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Abstract: Depending on unique operation characteristics for voltage applied on valve side winding of the converter transformers, it is extraordinarily significant to study the partial discharge (PD) behavior with oil-paper insulation under combined AC–DC voltage. Therefore, this paper investigated PD inception characteristics by pulse current methods with needle-plate electrode system under combined AC–DC voltage. Furthermore, 3D electric field distributions versus combined AC–DC voltage in different ratios were calculated by Finite Element Analysis (FEA). An experimental conclusion was drew that AC partial discharge inception voltage (PDIV) in pure oil would decrease linearly with the DC component increasing but the inception voltage with oil-paper insulation appeared to be independent of DC voltage and dependent of AC voltage. And 3D electric field distribution deduced from simulation provided a supplementary proof on the experimental results. Moreover, high speed photography was used to capture emitted light produced by discharge, estimate streamer velocity (1.8 km/s) and record streamer initiation and propagation process in oil gap. Previous studies have shown that the prebreakdown phenomena involving the generation and propagation of vapor channels through the oil could be divided into a three-stage process. [Copyright &y& Elsevier]

Abstract: In this paper we describe electrophoresis of charged particles in a thin layer of a nonpolar liquid between two insulating substrates because this configuration is common in recently developed in-plane electronic paper. In the in-plane electrophoresis experiments a model system of charged inverse micelles in dodecane has been used which is well understood from studies of out-of-plane electrophoresis. The transient current due to drift and diffusion of charged inverse micelles is measured in thin in-plane devices upon application of a voltage step. For the modelling of the transient dynamics of charged inverse micelles without chemical reactions or convection a 1-dimensional approximation of the Poisson–Nernst–Planck (PNP) equations is developed. This approximation is valid for a sufficiently thin in-plane device and allows much faster calculations. Firstly, it is verified in the case of a sufficiently thin in-plane device and high applied voltage that the 1-dimensional approximation is in good agreement with the solution of the full 2-dimensional PNP equations with finite elements implementation. Then, the 1-dimensional approximation is used to study the transient current and trajectories of trace amounts of charged colloidal particles in different regimes depending on the screening of the electric field. Also a comparison is made to the well-studied case of out-of-plane electrophoresis. Finally, it is verified that for voltages much larger than the thermal voltage the experimental results are in good agreement with the 1-dimensional approximation, indicating that the charge transport dynamics of charged inverse micelles in the bulk are described well by the model. [Copyright &y& Elsevier]

• A multi-field coupling model and simulation platform are based on COMSOL5.3. • The effects of process parameters and reactor structure on coating silicon nitride film are studied concurrently. • Transforming dynamic coating problems into static problems for simulation research. This paper builds a physical model by using the finite element method on COMSOL simulation platform to simulate the in-line PECVD process. The in-line PECVD simulation model couples the flow field, thermal field, chemical reaction field and plasma field and is verified through experiments. In addition, a new simulation strategy is proposed to solve the problem of dynamic coating silicon nitride film. Through this simulation method, process parameters and structural parameters of the in-line PECVD equipment are optimized. Effects of microwave tube position, microwave shield size, total gas flow, pressure and temperature on main coating reaction region is studied. The results have shown that the position of microwave tube, the total gas flow and temperature have greater influence on the region of reaction zone, the concentration distribution of reactants and the thickness of SiN x H y film. Through optimizing process parameters and structural parameters, the coating rate of SiN x H y film can be increased from 0.0607 nm/s to 0.15 nm/s and the deposition thickness can be increased from 6.78 nm to 15.59 nm. The molar concentration of SiN x H y particles in the reaction region has grown by more than 23.5%. And the relative intensity of reaction field inside PECVD chamber has increased by 1.3–2.3, which is calculated by molar concentration ratio of SiN x H y particles. This paper provides a reference for the optimization of in-line PECVD equipment. [ABSTRACT FROM AUTHOR]

In this paper, a novel numerical simulation approach based on the finite element method for dynamically modeling the excavation process of shield tunneling is proposed, with the shield-ground interactions well captured. This method is capable of mimicking the alternating modes of advancing and stopping of a shield boring machine during underground construction, with the important effects of the cutterhead rotation and slurry support pressure considered. Under the cutting action, the soil at the excavation face would experience irreversible deformation and damage, such that additional support needs to be provided by the cutterhead blades and slurry to maintain stability. The impacts of key construction parameters are examined, including cutterhead rotary speed, advance rate, and slurry support pressure, on shield tunneling operations and ground responses. The numerical model is rigorously validated against physical model experiments. This work provides useful insights into the mechanistic processes in the stratum during shield tunneling, including the spatiotemporal evolution of ground deformation patterns and stress redistributions. The results offer valuable guidance for optimizing shield tunneling operations and enhancing tunneling safety and efficiency. [ABSTRACT FROM AUTHOR]

In this paper, we study a weak Galerkin (WG) finite element method for semiconductor device simulations. We consider the one-dimensional drift–diffusion (DD) and high-field (HF) models, which involves not only first derivative convection terms but also second derivative diffusion terms, as well as a coupled Poisson potential equation. The main difficulties in the analysis include the treatment of the nonlinearity and coupling of the models. The weak Galerkin finite element method adopts piecewise polynomials of degree k for the approximations of electron concentration and electric potential in the interior of elements, and piecewise polynomials of degree k + 1 for the discrete weak derivative space. The optimal order error estimates in a discrete H 1 norm and the standard L 2 norm are derived. Numerical experiments are presented to illustrate our theoretical analysis. Moreover, numerical schemes also work out for the discontinuous diffusion coefficient problems. [ABSTRACT FROM AUTHOR]

A high-pressure chamber is the main equipment required for simulating deep-sea operational environment and used for evaluating the performances of underwater equipment such as underwater vehicles under a preset pressure so that the possible malfunctions could be alarmed before deep-sea commissioning. In this paper, due to its current unavailability, a high-pressure chamber with the maximum working pressure of 60 MPa was designed, which has the inner diameter of 3 m and the height of 4 m, possesses the video transmission function and allows most of the small-scale underwater vehicle's overall stability and capacity to be tested possible. To tackle the leakage and ensure the stability of the chamber, this paper proposes a novel sealing method, which adopts the combination of anti-shear block device and four O-ring seals and has the advantage of no need of manual pre-tightening and of sufficient shear resistance. The performance and strength analysis of the chamber were carried out by Ansys/Workbench finite element analysis software. Furthermore, The high-pressure chamber was manufactured and its experiment verification results indicate that with larger containment volume and more advanced control system it could work reliably, which made it feasible for its engineering application. • A high-pressure chamber is the main equipment required for simulating deep-sea operational environment. • With the maximum working pressure 60 MPa, the high-pressure chamber has the inner diameter of 3 m, the height of 4 m. • The chamber possesses the video transmission function. • The performance and strength analysis of the high-pressure chamber were carried out by Ansys/Workbench FEA.. • Both the simulation and the experiment show that the chamber works reliably and is feasible for engineering application [ABSTRACT FROM AUTHOR]

Abstract Terrestrial laser scanning is extensively adopted in the area of high-precision monitoring and three-dimensional measurement. Architectural structures today are increasingly complex and health monitoring plays an important role in guaranteeing their safety. Therefore, how reliability deformation monitoring can be improved is one of the key problems in the field of engineering. This paper combines the three-dimensional laser scanning technology and finite element method (FEM) to investigate the deformation mechanism of arched structures. Within this paper, we simulated arched structures using the FEM, which is consistent with the result of terrestrial laser scanner (TLS) measurement. We aimed at constructing an intelligent and efficient FEM model which can be extensively applied in the monitoring of many constructs, such as bridges and ancient architecture. The focus in this research lies mainly on deformation analysis, which is based on FEM model simulation with the calibration of TLS measurement. [ABSTRACT FROM AUTHOR]

Highlights • Both macrocrack and microcrack growth simulations by using the extended finite element method (XFEM) are presented. • The formulations of three typical frameworks of the XFEM are introduced. • The simulations of brittle and ductile crack growth under monotonic and cyclic loadings are demonstrated. • The outlook of the XFEM on crack growth simulations is pointed out. Abstract During the latest 20 years, the extended finite element method (XFEM) has been gradually used to investigate the crack growth behaviors of different materials in combination with various mechanics models and became the most popular computational tool in analyzing crack problems. This paper classifies three typical theoretical frameworks of the XFEM, namely the linear elastic fracture mechanics, the cohesive zone model and the elastic-plastic fracture mechanics based XFEM. A review of brittle and ductile crack growth under both monotonic and cyclic loadings using the XFEM was given from both macro-scale and micro-scale after a systematic literature survey. In contrast, the framework of the XFEM for modeling brittle fracture is the most comprehensive and widely used theory, but the theory for the ductile crack growth has still to be developed. Additionally, the XFEM becomes more complicated in microcrack growth simulations than macrocrack by considering the effects of microstructures of materials. The XFEM can introduce an arbitrary discontinuity into the finite element and can be employed to analyze different crack growth problems in engineering materials and structures, this paper is served as a valuable reference for the future study in this field. [ABSTRACT FROM AUTHOR]

The numerical modelling of the internal heat generation in passenger vehicle tyres using finite element analysis is a well-known numerical approach. However, this application is rather uncommon for earthmover tyres. This paper describes the development of a finite element model of a 23.5R25 earthmover tyre for the numerical modelling of the temperature distribution in the tyre cross-section at steady-state heat transfer conditions using an uncoupled analysis procedure. Considering the non-linear behaviour of the rubber compounds used for the manufacturing of these tyres, as well as the complexity associated with the composite structural aspects of the tyre, the material properties used for the proposed numerical model were established experimentally. In the analyses completed, the tyre behaviour was studied by simulations at various inflation pressures, loads and rolling velocities. The numerical tyre defection was within an 8% deviation from the actual tyre behaviour. Thermal simulation results were used to derive an equation that can be used to predict the maximum temperature that would occur in the tyre’s cross-section as a function of its vertical deflection, its forward rolling velocity and the ambient temperature of the surroundings. The numerical models and simulations presented in this paper were completed using MSC.Marc/Mentat. [ABSTRACT FROM AUTHOR]

This paper proposes a computerized approach based on the influence coefficient method to solve the statically indeterminate problem of multiple loaded contact tooth pairs in planetary gear drives. The influences of the deformation on the loaded contact characteristics are divided into three categories according to the relation of the acting load and the deformation on the specific tooth pairs, the gears and the gear pairs, respectively. Not only the contact and bending deformation of the engaged teeth, but also the planet shaft deflection and the twist deformation of the carrier and the sun gear are involved in the model. With discretized contact region of each tooth pair, three-dimensional contact patterns with distributed stresses, including the concentrated stress due to edge effect and tip corner contact, can be simulated. The simulated results are verified to have a good agreement with FEM. A numerical example of a planetary gear set with non-modified flanks and the error-free condition is analyzed in the paper. The effects of the deformation, the variations of the shared loads, the contact stress, the loaded transmission errors, and the contact patterns with the distributed contact stresses in the cases with/without tip corner contact are discussed. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of the transient contact solutions of wheel-rail frictional rolling impacts calculated by an explicit finite element model of the wheel-insulated rail joint (IRJ) dynamic interaction. The ability of the model to simulate the dynamic behavior of an IRJ has been validated against a comprehensive field measurement in a recent paper (Yang et al., 2018). In addition to the measured railhead geometry and bi-linear elastoplastic material model used in Yang et al. (2018), this study adopts a nominal railhead geometry and an elastic material model for the simulations to provide an overall understanding of the transient contact behavior of wheel-IRJ impacts. Each simulation calculates the evolution of the contact patch area, stress magnitude and direction, micro-slip distribution, and railhead nodal vibration velocity in the vicinity of the joint during the wheel-IRJ impacts. The simulations apply small computational and output time steps to capture the high-frequency dynamic effects at the wheel-IRJ impact contact. Regular wave patterns that indicate wave generation, propagation and reflection are produced by the simulations; this has rarely been reported in previous research. The simulated waves reflect continuum vibrations excited by wheel-rail frictional rolling and indicate that the simulated impact contact solutions are reliable. [ABSTRACT FROM AUTHOR]

In this paper we consider the simulation of the dynamic behaviour of deep drawn components by means of the finite element method (FEM). The deep drawing process involves high deformations which result in an irregular thickness distribution in the manufactured component. The thickness variation therefore has to be taken into account in the dynamic FEM simulation, since a reference model based on the initial thickness of the blank material often fails to accurately represent the dynamic properties of the final component. In order to properly account for this variation, two approaches are considered in this paper: the first one consists in simulating the forming procedure with the FEM and subsequently using the resulting geometry for the dynamic analysis. The second approach consists in the generation of an FEM model for the dynamic analysis starting from laser scan measurements on the manufactured component. Both approaches are analysed in detail and are validated with experimental measurements. It is found that the framework based on surface measurements provides slightly more accurate results but the purely numerical procedure is still a useful and faster methodology to obtain engineering accuracy. [ABSTRACT FROM AUTHOR]

The present paper focuses on the discretization and implementation of the Thick Level Set (TLS) approach for quasi-brittle failure when dealing with both local and non-local development of damage. The TLS damage model introduces a length scale and nonlocality in the Fracture Process Zone (FPZ) and it handles the continuous to discontinuous failure transition. The added nonlocality is limited to the FPZ and therefore the model is local away from the FPZ or before its emergence. It leads to concurrent development of local and nonlocal damage during simulations. This paper presents a space–time discretization that handles concurrent computations in a unified manner. It is based on an explicit time discretization written as a predictor–corrector scheme and a space discretization that uses specific approximation functions (modes) that embed nonlocality. It also uses an alternative implementation of the eXtended Finite Element Method (X-FEM) enrichment used in the TLS which is based on virtual nodes. [ABSTRACT FROM AUTHOR]

To fill the research gap of estimating crack-tip opening displacement (CTOD) under compressive portion within a cyclic loading, a numerical study is conducted in this paper to quantify the influence of compressive stress on CTOD, and a calculation model of CTOD is established for center-cracked plates under tension-compression loading. The residual CTOD and the variable quantity of CTOD are introduced. Based on a series of finite element analyses, a simple relationship between the variable quantity of CTOD and compressive stress is obtained, which considers the influences of plate width, crack length, stress level (the maximum tensile and compressive stresses) and material property (yield stress, elastic modulus and material hardening). Finally, an example is given and the method in this paper is validated. The proposed calculation model of CTOD has a wide application range and is applicable for finite plates of different materials under tension-compression cyclic loading. [ABSTRACT FROM AUTHOR]

Pulsed water jets have been widely applied in the field of underground mining because of their unique advantages. Revealing the mechanical mechanism of rock breaking under a pulsed water jet is significant in advancing the application of pulsed water jets in the rock crushing process. Based on continuum mechanics and interpolation theory, this paper establishes a numerical model to simulate the propagation of stress waves in rock by adopting the method of smooth particle hydrodynamics (SPH). According to the simulation results, this paper presents a quantitative approach to schematize the propagation of stress waves in the time-space dimension. The waveforms of stress waves in the selected path and the effective stress history of test particles are obtained to quantitatively describe the propagation of stress waves. Relying on the approach, the effects of jet velocity and rock properties on the propagation of stress waves are investigated. The results show that in the rock model, the influence area, propagation speed and attenuation rate of the stress wave all increase with increasing jet velocity. Moreover, the mean effective stress of a test particle in the numerical model increases with increasing jet velocity. Of the rocks considered in this paper, granite shows the greatest mean effective stress acting on the test particle, propagation speed, and attenuation rate of the stress wave. [ABSTRACT FROM AUTHOR]

The reliability analysis of engineering structural systems with limit state functions defined implicitly by time-consuming numerical models (e.g. finite element analysis structural models) requires the use of efficient solution strategies in order to keep the required computational costs at acceptable levels. In this paper, an adaptive Kriging surrogate model with active refinement is proposed to solve component reliability assessment problems (i.e. involving one single design point) with nonlinear and time-consuming implicit limit state functions with a moderate number of input basic random variables. The proposed model, in the first stage, uses an adaptive Kriging-based trust region method to search for the design point in the standard Gaussian space and predict an initial failure probability based on the first-order reliability method as well as sensitivity factors for the input basic random variables. This initial prediction is then verified or improved efficiently in a second stage using Monte Carlo simulation with importance sampling based on a Kriging surrogate model defined iteratively around the design point using an active refinement algorithm. A convergence criterion that detects the stabilization of the failure probability prediction during the active refinement process is also proposed and implemented. The usefulness of the proposed adaptive Kriging surrogate model in terms of accuracy and efficiency for reliability assessment of engineering structural systems is shown in the paper with two relevant numerical examples, involving a highly nonlinear analytical limit state function in two-dimensions and an advanced nonlinear finite element analysis structural model in a larger dimensional space. [ABSTRACT FROM AUTHOR]

As the main variable loads during the service stage of Submerged Floating Tunnels (SFTs), traffic loads is an important part in the studies of SFTs’ dynamic response. On the basis of the characteristics of moving vehicles and the structural characteristics of SFTs, this paper puts forward the calculation formula of traffic loads, with a comprehensive consideration of different influencing factors. In this paper, in order to obtain the degrees of influence of such factors on the calculated values of traffic loads and the dynamic response of SFTs and the weight of each factor, the author uses the orthogonal experiment method and the analytic hierarchy process, combining them with a simulation of the finite element software. It is expected to provide reference for related researches on SFTs. [ABSTRACT FROM AUTHOR]

In this paper, supermode characteristics of a dual-core fiber and a four-core fiber are analyzed by a simple couple-mode theory. The effective refractive index and corresponding relative error of each supermode are investigated in detail with different gapsize, relative refractive index and core radius using numerical method and finite element method. Both adjacent coupling and non-adjacent coupling are taken into consideration when keeping single mode condition of each core. The magnitude of relative error can achieve 10 −5 and 10 −4 for a dual-core structure and a four-core structure, respectively. The obtained results clearly show the validation of numerical method compared with finite element method. One is going to benefit from the succinct equation expressions in this paper when designing and analyzing supermode supporting fiber structure. [ABSTRACT FROM AUTHOR]

In metal machining, due to the material around the cutting edge subjected to high pressure, the subsurface generates a plastic deformation layer. And near the edge of finished surface the plastic deformation layer acts as a Poisson burr. This paper proposes an analytical model to predict the sizes of Poisson burr based on Flamant and Boussinseq equations in the plastic deformation problem. Besides the mechanical loading, the thermal effects are also taken into account in this model and assumed as moving heat sources during the cutting. The finite element simulation of aluminum 6061 alloy is utilized to verify the results of theoretical analysis. The results show that the sizes of Poisson burr has a great sensitivity to material properties and processing parameters. In addition, due to the serrated chips and brittle fracture of high strain rate, the Poisson burrs are not continuous along the longitudinal cutting direction. Through comparative study it is found that the theoretical model describes burr sizes with considerable accuracy. As a result, this paper may provide a better understanding the mechanism of Poisson burr formation and the theoretical basis of processing parameters optimization. [ABSTRACT FROM AUTHOR]

This paper is concerned with the finite element simulation of debonding failures in FRP-strengthened concrete beams. A key challenge for such simulations is that common solution techniques such as the Newton–Raphson method and the arc-length method often fail to converge. This paper examines the effectiveness of using a dynamic analysis approach in such FE simulations, in which debonding failure is treated as a dynamic problem and solved using an appropriate time integration method. Numerical results are presented to show that an appropriate dynamic approach effectively overcomes the convergence problem and provides accurate predictions of test results. [ABSTRACT FROM AUTHOR]

The paper discusses membrane instability phenomena by a Fourier-related double scale approach that was introduced recently. This leads to a reduced-order model that is able to capture the main features of the wrinkles with few degrees of freedom. The paper focuses on the corresponding finite element procedure, its implementation and evaluation and applications to various cases of loading and boundary condition. The finite element model has first been implemented in a home-made code, the nonlinear system being solved by the Asymptotic Numerical Method (ANM), which has advantages of efficiency and reliability for stability analyses. It has also been implemented as a user element in a commercial software to evaluate the effectiveness of the reduction technique. Various loading cases were considered and the numerical tests establish that the reduced model can predict the wrinkling patterns, even when there are few wrinkles. The numerical results highlight the strong influence of a dimensionless parameter for wrinkling initiation. [ABSTRACT FROM AUTHOR]

In this paper, we develop a novel second order in time, decoupled, energy stable finite element scheme for simulation of Cahn-Hilliard-Hele-Shaw system. The idea of scalar auxiliary variable approach is introduced to handle the nonlinear bulk. An operator-splitting strategy is utilized to fully decouple the coupled Cahn-Hilliard equation and Darcy equation. A full discretization is built in the framework of Galerkin finite element method. The unique solvability of numerical solution and preservation of energy law are rigorously established. Numerical experiences are recorded to illustrate the features of the designed numerical method, verify the theoretical results and conduct realistic applications. [ABSTRACT FROM AUTHOR]

Composites consisting of carbon fiber and epoxy resin matrix are modern material for wide range of application (automotive, aeronautics, sport industry). In this paper several type of composite material based on bisphenol A epoxy resin and plain/twill carbon cloth was prepared. Subsequently composite consisting from carbon cloth/epoxy resin and carbon nanotubes was prepared to prove the improvement of mechanical properties. Second part of paper describes the possibility of simulation of composite part using NX8 and Nastran solver. Results from real tensile test and simulation were then compared. [ABSTRACT FROM AUTHOR]

The spiral shafts are usually fabricated by the cutting, this paper uses the cross wedge rolling process of the spiral shaft parts. Firstly, according to the deformation stages of rolling narrow spiral step, accurate shaping surface of the mold is designed. Meanwhile, this paper finds that the starting point of the shaping curve is not in the stretching stage but advances to the knifing stage. Secondly, based on the FE software DEFORM-3D, the rigid-plastic finite element model of the cross wedge rolling of spiral shaft parts was established, and the rolling process was simulated. The forming qualities in both cases of having shaping curve and no shaping curve were compared, from which we can find that the forming quality of having shaping curve is better, it also shows that the shaping curve is correct, and the process of cross wedge rolling of spiral shaft is feasible. [ABSTRACT FROM AUTHOR]

The paper presents a simplified analytical method to examine the energy absorbing mechanisms of small-scale stiffened plate specimens, quasi-statically punched at the mid-span by a rigid indenter with a knife or a flat edge shape. To validate this method, experiments and numerical simulations are conducted on specimens scaled from a tanker side panel limited by one span between the web frames and the stringers. Therefore, the paper provides practical information to estimate the extent of structural damage within ship side panels during collision accidents. The experimentally obtained force–displacement responses and shapes of the deformation show good agreement with the simulations performed by the explicit LS-DYNA finite element solver. The numerical results manage to describe the process of initiation and propagation of the material fracture in the side panel specimens and provide detailed information of the energy dissipated by each structural component and its contribution to total energy during the entire deformation process. The analytical method derives expressions to estimate the relation between the plastic deformation and the energy dissipation of the stiffened plates. Both the plate and the stiffener elements dissipate the energy through rotation of the plastic hinges at the applied load and the support and the membrane tension over the plastically deformed region between the loading and the supports. The proposed simplified expressions give a good agreement with the experimental and numerical results. [ABSTRACT FROM AUTHOR]

This paper presents a hybrid finite-element/boundary-element method for fluid–structure-interaction simulations of inflatable structures. The flow model consists of the steady Stokes equation, which admits a boundary-integral formulation. The structure is represented by a Kirchhoff–Love shell. The boundary-element approximation of the Stokes equation reduces the flow problem to an integral equation on the actual structure configuration, thus obviating the need for volumetric meshing of the strongly deforming fluid domain. The Stokes model moreover exhibits a lubrication effect that acts as an intrinsic mechanism to treat the ubiquitous self-contact that occurs in inflation problems. The aggregated fluid–structure-interaction problem, composed of the boundary-integral equation and the Kirchhoff–Love shell connected by dynamic and kinematic interface conditions, is approximated by means of isogeometric discretizations to accommodate the smoothness requirements on the approximation spaces imposed by the flexural rigidity in the Kirchhoff–Love shell and to provide an accurate and smooth representation of the boundary for the boundary-element method. Auxiliary results presented in this paper are: (1) a parametrization-free Kirchhoff–Love formulation; (2) establishment of a cubic relationship between distance and tractions due to the lubrication effect; and (3) the interpretation of the Lagrange multiplier pertaining to fluid incompressibility as the total excess pressure. [ABSTRACT FROM AUTHOR]

Pull-through failure of bolted joints in composites is due to the relatively low through-thickness properties of laminated materials. Recently it has been identified that pull-through failure also plays an important role in the ultimate bearing load and total energy absorption of bolted joints, especially under dynamic conditions. It has been previously found that bolted joints loaded in bearing exhibit rate sensitivity whereas bolts loaded in pull-through experience very little sensitivity, for nearly identical joint configurations. The primary focus of this paper was to use explicit finite element simulation of pull-through failure to shed light on discrepancies between experimentally observed rate sensitivity for seemingly similar tests. The paper uses the stacked-shell modelling approach to efficiently model the interaction of delamination and ply failure under the complex dynamic load state. The results of the simulation indicated that the properties of the interface susceptible to loading rate sensitivity, Mode I and II strain energy release rates (SERRs), did not have a great effect on the overall joint response; despite the prevalence of delamination during the failure process. A weak relationship between Mode II SERR and joint response was discovered which was consistent with experimental observations. [ABSTRACT FROM AUTHOR]

Leveling is a process used to minimize the bending defects in the steel industry. It plays an important role in delivering the desired material properties and product standards. This paper presents an analytical model for predicting the leveling process for H-beams with strong and weak axis bending defects. In this paper, an analytical model is first developed with the computational procedure of describing the continuous bending and reversed bending process, as well as the unloading process. Then, the developed analytical model and computational procedure are evaluated by a comparative study of results obtained from experimental data. Finally, the leveling process including curvature, trajectory, bending and residual stress distributions are evaluated for typical H-beam made of construction steel using the developed method. It is found that defective H-beam with different initial curvature tends to be flatted after the leveling process and the developed analytical model is much superior than finite element based modeling approach in terms of computational efficiency with the same level of accuracy. [ABSTRACT FROM AUTHOR]

This paper describes the numerical simulation of failure mechanisms of coated forming tools and explains the procedure of a finite element analysis (FEA) of the coating - substrate - system. The development of a static failure model is explained using the examples of thermally sprayed and amorphous carbon coatings. Furthermore, its implementation into the FE model is demonstrated. Sprayed thick coatings are used initially, the developed methods are then transferred to amorphous thin coatings. Necessary thermomechanical material properties, especially in the case of thin coatings, as well as system characteristics such as adhesion strength are insufficiently known. Together with FEA several techniques are employed to determine applicable model parameters using parameter identification. The paper only considers monolayers. In a first approximation both substrate and coating are considered homogeneous and isotropic. [ABSTRACT FROM AUTHOR]

This paper presents a model for the simulation of cracks in thin-walled structures using Trefftz-elements (T-elements) for crack tip regions. These elements are based on exact solutions to the governing differential equations and inner boundary conditions, resulting in high resolutions of the stress/strain fields. The T-elements are combined with standard elements using an extended variational principle. Beside this formalism the paper presents the derivation of particular solutions for a straight 2d-crack including a Dugdale strip-yield zone. The results are validated against high-resolution standard finite element simulations. Finally a crack propagation algorithm and some future enhancements are discussed. [ABSTRACT FROM AUTHOR]

This paper presents an investigation on the cause of severe vibration problem of a coach with four-cylinder engine running at an idle state using vibration and impact hammer modal experiments to obtain the main vibration frequency components and the natural characteristics of the coach. The vibration results indicate that the main vibration component comes from the vibration transmitted from the engine to the chassis frame, which is closely related with the engine idle speed. Based on structural simulation analysis of the coach's chassis frame and comparison with modal testing, the coach severe vibration problem was due to coupling resonance between the engine idle frequency and the fourth natural frequency of the chassis frame. The solution to eliminate the vibration problem is provided by changing the local structure stiffness of the chassis frame. The contribution of this paper lies in providing a solution to solve similar problems. [ABSTRACT FROM AUTHOR]

In this paper, the chemotaxis partial differential equations models which describe the movement by one community in reaction to one chemical or biological signal are given and solved numerically on surfaces. The models and the numerical method concerned are in terms of a generic form of chemotaxis models. We develop a new semi-implicit finite element scheme based on the gradient and Laplacian recoveries to linearize the equations. Meanwhile, we modify the proposed semi-implicit scheme as a characteristic form and present a novel strategy for the discretization of characteristic derivative on surface. The lumped mass modification is employed for positivity preservation. And the related analysis results are provided. We investigate the accuracy and convergence of the proposed method by numerical tests. And the simulations of blowing-up solution, pattern formulations and aggregations of bacteria demonstrate the applicability of the proposed methods. [ABSTRACT FROM AUTHOR]

Misalignment is a prevalent problem in rotor machinery. This paper proposes a numerical analysis for the mixed EHL of finite-line contacts considering tilting loads based on FEM. The Reynolds and linear elasticity equations, and Greenwood-Tripp contact model are coupled in an iterative process to solve the fluid-solid/solid-solid interaction under the compound external force and moment. Lubrication characteristics at both ends of the cylinder are analyzed and an asymmetric profile design scheme is presented to improve the lubrication performance at the cylinder's lower end. It is found that proper profile parameters can reduce EHL pressure by 40%, increasing the minimum oil film thickness by up to 100%, and thus reduce asperity contact pressure by up to 50%. • An FE model for the mixed EHL analysis of finite line contacts is developed. • The compound loading condition including the external force and moment is considered. • Lubrication characteristics of tilted finite line contact are analyzed and disclosed. • The asymmetric profile design scheme is proposed to improve lubrication performance. [ABSTRACT FROM AUTHOR]

Abstract: In the present paper the effect of graphite nodularity in the microstructure of cast iron is assessed with respect to its machinability at orthogonal cutting. A micro-structure based model of the cast iron material has been developed based on analyses of micro-graph images. The image analysis combines pearlitic grains with graphite nodules to produce the micro-structures. Continuous deformation behavior of pearlite and graphite phases is described using the Johnson–Cook (JC) viscoplasticty model including temperature dependence. Of particular concern is the modeling of the chip formation, induced by the micro-structure morphology and the mechanical behavior of the work piece material in the vicinity of the insert. This is described by the element deletion methodology along with the Johnson–Cook failure criterion to realize the fracture kinematics. A parametric study is carried out by varying the nodularity of the graphite. To validate the model, the finite element results are compared to machining test results carried out on a Compacted Graphite Iron (CGI) material in a related paper. It turns out that the FE-simulated and experimentally observed cutting force and chip formation compare fairly well. [Copyright &y& Elsevier]

Abstract: The present series of papers summarizes the results of a three-year research project on the realistic simulation of car audio sound in car passenger compartments using a combined Finite Element (FE) and Geometrical Acoustics (GA) approach. The simulations are conducted for the whole audible frequency range with the loudspeakers of the car audio system as the sound sources. The challenges faced during the project relate to fundamental questions regarding the realistic sound field simulation in small enclosures with strong modal and diffraction effects. The paper denoted here as Part I focuses on boundary and source representations in the FE and GA domain and suggests guidelines for a best-possible acquisition of the required data. Since a straight-forward determination of the boundary and source characteristics is mostly hampered by the immense complexity and inhomogeneity of the materials and loudspeaker configurations inside a car compartment, different measurement and calculation methods have been applied to determine the required data and quantify the corresponding uncertainty. The paper clearly points out the strength and weaknesses of the applied methods depending on the considered frequency range and material characteristics. In order to keep the complexity of the FE simulations at a manageable level, all passive boundaries were considered as locally reacting with impedance conditions. Part II of the study applies the obtained data in combined FE-GA room acoustic simulations and compares the simulated room impulse responses (RIR) with corresponding measurement results. In a final step the observed differences in the RIRs are related to the uncertainty and inherent errors in the boundary and source representation. [Copyright &y& Elsevier]

Abstract: The present series of papers summarizes the results of a three-year research project on the realistic simulation of sound fields in car passenger compartments using a combined Finite Element (FE) and Geometrical Acoustics (GA) approach. The simulations are conducted for the whole audible frequency range with the loudspeakers of the car audio system as the sound sources. The challenges faced during the project relate to fundamental questions regarding the realistic sound field simulation in small enclosures with strong modal and diffraction effects. While Part I of this series of papers focusses on the determination of the boundary and source conditions for the simulation model of the car compartment, the present paper, denoted here as Part II, presents extensive objective and subjective comparisons of the corresponding room acoustic measurement and simulation results. By applying the FE method to the low frequency part of the room transfer function (RTF) the study aims at the quantification of potential objective and subjective benefits with regard to the simulation quality in small rooms, when compared to a purely geometrical acoustics approach. The main challenges and limitations in the simulation domain are due to the very small volume, the difficult to determine source and boundary conditions and the considerable diffraction effects (especially at the seats) in the car passenger compartments. In order to keep the complexity of the FE simulations at a manageable level, all boundary conditions were described by acoustic surface impedances and no fluid-structural coupling was considered in the FE simulation model. While the results of the study reveal that an overall good agreement regarding the energy distribution in time and frequency domain is generally possible even in such complex enclosures, the results also clearly show the limitations of the impedance boundary approach in the FE domain as well as the strong sensitivity of the simulation results with regard to the uncertainty in the boundary and source conditions in both simulation domains. It can thus be concluded, that possible fields of application of the FE extension in room acoustic simulations lie in the prediction of the modally dominated low frequency part of the RTF of well defined rooms and in the prediction of sound fields that are strongly affected by near-field or diffraction effects as in the car passenger compartment. However, due to the considerable problems in the determination of realistic boundary conditions for the FE model, improved measurement techniques are urgently needed to further improve the overall simulation quality. [Copyright &y& Elsevier]

Abstract: In this paper the Particle Finite Element Method (PFEM) is applied to the simulation of the sea-landing of an unmanned aerial vehicle (UAV). The problem of interest consists in modelling the impact of the vehicle against the water surface, analyzing the main kinematic and dynamic quantities (such as loads exerted upon the capsule at the moment of the impact). The PFEM, a methodology well-suited for free-surface flow simulation is used for modelling the water while a rigid body model is chosen for the vehicle. The vehicle under consideration is characterized by low weight. This leads to difficulties in modelling the fluid–structure interaction using standard Dirichlet–Neumann coupling. We apply a modified partitioned strategy introducing the interface Laplacian into the pressure Poisson's equation for obtaining a convergent FSI solution. The paper concludes with an industrial example of a vehicle sea-landing modelled using PFEM. [Copyright &y& Elsevier]

Abstract: Streamer discharges are important both in theory and industry applications. This paper proposed a local discontinuous Galerkin method to simulate the convection dominated fluid model of streamer discharges. To simulate the rapid transient streamer discharge process, a method with high resolution and high order accuracy is highly desired. Combining the advantages of finite volume and finite element method, local discontinuous Galerkin method is such a choice. In this paper, a simulation of a double-headed streamer discharge in nitrogen was performed by using 1.5-dimensional fluid model. The preliminary results indicate the potential of extending the method to general streamer simulations in complex geometries. [Copyright &y& Elsevier]

Abstract: Electromagnetic tomography (EMT) has potential practical value in the fields of industrial and biomedical detection. The sensitivity, stability and accuracy of the sensor system are significant in the detection of EMT. In this paper, the EMT excitation condition is analyzed through the COMSOL Multiphysics finite element analysis software. The effects on a sensor array of 8 equally spaced inductive coils are discussed in terms of two effects: the direct effect on the received signals due to the change of the excitation condition and the effect of variations on the sensitivity, which is calculated through the received signals. The relationship between the exciting frequency and the received signal is discussed both in the simulation and the experiment; a multi-coil excitation strategy is proposed, and the comparisons are presented. The results clearly show that the higher exciting frequency led to the higher received signal. The selection of the excitation strategy should be considered based on the object field distribution, and it is necessary to increase the coil number for the multi-coil excitation strategy to obtain a better performance. This paper estimates the sensing field status according to the simulation results and provides a theoretical foundation for image reconstruction optimization. [Copyright &y& Elsevier]

Abstract: In this paper we present a twin adaptive strategy hp-HGS for solving inverse problems related to 3D DC borehole resistivity measurement simulations. The term “simulation of measurements” is widely used by the geophysical community. A quantity of interest, voltage, is measured at a receiver electrode located in the logging instrument. We use the self-adaptive goal-oriented hp-Finite Element Method (hp-FEM) computer simulations of the process of measurements in deviated wells (when the angle between the borehole and formation layers are < 90 deg). We also employ the hierarchical genetic search (HGS) algorithm to solve the inverse problem. Each individual in the population represents a single configuration of the formation layers. The evaluation of the individual is performed by solving the direct problem by means of the hp-FEM algorithm and by comparison with measured logging curve. We conclude the paper with some discussion on the parallelization of the algorithm. [Copyright &y& Elsevier]

Abstract: Chatter vibration is a major cause of limitations in increasing material removal rate in machining. Machining chatter is caused by the interaction between tool and work-piece. Various nonlinear phenomena in the machining process affect the occurrence of chatter. Finite element simulation of chip formation allows for incorporation of various factors in the chip formation process. It can therefore be used to simulate the occurrence of chatter in practical conditions and to predict the conditions that lead to stable cutting. In this paper, a one degree of freedom dynamic model of the cutting tool is used to simulate the interaction of machining dynamics with the thermo-mechanical chip formation in orthogonal conditions. In this way, the effects of various phenomena such as friction, plastic deformation, heat generation and process damping on the occurrence of chatter may be investigated. In particular, the effect of heat rise in the cutting zone is investigated in this paper, which has not been reported in the literature before. It is shown how rising the temperature in the cutting zone can affect occurrence of chatter. Simulation results are presented and stability lobe diagram is obtained from simulation. [Copyright &y& Elsevier]

Abstract: In this paper, three-dimensional (3-D) open cloaks were designed based on the coordinate transformation method. When the transformation center point is close to the boundary of the cloaks, the material parameter tensors in the near-boundary areas of the cloaks approximate to those in the background, so the near-boundary areas can be designed to be open. Full wave simulations based on finite element method verified the open cloaks we designed. Open cloaks can exchange information and materials with background media. Using the design method proposed in this paper, the boundary of open cloaks can be arbitrarily shaped, which greatly enhances the applicability of open cloaks. [Copyright &y& Elsevier]

Abstract Parameter-adaptive variational mode decomposition (VMD) has attenuated the dominant effect of prior parameters, especially the predefined mode number and balancing parameter, which heavily trouble the traditional VMD. However, parameter-adaptive VMD still encounters some problems when it is applied to the data from industry applications. On one hand, the mode number chosen using parameter-adaptive VMD is not the optimal. Numbers of redundant modes are decomposed. On another hand, parameter-adaptive VMD has much space for the improvement when it is applied to compound-fault diagnosis. To solve these issues and further enhance its performance, an improved parameter-adaptive VMD (IPAVMD) is proposed in this paper. Firstly, a new index, called ensemble kurtosis, is constructed by combining with kurtosis and the envelope spectrum kurtosis. It can simultaneously take the cyclostationary and impulsiveness into consideration. Secondly, the optimization objective function of grasshopper optimization algorithm is improved based on the ensemble kurtosis. The improved method chooses the mean value of the ensemble kurtosis of all modes rather than that of the individual mode as objective function. Thirdly, to extract all potential fault information, an iteration algorithm is used in the new method. Benefiting from these improvements, the proposed IPAVMD outperforms the traditional parameter-adaptive VMD and further expands the application to compound-fault diagnosis. It has been verified by a series of simulated signals and a real dataset from the axle box bearings of locomotive. Highlights • Benefiting from the proposal of ensemble kurtosis and new optimization objective function, IPAVMD can provide a better solution for the selection of VMD prior parameters. • IPAVMD can obtain the satisfying decomposition results with higher efficiency than the original parameter-adaptive VMD method. [ABSTRACT FROM AUTHOR]

Abstract Finite element models of biomedical applications increasingly use anisotropic hyperelastic material formulations. Appropriate material parameters are essential for a reliable outcome of these simulations, which is why planar biaxial testing of soft biological tissues is gaining importance. However, much is still to be learned regarding the ideal methodology for performing this type of test and the subsequent parameter fitting procedure. This paper focuses on the effect of an unknown sample orientation or a mistake in the sample orientation in a planar biaxial test using rakes. To this end, finite element simulations were conducted with various degrees of misalignment. Variations to the test method and subsequent fitting procedures are compared and evaluated. For a perfectly aligned sample and for a slightly misaligned sample, the parameters of the Gasser-Ogden-Holzapfel model can be found to a reasonable accuracy using a planar biaxial test with rakes and a parameter fitting procedure that takes into account the boundary conditions. However, after a certain threshold of misalignment, reliable parameters can no longer be found. The level of this threshold seems to be material dependent. For a sample with unknown sample orientation, material parameters could theoretically be obtained by increasing the degrees of freedom along which test data is obtained, e.g. by adding the data of a rail shear test. However, in the situation and the material model studied here, the inhomogeneous boundary conditions of the test set-ups render it impossible to obtain the correct parameters, even when using the parameter fitting method that takes into account boundary conditions. To conclude, it is always important to carefully track the sample orientation during harvesting and preparation and to minimize the misalignment during mounting. For transversely isotropic samples with an unknown orientation, we advise against parameter fitting based on a planar biaxial test, even when combined with a rail shear test. [ABSTRACT FROM AUTHOR]

Abstract In a hyper-connected society, IoT environment, markets are rapidly changing as smartphones penetrate global market. As smartphones are applied to various digital media, development of a novel smart product is required. In this paper, a Smart Product Design-Finite Element Analysis Process (SPD-FEAP) is developed to adopt fast-changing tends and user requirements that can be visually verified. The user requirements are derived and quantitatively evaluated from Smart Quality Function Deployment (SQFD) using WebData. Then the usage scenarios are created according to the priority of the functions derived from SQFD. 3D shape analysis by Finite Element Analysis (FEA) was conducted and printed out through Rapid Prototyping (RP) technology to identify any possible errors. Thus, a User Customized Smart Keyboard has been developed using SPD-FEAP. Graphical abstract Image 1 Highlights • Quantitative and qualitative analysis of user requirements. • 3D shape analysis by FEA. • User customized smart keyboard verification via RP. [ABSTRACT FROM AUTHOR]

Molecular Communications is a research area which combines the expertise of two main fields of science: biology and engineering. This multidisciplinarity, in addition to being a fruitful strength, makes knowledge exchange between researchers difficult. This issue has led to the definition of a new markup language, named Molecular Communication Markup Language (MolComML). It contributes to the harmonization of cross-disciplinary research activities. By leveraging the typical flexibility of markup languages, it specifies the essential components of generic molecular communication scenarios, by combining both numerical analysis and experimental synthesis. In this paper we illustrate the architecture of MolComML and focus on its peculiarities that allow describing molecular communications systems. In addition, we evaluate the performance of some molecular communication systems by using different simulation packages, configured by using the MolComML, in order to demonstrate both its portability and the possibility of combining different platforms for creating complex simulation tools. [ABSTRACT FROM AUTHOR]

Abstract: The system of equations arising in finite element simulations of components made of ferroelectroelastic materials is non-linear if the loading is sufficiently high. The Newton–Raphson method represents a widely used iterative technique to solve this system of non-linear equations. However, if the scalar potential formulation is utilised, convergence difficulties may occur. This circumstance can be primarily attributed to the specific form of the non-linear response of typical ferroelectroelastic materials being subjected to electrical loading. The present paper is devoted to modifications of the Newton–Raphson method, which are capable of improving the convergence behaviour experienced in the finite element iteration. We extend an existing modification to the fully coupled, ferroelectroelastic case. Additionally, a new modification of the Newton–Raphson method is proposed. This method applies an iteration algorithm, which is virtually equivalent to the iteration algorithm of the unmodified Newton–Raphson method combined with the vector potential formulation. An important feature of both modifications is that they are applied on the integration point level. Therefore, the global non-linear finite element iteration scheme remains unchanged. Finally, the practicability of the modifications discussed in the paper is shown in a numerical example. [Copyright &y& Elsevier]

Abstract: During the well publicised Cardington structural fire research programme, parts of some connections suffered fracture during cooling. This led some to believe that fire spread and structural collapse may occur during the cooling stage of a fire and therefore this issue should be considered in structural fire engineering design. This paper focuses on steel framed structures using concrete filled tubular (CFT) columns and the objective of this paper is to find means of reducing the risk of structural failure during cooling. It reports the results of a study using the general finite element software ABAQUS to numerically model the behaviour of restrained structural subassemblies of steel beam to CFT columns and their joints both in fire, emphasising on the cooling stage. Validation of the finite element model was achieved by comparing the simulation and test results for the two fire tests investigating cooling behaviour, recently conducted at the University of Manchester on similar structures. In these two tests, the test assembly was heated to temperatures close to the limiting temperature of the steel beam and then cooled down while still maintaining the applied loads on the beam. One of the tests used reverse channel connection and the other test used fin plate connection. The finite element models give very good agreement with the experimental results and observations. Remarkable differences in tensile forces in the connected beams were observed during the tests depending on the beam temperature at which cooling started. This leads to the suggestion that in order to avoid connection fracture during cooling, it may be possible to reduce the limiting temperature of the connected beam by a small value (<50°C) from the limiting temperature calculated without considering any axial restraints in the beam. [Copyright &y& Elsevier]

Abstract: This paper presents a computational microstructure model to predict the fracture-related behavior of heterogeneous and viscoelastic bituminous paving mixtures. In addition to the consideration of the complex geometric characteristics and viscoelastic behavior of the mixture, this study implements a rate-dependent cohesive zone model into the mainframe of ABAQUS in the form of a customized user element (UEL) subroutine. This enables model fracture as a gradual and rate-dependent phenomenon in which the initiation and propagation of discrete cracks take place in the mixture microstructure. In order to validate the model, experimental programs are developed for model inputs and outputs, and microstructural simulations of a two-phase mixture specimen are conducted. Model simulation results agree well with test results. The results presented in this paper imply that a computational microstructure model such as the one herein can be an efficient tool to estimate the effects of small-scale design variables on overall mixture performance with significant savings in experimental costs and time. [Copyright &y& Elsevier]