In this paper, a prediction method of the maximum principal strain of a core/shielding wire contained in a coaxial cable, which is related to the life-cycle of the wire, is proposed. If the central axis of a wire is assumed to be twisted around a virtual cylindrical surface when a coaxial cable is straight and a virtual toroidal surface when the cable is bent, the shape of the wire can be described by the first and the second fundamental form of their surfaces in the differential geometry. The potential energy of the wire, which is bent, twisted, expanded, and/or contracted, is also formulated based on the differential geometry. Friction of the wire against the virtual surface is modeled as a virtual spring in the circumferential direction of the surface and its elastic energy is included in the total potential energy of the wire. Then, the stable shape of the wire can be computed by minimizing its total potential energy under geometric constraints. After that, the maximum principal strain is estimated from the shape of the wire. As a result of simulation, it was founded that a core wire is broken by bending fatigue before the shielding wire is if they have the same radius and rigidity.
Cellular manufacturing systems are well known as flexible manufacturing systems for assembly processes. Single workers carry out all assembly processes of products in the typical cellular manufacturing systems. The cellular manufacturing systems are required to cope with dynamic changes of product mix and production volumes. The workers are not able to be trained by repeating same assembly processes. The objective of this study is to propose a work instruction system for workers to understand the assembly processes quickly and reduce their assembly times of products without repeating same assembly processes. According to the learning curve of workers, it is important that the assembly time should be reduced from the first time the workers assemble the products in order to increase the productivity of cellular manufacturing systems. This study firstly records workers' assembly processes by using video equipment and analyzes the learning processes of the workers in order to propose an effective strategy for the workers to reduce the assembly processes in the cellular manufacturing systems. According to the proposed strategy, a prototype of a work instruction system is developed for an assembly cell. The prototype system provides a graphical user interface explaining the information of assembly processes for the workers to facilitate understanding the assembly processes. Some experiments are carried out for assembling a toy car built with Lego blocks in order to evaluate the effectiveness of the developed work instruction system. Experimental results of the proposed work instruction system are compared with the ones of a simple work instruction system. Through the comparison, it is recognized that the proposed work instruction system is superior to the simple work instruction system from the viewpoint of the reduction of assembly times.
This paper proposes a method for stability-directed capacity requirements planning (CRP). The stability signifies here the sustainability of manufacturing systems and the predictability of CRP under the dynamic environment. In our CRP method, the probability of overload of each operation order is calculated, and then the starting times of operation orders are determined so as to minimize such overload probabilities. In computational experiments, the proposed method is compared with two conventional methods in terms of the machine utilization and the schedule stability. The experimental results demonstrate the effectiveness of the proposed method.
This paper deals with an education planning method of human operators considering production plans. The human operators carry out machining operations by using manual machine tools based on their skills in target manufacturing systems. The individual human operators can obtain new skills to operate the machine tools by receiving trainings. New education planning method is proposed based on mixed integer programming problems in this research. The mixed integer programming problem determines suitable numbers of the trainings and that of the machining operations executed by the human operators for productions. Objective functions of the mixed integer programming problem are minimizing overtime hours and maximizing sum of training priorities. The training priorities represent indices of required skills according to production plans, and number of the skills which have already been obtained. Some case studies have been carried out to verify the effectiveness of the proposed education planning method.
The effect of liquid temperature on cavitation erosion has been studied by several researchers. The general trend is that the erosion rate shows a maximum at approximate average of boiling and freezing temperatures in some liquids. However, the erosion mechanisms of these phenomena have not been clarified. In this study, cavitation erosion tests were carried out by using a SUS304 stainless steel in deionized water at different liquid temperatures and pressures. We summarized the test results by using the Celsius temperature and the relative temperature as a temperature parameter, and discussed the effect of temperature on the mass loss rate. In addition, cavitation bubble behavior depending on the thermodynamic effect was observed by high speed camera. Moreover, the cause of the temperature effect of cavitation erosion is discussed in terms of viscosity, air content, surface tension and distribution of bubble collapse impact loads. As a result, the mass loss rate of SUS304 indicates a maximum at a relative temperature TR of 40-50 ° and the rate decreases with increasing or decreasing the relative temperature in deionized water. These tendencies are similar to that in other researches. Therefore, the relative temperature is suitable for the evaluation of temperature dependency under different pressures. In addition, we explained that the cause of the decreased mass loss rate is to strengthen the thermodynamic effect in high temperature region and to change in the distribution of bubble collapse impact loads in low temperature region.
This paper describes the development of tension, torsion, and combined tension-torsion creep testing machine with hydro static thrust bearing, criterion on creep rupture strength under biaxial stress states was examined. Tension, torsion, and combined tension-torsion creep tests were carried out at 873 K in air employing the developed creep testing machine and hollow cylindrical specimen of Mod.9Cr1Mo steel. Ratio of rupture time tR/tR* increased with the decreasing principal stress ratio λ at constant Mises' equivalent stress, where tR, and tR* denote rupture times for biaxial and tension creep tests, and λ expresses ratio of minimum principal stress to maximum principal stress. Hayhurst's stress successfully correlated with tension, torsion, and combined tension-torsion loading creep lives but Mises' type equivalent stress and maximum principal stress were inadequate to predict creep lives of Mod.9Cr1Mo steel. Oxide film and micro cracks on specimen surfaces were observed using SEM. Micro cracks and oxide film cracks initiated to the perpendicular direction to maximum principal stress axis for -1≦λ≦0. Main crack grew in direction perpendicular to specimen axis independent on the maximum stress ratio λ. The residual lives under biaxial stress states were estimated using Omega method. The Omega method was able to estimate the residual lives within a factor of 4 under biaxial stress states.
The deformation of solder shows the unique characteristics which differs from one of other engineering materials remarkably, as it is accompanied with the large creep deformation at room temperature. This deformation behaviour appears in a typical stress-strain relationship in loading, unloading and reloading path. In the present study, the tensile test of Sn-37Pb solder subjected to loading, unloading and reloading under a constant strain rate was carried out at room temperature. The constitutive equations of elasticity, plasticity and creep of the tested material were independently obtained from the stress-strain relationship under loading or reloading path. A typical stress-strain relationship of Sn-37Pb solder with time-dependent deformation was correctly reproduced by the simulation of the numerical analysis of the Runge-Kutta method and the finite element method using these constitutive equations.
This paper describes the elucidation about the influence of electrolyzed oxidizing water (It abbreviates as EO water) on copper nickel alloy for lead frame. First, the etching characteristics of EO water against the surface of copper nickel alloy for lead frame was clarified using chemicals for comparative immersion experiments. The comparative study showed that as for the etching efficiency on copper iron alloy, Na2SO4 EO water was superior to H2SO4 solution, and NaCl EO water was superior to HCl solution. Also, EO water has the selective etching tendency to Cu element in copper nickel alloy for lead frame like chemicals. As for the relationship between immersion time and etching depth, Na2SO4 EO water is same as NaCl EO water, and become proportional connection. Next, by the observation using SEM image, the influence of EO water on the surface shape of copper nickel alloy for lead frame was clarified. The results indicated that Na2SO4 EO water did not have a big influence on the surface shape. However, when using NaCl EO water, the dimples occurs, and when using H2SO4 solution, projection occurs in the surface. Lastly, as for the test piece after heating processing, it did the surface oxidation layer removal experiment by the immersion. The results show that EO water can remove the surface oxidation layer like chemicals, and Na2SO4 EO water remove the surface oxidation layer more efficiently than NaCl EO water
In this study, high-speed tensile testing for notched specimen is conducted to investigate the impact property of Polydimethylsiloxane copolymerized Polycarbonate (PDMS-PC) compared with Polycarbonate (PC). Depending on the test temperature and tensile speed, brittle or ductile fractures are observed for PC. However, only ductile fractures are seen for PDMS-PC even at the high speed 7000mm/s and low temperature 243K. The impact properties are also considered in terms of the time-temperature superposition principle. Then, master curves for the final fracture elongation for both PC and PDMS-PC are constructed in terms of the strain rate at the notch in conjunction with shift factors. The fracture behavior can be predicted for the wide range of impact speed under various temperatures from these master curves.
The noise and vibration caused by pressure pulsation are one of detrimental problems in hydraulic systems. A Helmholtz type hydraulic silencer, which is based on the resonant phenomena of a mass-spring-damper system for its attenuate principle, is known as one of the most practical silencers in the hydraulic systems. In the previous researches, the transmission loss characteristics of the Helmholtz type hydraulic silencer were modeled by a distributed parameter model. However, in the design case that the ratio of the length and diameter L/D of the cylindrical volume is smaller, the resonance frequency of the existing model begins to deviate from the experimental results and the disparity increases with decreasing the ratio of L/D. The purpose of this research is to clarify the influence of a neck and volume geometry on the attenuation characteristics. In particular, a mathematical model that considers the flow for the radial direction of the cylindrical volume is newly proposed for the design case that L/D is smaller. The transmission loss characteristics of the Helmholtz type hydraulic silencer are investigated theoretically for both the proposed model and existing models. In addition, the experimental examination of the influence of volume geometry on the attenuation characteristics is carried out in order to verify the theoretical investigations.
A liquid jet is important in various mechanical systems such as medical applications. Recently, a method for generating a thin jet by a laser-induced shock wave is proposed in a previous research. In this paper, we adopt another method for generating a thin jet as a possible alternative method. In order to investigate similarity between both jets generated by each method, we compare the velocity of the jet in our systematic experiments with a semiempirical relation reported by the previous research. We drop a liquid-filled test tube with a rounded bottom on the floor, leading to the emergence of a thin liquid jet into the air. The experimental parameters are the depth of a liquid, the diameter of the test tube, and the impact velocity. Within certain experimental conditions, our experimental results agree well with the semiempirical relation. It suggests that the jet generated by our method has similarity to the jet in the previous research. In other conditions, however, we find a remarkable fact that the jet can be faster than the value predicted by the semiempirical relation. In this case, we observe cavitation bubbles inside a liquid. We further investigate a relation between a liquid jet and the cavitation number using a high-speed camera. We introduce the cavitation number as a criterion for describing the condition of the cavitation occurrence. The criterion is confirmed by additional experiments. We also find a strong relation between the maximum volume of cavitation bubbles and the jet velocity.
The design limits of a hot water fired absorption chiller in a cycle simulation were examined. The authors have already proposed how to determine the lowest limiting value of the smaller of the two temperature differences to get a logarithmic mean temperature difference when designing each element. This new algorithm was applied, based on the trend toward the hot water fired absorption chiller that employs a multi-stage absorption system. After performing a cycle simulation, the effects of stage number for the lowest hot water temperature that could be used in air conditioning were clarified. As a result, it was found that the limits of stage number were existed. It was also found that the lowest limiting temperature of hot water could be theoretically determined in the condition of the infinite-stage absorption system.
Prandtl number (Pr) effects on characteristics of the thermal boundary layer were investigated by means of Direct Numerical Simulations (DNS) in high-Reynolds number turbulent channel flows. The molecular Pr conditions were changed from 0.71 to 25.0, and the Reynolds number based on the friction velocity and channel half-width was kept to 1000 in all cases. The mean temperature profiles were good agreements with Kader's empirical equations except for the case of Pr = 25.0. The thicknesses of thermal conduction sub-layer became thinner in proportion to a one third power of Pr. On the other hands, the peak wall-normal heights in temperature intensity became thinner in proportion to a one half power of Pr. In both thermal layers of the conduction and logarithmic, results of quadrant and Kullback-Leibler Divergence (KLD) analyses were shown analogous characteristics in all Pr cases. On the other hand, in the buffer layer, the contributions of sweep and ejection events on wall-normal turbulent heat flux and distribution of KLD were shown the different distributions between in cases of Pr = 0.71 and Pr = 5.0, 25.0.
A loop thermosyphon is known that it has higher heat transfer performance without a pump. Thus, we have applied new loop thermosyphon to cool CPUs of a rack mount server. Thermosyphon uses gravity to return refrigerant from the condensation part to the evaporation part. Therefore, when it is working, the water level in the condenser side should be higher than the evaporator side. In addition, the height of the new loop thermosyphon is designed low with 67.4mm to put it on a rack mount server. Hence, when the surrounding system and the loop thermosyphon incline, it is thought that water surface exists inside of the condenser. It causes decrease of heat transfer performance of loop thermosyphon. Hence, it is important to make clear how the performance changes by inclination angle of the system. To this purpose, the heat transfer performance of the loop thermosyphon has been measured as a function of inclination angles. As the result, it is found that thermal resistance of the condensing part and sub-cool degree at out-let of the radiator increase with increase of inclination angle. And the sub-cool degree has a correlation with vapor temperature of the loop thermosyphon. In addition, we confirmed the tendency of this correlation can be predicted by thermal circuit model of the radiator. These results show the thermal resistance changes of the loop thermosyphon by inclination angle are caused by water surface level changes in the condensing part.
Inorder to clarify the process of Accident of Fukushima Nuclear Plants, an accident scenario of Fukushima Daiichi Nuclear Power Plant, Unit 3 is analyzed from the data open to the public. Phase equilibrium process model was introduced in which the vapor and water are at saturation point in the vessels. The present accident scenario assumes that the high pressure coolant injection system (HPCI) did not worked properly, but the steam in the reactor pressure vessel (RPV) leaked through the turbine of HPCI to the suppression chamber since 12/3/2011 12:35. It is assumed that the Tsunami flooded the torus room where the suppression chamber was placed. Proposed accident scenario agrees with the data of the plant parameters obtained just after the accident. It is estimated that the water injection by HPIC was stopped since around at 13/3 19:00 and the water level in RPV decreased since then. It is estimated that the RPV broke at 14/3 8:55 and water could injected from fire engines due to the depression due to the rupture of RPV. There was little water left in RPV at the time of the rupture. If the present scenario is correct, the behavior that operators in the plant stopped HPCI at 13/3 2:42 did not affect seriously on the RPV rupture. If HPCI was working properly until the operators stopped it, the plant parameters obtained in the accident cannot be explained.
This paper validates the accuracy of the dynamic heat-exchanger model that deals with any combination of phase states like water and steam inside heat-exchanger tubes. A unique feature of the model is to constrain the mass flow of water and/or steam calculated by momentum balance to satisfy thermodynamic relationships by means of reducing the difference between the density based on a thermodynamic relationship and the density determined on the basis of the deviation of the inlet and outlet mass flows. In this paper, the simulation results are compared with actual operating data in static and transient states of a once-through evaporator in which the water inside tubes is heated to evaporate by high-temperature gas outside tubes. The static simulation results show that the temperatures of the water and/or steam and the gas are predicted with an accuracy of 5% for temperatures, mass flows, and pressures. The simulation successfully reached the balanced equilibrium of the heat flow between the water and/or steam and the gas without numerical oscillations. The transient simulation results show that the proposed model reduced the mean deviation to actual operating data by 77% compared with the conventional model for selected times where the mass flow changed from increase to decrease and vice versa. In short, the proposed model improves the accuracy in dynamic response of mass flow.
From the viewpoint of safety design of nuclear reactor and economic terms, for PWR, it is important to clear the mechanism of DNB and predict accurately the critical heat flux under vertical subcooled flow boiling condition. So, in this research, a prediction model of the CHF under vertical subcooled flow boiling condition was developed. The model is based on the vapor blanket mechanism and the homogeneous nucleation mechanism. Additionally, the model accounts for a new phenomenon called in this research as overheating phenomenon of the heated surface. The method was evaluated by comparing the prediction results with experimental data for a vertical circular tube under high pressure, subcooled flow boiling and non-uniform axial heat flux condition. It was found from the evaluation results that the method developed in this research was able to predict accurately both of the CHF and the CHF location.
For passive vibration isolation systems, a friction damper has an advantage that large damping is achieved using a simple mechanism and it is easy to maintain. However, the ordinary friction damper of constant frictional force has performance limitations, because the isolation characteristic declines when the friction force is large, while resonant peak becomes large when the friction force is small. Furthermore, the displacement remains apart from the equilibrium position after the disturbance has disappeared. It is known that these problems are avoided when the friction force varies depending on the relative displacement. Recently, authors proposed a damper where the friction force varies in proportion to the relative displacement by combining a cylindrical block and a tilt lever supported with a pivot. In this paper, we propose much more simple mechanism that consists of a cylindrical block and a tilt lever supported with a leaf spring instead of a pivot. When the cylindrical block moves and pushes the tilt lever, the normal and friction forces at the contact surface vary according to the displacement of the cylindrical block. The expected characteristic is verified by the numerical simulation and the experimental results. The numerical simulation also investigates the effects of the geometrical parameters as the design guideline.
Magneto-Rheological (MR) grease has been applied to a controllable clutch system, and its performance was investigated experimentally. MR fluid is known as a functional fluid whose yield shear stress can be controlled reversibly by the applied magnetic field strength. But its peculiar characteristics may change as time passes because of sedimentation of dispersed iron particles. To overcome this defect, grease has been adopted as a carrier fluid of particles. Three-dimensional structure of thickener developed in grease is expected to prevent iron particles from settling out. In this paper, a controllable clutch system was designed and constructed to investigate the performance of MR grease clutch system. It was shown experimentally that the transmitted torque could be controlled quite smoothly by the applied electric current to the coil equipped inside of clutch system, and the response time was estimated about 0.12 s at the fastest. However, the transmit torque decreases as time passes because of the effect of temperature rise. To stabilize the output torque, the electric current to coil was controlled by a simple feedback control system.
This paper describes a spectroscopic sensor for measuring a wavelength of the light from objects in two-dimensional omnidirectional area. I developed the spectroscopic sensor, in which vertical slits, a horizontal slit, a cylindrical reflective grating, a projection cylinder, a hyperboloid mirror and a camera. The light from the objects enters the spectroscopic sensor though the vertical slits and the horizontal slit from the omnidirectional area in the two-dimensional plane. The entered light is dispersed by the cylindrical reflective grating in the sensor. The dispersed light is projected on the projection cylinder. The camera takes the dispered light image projected on the projection cylinder though the hyperboloid mirror. The wavelength of the light is estimated by positions of the dispersed light projected the projection cylinder on an image sensor of the camera. I made up a hardware of the sensor. I took actual light experimentally by using the developed sensor. I checked measuring accuracy of the sensor to evaluate the performance of the sensor. The results have shown the usefulness in the developed sensor for measuring the wavelength of the light from the omnidirectional area in the two-dimensional plane.
When the recording density of an optical disc increases, allowable tilt angle between the optical disc and the objective lens decreases. An objective lens actuator for an optical disc drive which is a kind of information processing equipments is needed to have little tilting action when it moves the objective lens in the focusing and tracking directions. We developed a new objective lens actuator with two configurations to reduce the rolling moment generated in the focusing coils and in the tracking coils of the actuator. One configuration is an arrangement in which the tracking coils and magnets at one side of the actuator are arranged reverse to those at the other side. In this configuration, magnetic flux density affecting the tracking coils at one side of a holder holding the objective lens increases at one side of the tracking coils, and magnetic flux density affecting the tracking coils at the other side of the holder increases at the other side of the tracking coils. The other configuration has an inner magnet placed inside the focusing coil. In the second configuration, the inner magnets produce magnetic flux density in the tracking direction affecting the focusing coils in addition to magnetic flux density by the magnets. This actuator cancels the deviation of magnetic flux density when it moves the objective lens in the focusing and tracking directions, and therefore the rolling moment is reduced. Experimental results show that the tilt angles of the developed actuator applying electric current to the tracking coils and to the focusing coils are reduced to 20% and 10%, respectively, of the values for a conventional actuator.
Backlash occurs in gear drive systems that are used with machine tools and transport mechanisms. The problem with backlash is that it reduces positioning accuracy and tends to cause vibrations. In this paper, a twin-motor drive method that compensates for backlash by master-slave control is adopted. In full-closed loop control of master motor, the position is controlled by using a linear scale mounted externally which detects the machine position directly and feeds it back, whereas in semi-closed loop control of slave motor, the position is determined by using a rotary encoder mounted inside the motor which detects the motor position directly and feeds it back. An integral control factor on the master motor is required to minimized positioning errors when using a combination of semi-closed loop control (slave motor) and full-closed loop control (master motor), and a P ( proportional ) control system without I ( integral ) control factor neither on position nor velocity control is adopted as the slave motor's semi-closed loop control system, allowing the slave motor for a follow-up control after the master motor and to compensate for and eliminate mechanical backlash. We confirmed the effectiveness of this control method by simulation and experiment. Slave motor locates itself and master motor into final position by automatically adjusting the gap between itself and the master motor. At final positioning, the phase between main motor and slave motor is automatically controlled to compensate for the backlash upon positioning. It is shown that this method improves the positioning accuracy of the system.
Double Series magnetic suspension is applied to force measurement. In a double series magnetic suspension system, two floators are suspended with a single electromagnet. The attractive force of the electromagnet directly acts on the first (upper) floator in which a permanent magnet is installed. The motion of the second (lower) floator is controlled indirectly through the attractive force of the permanent magnet. When PID control is applied to the second floator, the first floator displaces proportionally to external force acting on the second floator. Therefore, the force can be estimated for the displacement of the first floator. When the parameters are set appropriately, even small force leads to large displacement so that the proposed measurement method is suitable for noncontact measurement of micro force. An apparatus was fabricated for experimental study on the proposed measurement method. Its effectiveness was demonstrated experimentally.
This paper describes a camera system with a small fast dimming mechanism and a camera. A developed camera system has two features. The small dimming mechanism is fast and sequential dimming using two polarizing filters. One polarizing filter is fixed, and another polarizing filter is rotating fast. The camera system automatically determines blown out highlights in token images by the camera. The camera system sequentially outputs a light image without the blown out highlights. Entered light to the camera system is not polarized light but natural light. The developed camera system has some characteristics below. The camera system can control frame rate to take a moving object without relation to dimming capability. The camera system can control an iris to take a deep or shallow image with depth of field without relation to dimming capability. The camera system can control dimming step with the frame rate. I checked performance of the camera system to take some object images with the blown out highlights, and output image by the camera system using the developed camera system.
In this paper, in order to improve the low frequency noise insulation performance of a noise barrier, a new type of hybrid active noise control (ANC) system is proposed. The proposed system is a combination of feedforward and feedback controller. The reference signal for the feedforward controller is generated in the feedback part, so the reference microphone is not necessary. The feedback controller is used for controlling the acoustic boundary to insulate the diffraction noise, and the feedforward controller is used for reducing the noise at the error microphone which is set to be near the ears of people. As a preliminary work, this paper validated the effectiveness of the proposed ANC system both by simulations and by an experiment. The result shows that the active noise insulation provided by feedback controller and the noise attenuation provided by feedforward controller accumulated in the control area, so that the proposed ANC system has better control performance than individual feedforward or feedback ANC system.
A pressure wave generated by a compressor propagates in an air-conditioner piping system and causes a noise problem. The flow condition in the air-conditioner piping system becomes often a one-component two-phase flow, and attenuation of the pressure wave in the one-component two-phase flow is larger than the two-component two-phase flow because of the effect of the mass transfer. It is also important for the safety of nuclear reactors to understand the characteristic of pressure wave problems in the one-component two-phase flow. In this paper, we propose a concentrated mass model to analyze the pressure wave problems in the one-component two-phase flow. This model consists of masses, connecting springs, connecting dampers, and nonlinear base support dampers. The connecting spring and the connecting damper are derived from the compressibility of the gas phase and the effect of the mass transfer when the phase-change occurs. And the nonlinear base support damper is derived from the pipe friction. Additionally, an experiment on an air-conditioner piping system is performed, and the experimental results are compared with the numerical result in order to confirm the validity of the model. The numerical computational results agree very well with the experimental results. Especially, the attenuation of the pressure wave generated by the phase-change is numerically reproduced. Therefore, it is concluded that the proposed model is valid for the numerical analysis of the pressure wave problem in the two-phase flow.
Recently, evaluation of muscular fatigue and the fatigue recovery level is needed in the fields of medical treatment, welfare and work place, etc. In order to prevent bodily damage resulting from working and improve the efficiency of rehabilitation for occupational injured people, an accurate and simple method of evaluation of muscular fatigue is preferred. There is also a need for assessing the effectiveness of physical training treatment for physically handicapped people by analysing the data of muscular fatigue. Besides the personal needs of individuals, many companies in labor-intensive industry find it is essential to apply the assessment of muscular fatigue for manual workers during production to prevent economic loss and the reduction of labour force occurred by occupational diseases. However, there are no method nor apparatus which measure the muscular fatigue precisely and easily so far. The most commonly used method for the assessment of muscular fatigue is detecting the frequency transition of electromyogram (EMG), but it has certain drawbacks of being complicated and less efficient. Moreover, the fatigue may not be detected in isotonic contraction using the current method. In this study, a new method of measuring the muscular fatigue is investigated. We propose to apply near-infrared spectroscopy (NIRS) to measure the amount of oxygenated hemoglobin and deoxygenated hemoglobin and define the result data as a new index, ΔHbt, for evaluating the muscle fatigue. The validity of measuring ΔHbt to assess the muscular fatigue is shown by comparing the experimental results of using EMG and NIRS evaluations.
Thin steel panels are widely used for body structure of automotive. They are usually treated with damping sheet and covered with multi-layered sound-proof structure to secure quietness inside passenger compartment. Vibration and noise level induced by external excitation should be predicted to design configuration of damping sheet and multi-layered sound-proof structure. This paper proposes an approximate analytical method that gives a dynamic response for a clamped flat panel covered with multi-layered sound-proof structure and coupled with rectangular parallelepiped acoustic cavity. Equivalent properties of bending stiffness and mass density are applied for a panel treated with unconstrained damping sheet. Transfer matrix formulation is utilized for multi-layered sound-proof structure by assuming that the longitudinal wave propagation is dominant. For transfer matrix in a sound-absorbing layer, analytical solutions for Helmholtz equations of Biot's model are used. Flat panel and acoustic cavity are represented by using modal expansion and coupled equations are solved combined with transfer matrix of multi-layered sound-proof structure. Numerical studies are performed for several multi-layered sound-proof structures by using 2 sound-absorbing materials and 1 sound-insulation material. The results by the proposed method are verified by comparing with numerical solutions by a finite element analysis and are proved to give an valid solution with a much shorter time by a factor of 30.
For the past several years, large scale earthquakes happened. A lot of industrial facilities were damaged. For example, a lot of power plants were stopped in The 2011 off the Pacific coast of Tohoku Earthquake or The Southern Hyogo prefecture earthquake in 1995. These earthquakes have larger acceleration level than the seismic design level. Therefore, the earthquake proof measures are required. In this study, earthquake proof effect of the beam and the long column having initial twist is focused. The design guidelines for application to the pre-twisted beam structure and the long column structure is proposed. The pre-twisted beam and long column are modelled by FEM and calculated. The natural frequency of the pre-twisted beam and long column are related to the Young's modulus, density, length and cross-sectional area. The tendency of the natural frequency respected to the total twisted angle and the aspect ratio of the cross-section is obtained considering the vibration mode and the natural frequency. Furthermore, when attention is focused on the vibration mode, the influence of the total twisted angle is different for the modal shapes, and the case where the modal shapes are interchanged is shown. The acceleration response to the vibration input is determined by the natural frequency of the primary cross-section, the aspect ratio and boundary conditions. In order to evaluate the response reduction effect, the acceleration amplification respected to the total twisted angle and the 1st natural frequency of the system is analyzed. And the response reduction map is proposed. Using this map, it is possible to estimate the advantage of the pre-twisted effect for the vibration characteristics in a simple manner.
The purpose of this paper is to present a new folding method of spherical membrane by using origami technique. Because a creation of folding method for closed structures such as spherical shell has been one of the most difficult tasks within the works of origami, it has been left up to the present. In order to design these structures, firstly, a folding method of a circular membrane both in radial and circumferential direction is newly developed. By gluing two circular membranes at their peripheries, fundamental foldable model for designing 3-D structure is manufactured. A new design method of foldable spherical membranes with efficient foldablity was devised by using this concept,
Mars airplane is one of the candidate payloads of JAXA's next Mars exploration program. Airborne observation of Mars is expected to fill the “gap” between rovers, which provides a detailed observation but a limited area of coverage, and orbiters, which can cover a wide range of area but with a limited resolution. Two key challenges to realize a Mars airplane are 1) unavailability of GPS for localization and 2) limited computing power due to tight restriction on the mass of on-board instrument. We address these issues by developing a computationally tractable vision-based navigation and guidance algorithm. Our approach is based on an efficient feature detector and descriptor, Oriented FAST and Rotated BRIEF (ORB), combined with the information from an inertial measurement unit (IMU) using the extended Kalman filter (EKF) method. In this paper, we demonstrate the proposed ORB/EKF-based localization method by simulations using image data from Mars Reconnaissance Orbiter, and obtain the result which is 4.4 times faster than a general method.
This paper describes how to reduce degrees of freedom for the absolute nodal coordinate formulation (ANCF) of three-dimensional beam made up of 24 degrees of freedom beam elements by applying the component mode synthesis. The stiffness matrix of the ANCF Bernoulli-Euler beam is introduced to the equation of motion of 24 dof ANCF beam element. Since the bending stiffness matrix of the ANCF Bernoulli-Euler beam is constant, the Craig-Bampton method is applicable to the equation of motion to reduce degrees of freedom of beam structure which is composed of 24 dof ANCF elements. To examine the effectiveness and the efficiency of the presented method, three numerical examples were performed with comparing the results obtained by the conventional ANCF beam elements. In examples of the pure torsional deformation and the free-fall behavior under the gravity field, the presented method was verified to be capable of expressing the torsional deformation and large deformation precisely as well as the conventional ANCF, in spite of the dof of the presented method being reduced to be the half of the conventional ANCF. In the example of the cantilevered beam subjected by the screw driving constraint under the gravity, the presented method was also verified to express the large bending and torsion coupled deformation well.
To quantitatively predict leakage rates through gasket/flange interface, it is important to observe contact conditions at seal surfaces because the leakage path consists of the non-contact portions between the flange and gasket surfaces. The contact surfaces of the flanges were finished by lathe turning. In this study, we observed real contact area on gasket surfaces using a laser microscope with a wide field of view. The observations indicated that the leakage paths on the gasket surfaces were in the radial direction perpendicular to a lathe-turned groove and the circumferential direction along the groove. As the closing loads increased, the leakage paths in the radial direction disappeared and only the leakage path in the circumferential direction remained. The critical contact pressure where the leakage paths in the radial direction disappear was determined from the observation of the contact surface of the gasket. Over the critical contact pressure, the leakage rates obtained from the experiments showed good agreement with the calculated values under the assumption of laminar flow along the turned groove. Under the critical contact pressure, the recalculated values considered the leakage paths in both the radial and circumferential directions approached the experimental values.
As a material of bearing alloy for layer-structured journal bearings, soft metals such as white metal are commonly used. If a pressure of fluid on a bearing surface becomes high due to severe service condition, a layer of bearing alloy may suffer macro-scale plastic deformations, because its yield stress is relatively low than back metal and housing. Because a behavior of a shafting is strongly affected by the shape of bearing surface, discussions about a development of plastic deformation will provide interesting information for design and maintenance of bearings. In this paper, static analyses of journal bearings are performed including a consideration of plastic deformation. As a simulation model, a bearing structure is divided into two layers. The first layer means bearing alloy, which is expressed by one-dimensional stress strain characteristic. And the second layer means combined structure of back metal and housing. From the results of calculation, the ratio of stiffness between the two layers becomes useful indicator to predict a behavior of bearing surface. And effects of residual plastic strain become significant in case the stiffness of second layer is high.
The influence of the complicated behavior of the components of a planetary gearset (i.e., sun gear, carrier and ring gear) on transmission error is still unexplained. Accordingly, to elucidate that influence, the transmission error and misalignment of each component of one planetary gearset were experimentally measured at a time under a condition in which the fixed carrier position was varied. The measurement result shows that, under that condition, the state of misalignment fluctuates and the transmission error changes according to that fluctuation. Although the fluctuation of misalignment (in the form of eccentricity or inclination) is generally in a circular orbit, in this experiment, it was found to be in a near-elliptical orbit. By taking such misalignment fluctuation into account when calculating transmission error of the planetary gearset, it was found that the calculated behavior of transmission error replicates the above-described experimental measurements approximately.
We investigate estimation methods of aerodynamic coefficients for a ball in sports by using characteristic quantities of its trajectory. One method is based on the quantities representing the whole shape of trajectory while the other utilizes local quantities such as curvature and/or torsion. In the former, the flight distance and the maximum height are measured, and the motion equation predicts numerical values of these quantities with measured initial conditions and preset aerodynamic coefficients. Then the optimal combination of the aerodynamic coefficients is determined by minimizing the error between the measured and estimated values of the characteristic quantities. This method is applied to estimate drag and lift coefficients of a soccer ball in back-spinning, and the result shows that the averaged values of CD and CL are 0.205 and 0.237, respectively. In the latter method, the expressions between the aerodynamic coefficients and the geometrical quantities of trajectory are derived, which suggests that the piecewise quadratic interpolation on a trajectory provides the aerodynamic coefficients. This method enables to locally estimate the coefficients, and therefore clarifies the variation of the coefficients along a trajectory. Measured data for a table tennis ball is analyzed with the method and we obtain successfully the drag and lift coefficients in flight condition. The results indicate the qualitative difference of spinning effect in drag and lift coefficients.
The most serious head injury resulting from shaken baby syndrome (infant brain injuries resulting from violent shaking attributed to child abuse) is acute subdural hematoma (ASDH). ASDH in infants has a high mortality rate and results in serious permanent injury. However, medical practitioners rely on experience and intuition to determine the cause of infant head injuries because it is difficult to gather accurate evidence from third parties. Therefore, in this study, we have conducted vibration experiment and simulation analysis reproducing the shaking action to provide a scientific basis for the determination of shaken baby syndrome. The finite element model of a six-month-old-infant head is constructed from adult head models and CT scan images of an infant head. The input value is defined as head angle and head displacement obtained from the vibration experiments using a six-month-old-infant dummy. ASDH is caused by the relative rotational motion between the skull and the brain with a rupture of the bridging veins that connect the skull and brain. Accordingly, we have evaluated the relative movement between the skull and brain and measured the stretch ratio of the bridging veins. Then compared this ratio with the threshold, which is the rupture value. As a result, the violent shaking action regarded as shaken baby syndrome abuse ruptures the bridging veins and causes ASHD. As the brain movement follows the skull, the bridging veins are stretched greatly depending on the forced skull movement and the brain's inertia. And the risk of ASDH to occur is high enough to vibrate the infant longer because the stretch ratio increases as time passes in the simulation.
In previous report, the interlock system of a pneumatic driving system have been studied and proposed based on the principle of safety. In this paper, we propose again that the interlock system is recognized high on the level of integrity as the safety-related parts of the international standard ISO13849. An accident may happen when failure of safety device may occur on the accidentally happened dangerous condition. It is a claim in this paper that in the safety system, failure of safety device shall not be simply in the safe side, it is necessary to stop the system by shutting off the power supply. The interlock system satisfies the function on the condition of fail-safe and it is recognized high level of the evaluation from the point of view of risk-based international standards (ISO12100, ISO13849). And it is further expected an ideal safety-related systems which may not give any harmful effects and that this system is also expected to be recognized as the top-level category of qualification. Conclusion of this paper is that there are no contradiction between differently based validation according to the international standards and the principle of safety.
The maximum deceleration or average deceleration during the collision is used to assess occupant safety in regards to the crashworthiness design of railway vehicles. However, the deceleration history experienced by the passengers during the collision is not always the same as the deceleration history of car body because the passengers are not restrained by seatbelts. Secondary impact of passenger to a partition panel at end saloon in different deceleration histories was investigated by calculations using a numerical simulation model of the Hybrid Ⅲ 50 percentile dummy that is built into the LS-DYNA computer program. In order to validate the calculation model, a sled test to simulate a secondary impact at the end saloon was conducted. It was found that there is correlation between the maximum of integration of deceleration history(MID) and secondary impact velocity(SIV) of the crash dummy and there are relations between SIV and injury parameters such as HIC15 and femur load specified in 49 CFR571. 208 Passenger Equipment Safety Standards. More specifically, the calculation results showed that the SIV of the head and the SIV of the knee are represented by the MID + 1m/s and the MID -1m/s respectively for conservative evaluation at the end saloon of express trains in Japan. In addition, calculation results showed that the upper limit of the SIV to partition panels for HIC15 and femur load within their criteria is 6m/s. As a consequence, it is thought when the MID is lower than 5m/s, HIC15 and femur load is lower than their criteria for conservative evaluation at the end saloon of express trains in Japan.
This paper describes two kinds of control method for parallel two-wheeled inverted pendulum. It is a method that is controlled by the torque input and is controlled by the velocity input. Generally, the equation of motion of this system is expressed by the torque input. From this equation of motion, equation of the velocity input was derived using back calculating equation of the torque input. Equation of the velocity input becomes hierarchical structure. To perform velocity input, we controlled the motor of second order system to first order system using discrete robust model matching control. In the both of control system, i.e, torque and input and velocity input, optimal regulator is employed. Robust stability was confirmed using sensitivity function. We compared performance of torque and velocity input with simulation and experiment using actual test vehicle.
Primary study on identifying deviations in the alignment of ground coils (ground coil irregularities) for magnetically levitated systems is conducted. The ultimate goal of this study is to introduce an active suspension system with preview in the future. First, the amount of irregular forces caused by twenty four types of ground coil irregularities is calculated respectively. The calculation results clarify that the irregular forces are complexly caused by various combinations of ground coil irregularities, and this shows that identifying ground coil irregularities by vibrations of the moving vehicles is appropriate toward the preview vibration control. Next, this paper refines an identifying method, which is originally developed for conventional wheel-on-rail systems, utilizing car body acceleration and Karman filter. To exclude a harmful influence originated by the spatial filter effects of onboard magnets, application of an impulse response of a particle model, instead of a rigid body model, and correction using the second order system compensational filter are proposed. Numerical simulation results show that the proposed method enhances the identification accuracy and widens the band of frequencies in which the irregularities can be identified. Finally, fundamental experiments are conducted in the test stand which can simulate vibrations of the moving vehicles in a range of frequencies sensitive to ride quality. The ground coil irregularities in the intended band of frequencies are experimentally identified with satisfactory accuracy by the proposed method, and the experiment technically enhanced the prospect of identifying the ground coil irregularities by car body acceleration.