Aluminum alloy foams were fabricated through the melt route using aircraft grade aluminum alloy, the compositions of which were equivalent to A2024 and A7075. It became possible to fabricate aluminum foam by the thickening effect of Al-Cu melt caused by adding Zn and Mg. Porosity increased as the TiH2 decomposition proceeding. After the end of TiH2 decomposition, the pore coarsened. Cell walls of the fabricated aluminum alloy foams and the thickened master alloy were hardened and strengthened by heat treatment. The first peak stress of the fabricated aluminum alloy foams were improved by heat treatment. The compressive strength of fabricated aluminum alloy foams increased with decreasing porosity.
In order to investigate possibility of application of friction stir process to plastics, effects of process parameters such as rotation speed and plunging speed of a tool on temperature distribution during FSSW (Friction stir spot welding) were studied in experimentally as well as analytically in PVC (Polyvinyl chloride). Joining strength of FSSWed PVC joint was evaluated under tensile shear loading. According to the results of temperature measurement, the maximum temperature observed during the process was lower than the melting temperature and thermal decomposition temperature of PVC. Effect of rotation speed of a tool was significant for change in the maximum temperature, but that was not significant for change in size of area friction stirred. Plunging speed significantly affected the maximum temperature and the temperature distribution. It was considered that the size of area friction stirred would be predicted based on the temperature distribution, because size of area with temperature above grass transition temperature of PVC almost coincided with size of area friction stirred. According to result of tensile shear test, it was speculated that the strength of the joint could be controlled by plunging speed, but not rotation speed because of that plunging speed strongly affected the temperature distribution in FSSWed PVC joint during the process. Loading mode changed with change in the stir zone size affected the tensile shear strength of the joint.
Recently it was reported that a periodic nanostructure was formed by femtosecond pulse laser (λ = 800 nm, fr = 1 kHz) irradiation at the fluence slightly above the ablation threshold over the surface of diamond-like carbon (DLC) films. Our previous studies have demonstrated that the nanostructure can decrease a friction of the surface. However, because DLC films have the various features according to the binding conditions, it is important to clarify a formation mechanism of the nanostructure for controlling the shape. In this paper, we reveal a relationship between laser irradiation conditions and the shape of nanostructure such as pitch and depth experimentally. Furthermore we adapt theoretical curve on interaction between laser beam and electron plasma wave, and the experimental results. As a result, it suggested that the formation of nanostructure with low fluence is caused by interaction between laser beam and electron plasma wave, and the pitch of nanostructure is finer with less ablation than conventional mechanism.
Orientation changes during fatigue crack initiation process in ferrite steels with different grain size were evaluated by the electron backscatter diffraction (EBSD). EBSD measurement and fatigue test were alternately carried out using small specimen. Crystal rotation was evaluated by two misorientation parameters; Grain Reference Orientation Deviation (GROD), which is misorientation between measuring points and the average orientation in each grain, and crystal misorientation at the same point before and after fatigue testing (Δθ). Both parameters are increased and then constant at crack initiation. The variation of GROD is about 0.1° and that of Δθ is about 2.0° regardless of grain size. Therefore, Δθ is more sensitive to orientation change under cyclic loading. In addition, the large Δθ area shows better agreement with fatigue damaged area (crack and slip band) than large GROD area. These results suggest that Δθ is quantitative parameter for evaluation of fatigue damage dominating fatigue crack initiation.
Load carrying capacity of austenitic stainless steel component is increased due to hardening caused by neutron irradiation if no crack is included in the component. On the other hand, if a crack is initiated in the reactor components, the hardening may decrease the load carrying capacity due to reduction in fracture toughness. In this paper, in order to develop a failure assessment procedure of irradiated cracked components, characteristics of change in failure strength of stainless steels due to cold working were investigated. It was experimentally shown that the proof and tensile strengths were increased by the cold working, whereas the fracture toughness was decreased. The fracture strengths of a cylinder with a circumferential surface crack were analyzed using the obtained material properties. Although the cold working altered the failure mode from plastic collapse to the unsteady ductile crack growth, it did not reduce failure strengths even if 50% cold working was applied. The increase in failure strength was caused not only by increase in flow stress but also by reduction in J-integral value, which was brought by the change in stress-strain curve. It was shown that the failure strength of the hardened stainless steel components could be derived by the two-parameter method, in which the change in material properties could be reasonably considered.
Polishing performances of glass using epoxy resin polishing pads from the aspect of their mechanical properties are described. Material removal rates are independent to the hardness of the epoxy resin pads. The different types of epoxy resin pads are produced by varying the composition of the resin and the curing agent. Dynamic mechanical analysis (DMA) of the epoxy and conventional urethane resin polishing pads was conducted to investigate the relationship between the material removal rates and the mechanical properties of the epoxy resin polishing pads. DMA measurement indicates that the epoxy resin polishing pads showed a significant difference in the storage and loss modulus compared to the conventional urethane pads. Moreover, the epoxy resin pads showed a higher loss tangent (tan δ) than the urethane resin polishing pad. From the investigation of the relationship between the material removal rates and tan δ of the polishing pads, the strong positive correlation between the material rate and tan δ is observed. Finally, the dependence of polishing conditions on the material removal rate by the epoxy and urethane resin pads is evaluated. It is found that the difference in the material removal rate between the epoxy and urethane resin pads becomes larger under a condition of a low abrasive concentration and a high rotation rate.
In order to investigate the effects of hydrogen gas pressure pH2 and test frequency f on the fatigue crack growth (FCG) properties of low carbon steel in hydrogen gas atmosphere, the FCG tests using compact tension specimens were conducted under various combinations of pH2 = 0.1 ～ 90 MPa and f = 0.001 ～ 10 Hz. At pH2 of 0.1, 0.7 and 10 MPa, the FCG rate increased with a decrease in f and then peaked out. In the lower frequency regime, the FCG rate decelerated and became nearly equivalent to the FCG rate in air. Also at pH2 of 45 MPa, the hydrogen-induced acceleration showed an upper limit around f of 0.01 ～ 0.001 Hz. On the other hand, at pH2 of 90 MPa, the FCG rate monotonically increased with a decrease in f, and eventually the upper limit of FCG acceleration was not confirmed down to f = 0.001 Hz. The laser-microscope observation at specimen surface revealed that the hydrogen-induced acceleration always accompanies a localization of plastic deformation near crack tip, i.e. at a low test frequency, the slip localization at crack tip was not observed even in hydrogen gas. These results inferred that the influencing factor dominating the hydrogen-induced acceleration is not the presence or absence of hydrogen in material but is how hydrogen localizes near the crack tip. Namely, a steep gradient of hydrogen concentration can result in the slip localization at crack tip, which enhances the Hydrogen Enhanced Successive Fatigue Crack Growth (HESFCG) proposed by the authors. It is proposed that such a peculiar dependence of FCG rate on test frequency can be unified by using a novel parameter “(pH2∙f)1/2” which represents the gradient of hydrogen concentration near crack tip.
Hot water in a main pipe flows into a branch pipe and forms a thermally stratified layer with cold water at a bent section. Fluctuation of the thermally stratified layer may initiates thermal fatigue crack in the branch pipe. The fluctuation mechanism of penetration depth induced by the main flow in the branch pipe with a closed end was investigated by experiments and numerical simulations. Three flow patterns were observed on the cross-section plane in the branch pipe. They were flow parallel to the cross section direction, flow consisted of small vortexes and a large swirl flow. Generation period of the large swirl flow at L/Db = 4.0 was nearly equal to fluctuation period of the penetration depth. It was shown the large swirl flow which generated periodically around L/Db = 4.0 moved downward in the branch pipe and caused the fluctuation of the thermal stratified layer.
The flow characteristics of round air jets with tapered annulus was investigated experimentally. The divergent and convergent tapered annulus was installed concentrically inside of the round nozzle. The effects of the length of annulus, the diameter of annulus on the mean and fluctuating velocities, and the velocity ratio of the inner jet to outer jet at the nozzle exit were examined by the hot-wire measurement and flow visualization. In the case of the jets with the divergent tapered annulus, the outer jet was accelerated and the inner jet was decelerated. The spread of jet with the divergent tapered annulus increased in the near field of the jet. On the other hands, with convergent tapered annulus, the outer jet was decelerated and the inner jet was accelerated. The spreads of round jet with the convergent tapered annulus was smaller than the other jet. It is found that the flow characteristics of a round jet with tapered annulus was the similar to that of a plane jet with deflecting plates.
Arc behavior under an alternating magnetic field to the arc is theoretically investigated. It is known that the arc profiles are influenced by various operating parameters such as an imposed magnetic flux density, an arc current, a flow rate to the plasma gas and so on. Therefore theoretical analysis on the arc is complicated. In the present work, the authors investigated a new approach to understand the arc behavior driven by the alternating magnetic field. A characteristic time and a characteristic length were defined. Using these characteristic time and length, the fundamental equations which governed the arc behavior were rewritten into the non-dimensional forms. Appropriate choices of these characteristic values made it possible to eliminate the influences of the various operating parameters from the non-dimensional equations. As the result, numerical analyses became very easy. Non-dimensional arc profiles obtained from the non-dimensional differential equations were rearranged into real arc profiles by the simple inverse conversions from the non-dimensional values to the real dimensional ones. Influences of the operating parameters appear again in the arc behavior through the inverse conversion processes.
Pressure drop tests of single-phase and two-phase flows through a packed bed with micrometer size diameter particles under laminar upward flow conditions were carried out to develop the new pressure drop model for two-phase flow through a packed bed. A new pressure drop model for two-phase flow was developed based on the experimental results with air-water, helium-water flow and each single phase in 50 mm I.D. columns packed with glass beads of 53 μm and 108 μm diameter. From single-phase experimental results, it was confirmed that the Kozeny-Carman equation could be used for the single-phase liquid and the single-phase gas respectively as the pressure drop equations. The new two-phase flow pressure drop model included the Kozeny-Carman equation for single-phase liquid flow pressure drop and a two-phase flow friction multiplier. For the two-phase flow friction multiplier, the Chisholm equation with the Lockhart-Martinelli parameter X2 was used, based on the separated flow model. The Lockhart-Martinelli parameter X2 for the packed bed was derived from the Kozeny-Carman equation. The experimental constant in the two-phase flow friction multiplier in the Chisholm equation was determined from the experimental results. The new model predicted the experimental results of the pressure drop for two-phase flow through a packed bed with micrometer size diameter particles within ±20 % error.
Frictional pressure drop of turbulent upward flow with micro bubbles in a vertical pipe was investigated. To investigate relation between pipe diameter and the frictional pressure drop, three different pipes whose diameters are 5.9, 13 and 16 mm were used. Range of the Reynolds number is from 11000 to 48000. Two kinds of micro bubble generation methods which are pressurized dissolution and shearing methods were used to investigate the frictional pressure drop for a wide range of void fraction α. The conclusions obtained are as follows: (1) the frictional pressure drop of the turbulent upward flows in the vertical pipes increases or decreases by the presence of the micro bubbles, (2) the micro bubble generation method does not affect the drag reduction ratio DR, (3) DR takes a high value at low JL and Re and mainly decreases with increasing JL and Re, (4) DR depends on the pipe diameter, D, at the fixed JL and α, (5) DR depends on D at the fixed Re and α, and increases with D at the fixed Re and α for low α (≤ 0.13%), (6) DR tends to take a positive value for low α (≤ 0.15%), and increases with decreasing α in this condition, (7) the drag increase or reduction of the turbulent upward flow with the micro bubbles in the vertical pipe does not agree with a transition diagram of frictional drag reduction proposed by Murai (2014), (8) the drag is reduced for 0 < α < 0.15% and 11000 < Re < 45000, and mainly is increased for the rest region.
This paper focuses on the behavior of shock waves formed in an underexpanded impinging jet. The jet becomes underexpanded when the pressure ratio exceeds the critical value across the convergent nozzle discharging it. When a flat plate is placed perpendicularly to the jet, the strong shock wave called ‘plate shock' appears in the flow field near the plate. The underexpanded jet discharged from a nozzle into the atmosphere is often used for industrial applications, e.g., an assist gas of laser cutting and a cooling jet in glass tempering process. The jet impinges on the work piece and spreads out on its surface. So this study concentrates on the relation between the jet oscillation and the location of the work piece and especially discusses behavior of shock formed in jet. The impinging jet was formed under conditions of different nozzle pressure ratios and nozzle-plate spacings and was visualized using the shadowgraph and schlieren methods. The instantaneous shape of jet was measured through analyzing the pictures taken at random under each condition and the oscillation pattern was examined. In addition, under the same conditions, a numerical study was carried out using TVD scheme. As a result, it was found that the oscillation pattern of plate shock depends on its location and the nozzle pressure ratio.
Appropriate relation among the inertia, suspension characteristics and brake force distribution will be required for achieving comfortable motion of vehicle and stable contact forces at braking. At a forethought stage where the design concept is decided, we usually do not know the detail specifications of inertia and suspension; therefore, simple analytical models would be desired to check the inertia and suspension characteristics for comfortable ride. In this paper, we propose a simple analytical model to express 2-dimenstional motions of a vehicle, at side view while braking. In the model, we can change the brake force distribution which include transitionally change, from the start of braking to the end. Then, we analyze by using the proposed model, how the brake force distribution influences the vehicle vertical and pitch motion, and contact forces at side view. The model is composed of the mass and the moment of inertia, of the suspension characteristics which are expressed two virtual links, springs and dumpers. In the model, the virtual links convert the horizontal brake forces into vertical reaction forces. The friction property fluctuations between brake pads and rotors may change the brake force distribution. This paper presents one method which makes it possible to design brake force distribution, having small influences to the vehicle motions and the contact forces, and to clarify the required characteristics for inertia and suspension at the forethought stage. The proposed model and the numerical calculation method with the model are confirmed by experiments.
In this paper, we propose a hand-over motion model based on analyses of hand motions and voice utterances of humans. This model generates a motion in which a robot hands over an object to a human accompanied by a voice greeting. In this model, a hand-over motion is generated based on the analyses of human hand-over motions; in particular, the timing between the voice utterances and the release motions of humans is analyzed. Then, the model generates the release motion of a robot in response to a voice utterance from a human. Furthermore, using the proposed hand-over motion model, two types of hand-over robot systems are developed. The first type is a human-arm handing-over robot system which is fabricated according to the average size of a human arm. The other type is a Cartesian-coordinate handing-over robot system. The effectiveness of the proposed model is demonstrated by sensory evaluation using these hand-over robot systems. Furthermore, using the Cartesian-coordinate handing-over robot system, the number of degrees of freedom is analyzed in order to generate a handing-over motion which is preferred by humans.
As the demand for robots grows in society, the environments in which robots will be needed are becoming increasingly diversified. Robots will therefore have to possess high mobility so that they can maneuver safely and smoothly in these environments. One type of vehicle that is now attracting attention as a means of achieving such motion is the Omni Directional Vehicle (ODV). The ODV has great potential for use in a wide variety of fields including wheelchairs and transport robots, and the ODV has consequently been the subject of many studies. In past research, many types of special wheels and mechanisms have been devised and developed to achieve omnidirectional motion. The complicated structures of these special wheels, however, have generated problems in terms of durability and stability making it difficult to increase vehicle size and speed. In this paper, we consider application of omnidirectional motion to motorized wheelchairs and mobility scooters or to even vehicles larger in size, and we focus on a modular ODV that uses conventional wheels with a durable configuration and achieves omnidirectional motion by a simple mechanism. In this type of ODV, a wheel module is taken to be one unit, and we achieve omnidirectional motion through distributed coordination of multiple units. We also propose a technique for improving the efficiency of motor operation by distributing the environmental load generated by movement. To demonstrate the effectiveness of the proposed technique, we conducted simulations and an experiment with actual equipment using the developed OVD. The simulations were performed under a variety of conditions and showed that omnidirectional and efficient motion could be achieved by the proposed technique. The experiment with actual equipment examined the case of automatic driving and driving with a human on board and showed that the load applied to each wheel module by road conditions could be compensated for and that the load on motors could be minimized.
We propose a technology for manipulating the position and attitude of an object on a planar surface in a contactless manner. This technology involves multiple ejectors that stream jets of compressed air onto an object from various directions. By regulating air jet directions and volumes, the object can be actively "force closured" and its position and attitude can be manipulated freely. As the first step of this research, we discuss the fundamental ideas and the technological challenges as a manipulation method. Next we provide a preliminary investigation with one degree-of-freedom experimental system. Based on this, we examine two DOF system with three air jets and finally three DOF system with four air jets.
The objective of this study is to develop the variable control mechanism to amplify the operating range of the end-effector of the wearable haptic device. The conventional haptic devices are classified into passive haptic devices and active haptic devices by means of the force display conditions. The passive haptic device has a wide operating range and a high bandwidth of the dynamic characteristics in the force non-displayed condition. On the other hand, the active haptic device provides accurate resistive force for the operator by changing the posture of the device by the active actuators. In this study, the variable control mechanism which has both of these advantages is developed. The proposed mechanism is able to control the mechanical connection between the active actuator and the end effector of the haptic device. In addition, the force detection mechanism and the angle detection mechanism of the wrist for the force feedback control are developed to display an accurate force. The experiments of the transition between the unconstraint condition and the constraint condition of the end effector were carried out to confirm the effectiveness of the variable control mechanism. The experimental results show that the proposed haptic device with the proposed mechanism is able to improve the dynamic characteristics of the end-effector and to amplify the operating range of the end-effector of the wearable haptic device.
A pneumatic servo seems to be effectively applied to many varieties of gripping or compressing works, because its high compressibility is useful to the force control. In the force control system, the characteristic of the object is comprised in the closed loop, so its influence has to be considered in the design of controller. However, it is generally unknown and often changes during operation. In particular, the characteristics of the plant changes significantly, when the object is moving. To cope with these problems, more intelligent control schemes are required. In this paper, we propose a design scheme of a model reference adaptive control with Neural Network for a force control system with pneumatic servo. The effectiveness of the proposed design scheme is confirmed by experiments using the existent pneumatic servo system.
We investigate vibration energy reduction method in harmonic vibration. A beam structure modeled by Finite Element approach is used as an example. Not only resonance condition but also non-resonance condition in which no particular mode is dominant, is evaluated. Focusing on energy dissipation of damping addition, a process of finding effective damping addition area is investigated. The method using distribution of dissipation power, and the method using dissipation sensitivity analysis of the vibration energy are proposed. In the resonance excitation case, the optimum damping layout for vibration suppression can be determined by both methods. On the other hand, in the non-resonance excitation case, no obvious correlation is found between the optimum damping layout and the distribution of dissipation power. However, the sensitivity analysis leads the optimum damping layout even if the excitation frequency is non-resonance.
A servo system is generally utilized because it excels at the tracking performance and the disturbance cancellation. However, it sometimes causes an undesirable overshoot in transient responses caused by temporary disturbances such as the impulse disturbance. In such cases, the transient response becomes deteriorated in comparison with the one by the regulator. A method for the improvement of the transient response of the servo system by using controller switching has been proposed. In the method, the controller is switched appropriately between servo system and regulator based on estimated disturbance signal. In addition, the stability of the proposed system is guaranteed by the common solution of Lyapunov inequalities. It is verified that a switching control method improves the transient response which is caused by temporary disturbances such as the impulse disturbance. However, tracking performance sometimes deteriorates when the tracking command and the disturbance are applied to the system at the same time. In the present paper, a novel method for improvement of deterioration in tracking performance by using two degrees of freedom control structure is proposed. By the method, it is possible to improve the tracking response as well as the transient response which is caused by the temporary disturbances. The effectiveness of the proposed method is verified by the two-inertia vibration experimental system by numerical simulations and experiments.
In space engineering application, diffuse acoustic field is one of the critical design consideration of spacecraft structure. Diffuse acoustic field has equal probability of mutually uncorrelated plane waves from all incident angles over a half-space. Some prediction methods for vibroacoustic response have been developed based on the assumption that the diffuse acoustic excitation can be regarded as a uniformly distributed delta correlated excitation (rain-on-the-roof excitation). This is because a normalized cross-correlation in diffuse acoustic excitation, which is expressed by a sinc function, may be written simply by delta function. In previous researches, it has been assumed that a sinc function can be described by separation of variables, while the application of an exact formula to a simplified normalized cross-correlation in diffuse acoustic excitation has never been discussed, despite its necessity. This paper provides the exact analytical method for a structure subjected to diffuse acoustic excitation applying uniformly distributed delta correlated excitation, based on joint acceptance theory. The method is applied to diffuse acoustic excitation of a flat panel for which several boundary conditions are assumed, so that the results can be compared with those of direct calculation in the diffuse acoustic field, to validate the method for structural designing.
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 is occurred by 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 thin plate. In this paper, development of experimental equipment and applying the proposed identification method to measured vibration characteristics of a thin aluminum plate is investigated. Then, it shows the results of comparison between the identified tension distribution and directly measured value by the strain gauges. As a result, it is shown that identified tension distributions well corresponded to the values measured by strain gauges.
In magnetic hard disk drives, it is important to evaluate head wear durability in relation to lubricant layer because the head-disk spacing has to be reduced to ~1nm to achieve a high density recording above 1 Tb/in2. This paper presents a new one dimensional diffusion equation to evaluate the replenishment process of a depleted lubricant groove in submonolayer thickness region. Basic equation is derived from a hypothetical concept that the ratio of submonolayer lubricant thickness to monolayer thickness is equal to that of local molecule density to bulk density. Equation of disjoining pressure is also modified from this concept. The local effective viscosity in submonolayer region is assumed to change linearly between solid boundary and monolayer thickness. The derived diffusion equation is nonlinear with respect to lubricant thickness. Calculated examples of spreading and replenishment behaviors are shown in comparison with those of the conventional theory. It was found that the spreading and replenishment speed similar to the experimental data can be obtained by using a realistic viscosity in submonolayer region compared to the conventional theory.
Metallic nanodot array is attracting attention for biosensors attributed to the localized surface plasmon resonance (LSPR). In this paper, ordered metallic (gold and silver) nanodot arrays are fabricated by combination of Nano Plastic Forming and annealing process. The LSPR properties of the fabricated metallic nanodot arrays are investigated by measuring the extinction spectra. Effects of morphology of a nanodot array on the LSPR properties are studied. Sensitivity of LSPR peak wavelength against refractive index of the dot surrounding medium is investigated. It is found that the ordered nanodot array exhibits much sharper spectra peak than the random nanodots. The extinction spectra are affected by the size and the shape of the nanodot. The sensitivity of LSPR sensor increases with the increase of dot diameter. The highest sensitivity obtained in this experiment is 208nm/RIU by using a gold nanodot array with average diameter of 196nm. Furthermore, an analytical model based on Kuwata's theory is used to investigate the plasmonic properties of the metallic nanodot. The theoretical results show good agreement with the experimental data. In addition, the possibility for LSPR sensor with higher sensitivity is discussed and predicted by using this model.
In the 21st century, as it is important to produce the products with high accuracy, high quality and eco-friendly, the most of manufacturers need several daring plans, unique ideas and new technologies. For example, in machine tool technology, restraint of vibration on the machine tool was required for high accuracy and quality, and several countermeasures using costly equipment and large quantity of electrical energy were used for the restraint, however those countermeasures are not enough. Therefore a machining using alkaline water with polymer for decreasing vibration of machine tool was investigated. Relationships between the mixed polymer in the alkaline water and the damping ratio or coefficient of friction were firstly investigated. Corrosion resistance of alkaline water was also investigated. Then effect of alkaline water with polymer for restraining vibration during cutting was calculated by FEM simulation. The effects of alkaline water with polymer were lastly evaluated regarding noise and vibration on a machine tool, surface roughness on a work piece and the tool life in the experiment. It is concluded from the results that; (1) The optimum percentage of the polymer for the damper was 6 wt%, (2) There are the corrosion resistance of several materials without aluminum, copper and their alloys in alkaline, (3) Vibration during cutting was restrained by alkaline water with polymer.
The relationship between the elements included in materials and the fire ball obtained by spark test, that is simple, has been examined by using SEM photographing of the fire ball. From experimental results, the kind of steel material could be estimated from fireball's image of SEM. The following contents would be pointed out as the results. The size of fire ball becomes large with the increase in the contained carbon. The size of alloy steels becomes about the double of fire ball of carbon steel. When nickel element is contained in a material, the surface of fire ball shows the delamination. When the many chromium components are contained the size of fire ball becomes large, and many holes occur in the fireball. The presence of molybdenum element in the steel shows the smooth texture at the surface of the fireball. The wrinkles appear at the surface of the fireball by the presence of tungsten element, and the many holes occur in the fireball. Whether the material is ductile or brittle we would be estimated from the pattern of deformation of the hole of the fire ball. The kind of material would be able to distinguish from the qualitative properties of the fire ball.
In the 21st century, as it is important to produce products with care for protecting the earth, a producer must be careful to conserve energy, save resources and reduce waste which pollutes environment. On the other hand, in case of a machine tool, much lubricating oil was used for smooth drive, electrical energy of forced cooling was used for high accuracy and much cutting oil was also used for lubrication and cooling. This is large problem for protecting the earth. Therefore behavior of a machine tool in mist of strong alkaline water were investigated and evaluated. Properties of strong alkaline water were firstly investigated for alkali-proof, corrosion and safety of health. Then the bench lathe was remodeled in the vessel with mist of strong alkaline water (pH12.5), thermal deformation between the spindle and the tool post was measured for evaluation of accuracy. And cutting using CNC milling machine in the vessel with mist of strong alkaline water was performed for investigating the effect of water evaporation in the strong alkaline water. It is concluded from the results that; (1) Alkali-proof regarding several elements of a machine tool and safety of health were cleared in the experiment, (2) Thermal deformation of the bench lathe was very small in spite of no-forced cooling, (3) Accuracy of the machine tool was very good and the tool life was very long in spite of no-cutting oil, (4) Mist of strong alkaline was eco-friendly.
This paper proposes a method for determining optimal back-pressure profile in forging using a sequential approximate optimization (SAO). In forging, it is important to minimize an unfilled area for improving the product quality. To achieve this objective, we consider that back-pressure profile that varied through the stroke is valid. Unfortunately, the optimal back-pressure profile is unknown in advance, and large forming energy is generally required to obtain the high product quality. In order to determine the optimal back-pressure profile, this problem is formulated as a multi-objective optimization. Thus, the unfilled area is taken as the first objective function, and the forming energy is also taken as the second one. Computer-aided engineering (CAE) is used, but the numerical simulation in the forging is so expensive that the SAO using the radial basis function network is adopted. The pareto-frontier is identified with a small number of simulation runs. In this paper, the axial symmetric forward extrusion of aluminum alloy is used as the forming model. First, the experiment is carried out to construct the finite element analysis model. Using this model, the pareto-frontier is identified. To examine the validity of the optimal back-pressure profile, the experiment using the servo press is conducted. Through the numerical simulation and the experiment, we can confirm that the product quality is improved with the optimal back-pressure profile.
We already analyzed the mechanical loss factors of a commercially available geared motor, which consists of an induction motor with a rated power of 90W and a parallel gear reducer. The load independent loss holds some high proportion of the total loss, and is due to the grease stirring and the oil seal friction. The load dependent loss increases almost linearly with the applied torque, and is mainly caused by gear mesh friction which is relevant to the grease characteristics. Therefore, the grease has an important role in the loss reduction. In this paper, we studied the influence of grease characteristics on loss torque, that are the cone penetration and both the kinematic viscosity and the kind of base oil. The result shows that, the loss of grease stirring, or load independent part, depends on both the kinematic viscosity of base oil and the cone penetration. The loss of gear mesh friction, load dependent part, is not related to the cone penetration nor the kinematic viscosity of base oil. It is evaluated in terms of the mean friction coefficient of tooth flank, μmG. It was found 0.09 to 0.11 when using the grease with the lithium soap and the mineral base oil, and it was 0.07 to 0.08 with the aluminum complex soap and the synthetic base oil. For the loss reduction, the grease should be composed of a base oil having low kinematic viscosity and the appropriate thickener to make the cone penetration as high as desired.
This study proposes the braking assistance system for train drivers when stopping at a station to prevent the drivers from overrunning and running time delay. The assistance system informs the driver visually of the brake onset position, which is calculated by the assumed deceleration, the present vehicle velocity and the desired stopping position. This study conducts two experiments using the train-driving simulator with three participants. One experiment examines the effects of the driving assistance system on the braking behavior with the mental calculation, which assumes the mental workload. The assistance system makes it possible to decrease the dispersion of the brake onset timing and the running time. The other experiment examines the effects of the brake onset timing on the running time and the safety margin to make the vehicle stop at the desired position. The brake onset timing is adjusted by changing the assumed deceleration. Obtained results show a good correlation between the assumed deceleration and the running time, and the later brake onset timing contributes the shorter running time. In addition, a good correlation between the assumed deceleration and the minimum value of the predicted stopping position, i.e. the safety margin, is also observed, and the later brake onset timing deteriorates the safety margin.
Aiming at the flight control design of small helicopters for large flight envelopes, a comprehensive modeling of small electric helicopters, based on the analyses of main blades divided into elements on which air speeds and aerodynamic forces are calculated, is performed. First, coordinates that are suitable for clockwise rotors are determined, and then, mathematical expressions of the blade motion dynamics are derived. Next, the interaction between the stabilizer and main blades by linkage mechanisms is modeled to represent it as the bidirectional transfer of blade angles and forces. Stabilizer equations of motion are derived on the basis of harmonic decomposition and high-frequency mode deletion to make them numerically stable and less complex. The developed model is validated by a comparison between simulation results and flight test data using a 2.5-kgf lightweight, ultra-small electric-driven helicopter. It is confirmed that dynamics precision of the developed model is good and suitable for flight control system development and evaluation. In addition, several studies about the development and the operation of autonomous small helicopters are made based on the result of flight performances and dynamics analyses by using flight envelopes and frequency responses calculated by the developed comprehensive model.
This study proposes a driving assistance system to inform the notch operation timing for train drivers. The assistance system indicates visually the notch-off position where the driver releases the accelerator. The notch-off position is calculated by the present vehicle acceleration, velocity and position by assuming the constant acceleration. The assistance system also indicates the brake onset and the predicted stopping positions. Two experiments are conducted by using the train-driving simulator. One experiment examines the effects of the notch-off and brake onset timing on the vehicle velocity and the running time. The assistance system makes it possible to adjust the vehicle velocity and the running time. The other experiment examines the three running patterns by combination of the notch-off and the brake onset positions. With the time recovering pattern, which is combination of the higher notch-off velocity and the later brake onset timing, the assistance system realizes the shorter running time in comparison with the standard running pattern. With the energy saving pattern, which is combination of the lower notch-off velocity and the later brake onset timing, the assistance system prevents the time delay by the later brake timing even if the velocity is lower than the standard running pattern.
In this paper, a novel trajectory generation method for numerical analysis of a vehicle dynamics has been investigated. An obstacle layout method which lays obstacles around preliminarily given course shape can easily provide a state variable inequality constraint of the optimal control theory. To arrange any convex-area such as circles, squares and rectangles, obstacles are defined by the p-norm function. The time-optimal problem is constructed using the proposed method and it is solved by the pseudospectral optimization technique. Numerical results show that the proposed method yields feasible optimal trajectories for given course shapes including oval circuit.
This paper describes evaluation analysis for the space verification experiment of a tethered space robot on the sounding rocket "S-520-25." The S-520-25 rocket was launched on August 31, 2010. The tether was extended and kept its tension, and attitude control of the tethered space robot was performed. However, experimental results included non-linear dynamic motion, though the attitude control is designed under assumption of linear motion. Then, the space experimental results have been examined by mechanical dynamics software ADAMS. Non-linear motion can be evaluated qualitatively by simulation, and effectiveness of the attitude control has been confirmed.