Corrosion Damage Evolving Process in Concrete under Marine Environment
Authors: Zhang Qin , Guo Li , Guo Xiao Ming
Published: July 2016

Chloride penetration could lead to the rebar corrosion and cause the durability problem in concrete structure under marine environment. It is a coupling process between chloride penetrating and corrosion damage evolving in concrete. This paper proposed an analysis method to deal with this coupling problem. The corrosion damage degree was considered as an internal variable in coefficients of chloride diffusion. Additionally, the interfacial boundary displacement values varied with chloride concentration and service time of concrete structure. This iterative computing algorithm was tackled as user subroutine packaged into software ABAQUS. The numerical examples were given to confirm the reliability of the developed model. The results show that corrosion expanded damage accelerates chloride ions diffusion and vice versa.
Finite Element Modeling of Bolted Cold-Formed Steel Storage Rack Upright Frames
Authors: Talebian Nima , Gilbert Benoit P. , Baldassino Nadia , Guan Hong
Published: July 2016

Steel storage racks, commonly assembled from cold-formed steel profiles, are braced in the cross-aisle direction, where bracing members are typically bolted between two uprights forming an “upright frame”. Especially for high-bay racks and racks supporting the building enclosure, accurately determining the transverse shear stiffness of upright frames is essential in calculating the elastic buckling load, performing earthquake design and serviceability checks. International racking specifications recommend different approaches to evaluate the said transverse shear stiffness. The Rack Manufacturers Institute (RMI) Specification conservatively uses an analytical solution based on Timoshenko and Gere's theory while the European (EN15512) and Australian (AS4084) Specifications recommend testing to be conducted. Previous studies have shown that Finite Element Analyses (FEA), solely using beam elements, fail to reproduce experimental test results and may overestimate the transverse shear stiffness by a factor up to 25. This discrepancy is likely attributed to the local deformations occurring at the bolted joints. In this paper, a commercially used upright frame configuration has been modeled using shell elements in FEA and the response is verified against published experimental test results. A good correlation is found between the FEA and test results, concluding that shell elements are able to fully capture the behaviour of the upright frame. Future studies on the use of the FE model are also presented.
A New Approach for Determination of the Attenuation Bandwidth of a Resonating Metamaterial
Authors: Banerjee Arnab , Das Raj , Calius Emilio P.
Published: July 2016

Due to the presence of internal structures, metamaterials, a new class of artificial materials, can be engineered to have various unconventional properties during wave interaction. They can be rationally designed to offer controlled mechanical, acoustic or electromagnetic properties through resonant electromagnetic, acoustic or mechanical structures inside the metamaterial. Due to these properties, metamaterials have been effectively used for cloaking, wave guiding and designing filters in the field of optics, electromagnetics, acoustics and elastodynamics. In this paper, a Fourier transfer based methodology is proposed to determine the attenuation bandwidth of a metamaterial instead of using conventional Bloch’s theorem. The applicability of this method is wider than that of Bloch’s theorem, because this method allows analysis beyond the necessary periodicity of the metamaterial. All the governing equations are non-dimensionalised to effectively quantify the attenuation bandwidth at the lower and higher frequency range of the resonating frequency of the internal structures present in the matrix of the material. The attenuation bandwidth is characterized into low and high frequency parts to determine the effect of the variation of the mass ratio and the number of the repeating units on the attenuation bandwidth of the 1D metamaterial chain.
Two-Layer Red Blood Cell Membrane Model Using the Discrete Element Method
Authors: Barns Sarah , Sauret Emilie , Saha Suvash , Flower Robert , Gu Yuan Tong
Published: July 2016

The red blood cell (RBC) membrane consists of a lipid bilayer and spectrin-based cytoskeleton, which enclose haemoglobin-rich fluid. Numerical models of RBCs typically integrate the two membrane components into a single layer, preventing investigation of bilayer-cytoskeleton interaction. To address this constraint, a new RBC model which considers the bilayer and cytoskeleton separately is developed using the discrete element method (DEM). This is completed in 2D as a proof-of-concept, with an extension to 3D planned in the future. Resting RBC morphology predicted by the two-layer model is compared to an equivalent and well-established composite (one-layer) model with excellent agreement for critical cell dimensions. A parametric study is performed where area reduction ratio and spring constants are varied. It is found that predicted resting geometry is relatively insensitive to changes in spring stiffness, but a shape variation is observed for reduction ratio changes as expected.
A Review of Skin Buckling Theory in Composite Members
Authors: Dong Jiang Hui , Ma Xing , Mills Julie E. , Yan Zhu Ge
Published: July 2016

This paper provides a comprehensive review of various methods used for skin buckling analysis in composite components. The skin buckling phenomenon is one of the governing criteria in composite design. It is a kind of contact buckling in which partial sections of skin buckle away from the filler material. In general, the problem can be modelled as a thin plate (skin) in unilateral contact with elastic medium (filler material). The theoretical analysis of contact buckling is complicated due to the nonlinearity arising from changing contact regions. To simplify the calculations, the filler material was usually modelled as a tensionless elastic foundation. The skin buckling coefficient varies in terms of the relative foundation stiffness factors. Because the Eigen-value method is not applicable to nonlinear systems, the finite element (FE) method was usually employed for post-buckling analysis, while initial buckling performance was investigated through analytical or semi-analytical methods such as rigid foundation model, infinite plate model and finite plate model. The compressive buckling and shear buckling problems for thin plates resting on tensionless foundations have been solved successfully. However, there are still urgent needs for future research on the topic. For example, the load carrying capacity of the buckling plates needs to be formulated for practical application. Complicated problems with complex loadings and/or corrugated skins need further investigation as well.
Analysis of Gear Strength by Static and Dynamic Finite Element Methods
Authors: Zhou Chang Jiang , Chen Si Yu , Ma Lin
Published: July 2016

As key factor of numerical simulation for gear strength, namely determination of effective loads between meshing teeth profiles, their numerical calculation principles of static and dynamic finite element methods are analyzed according to the loads on gear teeth. The static analysis of gear strength can be classified to effective statics and static contact analysis, and the numerical simulation method for face distribution as the rule of Hertz contact is advanced. The differences between static and dynamic contact and their influences in results are researched. Compared with the empirical formulas, the analytical results about bearing capacity of gear drive under different effective loads show: (1) As the sequence of concentrated force, linear distribution force, face distribution force as the rule of Hertz contact, static contact analysis, the accuracy and reliability of calculating results under different effective loads are improved, especially the results from face distribution and static contact being very close. (2) Dynamic contact analysis can be used to simulated the effect well. The above studies could be referenced to calculation in bearing capacity of gear drive.
Simulations of Fall Cone Test in Soil Mechanics Using the Material Point Method
Authors: Llano-Serna M.A. , Farias M.M. , Pedroso D.M. , Williams David J. , Sheng D.
Published: July 2016

The material point method is a particle-based method that uses a double Lagrangian-Eulerian discretisation. This approach has proved its functionality for the simulation of large deformation problems. Such problems are frequent in geotechnical engineering, more specifically those related to penetration during pile driving and conventional in situ tests such as the Cone Penetration Test. The shallow laboratory fall cone test is considered in this paper. This test is widely used for the determination of the liquid limit of clays, but it is also used to study the relationship between penetration (h) and the undrained shear strength of clays (su). Simulations are verified against laboratory vane shear tests and fall cone tests performed on samples of kaolin clay at different moisture contents. Calibrations using a simple penetration-strength (h-su) model are made based on a single coefficient named the cone factor (K). The numerical results closely match both the experimental data and analytical solutions available in the literature.
Dynamic Analysis of Unsaturated Soils Subjected to Large Deformations
Authors: Ghorbani Javad , Nazem Majidreza , Carter John Phillip
Published: July 2016

This paper deals with the large deformation analysis of partially saturated soils subjected to dynamic loading. The so-called ‘mixture’ theory is employed to consider the hydro-mechanical coupling involved in this kind of problem. The finite element method is used to discretise the problem domain and the generalized-α algorithm is employed to integrate the governing equations over time. Some of the most challenging aspects of dynamic analysis of partially saturated soils will be discussed. One of the key challenges is selecting a consistent constitutive model within the theory of mixtures that can incorporate the pore suction forces into the description of stress. The necessity of such incorporation has frequently been reported in experimental studies of unsaturated soils. To tackle this problem, a unique strategy for integrating the constitutive model for unsaturated soils is adopted. Moreover, an absorbing boundary condition, which prevents wave reflection from rigid boundaries, is introduced and implemented into the numerical algorithm. Finally, a solution for the problem of dynamic compaction of soil in a partially saturated condition is presented.
Enriched Finite Element for Modelling Variable Boundary Conditions in Unsaturated Seepage Problems
Authors: Pedroso D.M.
Published: July 2016

Partial differential equations such as models for flow in unsaturated porous media are difficult to be solved when space-time variable boundary conditions are included. A general solution to this problem is discussed in this contribution and is devised in such a way that the face with variable boundary condition can be subjected to Dirichlet, Neumann or the so-called Signorini/ambiguous boundary conditions, considering the transition from one type to another. A method based on the enrichment of finite elements that is able to accurately model seepage with these complex boundary conditions is discussed. Simulations are presented illustrating the capabilities of the new method in 2D and 3D, including cases where the free surface varies due to rain.
Probabilistic Reliability Assessment of Slope Stability Problems with Genetic Algorithms
Authors: Tun Y.W. , Pedroso D.M. , Scheuermann Alexander
Published: July 2016

Uncertainty estimation and consideration in engineering is an important practice to design reliable structures especially in geotechnical engineering since the level of control with regards to the material parameters is much lower. Research has been conducted in order to assess the reliability of geotechnical works using probabilistic methods where challenges in computing the probability density function and predicting the critical failure region must be first overcome. One method to solve this problem is the Monte Carlo simulation; however it requires a high computational effort. Alternatively, reliability indices such as the Hasofer-Lind (HL) index can approximate the probability of failure Pf with fewer computations. Nonetheless, yet an optimisation problem needs to be solved. In this work, a genetic algorithm is developed to compute the HL index using the limit equilibrium method to search for the critical failure surface. Study cases and the analysis of the Vajont landslide are presented in order to illustrate the method.
Assessment of a Method to Model 2D Discontinuities with Enriched Finite Elements and Level Sets
Authors: Schmidt Patrick , Pedroso D.M. , Mühlhaus Hans , Scheuermann Alexander
Published: July 2016

The computational treatment of discontinuities within the framework of the finite element method (FEM) is a requirement for simulations of fracturing of solids and has become a challenging topic in computational mechanics. Particularly popular amongst the advanced schemes is the extended finite element method (XFEM) which is based on enrichment of shape functions and falls within the framework of the partition of unity method. Because there is no simple way to track the interface of discontinuities, the computer implementation of the XFEM is not as straightforward as the FEM. One method to solve the interface tracking problem is the level set method (LSM) which introduces another partial differential equation. The level set equation describes the change of an interface due to a known velocity field. To obtain its solution, the FEM can also be employed. This contribution investigates the XFEM-LSM technique with element enrichment and the integration of discontinuous elements for the modelling of cracks or material interfaces. Numerical experiments illustrate the capabilities and accuracy of the resulting formulation.
Discrete Modelling of Soil-Inclusion Problems
Authors: Thoeni K. , Effeindzourou A. , Chareyre Bruno , Giacomini A.
Published: July 2016

A generalised approach for the modelling of arbitrary shaped deformable structures in the framework of the discrete element method is presented. Minkowski sums of polytopes and spheres are used to describe the geometry of rounded cylinders and particle facets. In the current formulation, these new elements can be deformable. Their deformation is defined by the set of positions and orientations of their nodes. The elements can be connected to form arbitrary structures, such as grids and membranes. The constitutive behaviour of such connections is defined via an elastic perfectly plastic beam model. Contacts between other not connected structures or particles are detected based on three simple primitives: spheres, cylinders and thick rounded facets. The introduction of a virtual sphere at the contact point not only allows for straightforward contact handling but as well for the use of standard contact models based on sphere–sphere interactions. Hence, there is no need for developing new contact models. The approach is implemented into the open-source framework YADE. The capability of the newly developed approach for the modelling of soil–inclusion problems is presented.
Finite Element Simulation for Nonlinear Finite Element Analysis of FRP Strengthened RC Beams with Bond-Slip Effect
Authors: Pathak Prabin , Zhang Yi Xia
Published: July 2016

A new simple, efficient and accurate finite element model denoted as FEM-B is developed for the analysis of structural behavior of FRP strengthened RC beams with bond-slip effect. Geometric nonlinearity and material nonlinear properties of concrete and steel rebar are accounted for this model. Concrete, steel, FRP and adhesive are modelled as Solid 65, Link 180, Shell181 and Solid 45 respectively. Concrete is modelled using Nitereka and Neal’s model for compression, isotropic and linear elastic model before cracking for tension and strength gradually reduces to zero after cracking, whereas steel is assumed to be elastic perfectly plastic material. The material of FRP is considered to be linearly elastic until rupture, and adhesive is assumed to be linearly elastic. The bond slip between concrete, adhesive and FRP is based on the bilinear law, which is modelled using spring element Combin 39.The developed new finite element model FEM-B is validated against experimental results, and demonstrates to be effective for the structural analysis of FRP strengthened RC beams.
The Influence of Incoming Boundary Layer on the Flow around the Surface Excrescence
Authors: Bi Yao Zu , Thornber Ben
Published: July 2016

This paper is concerned with the accurate prediction of parasitic drag due to excrescences introduced by structural repairs to aircraft wings and fuselage. Numerical computations are carried out to quantify the effect of isolated surface excrescences in a turbulent boundary layer on a flat plate. Both step excrescence in 2-D domain and wall-mounted hexahedron in 3-D domain are considered in the investigation. Various approaches for calculating drag coefficient increments for wing repair plates are presented. Menter's Shear Stress Transport (SST k-ω) turbulence model is employed here for its accurate prediction of aeronautics flows at typical repair locations with strong adverse pressure gradients and separation. Solutions are obtained via a high-order numerical scheme and an implicit time-marching approach on a multi-block structured mesh. A grid resolution study was carried out to confirm the accuracy of the computations. From the results curves are drawn showing the variation of parasitic drag components for a range of controlled speed (Mach 0.1 to 0.8), local Reynolds number (104 to 107) and the height of excrescence (y+=102 to 104).
XFEM Fracture Modelling for Implant-Supported Fixed Partial Dentures
Authors: Zhang Zhong Pu , Liao Zhi Peng , Yoda Nobuhiro , Li Wei , Sasaki Keiichi , Hong Guang , Swain Michael V. , Li Qing
Published: July 2016

The dental implants have been increasingly used for replacing missing teeth over the past three decades. However, its mechanical strength remains a major concern to dental clinicians and patients. To investigate failure modes and fracture loads of implant-supported fixed partial bridge, eXtended Finite Element Method (XFEM) was employed in this study. The 3D finite element (FE) models simulating full mandibular teeth and implant-supported three-unit fixed partial denture (FPD) were developed to determine the crack initiation and propagation in the dental prostheses. The failure modes and fracture loads are compared for three typical treatment scenarios: namely three-unit FPD supported by two implants at left second premolar and first molar (named as cantilever Model-IIP), second premolar and second molar (bridge Model-IPI), and first and second molars (cantilever Model-PII). The XFEM analyses show that the bridge Model-IPI exhibited considerably high fracture resistance than the other two configurations. Model-IIP displays the worst fracture strength of these three case scenarios. The results provide a basis for clinical assessment of mechanical strength for implant-supported FPD or other restorative devices.
A Hypersonic Aircraft Optimization Tool with Strong Aerothermoelastic Coupling
Authors: Munk David J. , Vio Gareth A. , Verstraete Dries
Published: July 2016

The design and optimization of hypersonic aircraft is severely impacted by the high temperatures encountered during flight as they can lead to high thermal stresses and a significant reduction in material strength and stiffness. This reduction in rigidity of the structure requires innovative structural concepts and a stronger focus on aerothermoelastic deformations in the early design and optimization phase of the design cycle. This imposes the need for a closer coupling of the aerodynamic, thermal and structural design tools than is currently in practice. The paper presents a multi-disciplinary, closely coupled optimization suite that is suitable for preliminary design in the hypersonic regime. The time varying temperature distribution is applied through an equilibrium analysis, and is coupled to the aerodynamics through the Tranair® solver. An analysis of the effect that the aerothermodynamic coupling has on the sizing of the aircraft is given, along with the effect of skin buckling. It is shown that the coupling of the aerothermodynamics drives the sizing of the structure and therefore must be considered for hypersonic applications.
The Research of Calculation Method on Vertical Natural Frequency of the New Full-Prefabricated Floor
Authors: Sun Chong Fang , Liang Shu Ting , Zhu Xiao Jun
Published: July 2016

New-type floor is composed of three kinds of slabs joined together through fittings. It is a kind of anisotropic two-way slab. In order to study the calculation method of natural frequency, series method, variable thickness method and variable stiffness method are adopted to calculate the natural frequency. The calculation results of three methods are compared with test result and numerical simulation result. The conclusion is that the calculation result of the variable stiffness method is the closest to the real natural frequency of new-type floor.
A Non-Intrusive Polynomial Chaos Method to Efficiently Quantify Uncertainty in an Aircraft T-Tail
Authors: Cheema Prasad , Vio Gareth A.
Published: July 2016

The problem of developing robust methods for uncertainty quantification (UQ) is of major interest in the engineering and scientific community. To quantify uncertainty, probabilistic models have been developed where traditionally Monte Carlo (MC) methods were used to capture uncertainty bounds. In the engineering context, UQ methods can be practically implemented to limit the amount of prototype redesigns. However MC methods are computationally inefficient due to the large number of samples required to obtain an accurate solution. Polynomial Chaos (PC) methods have recently emerged as an efficient method of probabilistic quantification in lower dimensions compared to MC. This paper will show the ability of a non-intrusive PC method to efficiently quantify uncertainty through first and second order statistics. This approach will lend itself to the treatment of a finite element T-Tail model, using Nastran as a black box around which PC curves can be fit based on its outputs.
A Numerical Study of Micro Hydro Deep Drawing of SUS304 Sheets
Authors: Luo Liang , Jiang Zheng Yi , Wei Dong Bin , Sato Hideki , Furushima Tsuyoshi , Manabe Ken-Ichi
Published: July 2016

Micro forming is a promising technology and has drawn global attentions due to the urgent requirements on miniaturised products. Micro hydro deep drawing (MHDD) is a typical micro forming method and its products are widely applied in various fields, such as micro electro-mechanical systems (MEMS), medical and aerospace areas. However, tiny sizes of both products and tools are obstacles to investigate this novel technology. Therefore, finite element method (FEM) is adopted and modified to study the influence of processing parameters on micro drawing process and produced products. In this study, a normal hydro deep drawing model was developed, and then a voronoi blank model was generated to consider the size effects of materials. Additionally, a surface layer model was created based on the voronoi blank model. Therefore, the open and closed lubricant theory can be fulfilled and friction behaviour in MHDD can be considered. Subsequently, different processing parameters, such as hydraulic pressure and material inhomogeneity, were investigated. Simulation results indicate that a proper hydraulic pressure improves drawability and shape accuracy of the drawn cups. Moreover, material inhomogeneity affects the quality of drawn cups.
Representative Volume Element-Based Modelling of Closed-Cell Aluminum Foams
Authors: Liu Cheng Jun , Zhang Yi Xia , Yang Chun Hui
Published: July 2016

This paper presents a representative volume element (RVE)-based modelling method to capture the mechanical behaviour of aluminum foams under compressive loadings. Octadecahedron is selected as a geometric basis shape to form closed cells of the aluminum foams in the microstructured RVE model to simulate the mechanical behaviour under compressive loadings. The stress-strain relationship obtained from the numerical modelling is compared to that from experimental study and agreements between these results demonstrate the validity of the proposed RVE model. Through observing the deformation evolution of cells during a compressive loading process, the failure modes of aluminum foams are identified and analysed using the proposed RVE model. Further the influence of strain rate on the mechanical behaviour of aluminum foams under compressive loadings is numerically studied via a parametric study.
Ultrasonic Imaging of a Crack Using Modified Time Reversal
Authors: Guinto Jed , Blanloeuil Philippe , Wang Chun H. , Rose Francis , Veidt Martin
Published: July 2016

A majority of the research in Structural Health Monitoring focuses on detection of damage. This paper presents a method of imaging crack damage in an isotropic material using the Time Reversal imaging algorithm. Inputs for the algorithm are obtained via computational simulation of the propagation field of a crack in a medium under tone-burst excitation. The approach is similar to existing techniques such as Diffraction Tomography which makes use of the multi-static data matrix constructed using scatter field measurements from the computational simulation. Results indicate excellent reconstruction quality and accurate estimation of damage size.
Numerical Simulations of 3D Metallic Auxetic Metamaterials in both Compression and Tension
Authors: Ren Xin , Shen Jian Hu , Ghaedizadeh Arash , Tian Hong Qi , Xie Mike
Published: July 2016

Auxetic materials exhibit uncommon behaviour, i.e. they will shrink (expand) laterally under compression (tension). This novel feature has attracted intense research interest. However, most of previous works focus on auxetic behaviour in either compression or tension. Most of the auxetic materials are not symmetric in tension and compression under large deformation. Studies on the auxetic performance of metamaterials both in compression and tension are important but rare. As an extension of our previous research on compressive auxetic performance of 3D metallic auxetic metamaterials, numerical simulations were carried out to investigate the auxetic and other mechanical properties of the 3D metallic auxetic metamaterials in tension. The preliminary results indicated that the designed 3D metallic auxetic metamaterials exhibited better auxetic performance in compression than in tension. By increasing a pattern scale factor, auxetic performance of the 3D metallic auxetic metamaterials under tension can be improved. With proper adjustment of the pattern scale factor, an approximately symmetric auxetic performance could be achieved in compression and tension.
A Study of Abrasive Wear on High Speed Steel Surface in Hot Rolling
Authors: Phan T. Hoang , Tieu Ahn Kiet , Zhu Hong Tao , Kosasih Bu Yung , Wu Qiong , Fan Qun , Sun Da Le
Published: July 2016

In hot rolling, the thermal cyclic of work rolls causes a superficial oxide scale, which plays an important role on the contact friction and wear. The asperities of oxidised strip surface and wear debris slide over the High Speed Steel (HSS) work roll surface which comprises of hard carbides within an iron matrix under high pressure and velocity. Abrasive wear occurs and the particles will be removed from HSS surface. The current study introduces the Discrete Element Method (DEM) to investigate this abrasive wear phenomenon. The model successfully provides a physically based abrasive roll wear predication of HSS work roll with the consideration of carbides and oxide layers. It has been found that the carbide shape in the HSS roll affects the wear significantly, which has not been reported by previous numerical simulations and is the main focus of this research.
Validating the k-ω Turbulence Model for 3D Flows within the CFD Solver Eilmer
Authors: Stennett Samuel , Chan Wilson , Gildfind David E. , Jacobs Peter
Published: July 2016

The computational fluid dynamics solver Eilmer has proven useful to The University of Queensland’s Centre for Hypersonics for its ability to simulate high-speed compressible flows. In Eilmer, turbulence is modelled using Wilcox’s 2006 k-ω model. While the turbulence model implementation has been validated for two-dimensional and axisymmetric flows, validation is required for three-dimensional flows. The present paper describes the progress of the validation of the k-ω turbulence model for two three-dimensional test cases. A case featuring Mach 4.5 air flow over a flat plate produced results that correlated with previous numerical results within 4%. A second case featuring the injection of Mach 1 air into a Mach 4 air cross-flow produced results indicating that the code successfully captured the main flow features.
A Comparative Aerodynamic Investigation of a 20° SAE Notchback Model
Authors: Nader Andre , Islam Asiful , Thornber Ben
Published: July 2016

A 20° SAE Notchback model was utilised in a comparative study between RANS methods with both unstructured and structured grids and Implicit DES methods with structured grids. Experimental data acquired in the Loughborough University wind-tunnel with this Notchback geometry was utilised in this investigation to gauge the accuracy of the two methods. The pressure coefficient at 5 elevations on the base surface of the model was monitored, with the Implicit DES method yielding the lowest mean error of 2.7% against the 13% resulting from RANS.
Experimental Research and Application of Super-Retarding Mortar
Authors: Feng Xin , Zhou Xian Yan
Published: July 2016

In scores of experiments indicates that the super-retarding mortar, keeping plasticity long-term, can make cement setting and hardening at a slower speed through chemical additive. Based on large numbers of orthogonal tests and theoretical analyses, the super-retarding mortar which satisfies the demands of actual engineering was developed successfully in present paper. And it is consist of cement, sand, water and composite retarder blended in an appropriate rate. From 0°C to 40°C, setting time can be adjusted from 1 day to 22 days in the light of to the engineering requirements, and after condensation, it begins to harden gradually and ends with the compression strengthen over 30MPa. Experiments were employed to test the influences of accession amounts of composite retarder dosage on setting time and compression strengthen of super-retarding mortar. Besides, the retarding mechanism was studied, and the super-retarding mortar was applied to experimental models. The results show the super-retarding mortar can be applied to the actual engineering, and it can be treated as the theoretical reference for the actual project application of the new prestressed concrete system.
Study on Mechanics Performance of Suspension Bridge with 1960 MPa Cable Wire
Authors: Wang Hao Lei , Zhu Chao
Published: July 2016

In suspension bridge, the main cable is the major bearing member, instead of the 1770MPa cable wire normally adopted in current design, the application of cable wire strengths up to 1960MPa can lighten the dead weight, reduce the size of tower and anchorage, and shorten the construction period, obtain economical design. In this paper, a under-construction suspension bridge with span of 1688m is taken as a case-study, Comparative analyses are performed mainly focusing on basic parameters, carrying efficiency of main cable, static behavior and dynamic properties as different high strength cable are adopted in this suspension bridge. The results show that compared with 1770MPa main cable, using 1960MPa main cable in suspension bridge is benefit for improving the carrying efficiency of main cable, the steel consumption is also saved by 13%, but the vertical stiffness of the structure is reduced partly; the changes of main cable slightly affect the natural vibration frequency of girder, but have greater influences on vibration of main cable.
A Novel Conceptual Approach for Predicting the Mechanical Properties of Recycled Aggregate Concrete
Authors: Pepe Marco , Koenders Eduardus , Dias Toledo Filho Romildo , Martinelli Enzo
Published: July 2016

The construction sector is more and more committed to reduce its environmental impacts. One of the key actions undertaken in the last decade deals with the ability of turning construction and demolition waste into new raw materials. For instance, the use of recycled aggregates for producing new concrete was one of the most investigated. Thus, in the last decade, plenty of researches were involved in project on characterising the mechanical behaviour of concrete made with recycled aggregates. However, these projects were mainly experimental in nature and generally led to merely empirical formulations. Conversely, this paper is intended at providing a contribution for predicting the mechanical properties of Recycled Aggregates Concrete (RAC). Particularly, it aims at quantifying the effect of replacing ordinary aggregates with Recycled Concrete Aggregates (RCA) on the resulting compressive strength of RAC. To this end, a conceptual model considering both the relevant physical properties of regular and recycled aggregates, including the attached mortar content, and the hydration reactions of Portland cement paste is proposed. The actual predictive capacity of the proposed model is assessed through an experimental validation against experimental tests carried out on several concrete batches produced with various values for the different keys parameters, such as the nominal water-to-cement ratio, the aggregates replacement ratio and the initial moisture condition of aggregates. Both the experimental data and the theoretical formulations proposed in this paper stem out from the inter-university collaboration developed as part of the EU funded EnCoRe Project (www.encore-fp7.unisa.it).
Soil-Structure Interaction on the Dynamic Response of Bridge Piers
Authors: de Angelis Alessandra , Mucciacciaro Michele , Sica Stefania , Pecce Maria Rosaria
Published: July 2016

The paper analyses the effect of Soil-Structure-Interaction (SSI) on the modal dynamic response of simply-supported span girder bridge with wall piers founded on caissons. A parametric analysis has been carried out in the hypothesis of linear elastic behaviour of all materials (soil and structure) to identify the influence of various design factors, such as the height of the pier, the caisson embedment below the ground level and the soil mechanical properties. The goal of the paper is to highlight SSI effects on the dynamic behaviour of bridges. This is a crucial aspect to be accounted for in order to support monitoring activities on bridges, aimed to structural identification or assessment of structure response under serviceability conditions, or also to have preliminary information for the seismic analysis of the bridge.
Seismic Assessment of Masonry Building Clusters with a Dedicated NLA Software
Authors: Vailati Marco , Monti Giorgio , di Gangi Giorgia
Published: July 2016

A building context as complex as that of many historical centers in Europe is the typical scenario where more and more technicians found themselves at work. In addition to the usual difficulty of dealing with the complexity of masonry building clusters, they particularly feel the lack of the essential support of dedicated computational tools. In fact, the calculation codes currently available do not address modeling and analysis of building clusters in a personalized manner. VENUS, Italian acronym for Nonlinear Assessment of Structural Units, is a software developed in C++, which deals with the seismic assessment of building clusters in an integrated manner, accompanying the practitioner from the early stages of defining the level of knowledge, to the management of the design quantities, until the graphic elaboration of the results. Finally, it allows to test the effectiveness of a local intervention with traditional and innovative strengthening techniques and to evaluate its effects on the global response. Finally, a brief description of a stochastic approach foreseen in a future version of the software is discussed.
Seismic Energy Demands in Steel Moment Frames
Authors: Dogru Selcuk , Aksar Bora , Akbas Bulent , Shen Jay , Seker Onur , Wen Rou
Published: July 2016

This study presents an energy approach to the seismic evaluation of steel moment resisting frames. A structure subjected to strong ground motion is supposed that it shows nonlinear behavior. Energy parameters is a way to specify the structural damage. Input energy is depend on the characteristics of the structure and ground motion. Structural design can be defined as the equilibration of the input energy and the energy dissipation capacity of the structure. Structures subjected to eartquake are supposed to dissipate all the input energy. Studies based on energy concepts are usually applied to single-degree-of-freedom (SDOF) system. For multi-degree-of-freedom (MDOF), more researches and new simpler methodologies are still needed in performance based evaluation including energy parameters. In this study , low – medium and high rise steel moment frames and will be studied in linear and nonlinear time history analysis. The results obtained from these analysis are reviewed for seismic energy demands.