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Hepatic injury induced by blunt abdominal impact is a major cause of death in vehicle crashes. However, few works have been done effectively in cadaver experiments to clarify the liver's specific dynamic behavior and mechanical characteristics. This paper described the dynamic behavior and mechanical characteristics of the liver under blunt impacts to the upper abdomen with the finite element model (FEM) of the Chinese human body — the 50 percentile-sized male (CHUBM-M50). The simulation matrix, three directions (frontal, oblique, lateral), and four speeds included in each group were designed with a 23.4 kg, rigid cylindrical impactor aligning the T11 level. The liver deformation contours displayed compression against the spine and rotation in the horizontal plane, which were the two main features in liver motion. Pressure distribution in the liver capsule and parenchyma was discussed to elucidate the biomechanical characteristics related to impact direction. Generally, the stress distribution in the capsule was 10 times higher than that in the parenchyma. A discussion of the injury mechanism of the liver capsule and parenchyma observed in the simulations was given upon the pressure distribution. It demonstrated that the capsule could protect liver parenchyma at low-speed impacts and should not be neglected for understanding liver injury mechanisms. [ABSTRACT FROM AUTHOR]

Compared with the clearance-sealed pistonphone, the membrane-sealed pistonphone can realize the sound pressure at very low frequency and very high sound pressure for its lower leakage. However, the membrane-sealed pistonphone also brings the problem that the compressed volume cannot be decided precisely because of the deformation of the membrane, which results in the inaccurate calculation for the sound pressure in the chamber. In this paper, a sound pressure formula for the membrane-sealed pistonphone is derived according to an analysis of the characteristics of the ideal membrane. The static and the dynamic deformation of the membrane are studied. Then, the effects of the thickness, the sealed width, the extension ratio, and the modal vibration of the membrane are studied through the finite element method. The results show that the deviation of the sound pressure level obtained from the ideal sound pressure formula can be reduced to less than 0.1 dB when the sound pressure level is lower than 174 dB and the membrane is specially designed, which indicates that the influence of the membrane on the sound pressure is almost negligible. [ABSTRACT FROM AUTHOR]

Complication rates of anterior cruciate ligament reconstruction (ACL-R) were reported to be around 15%. Although it is a very common arthroscopic surgery with good outcomes, breakage and migration of fixators are still possible to occur due to stability issue. One of the factors that affects the mechanical stability of fixators is its length. Therefore, the aim of this paper is to analyze the biomechanical effects of different lengths of fixators (cross-pin technique) towards the stabilities of the knee joint after ACL-R. Finite element analyses of knee joint with DST grafts and fixators were carried out. Mimics and 3-Matic were used in the development of knee joint models, while the grafts and fixators were designed by using SolidWorks software. All models were remeshed in the 3-Matic and numerical analysis was performed via MSC.Marc Mentat software. A 100 N anterior tibial load was applied onto the tibia to simulate the anterior drawer test after the surgery and proximal femur was fixed at all degrees of freedom. Based on the findings, cross-pin with 40 mm in length provided the most favorable option for better treatment of ACL-R, where it could promote osseointegration and preventing fracture. [ABSTRACT FROM AUTHOR]

In this paper, the lateral torsional buckling (LTB) behavior of multi-layered long-span laminated glass (LG) beams is investigated through full-scale model test and numerical simulation. In the test program, the LG beams consisting of up to four glass plies and spanning 5000 mm are constructed and tested. The load-displacement curves and development of strain in glass plies are recorded, based on which the deformation and stress state of buckled LG beams are analyzed, and the strength checking criterion is provided. The test results are also used to determine the shape and amplitude of initial imperfection through statistical analysis and to validate a numerical model based on the finite element method (FEM). Parametric analysis based on the FEM model is then conducted to investigate influential factors on the LTB resistance of LG beams, among which the influence of shape and amplitude of initial imperfection is emphasized. For the LTB design of LG beams, the applicability of existing formula to determine the critical buckling moment through effective stiffnesses is evaluated for multi-layered LG beams with the test and numerical results. Finally, the design buckling curves adopting the Ayrton–Perry formula (APF) are proposed and validated for LG beams categorized with glass type and load duration. [ABSTRACT FROM AUTHOR]

This paper is concerned with a numerical study on the dynamic response of a high-speed rail (HSR) system subjected to unsupported sleepers using the moving element method (MEM). A three-phase computational scheme in conjunction with the MEM is proposed to account for the motion of the unsupported sleepers in relation to the truncated rail segment in the moving coordinate system. The accuracy of the proposed computational scheme is examined by comparison with available analytical results in the literature and against the finite element method using commercial software. A parametric study is conducted using a computational model consisting of a 10-degree of freedom train model and a three-layer ballasted track model to investigate the effect of unsupported sleepers on the dynamic response of the HSR system. Various factors affecting the response of the HSR system, including the speed of the train, the number of unsupported sleepers and the distance between the unsupported sleepers, are examined and discussed. [ABSTRACT FROM AUTHOR]

Let S p be the standard Sierpiński carpet and QS (S p) the group of quasisymmetric maps of S p onto itself, where p ≥ 3 is odd. Mario Bonk and Sergei Merenkov proved that QS (S p) is finite dihedral and that QS (S 3) is the isometry group of S 3 . They conjectured that QS (S p) is the isometry group of S p for any odd p ≥ 3. In this paper, we shall verify this for p = 5. [ABSTRACT FROM AUTHOR]

In this paper, several finite element models of an equine stifle joint with varying meniscal properties and attachments are compared to understand the effects of meniscal attachment complexity and material property changes on bone stresses. We found that the complexity in the meniscal attachment is critical when evaluating tensile stresses in the bone. We also demonstrate that simplified material properties may be justified when the relationship between each material property and the desired output variables is well understood. The choice of the most efficient, and yet appropriate, meniscal modeling method depends on the goals of the model. [ABSTRACT FROM AUTHOR]

A novel plate-type acoustic metamaterial with a high sound transmission loss (STL) in the low-frequency range (1000 Hz) is designed, theoretically proven and then experimentally verified. The thin plates with large modulus used in this paper mean that we do not need to apply tension to the plates, which is more applicable to practical engineering, the achievement of noise reduction is better and the installation of plates is more user-friendly than that of the membranes. The effects of different structural parameters of the plates on the sound-proofed performance at low-frequencies were also investigated by experiment and finite element method (FEM). The results showed that the STL can be modulated effectively and predictably using vibration theory by changing the structural parameters, such as the radius and thickness of the plate. Furthermore, using unit cells of different geometric sizes which are responsible for different frequency regions, the stacked panels with thickness 16 mm and weight 5 kg/m2 showed high STL below 2000 Hz. The acoustic metamaterial proposed in this study could provide a potential application in the low-frequency noise insulation. [ABSTRACT FROM AUTHOR]

Cable-arch structures, having features of the flexibility of cable and rigidity of arch, have often been used in structural and bridge engineering. It is important to fully understand the behavior of such a structure under various conditions. For this purpose, in this paper, linear and nonlinear elastic buckling analysis of four cable-arch related structures, including tied cable-arch structure, pure arch, tied arch and cable-arch, were conducted using the finite element methods under different boundary and load conditions with the stability of these structures compared. Furthermore, the parametric analysis was carried out to investigate the influence of numbers and inclined angles of hangers and cables, materials of cables and stiffness of tie beam on the buckling behavior of tied cable-arch. The results indicate that the stability of pure arch and tied arch can be enhanced by anchoring cables on the arch rib due to the increase in stiffness. Moreover, the weaker the stiffness of an arch, the greater the cable's contribution to structural stiffness. The stability of a tied cable-arch is quite sensitive to the inclined angle of hangers and cables, the number and materials of cables, and tie bar, but not to the fracture of two hangers. The study gives us a complete understanding of the elastic buckling behavior of circular tied cable-arch structures. [ABSTRACT FROM AUTHOR]

This paper studies the size-dependent dynamic behavior of electrostatically actuated microaccelerometers using the modified couple stress theory. The device is modeled as a cantilevered microbeam with an electrostatically actuated proof mass attached to its free end. The equation of motion is derived based on the Hamilton's principle and solved both numerically (using the finite element and finite difference methods) and analytically (using the perturbation technique) and the dynamic response and pull-in instability of the device is studied. The results of these methods are compared and the source of error in the analytical results at high values of external acceleration is discussed. Furthermore, the results are compared with those evaluated based on the classical theory. It is found that for cantilevered accelerometers with a beam thickness of the order of the material length scale parameter, the classical theory gives a rough estimation of the dynamic response of the system. In this situation, the error of using the classical theory may change the prediction of the system behavior from unstable to stable. [ABSTRACT FROM AUTHOR]

This paper concerns the vibrational behavior of concentric double-walled and triple-walled carbon and boron nitride nanotubes using the finite element method. Armchair and zigzag nanotubes with different lengths and diameters are considered. Moreover, different boundary conditions are applied on the nanotubes. It is observed that in double-walled nanotubes, when the inner and outer layers are respectively from boron nitride and carbon, the frequencies are larger than those in the reverse arrangement. Investigating the effect of diameter on the first 10 natural frequencies of double-walled and triple-walled nanotubes showed that nanotubes with larger diameters possess smaller frequencies. The effect of diameter is more significant for higher modes. Finally, comparisons are made between the vibrational behavior of concentric carbon and boron nitride double-walled and triple-walled nanotubes. Considering the effect of vacancy defect on the vibrational characteristics of the nanotubes revealed that when all of the walls of the nanotubes are defective, the largest diminish occurs for the fundamental natural frequencies. [ABSTRACT FROM AUTHOR]

The paper presents the results of numerical analyses of elasto-plastic buckling of steel reinforcing bars. Bars with different geometrical parameters made of steel with various mechanical characteristics were analyzed. The commercial program COSMOS/M based on the finite element method was used. It follows from the results that slenderness is not the only parameter that affects the elasto-plastic buckling of reinforcing bars. Such parameters as the length of the plastic plateau, ultimate stress and the plastic hardening module play an important role as well. [ABSTRACT FROM AUTHOR]

The paper presents the application of the differential transformation method (DTM) to the stability analysis of nonuniformly loaded beams under bending. The main advantage of the method is the possibility to obtain the semi-analytical solution for the critical loads of the beam undergoing lateral-torsional buckling. To determine the critical load, the system of two coupled ordinary differential equations with variable coefficients and parameters have to be solved. Numerical analyses were carried out for three different types of load functions: (i) Uniformly distributed load, (ii) linearly varying load and (iii) sinusoidally distributed load. The results were compared with the solutions computed by the finite element method (FEM) and those obtained by the authors using the variational iterative method (VIM). In each case, it was found that the difference with reference to the existing one does not exceed 3%, which testifies the effectiveness of the DTM used. Nevertheless, it should be emphasized that the number of terms of the approximation series used is fairly large and therefore the calculation of higher critical loads can be very time-consuming. [ABSTRACT FROM AUTHOR]

Behaviour analysis loop is largely performed on virtual product model before its physical manufacturing. The last avoids high expenses in terms of money and time spent on intermediate manufacturing. It is gainful from the reality to the virtuality but the process could be further optimized especially during the product behaviour optimization phase. This process involves repetition of four main processing steps: CAD design and modification, mesh creation, Finite Element (FE) model generation with the association of physical and geometric data, FE Analysis. The product behaviour analysis loop is performed on the first design solution as well as on the numerous successive product optimization loops. Each design solution evaluation necessitates the same time as required for the first product design that is particularly crucial in the context of maintenance. In this paper we propose a new framework for CAD-less product optimisation through FE analysis which reduces the model preparation activities traditionally required for FE model creation. More concretely, the idea is to directly operate on the firstly created FE mesh, enriched with physical/geometric semantics, to perform the product modifications required to achieve its optimised version. In order to accomplish the proposed CAD-less FE analysis framework, modification operators acting on both the mesh geometry and the associated semantics need to be devised. In this paper we discuss the underlying concepts and present possible components for the development of such operators. A high-level operator specification is proposed according to a modular structure that allows an easy realisation of different mesh modification operators. Here, two instances of this high-level operator are described: the planar cracking and the drilling. The realised prototypes validated on industrial FE models show clearly the feasibility of this approach. [ABSTRACT FROM AUTHOR]

We study finite element approximations for positive solutions of semilinear elliptic eigenvalue problems with folds, and exploit the superconvergence of finite element methods (FEM). In order to apply the superconvergence of FEM for Poisson's equation in [Chen & Huang, 1995; Huang et al., 2004, 2006; Lin & Yan, 1996] to parameter-dependent problems with folds, this paper provides the framework of analysis, accompanied with the proof of the strong monotonicity of the nonlinear form. It is worthy to point out that the superconvergence of the nonlinear problem in this paper is different from that in [Chen & Huang, 1995]. A continuation algorithm is described to trace solution curves of semilinear elliptic eigenvalue problems, where the Adini elements are exploited to discretize the PDEs. Numerical results on some sample test problems with folds and bifurcations are reported. [ABSTRACT FROM AUTHOR]

In this paper, a new type of honeycomb structure is proposed to enhance the energy absorption capacity for a honeycomb structure, and investigated its energy absorption efficiency (absorbed energy per unit volume) by finite element method (FEM). This model has small arc-shaped parts on the double cell wall, and can be manufactured by a similar way of standard honeycomb structures. Also, the proposed structure has large rigidity of plastic bending without increasing the mass. In this paper, effects of geometrical properties on the energy absorption characteristics are discussed. [ABSTRACT FROM AUTHOR]

In order to increase greatly the calculation accuracy and the computation speed for complex electromagnetic fields in modern physics, a new finite element method, which has the high computation accuracy, fast computation speed and less computer storage requirements, is presented in this paper. The new method with a high-order finite element without internal nodes is introduced to compute and analyze some complex electromagnetic fields in the electron accelerators. In this paper, the complex electromagnetic field in an electromagnetic device has been calculated successfully by the finite elements, and the electromagnetic properties of the electromagnetic device under the specific work condition is analyzed and evaluated. Good agreement is found between the computed values and the experimental values. [ABSTRACT FROM AUTHOR]

The simulation comparison research of two types of high-order triangular finite element methods for the numerical simulation of two-dimensional nonlinear electromagnetic fields is presented in this paper. The comparative study has been done in many ways, such as the accuracy of computation, the computation time and computer storage requirement. The comparative results obtained in this paper are very useful to calculation methods used in electromagnetic fields in modern physics fields. [ABSTRACT FROM AUTHOR]

This paper is an attempt to improve the quality of Gouraud shading with minimum increase in the computation requirements. It presents algorithms for intermediate quality shading i.e. the quality of shading is better than Gouraud shading and nearly comparable to the quality of bi-quadratic Phong shading, at the same time, algorithms are very fast as compared to bi-quadratic Phong shading. Three algorithms are discussed. The first algorithm uses hybrid shading in which bi-quadratic interpolation of intensity is performed on the edges of a triangle and linear interpolation of intensity is performed on the scan line. Hybrid shading, in which bi-quadratic interpolation of normals is performed on the edges and linear interpolation of intensity is performed on the scan line, has been proposed in the second algorithm. In the third algorithm, bi-cubic interpolation of intensity is performed on the edges and linear interpolation of intensity is performed on the scan line. The paper also presents an incremental method for fast calculation of area coordinates and shape functions enhancing the speed of the algorithms. [ABSTRACT FROM AUTHOR]

In the companion papers [1,2], authors introduced the concepts of k-version of finite element method and k, hk, pk, hkp-processes of the finite element method for boundary value problems described by self-adjoint and non-self adjoint operators using Ĥk,p(Ω) spaces with specific details including numerical studies for weak forms and least square processes. It was demonstrated that a variationally consistent (VC) weak form is possible when the differential operator is self-adjoint, however, in case of non-self-adjoint operators the weak forms are variationally inconsistent (VIC) which lead to degenerate computational processes that can produce spurious oscillations in the computed solutions. In this paper we demonstrate that when the boundary value problems are described by non-linear differential operators, Galerkin processes and weak forms can never be variationally consistent and hence result in degenerate computational processes and suffer from same problems as in the case of non-self-adjoint operators plus more due to the presence of non-linearity. In the proposed mathematical and computational frame-work, upwinding methods are neither required nor used. The k-version of FEM over Ĥk,p spaces for the Galerkin method with weak forms, though meritorious in comparison to Ĥ1,p(Ω) spaces, but it is plagued due to problems arising from variational inconsistency. We demonstrate that the order of the space k in Ĥk,p(Ω) Hilbert spaces is an independent parameter in all computational processes in addition to the characteristic length h of the discretizations and the degree p of the local approximations. This gives rise to k-version of finite element method and thus, associated k, hk, pk, and hpk processes. The global differentiability of a finite element solution is only dependent on k. The h, p and hp-adaptive processes can not yield global differentiability of order higher than the order of the space containing the local approximations. It is shown that variational consistency of the integral forms and higher order global differentiability of a computed solution by increasing k in Ĥk,p(Ω) spaces are two most important features of mathematical and computational frame work if one wishes the computational process to (1) be non-degenerate and (2) yield solution with the same characteristics in terms of global differentiability as the theoretical solution. In this paper, we illustrate the important variational aspects of the least squares finite element processes for non-linear partial differential equations of stationary processes. Variationally consistent least squares finite element method (LSFEM) using p-version basis functions in Ĥk,p(Ω) spaces provides a remarkably general framework for numerical simulation of any BVP described by non-linear differential operators in which any desired order of global smoothness or global differentiability is achievable. The proposed mathematical framework indeed allows one to numerically simulate characteristics of the theoretical solutions of any non-linear BVP regardless of the nature of the differential operator. Stationary one-dimensional Burgers equation is used as a model problem to present supporting numerical studies. Many issues and concepts related to upwinding methods and the behaviors of commonly encountered problems in Galerkin method for non-linear differential operators in BVP are considered, discussed and explained. [ABSTRACT FROM AUTHOR]

Elimination of stator oscillations in electromotors is among the least studied, but important problems that can influence the electric performance, mechanical wear and tear and acoustical noise. In this paper, we focus on a switch reluctance motor (SRM) designed and prototyped for eventual production in Iran. The stator oscillation problems due to radial forces in SRMs have been reported as more acute as compared to similar motors. Due to the complicated mechanical and electrical structure of SRMs, obtaining any analytical model for its acoustical noise is quite impossible. This necessitates using numerical and experimental methods for obtaining an approximating model for acoustical noise. Since, off line simulation can be carried out, finite element (FE) analysis can be utilized so as to generate enough data for identifying a valid model. In this paper, we introduce a neuro-model with excitation current (amp) and position of stator (degree) as inputs and acoustical noise (db) as output. We performed two subsequent FE analysis using ANSYS package. Our first magnetic analysis is aimed at getting magnetic forces on the body of the stator and rotor, by exerting excitation current. In the second acoustical analysis, we give the magnetic forces, resulting from previous corresponding analysis, to the model and get the acoustical noise. We consider the acoustical behavior of the motor, in its inside and outside spaces, separately. Our approach is quasi-static, since we performed some FEM static analyses for approximating the dynamic behavior of the motor. Some simulation results of a acoustic noise in a designed SR motor, using our proposed model, is also given. [ABSTRACT FROM AUTHOR]

This paper is devoted to the mathematical and numerical analysis of a strongly coupled flow and transport system typically encountered in continuum-based models of sedimentation-consolidation processes. The model focuses on the steady-state regime of a solid-liquid suspension immersed in a viscous fluid within a permeable medium, and the governing equations consist in the Brinkman problem with variable viscosity, written in terms of Cauchy pseudo-stresses and bulk velocity of the mixture; coupled with a nonlinear advection - nonlinear diffusion equation describing the transport of the solids volume fraction. The variational formulation is based on an augmented mixed approach for the Brinkman problem and the usual primal weak form for the transport equation. Solvability of the coupled formulation is established by combining fixed point arguments, certain regularity assumptions, and some classical results concerning variational problems and Sobolev spaces. In turn, the resulting augmented mixed-primal Galerkin scheme employs Raviart-Thomas approximations of order for the stress and piecewise continuous polynomials of order for velocity and volume fraction, and its solvability is deduced by applying a fixed-point strategy as well. Then, suitable Strang-type inequalities are utilized to rigorously derive optimal error estimates in the natural norms. Finally, a few numerical tests illustrate the accuracy of the augmented mixed-primal finite element method, and the properties of the model. [ABSTRACT FROM AUTHOR]

Let ℕ0 denote the set of all non-negative integers and 풫(ℕ0) be its power set. An integer additive set-indexer (IASI) of a graph G is an injective function f : V(G) → 풫(ℕ0) such that the induced function f+ : E(G) → 풫(ℕ0) defined by f+ (uv) = f(u) + f(v) is also injective. A graph G which admits an IASI is called an integer additive set-indexed graph (IASI-graph). An IASI of a graph G is said to be an arithmetic IASI if the elements of the set-labels of all vertices and edges of G are in arithmetic progressions. In this paper, we discuss about two special types of arithmetic IASIs. [ABSTRACT FROM AUTHOR]

Let G = (V(G), E(G)) be a simple, finite and undirected graph of order n. Given a bijection f: V(G) ∪ E(G) → Zk such that for each edge uv ∈ E(G), f(u) + f(v) + f(uv) is constant C( k). Let nf(i) be the number of vertices and edges labeled by i under f. If |nf(i) - nf(j)| ≤ 1 for all 0 ≤ i < j ≤ k - 1, we say f is a k-totally magic cordial (k-TMC) labeling of G. A graph is said to be k-totally cordial magic if it admits a k-TMC labeling. In this paper, we give some ways to construct new families of k-TMC graphs from a known k-totally cordial magic graphs. We also give a sufficient condition for an odd graph to admit no k-TMC labeling. As a by-product, we determine the k-totally magic cordiality of many families of graphs. [ABSTRACT FROM AUTHOR]

In this paper, we introduce new definitions of the Gray weight and the Gray map for linear codes over ℤ9 + uℤ9 with u2 = u. Some results on self-dual codes over this ring are investigated. Further, the structural properties of quadratic residue codes are also considered. Two self-dual codes with new parameters [22, 11, 5] and [24, 12, 9] over ℤ9 are obtained. [ABSTRACT FROM AUTHOR]

A finite word w ∈ {0, 1}* is balanced if for every equal-length factors u and v of every cyclic shift of w we have ||u|1 - |v|1| ≤ 1. This new class of finite words was defined in [O. Jenkinson and L. Q. Zamboni, Characterisations of balanced words via orderings, Theoret. Comput. Sci. 310(1-3) (2004) 247-271]. In [O. Jenkinson, Balanced words and majorization, Discrete Math. Algorithms Appl. 1(4) (2009) 463-484], there was proved several results considering finite balanced words and majorization. One of the main results was that the base-2 orbit of the balanced word is the least element in the set of orbits with respect to partial sum. It was also proved that the product of the elements in the base-2 orbit of a word is maximized precisely when the word is balanced. It turns out that the words 0q-p1p have similar extremal properties, opposite to the balanced words, which makes it meaningful to call these words the most unbalanced words. This paper contains the counterparts of the results mentioned above. We will prove that the orbit of the word u = 0q-p1p is the greatest element in the set of orbits with respect to partial sum and that it has the smallest product. We will also prove that u is the greatest element in the set of orbits with respect to partial product. [ABSTRACT FROM AUTHOR]

In this paper, the nonlinear transient thermal stress analysis is conducted for temperature-dependent hollow cylinders subjected to a decaying-with-time thermal field. By the finite element method, the highly nonlinear governing equations are solved. The time histories of temperature, displacement, and stress due to the decaying-with-time thermal load are computed. A sensitivity analysis includes the effects of exponent of the decayed heat flux and temperature-dependency of density and material properties is carried out. Numerical results show some interesting characteristics of the thermoelastic behaviors of the hollow cylinders studied. In particular, the effect of temperature-dependency of the material properties on the thermoelastic parameters was demonstrated to be significant. [ABSTRACT FROM AUTHOR]

This paper deals with an axisymmetric transient eddy current problem in conductive nonlinear magnetic media. This means that the relation between the magnetic field and the magnetic induction, the so-called H-B curve, is nonlinear. The source of the problem is the magnetic flux across a meridian section of the device, which leads to a parabolic nonlinear problem with nonlocal boundary conditions. First, by applying some abstract results, we prove the existence and uniqueness of the solution to a weak formulation written in terms of the magnetic field. Then, we compute the numerical solution of the problem by using a finite element method combined with a backward Euler time discretization. We derive error estimates in appropriate norms for both the semidiscrete (in space) and the fully discrete problems. Finally, we show numerical results which allow us to confirm the theoretical estimates and to assess the performance of the proposed scheme. [ABSTRACT FROM AUTHOR]

The use of finite element methods to determine the coUapse behavior of steel portal frames in fire requires temperature, large deformation, complex geometry, boundary conditions and degradation of material stiffness to be taken into account. For such analyses, the cost of computation is important as well as the accuracy, robustness and stability of the analyses. The implicit dynamic method is a rigorous technique that considers the equilibrium of every time step.However, convergence may become an issue, particularly if the frame undergoes structural instability while using a direct time incrementation scheme. In contrast, the explicit dynamic method does not require the equilibrium criteria to be met in every time step, and thus convergence problems are not encountered, although the cost of computation may be tremendous if the natural time scale is used. This paper presents a comparison between the efficiency, stability and accuracy of computations using the implicit and exphcit dynamic methods, in determining the collapse behavior of portal frames at elevated temperatures; the models are quasi-static since inertia forces are ignored. It is found that similar results can be obtained using both the implicit and exphcit dynamic methods, although the analysis times differ significantly. It is shown that, if the applied artificial uiertia forces, in terms of residual forces, are magnified and an automatic time incrementation scheme is activated in the imphcit dynamic method, then this method shows significant superiority over the explicit dynamic method both in terms of the cost of computation and the accuracy of results obtained for such structures. [ABSTRACT FROM AUTHOR]

This paper is devoted to the derivation of an a posteriori residual-based error estimator for the A-φ magnetodynamic harmonic formulation of the Maxwell system. The weak continuous and discrete formulations are established, and the well-posedness of both of them is addressed. Some useful analytical tools are derived. Among them, an ad hoc Helmholtz decomposition is proven, which allows to pertinently split the error. Consequently, an a posteriori error estimator is obtained, which is proven to be reliable and locally efficient. Finally, numerical tests confirm the theoretical results. [ABSTRACT FROM AUTHOR]

This paper presents a one-dimensional (1D) finite element formulation for the nonlinear stability analysis of framed structures with semi-rigid (SR) connections. By applying the updated Lagrangian incremental formulation and the nonlinear displacement field of thin-walled cross sections, the equilibrium equations of a straight beam element are first developed. Force recovering is performed according to the external stiffness approach. Material nonlinearity is introduced for an elastic-perfectly plastic material through the plastic hinge formation at finite element ends. To account for the SR connection behavior, a special transformation procedure is developed. The effectiveness of the numerical algorithm discussed is validated through the test problems. [ABSTRACT FROM AUTHOR]

The struts in a beam string structure (BSS) may buckle laterally under compression. The lateral buckling of the struts is determined not only by the rotational stiffness of the beam-strut joints and the length and bending stiffness of the struts, but also by the rise and lateral stiffness of the beam, the number of struts, and the layout of strings. In this paper, the multi-strut BSS with several types of layout of strings is studied. An analytical method for estimating the lateral buckling load of the struts in BSS is proposed. Parametric studies are carried out to investigate the variation of the lateral buckling of the struts in the BSS for different string layouts. In the end, the validity of the proposed method is examined by means of numerical simulations using the geometrically nonlinear finite element method. [ABSTRACT FROM AUTHOR]

This paper presents a numerical investigation of the feasibility of condition monitoring of untrenched pipelines at seabed through ambient vibration measurements. A finite element (FE) model is developed to calculate the dynamic responses of pipelines to ambient wave forces. The model takes into consideration the interaction between the ocean waves, submarine pipeline, and seabed. The fluid around the pipeline is simulated using the acoustic fluid elements, while soil is simulated by springs and dashpots. The ambient hydrodynamic force in the marine environment is simulated based on the Joint North Sea Wave Observation Project (JONSWAP) spectrum. The transfer function from the wave surface elevation to the wave force is used to get the wave force spectrum. The dynamic responses of the pipe structure with different assumed damage conditions to the ambient wave forces are calculated. The calculated dynamic responses are assumed as measured ambient vibration data in condition monitoring to extract the pipeline vibration properties, which in turn are used in the FE model updating calculation to identify the pipeline conditions. Different noise levels are introduced into the calculated dynamic responses to simulate uncertainties that may arise from measurement and ambient hydrodynamic environment. The effect of noise levels on the extraction of pipeline vibration properties, and on the identification of the pipeline conditions is investigated. [ABSTRACT FROM AUTHOR]

This paper reports the results of a numerical investigation concerning the elastic and elastic-plastic post-buckling behavior of cold-formed steel-lipped channel columns affected by local/distortional/global (flexural-torsional) buckling mode interaction. The results presented and discussed are obtained by means of analyses performed in the code ABAQUS and adopting column discretizations into fine four-node isoparametric shell element meshes. The columns analysed (i) are simply supported (locally/globally pinned end sections with free warping), (ii) have cross-section dimensions and lengths ensuring equal local, distortional, and global (flexural-torsional) critical buckling loads, thus maximizing the mode interaction phenomenon under scrutiny, and (iii) contain critical-mode initial geometrical imperfections exhibiting different configurations, all corresponding to linear combination of the three "competing" critical buckling modes. After briefly addressing the lipped channel column "pure" global post-buckling behavior, one presents and discusses in detail numerical results concerning the post-buckling behavior of similar columns experiencing strong local/distortional/global mode interaction effects. These results consist of (i) elastic (mostly) and elastic-plastic equilibrium paths, (ii) curves and figures providing the evolution of the deformed configurations of several columns (expressed as linear combinations of their local, distortional, and global components) and, for the elastic-plastic columns, (iii) figures enabling a clear visualization of (iii1) the location and growth of the plastic strains, and (iii2) the characteristics of the failure mechanisms more often detected in this work. [ABSTRACT FROM AUTHOR]

In this paper, four three-node triangular finite element models which can readily be incorporated into the standard finite element program framework are devised via a multi-field variational functional for the bounded plane Helmholtz problem. In the models, boundary and domain fields are independently assumed. The former is constructed by nodal interpolation and the latter comprises nonsingular solutions of the Helmholtz equation. The equality of the two fields are enforced along the element boundary. Among the four devised models, the most accurate one is 1/3 to 1/2 less erroneous than the conventional single-field model in most examples. [ABSTRACT FROM AUTHOR]

In this paper, we introduce new finite elements to approximate the Hellinger Reissner formulation of elasticity. The elements are the vector-valued tangential continuous Nédélec elements for the displacements, and symmetric tensor-valued, normal-normal continuous elements for the stresses. These elements do neither suffer from volume locking as the Poisson ratio approaches ½, nor suffer from shear locking when anisotropic elements are used for thin structures. We present the analysis of the new elements, discuss their implementation, and give numerical results. [ABSTRACT FROM AUTHOR]

This paper is concerned with the numerical computation of cavitation in nonlinear elasticity. The Crouzeix-Raviart nonconforming finite element method is shown to prevent the degeneration of the mesh provoked by the conventional finite element approximation of this problem. Upon the addition of a suitable stabilizing term to the elastic energy, the method is used to solve cavitation problems in both radially symmetric and non-radially symmetric settings. While the radially symmetric examples serve to illustrate the efficiency of the method, and for validation purposes, the experiments with non-centered and multiple cavities (carried out for the first time) yield novel observations of situations potentially leading to void coalescence. [ABSTRACT FROM AUTHOR]

In this paper, we present a mathematical model for pricing a particular financial product: the ratchet cap. This derivative product depends on certain interest rates (whose dynamics we assume that follow the LIBOR market model). The pricing model is rigorously posed in terms of a sequence of nested Cauchy problems associated to uniformly parabolic partial differential equations. First, for each problem the existence and uniqueness of solution is obtained. Next, this analysis allows to propose a new and more efficient numerical method based on the approximation by computable fundamental solutions of constant coefficient operators. The advantage in terms of computational time of this new modeling and analytically based approach is illustrated by comparison with the classically used Monte Carlo simulation and a characteristics Crank-Nicolson time discretization combined with finite elements strategy. [ABSTRACT FROM AUTHOR]

This paper presents the details of studies conducted on brick masonry units and wall panels. The investigation includes, compressive strength of brick unit, prisms, flexural strength evaluation, and testing of reinforced brick wall panels with and without opening. Nonlinear finite element analysis (FEA) of brick wall panels with and without opening has been carried out by simulating the actual test conditions. Constant vertical load is applied on the top of the wall panel and lateral load is applied in an incremental manner. The in-plane deformation is recorded under each incremental lateral load. Displacement ductility factors and response-reduction factors have been evaluated based on experimental results. From the experimental study, it is observed that fully reinforced wall panel without opening performed well compared to other types of wall panels in lateral load resistance and displacement ductility. In all the wall panels, shear cracks originated at loading point and moved toward the compression toe of the wall. The force-reduction factors of a wall panel with opening are much less when compared with fully reinforced wall panel with no opening. The displacement values obtained by nonlinear FEA were found to be in good agreement with the corresponding experimental values. The difference in the computed and experimental values is attributed to the influence of mortar joint which was not considered in FEA. The derived response-reduction factors will be useful for adopting elastoplastic design procedures for lateral forces generated due to earthquakes. [ABSTRACT FROM AUTHOR]

In this paper, we discuss the problem of heat exchange in composite plane wall whose heat transmitting coefficient is not a locally periodic function. For that problem, we present a method of multiscale asymptotic expansions and then propose its corresponding FE algorithm. Of course, we give comprehensive theoretical analysis for the FE algorithm. Finally, we use numerical experiments to investigate them. [ABSTRACT FROM AUTHOR]

In this paper, a new adaptive finite element (FE) framework based on the variational multiscale method is proposed and applied to simulate the dynamic behaviors of metal under loadings. First, the extended bridging scale method is used to couple molecular dynamics and FE. Then, macro damages evolvements of those micro defects are simulated by the adaptive FE method. Some auxiliary strategies, such as the conservative mesh remapping, failure mechanism and mesh splitting technique are also included in the adaptive FE computation. Efficiency of our method is validated by numerical experiments. [ABSTRACT FROM AUTHOR]

This paper presents the results of dynamic responses and fire resistance of concrete-filled steel tubular (CFST) frame structures in fire conditions by using the nonlinear finite element method. Both strength and stability criteria are considered in the collapse analysis. The frame structures are constructed with circular CFST columns and steel beams of I-sections. In order to validate the finite element solutions, the numerical results are compared with those from a fire resistance test on CFST columns. The finite element model is then adopted to simulate the behavior of frame structures in fire. The structural responses of the frames, including the critical temperature and fire-resisting limit time, are obtained for the ISO-834 standard fire. Parametric studies are carried out to show their influence on the load capacity of the frame structures in fire. Suggestions and recommendations are presented for possible adoption in future construction and design of similar structures. [ABSTRACT FROM AUTHOR]

An increasing amount of attention has been paid on the study of thermodiffusion effects on mass transport. This paper presents a novel mathematical model for an entire proton exchange membrane fuel cell (PEMFC) with focus placed on the modeling and assessment of the role of thermodiffusion that has been usually neglected in previous fuel cell research work. Built upon the equations of continuity, momentum, energy, species concentrations, and electric potentials in different regions of a PEMFC, a set of nonlinear partial differential equations are numerically solved using finite element methods. The simulation results demonstrate that the thermodiffusion has a noticeable impact on transport of species in an operational PEMFC. [ABSTRACT FROM AUTHOR]

In this paper, we consider the evaluation of flux integral outputs from reduced basis solutions to second-order PDEs. In order to evaluate such outputs, a lifting function v⋆ must be chosen. In the standard finite element context, this choice is not relevant, whereas in the reduced basis context, as we show, it greatly affects the output error. We propose two "good" choices for v⋆ and illustrate their effect on the output error by examining a numerical example. We also make clear the role of v⋆ in a more general primal-dual reduced basis approximation framework. [ABSTRACT FROM AUTHOR]

In this paper, a new technique is presented for structural acoustic analysis in the case of nonconforming acoustic–solid interface meshes. We first describe a simple method for coupling nonconforming acoustic–acoustic meshes, and then show that a similar approach, together with the coupling operators from conforming analysis, can also be applied to nonconforming structural acoustics. In the case of acoustic–acoustic interfaces, the continuity of acoustic pressure is enforced with a set of linear constraint equations. For structural acoustic interfaces, the same set of linear constraints is used, in conjunction with the weak formulation and the coupling operators that are commonly used in conforming structural acoustics. The constraint equations are subsequently eliminated using a static condensation procedure. We show that our method is equally applicable to time domain, frequency domain, and coupled eigenvalue analysis for structural acoustics. Numerical examples in both the time and frequency domains are presented to verify the methods. [ABSTRACT FROM AUTHOR]

This paper presents the elastic strain energy, the potential energy with the second order terms of finite rotations, and the kinetic energy with rotary inertia effect for thin-walled composite beams of mono-symmetric cross-section. The equations of motion and force-displacement relationships are derived from the energy principle and explicit expressions for displacement parameters are given based on power series expansions of displacement components. The exact dynamic stiffness matrix is determined using the force-displacement relationships. In addition, the finite element model based on Hermitian interpolation polynomial is developed. In order to verify the accuracy and validity of the formulation, numerical examples are solved and the solutions are compared with results from ABAQUS's shell elements, analytical solutions from previous researchers and the finite element solutions using the Hermitian beam elements. The influence of constant and linearly variable axial forces, fiber orientation, and boundary conditions on the vibration behavior of composite beam are also investigated. [ABSTRACT FROM AUTHOR]

In this paper we prove convergence of adaptive finite element methods for second-order elliptic eigenvalue problems. We consider Lagrange finite elements of any degree and prove convergence for simple as well as multiple eigenvalues under a minimal refinement of marked elements, for all reasonable marking strategies, and starting from any initial triangulation. [ABSTRACT FROM AUTHOR]

This paper presents a theoretical analysis to the fracture behavior of the large single-domain YBCO superconductor with a center slant crack under electromagnetic force. The stress intensity factors are obtained by using the coupled finite element and infinite element numerical method. Numerical results are computed for two activation processes. For the zero-field cooling (ZFC) magnetization processes, the stress intensity factors increase as the applied field becomes large during field descent. For the field cooling (FC) magnetization processes, the stress intensity factors are obvious differences between the two cases when bfc > 1 and bfc ≤ 1. In addition, the predicted crack growth is the Mode-I fracture mainly. In this case, the numerical results developed in the present work are considered to be available for providing quantitative predictions of the fracture mechanism of superconductor both in theory and applications. [ABSTRACT FROM AUTHOR]

Most of finite volume schemes in the Arbitrary Lagrangian–Eulerian (ALE) method are constructed on the staggered mesh, where the momentum is defined at the nodes and the other variables (density, pressure and specific internal energy) are cell-centered. However, this kind of schemes must use a cell-centered remapping algorithm twice which is very inefficient. Furthermore, there is inconsistent treatment of the kinetic and internal energies.1 Recently, a new class of cell-centered Lagrangian scheme for two-dimensional compressible flow problems has been proposed in Ref. 2. The main new feature of the algorithm is the introduction of four pressures on each edge, two for each node on each side of the edge. This scheme is only first-order accurate. In this paper, a second-order cell-centered conservative ENO Lagrangian scheme is constructed by using an ENO-type approach to extend the spatial second-order accuracy. Time discretization is based on a second-order Runge–Kutta scheme. Combining a conservative interpolation (remapping) method3,4 with the second-order Lagrangian scheme, a kind of cell-centered second-order ALE methods can be obtained. Some numerical experiments are made with this method. All results show that our method is effective and have second-order accuracy. At last, in order to further increase the resolution of shock regions, we use an adaptive mesh generation based on the variational principle5 as a rezoned strategy for developing a class of adaptive ALE methods. Numerical experiments are also presented to valid the performance of the proposed method. [ABSTRACT FROM AUTHOR]

A material identification program AFDEX/MAT is presented in this paper. The program is based on the method for acquiring true stress-strain curves over large range of strains using engineering stress-strain curves obtained from a tensile test coupled with a finite element analysis. In the method, a tensile test is analyzed using a rigid-plastic finite element method combined with a perfect analysis model for its associated simple bar to provide the information of deformation. An initial reference true stress-strain curve, which predicts the necking point exactly, is modified iteratively to minimize the difference in tensile force between the experiments and predictions of the tensile test. It was applied to identifying the mechanical behaviors of two new pre-heat treated steels of ESW95 and ESW105 and a conventional Cr-Mo steel of SCM435. The predictions are compared with the experiments for the tensile test of the three materials, showing an excellent similarity. [ABSTRACT FROM AUTHOR]