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Self-centering rocking braced (SCRB) system provides enhanced seismic performance and reduced post-earthquake residual drift. However, the effect of higher modes is controversial, affecting shear demands and bending moments in the structure. This functional deficiency is addressed by developing SCRB frames equipped with buckling-restrained columns (BRCs) and buckling-restrained braces (BRBs), performing as exchangeable fuse frames. The system consists of external columns branching off from the main core and connected to it via butterfly-shaped fuses, and BRC and BRB are incorporated into the core at four different height levels to be compared with conventional SCRB as the baseline. Three sets of 12-, 16- and 20-story structures are numerically developed in OpenSees finite element framework with regard to geometrical and material nonlinearities, making a total of 12 SCRB prototypes. The suit of 22 ground motions used in FEMA P695 was scaled to DBE and MCE hazard levels and applied to the structures. Results indicate the capability of the new system in reducing the destructive effects of higher modes, especially in the case of a fuse frame located in the middle of the height. In addition, the core moment and shear force largely reduced, almost 60%, in higher positions of the fuse frame, while those configurations led to large residual drift at the restrained level. However, all structures met the DBE-level 2% drift target. Moreover, increasing structural height nearly reduced seismic demands and increased response reductions. Overall, the system demonstrated acceptable performance in terms of high capacity for energy absorption.

To satisfy the performance and technological requirements of large-scale dynamic machines, the foundation is evolving toward considerable size and complex structure. This makes it vibrate asynchronously, and the existing relevant guidelines and specifications that consider the foundation as a rigid body are no longer applicable. Initially, by referencing the concept of the participating mass of soil (the mass of surrounding soil that vibrates synchronously), the concept of participating mass of large-scale complex dynamic machine foundations is proposed. Subsequently, the theoretical and corresponding numerical solutions are given based on the elastic half-space theory and finite element analysis. Furthermore, referring to the prototype of the foundation of the NFEES in China, a refined finite model encompassing the surrounding soil, multilayer complex machine foundations is established. After validating the numerical model, the vibration response and the participating mass of the foundation are analyzed. Additionally, parameterized analyses are conducted by varying factors such as the overall and local stiffness of the foundation, the presence of piles at the bottom of the foundation, the integration of a large shaking table foundation and an underwater shaking table foundation. Results indicate that the foundation of the large shaking table demonstrates vibration synchronization during operation, and the participating rates exceed 80%. The piles at the bottom and the separation of the large shaking table foundation from the underwater shaking table foundation perform effectively to reduce the vibration response and enhance the synchronization of the foundation vibration. The vibration response calculated by the numerical model can be directly applied to assess whether the foundation design satisfies the vibration limit requirements, and the parameterized analyses can provide suggestions for the dynamic design and analysis of similarly large-scale complex dynamic machine foundations.

The main cable displacement-controlled device (DCD) is the key component in coordinating the displacement and the internal force distribution of the continuous suspension bridge. In order to study the influence of DCD on the seismic performance of the structure, a three-span continuous suspension bridge was taken as the engineering background. The influence of different forms of DCD on the displacement and internal force responses of bridge structures under traveling wave action was investigated through numerical simulation. The research results show that different forms of DCD are beneficial in suppressing the displacement and internal force response under earthquakes. Apparent wave velocity and DCD type have an impact on the peak value and occurrence time of each calculated indicator. The improvement of DCD stiffness is beneficial to reducing the amplitude of structural displacement response and tower bottom bending moment response. With the increase of apparent wave velocity, the control effect of DCD on displacement and moment response becomes more obvious. DCD can slightly reduce the shear and torque time history ranges at the tower bottom, but both are not sensitive to the presence of DCD. The form of DCD depends on the topographic factors of the bridge site and the design requirements of related components.

The special configuration and elongated geometrical appearance of the helical strand give it properties of tensile–torsion–bending coupling as well as macroscopic geometrical nonlinearity. Simulating small-scale strands using solid elements in finite element software reproduces these properties but is time-consuming. Current methods of modeling large-scale strands using cable elements or beam elements can account for geometric nonlinearities, but often fail to adequately consider the tensile–torsion–bending coupling characteristics of the strand cross-section. This study presents a new finite element method for modeling strand structures. This analysis method adopts the rigid body rule to handle the geometric nonlinearity of strand structures, considering the tensile–torsion–bending coupling characteristics of the strand cross-section, while remaining acceptable in terms of analysis time. The analytical method can provide the strand structure’s displacement and the parameters of the tension–torsion–bending coupling characteristics of the strand element. The results obtained from the proposed analytical method were compared with those from numerical modeling and experimental testing, confirming the validity of the analytical method.

This paper presents a new, efficient, accurate, and unconditionally stable second-order time-stepping method for the incompressible thermal micropolar Navier–Stokes equations (TMNSE) using mixed finite elements. The method linearizes the nonlinear convective terms in the momentum equation, microrotation equation, and temperature equation, requiring the solution of a linear problem at each time step. The discrete curvature of the solution is added as a stabilizing term for linear velocity $u$, microrotation velocity $w$, pressure $p$, and temperature $T$ in the equations, respectively. Curvature stabilization ($u^{n+1}-2u^n+u^{n-1}$) is a new concept in computational fluid dynamics (CFD) aimed at improving the commonly used velocity stabilization ($u^{n+1}-u^n$), which only has first-order time accuracy and has adverse effects on important flow quantities such as drag coefficients. We derive a priori error estimates for the fully discrete linear extrapolation curvature stabilization method. The theoretical results and effectiveness of the new method are verified through a series of numerical experiments for $𝜃=\frac{1}{2}$, $\frac{3}{4}$, $\frac{5}{6}$, and $1$ in 2D and 3D, respectively. In particular, this work considers the thermal cavity-driven flow experiment to validate the numerical scheme and obtains good results.

This paper reports on our early experience with solving large scale finite element dynamic problems on the Connection Machine. We describe a distributed data structure that allows very efficient massively parallel computations on irregular two and three dimensional finite element meshes. The often encountered mesh irregularities inhibit the use of the NEWS communication package. We propose an alternative approach to interprocessor communication that is based on an optimal mapping of the processors onto the finite elements of the irregular mesh. Our parallel data structure and processor mapping are applied to finite element wave propagation problems on the CM-2.

Radial stress distribution and plastic damage zones evolution in ceramic coating/metallic interlayer/ductile substrate systems under spherical indentation were investigated numerically by axisymmetric finite element analysis (FEA) for a typical ceramic coating deposited on carbon steel with various indenter radius-coating thickness ratios and interlayer thickness-coating thickness ratios. The results showed that the suitable metallic interlayer could improve resistance of ceramic coating systems through reducing the peak tensile radial stress on the surface and interface of ceramic coatings and plastic damage zone size in the substrate under spherical indentation.

In this study we analyzed the deformation of the polymeric rod impacting on the rigid wall which is called "Taylor impact test."" We simulated three-dimensional Taylor impact test depending on the various polymeric materials using the explicit finite element method by employing DYNA3D code. In simulation, polymeric materials were modeled using viscoelastic constitutive relations with the relaxation time and shear modulus. We have carried out the numerical simulation for the transient deformation characteristics and discussed effects of the viscoelastic constants on the deformation of the polymeric rod under impact.

An effort has been made to create an integrated Crystal Plasticity FE (CPFE) system. This enables micro-forming process simulation to be carried out easily and the important features in forming micro-parts can be captured. Firstly, based on Voronoi tessellation and the probability theory, a VGRAIN system is created for the generation of grains and grain boundaries for micro-materials. Numerical procedures have been established to link the physical parameters of a material to the control variable in a gamma distribution equation. An interface has been created, so that the generated virtual microstructure of the material can be inputted in the commercial FE code, ABAQUS, for mesh generation. Secondly, FE analyses have been carried out to demonstrate the effectiveness of the integrated system for the investigation of uncontrollable curvature and localized necking in extrusion of micro-pins and hydro-forming of micro-tubes.

The straightness of the 100-meter rail after straightening is directly affected by the bending deformation during cooling before straightening, and the analysis of the temperature field in the cooling process is the basis of studying the bending deformation. By analyzing the heat boundary conditions in the cooling process, the temperature field was calculated and its variable law was analyzed by using the 3-D transient non-liner finite element method. The factors such as the solid-state phase change and the physical parameters with change of the temperature were considered, and the numerical results were coincident with the experimental data. The results show that the velocities of temperature changing at different positions of the rail's cross-section are different in the cooling progress, and the phase change and the irregular cross-section of rail are important influencing factors.

The interest in the effects of shock on HDDs has come into currency due to the reduction of the flying height of the head/disk interface and the increasingly hostile environments encountered in the usage of many consumer electronics and portable devices. This paper discusses the shock pulse amplitude and width effects on the shock response of an operational disk drive. The drive is subjected to half sine acceleration shock pulse with varying amplitude and width. A finite element model of the hard disk drive is developed in the commercially available finite element package, ANSYS/LSDYNA. The air bearing between the disk and the slider is modeled by nonlinear springs. The contact between the disk and the slider is also considered. It is found that the shock response of the drive is sensitive to both the shock pulse amplitude and width.

The effects of power-law plasticity (yield strength and strain hardening exponent) on the plastic strain distribution underneath a Vickers indenter was systematically investigated by recourse to three-dimensional finite element analysis, motivated by the experimental macro- and micro-indentation on heat-treated Al-Zn-Mg alloy. For meaningful comparison between simulated and experimental results, the experimental heat treatment was carefully designed such that Al alloy achieve similar yield strength with different strain hardening exponent, and vice versa. On the other hand, full 3D simulation of Vickers indentation was conducted to capture subsurface strain distribution. Subtle differences and similarities were discussed based on the strain field shape, size and magnitude for the isolated effect of yield strength and strain hardening exponent.

The initial stress is induced during film formation and is partially counterbalanced through curvature changes. Therefore, it is commonly evaluated by the measured residual stress. Initial stress may directly affect the film formation rather than residual stress in progressively deposited films. In the present work, we introduced a multiple layer model for progressively deposited films to obtain a quantitative solution for estimating the initial stress. The results showed that residual stress in the last layer is equal to the initial stress when layer number approaches infinity. In particular, the initial stress, σ_i in deposited film could be determined using the equation, σ_i = σ_St/β, in which σ_St is the averaged residual stress in films calculated by Stoney formula and β is the correction factor. The value of β varied between 0 and 1, depending on relative modulus and relative thickness of film and substrate. Finally, using element birth and death technique, a finite element model was presented to verify the analytical multiple layer model. Good agreement was obtained between the analytical and FE results.

The residual stress beneath the surface is crucial to the safety of the structures. Neutron Diffraction and Hole-drilling are the two methods being used to measure the inner residual stress. Longitudinal Critically Refracted (LCR) wave transmission that is propagated parallel to surface also can be used for measuring residual stress, but measurements are within an effective depth and need to be further studied. In this paper, the parameters of K are separately tested in WZ, HAZ and BM zone. The welding process of 6082-T6 aluminum alloy welded joints is simulated in SYSWELD, the finite element model has been verified by the X-ray diffraction method. The residual stress value calculated by SYSWELD and the values obtained from the ultrasonic measurement show a good agreement. It is demonstrated that the residual stress of 6082-T6 aluminum alloy welded plate can be evaluated by using the ultrasonic method.

The custom design of a composite material requires the knowledge of its effective behavior which depends on several parameters such as the properties of the constituents, their distributions, shapes and sizes. In thermal conductivity, all these parameters have a direct and significant influence on the effective thermal conductivity (ETC) of composites. These parameters act differently on the behavior of the composite according to its use as much as a good conductor by improving its ETC or by reducing it by considering it as an insulator. The main goal of this work is an extensive study of all possible situations of ETC by a numerical homogenization technique based on the Finite Elements Method. For this purpose, the two main categories of composites, namely the periodic composites represented by the unit cell and the random RVE, are considered. For each category of composite, different contrasts, different particles’ volume fractions, aspect ratios, positions, and orientations are studied. In order to ensure the simulation results are effective and representative, two boundary conditions, namely Uniform Temperature Gradient Boundary Conditions (UGT) and Periodic Thermal Boundary Conditions (PBC), were imposed on all considered microstructures. The results of this study constitute a synthesis of the effective thermal conductivities of all the possible situations which can be summarized as follows: On the one hand, the reinforcements shape effect is very important irrespective of the nature of the periodic and random composites and on the other hand, the two types of composites do not have the same behavior as that for the reinforcements with a circular or almost circular shape. This study also emphasizes the situations where the ETC can be estimated analytically and when homogenization is necessary. From a practical point of view, and on the basis of the obtained results, this study made it possible to show clearly in which situation the composite becomes more conducting and in the opposite case when it becomes more insulating.

Uniaxial loading tests of copper with inter-atomic potential finite-element model are carried out to determine the corresponding ideal tension and compression strength using the modified Born stability criteria. The influence of biaxial stresses applied perpendicularly to the [100] loading axis, on the ideal strength is investigated, and tension-compression asymmetry in ideal strength under [100] loading is also studied. The results suggest that asymmetry for yielding strength of [100] nanowires may result from anisotropic character of crystal instability. Moreover, the results also reveal that the critical resolved shear stress in the direction of slip is not an accurate criterion for the ideal strength since it cannot capture the dependence on the loading conditions and hydrostatic stress components for the ideal strength.

A computational fluid dynamics (CFD) is coupled with a computational structural dynamics (CSD) to simulate the unsteady rotor flow with aeroelasticity effects. An unstructured upwind Navier-Stokes solver was developed for this simulation, with 2nd order time-accurate dual-time stepping method for temporal discretization and low Mach number preconditioning method. For turbulent flows, both the Spalart-Allmaras and Menter's SST model are available. Mesh deformation is achieved through a fast dynamic grid method called Delaunay graph map method for unsteady flow simulation. The rotor blades are modeled as Hodges & Dowell's nonlinear beams coupled flap-lag-torsion. The rotorcraft computational structural dynamics code employs the 15-dof beam finite element formulation for modeling. The structure code was validated by comparing the natural frequencies of a rotor model with UMARC. The flow and structure codes are coupled tightly with information exchange several times at every time step. A rotor blade model's unsteady flow field in the hover mode is simulated using the coupling method. Effect of blade elasticity with aerodynamic loads was compared with rigid blade.

Consider a binary substitutional solid solution not in equilibrium with a fluid rich in either solid component. At the interface, depending on the chemical energy, the solid may selectively lose or gain atoms from the fluid. Any atom exchange upsets the nominal composition; thereby stresses are generated in the solid by simultaneous action of lattice dilation and interdiffusion. As stresses build up, the local changing volume tends to split up into islands in an effort to escape from stresses, while curvature tends to amalgamate the islands in an effort to minimize surface energy. This competition could lead to substantial corrugations of the solid-fluid interface. These corrugations and the thresholds for noticeable competition between stresses and curvatures had an old tradition in chemo-mechanical models of sharp interfaces beginning with Srolovitz (1989). However, stresses were generally considered as a mere cause of external loads, so a pure solid was tacitly asserted. This paper couples elasticity with a conserved-phase field model to mainly investigate the effect of compositional strain on the interface instability process between a binary solid selectively interacting with a fluid. The chemical energy barrier is considered, however, uncoupled from stress, and the mobility quadratically dependent on the gradient of composition. Under initial enforced sinusoidal perturbations, results of simulations showed that the compositional strain parameter can dramatically alter the effect of the chemical energy barrier on the critical wavelength of perturbations that trigger interface instability.

Azimuthal electromagnetic wave logging-while-drilling (LWD) technology can detect weak electromagnetic wave signal and realize real-time resistivity imaging. It has great values to reduce drilling cost and increase drilling rate. In this paper, self-adaptive hp finite element method (FEM) has been used to study the azimuthal resistivity LWD responses in different conditions. Numerical simulation results show that amplitude attenuation and phase shift of directional electromagnetic wave signals are closely related to induced magnetic field and azimuthal angle. The peak value and polarity of geological guidance signals can be used to distinguish reservoir interface and achieve real-time geosteering drilling. Numerical simulation results also show the accuracy of the self-adaptive hp FEM and provide physical interpretation of peak value and polarity of the geological guidance signals.

This paper describes a data-driven approach to predict mechanical properties of auxetic kirigami metamaterials with randomly oriented cuts. The finite element method (FEM) was used to generate datasets, the convolutional neural network (CNN) was introduced to train these data, and an implicit mapping between the input orientations of cuts and the output Young’s modulus and Poisson’s ratio of the kirigami sheets was established. With this input–output relationship in hand, a quick estimation of auxetic behavior of kirigami metamaterials is straightforward. Our examples indicate that if the distributions of training and test datasets are close to each other, a good prediction is achievable. Our efforts provide a fast and reliable way to evaluate the homogenized properties of mechanical metamaterials with various microstructures, and thus accelerate the design of mechanical metamaterials for diverse applications.