This paper describes development of high performance CFRP/metal active laminates mainly by investigating the kind and thickness of the metal. Various types of the laminates were made by hot-pressing of an aluminum, aluminum alloys, a stainless steel and a titanium for the metal layer as a high CTE material, a unidirectional CFRP prepreg as a low CTE/electric resistance heating material, a unidirectional KFRP prepreg as a low CTE/insulating material. The aluminum and its alloy type laminates have almost the same and the highest room temperature curvatures and they linearly change with increasing temperature up to their fabrication temperature. The curvature of the stainless steel type jumps from one to another around its fabrication temperature, whereas the titanium type causes a double curvature and its change becomes complicated. The output force of the stainless steel type attains the highest of the three under the same thickness. The aluminum type successfully increased its output force by increasing its thickness and using its alloys. The electric resistance of the CFRP layer can be used to monitor the temperature, that is, the curvature of the active laminate because the curvature is a function of temperature.
Microftacture process of 3 mol% yttria stabilized zirconia (3Y-TZP) for artificial joints was evaluated using the acoustic emission technique. In order to investigate the effects of environment and strain rate on the microftacture process, four point bending tests were carried out in air and physiological saline (P.S.) at various loading rates. From the results of AE behavior, rapid AE increasing point was observed before the final unstable fracture. It was suggested from the previous work that the AE increasing point corresponds to the maincrack formation. The critical stress for maincrack formation, sigma(C), was determined from the bending stress at the AE increasing point. The critical stress as well as bending strength, sigma(B), decreased in physiological saline. In particular, the decrease in critical stress was remarkable. It was then understood that stress corrosion cracking (SCC) by water in physiological saline affected maincrack formation rather than the final fracture. Consequently, it was suggested that the evaluation of o-C is essential for the reliability assessment of bioceramics.
Thermo-mechanical behavior in a rod subjected to a pulsed heat input was investigated by numerical simulation using the hyperbolic thermo-elasticity theory derived from the thermal dynamics in the present paper. Unlike the classical thermo-elastic theory with the parabolic energy equation and the hyperbolic motion equation, temperature response and thermal stress due to the temperature change exhibit significant wavy characteristics in the hyperbolic thermo-elasticity theory which is based on the non-Fourier heat conduction. The whole region of the rod is split into the heat disturbed region and the heat undisturbed region by the thermal wave front which is determined by the propagating velocity of the heat wave. The heat wave and elastic wave travel in the body at a finite velocity and reflect at the end of the rod. Thermal shock due to the discontinuous jump in thermal condition, and the reflection of thermal stress at the end terminate of the rod are significant during the heating process.
A prototype of autonomous mobile robot with two vision sensors for automatic welding of steel plates was constructed. The robot can move straight, steer and turn around the robot center by controlling the driving speed of the two wheels respectively. At the tip of the movable arm, two CCD cameras are fixed. A local camera observes the welding line near the welding torch and another wide camera observes relatively wide area in front of the welding part. The robot controls the traveling speed in accordance with the shape of the welding line. In the case of straight welding line, the speed of the robot is accelerated and the welding efficiency is improved. However, if the robot finds a corner of welding line, the speed is decelerated in order to realize the precise seam tracking and stable welding. Therefore, the robot can realize precise and high speed seam-tracking by controlling the travel speed. The effectiveness of the control system is confirmed by welding experiments.
This study proposes a MEMS microgripper design based on a compliant mechanism, utilizing the multi-input method to obtain greater output force and displacement. The compliant mechanism is very effective because the mechanism has flexible pieces that transmit force or deliver motion. The design domain is formed by the ground structure parameterization of the optimal topology. The goal is to obtain the optimal topology layout through computer simulation. This study combines insights from the topology optimization of the compliant mechanism and the piezoelectric microactuator to design a microgripper and to analyze outputs and displacement with different parameters under topology optimization.
By folding a thin flat sheet with periodically set slits or punched out portions into the third dimension, ultra-lightweight strong and functional core models are newly devised. The basic idea of this modeling arises from the application of origami technique to engineering. Based on the space filling models, fundamental flat cores and skew type sponge cores have been newly developed. By applying these models, such modified core models as curved cores and 3D honeycomb core are newly devised.
This paper describes the results of our numerical and experimental studies of the nonlinear bending behavior due to domain wall motion in functionally graded piezoelectric actuator under alternating current electric fields. A nonlinear three-dimensional finite element method is employed to simulate the dynamic response of cantilever functionally graded piezoelectric actuator. A phenomenological model of domain wall motion is used in computation, and the effects of ac electric field amplitude and frequency, number of layers, and property gradation on the deflection and internal stresses of the functionally graded bimorphs are examined. It is shown that the predicted deflection results, obtained from the numerical model, agree well with the corresponding experimental results.
In this paper a finite element method is presented to study the effects of delamination on free vibration characteristics of graphite-epoxy composite pretwisted rotating shells. Lagrange’s equation of motion is used to derive the dynamic equilibrium equation and moderate rotational speeds are considered wherein the Coriolis effect is negligible. An eight noded isoparametric plate bending element is employed in the formulation incorporating rotary inertia and effects of transverse shear deformation based on Mindlin’s theory. To satisfy the compatibility of deformation and equilibrium of resultant forces and moments at the delamination crack front, a multipoint constraint algorithm is incorporated which leads to unsymmetric stiffness matrices. Parametric studies are performed in respect of location of delamination, fibre orientation, rotational speed and twist angle on natural frequencies of cylindrical shallow shells. Numerical results obtained for symmetric and unsymmetric laminates are the first known non-dimensional frequencies for the analyses carried out here.
We developed a method for fabricating a three-dimensional spiral micro-inductor with high inductance using the LIGA process. The spiral inductor created had a diameter of 0.5 mm, and a length of I turn. The width of the spiral line was 10 mu m, the pitch was 20 mu m, and the number of turns was 15. It was made of plated copper. The master was a brass round bar coated with PMMA resist. Deep X-ray lithography was employed to fabricate a master for a metallic mold at the NewSUBARU synchrotron radiation facility, University of Hyogo. The inductor core was made of resin by injection molding. It has a spiral micro flute on the surface. We chose the worm injection molding technique in order to avoid the parting line across the spiral line. The worm injection molding was the method-for demolding the work such as that used in loosening a screw.
The purpose of the present study is to analyze the circuit connection reliability of printed wiring boards (PWBs) in relation to the thermal stresses obtained by FEM and to apply the FEM data to a data-mining method in order to clarify the factors that influence the thermal stress of the copper plating on the drilled hole walls. The following are the conclusions obtained herein: (1) Decreasing the thickness of the build-up layer is effective in reducing the thermal stress of the copper plating. (2) Using the data-mining method, new factors that were hidden in the data, such as the coefficient of thermal expansion in the Z direction, were revealed, despite the presence of other complex factors.
Fiber-matrix interfacial adhesion in composites is traditionally evaluated by means of a stress-based parameter. Recently, an interfacial energy parameter is suggested to be a valid alternative. However, the energy-based approaches overestimated the energy release rate to initiate the interfacial debonding (interfacial energy), since the plastic deformation in the vicinity of the debonding was neglected for simplicity. An effect of the plastic deformation on the interfacial energy of a fiber-reinforced polymer matrix composite is studied to evaluate the initiation of the interfacial debonding. The fragmentation tests with a model of glass fiber-reinforced vinylester matrix composite were performed, and the interfacial energy with the energy balance method taking into account an energy dissipation of the plastic deformation was calculated. The following results are confirmed; the plastic deformation has a significant influence on the interfacial energy, and the energy balance scheme taking into account the plastic energy dissipation leads to the constant interfacial energy without reference to the amount of the released potential energy. The differences between our model and the previous one are discussed.
A woodpecker strikes its beak toward a tree repeatedly. But, the damage of brain or the brain concussion doesn't occur by this action. Human cannot strike strongly the head without the damage of a brain. Therefore, it is predicted that the brain of a woodpecker is protected from the shock by some methods and that the woodpecker has the original mechanism to absorb a shock. In this study, the endoskeltal structure, especially head part structure of woodpecker is dissected and the impact-proof system is analyzed by FEM and model experiment. From the results, it is obvious that the woodpecker has the original impact-proof system as the unique states of hyoid bone, skull, tissue and brain. Moreover it is considered that woodpecker has the advanced impact-proof system relating with not only the head part but also with the whole body.
A robust optimal design of a bulk-micromachined, decoupled vibratory microgyroscope was carried out to determine geometric dimensions such that the gyroscopic performance is least affected by a fabrication tolerance. Electro-mechanical vibration analysis considering the sensing electrodes and the electronic signal processing were performed to obtain the frequency responses that influence the gyroscopic performance. A statistically distributed lateral over-etching (LOE) developed in the fabrication process was selected as a fabrication tolerance factor. The dimensions of the driving and sensing spring are selected as design variables which are the sum of deterministic mask dimensions and the LOE. To minimize the influence of LOE on the decoupled vibratory microgyroscope performance, the multi-objective function was formulated so as to minimize the sensitivities of the frequency difference with respect to the LOE. As a result, the standard deviation of the frequency difference and the driving natural frequency are reduced to 78% and 8%, respectively, through the Monte Carlos Simulation (MCS).
In cementless total hip replacement, initial stability of the femoral component is important in the long term fixation of the femoral stem. Initial stability is closely related to the relative displacement between the prosthesis and the cancellous bone of the proximal femur. After implantation of the prosthesis, the surrounding bone is partially shielded from load carrying and starts to resorb. Stress shielding causes the loss of the proximal bone. The stress distribution of femur must be assessed to predict stress shielding. The initial stability and the stress shielding were investigated for two loading conditions approximating a single leg stance and stair climbing. Two types of stems involving a distal filling and a distal short stem were studied by the finite element method to investigate the biomechanical distal filling effects. The distal short stem produced less stress shielding at the proximal bone than the distal filling stem, while both types of stems seemed to satisfy the initial stability requirement.
Since the ceramic has excellent qualities in light weight, abrasion resistance and heat resistance etc, compared with the metal, it has been actively examined in order to apply for the structures such as gas turbine and turbo charger etc, which require high strength and heat resistance. But it is not desirable to be used for the structural material since the ceramic is fragile, so the join with the metal with abundant toughnees has been studied. However, during the cooling process, the joint residual stress develops on the ceramic/metal joint by the difference in thermal expansion coefficient between two materials and it affects the bending strength significantly. Also, in order to use the joint material as the structural material, the study about the fatigue of thermal cycle of actual use statement is necessary. Therefore, to ensure security and improvement of the bending strength of joint material, the state of residual stress distribution to the high temperature-thermal cycle, and studied the effects of thermal cycle and state of residual stress distribution on the strength of joint material as well.
Characteristics of hydrogen permeation in the stainless steel 304 modified by either facing, ion sputtering, carbon coating or annealing were investigated in order to establish the safe hydrogen-energy-infrastructure using welding. A stationary hydrogen flux from the stainless steel surface was measured by using a system with an orifice. The pressure difference of the specimen was able to maintain constant by controlling the gas flow rate from the orifice in low pressure vessel. The hydrogen permeability was low in two cases of a thin stainless steel with fine facing and that annealed at 1370 K for 2 hours. In these cases, the specimens' surfaces were considered to play hydrogen trap role and to prevent from pairing hydrogen atoms. On the other hand, high hydrogen permeability was obtained in the case of Argon plasma cleaning a low-pressure-vessel side surface. These results suggest that oxide film on the specimens' surface prevent hydrogen desorption.
This report reveals gigacycle fatigue properties for a modified-ausformed V-added steel with the chemical composition of 0.3 C-0.3 Si-1.0 Cr-0.7 Mo-0.3 V in mass %. Modified-ausformed and oil-quenched steels were prepared for fatigue tests, followed by tempering at 400 degrees C and 600 degrees C. The tensile strengths of the 600 degrees C tempered steels were almost equal to those of the 400 degrees C tempered versions because of secondary hardening due to fine precipitation of vanadium carbides. The fatigue properties of the 600 degrees C tempered version of oil-quenched steel (QT600) showed little difference from the 400 degrees C tempered version (QT400) in spite of the fine precipitation of vanadium carbides. The modified-ausformed steels (AF400 and AF600) revealed higher fatigue limits at 5 x 10(9) cycles than the oil-quenched versions (QT400 and QT600), although the difference between AF400 and AF600 was small. The remarkable difference between AF400 and AF600 was fatigue strengths at around 10(6) cycles, i.e. the fatigue strength of AF600 at those cycles was higher than that of AF400. Based on the above results, the effect of the fine precipitation of vanadium carbides was small on the gigacycle fatigue properties, while modified-ausforming could improve those properties. On the other hand, the multiple effects of the fine precipitation and modified-ausforming was large on the fatigue strength at around 10(6) cycles.
Two-dimensional displacement measurement using digital image correlation with lens distortion correction is described in this paper. A single cross-grating is used as a calibration reference. Using two-dimensional Fourier transform, the phases of the grating pattern are analyzed and lens distortion distribution is obtained from the unwrapped phase maps. After detecting lens distortion, the coefficients of lens distortion are determined using the least-squares method. Then, the displacement distributions without the lens distortion are obtained. The effectiveness of the method is demonstrated by applying the proposed method to the rigid body translation test and the uniaxial tension test. The results show that the proposed distortion correction method removes the effect of lens distortion from the measured displacements. By the proposed method, accurate measurements can be performed even if images are deformed by lens distortion.
The objectives of this study are to introduce the use of a photodiode camera for measuring surface strain on soft tissue and to present some representative responses of the tendon. Tendon specimens were obtained from the hindlimbs of canines and frozen to -70°C. After thawing, specimens were mounted in the immersion bath at a room temperature (22°C), preloaded to 0.13N and then subjected to 3% of the initial length at a strain rate of 2%/sec. In tendons which were tested in two blocks of seven repeated extensions to 3% strain with a 120 seconds wait period between, the surface strains were measured with a photodiode camera and near the gripped ends generally were greater than the surface strains in the middle segment of the tendon specimens. The recovery for peak load after the rest period was consistent but the changes in patterns of surface strains after the rest period were not consistent. The advantages of a photodiode measurement of surface strains include the followings: 1) it is a noncontacting method which eliminates errors and distortions caused by clip gauges or mechanical/electronic transducers; 2) it is more accurate than previous noncontact methods, e.g. the VDA and the high speed photographic method; 3) it is a fully automatic, thus reducing labor for replaying video tapes or films and potential errors from human judgement which can occur during digitizing data from photographs. Because the photodiode camera, employs a solid state photodiode array to sense black and white images, scan targets (black image) on the surface of the tendon specimen and back lighting system (white image), and stored automatically image data for surface strains of the tendon specimen on the computer during cyclic extensions.
