The finite element method program becomes multifunctional as the computational mechanics technique develops, and it will be necessary to add more functions according to the progress of the research in the future. Naturally, it is not possible to correspond to the function addition of the kind of not assumed at first, though the possibility of the function addition is necessary to consider in any program. The use of the design pattern is advanced to correspond to more complex programming, though object-oriented approach is paid attention for more flexible programming. Here, the outline and directions of the Option pattern designed for the FEM program enhancing are demonstrated.

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[in Japanese]

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In recent years, mechanism design becomes more and more complicated to achieve higher mechanical function and efficiency. It is necessary to create appropriate configuration and geometry at the upstream design for the detail stage. In our study, a simple algorithm is proposed for generating gear mechanism under design specifications. The design specifications are input torque, output torque and rotation direction. The spur gear train is generated by using the Monte Carlo method and the conjugate gradient method. In this report, the convergence criterion to transit to the conjugate gradient method from the process using the Monte Cairo method is discussed.

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The purpose of this study is the development of obstacle avoidance algorithm for quadrupedal walking robot in response to environment. Stepping points are generated by using neural network. Training data for neural network are optimum stepping points generated by using the genetic algorithm based on the mechanism of robot model and the obstacle. A large number of training data are required because obstacles have various sizes and shapes. We compare optimum stepping points generated by using the genetic algorithm to make a search for starting position of stride adjustment. Some numerical results of the stride adjustment are shown for several obstacle environments.

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A large space reflector consisting of radial ribs and hoop cables is considered to satisfy rigorous design requirement of a high shape precision as well as lightweight. Due to difficulty of verification of such a large and high-precision space structure by on-ground testing, a simulation-based verification is required. As the first step of establishment of the simulation-based verification, this research investigates the computational accuracy of several nonlinear finite element codes in comparison of numerical solution based on Elastica for the simplified beam model that allows large deformation. Then, sensitivities of deformation with respect to Young's modulus and applied load are investigated.

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In this paper, we numerically study the formation and breakup of an axisymmetric immiscible, viscous and laminar compound jet flowing in a coflowing immiscible outer fluid. We use a front-tracking/finite difference method to track the evolution and breakup of the compound jet, which is governed by the incompressible Navier-Stoke equations for Newtonian fluids. The method is modified to account for three-fluid flows. The density and viscosity jumps at interfaces are distributed to the nearby grid points by using area weighting and solving Poisson equations. Thereby, we investigate the effects of interfacial tensions, in terms of the Weber number We and interfacial tension ratio σ_<21>, on the various modes of the compound jet breakup: inner dripping - outer dripping, inner dripping - outer jetting, and inner jetting - outer jetting. Numerical results show that the transition from dripping to jetting is affected not only by the Weber number but also by interfacial tension ratio since the compound jet possesses two different interfaces, i.e., either decreasing We or increasing σ_<21> promotes the dripping regime. In addition, the orifice ratio also affects the transitional values of We and σ_<21>, i.e., as it increases the transition We decreases and the transition σ_<21> increases. The transition from dripping to jetting is mapped in the We - σ_<21> parameter space. However, the variations of We and σ_<21> do not affect the aspect ratio of the compound drops.

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An iterative domain decomposition method is applied to numerical analysis of 3-Dimensional (3D) linear magnetostatic problems taking the magnetic vector potential as an unknown function. The iterative domain decomposition method is combined with the Preconditioned Conjugate Gradient (PCG) procedure and the Hierarchical Domain Decomposition Method (HDDM) which is adopted in parallel computing. Our previously employed preconditioner was the Neumann-Neumann preconditioner. Numerical results showed that the method was only effective for smaller problems. In this paper, we consider its improvement with the Balancing Domain Decomposition (BDD) preconditioner. Also, we discuss a unified approach for the construction of BDD preconditioners in various applications including elastic problems, heat transfer problems and incompressible viscous flow problems besides magnetostatic problems.

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A coupled transient hydrogen diffusion-elastoplastic analysis that includes the effect of hydrogen on material softening in the microscale, is implemented to simulate the necking event in the presence of hydrogen. Results show that at the onset of necking, lattice sites are depleted by the increased number of trap sites due to plastic strain localization. When necking occurs, the hydrogen concentration in lattice sites is strongly affected by the loading time. In the presence of hydrogen perturbation, the stress-strain curve measured at the central point of the sample is seen to contain four distinct regions: an initial region of elastic response where the stress is less than initial yield stress; Stage I, a region of easy glide; Stage n, a region of linear hardening; and Stage HI, a region of parabolic hardening. It is worth mentioning that these three stages closely resemble the shear stress-strain response of single crystals.

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[in Japanese]

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To establish drop impact simulation technology of air conditioning outdoor units, firstly, we made constitutive equation of the packing materials and confirmed its precision by drop impact experiments of test pieces. Next, we conducted drop impact experiments and analyses of bottom frame installed a compressor and a weight to verify validity of the modeling of the sheet metal. Finally, we carried out drop impact experiments and analyses of an air conditioning outdoor unit to confirm validity of the modeling of screw joints of the sheet metals. This paper describes the development method for our drop impact simulation technology of air conditioning outdoor units, and introduces an example of the application of the simulation technology in the early development stages of air conditioning outdoor units.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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This paper presents a numerical study on trabecular bone of human lumbar vertebra by using the homogenization method to predict the macroscopic properties. Series set of micro-CT images of healthy and osteoporotic vertebral trabecular bone is used in this digital image-based modeling technique to develop the microstructure model. The macroscopic homogenized properties that include the Young's moduli and shear moduli was obtained in this study to investigate the change of degree of anisotropy in vertebral trabecular bone. Then, the comparison between the predicted macroscopic homogenized properties and the experimental result performed by Keyak is discussed.

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This paper aims at analyzing the interface strain using finite element method between bone and muscle in the human buttock. Research focuses on how fibril tissue damage might cause pressure ulcers and how different loading condition affects the interface strain between bone and muscle. The damaged interface was then modeled as interface crack. A manual mesh was created for this research in order to get more accurate result at the interface. Furthermore, the interface strain/stress was calculated in the local coordinate system of a normal and tangential direction along the curved interface. It was found that the changes in loading direction gave effects on strain at the tip of the breakage.

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Aortic aneurysm is a pathology that involves the enlargement of the aortic diameter and has risk factors including aortic dissection. Aneurysm wrapping and stent placement has been used in the treatment of aneurysms. This study aimed to investigate the biomechanical effects of wrapping and stenting on aneurysm. The three-layered aortic aneurysm were created and fluid structure interaction were simulated in wrapped model and stented model. The results provide quantitative predictions of flow patterns and wall mechanics as well as the effects of wrapping and stenting.

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In ductile fracture, the cup and cone fracture which occurs at the neck of a specimen is produced by the coalescence of internal voids, which in turn grow by plastic deformation under the influence of a prevailing stress triaxiality. In this study, we link simulations at a macro-scale tensile model to that of micro-scale void models to investigate the effects of hydrogen on the tensile properties of metals and alloys. The tensile test model is used to find out the hydrogen effects at the macro-scale while the internal void model is used to find out the influence of hydrogen on the void growth, which may serve as a mechanism of hydrogen embrittlement. Loads in micro-scale are imported from the displacement results of the macro-scale tensile model. The results are qualitatively verified by experimental observations in previous studies.

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The procedure for the fatigue crack initiation life prediction of railway rails has been developed. It consists of finite element (FE) analyses that account for the local material response generated by the contact load between wheel and rail. The Chaboche model was used to simulate the material response that was important in rolling contact situations. The results obtained from FE analyses were combined with the theory of critical distance and the modified Wohler curve method to predict fatigue crack initiation life in the railhead. The predictions were compared to the data obtained from the investigation in the field.

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The fatigue can occur by varying stress caused by varying load during operation. Subsequently, it is important to consider the uncertainty in the finite element analysis. Monte Carlo simulation is widely used to solve problems that take the uncertainty of the load condition into consideration. However, dynamic analysis takes longer time than linear static analysis. Hence, in this study, fast dynamic analysis using block second order Arnoldi method, which is one of the techniques of the model order reduction, is applied to the Monte Carlo simulation. Its accuracy and usefulness are shown through comparison with the analysis by explicit method.

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The Monte Carlo method is commonly used in the simulation considering uncertainties such as material properties and boundary conditions. However, non-linear analysis is much more time consuming than linear one, because a large number of analyses are required in the Monte Carlo Simulation. To put the Monte Carlo simulation for non-linear problem into practical use, this study proposes to linearize the strongly history-dependent nonlinear problem based on the idea to simulate instantaneous state in the history as linear problem. This idea was applied to the simulation of clinical microneedle insertion into human skin. The instantaneous situation in the nonlinear phenomena with variety of uncertainties could be modeled by initial stress in linear analysis.

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[in Japanese]

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Tsumani simulations by particle methods have been performed using a real geometry of sea side area of Shonan district. In this study SMAC-SPH method which is one of the incompressible viscous flow analysis has been used to solve the big wave motion on the coast area. We used the map contours to make three dimensional data of a bay side area, and the houses and buildings were modeled on the land geometry. The results of the Tsunami simulations have been visualized using CG techniques. It was concludede that the details of Tsunami behaviors on a bay side area have been cleared by SPH particle analysis.

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This paper provides a brief overview on computational methods with emphases on numerical methods that combines the finite element method (FEM) with the meshfree techniques. We introduces first a general fundamental theory for computational methods, the G space theory, that accommodates much more types of techniques for creating shape functions for numerical methods. Weakened weak (W2) formulations are then used to construct methods with meshfree technique in finite element settings, which ensures spatially stability and convergent to exact solutions. We next present examples of some of the possible W2 models, and show the major properties of these models. It is shown that the stiffness W2 models is "softer" compared to the FEM model and even the exact model, allowing us to obtain upper bound solutions with respect to both the FEM and the exact solutions. W2 models are also found less sensitive to the mesh quality, and triangular meshes can be used with excellent accuracy, which opens widely a window of opportunity for adaptive or automatic analysis of various types of problems, including fracture mechanics, plates, shells and membranes, contact problems, acoustics, heat transfer, non-linear problems, bio-mechanics, shakedown analysis, real-time computation, inverse and optimization problems.

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[in Japanese]

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