Shape memory polymers (SMPs) have thermomechanical property drastically altering around the glass-transition temperature (Tg), temporary shape fixity and shape recovery property, and so on. To understand the mechanisms of such unique properties and design products including SMPs optimally, a mathematical model which is simple yet can represent these properties reasonably and accurately is necessary. Especially, it is important for the model to be able to consider the effect of temperature and strain history on the properties because the properties are considered to depend on not only the temperature and the strain themselves but also their history. Therefore, in this paper first the effect of the temperature and strain history on the shape fixity and shape recovery properties was examined. Then, a micromechanical model of SMP was developed to describe this effect. This model consisted of a lot of unit elements having four springs, two dash pots, one latch, and one thermal expansion element. Different Tg was assigned to each element because Tg depends on local condition inside of SMP and distributed in general. It was found from the experiment that the temperature and strain history applied to SMP when the shape is gradually frozen has an influence on the shape recovery process. With respect to the model, it was shown that the proposed micromechanical model can capture the thermomechanical behaviors of SMP and, especially, the temperature and strain histories dependence on the shape recovery process quite well.
Effect of calcium carbonate (CaCO3) particle dispersion on the mechanical properties of polypropylene (PP)/montmorillonite (MMT) composites was investigated. These composites were fabricated by melt-mixing using a twin-screw extruder, and the dumbbell shaped specimen was also fabricated by injection molding. Tensile and notched Izod impact tests were conducted by using dumbbell shaped specimens. The results showed that CaCO3 particle dispersion improved the elongation at break and notched Izod impact strength of PP/organized MMT composites. This mechanism was discussed from MMT dispersion and fracture surface observations using a scanning electron microscopy. It was found that organized MMT was well-dispersed by dispersed CaCO3 particle. The reason was thought to be that localized shear stress near MMT was increased by increase of localized viscosity near MMT due to CaCO3 particle dispersion. Well-dispersed MMT improved the the stability of plastic deformation at quasi-static loading and energy dissipation at impact fracture, resulting in the improvement of the elongation at break and impact strength of PP/MMT composites. In addition, CaCO3 particle dispersion also improved the tensile modulus of PP/MMT composites. This mechanism was discussed from interparticle distance of MMT and CaCO3 calculated by Tyuzyo's equation. From the above results, it was suggested that CaCO3 particle dispersion was an effective way for improvement of mechanical properties and impact strength of PP/MMT composites.
Recently there are some attempts to use piezoelectric material bonded to the surface of structure component for vibrational control, fracture control and strain monitoring. This paper presents stress-strain analysis around piezoelectric material bonded to the surface of a semi-infinite plate by integral equation method. In the analysis, general equations of the theory of elasticity and piezoelectric material are shown, the contact stress distributions of interface are replaced by continuous distributions of concentrated forces. The singular integral equation is obtained from boundary conditions of the interface. By solving simultaneous equation derived from the integral equations, stress and strain component are formulated. And several analysis results are shown by graphical representation. From analysis results, the effects of stiffener, piezoelectricity and material constants are discussed. And verification experiments are conducted, the error between analysis result and experimental result is within about 20 percent. The verification of analysis results is confirmed by experiments. Furthermore, with a view to development of fracture control method by using piezoelectric materials, we constructed strain-controlled experiment system by using analysis theory. The effects of strain release are shown.
Numerical analysis of the elastic stress field around a wedge-type disclination is first presented. Disclinations are lattice defects accompanied by multi-valued displacement field. The discontinuity in displacement is dealt with finite element method in two different ways; one is to build up finite element model with rotational discontinuity in its original shape, and the other is to give the initial strain capable of expressing the displacement field. Good agreement with the analytical solution in elasticity was obtained in both of the two methods. It is suggested that the initial strain method may be more appropriate when solving complex structures numerically because it does not need starting with cut-and-joint procedure to create a disclination.
Although honeycomb panel is widely used in various structure, its adhesive to glue honeycomb core and plate may burn by fire, leading to the requirement of another lightweight and high stiffness panel. Recently, we have developed truss core panel's structure that has equivalent bending stiffness as honeycomb panel, stronger in shear and safer in a fire than honeycomb panel. However, it is difficult in general to form truss core. Multi-stage press forming process was investigated, but it cannot manufacture high aspect ratio structure because of the limit of press forming process. The main objective of this research is to develop a new process for truss core panel by using bending method, suggesting an ability to manufacture a wider range of structure than before. In this paper, firstly the comparison between two different ways of punch arrangement is discussed. Then we evaluate the effectiveness of a springback reduction method by increasing pressure from the punch to the material.
The common purpose for vehicle development has always been lowest fuel consumption. Therefore, engine and motor hybrid vehicles, and plugin hybrid vehicles are rapidly prevailing. The electricity plays an increasingly important role as a power source for those vehicles. This work aims at developing a new cooling fan for vehicle engine. This fan can operate as a cooling fan at low vehicle speed. At high vehicle speed, however, the fan is rarely used as a cooling fan. Therefore the fan can be used as a wind turbine, which generates electric power. We have developed a new fan rotor that can operate both as a cooling fan with the same performance as the current fan and a wind turbine at higher performance than the current fan.
The stability of high-speed liquid lithium sheet jets was analytically studied for the neutron source in Boron Neutron Capture Therapy (BNCT), which makes cancers and tumors curable with cell-level selections and hence high QOL. The object of our research is to realize the thin and high-speed plane sheet jets of liquid lithium in a high-vacuum as an accelerator target. Linear analysis approach is made to the stability on thin plane sheet jets of liquid lithium in a high-vacuum, and then our analytical results were compared with the previous experimental ones. We proved that the waves of surface tension on thin lithium sheet jets in a high-vacuum are of supercritical flows and neutral stable under about 17.4 m/s in flow velocity and that the fast non-dispersive anti-symmetric waves are more significant than the very slow dispersive symmetric waves. We also formulated the equation of shrinking angle in isosceles-triangularly or isosceles-trapezoidal shrinking sheet jets corresponding to the Mach angle of supersonic gas flows. This formula states universally the physical meaning of Weber number of sheet jets on the wave of surface tension in supercritical flows. We obtained satisfactory prospects (making choice of larger flow velocity U and larger thickness of sheet a) to materialize a liquid target of accelerator in BNCT.
When a train travels through a tunnel at high speed, large pressure variations are generated in the tunnel. They impose loads on tunnel lining, equipment inside the tunnel, and the train. It is thus necessary to accurately estimate these pressure variations in order to specify the design loads for them. Model experiments are effective in investigating these pressure variations. In the model experiments, we have used axisymmetric train models, because the train model is launched by friction drive consisting of some pairs of vertically aligned wheels. However, the experiments using axisymmetric train models can not accurately simulate the pressure variations in the area close to the passing train. Therefore, we have developed a launcher which can shoot an actual shape train model at the maximum speed of 250km/h by rotating wheels, and performed model experiments using both the actual shape models and the axisymmetric models. The results show that the pressure variations in the area close to the train using actual shape train model and actual shape tunnel model agree well with those of field measurements, and the magnitude of the pressure variations is inversely proportional to a square of an observation distance. Furthermore, the results have been verified by an acoustic analysis.
Recently, the micro-bubble technologies are applied in a wide field, and grow to the field close to the human lives. Though many methods of micro-bubble generation have been proposed, pressure loss of a venturi tube is less than among others. The studies on micro-bubble generation with venturi tube have ever seen, but the generation mechanism of a micro-bubble is not fully evident. The purpose of this paper is to make the micro-bubble generation mechanism experimentally clear. In conclusion, by inspecting the images of high-speed camera, the water jet occurs on the trailing edge of a bubble when its leading edge arrives at the throat inlet and divides it into two parts in the throat section. Then, passing through the diffuser, outer shapes of the two parts become unstable and break down into micro-bubbles. It is clear that the mechanical conditions of this occurrence are based on the accelerations at a nozzle and a diffuser. Then, the generated bubble size is distributed around a peak of about 200µm.
In a PWR plant, a steam-water two-phase flow may exist in the pressurizer spray pipe under a normal operating condition since the flow rate of the spray water is not sufficient to fill the horizontal section of the pipe completely. Initiation of high cycle fatigue cracks is suspected to occur under such thermally stratified two phase flow conditions. Experiments for a steam-water flow have been conducted to investigate the temperature fluctuation phenomena. It has been shown that the wall temperature fluctuations were not caused by the waves on the water surface, but were caused by temperature fluctuations in water layer below the interface. An experiment with visualization test section of rectangular pipe was conducted to investigate the temperature fluctuation mechanism in water layer in this paper. The black stripe pattern was observed below the steam-water interface due to the density change. The water temperature fluctuations had the dominant frequency of about 1Hz. The Richardson number calculated with the measured temperature and velocity gradient was larger than 0.25. The dominant frequency of temperature fluctuations was nearly equal to the Brunt-Väisälä frequency. It was shown that the temperature fluctuations in water layer below the interface were caused by the internal gravity wave in the thermal stratified flow.
The relationship between the kinetic energy of spraying medium and pulverization work for forming powder using molten metal in gas atomization process has been experimentally studied, which intends improvements of manufacturing fine powder in atomization process. Compressed air was ejected through 1.0, 1.2, 1.5 mm diameter 6 nozzles forming a reverse conical jet whose apex angle is 30 or 40 degrees. The velocity distribution of the gas jet is measured using Pitot tube attached to a traversing equipment. The kinetic energy and momentum of the gas jet were calculated based on measurements of the gas velocity distribution. The gas jet power at the horizontal plane including the geometrical focus was about 15～25 % of the compressing power and it decreases in downstream direction. With the molten metal tube fitted into the atomizing nozzle, molten tin was poured into the gas jets and the powders were produced by gas atomization. The distribution of the particle size was measured by sieving. Median diameters of the powders decreased in accordance with the gas jet power, though they exhibited a lower limit value in higher power region. The surface energy of the powder which is regarded as the pulverization work was obtained by multiplying the powder surface and the surface tension for each particle size section. The pulverization work to form powder is as small as about 1/1000 of the jet flow energy.
In this research, we propose a telepresence robot that avoids speech collisions occurs in remote conversations. In face-to-face conversations, humans predict the next speaker by seeing others' gestures. However, it is difficult to predict it at 2D video chat situations. The failure of prediction causes speech collisions and awkward conversations. To solve the problem, we propose the telepresence robot that conveys 3D spontaneous gestures. The proposed system employs Kinect as a gesture input device and conveys unconscious gestures to telepresence robot. We conducted experiments with subjects and confirmed the efficiency of the proposed system.
This paper describes a monocular stereo system that can switch its viewpoint hundreds of times of more in a second using a four-pinhole viewpoint switching iris mechanism. Our system can measure the three-dimensional information of a moving object correctly using two different viewpoint images, which are selected from the four switched viewpoint images in a short interval using a four-pinhole viewpoint switching iris mechanism, corresponding to the moving direction of the object. Using a prototype of monocular stereo system that consists of the four-pinhole viewpoint switching iris mechanism and an offline high-speed video camera, we verified its effectiveness in monocular stereo measurement by performing several experiments of moving objects.
We have investigated reconstruction of the pipe-undulation shape throughout the length of a pipe from the measured data of the interior profiles by using a laser-beam scanning sensor. This sensor has been studied for detailed noncontact mapping of the interior geometry of pipes. The sensor, which is based on the optical triangulation, employs a laser-beam scanner placed between a laser diode and a position sensor. In this article, we study on three error factors to make pipe-undulation shape measurement highly accurate. First, we considered errors (a) caused when there is no gravitational sensor (when there is difference between the measuring direction and the perpendicular (starting) direction ). Next, we study errors (b) caused by vibration while running. In the last, we checked errors (c) caused by trip-meter outputs. We find that errors (a) and (b) are comparable, and large enough to influence the pipe-undulation shape measuring results. And the errors (c) are small compared to the errors (a) and (b).
In this paper, the system in consideration of the characteristic of the sensor information gathering on the personal mobile terminal was proposed introducing XML notation form. Then, we describe the composition of the gait outline monitoring system using the acceleration sensor and GPS information that assumes the application to the healthcare. We conducted gradual experiments, and examined the effect of the application and the extensibility of the system. In the first step, fundamental data accumulation application was built and basic examination about the feature of the walk obtained from the acceleration and GPS measurement at the time of a walk of the user who attached the mobile terminal to the body was performed. In the following step, the information acquired from the sensors used in the health care field was compared with the information acquired from the sensors of a mobile terminal. Furthermore, the application which accumulates measurement data and the input data from a user was built for the purpose of quantitative grasp of the state of the rheumatism illness. The validity of the proposal system was checked from a viewpoint of the correspondence to change and extension of the data collection which took into consideration the characteristic of the sensor information gathering on the personal mobile terminal in a series of experiments.
In this research, we propose a high accuracy linear positioning mechanism using singular configuration of manipulator. First, we introduce a basic mechanism using singular configuration. Then, we describe the linear positioning mechanism which is developed with the principle of the basic mechanism. By analyzing theoretical precision of the mechanism, we show that the mechanism can achieve more accurate and faster positioning than simple crank slider mechanisms and linear actuators. From results of basic experiment, we confirm the validity of the mechanism precision using singular configuration. After that, we also confirm the mechanism precision by peg-in-hole application experiment. Finally, we discuss a design method for the mechanism with desired motion distance.
Nowadays escalator has become a regular part of our lives. This time we introduce our research giving attention to the hand rail of escalator. A hand rail is usually made of three main parts which are ‘Cover made of urethane to shape forms', ‘Tensile carrier made of steel to provide tensile strength' and ‘Sliding layer made of cloth to decrease friction between a hand rail guide and a hand rail. The purpose of this research is to develop an analytical model of the hand rail which is able to reproduce buckling when the hand rail is bended in under side direction. At first we tried bending tests making simple test pieces, because the hand rail has a complicated structure. Based on the test results, we developed an analytical model which includes suitable material parameters and elements. Next, we tried buckling tests and found that the initial form of the hand rail influences buckling dramatically making a comparison between tests and simulations. So we improved our analytical model considered the initial form. Finally we could confirm consistency between the experiments and the simulations reproducing buckling.
This paper proposes active control system based on feedback control and an wave generating actuator with a vertical-vibrating plate, in order to attenuate standing-wave oscillation by unkown disturbance contamination in water wave tank. The validity of the system is examined by control experiments. The water wave tank is about 0.9 m in length, and has two actuators symmetrically located in the tank (one for disturbance generation and one for attenuation control) and two water-level sensors (one for control measurement and one for performance evaluation). First, the plant model is identified based on frequency response experiments, and the validity of the model is shown by a numerical analysis with the boundary element method. Secondly, the feedback controller is systematically designed by H∞ control synthesis so that the robust stability is guaranteed against plant uncertainty, and the validity of the system is shown based on the symmetry locations of actuators. Finally, control experiments are examined by using sinusoidal and random signals as unknown disturbance. It has been shown that the frequency components of resonance from the 1st to 4th modes are reduced by 20%～60%,which shows the desired performance of the proposed system to attenuate standing-wave oscillation.
This paper discusses component mode synthesis (CMS) to solve the complex eigenvalue problem that expresses the disk brake squeal equation. The disk brake squeal is known as self-excited vibration; the real and imaginary parts of the complex eigenvalue indicate the damping coefficient and natural angular frequency, respectively. The modes that have a negative damping coefficient cause disk brake squeal. Therefore, calculating the eigenpairs (eigenvalues and eigenmodes) with accuracy is important. To solve the complex eigenvalue problem, a direct solver, such as the Hessenberg method, and an iterative solver, such as the Lanczos method, are used. By using a direct solver, all eigenpairs can be calculated with high accuracy, but the computational cost is large. Consequently, its application is limited to small DOF problems of approximately 10,000 DOF. On the other hand, calculating the eigenpairs of large DOF problems by using an iterative solver is possible; this also has disadvantages, such as missing actual modes and accepting quasi-modes. To overcome these disadvantages, a CMS that uses both a direct solver and an iterative solver is used. By using CMS, avoiding the disadvantages of missing actual modes and accepting quasi-modes while still using fewer computer resources than the direct solver alone is possible. However, the calculated eigenpairs contain computational error caused by CMS. In this paper, to improve the accuracy of CMS, a novel CMS method adapting residual stiffness is proposed. Here, novel CMS is formulated, and the advantage it offers is shown by applying the direct solver, the previous CMS, and the novel CMS to the finite element models of a disk brake.
Recently, in a mechanical structure development focusing on noise and vibration, a numerical analysis like finite element method is the most famous method to expect and improve noise and vibration characteristics of the structure. However, the method is not taken account of uncertainties in structure like part shapes and connecting parts in many cases. It leads to differences between actual these characteristics and results from numerical analysis. And, the quality of the product is probably deteriorated by the uncertainties. Therefore, it is important to suppress the variation of the noise and vibration characteristics by the uncertainties, which is called robust design. In this paper, it is discussed about robust design method to minimize the variation of the eigen frequency by the uncertainties. The robust design method is based on stochastic finite element method and structural optimization. To evaluate the ability of the method, the robust design method is applied to an FE model and a spring mass system, and the method is also tested by the actual structure to confirm the performance.
This paper proposes an obstacle detection method using reflective intensity of the Laser Imaging Detection and Ranging (LIDAR) in close range for the brush cutter. So far, the authors proposed a brush cutting robot equipped with commercially available brush cutter and verified its autonomous mowing capability. In order to safely operate a brush-cutting robot, stone obstacles on the vegetation around the brush cutter should be detected and avoided. The 3D-LIDAR consisting of a combination of the 2D-LIDAR and tilting mechanism is used to collect the environmental information around the brush cutter. This study attempts to identify stone obstacles on the grass using reflective intensity of the 3D-LIDAR. Correction formula of the LIDAR intensity of the grass is developed for the influence of wetness and ambient light. Outdoor experiments under different weather conditions resulted in successful detection of stone objects in the grass field.
Suspension of a vehicle plays an important role on the vibration insulation mechanism for reducing the structure born road noise. Using a low stiffness suspension bush is one of the typical countermeasure for the vibration insulation, but such a countermeasure makes the driving stability and the handling comfort worse. The suspension design which achieves the both performance at high level is required in the automotive industry these day. As one of the possible way to achieve the requirement, the road noise reduction by the suspension geometry which has not been investigated so far is presented in this paper. For simplicity, the two dimensional simple model considering a multi-link suspension which consists of the rigid links as suspension and the simply supported elastic beam as body is used. The motion of the suspension forms the energy flow from the road surface to the vehicle body to which the suspension is connected at multiple points. The energy flow which doesn't supply power to the vehicle body is found by the shape optimization based on the sensitivity analysis with respect to the suspension geometry. The shape optimization result shows maximized negative input power contribution at frequencies of interest. And the energy flow change is done by making the particular mode hardly resonant by having node of its mode shape at the excitation point. Moreover, the effect of the mode shape change appears as input power reduction at other frequency range. These effects are analysed by input power modal expansion.
Micro total analysis system, or µTAS, is a promising tiny analysis system for medical and biochemical analysis. Droplet µTAS in particular handles samples in droplet state, resulting in reducing the amount of sample volume and the inspection time. Therefore, this study aims to realize a novel but simple droplets mixing device for droplet µTAS using electro-conjugate fluid (ECF). The ECF is a kind of functional fluid suitable for micro fluidic devices, which produces a jet flow under a non-uniform electric field applied. This study introduces this attractive fluid to realize a rotational flow which is generated in a tiny cylindrical chamber. When droplets are instilled to the ECF rotational flow, they may be subjected to the centripetal force due to density difference between droplets and ECF, resulting in droplets move to the center of the chamber and mix each other. According to this concept, we first tested cytotoxicity of the ECF, and then we designed an electrode shape required to generate the ECF rotational flow and fabricated a prototype of the mixing device. Furthermore, we optimized the rotational speed of the rotational flow for droplets mixing. As a result, the ECF rotational flow with 6 rps to 8 rps could move 0.3 µl water droplets to the center of φ18 mm chamber. Finally, we conducted a mixing experiment of two droplets and proved that the two droplets mixed in 3.96 s, without any complex controller. According to the cytotoxicity test, this mixing time was short enough for biological samples not to be influenced by the ECF.
In this study, elastic-plastic fracture mechanics analysis are carried out for two-dimensional (2D) solids using the wavelet Galerkin method (WGM) and the extended finite element method (X-FEM). In the proposed approach, severe stress concentration near crack tip is approximated by multilevel wavelet basis functions. In addition, discontinuous enrichment functions and tip enrichment functions of the X-FEM are introduced to represent crack geometry in the WGM. To discuss elastic-plastic stress field near crack tip, J-integral and HRR (Hutchinson-Rice-Rosengren) singular stress fields are evaluated. In numerical examples, elastic-plastic fracture mechanics analyses of 2D solids are analyzed to verify the proposed approach, and accuracy of the numerical results is critically examined.
System modeling and simulation technique is aimed at the support of model-based product development. Although the technique supports analysis of systems with numerical simulation, it does not support design processes at the early stage of product development. In order to utilize the functions of system modeling and simulation techniques at the early stage of model-based product development, the paper proposes methods to analyze and visualize the parameter network of a product model, which is derived from physical phenomena that jointly construct an equation system for numerical simulation representing the model behavior. The paper also presents a method to classify simulation variables in the parameter network based on its network structure and the results of numerical simulation processed with a machine learning technique. The presented methods are demonstrated using a simple electric vehicle model described with the Modelica language.
Various kinds of wound roll defects such as telescoping, dishing, starring, and wrinkles often appear in many manufacturing lines of web handling. In order to investigate how the dishing or telescoping is developed and to get fundamental knowledge of these roll defects, several web winding processes are simulated by using a simple three dimensional FEM model which is composed of an isotropic web and a rigid core. In the simulation, effects of core inclination, unbalanced web tension, and constraint of lateral displacement of the web end on both a lateral shift of web and an edge shape of wound roll are investigated. The results show that (1) when the web is wound around the inclined core, the web shifts at first to the side where the web becomes loose due to the core inclination, and then it returns almost to the original position, if the web end is constrained not to move in the lateral direction. As the results, edges of the wound roll have a curved shape instead of a flat plane. (2) When the web is wound under the condition of unbalanced tension distribution in the width direction, the web shifts at first to the side where the web tension is larger, and then it returns like the case of the inclined core, if the web end is constrained. But if the web end can move freely in the lateral direction, most part of the web are correctly wound in spite of the unbalanced tension condition and the edges of the wound roll become flat except a few outer layers of the roll. These tendencies of the web shift may hold good for any web with different length. Both the web shift and the roll edge shape described in the above can be explained by knowing the web deformation during winding and the normal entry law of the web. (3) The telescoping suddenly occurs when an axial load acting on a wound roll increases gradually. The axial load where the telescoping occurs gets larger as a winding tension or a friction coefficient increases.
Since service is an artifact as well as physical product, we can observe both function design and activity design of service in a conceptual design phase. Activity design requires designers to deploy all designed functions into activities in service delivery process. However, it is difficult for non-experienced designers to model complicated service delivery processes such as conditional branches and exception handlings while assuring the relationship to functions. To solve this problem, the authors propose a design support of constructing service delivery processes using a collection of structure patterns of processes called Workflow Patterns. In this paper, we make the Workflow Patterns hierarchized by the ISM method so that designers can easily choose a pattern among them according to purpose. The proposed method was implemented on a CAD system for service, and its effectiveness was verified through an evaluation experiment. As a result, it was revealed that the proposed method is especially effective in the case of constructing processes including conditional branches.
From a point of view of handling and stability, it is important to bring automotive tires into contact with the road correctly. If the contact state of the tire is known while moving, more advanced vehicle control can be carried out. However it is difficult to know whether tires contact with road correctly and tires produce the force enough to drive safety while moving. In this research, we formulate how to estimate contact patch's condition and side force, slip angle, camber angle of the tire using tire tester machine by measuring the deformation of tires with the strain gauges of three places attached in the inner. In addition to the strain in the circumferential direction of the prior art, the lateral direction is measured newly. From the measurement results, the vertical load could be estimated from the contact length of the middle, the lateral force and slip angle could be estimated from the relationship between the lateral force and slip angle the ratio of the contact length of the left and right, camber angle could be estimated from the relationship of the difference between the right and left lateral strain and the ratio of the contact length. By mounting a tire with a strain gauge, it is possible to clarify vertical load, slip angle, camber angle, which is a parameter necessary for the vehicle state estimation.