This study focused on ruptures due to bending deformation of steel pipe that is operated with a high design factor. The design factor refers to the ratio of the hoop stress from internal pressure to the yield strength of pipe material. Bending experiments were conducted on steel pipes with a high design factor, and the failure mode was investigated. Ruptures occurred on the tensile side of the pipes and were accompanied by local reduction of the wall thickness (i.e., necking), which indicated strain localization. To evaluate the deformability of the pipes, a method based on finite-element analysis (FEA) was developed to predict the displacement at the rupture. The yield surface shape and true stress-strain relationship after uniform elongation had to be defined based on the actual properties of the bend material. The yield condition under the biaxial stress condition was measured with the biaxial tensile test and approximated with Hill's yield function. The true stress-strain relationship, including after uniform elongation, was determined by the inverse calibration method. Rupture by bending was predicted under these conditions. In contrast, the von Mises yield criterion, which is commonly used in cases of elastic-plastic FEA, overestimated the deformability; the true stress-strain relationship assumed by linear extrapolation after uniform elongation could not simulate the rupture. The FEA showed that rupture is dominated not by the fracture criterion of the material but by the initiation of strain localization, which is a deformation characteristic of the material. These ruptures are due to the rapid increase in local strain after the initiation of strain localization, which causes the fracture criterion to suddenly be reached.
A procedure for obtaining the load carrying capacity of cracked components of ductile material conducting by an elastic-plastic finite element analysis (FEA) was discussed. First, tensile tests using stainless steel plate specimens with through wall or part-through wall crack were performed. The deformation and strain were measured by the digital image correlation technique. Ductile crack initiation behavior was also observed. The tests was simulated by the elastic-plastic FEA. It was shown that the maximum load obtained by the FEA was about 1.15 times that obtained by the tests. The FEA using the stress-strain curve estimated by the K-fit method, in which the curve is estimated using the yield and ultimate strengths, agreed well that obtained using the curve by the tensile test. The FEA was also performed for simulating four point bending tests of cracked stainless steel pipes. Since the drop in applied load caused by ductile crack penetration of wall thickness was difficult to simulate, the stress penetration criterion was newly proposed. It was shown that the load for crack penetration could be predicted by the stress penetration criterion. Finally, the procedure for performing the FEA using the K-fit method and the stress penetration criterion was discussed for applying fitness-for-service assessments. The procedure allows deriving the load carrying capacity of cracked components which has a complex geometry or has inhomogeneous material properties such as welding portion.
An ejector-driven fuel recirculation system was designed for 1kW-class solid oxide fuel cell (SOFC), and the power generation experiments were carried out to validate the design procedure and to investigate the fuel recirculation SOFC of the stack performance. An ejector was designed and manufactured taking into account the pressure loss along the anodic loop and the condition of the carbon deposit. The variable mechanism of fuel flow passage in the ejector nozzle enabled to adjust the recirculation ratio of the anode off-gas under constant fuel flow rate. The recirculation ratios were determined from both gas analysis method and the measurement of pressure drop along the anodic loop. The power generation experiments at variable recirculation ratios verify the validity of the design method proposed for the ejector-driven fuel recirculation system in this paper and that the recirculation ratio has not affected the performance of the SOFC stack under the experimental conditions in this paper.
A combined heat and power (CHP), sometimes called as cogeneration, is generally independently installed into buildings without networked to the power grid, but unbalanced heat/electricity ratio of the CHP output and the demand significantly limits CHP’s performance. This study investigates the effect of the networked CHP system to the power grid on CO2 reduction and cost. The networking concept of CHPs is that CHPs are installed to buildings with large heat demand, and excessive electricity is consumed in buildings in the network via power grid. The analysis was applied for a model area in Sapporo, which is an urban residential area covered by electric feeders from a distributing power substation. The results show that the networked CHP system can reduce CO2 significantly compared to the non-networked system with the same cost. This is due to the fact that CHPs can be operated for the heat demand without limited by the electricity demand of the building by the networking, and their capacities of the system can be utilized effectively. Therefore, the maximum CO2 reduction extent is also increased. These results indicate the significance of the networking concept. Sensitivity analysis of the results for the unit costs and CO2 emission factors of the grid power was also made, and the networking effect was confirmed for various conditions. The paper also investigates the suitable type of CHPs installed to households, showing that fuel cell can reduce larger amount of CO2 than gas engine with the networking condition.
A laser 2-focus velocimeter (L2F) was used for measurements of velocity and size of droplets in diesel fuel sprays. Diesel fuel was injected intermittently into the atmosphere using a 8-hole injector nozzle. The diameter of the nozzle orifice was 0.112mm. The rail pressure was set at 40MPa by using a common rail system. The period of injector solenoid energizing was set at 0.8ms to investigate the spray behavior under small valve opening. The L2F had a micro-scale probe which consists of two foci. The focal diameter was about 3μm, and the distance between two foci was 20μm. The data sampling rate of the L2F system was markedly high as 15MHz. L2F measurement was conducted at 10mm downstream from the nozzle exit. Temporal and spatial changes in the velocity and size of droplets inside sprays were investigated near the nozzle orifice and were correlated with the needle valve lift of the injector nozzle. Spray images were taken by using a 180ns spark light source, and temporal changes of the spray width were estimated. The spray was divided into two regions; the inner region and the periphery region. The results showed that temporal changes in droplet velocity at the spray center corresponded with the temporal changes in needle valve lift. The droplets’ Weber number in the inner region was larger than that in the periphery region of the spray. It was found that the turbulence intensity of droplet velocity was strongly correlated to the size of droplet in the inner region of the spray.
Ammonia is regarded as one of the alternative fuels, since the physical properties of Ammonia is a suitable fuel for transportation and storage as a “hydrogen carrier”. Also, a large amount of ammonia can be produced easily through the Haber-Bosch process with low price. To use ammonia as the alternative fuel, it is necessary to pay attention to Fuel-NOx formation. In this study, the oxygen-enriched combustion was applied to an ammonia/N2/O2 premixed flame to make the flame stable. The effects of the oxygen-enriched combustion on characteristics of NOx formation and on the unburned ammonia remained in the burned gas were evaluated. Results showed that NO concentration reached to 1.2%, and unburned ammonia wasn't detected in all O2 concentration conditions of fuel lean mixture. Also, NO concentrations sharply decreased between φ = 1.0 to φ = 1.4. At the condition of φ = 1.4, NO concentration was 600 ppm. Unburned ammonia wasn't detected between the condition of φ = 0.9 to φ = 1.1, and over the condition of φ =1.2, ammonia concentration was increased steeply. The sum of (NO + NH3) became the minimum value around the condition of φ = 1.3 and φ = 1.4. These characteristics that the NOx formations depended on equivalence ratio were the same characteristics of NOx formation when propane is added to NH3 as a fuel.
Hydrogen supply infrastructures such as hydrogen production and filling stations are expected to accelerate the penetration of fuel cell vehicles. This study focuses on a hydrogen material flow from the production to the consumption sector to discuss hydrogen supply potential in Japan. Both the hydrogen supply capacity and demands are investigated to estimate hydrogen sales and its self-consumption status based on the current data. The difference between the supply capacity and consumption quantity is defined as a surplus hydrogen capacity. Detailed estimation indicates that the surplus hydrogen capacity affords to supply high purity hydrogen up to 8,700 million Nm3 a year, which is equivalent to 3.3% of the final energy consumption in Japan's transportation sector in 2012.
This paper provides a supercritical pressure cold energy utilization system of the cryogenic fluid. As a specific example, there is a supercritical pressure cold energy power generation system according to the liquefied gas. The system is named LSG. LSG is a method that uses the cold exergy of the liquefied gas as the pressure exergy than the temperature exergy. LSG is a two-fluid cycle that equipped with a booster pump to boost up a supercritical pressure in the liquid state, and the primary power generator of Rankine cycle system, and the secondary power generator of Direct expansion system. The ability of LSG, in case the gas supply pressure is low, so the maximum power generation case, power generation per unit is 433kJ/kg (120kWh/t) in the actual correction value. As a result of LSG, it is possible to recover up to 42-46% of the cold exergy as electric power.
The submerged Branching Unit (BU) connects the optical submarine trunk cable and the branched two optical submarine cables by the gimbals joints attached between BU and each cable coupling (CPL). This paper shows the geometrical condition to pass the BU through the bow sheave of the cable ship within the limited bending angle of the gimbals joint. The bending angles of the gimbals joint of the branched two cables are derived by solving the geometrical condition numerically and tell us that the selected size of the bottom width of the sheave will have the suitable size of the CPL boots diameter to keep the bending angle within the limited angle. We accordingly select the size of the bottom width of the sheave and the suitable size of the CPL boots diameter. The tensile test result of the bending angle of the gimbals joint of the BU with the suitable size of the boots diameter installed on the test facility sheave being modified to the selected size of the bottom width demonstrates the validity well of the solution of the geometrical condition. The BU was successfully laid to and recovered from more than 6,000 m deep in the Pacific Ocean with the modified bow sheave and the suitable CPL boots.
Some acoustic problems such as interior noise analysis of vehicles need to be treated as structural-acoustic coupled problems because the coupling effect cannot be ignored. To solve such problems, the finite element method (FEM) has been used. However, the acoustic space is described by sound pressure and the structure is described by displacement. Therefore, the mass matrix and stiffness matrix of FEM are asymmetric, and it takes a long time to conduct eigenvalue analysis. In our previous studies, we proposed a concentrated mass model to perform acoustic analysis. In this study, we propose a concentrated mass model to analyze a coupled system of two-dimensional acoustic space and a membrane. This model consists of mass points and connecting springs. The advantage of this model is that the mass matrix and stiffness matrix are symmetric because both the acoustic space and the membrane are described by the displacement of the mass points. We conducted eigenvalue analysis and compared the proposed model with FEM. There are some modes such as spurious modes and zero-frequency modes that are physically meaningless. However, excepting these modes, the eigenvalue analysis result obtained using the proposed model agrees with the natural frequencies and natural modes obtained by FEM. Moreover, the eigenvalue analysis result becomes more accurate as the mass points of the acoustic space are placed closer to the mass points of the membrane because the boundary conditions are satisfied. Furthermore, we compared the proposed model with FEM in terms of the time required for the eigenvalue analysis. Because the mass matrix and stiffness matrix of the proposed model are symmetric, its eigenvalue analysis is faster than that of FEM, whose matrixes are asymmetric. Therefore, we conclude that the proposed model is valid for the coupled analysis of two-dimensional acoustic space and membrane vibration and is superior to FEM in terms of calculation time.
Seat position and angle are adjusted electrically in the power seat of an automobile, and the quality of the vehicle's interior is degraded by fluctuating sound frequencies related to that seat. In this research, a sound stabilization design for the operating sound of the power seat was proposed considering the uncertainty inherent in the production assembly. Initially, the fluctuations' influence on the sound quality was evaluated by varying the frequency and the Sound Pressure Level of the operation sound, and a standard value for the sound stabilization was determined by utilizing the Taguchi method to consider the SN ratio. Next, the Taguchi method was adapted to consider a simplified model of the joint elements of the seat slide. Then, an optimal control factor for sound stabilization was specified. The sound stabilization was applied, leading to a target value for the optimal control factor that was specified in the simplified model for the joint of the power seat. Finally, that target value was optimized using the optimal control factor. We concluded that it is possible to achieve sound stabilization of power seat operation while considering the uncertainty in production assembly in this research.
Because the flying height between a magnetic head and magnetic disk surface in hard disk storages is to be decreased to less than 1 nm, the head wear reliability due to intermittent asperity contacts and slider instability become critical issues. Nevertheless, detailed asperity characteristics of perpendicular magnetic disk have never been reported in open literatures. This paper presents the detailed features of surface texture parameters intrinsic to the perpendicular magnetic grains of commercially available magnetic disk drives (500 GB/platter), i.e., mean asperity height, asperity density, distance between the nearest asperities, radius of curvature of the asperities, and their histograms in addition to typical roughness parameters. It was found that mean asperity height is ～0.5 nm, asperity density ～5000 μm-2, nearest asperity distance ～11 nm. The asperity radius of curvature has an anisotropic nature, probably due to lubricant molecular conformation, but its averaged value is ～20 nm. Various parameter values of mountain and valley are also presented. On the basis of the measured roughness parameter values, the previous analytical results for the head-disk interface characteristics are reviewed.
The popular sports entertainment, billiards, is rich in mechanical issues such as 3D finite rotation, collision, contact and friction, evoking a research interest in rigid-body dynamics, nonlinear CAE and computational mechanics. However, the 3D nonlinear behavior of a rigid ball has so far hardly received the attention of scholars to exercise the mechanical modeling skill. The represent study focuses, therefore, on 3D nonlinear billiard dynamics and attempts to precisely predict the ball behavior in finite rotational motion with collision, contact and slip friction. In dependence upon ball situations, 4 different models are proposed. They are namely, rotation model, strike model, collision model and reflection mode. The rotation model is an elementary model and describes the 3D ball motion after a cue strike and subject to table friction only. The strike model is useful to study the effects of cue striking. For simplicity, the strike points are limited to the ball center, 12, 3, 6 and 9 o'clock' in the ball projection. The collision model ignores the ball-to-ball friction and the law of conservation of momentum holds to predict the velocities of two balls after collision. The reflection model simulates the ball-to-cushion contact in bank shots. Incidence angle, translational and rotational velocities, cushion elasticity and frictional properties may be variable in a parameter study. In all these 4 models, the ball is assumed to be in contact to the table surface. Masse or jump shots are excluded in modeling. The equations of ball motion are time-integrated by forward Euler method. The models are verified and validated in numerical examples including optimization and parameter studies. All computed results well agree with the hustler’s experiences in game practice. The present research work will contribute to develop a skill-up program of professional hustlers.
Recently, printed circuit boards (PCBs) have become multi-layered and complex. It is to provide both multiple functions and to be compact with the development of electronic device such as smartphones. Processing by CO2 laser is frequently used as an effective method of generating blind via holes (BVHs) to connect the circuit layers of multi-layer board. However, there are some kinds of laser drilling methods in this manufacturing field. Among them, Cu direct laser processing is attracted attention, which is a drilling method of both the surface Cu circuit layer and insulation substrate layer at the same time. In the present report, we propose a laser irradiating controlling method based on monitoring the variation of processing luminance when generating the BVH. Especially, we perform the BVH drilling of high heat radiation PCBs, which becomes to be use for high performance electronic devices, and investigate the influence of laser irradiation condition on the drilled hole quality. As a result, the proposed method is found out to be effective to achieve the high BVH quality in the PCB manufacturing fields.
Hybrid electric vehicles, which have an internal combustion engine (ICE) and electric motor(s) (EMs), are effective to improve fuel consumption and exhaust emissions. We had constructed a novel energy management system (EMS) considering torque control strategy, in which a function called the torque control function was introduced to reduce CO2 and NOx emissions. However, only the regenerative braking was used for battery charge in the EMS. In this paper, an improved EMS considering the battery charge by ICE is proposed. To charge the battery, a charge torque considering the target state of charge (SOC) is newly introduced. To determine the torque control function and the charge torque, a sequential approximate optimization using a radial basis function network is adopted. CO2 and NOx are then simultaneously minimized. A multi-objective design optimization is the formulated, and the torque control function and charge torque are determined with a small number of simulation runs. Through the numerical simulation, the validity of proposed EMS is examined.
Owning to the different mechanical behaviors of the instinct materials, inlaid structures composed of dissimilar materials have potential for industrial application, such as vibration suppression. The shape and position of inlaid components strongly affect the mechanical behaviors of inlaid structures. Thereby, we propose a shape optimization method for designing inlaid structures in terms of stiffness problem in the present work. This study focuses on the design optimization of 2-dimensional structures with inlaid components for enhancing their stiffness by optimizing the shape and position of inlaid components. We use compliance as the objective function and minimize it under the area constraint of inlaid components. The proposed shape optimization method is a type of gradient method that was named as the H1 gradient method. We derive the shape gradient function based on the material derivative method and apply it to the proposed shape optimization method for determining the optimal shape and position of the inlaid components. Design examples of 2-dimensional inlaid structures are presented in this study to verify the effectiveness and feasibility of the proposed optimization method, and the results show that stiffness of inlaid structures can be significantly enhanced according to the shape design optimization, especially for a inlaid structure with a higher differential Young's modulus of the instinct materials.
The long cane has been the most widely used mobility aid for the visually impaired people in spite of many other aid systems. The purpose of this study was to investigate canes that are currently being used at the special needs education school for the visually impaired and to produce new long canes experimentally and evaluate it for visually impaired children. An 8-item-questionnaire was developed and distributed to 71 all the Japanese special needs education schools for the visually impaired. 83.1% subjects who received the questionnaire completed it properly. The new types of the long cane were assessed for their ability to transmit the vibration and their sensitivity to tactile information, flexibility, and durability. The materials that are used in new long cane shafts were carbon fiber, aluminum and composite material of carbon fiber and aluminum at three kinds of the most commonly used materials. The tips that are used in new long cane were standard (pencil), marshmallow, and teardrop at the types of three categories. According to questionnaire results, the visually impaired children tend to use a straight cane, and a rubber golf grip standard-type cane tip in the special needs education school for the visually impaired, even though there are many kinds of cane tips. In these experiments of the new long cane, it was found that the lightweight canes, the regulating mechanism of cane's lengths and the combination of tips and grip might be associated with a visually impaired children's performance.
Space structures encounter various severe environments in space. One of these environments is severe thermal condition where the difference of temperature during day-time and night-time is about 200 degrees Celsius. During this eclipse time, the midpoint of the large deployable reflector (LDR) mounted on the Engineering Test Satellite -VIII (ETS-VIII) was confirmed to deform by approximately 5 mm, which led to a 65 km transition of the footprint of communication beam on the surface of the earth. This phenomenon was assumed to be caused by thermal deformation of the LDR. It was not a critical issue for the ETS-VIII because the communication beam from the LDR tended to spread in the wide range. However, highly accurate pinpoint communication beams are expected to be required in the future, and this transition of the beams may affect the performance of such satellites. Therefore, in this study, a means to suppress the thermal deformation is proposed and demonstrated by focusing on the internal force generated at the springs used to deploy the antenna. According to the numerical results obtained from finite element analyses, the thermal deformations at all apices that support the reflectors were suppressed at a high correction rate by adjusting the coefficients of thermal expansion in the structural members and by controlling spring forces differently in four areas depending on the distances from the constraint point. These results indicate that the transition of the communication beam on the surface of the earth can be decreased to a range of 5 to 10 km.