In this research, it was tried that controlling of direction of CNFs in a composite material by applied electric filed could be established. In the experiment, suspension which contains the CNFs in uncured epoxy resin without hardener was dropped between two pairs of cathodes. The ratio of frequencies of applied sinusoidal voltages and phase angle between the voltages was changed. The CNF arrangement configuration was varied with the phase angle, when the applied voltage frequencies were the same, although the configuration was not changed in the different frequency couples. Moreover, it was theoretically obtained that time average of moment of force occurred in a long, slender object in media that has high electric conductivity, like the CNF, is proportional to the difference of ‘principal square means of electric field’, and the time average of the moment of force becomes 0 when the long, slender object is arranged in the direction of ‘major principal square mean of electric field’. Based on the theoretical result, the direction and intensity of the CNF arrangement were estimated in the experimental condition, and the analytical result were compared with the experiment result. Furthermore, the reason that the configuration is not changed with the phase angle in the different frequency couples was theoretically demonstrated.

抄録全体を表示

Mechanical properties and dimensional accuracy of FRP parts depend on molding process. The authors have been developing a new simulation method to predict them by considering molding process. This paper describes an overview of the process simulation. Some new characteristics were proposed to analyze curing process of the matrix resin and its residual stress because the temperature gradient of the mold during the curing process would affect the thermal deformation and residual thermal stress in the FRP parts. Not only the finite element model of the FRP parts but also that of the mold were prepared. The characteristics data to predict the cure temperature were acquired first by evaluating quantity of heat required to complete the cure reaction, experimentally. The relation between the heating up ratio and the deformation of FRP parts was evaluated both analytically and experimentally, by changing the curing profile systematically. The amount of the deformation of the FRP parts agreed well with the prediction by the simulation.

抄録全体を表示

Poly(lactic Acid) screws were fabricated using forging process. The process consisted of two-step, which included bar molding by drawing and threading. Molding temperatures were selected as 70 and 100℃. Machine-cut screws were also fabricated for comparison. In order to evaluate mechanical properties, pullout, shear and twists tests were conducted on the specimens. Higher pullout and shear strength were obtained for the screws forged at 70 ℃. Twist strength were almost the same values for screws molded at any conditions. However ductile behavior was observed for screws molded at 70℃. These results suggest that the forging at 70℃ is the best molding process.

抄録全体を表示

This study has examined the forming process and its characteristics of bell structures with the use of batch type foaming that the blowing agent of a supercritical fluid was used. In this study, various forming methods have been tried for bell structures together with a series of impact tests and acoustic tests of the structures, followed by evaluation of shock absorption and sound insulation for inclusion of particles. The trial succeeded in forming the bell structures including various kinds of balls by means of batch type foaming. As results, the following have been confirmed. (1) Bell structures exhibit shock energy absorption effect. (2) Bell structures exhibit sound insulation effect. (3) A simplified model to represent the motion of particles in the air gap of a bell structure and associated frictional force was shown, and a relationship between the air gap and particles that affects a damping characteristic was studied. The results suggest that the distance between the air gap inner wall and the particles makes a great contribution as an element for enhancing the damping characteristic.

抄録全体を表示

A method for determining boundary conditions and analyzing stresses and strains in two-dimensional elastic body from measured displacement distribution is described. Displacement distributions obtained by optical methods are represented by the superposition of the displacements obtained by finite element analyses under the boundary condition of unit force at a point on the boundary. The nodal force vector along the boundary of the analysis region is then determined from the measured and computed displacements using the method of least-squares. The stresses and strains inside the analysis region are obtained from the nodal forces along the boundary by direct analysis. The validity is demonstrated by applying the proposed method to displacement distributions obtained by finite element analysis and those obtained by digital image correlation. Results show that the stresses can be computed from the measured displacements accurately by the proposed method. Furthermore, the stresses near free boundaries and stress concentration region can be determined easily. As stresses can be evaluated easily and accurately, it is expected that the proposed method can be applied to various problems in solid mechanics.

抄録全体を表示

Effects of fluid properties on stress relaxation behavior in a liver of a pig were investigated. First, compression and relaxation tests were carried out for various liquid viscosities and fluid pressures using liver of a pig. In the compression tests, the fracture strain was dramatically increased with increasing viscosity of liquid while the fracture strain decreases with increasing viscosity. The hardening ratio increases with increasing pressure of fluid. In contrast, Young's modulus for zero-load decreases with fluid pressure. In the relaxation tests, the change in relaxation ratio with time became gradual with increasing viscosity of liquid. However, it rapidly decreased with increasing pressure of fluid. Two-step compression tests were then conducted to clarify the effects of primary and final tightening of a plastic tourniquet. The values of stress gradient and stress for the final tightening in the normal compression tests were almost the same as those in the two-step compression tests. However, stress gradient in the second compression exhibited only a linear behavior. The second relaxation behavior became gradual with increasing the first relaxation time. It was found that movement and outflow of liquid end at around 300 seconds after the start of the first relaxation.

抄録全体を表示

Thermoplastic Polyamide (PA) is known as Nylon®, and its FRP are one of the engineering plastics. It is very important for them to reveal accurately the visco-elastic behavior. Furthermore, PA is a crystalline polymer, and it is necessary to consider the effect of crystallization on mechanical properties. The purpose of this study was to make clear the effect of crystallization and fiber volume fraction on creep behavior of PA. The creep test was performed using the materials which adjusted crystallinity on each composite with various fiber volume fractions. As a result, these materials conformed to Arrhenius type of time-temperature superposition principle, and crystallinity and fiber contents work on creep behavior as not only the effect of reinforcement but also of time retardation. To compare the creep behavior on these effects, we made the grand master curves for crystallinity and fiber volume fraction. Obtained two grand master curves were compared each other, the shapes of these curves are similarly, and we tried to superpose them, and we got the great grand master curve. Therefore, the creep behavior including each conditions have the same behavior. Using these curves and shift factors, we can calculate the creep behavior, and estimate the creep behavior with the effect of arbitrary time, temperature, crystallinity and fiber contents.

抄録全体を表示

Fatigue properties of surface film bonded materials with resin interlayer have to be discussed because these materials are often used in electronic parts and their expected electronic function must be maintained in operation. As a model specimen, pure copper films with the thickness of 100μm were bonded to steel base plates with epoxy resin. Using these specimens, fatigue testing was conducted under compressive and tensile mean stresses, and then fatigue crack initiation behavior inside the notch hole was observed using SEM (Scanning Electron Microscope) and fatigue crack propagation behavior on the surface film was observed in relation to the roughness pattern measured by laser-microscope. As a result, fatigue damage inside the notch root showed that cracks were caused at a few sites and connected through the thickness of film, irrespective of slip lines, during fatigue with each mean stress. In addition, fatigue crack propagation rate on the surface film increased near the notch with zigzag roughness of relatively smaller and larger region around crack for the compressive and tensile mean stresses, respectively. The fracture surface and the zigzag roughness around fatigue cracks were discussed in relation to the compressive and tensile mean stresses using an atomic potential energy model.

抄録全体を表示