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The aim of the present paper is to provide an efficient numerical technique to evaluate the linear elastic stress parameters to use in an existing fatigue model. The model allows to assess the tensile fatigue limit of components weakened by defects, cracks, sharp as well as blunt notches with an arbitrary notch opening angle. To apply the fatigue model, both the elastic stress concentration factor of the notch and the notch stress intensity factor of the corresponding sharp notch must be evaluated. Therefore, in principle two different linear elastic stress analyses should be performed. The novel technique proposed in the present paper involves only a single linear elastic stress analysis, consisting of a sharp and coarse finite element model: sharp because the notch tip radius is set to zero, and therefore a sharp V-shaped notch is modelled; coarse because coarse patterns of finite elements can be employed. Approximate values of the elastic stress concentration factor and of the notch stress intensity factor calculated from the sharp and coarse finite element model are compared with very accurate estimations obtained from dedicated analyses. To illustrate the fatigue assessment procedure, experimental notch fatigue limits taken from the literature and characterised by a variety of geometrical configurations are compared with theoretical estimations. [ABSTRACT FROM AUTHOR]

Diffusion modeling is essential in understanding many physical phenomena such as heat transfer, moisture concentration, and electrical conductivity. In the presence of material and geometric discontinuities and nonlocal effects, a nonlocal continuum approach, named peridynamics (PD), can be advantageous over the traditional local approaches. PD is based on integro-differential equations without including any spatial derivatives. In general, these equations are solved numerically by employing meshless discretization techniques. Although fundamentally different, commercial finite-element software can be a suitable platform for PD simulations that may result in several computational benefits. Hence, this paper presents the PD diffusion modeling and implementation procedure in a widely used commercial finite-element analysis software, ANSYS. The accuracy and capability of this approach is demonstrated by considering several benchmark problems. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents an elastoplastic finite element analysis of the seismic response of tunnels constructed in soft soils. The behavior of the soil material is described using a cyclic elastoplastic constitutive relation involving both isotropic and kinematic hardening. The paper is composed of three parts. The first part includes a brief presentation of the numerical model used in the analysis; the second one concerns analysis of the seismic response of a tunnel constructed in a soft soil; the last one presents a study of the influence of the plasticity and soil dilatancy on the seismic response of tunnels. Analyzes show that the plastic deformations induce an important reduction in the seismic-induced bending moment in the tunnel, while the soil dilatancy moderately affects the bending moment in the liner. [Copyright &y& Elsevier]

Stiffened plates are the most common structural units used in different structural applications ranging from buildings and bridges to ships and offshore structures. The present paper aiming at investigating the influence of using Y-stiffeners profile instead of conventional stiffeners on the load carrying capacity of ship deck panels under vertical hull girder bending moment. ANSYS (Release 15.0) nonlinear finite element software was used to verify the ultimate strength results obtained from applying the International Association Classification Societies-Common Structural Rules (IACS-CSR) on both conventional and novel deck panels. The developed numerical model with conventional stiffeners profile was validated in a good agreement with a benchmark study results included in the International Ship Structures Committee (ISSC). Furthermore, both analytical and numerical simulation results were in good agreement that demonstrates the capability of using IACS-CSR for designing the new stiffeners profile in practical applications. In comparison with the conventional stiffeners profile, the proposed Y-stiffeners resulted in a considerable increase in the panel safety margin to weight (area) ratio and higher ultimate strength. Moreover, the numerical simulations provided that implementing the Y-stiffeners profile can also rise the first yielding stress point of the structural response with nearly the same strain absorption in comparison with T-stiffeners profile. [ABSTRACT FROM AUTHOR]

Abstract: A new scheme for implementing a reduced order model for complex mesh-based numerical models (e.g. finite element unstructured mesh models), is presented. The matrix and source term vector of the full model are projected onto the reduced bases. The proper orthogonal decomposition (POD) is used to form the reduced bases. The reduced order modeling code is simple to implement even with complex governing equations, discretization methods and nonlinear parameterizations. Importantly, the model order reduction code is independent of the implementation details of the full model code. For nonlinear problems, a perturbation approach is used to help accelerate the matrix equation assembly process based on the assumption that the discretized system of equations has a polynomial representation and can thus be created by a summation of pre-formed matrices. In this paper, by applying the new approach, the POD reduced order model is implemented on an unstructured mesh finite element fluid flow model, and is applied to 3D flows. The error between the full order finite element solution and the reduced order model POD solution is estimated. The feasibility and accuracy of the reduced order model applied to 3D fluid flows are demonstrated. [Copyright &y& Elsevier]

Abstract: Thin layers with material properties which differ significantly from those of the adjacent media appear in a variety of applications, as in the form of fiber coatings in composite materials. Fully modeling of such thin layers by standard finite element (FE) analysis is often associated with difficult meshing and high computational cost. Asymptotic procedures which model such thin domains by an interface of no thickness on which appropriate interface conditions are devised have been known in the literature for some time. The present paper shows how the first-order asymptotic interface model proposed by Bövik in 1994, and later generalized by Benveniste, can be incorporated in a FE formulation, to yield an accurate and efficient computational scheme for problems involving thin layers. This is done here for linear scalar elliptic problems in two dimensions, prototyped by steady-state heat conduction. Moreover, it is shown that by somewhat modifying the formulation of the Bövik–Benveniste asymptotic model, the proposed formulation is made to preserve the self-adjointness of the original three-phase problem, thus leading to a symmetric FE stiffness matrix. Numerical examples are presented that demonstrate the performance of the method, and show that the proposed scheme is more cost-effective than the full standard FE modeling of the layer. [Copyright &y& Elsevier]

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]

This paper presents a practical approach based on High Dimensional Model Representation (HDMR) for analysing the response of structures with fuzzy parameters. The proposed methodology involves integrated finite element modelling, HDMR based response surface generation, and explicit fuzzy analysis procedures. The uncertainties in the material, geometric, loading and structural parameters are represented using fuzzy sets. To facilitate efficient computation, a HDMR based response surface generation is employed for the approximation of the fuzzy finite element response quantity. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, single and bi-layered tube hydroforming processes were numerically simulated using the finite element method. It was found that the final bulges heights resulted from the models were in good agreement with the experimental results. Both types of modeling have been kept with the same geometry, tube material, and process parameters to compare between the obtained hydroformed products (branch height, thickness reduction, and wrinkling) using different loading path types. Results were discussed. [Copyright &y& Elsevier]

Abstract: In this paper we present a new local remeshing algorithm that is dedicated to the problem of erosion in finite element models whose grid follows the movement of the free surface. The method, which we name Surface Lagrangian Remeshing (SLR), is adapted to 2D Lagrangian models which couple surface erosion with deformation of Earth materials. The remeshing procedure preserves nodes defining the surface submitted to erosion and removes nodes belonging to surface elements whose internal angles or area is critically low. This algorithm is ideally suited to track long term surface evolution. To validate the method we perform a set of numerical tests, using triangular finite elements, which compare the results obtained with the SLR algorithm with global remeshing and with analytical results. The results show good agreements with analytical solutions. Interpolation errors associated with remeshing are generated locally and numerical diffusion is restricted to the remeshed domain itself. In addition this method is computationally costless compared to classical global remeshing algorithm. We propose to couple the SLR method with the Dynamical Lagrangian Remeshing (DLR) algorithm to enable local remeshing only of Lagrangian models coupling large deformation of Earth materials with large erosion. [Copyright &y& Elsevier]

Abstract: In this paper, we consider a mathematical model which describes the dynamic contact between an elastic body and an obstacle. The process is assumed to be dynamic and the contact is modeled with the normal compliance. We present a variational formulation of the problem and prove the existence and the uniqueness of a weak solution. An efficient numerical method is presented to analyze this dynamic contact. This approach exploits the augmented Lagrangian concept and a special time integration algorithm. This is exploited to study the dynamic contact between the rotor and the stator inside an ultrasonic motor SHINSEI USR 60. Numerical results are presented and show the interest of this method to forecast the origin of the principal failure mode of this motor. [Copyright &y& Elsevier]

Abstract: The anchoring of structure elements in a reinforced concrete foundation is often performed by means of cast-in-place anchors. Their main function is to transfer normal loads, tension and compression, and possible shear loads according to the force transferred to the base of the structure. This study is limited to the study of long and smooth anchor rods with an anchor washer on the end, embedded in concrete. The anchor rods are prestressed in order to minimize the effects of fatigue. In normal practice to design these anchors the long-term behaviour of concrete is not taken into account although concrete creep involves a decrease in the initial prestress level. This paper presents the experimental results of pullout and relaxation tests and a finite element modelling of the joint. The time-dependent behaviour of concrete is taken into account in a visco-elastic analysis using the creep laws given in Eurocode 2. The numerical results are coherent with the measurements obtained in experimental tests. The decrease in the prestress is correctly simulated and its evolution in time can be estimated. [Copyright &y& Elsevier]

Abstract: In this paper we present a hyperelastic rod model that takes into account self-contact forces. The model is based on Cosserat rod theory that incorporates shear, elongation, flexure and twist deformations. The problem of avoiding self-penetration of parts of the rod is handled by the introduction of a contact distance function and the incorporation of associated contact forces. We present a penalty method for the treatment of the multi-valued and non-differentiable contact law. We also describe an augmented Lagrangian formulation of this problem. We then give the details of the finite-element discretization of the elastic rod self-contact problem as well as some numerical examples. [Copyright &y& Elsevier]

Abstract: This paper develops a modelling methodology for studying relations defined a priori in two dimensions, z = u(x, y), for which experimental data are known. An innovation is that the methodology is based on bi-dimensional finite element techniques, in which the model’s value consists of a finite number of points, making it possible to obtain its value at any point. Its application permits obtaining representational models of the relation. A computational algorithm is presented; its program has been called Finit Trap 2D, which generates families of models. It has defined criteria for model selection based on information parameters. This scientific research technique complements those existing in scientific literature for generating mathematical models based on experimental data [Cortés M, Villacampa Y, Mateu J, Usó, JL. A new methodology for modelling highly structured systems. Environmental modelling and software 2000;15(5):461–70, S-PLUS 2000. Guide to statistics, vosl. 1–2. Mathsoft Inc.; 1999, SPSS 12.0. Guide to statistics, Mathsoft Inc.; 2003, Verdu F. Un algoritmo para la construcción múltiple de modelos matemáticos no lineales y el estudio de su estabilidad, Thesis Doctoral, Universidad de Alicante; 2001, Verdu F, Villacampa Y. A computational algorithm for the multiple generation of nonlinear mathematical models and stability study. Advances in Engineering Software 2008;39(5):430–7, Villacampa Y, Cortés M, Vives F, Usó JL, Castro MA. A new computational algorithm to construct mathematical models. In: Ecosystems and sustainable development II. Advances in ecological sciences, vol. 2, WIT Press: Southampton, Boston; 1999], and will be useful in the effort to simplify the model. It should be emphasised that representational models have been generated from bi-dimensional finite element models. This will naturally lead to their future application in processes described by partial differential equation whose coefficients are functions, A(x, y) for which only experimental data are known. [Copyright &y& Elsevier]

Abstract: In this work, a mathematical model for small vibrations of an elastic string with moving boundaries is discussed. Global existence and uniqueness of solutions have been established in [M.A. Rincon, I.-S. Liu, Existence and uniqueness of solutions of elastic string with moving ends, Math. Methods Appl. Sci. 27 (14) (2004) 1641–1655]. The objective of this paper is to obtain the error estimates of solutions in Sobolev spaces for the semi-discrete problem, with discretization of space variable and continuous time. The analysis is based on Galerkin finite element method. [Copyright &y& Elsevier]