An accurate fracture estimation of carbon fiber reinforced plastic (CFRP) is indispensable for adequate design with reliability and economization of high pressure hydrogen tank made by filament winding (FW) method for automobile. Authors have approached to the burst pressure estimation problems of the tank substituted by cross shape specimen representing fiber bundle situation in CFRP layer of the tank. The specimen is manufactured by filament winding machine to form crimps of fiber bundles crossover by right angle. Its mesoscopic structure of fiber bundle and matrix resin is precisely modeled for the finite element analysis. Highly non-linear material model of resin strength has been developed to predict breakage load and elongation of the specimen under biaxial tensile test. We have elucidated strain-rate dependency and tension-compression asymmetry in resin strength, and transverse strength of fiber bundle govern the fracture process of the specimen. Other types of specimens, such as unidirectional, crossover by 45 degrees with crimps and layered by right angle, are employed to demonstrate the validity of the proposed methodology.
The surface velocity model is proposed for modelling the flow caused by a DBD plasma actuator. While numerical model presented up to now for the DBD plasma actuator, i.e. Suzen’s model, needs to calibrate the five parameters that must be determined by comparison with the experimental results, the surface velocity model presented here requires calibrating three parameters only. The flow by the surface velocity model is compared with the experimental results and that of Suzen’s model. When DBD plasma actuators are activated on the surface of the flat plate or on that of the circular cylinder, the induced flow appears near the electrode. And then the temporal and spatial development of the flow by the surface velocity model is consistent with the results from the experiment and the Suzen’s model. The surface velocity model is very easy to use compared with the Suzen’s model, and it can well simulate the induced flow caused by the plasma actuator.
In this paper, a numerical simulation for a standing-wave thermoacoustic refrigerator using the equations of conservation law are proposed. In this simulation, the gas flow in the thermoacoustic refrigerator is expressed by the quasi one-dimensional model to reduce the computational load. Since the equations of conservation law are solved directly in the simulation in contrast to the conventional analysis applying the thermoacoustic theory, our simulation is excellent in adaptability and extensibility and can be used for developing actual machines. The equations of continuity, motion, energy and the state of the gas were solved utilizing a TVD scheme for the spatial difference and Heun’s method for the time difference. The numerical simulations were performed on ten types of thermoacoustic refrigerators having regenerators of different thermophysical properties and hydraulic diameters, and the simulation results were compared with the corresponding experimental results. As for the results, a heat pump effect, or thermoacoustic refrigerating effect, was observed successfully by means of our simulation. The highest thermoacoustic refrigerating effect was obtained when a product ωτ of angular frequency of sound wave ω and thermal relaxation time τ was around 5, and the result agreed well with the previous research. Furthermore, the simulation results of thermoacoustic refrigerating effect for the different types of refrigerators were consistent with experimental results within an error of 10%. These results verify the validity of our proposed simulation method.
The combustion in a rotary engine has been investigated in terms of the flame propagation on the rotor flank and the information obtained simultaneously from the working chamber pressure. An experimental overhanging eccentric shaft-type single rotor engine was used, which was equipped with a multichannel packaged slip ring to take out the signals of 15 uniformly-spaced ionization gaps on the rotor flank. The measurements were made under the experimental conditions of various air fuel ratios, ignition modes (leading spark plug only and trailing spark plug only, dual spark plugs and triple spark plugs) and intervals between leading and trailing spark timings. The effects of flame propagation patterns on P-V diagrams, heat release rates, indicated mean effective pressures and indicated specific fuel consumption ratios are discussed. The flame propagation at the center in the rotor width direction was found to occur in order of the front part, the rear part, the center part of the rotor recess, the front part of the leading side of the rotor, and the rear part of the trailing side. Also the flame could propagate to both corners on the rear part of the trailing side of the rotor later than 150°ATDC.
Partial combustion is applied for tar reduction in the gasified-gas of woody biomass. An inverse diffusion flame was formed in partial-combustion-type gas reformer. Pyrolysis and polymerization of tar occur simultaneously at the vicinity of the combustion reaction zone where exothermic reaction is active. Since soot formation could be a significant problem in the partial-combustion-type gas reformer, it is desirable to suppress soot formation. Temperature is one of the most important properties in the process of reforming tar, and it governs the decomposition of tar and the formation process of soot. In this study, we tried temperature measurement for inverse diffusion flame formed in partial-combustion-type gas reformer by two color pyrometry. A calibration method of two color method using radiation from thermocouple are proposed. Furthermore, the influence of the concentration of carbon dioxide and steam in the oxidizer agent on the temperature field of the inverse diffusion flame are investigated by using the partial combustion gas reformer. The flame structure taking into consideration the flame temperature of the inverse diffusion flame was clarified. Results show that the presence of carbon dioxide and steam in the oxidizer affects the temperature field of inverse diffusion flame. With the concentration of carbon dioxide and steam in the oxidizer increases, the flame temperature decreases. We also find that adding carbon dioxide or steam into the oxidizer affects the accuracy of the temperature result which used two color pyrometry.
Purpose of this paper is to reduce the response of rocking vibration mode of vertically isolated equipment. The rocking vibration is the motion that the top of equipment vibrates as the fulcrum in a bottom end. According to the low vertical stiffness of vertically isolated equipment, the rocking vibration is largely excited by horizontal earthquake motion. In this paper, a dynamic absorber is developed in order to apply to the rocking vibration of the vertically isolated equipment. The proposed system is a rolling pendulum type dynamic absorber using magnetic damper, which is composed of circular rails, a rolling body including magnets and a conductor plate. The design method for the dynamic absorber and the evaluation method for vibration reduction effect are showed in this paper. The dynamic characteristics are also examined by vibration test. It is confirmed from the vibration tests using a rocking model apparatus that the proposed dynamic absorber is effective for rocking vibration reduction.
A magnetic suspension system with three flux-path control mechanisms are developed to achieve three-dimensional positioning of the suspended object (floator). In the flux-control mechanism, a ferromagnetic control plate is located in the lateral direction of the magnetic source (permanent magnet). It was shown that the attractive force acting on the floator could be varied by moving the control plate in the vertical direction. In addition, the lateral force was generated by using two control plates located on both sides of the floator and moving them differentially. In this work, an apparatus is fabricated which has three flux-path control mechanisms. The configurations of the apparatus are described. Stable suspension is achieved and basic characteristics are studied. In addition, 3-degree-of-freedom (3-DOF) control suspension is achieved by moving three control plates individually. The 3-DOF control is evaluated by moving the floator in circular orbits.
The 2011 off the Pacific coast of Tohoku Earthquake had the largest energy in recorded history of Japan and it caused severe damage. The damage occurred in a large area as well as the Tohoku in various ways. Electric power was one of them. Therefore, rolling blackouts were carried out with lack of power supply in a part of the East Japan. The electric power is indispensable because restoration activity advances at a disaster area. Moreover, Japan is the highly advanced information society. The steady supply in case of the emergency is expected while a large earthquake whose seismic center is Nankai trough is predicted. Therefore, it is necessary to improve seismic proof construction of power plants. At present, the most common type of power generation in Japan is thermal. Even among them, coal-fired power plants become base load power. A proposal of authors is application of vibration control using damper to boiler structures. This study shows the effects while the earthquake with long period component and long duration was used. It is concerned that the damage of the high-rise structure like boiler structure becomes critical by the long period component. Moreover, the durability of the structures and devices is required higher than conventional by the long duration. In this study, authors developed a damper to use for vibration control of the boiler structure and showed the analytical and experimental results of applicability for the earthquake with long period component and long duration of it.
This paper presents a theoretical analysis of the dynamic interaction of a vehicle-passenger-inclined highway bridge. The mathematical vehicle-passenger model has 12 degrees of freedom: a vehicle model with four masses has six degrees of freedom, and an occupant model with four masses, which is the hinged beam model, has six degrees of freedom. The modal analysis technique using equations of motion are adapted for an inclined highway bridge. By considering both longitudinal and transverse vibrations, the governing differential equations of motion for the bridge are derived. The random roughness of an actual highway surface has been considered in the analysis. During application of the analytical system, the effects of an inclined angle of the highway bridge and speed parameter on vehicle and human dynamic behavior are investigated. The inclined angle is examined in the range of -20° to +20°, and the speed parameter is examined in the range of 0.02-1.5. These factors are found to exert significant influence on the mechanical behavior of vehicles, passenger, and inclined highway bridge. Some results are presented in the form of parametric plots.
Dynamical Energy Analysis (DEA) has been introduced as a mesh-based high frequency method modelling structure borne sound for complex built-up structures. This has proven to enhance vibro-acoustic simulations by making it possible to work directly on existing finite element meshes circumventing time-consuming and costly remodeling strategies. In addition, DEA provides detailed spatial information about the vibrational energy distribution within a complex structure in the mid-to-high frequency range. DEA has been used to calculate the structure borne sound of an assembled agricultural tractor and good agreement between measurements and DEA calculations has been shown. In particular, it has been demonstrated that DEA can model shell structures accurately. However, it is still difficult to model a solid structure because currently DEA is based on wave transmission calculations through plate/plate junctions. Additionally, accurate FE meshes of assembled complex structures are often not available due to the uncertainties of modelling welds, bolts and rubber bushes between components. We propose here to integrate measurement data into DEA to improve the effectiveness of DEA modelling. Advanced Transfer Path Analysis (ATPA) is employed to extract energy transmission characteristics of a structure. The direct transfer functions between interface points are calculated using ATPA based on measured frequency response functions. DEA elements connecting interface points and representing energy transmission characteristics of the structure are created based on the ATPA result. The proposed method is verified with a finite element model of a simple structure.
Human safety is essential for nursing care robots, which have codependent relationships with human. The international safety standard for personal care robots (ISO 13482) is the key to human safety. In this standard, protective measures for risk reduction, which are implemented using the control system, has to be developed based on functional safety standard. A lot of time is needed to do that. Initial investment for developing nursing care robots has to be held down because they are generally low-volume production and it is difficult to recover the investment. In addition, users demand low-cost products. Therefore, it is very important to achieve the functional safety suitable for "low-volume production" and "low cost product", which are required for nursing care robot. Under such circumstances, we developed the rise assisting robot “Resyone Plus”, based on such a concept of functional safety, which can realize "low-volume production" and "low cost product". And we acquired the certification of ISO 13482 about this robot and realized its commercialization. This paper reports a concrete example of how to develop it.
In this study, the estimation of a defect depth in concrete is carried out based on the finite element and the adjoint variable methods. As the governing equation, the equation of motion is employed, and the finite element and Newmark’s β methods are applied to discretize the equation in space and time, respectively. The estimation of the response of the displacement at observation point and a defect depth is carried out by using based on the adjoint variable method. In the numerical experiment, the defect depth is estimated using the observed displacement value. Results of numerical experiment and some discussions are shows in this paper.
The equation, which expresses the influence of cutting conditions such as cutting speed, depth of cut and feed rate on the cutting temperature of the workpiece, is investigated by the dimensional analysis. In this analysis, thermodynamical basic dimension system is used. The equation derived consists of the factors of cutting speed, depth of cut, feed rate, specific cutting energy, and volumetric specific heat and thermal conductivity of the workpiece material, and the equation is compared with those which were derived by the other researchers. The experiments are carried out by turning under the various cutting conditions, and the results obtained are compared with the analytical results. The cutting temperature is measured by the two-color pyrometer with an optical fiber which is developed by the author. Ti-6Al-4V, S50C, Inconel718, SUS304 and Aluminum are used as the workpiece materials and Al2O3 tool is used as a cutting tool. The analytical equation makes it possible to estimate the cutting speed under which the cutting temperature reaches the melting point of the workpiece material. The specific cutting energy which is necessary for making a chip of unit volume is estimated using the volumetric specific heat and the melting point of a workpiece material. In other words, the energy used for cutting is equal to the energy used for melting the work material.
Rzeppa constant velocity joints are mainly used in the drive shafts of front wheel drive vehicles. This type of joint transmits driving torque through balls provided in the joint. The ball force that transmits the torque fluctuates periodically when a joint angle exists between the two transmitting axes. Although this ball force fluctuation influences joint performance aspects such as strength and durability, the reason why the ball force fluctuates is not clarified yet. To reduce ball force fluctuation, it is necessary to clarify the essential mechanisms behind the periodic fluctuation. First, this paper assumes that the ball forces are balanced with the secondary moment related to the driving torque and joint angle. A basic waveform of the ball force was constructed based on this assumption. In addition, a detailed analysis model of a Rzeppa joint was constructed, including the contact and friction forces acting on multiple parts of the joint, based on a multibody dynamics approach. This detailed joint model was validated by ball forces measured in an experiment, and converted into an ideal joint model disengaged from design and production restrictions. The basic waveform of the ball force was validated using analysis results computed using this ideal joint model. The theory that the ball forces are balanced with the secondary moment was validated. Moreover, the contribution of the design parameters of the detailed joint model to the ball force waveform was identified by conversion to the ideal model.
The reduction of the aeroacoustic bogie noise that is generated by the Shinkansen high-speed trains travelling faster than 300 km/h is an important environmental issue. Currently, the amount of aeroacoustic bogie noise can be quantitatively estimated at the measuring points based on a spatial distribution of the sound pressure level (SPL) that is obtained by a two-dimensional microphone array in a wind tunnel test. However, it is necessary to appropriately consider noise generation and sound field with respect to various acoustic properties such as ground reflection and insertion loss of a bogie side cover. In this study, the transfer function between the integrated spatial distribution of SPL and the results that are obtained by an omnidirectional microphone are calculated by a numerical method. The aforementioned transfer function is calculated based on the bogie conditions that the side cover would be set and that the ground reflection effect would also be included. The transfer function is observed to change significantly in the lateral direction in low-frequency regions, especially in the 125 and 160 Hz bands. These spatial trends are also confirmed using an acoustic test that is based on the reciprocal theorem, and it is observed that these trends are caused by the interference between the reflection waves from the ground, the cavity upper wall, and the side covers. The SPL of the aeroacoustic bogie noise of Shinkansen trains can be estimated using this transfer function and can be compared with the results that are obtained from the field tests.
The crash safety structure of the railway vehicles is effective as one of the safety measures against the train crews and the passengers in the event of a collision accident. However there is no standard for crash safety in Japan. In order to discuss guidelines for the crash safety design of the vehicle structure, it is important to grasp the actual situation of collision accidents in Japan. Therefore, firstly the authors performed the statistical analysis of serious level-crossing accidents for the past 30 years. Secondly, we carried out finite element analyses of a level crossing accident with a dump-truck under various conditions (collision position, collision angle, collision speed and mass of the load on the dump-truck) based on the result of the statistical analysis. We also evaluated their results in terms of the contact force, the deformation energy of the rail vehicle, the deformation amount of the cabin, the mean deceleration of passenger’s area (conformable to European standard), the maximum deceleration of the passenger’s area and the secondary impact velocity of the passenger (American standard). The degree of correlation among these results was discussed. The analyses showed that the horizontal collision position of the dump-truck and the collision speed had a comparatively large effect on the safety of passengers, and further that the mass of the load on the dump-truck also affected it when the secondary impact velocity was used as an evaluation index.