A spring washer is widely used as a method for preventing loosening. However, experimental results presented by Sakai and Yamamoto et al., show that the performance of a spring washer as a loosening prevention mechanism is at best equal to that of a washer-less joint, if not worse. In this paper we analyzed loosening under shear loading and as a result were able to explain the mechanism that accelerates loosening in the framework of the three-dimensional finite element method (FEM). A spring washer causes non-uniformity of contact pressure at the washer interfaces, because of its asymmetric shape. When a bolted joint with a spring washer is subjected to shear loading, sticking area on the contact surfaces of the spring washer is limited to two corner points before the bearing surface undergoes gross slip. One of these points is on the upper surface of the spring washer and the other is on the lower surface. In this situation the nut rotation around these sticking points results in drastic loosening. We also conducted comparative simulation with Sakai's experimental results. Compared with experimental results, the bolted joint with the spring washer is easy to loosen according to the simulation results. It is believed that the difference comes from the spring washer's edge cutting into the contact surface of the nut, something not included in this simulation.

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The designs of on-board electronic devices used in automobiles need to satisfy not only electronic requirements but also physical requirements such maintaining sufficient stiffness under loads. The development of multi-disciplinary optimization methods that also handle multi-physics issues can facilitate a systematic approach to the design of such devices. In this study, we propose a new multi-disciplinary topology optimization method that handles multi-physics phenomena, namely, the coupling of electromagnetic wave propagation problems with static structural mechanics problems. The Finite Difference-Time Domain method is used to solve the electromagnetic wave propagation problem, while the static structural mechanics problem is solved using the Finite Element Method. New relaxation schemes for the design domain and design variable settings are proposed to deal with the use of the different numerical methods. The integral reflection electric energy and the mean compliance are formulated as objective functions to be minimized in an optimization problem. A multi-objective function is also formulated based on a weighted sum formulation to deal with the two objective functions. The optimization algorithm is constructed based on sequential linear program-ming. A design example of a multiple-band dielectric resonator antenna is provided to show the usefulness of the proposed method.

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We investigate the characteristic deformation behavior of carbon-black (CB) filled rubber using three-dimensional finite element model with the molecular chain network model and homogenization method. The deformation behavior of CB filled rubber under macroscopically uniform tension has been examined. The results reveal the effect of CB volume fraction, particle shape and distribution pattern on substantial enhancement of the resistance to macroscopic deformation. Especially, CB with botryoidally aggregated structure suggested the presence of low deforming region between asperities of CB surface. The low deforming regions act to increase the net CB volume fraction, which enhances the resistance to macroscopic deformation and hysteresis loss. Furthermore, the effects of volume fraction and in aggregation of the distribution of CB on deformation behavior of CB filled rubber are discussed.

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In this paper, the crushing behavior of stepped circular tube is studied by axial compression with finite element method. It is found that two-and-more steps of stepped circular tubes are considered as a combination of two steps of stepped circular tubes, which the crushing behavior relevant to compressive load and deformed displacement can be predicted. In comparison with the compressive load from finite element method, the predicted one is a little greater due to the difference of boundary conditions. The mechanism of telescopic deformation of stepped circular tube is mainly composed of bending, rotating, and stretching. However, another mechanism is appeared when the length between radii of steps is short enough. As far as geometric parameter concerned, the longer the axial length of stepped circular tube is, the higher degree of rotating angle becomes. And, the initial load grows with the increase of fillet radius. Further, the average of compressive load is also investigated.

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The large-scale cast steel has been used in broad fields of industries, such as power generation, construction, vessels, and automobiles. In the solidification process of a hummer used for press machine, for example, sometimes defects such as shrinkage cavity, segregation and cracks appear at hummer's surface. Shrinkage cavity and segregation can be predicted by performing non-steady state heat transfer analysis; and therefore such two types of defects can be eliminated by using chills which control solidification process. However, uneven cooling rates at different regions of the large-scale cast steel generate thermal stresses, which cause solidification cracks, between the chills. For causing those cracks, thermal stress may be important; however, there have been few studies for this thermal stress analysis. In this study, a three dimensional thermal elasto-plastic stress analysis has been performed by using finite element method in connection with three dimensional non-steady state heat transfer analysis, including interaction between the temperature and stress field. The results provide further understanding of the observed solidification crack failure for large-scale cast steel.

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The reliance of the material properties on the numerical analysis has been studied, focusing the encapsulant of POP (Package on Package). The result of the numerical analysis with the material properties, that the material supplier had announced, did not support the result of the actual hardware testing. Through the research process, I had focused the material properties, and then, the material properties were measured actually with the hardware test piece of parts constructing this product. As the result, the order difference between the material supplier announced data and the measured data was observed. It was recognized strongly that the reliance of the material properties is extremely important, and became possible to study the optimized parameter of the encapsulant with the numerical model in which the measured data was applied.

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In shape memory polymers, large strain can be fixed at low temperature and thereafter can be recovered at high temperature. If the shape memory polymer is held at high temperature for a long time, the secondary-shape forming with irrecoverable strain appears. The secondary-shape forming can be applied to a new simple method of fabricating shape-memory polymer elements. In the present paper, the influence of the strain-holding conditions on shape recovery and the secondary-shape forming in polyurethane-shape memory polymer is investigated by the tension test for film and the three-point bending test for sheet. The higher the shape-holding temperature and the longer the shape-holding time, the higher the rate of secondary-shape forming is. The equation to express the rate of secondary-shape forming is formulated.

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In a thermal spraying process, a lot of molten powders are impinged continuously onto a substrate due to a high-temperature plasma flow, and the coating is deposited consequentially. Thus, powder size, powder material, powder velocity, powder temperature and substrate temperature as the process parameter affect the mechanical properties and adhesion of coating. The understanding of fundamental physical principle for the spread and solidification of splat is essential to determine the relation between the coating properties and the process parameter. Relatively few experimental studies have been done to examine about a molten metal droplet impact. The simple model had been also developed to estimate quantitatively the flattening of a splat. However, there are no papers for the splat cohesion property, in spite of an essential one in characterizing the coating adhesion. In this study, the splat cohesion property for molten metal particle (Sn 60%-Pb 40%) dropped onto the substrate (SUS304 stainless steel plate) is examined based on a free fall experimental procedure, which could be simply simulate a powder deposition process in a thermal spraying. Influence of kinetic energy of the impact droplet and the substrate temperature on the flattening of splat and the cohesion is shown. The splat cohesion strength will be tried to estimate based on an energy balance consideration.

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This paper deals with a stress control problem of a composite disk consisting of a transversely isotropic structural layer onto which a piezoelectric layer of crystal class 6mm is perfectly bonded. A number of electrodes are arranged concentrically on the top surface of the piezoelectric layer. When a heating temperature distribution acts on the bottom surface of the composite disk, the maximum thermal stress in the structural layer can be controlled by applying an appropriate electric potential to each electrode. The applied electric potentials are determined by using the quasi-Newton method based on the BFGS updating formula in the case where stress constraints are imposed on the piezoelectric layer. The exterior penalty function method is employed in order that the optimization problem with stress constraints is transformed to that without stress constraints. Numerical calculations have been carried out for a composite disk which consists of a CFRP layer and a cadmium selenide layer. Finally, numerical results are shown in tables and figures.

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The fatigue strength of weld surface of truck frames has been estimated according to the fatigue limit diagram in JIS E 4207, “General Rules for Design of Truck Frames for Railway Rolling Stock”. However, it is impossible to predict the fatigue life by using this fatigue limit diagram. This study has proved the possibility of fatigue life estimation for welds of truck frames according to the Modified Miner's rule. In order to estimate the fatigue life, three items are used such as the S-N diagram assumed from allowable stress in JIS E 4207 or fatigue design curve of JSSC, relation of crack occurrence vs. running distance and stress frequency distribution in service load.

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In the United States and Japan, baseball is a very popular sport played by many people. However, the ball used is hard and moves fast. A professional baseball pitcher in good form can throw a ball at up to 41.7 m/s (150km/hr). If a ball at this speed hits the batter, serious injury is quite likely. In this paper we will describe our investigations on the impact of a baseball with living tissues by finite element analysis. Baseballs were projected at a load cell plate using a specialized pitching machine. The dynamic properties of the baseball were determined by comparing the wall-ball collision experimentally measuring the time history of the force and the displacement using dynamic finite element analysis software (ANSYS/LS-DYNA). The finite element model representing a human humerus and its surrounding tissue was simulated for balls pitched at variable speeds and pitch types (knuckle and fast ball). In so doing, the stress distribution and stress wave in the bone and soft tissue were obtained. From the results, the peak stress of the bone nearly yielded to the stress caused by a high fast ball. If the collision position or direction is moved from the center of the upper arm, it is assumed that the stress exuded on the humerus will be reduced. Some methods to reduce the severity of injury which can be applied in actual baseball games are also discussed.

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In this study, we try to develop a new head injury criterion in the automotive crash accident, which is evaluated by the hydrostatic pressure. Main subject of this study is to find the threshold value of the functional injury of the brain nerve cell, which is obtained by the impact loading experiment. PC-12 cultured nerve cell is employed to imitate the human's nerve cell and measure the critical pressure value for the occurrence of damage. We observed the cytoskeleton injury, and evaluated the decreasing ratio of fluoro-area caused by hydrostatic pressure loading. The disappearance area of fluorescence is caused by the creation of the actin rods and which means F-actin structural disorder. It reveals that the cytoskeleton injury depends on the hydrostatic pressure loading, and the injury threshold value, such as the critical pressure, is obtained. Finally, an availability of our new head injury criterion based on the nerve cell injury is confirmed.

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Skin of sausage and salami called “Casing”. Casing is cylindrical film and a typical composite consisting of cellulose short fiber and collagen. Casing is expanded in the circumferential direction when meat is stuffed. Sometimes, casing is longitudinally broken during the meat stuffing process due to strain concentration caused by the unequal distribution of the thickness and the stiffness. Firstly, structural factors governing the failure of casing were examined from viewpoints of controllability and mechanical influence on the failure. The Damage Theory was extended in the incremental fashion to predict the failure. Here, the fiber orientation and the distributions of fiber aspect ratio were taken into account. The strain at failure was then predicted. Next, the Taguchi Method was used to analyze the effect of internal structure factors on the strain at failure. We concluded that (1) using low aspect ratio cellulose fibers and (2) setting the extrusion rate high are the practical ways to produce more reliable (flexible) casings.

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