Geometrical nonlinear analysis of shell structures is conducted. Particularly, finite rotation problem is addressed. Concept of convected coordinates is introduced to effectively deal with the curvilinear surfaces. Nodal integration is performed by Stabilized Conforming Nodal Integration (SCNI). Equilibrium equations are derived by total Lagrangian formulation with Green-Lagrange strains and Second Piola-Kirchhoff stresses. Accuracy and effectiveness of present formulation are demonstrated by a numerical example from literature. The obtained meshfree results are verified by Finite Element Method (FEM) based reference solutions obtained by the authors.

Optimal velocity (OV) model, one of the car-following models, is suitable for reproducing the k-Q curve in highway traffic data or the car-following motions in observed traffic flow, although the intrinsic parameters have to be fixed, depending on each traffic situation. In this paper, we propose the OV model, whose parameters are fixed by the stopping distance depending on the reaction time, and combines it with cellular automaton (CA), to apply it to the large-scale traffic simulations on the road networks. An illustrating example concerning an evacuation around Koto-delta region has been presented, to indicate the effectiveness of OV-CA model in accounting for the traffic congestion and the capacities of the road network.

In nondestructive inspection method using magnetic flux density leakage, a new response function has been proposed to reflect the total amount of magnetic flux penetrating the magnetic sensor. As a result of inverse analysis using the proposed response function, the ability to restore the defect shape was improved as compared with the case using the conventional response function in the low lift-off region.

Recently, the author has attempted to predict ductile fracture during tensile testing of a sheet and a bar from a microscopic viewpoint. The author's proposed model of void coalescence is based on the two-dimensional void model proposed by Thomason and the two-dimensional void model proposed by Melander and Ståhlberg, which were also derived from a microscopic viewpoint. In this study, the ellipsoidal void model, which was proposed by the author previously, is evaluated by the upset forging of a cylinder, which is one of the fundamental forging process. A number of experimental researches on the prediction of ductile fracture during the upset forging of a cylinder have been performed. However, researches on the effect of prestrain applied to a cylinder on ductile fracture have hardly been performed. Hence, in this study, the effect of prestrain, which is applied to a bar by drawing, on ductile fracture during upset forging of a cylinder, has been clarified numerically and experimentally.

Phase-field simulations were performed to elucidate the effect of internal stress field on the pearlite transformation in eutectoid steel. We constructed a phase-field model by assuming the Isaichev orientation relationship between ferrite (α) and cementite (θ) phases. The α and θ phases cooperatively grew and a large amount of elastic energy occurred in the pearlite region. In particular, the elastic energy in θ phase was found to be extremely high. From the simulations with/without considering the elastic energy, it was revealed that the transformation velocity decreased due to the presence of the internal stress field.

To realize Predictive Maintenance, the combination of many sensors, big data by IoT, and AI technology for anomaly detection is thought to be necessary, but machine design technology should also be discussed. In this study, an AI-assisted methodology using Grad-CAM to optimize the dynamic characteristics of a metal ALM part and improve the accuracy of anomaly detection by Deep Learning is proposed.

In this paper we propose a coupled model and parallel analysis system for pipe cooling in simulation of large-scale thermal conduction. We model heat transfer in the pipe as a one-dimensional (1D) convection-diffusion equation, and develop a discontinuous Galerkin-based solver. This 1D equation is coupled with the three-dimensional (3D) heat conduction equation by using a staggered coupling scheme with a subcycling technique to deal with different time increments in the 1D and 3D analyses. We develop a parallel analysis system based on a finite element based parallel solver for thermal conduction, ADVENTURE Thermal.

In distributed implementations of stencil AMR applications, the inter-node communication time often represents a major performance bottleneck. Thus minimizing communication is an objective as important as maintaining a good load balance. We propose a new domain partitioning method for block-based AMR applications based on the multi-phase-field (MPF) model. The MPF model for polycrystalline growth minimizes the interfacial energy and forms a convex shape for each crystal grain. In our method, each phase of the MPF model represents a computational sub-domain. We show that the MPF partitioning can successfully keep the load balance and reduce the communication cost.

An adaptive mesh refinement (AMR) method locally assigning high-resolution grid is useful for reducing the computation time and memory usage of the lattice Boltzmann method. In this study, we propose multiple GPU implementations of the lattice Boltzmann method with an octree-based dynamic AMR method. Dynamic domain decomposition by the Morton curve equally distributes the number of lattice points to each GPU. We conduct a weak scaling measurement from 8 GPUs to 128 GPUs, and the parallel efficiency is 98%. The performance has increased 1.37 times by hiding communication overhead by overlapping communication and calculation. We demonstrate a simulation of flow around a sphere adopted high-resolution mesh near the sphere and vortexes.

Wiredrawing is successfully to producing high-strength and small-diameter wires. Products produced using this process are used in a wide range of industries. In recent years, miniaturization and weight reduction of components have progressed, and extra fine wires having a reduced diameter as well as high performance are required. Drawing limit of the current metallic wire is several micrometers in diameter, so realization of nanowire is nearly coming. When a metallic material undergoes plastic deformation, a phenomenon called dislocation occurs. Understanding the mechanism of dislocation is important for predicting mechanical properties of metallic materials. In this study, molecular dynamics method which can observe dynamic dislocation behavior is used. We are clarifying strengthening mechanism by dislocation concerning the effect of crystal orientation and temperature. Conventional wiredrawing condition is applied to nano-sized iron single crystal (α-Fe) model with many-body (FS) potential, and by changing the temperature conditions, some simulations are performed. In results, with temperature control, when the temperature is high, the number of dislocation lines inside the wire increases because SS (Statistically Stored) dislocations (including immobile dislocation, entanglement between dislocation lines, and etc.) increase by virtue of thermal activation in addition to GN (Geometrically Necessary) dislocations. With no temperature control, rapid temperature rise between the die and the wire is observed. This results agree well with the simulated case of actual (larger scale) processing. In conclusion, temperature dependence of the number of dislocations is clearly observed in the case of nanowires, where the influence of SS dislocation is dominant.

Osteocytes buried in bone matrix are believed to regulate bone metabolism in response to interstitial fluid flow within a lacuno-canalicular porosity. In the osteocyte mechanosensing, pericellular matrix, including proteoglycan and tethering elements, is suggested to amplify the strain of osteocytes via the fluid flow. In order to verify the strain amplification effects of the pericellular matrix, we evaluated the flow-induced strain of osteocyte processes in silico by using fluid-structure interaction simulation. The results showed that the proteoglycan is a key component in the strain amplification, while the tethering elements can prevent excess strain concentration on the osteocyte processes.

In this study, ie investigate the effect of biaxial deformation on ultimate sielling characterized by limiting chain extensibility of elastomers. Limiting chain extensibility is introduced into the Flory–Rehner theory. To obtain a single unified inequality, stretches are normalized using the material constant that accounts for limiting chain extensibility. Using the derived inequality, systematic analysis provides the ultimate values of sielling ratio under biaxial loading.

The intravascular-treatment stent for cerebral aneurysms is one of the brained stent-mesh devices and used to reduce inflow into aneurysms or assist the coil embolization. Clinical observations reported stent deployment into the curved arteries may cause incomplete stent expansion but this mechanism is still an open question, and thus understanding of the mechanical characteristics of the stent is hopeful. The present study aims to represent mechanical characteristics of the stent in the deployment process in curved arteries by a computational simulation. The stent was modeled to be a set of metallic wires which obeys Euler-Bernoulli beam theory and mechanical state of the stent was represented by solving the equation of motion based on the corotational formulation with considering multiple contacts. Present results successfully represented the mechanical behavior of the stent in the deployment process into catheter and curved arteries. It also demonstrated the stent expansion in the arteries results in the release of bending energy in the wires constituting the stent.

In this study, we propose a material orientation optimization method for optimum design of laminated composite shell structures. Tsai-Hill criterion is employed for evaluating the strength, and its maximum value is minimized. The issue of non-differentiability inherent in this min-max problem is avoided by transforming the singular local measure to a smooth differentiable integral functional using the Kreisselmeier-Steinhauser function. The optimum design problem is formulated as a distributed-parameter optimization problem, and the sensitivity function with respect to the material orientation variation is theoretically derived based on the variational method. The optimal material orientation variations are determined by using the H¹ gradient method with Poisson's equation, where the sensitivity functions aforementioned are applied as the Robin condition to vary and optimize the material orientation. The optimal design example shows that the proposed method can effectively obtain the optimal smooth material orientation distribution and maximum strength measured by the Tsai-Hill failure criterion.

We survey the optimum structure of micropolar materials under momentum loads as mechanical boundary conditions, which can be applied in two ways; one is couple of forces (CF-condition) and the other is the momentum load at a loading point (ML-condition). Though these two conditions of loading are macroscopically equivalent, the optimum structures for each boundary condition are different because of local stress conditions. Therefore, the decay of end effect is evaluated as a numerical result of stress distribution under the self-equilibrated load. Both symmetric and anti-symmetric parts of stress components decay within the width of a plate under CF-condition, however some area around loading points is required to decay end effects in the process of optimization. We also get the results of slow decay of end effects under ML-condition, and those effect should be considered in practical optimization problems under multiple loading points.

In the design of the structure, it is important to catch the fluid force acting on the circular cylinder that is arranged in a uniform flow. This study is performed by simulation of the flow around the circular cylinders. The fluid force of the cylinders arranged by various gaps between centre-to-centre of the cylinders one reported in this paper.

A weakly compressible scheme for low-Mach number gas-liquid two-phase flows have been developed for a fullexplicit time integration to avoid solving Poisson equation. We introduce the fractional splitting method and directional splitting method to solve Euler equation which an efficient semi-Lagrangian scheme is applicable to. To describe the gas-liquid interface the conservative Allen-Cahn equation, which is one of the phase-field models, combined with the continuum equation is introduces. The accuracy of numerical results of two-phase flow strongly depends on the mesh resolution near the interface. The AMR (Adaptive Mesh Refinement) method greatly reduces the computational cost, since it is possible to assign high-resolution mesh to the region around the moving interface. We have developed a code to solve the equation in a manner of the tree-based AMR. Fractional step method and the directional splitting method helps to reduce the implementation difficulties of AMR method. We successfully carried out some violent two-phase flow simulation and flow including very thin liquid film by using the method which is combined weakly compressible scheme with AMR method.

This study aims at developing a topology optimisation system based on the boundary element method, boundary representation with level set function, time evolution of level set function and adjoint variable method, in order to apply the system to simulate the cerebral infarction treatment using ultrasonic focusing. Specifically, we introduce the linear tetrahedron elemet to discrtise the fixed design domain with an arbitary shape. Then, we consider to improve the quality of the boundary element mesh generated from an equivalued surface of the level set function by means of the quadric edge collapse decimation (QECD) and Loop surface subdivision (LSS). Numerical examples shows the capability of our system to perform topology optimisations efficiently.

We simulate the cryogenic liquid helium to observe superfluid by the path integral molecular dynamics, which maps the quantum systems into the classical molecular dynamics. This method gives correspondence between the quantum systems and the classical systems, thus the classical simulation methods are applicable to a simulation of liquid helium. A uniform source-and-sink scheme is a method to compute the viscosity of classical fluids by momentum exchange of particles. By introducing the two-fluid model which reasonably describes the superfluid, this method is applicable to the viscosity calculation of the superfluid helium. The results show that the viscosity decreases below about 2K.

Insects have developed their high-performance maneuverability using flapping flight in the process of their evolution. In this study, a partitioned method based on our partition model for their flapping flight, which consists of the subsystems of the wings, the body and the control, is proposed to analyze their maneuverability. Here, the proposed method is applied for a maneuver, which is assumed as the perturbation from the static hovering state. In this case, a specific analysis procedure reduced from the proposed method is the one way coupling from the wing to body subsystems, i.e. the insect flapping wings are analyzed using a finite element method for the fluid-structure interaction, the resulted thrust force acts on the insect's body, and its motion is calculated using the equation of motion of a rigid body. The fundamental performance of the proposed method is demonstrated from the comparison between the present results and the actual observation with respect to the yaw, roll, and pitch as three basic modes of maneuver.

In FBR plants the head plate constitutes a part of the boundary of the containment vessel (CV), therefore, it is a very important issue if the function as the boundary is maintained or not in the case of severe accident (SA). And also it is important to evaluate the leak rate from the penetrated crack of the head plate after loss of boundary function, in order to estimate the effect of released fission product (FP) out of CV. In this paper the concept of evaluation flow from the modeling of head plate thickness distribution to the estimation of leak rate is described. And also, as the first step the modeling of head plate thickness distribution for 3 dimensional analyses based on the measurement data of head plate specimens is discussed, which possibly relates to the three dimensional deformation patterns observed in the tests and the length of penetration cracks.

In FBR plants the head plate constitutes a part of the boundary of the containment vessel (CV), therefore, it is a very important issue if the function as the boundary is maintained or not in the case of severe accident (SA). And also, it is important to evaluate the leak rate from the penetrated crack of the head plate after loss of boundary function, in order to estimate the effect of released fission product (FP) out of CV. In this series of papers, the concept of evaluation flow from the modeling of head plate thickness distribution to the estimation of leak rate is described. In the second step of flow, deformation behavior and boundary failure are simulated. In this paper, first, the deformation behavior observed in the test was simulated by finite element analysis (FEA) using 3-D model considering thickness distribution. Next, special criterion of crack generation based on cumulative plastic strain was installed in FEA code. By this FEA, the crack did not penetrate, however, the crack initiation and its location of test were simulated very well.

In FBR plants the head plate constitutes a part of the boundary of the containment vessel (CV), therefore, it is a very important issue if the function as the boundary is maintained or not in the case of severe accident (SA). And also it is important to evaluate the leak rate from the penetrated crack of the head plate after loss of boundary function, in order to estimate the effect of released fission product (FP) out of CV. In this paper as the third step of evaluation flow from the modeling of head plate thickness distribution to the estimation of leak rate, a simplified evaluation method referred to sample leak rate test results of cracked head plate specimens after pressure endurance test is discussed.

In this paper, we propose a substitution approach for de-coupled multiscale analysis of composite plates with in-plane periodic heterogeneity, which includes nonlinear properties. An in-plane periodic local structure which is called in-plane unit structure (IPUS) is extracted from the composite plate. Then a numerical plate testing for the IPUS is performed and the relationship between macroscopic resultant stress and generalized strains is obtained. We postulate that an equivalent homogeneous laminated structure can be substituted by the original macroscopic composite plate. Using the mesoscopic substitution model of this homogeneous laminated structure, the material properties of each layer which provide the equivalent behaviors to the ones of the original IPUS are identified by an optimization method. To validate the proposed approach, we compare the analysis results of the macroscopic substitution model with the ones of the original composite plate.

Recently, data assimilation technique has been becoming powerful tool to estimate materials parameters in the phase-field simulations. In this study, we focus on the adjoint method, which is one of data assimilation techniques, to estimate the thermodynamic parameters in Gibbs energy function from the composition profile data obtained by the conventional diffusion coupling method. The adjoint method is applied to the inter-diffusion theory, which provides the adjoint equations with respect to the initial composition field and the materials parameters utilized in the diffusion simulation. As a result, it is demonstrated that the proposed method can be possible to estimate the thermodynamic parameters in Gibbs energy function from the coupling composition profile data. This approach is quite effective because it opens the new methodology to use the experimental data, i.e. the entire composition profile, which has not been utilized for evaluating the thermodynamic parameters in Gibbs energy functions.

The Japan Association for Nonlinear Computer Aided Engineering (JANCAE. President: Kenjiro Terada, Tohoku University), which is a non-profit organization, holds lectures every year since 2001 as a place to learn the theory and technology related to nonlinear simulation, and so many people have participated so far. Over the last decade, it has held working groups that have not only lectures, but also practices, where participants learn the theory and the numerical simulation method of the material models, develop and verify the user-subroutine libraries. This paper looks back on these activities and presents future agenda.

Influence of non-uniform deformation on lattice strain development in bicrystals was numerically investigated by a crystal plasticity finite element method. Focusing on interactions through the grain boundaries owing to plastic incompatibility, the numerical analysis of tensile loading of a bicrystal and constituent single crystals were performed. The numerical result of the bicrystal model indicated non-linear lattice strain development whereas the constituent single crystal models showed nearly linear development of lattice strain. To evaluate the influence of orientation relationship between grains in each bicrystal on lattice strain development, calculations of tensile loading of bicrystals with different crystal orientations were also analyzed. The results exhibited significant influence of the orientation relationship on lattice strain development. Finally, mechanism of lattice strain development was discussed in terms of active deformation modes and lattice rotation.

Atomic force microscopy (AFM) has been widely used to measure surface topography, friction force, adhesive force, and deformation response at nanoscale. In particularly, AFM nano indentation enables to measure deformation response at molecular level in polymer materials. This study aims to investigate the mechanism of elasto-plastic deformation by using AFM experiment and molecular dynamics (MD) simulation. To drastically improve computational efficiency, a new coarse-grained (CG) force field is first developed for Polycarbonate (PC) based on full-atom MD simulations. Using the newly developed force field and CG MD simulation, nano indentation loading on to PC is computed. During a loading process, reaction force (which comes from the interaction force between indenter probe and polymer surface) shows increasing with respected to the penetration depth. Energy variations associated with bond stretching, bending and torsion are further investigated to obtain useful insights of the deformation process. It is found that their potential energy significantly changes with respected to the penetration depth. Based on the variation of potential energy, we discussed mechanism of yielding onset and plastic deformation during AFM nano indentation test.

We develop a numerical model of gastric mixing and emptying using an anatomically-realistic geometry of the stomach and duodenum. We simulate flow in the stomach and duodenum using the multiple-relaxation-time lattice Boltzmann method. Graphics processing unit (GPU) computing is performed with an adaptive sub-domain method. We investigate the effect of the viscosity of gastric contents on the mixing efficiency and emptying rate using the numerical model.

Relationships between generalized stacking fault energy and atomic elastic stiffness, B_ij^a ≡ Δσ_i^a/Δε_j, are studied for 8 fcc, 4 bcc and 4 hcp elements by EAM potential. The 1st eigenvalue of B_ij^a , or the solution of the eigenequation B_ij^a Δε_j = η^aΔε_i, never shows negative value in the GSF deformation path for 8 fcc and 2 bcc elements, while it does for 2 bcc and 4 hcp elements. We also discussed the change in the η^a(1) under local separation in (001) atomic planes.

In general, piezoelectric bimorph for actuators and sensors is thin and includes electrodes and shim plates. Therefore, this study deals with the thin composite piezoelectric bimorph. Solid elements can describe the various type of distributions of electric potential over the thickness. However, shell elements are more appropriate for the thin structural analysis. Therefore, instead of using piezoelectric solid elements or piezoelectric shell elements, solid elements and shell elements are used to simulate the electrical field and the structural field, respectively. The coupled algorithm is based on the block Gauss-Seidel method and a novel transformation method between the solid and shell variables. In the structural analysis, the rule of mixtures about the bending rigidity and the mass is used. In the electrical analysis, the single piezoelectric solver is used to obtain the potential distribution in the composite piezoelectric bimorph using a pseudo-piezoelectric treatment for the conductor. Finally, this study illustrates the very accurate potential distributions in the actuator and sensor modes of the thin composite piezoelectric bimorph.

Diffusion mechanisms for one to three carbon interstitials in BCC iron are studied using new Fe-C interatomic potential. Firstly, carbon diffusion and stability are investigated by using nudged-elastic band method. The diffusion paths are also verified and analyzed by constructing potential energy landscapes. Finally, diffusion rates are calculated based on the transition state theory at different temperatures to study the precipitation of carbon in iron bulk. For the case of 1C, the diffusion barrier from O-site to 1NN O-site is about 1.106×10^-19J. In the case of 2C, two carbon atoms tend to form a C-C pair, where both are shifted off the O-sites. The C-C binding energy is about -0.224×10^-19J. In 3C case, the third carbon prefers to bind to 2 pre-located C atoms in the neighbor cells with a binding energy of -1.057×10^-19J. In addition, from diffusion rate calculations, it shows that carbon atoms tend to combine to stable pairs instead of larger clusters.

In wiredrawing process used for the manufacture of steel wires and rods, it is possible to increase the strength while maintaining ductility by controlling the microstructure of the wire material. In this study, pearlite steel which is eutectoid alloy composed of ferrite (α) and cementite (θ) phases is investigated. Generally speaking, microstructure of steel plays an important role in determining its mechanical properties, such as toughness and strength. In particular, the co-existence of α and θ phases both in lamellar structure greatly affects pearlite structure and properties. Wiredrawing and nano-indentation tests of pearlitic steel were carried out by molecular dynamics method. The behavior of carbon(C) atoms in wiredrawing process, the plastic deformability of θ phase under nano-indentation test are observed, and their effect on dislocation propagation near the pearlite interface is evaluated. It was found that wiredrawing simulation of pearlite steel was successfully carried out, whereas agglomeration of C atoms occurs with increase of plastic strain, and migration of C atoms into α phase via dislocation seems suppressed. In the interfacial relation proposed by Isaichev, dislocation lines are particularly much observed, and plastic deformation tends to be enhanced. In the indentation test, dislocation is often emitted from α phase side and subsequently it interacts with a dislocation already generated at structural relaxation. It is guessed that the dislocation generated on the α phase side propagates into the θ phase.

Graphene sheet (GS) which is the most fundamental structure of nano-carbon materials attracts attentions as an application for a new device of nano-elestromechanical system (NEMS). In this study, we focus on the mass sensing character of GS, and investigate the vibration behavior of GS with a particle added at the center of rectangular specimen by using molecular dynamics method. We obtain a temporal evolution of displacement of atoms and identify the vibration frequencies of GS with various added-mass using the fast Fourier transformation analysis. We also consider the vibration properties of GS with Stone-Wales (SW) defects. As a result, the vibration frequencies of GS significantly decreased with increasing of mass. The vibration frequency depends on the aspect ratio of GS, and it becomes smaller as the aspect ratio of GS become larger. The vibration frequencies of GS with SW defects is higher than the perfect GS. The vibration frequency is also affected by the position of the SW defect. When GS with two SW defects, the vibration frequency decreases as the distance between the SW defects increasing.

The air traffic demand is rapidly growing in recent years on the background of economic growth of Asia-Pacific area and popularization of Low-Cost Carriers (LCCs). Every aircraft is planned to fly along the flight plan. However, most of all aircraft are not able to follow the scheduled plans due to various factors. One of the severe factors is the over-capacity of the arrival airport. When the number of aircraft exceeds the capacity of the airport, the air traffic controller does not allow airplanes to land. In this case, aircraft have to take a detour, so-called "vectoring," or keep making circles on the particular points, so-called "holding" to adjust the arrival time. These time adjustments affect not only the delay of arrival time but also an increase in fuel consumption. If there is an efficient way to prepare a schedule with less time adjustment beforehand, it will be useful for future air traffic control. The objective of this study is to make efficient flight schedules with less congestion and enough resilience against traffic problems. In this study, we conduct a preliminary multi-objective optimization for aircraft by using NSGA-II. The objective functions are (1) minimization of averaged arrival-delay, (2) minimization of the ratio of the number of delayed aircrafts, and (3) minimization of the mean fuel consumption. The design variables are the departure-time offset of each domestic aircraft for Tokyo International Airport. We adopt a cellular automaton for simulating air traffic. As the result of optimization, a lot of optimal solutions, so called non-dominated solutions, are obtained. These solutions can decrease not only the arrival-delay time but also fuel consumption. The results indicate that the slight takeoff-time differences as the result of the adjustment of the spot assigns and taxing routes effect profoundly on the air traffic flow.

Density evolution of atomic vacancies in hexagonal close packed (HCP) metal single crystals subjected to cyclic loading is numerically evaluated by using a crystal plasticity software code. Slip deformation is evaluated by dislocation density-based models and generation rate of atomic vacancies is given by the model proposed by Essmann and Mughrabi (1979). Cyclic stress-strain curve, evolutions of plastic work density, SS dislocation density and atomic vacancy density are shown. It is emphasized that the atomic vacancy density does not show a linear dependence on the plastic work density or accumulated plastic strain.

This paper describes a multiscale stochastic stress analysis of a unidirectional fiber-reinforced composite materials considering the quasi-periodicity of material properties in microstructure. Since a microscopic random variation will cause a random response of an equivalent material property or mechanical response of a composite structure, the analysis is important for reliability evaluation of a composite structure. For this purpose, an efficient computational method is proposed in this paper. As a numerical example, the coefficient of variation of the maximum stresses observed in the microstructure of a composite material caused by a random variation of an elastic property of a component material is estimated. From the numerical results, effectiveness of the proposed method is discussed.

Cholesterol molecule is abundant in phospholipid bilayers of animal cell membranes and is known to prevent rupture of the bilayer under mechanical stretching. Recent molecular dynamics simulation studies showed that the mechanical stretching induces the phase transition to the interdigitated phase in the phospholipid/cholesterol bilayer and also showed that the interdigitated bilayer could withstand larger areal strain without rupturing than non-interdigitated bilayer. However, the molecular-level reason why the interdigitated bilayer is hard to rupture is still unclear. The bilayer rupture by stretching is initiated by the permeation of water molecules into the bilayer inside. Thus, to clarify the effects of the interdigitation on the initiation of the bilayer rupture, the water permeation through the bilayer, we performed a series of molecular dynamics simulations of the stretched phospholipid/cholesterol bilayers. To evaluate the water permeability change, we calculated the potential of mean force (PMF) of the water molecule in the bilayer. PMF means an energetic barrier for the water permeation and is a dominant factor for determining the water permeability. We found that the maximum height of the PMF for the interdigitated bilayer is larger than those for non-interdigitated bilayers. This implies that the phase transition to the interdigitated phase impedes the water permeation and might also impede the subsequent bilayer rupture. We suspect that the decrease in the water permeability with the stretch-induced phase transition might be a molecular-level reason why the cholesterol-containing bilayer is hard to rupture under stretching.

The phenomena of a ping-pong ball rising in water driven by buoyancy is studied through numerical simulation. To investigate the interaction between ping-pong ball and its surrounding fluid flows, cumulant lattice Boltzmann method and direct forcing immersed boundary method are combined for the coupled computation. Introducing the virtual mass approach enables the solver to deal with very light objects like the ping-pong ball. Adaptive mesh refinement for LBM with GPU parallel computing is implemented, greatly saving the memory usage and accelerating the computation.

The 2016 Kumamoto Earthquakes caused serious damages not only for private houses but also for infrastructures in Kumamoto prefecture. Many bridges were damaged by the seismic waves. In this study, we focused on the Aso Bridge which collapsed immediately after the main shock. A huge landslide happened after the earthquake and Aso Bridge, which was constructed in the same location of the landslide, totally collapsed. It is difficult to get consensus on the main reason of Aso Bridges collapse, since there is no observation date. On the other hands, it is important in earthquake-resistant designing of bridges to investigate critical factors and failure processes. In this paper, a numerical analysis of the Aso Bridge failure is conducted by ASI-Gauss method, which is a branch of finite element method, in order to investigate the collapse process.

For an atomistic insight in the cutting phenomenon, we performed molecular dynamics simulations of indentation/cutting on Ni work by rigid Fe edge. Three edge shapes are adopted, 90°triangle, parabolic and small saw tooth on triangle edge. The work Ni is smoothly detached from edge surface at the tip of the small saw tooth, resulting in the smoothest cut surface.

In order to obtain some fundamental aspect of Ni plating on Al alloys, the surface energies of Ni, Al, Fe,Cr, Mo, P , Zn and the interfacial / peeling energies between Ni and Al are investigated by DFT calculation. The interfacial energy is evaluated from the energy difference with the bulk Ni and Al, while the peeling energy is from that with free surfaces of Ni and Al.We also discussed the influence of the third element, (Cr, P, Mo, Zn), by substituting Al atoms on the surface/interface.

Predicting the results of numerical analysis of dynamic analysis is very difficult because it is necessary to handle time series data tracking momentarily changing analysis results. Therefore, we propose to predict numerical analysis results of dynamic analysis by using Convolutional LSTM, which is a method of handling temporally continuous moving images and predicting images of the next frame from the current image and past images. We changed the input of ConvLSTM from image to physical quantity. We used this prediction technique for numerical fluid dynamics problems. An analysis result physical quantities of the next step is predicted from the physical quantities of analysis result of the some step and the prediction result is verified.

In this study, we analyze the mechanical responses of the two types of laminated cellular structures using finite element models based on a homogenization method. In the numerical simulations, we obtain the homogenized elastic modulus tensors for the two structural units and show that the cellular structure, which is bridged by additional beams, exhibits strong auxeticity with high negative values of Poisson's ratio in the lamination direction, while retaining the in-plane negative Poisson's ratios. We then assess the sensitivity of the linear and nonlinear out-of-plane response to changes in the component geometry. According to the analytical results, we propose a simple periodic framework consisting polyhedron blocks and spherical joints, which can represent the similar auxetic behavior the cellular structure exhibits in the in-plane and out-of-plane directions.

In this study, the influences of internal resonance modes in cavity of cylindrical acoustic cloaking medium on the cloaking performances were investigated using numerical simulations. In modal analysis, it was found that there are six resonant modes in the cavity in 50 Hz ~ 300 Hz frequency range, and their quality factors was calculated. When these resonances occurred in the cavity by a point source, sound waves propagated to outside through the cloaking medium. Then we investigated the frequency dependence of cloaking performance in planar wave and cylindrical wave conditions. In both case, cloaking accuracy got worse remarkably at three resonance frequency of which the quality factors were relatively low compared with the others. It was considered that because of incompleteness of the medium structure incident sound waves penetrate in cloaking area, then resonances occur at its frequency and propagate to outside, as the result, the leaked waves disturb the background condition.

In order to develop electronic devices, various engineering materials such as polymers and metals are modeled to carry out CAE analysis to evaluate the structural strength of those devices. In this study, a series of tension tests for PC/ABS, SUS304, and so on were carried out within a wide range of strain rate from 10^-2 to 10² s^-1. Then, the practical models of those materials were made by taking the piecewise linear interpolation of experimental flow stress–plastic strain relationship and its strain rate dependence into consideration and were tested by applying to a simple numerical simulation of drop test for an electronic device using explicit FEM code LS-DYNA with changing impact velocity. The effect of the accuracy of material model on the dynamic response of that device was estimated, and it was found that the increase of flow stress with the strain rate was not negligible even when the impact velocity was not so high.

Recently colloidal systems are used as a material for experimental simulations. Crystalline and amorphous structures can be formed in colloidal systems, and they are used for observation of atomic-scale structural changes under shear deformation and relaxation phenomena. We here show our recent experimental results on crystallization of a hard-sphere colloidal glass. Colloidal glasses were formed by settling silica particles dispersed in colloidal suspensions rapidly using the centrifugation. Structural changes in the colloidal glass were observed using a confocal laser scanning microscope with applying mechanical oscillations, and we observed that there was a specific frequency where crystallization was accelerated. In the presentation, detail of the experimental setup and the results are described.

Dislocation sub-structures can be a key factor for understanding the plasticity of metals. This study reproduces GNBs (Geometrically Necessary Boundaries), which are the representative microstructures and whose detail structures are recently identified, with dislocation dynamics and evaluates those based on FTMP (Field Theory of Multiscale Plasticity). We simulate the formation process of four typical GNBs, i.e., GNB2, GNB3, GNB4, and GNB7. FTMP-based duality diagrams show that the ultimate morphology of the GNBs aligns on the upward convex curve. This result can indicate the hypothesis; the stable dislocation sub-structures tend to change their shapes against disturbances, while the unstable those firmly stand the action. We also evaluate Shannon entropy of the GNBs by box counting method. It turns out that the entropy is proportional to the logarithm of the duality coefficient, which is the ratio of the incompatibility and the fluctuation part of energy.

The generalized continuum mechanics has a long history which has challenged to implement the more intrinsic properties equipped in the condensed matters into the conventional continuum. Microcontinuum field mechanics theoretically systematized by Eringen covers the more general degree of freedom (dof) into the material point. In the present paper, the micromorphic theory with the microscopic deformation gradient tensor as a director of additional dof has been introduced into the beam theory. Even if the microscopic framework structure does not have any characteristic length of nonlocality, the macroscopic nonlocality can be inspired due to the analogy between the angle of deflection and rotation director. Also the macroscpoic characteristic length can be estimated with the order of micrometer size using the 2-scale homogenized finite element method.

Since electrical contact resistance is an important property in the numerical simulations for resistance spot welding, a multiscale coupled finite element (FE) procedure for resistance spot welding is proposed to evaluate the high accuracy of the electrical contact resistance. This analysis consists of macroscopic coupled FE analysis for the resistance spot welding and microscopic the electrical contact resistance analysis using three-dimensional thermal elasto-plasticity contact FE simulation. A rigid plate is contacted to the micro-FE model with contact pressure and temperature that are obtained by macro-analysis, to calculate electrical contact resistance by elasto-plasticity contact FE analysis including large deformation theory combined with electric FE analysis based on the phi-method. In this study, to analyze realistic electrical contact resistance of steel sheet contact in the micro-scale analysis, an oxide film Fe2O3 on the surface is considered. The oxide film is introduced into the surface of the micro-FE model. The electrical contact resistance with the oxide film was higher accuracy than without one.