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An epiretinal membrane (ERM) is a fibrocellular proliferation on the inner surface of the retina causing blurred and distorted central vision. Surgery is the only effective method for ERM removal. This paper investigated the mechanical properties of ERM peeling using the finite element (FE) method. A FE model of ERM formation on the retina surface was constructed. The failure criterion was applied to the attachment pegs to represent the adhesive force between the ERM and retina. The simulation results were consistent with the experimental data in published research. The maximum peeling force was 4.1 mN at a peeling velocity of 2 mm/s and an angle of 30°. The peeling force was minimum at the peeling angle of 45° and increased with the increase in peeling velocity and Young's modulus of the membrane. The outcome of this paper can improve the safety and efficiency of ERM removal. [ABSTRACT FROM AUTHOR]

The bone lacunar-canalicular system (LCS) is a unique complex 3D microscopic tubular network structure within the osteon that contains interstitial fluid flow to ensure the efficient transport of signaling molecules, nutrients, and wastes to guarantee the normal physiological activities of bone tissue. The mass transfer laws in the LCS under microgravity and hypergravity are still unclear. In this paper, a multi-scale 3D osteon model was established to mimic the cortical osteon, and a finite element method was used to numerically analyze the mass transfer in the LCS under hypergravity, normal gravity and microgravity and combined with high-intensity exercise conditions. It was shown that hypergravity promoted mass transfer in the LCS to the deep lacunae, and the number of particles in lacunae increased more significantly from normal gravity to hypergravity the further away from the Haversian canal. The microgravity environment inhibited particles transport in the LCS to deep lacunae. Under normal gravity and microgravity, the number of particles in lacunae increased greatly when doing high-intensity exercise compared to stationary standing. This paper presents the first simulation of mass transfer within the LCS with different gravity fields combined with high-intensity exercise using the finite element method. The research suggested that hypergravity can greatly promote mass transfer in the LCS to deep lacunae, and microgravity strongly inhibited this mass transfer; high-intensity exercise increased the mass transfer rate in the LCS. This study provided a new strategy to combat and treat microgravity-induced osteoporosis. [ABSTRACT FROM AUTHOR]

Phase change material (PCM) mixed in soil can effectively adjust the subgrade temperature. In order to analyze the temperature field change of soil containing PCM more accurately from the microscopic point of view, it is a key problem to construct a refined geometric model. This paper scans the fracture plane of soil containing PCM through the stereoscopic microscope and prepares the label image corresponding to the sample image. Then a U-Net semantic segmentation model is established, which can accurately recognize PCM area and soil area. Finally, a geometric model of soil containing PCM that is consistent with reality is established, and its heat transfer characteristics are analyzed by finite element method. The accuracy evaluation of the segmentation model and the visualization of the recognition results show that the evaluation indexes of U-Net are the best. P, R, F1, and MIoU of U-Net are 0.889, 0.918, 0.903, and 0.901, respectively. The refined model established in this paper can not only observe the overall temperature regulation effect of the material but also accurately describe the internal temperature distribution details of soil containing PCM during heat transfer. Through numerical simulation, it is found that the maximum temperature of mixture decreases by 1.6 °C and the minimum temperature of mixture increases by 2.3 °C. [ABSTRACT FROM AUTHOR]

The behavior of steel bolted connections is a complex structural problem which involves various factors such as material nonlinearity, large deformation and contact. The investigation of this behavior is one of challenging subjects in structural analyses. Unlike other structural modelling, the connections of bolted structures involve a large number of contacts, which are critical to the behavior of the joints. This paper focuses on investigating the behavior of a type of the external diaphragm which is used in rectangular hollow section column-to-beam bolted connections. The creation of a reliable finite element model is a primary aim of this research. The ABAQUS finite element package is used to simulate the experimental behavior, and three highly complex 3D finite element models are created, accounting for material nonlinearly, large deformation and contact behavior involved in the models. The connection models have been analyzed under some loading conditions up to failure. Comparisons with experimental data show that the models have high levels of accuracy, and these models may be used to gain an insight into important issues such as the connection tying force capacity of an external diaphragm, bolt and plate bearing behavior, and bolt shearing. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to address a class of hybrid optimal control problems constrained with hyperelasticity and constant global volume. This type of problems can intervene for example in the mechanical aspects of cardiac activity. The time deformation of the heart tissue is modeled with the elastodynamics equations dealing with the displacement field as main unknown. These equations are coupled with a pressure whose time variations are aimed to be maximized. This pressure variable corresponds to a Lagrange multiplier associated with the so-called global injectivity condition, translating the fact that the total volume of the domain remains constant. We develop an optimal control approach in a general framework that covers in particular the maximization of the variations of this pressure, and also the time the maximum is reached, defining what we call a hybrid optimal control problem. Mathematical analysis based on the $ \mathrm {L}^p $ Lp-parabolic maximal regularity is provided for the state equations and the rigorous derivation of optimality conditions. Numerical simulations for a toy-model illustrate the capacity of the approach. [ABSTRACT FROM AUTHOR]

This paper examines the dynamic performance of the pantograph passing through an overlap section of the catenary system, using a China's high speed railway with the 4-span overlap as an example. The pantograph and catenary system are simulated as a lumped mass model and finite element model, respectively. The model is verified according to EN50318:2018. The model is also assessed against an experimental study of the contact force and uplift of contact wire at 300 km/h. Then the contact force and uplift of contact wire at the speed of 150–350 km/h are calculated. The research shows that when the pantograph passes through the overlap, the maximum contact force increases beyond 14%, the standard deviation of the contact force increases by more than 26%, and the increase of the vertical displacement exceeds 38%, which becomes more apparent with the increase of speed. Under the influence of aerodynamic force, when the running speed increases from 150 to 350 km/h, the mean contact force in the knuckle-downstream and knuckle-upstream orientation increase by 59.49% and 97.85%, respectively. As a result, the contact force and vertical displacement increase greatly when passing through the overlap section, which could affect the current collection quality. [ABSTRACT FROM AUTHOR]

In this work, the results of a detailed art technological investigation of the icon Last Supper from the Russian Memorial Church in Leipzig (Germany) are presented. The icons of the iconostasis of the church were made in the workshop of N.S. Emelyanov in Moscow in 1912. The investigation showed that the painter in principle technologically adhered to the traditional way of making icons. The panel is made of boards of lime wood with two crossbars on the reverse. The paint was applied to a chalk ground over a textile layer. The traditional iconographer's palette was expanded by a few contemporary pigments. The binding agent is classic egg tempera. Originally, the layers of paint had an oil varnish (olifa). The main aim of the project VirtEx, introduced in this paper, is to expand existing methods with numerical material and structural models to be able to predict quantitatively the behaviour of wooden artefacts under loads due to climate changes as well as mechanical loads. The detailed art technological investigation provides the required data for the computer models. The numerical data can then be validated with technologically exact copies and replicas. In the introduction to the article, the current state of research on icon painting techniques is also outlined. [ABSTRACT FROM AUTHOR]

Pile safety has received increasing attention in marine engineering, especially in the field of local scour. In this paper, a finite element numerical model is established for local scour around a cylinder in steady currents. The flow is described by unsteady Reynolds–averaged Navier–Stokes equations with a traditional k − ε turbulent closure model. The proposed scour model takes bed load into account. The Exner equation is solved to determine the bed variation and the moving mesh approach is used to capture the evolution of the bed. When the resulting slope exceeds the angle of repose, a novel sand-slide model based on Rodrigues' rotation formula is used to prevent simulation distortion. All the equations are discretized by the two-step Taylor–Galerkin algorithm, and the resulting approach is fast to implement with second-order accuracy in space. The numerical results are found to be in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

In this paper, an efficient numerical scheme is proposed to simulate the high-frequency dynamic mechanical response of single-crystalline Ni–Mn–Ga samples. First, based on a three-dimensional setting, the governing equation system for a single-crystalline Ni–Mn–Ga sample is set up, which is composed of the equation of motion and the twin interface movement criteria. In order to solve the governing system, an iterative numerical algorithm is proposed, in which the finite element method and the NewMark-β method are applied. To demonstrate the efficiency of this numerical scheme, the response of a single-crystalline Ni–Mn–Ga sample under some typical loading conditions are studied. In the numerical simulations, a specific discretisation of the sample is adopted, such that the possible positions of the twin interfaces in the sample can be naturally inherited. With the obtained numerical results, the mechanical behaviours of the sample under the different loading conditions are predicted, which show good consistency with the experimental results. The distribution of variant state and the propagation of twin interfaces in the sample can also be simulated. The numerical scheme proposed in the current work is helpful for the design of novel sensors or actuators based on single-crystalline Ni–Mn–Ga alloys. [ABSTRACT FROM AUTHOR]

Catenaries are large cable structures which transmit electric current to trains through sliding contact with a pantograph. The finite element method is widely used to model this dynamic interaction problem and obtain the contact force between the pantograph and the catenary. As an alternative, analytical models can also be used to study catenary dynamics, although they require certain simplifications of the features considered in numerical models. In this paper, an analytical model composed of an infinite string and a visco-elastic support is introduced and enhanced by considering a Kelvin-Voigt damping model and the initial height of the contact wire. Considering the finite element (FE) model as a reference, the analytical model parameters are properly adjusted through static and wave propagation analyses to achieve similar behaviour in both the analytical and the FE models. To check the performance of the proposed model, the steady-state response of the pantograph–catenary coupled system is calculated and compared with the results of the FE model. Finally, the analytical model is used to analyse the interference phenomenon produced during two-pantograph operation. [ABSTRACT FROM AUTHOR]

In order to accurately use numerical analysis results to evaluate seismic performance, a quantitative relationship between the parameters of the ideal finite element model (FEM) and full-scale test model (FTM) of historic timber structures must be established. In this study, a single-story full-scale timber structure with four columns and Dou-gongs that was common during the Song dynasty of China (A.D. 960–1279) was taken as the object, and pseudo-static test (or simulation) analysis was carried out on the FTM and the corresponding FEM. The numerical model was consistent with the test model in terms of the structural deformation pattern and stress characteristics of the key nodes. The key-point loads of the skeleton curves, stiffness ratio, ductility coefficient, and stiffness relationship were quantitatively established for the two models. Accordingly, approximate formulas for the above relationships were proposed. [ABSTRACT FROM AUTHOR]

There has been a systematic review of studies that used FEA in dental sciences, but no adequate risk of bias (RoB) analysis technique has been developed. Therefore, the development and validation process of RoB in studies using the finite element analysis in dentistry (ROBFEAD) tool is described. In the first phase of development, the scope of the tool and possible modifications were covered, and validation was done in the second phase. The developed tool comprised 6 domains and a total of 22 guiding questions in these domains. This article proposes the development and validation of ROBFEAD, a tool for measuring RoB in finite element research in dentistry. [ABSTRACT FROM AUTHOR]

This study is proposed for the numerical simulation of the peristaltic mechanism using the finite element method with the Galerkin residual technique to explore peristaltic transportation under the action of an externally applied magnetic field passing through an inclined asymmetric channel saturated with porous media. The Navier-stokes equations are solved for the peristaltic mechanism non-linearly by the exemption of lubrication theory to study the inertial effects. The numerical simulations and results are obtained by applying the finite element method based on quadratic triangular elements. It is observed that pressure rise per wavelength is enhanced by increasing the angle of inclination 0.8 ≤ Q ≤ 1.4. [ABSTRACT FROM AUTHOR]

In this work, we study a new thermoelastic model with two temperatures from the numerical point of view. The problem is written as a coupled linear system whose unknowns are the displacement field and the conductivity and thermodynamic temperatures. An existence and uniqueness result recently proved is recalled. Then, a fully discrete approximation is introduced by using the finite element method and the classical implicit Euler scheme. A main a priori error estimates result is proved and, under some appropriate regularity conditions on the continuous solution, we obtain the linear convergence. Finally, some numerical simulations are presented to demonstrate the numerical convergence and the discrete energy decay. [ABSTRACT FROM AUTHOR]

When a penstock serves a water supply purpose for multiple hydrogenerators in a hydroelectric power plant (HPP), a bifurcation structure should be installed between the main pipe and the branch pipes. This study focuses on a rib-strengthened steel bifurcation structure (RSSBS) with an emphasis on its hydraulic load-bearing mechanism. The finite element method is used with the contact and material non-linearities considered. The numerical simulation results agree reasonably well with in-situ measured data. Our research has underlined the critical role of the crescent-shaped rib (CSR) in lessening the stress-concentration at the bifurcation. The CSR is found to separate from the surrounding concrete under the internal water pressure (IWP), thus causing less IWP to be transmitted to the concrete. Despite the fact that the CSR is not in tension-stress-only status, however, the tensile-stress level is well within an acceptable range. In this context, the CSR should not necessarily be in tension-stress-only status, which is recognized as an ideal stress state in the conventional design philosophy. The findings also suggest that the importance of the concrete should not be stressed too much in the structural design of RSSBSs considering its backfilling role. The role of the crescent-shaped rib in strengthening local stiffness is underlined. The rib is found to separate from the concrete under the internal water pressure. The simulation results agree reasonably well with in-situ measured data. [ABSTRACT FROM AUTHOR]

The modelling and simulation of forging has reached a matured stage, but the friction and friction models got only scant attention; this work intends to fill up that gap. Here, arbitrary Lagrangian-Eulerian (ALE) finite element method (FEM)-based numerical simulations are carried out for the forging of aluminium workpiece by considering two friction models – Coulomb-Siebel and Tresca. A relation between Coulomb's coefficient of friction and friction factor has been established based on the slab method. The forging load is obtained by calculating the reaction force on the die as well as from energy method. Energy method provides more accurate and consistent results. Forging load and bulge increase with the friction, but at high friction, the effect is minimal. Bulge is found to be more sensitive to friction than the forging load. The distribution of normal stress is quite different on the die-workpiece interface compared to that on a parallel plane in the interior. The phenomenon of fold-over observed at high friction and high reduction observed in a Lagrangian formulation is absent in ALE formulation. The fold-over phenomenon occurs due to mesh distortion. It is not observed in a workpiece with round corners, even while using Lagrangian formulation. [ABSTRACT FROM AUTHOR]

The mobility of pelvic organs is the result of an equilibrium called Pelvic Static characterizing the balance between the properties and geometries of organs, suspensions and support system. Any imbalance in this complex system can cause of pelvic static disorder. Genital prolapse is a common hypermobility pathology which is complex, multi factorial and its surgical management has high rate of complications. The use of 3 D numerical models and simulation enables the role of the various suspension structures to be objectively studied and quantified. Fascias are connective tissues located between organs. Although their role are described as important in various descriptions of pelvic statics, their influence and role has never been quantitatively objectified. This article presents a refine Finite Element (FE) model for a better understanding of biomechanical contribution of inter-organ fascia. The model is built from MRI images of a young volunteer, the mechanical properties derived from literature data to take into account the age of the patient and new experimental results have enabled an order of magnitude of the mechanical properties of the fascias to be defined. The FE results allows to quantify the biomechanical role of the fascia on pelvic mobility quantified by an analysis of dynamic MRI images and a local mapping of the gap between calculated and measured displacements. This improved numerical model integrating the fascias makes it possible to describe pelvic mobilities with a gap of 1 mm between numerical simulations and measurements, whereas without taking them into account this gap locally reaches 20 mm. [ABSTRACT FROM AUTHOR]

To investigate the temperature field of the surface of AlSi10Mg(Fe) with the aluminum oxide layer being removed using pulse laser, the physical model of composite material of aluminum oxide, removed using pulse laser, and aluminum alloy is established by using COMSOL Multi-physics, which calculates the temperature field and the removal effect in the case of different laser scanning linear velocity and laser energy density by solving thermo-physics equations. The influence of different laser parameters on the removal effect is also discussed. Based on the simulation and experiment, it shows that the aluminum oxide removal effect peaks in the case of 15 j/cm2 for laser energy density. [ABSTRACT FROM AUTHOR]

When the fracture normal forms an angle relative to the borehole axis, the induction logging response to the fractured formation consists of two contributions: one is the volume contribution caused by the eddy current, and the other is the charge contribution caused by the cumulative charges on the upper and lower boundaries of the fracture; both contributions are nonlinear. Researching the distribution of surface charges and eddy current in inclined fractured formations is of great significance for logging analysts and geologists to fully understand induction logging laws in such setting. However, there is insufficient research on this aspect. In this work, first, an electromagnetic field calculation method under the condition of existing cumulative charges at the interfaces was developed. Second, an induction logging numerical simulation model of inclined fractures based on the three-dimensional (3D) finite element method (FEM) was established, and the distribution laws of cumulative charges and eddy current in fractures under different dip angles were summarised. Third, we used the annular conductive region in the fracture as the object of our research, and analysed the influence law of different conductive regions distribution on induction logging. Finally, we carried out physical experiments to verify the numerical results and achieved good agreement between the two results. Hence, it proves the validity of the methods and conclusions. [ABSTRACT FROM AUTHOR]

To improve the understanding of wheel/rail contact behaviour and damage mechanisms in turnouts, the 3D explicit finite element model of a wheelset rolling over a switch is introduced. This takes into account the arbitrary geometrical profile of the wheel-rail system, the relative motion between switch/stock rail, the nonlinear materials and actual moving postures of the wheelset. Precise frictional rolling contact solutions and dynamic response, including contact stress, surface shear stress, microslip, roll angle and lateral displacement, are all studied to obtain a better understanding of the wheel-rail frictional rolling contact behaviour in the switch panel. The simulated results are then verified through field tests on the Qingdao-Jinan line. The results indicate that the proposed explicit finite element method can be an efficient tool for solving the problems of frictional rolling contact behaviour and damage mechanism in switch panels. [ABSTRACT FROM AUTHOR]