In recent years, quadruped robots have gained popularity in space exploration due to their ability to jump effectively in low-gravity environments. This capability allows for rapid and efficient movement. However, when these robots experience airborne periods due to prolonged jumping, they risk falling over upon landing if their posture during flight is not adequately controlled. The goal of this study is to develop an aerial posture control method for quadruped robots using deep reinforcement learning. Our proposed method is inspired by the “cat twist,” a natural maneuver in which cats adjust their body position mid-air when falling from Under this aerial posture control method, a quadruped robot can the jump from a crouched position, manage its orientation in mid-air without external assistance, and execute appropriate movements until landing on a slope. The effectiveness of this method is verified through simulations conducted in Unity.

In recent years, various approaches have been made in the control of robots using machine learning. Among them, research on deep reinforcement learning, which combines deep learning and reinforcement learning, has progressed. This learning method enables the learning of continuous behaviors by storing discretized Q-tables in neural networks. Examples of its application include tripod gait generation for quadruped robots and trajectory planning for industrial manipulators, contributing to learning complex behaviors. In this study, using virtual environments, we investigate reward conditions for hexapod robots performing tripod gaits, analyze variations under altered rewards, and identify key behavior factors．

This paper describes a method for deriving optimal operations to enhance the efficiency of a weeding robot designed for rice paddies. The robot's operation must cover the entire paddy with minimal overlap while avoiding collisions with obstacles. To enable the robot to perform such tasks, we developed a learning algorithm based on Deep Reinforcement Learning, specifically a Deep Q-Network. The agent's actions involve directing the robot in one of eight possible directions. The inputs to the neural network include the robot's position, orientation, and images representing the work progress. After one million training steps, we observed a trend of improving performance per episode as training progressed. In future research, we will aim to achieve task completion by increasing the number of training steps and incorporating improved methodologies.

A multi-agent system (MAS) consists of multiple autonomous agents. The overall behavior of an MAS is determined by the local interactions among its agents. In recent years, research on MAS for unmanned aerial vehicles (UAVs) has gathered attention. Quadcopters are the most popular among UAVs because of their versatility. In MAS with UAVs as agents, collision avoidance must be taken into account to prevent propeller damage and crashes. Conventional research on MAS for UAVs has largely focused on formation control for a fixed network structure. Considering the future development of UAVs, the case of network dynamically changing must be considered. A collision avoidance algorithm for MAS for UAVs with dynamically changing network structures is required. Specifically, we propose a control method that considers collision avoidance based on funnel control which is one of the high-gain adaptive controls. We perform a simulation study and demonstrate the effectiveness of the proposed method for solving the MAS consensus problem with collision avoidance.

While the water pipeline network plays an important role as social infrastructure with a penetration rate of over 98 %, the deterioration of reliability of existing pipelines due to age-related deterioration is a serious issue. To address this issue, this study proposes a new pipeline inspection method using an in-pipe traveling robot equipped with a soft actuator. In particular, we focus on the development of an in-pipe traveling robot that can follow changes in pipe inner diameter and has high traveling stability, and we have conducted a basic study to realize a branch pipe traveling robot. The robot developed in this study has a bellows-type displacement mechanism arranged in a 2 x 2 matrix, and employs a method to control the displacement direction of the robot by controlling the supply pressure to each body section individually. This control method is intended to achieve smooth running in right-angled and T-angled pipes. This paper describes the details of the robot mechanism design and the supply pressure control method.

In this paper，we describe the fabrication of a pinching mechanism with a cylinder type gas-liquid phase-change actuator，Pneumatic actuator is used for endoscopic surgery support robot．However pneumatic actuator have some faults．Its peripheral equipment is large and makes oscillation and electromagnetic noise．These adversely affect medical equipments．We think that new actuator which does not have those faults is necessary．We suggest a gas-liquid phase change actuator．It is an actuator which big power is got from in the small size．And it can work only with DC power supply such as dry cells．Its device is small and has a small influence to give medical equipments．In this study，we aim to design，compare and examine three pinching mechanisms for actuators using the principle of leverage and investigate their characteristics．We created a cylinder-type actuator that can move a piston using a gas-liquid phase change．The actuator was used to operate three pinching mechanisms with different actuator arm size ratios，and the closing speed and pinching force were measured．As a result，it was found that the longer the driving arm, the stronger the force，and the longer the driven arm，the better the responsiveness．From this，it was thought that the design could be determined based on the required performance and arm ratio，so that the right material could be designed for the right place．

In this paper, we discuss the fundamental characteristics of the TBBA (Triangle arrangement Bending Bellows Actuator), which is used as an actuator for small-diameter pipe inspection robots, and consider its implementation for robot applications. Although various tests are conducted for the early detection of colorectal cancer, the screening rate in Japan remains low compared to other OECD countries. This is attributed to the fact that Japan has fewer physicians per 1,000 people among OECD nations and an even smaller number of physicians capable of performing endoscopic examinations. The authors propose the use of autonomous intestinal robots as a solution and conduct prototype research. This study aims to optimize the control system by equipping the robot with a TBBA. The paper includes the measurement of the bending direction of the TBBA, the bending radius and bending length, the examination of the optimal supply pressure and control method for the TBBA, and the investigation of the supply pressure and control method for the entire robot.

In this paper, we describe the robot with link mechanism brake for small diameter pipe. There are various methods for inspecting water pipes. Destructive testing and non-destructive testing have issues related to cost and safety. To address these issues, it is proposed to perform inspections using robots that autonomously travel inside the pipes. This study aims to expand the range of pipe diameters that can be inspected by prototyping an internal pipe-running robot using a linkage mechanism, to inspect a variety of pipe diameters. The performance characteristics of the two types of robots that were prototyped were compared in terms of factors such as running speed and towing force, to examine which type of structure is most effective for pipe inspections.

Generally, for a robot to climb steps, it needs to move its center of gravity from the lower step to the upper step. Therefore, the problem of a mobile robot climbing steps can basically be interpreted as the problem of how to move the center of gravity from the lower step to the upper step. Conventional solutions to this problem include leaving the wheels on the ground and lifting the body high, using legs, using crawlers, and using a multi-jointed body. Among these, multi-jointed movement moves the center of gravity seamlessly from the bottom to the top of the step by moving many joints up the step in sequence, which is difficult for small robots with limitations on overall length and vehicle height because the number and size of the joints cannot be made large enough. In this research, we aim to expand the range of robot activity by using liquid transportation to move the center of gravity and climbing steps by using joint movement with a small robot.

In this paper，we describe the made of a crawler type of omni directional mobile robot that can run on sandy terrain．The omnidirectional mobile mechanisms are often used in robots that perform complex movements．However，the omnidirectional mobile mechanisms does not operate accurately in a sandy terrain because the passively moving rollers become buried in sand．Therefore，by using fin-shaped parts with different force of resistance in the orthogonal directions for the crawler belt，uses differences in resistance to enable omnidirectional movement．The robot consists of four crawlers whose belts are made of fin-shaped parts with different force of resistance in the orthogonal directions to enable movement in all directions，a loading platform，and electrical circuits for control and status monitoring．

In recent years, many robots have been developed that use suction. The most fundamental solution to this problem is to increase the robot's suction force. However, the friction on the contact surface increases with the increase in the clamping force. This increase in friction can be fatal to the robot's operation. Therefore, it is necessary to reduce the friction during suction while maintaining or increasing the suction force. This paper presents an experimental analysis of a method to reduce suction friction by applying air pressure to the suction cup. In this study, a chamber for applying air pressure is included at the bottom of the designed suction cup, in addition to the vacuum section. A system to measure static friction using a blower containing a suction cup was constructed, and experiments were conducted to determine under what conditions friction is reduced using a pressure gauge and a force gauge. Based on the measurement results, we discussed the results and proposed the conditions for reducing friction in suction cups using pneumatic pressure.

In biological systems, tails serve as auxiliary organs that assist in both locomotion balance and object manipulation. Drawing inspiration from these natural capabilities, we present a novel tail mechanism designed for integration with our quadrupedal lizard-inspired robot, SAURUS-II. The proposed mechanism requires large range of motion, high operational velocity, and substantial load-bearing capacity. To achieve these performance requirements, we developed an innovative design incorporating two interconnected parallel link mechanisms for the main load-bearing structure, driven by an active parallel link mechanism powered by dual rotary actuators. To optimize the design parameters, we conducted mechanism analyses of the workspace, statics, and velocity characteristics. Our results demonstrate that the tail mechanism can generate forces up to 200 N and achieve velocities up to 0.48 m/s at its distal end. Through this analysis, we established optimal link lengths of 180 mm, 40 mm, and 200 mm for the tail mechanism components.

In this paper, we describe the design of a snake-type Mobile robot. To inspect the inside of the intestine, a robot is inserted into the intestine. However, the intestine is folded and has different internal diameters in different places. To develop a robot capable of traveling through pipes with varying inner diameters, we propose a Mobile robot that mimics the accordion-like motion of snakes. This motion is a method of moving inside pipes and vertical holes. The snake-type Mobile robot is composed of three body segments to enable accordion motion. The front and back body sections consist of actuators that can flex, serving as braking mechanisms to hold the tube. The central section includes actuators that generate the displacement necessary to propel the robot and functions as the driving mechanism.

This paper describes development of an in-pipe mobile robot driven by pneumatic pressures．Town gas is supplied to houses through polyethylene pipes laid under the road．It is necessary to inspect these pipes regularly caused by the gas lesak owing to earth load and oscillation for driving cars on the road．So we manufactured in-pipe robot driven by pneumatic pressures on the model of a green caterpillar．The robot is structured by two somite and three suction brakes．In this work，we researched in which the robot traveled in rusted pipes，bent pipes，and pipes with steps.

In this paper, we describe rehabilitation (hereafter referred to as "rehabilitation") is necessary to improve the quality of life (QOL) and reintegration into society for those who have lost the use of their hands and fingers due to accidents or diseases. Rehabilitation is performed in stages by qualified physical therapists and occupational therapists, and includes splint therapy to release contractures, joint range-of-motion exercises to normalize joint function, and muscle strengthening exercises to restore muscle strength necessary for daily activities. Ideally, these rehabilitation activities should be continued on a daily basis. It is said that rehabilitation for the elderly should be conducted seamlessly in a familiar community with the patient at the center of the rehabilitation program. However, it is difficult for patients whose homes are located in remote areas or who require assistance for transportation to go to the hospital. Therefore, the authors are conducting research on a device that supports rehabilitation at home in order to improve the continuity of rehabilitation.

In this paper, we describe rehabilitation (hereafter referred to as "rehabilitation") is necessary to improve the quality of life (QOL) and reintegration into society for those who have lost the use of their hands and fingers due to accidents or diseases. Rehabilitation is performed in stages by qualified physical therapists and occupational therapists, and includes splint therapy to release contractures, joint range-of-motion exercises to normalize joint function, and muscle strengthening exercises to restore muscle strength necessary for daily activities. Ideally, these rehabilitation activities should be continued on a daily basis.It is said that rehabilitation for the elderly should be conducted seamlessly in a familiar community with the patient at the center of the rehabilitation program. However, it is difficult for patients whose homes are located in remote areas or who require assistance for transportation to go to the hospital. Therefore, the authors are conducting research on a device that supports rehabilitation at home in order to improve the continuity of rehabilitation. However, the rehabilitation support devices currently available are large and very heavy, with compressors, vacuum pumps, and other equipment, making it difficult to use them at home. Currently, the operation of rehabilitation support devices has a problem where the air supplied to the actuator is momentary, resulting in discontinuous movements that differ from the original rehabilitation motions. Therefore, in this study, we installed flow resistances in the piping system of a bellows actuator and conducted experiments to clarify how the magnitude of the flow resistance affects the actuating force. The findings are reported in this paper.

Research on guide robots that lead people to their destinations has been actively conducted. During the guiding task, the robot is generally required to maintain a consistent distance from the people it guides. However, the appropriate distance between the robot and the guided person is expected to vary from person to person. In this study, we examine voice commands suitable for adjusting the user-robot distance according to the user’s needs. Based on experimental results, two suitable voice commands were selected.

In this report, we propose a risk evaluation method for human-coexisting robots by calculating the exposure frequency of humans in the same narrow environment. Specifically, predicted on narrow environment will impact human's movements, we assume that obstacles such as walls will accumulate the risk of collisions, and a reflection of human’s assumed evasion movement will help to visualize and quantify the risks. Then we evaluate the motion of humans by calculating the probability of presence of humans by recorded footage. By combining the reflected human movement to the footage, we calculate the environment-affected probability of human presence and evaluate the risk by calculating the exposure frequency. To test the validity, we ran simulations based on python and calculated the exposure frequency for human and robot’s footage with our proposed method and compared with conventional method. Then we ran the same process with recorded trajectory data of human and robot role to prove the validity in real situation.

A 2DOF (degrees of freedom) manipulator driven by two 1DOF geared five-bar modules is proposed. The geared five-bar module is realized by interlocking two joints of a five-bar linkage by means of gears, and can easily switch its motion trajectory by reconfiguring the gears. Consequently, the manipulator is expected to have multiple operation modes with different kinematic properties. The objective of this research is to develop working model of such a manipulator that can switch kinematic properties depending on the tasks. In this paper, the above functions are verified through kinematic analyses and basic motion experiments using prototype working models of the geared five-bar module and the 2DOF manipulator. The kinematic analyses include the solutions to the direct kinematics and the inverse kinematics problems, the movable range analysis, and the manipulability analysis based on the Jacobian matrix (The shapes of the manipulability polytopes change depending on the operation modes).

In this paper, to improve the responsiveness of the TCPA, we examined a combination of TCPA and servomotor actuators during bending and extension movements using a finger-joint manipulator. In particular, the arrangement, number, and voltage of TCPAs were mainly evaluated using the design of experiment method. The results showed good results in the flexion motion, but there was room for improvement in the extension motion.

In this study, ROS2 Network is used to remotely control a six-degrees-of-freedom robotic arm. Specifically, the goal is Hunam Hand Tracking, which performs hand detection processing on images from the 3D Camera and transmits the calculated control amount to the robot control computer. By achieving the goals of this research, it will be possible to visualize the control flow using MATLAB, and it will be possible to remotely transmit the generated control amount to the robot using the ROS2 network. In this study, we used MediaPipe and Simulink to generate robot control quantities. In the future, it will detect not only hands but also various objects, and generate control quantities in real time. Additionally, we assembled a 3D model by using MATLAB/Simulink, and a simple real-time motion simulation was performed using a ROS2 Subscriber. This allows the motion status of the remote robotic arm to be monitored on a local PC.

To improve stability when walking on rough ground, a flexible foot mechanism was designed based on the geometry obtained through topology optimization. The foot is equipped with springs, dampers, and plate springs to follow the ground and reduce the effect of rough ground. Analysis and testing on the actual product confirmed the reduction of inclination in several rough terrain patterns and demonstrated the foot's ability to reduce reaction forces from rough ground.

This paper discusses the development of a robot for sewer pipe repair operations. In recent years, the number of aging sewer pipes has been rapidly increasing, while the workforce engaged in sewer pipe maintenance has been steadily declining. As a result, improving the efficiency of sewer pipe repair operations has become an urgent issue. One common repair method is the ”Alpha Liner Method,” which involves forming a new pipe inside the old sewer pipe using light-curing resin. During this process, lateral connection openings are sealed off and must be re-opened by drilling. Currently, the drilling machine is manually transported to the drilling site, which is labor-intensive and inefficient, placing a significant burden on workers. In this study, we developed a robot capable of drilling lateral connection openings without human effort by utilizing actuators. The robot employs mecanum wheels for omnidirectional movement, allowing it to roll and rotate inside the pipe and drill openings positioned at various angles. The performance of the robot ’s mobility was evaluated.

This paper describes the development of a wire-driven wall-moving robot equipped with an IH type paint-coating remover. When removing deteriorated paint from steel bridges for maintenance, it is necessary to heat the paint using an IH type paint-coating remover. However, the equipment is heavy and has a wide working range, so it is necessary to mechanize the work. To mechanize the work, the equipment must be mounted and moved on the wall surface. Magnetic suction and vacuum suction are the methods used to move the equipment on the wall surface, but both are susceptible to the condition of the wall surface and have safety issues during the movement. In this paper, we propose a method that uses a wire to move the wall surface in all directions with only a winding motion. If the wire is always connected to the frame, the possibility of falling can be reduced and safety during movement can be ensured. It is possible to minimize the impact of power loss or unexpected external forces on the robot.

To achieve higher storage capacities in Hard Disk Drives (HDDs), it is essential to enhance the positioning accuracy of the magnetic head, which is responsible for reading and writing data. This research aims to design an optimal high-order filter for the positioning control system to minimize the positioning error of the magnetic head in HDDs. In this study, high-order filters are constructed by sequentially combining second-order filters in parallel. A parameter optimization problem was also formulated for the high-order filter to further improve positioning accuracy, and a genetic algorithm was employed to solve it. The effectiveness of the proposed method was verified through simulations using the HDD benchmark problem developed by the IEEJ Industry Applications Society. The results confirmed that incorporating high-order filters into the HDD positioning control system significantly improved positioning accuracy.

In recent years, EVs have been used in a wide variety of machines, from transmitting power to sending and receiving information. Mechanical elements that used to consist of shafts and wires have been replaced by electronic controls, allowing for miniaturization. However, with the shift to EVs, the effect of wear under electric current has become an issue. Unlike normal wear, wear under electric current causes arc discharge and melting due to the application of electricity, resulting in extensive damage. This affects signal transmission and reception when it occurs at terminals. In addition, natural phenomena such as rain must be considered for railway pantographs, and it is necessary to anticipate natural phenomena such as rain, and it is necessary to understand the mechanisms under various conditions for safe and stable operation. Therefore, material selection is important and evaluation methods are necessary. In this study, it was investigated whether arc discharge and melting could be evaluated by acoustic emission (AE) sensing and whether external factors could be sorted out by machine learning were. The results confirmed that there was a remarkable difference in the frequency range where melting and arc discharge occurred, and that machine learning could classify wear patterns under the three conditions of no electric current, with electric current, and with electric current and water drop.

In this paper, the deep learning problem and the symbol grounding problem is discussed with combined them. For the analogy of the calculation mechanism of conventional von Neumann type computer ,the validity as an optimal solution by the solution process of the mountain climbing problem in optimal value problem in mathematics is clarified.In the stochastic process, the optimal solution corresponds to the likelihood value, so from these results, it can be confirmed that the conjugate gradient method in the simulation is suitable for artificial intelligence, and how the range of application can be expanded with considering human inclinations, which are difficult to quantify is discussed.

Since the invention of the transistor in 1947 and the emergence of Moore's Law in 1965, semiconductor devices have continued to develop dramatically to the present day. While the end of device scaling (the end of Moore's Law) has been called out many times, semiconductors have risen like a phoenix. While semiconductors around the world have been developing smoothly, what about Japan? In 2021, a report presented by the Ministry of Economy, Trade and Industry shocked the whole of Japan. In 1988, Japan boasted a global semiconductor market share of over 50%, but by 2020, it had fallen to less than 10%, and a threatening warning was issued that it may even be 0% by 2030. However, at the same time, there was great hope that the global semiconductor market would double in 10 years. This is truly a report of both threats and hope for Japan. Semiconductor manufacturing equipment has continued to support the world's semiconductors during this time. Mechanical Engineering (the Society of Mechanical Engineers) has continued to support the development of such semiconductor manufacturing equipment. In this article, I would like to look back on the history of semiconductors, manufacturing equipment, and the academic society activities that supported them.

The number of patients awaiting liver transplantation is increasing, but organ availability remains insufficient, leading to patient deaths during the wait. Decellularization technology offers hope by creating artificial organs. However, recellularization which injects multiple cell types via blood vessels, is essential for functionality provokes cell stagnation and blockages in vascular branches. In this study, we visualized cell-flow within vessel-branches and analyzed pressure and flow during cell injection process by two methods. The one is CFD-DEM coupled simulation in Y-shaped branch model. The other one is an experimental system, which is composed by Polydimethylsiloxane (:PDMS) microchannel, syringe pump, zoom-lens and high-speed camera. In both two methods, vascular occlusion was observed.

The phenomenon of water droplets impacting and solidifying on a low-temperature solid surface is called icing, and it is a major problem in various aspects of our daily lives, resulting in reduced aerodynamic performance of aircraft and increased load on power lines. In this research, as a model experiment of the icing process, a single water droplet was dropped onto a substrate and solidified. The strain generated in the substrate was measured during the process, and the effects of substrate temperature on the generation of strain and cracking were investigated. A coupled thermo-structural analysis using the finite element method was also performed to calculate the stresses in the ice film to examine drive force of the cracking. The results showed that the stress in the ice film increases rapidly due to the temperature change of the ice film, and causes the cracking at a certain temperature.

Austenitic stainless steels are widely used as important structural materials in the railroad field. SUS304, a representative grade of austenitic stainless steel, is used in a wide range of applications from car bodies to bogie parts due to its excellent corrosion resistance and workability. However, the 0.2% proof stress of conventional SUS304 is relatively low at around 200 to 250 MPa, limiting its use as a structural member requiring high strength. To address this issue, systematic investigations of material developments, focusing on heat treatment technologies, have been conducted.

This study investigated how vacuum and air heat treatment environments influence the mechanical properties and surface characteristics of Type 304 stainless steel. Microhardness measurements revealed that the surface hardness decreased significantly after heat treatment, with a more pronounced reduction observed in specimens treated in air compared to those treated in vacuum. This phenomenon can be attributed to the formation of an oxide film during heating and the effect of oxygen atoms that from the material surface, which enhanced the mobility of the transition. Previous studies have also shown that the average grain size approximates the film thickness. These results show that the atmospheric conditions during heat treatment have a significant effect on the strength of the final SUS304 steel.

The front of a vehicle has a crash box that maintains the shape of the front side member and crashes ahead of the front side member. Therefore, the crash box needs to be designed to have enough strength to absorb the impact energy. However, if the crash box is too strength, the front side member crashes instead of the crash box. Carbon fiber reinforced plastic (CFRP) has a high specific strength and specific rigidity. The CFRP can change the strength and rigidity by changing the number of prepreg layers or the direction of carbon fiber in the prepreg. This report focused on the direction of carbon fiber in the prepreg. We used a uni-direction Carbon fiber prepreg and manufactured shell-shaped CFRP specimens. The directions of carbon fiber in manufactured specimens were different from each other. Drop weight tests were performed to crush these specimens and investigate the effect of the fiber direction in CFRP specimen on impact absorption performance. From these results, the increase of prepreg continuing closer to the axial direction reduces the crush amount.

Carbon fiber reinforced plastics (CFRP) are used in a variety of industrial products. Because of the high heat resistance of CFRP, disposal and recycling processes for products used in its applications are not well established and many challenges remain. A flax fiber-reinforced plastics using natural fibers such as hemp and coir have been proposed to replace glass fiber and carbon fiber used in fiber-reinforced plastics. Authors focused the flax fiber reinforced plastic as impact absorption materials used for crash box in automobiles. In this report, we manufactured a specimen made of flax fiber and carbon fiber prepreg and evaluated impact absorption performance by drop weight test.

The propagation tests were conducted under the In-Phase（IP）, the Out-of-Phase（OP）, and the Dwell-IP types of thermomechanical fatigue loading conditions on single crystal Ni-based superalloys to investigate the small crack propagation behavior of naturally generated cracks on the specimen surface. In addition, the effect of phase angle and dwell time in the TMF loadings on small crack propagation was investigated. The Dwell-IP condition refers to a condition in which a high temperature tensile hold of 10 minutes is added at the maximum temperature of the IP condition. The experimental results indicated that the elastic deformation was dominant in the cyclic deformation behavior. However, slight creep deformation occurred during the high-temperature tensile holding under the Dwell-IP condition. The naturally initiated small cracks propagated perpendicular to the loading direction macroscopically. When crack growth rates correlated with the fatigue J-integral range, ΔJ_f, the crack growth rate is higher in order of Dwell-IP, IP, and OP conditions. The difference in crack growth rate due to the TMF condition might be related to the localized creep strain at the crack tip.

Temperature change during cyclic loading is measured by infrared camera to examine the energy dissipation associated with fatigue crack initiation and propagation. Four types of single crystal notched specimens with different crystallographic orientations were employed. Local slip deformation is quantified based on the crystal plasticity finite element analyses. It is revealed in the fatigue crack initiation test that the distribution and magnitude of second harmonic temperature and the local slip deformation are affected by the crystallographic orientation. However, the correlation between plastic shear strain and second harmonic amplitude is independent of the crystallographic orientation. It is also found in the fatigue crack propagation test that the magnitude of second harmonic amplitude depends on the fatigue crack propagation rate and the fatigue crack threshold in each orientation. However, the correlation between the plastic shear strain and the second harmonic amplitude is independent of the crystallographic orientation.

Ni-based sigle crystal superalloys are widely used in gas turbine blades due to their excellent high-temperature strength. However, cyclic loading due to mechanical vibrations and thermal stress can cause fatigue crack initiation and subsequent propagation. While prior studies have examined fatigue crack propagation in Ni-based superalloys, few have focused on the arrest of fatigue cracks, particularly considering the effect of crystallographic anisotropy. This study investigates the influence of crystallographic anisotropy on fatigue crack propagation and arrest behavior. Fatigue crack propagation tests were conducted at room temperature using four specimens with different crystal orientations. The results revealed significant effects of crystal anisotropy on crack propagation path, propagation rate, and ΔK_th. Crystal plasticity finite element analysis, incorporating experimentally observed cracks, demonstrated that the damage parameter based on plastic shear strain along the slip plane can effectively evaluate fatigue crack arrest.

The effect of tensile dwell on dwell-fatigue crack propagation in a wrought Ni-base superalloy, Inconel 718, was investigated, with particular attention to the effect of oxygen. Crack propagation tests were conducted in air or vacuum at 650 °C and by applying a single tensile dwell during pure fatigue loading under various stress intensity factor, K, conditions. Acceleration or retardation of the fatigue crack propagation was observed after the tensile dwell depending on the K condition, in air. On the other hand, neither acceleration nor retardation was observed in vacuum. Fracture surface observations showed that in air, the crack propagated in the intergranular-dominant mode during the acceleration, whereas the transgranular-dominant propagation occurred before the dwell and after the acceleration. In vacuum, the cracks remained transgranular over the entire periods of the tests. These results indicate that the acceleration induced by the tensile dwell is due to grain boundary embrittlement caused by oxygen diffusion.

A crack propagation analysis system has being developed by combining Isogeometric Analysis (IGA), which features high compatibility with CAD, precise geometric representation, and high-order continuity, with the singular patch method capable of representing stress singularities through geometric mapping. In particular, a method for generating the crack front curve after crack propagation and redefining IGA patches was proposed. The validity of the method was demonstrated through a surface crack propagation problems.

In this study, we propose a one-way coupled analysis method for finite strain elastic-plastic analysis, assigning displacements at a global finite element analysis method analysis assuming cracks to a local finite element analysis. The proposed method uses the least-squares method to smooth out the nodal displacements of the global finite element analysis, they are arranged to surface nodes of the local finite element model as displacement boundary conditions. We investigated identify the application conditions that can assure accuracy of present global-local analysis.

A vibration analysis method for predicting the natural frequency and damping ratio of ABS resin, which has excellent vibration absorption properties and contributes to weight reduction of automobiles, in relation to the bolt tightening force was investigated and its validity was compared with the results of hammering tests. In the analysis method, a contact model which simulates the interfacial stiffness of nominally flat surfaces between the plates by the contact of spherical asperities was introduced and computed using the FEM. Then, the effects of frictional damping and viscous damping in the damping capacity of the ABS resin with bolted joints were included. In the hammering tests, the natural frequency of the specimen was measured from the peak of the power spectrum obtained by the Fourier transform of the acceleration response, and the damping ratio was measured from the acceleration envelope obtained by the Hilbert transform. The same approach was also applied to S50C plates with bolted joints for comparison with the vibration characteristics of ABS resin. The elastic modulus of the interface and the damping coefficient by friction were then derived and applied to both ABS and S50C plates. The viscosity coefficient was applied to ABS resin plates only. The FEM results of both materials agreed with the hammering test results.

When a thin shell structured is buckled, the incremental change of external work and internal strain energy is not balanced each other. In such a case, the arc-length method is widely used to proceed the calculation. On the other hand, when the implicit integration does not converge, the explicit integration can be used to follow the last converged result of the implicit integration. But if this auto-switching process follows the pre-setting condition, the result of calculation would be highly influenced. In this paper, the effect of the auto-switching process against to its result is reported.

KIRIGAMI structure is a metamaterial whose mechanical properties can be controlled by cutting into the sheet. We focused on the energy absorption properties of KIRIGAMI during sudden braking, and found that the energy absorption properties changed when the design parameters were varied during braking tests. In the future, we will design KIRIGAMI so that its energy absorption properties can be used as a braking mechanism to achieve the desired physical properties that reduce damage to the human body.

We developed a simulation method that enables the simultaneous analysis of the behavior of magnetic moments and the viscous motion of spherical particles, from a viewpoint of application of magnetic hyperthermia therapy. The behavior of the magnetic moments was analyzed by solving the stochastic Landau-Lifshitz-Gilbert equation, while the viscous motion of the particles was evaluated using the Brownian dynamics method. We addressed a single-particle system to investigate the orientational properties of both the particle and the magnetic moment. If the magnetic anisotropy energy is significantly smaller than the thermal energy, the magnetic particle shows superparamagnetic behavior. The magnetic moment rotates within the particle and tends to incline in the magnetic field direction as the magnetic field strength increases. With respect to the magnetization curve, the present simulation method gives rise to the theoretical solution (the Langevin function). Furthermore, we conclude that the orientational characteristics of the particle and the magnetic moment are strongly influenced by the magnitude relationship between the magnetic field and the magnetic anisotropy.

The two-dimensional Navier-Stokes equations of motion were directly solved to simulate turbulent phenomena, including the generation of turbulence in parallel pipe flows. Divergence was prevented by increasing the viscosity of the cells that were likely to diverge. Divergence occured when trying to solve an external flow such as the flow around a cylinder, but by adding one more condition, it became possible to obtain pipe friction coefficients and drag coefficients that were almost consistent with the experimental results.

In the floating zone method under microgravity, while the production of high-purity, large-diameter silicon single crystals is promising, there is a problem of defects caused by Thermocapillary convection. Hydrothermal Wave (HTW) is known to be one of the causes of oscillatory flows that lead to defects in crystals, and real time control of HTW is necessary to achieve high quality crystals. Given the computational load, real time control of HTW is best achieved using a reduced order model. Therefore, this study aimed to investigate optimal wall boundary conditions to obtain CFD data that best match real HTW, with the goal of constructing an accurate reduced order model for HTW control. Three cases were investigated for the wall boundary conditions on the front and rear walls: (1) periodic boundary, (2) adiabatic wall, and (3) wall with an imposed linear temperature gradient. The results showed discrepancy between CFD solution and the experimental data, even with changes to the wall boundary conditions.

This study will be numerical and experimental to clarify the lingering phenomenon at the microvascular branch. Specifically, the deformed red blood cell flow simulation program based on the lattice Boltzmann method is used to perform numerical analysis of a single branch shape of 10 micrometers, and the branch shape will affect the red blood cell distribution characteristics and lingering phenomena.

Vortex tube is a simple device with no moving parts which could generate cold and hot air streams simultaneously with compressed air as a working fluid. Rectifier plate is an effective addition to vortex tube design, optimizing performance for industrial cooling applications. The inclusion of a rectifier plate within the vortex chamber alters the flow dynamics, thereby affecting the temperature separation process. In this study, we analyze numerically the cooling performance of a vortex tube with an integrated rectifier plate to enhance temperature separation. Using computational fluid dynamics (CFD), this study explores flow structure inside the vortex tube, the effects of rectifier plate geometry and positioning on temperature differential and pressure drop.

Magnetic particle suspensions subjected to an external magnetic field exhibit an increase in apparent viscosity, and this phenomenon is called the magnetorheological effect. Typical applications of these suspensions are mechanical dampers and actuators. The magnetorheological properties depend on the internal structure of aggregates and the orientational characteristics of the particles. In the present study, we investigated a suspension of ferromagnetic rod-like particles under a simple shear flow, focusing on the internal structure of particle aggregates and the orientational characteristics of the particles using Brownian dynamics simulations. An external magnetic field was applied perpendicular to the flow field. The results obtained here are summarized as follows. As the influence of the flow field increased, the internal structure of aggregates became unstable. When the effects of the external magnetic field and the flow field were comparable, the rod-like particles inclined from the magnetic field direction toward the flow field direction. These results suggest that the internal structure of aggregates and the orientational characteristics of magnetic particles can be controlled by the flow field and external magnetic field.

In the floating-zone method, high-purity single crystals are produced by melting and recrystallizing polycrystalline materials using a ring-shaped heater. However, unsteady thermocapillary convection, driven by non-uniform surface tension gradients caused by temperature variations on the molten material, can introduce undesirable defects in the crystals. To address this issue, suppression of unsteady thermocapillary convection is essential for fabricating high-purity crystals. In this study, oscillation suppression control was applied to unsteady thermocapillary convection in a full-zone liquid bridge, a physical model of the floating-zone method. The control strategy employed an additional ring-shaped heater with a time-independent heat output. The suppression performance was evaluated based on the temperature oscillations at the liquid bridge's free surface. The results showed that suppression effectiveness decreased with increasing convection nonlinearity but improved with a larger wire diameter in the additional heater, provided that the additional heater was positioned below the liquid column. These findings provide valuable insights for optimizing crystal growth processes.

A study was conducted to investigate the effect of channel length and width on the red blood cell (RBC) partitioning occurring within bifurcating microchannels. Existing experimental data were used as a framework for the modelling program. The outcome of the modelling results was validated against the experimental results to ensure the program aligns with existing outcomes. The results show that the RBC distributions before the bifurcation point affect the amount of RBC entering each daughter branch. Furthermore, the study suggested that the channel length plays a crucial role in the RBC distribution within the vessel.