High tensile strength steel is very attractive because of its light weight and high strength. Therefore, it is being used for automotive frame parts. However springback is remarkably generated in sheet metal forming, and it is difficult to obtain a desired shape. In addition, wrinkling and tearing easily occur due to the low formability. The variable blank holder force (VBHF) which the BHF varies through the stroke and blank shape have direct influence on the springback, the wrinkling and the tearing. This study proposes a method to determine the optimal VBHF and blank shape for decreasing the springback. Both the torsion angle of top of the product surface and the flange angle are evaluated for springback. The numerical simulation is so intensive that a sequential approximate optimization using radial basis function network is adopted to determine the optimal VBHF trajectory and blank shape. Through the numerical simulation, the validity of the proposed method is confirmed.

In the partitioned coupled analysis using independent analysis of two fields, numerical values are transferred in a coupled surface which is a boundary between different fields. If a coupled surface is inconsistent, errors are generated in this transfer and the convergence of the block iteration method is highly influenced by a problem such that the numerical values which should be preserved is not preserved. Quantitative evaluation of these problems is important for practical large-scale coupled analysis. In this research, we evaluate and verify the error of the existing method concerning interface data transfer at the boundary surface for various analysis conditions and discuss how to reduce the error.

In recent years, 3D-printed Carbon Fiber Reinforced Plastic (CFRP) composites is receiving a lot of attention in additive manufacturing field. This method can make CFRP composites containing curved fiber by 3D printer^[1]. In order to apply it to mechanical structure, it is important to reveal mechanical properties of 3D-printed CFRP composites. In this study, we conduct modal and buckling analysis by FEM in a lot of plate models containing curved fiber and investigate the similarity of mapping data in 2-dimensional data by the statistical method with results obtained from buckling and modal analysis. Specifically, we reduced data such as buckling loads and natural frequencies onto 2-dimensional features by machine learning algorithm and it is mapped by clustering on 2-dimensional plane. It demonstrates we can explore the model having desired properties when we design the curved fiber CFRP composites plate by considering the relation between the mapping visualization and each model.

Damages of the refractory are main factor of destabilizing the steel production. For this reason, development of numerical methods for evaluating the strength and lifetime is important problem in order to stabilize steel production. Generally, refractories exhibit heavily non-linear behavior such as cracking. Therefore, there is concern over the failure of non-linear analysis or worsening of a convergence using general purpose finite element pre-package program. In this study, the smeared cracking model, linear elastic- brittle failure model, and the maximum principal stress criterion were added to original in-house finite element program. Also, the validity and the robustness were confirmed through a simple numerical example.

Origami, the ancient art of folding a flat-piece of flexible material such as paper into a 3D shape, has attracted the attention of the scientific community. Origami design of 2D crease pattern originally is developed for human. However, in order to receive the folding pleasure, some crease patterns even are difficult to fold by hand. One of the most interesting applications of origami is in robots, so origami robot is designed to emancipate human from the hard work, but some of these robots use complex mechanisms to work properly. Here, we try to search for a breakthrough strategy from the point of crease pattern design. Two powerful candidate works are discussed. One is to develop the crease pattern from tree structure; another one is to design crease pattern of approximate object. However, we think that there are still undiscovered, we try to aim the general methods of improving the crease pattern and consider the requirements that should be provided for the robot.

In recent years, road collapse, which is thought to be caused by aged deterioration of sewer pipes, is occurring in various places, and from now on, there is concern that road collapse damage tends to increase with increasing aging pipeline. In this study, a three-dimensional numerical analysis coupled with Smoothed Particle Hydrodynamics (SPH) and Distinct Element Method (DEM) is conducted to elucidate the road caving collapse caused by damage of sewer pipe. It is attempted to construct a model that can analyze from dry soil to unsaturated soil and saturated soil by considering the apparent cohesive force associated with water content in the method of the previous study.

Many high-rise buildings have been made due to the improvement of earthquake resistance and wind resistance performance of buildings. It is important to consider the safety and stability of such buildings. Especially in urban areas buildings are built in various sizes.In this research, when two prismatic structures were arranged in parallel, three dimensional numerical calculation was done with the aim of capturing the aerodynamic characteristics of those structures. For numerical results, we show the fluid force acting on a structure and the flow behavior around a square prism when changing the interval between two prisms

This paper deals with damped responses using FEM and Statistical Energy Analysis (SEA) for two panels connected in an L shape with an acoustic black hole and a viscoelastic damping layer. A plate with the acoustic black hole proposed by Kryrov has a sharply tapered edge followed by high power functions of the propagation distance. On the surface of the black hole, a thin viscoelastic material are laminated. When the black hole is installed in the plate, bending waves never reflect theoretically at this tapered edge. By changing the length of the black hole, FEM and Modal Strain Energy method are applied to obtain the internal loss factors to account for damping coupling between substructures with the black hole. Effects of the black hole on coupling loss factors which are related with the energy flow in waves are also investigated

Insects achieve their remarkable flight by flapping their flexible wings with flexible musculoskeletal system. While the flexibility in the driving mechanisms and the flapping wings are known to reduce the power consumption to generate the aerodynamic forces, their effects on the response to the aerodynamic disturbances attract less attention in spite of their capability to adjust the shape or kinematics of flapping wings passively in response to the air flow. In this study, two sets of computational fluid-structure interaction analyses of a hovering hawkmoth were performed to investigate the effect of the flexibility of driving mechanisms or flapping wings on the gust response of a flapping wing flyer. It was found that more flexible mechanism can reduce the power consumption by the resonance but becomes more sensitive to the gust than less flexible driving mechanism. The results imply that, with the flexible mechanisms, there is a trade-off of the efficiency and the robustness of the flapping wings. The passive deformation of the flapping wings was found to reduce the changes in the aerodynamic forces or torques due to the gust. Therefore, in order to develop an efficient and robust flapping-wing robot, it is of great importance to design the flexibility of both of the mechanism and flapping wings.

A first-order hexahedral element(H6 element)-based smoothed finite element method (S-FEM) with a deviatoric /volumetric split for nearly incompressible materials was developed to achieve highly accurate deformation analysis of large-strain problems. In the proposed method, the deviatoric part of the deformation gradient at the integration point is derived from the deformation gradient based on the beta finite element method (i.e., an S-FEM), whereas the volumetric part of the deformation gradient is derived from the deformation gradient on the basis of the standard FEM with reduced integration elements. This method targets H6 elements that are automatically generated from tetrahedral elements, which makes it quite practical. This is because the FE mesh can be created automatically even if the targeted object has a complex shape. This method eliminates the phenomena of volumetric and shear locking, and reduces pressure oscillations. The proposed method was implemented in the commercial FE software Abaqus and applied to the large-deformation shear and contact problems to verify its effectiveness.

This paper describes vibration analysis using finite element method with Model Strain Energy Method for steel panel connected by nonlinear concentrated springs under impact load. The panel is composed of steel layer having an Acoustic Black Hole with a viscoelastic damping layer. Finite element for the nonlinear springs with hysteresis are expressed and are connected to the panel modeled by linear solid finite elements in consideration of complex modulus of elasticity. We calculated modal loss factors and transient responses including internal resonances in the eigen modes including coupled motions between the non-linear springs and the panel. From the dominant eigen modes and the time histories, we clarified effects of an Acoustic Black Hole and non-linear springs on the nonlinear damped responses.

In recent years, a series of deep learning (DL) techniques has made it possible to recognize voice and images with high accuracy. In particular, Convolutional Neural Networks (CNNs), one of the DL models, have made great results in image recognition. In general, many techniques are proposed for CNN to escape from a local minimum of a loss function so that the CNN's estimation error is minimized according to the task to be achieved. Topology optimization is one type of structure optimization methods. In addition to the outer shape of a target structure, the topology of the structure such as the number of holes is also optimized in topology optimization. Compared with size-optimization schemes and shape-optimization methods, topology optimization has a high degree of freedom in the design variable, which would greatly improve the structural performance. However, there is a problem in the conventional topology optimization methods. Topology optimization solution often falls into a local optimum and cannot reach the unambiguous global optimum. In this study, to overcome this problem, we combined the CNN techniques to the SIMP method (i.e., one of the conventional topology optimization schemes). We used a CNN which estimates compliance value of a structure as a support tool for the SIMP method. We tested the possibility that the combined method can generate a better design (i.e., closer to the global optimum) than that constructed using only the SIMP method.

This paper describes hybrid vibration analysis using Statistical Energy Analysis (SEA) and FEM for two panels connected in L-shape with an acoustic black hole having a damping layer. The side edges in the L structure are fixed. And the other edges have free boundaries. Usually, modal damping is affected by not only shape of panels but also their boundaries. Thus, to account for couplings in damping between substructures, internal loss factors are evaluated using FEM and MSE (Modal Strain Energy) method. To clarify wave propagation, coupling loss factors are identified. Effects of the acoustic black hole with fixed edges on these SEA parameters are studied.

In this paper, dynamic responses of male and female palms were investigated. Transient responses when a levitating block collided with the palms were measured. The impact force is measured using Levitation Mass Method (LMM) proposed by Fujii. Then, experimental results using LMM were reproduced by numerical simulation using FEM. In order to reproduce characteristics of palms of living bodies, they are modeled using nonlinear complex restoring force element. This nonlinear complex element is connected to the levitated block modeled with three-dimensional finite elements. The experimental data were compared with those calculated ones using FEM.

In this paper, we discuss a fast simulation method for magnetic-mechanical coupling analysis of a large scale Interior Permanent Magnet (IPM) motor by using the coarse-grained Magnetic Beads Method (MBM). The magnetic field distribution of the IPM motor gradually changes in the direction of motor rotation axis. The coarse grained model is applied only in the motor rotation axis, and reduces the total number of beads while maintaining the sufficient calculation accuracy. We apply the coarse grained MBM to a high power density IPM motor. When the number of beads in the direction of motor rotation axis is larger than 3, it is confirmed that the relative calculation error of averaged torque is - 6.7 [%] compared with experiments. The calculation speed is 800 times higher than the non-coarse-grained model.

It is well-known that structures vibrate complexly under the fluid force. The cross-flow amplitudes of a square cylinder increases with variation of the reduced velocity. The galloping vibration characteristics of a square cylinder is captured in this study. The cross-flow vibration of the square cylinder with an angle of attack is reported in this paper.

This paper deals with impact response analysis using finite element method for a curved rectangular panel with an elastic frame supported by nonlinear concentrated springs. The rectangle panel has two curvatures along its two diagonals. Finite element for the nonlinear springs are expressed and are attached to the elastic frame with the panel modeled by linear solid finite elements. A viscoelastic damping material is laminated on the steel panel. The damping layer is also modeled by solid elements in consideration of complex modulus of elasticity. The restoring force of the springs have cubic nonlinearity and linear hysteresis damping. The transient responses are computed including nonlinear resonances in the coupled modes among the nonlinear springs, the panel and the frame. Effects of the damping layer and the curvature on nonlinear vibration phenomena are investigated.

In order to realize a comfort industrial product with a safe structure, vibration suppression is an important technology both industrially and environmentally. Therefore, in this report, the base plate in the sound absorbing double wall structure has an acoustic black hole. A model is applied under the condition that the damping material is on the surface of the black hole. The base plate is fixed on the opposite edges of the black hole. The other edges have free boundaries. Numerical analysis is performed to clarify changes of vibration reduction and vibration transmission from the base plate to the cover plate using FEM and MSKE method proposed by Yamaguchi et al.

Utilization of medical stents is one of effective treatments for stenosis and occlusion occurring in a living body's lumen indispensable for maintenance of human life such as superficial femoral artery (SFA) occlusion. There are concerns about the occurrence of fatigue fractures caused by stress concentrations in the conventional stents, and stents having high strengths and high flexibilities are desired and required. Therefore, in this research, applicable mesh structures as applied for medical stents based on the design concepts of high strength, high flexibility are interested to solve various problems of conventional stents. However, it is costly to fabricate meshed stents, so it is difficult to make mass production. Therefore, the purpose of this research is to improve the accuracy of analytical approach so that the compressive properties of meshed stents can be accurately grasped without specimen experiments. Shape design of the meshed stents is performed using 3-dimensional CAD software Solid Works. Then experimental and analytical evaluations on compressive properties of sample meshed stents aim at improvement of analytical accuracy. From the comparisons between analytical and experimental results, the validity of analytical evaluation on the compression rigidity of prototype meshed stent specimens using flat plate simplified jig model was confirmed by comparison with the experimental jig model.

Threaded fasteners using bolts are widely applied in industrial field as well as various fields, having loosening problems and causing many accidents. Nuts or the like with spring washers are used as countermeasures against loosening of the screw fastening bodies. However, there remains the problem that efficient loosening prevention method can’t be obtained in the case where increases in the kind of parts and lock nuts can’t be used. In this study, the purpose is to obtain self-loosening preventable threaded fasteners by introducing lateral cuttings on bolt structures. Different patterned lateral-cuttings as applied on bolt structures are introduced through three dimensional CAD modeling tools. Analytical approaches for evaluations on the self-loosening preventable effects of threaded fasteners and strength performance of lateral-cutting applied bolt structures were performed using finite element method and results are reported in this study. Comparing slackness test results with analytical results and more details on evaluating mechanical properties of lateral-cutting applied bolt structures will be executed in future study.

Wave scattering problems for periodic structures are of interest since they have many applications in engineering and science. In this study, we apply the fast direct solver of the Martinsson-Rokhlin type to one-periodic transmission problems using multi-trace boundary integral equation formulation. We point out that the numerical accuracy of the well-known PMCHWT formulation decreases when the contrast between the interior and the exterior dielectric constants is small. We show that this inaccuracy can be avoided with the help of the multi-trace boundary integral equations. We also apply the Ewald's method to speed up the evaluation of periodic Green's function. Finally, we demonstrate the validity of the proposed method with several numerical examples and compare its performance with that of the periodic fast multipole boundary element method based on the PMCHWT formulation and GMRES.

In recent years, deep learning using convolution neural network (CNN) has made great achievements in the field of image recognition. However, there are few applications of deep learning using convolution neural network in the field of numerical simulation. In this study, we propose a new multiscale analysis method, termed the “CNN-based DDM” which combines CNN with a multiscale technique, the domain decomposition method (DDM) In the DDM, we first divide an entire (global) domain into multiple local domains. We then analyze each local domain by a conventional numerical scheme, e.g., a standard finite difference method (FDM) solver, and obtain relation between dependent-variable values at outer grid points of the local domain. The global domain can be analyzed efficiently and rapidly using the relations of all the local domains. In the proposed “CNN-based DDM”, the CNN constructs the relation between variable values at outer grid points of each local domain based on the shape, size, and material property distribution of the local domain. We analyzed the linear steady state heat conduction fields with 2-dimentional non-periodic and heterogeneous thermal conductivity distribution using the proposed method, DDM and FDM, respectively. The proposed method calculated the temperature distribution almost equivalent to that calculated by FDM. We tested two types of CNNs. The smaller CNN conducted the local analysis more quickly than the standard FDM. From the above, it is suggested that the proposed method is useful for reducing the computational cost of the DDM.

A space-time boundary element method (BEM) for the heat equation in 2D is discussed. The space-time method is one of discretisation methods for time-domain problems, which deals with the time axis as an additional axis to the space. In this paper, we describe an implementation of the space-time BEM preconditioned with the Calderon preconditioner. Accuracy of the method and the effectiveness of the preconditioning are verified through a numerical example.

Metallic parts production with 3D printer highly attracts attention as innovative metal forming technology. However, 3D printer Technology is only applicate for limited geometries due to difficulties that are mainly caused by thermal deformation in case of metallic parts forming. In order to predict the deformation induced by thermal energy in virtual shceme, we have been working on development of software and achieved this goal. The inherent strain approach we took assumes that final deformation is caused by accumulation of the thermal strain induced by laser melting process. With this approach we can estimate deformation acceptable calculation time such as less than 1 hour. However, it is still difficult to search for the optimum forming condition with deformation prediction technology. In this paper we introduce design compensation shceme as a virtual serch algorithm for the near net shape additive manufacturing condition.

The floating/fixed ocean structures such as wind power plants and other structures on offshore have to be taken account of safety in rough sea and tsunami. It is necessary to predict behaviors of floating structures and fluid. The structures in the ocean are subjected to forces from the fluid. Particle methods of fluid dynamics have advantages for predicting the stabilization and the safety than other numerical methods. In the present paper, the behaviors of the floating structures are predicted by using δ-SPH method.

Residual stresses in electronic packages cause variations of electronic characteristics of semiconductor devices. This paper presents experimental and numerical evaluations of the stress-induced changes of direct-current (DC) characteristics of n-type SOI (Silicon on Insulator) MOSFETs (Metal-Oxide-Semiconductor Field-Effect-Transistors). Especially, interaction between mechanical stress and parasitic bipolar effects on DC characteristics of SOI device is investigated. The DC characteristics variations of SOI MOSFETs under uniaxial-stress are evaluated using a 4-point bending method. In addition, the stress-induced variations of DC characteristics of SOI MOSFETs are simulated by device simulation. The device simulation includes an electron mobility model for considering the effects of mechanical stress It is demonstrated that the experimental results of stress effects in SOI MOSFETs can be predicted qualitatively by the device simulation.

In the additive manufacturing of metal structures, the work piece experiences deformation due to the thermal strain generated during melting and solidification processes. A commonly adopted approach to predict such deformation is to perform a thermo-elasto-plastic finite element analysis (TEP-FEA). However, for additive manufacturing process of highly complex models, unrealistically long computational time is required to obtain acceptable accuracy. By contrast, the inherent strain method has been proven to be extremely fast and fairly accurate in order to predict deformation due to thermal strain by arc welding; therefore, an attempt was made to extend the inherent strain method to the additive manufacturing process. Furthermore, by combining the hierarchical domain decomposition method (HDDM), the inherent strain method out-performed the TEP-FEA with remarkable speedup while attaining high prediction accuracy.

We investigated the impact of observation position for data assimilation using sensitivity analysis. The impact of observation position was evaluated by an observability index proposed by Kang et al. (2009). We conducted an identical twin experiment to evaluate the assimilated results using the WRF forecasting model. Three-dimensional variational data assimilation (3D-VAR) method was employed to assimilate observations of wind, whose locations were selected based on the observability index. The empirical observability Gramian matrix composed from time series of model outputs was used to obtain a map of observability index in the WRF domain. The results showed the correlation between the improvement of accuracy and the map of the observability index in the case where one observation was considered.

Simulation of a large number of deformable bodies is important to understand ballasted railway track dynamics, in which complex high-level modeling is required to address both multi-body contact and viscoelastic deformation. In this study, a quadruple discrete element method (QDEM) was developed for viscoelastic multi-body dynamics using a simple algorithm based on discrete element modeling, which can easily incorporate the contact algorithm used in the ordinary discrete element method (DEM). The sleeper motion modeled using QDEM was coupled with the rail motion modeled using a finite element method (FEM), and then the traffic impact response of a ballast particle and sleeper was analyzed. The spatial distribution of ballast particle displacement induced by the passing of a wheel was clearly revealed: both the traveling and accelerating directions of a train were shown to affect the longitudinal ballast layer motion, and the lateral ballast motion was shown to depend on the sleeper's vibration characteristics. Moreover, the ballast particle displacement was assumed to become large under the center of the sleeper because of the sleeper's vibration characteristic, which fit well with the ballast's vibration characteristic. This study suggests that the proposed QDEM-FEM can provide greater insight into the impact response of ballasted railway tracks.

High tensile steel, such as dual-phase steel consisting of ferrite and martensite, is still widely used in several industries. From a research and development point of view, it is important to clarify relationship between morphology or characteristics of each constituent phase and macroscopic mechanical properties. For the pursuit of such research, multiscale simulation is considered to be one of the effective tools. In this study, 3 dimensional microstructure of martensite phase inside a dual-phase steel sample was observed and visualized by serial sectioning method, and several microstructure RVE models based on the above observation were generated. Using these models, a multiscale FE simulation based on homogenization elasto-plasticity theory was conducted. From the above computational results, effect of internal microstructure, such as volume fraction and 3 dimensionality of high strength martensite phase, on macrosocpic tensile property of ferrite-martensite dual-phase steel was investigated.

In recent years, the number of flights is drastically increasing, and arrival delays are occurring every day worldwide, even growing especially in the Asia-Pacific area. Originally, all aircrafts are planned to fly along the flight plans. However, under existing conditions, aircrafts are not completely able to follow the planed route due to various factors during flights. The most common factor is the limitation of the runway and airport throughput. When the arrival airport is already over the limitation, some flights are controlled by air traffic controllers' instructions, for example, “Holding” and “Vectoring” etc. Arrival delays in the air traffic impact on various socio-economic problems. Especially in Japan, frequent delays are observed every day in Tokyo International Airport, which is the world 5th busiest airport in passenger transport. About 70% domestic flights concentrate to the Tokyo International Airport. Moreover, 1.5 times more international and cross over flights are estimated in year 2035. In addition, it is concerned that the number of aircraft exceed the air traffic controllers' capabilities by year 2025. A key of enhancing future Air Traffic Management (ATM) is deployment of the automation systems, which support air traffic controllers by eliminating air traffic congestion. Prior to design the automation system, this study builds computer simulation environments based on agent models, which enable us to simulate the future air traffic targeting Tokyo International Airport. The objective of this study is to solve socio-economic problems by indicating bottle necks of the traffic congestion by simulating future air traffic via proposing ATM models. In this paper, we describe the evaluation of reproducibility of air traffic model using Step Back Cellular Automaton (SBCA) that based on Cellular Automaton method. Additionally, BADA is used for calculation of aircraft in this method.

In this research, an optimization design of the lattice structure is investigated, which is based on the ground structure method. In recent years, as a result of the rapid development of additional manufacturing technology, it has become possible to manufacture complicated shapes including periodic lattice structure. However, in real metal lattice samples, geometric imperfections, such as irregularities and geometric constraints on the surface of the beam elements, i.e. the maximum overhang angles exist in every unit because of the stochastic influence of feasible processing path. So in this study, a lattice structure was targeted as the shape before optimization, and a new ground structure method which does not leave elements with small cross sectional area was proposed. Here, the lattice structure studied in this paper can be manufactured by the selective laser melting machine. In addition, the effect of geometric constraints caused by AM manufacturing techniques on optimized results are discussed based on robust topology optimization combining perturbation methods for quantifying uncertainty. In the end, a robust topology optimization was discussed as a problem to minimize expected value and standard deviation of compliance.

There is an increasing demand for “impurity gettering” technology for removing metal impurities from the active region of Large Scale Integration (LSI), such as Complementary Metal Oxide Semiconductor (CMOS) image sensors. Since the efficiency of impurity gettering is determined by the competition of target metal atoms between an internal gettering site and the silicon (Si) wafer surface, an understanding of both the gettering mechanism and the stability of metal atoms near the Si (001) wafer surface is necessary. Density functional theory calculations are preformed to investigate the stability of twelve metal atoms (Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Hf, Ta, and W) near the Si (001) surface. The main results are as follows. (1) Metal atoms are more stable up to around fifth layer from Si (001) surface. (2) Surface gettering is energetically very favorable in comparison to the internal B gettering. By taking into account all possible atomic configurations, the ratio of the thermal equilibrium concentration in the i-th layer and that in the bulk of Fe atom was obtained.

Parametric loudspeakers create localized audible sound fields by using ultrasound characteristics. This sound field is governed by Westervelt equation. In this paper, we use an approximation to Westervelt equation by separating the linear terms and the nonlinear terms, and solve the initial value problem via FDTD. We also verify the reproduction of the audible sound field created by parametric loudspeakers.

In this study, the pressure drop and heat transfer characteristics of sandwich structure containing open-cell core were studied by using numerical simulation. The effect of micro-architecture, cell size and relative density on these parameters were investigated. In this paper, three types of open-cell (Cubic, BCC and BCCZ) were discussed. There is a trade-off relationship between pressure loss and heat transfer characteristics. Also, the numerical results are fitted to conventional approximate equations and the values of fitting parameters for three structures are calculated.

This study considers the stability of time domain BIEMs for the wave equation in 2D. We show that the stability of time domain BIEMs is reduced to a nonlinear eigenvalue problem related to frequency domain integral equations. The sign of imaginary parts of eigenvalues determines the stability of time domain BIEs. We confirm this conclusion with some numerical experiments.

Nonlinear analysis of sloshing of a cylindrical tank is, in this paper, carried out by the use of the Navier-Stokes equations. The height of the free surface is obtained from the computation of the equation of height function. On the other hand, the computation of sloshing has been performed by using the Laplace equation based on potential theory. by many researchers and the validation of our methodology is fully shown from this study.

In extreme environments such as space and disaster sites, it is difficult to rescue vehicles or mobile robots once they are stuck; therefore, it is important to evaluate the traveling performances of vehicles. In addition, the realization of real-time simulation is ideal under extreme environments because it is also difficult to obtain accurate information about the terrain in advance. Therefore, numerous studies on the multibody dynamics analysis using terramechanics theory have been carried out to numerically evaluation of vehicle traveling performances. However, there are restrictions on applicable shapes and motions in conventional terramechanics analysis models. In this study, terramechanics analyses models based on the resistive force theory (RFT) are proposed, which might be applied to real-time simulation. First, we extended the RFT analysis model to describe the packing effect of the soil particle to apply RFT to rigid wheels with grousers. Then, the effectiveness of the proposed model is verified by comparing it with results obtained from model experiments.

Tribological phenomena such as friction, wear and lubrication relate to mechanics, condensed matter physics and chemistry as a complex system. There are less experimental methods to observe insitu the microscopic dynamics of the tribology. It is difficult to predict the tribological behavior theoretically. In present study, dynamics of lubricating oil is simulated by molecular dynamics method in order to clarify the atom level nature of the fluid lubrication. Simulated model consists of Poly-alpha-olefin (PAO) fluid between metallic plates. Microscopic dynamics is analyzed by the molecular length and the orientation of molecule. The magnitude of interaction between the solid surface and molecular liquid affects the structure of lubricating molecules as well as the macroscopic viscosity.

Because the collapse of the cavitation bubble occurs in microscale for the very short period of time, the experimental observation of its process is limited. Nature of the collapse of the cavitation bubble has not been understood completely. In present study, the collapse phenomena of the cavitation bubbles in Lennard-Jones liquid phase are simulated by molecular dynamics (MD) method under various conditions. We have made effective visualization of the time series data of the simulated collapse process.

To improve the fuel efficiency of aircraft and to reduce carbon dioxide emissions, the application of ceramic matrix composites (CMC) to aircraft engine turbine blades is expected. CMC is lighter than Ni-based superalloys conventionally used for turbine blades and has high a heat resistance and a corrosion resistance. However, ceramics are brittle materials, and thus micro cracks due to collision of foreign object particles and thermal shock can be catastrophic damage. To compensate for those disadvantages, self-healing ceramics are proposed. Self-healing ceramics can autonomically repair micro cracks by using the oxidation reaction. In this study, we conducted the finite element analysis (FEA) of particles composite-typed self-healing ceramics by use of damage-healing constitutive model based on oxidation kinetics. In the present FEA, the strength recovery behavior by oxide filling and the distribution of the healing agent of the test piece are taken into consideration. We then analyzed the effect of compound ratio of self-healing agent (SiC particle) on the self-healing behavior under arbitrary temperature and oxygen partial pressure conditions.

Origami engineering is a subject that is concerned with various science technologies based on the social requirements by using the lowest cost for the maximum efficient products. One of the most important origami engineering is the energy absorbing problem. The existing disaster prevention fence of absorbing energy is mostly used by nets and ropes. However, the extra-long materials, which can be used in the construction, cannot effectively absorb the high energy of falling rocks and landslides due to the flexible characteristic of the cylindrical section hollow structure. So from the points of the efficient use and the lightweight, we consider to use origami structures to improve the extra-long construction materials to seek high energy absorption.

A novel numerical simulation method based on finite element analysis (FEA), which can evaluate the fracture probability caused by the characteristics of flaw distribution, is considered an effective tool to facilitate and increase the use of ceramics in components and members. In this study, we propose an FEA methodology to predict the scatter of ceramic strength. Specifically, the data on the microstructure distribution (i.e., relative density, size and aspect ratio of pore, and grain size) are taken as the input values and reflected onto the parameters of a continuum damage model via a fracture mechanical model based on the circumferential circular crack emanating from an oval spherical pore. In addition, we numerically create a Weibull distribution based on multiple FEA results of bending and tensile tests. The results suggest that the proposed FEA methodology can be applied to the analysis of the fracture probability of ceramics, including the size effect.

Traffic jams frequently occur in urban areas is a serious social problem. Signal control and route guidance are considered to be effective for alleviating traffic congestion. However, signal control optimization has a possibility that another congestion may occur at a place away from the area where it operates. Therefore, we try to solve traffic congestion by combining traffic demand control by route guidance with signal control optimization. By using two types of control method in different scale of control target, we try to achieve solving local congestion and increasing the total traffic volume simultaneously. Since route guidance has long time delay that its control effect appears, we propose a simple model to predict future traffic conditions and control method based on it. We construct a glocal control system, exchanging information between signal control and route guidance. Moreover, the effect of the proposed method is revealed by simulation.

Numerical simulation techniques for the prediction of the dynamic behavior of snow can be exceedingly effective tool for developing snow blowers and snow tractors. However, since the snow characteristics are widely changed due to climate, snowfall density and geographical features, it is needed that new snow model which can represent the difference of dynamic behavior influenced by the quality of snow. In this study we try to model such snow character on the basis of Discrete Element Method (DEM). In addition to conventional DEM, we developed a new model to simulate compression behavior of snow. The diameter of the compressed particle is reduced with compression force loaded on the particle, and the modulus of elasticity is changed depending on the amount of compression. As examples, the numerical simulations are carried out for simulating the actual load test of snow by a rectangular plate. The numerical simulation results has indicated the possibility that the new model can simulate the dynamic behavior of snow.

Many devices have been developed in order to reduce seismic response of mechanical system. Base isolation system is one of them. Friction characteristic is used to reduce seismic response in some of base isolation systems. The authors have developed base isolation system with friction for mechanical system. Seismic response generally decreases with the increase of friction coefficient. However, it is observed in experiment that acceleration response increases with the increase of friction coefficient in some conditions. In this paper, this phenomenon is examined using equivalent linearization method. Mechanical system is modeled as a single-degree-of-freedom system and seismic excitation is simulated as nonstationary filtered white noise. It is found that acceleration response increases with the increase of friction coefficient in some conditions.

Multi-phase-field (MPF) method is one of the most effective ways to simulate complex microstructure evolutions. Recently, the non-equilibrium MPF (NEMPF) model has been proposed by Steinbach et al. The advantage of the model is its efficiency and flexibility for simulating microstructure evolutions under strong non-equilibrium interface condition. On the other hand, the concept of the cyclic phase transformation was proposed in order to investigate the effects of the diffusion of substitutional alloy elements on the austenite-to-ferrite and the ferrite-to-austenite transformation behaviors. In this study, the NEMPF model coupled with CALPHAD database is applied to two-dimensional simulation of the cyclic phase transformation in Fe-C-Mn-Si quaternary alloy. The results showed that the Mn and Si spikes are formed at the ferrite/austenite interface, resulting in the transition of NPLE and PLE mode.

In this paper, new 3D J-integral andΔJ-integral for large strain elastic-plastic problems based on the domain integral method are presented. Their rigorous derivations are presented first. Then a numerical example for the new 3D J-integral is shown. The results show that the new 3D J-integral does not depend on the size of the integral domain. Therefore, the proposed J-integral and ΔJ may become effective engineering tools for nonlinear fracture mechanics.

Amstutz's method in which the level set function is evolved by the spherical linear interpolation of the topological derivative and level set function is one of the promising topology optimisations since its convergence property is mathematically analysed. It is, however, difficult for the Amstutz's method to control the complexity of optimal solutions. We have proposed to use the B-spline surface for the level set function, which enables us to use the number of control points or the degree of the B-spline as such parameters to control the complexity of optimal solutions. In this study, we apply the proposed method to the problem of controlling the natural frequency and try to expand the applicability of the methodology.

During induction bending of a steel pipe, a very complicated phenomenon occurs due to electromagnetic induction, heat conduction, plastic deformation and change of material properties depending on temperature which interact with each other. The numerical model to simulate the phenomenon using a general purpose FE analysis program ADINA is constructed. The authors discuss the possibility of the thermal-mechanical coupled analysis omitting electromagnetic analysis in which internal heat generation in the steel pipe originally by electromagnetic induction is replaced by external heat transfer. Analysis results show a certain good agreement with experimental results so that the simplified simulation model would like to be improved to be available for other electromagnetic induction conditions.