This research is the proposal to design and verification a new magnetically driven multi-ferroic composite actuator material which is characterized by large strain as well as rapid response speed. The composite actuator material is designed to consist of magnetostrictive Ni matrix and superelastic TiNi alloy fiber fillers whose volume fraction was changed. Spark plasma sintering (SPS) method which is characterized by short time and low temperature processing was used for joining of these two different material elements. Cross-sectional observation by laser micrograph, mechanical compression test, and magnetostriction measurement were carried out to verify the perfection of the adhesion state between TiNi filler and nickel matrix as well as the amplification effect of a magnetostriction. As the experimental result, the amplification effect of about a maximum of 1.5-time magnetostriction was verified experimentally in the composite actuator.
In the present study, a test system was constructed in order to investigate the deformation behavior of shape memory alloy under thermo mechanical loadings, for example, tensile loading-unloading and heating-cooling under constant stress. Then, thermo mechanical loading tests were conducted for shape memory alloy wire. Also, we analized the deformation behavior of shape memory alloy under thermo mechanical loadings by using conventional macroscopic constitutive equation. As a result, it is not easy for conventional constitutive equation of shape memory alloy to analize the deformation behavior under complicated thermo mechanical loadings. It is necessary to construct the novel constitutive equation of shape memory alloy based on the mechanism of deformation.
The effect of kind and thickness of the metal layer and thickness of the CFRP (Carbon Fiber Reinforced Plastics) layer on the thermal deformation characteristic of active laminate was examined experimentally and compared with theoretical value obtained from three-layered beam model. Various types of the laminate made of the metal layer, that is, aluminum, 2024 aluminum alloy, SUS304 stainless steel, zinc and titanium, a unidirectional CFRP prepreg and a unidirectional KFRP (Kevlar Fiber Reinforced Plastics) prepreg to insulate them were fabricated by hot-pressing at 393 K. The main results are as follows: (1) The experimental values of the curvature of the active laminate using mono-layers of CFRP and KFRP prepregs correspond with theoretical values. (2) Actuation of active laminate was examined and it was theoretically found that aluminum and magnesium can realize high level of actuation, and it was experimentally found that aluminum and 2024 aluminum alloy can realize high level and unidirectional actuation, and SUS304 stainless steel can realize similar actuation, but causes snap-through around 393 K. (3) The effect of CFRP thickness on the curvature of active laminate at 313 K was experimentally examined and it corresponded well with theoretical values.
This study was focused at investigating the characteristics of a new smart-piezo-sensor for assessing the integrity of structures. We prepared two types of smart piezo-sensor layers such as a linear strip and planar sheet to investigate the characteristics of signal propagation in the sensor layer as well as the overall performance of each sensor. These smart-piezo-array-sensors, called Smart Active Layer (SAL), were fabricated by using a piezoelectric element and protection polymer layer. The performance of this sensor system was verified by simulating the wave propagation through several test conditions such as a patched layer on the thin plate, embedded layer between reinforcing FRP sheet and the surface of concrete beam, and an embedded layer into the model aircraft wing. When the cracks existed between the sensors and AE sources, the amplitude of propagated waveforms showed an additional decrease as expected. It can explain that a crack interferes with the progress of the wave produced by pulse-input event. Also, the known distance between each sensor element on the SAL allowed the sensors to detect the location of defects automatically. From the laboratory experimental study, we confirmed that the characteristics of wave propagation of the patch/embedding type smart-piezo-sensor affected an overall performance in detecting an elastic wave.
In order to evaluate the strain rate dependence of the dynamic flow stress of aluminum alloys, 2017-O and -T4, high strain rate tests were performed at strain rates ranging from 1×103s -1 to 3×104s -1, and strain rate reduction tests were also conducted in the strain rate range from about 1×104s -1 to 3×104s -1, and the reduction in strain rate is 58.6%. A steep increase in the flow stress was observed for 2017-O at the strain rate of about 4 ×103s-1. For 2017-T4, the above phenomenon was observed at the strain rate of about 1 ×104s -1. A simplified model for dislocation kinetics under dynamic plastic deformation is used which can represent a transition in the rate controlling mechanism of dislocation motion from a thermally activated process to a viscous drag. It is confirmed that the steep increase in the flow stress of 2017-O and -T4 observed at the above-mentioned high strain rates is attributed to the rate dependence of the viscous drag on the dislocation motion and furthermore,the increase in the mobile dislocation density shifts the transition region, or the strain rates in which the steep increase in the flow stress becomes to appear, to the higher strain rate side.
Investigations have been carried out on the dispersion behavior and entrapment time of low density particles into a water bath. Particle holdup, vortex initiation time and vortex arrival time have been measured. The particle holdup is defined as the ratio of the sum of particle passing time at a laser beam to the total measurement time. The vortex initiation time is defined as the period from the start of impeller rotation to the initiation of a vortex tube, and the vortex arrival time is defined as the period from the start of impeller rotation to the moment at which the vortex tube arrives at the impeller. The following results are obtained. (1) The particle holdup in offset agitation is higher than that in centric agitation. (2) The mass of the particles placed on the bath surface affects the particle holdup. (3) Empirical equations are proposed for the two characteristic times as functions of the rotation frequency of impeller and the geometrical parameters such as the depth of the water bath and the height of the impeller position.
Observation has been made on the behavior of a single large bubble rising in an inclined circular pipe filled with water. The inner wall of the pipe is wetted by water. It is coated with fluororesin to get it to be poorly wetted. In the inclined poorly wetted pipe, the rising velocity of a single bubble increases with an increase in the inclination angle, exhibits a mild peak, and then decreases. The wake formed behind the bubble and the shearing and buoyancy forces acting on the bubble are mainly responsible for this phenomenon. In the wetted pipe the rising velocity of a single bubble agrees with the equation proposed by Bendiksen et al. An empirical equation is proposed for the rising velocity of a bubble in the poorly wetted pipe.
A previously observed optical interferometric band pattern (the white-band, WB) interpreted as representing localized strain has been compared with a mechanical band structure known as the Lüders line. A WB can be observed in a fringe system formed with the subtraction method of electronic speckle-pattern interferometry (ESPI) applied to in-plane displacement of a plastically deforming metal specimen. The front of Lüders line (FLL) is known to be representing a yield location. Experiments have been carried out to compare the locations of WBs and FLLs on the same specimen to explain the meaning of WBs. The experimental results indicate clear correlation between the WBs and FLLs under monotonic tensile loading and under cyclic tensile loading, proving experimentally that WBs and FLLs are the visualization of the same physical phenomenon but the each strain sensitivity is not the same.
Fractographic analysis was performed on root-fractured tooth by analyzing three-dimensional structure constructed from SEM images. Human fractured tooth was observed using SEM and quantitatively analyzed using a newly introduced image analysis method, in which a cross-angle between surfaces could be determined using stereo pair of SEM images. The result showed that the angle between the lumen of the pulpa dentis and the fractured surface ranged from 100°-135° in the area where dentinal tubles were abundant while ca. 100° near the root of tooth where dentinal tubles were less observed. The angle between fractured surfaces was ca. 110°, which was independent on the position. This result indicates that there would be a significant correlation between the direction of crack path and the presence of dentinal tubles. The proposed method should be useful to evaluate failure analysis of tooth.
The present paper is concerned with the development of novel type of micro wind energy converter using insect wings. A series of experimental studies were conducted on the function of wing apparatus of flying insects. In the first place, the structural properties of insect wings were studied through measurements of certain morphological parameters. The scanning electron microscopic observation showed the morphological characteristics of a fly wing. In the second place, the novel type of micro wind energy converter was proposed and constructed. The energy converter is composed of the permanent magnet, magnetic fluid, coil, and insect wings. The micro energy converter may convert the air flow energy into electric energy. In the third place, the power generation characteristics of the micro wind energy converter using fly wings were examined based on the research of insect wing morphology. It was found that the micro wind energy converter shows higher output voltage.
Contamination of bays and lakes is one of serious problems in many countries. Many kinds of heavy metals and organic materials are usually contained in the sediments on the bottoms of the bays and lakes. In this research we mention about the treatment of contaminated sediment using a swirl motion of a bubbling jet and ozone. As a first step, we investigate the condition under which the swirl motion preferably occurs in a bottomless cylindrical vessel. Secondly, the period, amplitude, starting time, and damping time of the swirl motion are measured. Theoretical and empirical equations proposed previously are compared with the measured values of these quantities.
The main objective of this study is to clarify experimentally the vibration characteristics of tube bundle subject to an upward cross flow. In-line array of tubes widely used in shell-and-tube type of heat exchangers was simulated by transparent glass rods mounted flexibly over the whole tube bundle. Displacement of the vibrating rods was captured by high speed video camera whereas instantaneous velocity fields around the rods were obtained by Particle Image Velocimetry (PIV). The results confirmed that the vibration characteristics of tube bundle are closely related to the velocity fluctuation of the surrounding flow field.
The Split Hopkinson Pressure Bar Method with viscoelastic stress bars is widely used as a technique for the evaluation of the dynamic properties of such materials. The validity of the Viscoelastic SHPB Method is examined. In this method, the stress and the strain of a specimen are calculated by considering the average of the data collected from both ends of the specimen. Therefore, the accuracy of the dynamic properties of viscoelastic materials depends on the experimental condition. The shape of the waves at the boundary side of the stress bar and the specimen are obtained numerically by using the Elementary theory, and the stress distribution in the specimen is analysed. It is necessary to measure the reflected and transmitted strain waves of moderate size and to almost equal the load on both ends of the specimen with this method. When the ratio of the stress bar and the specimen of mechanical impedance is about 15-20%, these requirements are met, and the dynamic properties of viscoelastic materials can be evaluated with good precision. The value of the complex compliance comes to vary, except under this condition, so this method can not be used well.
Spectacle frames can be classified into two types, namely full-rim and rimless types, on the basis of the method they use for retaining the lenses. In this study, we measured the displacement distribution of these two marketed spectacle frame types by estimating the opening load exerted on the temples of the spectacles when they are worn. In this experiment, we employed light sectioning, which involves scanning an object using a laser beam. The displacement distribution was measuring the spectacles' profiles before and after application of a load. The temple exhibited two-step displacement distribution in which the displacement gradient was large at a distance of approximately 40 to 50 mm from the end piece. We also conducted FEM analysis to investigate the influence of the rims on the mechanical characteristics of the spectacles. We found that the rimless spectacles should fit well and produce no discomfort since their temples are well displaced resulting in little pressure being applied to the head. Because the screw section is under great stress in rimless spectacles, however, they have a much greater risk of lens damage than full-rim spectacles.
First, a variational principle is derived to minimize the errors and noises associated with experimental temperature measurements. This variational principle assures also the satisfaction of the governing steady-state heat conduction equation. On the basis of this variational principle, an intelligent hybrid experimental measurement and finite-element method is developed for the measurement of temperature field, and for the subsequent visualization of higher-order quantities such as the heat flux distribution. Furthermore, a concept is presented for self-restoring heat generation that automatically restores the errors and noises in the experimentally measured temperature field. The present intelligent hybrid method successfully demonstrates automatic detection and automatic elimination of experimental measurement errors, and smooth visualization of heat flux distribution.