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Fluid–structure interaction (FSI) problems with large fluid deformations can be a great challenge for numerical simulations using conventional methods. In this paper, we propose a novel hybrid approach of an improved S moothed P article hydrodynamics and smoothed finite E lement M ethod (SPEM) for modeling FSI problems. In SPEM, the edge-based smoothed finite element method (S-FEM) is developed in Lagrangian frame and is used for the first time to model both elastic structures and incompressible flows. For fluid regions with large deformations, the associated finite elements are adaptively converted into particles and the corresponding regions are subsequently modeled using the decoupled finite particle method (DFPM), which is an improved smoothed particle hydrodynamics (SPH) method suitable for modeling incompressible flows with free surfaces. A ghost particle-based interface algorithm to couple existing S-FEM elements and DFPM particles is developed in SPEM to implement the modeling of FSI problems. As the smoothed FEM and decoupled FPM are enhanced FEM and SPH respectively and DFPM is only used for local fluid regions with large deformations, it is expected that SPEM is more accurate and more efficient than the existing coupling approaches of conventional FEM and SPH. Five numerical examples are tested using the proposed SPEM and the comparative studies with results from other sources reveal that SPEM is an effective approach for modeling FSI problems with large fluid deformations. • A smoothed particle element method (SPEM) is developed for modeling fluid–structure interactions. • The Lagrangian smoothed FEM (S-FEM) is used for modeling both structures and fluids. • The decoupled finite particle method (DFPM) is employed to model fluid regions with large deformations. • A ghost particle-based interface algorithm is developed to couple S-FEM and DFPM. • SPEM is more accurate and efficient than existing FEM-SPH or pure SPH approaches. [ABSTRACT FROM AUTHOR]

Highlights • The finite particle method (FPM) is integrated with particle shifting technique (PST). • FPM-PST shows better performance in accuracy and stability than conventional SPH. • FPM-PST is effective in modeling particulate flows with thermal convection. • Thermal convection has significantly different effects on the motion of hotter and colder particles in the fluid. Abstract Particulate flows with thermal convection are very challenging to simulate numerically due to the existence of constantly moving boundaries and complex heat-fluid coupling effects. Meshfree and particle methods have special advantages in modeling complex fluid flows with moving boundaries. However, previous works based on meshfree modeling mainly focused on either particulate flows only with momentum exchange or natural thermal convection. In this paper, a finite particle method integrated with particle shifting technique (FPM-PST) is developed for modeling particulate flows with thermal convection. FPM is an improved smoothed particle hydrodynamics (SPH) method with better accuracy while extremely irregular particle distribution may lead to ill-conditioned corrective matrix and terminate the simulation. PST can achieve regular particle distribution through shifting highly disordered particles while current PST is based on conventional SPH of poor accuracy. A number of numerical examples demonstrated that FPM-PST is a novel approach for modeling thermal particulate flows with good performance in accuracy and stability. It has better accuracy than the conventional SPH and can obtain comparable results with those from other sources. The unphysical voids can also be avoided by FPM-PST. From the FPM-PST simulations, it is observed that at relatively low Reynolds numbers thermal convection between hotter or colder particles and the fluid causes significant increase or decrease in the drag force acting on particles, while the thermal convection has little influence on the particle motion at relatively high Reynolds numbers. [ABSTRACT FROM AUTHOR]

Smoothed particle hydrodynamics (SPH) is a meshfree Lagrangian particle method, and it has been applied to different areas in engineering and sciences. One concern of the conventional SPH is its low accuracy due to particle inconsistency, which hinders the further methodology development. The finite particle method (FPM) restores the particle consistency in the conventional SPH and thus significantly improves the computational accuracy. However, as pointwise corrective matrix inversion is necessary, FPM may encounter instability problems for highly disordered particle distribution. In this paper, through Taylor series analyses with integration approximation and assuming diagonal dominance of the resultant corrective matrix, a new meshfree particle approximation method, decoupled FPM (DFPM), is developed. DFPM is a corrective SPH method, and is flexible, cost-effective and easy in coding with better computational accuracy. It is very attractive for modeling problems with extremely disordered particle distribution as no matrix inversion is required. One- and two-dimensional numerical tests with different kernel functions, smoothing lengths and particle distributions are conducted. It is demonstrated that DFPM has much better accuracy than conventional SPH, while particle distribution and the selection of smoothing function and smoothing length have little influence on DFPM simulation results. DFPM is further applied to model incompressible flows including Poiseuille flow, Couette flow, shear cavity and liquid sloshing. It is shown that DFPM is as accurate as FPM while as flexible as SPH, and it is very attractive in modeling incompressible flows with possible free surfaces. [ABSTRACT FROM AUTHOR]

Local instability of a compound slope is commonplace in practice. Extant analytical solutions only considered the single global failure pattern, which results in an inaccurate assessment of slope stability. This paper develops a unified analytical framework to account for the local and global instability of a compound slope. A failure pattern coefficient is proposed for the determination of instability behaviors. On this basis, the kinematically admissible three-dimensional (3D) failure mechanism is modified to describe the collapse of slopes. Under the framework of the upper-bound theorem of limit analysis, the external work rates and the internal dissipation rates can be calculated from the unified failure mechanism. The strength reduction technique is introduced into the work rate balance equation, and then the explicit solution of the safety factor is derived. The critical safety factor and slip surface are obtained through a hybrid optimization of the objective function. By way of example, the present solutions are compared with previous solutions and the results of the finite element method. Good agreements of the safety factor and slip surface show the good capability of this study to implement the stability analysis of compound slopes. A detailed parametric study is carried out to reveal the influence of slope geometry, soil strength, and external excitation on slope stability and failure pattern. The method presented in this paper provides a more rigorous solution for the stability assessment of compound slopes. [ABSTRACT FROM AUTHOR]

Abstract: This paper theoretically proposed a series of formulae for a novel tensile testing method to extract the residual stress in the surface film on metallic substrates. Finite element calculations were conducted to verify the accuracy and reliability of the proposed formulae. From the tensile stress–strain curves of metallic substrates with and without a surface film, one can evaluate the residual stress in the film using these formulae. A tarnish film on a brass substrate formed after immersion in Mattsson’s solution was tested to demonstrate these methods, and the obtained residual stress showed a low difference below 6.8%. [Copyright &y& Elsevier]

Abstract: An asperity profile function has been proposed that describes the isotropic rough surface of a material. The function is parameterized with three new roughness parameters that control the root mean square height, the slope and the curvature of the rough surface, respectively. Unlike the roughness parameters used in the well known Greenwood–Williamson model, the three parameters introduced in this paper are independent of each other, which is an advantage as this facilitates the characterization of the isotropic random surface of the material. However, a disadvantage with this parameterization is that the roughness parameters are not linked to a contact area equation any more, like the Hertz equations that express contact with linear materials. Different asperity profiles defined by the new roughness parameters were analyzed by a 2D axial symmetric FE-model. The numerical results suggest a procedure for developing a contact area function that are parameterized with the three new roughness parameters, which is also suitable for nonlinear brittle materials. [Copyright &y& Elsevier]

Abstract: It is well known that residual stresses influence the ductile fracture behaviour. In this paper, a numerical study was performed to assess the effect of residual stresses on ductile crack growth resistance of a typical pipeline steel. A modified boundary layer model was employed for the analysis under plane strain, Mode I loading condition. The residual stress fields were introduced into the finite element model by the eigenstrain method. A sharp crack was embedded in the center of the weld region. The complete Gurson model has been applied to simulate the ductile fracture by microvoid nucleation, growth and coalescence. Results show that tensile residual stresses can significantly reduce the crack growth resistance when the crack growth is small compared with the length scale of the tensile residual stress field. With the crack growth, the effect of residual stresses on the crack growth resistance tends to diminish. The effect of residual stress on ductile crack growth resistance seems independent of the size of geometrically similar welds. When normalized by the weld zone size, the ductile crack growth resistance collapses into one curve, which can be used to assess the structural integrity and evaluate the effect of residual stresses. It has also been found that the effect of residual stresses on crack growth resistance depends on the initial void volume fraction f 0, hardening exponent n and T-stress. [Copyright &y& Elsevier]

Abstract: Finite element analyses using COMSOL have been carried out to study the heat transfer behavior and storing capacity of concrete walls with air cavities, and to explore the possibility of using one-layer and two-layer one-dimensional models with equivalent thermal conductivity and mass density to represent the effect of concrete walls with air cavities in a building energy simulation. Three typical wall geometries were chosen and both stationary and transient analyses have been carried out. The stationary analyses were performed first to find the equivalent thermal conductivity which was further used in the transient analyses to fit the equivalent mass density. Because of the presence of air cavities the equivalent thermal conductivities are always smaller than the bulk thermal conductivity. However, for the one-layer model an exaggerated equivalent mass density as high as two times the bulk density should be used in order to simulate the heat storing capacity of the concrete walls with air cavities. The values of the fitted equivalent mass density are strongly dependent on the wall thickness. [Copyright &y& Elsevier]

Abstract: This paper illustrates an efficient contour integral procedure to obtain stress intensity factors in combination of the asymptotic analysis with finite element analysis. Note that this set-up is very general: the material can be anisotropic elastic, and the specimen can be built as a bi-material system, notches of arbitrary opening angle can be analyzed (γ =0→crack, γ =180°→free edge). The purpose of this technical note is to comment on three issues in the notch mechanics: the interpretation of the eigenvalue equation, the definition of stress intensity factors, and the effect of the outer contour location on H-integral evaluations. [Copyright &y& Elsevier]

Liquid sloshing flows interacting with deformable structures are difficult to be numerically simulated due to the co-existence of moving fluid-structure interfaces and breaking free surfaces. As a Lagrangian and particle-based method, the smoothed particle hydrodynamics (SPH) method has natural advantages in handling free-surface flows. The smoothed finite element method (SFEM) provides a reliable tool to capture the associated structural deformations, and it can solve the "overly-stiff" problem in the conventional FEM. In this work, the coupling strategy of an improved SPH version and SFEM is integrated with advanced fluid modeling techniques, and is extended and validated for modeling liquid sloshing with rigid or deformable structures. Both the rigid wall boundaries and deformable structures are reproduced by the elements, whereas the fluid particles with a different resolution can be adopted. The integrated δ -SPH model can significantly alleviate the spurious high-frequency noise of the computed impact pressure in a sloshing process. The particle shifting technique helps improve both accuracy and robustness of the fluid flow model. The virtual particle coupling strategy is effective to transfer information between SPH particles and SFEM elements. Various numerical tests show that the present coupling approach is very effective for modeling violent sloshing with deformable baffles or deformable container walls. This method is more accurate than the conventional coupling of SPH-FEM and can obtain results very close to the experimental observations compared with some numerical approaches from other sources. [ABSTRACT FROM AUTHOR]

Abstract: This paper addresses the residual stresses and their effect on microcracking in polycrystalline ceramic materials. Residual stresses at microstructural level in titanium diboride ceramics, as a result of thermal expansion anisotropy, were analyzed by finite element method using Clarke’s model. Damage mechanics based cohesive zone model was applied to study grain boundary microcracking, propagation and arrest. Quantitative relations between temperature variation, grain boundary energy, grain size, final microcrack length as well as microcracking temperature are established. [Copyright &y& Elsevier]

Abstract: A nanoindentation-based flat punch method has been developed to determine the stress–strain behaviour of single micron-sized Ugelstad polystyrene-co-divinylbenzene (PS–DVB) particles in compression. Five groups of particles with identical chemical compositions but different diameters have been tested. The diameter of the PS–DVB particles varied from 2.6μm to 25.1μm. Constant relative deformation rate has been applied with two maximum strain levels of 5% and 10%. Results show that the particle compressive stress–strain behaviour is strongly size-dependent. The smaller the particle size is, the stiffer the particle behaves. Analyses indicate that the pre-load and adhesion during the flat punch test play a minor role on the size effect. The presence of a core–shell structure can possibly be a main contribution to the size effect. Finite element analyses have been carried out to demonstrate this surface shell effect. [Copyright &y& Elsevier]

Abstract: In this study we focus on the fracture behavior of two types silicon-thin film glass-silicon (Si-Glass-Si) triple stacks specimens with a sharp corner. We determine the notch stress intensity factor K n for both specimens using a combination of the Williams eigenfunction expansion method, Stroh’s sextic formalism, finite element analysis, and the path-independent H-integral. Empirical solutions of dimensionless stress intensity factors are proposed for two typical specimens, and the dependence of geometry is analyzed. Furthermore, the effect of glass thickness on stress intensity is explored for anodic-bonded Si-Glass-Si triple stacks. We discuss the feasibility of using a critical value of K n to correlate the failure results for both specimens with various bond area and glass thickness. [Copyright &y& Elsevier]

Abstract: Micron-sized metal coated polymer particles are used in developing anisotropic conductive adhesives (ACA). The mechanical properties of polymer particles are of crucial importance for the reliability and design of ACA. In this paper we present a method to determine the mechanical properties of polymer sphere particles under large deformation by using a flat punch test-soft elastic sphere against a rigid flat. Finite element analyses have been carried out to study large deformation contacts. It has been shown that the classical Hertz solution works only for very small sphere deformation (less than 1% compression strain) and Tatara’s solution works well for sphere compression up to 20%, beyond that large strain effect should be considered. For compression less than 20%, both the compression stress–strain curves and lateral expansion strain–compression strain curves can be normalized by a function of the Poisson ratio. Based on the finite element results, explicit equations describing these relations are presented for determining the Young’s modulus and Poisson ratio of polymer particles at large deformation. The proposed method has been applied to analyze the experimental results of typical polymer particles used for conductive adhesives from a specially built capacitance-based flat punch test. [Copyright &y& Elsevier]

Liquid sloshing in partially filled containers is widely observed in various engineering systems where the forces exerted by the liquid on tank walls may result in the instability of tank or even a structural failure. To enhance the hydrodynamic damping ratio and consequently decrease the sloshing forces, baffles have been designed as effective internal components inside containers in most of the practical engineering problems. In this work, we numerically investigate the sloshing mitigation using elastic baffles through our recently developed methodology based on the coupling strategy of smoothed finite element method (SFEM) and an improved version of smoothed particle hydrodynamics (SPH) offering better accuracy. First, we simulate a benchmark problem of sloshing flow interacting with an elastic baffle installed in a container, and the numerical results agree well with the experimental data. Further, various cases are conducted to study the sloshing mitigation by using deformable baffles with different configurations and elasticities. Our current observations and findings based on the simulation results demonstrate that the impact pressure on the tank wall is significantly influenced by the geometric orientations and complex configurations of elastic baffles. The timing of sloshing flow impacting on the container wall can be passively controlled by adequately choosing the baffle elasticity. The damping performances of different elastic baffles are quantified by the numerically obtained Pressure - E b a f f l e lines. The relevant analysis in this paper can greatly help explore the effective solutions to mitigate the liquid sloshing in engineering systems. • The coupling method is extended to investigate the sloshing mitigation using elastic baffles. • The coupling method obtains smooth pressure/stress fields and accurate structural deformations. • The damping effects of complex deformable baffles are comparatively studied. • The sloshing flow impacting on the container can be passively controlled by choosing the baffles. • The elastic baffles with the best damping performance are determined by the P- E b a f f l e lines. [ABSTRACT FROM AUTHOR]

Highlights: [•] It is shown that the geometrical nonlinearity of silicon wafers affects the SIFs significantly. [•] The FE analysis illustrated some limitations with the Newman–Raju approach in calculating SIFs for thin wafers. [•] The results showed that the Newman–Raju solution predicts vanishing SIFs of the surface point (ϕ =0) for long surface cracks . [•] The results show that for long surface cracks, finite element modeling is necessary for calculating the SIFs. [Copyright &y& Elsevier]

Abstract: The size dependence of the tensile properties and necking effect of pure copper exposed to various heat treatments are investigated in this paper using round bar cross-section specimens through experimental and 3D finite element methods (FEM). The results show that the total and post-necking elongation increased dramatically as the specimen diameter increased. The size effects on necking and stress distribution of different diameter specimens are analysed. These results show that the post-necking deformation length is only dependent on the diameter of the specimens and is independent of the specimen’s gauge length, which results in the size dependence of the post-necking elongation. Moreover, FEM simulations show that the size dependence of the tensile properties can be eliminated when the ratio of the gauge length to the diameter is larger than 10. [Copyright &y& Elsevier]

Abstract: In this study the frictionless contact of a power-law hardening elastic–plastic sphere in contact with a rigid flat has been investigated by the finite element method. The strain hardening exponent n varied from 0 to 1, with material properties changing from elastic–perfectly plastic to elastic. Parameters such as contact load, contact area under both loading and unloading have been calculated for a wide range of contact interferences. Based on the finite element results, analytical and dimensionless expressions of these contact parameters versus the contact interferences during loading have been presented. In addition, the load–deformation equations at unloading and the residual interference after complete unloading for a large range of maximum interferences are given. [Copyright &y& Elsevier]

Abstract: Infiltration of liquid aluminum in three TiB2 materials with significantly different microstructures at 1000°C has been studied. The results show large differences in resistance towards aluminum penetration. A TiB2 material containing transition metal sintering aid, displayed a low resistance towards penetration of liquid aluminum along grain boundaries. Grain boundary penetration was also observed in a second material containing an oxycarbide secondary phase TiC1−x O x , while Al infiltration could not be detected after 100h, in a third material with apparently no secondary phases. The flexural strength, hardness and stiffness of the exposed material showing the lowest resistance towards penetration of aluminum, decreased due to penetration along grain boundaries, and the fracture mode changed from transgranular to intergranular. The experimental observations were analyzed using a two-dimensional finite element model, reproducing the observed reduction in the stiffness due to aluminum infiltration. [Copyright &y& Elsevier]

Many petroleum companies expand their activities further north towards the Arctic region, resulting in design temperatures down to −60 °C, which is much lower than what is usual for most current petroleum installations. As properties of steels are temperature dependent, it is of great interest to evaluate the effects of low temperature on the crack driving force in steels. The present work investigates these effects numerically using a finite element model of a single-edge-notched-tension (SENT) specimen with crack depth a / W = 0.5 . The effects of Lüders strain and yield strength are studied for gross stress levels σ G / σ y ≤ 0.5 , and it is shown that an increase in yield strength and Lüders strain, as a result of Arctic temperature, intensifies the crack driving force. An approximate model that can be used to estimate the crack driving force based on yield strength, Lüders strain and loading is proposed. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a novel three-dimensional finite element for gradient elasticity. The new finite element BR153L9 is a straightforward extension of the two-dimensional element QU34L4 developed by Shu et al. (1999) , which is based on a mixed-type formulation. Within this paper the derivation of the mixed-type finite element scheme is reviewed and details of the implementation are given. Finally, numerical results of an extended patch test and a benchmark test with the three-dimensional finite element are presented in order to validate the formulation and prove the convergence. [Copyright &y& Elsevier]