LE-9 rocket engine for H3 launch vehicle is being developed for realizing high performance, low cost and high reliability. Thermal fatigue life prediction on a combustion chamber structure with multiple cooling holes is important for design of rocket engine. In this paper, focusing on very low cycle conditions below 200 cycles, strain-controlled fatigue and creep-fatigue tests have been conducted at 558℃, using perforated copper-alloy plate specimens simulating cooling holes of combustion chamber for a rocket engine. Creep-fatigue life was defined based on 25% stress drop (N₂₅) from steady state, where about 2mm-length cracks were found. Strain measurement using digital image correlation method was performed during fatigue tests for confirming strain distribution in the test specimen. Strain distribution from inelastic FEM almost agreed with that from the measurement. Creep-fatigue life prediction was carried out for perforated plate specimen, combining inelastic FEM with both the linear damage rule based on creep rupture time fraction and the strain range partitioning method. Life prediction accuracy was discussed based on both the definition of creep-fatigue life depending on detectable crack length and the choice of stress-strain behavior. Under the very low cycle conditions, the predicted life using the averaged stress-strain behavior within a gage length of 2mm, i.e. detected crack length, was within a factor of 2 when compared with experimental life.

A loading sequence effect on fatigue life was investigated for piping under seismic loading. A fatigue assessment method which can consider the loading sequence effect conservatively was proposed using the effective strain range. Variable strains in the pipe wall were obtained by finite element analyses. A seismic loading was applied to a system of pipes in the analysis. Fatigue tests were conducted using strains obtained by the analysis. Damage factors at failure calculated by Miner’s rule were less than 1.0 and the minimum value was 0.43. It implies that Miner’s rule predicted non-conservative fatigue life. Crack growth tests were also conducted to examine the reduction of the fatigue life. It was shown that a single overload strain decreased crack opening strain and increased the effective strain range. The increment of the effective strain range accelerated the crack growth rate after the overload and reduced the fatigue life. The damage factor for the strain under seismic loading was recalculated using Miner’s rule and the strain ranges which added the maximum increment of the effective strain range. The recalculated damage factors were larger than 1.0 under most conditions. The proposed procedure is available to predict the fatigue life of piping under seismic loading.

In order to investigate the effects of external and internal hydrogen on fatigue crack growth (FCG) properties of austenitic stainless steels SUS304, SUS316 and SUS316L, two series of tests were conducted. As the external hydrogen series test, ΔK-increasing (ΔP-constant) and ΔK-constant (ΔP-decreasing) tests were conducted in 115 MPa hydrogen gas at room temperature and stress ratio, R, of 0.1 using non-charged specimens. As the internal hydrogen series test, ΔK-increasing (ΔP-constant), R-constant (ΔK-decreasing) and P_max-constant (ΔK-decreasing) tests were conducted in air at room temperature and R = 0.1～0.9 using hydrogen-charged specimens exposed to 68 MPa hydrogen gas at 300℃. Comparing the results of the austenitic steels with those of low alloy steel SCM435, carbon steel SM490 and aluminum alloy 5083-O, the effects of material type and hydrogen on FCG rate, da/dN, and fatigue crack growth threshold, ΔK_th, are discussed. FCG at R of 0.1 was accelerated by hydrogen in the intermediate ΔK regime. The relative FCG rates, (da/dN)_H/(da/dN)_air, in the external and internal hydrogenated conditions corresponded to each other. The upper limit of (da/dN)_H/(da/dN)_air was 10.6 for SUS304, 3.3 for SUS316 and 2.4 for SUS316L. On the other hand, the upper limit was 27.7 for SCM435 and 45.0 for SM490B. FCG was not accelerated by external hydrogen in 5083-O. ΔK_th values of non-charged and hydrogen-charged specimens obtained under various R ranging from 0.1 to 0.91 were almost the same in SUS304, SUS316L and SCM435. That is, ΔK_th was not affected by internal hydrogen. The fact was understood by considering that ΔK_th is the critical stress intensity factor range below which dislocations are not emitted from fatigue crack tip.

A direct numerical simulation (DNS) of a planar jet with a second-order chemical reaction is performed using four different Schmidt number (Sc = 1, 2, 4, 8). Reactant A is contained in the jet flow and reactant B is contained in the ambient flow. The chemical reaction ( A + B → P ) proceeds by molecular mixing of the two reactants in the jet. The results show that the higher Sc becomes, the finer the structure of the product concentration becomes. The region where the reaction occurs changes depending on the Sc. Mean concentration and mean production rate conditioned on the distance from the T/NT (Turbulent/Non-Turbulent) interface is calculeted. The change in the conditional mean concentration of the reactive species near the T/NT interface occurs within the order of Taylor’s microscale regardless of the difference in Sc. In the chemical reaction field, the slope of the concentration change at T/NT does not differ much depending on the Sc. When the Sc is high, the mean production rate decreases. This is because the molecular diffusion is weak and small-scale concentration fluctuation occurs at high Sc. It also found that the thickness of the reaction layer becomes thinner as the Sc increases and the thickness of the reaction layer is scaled on the Bachelor scale η_B.

Synthetic fuel derived from renewable energy is expected as a means of reducing CO₂ in internal combustion engines. OME (OxyMethylene Ether) can be handled like a diesel fuel because its specification of distillation is almost same with it. Therefore, it is expected to introduced in the market as alternative or additional fuel. In this report, fuel properties, engine performance, combustion characteristics and exhaust emission of OME and its diesel blended fuels were investigated.

The energy density was decreased with increasing of OME blending ratio because the energy density of OME is lower than that of diesel fuel. Since OME fuel has the effect of expanding rubber materials, an immersion test of rubber material was conducted with OME blending diesel fuel. As the result, exceeding permissible range was observed with beyond 10% OME blending. Engine power was decreased under same injection quantity condition with increasing OME blending ratio because of its lower energy density. In the test under the same torque condition, blending OME with diesel fuel resulted in deterioration of thermal efficiency and reduction of SOOT, HC, and CO emissions.

Various impact and vibration isolation devices have been widely used to protect anti-vibration devices. These devices are mainly composed of the spring, the damper, and the actuator. This paper proposes another new simpler method to insulate the impact disturbance by using center of percussion (COP). The experimental apparatus according to the principle of COP was prepared to investigate the effectiveness of the impact force isolation. The experimental apparatus is composed of the horizontal one link arm, the pendulum typed hammer to hit the side surface of the one link arm, the force sensor to detect the impact force that acts on the rotating shaft of the one link arm, and the torsion spring. Although the torsion spring is not always necessary in the principle of COP, it plays a role to put back the initial position of the one link arm. For this reason, it is considered that the actual application to the impact isolation needs the torsion spring. The influence of the torsion spring, and the relationship between the hammering point and the impact force on the rotating shaft were investigated. As a result, it was confirmed that the transmission of the impact force was the lowest at the hammering point under the condition of COP. Moreover, numerical simulation of the experimental apparatus was conducted for the theoretical validation. It was confirmed that the simulation results agreed with the experiments. Finally, a low impact pushcart was prototyped as a practical application of the proposed method. Experiments passing over a bump of the pushcart indicated the effective reduction of the impact force by COP.

Most living organisms need locomotion to achieve a series of goals, such as eating, escaping, and breeding. In short, locomotion refers to the periodic activities of various parts of the body and their coordination mechanisms, such as walking, jumping, etc. Each locomotion is characterized by the animal’s body and its surroundings. The common of almost all locomotion is motion of the body center such as the trunk. Therefore, we believe that the periodic movement of the central part of the body is important for achieving movement. In this study, we focused on walking with limbs. We believe that the trunk movement using limbs is a combination of periodic movements of each limb. A central pattern generator (CPG) is used for generating periodic motion. We make robot generate gait to show that walk is the motion of a center part of a body. We propose a discrete control method of leg periodic motion using a ground signal to generate gait. In the periodic adjustment of the proposed method, the leg’s motion period is changed according to the CPG phase when the grounding state of the leg is switched. We use a modular legged robot to verify the proposed control method. We did experiments and simulations using a real robot and a physics engine. It is confirmed that although the initial stage of each leg movement is random, specific gait will be generated over time. Some gaits are gaits that are shown by animals, such as Tripod and Direct Wave.

This study presents a dynamic stability analysis of the self-excited vibration of a plate supported by air pressure. In the analysis, the unsteady fluid force acting on the plate surface is calculated based on the theory of two-dimensional leakage flow. The model built in the dynamic stability analysis applies iterative calculation using a numerical solution to determine the floating displacement of the plate, its steady state, and the pressure and rate of air that flow through the bottom of the plate. This model demonstrates the dynamic stability of the plate when it vibrates close to the steady state. In addition, the local work done by the unsteady fluid force acting on the plate (bottom surface) is calculated, and the region on which the excitation fluid force acts is examined. Furthermore, the fluid force acting on the plate is separated into factors such as compressibility and viscosity. This is necessary for analyzing the effect of the work done by the fluid force derived from these factors on the dynamic stability of the system. The results reveal a critical factor for the occurrence of self-excited vibration; additionally, the detailed instability mechanism of the self-excited vibration is discussed.

In recent years, automobiles have improved the comfort inside the vehicle due to the improvement of noise reduction technology. However, there is a problem of road noise caused by the vibration of contact between the tire and the road surface. Damping materials, known as solutions to this problem, have limited maximum expected damping and may also be mass inefficient. In this study, we propose a method to create a high damping structure by multi-material topology optimization using viscoelastic material, structural material and void. The projection method is used as the shape representation method, and an interpolation function for the loss elastic modulus is proposed. In addition, we formulate an optimization problem with constraints that can meet the weight and rigidity required for structural members. In the numerical example, a half model of an automobile frame is used. As a result, a structure with a high damping ratio that satisfies the constraints is obtained. It is shown that the damping mechanism of the optimal structure forces shear deformation, tension and compression on the viscoelastic material. It has also been shown that damping structure can be obtained with a 78% rigidity of a compliance minimization structure. It is considered to be multimodal because a slight change in the filter radius changes the shape and damping ratio.

The prior research includes the development of a speech-driven embodied entrainment computer-generated character called ”InterActor”, which automatically generates communicative motions and actions such as nods for entrained interaction from voice rhythm based on only speech input. However, the conventional InterActor generates only positive actions and back-channels without negative reactions, which may promote negative emotions of the user in the case of negative utterances such as self-denial. In this study, we developed an embodied character system with a delayed voice back-channel based on negative emotional expression utterances. Two experiments were performed to confirm the evaluation of back-channel feedback timing by sensory evaluation. In the first experiment, the timing of the voice back-channel to nodding motion was examined. In the second experiment, the timing of the voice back-channel to nodding motion in negative utterances was examined. As a result, it was shown that the timing of the voice back-channel delay of about 600ms was allowed from the start of the nodding motion estimated by InterActor. In negative utterances, the timing of allowance was about 900ms. Finally, we developed a prototype system based on the speaker’s emotional state using speech recognition.

Directed lubrication tilting pad journal bearings are used for high peripheral speed conditions. In the bearing, oil is supplied between pads and it mixes outlet oil from an upstream pad at oil inlet region. But in some cases, especially high speed or low oil supply flowrate, a starve region where clearance between a journal and a pad is not satisfied with lubricant occurs. In this research, a new oil film inlet temperature prediction model is proposed to consider the starve region occurrence. The rotation test for the bearing under a high peripheral speed and low oil supply flow rate condition, which starve region occurs, is performed to verify the model. By comparison with test result, the author confirm that the model can predict the oil inlet temperature and pad temperature distribution precisely.

The application of optical products using Laser or LED (Light Emitting Diode) spreads through industry and other fields, and the precise adhesive bonding technology becomes more important. In this paper, for the optimization of UV (Ultra Violet) curing adhesive bonding using UV Lamp or UV LED irradiation, two evaluation methods of UV curing condition were investigated. One is UV curing speed measurement by peak temperature time using thermography, and the other is UV curing end time estimation by adhesive transmittance change. Furthermore assuming 3D position jointing for small Laser Diode optical system, the relationship between adhesive thickness and UV cure depth was optimized. To observe UV curing shrinkage, the visualization of shrinkage part using image processing was tried, and the real time shrinkage measurement using displacement meter was demonstrated. The required UV irradiation energy can be estimated and the UV curing shrinkage about micro meter level can be measured. By applying these evaluation methods for acrylic and epoxy type UV curing adhesives, the comparison of UV irradiation energy and UV curing shrinkage becomes easier, and it is useful to optimize the irradiation condition in the viewpoint of high precision UV adhesive productivity.

Production simulation is useful to predict and optimize future production, but it requires effort and expertise to create accurate simulation models. For instance, operational control rules, such as job sequencing rules and resource assignment rules, are modeled based on interviews with shop-floor managers and some assumptions since those rules are tacit in general. Since operational control rules determine the dynamic behavior of production systems, it is important to model these rules accurately. In this paper, we consider a data-driven approach to model operational control rules. We develop job sequencing rule identification methods that automatically model operational control rules from historical production data using machine learning techniques. These methods are evaluated based on accuracy and robustness against uncertainty in human decision making using computational experiments and actual factory data.

Japanese traditional fan has the variety of three-dimensional expression that differs from two-dimensional expression. The image painted on the fan deforms, when it is folded into convex-concave configuration and fixed to the bamboo bones，due to the difference between the shrinking percentage of the outer arc and the inner arc. Many of the fans made until the Edo era are thought to be painted in consideration of the deformation, but this idea is not recognized in the field of traditional Japanese art. Therefore, many culturally valuable fans, which are more or less damaged due to aging, have lost their bones and damaged edges, and stretched flat like paintings. The fan surface is preserved but the original value of the fan is lost. In this study, we create a digital fan model by proposing approximate formulas for clarifying the deformation on the fan face according to parameters such as length of the bamboo bones, to support the opinion that three-dimensional configuration is essential for folding fans. We then validate the digital model with an actual fan. Regarding shape and area, there was good results, although further study is necessary to improve it. Furthermore, we obtain the original plan view from images of the folded fan as a reverse problem, which is useful for product development that makes use of the characteristics of folding fans.In future study, we would like to upgrade this model to the tool that assists the difficult task of reproducing folding fan without its original configuration. Also we would like to capture precious folding fans in three-dimensional space applying this model and to exhibit those fans in a digital museum, to give opportunities not only to enjoy the value of them but also to encourage the research of the Japanese traditional culture.

To clarify the parameters of a crown roller and a tapered roller that affect the automatic aligning of an elastic belt, we propose an analytical method that can quantitatively predict the movement of the belt along the width direction. In this analytical method, we assumed that the movement of the belt along the width direction occurs owing to the inclination of the belt generated by its velocity distribution. The validity of the proposed analytical method was examined by comparing the calculated and experimental results of movement along the width direction. Good agreement was noted between the calculated and experimental results. Furthermore, it was confirmed that the automatic aligning of the belt is significantly affected by the tilt of the belt generated by the velocity distribution along the width direction. Additionally, it was observed that the radius of curvature of the crown roller and the taper angle of the tapered roller affect the movement along the width direction, whereas the velocity has no effect. Finally, we clarified that belt width affects the movement along the width direction in the case of the crown roller, whereas it has no effect in the case of the tapered roller.