In order to reduce the leakage flow rate and improve the precessing motion of non-contacting seals, seals with variously shaped concaves and grooves on the sliding surface of the seal have been proposed. In the numerical analysis of such non-contact seals with concavities and grooves, the grid points are set according to the concavities and grooves. On the other hand, with the recent progress in machining technology, the degree of freedom in machining the sliding surface shape has increased, and the shape is expected to become more complex. In other words, the conventional numerical analysis model that uses grid points to match the actual shape as described above is expected to become difficult to analyze, and a model that allows more flexible numerical analysis is required. In this study, a bulk flow model is used to analyze the effect of surface texture on the flow of a non-contact seal with a surface texture on the seal sliding surface. The effectiveness of the proposed analysis method is then compared with the static and dynamic characteristics obtained from conventional numerical analysis models and experiments. As a result, the following points were clarified. For a damper seal with irregularities on the seal side, the dynamic characteristics of the liquid film can be predicted relatively accurately by setting the value of the dimensionless empirical turbulence coefficients to match the leakage flow rate over a wide range of speeds. The best agreement with the experiment is obtained when the seal clearance is set to be the clearance at the land and the dimensionless empirical turbulence coefficients is set to be the same for the seal side and the rotor side.

Self-excited vibrations of a pipe conveying fluid have been studied as an essential problem of unstable phenomena on non-conservative continuous systems. In this system, double Hopf bifurcations can be produced in the range of certain parameters. In this study, we investigate the nonlinear interactions between two unstable modes. By using Lyapnov-Schmidt reduction method, we obtained the amplitude equations which govern the nonlinear interactions between two unstable modes. In this study, we explain mechanism of nonlinear interactions on amplitude equations. Furthermore, we conducted additional experimental results of non-planar mixed modal self-excited vibrations.

The number and arrangement of actuators are different between robots and humans. In most of the articulated robots, each joint has its own actuator, and each joint is driven independently. On the other hand, humans have mono-articular muscles that move only one joint and bi-articular muscles that move two adjacent joints simultaneously. Recent studies have shown that the bi-articular muscles contribute greatly to stiffness control and trajectory control. In addition, it has been shown that it is possible to control the stiffness of the robot by introducing bi-articular actuators that simulates the bi-articular muscles. The purpose of this study is to realize the force control and the stiffness control simultaneously of an actual 4-link and 3-joint leg robot by introducing bi-articular actuators. In the real robot, it is difficult to control the force and stiffness because the resistance force is generated by the friction generated in the gears. Therefore, we need the friction compensation to control the force and stiffness for the leg robot. We used the strain gauge for friction compensation. Friction compensation is possible by using a strain gage to feedback the external force. We studied a method to control the stiffness of the leg robot by using friction compensation with external force feedback and performed. We also studied the evaluation method of force and stiffness control for the leg robot.

We developed a foldable 6DOF manipulator that combines tensegrity structures and parallel mechanisms. This manipulator is composed of four tensegrity structures (consisting of nine wires and three rods) and three 2DOF parallel mechanisms, which are connected via 18 double equivalent spherical joints (two equivalent spherical joints that share a center of rotation). The double equivalent spherical joint is designed so that the ends of two limbs of the parallel mechanism and the end of one rod of tensegrity structure share one point. Each tensegrity structure is equipped with turnbuckles to adjust the tension, which enables the manipulator to be deployed and folded. Moreover, numerical solutions of the direct kinematics problems of the parallel mechanism and the 6DOF manipulator were obtained by the convergence calculations using Jacobian matrices, where the matrices are derived based on the conditions of the static equilibrium. By using the solution, a simulator was developed to visualize the range of motion of the manipulator, and it was confirmed that its width was 1.3[m], depth was 1.4[m], and height was 0.4[m]. We also developed a control system using an analog servo circuit with position feedback loop, and devised an algorithm for hand position control of the 6DOF manipulator based on the sequential calculation of the Jacobi matrix. As a result of experiment, it was possible to control the hand position, although position errors were observed due to the modeling errors and the elongation of the wires.

In recent years, the need to hold teleconferences and perform remote work has increased rapidly, owing to advancements in information technology (IT) and the spread of infectious COVID-19. Many companies utilize IT to achieve efficient production. The purpose of this study is to develop a predictive maintenance technique for achieving efficiency of manufacturing equipment automatically. To achieve this purpose, we constructed regression models through machine learning. The models were based on numerous data of the working machine using installed sensors to record data online. The regression models and some analysis methods were used to determine the tendency of the machining cloud. The tendency is the error between the predictive value and the actual measurement value. If this tendency remains the same in the future, it will predict when a fault occurs in the machine. Furthermore, it will facilitate predictive maintenance automatically. After this, the tendency was monitored, and the exact schedule of a breakdown of the manufacturing equipment was developed.

In the fields of engineering and medicine, there are increasing demands for measuring internal temperature and its distribution in a medium. Although the ultrasonic thermometry based on pulse echo measurement is often used for industrial materials, the method cannot always be applicable in some cases such as an application in human body estimation. In this work, feasibility examination on temperature measurement by ultrasonic scattered waves has been made. Internal temperature of a medium is determined from the relative change in the velocity of ultrasonic scattered wave. In order to verify the validity of the proposed method, numerical simulations and experiment with an agar gel are performed. As the results, the usefulness of the proposed method was demonstrated.

Elderly people are more likely to have the proximal femur fractures because of osteoporosis and so on, even with a slight external force due to a fall. Intertrochanteric fractures, which is one of the proximal femur fractures, have a wide variety of fracture patterns. A suitable treatment is required for each fracture pattern. To investigate the relationship between fall situation and fracture pattern leads to understand these fracture conditions and is important for early recovery. The aim of this study was to investigate the repeatability of the intertrochanteric fracture pattern using dynamic FE analyses in consideration of failure of bone element. As a result of the analysis, the fracture pattern of the intertrochanteric area of the femur similar to that of Type I, 3-part A of the 3DCT classification was obtained.

In order to realize the early detection of osteoporosis, the development of a device that enables simple screening is desirable. We have focused on a simple bone density evaluation method using near-infrared light and have studied its reliability. In this study, we propose a bone mineral density (BMD) prediction model, which uses optically-measured bone density data and machine learning techniques. For 177 participants, we measured with the optical bone densitometer that we have developed before and dual-energy x-ray absorptiometry (DXA). A BMD prediction model is created by using optically-measured bone density, age, weight data as features, and BMD value determined by DXA as target data. We evaluate the generalization performance of the model using cross-validation. As a result, The BMD predicted by the machine learning model shows a strong correlation with the BMD determined by DXA. Besides, the area under the curve (AUC) of the receiver operating characteristic value for evaluating the osteoporosis discrimination performance is equivalent to that of the equipment currently used for osteoporosis screening (osteoporosis: AUC = 0.856, osteopenia + osteoporosis: AUC = 0.747).

The number of deaths caused by drowning in bathtubs has been increased because of medical symptoms such as stroke of seizures in Japan. The objective of this research is to design and develop a new drowning prevention device for using at bathrooms. The proposed device consists of supporting parts and mechanical parts with an air cylinder. Pressure sensors putted on the device detect changes of posture of user as unusual situations in bathtubs. Effectiveness of the proposed device was verified by several experiments. The experimental results are also shown in the paper. The device was fixed on a wooden frame, and chin heights of 3 subjects and pressure sensor value were measured during changes of posture. The proposed device appropriately detected posture changes of subjects, and the device was able to maintain the height of user’s chin for breathing, and this device had sufficient performance to prevent drowning accidents in bathtubs.

Recently, the field of autonomous driving has been developed remarkably and the technology primarily focuses on avoiding conflicts and conforming to traffic rules, which are for safety. However, the degree how much uncomfortable or stressed those in such cars feel should be different among individuals. Therefore, we need to make the degree of their individual stress quantified to get them in order to feel less stressed then. So, we conducted an experiment showing the participants various decelerating situations while they are in autonomous driving cars on simulation reproduced by virtual reality for the sake of making sure whether human’s pupil diameter would be an objective indicator that reflects human’s discomfort objectively in autonomous driving cars. As the result, we were able to make sure there seems to be a correlation between human’s pupil dimeter and their subjective discomfort, but unable to see the degree of their discomfort is involved with that of pupil diameter transition.

Much information can generally be obtained from sight. However, it is difficult for visually impaired people to obtain information from the visual sense. Currently, Braille displays capable of acquiring information from tactile sensing have been developed and commercialized. However, they are large, heavy, and not suitable for carrying. Thus, to overcome these problems, we have developed a Braille unit composed of two moving belts, and all Braille characters can be displayed by independently positioning each belt. This paper reports the contact determination method of fingertip for the belt-driven Braille unit, which is necessary to continuously display serial Braille characters corresponding to the up/down of fingertip．

In order to clarify the psychological stress by the seat vibration on its occupant in the vehicle, the vibration transfer characteristics from each part of the seat to the occupant were investigated. The experiment was conducted in an idling-state vehicle, and was investigated by applying the operational transfer analysis to the vibration measurement results of the seat and the occupant. As a result, it is clear that even when subjects with the same height and weight were seated on the same seat, the body position and vibration mode at which vibration was maximized were different, which causes a difference in psychological stress to them. It was also found that these differences may be caused by the difference in the characteristics of the center of gravity of the subjects.

Recently, the demand for nursing care services has increased in Japan with the aging of the population. However, there is a chronic labor shortage of caregivers because of high turnover rates due to their occupational illnesses. In particular, so-called back pain is the most common occupational illness, and transfer assistance by caregivers is one of the major causes of back pain. To reduce the physical burden on caregivers, we have developed a nursing bed with a maneuvering chair needing no transfer assistance. In this developing process, we also produced a sheet push-pull mechanism that transfers the care-receiver on the nursing bed to the maneuvering chair side. This paper reports the feeling of use and usability of the sheet push-pull mechanism.

Cartesian-Mesh CFD solvers have a problem of inaccurate drag force calculation because the grid does not conform to the object. This is attributed to the fact that near-field drag calculations are performed on the surface of the object, which is represented as a staircase. To avoid this problem, the wake integration method, which calculates the drag from the wake region, has been proposed. However, It is not easy to determine the appropriate integration region. In this research, in order to simplify the selection of the wake region in the drag calculation of the Block-Structured Cartesian Mesh using the wake integration method, deep learning was performed using 70 visualized entropy drag image data. As a result, the prediction worked well for some test data. However, we found that further validation is needed to improve a generalization capability of the network model.

In this study, a two-dimensional compressible block-structured Cartesian mesh CFD solver was used to perform a numerical analysis of the cross-sectional shapes of the NASA-CRM main and tail wings. The purpose is to investigate the influence of aerodynamic interference between the main wing and the tail. As a result, it was revealed that the lift coefficient and the pitching moment coefficient tend to increase by employing finer mesh. In addition, the flowfields slightly differ with/without the refinement between the main wing and the tail when the wake from the main wing affects the tail.

In this paper, we describe multi-disciplinary optimization (MDO) of a split-tip winglet (STW) model for the TRA2012A commercial jet aircraft model. The STW configuration is expressed by attaching a small wing under the main winglet. The onboard fuel weight, main wing structure weight and the sum of these weights are objective functions, and are minimized respectively in a fixed aircraft operating range for the MDO. The independent component analysis is applied to non-dominated optimal designs obtained from the MDO, and then dominant shape deformation modes are extracted. Design knowledge to improve multi-disciplinary performance is investigated from the modes.

Airfoil shapes of a small vertical axis wind turbine (VAWT) are optimized considering changes in the number of airfoil blades. Airfoil shape parameters, solidity, and number of blades are considered as design variables in this study. The shape optimization is performed using a surrogate model-based global optimization approach. The performance is evaluated by two dimensional unsteady incompressible computational fluid dynamics simulations using ANSYS Fluent. Under our specified design condition, the rotor having two blades is greater performance than that having others blades. The obtained optimal airfoil shape has thicker and positive camber than that of ClarkY airfoil shape. This geometry contributes to obtain a stronger torque from the fluid force and improve VAWT performance.

In this study, the commercial thermo-fluid analysis software scFLOW was used to perform a numerical analysis of the cooling effect of water mist spraying accompanied by the ejection of compressed air from the nozzle. Firstly, a simple nozzle model was used to validate the influence of the sprayed water mist as well as the amount of water mist particles. As expected, the plate was much cooled when the amount of water mist increased. More realistic nozzle model was then used to conduct the cooling analysis for a heated plate. The result showed the vaporization of the water mist particles on the plate increased the cooling effect.

In the field of shape design of machine tools and electronic devices with thermal deformations, shape optimization of thermal elastic fields coupled with thermal conduction and elastic fields is becoming more and more important due to the increasing demand for higher performance. In this paper, we formulate the shape optimization problem for maximizing the stiffness or controlling the displacement in a three-dimensional unsteady thermal elastic field using the adjoint variable and the Lagrange multiplier methods, and theoretically derive the shape gradient function as the sensitivity for updating the shape. The traction method was applied based on the derived shape gradient function, and the validity of the method was confirmed by using the numerical analysis program based on the FreeFEM.

The aging of concrete structures such as infrastructures is becoming a problem in Japan. To automate the maintenance of concrete structures, there is a demand for a system to estimate the location of defects inside concrete structures. In this paper, we propose a method for identifying the location and shape of 3D cavities in concrete structures using machine learning. Acceleration time history data obtained from hammering tests are used as training data, and a convolutional neural network, which is generally utilized for image recognition, is applied to estimate the cavity position and shape. Since the convolutional neural network can retain relative positional relationships within the input information, it can input acceleration response data while maintaining information on the positional relationships of multiple sensors and is considered to be suitable for estimating the location of cavities in concrete structures. For the hammering test data, preprocessing by dividing the acceleration response waveform by the maximum impact force was performed to eliminate the effect of impact force, and it was confirmed that the preprocessing significantly improved the accuracy of cavity location estimation. In this paper, we challenged to estimate the 3D position of internal cavities in concrete structures and presented numerical results and discussion.

Micromotion and stress shielding are issues of cementless stems. In order to avoid them, it is desirable to increase the friction of the proximal part and reduce the elasticity of the distal part of the stem. However, it has not been clarified how the high friction in the proximal part affects the stress transfer of bone. Therefore, we performed finite element analysis using the finite element model of the femur and the customized AM stem with low elasticity we are developing. The bone model was constructed based on femur CT data of a woman. Two bone models were prepared, one that simulated the inside as cancellous bone and the surface as cortical bone, and the other that defined both the inside and the surface as cortical bone. Stem models were prepared with different friction coefficients in the proximal region and elastic moduli in the distal region. When assembling them, we defined friction and coherent mating at the proximal contact and did not apply at the distal contact. In this analysis, we assumed walking conditions, the assembly were applied loads based on the report by Heller et al. Then, the distal end of the bone and the stem head were restrained. Focusing on Gruen’s zone 1 and 7, we investigated the effect of high friction in the proximal part of the stem. As a result, the effect of increasing friction in the proximal part was more pronounced when in contact with cortical bone than in cancellous bone. In fact, since the cementless stem is fixed in contact with the cortical bone, this result suggests that high friction can reduce stress shielding.

In this study, we aim at revealing the damage behavior of HAp sprayed coating on the surface of acetabular cup subjected to cyclic loading using AE (Acoustic Emission) method and IR (Infrared thermography) methods. Loosening of acetabular cups, a major cause of revision surgery of total hip joint, can be attributed to the delamination or wear of plasma sprayed HAp coating on the surface of Ti alloy substrate. However, complex relationships between damages in several places with the extent of displacement of the acetabular cup were not experimentally unveiled. Fatigue test was conducted in SBF(simulated body fluid), and the displacement of acetabular cup embedded in simulated bone was measured by two cantilever pairs. Acoustic emissions from delamination or wear of HAp coating were also measured by AE method, and the temperature change due to friction and wear near the top was measured by IR method. The noise of AE waveform can be removed by DWT (Discrete Wavelet transform), and the measured AE signals were then analyzed its frequency after FFT (Fast Fourier Transform). The analyzed result could estimate the process in which delamination occurs in the initial stage of test and then friction and wear occur. The rotation displacement of acetabular cup could be associated with cracking or delamination of the HAp sprayed coating, friction and wear at the interfaces between simulated bone and acetabular cup. The subsidence displacement of acetabular cup can be caused by collapse of the simulated bone accompanied by an increase in AE energy as well as an increase in dissipated energy. Combined analyses using AE method and IR method clarified that the inelastic damages in simulated bone at the top of acetabular cups could lead the acceleration of both normal and rotational displacement of the acetabular cup whereas interface damages also attributed to exaggerate the displacement by deteriorated fixation.

This research aims at revealing relationships between pores size distribution in porous components with its mechanical properties applying critical porosity by percolation theory. The surgery of artificial hip joints has been persistently increasing due to super-aging society. However, the service lives of the artificial hip joints are unexpectedly limited by loosening, and the extents of loosening highly depends on mechanical property of embedded natural bones. This proposed optimization method is to seek for higher strength of porous components with maintaining its light weight. Compression test of porous polyurethane/alumina composite (simulated bone) showed a critical porosity of approximately 50 % in both yield strength and Young’s modulus. FEM simulations suggested a compatible critical porosity in stress concentration factors which suggest higher stress. The difference in estimated critical porosities can be attributed to stability of deformation in FEM simulations. A framework of determining optimal pores distribution considering interaction of stress concentration is discussed, and optimization method is then considered.

This study aims at revealing the effect on composition on antibacterial properties of hydroxyapatite/titania composite coating deposited by suspension plasma spray. HAp/TiO₂ coating is used for biomedical application especially for antibacterial coating. However, in order to widely use it safely, visible-light sensitivity is important. TiO₂ coating is not effectively activated by visible-light, therefore Suspension Plasma Spray (SPS) system have been used to adjust crystallographic phases of TiO₂ in order to provide them visible-light sensitivity. Prior to deposition, substrates were grit blasted, cleaned ultrasonically and heated to enhance adhesion strength. Microstructure of coating of different composition was then characterized using XRD & RAMAN to identify its crystal structure. All results demonstrated that SPS could transform Ti₂O₃ into TiO₂ with mixed phases. Particularly, XRD data identified Ti₄O₇ & Ti₃O₅ phases, which usually show photocatalytic activity due to oxygen vacancies. Antibacterial test using bacteria is also conducted, and the optimized composition was determined. SPS could produce enhanced antibacterial coating of HAp/Titania composite.

This study aims at investigating loosening behavior of an acetabular cup by interfacial damages. Super-aging society is one of the most popular problems in developed country such as Japan. As a consequence, the need for reliable and durable artificial hip joint replacement also increase since its life span is still a noticeable issue. Among the factors affecting service life, interfacial damage phenomenon have a high impact on dislocation of acetabular cup which lead to loosening of the acetabular cup. In order to investigate effect of interfacial damage on dislocation of acetabular cup, 3 dimensional model of acetabular cup structure was used. Interfacial crack growth was simulated using fracture mechanics model. Validation of stress distribution with theoritical model support the use of fracture mechanic. With higher loading amplitude, the interfacial crack growth mechanism varied which induced an increases in vertical displacement of acetabular cup. The risk of loosening of acetabular cup was quantified using safezone concept.

The purpose of this study was to evaluate the effect of the elastic modulus gradient on the osteoclastic dissolution behavior of the polymer-blend substrate systems. Here, polycaprolactone (PCL) and polylactic acid (PLA) were used to prepare the polymer-blend substrate systems. As the reference materials, neat PCL and PLA substrates were also prepared. The osteoclasts were differentiated from the hematopoietic stem cells. The osteoclastic substrate dissolution behavior was evaluated using a FT-IR. As a result, the activation of the osteoclasts was evident on the neat PLA substrate rather than on the neat PCL substrate, owing to their elastic modulus. In addition, it was confirmed that osteoclasts were more activated on the PLA side, which has the higher elastic modulus, than on the PCL side. It was also confirmed that the difference in the activation degree of osteoclasts decreased with increasing culture period. Therefore, it can be considered that the elastic modulus gradient function of the prepared polymer-blend substrates would be successfully achieved, resulting in the regulation of the osteoclastic activity.

We performed direct numerical simulations to investigate the characteristics of the turbulence structures in axial flow along a thin cylinder with small radii. In this study, the high-speed air flow in axial direction along a thin cylinder were simulated by solving the fundamental equations of compressible flow with density variations. Then, the velocity fluctuation intensities and the friction coefficient were compared to observe the turbulence structures. As a result, the turbulence seems to become laminar when the radius of the cylinder decreases because the vortex structures of the turbulence disappears and the turbulence structures is different from that of a flat plate. However, the friction coefficient at that time is consistent with the value of the prediction formula, and laminarization is not observed in terms of the friction coefficient. In summary, in the flow around a cylinder with the sufficiently small radius, it was found that although there was a tendency for the flow to become laminar, the flow was not completely laminarized and the structures with the characteristics of turbulence and laminar flow existed. Furthermore, the structures are sustained by the velocity streaks leaving surface of the cylinder.

In this study, the flow behavior of highly concentrated CNF suspensions in the shear flow was investigated with stress sweep tests. A stress-controlled rheometer was used as the experimental apparatus to induce the shear flow. Stress sweep tests were conducted after the pre-shear flow and the certain rest time. Consequently, the CNF suspensions indicated twice yielding-like behaviors. In the case of flow-reverse, the flowability was improved up to the first yielding compared to the case of flow-forward. The same behavior was observed for the other concentrations, and the yielding behavior was remarkably appeared as the concentration increased. In order to quantitatively evaluate flowability, the strain profiles up to the first yielding was approximated by exponential function. The flowability was evaluated by the exponent b, which is the slope of the approximate line. As a result, it was found that the flowability in the case of flow-reverse increased with the increasing of the stress sweep rate, while the improvement of flowability in the case of flow-forward was not observed.

High environmental load was reported in the dyeing process. In this study, we focused on effect of fine bubble (microbubble and ultra-fine bubble) mixtures in the dyeing process. Dyeing experiments on the silk, cotton, and synthetic fibers were conducted. High dyeing rate on the synthetic fiber by using both microbubble and ultra-fine bubble was obtained. However, the dyeing rate on the silk or cotton by using microbubble was reduced. Moreover, relationship between the electrical double layer and the test liquids was discussed.

In previous studies, environmental load of surfactant solutions was widly reported. Thus, electrolyzed water has been attracting attentions as an alternative for surfactant solutions. However, the cleaning-tests, which were used by the electrolyzed water, were done by the soaking-test. In this study, combination between an alternating flow and alkaline electrolyzed water (including ultra-fine bubble) was investigated. It was confirmed that the washing rate of electrolyzed water approximate agreed with that of anionic surfactant solutions. Moreover, washing rate of ultra-fine bubble mixtures was approximate 6%-higher than that of electrolyzed water alone.

“Visualization and measurement of thermal fluid flow” is a fundamental topic of interests in the research field of engineering, and the research becomes active since last 50 years. In this presentation, the previous research activity of our research group is summarized for the purpose of future development of this research area in the organized session of Hoku-Shin-Etsu Mechanical Engineering Conference. The research topics considered here are: (1) Flow visualization study around a Savonius turbine using smoke-wire method and particle image velocimetry (PIV), (2) Three-dimensional measurements of temperature field of Rayleigh-Bernard convection at high Rayleigh number using thermo-sensitive liquid crystal thermometry, (3) Evaluation of pressure field around a rotary oscillating circular cylinder in a uniform flow based on PIV measurement and Poisson equation, (4) Measurement of three-dimensional temperature field in combustion flame by flame reaction method combined with tomographic reconstruction analysis, (5) Measurement of three-dimensional shockwave formation of a cavitating jet impinging on wall using cross-schlieren imaging. These visualization and measurement techniques are fundamental basics for investigating the physics of thermal fluid flow of interests and will provide a future development of research area combined with new developments of laser illumination, imaging and computational techniques.

In this study, direct numerical simulation (DNS) and linear stability analysis (LST) of supersonic jets are used to investigate the effects of Mach number on jet transitional structures due to helical mode pair (m=±3) amplification. The jet Mach number is from 2 to 3, which is assumed to be the correctly expanded jet. Numerical results show that in the initial stage of the transition, the vortex structure develops into a Λ-shaped structure, and a region with a large positive radial velocity component appears. This positive radial velocity transports momentum in the radial direction and causes the jet to diffuse.