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Thin elastic circular rings can be subject to various loading profiles when used to stiffen long pipes or aboveground cylindrical storage tanks. Specific nonuniform loading profiles have been used by many researchers in theoretical analyses. However, real loading patterns may deviate slightly from the theoretical approximation. The sensitivity of rings to initial imperfections is highlighted in this work. This study investigates the effect of small imperfections in nonuniform loading of the cosine form. A Duffing-type nonlinear differential equation was solved using a perturbation technique to describe the effects of a “follower” loading normal to a ring with large deformations. It is found that the lower buckling mode will govern with the existence of any magnitude of imperfection corresponding to the shape of the fundamental mode. [ABSTRACT FROM AUTHOR]

Purpose: To develop a method for intra-patient registration of pre- and post-contrast abdominal MR images with large local deformations and large intensity variations.Method: A hybrid method is proposed to deal with this problem. It consists of two coupled techniques: (1) descriptor matching (DM) at the original resolution using a discrete optimization strategy to avoid getting trapped in a local minimum; (2) continuous optimization to refine the registration outcome based on autocorrelation of local image structure (ALOST). Our method—called DM-ALOST—has become insensitive to the local uptake of contrast agent by exploiting the mean phase and the phase congruency extracted from the multi-scale monogenic signal. The method was extensively tested on abdominal MR data of 30 patients with Crohn’s disease.Results: DM-ALOST produced significantly larger mean Dice coefficients than two state-of-the-art methods (p<0.05).Conclusion: Both qualitative and quantitative tests demonstrated improved registration using the proposed method compared to the state-of-the-art. The DM-ALOST method facilitates measurement of corresponding features from different abdominal MR images, which can aid to assess certain diseases, particularly Crohn’s disease. [ABSTRACT FROM AUTHOR]

Summary: This paper presents a high fidelity homogenization method for periodically layered composite structures that accounts for plasticity in the matrix material and quasi‐brittle damage in the reinforcing layers, combined with strong geometrical nonlinearities. A set of deliberately chosen internal kinematic variables results in a rigorous representation of the kinematics of the 2 constituents, which in turn allows for complex constitutive laws per constituent to be used directly in the formulation. The model accounts for hyper‐elastoplastic behavior in the matrix phase and hyper‐elastic behavior in the reinforcement as well as for the bending stiffness of the reinforcement layers. Additionally to previously proposed models, the present method includes Lemaitre‐type damage for the reinforcement, making it applicable to a wider range of engineering applications. The capability of the proposed method in representing the combined effect of plasticity, damage, and buckling at microlevel within a homogenized setting is demonstrated by means of direct comparisons to a reference discrete model. [ABSTRACT FROM AUTHOR]

This work shows a sequence of numerical models for the simulation of the Presta joining process: a well-established industrial process for manufacturing assembled camshafts. The operation is divided into two sub-steps: the rolling of the shaft to widen the cam seat and the joining of the cam onto the shaft. When manufactured, the connection is tested randomly by loading it with a static torque. Subsequently, there are three numerical models using the finite element method. Additionally, a material model of finite strain viscoplasticity with nonlinear kinematic hardening is used throughout the whole simulation process, which allows a realistic representation of the material behavior even for large deformations. In addition, it enables a transfer of the deformation history and of the internal stresses between different submodels. This work also shows the required parameter identification and the associated material tests. After comparing the numerical results with experimental studies of the manufacturing process for steel-steel connections, the models are used to extend the joining process to the utilization of aluminum shafts. [ABSTRACT FROM AUTHOR]

Indentation testing, also refereed to as tonometry in medical diagnostics, is one of the most frequently used methods for studying the properties of soft biological tissues. In the case of lymphedematous tissues, characterized by abnormal accumulation of excess interstitial fluid, the indentation method constitutes an objective alternative for the standard manual palpation test, that is used for evaluation of elastic modulus and time dependent tissue response related to finding parameters of effective compression therapy. This paper focuses on the numerical modelling of a deep indentation test for which the flat cylindrical tip with a surface area of 1 cm2 penetrates the tissue at a constant rate until 1 cm depth is reached. The indentation generates large deformations of skin and subcutaneous tissue and squeezing of part of the interstitial fluid from the compressed region. The skin is modelled as an isotropic neo-Hookean solid and subcutaneous tissue is modelled as a fluid saturated porous matrix. The effective stress law, isotropic neo-Hookean elastic matrix and the Darcy's type of interaction force between phases are adopted for the subcutaneous tissue. The finite element simulations deliver results for time dependent indentation force and pore pressure under the indenter for different and relevant to real tissues properties. The role of the properties and the presence of skin are analysed. The values of maximum reaction force and relaxation time are compared and evaluated as descriptors of mechanical properties of tissues. [ABSTRACT FROM AUTHOR]

This paper adapts the large deformation diffeomorphic metric mapping framework for image regis- tration to the indirect setting, where a template is registered against a target that is given through indirect noisy observations. The registration uses diffeomorphisms that transform the template through a (group) action. These diffeomorphisms are generated by solving a ow equation that is defined by a velocity field with certain regularity. The theoretical analysis includes a proof that indirect image registration has solutions (existence) that are stable and that converge as the data error tends to zero, so it becomes a well-defined regularization method. The paper concludes with examples of indirect image registration in 2D tomography with very sparse and/or highly noisy data. [ABSTRACT FROM AUTHOR]

Within the framework of the model of large deformations, the deformation of a material exhibiting elastic, viscous, and plastic properties and placed between two rigid cylinders is investigated when turning the internal cylinder. The accumulation of irreversible deformations prior to the onset of plastic flow and upon its termination is associated with creep. Reversible and irreversible deformations according to the model in question are determined by differential transport equations. To calculate the displacement fields, stresses, and reversible, irreversible, and complete deformations, a system of partial differential equations is obtained, for which a finite-difference scheme is constructed. [ABSTRACT FROM AUTHOR]

Within the framework of the theory of large elastoplastic deformations generalized to the case of viscous and thermophysical properties of materials, we give a solution of a sequence of coupled problems on the onset and development of a flow in a material layer filling the gap between two rigid coaxial cylindrical surfaces under increasing pressure drop and on the subsequent flow deceleration under decreasing pressure gradient. Here the thermophysical and deformation processes are coupled, and the yield stress depends on temperature. Heat production due to the layer material friction against the rough cylindrical boundary surfaces is taken for an additional heat source. [ABSTRACT FROM AUTHOR]

In the framework of the theory of large deformations, we obtain the solution of a boundary value problem on the flow of an elastoviscoplastic material in a gap between two rigid coaxial cylindrical surfaces under pressure drop changing with time. It is assumed that slip of the material is possible on both surfaces. We consider reversible deformation, the development of viscoplastic flow under the increasing and constant pressure drop, deceleration of the flow under the decreasing pressure drop, and the unloading of the medium. [ABSTRACT FROM AUTHOR]

In a novel way, nature evolves cellular structures to obtain mechanically efficient materials. Natural cellular materials combine low weight with superior mechanical properties to provide optimum strength and stiffness at low density such as trabecular bone, hornbill bird beaks, and bird wing bones. Inspired by these naturally architected cellular materials, humankind has also developed lightweight cellular materials for a broad range of applications consisting of structural components, energy absorption, heat exchange, and biomaterials. In this paper we present a highly efficient computational method to predict the bulk elastic-plastic homogenized mechanical properties of low-mass metallic systems with architected cellular microstructures. The proposed methodology provides a computational framework for the analysis, design, and topology optimization of such cellular materials. With a view for Direct Numerical Simulation of a cellular solid or structure with millions of cellular members, and considering the plausible deformations in each member, each such member is sought to be modeled by using only one or only a very few nonlinear three-dimensional (3D) beam elements with 6 degrees of freedom (DOF) at each of the 2 nodes of the element, and the nonlinear coupling of axial-torsional-bidirectional bending deformations is considered for each element. The effect of plasticity in each member is included using the mechanism of plastic hinges which may form at any point(s) along the length of each element or member. To make Direct Numerical Simulation of a micro-latticed cellular solid possible for its eventual applications, the tangent stiffness matrix for a spatial beam element undergoing large elastic-plastic deformation is explicitly derived using a Reissner-type mixed variational principle in the co-rotational updated Lagrangian reference frame. In order to avoid the inversion of the Jacobian matrix, a Newton homotopy method is employed to solve the tangent-stiffness equations. We are developing a code called CELLS/LIDS [CELLular Structures/Large Inelastic DeformationS] providing the capabilities to study the variation of the mechanical properties of the low-mass metallic cellular structures by changing their topology. Thus, due to the efficiency of this method we propose to employ it for topology optimization design, and for impact/energy absorption analyses of elastic-plastic micro-cellular structures, and then micro-architecting them for desired elastic-plastic properties. [ABSTRACT FROM AUTHOR]

The ductility of a column is one of the most important characteristics of a structure subjected to unexpected overloads, load reversals, blast loads or dynamic impacts. Structural ductile members are capable of dissipating large amounts of energy by undergoing large deformations before failure, hence providing early warning to the occupants of the building. Previous analyses conducted by the authors suggest that, in addition to the type of column (steel, reinforced concrete and composite steel–concrete), the applied measure of ductility as well as other factors (the materials used and the loading and boundary conditions) have a significant influence on a column’s ductility. This paper proposes a new approach to the analysis of the ductility of columns. This approach distinguishes between the column’s pre-peak, post-peak and total ductility, and develops ductility parameters based on the displacement and energy for each of these ductility types. Based on experimental and numerical research on two-chord composite steel–concrete columns subjected to vertical monotonic loads, the influence of concrete strength and batten plate spacing on the columns’ vertical ductility is evaluated. It is concluded that designing two-chord composite steel–concrete columns to have small batten plate spacing and a relatively low concrete strength class can maximise the vertical ductility. [ABSTRACT FROM PUBLISHER]

A multiscale modeling framework for polycrystal materials is established, using a combination of an extended vertex model and a crystal plasticity formulation. The 2D vertex model is cast to incorporate a range of mesoscale processes such as grain structure evolution and the influence of second-phase particles. It is combined with a finite strain crystal plasticity formulation whereby also texture development and stored energy accumulation is traced. Computational efficiency is enhanced by GPU-parallelization. The full model captures a wide range of microstructure processes such as dynamic recrystallization, grain growth, texture evolution, anisotropic grain boundary properties as well as particle pinning effects. The macroscale material behavior is directly coupled to the evolving microstructure, for example in terms of a grain size dependent flow stress behavior. Illustrative numerical examples are provided to show the capabilities of the model. For example, the interplay between particle strengthening and grain size influence on macroscopic flow stress behavior is shown, as well as effects due to dynamic recrystallization. Special attention is given to the formulation of the vertex model as the combination of stored energy, particle pinning and anisotropic grain boundary properties give rise to intricate topological transformations which have not been previously addressed. [ABSTRACT FROM AUTHOR]

We study the dynamics of one-dimensional slender structures such as cables, arches and flexible springs, that carry a moving load or mass. In the case of a moving mass we assume that inertial effects can be ignored. The geometrically-exact Cosserat rod theory is used to model the structure, which is allowed to undergo arbitrary three-dimensional flexural and twisting deformations. We use the generalised-α method for both the spatial and temporal discretisation of the equations of motion and Newton iterations to solve the resultant system of algebraic equations. This numerical scheme has good properties of second-order accuracy, unconditional stability and allows for tunable numerical dissipation. The theory is applied to a cable problem motivated by motorised transport systems such as inspection devices moving along bridge or powerline cables. Large deformations are found to have a resonance-detuning effect on the cable. We also consider the problem of an arch subject to a load that would lead to in-plane collapse if it was applied statically. Movement of the load is found to have a stabilising effect on the structure with collapse delayed at small velocities and suppressed altogether at sufficiently high velocity. [ABSTRACT FROM AUTHOR]

The aim of our work is the numerical modeling of two dimensional mechanical-thermal material mixing observed in stir welding process using a high order algorithm. This algorithm is based on coupling a meshless approach, a time discretization, a homotopy transformation, a development in Taylor series and a continuation method. The performance of the proposed model is the consideration of large deformations in the formulation of the posed problem. For the spatial treatment, we use the moving least squares approximation which will be applied directly to the strong form formulation of conservation equations. Each collocation point holds mechanical-thermal variables. The high order algorithm and the homotopy transformation allow reducing the number of tangent matrices to decompose and to avoid iterative procedure. Comparisons with the classical iterative solver (Jamal et al. in J Comput Mech 28:375-380, 2002) are performed. Numerical results reveal that a few number of matrix factorization is needed with the proposed approach, decreasing the computation time. [ABSTRACT FROM AUTHOR]

A hexahedral-dominant finite element mesh can be easily constructed by cutting regular hexahedral elements in a simple block with CAD surfaces representing outer surfaces of a geometric model. Polyhedral elements with straight edges but possibly non-planar faces are generated at the domain boundaries, while regular hexahedral elements remain in the interior region. Shape functions for polyhedral elements are derived from moving least square approximation based on a tetrahedral subdivision of polyhedral domains by a centroid-based subdivision technique. The polyhedral shape functions in this study have similar properties to conventional finite element shape functions in terms of continuity and completeness within elements, compatibility across inter-element boundaries and the Kronecker-delta property. Furthermore, the present approach using hexahedral-dominant meshes with polyhedral elements at domain boundaries is successfully applied to solve large deformation problems of hyperelastic and elastic–plastic materials. [ABSTRACT FROM AUTHOR]

This paper discusses the buckling and post-buckling of thick composite plates having large initial geometrical imperfections. Within the theory of large transformations, the proposed formulation uses generalised forces and deformations derived from the energy conjugacy of the second Piola-Kirchhoff stress and Green-Lagrange strain. In addition, it provides partial differential equations of equilibrium that are easy to solve using common techniques such as the Galerkin-Ritz method. Unlike existing contributions, which are (i) limited to imperfections that are proportional to current deformations, (ii) address small to moderate initial imperfections only, and/or (iii) require advanced and time consuming numerical methods, the present approach is based on analytical solution and takes into account large initial imperfections. Despite the complexity of the energy balance formulation, the resulting governing equations are simple and applicable to design practical composite structures. The proposed model was compared to numerical results obtained using the finite element method. Overall, good agreements have been obtained when the assumptions fall within the range of validity of the commercial software used for simulation. [ABSTRACT FROM AUTHOR]

We present some novel equilibrium shapes of a clamped Euler beam ( Elastica from now on) under uniformly distributed dead load orthogonal to the straight reference configuration. We characterize the properties of the minimizers of total energy, determine the corresponding Euler-Lagrange conditions and prove, by means of direct methods of calculus of variations, the existence of curled local minimizers. Moreover, we prove some sufficient conditions for stability and instability of solutions of the Euler-Lagrange, that can be applied to numerically found curled shapes. [ABSTRACT FROM AUTHOR]

Botanical simulation plays an important role in many fields including visual effects, games and virtual reality. Previous plant simulation research has focused on computing physically based motion, under the assumption that the material properties are known. It is too tedious and impractical to manually set the spatially-varying material properties of complex trees. In this paper, we give a method to set the mass density, stiffness and damping properties of individual tree components (branches and leaves) using a small number of intuitive parameters. Our method is rooted in plant biomechanics literature and builds upon power laws observed in real botanical systems. We demonstrate our materials by simulating them using offline and model-reduced FEM simulators. Our parameters can be tuned directly by artists; but we also give a technique to infer the parameters from ground truth videos of real trees. Our materials produce tree animations that look much more similar to real trees than previous methods, as evidenced by our user study and experiments. [ABSTRACT FROM AUTHOR]

Underwater implosion, the rapid collapse of a structure caused by hydrostatic pressure, is a fully coupled, highly dynamic and nonlinear fluid-structure interaction (FSI) problem. The primary motivation behind studying implosion is the short-duration, high-pressure pulse generated in the surrounding water. This paper presents a simplified analytic method to estimate the energy in the pressure pulse, based on potential flow theory. The method accounts for the varying fluid pressure and accompanying FSI. The focus is on long, thin, unstiffened metallic cylindrical shells that collapse in mode 2. The implosion pulse energy is shown to be equal to the maximum system kinetic energy developed during collapse. The kinetic energy is calculated using an energy balance approach and analytic solutions for plastic energy dissipation and energy required to compress the internal air. The time-varying fluid pressure, and subsequently the work done by the fluid on the cylinder, is found using a novel explicit time-stepping methodology. The result is a pseudo-coupled analytic solution for the fluid pressure time history and implosion pulse energy. Solutions for pulse energy agree with RANS numerical simulations within 5%. [ABSTRACT FROM AUTHOR]

This paper presents the numerical modelling of one and two-dimensional poroelastic solid flows, using the material point method with double point formulation. The double point formulation offers the convenience of allowing for transitions in the flow conditions of the liquid, between free surface flow and groundwater flow. The numerical model is validated by comparing the solid flow velocity with the analytical solution. The influence of the Young's modulus on the solid flow velocity is discussed for both one and two-dimensional analysis cases. The effect of the shape of the two-dimensional solid is investigated. It is shown that the solid stiffness has an effect on the poroelastic flow velocity, due to swelling and bending for the one and two-dimensional cases, respectively. The shape is found to be an important factor on the flow velocity of the poroelastic solid. [ABSTRACT FROM AUTHOR]

Triangular-plate Added Damping and Stiffness (TADAS) dampers are special kinds of passive control devices that can be used in seismic design and retrofitting of structural systems. However, when exposed to large deformations, primary members of a structure can be in danger of serious damage due to improper geometric characteristics of these dampers. In this study, response of a one bay frame equipped with a TADAS device, previously tested in the laboratory, was simulated using a detailed FE model in ABAQUS. A monotonic analysis was then conducted on the TADAS damper alone, which indicated that in large deformations, TADAS damper pins hit the top of the holes, resulting in an abrupt stiffness increase in the damper. Seismic analysis of a six story moment resisting frame with TADAS dampers, using a series of twelve scaled earthquake ground motions, was also conducted in OpenSees which indicated that with sudden stiffness increase in dampers, the value of moments in beams as well as axial forces in braces will increase, causing possible damages in these areas. At the end, a method for calculating the optimal height for the holes in the damper was proposed, which is shown to be in good agreement with detailed ABAQUS models. [ABSTRACT FROM AUTHOR]

Form changes of a cross-reinforced toroidal body under butt-end torsion and rotation are investigated on the basis of carcass theory of fibrous media at large deformations, including macro- and micromechanical levels of analysis. The form changes are considered as the result of external loadings specified by the field of carcass displacements. This field, which is an integral manifestation of internal fields of the body during its deformation, is determined on the macrolevel. The internal fields are found by solving boundary-value problems on the micromechanical level for the nodal blocks of material on the basis of the model of a piecewise homogeneous medium. Configurations of the body at the values of torsion angle and rotational speed close to limiting ones are presented. The configurations of material blocks in the deformed body, which reflect its internal fields, are illustrated. The regions of folding in the binder close to butt-end sections, where the body is connected with nondeformable shafts, are revealed. [ABSTRACT FROM AUTHOR]

The results of a comprehensive mechanical analysis of five silicone-based elastomers are presented. Large strain monotonic tests were performed under uniaxial, strip biaxial and equi-biaxial stress states. Based on the multiaxial experimental data, hyperelastic constitutive models were determined for each material. The small strain elastic modulus ranges from 49 kPa to 1.5 MPa, and the materials show different degrees of non-linearity of their stress-strain response. Data on the time and history dependence allow determining the deviation from the behavior predicted using a non-dissipative hyperelastic constitutive model. Next to representing a guideline for a comprehensive characterization of highly deformable materials, the present results provide data which can be used for the selection of an appropriate material, depending on the specific application. The corresponding models can be used to simulate the performance of each elastomer in applications involving large strains and multiaxial loading states. [ABSTRACT FROM AUTHOR]

Traumatic brain injury (TBI) is a devastating problem for people of all ages, but the nature of the response to such injury is often different in children than in adults. Cerebral vessel damage and dysfunction are common following TBI, but age-dependent, large-deformation vessel response has not been characterized. Our objective was to investigate the mechanical properties of cerebral arteries as a function of development. Sheep middle cerebral arteries from four age groups (fetal, newborn, juvenile, and adult) were subjected to biaxial loading around physiological conditions and then to failure in the axial direction. Results show little difference among age groups under physiological loading conditions, but response varied significantly with age in response to large axial deformation. Vessels from all age groups reached the same ultimate stretch level, but the amount of stress carried at a given level of stretch increased significantly with age through the developmental period (fetal to juvenile). Our results are the first to identify changes in cerebral vessel response to large deformations with age and may lead to new insights regarding differences in response to TBI with age. [ABSTRACT FROM AUTHOR]

This paper presents a computational framework for modelling of fluid pressurised fracture propagation in saturated porous media. The framework rests on the principle of the variational phase-field theory to predict the fracture propagation pathway. The paper sets out the variational formulations and associated weak forms of the partial differential equations describing the pressure-deformation interplays of the fracturing domain, which are solved in the context of the Updated Lagrangian Finite Element method. The proposed formulation reflects the impact of the temporal evolution of the porous media attributes such as porosity, compressibility, permeability, and mechanical stiffness, on the nonlinear hydro-mechanical behaviour of the porous media during the fracture propagation. The inertial effect of the nonlinear flow inside the fracture is resolved using Forchheimer equation. Robustness of the modelling framework is examined by simulating benchmark examples. The effects of poroelastic characteristics of porous media such as the compressibility of solid skeleton and drained bulk modulus on the hydro-mechanical and cracking behaviour of porous rocks and on the total energy of the system are addressed. The nonlinearity of the fluid flow is found to be influential on the length of the leak-off and flow-back regions across the fractured zones, and on the amount of the fluid to be exchanged between the fractures and the porous zone, which is important in the prediction of the productivity of the fracking process in engineering applications. [ABSTRACT FROM AUTHOR]

Unsupervised deep learning techniques have gained increasing popularity in deformable medical image registration However, existing methods usually overlook the optimal similarity position between moving and fixed images To tackle this issue, we propose a novel hierarchical cumulative network (HCN), which explicitly considers the optimal similarity position with an effective Bidirectional Asymmetric Registration Module (BARM). The BARM simultaneously learns two asymmetric displacement vector fields (DVFs) to optimally warp both moving images and fixed images to their optimal similar shape along the geodesic path. Furthermore, we incorporate the BARM into a Laplacian pyramid network with hierarchical recursion, in which the moving image at the lowest level of the pyramid is warped successively for aligning to the fixed image at the lowest level of the pyramid to capture multiple DVFs. We then accumulate these DVFs and up-sample them to warp the moving images at higher levels of the pyramid to align to the fixed image of the top level. The entire system is end-to-end and jointly trained in an unsupervised manner. Extensive experiments were conducted on two public 3D Brain MRI datasets to demonstrate that our HCN outperforms both the traditional and state-of-the-art registration methods. To further evaluate the performance of our HCN, we tested it on the validation set of the MICCAI Learn2Reg 2021 challenge. Additionally, a cross-dataset evaluation was conducted to assess the generalization of our HCN. Experimental results showed that our HCN is an effective deformable registration method and achieves excellent generalization performance., Competing Interests: Declaration of competing interest There are no potential conflicts of interest to report., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

In this paper, the research method of large deformations of hyperelastic solids using the Finger strain measure is considered. The kinematics of continua motion is given; the stress state is described by the Cauchy – Euler tensor of the true stresses. Much attention is given to the algorithm of the linearized constitutive equations in terms of the Cauchy – Euler stresses. Also, there is an example of obtaining the linearized physical ratio in the Cauchy – Euler stresses for material, which is described by Mooney – Rivlin potential. The numerical implementation is based on a finite-element method within the framework of incremental methods. To verify efficiency of the technique, several problems were solved: the problem of plane strain of the square strip and the problem of elastic deformation of the plate under uniform pressure. The results obtained do not contradict those that have been published before.

Dynamic relaxation method is an iterative procedure for solving the simultaneous system of equations. This technique is used in the static and dynamic nonlinear structural analysis. One of the most important parameters in this approach is fictitious damping factor. If this factor is selected more accurately, convergence rate will rise. In this paper, inverse vector iteration method is utilized to find the damping factor in the dynamic relaxation iterations, and a new formulation is proposed. The geometric nonlinear analysis of several plane and space trusses and also structural frames are performed using the suggested method. The numerical results indicate that the convergence rate improves compared with the conventional dynamic relaxation procedure so that the number of iterations and the analysis time decrease significantly. Consequently, the authors' technique makes the solving process faster and more capable.

Pre-existing voids distributed as a single, but inclined layer are used to represent material defects leading to void growth and strain localization in a sheet. Small elastic but finite plastic strain deformations are accounted for in an elastic-plastically anisotropic material hardening three-dimensional finite element framework. Localization is here defined as the stage of deformation, where the straining in the layer relative to the overall prescribed straining grows to infinity, i.e 1 0 4 or higher. Three different materials are consider using the classical Hill-48 anisotropic yield surface (Hill, 1948). As a reference case, one of them is the isotropic Mises case, whereas the other two are anisotropic cases. Yield surfaces and Lankfords coefficients are provided for all three materials. For each material two different void volume fractions and several different loading triaxialities as well as void band inclinations are presented and compared. The strain for localization is given and corresponding deformed void band orientations are discussed. Qualitatively, the responses of the two anisotropic sheets are similar to that of the isotropic Mises case: A minimum in strain at a distinct initial void-band orientation can be identified. Except for one case, all cases studied here result in a simple shift of the critical strain level at localization. However, under uniaxial plane strain tension the isotropic and anisotropic sheet localizes at almost the same value of straining. [Display omitted] • 3D finite element studies of plastic anisotropy on localization in a void-sheet. • Sheet imperfections represented by voids in a band in an inclined angle, ψ. • Anisotropy is represented by the Hill yield surface (Hill, 1948). • Two different plastically anisotropic materials are considered, denoted V and VIII. • Material V localizes at higher angle, ψ , but at lower strain than for Mises. • Material VIII localizes at lower angle, ψ , but at larger strain than for Mises. [ABSTRACT FROM AUTHOR]

In this work, an approximate analytical solution was given for the large deformation of a cantilever beam subjected to a uniformly distributed load using elliptic integrals and Jacobi elliptic functions. The formulation is based on reducing the differential equation of the problem to the same one that describes the classical, force-loaded elastica by introducing a modified arc length parameter. A new, intuitive formula was given for the relation between the deflection angle and the non-dimensional load. The results were validated by the nonlinear shooting method with the Matlab program. The method can be used only in the case of one inflection point, but gives accurate results even for extremely large deflections. [ABSTRACT FROM AUTHOR]

Dielectric elastomers belong to a larger group of materials, the so-called electroactive polymers, which have the capability of transforming electric energy to mechanical energy through deformation. VHB 4910 is one of the most popular materials for applications of dielectric elastomers and therefore one of the most investigated. This paper includes a new micromechanically motivated constitutive model for dielectric elastomers that incorporates the nearly incompressible and viscous time-dependent behaviour often found in this type of material. A non-affine microsphere framework is used to transform the microscopic constitutive model to a macroscopic continuum counterpart. Furthermore the model is calibrated, through both homogeneous deformation examples and more complex finite element analysis, to VHB 4910. The model is able to capture both the purely elastic, the viscoelastic and the electro-viscoelastic properties of the elastomer and demonstrates the power and applicability of the electromechanically coupled microsphere framework. [ABSTRACT FROM AUTHOR]

The main purpose of this paper is the nonlinear analysis of bending plates with the finite difference. Based on the variable damping, the dynamic relaxation technique will be utilized. In order to achieve proper convergence, the velocity, kinetic energy and two successive displacement ratio criteria are used. For various bending plate samples, the results of constant and variable damping are compared. Numerical examples show that the variable damping is better than the constant damping. However, author's scheme reduces the number of iterations and the time duration. The finite difference method is very sensitive to the choice of some factors. A slight change in the amount of these parameters will increase the number of iterations and the time duration. Moreover, sometimes the solution procedure is divergenced. Another goal of this article is presenting a brief review of the dynamic relaxation approach in solving the bending plates. [ABSTRACT FROM AUTHOR]

The use of the blanking process has been widely spread in mass production industries. In this technique, the quality of the final product is directly related to the setting parameters of the process and the material response of the sheet. In the present work, a general framework based on the finite element method for the simulation of the sheet metal blanking process is presented. The proposed approach properly addresses all the numerical challenges related to blanking. First, an extension of elasto-viscoplastic constitutive equations for the large strain regime is used to take into account the material strain-rate sensitivity. Then, the inertial effects coming from high velocity operations are considered by means of an implicit time integration scheme. Moreover, the frictional contact interactions are simulated with the classical Coulomb law and an energetically consistent formulation of area regularization. Finally, ductile fracture is modeled thanks to the element deletion method coupled with a fracture criterion. The blanking process is then simulated for different setting parameters. The accuracy of this approach is evaluated by comparing the numerical predictions to experimental results for both quasi-static and dynamic conditions. Good agreement is found between experimental and numerical results for all cases. [ABSTRACT FROM AUTHOR]

In this work, we present the application of a newly developed implicit second-order Material Point Method (MPM) on offshore geotechnical applications. The presented second-order MPM uses a special set of piecewise quadratic shape functions to circumvent the well-known issue of producing zero nodal mass contributions. To mitigate the effect of the standard MPM to produce highly oscillating stresses across cell interfaces, we have carried over our ideas obtained from the derivation of the second-order MPM to the Dual Domain Material Point (DDMP) Method, too. The resulting second-order DDMP Method produces a smoother stress distribution across the entire computational domain while being able to profit from the improved convergence rates of second-order finite elements. In a numerical example from geotechnical engineering applications, we illustrate the practical application of our enhanced Material Point and DDMP Methods by simulating a cone penetration. [ABSTRACT FROM AUTHOR]

This paper presents the numerical modelling of one and two dimensional poroelastic solid flows, using the Material Point Method with double point formulation. The double point formulation offers the convenience of allowing for transitions in the flow conditions of the liquid, between free surface flow and groundwater flow. The numerical model is validated by comparing the solid flow velocity with the analytical solution. The influence of the Young's modulus on the solid flow velocity is discussed for both one and two dimensional analysis cases. It is shown that the solid stiffness has an effect on the poroelastic flow velocity, due to swelling and bending for the one and two dimensional cases, respectively. [ABSTRACT FROM AUTHOR]

Results of an analysis of form changes of a toroidal body highly filled with fibers at large torsional deformations and rotational motions are presented. The body is reinforced in the meridional direction. The investigation was carried out by using the two-level carcass theory of fibrous media at large deformations, according to which the macroscopic fields of a reinforced body are determined by its internal fields. These fields are represented by the material configurations of nodal material blocks of the body, for which, on the basis of the model of a piecewise homogeneous medium, boundary-values problems of the micromechanical level of the theory are solved. The results obtained are compared with those for a homogeneous body. The congruent deformation of the homogeneous body at which its initial form and dimensions are practically restored upon superposition of torsion and rotation is determined. [ABSTRACT FROM AUTHOR]