In order to incorporate the mean stress effect in the design fatigue curve for designing nuclear power plant components, change in fatigue strength due to the mean stress and root causes of the change were investigated for Type 316 stainless steel. First, 20% cold work was applied to specimens of Type 316 stainless steel in order to reduce the cyclic strain hardening and softening during fatigue tests, and then, the specimens were subjected to stress controlled fatigue tests under the mean stress in air at room temperature. Although the mean stress tended to show a beneficial effect on the fatigue life under the same stress amplitude, it had a detrimental effect under the same strain range. It was shown that the reduction in fatigue life was brought about by the change in the effective strain, which was caused not only by the rise in the crack opening point but also by ratcheting deformation during the fatigue tests. The mean stress had little influence on the fatigue limit for the strain range. It was concluded that, although the mean stress reduced the fatigue life in the stress controlled fatigue tests, its effect did not need to be considered in the design fatigue curve because no significant change in the effective strain range occur in actual components.
Disc brake is one of the most important auto mobile components and the toughest frictional components. Nowadays, the lightweight disc brake is needed for better fuel-efficient. To reduce the weight, high frictional and low aggressive brake pad is required. However, generally high friction cannot provide low wear of counter-part, therefore to make such brake pad is difficult. In addition, including many kinds of materials such as abrasive, binder, filler and so on, we cannot design it theoretically. In order to overcome these issues we focused on abrasive shape in brake pad, especially focused on open angle of abrasive φ and the important index “degree of wear fab”. If degree of wear fab decreases with open angle φ of abrasive and reduction of wear is more than reduction of friction, we can propose the high frictional and low aggressive brake pad which includes small open angle abrasive. In order to validate our proposals, we conducted the scratch test using Vickers indenter and Knoop indenter. As a result of the scratch test, we clarified that the ratio of wear coefficient to friction coefficient K / μ is correlated with degree of wear fab, and in the region of ploughing and wedge, degree of wear fab decreased with decreasing open angle φ. Due to these phenomena, the ratio of wear coefficient to friction coefficient K / μ decreased with decreasing open angle φ in the region of ploughing and wedge. Thus it was valid that small open angle abrasive provides high friction and low aggressiveness.
In this paper, we present a shape identification method of free-form shells for controlling the static deformation mode to the desired one. It is assumed that the shell is varied in the out-of-plane direction to the surface and the thickness is constant. As an objective functional, a squared displacements error norm on the prescribed surface or at the loading points is utilized. A parameter-free shape optimization problem is formulated, and the shape sensitivity, called shape gradient function, is theoretically derived using the Lagrange multiplier method and the formula of the material derivative. The optimal shape is determined by the free-form shape optimization for shells, in which the derived each shape gradient function on the design surface is applied as the fictitious traction force to change the form. Several calculated examples show the effectiveness of the proposed method for the shape identification of free-form design of shell structures with a desired static deformation mode or required sriffness.
A pressure-sensitive dot array sensor has been developed by means of an inkjet printing device on an anodized aluminum (AA) substrate. Pressure-Sensitive Paint formed on AA substrate (AA-PSP) has been used for unsteady pressure measurements due to its high-speed responsiveness. A bi-luminophore AA-PSP is demanded for precise pressure measurements, because PSP needs the temperature correction. However, a conventional bi-luminophore AA-PSP prepared by a dipping method does not work well due to the interference between the two luminophores. To overcome this problem, we have been developing the isolated dot arrays of PSP and TSP formed on an anodized aluminum substrate by an inkjet printing method. As the first step of realizing the combined AA-PSP・TSP, we fabricated a pressure-sensitive dot array sensor on an anodized aluminum substrate using Ru(dpp)3 as a pressure-sensitive luminophore. Ru(dpp)3 was dissolved in four different solvents: methanol, dichloromethane, chloroform and the mixed solvent of dichloromethane and chloroform, and the effect of the solvents on PSP dots was investigated. The formed PSP dots exhibited significantly different properties, such as the luminescence intensity distribution and pressure sensitivity, depending on the solvents. The PSP solution with methanol resulted in the O-shaped stain of luminophore due to the “coffee-ring effect”. The PSP solution with dichloromethane and that with the mixed solvent of dichloromethane and chloroform formed dots with uniform luminescence intensity distribution. In addition, the PSP with dichloromethane or dichloromethane + chloroform had comparable pressure sensitivity with conventional AA-PSP prepared by a dipping method, while the PSP with methanol showed very poor pressure sensitivity.
Vapor explosion is thought to occur under liquid-liquid contact condition. In addition, it is reported that a mass of grains and water also cause the transient boiling phenomena. However, it is not clearly defined that the phenomena with the grains are vapor explosion. Thus we focused on the transient boiling phenomena with clod of grains. The objective of the present study is to clarify the behavior and specific quality of transient boiling phenomena with the clod. We heat the clod which consist of grains less than 100 μm and inject it into the tank filled with water. The boiling behavior and pressure data were obtained by a high speed camera and a pressure transducer. From experimental results, it is confirmed that the vapor explosion similar to the liquid-liquid condition occurred by the clod. In addition, it is clarified that the vapor film holding time increased as the water temperature increased. Furthermore, it is also clarified that the occurrence condition of vapor explosion can be estimated by TIZ (Thermal Interaction Zone) which is used to define the occurrence condition of vapor explosion in liquid-liquid condition. In contrast, we found that the occurrence of vapor explosion with the clods is influenced by the hardness of the clods which is the characteristics of the clod of grains. From these results, it is also clarified that the process of disengagement of the grains is the trigger mechanism of vapor explosion with the clod. These results indicate that the vapor explosion with solid-liquid contact condition which is not assumed in the previous work can occur.
The paper examines the effects of research and development (R&D) on the capital cost reductions and the introduction of renewable energy technologies, namely solar photovoltaics (PV) and wind technologies. The proposed model in the study deals with the dynamics of technological learning. Functional form is a new kind of three-factor learning curve as a function of the cumulative capacity and the knowledge stock accumulated by public and private R&D expenditures. An econometric analysis is used to identify the influence of the knowledge stock on the capital costs of renewable energy technologies. Moreover, the study clarifies the relationship between the cost reductions and the market penetration. If the expenditures for public and private R&D in 2010 are fixed until 2050, then the model predicts that the capital costs of solar PV systems in 2050 become $1,750 /kW. Sensitivities of the annual R&D growth rate for the technologies are tested. The model also provides important results that the increase by four times of R&D budgets is necessary in order to reach the cost reduction targets by the Japanese government. The proposed methodology herein is helpful for decision makers to forecast how the costs of renewable energy technologies will change, and thereby providing the basis for R&D planning.
Heat density of high-load electronics such as high-performance servers and the inverters used in vehicles has been increasing as the result of higher processing speeds and computational scale, and higher output, etc. We therefore investigated an air-jet cooling structure that uses a plate-fin heat sink with the objective of developing an air-cooling structure that can provide efficient, uniform cooling for high-density mounting configurations in high-load electronics. The plate-fin heat sink mounted on a semiconductor package was cooled by an air jet injected from a rectangular nozzle mounted on top of the heat sink. The heat sink shapes and nozzle width, as well as the blower power, were changed to investigate the effect on heat transfer. This allowed the optimal parameters to be found for the nozzle width, the fin spacing, and the fin height of the heat sink, thereby resulting in a maximum heat transfer coefficient. Also, the flow pattern in the heat sink was visualized qualitatively. The results show the heat transfer coefficient of the air jet cooling is larger than that of parallel flow cooling under constant blower power consumption. And it takes maximum values with H/Wf= 0.35-0.4, which is unique phenomenon to an air jet cooling and is not seen in parallel flow cooling.
This paper presents the temperature and velocity measurements to clarify effects of inclination angle of a heated plate φ on natural-convection heat transfer enhancement by millimeter bubbles. In the range 0≤φ≤30˚, the heat transfer coefficient with bubble injection is much higher than that without injection, and the ratio of the heat transfer coefficient with bubble injection to that without injection (heat transfer coefficient ratio) ranges from 3.0 to 5.0. This is due to enhancement of both the transport of the warm liquid toward the downstream region and the mixing of warm liquid and cool liquid. The former results from the bubble-induced liquid entrainment, and the latter is mainly due to the increase in the liquid velocity fluctuation induced by a combination of the bubble motion and the vortex shedding from the bubble interface. Moreover, the significant bubble-induced liquid entrainment and the unsteady vortex occur near the heated wall at higher inclination angle of the heated plate. Hence, the heat transfer coefficient ratio increases with increasing inclination angle of the heated plate.
Despite intensive investigations on bubble dynamics, many unknown items are remained concerning bubble coalescence. The objective of the study is to investigate experimentally the characteristics of formation, temporal change in thickness distribution and rupture phenomena of liquid film formed between twin approaching bubbles by the liquid thickness measurement for water applying the improved laser extinction method. The coalescence of horizontally contacting twin bubbles was experimentally studied in constant temperature air–water system. The variation and the distribution of liquid film thickness between twin bubbles were investigated. The experimental parameters were the air flow rate and the measuring position of liquid film thickness. The bubble approach velocity and the close contact duration of bubbles were measured by analyzing the images taken simultaneously with the film thickness measurement. Deformations of bubbles were intensified with increasing bubble approach velocity, and bouncing occurs with an increase in the area of liquid film formation between bubbles. There were two types of liquid film thickness distribution just before coalescence. When bubble coalescence occurs rapidly, the liquid film thickness at near center was thinnest and was increased with distance from center and the thinnest thickness appeared just before coalescence was approximately 1.0 μm. When bouncing occurs, the ring-shaped thinner area in liquid film emerged and shifted from center to the outside of liquid film with increasing approach velocity and close contact duration. The liquid film thickness at commencement of rupture in the ring-wise area with thinner film thickness was approximately 0.3 μm.
This study aims to investigate the horizontally oriented internal two-phase flow induced force fluctuations. Gas-liquid two-phase flow experiments were conducted on 90 degree pipe bend, oriented horizontal-downwardly. Multiple tri-axial force transducers were utilized to measure the dynamic force signals, and related two-phase flow parameters such as volumetric fluxes, void fraction and local pressure fluctuations were measured at various horizontal two-phase flow regimes. Unlike upward two-phase flow, horizontal-downward elbow orientation significantly altered the two-phase flow structure. Spectrum analysis was conducted to investigate the linkage between two-phase flow characteristics and force fluctuation. Results show that the predominant frequency of the fluid force peaks in the slug flow regime at a constant liquid flow rate, similar to the upward two-phase flow condition. Based on the database developed in the current experiment, previously developed force fluctuation model was utilized to assess its performance, and it was found that the model is capable of predicting these parameters with satisfactory accuracy.
This paper presents the control method for the continuous operation of air type anti-vibration apparatus under earthquake ground motion. Air type anti-vibration apparatus is essential for semiconductor exposure machine. When earthquake ground motion strikes, the process of the stopping semiconductor exposure machine is often executed. It leads to low production throughput of semiconductor devices. In previous study, we show that there is a tradeoff between the acceleration of the table and the relative displacement. By switching control based on this tradeoff, the vibration of the acceleration of the table or the relative displacement can be suppressed under earthquake ground motion. However, this method cannot suppress immediately the acceleration of the table or the relative displacement when earthquake ground motion strikes. This paper extends method of this switching control. Concretely, observation area as far from air type anti-vibration apparatus is created. This observation area analyzes the priority of earthquake ground motion. The logic for analyzing the priority of earthquake ground motion explains. By utilizing the priority of earthquake ground motion, the faster switching control attempts. In this simulations, earthquake ground motion which occurred at past is used. Furthermore, we perform experiment with the switching control. This experiment shows that transient response does not occur when the control is switched under vibration.
In this research, a new concept named Dynamic Reconfiguration Manipulability (DRM) is proposed, which gauges dynamical shape-changeability by using a redundancy of the robot on the premise that a primary task be given at hand. The DRM represents simultaneously how much acceleration each intermediate link can be generated and what direction the acceleration be realizable by normalized torque inputs, helping optimize designing and controlling of robots. Appropriateness and usefulness of the DRM have been confirmed by applying it to redundant manipulators and by comparing the DRM with known concept of Avoidance Manipulability.
Road noise is one of the main sound sources exciting passenger car interior noise. This noise is excited by road roughness. Vibration and noise characteristics in road noise have strong interaction with tire vibration characteristics. Car manufactures are keenly interested in studies on the prediction of NVH (Noise, Vibration and Harshness) performance, including viewing tire as substructure. Tire vibration has complex behavior due to tire contact with the road and rolling. In this paper, we focus on the effect of contact between tire and road as against tire vibration. First, experimental modal analysis is performed to grasp the tire vibration on the non-contact and contact condition. As a result, it was clarified that natural frequency and mode shapes change on the contact condition. Second, we studied the factor of changing tire vibration characteristics between contact and non-contact using a tire model. A tire on the non-contact condition was expressed as a shell model. Based on the tire model, we performed vibration analysis using the reseptance method and definition of eigen function. From this study, it was found that prediction accuracy by receptance method depends on the number of approximate modes. The best method for determing the number of approximate modes is based on the experiment. Additionally, analysis method by definition of eigen function also is valid sufficiently.
Recent years, we receive the full benefit of vehicle by the rapid progress of motorization with the development of economy. By contrast, environmental problem occurs from vehicle noise. The noise in Engine and Intake-Exhaust system which is typical source of noise until now has been improved because noise regulation advanced. This situation makes the tire contribution rate to vehicle interior noise increasing relatively. And the reduction of tire noise is the serious problem that we have to work on. It is important to reconstruct the input into the body from road to spindle and suspension for accurate prediction. One of the problems is how to express the tire vibration characteristics in operational condition, which are complex. It is difficult to construct a tire model that expresses the vibration characteristics on the contact and rolling condition because of the rolling effect, contact patch restriction, the property of rubber. In this study, we set a goal of performing vibration analysis on the contact and rolling condition and clear up the vibration characteristic analytically. First, Introducing tire vibration model based on the cylindrical shell theory and applying the receptance method for tire model. Additionally, we derived the mode shape function and the frequency equation on the contact and rolling condition. Secondly, we calculated natural frequency and mode shape on the contact and rolling condition. After that, we clarified the tire vibration characteristics analytically in the difference condition such as rolling speed. From this study, it was found that natural frequency on the contact and rolling condition depends on adapting mode numbers. Additionally, mode shape on the contact is determined by the components of forward wave and backward wave of the non-contact and rolling condition.
A smart sensor is required if we are to popularize health monitoring using the vibration of a structure. It is used to evaluate the vibration characteristics of the structure. To detect the variance in the vibration characteristics from the vibration data of a structure, a time-frequency analysis technique that can detect the change of the frequency components of the vibration data over time is needed. In a previous report, we have proposed a real-time data processing method with arrayed narrowband band-pass filters based on a single degree of freedom vibration system for the evaluation of structural vibration characteristics. This method is applicable to processors with low computation loads and memory capacities. In this paper, the relation between the parameter setting and the accuracy of the evaluation result when the proposed method is applied to several vibrational environments is examined. Concretely, accuracy and the stability of the estimated result of the natural frequency of the structure were examined when a steady state noise is included to the response of the structure. Furthermore, a similar examination was conducted for the measurement data of the microtremor response of the pier model where the unsteady input is applied. Moreover, to obtain the criterion of the evaluation accuracy of the proposed method, the estimate was compared with AR model. As a result, it is clarified how each parameter of the proposed method was related to the estimation accuracy of the natural frequency. The proposal method showed that the influence on the noise was less than the AR model.
This paper proposes a method for automatic tracking of multiple humans in various scenes using a stereo camera. Surveillance cameras are increasing these days for security. Typically, images of a camera are stored and are surveyed after an incident occurred. It is required to use the cameras online, and real-time automatic human tracking is required. The proposed method detects candidate regions of humans using “Subtraction Stereo”, which restricts stereo matching to foreground regions extracted by subtraction and obtains distance information for the regions. Human tracking is carried out for the extracted regions by using Particle Filter. Particle Filter consists of four steps, i.e., prediction, calculation of likelihood, data association, and resampling. Three features: distance, color, and direction of motion are used in the Particle Filter of the proposed method to achieve robust human tracking. When humans with similar cloth colors pass each other, occlusion occurs and human tracking often fails with distance and color only. The proposed method achieves the robustness to the occlusion by explicitly considering the direction of human motion. The proposed method is evaluated through experiments using a stereo camera that simulates a surveillance camera in real scenes. Tracking accuracy of more than 90% is achieved in three different scenes, which shows the effectiveness of the proposed method for human tracking.
The reduction of noise and vibration in the development of new automobile bodies is challenged by the directly competing requirement of lightening the body. Numerical analysis techniques such as sensitivity analysis and structural optimization are widely used to meet these requirements, as they provide optimized material thickness distributions and other parameters. Still, there have been few examples where the material thickness distributions found in numerical calculations have actually been used in designs. It is important to gain a better understanding of the material thickness distribution's effect on variations in both the stiffness and mass and the noise and vibration in order to design structures that can actually be manufactured. Currently, there is no precise understanding of the mechanisms through which material thickness affects the variations in the stiffness and mass or noise and vibration. The current results from sensitivity analysis and structural optimization cannot be considered to provide enough information to be of use in design. In this paper, mutual mean compliance was applied to a vibro-acoustic system in an attempt to gain a quantitative understanding of the variations in stiffness and mass of component structures and of the variations in noise and vibration. This paper presents a formulation for mutual mean compliance and addresses in turn the structure system, the acoustic system, and the contribution of coupling between the two. In addition, the mutual mean compliance is separated into the contributions of the component structures, and it is shown that the contributions of the stiffness mass values to the responses of interest can be identified. Mutual mean compliance is applied to a simple automobile body model and countermeasures against noise and vibration are verified to be effective.
The topology optimization method using the level set method and incorporating a fictitious interface energy derived from the phase field method was proposed by part of the authors. The method has been applied to several structural and multidisciplinary design problems. However, the method has not been applied to the plate bending structural design problem using the two-dimensional plate bending element model yet, regardless that the thin plate structures are widely used in engineering applications that require lightweightness. This paper extends the topology optimization method to the thin plate structure for maximizing stiffness under out-of-plane deformation by using the thin plate bending elements based on Reissner-Mindlin theory. The structural design problem using the thin plate bending elements is formulated as the mean compliance minimization under volume constraint problem. Through simple numerical examples, effects of the proposed method are illustrated. At first, the method significantly reduces computational cost for the thin plate maximizing stiffness design problem in comparison with the three-dimensional solid model. The obtained optimum configuration is shown to be equivalent to that of the three-dimensional solid model. Then, it is shown that the advantages of the method such as high convergence property, low initial design dependency, and the effect of the regularization parameters on the complexity of the configuration are also held in the plate bending element model.
Almost all geometric deviations that occur on a machine tool can be detected most precisely with the laser measurement system. However, the roll cannot be detected yet since the interferometer for it is not present. The purpose of the study is to propose a practical laser measurement method of the roll on a machine tool, and to confirm an efficiency of the method. The developed system consists of an interferometer and a V-shaped reflector. The interferometer is mainly composed of a corner cube prism, a polarized beam splitter, three quarter wave plates, and a bi-prism. In order to increase the amount of change of the laser path length with respect to the change of the roll, retroreflective prisms are attached to the rear side of the interferometer. The sensitivity and the dispersion of roll measurement data are improved by increasing number of the retroreflection. The developed system and a conventional roll measurement system which uses a long-sized plane mirror are mounted on a machining center, and measurements of the roll are pursued simultaneously. The data obtained by the developed system show the same tendency as method using the long-sized plane mirror. From the results, the availability of the developed system to detect the roll that occurs in a comparatively long travel, about 1m, is confirmed.
The congestion in an exhibition space might make us uncomfortable and cause an accident. In this paper, we design an amenity space with safety and comfort by optimizing the layout of exhibits. A human flow in an open-plan exhibition space is modeled by a vector field that is calculated by a coordinates transformation and projection of a virtual vector field. Based on the model, the layout of the exhibits is optimized. The simulation results show that the proposed method reduces the congestion, and the visitors view the exhibits in a short time with large satisfaction. The experimental results using swarm of mobile robots controlled autonomously or by human, shows the validity of the human model and the effectiveness of the proposed method.
We propose a method for the assessment of the optimum diameter of a pipe that is required for easy grasping, called the one point selecting method. A simple sensory evaluation method was investigated to verify the utility of this new method by comparing the new method with other paired comparison method. The one point selecting method initially utilizes the sense of sight, and then the sense of touch. The paired comparison methods used for the comparison were the paired comparison method of Nakaya and the cyclic method of Nagasawa. The subject of the sensory evaluation was the grasping of the cylindrical pipe. In the sensory evaluation, each cylindrical pipe had the same shape and texture, and the diameter intervals of 2mm, 5mm and 10mm were used. The optimum diameters obtained by the one point selecting method were close to the diameters determined by the paired comparison method and the subjective assessment method. The measurement time of the one point selecting method was shorter than that of the other methods. The number of times an assessment was carried out by one point selecting method was less than that of the other methods. The optimum diameter obtained by the one point method, validity and reproducibility was found. The experimental results of the sensory examination show that the one point selecting method can perform sensory evaluation with fewer subjects and with a diameter interval range of 2min to 10mm.