In the present paper, an adhesive contact between a half-region with axisymmetric wavy surface and a rigid indenter with a profile described by a power-law is analyzed. At first, solutions with and without the adhesive force are derived using the Guduru's theory. A numerical analysis of the adhesive contact is conducted simultaneously using a conjugate gradient method and a convolution integral. In the numerical analysis, the van der Waals force described by the Lennard Jones potential is employed as the adhesive force. The obtained result in the theory is well agreed with that in the numerical analysis. Next, an axisymmetric adhesive contact problem between an elastic wavy surface and a rigid indenter is solved using the JKR theory and the developed numerical method. The result of derived solution based on the JKR theory is compared with that considering the van der Waals force. When the amplitude of wavy surface, A, is less than the atomic equilibrium distance, ε, the maximum adhesion forces for the theory and the numerical analysis are well agreed with each other. On the other hand, in case of A > ε, the adhesion force for the numerical analysis is less than that for the theoretical analysis. In the theoretical analysis, it is assumed that the valley part adheres to the indenter regardless of the wave amplitude. In case of the numerical analysis considering the van der Waals force, the valley part does not adhere to the indenter in A > ε. The maximum adhesion force considering the van der Waals force in the approaching process of the indenter is compared with that in the separating process. In case of A = ε, the maximum adhesion force in the separating process is about 2.4 times that in the approaching process.
Mechanical properties and damage onset stress in 24 or 25-ply unidirectional CFRP laminates that contain different thicknesses and gap lengths of fiber discontinuity are investigated by tensile testing and analytical model. Same damage behavior, as with previously reported, that interlaminar delamination between fiber continuous and discontinuous plies follows after crack initiation at the edge of the discontinuous fibers is observed even if thinner and longer gap of the fiber discontinuities are introduced. It has been shown that the laminates with long gap fiber discontinuity show higher stress of crack onset than that with short gap, and the crack onset stress decreases with the number of the discontinuous plies. A similar trend can be seen for the onset stress of the interlaminar delamination though no delamination has been observed in the short and long gap 1-ply and long gap 2-ply discontinuous laminates. The crack onset stress is evaluated by representing the energy release rate with crack initiation by using stress change in shear-lag model. Due to the fact that the relation between the number of discontinuous plies and crack onset stress can be predicted for both short and long gaps of fiber discontinuity by assuming a certain value of critical energy release rate, it is shown that the crack onset behavior is not affected by thickness and gap length of the fiber discontinuity. Another analytical model with an assumed critical energy release rate has successfully predicted the delamination onset stress regardless of sizes of fiber discontinuities by applying the exact thicknesses of continuous and discontinuous plies. By comparing the predicted delamination onset stress and fracture stress of the laminates, it is concluded that two and more fiber discontinuous plies can affect the overall damage behavior of the laminates.
The high strength bolts and nuts are widely used in engineering structures. To investigate the pitch difference on the fatigue strength of bolt, a slight pitch difference is considered between the bolt and nut. Here, the pitch of the nut is α μm larger than the pitch of the bolt. The fatigue experiment is conducted with varying pitch difference. The results show that the fatigue life is extended to about 1.5 times of the one of normal bolt and nut by introducing the suitable pitch difference under the high stress amplitude. According to the detailed observation on the fractured specimens, it is found that the fractured positions and the crack distributions vary depending on the pitch difference. To clarify the improvement mechanism of the fatigue strength, the finite element method is applied to calculate the stress amplitude and mean stress at each bottom of bolt threads. It is found that the finite element analytical model considering the incomplete nut threads is useful for predicting the crack initiation under different pitch difference introduced.
This paper clarified the effects of solid lubricating sheet for reduction of burr generation and lowering of cutting temperature through examining of drilling in titanium alloy for aircraft. Titanium alloy is difficult to drilling. Moreover worker cannot use plenty of lubricating oil in drilling. So drills are exchanged frequently even if the cost increases. In this study, the temperature of work pieces made of Ti-6Al-4V were measured by thermo camera while drilling. As the results, a height of back burr increases rapidly around 350～400℃ and more. Moreover, in specific range, the solid lubricating sheet can be decreased height of back burr and lowering of cutting temperature compared to without it.
This study describes an efficient estimation method of the structural failure probability based on a limited directional importance sampling simulation. The sampling space is limited to a predetermined directional domain effective to the structural failure probability. In the preliminary stage, executing specified sample numbers of directional simulations, and the conditional failure probabilities in the sampled directions are evaluated by calculating the respective radial distances from the origin to the failure surfaces and determine the minimum radial distance. The conditional failure probabilities in the sampled directions having the radial distances smaller than the minimum radial distance+3 are considered to be effective to the structural failure probability, while the conditional failure probabilities in the other sampled directions having the radial distances larger than the minimum radial distance+3 are considered to have ineffective contributions to the structural failure probability. Then the directional domain containing the conditional failure probabilities having these smaller radial distances is referred to as a limited directional sampling domain, where a directional importance sampling probability density is constructed on the basis of the respective upper probability of the chi-square distribution per unit hypersurface area. By using the directional vector samples generated from the directional importance sampling probability density constructed in the limited directional sampling domain, a directional importance sampling simulation is executed to estimate the structural failure probability. This is referred to as a limited directional importance sampling simulation. Numerical examples to estimate the failure probability of structures with multiple and nonlinear limit state functions are presented to illustrate that the proposed method gives accurate estimations effectively.
In this study, the damage process of Thermal Barrier Coatings (TBC), which were exposed at 1273K for 500hours in advance, under tensile loading was observed continuously, and the influence of exposure temperature on crack initiation strength and interface strength was clarified quantitatively based upon interfacial fracture mechanics. TBC/IN738LC specimen, which is consisted of yttria-stabilized zirconia as top coat (TC) and CoNiCrAlY as bond coat (BC) in TBC, was prepared and the high-temperature exposure treatment was then conducted before tensile test. Continuous observation of damage process was revealed that (i) interfacial crack propagated along the interface between TC and BC in exposed TBC tested at room temperature however the crack propagated along BC/substrate interface in as-sprayed TBC, and (ii) interfacial crack propagated along TC/BC interface in the exposed TBC specimen as well as as-sprayed one. It was considered that the crack propagation path was changed by strong effect of a high-temperature exposure treatment. Quantitative evaluation also revealed that critical strain up to crack initiation in TC was increased by the exposed treatment and number of cracks per length was decreased in contrast with the critical strain. The exposure treatment stiffened top coat layer, which means that cohesive strength between splats became stronger. The interfacial fracture energy of the exposed TBC specimen was lower than that of as-sprayed one. Therefore, in order to assess precisely remaining life of main hot-parts of gas turbine, data for as-sprayed TBC is needed as initial information.
The purpose of this study is to investigate the dominant factor on the fracture strength of thin film comprising of copper (Cu) helical nano-elements, which are grown by the glancing angle deposition technique. By changing the deposition angle in the GLAD, three types of thin films with different number density of Cu helical nano-elements are produced. Crack initiation experiments are carried out using cantilever specimens where the thin film is constrained by a substrate and a stainless cantilever. Near the edge of thin film, the critical forces applied to Cu helical nano-elements at the fracture are mostly consistent regardless of the number density of nano-elements although the critical average stresses are different. This result signifies that the fracture of the thin film is governed by the strength of nano-element.
In fluid power systems, a Helmholtz type hydraulic silencer is often utilized in order to attenuate pressure pulsations, which are detrimental to the system because of the vibration and noise that they generate. The silencer has the important feature that it is effective within a narrow band range around the resonance frequency. Therefore, it is very useful to be able to predict the attenuation characteristics by means of a mathematical model. Previous research has shown that there are noticeable discrepancies between the experimental values and calculated results when the ratio of the volume length L to diameter D is comparatively small. In this paper, a novel distributed parameter model was proposed in order to examine these discrepancies. The mathematical model was derived by taking into account the elastic deformation on the upper and lower vessel walls of a Helmholtz silencer with a flat volume. The analysis revealed that the resonance frequency of the silencer is reduced by a reduction in the volume length or by a reduction in the cover thickness. The reason for this is the reduction of the effective bulk modulus. In addition, experimental work was conducted to examine the attenuation characteristics under various conditions. The experimental results were found to correspond to the mathematical model qualitatively.
Synthetic jets are produced by periodic ejection and suction of fluid from an orifice induced by movement of a diaphragm inside a cavity, and a synthetic jet actuator is a useful tool for active flow control. The synthetic jet actuators are low operating power, zero-net-mass-flux and very compact devices which have demonstrated their capability in modifying the subsonic flow characteristics for boundary layer flow control. For the synthetic jet, the effect of the orifice shape on the vortex ring behavior has not been completely clarified yet. In the present study, the deformation process of the vortex ring in a quiescent fluid formed by a synthetic jet and the interaction between the vortex ring and a crossflow were investigated by using three types of orifice shape (a circular and two rectangular orifices). Furthermore, the three-dimensional vortex structure in the boundary layer was depicted by means of a scanning stereoscopic PIV measuring system. The breakdown of the vortex ring in quiescent flow occurs at a short distance from the orifice exit for the rectangular orifice. In the case of the synthetic jet into the crossflow, the jet deflects towards the crossflow direction with a shorter distance and vortices exist near the lower wall for the rectangular orifice with the long side of the orifice set in the spanwise direction in contrast to the other orifice shapes.
Measurement and numerical simulation of the interfacial area concentration and the void fraction were carried out to develop transport equation of interfacial area concentration to fulfill the requirements of an improved prediction accuracy of gas-liquid two-phase flow behavior. Measurements in a vertical upward air-water two-phase flow were conducted at the conditions of ambient temperature and atmospheric pressure. Test section was a round tube of 50 mm in inside diameter. The superficial gas velocity and the superficial liquid velocity ranged from 0.02 to 0.12 m/s and from 0.17 to 0.85 m/s, respectively. Two types of bubble generator were used in this study. One is that air was injected from the wall of the flow channel to the water (wall injection type). The other one is that air was injected from the pipe located at the center of the flow channel (pipe injection type). Measurements of the void fraction and the interfacial area concentration were performed using double sensor electrical resistivity probe at five axial locations of z = 45, 275, 575, 805, and 2365 mm for the wall injection type of bubble generator and z = 110, 410, 640, 1170, and 2230 mm for the pipe injection type of bubble generator, and transverse locations from r = 0 to 23 mm. In the numerical simulation, a transport equation of interfacial area concentration was developed in the previous study. This equation is validated by the previous and present experimental data. Consequently, good agreement is obtained between these results.
An abrasive suspension jet (ASJ) formed by propelling abrasive suspension through a nozzle has a greater cutting capability than the conventional abrasive water jet. However the cutting capability of submerged ASJs decreases drastically with increasing the standoff distance and the pressure around the jet. A sheathed nozzle with ventilation for ASJs has been developed as a mean of extending the effective stand-off distance and improving the cutting capabilities under submerged condition. In the present investigation, cutting tests by ASJs in air and under submerged condition are conducted with specimens of aluminum alloy. Air coated ASJs are formed by using a sheathed nozzle with ventilation. The relative cutting depth is defined as the cutting depth under submerged condition divided by the cutting depth in air at the same standoff distance. The relative cutting depth is arranged effectually by the cavitation number based on the cavity pressure measured at the sheath.
While the Navier boundary condition, which claims the proportionality between fluid slip velocity and wall shear stress (Qian et al., 2003, Bocquet and Barrat, 2007), was established by Thompson and Troian (1997) for a single-phase Newtonian fluid flowing along an atomically defect-less solid wall under a wide range of shear rate conditions, its validity for flows with a contact line has not been proved yet even for the simplest pairing of a monoatomic fluid and a solid with a face-centered cubic structure. In the studies of Qian et al. (2003, 2006) the static wall shear stress was subtracted in the formulation of their Navier boundary condition, but as we show, it is not physically justified. Ren and E (2007) formulated a Navier boundary condition in terms of the fluid slip velocity and wall shear stress integrated through the region containing the contact line in a similar fashion to the present work, providing no physical grounds regarding their particular choice of the integration region and the interfacial region. We performed molecular dynamics simulations of Couette flows where two immiscible liquids with an identical molecular mass and identical interaction potentials were driven by two parallel solid walls so that steady flows with moving contact lines were formed. Based on the detailed analysis of stress tensor and slip velocity distributions both for static and dynamic cases, we show that the Navier boundary condition should be formulated in terms of the quantities integrated through the fluid-fluid interaction region in the first adsorption layer formed on the solid wall. In order to investigate the relevance of the Navier boundary condition as a boundary condition of the Navier-Stokes equation, the validity of Newton's law of viscosity between the first and second adsorption layers is also examined.
We have studied the spray atomization of a multi-swirl injector with three orifices. Hollow-cone spray interactions and the flow field inside the nozzle were investigated by experimental observations and numerical simulations. First, the effects of the spray interactions on the spray atomization were investigated by optically measuring the spray patterns and the Sauter mean diameter (SMD) using the laser diffraction. The spray patterns indicated that the sprays from each orifice interact under the orifices, and this interaction can be classified into two types: liquid-film collision and droplet collision. In the case of the liquid-film collision, the collided liquid films are supposed to merge and then break up into larger droplets. In comparison, droplet collisions have a small effect on the value of the SMD in our experiments. Second, numerical simulations were conducted to investigate the flow field inside the orifices. The simulation results showed that a liquid film was formed along the side wall of the orifice, and the liquid film of the three orifices was thinner than that of the single orifice. From the experiments conducted above, smaller SMD was measured in the case of three orifices with droplet collision. These facts imply that the droplet diameter is decreased in the case of the three orifices. Finally, we proposed a modified atomization model to calculate the mean droplet diameter of the hollow-cone spray from the film thickness and velocity at an orifice outlet. The film thickness and velocity were calculated by the internal nozzle flow simulation. Although the modified atomization model underestimates the SMD under the liquid-film collision condition, it agrees well with the measured SMD under the droplet collision condition.
We have investigated transition of aggregate structures of a suspension composed of cubic hematite particles in the situation of thermodynamic equilibrium. Monte Carlo simulations have been carried out in order to investigate the dependence of the transition of aggregate structures on the magnetic field strength for various cases of the magnetic particle-particle interaction strength. From the viewpoint of applying a magnetic particle suspension to a surface changing technology, we here consider a two-dimensional system of the cubic hematite particles. Radial distribution functions and order parameters are used for quantitatively discussing in the present results. The main results obtained here are summarized as follows. The cluster formation of magnetic particles significantly appears for a strong magnetic interaction larger than a certain value. In a weak applied magnetic field, the particles tend to aggregate to form thin chain-like clusters if the magnetic particle-particle interaction is relatively small. If the magnetic field is increased, these thin chain-like clusters become thick chain-like clusters. In no external magnetic field, the particles tend to aggregate to form clusters that have large grid-like structures if the magnetic particle-particle interaction is sufficiently large. If the magnetic field is increased, these clusters become thicker chain-like clusters with these grid-like structures. This clearly implies that an applied magnetic field induces the transition of aggregate structures in a cubic hematite particle suspension.
Recently, in the human-centered design of the car seat, mutual interactive relationship based on structural dynamics of the human-machine system has been analyzed, and this technique is used to the methodology for the automobile design. However, these topics have been studied for only vibration measurement in a steady state and studies to analyze human body behavior in practical lateral-directional transient acceleration have not been performed yet. The purpose of this study is to simulate biomechanical body behavior of vehicle occupant in lateral-directional transient acceleration. The proposed experimental device has characteristics of low cost and simplicity of use. The used experimental device is composed of the carriage, the car seat, rubber band, cushion, motion capture system and mobile force plate. In this paper, the seated body behavior with lateral-directional acceleration is simulated. Moreover, each joint angle and each ground reaction moment through the experiments are calculated and quantitatively evaluated by using this experimental device and singular value decomposition. As results of the experiments, each movement pattern reflected by lateral-directional transient acceleration is obtained as the remarkable feature quantities because the influences of the characteristic lateral-directional behavior on the human body are shown. Finally, the effectiveness of the proposed measurement technique and method to analyze the biomechanical behavior of vehicle occupant during lateral-directional transient motion and its quantitative evaluation based on singular value decomposition are validated.
The spent fuel taken out of a plant reactor is temporarily stored in a spent fuel rack. This fuel will often have to be stored in the rack for long periods before it can be moved to a reprocessing facility. Therefore, the spent fuel rack must have a high tolerance against big seismic loads. The free standing spent fuel rack has been developed as the optimal equipment meeting these requirements. It can be placed on the spent fuel pool floor without fixation to any support structure. Response of the free standing rack is reduced by the effect of the water and friction force on the spent fuel pool floor. For nuclear plant safety, it is necessary to understand the free standing rack behavior under earthquake in pools to verify the design of free standing racks and peripheral components. Several tests on a shaking table have been conducted on full-scale one free standing rack in air and in water, and sliding and rocking have been measured. The rack response is very complex and the study necessitates to take into account the sliding, the rocking, the effect of the water and of the arrangement of the fuel assemblies inside.
Recently, cooling fans have been used for not only general industrial machines but also precision machines, such as medical care products and optical equipment, and these generate more requirements about vibration limitations. The main vibration of cooling fans caused by rotating unbalance and resonance has been reduced, so electromagnetic vibration, which was not considered before, now has to be reduced. The purpose of this study is to control the electromagnetic vibration of 2 poles three-phase induction motors that rotate fast, such as for cooling fans. In this paper, it is shown that the type of magnet wire specification controls electromagnetic force and electromagnetic vibration by using the simulation results of a 2 dimensional magnetic finite element method (FEM), as well as a 3 dimensional structural FEM, both of 2 poles three-phase induction motor that has an output of 70W.
This paper presents a portable tree felling manipulator which has never been developed so far in Japan. A man-made forest is in an urgent need for logging. Furthermore, many fatal accidents and severe injuries occur during tree felling operations. These accidents are mainly due to cutting inaccuracies, with respect to falling directions of downed trees, of chainsaws operated by humans. And Japan's forests are precipitous, wet, humid and soft terrain, with great temperature fluctuations and a low logging road density. The device must withstand such environmental conditions. Based on these authors' research results, a set of design requirements is established. The manipulator must be as simple as possible as a mechanical apparatus so that operators may conduct maintenance and repair work themselves. And the manipulator must be small and light for one person to carry. And for reaching the stage of practical use, it is equipped with an engine chainsaw commonly used throughout logging sites. And then the prototypes that embodied ultimate simplicity in its shape and mechanism were devised. The authors developed the manipulator composed of 4 degrees of freedom required minimum. To operate the manipulator, and they also developed a control system with a software program that converts rotational motions of the manipulator joints into linear sawing motions. A demonstrative model was built, experimented on, evaluated for its performance using standard evaluation methods adopted by the forestry industry, and verified to be effective. The results of experiments clearly explain that the safety of the felling operation by the proposed manipulator was successfully demonstrated.
This study presented a contactless method to measure vibration-induced stress (vibration stress) using multiple laser displacement sensors and the applicability of the method was investigated using beam theory and vibration test. First, the measurement errors were discussed based on the beam theory when the method was applied to the measurement of piping vibration. The classification of the errors caused in the measurement was clarified and the measurement accuracy was estimated by taking these errors into account. Next, the vibration test by the random excitation using the beam-plate was conducted and the applicability and measurement accuracy of the presented method was examined. By comparing with the vibration stress values measured by the conventional method using strain gauges, the presented method was demonstrated to be applicable to the vibration stress measurement. Additionally the awaiting solution for the practical use was extracted.
Under earthquake condition, the response of the free standing rack is nonlinear and involves complex combination of motion, such as sliding, rocking, twisting, and impacts between the fuel assemblies and the rack cells and between the pool floor and the rack pedestals. To obtain an accurate simulation of the free standing rack, the seismic analysis requires careful considerations of these complex phenomena, and fluid coupling effects. This seismic evaluation method was validated by comparison to full-scale test results. However, the conservative evaluation method is required, since analysis results are not entirely consistent with the test results. In this study, authors obtained the margin of safety for free standing rack, and developed the seismic design method.
New robotic system that uses three dimensional measurement with solid object recognition—3D-MOS (Three Dimensional Move on Sensing)—based on visual servoing technology was designed and the on-board hand-eye-dual-cameras robot system has been developed to reduce risks of radiation exposure during decontamination processes by filter press machine that solidifies and reduces the volume of irradiation contaminated soil. The feature of 3D-MoS includes; (1)the both hand-eye-dual-cameras take the images of target object near the intersection of both lenses' centerlines, (2) the observation at intersection enables both cameras can see target object almost at the center of both images, (3) then it brings benefits as reducing the effect of lens aberration and improving the detection accuracy of three dimensional position. In this study, accuracy validation test of interdigitation of the robot's hand into filter cloth rod of the filter press—the task is crucial for the robot to remove the contaminated cloth from the filter press machine automatically and for preventing workers from exposing to radiation—, was performed. Then the following results were derived; (1) the 3D-MoS controlled robot could recognize the rod at arbitrary position within designated space, and all of insertion test were carried out successfully and, (2) test results also demonstrated that the proposed control guarantees that interdigitation clearance between the rod and robot hand can be kept within 1.875[mm] with standard deviation being 0.6[mm] or less.
The flatness of the metal thin plate shape is required in the production lines. Though, the convenient method for measuring small buckles of the thin plate has not been established. The tension distribution corresponding to the strain distribution occurs adding the strip running tension to the buckled thin plate. We propose an identification method by using natural frequencies and vibration modes, which are related to tension distributions of the thin plate. In this paper, a new tension identification method in the thin plate using modal analysis method is investigated. We develop a simplified dynamic model of the thin plate, and tension distribution is modeled by springs. A simplified model spring constants are obtained by the least-squares method, which minimize the difference between a simplified model modal parameters and the measured values. We applied the modal analysis method based on subspace system identification theory to measured vibration characteristics of the thin aluminum plate under operating lines. As a result, it is shown that identified tension distributions are valid result to the straightening line.
Dynamic model is necessary to predict the product performance in numerical simulation; strength of structure, noise and vibration. An experiment must be performed to identify the model parameter such as structural properties of installed or completed products because of preventing deterioration of prediction accuracy accompanying product dispersion and aging deterioration. Although several identification methods for elastic beams with frequency equation have been proposed in the previous studies. In these methods, the structural properties were derived from natural frequencies of the beam with/ without additional weights. The structural properties are not uniquely determined due to various factors such as boundary conditions and additional weights. Especially, no study deals with experimental conditions to enable the high prediction accuracy. This paper proposes novel methods to identify the structural properties of elastic beams of homogeneous, uniform cross-section in the lengthwise direction with free-free condition. In addition, the effects of controllable experimental parameters on the accuracy are examined. Two identification methods of the structural properties are derived; one is based on the frequency equation of the beam and the other is mass response method. It is necessary to measure natural frequencies of the beam with/ without additional weights on the beam to use both methods. The former can treat the change of mode shapes due to the additional weights, whereas the latter assumes that the mode shapes are unchanged. Finite element models are developed for validation of both methods. Various experimental conditions are adopted and the accuracy of the identified parameters by the both methods is compared. The mode shapes of the free-free beam are changed with additional weights. Thus, the method using the frequency equation is more applicable to the beam with the additional weights. Finally, the method based on the frequency equation of the beam is validated through the experiments.
Cervical Cord Injury(CCI) causes a upper limb dysfunction. In an individual with C5-level CCI, which is the most frequent of all eight types of CCI, flexion force can be exerted by the biceps brachii, while extension force cannot be exerted by the paralyzed triceps brachii. Without the ability of the triceps brachii to exert this force, individuals with a C5-level CCI cannot operate a wheelchair along a carpet or sloping road. In this study, we developed an exoskeletal wheelchair operational assistance robot. We first developed a upper limb motion assistance robot. We then analyzed the difference between the wheelchair operations of a healthy person and a C5-level CCI. We designed a control model that included a user and a wheelchair. The wearer's arm was modeled as a two-link manipulator, and the extension force and hand position were estimated using the equation of motion. The estimated extension force was compared with the driving force required to operate a wheelchair with the target velocity defined at the time of flexion of an arm. We then applied the proposed method via an exoskeletal robot. The effectiveness of the proposed method is demonstrated by the experiment of wheelchair operation with C5-level CCI.
Trans-femoral amputees are needed to regain moving pattern by refined rehabilitation program using load conditions on a prosthetic limb with the artificial knee joint. On the other hand, understanding loads applied on a prosthetic limb is important for biomechanical consideration of trans-femoral amputees. It is thought that inverse dynamics analysis is the most comprehensive method to obtain the joint reaction forces and the joint moments during gait for refining rehabilitation program of trans-femoral amputees. However, this method is highly constrained in respect to modeling of trans-femoral prosthesis and procedure of numerical computation. Alternatively, a multi-axis force/moment sensor can be used to directly measure loads applied on the middle part of trans-femoral prosthesis. In this paper, results of inverse dynamics analysis based on rigid link model and musculoskeletal model of human whole body by using motion capture system are compared with ones of direct measurement of lower thigh concerning trans-femoral prosthetic gait and comprehensive agreement is obtained. In addition, singular value decomposition extracted the pattern of operation with high correlation from joint force and joint moment also in the joint cooperation operation because quantitative evaluation technique of the various physical quantities during gait using principal component analysis has been proposed. Finally, the validity of inverse dynamics analysis and the effectiveness of the developed prosthetic gait training system to analyze comprehensive kinetic phenomena for trans-femoral prosthetic gait are validated. Especially, different specific loading pattern of downstairs walking will be useful to refine the rehabilitation protocol for trans-femoral amputees with a prosthetic limb.
This article presents a multi dynamic absorber for suppressing liquid sloshing in a floating roof tank. The presented multi dynamic absorber uses U-tubes set on the floating roof. Many seismic damages on floating roof tanks by the sloshing of the contained liquid in the tank due to long periodic components of earthquake were reported. Since the natural period of sloshing varies according to the liquid height, robustness for parameters variances such as natural period is required for the sloshing suppression device to obtain a good performance. From this point of view, a multi dynamic absorber is developed instead of the single dynamic absorber which is sensitive to the parameter variance. A multi degree of freedom mechanical model for sloshing of the contained liquid and the presented multi dynamic absorber on the floating roof of the tank is derived to design the optimal tuning and optimal damping for parameters of the multi dynamic absorber and to evaluate the sloshing suppression performance. Numerical simulations on two kinds of actual size floating roof tank are conducted to examine seismic response of the present device as well as the transfer function characteristics. As the result the presented multi dynamic absorber is effective to suppress the sloshing of the floating roof.
With the development of box structure like a car or train, noise reduction is required for such structures with cabin inside. Noise problem with structural vibration has been studied as coupled structural-acoustic system. In a previous research, we proposed an identification method for acoustic dominant coupled mode accompanied by resonance mode. It is considered to noise reduction by structural modification using a coupled mode characteristics. The purpose of this study is ”to carry out noise reduction for the acoustic dominant mode by the structural change ”. A method is proposed that modifies structural modal characteristics based on dynamic absorber mechanism. In the method, acoustic system is regarded as a main system and the structural system to be changed is regarded as an additional system. The proposed method is verified by FEM simulation. Results of numerical analysis are showing the sound pressure reduction effect. For validation of the practicality of the method, experiments using a car are carried out. The relationship between sound pressure reduction effect and excitation conditions to the structural system is verified. Through the experiments, it is shown that the noise reduction due to structural modification in the coupled system is possible. The necessary condition for applying the proposed method is also examined.
We propose a method that corrects effects of refractions and absorptions for underwater scan data obtained by general-purpose laser range finders (LRFs) using HOKUYO UTM-30LX (Top-URG). For measurements by LRFs in water, it is known that refractions make measurement distances longer and absorptions make reflection intensities weaker. In order to confirm those characteristics of measurements in water, we first conduct two basic experiments that Top-URG measures a target in the environment with the assumed turbid deep-sea and evaluate an accuracy and a performance of Top-URG in water. The first basic experiment is that Top-URG measures surroundings in a sink filled with water by changing the turbidity of the water. The second basic experiment is conducted by changing a location and an angle of a target. Next, we develop a method that (1) corrects scan data of Top-URG by considering a refractive index of water and (2) eliminates scan data with low reliabilities based on reflection intensities obtained by Top-URG using automatically calculated thresholds. We evaluate those two methods by using two types of target objects and seven situations. Our developed methods can correct distorted scan points by refractions in water and can eliminate ghost scan points which are not existent. We confirm that their performances for underwater scan data are effective enough to use Top-URG in water.
It has been said that the end of Moore’s law will be reached in 10 to 20 years. Three dimensional integration technology is expected to be a possible solution in the post-Moore era. The bonding of the metal electrode and insulator hybrid interfaces is one of key technique in three dimensional technology. The hybrid bonding technique is highly challenging issue. Surface activated bonding (SAB), which is a bonding method carried out at room or low temperatures, is expected to solve various problems which caused by heating process. Metal materials such as Cu or Al are easy to directly bond by SAB method at room temperature, but insulator materials such as SiO2 or SiN is very difficult. First, we investigated the bonding interface of Cu/Cu by transmission electron microscopy (TEM) observations. No intermediate layers or voids were visible at the bonding interface. The bonded specimen fractured not at the interface of the bonded Cu/Cu, but at the interface between the thermal oxide layer and Ti film by tensile test. The current-voltage characteristic of the bonding interface was linear. Secondly, we proposed a new bonding technique for bonding of SiO2/SiO2 using Si ultra-thin films by applying the SAB method. The amorphous Si layer with the thickness of about 7 nm was observed at the bonding interface by TEM observation. The bonded specimen fractured at the glue interface and not the bonded interface by tensile test. The bonding strength is estimated to be higher than the adhesive glue for tensile test. We have shown that the SAB method at room temperature is a bonding technique that can fulfill requirements for hybrid bonding, which serves as both mechanical bonding and electrical connection, in 3D integration technology.
In 1st report, the authors presented Galerkin-based meshfree modeling for folded plate structures. A flat shell formulation was developed including drilling rotation components, and multiple point constraint technique was introduced to model the folded plate structures. Effectiveness of the meshfree modeling and accuracy of the linear analysis were discussed. In 2nd report, the geometrical non-linear analysis is presented. The non-linear problems are solved employing total Lagrange formulation based on convected coordinate system. The drilling rotation is included in the meshfree discretization. In the numerical example, several geometrical non-linear analyses are analyzed to validate the proposed method.
This paper deals with the numerical analysis of coupling phenomena between fluid flow and the deformation of solid. The fluid is treated as a weakly compressible liquid and the solid is treated as a linear elastic body. Both fluid and solid are described by the smoothed particle hydrodynamics (SPH) method. The numerical method proposed in this paper needs no additional conditions at the interface between fluid and solid. When the contribution of stress terms to the momentum equations is considered near the interface, the SPH summation is extended to all particles regardless to their nature, that is a fluid particle or a solid particle. Thus, the coupling condition on the interface is automatically satisfied. To validate the performance of the present method, several benchmark problems are solved. Those problems are the well-known dam-breaking problem, the bending oscillation of a cantilever and the deformation of an elastic plate due to time-dependent water flow. The computed results are in good agreement with available experimental and numerical results. Finally, the present method is applied to the simulation of the fracture of an elastic plate due to water flow.
In this paper, study on the effects of axial feed rate on the gear accuracy is discussed. First, geometrical model of a skiving process was introduced. The model was assumed that the cutter was perfectly made and perfectly assembled to the skiving rig (i.e., no cutter manufacturing error and inevitable set-up error was taken into account). Based on this model, geometrical analysis under the condition of different axial feed rate was conducted, where profile deviation and lead deviation were calculated. Secondly, experiments under the same condition as the geometrical analysis were carried out. From geometrical analysis, it was found that the effect of axial feed rate on the profile deviation and lead deviation were very small (less than 1 µm), which makes it negligible practically. In both analysis and experiments, profile deviations and lead deviations increased as feed rate increased, and profile deviations were larger than lead deviations. However, the profile and the lead deviations obtained by experiments were much larger compared to those of analytical ones. Improvement of the model is needed, however, it was found that the model is useful in estimating the overall deviations in a skiving process.
Human arm operation in driving motion can be classified into the two categories of steering wheel and gear stick manipulation. In this study, the operational characteristics of a human-steering system were experimentally analyzed in consideration of the mechanical properties of the human arm and related effects on muscle activity. The results highlighted three points in particular: (1) positioning to facilitate operation as well as the operational direction of the steering column angle and fore-and-aft positions can be determined on the basis of force manipulability in consideration of human joint-torque characteristics; (2) subjects feel that handling is easier when arm muscle activity is low during steering wheel operation; and (3) arm positioning and body pressure distribution have a very significant effect on arm muscle loads. Comprehensive consideration of these results is expected to be useful in the design of human-vehicle steering wheel systems.
A transfer from a wheelchair to bed is difficult for wheelchair users without assistance. Because they must lift their bodies up and move from a wheelchair to bed by themselves. So transfer without assistants puts a strain on them and associated with a risk of fall. Some lifts or assist systems called transfer aids are developed to help transfer, nevertheless they needs assistance. Lifts need large space to use and it is hard to carry. To attach the transfer aids, wheelchair needs to be modified. The aim of our study is to develop a transfer aid which can be used by a wheelchair user without assistance. This transfer aid can attach to wheelchair without improvement. And it can be carried easily so wheelchair users can use it everywhere. The developed transfer aid has the spread mechanism that users feel trouble-free to spread the transfer aid. Only by the simple motion of two axis, wheelchair users can spread the transfer aid. The developed transfer aid succeeded to users transfer themselves. And users can transfer more safely and quickly because the developed transfer aid are attached firmly to a wheelchair. One user can transfer by cross direction by using developed transfer aid who usually transfers by forward direction.
Braille is a well-known communication tool for the visually impaired. In recent years, as a result of advances in Braille printing technology, the use of transparent resinous ultraviolet cured type (TRUCT) Braille has spread rapidly. As one of the most popular Braille printing technologies, the screen printing method is applied for printing TRUCT Braille. However, the screen printing method produces TRUCT Braille prints of poor quality. In this study, in order to improve the printing quality, we created a device for printing TRUCT Braille. Additionally, we evaluated TRUCT Braille readability for Braille beginner readers by focusing on horizontal and vertical Braille dot distances using our created device. From this study, we found that it was easy to print TRUCT Braille using our device. Braille beginner readers found it easy to read TRUCT Braille with adequate horizontal and vertical Braille dot distances. These findings support the use of TRUCT Braille for new Braille beginner textbooks, as well as for printing Braille signs in public facilities.