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Significant dimensional variations may occur in paper-based materials when subjected to changes in moisture content. Moisture induced deformations are governed by the swelling of individual fibres, which is transferred through inter-fibre bonds to the entire fibrous network. Complex interactions between mechanical and hygro-expansive properties take place in the bonding areas, affecting the overall material response. In most network models, the role of these inter-fibre bonds is not explicitly incorporated. This work presents a periodic meso-structural model for the discrete fibrous network, which considers the free-standing fibre segments and inter-fibre bonds. Despite its simplicity, the reference unit-cell enables the incorporation of relevant micro- and meso-structural features such as network structure, fibres and bond geometry and hygro-elastic properties. The proposed model is solved analytically through a proper homogenization strategy, allowing to recover the paper’s anisotropic hygro-mechanical response in terms of effective elastic constants and effective hygro-expansive coefficients, exploiting the coupling at the meso-structural level between hygroscopic and mechanical behavior. A comparison with experimental results obtained from the literature shows that the presented approach is quite accurate in predicting the overall paper response, thereby revealing the influence of several meso-scale parameters (e.g. fibre orientation, dimensions, mechanical strength). [ABSTRACT FROM AUTHOR]

This paper presents the analysis by the finite element method of the tensions and deformations produced in the mechanized support beams. The finite element method allows the analysis of physical phenomena that can be described with the help of mathematical models made up of systems of differential equations with initial and boundary conditions. From the results obtained in this paper, it was observed that the asymmetries with the greatest influence are those with respect to the vertical-longitudinal plane of the mechanized support [ABSTRACT FROM AUTHOR]

Reservoir simulation is critical to the design of reservoir development plan and has been extensively used. However, it is challengeable for to simulate the production process for fractured reservoirs, because of the fracture geometry and the fracture deformation. Specifically, three problems need to be solved. First, there is a lack of mathematical models that can predict the fracture deformation with acceptable precision. Second, the fracture deformation is stress-dependent; therefore, a geocoupled equation should be used to quantify the stress change, but the solution is extremely expensive. Third, the fracture geometries pose great challenges to traditional gridding techniques. This paper proposes a new geocoupling simulation method that is capable of modeling the complex fracture geometry as well as the fracture mechanical behavior. The geomechanical effects and the reservoir production performance are modeled through an implicit geocoupled model, which is developed based on the poro-mechanics theory. The fixed stress strategy is used to solve the geocoupled equations. Moreover, a comprehensive fracture modeling method is proposed, in terms of the fracture deformation model and the fracture gridding technique to model the fracture effects. Ultimately, this method is used to analyze two field-scale cases. The results demonstrate that this method exhibits good practicability and has practical significance for fractured reservoir development. [ABSTRACT FROM AUTHOR]

This paper presents a study on the metal cutting simulation with a particular numerical technique, the Particle Finite Element Method (PFEM) with a new modified time integration algorithm and incorporating a contact algorithm capability . The goal is to reproduce the formation of continuous chip in orthogonal machining. The paper tells how metal cutting processes can be modelled with the PFEM and which new tools have been developed to provide the proper capabilities for a successful modelling. The developed method allows for the treatment of large deformations and heat conduction, workpiece-tool contact including friction effects as well as the full thermo-mechanical coupling for contact. The difficulties associated with the distortion of the mesh in areas with high deformation are solved introducing new improvements in the continuous Delaunay triangulation of the particles. The employment of adaptative insertion and removal of particles at every new updated configuration improves the mesh quality allowing for resolution of finer-scale features of the solution. The performance of the method is studied with a set of different two-dimensional tests of orthogonal machining. The examples consider, from the most simple case to the most complex case, different assumptions for the cutting conditions and different material properties. The results have been compared with experimental tests showing a good competitiveness of the PFEM in comparison with other available simulation tools. [ABSTRACT FROM AUTHOR]

We consider foliations given by deformations d F + ϵ ω of exact forms dF in C 2 in a neighborhood of a family of cycles γ (t) ⊂ F − 1 (t). In 1996 Françoise gave an algorithm for calculating the first nonzero term of the displacement function Δ along γ of such deformations. This algorithm recalls the well-known Godbillon–Vey sequences discovered in 1971 for investigation of integrability of a form ω. In this paper, we establish the correspondence between the two approaches and translate some results by Casale relating types of integrability for finite Godbillon–Vey sequences to the Françoise algorithm settings. [ABSTRACT FROM AUTHOR]

Deformation behavior is an important fundamental characteristic of lignocellulosic fibers; it affects the application range of fiber materials and the properties of fiber-based products. For instance, the density of a paper sheet depends on the degree to which the wet fibers are able to conform to the shapes of adjacent fibers during pressing and drying. In this study, a model for revealing the contribution of inherent characteristics of lignocellulosic fiber to its deformation behavior was developed and compared with other general models. The response sensitivities of cross-sectional parameters, fiber cell wall composition, and structure to the deformation behavior were determined as 3.26, 0.26, and 0.06, respectively. The results showed that the cross-sectional geometry was the main contributor to the deformation behavior of lignocellulosic fibers, followed by the ratio of different fiber cell wall components, and the fiber cell wall structure. To develop a comprehensive understanding of fiber separation in industrial production, the inherent fiber properties contributing to deformation behavior were investigated. This data could guide manufacturers to manage the treatment of different fiber separation processes to obtain fibers with required deformability, and thereby meet the requirements of fiber-based products. [ABSTRACT FROM AUTHOR]

A beam formulation based on reproducing kernel particle method (RKPM) for the dynamic analysis of stiffened shell structures is presented in this paper. The kinematic description of a beam is obtained based on the Timoshenko beam theory. By using the principle of virtual power, the governing equations of a three-dimensional beam are derived. To obtain the numerical model of stiffened shell structures, two schemes are adopted: one is model stiffeners by the RKPM beam formulation, the other one is model the entire stiffened shell by the RKPM shell formulation. In the first scheme, the coupling model of RKPM shell and beam formulation is obtained by adding the corresponding quantities in their governing equations. In the second scheme, by determining the support domain of a stress point according to which component the stress point is located, the full shell simulation is achieved. The reliability and accuracy of those two schemes are verified by several numerical examples. [ABSTRACT FROM AUTHOR]

Anticracks (also known as rigid line inclusions) occur frequently in a variety of natural and engineered composites as very stiff and extremely sharp (almost zero-thickness) fibers or lamellae embedded in a softer matrix. In the linear elastic regime, similarly to cracks, anticracks generate a singularity in the stress distribution around the tip. Because of this similarity, existing analytical techniques and solutions (for simple cases) can be easily translated to anticracks. However, despite their importance in many biological and engineering composites, there has been surprisingly little development of numerical methods that would account simultaneously for the presence of multiple fibers or lamellae, arbitrary loadings and nonlinear behavior of the matrix. This paper presents the first numerical approach for rigid line inclusions, based on a meshfree scheme recently developed for multiple crack growth in elastic media. The inclusion of zero thickness is created as a crack, and a rigid motion (rotation and translation) is enforced at the anticrack faces. The equations of motion are solved according to a Total Lagrangian framework, and the matrix supposed hyperelastic. Contrarily to available analytical solutions, the degrees of freedom of the rigid motion are determined a posteriori as a consequence of the (discretized) elastic equilibrium, expressed in a variational approach. Results show that the proposed approach match well the analytical solutions and provides accurate stress intensity factors (SIFs) for relatively little computational cost. Moreover, the method can reproduce some peculiar features of the anticracks: unlike cracks, singularities also appear under compressive and parallel loads; moreover, for a certain combination of biaxial load, stress concentrations disappear. Finally, the paper presents examples drawn from biological and engineering composites: the reorientation of one or more fibers under large strains, resulting in a smart stiffening and strengthening mechanism. Reorienting towards the direction of applied load has structural importance since reinforcements can have the most effectiveness in withstanding loads. If the matrix is compliant, the reorientation is eased. [ABSTRACT FROM AUTHOR]

The paper discusses the way to improve the methodology of S-shaped working rolls grinding by taking into account its thermal deformations, which appear during the campaign by the contact with hot strips. An algorithm of working rolls grinding in hot condition is developed by using the mathematical model of the thermal expansion, which allows one to predict changes of the profile of S-shaped rolls. The algorithm and the results of its manufacturing approbation are presented in this paper. [ABSTRACT FROM AUTHOR]

In this paper the Verchery’s polar method is extended to the conceptual framework of the Reddy’s Third-order Shear Deformation Theory (TSDT) of laminates. In particular, a mathematical representation based upon tensor invariants is derived for all the laminate stiffness matrices (basic and higher-order stiffness terms). The major analytical results of the application of the polar formalism to the TSDT of laminates are the generalisation of the concept of a quasi-homogeneous laminate as well as the definition of some new classes of laminates. Moreover, it is proved that the elastic symmetries of the laminate shear stiffness matrices (basic and higher-order terms) depend upon those of their in-plane counterparts. As a consequence of these results a unified formulation for the problem of designing the laminate elastic symmetries in the context of the TSDT is proposed. The optimum solutions are found within the framework of the polar-genetic approach, since the objective function is written in terms of the laminate polar parameters, while a genetic algorithm is used as a numerical tool for the solution search. In order to support the theoretical results, and also to prove the effectiveness of the proposed approach, some new and meaningful numerical examples are discussed in the paper. [ABSTRACT FROM AUTHOR]

The need of efficient modelling of textile materials at meso-scale increased considerably in the last decade. Several approaches have been proposed which present different kinds of drawbacks, the most important being their high computation time. The present paper aims to present a new tool for modelling textile materials using the yarn as constitutive element. Because fibre tows length is much higher than their transverse dimensions, beam elements seem to be the most convenient structural finite element tool. Unfortunately, classical beam theories assume that the cross section acts as a rigid which cannot describe the transverse compression and shape change of the yarn. In this paper, we present a new 3D beam element with the aim to achieve the results with section changes while breaking from classical beam hypothesis. Firstly, we start from 2D beam element with thickness change by adding a transverse strain component, which is inspired by previous works on the shell elements. Secondly, the formulation is extended to 3D beam elements, two transverse normal strain components are added with coupling so that full 3D constitutive law can be used. Finally, some numerical examples are presented using the new 3D beam elements which show that the results are exactly the same as those given by 3D elements in ABAQUS/Standard. [ABSTRACT FROM AUTHOR]

Abstract  This paper deals with the characterization of creep properties and recoverability of double-wall corrugated paperboard with A and B flutes at different combined conditions of the ambient temperature 20°C with four kinds of relative humidities and five kinds of constant compression loads. The main feature of this paper is the evaluation on the creep properties and recoverability of double-wall corrugated paperboard with A and B flutes by a series of experimental studies on creep testing apparatus, the analysis of effects of relative humidities and constant compression loads on creep properties and recoverability, and the establishment of mathematical model of creep and time curves. By using Method of the Least Square and Method of Nonlinear Regression, the piecewise experimental formulas of creep and time curves have been obtained. The work provides basic data and introduces important mathematical relationships relevant to design applications for protective packaging for transportation and storage of goods. [ABSTRACT FROM AUTHOR]

This paper details the development and assessment of a new empirical creep model that belongs to the limited ranks of models reproducing full creep curves. The important features of the model are that it is fully standardised and is universally applicable. By standardising, the user no longer chooses functions but rather fits one set of constants only. Testing it on 7 contrasting materials, reproducing 181 creep curves we demonstrate its universality. New model and Theta Projection curves are compared to one another using an assessment tool developed within this paper. [ABSTRACT FROM AUTHOR]

This paper deals with modeling and model reduction methods intended to sandwich structures with viscoelastic materials. The modeling step is carried out by combining the First order shear deformation theory (FSDT) with the Golla–Hughes–Mc Tavish (GHM) model. The GHM model introduces auxiliary coordinates to take into account the frequency dependence of viscoelastic materials which, combined with the finite element method (FEM), leads to large order models. This paper focuses on the use of model reduction methods. The reduced models compared to the full model are illustrated by three numerical examples in order to outline the performance, the practical interest of these methods and their validity domains. [ABSTRACT FROM AUTHOR]

This paper is devoted to analytical and numerical studies of global buckling of a sandwich circular plate. The mechanical properties of the plate core vary along its thickness, remaining constant in the facings. The middle surface of the plate is its symmetrical plane. The mathematical model of the plate is presented. The field of displacements is formulated using the proposed nonlinear hypothesis that generalizes the classical hypotheses. The equations of equilibrium are formulated based on the principle of stationary total potential energy. The proposed mathematical model of the displacements considers the shear effect. The numerical model of the plate is also formulated with a view to verify the analytical one. Numerical calculations are carried out for the chosen family of plates. The values of the critical load obtained by the analytical and numerical methods are compared. The effects of the material properties of the core and the change of the plate radius on the critical load intensity are presented. [ABSTRACT FROM AUTHOR]

In this paper, we present new results of natural frequencies for the functionally graded beams based on Chebyshev collocation method and the third-order shear deformation theory (TSDT), without requiring any shear correction factors. The beams are assumed to be elastically supported by translational and rotational springs, or simply known as elastically restrained ends. The material compositions of the beams across the gradient direction are described by different mathematical models including the simple power law, exponential and Mori-Tanaka models, and their effects on the response of beams are analyzed. We first present the Chebyshev collocation formulation of the coupled differential equations of motion for free vibration of FGM beams considering different boundary conditions, and then verify the results obtained by the proposed approach against reference ones. A parametric study is also performed for parameters such as thickness, spring constant factor, material volume fraction index, etc. The present numerical results reveal that the proposed method can offer accurate frequency results for the FGM beams as compared with those available in the literature. The results also indicate that the spring constant factors have a significant effect on the frequencies of the beams. [ABSTRACT FROM AUTHOR]

Soft sensors have been widely used in industrial processes over the past two decades because they use easy-to-measure process variables to predict difficult-to-measure ones. Some success has been achieved by the dominant traditional methods of modeling soft sensors based on statistics, such as principal components analysis (PCA) and partial least square (PLS), but such sensors usually become inaccurate and inefficient when processing strong nonlinear data. In this paper, a new soft sensor modeling approach is proposed based on a deep learning network. First, stacked auto-encoders (SAEs) are employed to extract high-level feature representations of the input data. In the process of training each layer of a SAE, the Limited-memory Broyden-Fletcher-Goldfarb-Shanno algorithm (L-BFGS) is adopted to optimize the weights parameters. Then, a support vector regression (SVR) is added to predict the target value on the basis of the features obtained from the SAE. To improve the model performance, Genetic Algorithm (GA) is used to obtain the optimal parameters of the SVR. To evaluate the proposed method, a soft sensor model for estimating the rotor deformation of air preheaters in a thermal power plant boiler is studied. The experimental results demonstrate that the soft sensor based on the SAE-SVR algorithm is more effective than the existing methods are. [ABSTRACT FROM AUTHOR]

Polymer networks usually have many entanglements as well as a finite extensibility due to the uncrossability and the full stretching of the network chains. In this paper, the nonaffine model proposed by Davidson and Goulbourne is adopted to characterize the influence of entanglements and finite extensibility of the polymer chains on the mechanical behavior of hydrogels. The Davidson-Goulbourne model only contains three material parameters and has a simpler mathematical form than the Edwards-Vilgis slip-link model, which is the only model that has been adopted to characterize the influence of entanglements on the swelling deformation of polymeric gels so far. Some benchmark problems such as free swelling, constrained swelling, uniaxial tension, equibiaxial tension in the immersed state and uniaxial compression in the isolated state are analyzed, respectively, based on the new constitutive equations. The results show that entanglements as well as chain extensibility have important influences on the mechanical response of hydrogels. [ABSTRACT FROM AUTHOR]

The factor of safety of a slope ( Fs) is invariably assessed using methods underpinned by moment, force, and (or) shear strength equilibrium concerning slip surfaces. Each method inherently embeds some form of limitations, despite being popularly adopted in practice. In this paper, a new Fs is devised using the ratio of ultimate energy ( eu, upon sliding) over accumulated 'elastic' energy. The Fs is then reduced to a simple expression of the power to shear stress and shear strength, by taking soil as an elastic-plastic material obeying the Mohr-Coulomb failure criterion. This expression empowers significant efficacy in gaining the factor of safety (without involving energy or directions of shear stresses). The Fs values were calculated for three typical slopes concerning various mechanical properties (dilation, Poisson's ratio, and shear modulus) and effective computational strategies. All of the Fs values (to a congruous accuracy of available methods) were obtained in less than 1% the time of conventional numerical analyses. The proposed Fs, equally applicable to limit equilibrium methods, may be utilized in practice to expedite slope design. [ABSTRACT FROM AUTHOR]

This paper presents a nonlinear solution of a radial subgrade reaction-displacement ( pk- ur) curve for circular tunnel lining design in undrained clay. With the concept of soil shear strength nonlinearly mobilized with shear strain, an analytical solution of pk is obtained using the mobilized strength design method. Two typical deformation modes are considered, namely oval and uniform. A total of 197 orthogonally designed cases are used to calibrate the proposed nonlinear solution of pk using the finite element method with the hardening soil model. The calibration results are summarized using a correction factor, η, which is defined as the ratio of pk_FEM to pk_MSD. It is shown that η is correlated to some input parameters. If this correlation is removed by a regression equation, f, the modified solution f( pk_MSD) agrees very well with pk_FEM. Although in reality the mobilized soil strength varies with principal stress direction, it is found that a simple average of plane strain compression and extension results is sufficient to produce the above agreement. The proposed nonlinear pk- ur curve is applied to an actual tunnel lining design example. The predicted tunnel deformations agree very well with the measured data. In contrast, a linear pk model would produce an underestimation of tunnel convergence and internal forces by 2-4 times due to the overestimation of pk at a large strain level. [ABSTRACT FROM AUTHOR]

The plate-fin structure with high efficiency of heat transfer is a type of periodic pore material. The equivalent homogenization method has been proposed to design the strength of plate-fin structure, and it is essential to calculate homogenized elastic constants of the pore structure. This paper proposed an analytical model to calculate homogenized elastic constants of the plate-fin structure including the elastic modulus, shear modulus and Poisson's ratio. These proposed equivalent formulas have considered the effects of geometrical parameters. The finite element method and experimental study have also been performed to verify the analytical method. In addition, the effects of geometrical parameters on homogenized elastic constants have been fully studied. The results show that homogenized elastic constants by the proposed analytical model show a good agreement with results by FEM and experimental. It has been proved that the stretching deformation is the dominating deformation mechanism of the fin in Z -direction and only the fin paralleled to Y -direction can influence the tensile deformation in Y -direction. The homogenized elastic constants are strongly dependent on the geometrical parameters. This work provides theory formulas to calculate basic mechanical constants for conducting the full-scale design of plate-fin structure by equivalent homogenization method. [ABSTRACT FROM AUTHOR]

The normal contact stiffness of mechanical joint has immediate impact on dynamic characteristics and machining precision of machine tools. A fractal contact stiffness model considering the effect of asperity interaction is proposed in this paper. On the basis of elastic theory, the deformation of a given asperity is deduced. The relationship between contact stiffness, normal load and contact area is derived from Hertz contact theory and fractal theory. The effect of asperity interaction on contact stiffness is studied by comparing with fractal model. The fractal smoothness is defined from relation between fractal parameters and surface roughness. It is concluded that with the increase of the fractal dimension D  and the decrease of fractal roughness parameter  G , the contact stiffness of the joint increases, and the effect of asperity interaction becomes greater. The fractal smoothness also affects the normal contact stiffness and the effect of surface smoothness can be offset by the asperity interaction. Experiment shows that the proposed model is more in line with the actual load-stiffness relationship. The model reveals the factors that affect stiffness of the joint, which can provide a theoretical basis for improving the rigidity and precision of integrated machineries. [ABSTRACT FROM AUTHOR]

Under the load conditions of clamping force and riveting force, the part deformation problems are induced in the assembly process. For the component deformation problems of the thin-wall part assembly, in this paper, from the viewpoint of micro-aspect, the fractal theory model is proposed to analyze the relationship between the part deformation, loads, and contact area for rivet-joint parts; the micro-deformation values for different stages are solved and obtained through theoretical analysis. According to the self-similarity of fractal theory model, the change of the micro-convex body for contact surface will be researched to reflect the macro-deformation properties. Through the measuring experiment for thin-wall parts, the actual three-dimensional coordinate value of each measuring point is obtained before and after riveting assembly, and then, the wavelet neural network method (WNNM) is adopted to predict experiment deformation value based on the obtained deformation value after processing the coordinate value through fitting surface method. Hereby, according to the deformation value for every thin-wall part after processing experiment data, the fractal dimension value will be determined based on the fractal statistic method to analyze the deformation status of different stages. Through analysis and comparison, the results show that the variation regularity of deformation value based on two or three fractal deformation stages is well conformed to and similar to the experimental value and prediction value, which also verify the correctness and effectiveness of the theoretical model, and provide a theoretical basis for further research on thin-wall part assembly deformation from a micro-perspective and improving assembly accuracy quality in future. [ABSTRACT FROM AUTHOR]

An analytical solution of axial vibration problem formulated for a composite anisogrid lattice cylindrical shell with massive disks attached to its ends is presented in the paper. The lattice cylinder is analysed using a continuum model having effective stiffness parameters equivalent to the original anisogrid structure. Axisymmetric deformations of the vibrating shell are modelled using classic theory of orthotropic shells. A formula enabling rapid and reliable calculations of the frequency of axial vibrations is derived and verified using a finite element analysis. Based on this formula, effects of the geometry of lattice structure and masses of the disks are investigated. [ABSTRACT FROM AUTHOR]

In this paper reflection and transmission of compression and shear waves at structured interfaces between second-gradient continua is investigated. Two semi-infinite spaces filled with the same second-gradient material are connected through an interface which is assumed to have its own material properties (mass density, elasticity and inertia). Using a variational principle, general balance equations are deduced for the bulk system, as well as jump duality conditions for the considered structured interfaces. The obtained equations include the effect of surface inertial and elastic properties on the motion of the overall system. In the first part of the paper general 3D equations accounting for all surface deformation modes (including bending) are introduced. The application to wave propagation presented in the second part of the paper, on the other hand, is based on a simplified 1D version of these equations, which we call “axial symmetric” case. [ABSTRACT FROM PUBLISHER]

The strength of thin-walled stainless steel columns has been investigated extensively over the last few years. In European standards, the concept of section classification for determining the cross section capacity is used. In this system, for Class 4 cross sections, the effective width method (EWM) must be used to account for the effect of local buckling. Because of the complexity and limitations of this method, other methods have been developed, such as the direct strength method (DSM) for cold-formed thin-walled profiles and the continuous strength method (CSM), initially established for members made of nonlinear metallic materials. In the CSM, to take advantage of strain hardening, a deformation-based design approach using a continuous relationship between the cross-sectional slenderness and the cross-sectional deformation capacity is used. To a large extent, the CSM yields accurate predictions, especially in the low slenderness range where the current DSM design procedures for members submitted to pure compression tend to produce conservative predictions for materials with pronounced strain hardening such as stainless steel alloys. The present paper presents an extension of the traditional DSM, which provides accurate design strength predictions in the low slenderness range for stainless steel thin-walled section columns failing by distortional, local, and overall buckling. It contains practical information concerning the reference experimental data and draws conclusions about the justification of the proposed analytical formula. The paper is divided into three main parts: the description of the database, the establishment of the design model, and a reliability analysis of the method. [ABSTRACT FROM AUTHOR]

In this paper we analyze the free longitudinal vibrations of a kind of nonlinear one dimensional structured solid, modeling it as a discrete chain of masses interacting through nonlinear springs. The motion equations of this discrete system are solved numerically and the size effect associated to the structure of solid arises.In order to derive continuum models which capture this scale effect, we perform a non-standard continualization of the nonlinear lattice, as well as standard Taylor-based continualization up to different approximation orders. After we propose an axiomatic generalized continuum model, based on a version of the Mindlin general model but extended to finite deformations. Both formulations lead to the same continuous equation, which depends on a scale parameter. Meanwhile in the axiomatic model the scale constant need to be fixed independently, with the continualized one it is possible to obtain its value from the microstructural characteristic of the solid.The nonlinear equations corresponding to the continuum models are solved and, in contrast to other works, we compare the results obtained from the discrete system with those obtained with the continuum ones. This comparison pointed out the capability of the proposed axiomatic model to capture the size effects present in the structured 1D solid, both in the linear and nonlinear regimes. Moreover, the inability of the classical model to capture the scale features when they play a role has been clearly stated. [ABSTRACT FROM AUTHOR]

In this study, a new analytical model is proposed for estimating natural frequencies of retaining walls, and accordingly three closed-form formulas are presented for calculating the first three natural frequencies. In the first step, rigid body motion of retaining walls is taken into account and two closed-form formulas for calculating natural frequencies of the rigid mode of deformation are presented via exact solution. Next, applying the energy method, a new closed-form formula is developed for calculating the natural frequency of the flexural deformation mode. Another innovation of this paper is the modeling of the foundation soil with both torsional and translational springs that make it possible to consider rocking and sliding modes for retaining wall motion. Additionally, the effect of backfill soil interaction is taken into consideration by massless translational springs along the wall. The results thus obtained from the proposed formulas are then compared with numerical analysis using ANSYS software, and a good agreement was observed. [ABSTRACT FROM AUTHOR]

This paper presents a multiphysical model of a reversible sleeve air spring to be employed for design and simulation purpose. A multiphysical approach, combining fluid flow with solid mechanics, has been considered to study the interaction between the fluid and the solid structure of the air spring under different pressure conditions. Experimental tests have been developed applying several compression loads to the air spring and measuring the deformation and the reaction force for different values of the initial pressure. An experimental validation has been executed analyzing and comparing the mechanical behaviour of the actual prototype and the virtual model. In particular, the 3D deformation of the air spring has been acquired by means of the Reverse Engineering techniques and the results have been compared with the simulated ones. Moreover, the experimental and simulated air spring vertical stiffness have been matched in order to verify the accuracy of the multiphysical model. The validation procedure demonstrated that the simulation results fitted the experimental ones for different testing conditions. [ABSTRACT FROM AUTHOR]

Upwarping on the longitudinally coupled prefabricated slab track system caused by the rising temperature is a common distress, which deteriorates the mechanical properties of the coupled slabs and the vertical stability of slabs. The objective of this paper is to quantify the upwarping deformation on the slab subjected to temperature force and to find out the influence of different factors on the upwarping phenomenon of the slabs. An analytical expression is deduced using energy method, and a finite element model is also established to verify the analytical solution’s adequacy. The following main findings are drawn: (1) when the amplitude of the initial elastic misalignment we is equal to a half of the amplitude of the initial plastic misalignment wp and the half-wavelength lmin takes the most unfavorable value, the maximum relative error between the analytical solution and the result in FEM is only 2.64%, which demonstrates that the analytical solution correlates well with the FEM results. (2) lmin is closely related with wp. With the increase of wp, lmin becomes longer, and the maximum length of the half-wavelength is 7.769 m. (3) When the total amplitude we+wp exaggerates, the slab will be much likely to suffer upwarping. [ABSTRACT FROM AUTHOR]

The paper presents a mathematical model of the process of broadening during rolling of strips and sheets. A feature of the model is the consideration of the metal flow in two zones of plastic deformation hearth: advancing zone and lag zone. The mathematical model is based on the variational principle of minimum total capacity of rolling (the principle of Jourdain). In accordance with this principle, the metal flow velocities in the plastic deformation hearth should be varying. The velocity of the metal transversal flow in the hearth of deformation is represented as a power function of the transversal coordinate. Three parameters are to be varied: value of total broadening, value of broadening in the lag zone and degree of the dependence of transversal metal flow velocity. These parameters are determined by the Ritz method. Comparison of the results of experiments and the mathematical model showed adequacy. [ABSTRACT FROM AUTHOR]

Crystallization is generally considered as the most destructive factor of porous material, but few studies have reported the coupling effects among fluid flow, heat transfer, crystallization and deformation in porous media. In this paper, the driving forces of phase transition were studied initially and then the crystallization kinetics models were established. Moreover, constitutive relations related to saline frozen soil were discussed, and the expression of unfrozen water content in non-equilibrium state was improved. Finally, a thermo-hydro-salt-mechanical coupled model for fully saturated saline frozen soil with phase change was proposed. Validation of the model is illustrated by comparisons between the simulation and experimental results. The predicted values of frost heave, temperature and moisture distribution are consistent with the experimental data, and it is demonstrated that the presented crystallization kinetics approach is valid for studying heat and mass transfer coupled problem with phase change in porous media. [ABSTRACT FROM AUTHOR]

In this paper, we focus on the problem of the accuracy performance of 3D face modeling techniques using corresponding features in multiple views, which is quite sensitive to feature extraction errors. To solve the problem, we adopt a statistical model-based 3D face modeling approach in a mirror system consisting of two mirrors and a camera. The overall procedure of our 3D facial modeling method has two primary steps: 3D facial shape estimation using a multiple 3D face deformable model and texture mapping using seamless cloning that is a type of gradient-domain blending. To evaluate our method's performance, we generate 3D faces of 30 individuals and then carry out two tests: accuracy test and robustness test. Our method shows not only highly accurate 3D face shape results when compared with the ground truth, but also robustness to feature extraction errors. Moreover, 3D face rendering results intuitively show that our method is more robust to feature extraction errors than other 3D face modeling methods. An additional contribution of our method is that a wide range of face textures can be acquired by the mirror system. By using this texture map, we generate realistic 3D face for individuals at the end of the paper. [ABSTRACT FROM AUTHOR]

Abstract: This paper has been motivated by the need to reduce the number of live animal tests in the development of an automated live-bird transfer system (LBTS) for the poultry meat-processing industry. Simulation-based models have been developed, which carefully address key engineering issues prior to live animal tests so that physical experiments can be focused on understanding reflex issues such as fear and escape behavior. To gain insights into the effects of operational timing on the LBTS handling performance, the multibody dynamics is modeled numerically based on the method of explicit dynamic finite element analysis (FEA) using off-the-shelf FEA packages. The findings also offer information on contact forces and their locations acting on the object’s body and legs by the compliant fingers and grippers respectively for optimizing designs and avoiding damage to the object. Specifically, this paper discusses computational issues such as time-step considerations and highly damped behavior of compliant fingers when modeling using dynamic FEA methods. The FEA model has been validated by comparing simulated handling of an ellipsoidal object by a pair of robotic hands with multiple compliant fingers against published experimental data. It is expected that the FEA-based method presented here can be extended to a spectrum of applications where flexible multibody dynamics involving large deformable contacts and highly damped behaviors plays an important role. [Copyright &y& Elsevier]

Abstract: The proper interpretation of bubble rising in a liquid column is critical in the investigation of the water–vapour two phase flow and heat transfer. In this paper, the bubble behaviours are studied using the combination of Level Set Method (LSM) and moving mesh method in a collocated grid. Level set method is used to track the interface of the bubble, which has many advantages over other interface tracking methods such as it can accurately calculate the curvature of the interface and easily expand to three dimensions. But if the uniform grid was adopted, the bubble interface cannot adapt well with the grid which may cause great numerical errors. Hence, moving mesh method is implemented in this paper to increase the numerical accuracy. The numerical model developed in this paper is benchmarked with the experimental data. The results show that the grid distributions used in this paper can catch the interface continuously in space and time. The process of bubble starting from deformation until break into three small bubbles is clearly shown from the numerical results. In addition, the changing of bubble behaviour with the temperature and pressure is also investigated. It is found that as the pressure and temperature increase, the deformation process will slow down and this tendency accelerates. [Copyright &y& Elsevier]

Abstract: In this paper, we present within the finite element context the numerical algorithm for the integration of the thermodynamically consistent thermo-viscoelastic, thermo-viscoplastic, thermo-viscodamage, and thermo-healing constitutive equations derived in the first part of this paper. The nonlinear viscoelastic model is implemented using a recursive-iterative algorithm, whereas an extension of the classical rate-independent return mapping algorithm to the rate-dependent problems is used for numerical implementation of the viscoplasticity model. Moreover, the healing natural configuration along with the power transformation equivalence hypothesis, proposed in the first part of the paper, are used for the implementation of the viscodamage and micro-damage healing models. Hence, the thermo-viscoelastic and thermo-viscoplastic models are also implemented in the healing configuration. These numerical algorithms are implemented in the well-known finite element code Abaqus via the user material subroutine UMAT. A systematic procedure for identification of model parameters is presented. The model is then used to simulate the time-, temperature-, and rate-dependent response of asphalt concrete over an extensive set of experimental measurements including creep-recovery, creep, triaxial, constant strain rate, and repeated creep-recovery tests in both tension and compression. Comparisons of the model predictions and the experimental measurements show that the model is capable of predicting the nonlinear behavior of asphalt concrete subjected to different loading conditions. [Copyright &y& Elsevier]

The goal of this paper is to deal with a mathematical model which describes the quasistatic frictional contact between a viscoelastic body and a foundation. We are interested in the foundation which is made of a hard material covered by a thin layer composed of a rigid crust and a viscoplastic material with finite thickness. The mechanical damage, caused by excessive stress or strain, is emerged in the viscoelastic body during the contact process. We provide the variational formulation of the model which is a system consisting of a history-dependent variational–hemivariational inequality, a fully nonlinear integral equation and a parabolic variational inequality. Then, in order to solve this complex system, we deliver abstract results on a class of history-dependent variational–hemivariational inequalities. Finally, our abstract results are applied to derive the unique weak solvability of the frictional contact problem under consideration. [ABSTRACT FROM AUTHOR]

During the assembly process of CNC machine tool, the assembly dimensions are varied due to the effect of the component deformation caused by gravity. Hence, a mathematical model predicting assembly errors needs to be constructed considering component deformation before tolerance design process. This paper presents an assembly error model of linear axis of CNC machine tool to analyze the effects of component manufacturing error and deformation on axis based on the 3-2-1 localization theory. Thereafter, axis position and angular deviations are calculated under four different conditions, ideal condition, condition considering manufacturing error only, condition considering the effect of structure, and actual condition. At last, the effect of worktable gravity on Y-axis deformation is taken as an example to verify the model. This model can be used to verify the tolerance at tolerance design or to calculate modification amount in assembly process. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the layerwise model for laminates with imperfect interfaces and enhanced in Part 1 of this work is confronted with experimental results. The model calculations are validated by comparing its sliding predictions in double lap adhesive joints to the sliding measurements performed in a previous paper. The model predictions agree with the experimental results. Finally, the model is applied to the failure analysis in double lap joints and T-peel joints exhibiting adherend, adhesive and cohesive failures. The model calculations and pertinent failure criteria provide accurate predictions and may become a helpful tool suitable to the design of adhesive joints. [Copyright &y& Elsevier]

The objective of research in this paper refers to the theoretical and experimental determination of dynamic sizes that occur during the process of impact of railway wagons. At the process of wagons impact as well as at the time of changes of movement regime (starting, stopping, and braking), the longitudinal forces that significantly affect the stress-deformational state of the supporting wagon structure occur. In the process of developing and designing new types of wagons and in the process of identifying the behavior of existing types of wagons, it is necessary to know the values of the most important dynamic sizes that occur during the process of impact. In this paper, a method for determining these sizes is formed by using the theoretical models of impact of wagons. Results of numerical simulation of impact are compared with the results of experimental tests, which were conducted according to international regulations. Research has shown that the results of numerical simulations coincide with the results of experimental tests, with certain exceptions. It is concluded that theoretical model can be used in determining the most important dynamic sizes that occur during the process of wagons impact. [ABSTRACT FROM AUTHOR]

Abstract: The paper deals with modelling of hygro-thermal performance and thermo-chemical degradation of concrete exposed to high temperature. Several possible simplifications in modelling of heat and mass transport phenomena in heated concrete are considered and their effect on the results of numerical simulations is analyzed. A mathematical model of concrete at high temperature, already extensively validated with respect to experiments, is used as the reference model. It is based on mechanics of multiphase porous media and considers all important couplings and material nonlinearities, as well as different properties of water above the critical point of water, i.e. 647.3K (374.15°C). In this part of the paper, first physical phenomena, as well as heat and mass flux and sources in a concrete element are studied, both during slow and fast heating process, to examine the relative importance of different flux components. Then, the mathematical model of concrete at high temperature, developed by Authors in the last 10years, is briefly presented and for the first time all the constitutive relationships of the model are summarized and discussed in detail. Finally, the method of numerical solution of the model equations is thoroughly presented. In the companion paper (part II) a brief literature review of the existing mathematical models of concrete at high temperature and a summary of their main features and physical assumptions will be presented. Then, extensive numerical studies will be performed with several simplified models, neglecting chosen physical phenomenon or flux components, to evaluate the difference between the results obtained with the simplified models and with the reference model. The study will concern hygric, thermal and degradation performance of 1-D and 2-D axisymmetric concrete elements during fast and slow heating. The analysis will allow us to indicate which simplifications in modeling of concrete at high temperature are practically and physically possible, without generating excessive errors with respect to the full reference model. [Copyright &y& Elsevier]

This paper presents a methodology and a tool for magnetic and mechanical deformation coupling using numerical and analytical modeling. An analytical magnetic model using Coulombian approach is used and coupled with a mechanical deformation model for a cantilever beam to evaluate contact size and contact force. Such a coupling is not available using numerical solution. This paper details the deformation and contact analysis, which is validated by finite element simulation and also details the coupling approach. Such a modeling is dedicated to an optimization process of magnetic MEMS/NEMS in general and to magnetic nano switch in particular. [ABSTRACT FROM PUBLISHER]

Statistical data on traffic accidents in 2008 in Lithuania is presented. Referring to statistical data, 'grounding on an obstacle' makes one-tenth of all registered traffic accidents - 9.4% (an obstacle may be a road guardrail, a lamp post, a tree, a bar, a gate, etc.). Road guardrails of various types are installed on the shoulders and dividing strips of urban and suburban roads. They are as follows: reinforced concrete guardrails, cable guardrails and metal guardrails. Metal guardrails, consisting of Σ-shape metal posts and a protective W-shape horizontal beam, are most popular. The authors of the present paper examine the deformation processes of the elements of the above mentioned guardrail. A mathematical model of metal road guardrail was developed. Metal road guardrail was modelled using one-dimensional first-order finite elements, taking into account only elastic deformations, as well as the effect of soil on the buried post section of the guardrail. Based on the developed mathematical model of metal road guardrail, the deflections of its elements caused by the impact of a vehicle moving at varying speed were determined. The obtained values of deflections of guardrail elements (a protective W-shape horizontal beam and a Σ-shape post) presented in paper do not exceed the admissible values (of beam deflections). [ABSTRACT FROM AUTHOR]

Abstract: This paper is a continuation of the paper titled “Concurrent multi-scale modeling of civil infrastructure for analyses on structural deteriorating—Part I: Modeling methodology and strategy” with the emphasis on model updating and verification for the developed concurrent multi-scale model. The sensitivity-based parameter updating method was applied and some important issues such as selection of reference data and model parameters, and model updating procedures on the multi-scale model were investigated based on the sensitivity analysis of the selected model parameters. The experimental modal data as well as static response in terms of component nominal stresses and hot-spot stresses at the concerned locations were used for dynamic response- and static response-oriented model updating, respectively. The updated multi-scale model was further verified to act as the baseline model which is assumed to be finite-element model closest to the real situation of the structure available for the subsequent arbitrary numerical simulation. The comparison of dynamic and static responses between the calculated results by the final model and measured data indicated the updating and verification methods applied in this paper are reliable and accurate for the multi-scale model of frame-like structure. The general procedures of multi-scale model updating and verification were finally proposed for nonlinear physical-based modeling of large civil infrastructure, and it was applied to the model verification of a long-span bridge as an actual engineering practice of the proposed procedures. [Copyright &y& Elsevier]

Abstract: In recent years, dielectric elastomers have received increasing attention due to their unparalleled large strain actuation response (>100%). The force output, however, has remained a major limiting factor for many applications. To address this limitation, a model for a fiber reinforced dielectric elastomer actuator based on the deformation mechanism of McKibben actuators is presented. In this novel configuration, the outer cylindrical surface of a dielectric elastomer is enclosed by a network of helical fibers that are thin, flexible and inextensible. This configuration yields an axially contractile actuator, in contrast to unreinforced actuators which extend. The role of the fiber network is twofold: (i) to serve as reinforcement to improve the load-bearing capability of dielectric elastomers, and (ii) to render the actuator inextensible in the axial direction such that the only free deformation path is simultaneous radial expansion and axial contraction. In this paper, a mathematical model of the electromechanical response of fiber reinforced dielectric elastomers is derived. The model is developed within a continuum mechanics framework for large deformations. The cylindrical electro-pneumatic actuator is modeled by adapting Green and Adkins’ theory of reinforced cylinders to account for the applied electric field. Using this approach, numerical solutions are obtained assuming a Mooney–Rivlin material model. The results indicate that the relationship between the contractile force and axial shortening is bilinear within the voltage range considered. The characteristic response as a function of various system parameters such as the fiber angle, inflation pressure, and the applied voltage are reported. In this paper, the elastic portion of the modeling approach is validated using experimental data for McKibben actuators. [Copyright &y& Elsevier]

Abstract: The companion paper has reported the results from a test programme in which web cleat connections were subjected to various combinations of shear, tying and moment actions at elevated temperatures. These tests showed that web cleat connections have very good tying resistance and rotational capacity, mainly due to the large deformation of which the web cleats are capable. In this paper a mechanical model is developed to predict the behaviour of web cleats subjected to tying forces. This model considers the formation of four plastic hinges on each angle and the effect of the angles opening in enhancing their resistance. It is capable of representing the action of the angles in component-based models for web cleat connections, in which algorithms for other components, including bolts in tension, bolts in double shear and holes in bearing, are already available. Failure criteria determined from the tests have been introduced into the models for components such as web cleats and bolts in double shear. This enables the component-based assembly to predict the occurrence and the sequence of connection failure. The behaviour of the connection predicted by the component-based model shows good correlation with the test results, which indicates that the developed model can be adopted in structural frame analysis to consider connection failure. [Copyright &y& Elsevier]

Abstract: A mechanically attached roof system has flexible membranes that are exposed to environmental elements to achieve the waterproofing function. Wind induced loads can lift the roof membrane between attachment locations and cause fluttering. The membrane under tension induced by wind forces transfers stresses through fasteners at the attachment locations. By characterizing the membrane deformation with its slope and using a force-vector diagram, one can predict the critical forces on fasteners. This paper presents the use of a three-dimensional finite element (3D-FE) model for predicting membrane deformation. To validate the model, a series of benchmark experiments have been performed at the Dynamic Roofing Facility of the National Research Council of Canada. The experimental data are also used to evaluate the validity of a mechanical model. From this comparative exercise between the existing model and the newly developed one, the paper offers the designer the limitations at which the simplified mechanical model can be used. [Copyright &y& Elsevier]

The main goal of this paper is to get a mathematical model for the process of deep drawing force with the reduction of wall thickness. Mathematical model should have a correct analytic description of this deformation process and along with that a possibility to calculative deep drawing force and after that a possibility of optimization of the whole deformation process and force. In this paper experiment planning is presented, from defining significant factors (parameters), levels of variation, equipment for experiment performing, processing of receiving results with known analytic models and on the end structuring final mathematical model for deep drawing force. [ABSTRACT FROM AUTHOR]

Failure of granular media under natural and laboratory loading conditions involves a variety of micromechanical processes producing several geometrically, kinematically, and texturally distinct types of structures. This paper provides a geological framework for failure processes as well as a mathematical model to analyze these processes. Of particular interest is the formation of tabular deformation bands in granular rocks, which could exhibit distinct localized deformation features including simple shearing, pure compaction/dilation, and various possible combinations thereof. The analysis is carried out using classical bifurcation theory combined with non-linear continuum mechanics and theoretical/computational plasticity. For granular media, yielding and plastic flow are known to be influenced by all three stress invariants, and thus we formulate a family of three-invariant plasticity models with a compression cap to capture the entire spectrum of yielding of geomaterials. We then utilize a return mapping algorithm in principal stress directions to integrate the stresses over discrete load increments, allowing the solution to find the critical bifurcation point for a given loading path. The formulation covers both the infinitesimal and finite deformation regimes, and comparisons are made of the localization criteria in the two regimes. In the accompanying paper, we demonstrate with numerical examples the role that the constitutive model and finite deformation effects play on the prediction of the onset of deformation bands in geomaterials. [Copyright &y& Elsevier]

Development of accurate mathematical models of geomaterial behavior requires a more fundamental understanding of the localization phenomena; in particular, the important factors responsible for the inception and development of localized deformation. The objective of this paper is to implement and test the mathematical formulations presented in a companion paper to better understand the different failure processes in granular media, specifically the formation of deformation bands in geomaterials. Our approach revolves around the use of classical bifurcation theory combined with advanced constitutive modeling and state-of-the-art computation to capture the end members of the failures modes described in the companion paper, namely, simple shear, pure compaction, and pure dilation bands, as well as the combination modes described in the geological framework. The paper revisits the notion of the critical hardening modulus as it applies to the entire range of failure modes, elucidates the role of the third stress invariant and finite deformation effects on the localization properties, and describes some useful properties of the constitutive and algorithmic tangent operators as they relate to the capture of the onset of deformation bands in geomaterials. [Copyright &y& Elsevier]