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Thin-walled tubular deployable composite boom (DCB) has gained significant attention due to its lightweight, simple structure and high packaging efficiency. The experimental and numerical simulation methods were employed in this paper to investigate the folding behavior of the DCB. Using T700/epoxy unidirectional reinforced prepreg as raw material, DCB specimens were prepared by the vacuum bag method. To complete the folding experiments of DCB specimens, a folding mechanism was designed and manufactured. Folding experiments of DCB specimens were conducted and folding moment versus rotational displacement curves were measured. In addition, a Finite Element Model (FEM) was established to predict the folding behavior of the DCB. Different failure criteria were considered in the numerical analysis, including the Tsai‐Hill criterion and maximum stress criterion. Prediction results using the FEM were compared with experimental results, and both sets of results were in good agreement. It is shown that the DCB can achieve the folding function without failure. The research results in this paper are of great significance to the practical engineering application of the DCB. [Display omitted] • Six tubular deployable composite boom specimens and a precise folding mechanism were designed and prepared. • Folding experiments were conducted to measure the folding moment and rotational displacement curves. • A finite element model for predicting the folding behavior of the tubular deployable composite boom was established. [ABSTRACT FROM AUTHOR]

Nonlocal problems involving fourth-order terms pose several difficulties such as numerical discretization and its related convergences analysis. In this paper, the well-posedness of the extended Fisher-Kolmogorov equation with nonlocal diffusion is first analyzed using the Faedo-Galerkin technique and the classical compactness arguments. Moreover, we adopt a BDF2 scheme for time discretization and a mixed Galerkin scheme for spatial discretization. Then, we derive the optimal order convergence rates of the fully discrete system. Finally, some numerical simulations and convergence results are provided to confirm the theoretical results and the accuracy of the proposed scheme. [ABSTRACT FROM AUTHOR]

Understanding the formation of impact craters on planetary surfaces has fundamental importance in geology, impact dynamics, and planetary sciences. The finite element-smoothed particle hydrodynamics (FE-SPH) adaptive method combines the advantages of smoothed particle hydrodynamics (SPH) and finite element method (FEM) in solving hypervelocity impact (HVI) problems. Employing FE-SPH adaptive method is a new idea for the analysis of planetary impact cratering which is different from impact-simplified arbitrary Lagrangian Eulerian (iSALE). In this paper, we establish a complete numerical model of planetary impact cratering through the FE-SPH method, including material failure criterion, thermodynamic analysis, gravity preloading, etc. We reproduce the numerical results by Collins et al. (2012) and highly consistent results are obtained through comparative analysis. This study simulates the formation process of simple and complex impact craters, and the temperature, pressure, density, and geometric shape of the impact zone can be quantitatively obtained. We further analyze the distribution of polymorphs and rock fragmentations in the impact zone based on the theories of shock metamorphism. The proposed analysis method may assist geologists in conducting geological studies. • We establish a complete numerical model of planetary impact cratering different from iSALE. • We analyze the distribution of high-pressure polymorphs based on shock metamorphism. • The FE-SPH model has higher numerical precision for planetary cratering impacts. [ABSTRACT FROM AUTHOR]

• The effectiveness of thin-walled cellular beams manufactured by RFSSW was developed. • A parameterized finite element model (FEM) of the cellular beam was developed. • Results of numerical simulations and experimental tests were compared. • A parametric FEM model of the cellular beam was developed in the ADINA system. • The numerical model was used to analyze beams with different cross-sections. The paper presents analyses of thin-walled I-beams constructed from 6061-T6 aluminum alloy using refill friction stir spot welding (RFSSW). A parametrized finite element model of the reference cellular beam was developed, and the results from numerical simulations and experiments were compared. Subsequently, the validated numerical model was utilized to conduct an in-depth analysis of three additional beams featuring distinct cross-sections. To assess the weld behavior, experiments were conducted on samples composed of two sheets connected by two spot welds. The outcomes of these investigations underscore the suitability of RFSSW as a method for constructing thin-walled structures in civil engineering applications. [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]

• The flexural buckling behaviour of austenitic stainless steel semi-oval hollow section columns was studied. • Twelve pin-ended column tests were conducted. • FE models were developed to validate against the test results and then adopted to conduct parametric studies. • The codified buckling curves were evaluated and led to an overall good level of design accuracy. Semi-oval hollow section is an innovative cross-section profile and consists of one semi-circular flange, one flat flange and two flat webs. While the semi-circular flange (exposed to fluid or wind) offers a low level of hydrodynamic or aerodynamic drag, the flat elements facilitate connections with other members. The flexural buckling behaviour and resistances of austenitic stainless steel semi-oval hollow section columns are investigated in this paper. An experimental programme was firstly conducted on two austenitic stainless steel semi-oval hollow sections, with six column specimens of varying member lengths adopted for each cross-section, and included tensile coupon tests, initial geometric imperfection measurements and pin-ended column tests. Both 'C'-shaped flexural buckling (with failure specimens bowing towards semi-circular flanges) and 'reverse C'-shaped flexural buckling (with failure specimens bowing towards flat flanges) were observed upon testing. The experimental programme was accompanied by a numerical modelling programme, with finite element models developed to simulate the test results and then adopted to conduct parametric studies to generate further numerical data. On the basis of the test and numerical data, the relevant buckling curves for austenitic stainless steel circular hollow section columns, as provided in the European code, American specification and Australian/New Zealand standard, were evaluated for their applicability to austenitic stainless steel semi-oval hollow section columns. The evaluation results generally revealed that the codified buckling curves led to overall accurate and consistent flexural buckling resistance predictions when used for austenitic stainless steel semi-oval hollow section columns. [ABSTRACT FROM AUTHOR]

The bidomain equations form the state-of-the-art model of cardiac electrophysiology and describe normal or pathological propagation of the excitation wave through cardiac tissue. If based on mechanistic cell models and applied to anatomically realistic geometries, their discretization requires very fine resolutions both in space and time and renders the numerical solution an extremely challenging computational problem. In this paper, we address this challenge by combining space-time adaptive discretization with dynamic load balancing for parallel computing. We use multilevel finite element methods for the spatial adaptation of the mesh, embedded Rosenbrock time integration for an adaptive choice of step sizes, and non-overlapping domain decomposition for the parallelization. In order to further reduce the computational costs, we exploit the sparsity of local matrices during the assembly of global FEM matrices which ensure an optimal usage of memory. In numerical tests, we demonstrate the feasibility of our approach that a substantial reduction factor of computing time is achieved w.r.t the static grid computation and a good parallel efficiency is achieved. [ABSTRACT FROM AUTHOR]

Simulation of the failure process of non-intact rock containing initial cracks, voids, and other discontinuities is a research hotspot in rock mechanics and geotechnical engineering. The damage smear method has attracted wide attention due to its ability to realistically depict the complete failure processes of rock from the microscopic to the macroscopic scale. However, when portraying pre-existed discontinuities, the damage smear method suffers from major difficulties such as mesh dependency and stress singularity. To overcome the limitations of current methodology, this paper proposes a novel non-break modeling strategy inspired by the extended finite element method for dealing with embedded discontinuities, in which the discontinuity of the physical fields across crack faces or the void boundary, as well as the stress singularity at the crack tip, can be characterized by introducing appropriate enrichment functions, and the penalty method is used to impose frictional contact constraints. Applications of the combined method of the improved modeling strategy and damage smear analysis to laboratory-scale and engineering-scale numerical examples show a satisfactory approximation with the analytical solution or experimental observations, indicating that the current modeling strategy can further improve computational accuracy while retaining the advantages of the damage smear method. [ABSTRACT FROM AUTHOR]

• A modified GTN model considering the effects of anisotropy and shearing on micropore evolution is introduced. • The constitutive model is compiled into a VUMAT subroutine for numerical simulation to accurately predict the plastic deformation of aluminum alloy sheet. • The parameters in constitutive model are calibrated by inverse FE method and the validity of the modified GTN model is verified through the uniaxial tensile experiment. • A FE model of the mould-sheet coupling system is further developed to improve the forming performance. Traditional GTN meso-damage model, neglecting the effect of anisotropy or shearing on the evolution of microvoid, leads to the lower predictive capabilities of forming defects for aluminum alloy sheets. In this paper, a modified constitutive model of aluminum alloy sheet considering the effect of both anisotropy and shearing is proposed, and the corresponding model parameters are calibrated by inverse finite element method and uniaxial tensile test of the smooth strip sheet without hole. Then, the constitutive equation of the modified model is compiled into a VUMAT subroutine using backward Euler integration algorithm and FORTRAN language to perform subsequent numerical simulation in ABAQUS/Explicit, the validity of the proposed shear-corrected GTN model is also verified through the uniaxial tensile experiment of the strip sheet with a hole in the middle. Finally, finite element (FE) model of the mould-sheet coupling system is developed based on the modified GTN model, and the influence of punching speed, blank holder force, friction coefficient and dwell time on the forming performance of AA5052 aluminum alloy sheet is investigated. The results show that ductile fracture of aluminum alloy sheet is most prone to exist on the upper fillet of part. [ABSTRACT FROM AUTHOR]

• Proper quantification of joint rotational stiffness (JRS) of a flight intersection joint (FIJ) influences the dynamic characteristics of a flight vehicle. • JRS of an FIJ is often determined experimentally due to the lack of a right predictive model. • An analytical model is proposed to evaluate the JRS of a radial-type FIJ when subjected to an external bending moment. • Numerical analyses and experiments are performed on six different FIJ configurations. • JRS and moment-rotation behavior predicted by the proposed model are correlated with both experimental and numerical analyses. • Further, the effect of joint clearances on the behavior of FIJ is investigated through the present model. Joint rotational stiffness (JRS) of a flight intersection joint (FIJ) and its accurate quantification play an essential role in studying the dynamic modal characteristics of a flight vehicle. This JRS of a FIJ is mostly determined through elaborate experiments due to the non-availability of a reliable predictive model. Therefore, in this paper, an analytical model is proposed to evaluate JRS of a radial type FIJ when subjected to external bending moment. In this model, at first, the tensile and compressive part of the FIJ section is identified by determining the neutral axis position. The respective part's contributing stiffness is then estimated by employing a spring-mass model. Later, the JRS expression is derived from the moment equilibrium condition and expressed as a function of the stiffness of the tensile and compressive part and neutral axis position. Subsequently, finite element analysis (FEA) is conducted with different numbers of screws, followed by detailed experimental investigations. The proposed analytical model is validated with the results from FEA and experiments for different screw configurations of FIJ. Further, the proposed model is extended to account for the effect of joint clearances on the JRS and the corresponding moment-rotation characteristics of the FIJ. [Display omitted] [ABSTRACT FROM AUTHOR]

The particle sedimentation and phase change in the mushy zone are accompanied by a variety of complex transfer processes involving momentum, heat, and mass. It is very important to investigate the coupling process of particle settling and melting in the mushy zone for revealing the mechanism of the solid-liquid phase change. In this paper, the motion process and heat transfer characteristics of an elliptic particle as well as two particle interactions in the vertical channel were solved by the finite element method with the consideration of coupling of the phase change and motion. The Arbitrary Lagrangian-Euler Method (ALE) was employed to track the interface of the moving particle and fluid. Results show that the elliptical particle settles along the channel's center line vertically under gravity and undergoes phase change simultaneously. Uneven velocity and temperature fields surrounding the particle are generated by sedimentation, resulting in the particle with an irregular shape. When the initial position of the particle deviates from the center line, the particle deflects during the sedimentation and shifts both left and right in the X -direction. The different initial angles of settling also affect the sedimentation velocity and melting rate. When two particles settle simultaneously, they will lead to complex movement and heat transfer due to the interaction between each other. If the arrangement is eccentric, both particles undergo complex deflections during sedimentation, leading to different melting rates for the two particles. [ABSTRACT FROM AUTHOR]

The working environment of industrial fields where the Particulate Reinforced Composites (PRCs) are commonly used is complex. In these harsh environments, PRCs produce some nonlinear strains, such as plastic, thermal, and creep strains, which affect the performance of PRCs to some extent. In addition, the actual structure of PRCs contains a massive amount of inclusions, and the number of inclusions could reach the magnitude of millions or even tens of millions. For the large-scale numerical simulation of PRCs, ordinary displacement finite element requires a large number of meshes, which increases their computational complexity and unsolvability. For real PRCs with random particle distribution, homogenisation theory does not accurately capture the true state of stress concentration in PRCs. The Voronoi cell finite element method (VCFEM) can be a good solution to the drawbacks of the above two numerical simulation methods. The subject of the present work explores a modified complementary energy generalized function that takes the constitutive relationship of nonlinear strain into account, proposing a two-dimensional VCFEM, formulated with plastic, thermal, and creep strain. The simulation results are compared with the computed results of a commercial finite element software Marc to verify the validity and accuracy of the VCFEM. Results of the comparison show that the VCFEM has the advantages of simple meshing and faster computation under the same precision. The VCFEM, considering plastic, thermal, and creep strains proposed in this paper, lays the foundation for future large-scale numerical simulations of PRCs containing a large quantity of inclusion structures and can realistically capture the stress concentration state of PRCs. At the end of the article, the impact of the order of stress function on the calculation results is discussed. [ABSTRACT FROM AUTHOR]

Surface ruptures resulting from seismic faulting have the potential to inflict substantial damage to bridges straddling fault lines; hence, it is imperative to investigate the impact of ground motions documented on either side of fault rupture planes—termed as across-fault ground motion—on the seismic resilience of bridges. In this paper, the object of study is a three-span, simply supported beam bridge traversing a strike-slip fault. Utilizing the LS-DYNA finite element software platform, a sophisticated three-dimensional finite element model of the selected bridge is constructed, meticulously accounting for material damage nonlinearity and structural collision contact nonlinearity. A synthetic across-fault ground motion serves as the excitation for the seismic analysis of the bridge, systematically examining the influence of the fault-crossing angle (FCA), fault sliding rise time, and ground surface permanent rupture displacement on the dynamic response and seismic damage incurred by the simply supported beam bridge. The findings demonstrate that a diminutive fault-crossing angle (FCA) corresponds to an elevated risk of longitudinal beam collapse when a simply supported beam bridge does not intersect a fault vertically. The impact of the fault sliding rise time on the magnitude of seismic response and damage sustained by the simply supported beam bridge is relatively minuscule and can be neglected. Conversely, the ground surface permanent rupture displacement profoundly influences the dynamic response and seismic damage of the bridge. The emergence of fling-step pulses from the development of ground surface permanent rupture displacement amidst seismic activity induces a shift in failure mode-from the designer-intended bending failure to an unforeseen shear failure. • A FE model of a simply-supported beam bridge is established with consideration of material and contact nonlinearity. • The systematic parameter analysis of the simply-supported beam bridge is conducted. • The failure mode and damage process of the simply-supported beam bridge are revealed. • Recommendations for the seismic design of simply-supported beam bridges subjected to strike-slip faulting are drawn. [ABSTRACT FROM AUTHOR]

• This paper reports on calculation of dislocation density in 200 mm SiC crystal grown by PVT method. • Numerical study based on a model was carried out for modeling of dislocation density. • Evolution of crystal growth interfaces were captured using a dynamic mesh technique. Physical vapor transport (PVT) is the dominant method for growing 200 mm SiC crystals, and the crystals produced by this method still have dislocations, which affect the performance of the device. In this study, the finite element analysis of 200 mm SiC crystal growth has been conducted to investigate the influencing parameters on the dislocation density. The calculations are based on the model of multiple resistance heating. The transient heat transfer for the crystal growth is first calculated. A dynamic mesh technique is then employed to consider the shape evolution of the crystal during the growth. Finally, the distributions of the internal stress and dislocation density have been calculated based on the Alexander-Haasen model. The comparison among different parameters provides guidance for reducing the thermal stress and dislocation density in the 200 mm SiC crystal growth. [ABSTRACT FROM AUTHOR]

Numerical simulations are used in this work to investigate aspects of microstructure and microsegregation during rapid solidification of a Ni-based superalloy in a laser powder bed fusion additive manufacturing process. Thermal modeling by finite element analysis simulates the laser melt pool, with surface temperatures in agreement with in situ thermographic measurements on Inconel 625. Geometric and thermal features of the simulated melt pools are extracted and used in subsequent mesoscale simulations. Solidification in the melt pool is simulated on two length scales. For the multicomponent alloy Inconel 625, microsegregation between dendrite arms is calculated using the Scheil-Gulliver solidification model and DICTRA software. Phase-field simulations, using Ni–Nb as a binary analogue to Inconel 625, produced microstructures with primary cellular/dendritic arm spacings in agreement with measured spacings in experimentally observed microstructures and a lesser extent of microsegregation than predicted by DICTRA simulations. The composition profiles are used to compare thermodynamic driving forces for nucleation against experimentally observed precipitates identified by electron and X-ray diffraction analyses. Our analysis lists the precipitates that may form from FCC phase of enriched interdendritic compositions and compares these against experimentally observed phases from 1 h heat treatments at two temperatures: stress relief at 1143 K (870 °C) or homogenization at 1423 K (1150 °C). [ABSTRACT FROM AUTHOR]

This paper presents a quasistatic problem of an elastic body in frictional contact with a moving foundation. The model takes into account wear of the contact surface of the body caused by the friction. We recall existence and uniqueness results obtained in Sofonea et al. (2017). The main aim of this paper is to present a fully discrete scheme for numerical approximation together with an error estimation of a solution to this problem. Finally, computational simulations are performed to illustrate the mathematical model. [ABSTRACT FROM AUTHOR]

Abstract Loss of circularity when creating metal ring-shaped products by ring rolling is a significant industrial issue. This paper explores the previously tacit knowledge that plastic changes in curvature - required to maintain circularity - principally occur as material passes through the roll gap. Through a series of experiments and numerical simulations on half-ring workpieces, the 'free curvature change' is explored for the first time, finding that the ring can 'curl up' - the radius reducing by as much as -39% in a single pass - unless the inner roll is much smaller than the outer roll. An analytical model of free curvature change is proposed based on force equilibrium and compatibility. Under a range of 'normal' operating conditions this predicted free curvature change to within 7%. In (full) ring rolling the radius of curvature must continually increase. This paper proposes that regulation of curvature is achieved through bending moments at the roll entry and exit; largest when the tool size ratio is furthest from the optimum. This hypothesis is supported by Finite Element simulations of full ring rolling, finding entry and exit moments up to a quarter of the moment for a fully plastic hinge. This work could be of direct use to process designers in choosing tool sizes and guide roll force limits and suggests new ways to use guide rolls to better maintain circularity in challenging situations. [ABSTRACT FROM AUTHOR]

Abstract Over the last few decades, oil tankers and bulk carriers, which preferably adopting the concept of a single stern tube bearing, have been subjected to the mechanical damages on propulsion shaft bearings since such a concept overly requires a single bearing to support the full load of the propulsion shaft. This paper was to fundamentally address the problem of current practices of aligning a single stern tube bearing for commercial ships by determining the effective supporting point to balance the load of the propulsion shaft properly. Since selecting a case ship subjected to the damage on the stern tube bearing, it investigated the actual cause of the damage, thereby finding a practical way to enhance the sustainability of the propulsion shaft system using the single stern tube bearing. Computer-aided simulations using the finite element analysis as well as on-site measurements were carried out. Research findings revealed that the ignorance of the relative slope angle between the propulsion shaft and the aft stern tube bearing had led to misalignment, which resulted in adverse effects on the stability of the shaft system, and consequently damaged the stern tube bearing. Results of the analysis suggested that the degree of slope be taken into account when estimating the effective supporting point of the bearing. Finally, this paper pointed out that the establishment of a shaft installation guideline considering the effect of the shaft slope, thereby preventing wiping damage of the aft stern tube bearing would be an urgent task. Highlights • The limitations of the conventional process to verify the correctness of the shaft alignment were proven. • For uniform load distribution, the both ends of the stern tube bearing are to be considered the effective support points. • It provided the insight for developing an enhanced procedure to check the proper position of the propeller shaft. [ABSTRACT FROM AUTHOR]

Highlights • A reduced order model (ROM) encompassing the anatomical liver shape is created. • The ROM is able to reproduce the mechanical behavior with high fidelity. • The solution is computed in a 11 dimensional subspace. Abstract Background and objective This paper focuses on computer simulation aspects of Digital Twin models in the medical framework. In particular, it addresses the need of fast and accurate simulators for the mechanical response at tissue and organ scale and the capability of integrating patient-specific anatomy from medical images to pinpoint the individual variations from standard anatomical models. Methods We propose an automated procedure to create mechanical models of the human liver with patient-specific geometry and real time capabilities. The method hinges on the use of Statistical Shape Analysis to extract the relevant anatomical features from a database of medical images and Model Order Reduction to compute an explicit parametric solution for the mechanical response as a function of such features. The Sparse Subspace Learning, coupled with a Finite Element solver, was chosen to create low-rank solutions using a non-intrusive sparse sampling of the feature space. Results In the application presented in the paper, the statistical shape model was trained on a database of 385 three dimensional liver shapes, extracted from medical images, in order to create a parametrized representation of the liver anatomy. This parametrization and an additional parameter describing the breathing motion in linear elasticity were then used as input in the reduced order model. Results show a consistent agreement with the high fidelity Finite Element models built from liver images that were excluded from the training dataset. However, we evidence in the discussion the difficulty of having compact shape parametrizations arising from the extreme variability of the shapes found in the dataset and we propose potential strategies to tackle this issue. Conclusions A method to represent patient-specific real-time liver deformations during breathing is proposed in linear elasticity. Since the proposed method does not require any adaptation to the direct Finite Element solver used in the training phase, the procedure can be easily extended to more complex non-linear constitutive behaviors - such as hyperelasticity - and more general load cases. Therefore it can be integrated with little intrusiveness to generic simulation software including more sophisticated and realistic models. [ABSTRACT FROM AUTHOR]

Abstract In this paper, compressive material tests on unconfined/confined resin and steel reinforced resin were experimentally evaluated in order to validate the numerical results. The uniaxial model which combines damage mechanics and Ramberg-Osgood relationship is proposed in this paper to describe the uniaxial compressive behaviour of resin and steel reinforced resin. Numerical homogenization is conducted to predict the tensile and shear behaviour of steel reinforced resin after validated by compressive material test results. The friction angle β , the ratio of the yield stress in triaxial tension to the yield stress in triaxial compression K, and the dilation angle ψ of the linear drucker-prager plastic model are obtained based on experiments and numerical homogenization simulation. The confinement effects on resin and steel reinforced resin could be effectively simulated by combing above parameters and uniaxial compressive model. Finite element simulations on unconfined/ confined resin and steel reinforced resin material tests were conducted to validate the material parameters proposed in this paper. A good agreement is observed, indicating the model and parameters proposed in this paper could be effectively used in the finite element simulation of injected bolts. [ABSTRACT FROM AUTHOR]

Highlights • A structural model for pipewall hydrate deposition is established. • Mechanical parameters of pipewall hydrate deposition are calculated. • Mechanical properties and stabilities of pipewall hydrate deposition are simulated. • Influences of flow rate, deposition thickness and deposition length are investigated. Abstract The mechanical properties and mechanical stabilities of pipewall hydrate deposition are of great importance to the prevention and removal of pipeline hydrate plugging. In this paper, the mechanical properties and mechanical stabilities of pipewall hydrate deposition are quantitatively investigated by modelling and numerical simulation. First, a structural model for pipewall hydrate deposition is established based on particle packing theory. Using this structural model, the main mechanical parameters of pipewall hydrate deposition can be calculated. Then, numerical simulations using finite element method and ANSYS Mechanical APDL 14.5 are conducted based on the calculated mechanical parameters. Through the simulations, the structure deformation, internal stress distribution and failure of pipewall hydrate deposition when it is under the action of external forces are studied and the influences of flow rate, deposition thickness and deposition length are investigated. The results of this paper can provide guidance for pipeline flow assurance. [ABSTRACT FROM AUTHOR]

Highlights • CRB test was numerically simulated including asymmetry of loading. • CRB specimens made directly from polyethylene pipes were examined regarding the residual stress. • Influence of crack asymmetry on results of CRB test was evaluated. • Small effect of the residual stresses on CRB test was demonstrated. Abstract The Cracked Round Bar (abbreviated as CRB in the following) test is used as standardized accelerated testing method for simple ranking of polyethylene pipes based on measuring number of cycles to failure of the cyclically loaded CRB specimen. It can also be used for the slow crack growth rate evaluation of the tested material. This paper deals with the issue of asymmetrically growing cracks in CRB specimens and possible influence of the asymmetry on the results of CRB tests, both the number of cycles to failure and the crack growth rates. It is assumed that the asymmetry is caused by presence of residual stress in the CRB specimens. In the first part of the paper, residual stress in two polyethylene pipes (produced using different extrusion speed) is investigated. Then CRB specimens made from these pipes are also examined regarding the residual stress and the results are compared. The found residual stress distributions are used as input for the following finite element method (FEM) simulation of crack growth in the CRB specimens. The FEM model results are then evaluated and fatigue crack growth rates for asymmetrically growing cracks are calculated. They are compared to the results for symmetrically growing cracks and influence on the results and its significance is discussed. In the end, CRB specimen lifetime prediction is carried out and the influence of the asymmetry on the obtained number of cycles to the failure is also addressed. [ABSTRACT FROM AUTHOR]

Abstract As part of the LEAP-GWU-2015 exercise, a dynamic centrifuge test was conducted at the University of Cambridge on a 5° slope of medium dense Ottawa F-65 sand. The model preparation and saturation details are presented in this paper. This paper presents the experimental data recorded during small and large magnitude sinusoidal ground motions. After the experiment, numerical simulations of the experiment were performed using the finite element code Swandyne. The results from these numerical analyses are compared with the centrifuge test data and the deformations observed during the post-test investigations. The numerical analyses replicated many of the salient features of the test, such as the overall generation of excess pore pressures and attenuation of accelerations in the liquefying ground. More subtle results, such as the de-liquefaction shocks and the asymmetric response due to differences in upslope and downslope accelerations were less well captured in terms of the expected spikes in the dynamic excess pore pressures and accelerations. Overall, the combination of centrifuge testing and numerical analysis were found to complement each other well. Highlights • The effect of shaker translation on the model is explored in terms of accelerations and excess pore pressure generation. • Relative performance between the numerical analysis and experimental data are discussed for each earthquake loading. • The influence of high frequency components in the acceleration input were assessed using an additional numerical analysis. • Interpretation of the numerical analyses were guided by the discrepancies between predicted and measured pore pressures. [ABSTRACT FROM AUTHOR]

This paper presents results of a numerical finite element parametric study on elastic shear buckling and ultimate shear strength of cold-formed steel channels with longitudinally stiffened slotted webs. The following parameters were varied: channel height, thickness, flange width, flange lip length, longitudinal stiffener size, perforation pattern, aspect ratio, steel yield stress and boundary conditions. Channels with longitudinally stiffened solid webs subjected to shear load were also studied to provide reference data for comparison with the slotted channels. The parametric study described in this paper allowed us to develop equations for predicting the shear buckling coefficient of longitudinally web stiffened solid channels, as well as equations for predicting the elastic shear buckling load and the ultimate shear strength of channels with longitudinally stiffened slotted webs. The developed shear strength equations without and with tension field action are presented in the paper in the traditional and direct strength method formulations. The developed equations account for the studied parameters and showed good agreements with the finite element simulation results. [ABSTRACT FROM AUTHOR]

In this paper, we compare the failure behaviors of CFRP single and double (S–D) lap joints and analyze the effects of hygrothermal aging on these joints through a comprehensive experiment and simulation. Firstly, we analyze and compare the degradation pattern of the residual strength of S–D​ lap joints under three hygrothermal environments, and reveal the aging mechanism in conjunction with the macro/fine-view failure surfaces of the joints. Secondly, we elucidate the probability distribution of joint aging failure using the two-parameter Weibull distribution. Finally, we develop a finite element model to simulate the failure process of the cohesive behavior, and compare not only the bending moment and contact stress distribution of the two joints, but also analyze the damage condition of the CFRP matrix/fiber. We define environmental degradation factors to express the failure behavior of lap joints after aging. Through the above analysis methods, we find that hygrothermal aging can seriously damage the CFRP and adhesive properties. The mechanical performance of DLJs is significantly superior to that of SLJs, and they also exhibit better reliability. Therefore, DLJs can be substituted for SLJs in some application scenarios. Additionally, our paper provides new insights into the selection of an appropriate lap bonding method. • This paper evaluates the aging durability of single and double lap joints from multiple perspectives. • The failure behavior of single and double lap joints is comprehensively compared by numerical simulations. • This paper provides some new insights into the selection of an appropriate lap bonding method. [ABSTRACT FROM AUTHOR]

In order to meet the requirements of outfitting layout and light weight, circular or elliptical holes need to be opened on the web of the hull beam. Excessive opening will lead to stress concentration and reduce the bearing capacity of the beam. For the super-standard openings, the general strengthening method cannot guarantee the ultimate bearing capacity of the beam, and locally increasing the web to form a variable cross-section beam can compensate for the lost bearing capacity. In the present paper, the three-point bending load tests of variable cross-section opening beams and equal cross-section beams are carried out. Combined with the results of nonlinear finite element analysis, the ultimate bearing capacity and failure mode of transverse bending are compared, and it is verified that the ultimate bearing capacity of beams with variable cross-section openings is better than that of beams with equal cross-section. By changing the cross-section size and optimizing the transition form, the variable cross-section perforated beam is further improved and optimized to enhance the ultimate strength. • The three-point bending load tests of variable cross-section opening beams are carried out. • Considering the actual welding deformation, the ultimate strength prediction method of perforated beam is improved. • The variable cross-section perforated beam is optimized to enhance the ultimate strength. [ABSTRACT FROM AUTHOR]

With severe corrosion issues afflicting nearly half of all high sulfur gas fields, bimetal composite tubes have emerged as an optimal solution due to their superior corrosion resistance, mechanical properties, and cost-effectiveness. These tubes have gained widespread adoption in gas gathering applications. However, the evaluation of the corrosion performance of Incoloy 825 bimetal composite tubes within high sulfur gas field environments is yet to be adequately addressed. An investigation into the welding performance of both the base metal and weld is instrumental in ascertaining the safety and reliability of bimetal composite pipes. To this end, this paper presents a thermodynamically coupled finite element model of bimetal composite pipes, developed using SYSWELD software, and corroborates the model using the borehole method for empirical verification. The study further delineates the distribution of residual stress encountered during multi-layer and multi-pass welding of bimetal composite pipes. • Welding simulation of bimetal tubes validates residual stress distribution. • Compressive stress dominates base metal; cap-shaped tensile stress is on the weld side. • High-stress near fusion line and transition layer risks cracking in bimetal pipes. • Numerical modeling and verification lead to safe application of bimetal composite pipes. [ABSTRACT FROM AUTHOR]

This paper provides an experimental and numerical investigation into the compressive behavior of built-up H-section columns fabricated using H-SA700 steel. First of all, axial compression tests were performed on nine built-up specimens. Secondly, the 3D solid finite element (FE) models were constructed using ABAQUS, and their accuracy was verified by the experimental results. And then, the effects of slenderness ratio, web height-to-thickness ratio, flange width-to-thickness ratio, channel thickness, transverse bolt pitch, bolt diameter, and longitudinal bolt pitch on the compressive strength and buckling deformation of built-up members were analyzed. Finally, the applicability of the column curves from GB 50017–2017, EN 1993-1-1, and ANSI/AISC 360–16 for H-SA700 built-up columns were assessed, and the design curves were modified. The results indicated that slenderness ratio and channel thickness were the main parameters affecting the bearing capacity of built-up members. The design curves of current codes all underestimated the compressive strength of built-up columns around the weak axis under axial loading. In addition, modified column curves could provide a conservative design for built-up H-section columns. • Nine built-up H-section columns were tested under axial loading. • Finite element models applicable for built-up H-section columns were established. • The effects of six key parameters on the compressive behavior of built-up columns were analyzed. • The applicability of the design curves of the current code for H-SA700 built-up H-section columns was assessed, and the design curves were modified. [ABSTRACT FROM AUTHOR]

Ice sphere impacts are an important issue in the study of composite materials, polar engineering, and aerospace engineering. The traditional mechanics numerical methods, rooted in classical continuum mechanics, like the Finite Element Method (FEM), grapples with the challenge of spatial derivatives not existing at the crack tip or crack surfaces, rendering it unsuitable for addressing discontinuity-related problems such as fracture and failure. Developed particle method peridynamics shows great ability in handling such discontinuous problems. This paper establishes an ice sphere impact model using the peridynamics method. To verify the accuracy of our model, we compared the simulated results with the tested results of the high-speed impacting ice sphere and obtained that the predicted impact load and crack propagation of ice spheres are consistent well with the experiment results. An isolated damage zone was found to appear at the top region when the surface crack just extends across the hemispherical plane. This phenomenon happens due to that the impact wave propagating along the sphere center axis reaches the top end faster than the surface wave, making spalling damage occurred at the top region, and the encounter between the reflected wave and the surface wave would make the spalling damage more severe. • An ice impacting model was established based on the developed particle method (Ordinary State-Based Peridynamics). • An experimental setup of an ice sphere impacting was established, and the numerical models were verified. • A more in-depth study towards the damage behavior and the impacting wave propagating on the surface was conducted. [ABSTRACT FROM AUTHOR]

• Thin-walled lenticular composite booms with different design parameters were prepared, and free-end loading experiments and coiling experiments are conducted on the established experimental platforms. • The finite element model of thin-walled lenticular composite booms are established and simulations are conducted to analyze the mechanical response during free-end loading and coiling process. • The influences of ply numbers, ply angles, fiber types and fiber contents on the performance of TLCBs were analyzed through experiments and finite element simulations. As a kind of lightweight composite structure, thin-walled lenticular booms made of fiber reinforced composite are widely used in the aerospace field because of its high stiffness in the unfolded state. In this paper, the load-bearing and coiling characteristics of the thin-walled lenticular composite booms were studied, and the effects of different design parameters and material properties were compared. Thin-walled lenticular composite booms with different ply numbers, ply angles, fiber types and fiber contents were prepared. Free-end loading experiments and coiling experiments were conducted to obtain the load-displacement curves, coiling torques and binding forces. The finite element model was established and the simulation results were compared with those of experiments. It is shown that increasing the ply number, increasing the fiber content and using fibers with lower elastic modulus can significantly enhance the load-bearing capacity of thin-walled lenticular composite booms, meanwhile reducing its coiling capacity. The booms with orthometric ply angle have greater load-bearing capacity, but the ply angle has less effect than the ply numbers, fiber types and fiber contents. The results provide feasibility for the design of thin-walled lenticular composite booms suitable for the aerospace field. [ABSTRACT FROM AUTHOR]

This paper proposes a micromechanical model based on the finite element method (FEM) to analyze the ratchetting deformation of short glass fiber-reinforced polymer composites (SFRPCs). To reasonably consider the complex mechanical characteristics of the polymeric matrix under asymmetrical stress-controlled cyclic loading, a damage-coupled nonlinear viscoelastic-viscoplastic (VE-VP) cyclic constitutive model was constructed. The cyclic constitutive model of the matrix was introduced into the FEM model utilizing a user-defined material, and the corresponding experimental validation of the matrix was conducted. Subsequently, the cyclic constitutive model was introduced into the analysis of the micro-FEM model of the composites. The random orientation was considered to generate fibers in the FEM. Based on the analysis of the microscale representative volume element (RVE) model, the effects of different fiber content and cyclic peak stress on the ratchetting of SFRPCs were studied in detail. After validation, the effects of the fiber length and fiber stiffness on the ratchetting deformation of SFRPCs are discussed based on the developed micro-FEM model. The results show that the increase in the fiber length and fiber stiffness reduced the ratchetting deformation of SFRPCs within a specific content range. The model can assess the ratchetting deformation and damage evolution within the composites to provide more accurate predictions of the ratchetting deformation of SFRPCs and guide the expanded application of SFRPCs in structures. [Display omitted] • A damage-coupled nonlinear viscoelastic-viscoplastic cyclic constitutive model of the polymer matrix was proposed. • The constitutive model was introduced into microscale finite element model through the user-defined material subroutine. • Ratchetting deformation of SFRPCs was analyzed based on the constructed microscale representative volume element model. • Effects of fiber length and fiber stiffness on ratchetting deformation and damage of SFRPCs were investigated. [ABSTRACT FROM AUTHOR]

Textile-reinforced ceramic matrix composites are key structural materials for aerospace applications. In this paper, the influence of meso-structure and damage mechanisms on mechanical behavior of three-dimensional (3D) four-directional braided SiC/SiC composites is systematically investigated by using numerical simulations. First, periodic preform geometry model, also known as representative volume element (RVE), is reconstructed by using micro-computational tomography (μ-CT). Then, two damage mechanics models are employed to establish non-linear behavior of tows and matrix. Moreover, cohesive model is introduced to represent tow/tow and tow/matrix delamination behavior. It is noteworthy that homogenized tow model is derived from micromechanical model on fiber scale. Finally, macro stress-strain and failure behaviors of 3D braided SiC/SiC composites are simulated by meso-scale finite element analysis. Numerically simulated tensile modulus and strength of 3D braided SiC/SiC composites are compared with experimental results, exhibiting good consistency. Numerical simulations revealed failure mechanism and confirmed that, in addition to globally evolved damage process under tensile load, meso-scale preform caused stress concentration and subsequent local rupture behavior. Current research shows that reconstructed textile model realistically describes tensile mechanical behavior and damage evolution of 3D braided SiC/SiC composites. [ABSTRACT FROM AUTHOR]

Research on the interaction mechanisms between a bit and rock is a focus of the field of rock breaking theory in drilling engineering. The bottom hole shape, which directly affects the effectiveness of rock breaking at different positions around the bottom hole, is the key factor in research on the interaction between a bit and rock. This paper aims to discuss the influences of bottom hole shape on effectiveness of rock breaking. Firstly we established the mathematical model of rock breaking strength and used it as an evaluation index to analyze the influence of bottom hole shape on effectiveness of rock breaking. Secondly, the relationship between the rock breaking strength and cutting speed, cutting depth, rock lithology and bottom hole shape are verified by experimental approach and numerical simulation. The mathematical model of the relationship between the rock breaking strength and the bottom hole shape is established with a finite element method. Finally, this paper takes minimum rock-breaking energy consumption as the goal and introduces the “crown breaking work per revolution” as an objective function to optimize the bottom hole shape. This paper uses the fact that the shape of the bottom hole is symmetric and corresponds to the crown shape to determine the optimal design of a PDC bit crown profile by inverse design. This paper will help to expend the ideas of bit design and promote the development of research on rock breaking theory. [ABSTRACT FROM AUTHOR]

Continuum models of fracture should be equipped with a localization limiter to prevent pathological discretization sensitivity of finite element simulations. Moreover, stiffness recovery, called also crack closing effect, should be reproduced in the modelling of quasi-brittle materials when reversed loading is applied. In this paper the efficiency of two different established damage-plasticity models for concrete is assessed from the viewpoint of the two above-mentioned aspects. The first description is the so-called concrete damaged plasticity model, available in the ABAQUS package. In this model the plasticity theory is not only augmented with stiffness degradation and recovery, but also with the crack band approach and viscoplastic regularization. The gradient-enhanced damage description, which is the second one considered, can also be coupled to plasticity. In this model additional averaging equation prevents the pathological discretization sensitivity of fracture simulations. Two fields, displacements and averaged strain measure, are interpolated and suitable finite elements are programmed by the authors in the FEAP package. Basic concepts of the numerical analysis of the crack closing phenomenon are reviewed. Both models are capable of avoiding mesh-sensitivity, but it is achieved in a different manner and it is shown in the paper that the users of ABAQUS should employ the crack band options with particular care. Representative examples in the context of the examined issues are demonstrated: uniaxial tension of a bar and a cantilever beam. The results obtained using both the models are compared and the effects of regularization and crack closing are illustrated. [ABSTRACT FROM AUTHOR]

This paper examines the dynamic behaviour of square tubular T-joints under impact loading by means of experimental, numerical and analytical studies. Firstly, a high-performance drop hammer setup is employed to carry out the impact tests on five hot-rolled square tubular T-joints with different chord thickness and width ratio of brace/chord under three levels of impact height. The dynamic responses of tubular T-joints including the deformation patterns and the development of impact force and displacement are described. Based on the experimental results, the impact load-deformation relationships as well as the energy dissipation are further discussed to reveal the mechanical behaviour of T-joints, with emphasis on the effect of width ratio of brace/chord and impact energy. Complementary finite element model for simulating the tubular T-joints under impact is then proposed and validated against the available test results. Finally, the test results and numerical simulations are utilized to investigate the failure mechanism of T-joints under impact load. In particular, the local and global displacements of square chord are estimated by an equivalent area method, and the impact resistance of impacted joints is examined based on the yield line theory. In general, the investigation in this paper can also offer reliable test data and design suggestions to reasonably evaluate the impact behaviour of square tubular T-joints. [ABSTRACT FROM AUTHOR]

In the present paper, a two dimensional axisymmetric Finite Element Method (FEM) is developed to carry out a thermo-mechanical analysis on a horizontal storage tank intended to storage hot water for a domestic application. The purpose of these numerical simulations is to assess the thermo-mechanical behavior of a horizontal tank with evacuated tube collectors, and consequently to suggest a new design which ensures an optimum mechanical strength according to severe applied operating conditions in terms of temperature and pressure. To achieve this goal, a thermo-mechanical 1-way sequential coupling has been used as a solving method. The physical model suggested in this study and the simulations procedure was described under detailed assumptions. In fact, the main hypotheses in the current formulation were the thermo-elastic behavior of the tank's materials and the steady state assumption analysis. This paper outlines three studies that were performed to extend the lifespan of the horizontal storage tank, through the definition of a suitable material and an optimal design. The main conclusions of the assessment are that the optimal configuration which avoid the appearance of the stress concentration zones is the configuration (c), where Ri = 11 mm and Re = 14 mm, because the stress on the tank's shell was better applied. Moreover, the effect of the material's selection was carried out, and it was found that stainless steel is the optimal material. Last but not least, a set of simulations were conducted to investigate the tank shell thickness on which the thermo-mechanical constraints were applied. The thickness t = 2 mm was presenting an optimal mechanical behavior with regard to the studied operating conditions. [ABSTRACT FROM AUTHOR]

This paper summarises the findings of a Joint Industry Project (JIP) led by DNV GL on the treatment of residual stress on pipes undergoing high plastic deformation. The paper presents measured residual stresses and some of the full-scale test results supported by Finite Element Analysis (FEA) for the seamless pipes before and after high plastic deformation on selected girth welds. Several FEA models of the reeling simulation have been developed including mapping an initial axial residual stress (transverse to the weld) profile onto a seamless girth-welded pipe. The initial welding residual stress distribution used for mapping was based on a number of through thickness measurement along the circumference of the girth welds. The predicted residual stresses after reeling simulation was subsequently compared with experimental measurements. It is evident that FEA models can predict welding residual stress re-distribution during the reeling process, but some differences with measurements are present through the thickness. [ABSTRACT FROM AUTHOR]

Simulating multi-body dynamics with both rigid and flexible parts and with frictional contacts is a hard problem. We solve this by expressing the couplings between the bodies as position level constraints. The implicit treatment of the constraint directions gives us improved stability over velocity based methods. Then by employing regularization of nonlinear constraints and a convex minimization formulation, we bridge constraint-based methods to traditional force-based methods. In fact, the former are just a dual variables formulation of the latter. We solve this dual problem using position based dynamics (PBD). We show how PBD is a completely valid modeling technique and we extend it with an accurate contact and Coulomb friction model. We further show for the first time how the same solver can be used to simulate both rigid and deformable solids with two way coupling. For the soft bodies we introduce a novel form of linear finite elements expressed as constraints, that is more accurate than PBD mass-spring systems. More of our results include the energy conserving Newmark integrator and the accelerated Jacobi solver suitable for parallel architectures. Note that this paper is an extended and revised version of the conference paper published in [1]. [ABSTRACT FROM AUTHOR]

Simultaneous fracturing stimulations in horizontal well are effective tools for promoting productivity of unconventional reservoirs. However, fracture lengths and widths of some perforation clusters may be restricted due to the stress shadow effects. In this paper, a numerical model to simulate nonplanar fractures simultaneous initiation in porous media is established based on the extended finite element method (XFEM). The amount of fluid flowing into each fracture is dynamically calculated with a total injection volume in this model. Sensitivity studies of formation parameters on fractures geometry of simultaneous fracturing are presented. The in-situ stress contrast is found to be the main factor controlling the fractures propagation. The initiation of interior fracture will be restricted or compressed to be closed in the vicinity of the injection point. The influence of injection rate and perforation friction on fractures initiation is investigated. Strategies to optimize fractures geometry are presented through injection control of each fracture. The method presented in this paper can be used in horizontal well design to achieve reasonable fractures geometry. [ABSTRACT FROM AUTHOR]

The paper presents simplified analytical methods to assess the plastic deformation and failure of double-hull ship structures subjected to bulbous bow collision. To validate the methods, numerical simulations are conducted on double-hull tanker side structures including three frame spacings along the longitudinal direction and two stringer spacings along the vertical direction. The paper estimates the extent of damage within double-hull ship structures during minor ship-to-ship collision, where the inner hull does not participate in dissipating incident energy. In the analytical methods, the nose shape of striking bulbous bow is simplified as a hemisphere or a cylinder with hemispherical ends. This equivalence is validated against the similar numerical force-displacement responses using the actual bulbous bow and the simplified strikers. The analytical methods derive expressions to estimate the relation between the plastic deformation and the crushing force of the double-hull structures. The onset of fracture in the outer hull is evaluated by a simple formula based on experimental and theoretical analyses. Finally, the probabilistic structural absorbed energy until the rupture of specific struck ship with respect to the displacement of striking ship is assessed according to the statistical data of ship dimensions and the design principles of bulbous bow. [ABSTRACT FROM AUTHOR]

Operational spacecraft are facing a risk of collision with space debris objects. The net capturing method has been proposed to mitigate this risk on spacecraft. The mass-spring model is usually applied for net modeling by discretizing a cable into one or several mass-spring-damper elements in simulation. The absolute nodal coordinates formulation (ANCF) has also been applied to model the net, and this model is able to describe the flexibility of a net using less elements. However, the influence on the net behavior in simulation by the flexibility modeling of a net is not well understood and barely discussed. In this paper, flexibility models of a net are established based on the mass-spring model and the ANCF model,respectively. The influence on the net behavior by the flexibility modeling is, for the first time, analyzed via simulations. Two case studies of capturing a ball and a cube shaped targets are performed. It is found that the flexibility modeling has little influence on the net dynamics in simulation. Finally, the characteristics and benefits of the ANCF model are described and analyzed. A drawback of the ANCF model was found to be its inferior computational performance. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we present a numerical investigation about the metal transfer of GMAW with a new model based on the phase field model. Unlike most published work, the thermocapillary effect and mixture energy resulting from the new research of multiphase fluids are taken into model of phase transfer and interface change which is different from volume of fluid method (VOF) that has been widely used in welding problem. We discretize the whole model including continuity condition, Navier–Stokes equation, phase field model, energy equation and Maxwell's equations with a continuous finite element method in space and a midpoint scheme in time and a penalty formulation is applied to the continuity condition due to the stability in the pressure. Metal transfer of GMAW with pulse current is computed as a numerical example where the numerical result have been verified by the experimental data obtained by using a high-speed camera. Moreover, we also compare the numerical results with and without considering the thermocapillary effects to show that the new model has a higher precision in predicting the droplet in welding. Highlights • We present a new model with thermocapillary, mix-energy, phase field model for GMAW. • The accuracy of the new model is examined with the data of high-speed photography. • The new model has a higher precision in predicting the metal transfer than before. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fick pore diffusion model was applied to predict the adsorption breakthrough curves. • Behaviors of counter ion was considered in ion exchange adsorption process. • Evolution of mass flux along axial direction of adsorption column were studied. • Convection flux was almost 107–108 times larger than that of pore diffusion. • Adsorbent has a good repeatability in the adsorption/elution cycles experiments. In this work, the adsorption rate of geniposidic acid (GSA) on a fixed-bed column packed with porous adsorbents was studied, thoroughly by a Fick pore diffusion model based on numerical simulation and 3D visualization. Adsorption breakthrough curves of GSA were studied experimentally, under various operation conditions such as feeding concentrations, flow rates and packed column aspect ratio. For ion exchange adsorption of GSA onto the adsorbent used in this paper, a maximum adsorption capacity reached 637.5 mmol·L−1 at 298.5 K. Modeling method for an adsorption packed column was based on the coupling of mass transfer equations with a steady velocity field obtained from Navier-Stokes equation. A finite element method was adopted by COMSOL Multiphysics with proper mesh refinement, to solve the equation system. Moreover, the influences of operation conditions on the magnitude and direction of mass fluxes induced by convection and diffusion were analyzed in details. 3D data of Mass fluxes proved that the existence of forming period and transferring period of mass transfer zone (MTZ), which are important knowledge for comprehending the dynamics of adsorption process. The magnitude of convection flux was almost 107–108 times larger than that of pore diffusion flux. Average pore diffusion diffusivities of GSA and Cl− were fitted to be 5.19 × 10−10 and 1.71 × 10−9 m2·s−1, while their maximal mass fluxes were 9.366 × 10−3 and 3.926 × 10−3 mol m−2·s−1 in simulations, respectively. Finally, adsorption and elution recycle experiments proved the feasibility of the novel GSA adsorption technology in the future scaling-up process. [ABSTRACT FROM AUTHOR]

In this paper, a general framework is proposed for the analysis and characterization of observability and diagnosability of finite state systems. Observability corresponds to the reconstruction of the system’s discrete state, while diagnosability corresponds to the possibility of determining the past occurrence of some particular states, for example faulty states. A unifying framework is proposed where observability and diagnosability properties are defined with respect to a critical set, i.e. a set of discrete states representing a set of faults, or more generally a set of interest. These properties are characterized and the involved conditions provide an estimation of the delay required for the detection of a critical state, of the precision of the delay estimation and of the duration of a possible initial transient where the diagnosis is not possible or not required. Our framework makes it possible to precisely compare some of the observability and diagnosability notions existing in the literature with the ones introduced in our paper, and this comparison is presented. [ABSTRACT FROM AUTHOR]

A major difficulty in finite element analysis is the preparation of an effective mesh leading to a good response solution. In engineering analyses of complex components, oftentimes, much more time is spent to arrive at an adequate mesh than to obtain the solution of the established finite element model. The difficulty in meshing is due to the fact that finite elements need to abut each other and cannot overlap. This can lead to highly distorted elements, e.g. sliver elements, reducing the accuracy of solution. In practice, to establish an effective mesh, frequently, significant expertise in building meshes is needed, because great care must be taken in cleaning up the CAD geometry and preparing an effective mesh. The objective in this paper is to present a new finite element solution scheme including meshing in which the elements can overlap. The property that finite elements can overlap removes many of the meshing difficulties, leads to an effective meshing procedure and an overall easy-to-use solution scheme for an analyst or a designer. We first present the meshing scheme that we propose, which combines the use of traditional finite elements and overlapping finite elements. A particular feature is that the meshing procedure can be directly embedded in CAD driven solutions. We then present the theory used for the formulation of the overlapping finite elements and the coupling with traditional finite elements. We consider spherical and brick-shaped overlapping finite elements for which the theory is largely based on the formulation of the method of finite spheres. Finally, we illustrate the complete solution scheme in the analysis of some two-dimensional problems using the CAD geometry as the starting point. While the paper presents a new paradigm for analysis in CAD environments, with much potential, we realize that much further study and research is needed on some of the important ingredients of the method to render the complete procedure effective for general practical engineering analyses of static and dynamic problems. [ABSTRACT FROM AUTHOR]

The high speed railway, which acts as a safer and faster means of transportation, has grown rapidly around the world, especially in China. Meanwhile, the vibration induced by high-speed train (HST) arouses increasing concerns and cannot be ignored. This paper describes ground vibrations with three dimensional models formulated in the time domain using the finite element method (FEM). Absorbing boundaries and Rayleigh damping approach are used to prevent wave reflections from the artificial edges and to simulate the material damping, respectively. Investigations of ground vibration caused by unit load under different speeds and frequencies are given. An inclined classification of ground vibration and the sensitive frequency ranges of surface ground are then found. Moreover, the effects of subgrade treatment and sub-soil treatment on vibration isolation are discussed. It concludes that due to the attenuation effects of subgrade structures on high frequency range, noticeable reductions can be obtained in surface ground vibration. And when a high subgrade or a composite one is applied, the effects are better. The depth of sub-soil treatment would have more positive influence on ground vibration isolation and costs relatively less, compared with its replacement ratio and width. Negative influence may even occur when the sub-soil treatment width becomes larger. Additionally, some useful recommendations are proposed in this paper. [ABSTRACT FROM AUTHOR]