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The study of multibody systems with elastic elements involves at the moment the reevaluation of the classical methods of analysis offered by analytical mechanics. Modeling this system with the finite element method requires obtaining the motion equation for an element in the circumstances imposed by a multibody system. The paper aims to present the main analysis methods used by researchers, to make a comparative analysis, and to show the advantages or disadvantages offered by different methods. For the presentation of the main methods (namely Lagrange's equations, Gibbs–Appell's equations, Maggi's formalism, Kane's equations, and Hamilton's equations) a unified notation is used. The paper provides a critical evaluation of the studied applications that involved some of these methods, highlighting the reason why it was decided to use them. Also, the paper identifies potential research areas to explore. [ABSTRACT FROM AUTHOR]

Due to ethical issues and the very fine and complex structure of the cochlea, it is difficult to directly perform experimental measurement on the human cochlea. Therefore, the finite element method has become an effective and replaceable new research means. Accurate numerical analysis on human ear using finite element method can provide better understanding of sound transmission and can be used to assess the influence of diseases on hearing and to treat hearing loss. In this research, a three-dimensional (3D) finite element model (FEM) of the human ear of cochlea was presented to investigate the destruction of basilar membrane (BM), round window (RW) sclerosis and perilymph fistula, the key structures of the cochlea, and analyze the effects of these abnormal pathological states in the cochlea on cochlear hearing, resulting in the changes in cochlear sense structure biomechanical behavior and quantitative prediction of the degree and harm of the disorder to the decline of human hearing. Therefore, this paper can deepen reader's understanding of the cochlear biomechanical mechanism and provide a theoretical foundation for clinical otology. [ABSTRACT FROM AUTHOR]

The paper addresses the issue of local buckling of compressed flanges of cold-formed thin-walled channel columns and beams with nonstandard flanges composed of aluminium alloys. The material behaviour follows the Ramberg–Osgood law. It should be noted that the proposed solution may be also applied for other materials, for example: stainless steel, carbon steel. The paper is motivated by an increasing interest in nonstandard cold-formed section shaping in local buckling analysis problems. Furthermore, attention is paid to the impact of material characteristics on buckling stresses in a nonlinear domain. The objective of the paper is to propose a finite element method (FEM) model and a relevant numerical procedure in ABAQUS, complemented by an analytical one. It should be noted that the proposed FEM energetic technique makes it possible to compute accurately the critical buckling stresses. The suggested numerical method is intended to accurately follow the entire structural equilibrium path under an active load in elastic and inelastic ranges. The paper is also focused on correct modelling of interactions between sheets of cross section of a possible contact during buckling analysis. Furthermore, the FEM results are compared with the analytical solution. Numerical examples confirm the validity of the proposed FEM procedures and the closed-form analytical solutions. Finally, a brief research summary is presented and the results are discussed further on. [ABSTRACT FROM AUTHOR]

The aim of this paper is to determine the optimum amount of carbon fiber-reinforced polymer (CFRP) for strengthening columns in reinforced concrete (RC) frames suffering from weak column/strong beam condition. In this study, several parameters affecting the behavior of these frames including the level of columns' axial force, Length and thickness of CFRP laminates are analyzed numerically. Nonlinear static analyses, employing three-dimensional finite element models are performed by an implicit method on 98 model frames having different length and thickness of CFRP and axial load. The results revealed improvements in both strength and ductility of the system when the columns of higher axial load were strengthened; while in strengthening of the columns under lower levels of axial load, the influence of CFRP was only observed in the strength of the system. An optimization method which takes into account the cost of the utilized material and the strength of the system was proposed, and the optimum CFRP length and thickness were determined. [ABSTRACT FROM AUTHOR]

In recent years, a lot of progress has been made in the field of material modeling with artificial neural networks (ANNs). However, the following drawbacks persist to this day: ANNs need a large amount of data for the training process. This is not realistic, if real world experiments are intended to be used as data basis. Additionally, the application of ANN material models in finite element (FE) calculations is challenging because local material instabilities can lead to divergence within the solution algorithm. In this paper, we extend the approach of constrained neural network training from [28] to elasto-plastic material behavior, modeled by an incrementally defined feedforward neural network. Purely stress and strain dependent equality and inequality constraints are introduced, including material stability, stationarity, normalization, symmetry and the prevention of energy production. In the Appendices, we provide a comprehensive framework on how to implement these constraints in a gradient based optimization algorithm. We show, that ANN material models with training enhanced by physical constraints leads to a broader capture of the material behavior that underlies the given training data. This is especially the case, if a limited amount of data is available, which is important for a practical application. Furthermore, we show that these ANN models are superior to classically trained ANNs in FE computations when it comes to convergence behavior, stability, and physical interpretation of the results. [ABSTRACT FROM AUTHOR]

Two-phase, brittle-hard materials are widely used not only in the tool industry but also increasingly in the aerospace industry. Due to the two-phase nature, the materials have unique material properties adapted to the respective application. But the material properties also lead to challenging machinability. Therefore, two-phase, brittle-hard materials are mostly ground. The analogy process of single-grain scratching is used to analyse the material removal behaviour and design the grinding process. Since single-grain scratching is time-consuming and costly, it is desirable to substitute the analogy process with numerical simulation. This paper discusses the suitability of the Smooth Particle Hydrodynamic (SPH) simulation method in combination with the Finite Element Method (FEM) for single-grain scratching of two-phase, brittle-hard materials. The approach is validated using the examples of tungsten carbide-cobalt (WC-Co) cemented carbides and Silicon carbide fibre-reinforced silicon carbide (SiC/SiC) ceramics. For both applications, the material removal behaviour was optically analysed and in good agreement with the experimental results and theoretical assumptions. For SiC/SiC ceramics, several surface phenomena could be identified in the simulation as well as in the experimental results. The scratching forces were compared qualitatively and were in good agreement with the experimental results for both applications. [ABSTRACT FROM AUTHOR]

In this paper, we study and analyze the time fractional Ginzburg–Landau equation (FGLE) using finite element methods (FEMs) in space and L1 scheme in time. The unconditional optimal L 2 -norm error estimates are obtained based on the time-space error splitting technique. Using the relation between interpolation operator and Ritz projection operator, we obtain the superclose results in H 1 -norm. Furthermore, the global superconvergence results are established through the interpolation postprocessing technique. To overcome the weak singularity of the solution at the initial time and improve the computational efficiency, we adopt the nonuniform L1 scheme in the time direction and built corresponding fast algorithm based on sum-of-exponential technique. Finally, we provide several numerical experiments to verify the theoretical results and demonstrate the advantages of the fast algorithm. [ABSTRACT FROM AUTHOR]

Machine hammer peening (MHP) is a novel surface modification process that can strengthen and smoothen the treated parts in one process, significantly improving their fatigue performance. The strengthening effect is mainly due to the induced highly controllable residual compressive stress on the subsurface. However, the residual compressive stress induced by MHP is usually anisotropic, with the component perpendicular to the feed direction more significant than parallel. The anisotropic residual stress will have an adverse effect if the treated parts are subjected to multiaxial loads, which puts forward high demands to precisely tune such anisotropy. For this purpose, a finite element model with a velocity-based driving mode is first established in this paper, which can simulate the residual stress induced by MHP. The origin of the anisotropy is then revealed by analyzing the evolution of the simulated residual stress. Based on this, methods to precisely tune the residual stress anisotropy are proposed. The residual stress anisotropy can be precisely tuned by optimizing MHP parameters, including the overlap ratio, impact velocity, and MHP path. [ABSTRACT FROM AUTHOR]

In this paper, an ultra-compact electrochemical metallization–based tunable filter with a simple metal–insulator–metal (MIM) waveguide system was proposed. The device comprises a MIM waveguide and a resonator with active electrodes. The formation and rupture of conductive filaments in the resonant cavity because of electrochemical metallization can change the resonant wavelength, which leads to the tunability of the transmission characteristics of the filter. The transmission characteristics of band-stop filter and band-pass filter are analyzed by finite element method (FEM) simulation. Numerical results demonstrate that the transmission line of the filter can be shifted by forming and rupture of the conductive filament, which is controlled by changing the applied electric field in the case of fixed structural parameters. The proposed compact tunable filter is a potential candidate for a low power consumption large-scale integrated photonic circuit for applications in optical communication, modulation, and computation. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to propose a critical assessment of Young’s modulus determination of coated materials using Impulse Excitation Technique (IET). In this technique, the coated substrate is excited by an impulse and the acoustic vibrations are recorded. The frequency of the first bending mode is then used in a mechanical model to obtain the Young’s modulus of the coating. The existing models are based on two different theories: the flexural rigidity of a composite beam and the Classical Laminated Beam Theory (CLBT). The aim of the present paper is to assess the accuracy (trueness and precision) of the technique. For this, different models proposed in the literature are compared with a finite element model of the specimen for various conditions. The trueness and precision of models were evaluated and the best model was identified. Then a detailed uncertainty budget is performed to identify and quantify the most influent factors on the global uncertainty. [ABSTRACT FROM PUBLISHER]

The alternating current (AC) loss is a key consideration of the operation economy and stability of the high temperature superconducting (HTS) cables. In this paper, the sources of the AC loss in the HTS cable are analyzed firstly. The three-phase HTS cable, adopted in the 35 kV km-level HTS cable demonstrating project in Shanghai, China, is modeled by the finite element method (FEM) to calculate the AC loss by the COMSOL Multiphysics. The AC loss of the designed 35 kV HTS cable is 1.31 W/m. The theoretical calculation method is also implemented to verify the modeling results. Furthermore, considering the on-site conditions of the demonstrating project in Shanghai, China, the calorimetric method is conducted by measuring the temperature difference between the inlet and outlet of liquid nitrogen. The obtained results provide useful indications for the future design and research of HTS AC systems. [ABSTRACT FROM AUTHOR]

In this paper, a fatigue crack growth (FCG) behavior under variable amplitude loadings and for mixed modes is analyzed in terms of residual compressive stress zone. For that, the Chaboche non-linear kinematic hardening model is used to evaluate the crack behavior on AA2024-T3. At first, a series of FCG simulation is performed for a single edge notched tension specimen to highlight the influences of the crack length, the overload ratio, the stress ratio, the mean stress, the mixed mode, and the load sequence on the crack tip residual -stress zone under variable amplitude loadings. Besides, the size and shape of crack tip residual-stress zone are simulated for low/high, high/low block loadings and with/without overloads. Moreover, and according to the findings, a FCG code using the Python script and the extended finite element method (XFEM) Is improved. The developed code processes FCG behavior under variable amplitude loadings using the shape of residual stress distribution near the crack tip. The predicted results show a good agreement in simulating fatigue crack path under variable amplitude loadings with those published in the literature. The originality of this study is to simulate the fatigue crack path of cracked structures under variable amplitude loadings with the compressive residual stress model coupled with the XFEM for mode I and different mixed mode. [ABSTRACT FROM AUTHOR]

Dams play an essential role in water storage and supply, and ensuring their safety is of utmost importance. The presence of fissured soil poses a common engineering challenge in dam construction, as it has the potential to cause instability and failure. The study described in this paper employs numerical analysis to explore the impact of fissured soil on dam stability. The finite element method (FEM) software OPTUMG2 is utilized for this investigation. A 2D plane strain model of a dam was created and analyzed for different angles of fissured material. The first angle, α1, varied from 0° to 90° in 15° increments, while the second angle, α2, varied from 95° to 180° in 15° increments, additionally, we explore the combined effects of these angles (α1 with α2) to comprehensively assess the impact of fissured material on dam stability. The findings indicated a notable influence of the orientation of fissured planes on dam stability. Factors such as the factor of safety, slope surfaces, displacements, and deformations exhibited variations based on the specific orientation of the fissured material. Broadly, dams featuring fissured planes oriented closer to the vertical demonstrated greater stability compared to dams with fissured planes oriented closer to the horizontal. This research offers valuable insights into the impact of fissured soil on the stability of dams. The results can be used to develop better design and construction practices for dams in fissured soil areas. [ABSTRACT FROM AUTHOR]

Purpose: Acoustic multi-connected domains are common in floating platforms and underwater vehicles. In order to improve the calculation efficiency of the traditional boundary element method and avoid dealing with complex connected domain boundary conditions, a method combining finite element method with artificial boundary element method is proposed to calculate the acoustic scattering of multi-domain structures. Methods: In this work, based on near-field artificial boundary, the multi-domain fluid is divided into simple exterior domain and complex multi-connected interior domain. The FEM of Software Nastran is easy to employ for structures and complex multi-domain fluids. The artificial boundary element method is used to generate the exterior added fluid mass, added fluid damping and pressure load associated with incident wave. The codes developed by the author and DMAP language are used to generate the matrixes and to couple the FEM with artificial BEM. Results: The correctness and convergence of the proposed numerical method are further investigated. The simulation results are in good agreement with theoretical data and literature results. When the scale of the artificial boundary element is less than one tenth of the wavelength of sound wave, the calculated solutions tend to be stable. In the case of cavity scattering, compared with the traditional boundary element method, the calculation time of proposed method is reduced by nearly half with the same calculation accuracy. Conclusion: Furthermore, the numerical method presented in this paper can solve scattering problems involving fluid spheres, bubbles, and multi-body structures, as well as the reflection of free water surfaces. [ABSTRACT FROM AUTHOR]

Usually, the viscoelastic (VE) response of polymers for applications in composites is obtained in uniaxial strainor stress-controlled tests. However, analyzing multimaterial structures by the Finite Element Method (FEM) or by other numerical or analytical tools, a material model in terms of a complete set of compliance functions and/or relaxation functions is required. In this paper, a methodology and exact analytical expressions for calculating the whole set of VE functions is presented based on the relaxation modulus E(t)and Poisson's ratio v (t) determined in strain-controlled tests. The method is based on Laplace transforms, where an exact inversion is possible if a linear VE model with functions in Prony series is used. Results of the analytical model are compared with the FEM simulation, where specific boundary conditions to determine each particular VE function are used. Finally, the applicability of the so-called quasi-elastic method is investigated, where the expressions of elasticity theory are used to calculate a given viscoelastic function at an instant of time tk using the instant values of E(tk) and v(tk). For isotropic materials, the three approaches render almost coinciding results. [ABSTRACT FROM AUTHOR]

This paper describes a new numerical method – within an ANSYS Workbench finite element method environment – for simulating the kinetics of the Heat Build-up process in rubber under cyclic multiaxial loading. A novel measuring setup controls a multiaxial load which forces the heat build-up by combining the dynamic alteration torque and multi-planar bending. In this method, the experimentally determined Heat Build-up is calculated numerically from the strain energy density with the determined hyperelastic material parameters at room temperature. A new quantity, the so-called dissipation constant, is introduced which makes it possible to determine the dissipation energy of cyclically loaded specimen. The experiments and calculations were carried out for a broad range of loading conditions, varying in both bending angle and rotational speed. Finally, the agreement between the experimentally determined and the calculated data is discussed. [ABSTRACT FROM AUTHOR]

The core issue in the theoretical design of superhydrophobic surfaces is to elucidate the relationship between surface microstructure and wettability. In this paper, four two-scale array microstructure models with different shapes are proposed to predict the apparent contact angles (CAs) of EN-GJL-250 (Grey Cast Iron) surface under different wire-cut electrical discharge machining (WEDM) discharge parameters. The primary microstructure is the artificially designed semicircle, rectangular, sawtooth and square column array microstructure, and the secondary microstructure is the micro-nanostructure of the surface machined by WEDM. Firstly, the mechanical analysis of water droplets placed on the primary array microstructure is carried out by the force balance method. According to Newton's third law, equations containing CA parameters are listed. Secondly, the finite element method (FEM) was used to analogue simulation the distribution of material surface temperature and flow field in the WEDM single-pulse discharge machining process. The surface equivalent geometric model of WEDM was established by a uniform arrangement of single pulse pits obtained by simulation, the surface roughness coefficients under different discharge parameters were calculated, and the influence of the surface roughness coefficients on the surface wettability was studied. The numerical results show that the CA is jointly determined by the surface roughness coefficient under different discharge parameters, and the shape and size parameters of the microstructure. Finally, semicircle, rectangular, sawtooth and square column array microstructures were fabricated on EN-GJL-250 surface by high-speed WEDM. Experimental results show: The CA of water droplets on the square column array microstructure is the largest, the predicted values of the CA were in good agreement with the experimental values, and the average relative error was 7.83%. [ABSTRACT FROM AUTHOR]

Over the last decades, additive manufacturing (AM) has become the principal production technology for prototypes and components with high added value. In the production of metallic parts, AM allows producing complex geometry with a single process. Also, AM admits a joining of elements that could not be realized with traditional methods. In addition, AM allows the manufacturing of components that could not be realized using other types of processes like reticular structures in heat exchangers. A solid mold investment casting that uses printed patterns overcomes typical limitations of additive processes such as expensive machinery and challenging process parameter settings. Indeed, rapid investment casting provides for a foundry epoxy pattern reproducing the component to exploit in the lost wax casting process. In this paper, aluminium radiators with flat heat pipes seamlessly connected with a cellular structure were conceived and produced. This paper aims at defining and investigating the principal foundry parameters to achieve a defect-free heat exchanger. For this purpose, different device CAD models were designed, considering four pipes' thickness and length. Finite element method numerical simulations were performed to optimize the design of the casting process. Three different gate configurations were investigated for each length. The numerical investigations led to the definition of a castability range depending on flat heat pipes geometry and casting parameters. The optimal gate configuration was applied in the realization of AM patterns and casting processes [ABSTRACT FROM AUTHOR]

Plastic injection molding is one of the most popular manufacturing processes for mass production, and optimizing the mold cooling system is critical for reducing the cycle time and improving the final part quality. This paper develops a three-dimensional transient cooling simulation model based on the finite element method. Comparing with the conventional cycle-averaged cooling model that uses boundary element method, this method has two major advantages: First, the transient mold temperature is more accurate than the cycle-averaged mold temperature. Second, this method allows performing cooling simulation directly on the real-world mold models without the simplifications that required by the boundary element method. To speed up the transient cooling simulation, this method uses the cycle-averaged cooling model as initial condition and applies the heat flux conservation equations at the discontinuous mesh boundaries to eliminate the interface iterations. It is shown that this method finishes the transient cooling analysis in 478 s on the real-world injection molding mold with more than 6.9 million tetrahedral elements, which is a satisfactory time for practical usages. The simulation result is validated by the actual molding experiment. It is found that the maximum temperature error is less than 4% and the average temperature error is less than 1%. The validation proves the accuracy of this simulation method. [ABSTRACT FROM AUTHOR]

The main purpose of this paper is to investigate the interface relaxation FEM–BEM coupling method to resolve problems involving nonlinear fracture mechanics. In this coupling technique, the nonlinear portion near the crack tip is modeled by the finite element method (FEM) and the remainder of the domain which is linear elastic is discretized using the boundary element method (BEM). In the coupling procedure adopted here, there is no need to combine the coefficients matrices of FEM and BEM subdomains and separate computing for each subdomain with successive renewal of the variables on the interface are performed to reach the final convergence. To demonstrate the effectiveness of the developed approach, several practical problems of nonlinear fracture mechanics are analyzed. The conventional FEM computations are also performed, and a critical comparison of the results is made. [ABSTRACT FROM AUTHOR]

In this paper, a successive discharge material removal model is proposed to predict the surface roughness of the EN-GJL-250 (gray cast iron) under different discharge parameters of wire-cut electrical discharge machining (WEDM). Firstly, the finite element method (FEM) was used to analogue simulate the distribution of material surface temperature and flow field in the WEDM single pulse discharge machining process. According to the principle of energy conservation, the surface morphology and characteristic parameter size of a single pulse crater under different discharge parameters are simulated. Secondly, the discharge position is determined by the minimum gap width between the initial surface of the workpiece and the electrode wire during the establishment of the material removal model. Simulation results show that the magnitude of the single pulse discharge energy has an important influence on the morphology and characteristic size of the crater. Due to the different discharge energy, the increasing trend of crater radius, depth, and flanging height is not synchronized, and the increase of crater radius is more obvious and rapid. Meanwhile, the final morphology of the WEDM machined surface is determined by the morphology size of a single pulse crater and the location distribution of discharge points. Finally, the same discharge parameters are used to verify the surface quality of machined materials. Experimental results show that the surface morphology of the WEDM workpiece is in good agreement with the material removal model and the average relative error of surface roughness between the simulation results and the experimental results is 8.26%. [ABSTRACT FROM AUTHOR]

In this two-part paper we begin the development of a new class of methods for modeling fluid-structure interaction (FSI) phenomena for air blast. We aim to develop accurate, robust, and practical computational methodology, which is capable of modeling the dynamics of air blast coupled with the structure response, where the latter involves large, inelastic deformations and disintegration into fragments. An immersed approach is adopted, which leads to an a-priori monolithic FSI formulation with intrinsic contact detection between solid objects, and without formal restrictions on the solid motions. In Part I of this paper, the core air-blast FSI methodology suitable for a variety of discretizations is presented and tested using standard finite elements. Part II of this paper focuses on a particular instantiation of the proposed framework, which couples isogeometric analysis (IGA) based on non-uniform rational B-splines and a reproducing-kernel particle method (RKPM), which is a meshfree technique. The combination of IGA and RKPM is felt to be particularly attractive for the problem class of interest due to the higher-order accuracy and smoothness of both discretizations, and relative simplicity of RKPM in handling fragmentation scenarios. A collection of mostly 2D numerical examples is presented in each of the parts to illustrate the good performance of the proposed air-blast FSI framework. [ABSTRACT FROM AUTHOR]

Positive displacement motor (PDM), which is prone to high temperature fatigue failure, can be weakened in its application in deep and superdeep well. In order to study the forced state, deformation regularity and thermal hysteresis of PDM motor, the paper established the three-dimensional thermal-mechanical coupled Finite element model (FEM). Based on the theoretical research, experimental study and numerical simulation, the study found that the displacement of stator lining shows a sinusoidal variation under internal pressure, when adapting the general form of sine function to fitting inner contour line deformation function. Then the paper analyzed the hysteresis heat generating mechanism of the motor, learning that hysteresis thermogenous of stator lining occurs due to the viscoelastic of rubber material and cyclic loading of stator lining. A heartburn happens gradually in the center of the thickest part of the stator lining as temperature increases, which means work efficiency and service life of PDM will be decreased when used in deep or superdeep well. In this paper, we established a theory equation for the choice of interference fit and motor linetype optimization design, showing hysteresis heat generating analyzing model and method are reasonable enough to significantly improve PDM's structure and help better use PDM in deep and surdeep well. [ABSTRACT FROM AUTHOR]

The current paper analyzes the fracture of a traction elevator sheave and investigates the causes that led to failure. Visual inspection revealed a fracture sequence that led to the separation of the sheave into two parts along with some areas of extended corrosion. Key samples extracted from the sheave were subjected to optical microscopy and scanning electron microscopy analysis in order to ascertain the extent of corrosion, its effect on the material and also possible defects created during the casting process. The results of the microscopy analysis were consisted of both corrosion and casting defects leading to a significant increase of the probability of reduced mechanical properties of the material. Along with the initial visual inspection, a possible failure scenario was deducted and was then confirmed during finite element analysis. In order to proceed to the analysis, the geometry of the sheave has been reconstructed digitally. The two parts of the fractured sheave were digitized using 3D scanning and were then processed in order to create the CAD model used for the analysis. The simulation of the static and dynamic behavior of the object determined increased stress values at segments of the sheave that were consistent with the fracture sequence initially observed during visual inspection. [ABSTRACT FROM AUTHOR]

This paper proposes the first computational modeling of a miniaturized version of an electromembrane extraction (EME) setup to a chip format, where the donor solution is delivered by a syringe pump to the sample reservoir. This system can be used for extraction of different analytes e.g., ionic drugs in wastewater. To design, analyze and optimize the entire process of extraction, a deep understanding of the mechanisms responsible for the analyte transport plays a key role. However, the interplay between the passive diffusion, fluid flow (convective diffusion), and electrokinetically driven SLM transfer may result in different mass transport patterns. A two-dimensional numerical model is developed to study the mass transport as well as the recovery in this on-chip EME. In order to simulate the mass transport of different analyte species, the electric field distribution, and the fluid flow, we made use of the Nernst–Planck, Poisson and Navier–Stokes equations, respectively. For all three mentioned fields (mass transport, electric field and fluid flow), appropriate boundary conditions are assigned to the setup borders to mathematically represent the real conditions of the device. The governing equations are solved by finite element method. It was revealed that at higher sample flow rates, a lower system recovery is predicted, e.g., from 80 to 60%, while higher voltages (smaller than a critical voltage) amplifies the recovery up to e.g., 75%. The presented model can predict the impact of different factors, e.g., sample flow rate, applied voltage, and extraction time on the system recovery, which are qualitatively in agreement with experimental results. Article Highlights: Developing a numerical model for an on-chip electromembrane extraction. Modeling the electrodriven extraction by Poisson, Nernst–Planck and Navier–Stokes equations. The finite-element method (FEM) is utilized to solve the governing equations. The model can predict the major experimental observations in basic drugs. This approach can be extended to simultaneous extraction of different analytes and setups configurations. [ABSTRACT FROM AUTHOR]

Low-permeability reservoir is a porous medium of complex pore structure, which has the characteristic of narrow pore throat, poor connectivity and ultra-low permeability. At present, a lot of experimental studies confirmed that there are stress sensitive and threshold pressure gradient in low-permeability reservoir. It is incorrect to simulate the oil well production dynamic characteristics by numerical simulation method of traditional seepage theory. In order to evaluate the productivity of multi-stages fractured horizontal well in low-permeability reservoir, in this paper, a seepage mathematical model of multi-stage fracturing horizontal well considering the stress sensitivity and threshold pressure gradient is established based on the discrete fracture network model and solved by the finite element method. The results of numerical simulation show that the stress sensitive of reservoir matrix controls the evolution of reservoir physical properties, the threshold pressure gradient determines production time of oil wells and the fracture compression coefficient controls production. The sensitivity analysis shows that the increasing curves of the production reduction range due to the stress sensitive and fracture compression coefficient are logarithmic, and the curve of threshold pressure gradient and shut-in time is linear descent relation. When the stress sensitivity, threshold pressure gradient and fracture compression coefficient are considered separately, the production is reduced by 17.3, 54.7 and 35.5%, respectively. It has a great inhibiting effect on productivity due to stress sensitivity, threshold pressure gradient and fracture compression coefficient, and the productivity of the well will be overestimated if the above factors are not considered. The results can provide some theoretical guidance for fracturing optimization design and efficient development of low-permeability reservoir. [ABSTRACT FROM AUTHOR]

The deformation of ceramic shell poses a potential and uncertain threat on the dimensional accuracy of the final casting in the investment casting process. In this paper, a finite element analysis method (FEM), permafrost analysis methodology (PAM), is used to simulate the deformation of the ceramic shell in the firing process. In the PAM, the porosity and the phase transformation of the ceramic shell in the firing process are taken into consideration. The comparison of simulation and experimental results indicated that the PAM can predict the deformation of the ceramic shell with high accuracy. The work of this paper presents a new approach to simulate the deformation of the ceramic shell, and there is a great significance to improve the dimensional accuracy of the final casting in the investment casting process. [ABSTRACT FROM AUTHOR]

The complexity of adjusting ring rolling process parameters is always a great challenge for producing high-quality rings. Inappropriate adjustment of main process parameters, including mandrel feed speed, main roll rotational velocity and guide rolls forces, may lead to geometrical defects such as fishtail, non-circularity and polygon-shaped rings. In this paper, for the first time, the effects of noted main parameters on the above geometrical defects are thoroughly investigated using simulation by Abaqus\Explicit as well as experimental data obtained by radial–axial ring rolling (RARR) setup. Experimental results confirm the final ring geometry, which was obtained by the finite element method. The results show that the individual main process parameters such as mandrel feed speed and main roll rotational velocity have an insignificant effect on a non-circularity defect. However, lower mandrel feed speed-to-rotational speed ratios (F/RT) causes a slight decrease in the value of non-circularity. Furthermore, it was shown that increasing feed speed decreases the fishtail defect due to the diffusion of the plastic zone to the whole ring cross section. This effect can also be obtained by reducing the main roll rotational velocity. Thus, increasing mandrel feed speed improves ring geometrical quality if the process remains in stable condition. In addition to eliminating fishtail defect, the existence of axial rolls would enhance process stability by restricting ring motion and avoiding the ring wobbling and polygon-shaped defect forming in the final ring. [ABSTRACT FROM AUTHOR]

Neural networks (NN) have been studied and used widely in the field of computational mechanics, especially to approximate material behavior. One of their disadvantages is the large amount of data needed for the training process. In this paper, a new approach to enhance NN training with physical knowledge using constraint optimization techniques is presented. Specific constraints for hyperelastic materials are introduced, which include energy conservation, normalization and material symmetries. We show, that the introduced enhancements lead to better learning behavior with respect to well known issues like a small number of training samples or noisy data. The NN is used as a material law within a finite element analysis and its convergence behavior is discussed with regard to the newly introduced training enhancements. The feasibility of NNs trained with physical constraints is shown for data based on real world experiments. We show, that the enhanced training outperforms state-of-the-art techniques with respect to stability and convergence behavior within FE simulations. [ABSTRACT FROM AUTHOR]

In this paper a triple-band dielectric resonator antenna (DRA) is designed using a 0.8 mm thicker Arlan FR-25 substrate, having relative dielectric constant of 3.58 and loss tangent of 0.0035. The antenna works in three unique frequency bands of 15, 16.3 and 18.5 GHz, lying in the sub-20 GHz spectrum. A stack of ten radiating elements of AR100 material, are installed at the centre of the proposed antenna structure. The DRA is excited through an elliptical aperture in the metallic plane via a 50 Ohm microstrip feed line, etched on the rear side of the Arlan FR-25 substrate. Stacked parasitic elements are incorporated around the central radiating element for achieving enhanced gain. The proposed DRA gives satisfactory gain and fractional bandwidth of (8.06 dB, 12%), (10.7 dB, 3%) and (7.03 dB, 2.73%) at 15, 16.3 and 18.3 GHz bands, respectively. The simulation results of the DRA are compared and validated using three different analysis techniques i.e., FIT (Finite Integration Technique), FDTD (Finite Difference Time Domain) Method and FEM (Finite Element Method). The designed antenna can be used for future fifth generation (5G) systems (15 GHz), internet of things (IoT) based device-to-device (D2D) communication and satellite applications (16.3–18.3 GHz). [ABSTRACT FROM AUTHOR]

A tangential ultrasonic vibration-assisted gear grinding (TUVAGG) system was proposed in this paper to enhance the machining accuracy and performance of gears. Firstly, the longitudinal resonant vibration system of the TUVAGG was designed based on the non-resonant theory. The frequency equation and the displacement characteristics for the vibration system were obtained for the particular boundary conditions. Secondly, the vibration system composed of simplified disc and gear was simulated by the finite elements analysis method (FEM) and verified by the resonant measurement test. Finally, the vibration system effectiveness was verified through the ultrasonic vibration-assisted gear grinding test. The normal and tangential grinding forces in TUVAGG were lower by 7.4–28.2% and 8.9–18.9%, respectively, than conventional gear grinding (CGG). Besides, the grinding temperature and surface roughness in TUVAGG declined by 7.6–25.7% and 8.6–21.8% respectively compared with CGG, while the former tooth surface residual compressive stress and microhardness exceeded the latter ones by 13.2–29.3% and 8.9–12.7%. The non-resonant theory was suitable for the designation of longitudinal vibration system for TUVAGG, and also provided a novel process technology for gear machining. [ABSTRACT FROM AUTHOR]

The free vibrational frequencies of a multi-directional functionally graded (FG) structure are investigated for the first time in this paper considering the influences of variable grading (power-law, sigmoid, exponential) and porosity distribution (even and uneven type). Also, the structural properties (Young's modulus, density and Poisson's ratio) varied along with two different directions simultaneously, i.e., the longitudinal and transversional ones, respectively. The present multi-directional grading model of the FG structure is reconstructed mathematically for the numerical analysis by considering adequate state-space deformation kinematics with the help of higher-order displacement functions and shear stress continuity. The general motion equation of a multi-graded structure is expressed using Hamilton's principle and the finite element method including the necessary porosity effect. Initially, model consistency is verified and the eigenvalues obtained in the analysis are compared with the ones found in the literature. The comparison also includes the directional grading effect on their frequencies. Further, the influence of different parameters, i.e., power exponents (nz and nx), aspect ratio, thickness ratio, geometry, end support conditions, curvature ratio, porosity index, porosity distribution and material grading patterns, on the vibration characteristics of the multi-directional FG structure is computed. The analysis of the numerical results confirms that material grading; porosity distribution pattern and other design parameters have a significant influence on the frequency response characteristics of a single/multi-directional porous FG structure. [ABSTRACT FROM AUTHOR]

Thermal deformation is one of the principal factors that influence the machining accuracy of machine tools, and it can be improved by thermal error compensation. This paper presents a method of thermal error modeling using multisource information fusion, which can further improve the thermal error compensation accuracy. To set up a fusion model with optimal performance, two or more thermal error models should be established, from which a few models should be chosen to complement each other, and then combined into a synthesis model. In this paper, a dynamic thermal error model and a finite element model are combined to build a fusion model for lathe z-direction thermal error according to a fusion algorithm. The inputs for the fusion model are the values detected by the thermal sensors and the infrared imaging. An experiment carried out on a lathe verifies the validity of this modeling method. The results show that the multisource fusion model of thermal error can not only improve the prediction accuracy of thermal error over that of a single model, but also possesses better robustness. [ABSTRACT FROM AUTHOR]

In this paper a fusion metamodeling approach is suggested as a method for reducing the experimental and computational effort generally required for calibrating the parameters of FEM simulations models. The metamodel is used inside an optimization routine for linking data coming from two different sources: simulations and experiments. The method is applied to a real problem: the optimal design of a metal foam filled tube to be used as an anti-intrusion bar in vehicles. The model is hierarchical, in the sense that one set of data (the experiments) is considered to be more reliable and it is labeled as 'high-fidelity' and the other set (the simulations) is labeled as 'low-fidelity'. In the proposed approach, Gaussian models are used to describe results of computer experiments because they are flexible and they can easily interpolate data coming from deterministic simulations. Since the results of experiments are obviously fully accurate, but aleatory, a second stage ('linkage') model is used, which adjusts the prediction provided by the first model to more accurately represent the real experimental data. In the paper, the modeling and prediction ability of the method is first demonstrated and explained by means of artificially generated data and then applied to the optimization of foam filled tubular structures. The fusion metamodel yields comparable predictions (and optimal solution) if built over calibrated simulations vs. non-calibrated FEM models. [ABSTRACT FROM AUTHOR]

Polyethylene (PE) pipes are widely used in urban gas transportation systems but they are more prone to failure than steel pipes under the ground loads such as settlement, landslide and cyclic traffic load. This paper aims to study the position transfer law of failure location under the combined loading of non-uniform settlement and landslide, a numerical simulation model of buried PE pipe is developed in ABAQUS using a new method of non-uniform settlement displacement. The results show that the failure location will appear on the middle plane when the landslide is relatively small. With the increment of the settlement displacement, the failure location gradually appears on the symmetrical cross section, and the stress of turning point does not reach the yield stress. The crushing caused by the horizontal deformation under the action of landslide undermines the protective effect of the soil on the buried PE pipe, and the damage caused by the landslide to the pipe is more serious than that by the settlement. The result can provide a valuable reference and support for the safety assessment of buried PE pipe. [ABSTRACT FROM AUTHOR]

Temperature field distribution of a machine tool spindle system, especially the spindle bearing, directly determines the size and direction of the thermal errors, which will result in poor processing precision and degradation of mechanical property of the machine tool. Measurement and monitoring of spindle bearing temperature field are of great significance to enhance the manufacture precision of NC machine tool effectively. Traditional measurement methods of spindle bearing temperature field are single-point or two-point measurement and cannot be stuck to the bearing outer ring directly, thus the data being inaccurate. In this paper, a multipoint quasi-distributed sensing method based on embedded fiber Bragg grating (FBG) sensors was proposed to measure the temperature field of the outer ring of the bearing under three different working conditions: idling, uploading axial, and radial cutting force respectively. A traditional thermocouple had been used for measurement comparison and a finite element method (FEM) prediction method utilizing ANSYS Workbench software package had been presented for temperature distribution prediction. Experiment results showed that the measurement error between FBG and thermocouple was within 10%. The temperature distribution achieved by FBG sensors had great consistence with the simulation prediction model. It was demonstrated that this quasi-distributed sensing method can be applied to the measurement of spindle bearing temperature field distribution very well. Moreover, it can be seen as a significant means to effectively verify the thermal model of the spindle bearing integrated system. [ABSTRACT FROM AUTHOR]

This paper presents the development of a FE-simulation model to predict the mechanical stresses and thermal loads that a cutting tool of polycrystalline cubic boron nitride (pcBN) is subjected to, when machining AISI 316L. The serrated chip formation of AISI 316L has a major impact on the periodic loads acting on the cutting tool. Therefore, it is vital to correctly model this serrated chip formation. One of the major difficulties with FE-simulations of metal cutting is that the extreme deformations in the workpiece material, often leads to a highly distorted mesh. This paper uses the Coupled Eulerian-Lagrangian (CEL) formulation in Abaqus/Explicit, where the workpiece is modelled with the Eulerian formulation and the cutting tool by the Lagrangian one. This CEL formulation enables to completely avoid mesh distortion. To capture the chip serration process, the workpiece material is described with the Johnson-Cook damage model. The FE-simulation results are validated via comparison of the modelled cutting forces, chip serration frequency, and contact length against experimental ones. [ABSTRACT FROM AUTHOR]

Second-generation (2G) high-temperature superconducting (HTS) tapes are now capable of carrying very high transport current and promising for a wide range of applications. The critical current of HTS coils is important for applications, such as superconducting electric machines, superconducting magnetic energy storage, and superconducting magnets. Therefore, precisely and quickly calculating critical current of HTS coils is very important for designing HTS devices. This paper provides a fast algorithm for evaluating critical current of HTS pancake coil. The fast algorithm is realized through a stationary model, which is based on finite element method (FEM) software. The stationary model means that the model is solved by stationary study instead of time-dependent study. To validate this method, a pancake HTS coil was wound and its critical current was measured. Meanwhile, an axial symmetric stationary model was built according to the geometry of the measured HTS coil. By comparing measured and calculated results, the effectiveness of the stationary model was demonstrated. Moreover, the stationary model is compared with H formulation model. The calculated results by the two models are nearly the same. However, by using stationary calculation, the stationary model can remarkably speed up the computational process. Due to the advantage of calculating speed, the stationary model can be used to characterize and design large-scale HTS applications. [ABSTRACT FROM AUTHOR]

The geometry of the cladding pass cross section cannot be easily predicted in laser melting deposition. Due to the huge difference between the actual and the predicted cross section, it is difficult to conduct numerical simulations. In this paper, the finite element method (FEM) with thermal–mechanical coupling is performed. A novel cladding pass cross section model, isosceles trapezoid model, is proposed. The comparisons between the isosceles trapezoid model and the traditional model (disk model and rectangle model) are performed in terms of geometrical deviation, heat dissipation, temperature field, and stress field. The results show that the geometrical deviation and heat dissipation between trapezoid model and disk model is small, and that between trapezoid model and rectangle model is large. The trapezoid model has an additional degree of freedom for modeling, i.e., contact angle, which helps to conform complex cross section geometry more flexibility. The results of temperature field and stress field show that the deviation between the isosceles trapezoid model and the traditional models is small on the upper surface of the sample, and rectangle model has worse prediction results than the other two models at the interface between cladding pass and substrate. Finally, the validation experiment is carried out and the stress is measured by laser ultrasound technique. The experimental result matches the FEM result based on isosceles trapezoid model. [ABSTRACT FROM AUTHOR]

A thorough understanding of brain metabolism is essential to tackle neurodegenerative diseases. Astrocytes are glial cells which play an important metabolic role by supplying neurons with energy. In addition, astrocytes provide scaffolding and homeostatic functions to neighboring neurons and contribute to the blood–brain barrier. Recent investigations indicate that the complex morphology of astrocytes impacts upon their function and in particular the efficiency with which these cells metabolize nutrients and provide neurons with energy, but a systematic understanding is still elusive. Modelling and simulation represent an effective framework to address this challenge and to deepen our understanding of brain energy metabolism. This requires solving a set of metabolic partial differential equations on complex domains and remains a challenge. In this paper, we propose, test and verify a simple numerical method to solve a simplified model of metabolic pathways in astrocytes. The method can deal with arbitrarily complex cell morphologies and enables the rapid and simple modification of the model equations by users also without a deep knowledge in the numerical methods involved. The results obtained with the new method (CutFEM) are as accurate as the finite element method (FEM) whilst CutFEM disentangles the cell morphology from its discretisation, enabling us to deal with arbitrarily complex morphologies in two and three dimensions. [ABSTRACT FROM AUTHOR]

The main purpose of this paper is to investigate deeply the effect the contact pressure function on the thermo-mechanical behavior of the friction clutch system during the slipping time (heating stage). The other purpose is to explore theoretically the complex interaction among the contact pressure, sliding speed and frictional characteristics of frictional facings to specify the magnitude and distribution of the frictional heating generation on the contact surfaces of the dry friction clutch under different applied pressure. It was developed a numerical code based on finite element method (ANSYS/APDL 2019) to determine accurately the contact pressure, temperature and frictional heat generated on contact surfaces of the friction clutch disc that has two effective frictional faces at any instant during the slipping period. It was found a significant effect of the magnitude and variation of applied pressure during the heating phase on the surface temperatures, contact pressure and frictional heat generated. Where, the hot spot can be appeared when the applied pressure is constant. Under such circumstances, high amount of temperature and contact pressure focused on a small zone of the nominal contact area. This phenomenon is considered one of the main reasons for the early failure of the contacting surfaces of friction clutch. [ABSTRACT FROM AUTHOR]

Camshaft is a key part of marine diesel engines. However, the large residual stresses resulting from the induction hardening to which the cams are submitted may lead to cracks on their contacting surfaces. These cracks have great influence in the service life of the shaft. In order to find the relationship between the induction hardening process parameters and the residual stress field, the process was simulated by the finite element method, and the SYSWELD and ANSYS software were used. The temperature distribution during hardening process and stress field of the camshaft after the process were obtained and analyzed. The thickness of the hardening layer was calculated. The simulation results were validated by residual stress measurement experiments and showed a good agreement with the practice. The method reported on the present paper provides an efficient way to analyze the camshaft induction hardening process and avoid the surface failure of the cams. [ABSTRACT FROM AUTHOR]

In this two-part paper we begin the development of a new class of methods for modeling fluid-structure interaction (FSI) phenomena for air blast. We aim to develop accurate, robust, and practical computational methodology, which is capable of modeling the dynamics of air blast coupled with the structure response, where the latter involves large, inelastic deformations and disintegration into fragments. An immersed approach is adopted, which leads to an a-priori monolithic FSI formulation with intrinsic contact detection between solid objects, and without formal restrictions on the solid motions. In Part I of this paper, the core air-blast FSI methodology suitable for a variety of discretizations is presented and tested using standard finite elements. Part II of this paper focuses on a particular instantiation of the proposed framework, which couples isogeometric analysis (IGA) based on non-uniform rational B-splines and a reproducing-kernel particle method (RKPM), which is a Meshfree technique. The combination of IGA and RKPM is felt to be particularly attractive for the problem class of interest due to the higher-order accuracy and smoothness of both discretizations, and relative simplicity of RKPM in handling fragmentation scenarios. A collection of mostly 2D numerical examples is presented in each of the parts to illustrate the good performance of the proposed air-blast FSI framework. [ABSTRACT FROM AUTHOR]

For reduction of vehicle weight and higher fatigue property, the hot-rolled dual-phase steel 700DP was developed to produce wheel disc with multistage stamping process. The wheel disc is one critical component of wheel system whose forming precision is extensively concerned. The critical area of the part characterizes nonlinear strain path during the multistage stamping process, which makes it difficult to accurately evaluate the formability through standard forming limit curve (FLC) method. The concept of equivalent plastic strain was reported to be strain path independent. Hence, in this paper, the formability of 700DP steel was studied through tensile test, Nakazima test, and two-step nonlinear formability test. It was certified that the modeling using the equivalent plastic strain–based FLC (ep-FLC) had better agreement with the two-step nonlinear test results. Then based on current die shape, the feasibility of 700DP steel for wheel disc with three-stage stamping process was studied by finite element method (FEM) with both traditional FLC and ep-FLC. Furthermore, the corresponding experiments were conducted for validation. The results show that the location and critical condition for the occurrence of fracture can be more exactly predicted by the ep-FLC compared with the traditional FLC. The process parameters such as the radius of die corner were then optimized by the modeling analysis. Finally, the wheel disc was successfully manufactured with high precision and sound mechanical property. [ABSTRACT FROM AUTHOR]

In this paper, the design method of few mode elliptical ring core fiber (E-RCF) supporting up to 10 spatial linearly polarized (LP) modes is proposed. With the support of central circular hole, the maximum numbers of modes are generated using finite element method. Optical mode characteristics are optimized in two way; using the geometry properties of the elliptical ring core and radius of central hole region. Further, the mode performance is computed with the function of both ellipticity ratio (ρ) and wavelength. The results show that 10 distinct LP mode is adequately tuned in order to get higher index difference approximation ( Δ n eff ) to reduce the computational complexity. The results show for Δ n eff between the adjacent modes and reported as larger than 18.80 × 10−4 at ρ = 2.5 and larger than 17.30 × 10−4 at the wavelength of 2 μm. The work also describes the E-RCF sustainability in the IoT environment and it promises for better paly upon the user demand with transmitting dense of data. [ABSTRACT FROM AUTHOR]

The investigation concerns local buckling of compressed flanges of axially compressed composite channel columns. Cooperation of the member flange and web is taken into account here. The buckling mode of the member flange is defined by rotation angle a flange about the line of its connection with the web. The channel column under investigation is made of unidirectional fibre-reinforced laminate. Two approaches to member orthotropic material modelling are performed: the homogenization with the aid of theory of mixture and periodicity cell or homogenization upon the Voigt–Reuss hypothesis. The fundamental differential equation of local buckling is derived with the aid of the stationary total potential energy principle. The critical buckling stress corresponding to a number of buckling half-waves is assumed to be a minimum eigenvalue of the equation. Some numerical examples dealing with columns are given here. The analytical results are compared with the finite element stability analysis carried out by means of ABAQUS software. The paper is focused on a close analytical solution of the critical buckling stress and the associated buckling mode while the web–flange cooperation is assumed. [ABSTRACT FROM AUTHOR]

The friction model in the tool-chip interface has significant influences on predicting chip forms, cutting forces, and cutting tool temperatures, when simulating the chip formation using the finite element method. In this paper, the friction behavior in the tool-chip interface was investigated experimentally and numerically under cutting conditions. The friction tests were performed with different workpiece materials (AISI 1045 and Direct Aged Inconel 718) in combination with uncoated and coated cemented carbide cutting tools. Various process normal forces were applied to achieve different contact pressures. The experimental results showed strong influences of relative speeds, contact pressures, and contact temperatures on apparent friction coefficients. In addition, an advanced friction model was proposed and validated with 3D FE-simulations of the friction test. [ABSTRACT FROM AUTHOR]

Hydroforming is a metal forming technology that enables the fabrication of complex parts in a low cycle time. The process is based on the plastic deformation of a blank sheet using a pressurized fluid. This paper focuses on the design of a tube hydroforming (THF) process to replace the current cut-and-weld practice for components produced by a company. Specifically, the study focuses on the characterization and optimization of the THF process for stainless steel T-joint parts produced in two sizes: small and large. The new production must improve the final components' quality and maintain the technical requirements of the previous one, especially in terms of the parts' geometry (in particular, the third branch minimum height and thickness) and material (AISI 316L), with competitive production costs. Accordingly, the process optimization is performed in three sequential steps. Initially, the process is characterized by the material flow stress and the friction between a tube and die. Subsequently, this information is used to develop a finite element method (FEM) model, which is validated based on experimental data. The FEM is used to optimize the process parameters (pressure, stroke, and trust force of the counterpunch) to improve the final component quality and guarantee the specific dimensional requirements. Finally, further improvements of the process are implemented (initial precrash of the tube, optimal length of the blank tube, and calibration pressure to avoid wrinkles in the final component). After the THF process optimization, emphasis is placed on the punch geometry. A study is conducted to avoid stress concentrations that may cause punch breakage. The results of this study allow the minimization of tube thinning during the hydroforming process, and guarantee the target value for the third branch height with minimal material consumption. Moreover, the evaluation of different geometrical alternatives allows the stresses acting on the punches to be reduced by 45%. [ABSTRACT FROM AUTHOR]

The semi-circular bending (SCB) test is one of the most useful testing methods for determining the mode-I fracture toughness of rocks. An SCB specimen with an artificial notch is loaded at three points including two lower points and a single upper point during the test. In general, there are two types of geometries for artificial notches: straight through and chevron notches. The straight through notch is commonly adopted for the SCB (STNSCB) test as the suggested method for estimating mode-I fracture toughness of rocks in ISRM, while the cracked chevron notch SCB (CCNSCB) test using a specimen with a chevron notch has been performed by some researches. In this paper, by means of the commercial finite-element software ABAQUS, cracking behavior from the tip of an artificial notch during STNSCB and CCNSCB tests is analyzed with Extended Finite-Element Method (XFEM) to clarify crack front geometry in the process of cracking. The relationship between the crack length and the stress intensity factor can be obtained by analyzing stress intensity factors of the specimen with FEM, based on crack front geometries calculated with XFEM during the cracking process. Using this relationship, the minimum stress intensity factor at a critical crack length is determined for estimating mode-I fracture toughness of the rock for the CCNSCB test. Furthermore, by performing the SCB tests using Kimachi sandstone specimens with three different artificial notch geometries, fracture toughness of the sandstone is determined from the SCB test. Consequently, it is concluded that the values of fracture toughness from the test with three notch geometries are almost the same. [ABSTRACT FROM AUTHOR]

In this paper, the evolution of flow lines during the forging of bearing rings was investigated. The formation mechanisms of flow-line defects were revealed by a finite element method (FEM) simulation of the entire forging process. To avoid the flow-line disorder caused by the bearing ring manufacturing method, two hot forging processes were employed to optimize the flow-line distribution of an M50 steel bearing ring with a deviated groove. The simulation and experimental results show that the punching die and the location of the punching recess had a significant effect on the flow-line formation. The V-shaped punching pin and punching recess setting at the bottom of the billet resolved the flow-line disorder caused by the punching process. Finally, a bearing outer ring with a reasonable flow-line distribution was obtained. Furthermore, the improved hot forging process reduced the average grain size and improved the M2C carbide-aggregation phenomenon. Given the direction of the flow lines, the bearing ring exhibited mechanical anisotropy in the tensile direction. [ABSTRACT FROM AUTHOR]