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• A novel FEM-DEM coupling model is developed to study the interaction between the small wheeled mobile platform tire and forest soil. • The coupling model are accurately established in ABAQUS-PFC3D. • The accuracy of the model was verified by the soil-bin test. • The model can present the force evolution of forest soil and the stress-strain distribution of the tire when the tire is rolling. Due to forest soil environment being short of structured terrain, research of tire-soil interaction is critical to enhance the performance for small wheeled mobile platform in forest. A novel model coupled finite element method (FEM) and discrete element method (DEM), which can be used to investigate the interaction behavior between the small wheeled mobile platform tire and forest soil, was proposed in this paper. In particular, the tire model based on rubber parameters that were obtained by uniaxial tensile tests is established in ABAQUS. The mechanical parameters of the soil in forest were obtained by the standard of geotechnical test and the triaxial compression test. The soil model was established in PFC3D. Significantly, the novel tire-soil interaction model based on the coupling ABAQUS and PFC3D was proposed accurately. The drawbar pull, the sinkage and the soil vertical stress were obtained through the proposed tire-soil interaction model. Meanwhile, soil-bin tests for tire-soil interaction were established. The drawbar pull, the sinkage and the soil vertical stress were obtained in soil-bin tests, which were consistent with the results from the proposed tire-soil interaction model. The results validated the effectiveness of the coupling method and the accuracy of the proposed tire-soil interaction model. Moreover, the flow state of soil particles was described by the proposed tire-soil interaction model, which analyzed the forces evolution in the area where the tire was in contact with the soil. [ABSTRACT FROM AUTHOR]

• Software for random finite element simulation in LS-DYNA is presented. • Random field discretization is optimized through interpolation and clustering. • No changes to LS-DYNA finite element solver are required. • Existing LS-DYNA material models are integrated into the software. • Mathematical operations can be performed to manipulate random material properties. This paper presents a user-friendly software to assign spatially distributed material properties to nonlinear finite element models in LS-DYNA using discretized three dimensional random fields and random variables. The purpose of the software is to enable probabilistic analysis frameworks that incorporate results from LS-DYNA simulations with random material properties. The software leverages the existing well-established deterministic formulation of LS-DYNA by utilizing inbuilt material constitutive laws. K -nearest neighbors spatial interpolation and k -means clustering are implemented to streamline the generation and assignment of random fields to parts in LS-DYNA models. The functionality of the software is demonstrated through real-life safety assessments of two marine structural elements composed of steel-reinforced concrete. Analysis results demonstrated the robustness and efficiency of the software where it can be successfully integrated into analysis frameworks to evaluate the safety of structural members. [ABSTRACT FROM AUTHOR]

The use of fracture energy regularization techniques can effectively mitigate the mesh dependency of numerical solutions caused by the strain softening behavior of quasi-brittle materials. However, the successful regularization depends on the correct estimation of the crack bandwidth in Finite Element solutions. This paper aims to present an enhanced crack band formulation to overcome the strain localization instability especially for the higher-order elements developed in the framework of Carrera Unified Formulation (CUF). Besides, a modified Mazars damage method incorporating fracture energy regularization is employed to describe the nonlinear damage behavior of the concrete. To evaluate the efficiency of the proposed crack band formulation, three experimental concrete benchmarks are selected for the numerical damage analysis. By comparing numerical and experimental results, the proposed method can guarantee mesh objectivity despite varying finite element numbers and orders, indicating perseved fracture energy consumption within proposed higher-order beam models. • Application of CUF formulation with isotropic damage concrete model. • Regularizing tensile and compressive softening behavior for higher-order beam theories. • Comparison of the enhanced regularization technique with previously proposed method. • Validation of all structural responses with former laboratory experimental campaigns. • Modified Mazars damage model for concrete with fracture energy regularization. [ABSTRACT FROM AUTHOR]

This paper deals with the numerical simulation of the flow induced sound as generated in the human phonation process including vocal folds (VF) contact. The hybrid approach is used allowing to separate the acoustic and the biomechanical description of the considered problem. The two-dimensional fluid–structure interaction (FSI) problem is modelled by a simplified linear elastic model coupled to the incompressible Navier–Stokes equations in the arbitrary Lagrangian–Eulerian form and special attention is paid to the treatment of the contact problem in the FSI context. Following approach of [Sváček and Horáček, 2021] the incompressible flow model is modified by an addition of fictitious porosity term and the penalization inlet boundary condition is used. Further, the Lighthill acoustic analogy is applied for calculation of sound sources and their propagation through a vocal tract model. All partial differential equations, describing the elastic body vibration, the fluid flow and the acoustics, are approximated by finite element method. Numerical results of one-sided vocal fold paralysis are presented. • Numerical simulation of human phonation including contact. • Fluid–structure interaction problem modified to enable closed channel configuration. • Fictitious porous domain and penalization boundary condition provide relevant values. • Sound generation and propagation modelled by Lighthill aeroacoustic analogy. [ABSTRACT FROM AUTHOR]

Highlights • The paper Steps to increase practical applicability of PragTic software deals with the parallelization of the fatigue solver PragTic at the node level of the finite element model, and its scalability testing. • Because of the intended focus on multiaxial fatigue analysis, the parallelization at the plane level while searching for the critical plane is also discussed. • Impact of such changes is clearly demonstrated. Abstract This paper describes various methods for increasing the computational speed of an existing fatigue solver called PragTic. The paper describes the basic workflow of computational fatigue analysis, including multiaxial fatigue analysis as well. It documents some of the inefficiencies of the original PragTic version, and parallelization and scalability testing of the parallelized PragTic in three different case studies. These studies include a simple model example (hundreds of nodes) and a real world example (millions of nodes). The implemented parallelization techniques are tested using numerical experiments to demonstrate their parallel scalability. As an output of a unique analysis, the number of necessary and feasible evaluated planes in multiaxial analyses is monitored, and the outcome favoring integral methods for the multiaxial fatigue analysis is commented. [ABSTRACT FROM AUTHOR]

Helmholtz resonator is one of the most basic acoustic models in acoustic theoretical research and engineering applications. It is simple and effective to directly apply the theoretical formula for its resonant frequency calculation, but sometimes the calculation error is too large or even wrong. In this paper, the characteristics of Helmholtz resonators are studied based on the finite element numerical analysis. The influence of structural parameters and boundary conditions of the Helmholtz resonator on the resonant frequency is given, several related problems of the theoretical formula are supplemented and the relevant conclusions are obtained. The explanations employed in this paper could be used as a supplement to the theoretical formula for theoretical study and engineering applications of Helmholtz resonators. [ABSTRACT FROM AUTHOR]

The discontinuous Galerkin (DG) method is frequently used in computational fluid dynamics for its stability and high order of accuracy. A disadvantage of the DG method is its high computational demands. The aim of this paper is to weaken this drawback by means of parallelization of the DG algorithm. The computation is performed on a network of computers with distributed memory using the Java Remote Method Invocation, which is included in the Java programming language. The partition of the boundary value problem into n subproblems, which is then solved by n computers separately, is based on the overlapping Schwarz method. On basis of physical nature of the problem, the present paper proposes minimal size of the overlap that allows for only one Schwarz iteration thereby increasing efficiency of parallelization. The scalability and efficiency of the presented parallelization approach is demonstrated on several test problems. In order to stabilize the DG method in presence of shocks, a recently developed technique by Huerta et al. (Int. J. Numer. Meth. Fluids 69(10), 2012, 1614–1632), which introduces discontinuities in basis functions in regions with a shock, is adopted here. A modification of this approach, which lowers the computational and implementational demands, is presented here. [ABSTRACT FROM AUTHOR]

• The double influence function method including flattening deformation influence function and deflection deformation influence function are established and combined used to solve the deformations between the rolls. • A model,considering the dispersion distribution characteristics of backing roll,for calculating the contact pressure between the rolls of the Sendzimir 20-high mill based on the double influence function method is established. • The conjugate gradient method is used to solve the contact pressure between the rolls by combining the force balance equation, the moment balance equation and the deformation compatibility equation group of rolls system. • The solving accuracy of the model established is consistent with that obtained by finite element method and the computation time can be greatly reduced. This paper established a model for calculating the contact pressure between the rolls of the Sendzimir 20-high mill based on the influence function method with considering the dispersion distribution characteristics of backup rolls. Stone's and Hirschcock's formula are used to calculate the rolling force between the work rolls and the rolling stock. The force balance equations and the moment balance equations of the roll system are established to determine the relationship between the contact pressure of rolls and the rolling force. The deformation-compatibility equation is established by combining the flattening deformation, deflection deformation, and rigid displacement of the rolls and roll crown. The influence function method is used to solve the flattening deformation and deflection deformation between the rolls. The conjugate gradient method is used to solve the contact pressure between the rolls by combining the force balance equation group, the moment balance equation group, and the deformation compatibility equation group of the roll system. The contact pressure between rolls obtained by the model established is compared to that by the finite element method. The results show that the calculation accuracy of the model established in this paper is consistent with that of the finite element method. Significantly, the contact pressure between the backup roll and the second intermediate roll can be accurately calculated by considering the dispersion distribution characteristics of the backup roll, and the computation time can be greatly reduced. [ABSTRACT FROM AUTHOR]

• Solve nonlinear stress problems in shell structures using image processing technique. • Finite element results are transformed into image pairs to generate training dataset. • Mechanical behaviour, material properties and geometry are mapped to colour channels. • Solutions are generated in real-time with 5–10% error. In this paper, we propose a novel approach to solve nonlinear stress analysis problems in shell structures using an image processing technique. In general, such problems in design optimisation or virtual reality applications must be solved repetitively in a short period using direct methods such as nonlinear finite element analysis. Hence, obtaining solutions in real-time using direct methods can quickly become computationally overwhelming. The proposed method in this paper is unique in that it converts the mechanical behaviour of shell structures into images that are then used to train a machine learning algorithm. This is achieved by mapping shell deformations and stresses to a set of images that are used to train a conditional generative adversarial network. The network can then predict the solution of the problem for a varying range of parameters. The proposed approach can be significantly more efficient than training a machine learning algorithm using the raw numerical data. To evaluate the proposed method, two different structures are assessed where the training data is created using nonlinear finite element analysis. Each structure is studied for a varying geometry and a set of material properties. We show that the results of the trained network agree well with the results of the nonlinear finite element analysis. The proposed approach can quickly and accurately predict the mechanical behaviour of the structure using a fraction of the computational cost. All created data and source codes are openly available. [ABSTRACT FROM AUTHOR]

• The method of multi-threaded parallelization of the assembly and numerical factoring of the symmetrical sparse matrices, realized in the super-nodal finite element solver PARFES and oriented on multi-core computers of NUMA architecture, is proposed. • An algorithm for binding RAM to NUMA nodes is presented, which allows minimizing the access of the cores of each NUMA node to the memory of other NUMA nodes (to a distant memory). • Parallelization of the sparse matrix assembling uses atomic operations to avoid the collision between threads. It ensures a stable speed-up even in the case of a large number of threads. • Parallelization of the sparse matrix factorization is based on the use of a dependency vector that controls the mapping of computational tasks to threads. This approach proved its efficiency on numerous real-life examples of the finite element problems of structural and solid mechanics. This paper considers the implementation of PARFES – the direct supernodal method for solving systems of linear equations with symmetric matrices resulting from the finite element method applied to problems of structural and solid mechanics. Unlike previous publications describing the implementation of PARFES for multicore SMP computers, this paper focuses on the implementation of the solver on NUMA computers, where storing data in near memory of the corresponding processor is crucial for achieving high performance, which leads to significant changes in the basic solver algorithms. [ABSTRACT FROM AUTHOR]

• The paper presents a new geometrically nonlinear topology optimization method. • Explicit bars can reduce the design variables to enhance the efficiency. • The result of three-dimensional structure tends nonsymmetric due to buckling effects. In this paper, a geometrically nonlinear topology optimization method is presented for three-dimensional structures using moving morphable bars. The explicit geometrical shapes of moving morphable bars reduce the design variables, so the computational efficiency of the method can be enhanced by accelerating the convergence process. The element density function with respect to moving morphable bars is obtained by a Heaviside approximation of distance functions, which is modified without the coordinate transformation. Afterwards, the density function is skillfully applied to derive the geometrically nonlinear finite element analysis for three-dimensional structures. Besides, the topology optimization model is established, whose sensitivities are derived by the adjoint method. Numerical examples demonstrate the effectiveness of the proposed method, and show that for some symmetric design domains, the optimized results tend towards slightly nonsymmetric due to the buckling effects. [ABSTRACT FROM AUTHOR]

This paper presents an algorithm for coupling cohesive crack modeling with non-stationary heat flow. Firstly, the nonlinear system of equation, based on global formulations, for such a computational model is derived. The nonlinearity here comes from nonlinear relations in the crack. The relations refer to cohesion forces and to heat flux which both depend of crack opening and additionally are dependent of temperature difference between both sides of the crack. In the paper the discontinuities of displacement field and temperature field are both approximated using XFEM. All the analysis concerning crack surface is performed using local coordinate systems for each integration point. The local coordinate system is two-dimensional for both 2D and 3D analysis. The paper is illustrated with non-stationary thermo-mechanical examples for a domain with propagating crack. [ABSTRACT FROM AUTHOR]

This paper presents a numerical study of the response of axially loaded concrete filled steel tube (CFST) columns under lateral impact loading using explicit non-linear finite element techniques. The aims of this paper are to evaluate the vulnerability of existing columns to credible impact events as well as to contribute new information towards the safe design of such vulnerable columns. The model incorporates concrete confinement, strain rate effects of steel and concrete, contact between the steel tube and concrete and dynamic relaxation for pre-loading, which is a relatively recent method for applying a pre-loading in the explicit solver. The finite element model was first verified by comparing results with existing experimental results and then employed to conduct a parametric sensitivity analysis. The effects of various structural and load parameters on the impact response of the CFST column were evaluated to identify the key controlling factors. Overall, the major parameters which influence the impact response of the column are the steel tube thickness to diameter ratio, the slenderness ratio and the impact velocity. The findings of this study will enhance the current state of knowledge in this area and can serve as a benchmark reference for future analysis and design of CFST columns under lateral impact. [ABSTRACT FROM AUTHOR]

Recent multi-core designs migrated from Symmetric Multi Processing to cache coherent Non Uniform Memory Access architectures. In this paper we discuss performance issues that arise when designing parallel Finite Element programs for a 64-core ccNUMA computer and explore solutions for these issues. We first present the overview of the computer architecture and show that highly parallel code that does not take into account the aspects of the system memory organization scales poorly, achieving only 2.8× speedup when running with 64 threads. Then, we discuss how we identified the sources of overhead and evaluate three possible solutions for the problem. We show that the first solution does not require the application’s code to be modified, however, the speedup achieved is only 10.6×. The second solution enables the performance to scale up to 30.9×, however, it requires the programmer to manually schedule threads and allocate related data on local CPUs and memory banks and rely on ccNUMA aware libraries that are not portable across operating systems. Also, we propose and evaluate “copy-on-thread”, an alternative solution that enables the performance to scale up to 25.5× without relying on specialized libraries nor requiring specific data allocation and thread scheduling. Finally, we argue that the issues reported only happen for large data sets and conclude the paper with recommendations to help programmers to design algorithms and programs that perform well on such kind of machine. [ABSTRACT FROM AUTHOR]

• A Plug-in tool named lattice structure designer (LSD) has been developed for periodic lattice cell structures to work with ABAQUS finite element software. • This tool was developed via ABAQUS graphical user interface (GUI) based on python code. • The LSD tool works for three lattice families: BCC, pyramidal and tetrahedron configurations. • The tool can be further updated to add any other periodic lattice structures. • The tool has capability of applying boundary conditions and compression load been used to simulate the axial compression behavior of the adopted lattices. This paper presents the development of a lattice structure design (LSD) tool for building and analyzing different configurations of 3D-printed lattice structure (LS). This tool was developed via ABAQUS graphical user interface (GUI) based on Python code. Due to the extensive research activities in the field of lattice design using experimental and computational methods, there is a high demand for finding new techniques to reduce the computational time and human effort. Also, several challenges were revealed while creating finite element models for lattices of complicated geometries. These models showed the capability for capturing the elastic and inelastic mechanical responses of LSs during the compression test. Consequently, the LSD tool was designed not only to build lattice structures in a short time and simple way, but also to analyze the associated compressive mechanical behavior that goes beyond initial yielding to cover the entire crushing behavior. This paper examined many challenges involved in generating and decomposing the lattice geometry, creating hexahedron elements and optimizing the mesh density, assigning and inserting the material type, activating the face recognition to define the boundary and loading conditions, and conducting linear and polar patterns. Finally, to demonstrate the effectiveness of the new approach in designing and analyzing LSs, finite element results were validated with the previous experimental findings. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a new approach of structural domain partitioning for parallel processing based on an interface displacement frame method and using dual partition super-elements. Compatibility and equilibrium between the partitions is ensured at the level of the parent structure, where the dual super-elements handle the two-way communication of interface displacements/forces/stiffness and other analysis-specific entities. The proposed approach can be applied relatively easily to existing monolithic finite element analysis programs, and it offers more freedom to the user with regard to defining partitions, load balancing and isolating parts of the structure of specific interest. Several examples are used in the paper to demonstrate the benefits of the proposed approach. [Copyright &y& Elsevier]

Abstract: This paper presents an effective and accurate computational strategy for unreinforced brick masonry structures. Mesoscale descriptions allow a realistic representation of the nonlinear structural behaviour of URM, but can pose prohibitive computational demands for large-scale problems. To overcome this drawback, the computational strategy presented in the paper employs the domain partitioning approach, which is coupled with an accurate mesoscale finite element model. This allows the effective parallelisation of the nonlinear structural analysis simulation, where significant speed-up can be achieved in the nonlinear analysis of large masonry structures. The potential and effectiveness of the proposed computational strategy are shown through numerical examples, where full-scale masonry structures are considered. [Copyright &y& Elsevier]

Abstract: The paper describes how the medial-axis construction of a geometric domain can be used in the design of cable-membrane structures. The developed method can be used in a conceptual design tool suggesting different shapes to an architect. At the same time this method can also help in the discretisation of a cable-membrane structure by automatically generating finite element meshes of the structures. The paper includes examples to demonstrate the capabilities of the method. [Copyright &y& Elsevier]

Abstract: This paper examines the application of service oriented architecture (SOA) in finite element analysis. SOA is a technology for designing and developing interoperable services. These services can reside on the same computer or, more commonly, on distributed computers. The paper demonstrates how SOA can be used within the context of scientific computing. The implementation and application of SOA to equation solvers and finite element analysis is described. There are advantages in terms of software engineering, as it facilitates the separation of areas of complexity. SOA can be used on standalone computers, intranets and on the internet. The data transfer costs are examined. It is shown that SOA principles can be used to design applets that make use of finite element analysis and a simple example of this is described. [Copyright &y& Elsevier]

Abstract: The paper presents a method which can convert different types of finite element mesh files to one format. The paper considers only ASCII file representations of the finite element meshes, as this type of representation is usually available for all modeler and simulation software used by engineers. The conversion method is based on regular expressions. The paper also presents a classification of the mesh formats used by several types of engineering softwares. [Copyright &y& Elsevier]

Abstract: The present paper deals with the design and implementation of parallel load-balancing framework in an object-oriented finite element environment. The parallelization strategy is based on domain decomposition and message passing paradigms. The algorithmic and implementation aspects are discussed in detail. Paper also describes components of a complete adaptive strategy, i.e., the error estimator/indicator, projection operator and remeshing. The capabilities and performance of the developed framework are demonstrated on advanced engineering problems, showing the scalability of the implemented algorithm and advantages of dynamic load balancing when used in dedicated and nondedicated environments. [Copyright &y& Elsevier]

Traveling-wave tubes (TWTs) are popularly used as the microwave power amplifier in civil and military applications and have a high mechanical sensitivity. It is necessary to understand their vibration characteristics under all operating conditions. To address this issue, a CAD/CAE integrated rapid redesign system of vibration analysis with unified data architecture (UDA) has been developed and presented in this paper. The UDA is presented to make CAD and CAE be an organic entity. This system is composed of the following four layers: (i) CAD/CAE integrated design environment, (ii) parametric modeling and fast modeling platform with custom-built tools, (iii) accurate and fast finite element free vibration analysis solver based on rapid solving techniques of equation, and (iv) fast finite element random vibration analysis solver. The CAD/CAE integrated system concept is typically applied in loop design-analysis-redesign procedures. In this CAD/CAE integrated design system, the designers can freely and rapidly complete component design and performance analysis simultaneously instead of using two different software or two interface environment. To improve the accuracy and efficiency of large-scale finite element vibration analysis, especially for free vibration analysis, an improved Lanczos iteration method with a new three-level preconditioner is developed and pseudo excitation method is introduced to perform random vibration analysis. The new three-level preconditioner is composed of a multifrontal block incomplete cholesky preconditioner, a p -type multigrid preconditioner, and a block Jacobi preconditioner. The developed system has been applied to the design of TWTs and been found to shorten the design cycle significantly compared with ANSYS. [ABSTRACT FROM AUTHOR]

• An automatic algorithm for generating polyhedral meshes was systematically developed. • Hexahedral elements near the given STL surface were categorized into polyhedral volume topologies based on the MC algorithm. • Topology ambiguities of the MC algorithm were effectively resolved to provide an appropriate mesh for complex geometry. • The effectiveness was demonstrated through numerical analysis using the smoothed finite element method. Hexahedral meshes that exhibit the superiority in terms of solution accuracy and convergence rate are preferred to other types of meshes in the finite element analysis. However, the construction of the hexahedral meshes for complex geometries is still considered troublesome due to their poor geometric adaptability. This paper presents an efficient grid-based scheme to automatically generate polyhedral meshes including the hexahedral elements, and thus to provide hexahedral-dominant meshes for three-dimensional geometry with complex shapes. On the basis of the marching cube algorithm with a background grid composed of a regular arrangement of cubes, surface topologies for the background cubes are defined to represent the three-dimensional boundaries of a given domain. Then, in order to generate a three-dimensional finite element mesh, the surface topologies of the marching cube algorithm are systematically expanded to polyhedral volume topologies. Meanwhile, a topology ambiguity problem inherent in the marching cube algorithm is effectively resolved to generate an appropriate polyhedral mesh even for an arbitrary complex geometry. Several examples including biostructure modeling demonstrate that the proposed mesh generation scheme can easily discretize complex three-dimensional domains with hexahedral-dominant meshes, which are composed of the polyhedral elements near the domain boundaries and the hexahedral elements that come from the background cubes inside the domains. Furthermore, to show the applicability and effectiveness of polyhedral meshes in the finite element analysis, some structural analyses are performed using the smoothed finite element method that can be straightforwardly adapted to polyhedral elements of arbitrary shape. [ABSTRACT FROM AUTHOR]

• Software is presented for verifying Timoshenko beam finite elements. • A popular fiite element is shown to converge to the wrong answer. • An element modification sufficient for convergence is reviewed. Abstract The classic paper Han et al. Dynamics of transversely vibrating beams using four engineering theories , Journal of Sound and Vibration, 225, 1999, sets up the continuation problem that determines the exact vibrational frequencies and mode shapes of prismatic Timoshenko beams. This article presents a portable implementation of a solver for the problem. In order to reliably compute a complete set of modes, without redundancies, it is crucial to formulate the frequency equation as a continuation problem. The continuation problem is solved for a thickness parameter starting from zero thickness (the Euler beam), and increasing up to the finite thickness of interest. The continuation problem has a bifurcation point, at which a wave number variable passes from real to a purely imaginary value. For finite thickness, the continuation problem for all sufficiently high frequency modes crosses through this bifurcation. Han et al.[7] solve the continuation problem using an unspecified differential equation solver, and dummyTXdummy- do not discuss accuracy. Here a solution of the continuation problem using pseudoarclength continuation is presented. This article presents a description of how to compute this singularity exactly, and develops software that maintains full working precision. Furthermore the details of the computation of the mode shapes from the frequencies are presented for free-free, clamped-clamped and clamped-free boundary conditions. The source code is available under a MIT license from github in the TimoshenkoBeamEigenvalues repository. [ABSTRACT FROM AUTHOR]

Highlights • Structural test and analysis data in one consistent data model. • Using ISO 10303 STEP AP209 to keep the traceability between structural testing and analysis. • Improving data retention of structural test and simulation data using STEP. Abstract This paper proposes a method for incorporating FEA data and structural test data into one common standardized data model based on the ISO 10303 STEP Standard [1]. The proposed method takes advantage of data structures and elements defined in STEP AP209 Edition 2 [2] to provide traceability between analysis and testing phases; information such as sensor and finite elements, test and FEA load cases, and test and FEA results are included. It also presents an introduction to STEP and AP209e2, and discusses how it can be used in a Simulation Data Management environment. [ABSTRACT FROM AUTHOR]

Abstract: Stress peening forming is widely used in the aeronautics industry to induce curvatures in wing skins. Most of the investigations of stress peen forming are empirical and experimental. In this paper, a three step numerical model that can simulate this process was developed. First, an implicit Finite Element Analysis (FEA) with ANSYS where a prebending moment along the spanwise direction of the component was performed. Then, an explicit FEA with LS-DYNA simulating shot impacts on the pre-stressed component was executed in order to obtain the resulting stresses inside the component. Finally, an implicit FEA with ANSYS was performed for calculating the arc heights and the curvature radii of the component in chordwise and spanwise directions. Numerical analysis of the process shows that the prebending moments have an influence not only on the residual stress profiles but also on the curvatures of the deformed component in chordwise and spanwise directions. This model was used to establish a relationship between the prebending moment and the resulting arc heights and residual stress profiles. The numerical strategies developed in this paper supply a useful tool for studying and optimizing the stress peening process. [Copyright &y& Elsevier]

Abstract: In this paper the mathematical geometric models of the single-lay wire strands and double-lay wire ropes with defined initial parameters are presented. The present geometric models fully consider the single-helix configuration of individual wires in the strand and the double-helix configuration of individual wires within the wound strands of the ropes. The mathematical representation of the single and double helixes is in form of parametric equations with variable input parameters which determine the centreline of an arbitrary circular wire of the right hand lay and left hand lay strands and ropes of the Lang lay and regular lay construction. The concrete forms of the parametric equations are derived and presented. The application of the derived geometric analytical model is illustrated by numerical examples. Techniques for the implementation of the derived mathematical models in CATIA V5 software and procedures for the generation of the rope model are briefly presented. Correctness of the derived parametric equations and a performance of the generated rope model are controlled by visualizations. The application of the derived mathematical model and the development of a finite element model for the numerical simulation of the multi-layered strand under tension tests are treated in the second part of the paper . [Copyright &y& Elsevier]

Abstract: In the comparison with the theoretical analyses of wire strands reported in the literature where obviously single-layered strands with a construction of the 1+6 wires were modelled and analysed, this paper is focused on a multi-layered strand with a construction of the 1+6+12+18 wires. The geometric parametric equations developed in the first part of this paper are implemented in CATIA V5 software code for geometric modelling of the multi-layered strand. The methodology of their implementation and the approach for the generation of the strand geometric model are demonstrated. To predict the behaviour of the multi-layered strand under tensile loads, the mathematical geometric model is further implemented in a finite element program. For this purpose ABAQUS/Explicit software is used. The derived 3D geometric models of the multi-layered strands and the results of the finite element elastic behaviour analyses of the strand under tension loads are validated through comparisons with experimental and theoretical data available. The results obtained confirm the correctness of the derived parametric equations and mathematical and physical importance of the finite element model developed. [Copyright &y& Elsevier]

Highlights • Anisotropic PFM is coupled with multiscale finite element method to simulate complex fracture behaviour of the composite. • Fracture behaviour of composite is analyzed in presence of strong and weak interfaces. • An adaptive mesh discretization strategy is developed to handle multiple cracks in the composites. • Composite with weak interface has higher load carrying capacity & toughness as compared to composite with strong interface. • Refined mesh in the vicinity of crack can be re-converted into coarse mesh after crack propagation. Abstract In this paper, a new multiscale phase field method (MsPFM) has been proposed to simulate crack propagation in composites. The MsPFM inherits the merits of anisotropic phase field method and multiscale finite element method. It is known that phase field simulation requires dense meshing to represent a sharp crack, thus the main aim of the MsPFM is to achieve mesh refinement in the vicinity of diffused crack/cracks. The proposed method is also used to study the interaction of a pre-existing crack with weak or strong interfaces (between matrix-fibre or between laminates) in terms of crack arrest, crack deflection, crack coalescence, and multiple cracks initiation in composites. Various numerical experiments are performed to demonstrate the effectiveness of proposed MsPFM to simulate the aforementioned failure characteristics of the composites. The crack growth trajectory obtained by the MsPFM for few test cases is validated through standard extended finite element method. [ABSTRACT FROM AUTHOR]

Highlights • Proposed a pragmatic approach to static load estimation on a wing rib. • Finite Element (FE) Model of the wing rib was calibrated using measured data. • Successfully trained a range of neural networks using random data and FE strains as inputs. • Artificial neural network (ANN) model predicted the static load to a degree of accuracy. • ANN estimated load are in good agreement with experimental data. Abstract This paper presents a novel approach to predicting the static load on a large wing rib in the absence of load cells. A Finite Element model of the wing rib was designed and calibrated using measured data obtained from static experimental test. An Artificial Neural Network (ANN) model was developed to predict the static load applied on the wing rib, this was achieved by using random data and strain values obtained from the static test as input parameters. A number of two layer feed-forward networks were designed and trained in MATLAB using the back-propagation algorithm. The first set of Neural Networks (NN) were trained using random data as inputs, measured strain values were introduced as input into the already trained neural network to access the training algorithm and quantify the accuracy of the static load prediction produced by the trained NN. In addition, a procedure that combines ANN and FE modelling to create a hybrid inverse problem analysis and load monitoring tool is presented. The hybrid approach is based on using trained NN to estimate the applied load from a known FE structural response. Results obtained from this research proves that using an ANN to identify loads is feasible and a well-trained NN shows fast convergence and high degree of accuracy of 92% in the load identification process. Finally, additional trained network results showed that ANN as an inverse problem solver can be used to estimate the load applied on a structure once the load-response relationship has been identified. [ABSTRACT FROM AUTHOR]

Highlights • A new type of phononic crystals with micro perforated plate structure is proposed. • The new structure is applied to automobile and can reduce noise in the cab. • The sound insulation performance of some phononic crystals plates are analyzed. Abstract The sound insulation performance of plates obviously affects the noise inside vehicle. Phononic crystals are periodic structures composed of various elastic materials. In this paper, the sound insulation performance of commonly used phononic crystals plates are analyzed by FEM (Finite Element Method), and some relevant conclusions are obtained. Based on the common two-dimensional convex phononic crystals, combined with micro perforated plate, a new type of phononic crystals plate is proposed, and the new combined phononic crystals structure is applied to the front plate of some automobile. The analysis results show that the combined phononic crystals plate has obvious effect on the noise reduction of the cab. [ABSTRACT FROM AUTHOR]

Abstract: Modeling shot peening process is very complex as it involves the interaction of metallic surfaces with a large number of shots of very small diameter. Conventionally such problems are solved using the finite element software (such as ABAQUS) to predict the stresses and strains. However, the number of shots involved and the number of elements required in a real-life components for a 100% coverage that lasts a considerable duration of peening make such an approach impracticable. Ideally, a method that is suitable for obtaining residual compressive stresses (RCS) and the amount of plastic deformations with the least computational effort seems a dire need. In this paper, an attempt has been made to address this issue by using the discrete element method (DEM) in combination with the finite element method (FEM) to obtain reasonably accurate predictions of the residual stresses and plastic strains. In the proposed approach, the spatial information of force versus time from the DEM simulation is utilized in the FE Model to solve the shot peening problem as a transient problem. The results show that the RCS distribution obtained closely matches with that of the computationally intensive direct FEM simulation. It has also been established, in this paper, that this method works well even in the situations where the robust unit cell approaches are found to be difficult to handle. [ABSTRACT FROM AUTHOR]

Abstract: Computer Aided Design (CAD) and Computer Aided Engineering (CAE) are two significantly different disciplines, and hence they require different shape models representations. As a result, models generated by CAD systems are often unsuitable for Finite Element Analysis (FEA) needs. In this paper, a new approach is proposed to reduce the gaps between CAD and CAE software’s. It is based on new shape representation called mixed shape representation. This later, supports simultaneously the B-Rep (manifold and non-manifold) and polyhedral representation, and creates a robust link between the CAD model (B-Rep NURBS) and the polyhedral model. Both representations are maintained on the same topology support called the High Level Topology (HLT), which represents a common requirement for simulation model preparation. A new software environment for CAD/CAE integration based on the mixed representation is presented in this paper, thus a set of necessary tools is associated to the mixed shape representation which contribute to reduce as much as possible the time of model preparation process. [Copyright &y& Elsevier]

Abstract: With rapid development of engineering numerical computation methods and extensive application of finite element analysis software, the demands of post-processing of calculation results are more and more high. The quality and efficiency of plotting contour map are important factors in analyzing of calculated results and in multi-schemed comparison. In this paper, automatic plotting of contour maps is achieved by realizing of compatibility of VB6.0, an embedded programming method in VB software, with Surfer 8.0, a powerful plotting function provided by Surfer software. Based on the approaching introduced in this paper, a batch processing visualization software for contour maps is developed. That can improve the efficiency of the post-processing of finite element analysis significantly. [ABSTRACT FROM AUTHOR]

Abstract: When conducting a finite element analysis (FEA) one way to reduce the total number of degrees of freedom is to use a mixed-dimensional model. Using beam elements to model long and slender components can significantly reduce the total number of elements. Problems arise when trying to connect elements with different dimensions in part due to incompatible degrees of freedom between different types of finite elements. This paper focuses on problems that occur in coupling beams and solids, which means coupling 1D and 3D finite elements. This paper presents a mesh-based solution to these problems only using specific arrangements of classical 1D and 3D finite elements without requiring the use of additional constraint equations. Two alternative solutions are detailed, evaluated and compared in this paper through series of computational experiments. The implementation of both solutions is also presented and involves mesh and geometry processing operations along with an adaptation of boundary representation (BREP) classical data structures. [Copyright &y& Elsevier]

Abstract: This paper is concerned with the various solutions to the class of nonlocal boundary value problem with the help of finite element method for the class of Kirchhoff-type problemwhere is a bounded smooth domain, is continuous and has subcritical growth. Kirchhoff equation does not appear to have been previously studied in detail computationally and it is hope that this paper will help to provide a new idea in this direction. Here we solved the nonlinear function with the help of Newton Raphson method and quasi-linear term by using Scaling Iterative Algorithm, forward difference and with the help of these schemes; we used finite element method to solve the Quasilinear Elliptic Equation of Kirchhoff Type and discussed the behaviour. In order to numerically confirm our theoretical results and to demonstrate the performance of the algorithm, we develop a MATLAB program for solving Kirchhoff-type problem. [Copyright &y& Elsevier]

Abstract: The aim of this paper is to describe an efficient method to connect two independent softwares so as to jointly use best qualities of each software around a complex problem solved by the finite element method (FEM). This connection makes it possible to extend quickly and easily the applicability of new models developed in academic softwares, by their simultaneous use with commercial softwares. This is particularly interesting when these models are very difficult to implement directly in commercial softwares. Most of the commercial FEM applications allow users to add additional features, physical models or boundary conditions via a programming interface. Within these user routines, access to internal data structures is possible, either through subroutine parameters and global variables, or via internal modules for reading and storing data. We use these capabilities to link the commercial software ABAQUS and an academic object-oriented C++ software HEREZH++, via the user-defined mechanical material behaviour (Umat). In this interface, HEREZH++ computes the mechanical behaviour of material and the code coupling performs a communication procedure between ABAQUS and HEREZH++. This paper describes this architecture which allows to implement easily original behaviour law in the commercial ABAQUS code. The asynchronous code coupling is made with a named piped interprocess communication method and an interface written in c/C++. Several test samples are presented to show the efficiency and accuracy of the proposed implementations concerning the computational time. In particular, an industrial test is carried out with an original behaviour model of elasto–visco-hysteresis which would have been very difficult to implement directly in ABAQUS. [Copyright &y& Elsevier]

Abstract: In this paper a finite element methodology for the static and dynamic non-linear analysis of historical masonry structures is described and applied to a case study. A basilica-type masonry church is analysed in order to assess its structural behaviour and its seismic vulnerability with respect to the actual state of conservation. Moreover the actual efficiency of current techniques for repairing and strengthening are analyzed in order to evaluated their benefits. A quasi-static approach (the seismic coefficient method) for the evaluation of the seismic loads have been used (as indeed common in many analyses of the seismic behaviour of masonry structures). This paper addresses the concern of seismic analysis and vulnerability of a basilica-type church with a specific case study: the Farneta abbey. The comparison demand vs. capacity confirms the susceptibility of this type of buildings to extensive damage and possibly to collapse, as frequently observed. The analysis of repairing and strengthening techniques show the effectiveness of the usual structural reinforcement in term of increased seismic capacity. It is believed that the conclusions obtained with respect to the seismic assessment of masonry church can be extrapolated for the wide variety of historical basilica-type church. [Copyright &y& Elsevier]

In this paper, attention is restricted to mesh adaptivity. Traditionally, the most common mesh adaptive strategies for linear problems are used to reach a prescribed accuracy. This goal is best met with an h-adaptive scheme in combination with an error estimator. In an industrial context, the aim of the mechanical simulations in engineering design is not only to obtain greatest quality but more often a compromise between the desired quality and the computation cost (CPU time, storage, software, competence, human cost, computer used). In this paper we propose the use of alternative mesh refinement with an h-adaptive procedure for 3D elastic problems. The alternative mesh refinement criteria allow to obtain the maximum of accuracy for a prescribed cost. These adaptive strategies are based on a technique of error in constitutive relation (the process could be used with other error estimators) and an efficient adaptive technique which automatically takes into account the steep gradient areas. This work proposes a 3D method of adaptivity with the latest version of the INRIA automatic mesh generator GAMHIC3D. [Copyright &y& Elsevier]

The paper addresses the problem of seismic retrofitting of existing concrete structures through an innovative methodology based on low yield metallic shear panels. These panels are introduced in specific places in the concrete structure enhancing its strength and stiffness. However, the most important improvement concerns the energy dissipation capacity of the retrofitted structure. The paper presents a preliminary design methodology within the performance based design framework and details for the realization of the intervention. Elaborated non-linear finite element models are used in order to verify the quality of the results obtained from more simple models used in everyday engineering practice. [Copyright &y& Elsevier]

Slip between layers, material properties of layers and geometric non-linearities largely dictate both the bearing capacity and the ductility of a composite beam. That is why the accuracy of their modelling in the numerical analysis of the composite beams is of utmost importance. In the present paper we present a new strain-based finite element model which considers these issues in a highly effective manner. Each layer of the beam is modelled by geometrically exact Reissner’s beam model. The layers are assumed to stay in the contact during deformation but the relative tangential displacement (slip) is possible. The non-linear load–slip law of the interface is considered. The formulation is found to be accurate, reliable and computationally time-effective. The further objective of the paper is an analysis of the buckling force of axially compressed layered wood columns, being simply supported, fixed–pinned or continuous. We compare the present numerical results with the analytical values of [Girhammar UA, Gopu VKA. Composite beam-columns with interlayer slip–exact analysis, J Struct Engng ASCE 1993;199(4):1265–82] and with the values, recommended by the European code for timber structures [Eurocode 5, Design of timber structures, Part 1-1: General rules and rules for buildings, 1993; ENV 1995-1-1]. The comparisons indicate that the European code for timber structures provides very conservative estimates for the buckling load. [Copyright &y& Elsevier]

Abstract: This paper presents parallel computational strategies to implement explicit nonlinear finite element analysis code onto distributed memory parallel computers for solving large-scale problems in structural dynamics. Implementation details on both homogeneous and heterogeneous parallel processing environments are considered in detail in this paper. Implementation of an explicit nonlinear finite element dynamic analysis code on homogeneous systems is discussed first and this is later moved onto heterogeneous systems. Domain decomposition with explicit message passing is preferred for parallel implementation. The message passing implementation in the parallel algorithm is based on MPI (Message Passing Interface) libraries. Implementation aspects of overlapped, non-overlapped domain decomposition techniques, Dynamic Task Allocation (DTA) and clustering techniques for DTA and their relative merits are presented. The interprocessor communications are optimised by overlapping with computations to improve the performance of the domain decomposition based explicit dynamic analysis finite element code. The issues related to implementation of finite element code for nonlinear dynamic analysis on heterogeneous parallel computing environment are later presented. A new dynamic load-balancing algorithm is developed for this purpose and it is integrated with the domain decomposition based parallel explicit finite element code to test our algorithms on a coarse grain heterogeneous cluster of workstations. Numerical experiments have been carried out on PARAM-10000, an Indian parallel computer and also on cluster of Unix workstations. [Copyright &y& Elsevier]

Abstract: The research presented in this paper deals with parallel explicit finite element simulation with domain decomposition for seismic response analysis of shield tunnel, which is the non-linear and time dependent behaviour of complex structures in engineering. Such simulations have to provide high accuracy in the prediction of deformations and stability, by taking into account the long-term influences of the non-linear behaviour of the material as well as the large deformation and contact conditions. The limiting factors of the computer simulation are the computer run time and the memory requirement during solution of large-scale problems. To overcome these problems, a domain decomposition method and dynamic-explicit time integration procedure are used, and the latter is used for the solution of the semi-discrete equations of motion, which is very suited for parallel processing. Using the high performance computer ShenWei-I, the seismic response of shield tunnel in Shanghai is processed, and the number of nodes and elements in final finite element model exceeded 4.0 million and 3.8 million, respectively. The results reveal the weak position in the shield tunnel under Shanghai seismic wave. The paper provides references for the antiseismic design of the shield tunnel. [Copyright &y& Elsevier]

Abstract: W-Beam guardrail system has been in use as a standard for roadside safety barrier since 1950s. Recently, its safety performance standard has been upgraded to absorb impact from large vehicles. This performance standard requires guardrail system to be capable of capturing and redirecting a large range of vehicle types and sizes but its effects on safety of motorcyclists are not yet understood. The paper describes a three-dimensional computer simulation of the kinematics impact of motorcycle and dummy rider with W-Beam guardrail inclined at angles 45 and 90° to the initial direction of travel. The simulation is based on the test procedure recommended by ISO 13232 on the configurations for motorcycle–car impact. The focus of this study is not on the motorcycle change in velocity, but on the rider''s kinematics and acceleration vs. time history. Multibody model of motorcycle and finite element model of guardrail were developed in commercially available software. The simulation results are presented in this paper in form of kinematics and acceleration vs. time history. [Copyright &y& Elsevier]

This paper gives a bibliographical review of the object-oriented programming applied to the finite element method as well as to the boundary element method. The bibliography at the end of the paper contains references to papers, conference proceedings and theses/dissertations on the subject that were published between 1990 and 2003. The following topics are included: finite element method—object-oriented programming philosophy, mesh modelling, distributed/parallel processing, toolkits and libraries, object-oriented specific applications (aerospace, civil engineering/geomechanics, coupled problems, dynamical systems, electromagnetics, fracture mechanics and contact problems, material simulations/manufacturing, mechanical engineering, nonlinear structural simulations, optimization, others); boundary element method. Totally 408 references are listed. [Copyright &y& Elsevier]

This paper examines the application of the local multi-grid finite element method to model both a single inclusion in an infinite plate and unidirectional laminae consisting of square and hexagonal packed arrays of fibres. Single and arrays of holes are modelled by assigning a negligible inclusion/fibre modulus of elasticity. The paper demonstrates that the local multi-grid method provides a convenient and accurate method for modelling single and arrays of inclusions compared to conventional structured and unstructured finite element models. Convenient in that local inclusion/fibre ‘primitive’ patches greatly assist in generating meshes consisting of arrays of fibres, and accurate in that structured base and patch meshes can be used, even though interpolation is used between levels. [Copyright &y& Elsevier]

• A novel approach to study uplift resistance of suction caisson in NGI-ADP soils. • 2D finite element analysis for suction caisson. • Failure mechanism, respective calculated tables and charts are presented. • Machine learning approach for building empirical equation and sensitivity analysis. The paper presents a novel solution for evaluating the uplift resistance of caisson foundations in anisotropic clay using displacement finite element analysis (FEA) and artificial neural network (ANN). The commercial FEA PLAXIS code is used to examine the uplift resistance of caisson foundations with a built-in anisotropic soil model developed by Norwegian Geotechnical Institute (NGI) based on the Active-Direct Shear-Passive concept (NGI-ADP model). The uplift resistance is expressed by a dimensionless stability factor that is a function of four dimensionless design parameters, i.e., the ratio of depth to diameter, the adhesion factor at the interface between caisson and clay, the shear strength gradient ratio, and the anisotropic strength ratio. Using the produced numerical results, ANN is adopted as the data driven technique to propose an empirical equation to estimate the uplift resistance factor. Furthermore, a sensitivity study is implemented to evaluate the relative importance of the four considered parameters on the uplift resistance of the caisson. Design charts, tables and empirical equations are developed and can be used to assist in practical designs. [ABSTRACT FROM AUTHOR]

This paper presents a finite element continuous-discontinuous approach for the dynamic ductile failure analysis of shell structures. The continuum damage model based on continuous displacements is used in the continuous stage to describe the diffuse micro-cracking in ductile failure of high-strength steel before a macro-crack is formed. In the context of a fully integrated shear deformable shell formulation, a nonlocal modeling procedure based on a projection of mid-plane reference surface is introduced to regularize the element-wise strain fields induced by the continuum damage model. In the discontinuous stage, an incorporation of velocity discontinuities in shell finite elements is pursued by XFEM method when the damage variable exceeds a critical value and the transition from a continuous to a discontinuous model is permitted. A phantom-node approach is employed in the XFEM method to simplify the numerical treatment of velocity discontinuities in the shell finite element formulation. Several numerical benchmarks are examined using the explicit dynamics analysis and the results are compared with the experimental data to demonstrate the effectiveness and accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

Finite element (FE) analysis produces results, which, in most cases, gain in accuracy, as the size of the FE mesh is reduced. However, this is not necessarily the case when beam and shell element connections induce in-plane torsional effects in the shell. In such situations, shell elements either do not allow for an in-plane torsional stiffness, or, when present, the in-plane torsional stiffness is incorrectly affected by the sizes of the elements. To overcome this problem, we propose a macro- panel element that has fewer degrees of freedom, includes a new model for in-plane torsional stiffness, and produces results with sufficient accuracy to meet engineering requirements. The panel element is based on the principle of sub-structuring, i.e., the panel is meshed internally by smaller shell elements. As shown in the paper, the proposed panel element can be quite large, yet, it can give accurate analysis results. This work helps to overcome a common dilemma in practical use of finite element analysis, where finite element theory requires element sizes to be sufficiently small, but practical considerations suggest the use of large-size elements that simplify the modelling process and reduce excesses in generated results. A model built using macro-panel elements is equivalent to the model built using smaller shell elements, with the normal and shear stresses in the former being the same as the stresses in the finely meshed shell element model, We identify a number of performance benefits that become available as a consequence of modelling the shell elements at a higher level of abstraction. [ABSTRACT FROM AUTHOR]

This study develops a novel high-order three-scale (HOTS) computational method for heat conduction problems of axisymmetric composite structures with multiple spatial scales. The heterogeneities of the composites are taken into account by periodic distributions of unit cells on the mesoscale and microscale. Firstly, the multiscale asymptotic analysis for these multiscale problems is given detailedly. Based on the above-mentioned analysis, the new unified micro-meso-macro HOTS approximate solutions are successfully constructed for these multiscale problems. Two classes of auxiliary cell functions are established on the mesoscale and microscale. Then, the error analyses for the conventional two-scale solutions, low-order three-scale (LOTS) solutions and HOTS solutions are obtained in the pointwise sense, which illustrate the necessity of developing HOTS solutions for simulating the heat conduction behaviors of composite structures with multiple periodic configurations. Furthermore, the corresponding HOTS numerical algorithm based on finite element method (FEM) is brought forward in details. Finally, some numerical examples are presented to verify the feasibility and validity of our HOTS computational method. In this paper, a unified three-scale computational framework is established for heat conduction problems of axisymmetric composite structures with multiple spatial scales. [ABSTRACT FROM AUTHOR]