The magnetic properties of soft magnetic materials used in electric motors are serious information for realizing an energy-saving society. Correctly estimating the iron loss of silicon steel sheets in an electric motor leads to a highly efficient design of the electric motor. Therefore, we proceed developing the spin-dynamics simulator for calculate a hysteresis loss in the sheets. In this paper, we report a basic calculation method using the Landau-Lifshitz-Gilbert equation and a new treatment of the exchange interaction for particle spins larger than atomic spins.

In this study, we investigate the influence of filtering processes in topology optimization for stress distribution of the optimized structure. The strain energy is defined as the performance function, and the governing equation for the elastic deformation is introduced. The governing equation and the volume constraint condition are considered as for the constraint conditions of the performance function. The governing equation is discretized by the finite element method using isoparametric elements. The density method is applied to obtain the optimized structure, the density is updated by using the gradient of the Lagrange function with respect to density based on the optimality criteria method. The filtering process is generally employed to avoid the checkerboard type structure, and is frequently given by the constant value in design space. In this study, we propose that the filtering radius is adjusted by the value of the Mises stress in the design space, and investigate the effect of this filtering processes for optimized structures.

In this study, thermal deformation analysis is applied to express melting phenomenon of snow bank. The finite element method is introduced to discretize the governing equation in space, and numerical analysis is carried out by using FreeFEM. The thermal expansion coefficient in the thermal deformation analysis is estimated by comparing results between practical and numerical experiments.

For the prediction of tsunamis, floods and the efficiency of energy production using wave power, it is necessary to estimate the flow field with high accuracy. In this study, the extended Kalman filter FEM method, which is a combination of the extended Kalman filter and the finite element method (FEM), is used to perform data assimilation analysis based on water level measurement data by image analysis. In this paper, we present an example of a numerical experiment using measured water level data obtained in a real channel.

Crystalline polymers may have some size effects that show different deformation responses depending on size of crystalline phase with respect to that of specimen. In the previous report, the effect of difference in crystal size on deformation response is investigated conducting some tensile tests on a polypropylene specimen. However, there are some problems that the shape of crystalline phase in the unit cell is different from the shape of crystalline phase of PP observed in the experiment and the reason why the size of crystalline phase becomes larger as the cooling temperature is lower cannot be clarified. In the present report, the authors change the shape of crystalline phase in the unit cell and attempt to conduct the molecular chain plasticity FE by analysis applying the new unit cell. Furthermore, the reason for the size increase of crystalline phase at low cooling temperature is quantitatively explained on the basis of classic nucleation theory. In addition, it is indicated that experimental stress-strain curves are numerically reproduced.

An iterative domain decomposition method is proposed for numerical analysis of 3-Dimensional (3D) linear magnetostatic problems taking the magnetic vector potential as an unknown function. The iterative domain decomposition method is combined with the Preconditioned Conjugate Gradient (PCG) procedure and the Hierarchical Domain Decomposition Method (HDDM). Our previously employed preconditioner was the Neumann-Neumann preconditioner. Numerical results showed that the method was only effective for small number of subdomains. In this paper, we consider its improvement with a variant of balancing domain decomposition preconditioner (BDD-DIAG). Specially, we consider a well-known perturbed linear magnetostatic problem in which the coefficient matrix becomes positive-definite. Then, we give a sufficient condition which assures the positive-definiteness of the coarse matrix in BDD-DIAG.

To understand the behavior of bcc Fe-Cr binary alloys under severe plastic deformation (SPD) by computer modelling and molecular dynamics simulations, we construct a new polycrystal Fe-Cr atomic model containing four grains with different crystal orientations, of which the mass friction of Cr atoms is 20wt%. After thermal equilibration, we apply shear strain to the models under relatively higher temperatures. The ratio of system temperature to an experimental melting point of Fe-Cr binary alloys are chosen as 0.1, 0.3, 0.5, 0.7 and 0.9. At each temperature, the deformation with different shear strain rate is applied to the model, and we confirmed that these conditions affect the dislocation density. Both nucleation and annihilation of dislocations with edge or screw component are clearly observed in some grains. In other grains, the primary slip system of bcc lattice is well activated, and the secondary one is also to be formed as well. But the latter slip has not been completed up to making a perfect dislocation in the present simulation condition. It is also found that the behavior of dislocations with the primary slip system is mostly regardless of arrangement of Cr atoms.

The temperature-dependent equations of the isotropic hardening and the Young’s modulus are given for the elasto-viscoplastic constitutive equation in this article. The incorporation of these equations would be beneficial for the deformation analysis under variable temperature.

Carbon nanotubes (CNTs) are one of the most promising nanostructured materials for novel nano-devices utilizing its peculiar mechanical properties and functional aspects. In particular, CNTs can accommodate reversible buckling deformation under pressure, which exhibits large deformation at a critical stress or strain leading to abrupt change in the electronic properties. In this study, we carried out molecular dynamics simulations to investigate the effect of the Stone-Wales (SW) defect on the buckling behavior. Sharp peaks in the stress-strain curves corresponding to buckling become smooth and gradual change with the presence of the SW defect because it incorporates local strain. Critical stress and strain as functions of CNT radius also become less peaky due to the defect, suggesting practicality of using defects for realizing reliable nano-devices. Application of an artificial neural network model for the prediction of density of states was also attempted, revealing the need for further development of the model for better accuracy.

For the efficient flight, high-aspect-ratio wings with a low structural weight have been extensively investigated. It is well known that such wings are easy to be exposed to limit cycle oscillation (LCO) due to geometrical nonlinearity and nonlinear flow caused by large deformation. Although destructive vibration must be suppressed, the vibration can be a source of energy if a certain magnitude of vibration is allowed. Recently, the balancing problem between piezoelectric energy harvesting from LCO and its active control has been posed. It is a multi-physics problem with coupling among host structures, surrounding fluid, piezoelectric energy harvesters, piezoelectric actuators and sensors. In the present study, we propose high-fidelity coupled analysis for numerical evaluation of the problem based on the partitioned iterative method. In the numerical examples, we consider LCO of a cantilevered beam in axial flow. Then, using active control systems and energy harvesters, the suppression of the LCO is achieved while scavenging of energy.

A phononic crystal, an artificial periodic structure with different sound velocities and densities, exhibits typical characteristics, band gap, in its dispersion properties. The phononic band gap is designed not only for specifying stop band region for filter application but also for creating localized modes by introducing a defect in the periodic structure leading to a waveguide design. We aim to develop an algorithm of optimization for detailed phonon-band structures for the design of high-efficiency acoustic waveguides based on two-dimensional phononic crystals. Until now, the band structure of phononic crystal has often been determined by empirical/heuristic methods. In this study, we performed structural searches using several optimization algorithms for band gap maximization. Here we adopt the Metropolis Monte Carlo method, shape optimization, and topology optimization as representative optimization algorithms. By examining the results, we identify essential features in applying the algorithms to the complex problem, i.e. optimization of reciprocal space diagram from real parameters.

In the present paper, singular patch method and patch superposition method for two-dimensional linear elastic fracture mechanics analysis using the isogeometric analysis (IGA) are proposed. The singular patch method enables us to reproduce the so-called square root singularity in the stresses. The patch super position method reduces labor and time for IGA model generation. The proposed methods can be extended to the three-dimensional in a straight forward manner.

In recent years, the great attention has been paid to topological insulators with time-reversal symmetry in their dispersion properties. In the present study, we aim to develop a novel acoustic- and elastic-wave devices based on the concept of band topology in phonon dispersion of phononic crystals. We searched for structures showing topological phase transitions in 2D and 3D phononic crystals and evaluated the transmission efficiency in topological acoustic waveguides utilizing wave propagation through valleytronic edge mode. The results show that highly efficient acoustic/elastic wave propagations were possible in both 2D and 3D case and their robustness against back scattering at the bends was confirmed.

In recent years, the development process of automobiles has been more complex than ever. It is quite important to properly evaluate the influence on its performance caused by a design change in order to accurately assess the development status and to avoid reworking. However, detecting every important event and so-called outliers during highly complex vehicle crash is a difficult problem. This paper introduces deformation-mode decomposition using principal component analysis and distance measurement in its modal space. With this approach, differences in behavior are represented by the distance between two points in modal space so that the comparisons are objective and quantitative. Besides, subtle changes in the behavior of parts can also be captured compared with conventional approaches using scalar criteria such as distance between two structural points. An example case of this method has been demonstrated with a NCAC full car FE model, and the results with DIFFCRASH and EVENT DETECTION by SIDACT GmbH successfully visualized the change in behavior of the front side frame.

This paper presents a convolution quadrature time-domain boundary element method (CQBEM) for 2-D pure antiplane anisotropic with viscoelasticity. Three element standard viscoelastic model and the fundamental solution obtained by Wang and Achenbach are considered for the expression of viscoelastic and anisotropic properties. After the brief description of the developed CQBEM formulation is discussed, some numerical results obtained by using the CQBEM are demonstrated.

In this paper, we have developed a new micro-sphere based hyperelastic material model. This model combines the 8-chain model (Arruda & Boyce, 1993) and the affine-stretch micro-sphere model (Miehe et al., 2004), and consists of three material constants. Then, for implementation of this model to finite element method (FEM), analytical solutions for stress and tangential stiffness were derived. To verify the effectiveness of this model, it was applied to the three types of mechanical tests (uniaxial, pure shear and biaxial-tensile tests) of industrial rubber materials. As the result, the reproducibility of stress-strain relationship by this method was better than that of the present hyperelastic material model consisting of three material constants, and the good convergences of FEM were confirmed.

The power module is a key product for energy saving, and the joint between a wire and a semiconductor chip is one of the important parts from the viewpoint of structural integrity. This joint is damaged by repeated heat cycles caused by short operation of the power device. An example of damage to the Al-Si joint due to thermal fatigue is called the wire-liftoff, in which the Al wire peels off from the Si chip. To clarify this phenomenon exactly, it is necessary to apply the modified strain hardening rule proposed by ORNL to the transient creep behavior of Al. In addition, when performing the finite element thermal elasto-plastic creep analysis of a cracked structure to evaluate of its thermal fatigue strength, we may need a large amount of CPU time. In this study, we will deliver an interim report on the effect of reducing the CPU time in the temperature range of 0-300℃ by applying the creep multi-linear rule and convergence improvement measures.

We are developing a numerical method to solve shape optimization problems for the 3D wave equation with the help of the time-domain boundary element method (TDBEM) and the adjoint variable method (AVM). The TDBEM is useful to handle the underlying scattering problems in free space, but its computational cost can be huge. To overcome this issue, we exploit the fast TDBEM proposed by Takahashi (2014), which exploits the interpolation-based fast multipole method. Regarding the AVM, we basically follow the formulation by Bonnet (2002) , but we discretize the shape derivative through the control points that are introduced by approximating the surface of a scatterer with NURBS surfaces. Since the fast TDBEM uses the conventional mesh, we convert a NURBS surface to a mesh and vice versa. In this talk, we will verify our shape optimization system by comparing a reference solution in a certain problem. Then, we will demonstrate a shape optimization to focus a transient sound at a prescribed point.

When the non-Newtonian characteristics of the flow becomes stronger, the nonlinearity of the flow becomes stronger, and the numerical analysis becomes more unstable. Therefore, we studied a numerical model to realize the pressure-flow characteristics of the experiment even in numerical simulations of non-Newtonian fluids. In addition, we investigated the effect of complex geometry of a tube with non-Newtonian fluids, The non-Newtonian fluids simulation was conducted by power-law model, and immersed boundary method is employed to represent the corrugated tube. As a result, we confirmed that grid independency of the developed numerical model and good agreement with experimental data of pressure-flow rate characteristics.

The supersonic transport (SST) of Concorde has ended its commercial flight at 2003. One of the reasons is that shock waves generated at supersonic flow conditions increase the wave drag acting on SST which results in the deterioration in fuel efficiency. The reduction of the wave drag is required for the next generation SST, so that various conceptual designs have been proposed and investigated. In recent years, topology optimizations have attracted attention as advanced optimization methods with higher degree of freedom to represent various topologies. These methods can automatically propose an innovative/optimal topology which achieves the highest performance. Therefore, it can be an efficient tool to extract innovative design insights. So far, we have proposed a global optimization method for the topology optimization. In this study, we consider the advancement of the search strategy by dynamically changing the parameter of search radius which controls the balance between global/local search, from the latest histories of the objective function. Two analytic functions are minimized by the proposed strategy, and then it can be confirmed that the performance is improved in several conditions.

The purpose of this research is to realize low drag and low boom technology for supersonic transport (SST). Civil SST has not been realized since 2003 when the Concorde has finished its operation. The critical problems of the Concorde were noise relating to the sonic boom and poor lift-to-drag ratio (L/D). To develop a new type of SST configuration, a high lift configuration for fuselage is investigated and aerodynamic shape optimization is performed by a global optimization method using a Kriging response surface model. As a baseline configuration, we focus on a waverider configuration, which can generate lift force from high pressure of shock waves generated at its lower surface. As a result of the design and analysis, it is confirmed that waverider configurations are promising for efficient SST. The aerodynamic optimization of the waverider configuration is also performed, and then design knowledge related to the performance improvement is obtained.

Nanocarbon materials containing Diamond Nanothreads (DNT) are expected to be applied to nanoscale sensors. In this study, the mechanical and vibration characteristics of perfect DNT, DNT with isolated lattice defects, and DNT with continuous lattice defects are obtained using the molecular dynamics method. We consider the density of lattice defects affect the characteristics of DNTs. In addition, we will prove the validity of the obtained Young’s modulus and natural frequency of DNT by the continuum mechanics theory, and examine the applicability to nanoscale sensors. As a result, in all DNT, the frequency of DNT can be controlled by SW defect density and tensile strain. We also investigate the applicability of DNT with added mass as a nanoscale sensor.

Recently, with the advance of Micro Air Vehicle（MAV）and Mars exploratory airplane, there is a need to understand low Reynolds number flows. The objective of this study is to investigate the aerodynamic characteristics of a thin circular arc airfoil at low Reynolds numbers. Cartesian - mesh - based Computational Fluid Dynamics（CFD）was used to clarify the flow field of a thin circular arc airfoil with a camber of 3% chord at Reynolds numbers of 1.0 × 10³ and 1.0 × 10⁴. The results of this analysis were compared with the results of wind tunnel tests. As a result, qualitative agreement was obtained with the experimental results.

In a car body, there are thousands of resistance spot welds which may induces large deformation during manufacturing process. Therefore, it is strongly expected by automotive industries to develop a fast and simple prediction method for its deformation. Conventionally, the inherent strain method has been applied to line welding such as arc welding, and it has the advantage of short calculation time compared to the thermal elastic-plastic analysis. On the other hand, the application to resistance spot welding deformation has not been investigated so far. In this study, the inherent deformation due to resistance spot welding was defined based on the inherent strain method. In addition, the deformation of a vehicle part with 23 resistance spot welds was predicted using the inherent strain method and showed a good accuracy compared with the measurement.

As the foundation of a fast time-domain boundary element method (TDBEM) for electromagnetic scattering problems in 3D, we investigated the conventional TDBEM. Bearing the stability and computational complexity in mind, we employ the combined-field integral equation (CFIE) and introduce a vector field e such that e˙ = J, where J denotes the surface current density on a perfect electric conductor (PEC). We discretise J with the B-spline basis function for time and the Rao–Wilton–Glisson (RWG) basis for space. In this talk, we will show our formula tin and implementation and discuss the numerical results.

The Characteristic tensor method (CTM) is a new method to evaluate the singular stress field with a characteristic tensor (CT) which is calculated by averaging the stress in an infinitesimal volume at a crack tip. The CT has a linear relation with the stress intensity factor (SIF), which characterizes the singular stress field around a crack tip in an isotropic homogeneous elastic body. Even under mixed-mode loading conditions, the SIFs of each mode can be easily and efficiently estimated using CT. For the practical use in industries, the evaluation of the CTM for a three-dimensional crack under general three-dimensional stress state is necessary. In this study, the reliability and accuracy of CTM is investigated by estimating SIFs in several representative types of three-dimensional cracks where stress states are calculated by the finite element method. The results show that the SIFs estimated by the CTM have high accuracy even for mixed-mode conditions. It was, thus, demonstrated that CTM provides a practical and reliable approach for the efficient estimation of SIFs of three-dimensional cracks.

Multi-phese-field (MPF) method is one of the most effective ways to simulate complex microstructure evolutions and very useful for efficient material development. Recently, to simulate microstructure evolutions under strong non-equilibrium interface condition, the non-equilibrium MPF (NEMPF) model has been proposed. In this study, to verify applicability of NEMPF model, the simulation of solidification of solder alloys are performed using NEMPF model coupled with thermodynamic database. The results show that the growth process of the intermetallic compound during solidification can be reproduced by this analysis using the non-equilibrium MPF model.

Least Square Moving Particle Semi-implicit (LSMPS) method is an arbitrary high order accurate particle method. Recently, Matsunaga et al. presented an improved treatment of wall boundary condition for the LSMPS method. This improved treatment further enhances the accuracy and avoids the traditional fixed wall particles. However, complicated calculation of the volume integral is required for particle shifting near the wall boundaries. In this study, a particle shifting model with numerical integration on wall boundary meshes is proposed to facilitate the simulations with complex wall boundaries using the LSMPS method. Unlike the traditional wall particles, the resolution of the boundary meshes is adjustable, thus it is conducive to representing the detailed structure of the complex wall boundaries.

We construct a computational fluid dynamics (CFD) method adopting a multi-phase-field model (MPFM) and a lattice Boltzmann model (LBM) for simulations of microscopic incompressible viscous multi-phase flows. The CFD method adopts a set of conservation-modified Allen-Cahn (AC) equations for calculations of diffuse-interface advection and autonomous formation in the flow. LBM with two-relaxation-time (TRT) collision operator is employed as an explicit numerical scheme for solving the Navier-Stokes equations coupled with the set of AC equations for multiphase fluid flows with arbitrary number of phases. A 2D simulation of droplets demonstrates that the CFD method based on MPFM and LBM would be applicable to the complex microfluidic multiphase flows in bio- and medical-engineering fields.

In recent years, it has become quite feasible to create interatomic potentials using machine learning (ML) methodology. Such ML potentials are constructed on a general functional form and a large number of parameters, and they will reproduce the results of DFT calculations. The SNAP is one of the ML potentials, and as its advanced type there is the qSNAP. In this research, we actually construct SNAP and qSNAP for silicon (Si) and 3C-silicon carbide (SiC) crystal systems and confirm their reproducibility in MD simulations. Using a genetic algorithm, optimization calculations are performed so that the error of the elastic moduli are minimized. For 3C-SiC, elastic moduli are well reproduced by qSNAP. For Si, the lattice constant, elastic moduli, and melting point are well reproduced. Besides, the dimer structure in the free surface of Si {100},which has not been predicted by empirical potentials, is successfully obtained by qSNAP. Although the dislocation behavior has not sufficiently been reproduced yet, the improvement is expected by adding other data on stacking defects.

This study has investigated the effects of spring pitch on the correction factors, F_i (i=I, II and III) of the three modes of the stress intensity factors for semielliptic surface cracks on the surface of compression coil springs both inside and outside of the coils. For this purpose, 3D finite element stress analyses have been made on compression coil springs with surface cracks having normalized pitch p/R=0.8, 1.2 and 1.8, or the pith angle α=7.3°, 10.8°, 16.0°, respectively where p is the spring pitch and R the coil radius. The results showed that the correction factor F_I of the mode I stress intensity factor was larger on the wire surface outside of the coil than on that inside of the coil. The maximum F_I value was 0.66 outside for p/R=1.8 whereas 0.34 inside for p/R=0.8 at the eccentric angles of φ=30° and 150°. The F_I value became larger with increase in the p/R value outside whereas it became smaller with increasing p/R value inside. The F_I value was found dominant among the three modes of correction factors; i.e., the values of the mode II and the mode III correction factors, F_II and F_III, were nearly zero and slightly varied along the periphery of the cracks.

In this study, we use a two-dimensional crack propagation model created by using the moving finite element method based on Delaunay automatic element subdivision. The criterion for crack acceleration – deceleration is not established for dynamic fracture phenomena. Experimental results for dynamic crack propagation are required to clarify mechanism for crack acceleration. In order to decide conditions for the experiment to observe crack acceleration, moving finite element analysis is used to simulate virtual crack propagation in numerical specimen. In this numerical simulation, fracture toughness, and constant crack propagation rate are measured based on our previous study using experiments and numerical simulations for dynamic 3 point bending fracture. In this study, the numerical simulation results indicate possibility of dynamic crack acceleration in the numerical specimen under virtual fracture condition.

Bonding and forming of carbon fiber reinforced plastic by induction heating are required for medium-sized aircraft manufacturing. In this paper, electromagnetic and thermal conduction coupled finite element analysis method is described for induction heating of carbon fiber dry cloth. Experiments of induction heating are also performed to discuss the validity of analysis method and experimental method. Comparing the temperature of test pieces between analysis and experimental results, validity of both methods is confirmed for both aluminum sheet and carbon fiber dry cloth.

The plastic forming progress is analyzed using the rigid plastic finite element method (RPFEM). The RPFEM is required for the application of selective reduced integration, in order to avoid the volumetric locking behavior. Thus, the quadrilateral element is mainly used in RPFEM. The application of a three-node triangular element is desirable in the RPFEM, from the viewpoint of the remeshing procedure. This study investigated the volumetric locking performance of a three-node triangular element, which improved the numerical accuracy by applying a generalized finite element method (GFEM). The displacement function of GFEM terms assumed the linear, quadratic, and cubic form of equations. When the displacement function of GFEM terms was applied to the quadratic and cubic equations, the FEM accuracy was higher than that for a six-node triangular element. Next, a compression test was performed to examine the volumetric locking performance. The compression test results suggested that the three-node triangular element with GFEM required the application of selective reduced integration in order to avoid the volumetric locking behavior.

To obtain an optimum acoustic device with excellent performance in some frequency range (target band), we define the objective function as the squared effective sound pressure integrated over the target band in the topology optimization. To efficiently evaluate the objective function, the frequency response of the sound pressure is, first, estimated by the Pade approximation. Then, the rational polynomial approximation for the response of the´ integrand is derived from the Pade approximation. Finally, the closed-form approximation of the objective function´ is obtained after some manipulations on the integral of the rational polynomial approximation. The topological derivative of the objective function is derived from that of the sound pressure by the chain rule. It is confirmed that the approximation of the response is valid, and the intent of the objective function is achieved in the optimization.

This study aims to evaluate risk of loosening of acetabular cup by modeling of interfacial fracture and inelastic behavior. Increased demands for artificial hip joints in developed countries lead to the need for higher reliability and longer durability. Among the factors affecting service lives, interfacial damage phenomenon has a high impact on loosening of the acetabular cup. However, monitoring and/or quantification of this kind of damage using traditional experimental method is challenging. Thus, a 3 dimensional model of acetabular cup structure was developed. Next, interfacial crack growth between cup and bone was modeled in conjunction with inelastic behavior of surrounding bone to simulate interactive effects on loosening behavior of acetabular cup. Using fracture mechanic and elastic bone, interfacial crack propagated circumferencialy on the surface of acetabuler cup while inelastic bone cases showed crack growth isotropically. Strain accumulation below the loading point was observed which might be the cause of wear damage at high loading cycles.

When materials are cut with a knife, cutting resistance is a combination of (1) the reaction force (compressive) and (2) the frictional force between the knife edge and materials. When cutting resin material, the frictional force is dominant. Meanwhile, in the field of fracture mechanics, crack progress possibility is evaluated by the stress intensity factor which is calculated from energy release rate around crack tip. In this context, the relation between the calculated and measured cutting resistance are investigated, of which results are reported in this paper.

Due to severe tsunami damage caused by 2011 off the Pacific coast of Tohoku Earthquake and recent torrential rain disasters occurring in various places, the demand for predictive simulation technology have been rapidly growing. For disaster predictions, one needs to perform large-scale and high-resolution simulations which require highly expensive computational costs. Several approximation techniques have been developed to avoid them; however, many parameters are often determined based on empirical laws and approximated simulation could still be consuming considerable costs. In this context, this work presents the application of a class of neural networks, PINNs (Physics-Informed Neural Networks) to both forward and inverse problems. The characteristic of PINNs is its predictions of physical quantities of interest are guaranteed by physical laws, initial, or boundary conditions. This is because it forms the loss function as a combination of predictive and physical loss. Predictive loss is the difference between the ground truth and PINNs prediction, while physical loss is defined as how much PINNs prediction satisfies the governing equations and physical conditions. This paper investigates PINNs applicability by introducing a hyper parameter (weighting factor) to control the effect of predictive and physical loss and demonstrates its performance through numerical examples. Results suggest physical loss-weighted training is much more effective than predictive loss-weighted learning for both forward and inverse problems, especially when training data is corrupted with arbitrary noise.

Dual-phase Mg alloys consisting of α-Mg phase and LPSO (LPSO: Long period stacking ordered) phase are attracting attention because of its high specific strength and relatively high ductility. These alloys acquire excellent mechanical properties attributed to kink deformation, and a research has been conducted to reproduce kink deformations by numerical analysis using the crystal plasticity Cosserat model with disclination density proposed by the authors. However, few computational mechanical research has been conducted on the effect of the kink band on material hardening. In this study, the disclination-crystal plasticity Cosserat model is applied to a rectangular dual-phase Mg alloys with LPSO phase, and two-dimensional FEM analysis is performed to form a ridge-shaped kink during loading and reverse loading after loading. From the obtained results, influence of ridge-shaped kink band on work hardening is discussed in detail.

This study aims at observation of nanoscale friction behavior at Hydroxyapatite – Titanium Oxide interface using Molecular Dynamics simulation. Mechanical stability predicting of prosthesis demands clear understanding for mechanism of friction and wear between biocompatible coating and substrate. Classical models can not envision precisely friction in nanoscales. In the present work, simulation of sliding TiO2 on Hydroxyapatite surface was performed by molecular dynamics (MD) simulation and bonding behavior was modeled using ReaxFF reactive force field. Friction coefficient and wear process were discussed by incommensurate atomic position. Significant difference in simulation and classical model emphasizes dominant effects of bonding in friction behavior.

Articular cartilage is a composite of materials with widely differing biomechanical properties, in which 70% to 80% of the weight is water. Moreover, articular cartilage is characterized by a zonal composition of superficial zone, middle zone and deep zone. In this study, a FEM model is proposed to produce the distribution of the chondrocyte in each zone, in which the material property of the chondrocyte is given as a rubber-like material and that of the matrix is given as a gel, in which the penetration of water molecule occur. Employing with this proposed model, we investigate the development of water contents of articular cartilage under compression. The results show that the water contents is dependent on the material property of the chondrocyte and a lower stiffness of the chondrocyte leads to a remarkable localized distribution of the water content in the matrix.

In this paper, the formulation of isogeometric hyperelastic shell based on Kirchhoff–Love theory is presented. In the formulation, the normal stress in the thickness direction is considered. The upper/lower surfaces areas are properly considered to apply the traction on them. In particular, the boundary conditions on upper/lower and edge surfaces are discussed. The derived variational equations indicate the phenomenon that the bending moment and torque are converted into couples because of constraint of normal vector peculiar to Kirchhoff–Love shell.

The process of coating solutions is widely used in the manufacture of semiconductors, batteries, and films. In the development and manufacturing of these products, many experiments are conducted to improve the quality of the products and to speed up the manufacturing process. It would be useful if the number of experiments could be reduced by using simulation. In this paper, we propose a simulation model that takes into account the effect of viscosity change by solvent evaporation on spin coating, for which there are few examples of conventional simulations.

The new coronavirus (COVID-19) is spread by droplets and droplet nuclei generated by human coughs, sneezes, and conversations. In order to prevent infection, it is important to accurately predict the scattering behavior of droplets and droplet nuclei by numerical analysis. So far, a lot of numerical simulation using velocity profiles of exhaled air by a spirometer and flow velocity measurements at the mouth by PIV (Particle Image Velocimetry) have been reported. However, there is few cases in which simulation results have been compared and verified with actual measured flow velocity fields. In this study, we have developed a numerical simulation model that reproduces the actual measurements by visualizing coughs emitted by humans using a CW (continuous wave) laser and a high-speed camera, performing PIV analysis, and comparing the arrival distance of the measured cough airflow. In addition, as an application of the numerical model, droplet and droplet nucleus transport have been evaluated considering the effect of partitions.

Machine learning-based noise filtering could enable Scanning Transmission Electron Microscopy (STEM) observation to manage both high spatial and temporal resolution. Our developed U-net based noise filter trained by rapidly scanned STEM images and their Drift Corrected Frame Integration (DCFI) images, successfully removes not only statistical noise, e.g., Gaussian noise, but also the one that comes from the scanning process. Therefore, we can obtain clear images in high speed and/or low electron dose imaging condition by using the noise filter. We firstly apply the filter to a three-dimensional dislocation substructure imaging (electron tomography); it enables to reduce the total image acquisition time to 5 seconds, implying that precise configurations of microstructure could be obtained even if it requires time resolution. The denoise technique is also applied to an in-situ observation of Cu nanoparticles sintering process and successfully improves the quality of dataset. These outcomes demonstrate that the denoise technique enables STEM observation to capture wider phenomena and structures than TEM observation, therefore, it could be applied to in situ observation that analyses evolution of microstructures such as those under mechanical or thermal stimuli.

This research aims at developing the multi-scale structural optimization method considering interactions among stress concentration in porous composites by Lagrange multiplier method. Though durability of porous components is critical for service lives of loaded components such as bone etc, estimation method for optimizing strength of specific distribution of porosity has not been developed yet. Here we propose a structural optimization using Lagrange multiplier method. deviation of Persistent homology (PH) from a target state, which quantify aggregation of pores at macro scale is to be minimized. In micro scale, average of stress concentration factors (SCFs) by interactions among pores were also minimized. Objective functions are weighed respectively, linearly combined and then optimized using Lagrange multiplier method. Adjusting weight factors could simulate aggregation or dispersion behavior of pores under monotonic compression. Under the macroscopically regulated distribution, stress concentration factors were subsequently adjusted along to the direction of maximum principal normal stress values. Optimized pore distribution structure could significantly reduce maximum principal stress, which increased its structural strength.

Permeability is a very essential parameter in simulations for predicting macrosegregation. In our previous study, we have developed the permeability prediction method using phase-field and lattice Boltzmann methods [Acta Mater. 164 (2019) 237-249, Acta Mater. 188 (2020) 282-287]. In this study, we evaluate the permeability for columnar dendrites with developed secondary arms by the phase-field and lattice Boltzmann methods. As a result, it is concluded that the dimensionless permeability for flow of normal and parallel directions are approximated by Kozeny-Carman equation except for regions with developed secondary arms.

This study investigated whether adding yaw-wise rotation to an aircraft flap improves lift. The aircraft is optimized for cruising conditions and lacks takeoff and landing performance. Hence, high-lift devices, such as flaps, are used to compensate for the lift performance. Since flaps are devices that move along rails, the gap between the wing and the flap is constant in the span direction. However, since the flow field is three-dimensional, the gap should also have a spanwise distribution to improve lift. Thus, this study defined a design problem for lift maximization with the gap and the yaw-wise rotation angle as design variables. This problem adopted a surrogate model because of the small number of objective functions and design variables. A Kriging model modified to add multiple sample points optimized this problem. Consequently, the result revealed that adding a rotation angle ameliorated the lift.

This paper presents a convolution quadrature time-domain boundary element method(CQ-BEM) for wave propagation in micropolar elastic media. Time-domain boundary element method(BEM) is developed as an effective numerical approach for wave propagation. However, the convolution time-domain BEM is known to make unstable numerical solutions in the case of a small time step size. Besides, BEM is difficult to analyze the wave scattering problem with dispersibility, such as viscoelastic, fluid-saturated porous and micropolar elastic media. The formulation presented herewith improves these disadvantages using a convolution quadrature method(CQM). In this paper, the CQ-BEM formulation for micropolar elastic media is proposed because no numerical examples obtained by CQ-BEM for wave problems in micropolar elastic media are known to our knowledge. As numerical examples, 2-D micropolar wave scattering by a cavity is demonstrated by using the proposed method.