Accurate simulation of bolted joints is not always consistent with industrial requirements, since numerous nonlinearities in the vicinity of the bolt can lead to overly expensive calculations. For this reason, commercial finite element (FE) codes preferentially use substitutes for bolts, such as simplified models or connectors. In this paper, a nonlinear FE connector with its identification methodology

In this paper, different degenerated shell approaches in conjunction with a layer-wise (LW) model for composite structures are investigated using Finite Element method. The first one involves a classical LW model. The second one is based on a variable separation method, the Proper Generalized Decomposition (PGD), in which the displacement field is approximated as a sum of separated functions of the

The present paper is dedicated to the modeling of the non-linear behavior of reinforced concrete structures subject to transverse shear or torsion under monotonic and cyclic loading. The fiber beam element approach has been proved to be an interesting modeling strategy, but needs to be improved for shear effects. This can be achieved by enhancing the cross-section kinematics with a warping displacement

An immersed boundary shell element formulation based on Kirchhoff-Love shell theory is presented here that uses a background mesh consisting of uniform 3D B-spline elements within which the geometry and the boundaries are embedded. In this theory, rotation is assumed to be identical to slope which introduces second derivatives of deflection in the weak form. As a result, elements that provide tangent

The dissipated strain energy, representing a monotonically increasing state variable in nonlinear fracture mechanics, can be used to develop an arc-length constraint equation for tracking the energy dissipation path instead of the elastic unloading path of the response of a structure. This was the motivation for the development of a dissipation-based arc-length method, followed by its implementation

A high fidelity fluid-structure interaction simulation may require many days to run, on hundreds of cores. This poses a serious burden, both in terms of time and economic considerations, when repetitions of such simulations may be required (e.g. for the purpose of design optimization). In this paper we present strategies based on (constrained) Bayesian optimization (BO) to alleviate this burden. BO

Uncertainty quantification (UQ) within topology optimization (TO) is a growing trend, with designers recognizing that deterministic analysis does not reflect the natural variabilities found in real-world structural performance. Thus far the majority of works have dealt with uncertain loading and material properties; however, minimal research has considered uncertain boundary conditions (BCs), which

Uncertainty Quantification (UQ) is a key discipline for computational modeling of complex systems, enhancing reliability of engineering simulations. In crashworthiness, having an accurate assessment of the behavior of the model uncertainty allows reducing the number of prototypes and associated costs. Carrying out UQ in this framework is especially challenging because it requires highly expensive simulations

The limitations of the dynamic theories for the thin layered elastic structures, which very often have different physical and geometrical contrast properties of the layers in today's high-tech applications, bring a number of challenges in the numerical computation of the dynamic response. This is a strong motivation to develop a suitable computational methodology for accurate evaluation and implementation

In this paper, the construction of Ck basis functions is proposed for paraxial d-dimensional rectangular meshes with arbitrary hanging nodes and arbitrary polynomial degree distributions. The construction is based on the large-support approach introduced in [1] for C0 basis functions in 2D and uses hierarchical tensor-product shape functions which combine Hermite shape functions with Gegenbauer polynomials

This work exploits the high accuracy of the mixed 3−field u/e/p formulation to address materially non-linear inelastic problems including isochoric deformations. Motivated by the strain-driven format of several constitutive equations used in FEA, the mixed u/s/p formulation is reinterpreted, selecting the deviatoric strains as primary variables, together with the displacements and the pressure field

In this paper, we have modified the stress integration scheme proposed by Choi and Yoon [1]; which is based on the numerical approximation of the yield function gradients, to implement in the finite element code ABAQUS three elastic isotropic, plastic anisotropic constitutive models with yielding described by Yld2004-18p [2], CPB06ex2 [3] and Yld2011-27p [4] criteria, respectively. We have developed

This paper presents a new parallel mesh generation method leading to subdomains of shape well-suited to Schur based domain decomposition methods such as the FETI and BDD solvers. Starting from a coarse mesh, subdomains meshes are created in parallel through hierarchical mesh refinement and morphing techniques. The proposed methodology aims at limiting the occurrence of known pathological situations

Herein, we present a novel method for searching anti-resonance frequencies, using an eigenvalue analysis that does not need to search every dip of amplitude in the frequency response function. The eigenvalue equation is derived by utilizing the fact that the solutions of a forced vibration equation are equal to zero at anti-resonance frequencies. The characteristics of the eigenvalue problem are analyzed

We propose a geometrically nonlinear extended isogeometric analysis approach for cohesive fracture. A shifting technique is used to enforce compatibility in the direction perpendicular to the crack path, while a blending technique has been adopted to remove the effect of the discontinuity in the extension of the cohesive crack. Bézier extraction is employed to cast the formulation in a finite element

The simulation of complex material failure processes requires a precise differentiation of the involved failure mechanisms like fracture or plasticity. This is commonly achieved by using a so-called multisurface failure criterion, where each failure surface is related to a certain failure mechanism. In the case of plasticity, failure surfaces define the elastic domain of the material and any stress

This paper evaluates the performances of second-order finite elements for nodal lumped-mass explicit methods in nonlinear solid dynamics, with a particular emphasis on 10-node “serendipity” and 15-node “Lagrange” tetrahedral elements. Historically, many nonlinear explicit finite element codes have exclusively used first-order elements, until a fairly recent flurry of activity that has resulted in higher-order

This paper presents a trans-scale finite element model based on hydraulic-thermal-mechanical coupling equations of porous medium to simulate the behavior of concrete during freezing and thawing. Unlike previous models that regard concrete as homogeneous material, this paper aims to establish a macro-size concrete model with detailed micro-structure, the aggregates (mm) and air voids (μm) are randomly

We propose a new approach to the prediction of multiaxial fatigue with proportional and non-proportional loading based on a recently developed three-dimensional small-strain microplasticity-based constitutive theory. The core idea of the theory is to incorporate pre-full-yield microplastic deformations in a computationally efficient way. Fatigue life is then correlated to the accumulated (micro)plastic

A crystal plasticity based finite element (CPFE) framework is developed for performing representative volume element (RVE) calculations on two-phase materials. The present paper investigates the mechanical response and the evolution of microstructure of dual-phase (DP) steels under uniaxial tensile loading, with a special focus on void nucleation. The spatial distribution and morphology of the ferrite

A comprehensive theoretical and experimental investigation is presented of the behavior of polyurea composites subjected to high strain-rate impact loading. The composites under consideration consist of an assembly of steel sections and inserts manufactured from layers of polyurea or polyurea augmented with aluminum layers (AL). A finite element model (FEM) is developed to predict the dynamics of this

In the discretization of differential problems on complex geometrical domains, discretization methods based on polygonal and polyhedral elements are powerful tools. Adaptive mesh refinement for such kind of problems is very useful as well and states new issues, here tackled, concerning good quality mesh elements and reliability of the simulations. In this paper we propose several new polygonal refinement

For finite strain plasticity, we use the multiplicative decomposition of the deformation gradient to obtain a differential-algebraic system (DAE) in the semi-explicit form and solve it by a half-explicit algorithm. The terminology HERK is synonym of Half-Explicit Runge-Kutta method for DAE. The source is here the right Cauchy-Green tensor and an exact Jacobian of the second Piola-Kirchhoff stress is

A flapping motion is an important fluid–structure interaction (FSI) phenomenon. Although it has been extensively studied, there are still many unknowns. Because there are numerous parameters in the kinematics and morphology for flapping motions, it is difficult to experimentally determine parameter values that enhance flapping aerodynamics because of the associated time, cost, and space constraints

This paper proposes a semi-analytical interval method for static response bounds analysis of structures subjected to spatially uncertain loads. In the investigated problem, the external loads applied to the structure are spatially uncertain but bounded, which are quantified by an interval field model using upper and lower bounds. By introducing the interval field and its series expansion form into

The non-ordinary state-based peridynamics (NSPD) is a promising method for fracture analysis, and it can incorporate the constitutive relationship of classical continuum mechanics in peridynamics. However, the high computational cost is one of the main reasons limiting its usage. To improve computational efficiency of NSPD, a stability-enhanced peridynamic (PD) element is proposed to couple NSPD with

This paper presents the development of an ABAQUS™ plug-in for estimation of the effective properties of heterogeneous three-dimensional periodic media using the asymptotic homogenization method (AHM). The developed plug-in is user-friendly and requires only basic skills in ABAQUS™. All aspects of the plug-in development are presented, including the solutions found to implement this approach within

Almost all the mesh-free methods are restricted to 2-D problems owing to the difficulty in generating 3-D grids. One effective way to overcome this limitation is to utilize the concept of hierarchical modeling for elastic structures. It was introduced originally for the dimensionally-reduced analysis of 3-D structures, but it can be used for the reverse purpose. By assuming the displacement field in

To improve the impact resistance of reinforced concrete structures, a detailed understanding of the dynamic response is required. This study investigates this impact resistance using experiments in combination with 3D non-linear finite element (FE) simulations. The experiments made use of high-speed photography and digital image correlation (DIC), while a damage-plasticity constitutive model for concrete

Cellular ceramic materials possess many favorable properties that allow to develop efficient modern-day high-temperature thermal energy conversion systems and processes. The energy conversion within these porous media is governed by tightly coupled conduction–radiation physics. To efficiently design and optimize these systems, a comprehensive understanding of the conduction–radiation behavior within

This paper introduces the inverse finite element method using simple brick elements that can be used for shell analysis. The proposed element is the inverse counterpart of an existing Lagrangean-based “direct” trilinear hexahedral finite element that uses the approaches of reduced integration, assumed natural strains and enhanced assumed strain to prevent locking defects in shell modeling. Like the

The wave finite element method has been developed for waveguides and periodic structures with advantages in the calculation time. However, this method cannot be applied easily if the structure is subjected to complex or density loads and this is the aim of this article. Based on the finite element method, the dynamic equation of one period of the structure is rewritten to obtain a relation between

A mesh adaption approach for strongly coupled problems is proposed, based on a variational principle. The adaption technique relies on optimality properties of an energy-like potential and is hence free from error estimates and the associated computational cost. According to the saddle point nature of this variational principle, a staggered solution approach appears more natural and leads to separate

One of the main issues when dealing with the numerical optimization of mechanical structures is the balance between computation time and model accuracy. The work presented herein aims at accelerating global optimization by using the framework of Bayesian optimization on a quantity of interest together with multiple levels of fidelity. These multi-fidelity data are generated from a model-order reduction

In this work, we introduce a novel hp-adaptive strategy. The main goal is to minimize the complexity and implementational efforts hence increasing the robustness of the algorithm while keeping close to optimal numerical results. We employ a multi-level hierarchical data structure imposing Dirichlet nodes to manage the so-called hanging nodes. The hp-adaptive strategy is based on performing quasi-optimal

A background to the constitutive modeling of elastic-inelastic material response is provided to highlight the uniqueness of the Eulerian formulation of general nonlinear fully anisotropic thermoelastic-inelastic materials proposed in Rubin (1994) [1]. This model introduced Eulerian evolution equations for a triad of microstructural vectors that characterize elastic deformations and anisotropic orientations

Ground-borne vibrations are disturbing to human beings. In order to model and reduce these vibrations, the calculation of the harmonic Green's-functions of the soil is highly required since the most effective numerical solution to predict ground-borne vibration is to couple the finite-element and the boundary-element methods. In this work, we elaborate a direct space-frequency formulation that is especially

The extended finite element method (XFEM) and the level set method (LSM) are applied to simulate the solidification phenomenon and the behavior of the liquid-solid phase transition. The temperature-based energy equation is loosely-coupled with the incompressible Navier-Stokes (INS) equations and solved by XFEM using the Stefan condition to express the energy conservation law for phase change. The INS

Improving gas turbine performance depends almost exclusively on the maximum temperature of the combustion gases. This temperature is limited by the thermomechanical strength of the turbine vanes. In this work, a Chimera approach for overlapping grids in the finite element method (FEM) context is proposed to optimize the arrangement of several cooling passages within the vane to minimize its average

The cracking elements method (CEM) is a novel Galerkin-based numerical approach for simulating cracking and fracturing processes. It is a crack-opening approach that avoids precise descriptions of the mechanical states of crack tips and captures the initiations and propagations of multiple cracks without nodal enrichment or crack tracking. The CEM requires element types with nonlinear interpolation

We propose an adaptive curved virtual element method (ACVEM) which is able to combine an exact representation of the involved computational geometry and a dynamic tuning of the optimal mesh resolution through a robust and efficient residual-based a-posteriori error estimator. A theoretical analysis on the reliability of the estimator and a gallery of numerical tests supports the efficacy of the proposed

A new numerical method is presented for evaluating the effective properties of heterogeneous viscoelastic materials, and an efficient and high-fidelity Direct Numerical Simulation (DNS) is addressed by integrating the advantages of the quadtree Scaled Boundary Finite Element Method (SBFEM) and a temporally recursive adaptive algorithm. The quadtree technique that can be directly implemented with input

In case of very thin surface coatings, the coating layer is often ignored in a large-scale Finite Element Analysis. This is mainly due to extensive numerical cost required to capture the correct mechanical behaviour of the layer, especially if the coating is significantly softer than the substrate. To overcome the excessive computational cost, due to the full discretization of the thin layer, in large-scale

Experimental and numerical study regarding fracture in laser-processed steel components is addressed in the present work. Samples of stainless steel (SS) 316L were obtained by an additive manufacturing process, the directed energy deposition (DED), using different deposition orientations, and tested experimentally until fracture. Microstructural investigations, prior and after fracture, were performed

Although the Hughes-Winget rotation tensor is not strongly objective when stretching occurs during a time step it is very accurate when the incremental stretching during the time step is small, a condition that is almost always met in practice. Two types of evolution equations based on the Jaumann derivative are examined which show that the main source of error in the numerical algorithms is due to

The paper explores the ability of an explicit time integration procedure to simulate the dynamics of shear rupture between unbounded elastic blocks on frictional interface, modeled with the finite element method. The behaviour of the interface is governed by Rate and State (RS) friction laws, proposed to describe the rate dependent phenomena observed in experiments on rocks and many other materials

With the goal of improving upon the accuracy of D. Arnold's MINI element for finite strain plasticity, and more precisely calculate the elastic/plastic interface, we extend this element formulation to include, as nodal degrees-of-freedom, a function of the second invariant of the deviatoric stress, J2. A finite-strain J2 − u − p mixed formulation of the classical low-order tetrahedron element is introduced

This paper studies elasto-plastic large deformation behaviour of thin shell structures using the isogeometric computational approach with the main focus on the efficiency in modelling the multi-patches and arbitrary material formulation. In terms of modelling, we employ the bending strip method to connect the patches in the structure. The incorporation of bending strips allows to eliminate the strict

An approach to improve the membrane behaviour of the four-node shell element with 24 degrees of freedom DKMQ24 proposed by Katili et al. (2015) is presented. This improvement is based on a different approximation of drilling rotations, based on Allman's shape functions. Further, the element formulation is enhanced by the use of selective reduced integration of shear terms and by the proportional scaling

Simulation of restrained ring shrinkage and cracking of cementitious materials in a multiphysics simulation framework (MOOSE) is discussed in this paper. The 3D numerical model analyzes residual stress development and crack initiation/propagation in cement pastes by applying an eigenstrain which varies over the depth of the specimen based on the relative humidity of the pores as moisture diffuses from

Topology optimization techniques have been widely used in structural design. Conventional optimization techniques usually are aimed at achieving the globally optimal solution which maximizes the structural performance. In practical applications, however, designers usually desire to have multiple design options, as the single optimal design often limits their artistic intuitions and sometimes violates

A numerical model to take into account the effect of the stress state on the bond behavior between steel and concrete in reinforced concrete structures is proposed. It is based on a zero thickness element, adapted to large-scale simulations and the use of 1D elements for steel bars. The proposed model also assumes the definition of a bond stress – slip law which includes the confining pressure around

Higher order finite element (FE) methods provide significant advantages in a number of applications such as wave propagation, where high order shape functions help to mitigate pollution (dispersion) error. However, classical assembly of higher order systems is computationally burdensome, requiring the evaluation of many point quadrature schemes. When the Discontinuous Petrov-Galerkin (DPG) FE methodology

In this paper, we extend the concept of MINI element over triangles to star convex arbitrary polytopes. This is achieved by employing the volume averaged nodal projection (VANP) method over polytopes in combination with the strain smoothing technique. Within this framework, the dilatation strain is projected onto the linear approximation space, thus resulting in a purely displacement based formulation

In this paper, a novel data-driven nonlinear solver (DDNS) for solid mechanics using time series forecasting is first proposed. The key concept behind this work is to modify the starting point of iterations of the modified Riks method (M-R). The modified Riks method starts iterations at the previously converged solution point while the proposed method starts at a predicted point which is very close

For large-scale equipment, e.g. aerospace and architecture industry, it is valuable to guarantee that one structure could survive partial damages. Due to the location of the damage is unknown in prior, results in a high number of failure scenarios to be calculated when considering fail-safe requirement in topology optimization. In this article, we propose an efficient continuum topology optimization

Reliable numerical modeling of asphalt concrete (AC) is a complex problem due to a non periodic random structure of this material and a nonlinear behavior of its interacting constituents. Phenomena observed at the lower resolution highly influence the overall response of pavement layers made of asphalt concrete. In this paper, we focus on the selected aspects of its efficient numerical modeling using