In this study, the effects of shape uncertainty on buckling behavior of cubic lattice cellular structures are investigated using a homogenization theory of finite deformation. For this, the updated-Lagrangian formulation is employed in the homogenization theory to cosider finite deformation of struts in cubic lattice cellular structures. Buckling analysis is conducted at each incremental calculation to judge the buckling of struts. After buckling, buckling modes are calculated using the eigenvalue analysis. Using these methods, elastic buckling behavior of cubic lattice cellular structures with different strut shapes in uniaxial compression is analyzed to investigate the effects of shape uncertainty on their buckling behavior. It is shown that the buckling stress of the cubic lattice cellular structures strongly depends on the strut shapes.

Graphene is two dimensional structure with honey comb like hexagonal lattice with carbon atoms. Graphene nanoribbons (GNRs), graphene with nanoscale width, are expected to show a semiconductive property. Therefore next generation devices such as high-speed transistors and strain sensors using GNRs have been studied. However, schottky barrier should be decreased between electrodes and semiconductors. Dumbbell-shape GNRs (DGNRs) is proposed to solve this problem. This structure consists of an electrode part with wider GNR and a device part with narrower GNR. It is reported that electron orbital distribution is localized in DGNRs. In this study, we studied on electronic states and transmission property of DGNR17-7, which consists of AGNR17 and AGNR7, based on first principle calculation of density functional theory using SIESTA and TranSIESTA module. It is shown that the orbital distribution of HOMO of DGNR17-7 is correspond to that of electrode part. At the same time, band gap of DGNR17-7 gets smaller than AGNR7 by the effect of electrode part. In the analysis of I-V property, DGNR17-7 and AGNR7 shows same tendency. These result imply that the transmission property of DGNR17-7 is similar to device part and DGNR17-7 can be applied to devices as semiconductors.

Long-period stacking ordered (LPSO) magnesium alloys exhibit noticeable mechanical property due to a characteristic dislocation microstructure called kink band. In this study, we conduct numerical analysis for wall-shaped and ridge-shaped kink bands on the basis of two dimensional strain gradient elasticity. For the modeling of dislocation, we employed the extended isogeometric analysis, where a dislocation is taken into the weak form equilibrium equation through the body force. Present numerical analysis revealed that our models exhibit the characteristic deformations similar to the actual kinks observed in LPSO Mg alloys. In addition there is a steep change in rotational component of displacement along a dislocation array. More precisely, in the case of the ridge-shaped kink, the rotational component is confined within the kink band. In the case of wall-shaped kink, however, it shows non-local distribution throughout the elastic medium. These results indicate that the morphology as well as displacement field of kink bands depend significantly on the sign and the configuration of dislocations.

Infill structure - which consists of porous and solid phases over the structures, is getting a lot of attention due to its multi-functional performance, such as light weight, high-thermal convention and the potential redundancy. Nowadays, the manufacturing for this kind of geometrically complicated structure becomes possible by the recent development of Additive Manufacturing technology and furthermore topology optimization is often applied for the design to improve those structural performances. In infill topology optimization, too slender members often remain as a result of the severe density local constraints: this leads to undesirable local failure in the members even under small deformation. In this research, we propose a filtering method to avoid those thin members and local failure by introducing a variable length radius.

This paper presents a method to shorten the computational time for solving shape optimization problem. A volume minimization problem under the mean compliance constraint is chosen as an example of shape optimization problem. A shape optimization method based on the H¹ gradient method is introduced as a normal method. In this paper, we construct a matrix using the solutions of the state determination problem with respect to the domains obtained by a normal shape optimization method. By taking the singular value decomposition of the matrix, we obtain the left-singular vectors and use them as basis vectors of a transformation to reduce the degree of freedom of a target model. The feasibility of the proposed method is illustrated by testing the numerical scheme to a three dimensional linear elastic body of connecting rod type.

In this study, we perform analysis of linear elastic properties considering the influence of elastic strain energies of swollen elastomers. A closed form solution derived in the most general expression is used to introduce the Gent model in the Flory-Rehner theory. The effects of limiting chain extensibility are discussed.

Platelet aggregation and separation are important processes in thrombus formation. In our previous investigations, dissipative particle dynamics(DPD) has been used to simulate thrombus formation on orifice flow. In DPD, particle means platelet. However, the number of particles is vast when platelet concentration is the same as the blood. In this investigation, virtual particle model is used to decrease the number of particles. In our virtual particle model, several platelets are considered to be one virtual particle. In order to focus on the aggregation number in cases of different numbers of virtual particles, new variable of relative aggregation number is used. It is found that the relative aggregation numbers are almost the same although numbers of particles are different. It means that the probabilities of platelet aggregation are almost the same. So it is concluded that the aggregation number can be computed by using the model of virtual particle.

In nonlinear lattices, there is a spatially localized oscillation mode, which is called a discrete breather. Because the frequency increases due to nonlinearity and oscillation cannot extend to the whole system, spatially localized oscillation occurs. In this paper, we construct an appropriate initial condition of atoms in order to generate a discrete breather. We construct a system using the Newton method coupled with Large-Scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) in order to find initial conditions for discrete breather in crystals. We search for an initial condition that the positions and velocities of all atoms do not change very much after one cycle from the initial. We executed this system on two-dimensional crystal of graphene with 50 carbon atoms, and confirmed that the discrete breather with local oscillation which does not decay at the obtained initial condition.

In this paper, ductile fracture simulation under the multiaxial loading is examined. Ductility of the material is considered by damage model, moreover, crack propagation is described by the finite cover method. Predicting the crack propagation phenomena about the metal material is necessary for the engineering field. Finite element method (FEM) is widely used to predict the metalworking and fracture process involves necking, crack, and failure. However, FEM is not good at predicting crack propagation. The generalized finite element method is good at describing discontinuous field like a fracture. Finite cover method(FCM), which defines the multiple covers, is one of the candidates to describe the discontinuous deformation. Moreover, a lot of constitutive equation has devised in order to deal with complex material behavior. Though there are many material constants, they sometimes have no physical meaning. In this study, a simplified Lemaitre model with FCM is employed to crack propagation simulation under multi-axial loading by applying different combinations of normal and transverse loads to the model. Some respective examples show the result of crack propagation and examine the effect of the multi-axial loading.

Fermi-Pasta-Ulam (FPU) lattice known as a nonlinear lattice includes nonlinear terms explicitly. Therefore, we can evaluate nonlinear effects of FPU lattice straightforwardly. It includes, however, only the nearest neighbor interactions. In some cases, long range interaction plays an important role in dynamical properties in real crystals. We take the second nearest neighbor interactions into account in FPU lattice. We derive the nonlinear wave equation (modified Kortweg-de Vries – type equation) from the nonlocal FPU lattice as a continuum limit. Linear dispersion relationship of the wave equation is discussed. We also find as exact solution of soliton in the nonlinear wave equation analytically. We reveal that the velocity of the soliton is related to the second nearest neighbor interactions. We analytically evaluate the temporal evolution of the soliton and estimate the spectrum of the solitary wave using two dimensional FFT in case of different interactions. The result shows that the second nearest neighbor interactions affects the appearance of the lean of peak.

This research deals with the adhesive interface design of multi-material structures under multiaxial stress states using by shape optimization. The strength of the adhesive structure is evaluated with failure function that consists of stress invariants and material parameters dependent on the material properties of adhesives. The square sum of the failure function in the adhesive layer is defined as objective function. As an analysis model, uniform tensile force and torsional moment that yield tensile and shear stress in the adhesive layer were applied to a thin-walled cylinder model. Shape optimization based on H¹ gradient method were performed in the three different loading conditions of the analysis model that allowed different ratio of tensile and shear stress to be applied in the adhesive layer. The obtained results show that the optimal adhesive interface shapes with this method are reasonable, thus proposed method would contribute to design of the adhesive structures under multiaxial stress states.

In this paper, we propose a numerical procedure for large deformation problems of elastic membrane for surgical simulators. We employ Level Set method for geometrical representation of structures. Displacement fields is approximated by using the spline basis function with rectangular grid. We discuss validity of this technique by comparing the conventional Lagrangian technique.

We have implemented the design optimization of the three-dimensional geometry for a two-stage-to-orbit flyback booster under six objective functions regarding aerodynamics, aerodynamic heating, and structures to obtain the knowledge for designing reusable launch vehicle. It is important to view the relationship among the objective functions of other fields with aerodynamic heating under designing spacecraft. We defined many-objective problem to execute more realistic configuration design based on WIRES of Kyushu Institute of Technology and feedback the design knowledge. Accordingly, we used evolutionary computation as the optimization method and applied IBEA as evolutionary algorithm, which has appropriate result in many-objective optimization for searching design variables space and getting design information. Moreover, data analysis was carried out for the optimization result to reveal information in the objective space. Consequently, We revealed that the design strategy of configuration which improve each objective functions.

Stroke is the third leading cause of death and the number one cause of bedridden in Japan. Stroke occurs suddenly and is extremely difficult to predict. The purpose of this research is to predict cerebral aneurysm rupture with high accuracy by machine learning using medical data and engineering data, and to enable reasonable and optimal treatment according to the risk of rupture. In this study, we construct a classifier for predicting cerebral aneurysm rupture using clinical data and computational fluid dynamics simulation data of cerebral blood flow, and also extract dominant factors of rupture.

Deformation behavior of a thin liquid film on a solid substrate is investigated numerically, where the film is confined by a cylindrical solid surface across a gas layer. The evolution of the film surface profile is governed by a thin film equation, in which the disjoining pressure and the velocity of the substrate in the horizontal direction are taken into account. In such a confined geometry, the disjoining pressure includes a term associated with attractive force from the upper solid surface. The disjoining pressure in the present case becomes spatially nonuniform because the upper surface is not parallel to the substrate surface. The surface of the film with uniform thickness then becomes unstable. A liquid protrusion is formed below the cylindrical surface when the substrate remains at rest, whereas protrusions can be periodically produced and advected when the substrate moves horizontally at a constant speed.

It is important for safety and efficient orthodontic treatment to establish a technology to reconstruct the 3D configuration of each tooth from a dental CBCT data. The reconstruction can be achieved manually however it is complex and time-consuming process. It means the manual approach is not suitable for clinical use. The purpose of this research is to develop a method to reconstruct 3D configuration of each tooth from a CBCT data with the deep learning and level set method. The deep learning is employed to identify tooth region and level set method is employed to 3D STL model from the extracted tooth region.

It is expected to prediction of the initial tooth movement in order to be realize a safety and efficient orthodontic treatment. The prediction does not achieve only based on mechanical simulation, such as the finite element method, because the prediction has high degree of uncertainty. In order to overcome the difficulty, a data assimilation technique is employed. In orthodontic treatment three dimensional tooth alignment can be measured by a medical optical scanner every month. The measurement data is assimilated into a mechanical simulation. The study discusses a simple and effective prediction model for the initial tooth movement for the data assimilation.

For efficiently simulating multiphase flows with three or more phases, a conservative Allen-Cahn (AC)-type advection equation for interface is proposed on the basis of multi-phase-field model (MPFM). Based on the free-energy theory, an interface is autonomously formed as a finite volumetric zone between coexisting phases across which physical properties vary steeply but continuously. The MPFM-based AC advection equation with second-order differential diffusion term is numerically solved with use of a lattice Boltzmann method up to second order accuracy in both space and time. From a numerical benchmark test result of linear translation of three-phase interfaces in two dimensions, it is confirmed that the proposed AC equation has a potential to calculate multiphase interface advection more efficiently than the Cahn-Hilliard-type equation with fourth-order differential diffusion term.

Dendrite fragmentation is one of the most remarkable phenomena in solidification of alloys, because it would be potential nuclei of equiaxed structure. However, the mechanism of dendrite fragmentation is not clarified yet. In this study, a numerical model, which can simulate the dendrite fragmentation and following flow of a fragmented part, is developed by coupling phase-field method, lattice Boltzmann method and equations of motion. This model will be an effective prediction scheme of the dendrite fragmentation.

In this study, temperature dependence of elastic-viscoplastic behavior of plain-woven glass fiber-reinforced plastic (GFRP) laminates is experimentally observed, and the behavior is analyzed using a triple-scale homogenization analysis method. To this end, tensile tests of a plain-woven glass fiber/epoxy GFRP laminate are conducted under several temperature and strain rate conditions, showing its strong dependence on temperature. Using the experimental results, temperature-dependent elastic-viscoplastic parameters of the epoxy are identified. Using the obtained parameters and the triple-scale homogenization method, elastic-viscoplastic behavior of the plain-woven GFRP laminate is analyzed under several temperature conditions. It is shown that the macro/meso/micro elastic-viscoplastic properties of the plain-woven GFRP laminate significantly depends on the temperature conditions and loading directions. It is also shown that the results of analysis can accurately predict the experimental date in various temperature conditions and loading directions.

This study aims to develop a theoretical framework to construct a three-dimensional curved surface from pieces of an elastic sheet which is embedded in two-dimensional Euclidean space. Our formulation is based on the standard nonlinear elasticity within the framework of differential geometry. We first introduce the Riemannian manifolds which equip the metrics, g_[0] and g_[t], for reference and current configurations. The strain energy density is defined as a quadratic form of Green strain tensor under the assumption that elastic medium is isotropic in the reference configuration g_[0]. Then, the surface development problem ends up with a variational problem such that to find an embedding mapping which minimizes the strain energy functional. We solve the variational problem numerically using the isogeometric analysis (IGA). To this end, we first derive a weak form equilibrium equation from the first variation of the functional. The embedding mapping is approximated by a linear combination of non-uniform rational B-spline (NURBS) functions with the coefficients aⁱ_I. Consequently, the equilibrium equation yields a system of nonlinear algebraic equations for aⁱ_I and which is solved iteratively around a linearized solution by the Newton method. It should be noted here that present method consider in-plane deformation of the elastic sheet exclusively, i.e., two-dimensional isometric deformation, such as out-of-plane bending deformation, produces no strain energy.

Glass fiber plain woven fabric composites was analyzed by finite element method. Numerical results and strain energy distribution of GFRP was investigated. High dissipated strain energy of GFRP composites was in matrix resin part.

It is recognized that much energy is dissipated in matrix resin part.

In this study, we investigated the effect of flange part on stress wave propagation in the compression test of low strength material using flanged Split Hopkinson Bar method. Due to the flange with a larger radius than the input/output bar, a pair of reflected waves of compression and tension with apparently different shapes from the one-dimensional reflected wave depending on mechanical impedance mismatch was observed. Depending on the relationship between the elastic wave propagation speed in the input/output bar and the gauge position, the precursive reflected wave of compression corresponds to the rising time of the stress wave, and the tensile reflected wave propagated subsequently corresponds to the falling time. It was found that when the flange is used for impact compression test of low strength material, the effect of the flanges on the reflected wave becomes small. However, it was suggested that the transmitted wave may be affected in the impact compression test of low strength material.

Post-injection is a technology to reduce emissions of diesel particulate substance by the small amount of fuel injection after the main injection. However, fuel adhering to bore wall mixes into oil and loss of lubrication performance. We predicted the transport of diluted fuel around the piston ring and developed the three-phase flow simulation code considered air, fuel, and oil. We compared the behavior of two phase, three phase and experiment by liquid sloshing for the validation. The frequency of the movement of the liquid in the calculation was the same as the experiment. However, the difference in the height of the liquid phase at the left wall boundary of the liquid phase was seen. This is because that the behavior of the interface between the oil and the fuel can't be reproduced and how the liquid adheres to the wall surface is different. Consequently, it is necessary to consider the interfacial tension between liquid-liquid in three-phase flow analysis.

This study is devoted to investigate surface shape of the wall to lower temperature of film flow. Two-phase flow analysis is employed to predict temperature field of the liquid film flow in this study. As a validation, wettability and Weber number are changed with the grid resolution. Consequently, grid independency and rivulet flows which are in good agreement with previous studies are confirmed. Furthermore, increase of wetted area with Weber number is also clarified as same tendency as the previous cases. Now we investigate optimum geometry of the wall to lower the liquid temperature by using two-phase flow simulation.

In this research, we propose a microwave analysis method based on an iterative domain decomposition method. The simplified Berenger's PML is developed in which these eight corners are given the average value of all PML's layers. As for accuracy verification of the analysis solver, the absorbing performance of the PML is evaluated by using reflection coefficient based on S parameter. In the performance evaluation in high-frequency over 1 GHz, when the maximum side length is set to 1/20 of the wavelength, the error rate of between the numerical solution and the theoretical one is about serval percent using the PML of 8 layers. So, we have found that proposed method can calculate with high accuracy.

Chemical potential formulation of sub-lattice model is derived for phase-field method using CALPHAD interface tool. Numerical procedure obtained quasi-equilibrium composition in the interface region of phase-field method is also presented by based on parallel tangent rule.

Recently, Digital Technologies such as IoT and AI are evolving and expanding rapidly to the conventional Industries, and the Design and Development methodology of the Connected Products and the Smart Services are drastically changed to adapt to the new environment. Here, the Integration of Computational Engineering and AI is considered based upon Cyber Physical Systems (CPS), which is the key architecture of the IoT Technology.

In topology optimization, it is significantly important to appropriately formulate a structural design problem as a mathematical programming problem. However, determining the formulation is sometimes difficult because design requirements are often ambiguous and they do not directly correspond to mathematical indicators. Therefore, in this paper, the author presents a new framework for determining formulations of topology optimization problems. The proposed framework is based on knowledge discovery in databases (KDD), that is, the author proposes to incorporate topology optimization and KDD for determining appropriate formulations. In the proposed framework, various material distributions obtained by solving various topology optimization problems are collected as data records, and useful knowledges for determining formulations are extracted from the data records on the bases of KDD. The author also presents a numerical example to demonstrate the feasibility of the proposed framework and discusses some issues that should be resolved in future works.

In this paper, we utilized a simulation approach based on the dynamic explicit finite element method to evaluate stress distributions and bulk density of catalyst pellets filled in a reactor. We clarified that the shape of catalyst pellet affects its stress distribution and bulk density, and found an optimal pellet shape that can reduce average stress and increase bulk density in a reactor.