Search

Incremental bulk deformation processes have traditionally been difficult to simulate. This paper will argue that, despite advances in computation and software, they remain difficult to model. The main reason for this is the shortage of ideas on what is the real objective of FE modelling for such processes. Even a very detailed model and data obtained in simulation does not give answers to the main question - how to optimise the process parameters? High computational time and volume of information only aggravate the situation. All modern mathematical techniques of dimensionality reduction (such as POD/PGD) lose their power when the priorities and acceptable compromises of modelling are not clear. This paper tries to use a large volume of available experimental and modelling experience to illustrate this problem and look for possible break-through directions. [ABSTRACT FROM AUTHOR]

This paper presents a framework for nonlinear system identification of civil structures using sparsely measured dynamic output response of the structure. Using a sequential maximum likelihood estimation (MLE) approach, the unknown FE model parameters, the measurement noise variances, and the input ground acceleration time histories are estimated jointly. This approach requires the computation of FE response sensitivities with respect to the unknown FE model parameters (i.e., FE parameter sensitivities) as well as the FE response sensitivities with respect to the values of the input ground acceleration at every time step (i.e., FE input sensitivities). The FE parameter and input sensitivities are computed using the direct differentiation method (DDM). The presented output-only nonlinear FE model updating method is validated using the numerically simulated seismic response of a realistic three-dimensional five-story reinforced concrete building structure. The simulated building responses to a horizontal bi-directional seismic excitation is contaminated with artificial measurement noise and used to estimate the unknown FE model parameters characterizing the nonlinear material constitutive laws of the reinforced concrete, as well as the root mean square of the measurement noise at each measurement channel, and the full time history of the seismic base acceleration. The method presented in this paper provides a powerful framework for structural system and damage identification of civil structures, when the input excitations are not measured, are partially measured, or the measured input excitations are erroneous. [ABSTRACT FROM AUTHOR]

The interaction between an ensemble of cylinders and an inhomogeneous plane wave is introduced and is determined, in the present paper, through a rigorous theoretical approach. Scattered electromagnetic field generated by an indefinite number of infinite circular cylinders is analyzed by the application of the generalized vector cylinder harmonics (VCH) expansion. The exact mathematical model relied upon to represent this scenario considers the so-called complex-angle formalism reaching a superposition of vectorial cylindrical-harmonics and Foldy-Lax Multiple scattering equations (FLMSE) to account for the multi-scattering process between the cylinders. The method was validated by comparing the numerical results obtained with the use of the finite element method and a homemade Matlab code. [ABSTRACT FROM AUTHOR]

Finite element model updating is very effective procedure to determine the uncertainty parameters in structural model and minimize the differences between experimentally and numerically identified dynamic characteristics. This procedure can be practiced with manual and automatic model updating procedures. The manual model updating involves manual changes of geometry and analyses parameters by trial and error, guided by engineering judgement. Besides, the automated updating is performed by constructing a series of loops based on optimization procedures. This paper addresses the ambient vibration based finite element model updating of long span reinforced concrete highway bridges using manual model updating procedure. Birecik Highway Bridge located on the 81stkm of Şanlıurfa-Gaziantep state highway over Fırat River in Turkey is selected as a case study. The structural carrier system of the bridge consists of two main parts: Arch and Beam Compartments. In this part of the paper, the arch compartment is investigated. Three dimensional finite element model of the arch compartment of the bridge is constructed using SAP2000 software to determine the dynamic characteristics, numerically. Operational Modal Analysis method is used to extract dynamic characteristics using Enhanced Frequency Domain Decomposition method. Numerically and experimentally identified dynamic characteristics are compared with each other and finite element model of the arch compartment of the bridge is updated manually by changing some uncertain parameters such as section properties, damages, boundary conditions and material properties to reduce the difference between the results. It is demonstrated that the ambient vibration measurements are enough to identify the most significant modes of long span highway bridges. Maximum differences between the natural frequencies are reduced averagely from %49.1 to %0.6 by model updating. Also, a good harmony is found between mode shapes after finite element model updating. [ABSTRACT FROM AUTHOR]

In this paper, the effect of internal heat generation has been studied in a functionally graded (FG) thick hollow cylinder in context with thermosensitive thermoelastic properties. Initially, the cylinder is kept at reference temperature and the radial boundary surface under consideration dissipates heat by convection according to Newton's law of cooling, heat flux is applied at the lower surface, while the upper surface is insulated. The heat conduction equation due to internal heat generation is solved by integral transform technique and Kirchhoff's variable transformation is used to deal with the nonlinearity of the heat conduction equation. A mathematical model has been constructed for a nonhomogeneous material in which the material properties are assumed to be dependent on both temperature and spatial variable z. A ceramic-metal-based FG material is considered in which alumina is selected as ceramic and nickel as metal. The results obtained are illustrated graphically. [ABSTRACT FROM AUTHOR]

Sustainable development could have a significant impact on conventional construction, reducing or replacing steel and concrete as primary materials in structures. Bamboo, a natural resource, has been used as a general building material for decades in some regions of the world. Countries in Asia and South America have found many uses for bamboo because it grows rapidly and has excellent mechanical properties. The purpose of this paper is to test the designs of different configurations of bolted connections in order to create a composite bamboo I-shaped beam for further applications. Three different configurations of connections for a bamboo composite I-shaped beam were analyzed, with the purpose of identifying an optimal configuration that results in a stiffer, safer beam. A three-dimensional Finite Element Model (FEM) computational model was developed to identify areas of high stress concentration and maximum deflection for the various connection configurations. The findings of this paper are a first step in the process of considering and validating composite bamboo I-shaped beams as a primary construction material in structures such as bridges and buildings. [ABSTRACT FROM AUTHOR]

No one can deny the role of synthetic polymers as engineering materials - they are all around us in our everyday life. Also due to the constant progress in material engineering, polymers, and among them elastomers, find increasing usage in civil engineering. Computer modelling of elastomers requires special description of material and use of non-linear finite element method. Available, free and commercial software use many different approaches in elastomers modelling, thus comparison of results may display discrepancies. Even if used method is the same, its computer implementation may vary, therefore using various software, one can obtain differing output. The paper presents comparison of results obtained from four computational packages devoted to FEA: Abaqus, GetFEM++, Tochnog, FEBio. It can be seen as an overview of the software that can be used in modelling rubber-like components. It highlights differences in material description (for instance in names of hyperelastic laws and employed formulas) and used multi-field variational principles in modelling material's incompressibility. Examples included in the paper can be treated as benchmarks, that can be helpful in verifying third party software or the one developed by readers. [ABSTRACT FROM AUTHOR]

The main aim of this paper is to generalize the mixed affine quermassintegrals to Orlicz space. Under the framework of Orlicz-Brunn- Minkowski theory, we introduce a new affine geometric quantity by calculating the Orlicz first order variation of the mixed affine quermassintegrals, and call it Orlicz mixed affine quermassintegrals. The fundamental notions and conclusions of the mixed affine quermassintegrals and the related isoperimetric inequalities are extended to an Orlicz setting. The concepts and inequalities for Orlicz quermassintegrals of convex bodies are also included in our conclusions. The new Orlicz isperimetric inequalities in special case which yield the Orlicz Minkowski inequalities and Orlicz Brunn-Minkowski inequalities for the quermassintegrals, the affine quermassintegrals and the Orlicz affine quermassintegrals. [ABSTRACT FROM AUTHOR]

This paper presents a strain-based damage model to predict the stress-strain relationship and investigate the damage onset and evolution of the fibre and matrix of a fully bio-resorbable phosphate glass fibre reinforced composite under three-point bending. The flexural properties of the composite are crucial, particularly when it is employed as implant for long bone fracture. In the model, the 3D case of the strain and stress was used and the response of the undamaged material was assumed to be linearly elastic. The onset of damage was indicated by two damage variables for the fibre and matrix, respectively. The damage evolution law was based on the damage variable and the facture energy of the fibre and matrix, individually. A finite element (FE) model was created to implement the constitutive model and conduct numerical tests. An auto-adaptive algorithm is integrated in the FE model to improve the convergence. The FE model was capable of predicting the flexural modulus with around 3% relative error, and the flexural strength within 2% relative error in comparison with the experimental data. The numerical indices showed that the top surface of the sample was the most vulnerable under three-point bending. It was also found that the damage initiated in the fibre, was the primary driver for composite failure under three-point bending. [ABSTRACT FROM AUTHOR]

Physical modelling has a long established history for the investigation of metal forming and other manufacturing processes. In recent times however its place and importance has diminished somewhat as a direct consequence of advances made in numerical modelling techniques. This paper re-examines the place of physical modelling and by means of selected examples demonstrates the benefits of the approach. Physical modelling often provides an indirect representation of the physics under consideration and may often involve scaling and the use of cheaper substitute materials. A question posed that has in some respects contributed to the diminution of physical modelling is whether the physical model is representative of the physics involved. Related to this question is a new approach to scaled experimentation that has appeared in the recent literature. The new approach is founded on the scaling of space itself and although the idea that space expands and distorts is not new to physics (e.g. cosmology and general relativity) its application to physical modelling is considered completely novel. The scaling concept enables the physics of processes to be projected into a scaled space and vice versa, thus providing quantification of the validity of any physical model. This aspect fortifies a particular weakness in the physical modelling approach making its reappraisal particularly timely. Selected numerical and experimental trials are being designed to showcase and reveal the benefits, validity and renewed importance of physical modelling. [ABSTRACT FROM AUTHOR]

Micro forming is a promising technology with the trend towards miniaturisation in industry, and micro deep drawing (MMD) process is a fundamental micro forming method with potential applications in forming of cups, hollows and boxes and has great advantages comparing to other micro manufacturing methods. As the preferred material for electrical conductors, aluminium (Al)-copper (Cu) composite material processes advantages of the low density and cost of aluminium and good conductivity of copper. In this paper, MMD has been studied experimentally and numerically with a purpose of understanding the deformation behaviour of a two-layer Al-Cu composite in microscale. Al-Cu composite material was rolled to 50 µm in thickness and then annealed at 400 ºC. The drawability of the annealed composite was investigated by MDD experiments. FE models with Voronoi tessellations were established to simulate the Al-Cu composite material during MDD process. Considering the grain heterogeneity, each Voronoi tessellation has been assigned with different mechanical properties based on experimental data. The simulation results are in good agreement with the experiment ones. [ABSTRACT FROM AUTHOR]

The paper objective is to decrease a share of tool costs in the cost price of production manufactured at the expense of the composite and solid mills use control. In the course of research the authors used computer simulation with the finite elements. The studies proved that the composite cutters can compete with the monolithic cutters in terms of their efficiency while ensuring the required precision accuracy. Their cost is lower due to hard alloy savings. The outcomes of evaluation of the groove wall runout as a result of bending for cutters of different designs are given, and it is shown that the deviation is acceptable for engineering products. The effective application of both mills is shown. It is demonstrated that the smaller is the length of the required mill, the increasingly competitive composite mills become due to insignificant differences in their deformation compared to the deformation of the monolithic milling cutters and due to the considerable hard alloy saving. Thus, the greater length is required by the mill, the greater are the hard alloy saving, but also the greater is cutter deformation which reduces accuracy and processing performance. [ABSTRACT FROM AUTHOR]

Many engineering structures must be inspected or monitored throughout their serviceable life to ensure their safe operation. In the case of reinforced concrete structures, the most common cause of premature failure is corrosion of the steel reinforcement bars that must be pre-empted. Modal based techniques are popular, since they can potentially detect damage using sensors placed remotely from the damage site. However, changes in modal parameters due to damage can be masked by their sensitivity to environmental factors and changes to the boundary conditions that are unrelated to damage. In this respect, wave based techniques provide a potential alternative. In this paper, wave propagation is modelled in a damaged steel reinforced concrete beam. The damaged section is modelled in conventional finite elements and this is coupled to wave finite element models (WFE) of the undamaged sections on either side. This hybrid modelling approach facilitates a wave based analysis of a one dimensional structure with potentially geometrically complex damage. A numerical case study is presented for a locally damaged beam represented by a loss of thickness of one reinforcement bar. It is shown that some wave modes, that feature deformation of the cross section, exhibit a strong reflection close to their cut-on frequency. This is due to the difference in cut-on frequency between the damaged and undamaged sections. A damage detection method is outlined in which the amplitudes of incident and reflected waves of low wave number are compared. No a priori knowledge of the dispersion curves is necessary. In numerical simulations, a reduction in the ratio of the reflected to incident wave amplitudes is seen in the vicinity of cut-on frequencies. [ABSTRACT FROM AUTHOR]

This paper addresses a new method for estimating axial load in tie-rods using indirect measurements. This information is of great importance for assessing the health of the tie-rod itself and the health of the entire structure that the beam is inserted into. The method is based on dynamic measurements and requires the experimental estimation of the tie-rod eigenfrequencies and mode shapes at a limited number of points. Furthermore, the approach requires the development of a simple finite element model (FEM), which is then cross-correlated with the experimental data using a model update procedure. Extensive numerical simulations and experimental tests have demonstrated the ability of the new approach to yield accurate estimates of the tie-rod axial load and overcome various limitations of the methods currently available in the literature. [ABSTRACT FROM AUTHOR]

Currently, the design of remforced concrete deep beams with web openings is carried out using empirical or semi-empirical methods and hence their scope of application is limited. In particular, high strength concrete deep beams with various web opening configurations have been given little treatment. In view of this, a nonlinear layered finite element method (LFEM) for cracking and failure analysis of reinforced concrete structures is used to conduct a parametric study to investigate reinforced concrete deep beams various web opening behaviours. This paper initially presents comparisons of LFEM output with published test results to numerical techniques. The paper then focuses on a parametric study on the shear strengths of deep beams with varying web opening configurations such as opening sizes and locations. The results confirm that the current design methods are inadequate in predicting the maximum shear strength when web openings are present. A series of parametric study offers insight into the maximum shear strength of the deep beams being critically influenced by the size and location of web openings. [ABSTRACT FROM AUTHOR]

Abstract: The mathematical model for dissolved oxygen interaction with biochemical oxygen demand in an open channel flow is presented in this paper. We consider unsteady flow in one dimension. The model is in the form of partial differential equations which require to solve the dissolved oxygen coupled with the biochemical oxygen demand at the same corresponding position and time. For some specific flow cases, unsteady flows approach to certain stationary solutions which are possible to derive some corresponding exact solutions. However, for complicated flow problems, analytical solution cannot be derived. Efficient and accurate numerical method is required to solve numerically such the model. In this paper, we present the finite element method with linear basis function for solving the system. The accuracy of numerical solutions have been observed and compared with some existing exact solutions for some steady flow cases. To show the ability of our presented numerical scheme, the interaction between the dissolved oxygen and the biochemical oxygen demand is simulated for unsteady flow cases. Furthermore, the impacts of flow parameters such as flow velocity, kinetic reaction order, and diffusion coefficient have been simulated to observe the dissolved oxygen and biochemical oxygen demand dynamics. [Copyright &y& Elsevier]

Abstract: Based on the problem of underground vertical U-tube heat exchangers in ground source heat pump systems in Shenchi station of Shuohuang railway, the transient heat transfer physical and mathematical model of the soil and borehole temperature field is established. Finite element numerical simulation is made by virtue of MATLAB software. Through the method of numerical simulation, the paper analyzes the soil temperature, obtains the distribution of isotherms around the pipes and the scope of the heat transfer, and understands the heat transfer performance around the pipe intuitively. Based on the model and numerical solution, the paper analyzes the changes of temperature field about the soil around ground heat exchangers in different ways which involve geological conditions operating mode, layout, pipe depth, and pipe coupling interval situation, and then the dates are obtained to help the engineering design of ground heat exchangers. [Copyright &y& Elsevier]

Testing and validation processes are critical tasks in developing a new hardware platform based on a new technology. This paper describes a series of experiments to evaluate the performance of a newly developed MEMS-based wireless sensor node as part of a wireless sensor network (WSN). The sensor node consists of a sensor board with four accelerometers, a thermometer and filtering and digitization units, and a MICAz mote for control, local computation and communication. The experiments include calibration and linearity tests for all sensor channels on the sensor boards, dynamic range tests to evaluate their performance when subjected to varying excitation, noise characteristic tests to quantify the noise floor of the sensor board, and temperature tests to study the behavior of the sensors under changing temperature profiles. The paper also describes a large-scale deployment of the WSN on a long-span suspension bridge, which lasted over three months and continuously collected ambient vibration and temperature data on the bridge. Statistical modal properties of a bridge tower are presented and compared with similar estimates from a previous deployment of sensors on the bridge and finite element models. [ABSTRACT FROM AUTHOR]

Abstract: Due to the lack of coolant in dry machining processes, there is an increase of heat input into workpieces during the cutting process. As a result, an inhomogeneous temperature distribution occurs, which can lead to problems concerning compliance with critical tolerances, because of distortions of the workpiece. Using the FEM simulation it is possible to calculate and handle these distortions. This paper contains a mathematical model developed to calculate the surface heat flux as input data for FEM simulation. In comparison to former publications, this paper deals not only with single results, but rather with an overview of the results of the past two years. [Copyright &y& Elsevier]

The influence of valve setting's pretension force on the pressure difference caused by deflected disc at the valve opening point is studied in this paper. Taking piston valve setting for instance, based on finite element simulation and theoretical calculation, the mathematical relationship between pretension force and the pressure difference caused by deflected disc at the valve-opening point is found. Based on the mathematical model, the influence of piston valve body's elastic modulus and deflected disc's elastic modulus are analyzed. Finally the paper shows that the smaller the elastic modulus of piston valve body, the greater influence the pretension force has on the pressure difference, and the influence of the change of the elastic modulus of deflected disc on pretension force's function is very small. [ABSTRACT FROM AUTHOR]

Sheet panel assembly in automotive body manufacturing typically involves fixturing (including locating and clamping), joining (especially welding), and unclamping. Research has shown that the choices of fixturing schemes are important and that fixture optimization can generally improve the assembly dimensional quality with reduced assembly distortions. However, these research studies generally modelled weld guns as constant disturbances (such as deterministic forces) without considering the weld gun variations to avoid the complexity of Monte Carlo simulations. In the current paper, a fixture optimization model is formulated to minimize the assembly dimensional variations under welding gun variations. It is shown that, by using the proposed weld gun variations model, an assembly variation simulation can be converted to a deterministic assembly model, eliminating the need for Monte Carlo simulation. The efficiency improvement makes it feasible for a full scale optimization solution for optimal fixture locations with welding variations. The current paper further introduces the fixture-element models for continuous variable optimization in finite-element analysis, an enabler for fixture optimization. Numerical examples are shown to demonstrate the proposed methods. [ABSTRACT FROM AUTHOR]

Identification of electromechanical systems operating in open-loop or closed-loop conditions has long been of prime interest in industrial applications. This paper presents experimental on-line identification of an electromechanical system represented by a digital input/output model. The paper also bridges the theory and practice gap for applied researchers. Studies are carried out by formulating the mathematical model using differential equations and experimental discrete-time identification using on-line plant input-output data. A recursive least-squares method is used to estimate the unknown parameters of the system. Discrete-time data for the parameter identification are obtained experimentally from a setup constructed in the laboratory. A root-mean-square error criterion is used for model validation. Results are presented which show variations in parameters of the electromechanical system. It is demonstrated that identified model output and actual system output match. All tests are performed with no previous results from finite element simulations. [ABSTRACT FROM AUTHOR]

In general, the actual approach to achieve the dynamic parameters of bridge structures is supported to use standard FEM software. The final element model can be created by many different ways. The best way to obtain the objective results is to create at least two variants of FEM model. Currently, standard software of the FEM type is enabled to use variable types of elements. This paper shows the two basic models types of real slender road bridge. This bridge is named as: “The New Bridge over Danube”. This bridge is one of the Slovak capital dominants. For both models creation the historical documentation and the real dimension's measurements were applied. Both FEM models were created in the software of Scia Engineer v. 2013. Many existing slender long – span bridges are structurally adequate with respect to the maximum design axle loads, they may suffer from fatigue related to the cyclic application of modern freight equipment axle loads. Only the relevant FEM model can consider the real dynamic behaviour of the bridge. This is the idea for the best identification of dynamic parameters and FEM model tuning. [ABSTRACT FROM AUTHOR]

A very important research direction in today's dam engineering is related to structural ageing of concrete dams and ways to monitor structural and material characteristics changes to reduce and manage the associated risks. In situ ambient vibration measurements used to identify the dynamic characteristics of the structure and the development of hybrid models (the mathematical model bounded to a certain in situ measurement program and calibrated using the recorded data) represent an appealing method for the evaluation of the safety reserves of concrete water retention structures. However, mathematical modelling can be done with varying degrees of complexity and the results obtained for the couple dam model - recorded data can significantly vary depending on the size and complexity of the analyzed model. The presented study, developed for Gura Raului buttress dam in Romania, consisted in 2 measurements campaigns and the development of 4 mathematical models, via the finite element method, with different degrees of complexity - a representative maximum height block, a spillway block, the whole spillway made of 3 identical blocks and the complete dam made of 22 blocks. The paper presents the in situ measurement results, the calibration of the maximum height block based on the first measurement data set and the analysis of the results obtained for the other 3 models compared with the recorded data. [ABSTRACT FROM AUTHOR]

Mechanical models have the potential to characterize the behavior of complex steel joints, using for that the isolated behavior of its components, assembled according to their geometry. However, the mechanical models implemented in the current design codes are not prepared to deal with cyclically loaded joints, due to the complexity associated to load reversal. To overcome this difficulty this work makes to use of detailed finite elements models, to extract the needed force-displacement components response. The FE models are capable of representing the various connections components and the several sources of nonlinearity associated to them and are validated against existing experimental data. The discretized nature of the FE models is able to provide all the relevant information of any element, and even provide data that is typically unavailable from experimental tests, such as the contact or friction forces. Several models of bolted end plate beam-to column joints, with partial-strength classification in relation to the connected beam, have been developed using the ABAQUS FE package. A methodology to extract the needed force-displacement relationships of the column web components of the joint is presented and applied to the joints, through integration of stress and displacement fields. The results, presented in this paper, allow setting the base for a component-based model to simulate the dissipative behavior of steel connections subjected to cyclic loading conditions. [ABSTRACT FROM AUTHOR]

This paper deals with the numerical analysis of tunnelling-induced settlements on concrete framed structures founded on strip footings. In particular, a single frame with a variable number of storeys is taken into account in the present study, with an orientation perpendicular to the tunnel axis and a null eccentricity. The Finite Element simulations, carried out in three- dimensions with the code Abaqus, highlight the influence of the building stiffness and weight on the displacement field and provide an insight into the loading transfer mechanism occurring in the structural elements during tunnel excavation. [ABSTRACT FROM AUTHOR]

The work investigates the behaviour of a deep excavation that forms part of a wide basement located in Boston, Massachusetts, USA. The glacial marine clay deposit is modelled with a kinematic hardening model for structured soils, its reduced bubble model version and the well-known Modified Cam Clay model. The aim of the work is to assess the effects of the added features of the advanced model, such as small-strain stiffness, structure degradation and anisotropy, on the numerical prediction of the overall behaviour of the excavation. The first part of the paper provides a brief description of the site conditions, ground profile and construction sequences for the case study under consideration. Then, the soil model calibration process using experimental undrained triaxial, self-boring pressuremeter and constant rate of strain consolidation tests is discussed. Finally, the comparison of the predicted wall deflection and ground settlements profiles with observed movements is presented. [ABSTRACT FROM AUTHOR]

This paper addresses the definition of conventional primordial crack size by solving the inverse problem of traditional LEFM and implementation of this tool in the Russian CAx system APM WinMachine. The condition of the primordial origin of the crack with the principal stresses and classical criteria of strength are shown. A mathematical model for finding the conditional size of the crack is shown. The critical value of the parameter of fracture mechanics – the stress intensity factor (SIF) and the value of the stress concentrator are used for this purpose. The critical value of SIF was defined by experiment. A mathematical model has been implemented in the Russian CAX system APM WinMachine which uses a numerical finite element method (FEM). Output data (crack dimensions) of the mathematical model are used in solving the analytical problem to determine the SIF. The validity of the numerical and analytical calculation of the data is checked by comparing the SIF critical value obtained experimentally, with the analytical one. The calculations were performed on the example of solving the static problem with a different loading step. [ABSTRACT FROM AUTHOR]

The objective of the paper is to perform finite element analysis of a human foot model to study the dynamic behavior and the internal loading conditions during neutral standing on the planar ground. The foot structure is simulated to assist in the design of an instrumented shoe insole. Finite element model of a human foot was generated and the loading condition during neutral standing was used to evaluate the stress distribution. The comprehensive stress distribution of the human foot model subjected to several loading conditions can be specified by a computational model. The method of the research is by using computational tomography data of the bone and soft tissue structures of a human foot in developing a 3-D finite element foot model. An analysis was conducted to simulate the loading condition of human foot during neutral standing. A commercial CAD software package was used to generate the boundary surfaces and the solid models of all model components. The numerical stress analyses for the neutral standing of the foot model was done using a commercial finite element software package. Peak pressures were seen at the first metatarsal, fifth metatarsal, and under the heel. The foot plantar deformation of the neutral standing foot model was seen similar to the finite element foot model in previous literature. The present study offers a prior computational model, which is capable of estimating the comprehensive plantar pressure and is intended to aid researchers in investigating foot plantar pressure as well as to develop custom-made insoles. [ABSTRACT FROM AUTHOR]

This paper presents a detailed explanation on the design of a novel triple frequency rectangular slot antenna for wireless local area network (WLAN) applications in IEEE 802.11b/g/a systems. This proposed antenna operates in ISM band at frequency of 2.4 Ghz and also in C band at 4.85 Ghz AND 6.1Ghz. The antenna has been designed and simulated on a foam substrate with dielectric constant of 1.06 and a thickness of 7 mm. The design is analysed by Finite Element Method based HFSS Simulator Software (version 13.0) by which return loss, 3D polar plot and Gain of the antenna are computed. In addition, the measured results show good radiation characteristics at the three operating frequencies, proving the dual-band operation of the proposed antenna. [ABSTRACT FROM AUTHOR]

This paper proposes a novel channel assignment scheme that is based on finite projective plane (FPP) theory. The proposed scheme involves using a Markov chain model to allocate N channels to N users through intermixed channel group arrangements, particularly when channel resources are idle because of inefficient use. The intermixed FPP-based channel group arrangements successfully related Markov chain modeling to punch through ratio formulations proposed in this study, ensuring fair resource use among users. The simulation results for the proposed FPP scheme clearly revealed that the defined throughput increased, particularly under light traffic load conditions. Nevertheless, if the proposed scheme is combined with successive interference cancellation techniques, considerably higher throughput is predicted, even under heavy traffic load conditions. [ABSTRACT FROM AUTHOR]

In this paper, a mathematical model describing the process of non-Fourier heat transfer in biological tissues for generalized coordinate system during thermal ablation by electromagnetic radiation with Gaussian external heat source is studied. The boundary value problem governing this process has been solved using hybrid numerical method taking Legendre wavelet basis function. The result obtained from finite element Legendre wavelet Galerkin method (FELWGM) is compared with exact analytical solution and shows a good agreement. The effect of variability of time, generalized coordinate system, location of tumor or cancer, relaxation time and external heat source coefficient on temperature distribution is discussed in detail. It has been observed that treatment of tumor or cancerous cell is independent of the generalized coordinate system at the thermal ablation position. [ABSTRACT FROM AUTHOR]

This paper presents three-dimensional (3D) finite element analyses of plane-sided single-edge bend specimens to investigate the effect of the crack front curvature on the accuracy of the average J-integral (J) evaluated over the crack front using the plastic eta-factor-based approach specified in ASTM E1820-11. Specimens with average crack lengths of 0.3, 0.5, and 0.7 and thickness-to-width ratios of 1, 0.5, and 0.25 were analyzed. The analysis was based on the J2 deformation theory of plasticity and assumed stationary cracks with sharp crack tips. The curved crack front was characterized by a power-law expression proposed by Nikishikov et al. that was validated using crack front data collected in this study. The plastic eta factors specified in ASTM E1820-11 and proposed by Zhu et al. were employed. The analysis results indicate that the errors in the plastic eta-factor-based J were generally between - 7 % (i.e., underestimation) and 6 % (i.e., overestimation) for the specimens that had curved crack fronts with crack front curvature equal to the maximum allowable value specified in ASTM E1820-11. Based on the analysis results, crack front straightness criteria that are in most cases less stringent than those specified in ASTM E1820-11 are recommended. The suggested criteria could potentially lead to reduced specimen rejection rates and cost savings. [ABSTRACT FROM AUTHOR]

This paper presents the findings of an investigation on thermal behavior of mass concrete footings placed directly on soil using finite element analysis. A three-dimensional finite element model was developed to predict temperatures in a mass concrete footing-soil system and to assess cracking potential of the concrete at early age. Two bridge pier footings constructed in Florida were monitored for temperature development, and the measured temperatures were compared with the computed temperatures from the finite element model. The results show that the temperatures predicted by the model closely agree with those measured in the field. Several soils with varying thermal resistances were modeled in this study in order to find out which soils can be used as an insulator for mass concrete footings so that an insulation layer would not be needed at the bottom of the footings. The results suggest that dry sand and dry clay provide good insulation at the bottom of mass concrete footings, and soil with an R-value of 0.072 per m or greater (or thermal conductivity of 0.35 W/m-K or lower) would provide adequate insulation at the bottom of concrete footings to prevent early-age cracking in the concrete. [ABSTRACT FROM AUTHOR]

Gas pulsations in a compressor suction manifold radiate noise and reduce the efficiency of the compressor. The objective of this paper is to identify and quantify the effects of modeling assumptions and uncertainties in input parameters on the pulsation modeI output predictions and to estimate the sensitivity of the model to changes in the input design parameters. A unique method of sensitivity analysis is presented that uses the total pulsation energy in the suction manifold of a compressor as a measure of gas pulsations. This method is used to determine the sensitivity of the gas pulsations in the suction manifold to input design parameters. First, the gas pulsations in the suction manifold are calculated using linear acoustic theory. Second, the effects of varying several different design parameters of the suction manifold on gas pulsations are analyzed, and the three most important parameters are selected. Next, energy due to gas pulsations in the suction manifold due to these design parameter variations is calculated. Suction manifold radius was identified as the most critical parameter, followed by width and depth. The optimized values of manifold radius resulted in an overall reduction of up to 24% in the gas pulsation energy compared to the pulsation energy at the nominal design parameter values in the suction manifold. [ [ABSTRACT FROM AUTHOR]

This paper presents a stiffness analysis of a statically indeterminate wood-chair side-frame. Numerical calculations are carried out with a ‘linear elastic model’ for orthotropic materials. The mathematical model is solved by a ‘finite element method’. The matrix analysis of structure is carried out by a ‘direct stiffness method’. The frame joints are assumed to be ideally rigid and also as semi-rigid. Horizontal displacement of the top point of the back post is calculated for the most frequently used type of loading for the structure. The results of the calculation indicate that chair side frame becomes stiffer as the position of the stretcher is lowered and/or the stretcher cross section is increased. The results revealed that stiffness of joints in a frame had a considerable impact on the structure deflection. A satisfactory agreement was found between the numerical results and the results obtained by direct stiffness method. [ABSTRACT FROM AUTHOR]

This paper shows the effect of coarse aggregates in concrete with perfobond rib via experimental and FE analysis. First, the model of a single PBL in ordinary concrete was reproduced through a three-dimensional nonlinear FE model. Coarse aggregates were added to the model; it was found that the coarse aggregates around the perforation of PBL increased its initial load-carrying capacity. Furthermore, the interlocking of these coarse aggregates was found to affect PBL behavior after the peak of load-carrying capacity. Next, analytical numerical modeling of push-out tests of single PBL was performed to investigate the role of coarse aggregates. It was confirmed that the initial load-carrying capacity could be increased via the vertical loading stress from the steel to the coarse aggregates. Finally, the numerical modeling results were verified by actual push-out tests of single PBL with systematically sorted coarse aggregates. [ABSTRACT FROM AUTHOR]

The vibration of beams carrying uniform moving distributed masses is investigated in this paper. A finite element (FEM) based on the first shear deformation theory (FSDT) is assumed for the beam model. A ten degree of freedom beam element for the FSDT theory is considered. Combination of the element property matrices for moving mass and the associated overall property matrices for the beam determines the overall effective property matrices of the entire system. The equations of motion are integrated by applying the Newmark's procedures to obtain the system responses. The numerical results of vibration of beams are presented and, whenever possible, compared to the available results in order to demonstrate the accuracy of the present method. Effect of the Coriolis and centrifugal forces induced by the moving distributed mass are investigated. Numerical results reveal that all above mentioned parameters have significant influence on dynamic responses of inclined beams. [ABSTRACT FROM AUTHOR]

The static analysis of structures with arbitrary cross-section geometry and material lamination via a refined one-dimensional (1D) approach is presented in this paper. Higher-order 1D models with a variable order of expansion for the displacement field are developed on the basis of Carrera Unified Formulation (CUF). Classical Euler-Bemoulli and Timoshenko beam theories are obtained as particular cases of the first-order model. Numerical results of displacement, strain and stress are provided by using the finite element method (FEM) along the longitudinal direction for different configurations in excellent agreement with three-dimensional (3D) finite element solutions. In particular, a layered thin-walled cylinder is considered as first assessment with a laminated conventional cross-section. An atherosclerotic plaque is introduced as a typical structure with arbitrary cross-section geometry and studied for both the homogeneous and nonhomogeneous material cases through the 1D variable kinematic models. The analyses highlight limitations of classical beam theories and the importance of higher-order terms in accurately detecting in-plane cross-section deformation without introducing additional numerical problems. Comparisons with 3D finite element solutions prove that 1D CUF provides remarkable three-dimensional accuracy in the analysis of even short and nonhomogeneous structures with arbitrary geometry through a significant reduction in computational cost. [ABSTRACT FROM AUTHOR]

Abstract: Contact pressures in open die forging of axisymmetric parts are mainly influenced by friction and billet geometry through the shape factor. In this work, a FE model has been developed for analyzing the compression of axisymmetric billets, assuming different friction conditions and shape factors of the workpiece in order to evaluate the contact pressures behaviour under compression and to determine general trends. A constant friction factor law is assumed, m, and the shape factor is determined as the ratio between the height of the workpiece and its diameter, H/D. Additionally, results are compared with those obtained by the SM method to validate the numerical model. The results presented in this paper demonstrate that the area of highest wear is located in different positions depending on the original geometry of the workpiece, so this information could be considered as a useful guidance when designing dies in more complex compression processes as well as in other recent related processes such as multi-material forming. [Copyright &y& Elsevier]

A corrective surgery known as the craniofacial surgery is important for the improvement of a patient's appearance and in some cases a patient's physical abilities in terms of speech. The postoperative soft tissues prediction is often a hit considering the complex facial anatomy. Such surgical planning may be made simpler and more precise with the use of computational modelling of the relevant area. This paper presents a general framework for the simulation of soft tissue in order to predict the postoperative results of maxillofacial surgery based on the finite element method. Methods for the facial model preparation used in the analysis are described. A 3D facial model of the facial skin and the underlying lower jaw is modelled from a patient-specific CT data. In conjunction with the representation of soft tissue mechanical properties and boundary assignment, the models were submitted for a contact analysis for a computational postoperative appearance. Finally the simulation results are shown for the case study data. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a three-dimensional finite element model of rigid hemisphere repeatedly rolling over a rough flat surface under constant normal load is discussed. The aim of this research is to study the von Mises residual stress and plastic strain distribution and to determine the steady-state phase of the repeated rolling contacts. The results show that the change of residual stress distribution takes place in the first-two rolling cycles and there is no significant change for the residual stress from the second to third rolling cycle, i.e. the surface is run-in after a few cycles. The increase of the contact load affects the area of the von Mises residual stress at the surface and subsurface and also the number of the deforming asperities. The residual stress distribution is getting wider as the normal force increases. The plastic strain is captured after the third cycle of rolling. Small area of plastic strain is found for the rough surface for the low forces applied which indicates the surface deformed mainly elastically. The rough surface is predicted to be plastically deformed for the highest force applied. [Copyright &y& Elsevier]

Abstract: This paper presents a micromechanical unit cell model of 5-Harness satin weave fabric textile composite for the estimation of in- plane elastic properties. Finite element modeling of unit cell at mesoscopic level has been recommended over employing costly experimental setup for such sophisticated materials. The unit cell is identified based upon its ability to enclose the characteristic periodic repeat pattern in the fabric weave. Modeling of unit cell and its analysis for this new model are developed using an open source software, TexGen and a commercially available finite element software ABAQUS®. The scope of altering weave pattern and yarn characteristics is facilitated in this developed model. Several parametric studies were carried out in order to ascertain the effectiveness of the model and to investigate the effects of various geometric parameters such as yarn spacing, yarn width, fabric thickness and fibre volume fraction on the mechanical behavior of woven composites. Present analysis reveals that the values of Young's and shear modulus increased with increasing in the fabric parameters such as yarn width and fabric thickness. On the other hand it is decreased when the spacing between the yarns increased. A good comparision was obtained between the predicted results and available experimental and theoretical data in open literature for the developed unit-cell model and its suitability is tested for multi-scale analysis. The potential advantage of the present scheme lies in its ability which permits the textile modeling from building of textile fabric model to its solution including mesh generation undertaken using an integrated scripting approach thus requiring far less human time than traditional finite element models. [Copyright &y& Elsevier]

The purpose of this paper is to identify through experiments the finite element (FE) model of a building structure using a magnetorheological (MR) fluid damper. The FE model based system identification (FEBSI) technique evaluates the control performance of an MR damper that has nonlinear characteristics as equivalent linear properties such as mass, stiffness, and damping. The Bingham and Bouc-Wen models were used for modeling the MR damper and the equivalent damping increased by the MR damper was predicted by applying an equivalent linearization technique. Experimental results indicate that the predicted equivalent damping matches well with the experimentally obtained damping. [ABSTRACT FROM AUTHOR]

This paper presents a mixed formulation frame element with the assumptions of the Timoshenko shear beam theory for displacement field and that accounts for interaction between shear and normal stress at material level. Nonlinear response of the element is obtained by integration of section response, which in turn is obtained by integration of material response. Satisfaction of transverse equilibrium equations at section includes the interaction between concrete and transverse reinforcing steel. A 3d plastic damage model is implemented to describe the hysteretic behavior of concrete. Comparisons with available experimental data on RC structural walls confirm the accuracy of proposed method. [ABSTRACT FROM AUTHOR]