This paper describes how to produce a biodiesel fuel (BDF) from the waste soup of ramen noodles, especially focusing on the recovery process of the oil (triglycerides) from a large amount of waste soup or the oily wastewater disposed of by pouring it down the sink by a ramen restaurant. By combining a semi-transparent bucket (~6 L) with a cock and solvent extraction, it is shown that oil can be recovered easily from 300 or more bowls of ramen noodle waste soup, with an energy profit ratio (EPR) of more than 5.2. The initial cost of the bucket is about 1600 yen, so it has little effect on the price of the BDF produced from the oil in the ramen noodle waste soup, and it is shown that the increase in running cost to produce BDF by this method is about 2.3 yen/L if the rate of recovery of hexane (solvent) is over 99%, which is approximately equivalent to the production cost of waste-cooking-oil BDF production by previously reported methods. Furthermore, in the case of applying the proposed method based on the solvent extraction to the recovery of oil from the oily wastewater disposed of by a ramen noodle restaurant, it is shown that oil can be recovered from the waste soup of ramen noodles just after disposal as well as from the oily wastewater that spent one day in the grease trap. In the former case, EPR is 5.0, and the estimated amount of BDF is greater than 100 L/month for one restaurant. However, in the case of using the oily wastewater from the grease trap, EPR is less than 2.0 because of the reduction of yield of BDF due to a greater oxidation deterioration of the recovered oil, when the alkyl catalyst method is used. Therefore, it is desirable to recover oil from the oily wastewater at the drain pipe just after the sink.
This work assessed the fundamental characteristics of multifunction cavitation (MFC), that was high-temperature and high-pressure cavitation, through both experimental investigations. The application of ultrasonication to the floating cavitation of a water jet was found to produce microjets containing hot spots. MFC exhibited the capacity to perform nano-level hot work at a material surface, modifying the surface morphology and the surface electrochemical condition by hot spot melting. Ultrasonic irradiation of a water jet during floating cavitation was used to generate microjets with hot spots and this MFC process was employed to perform hot work on CFRP (Carbon Fiber Reinforced Plastics).
The prevention of excessive deformation by thermal ratcheting is important in the elevated temperature design of fast breeder reactors (FBR). In an experimental study that simulated a fast breeder reactor vessel near the coolant surface, it was reported that the long distance travel of temperature distribution causes a new type of thermal ratcheting, even in the absence of primary stress. Without excessive stress and travel distance, the inclement of the plastic strain derived from the above mechanism reduced each cycle of thermal transient, and finally reaches to approximately 0. In this paper, we investigate path independency on “saturated” distribution of plastic strain. For this purpose, we carried out several cases of finite element analyses with initial strain distribution, which simulated plastic strain distribution in the middle of accumulating. As the result, we confirmed that the shape of saturated distribution has small dependency on the shape of distribution in the middle of accumulating. Additionally, in the case using conservative initial strain distribution, further accumulation of plastic strain was not observed. This result suggests the possibility of the method that evaluate whether the accumulation of the plastic strain go beyond design limits.
Although HCCI combustion has high thermal efficiency, it has difficulties such as controlling its ignition timing and combustion. This study proposed a method to make HCCI combustion in gas engines possible, combining dedicated EGR, SI combustion, and HCCI combustion, i.e. multiple combustion modes engine system. In a DEGR system, one cylinder runs with a premixture of rich fuel and air to reform the part of its exhaust gas into hydrogen and carbon monoxide, which are introduced to other cylinders and promote combustion. In this study, the exhaust gas was introduced through a bypass from rich SI cylinder to HCCI cylinder. In the experiments, conditions of high thermal efficiency and combustion characteristics were investigated. It was revealed that DEGR made HCCI combustion possible on a condition that HCCI combustion was impossible. The more the DEGR rate was, the higher the thermal efficiency was, and the thermal efficiency reached a maximum value when the equivalence ratio of rich SI combustion was adjusted. We proposed the adjustment of premixed gas amount in Rich SI cylinder as a means of improving thermal efficiency, and it was successful.
In DFE, it is known that emission and thermal efficiency improve by dividing the diesel injection into two at low load. However, the effect by dividing the diesel injection more than two, has not been investigated. Therefore, in this study, the effect of multiple diesel fuel injections on the combustion and exhaust emission characteristics of DFE using natural gas (city gas 13A) was investigated at low load in experiments. The experiments were conducted using a single-cylinder engine with a common rail injection system, varying the number of fuel injection and injection timing. The injection timing was set so that the interval of the injection becomes the parameter. The total injection quantity in one cycle was fixed and equally divided in multiple injections. By adapting double injection, the thermal efficiency did not improve against single injection. Total hydrocarbon (THC) emissions improved in some injection conditions, however increased in other injection conditions. NOx emission increased in narrow injection interval, but improved in wide injection interval. Furthermore, by adapting triple injection, THC emissions and the thermal efficiency improved against single and double injection. Also, NOx emission increased in narrow injection interval, but in wide injection interval NOx emissions did not increase against single injection.
It is known that there is a large safety margin in the current fatigue damage assessment method for piping of nuclear power plants. One of the evaluation methods in order to rationalize it, there is a flaw tolerance method that estimates the continuable operation period by crack growth calculation assuming initiation of fatigue cracks even when the fatigue cumulative usage factor exceeds 1. It is already standardized by ASME Boiler and Pressure Vessel Code Section XI Appendix L in the United States, but the assumed initial crack shape was based on fatigue damage data and evaluation conditions in the United States. Therefore, in this paper, investigation of domestic fatigue data and evaluation conditions of Appendix L were performed, and the depth and length of the assumed initial crack for the flaw tolerance method were studied for the standardization in Japan. Multiple cracks due to fatigue tend to initiate on the inner surface of piping based on the operating experience. Therefore, assumed initial crack was modeled as an equivalent single crack with priority given to simplicity of the evaluation procedure, where the aspect ratio of the equivalent single crack was determined so that the failure probability of the equivalent single crack was equivalent to that of the assumed multiple cracks. The depth of the assumed initial crack was set as the allowable flaw depth of the JSME Codes “Rules on Fitness for Service for Nuclear Power Plants” to assure the detectability of the crack. Moreover, in order to be able to apply this method over a wide range, the aspect ratio of the assumed initial crack have been developed for many kinds of piping shapes and materials. Finally, residual lives of typical pipes with the assumed initial crack were evaluated assuming virtual loadings that roughly envelope realistic loadings and the continuable operation periods were surveyed.
Problems of space-curved beam structures have been extensively studied by many researchers. Stress analyses for the structural problems are conducted based on a finite element method, boundary element method, or frame structure method. In these methods, a stiffness equation, which is the connection between nodal displacement and force, is solved. The size of a stiffness matrix involved in the stiffness equation increases according to the number of nodes in the analysis model. In this study, the transfer matrix method (TMM) is considered as another analysis method to overcome such a difficulty. In principle, the TMM is based on calculating how the external force or displacement is transmitted to the structure using a state vector that involves both nodal displacement and force. With the use of the state vector, fewer fundamental equations are needed to obtain stress and displacement. However, application of the TMM has been limited to vibration problems. In this study, an incremental form for the TMM is formulated to apply the TMM to the elastic-plastic problem of space-curved beam structures, and the simple problem of a curved beam fixed at a ridged wall is solved to verify the TMM formulation.
Carbon nanotubes (CNT) have remarkable mechanical properties and low density. Since length of the CNT is limited, CNT yarn is regarded as a reinforced fiber of carbon fiber reinforced plastics. However, the CNT yarn does not have remarkable mechanical properties such as the individual CNT. The most popular way for improving the mechanical properties of the CNT yarn is to make composites with polymer such as polyvinyl alcohol or polyimide. If some functional groups such as carboxyl groups are introduced on the surface of CNTs, interaction between the CNTs and the polymer is improved and high mechanical properties will be obtained. In this study, untwisted CNT yarns were prepared by drawing vertical aligned CNTs through a die and functionalized with mixed acid. Mixed acid introduced not only the functional groups but also defects on the surface of CNTs. For reducing the defects, the CNT yarn was graphitized at a temperature of 2800°C before the mixed acid treatment. By the graphitization treatment, crystallinity of the CNT yarn was improved and amorphous carbon was removed. As a result of XPS analysis, a graphitized CNT yarn treated with mixed acid did not contain the functional groups. On the other hand, a graphitized CNT yarn treated with hot mixed acid (90°C) contained the functional groups. Crystallinity of this yarn was 4.5 times higher than the as-received CNT yarn. In addition, as a result of single fiber tensile tests, tensile strength of this yarn was increased by 79 % and Young’s modulus was increased by 173 % compared to the as-received CNT yarn.
This study demonstrated jet control through the generation of an intermittently induced flow via burst-modulation from a coaxial type, axisymmetric nozzle shape DBD plasma actuator (DBD-PA). Here, a lock-in phenomenon occurred and was characterized by synchronization of the burst-frequency (frequency of burst-modulation) and the jet-generated vortex within a specific burst-frequency range, which aimed to clarify the change in the development process of the jet by the driving condition of the DBD-PA where the applied voltage and burst-frequency were varied. In the main text of this study the Reynolds number that is based on mean velocity and nozzle diameter of the jet was set at 5000. The applied voltages for DBD-PA were Vp-p = 16 kV, 14 kV, and 12 kV, while the burst-frequency was fburst = 0.2–2.0fn ( fn: frequency of occurrence of the initial vortex of free jet is 716 Hz). Results of the control demonstration showed that the lock-in phenomenon occurred at 0.9–1.4fn for all applied voltages. In the downstream, when the driving condition was Vp-p = 14 kV and fburst = 0.7fn, diffusion was dominant in all driving conditions due to fast collapse of the developed vortex ring. Moreover, such collapse was gradual with higher applied voltage. At the end of the burst-frequency of the lock-in phenomenon range, where the driving conditions was Vp-p = 16 kV and fburst = 1.4fn, diffusion became more suppressed as compared to the free jet, as the vortex ring near the nozzle collapsed due to vortices pairing, and did not develop. This work emphasizes that changing the applied voltage and the burst-frequency of DBD-PA potentially promotes and suppresses the diffusion of the jet.
The effect of the expansion ratio on a backward-facing step flow is investigated experimentally. The expansion ratio ER ranges from 2.0 to 5.0. The Reynolds number based on the mean velocity and the hydraulic diameter of the inlet channel ranges from 2.0 × 103 to 7.0 × 103. This Reynolds number range includes laminar, transition and turbulent flows. The forward flow fraction, the wall static pressure coefficient and the local Nusselt number on the lower wall behind the step are measured. When the position of the reattachment point is nondimensionalized by the step height, it moves to the step side as the ER increases in the laminar region. However, the reattachment length is approximately the same in the turbulent region. For all Reynolds numbers, the pressure loss increases and the Nusselt number decreases as the expansion ratio increases. When the upstream flow transitions from a laminar to a turbulent flow, the pressure loss coefficient increases and the maximum Nusselt number decreases for all expansion ratios. For ER = 2.0, the position where the maximum Nusselt number appears is downstream of the reattachment point in the laminar flow and is approximately the same in the turbulent flow. In the case of ER = 4.0 and 5.0, the position is uptream from the reattachment point and is close to a constant value, regardless of the Reynolds number.
This paper introduces a novel robotic joint mechanism composed of antagonistically twisted round-belt actuator, which has multiple small-diameter round-belts in antagonistic location around the joint. This joint mechanism is developed by emulating muscle structure of human upper limbs, and can be activated by twisting each round-belt that is made of polyurethane materials. Especially, this paper shows position and force control by means of the proposed twisted round-belt actuators with traditional P/PI controllers. We clearly demonstrate that contact force on tip of the robot is able to follow desired sinusoidal trajectory with no errors by means of straightforward algorithm on the basis of voltage-controlled robot hardware. Through these experiments, we explain intrinsic characteristics of twisted round-belt actuator system and advantages of the structure in control performance.
In the pneumatic stage, the differential pressure is the driving force. For this reason, it is indispensable for fast positioning to change the pressure in the chamber instantaneously. The piston in the air cylinder moves when the stage is driven. As a result, the volume of the chamber increases or decreases during positioning. Therefore, the pressure in the chamber changes not only by the opening and closing operations of the left and right servo valves but also by the increase and decrease of the chamber volume. Here, in order to drive the stage under high-speed, the chamber volume must be rapidly changed. At this time, the influence of the pressure change due to the chamber volume cannot be ignored and the differential pressure becomes small. This hinders realization of fast positioning. Therefore, the pressure response is improved so that the pressure change due to the servo valves is more dominant than that due to the chamber volume. In this paper, we propose opening operation of the exhaust side valve. It was demonstrated that symmetrization of left and right pressure responses using the proposed method enables fast positioning. Furthermore, it was confirmed that similar effects can be obtained in the control system in combination with pressure feedback.
Remote-controlled robots, which are expected to perform useful tasks, are required to move as intended by operators. The information used to perceive the remote environment including the robot is limited and the operators usually have to perceive or predict motions of the robot through visual information included in a video image. The limitation makes the remote operation difficult. In order to investigate influences of the limitation, we measured operator’s predictions about a position of a remote robot. We had operators do tasks where they navigate the robot to a target. The task is divided into two parts. In the first part, the operators are requested to start the robot to move and given video or non-video stimuli. In the latter part, they are requested to stop the robot at the target without any visual information and the reaching position at which the robot has stopped is measured. Consequently, it was shown that the video stimuli modulate the reaching position of the robot. This means the operators' predictions are modulated. This effect should be caused by the difference between the velocity of the robot on the video stimuli and that on the non-video stimuli. In addition, we investigated influences of optic flows related to robots' motions by a similar task to the prior one. We gave the operators optic flow stimuli during the latter part of the task, while the video stimuli are given during the first part. Then, it was shown that the optic flow stimuli have additional effect on modulating the predicted reaching position which is already modulated by the video stimuli in the first part. It seemed that optic flows related to a robot's motion navigated in a remote environment may modulate a prediction of its operator. We may use this effect well when we operate robots remotely.
In the field of regenerative medicine, cell processing is currently done manually. The process is labor intensive and expensive, and its efficiency must be improved. Automatic cell culture apparatuses equipped with a vertical articulated robot have been proposed recently. However, automating all tasks of cell processing complicates the system constitution. The present study aims to develop a simple and rational cell processing system by combining the tasks performed by a robot with those performed by a human. Herein, we first analyze each task in the cell processing operation, verify whether a task can be efficiently performed by a robot and automated equipment, and decide the combination of the tasks. In a previous paper, we improved the efficiency of the task of discarding spent culture media in a flask by using a robot arm in the media change process. In the present paper, by focusing on the media change process, we examine the efficiency improvement of the task of injecting culture media by using a robot. We propose the configuration of an inspiration/injection port and an algorithm to estimate the start time of injection end motion from the flow rate and conduct a verification experiment. Our results show that a robot can perform the injecting task more efficiently than a human. Moreover, the risk of dripping can be reduced by using a robot.
There are several types of sound localization methods. In middle frequency around 1kHz, these methods are effective to detect the sound source location. However, for low frequency sound under 100Hz, almost sound localization methods do not have enough resolution to detect the sound source location. To overcome this problem, the author is now developing a new sound localization method, "Double Near-field Acoustic Holography method." This method is converted method of conventional Near-field Acoustic Holography method. The Near-field Acoustic Holography method has best resolution in all sound localization method. However, for low frequency sound sources lower than 100Hz, this method does not have enough resolution to detect the its position. The proposed Double Near-field Acoustic holography method is developed to improve the resolution of low frequency sound localization. In this paper, the experimental results with small speaker are reported. By these experiments, it is probed that the proposed Double Near-field Acoustic holography method has enough resolution to detect the position of the low frequency sound source.
Natural vibrations of acoustic space expand noise. Measurement of natural vibration is effective to reduce noise based on noise generation mechanism. Acoustic space has many natural vibrations in the noise frequency band. Multi-point excitation is useful for measuring natural vibration, which has mixed modes and high damping. Furthermore, it is necessary to cancel the influence of dumping to excite the modes individually. In this study, the new measurement principle of natural vibrations of acoustic space by multi-point excitation using decentralized control with local feedback control is proposed. An excitation system with local feedback control excites natural vibration without frequency adjustment and cancels damping in acoustic space. Excitation systems with decentralized control can have multi-point excitation without any adjustment of amplitude and phase each other. The proposed acoustic excitation system consists of a speaker, a microphone and a local feedback controller. The controller generates negative damping according to the sound pressure detected by the microphone and feeds it to the speaker. Firstly, it is confirmed that one acoustic excitation system is self-excited at resonance frequency and some resonance peak of the transfer function is sharpened by canceling the effect of damping. Secondly, multi-point excitation using decentralized control using four acoustic excitation systems is performed to excite many modes. All supposed modes are excited without adjustment of the excitation systems according to mode such as amplitude and phase. Finally, it is confirmed that acoustic excitation system has no limitation on the number of installations and has extensibility for higher-order mode excitation.
This paper proposes a method to construct a force control law for industrial robots by using the normalized cross-correlation (NCC) of human demonstration data. Conventionally there are two solutions where one is based on human demonstration data, and the other is based on numerical optimization. The former one gives the force control parameters efficiently, but the parameters may make the robot unstable. On the other hand, the latter can maximize the performance, but it requires an enormous number of trial and error. Taking into account the merit of each method, we consider combining the two approaches. In our proposed method, the force control laws are determined to maximize the NCC of the human demonstration data. The orientation of the coordinate system is also determined to maximize the NCC of the human demonstration data. Then, the parameters included in the force control law are optimized by the downhill simplex method. The proposed method was applied to a ring-shaped rubber packing assembly task, and it could realize an assembly with human-like performance. Moreover, some comparable experiments were also conducted, and it was confirmed that the proposed method can construct appropriate force controls.
This study proposes a novel step and stair lifting system for wheelchair. In general households, it is difficult for setting the step/stair lift to provide a large space at the front of the entrance, because the size of the system is very large. In addition, the system requires an actuator separate from the lifting drive for folding the platform and wheel-stops. As the number of actuators increases, the scale of the system also increases. Therefore, a stair and step lifting system were designed to satisfy these concepts as follows: 1) do not occupy the space in lower floor side, 2) stair and step common system, and 3) one degree of freedom mechanism. Based on these concepts, the proposed system has only one degree of freedom for driving rail to lift platform, and can be installed at both the stairs and the step by changing the inclination of the driving rail. In this paper, the designs for the step and stair of the proposed system are described. Furthermore, mechanisms for folding a platform and mechanisms for opening and closing wheel-stops are proposed using the lifting drive. For lifting motion, the disturbance observer is integrated to the control system. Finally, the effectiveness of the proposed systems are elucidated through the experiments.
With use of the numerical material testing (NMT) approach based on homogenization theory, a time-temperature reduction law is proposed for both relaxation and elastic properties in the orthotropic viscoelastic constitutive equation, which is supposed to represent the macroscopic material behavior of unidirectional fiber reinforced thermoplastics (FRTP) under various temperature environments. We start with dynamic viscoelastic measurements for polycarbonate (PC) under different ambient temperatures to evaluate the master curves of storage and loss moduli as well as loss tangent that exhibit the temperature- and time-dependent characteristics of its relaxation and elastic properties. Then, with the use of the obtained viscoelastic properties of the resin, a series of NMTs simulating macroscopic stress relaxation are conducted on a periodic microstructure (unit cell) model of the FRTP to characterize the macroscopic viscoelastic material behavior. Finally, the shift functions of the orthotropic relaxation and elastic properties in the assumed macroscopic viscoelastic constitutive law involving the proposed time-temperature reduction law are determined to clarify its time- and temperature-dependent characteristics.
Differential form is an alternative mathematical form to describe the field variables and the operators in electromagnetism. From the viewpoint of differential forms, discretization of electromagnetic field is divided into two steps, i) discretization of the exterior derivative operator (Maxwell’s equations), and ii) discretization of the Hodge star operator (constitutive equations). The first step, the discrete form of the Maxwell’s equations based on differential forms has been obtained by other researchers. In contrast, the discrete Hodge star operators (discrete constitutive equations) have not been obtained so far. In the previous studies, unsigned diagonal discrete Hodge star operators are defined using the unsigned area and length for circumcenter dual meshes, however, it does not lead to correct solution of partial differential equations in the general Delaunay meshes. In this paper, we propose a definition of the signed diagonal discrete Hodge star using the signed area and length operator for circumcenter dual meshes. Also, based on this definition, we propose a simple practical calculation method for the signed discrete Hodge star operators. The result of convergence experiment indicates that the signed diagonal Hodge star operators produce the correct numerical solution for the general Delaunay meshes. Therefore, this definition and calculation method for the signed discrete Hodge star operator provides us with the explicit dynamics formulation for finite element analysis of electromagnetic field.
In recent hobbing, the technologies of dry cutting have been developed in an attempt to improve the working environmental and prevent global environmental pollution. In this study, we investigated wear behavior (tool life), crater wear and finished surface roughness of various coated cutting tools when hardness of work material was changed by heat treatment in dry hobbing. Experiments were conducted by simulating hobbing by fly tool cutting on a milling machine. The results helped clarify the following points: (1) When the hardness of workpiece material SCM415 was changed to HB131, HB144 and HB161, the tool life obtained with all of the four kinds of coated cutting tools used in this experiment in the cases of cutting HB131 (annealing) and HB161 (as rolled) work materials is longer than the case of cutting HB144 (normalizing) work material. Especially AlCrSiN-coated tool is effective. (2) For various coated tools, the crater wear tends to decrease in the order of cutting HB144, HB131 and HB161 work materials, and when cutting HB161 work material with AlCrSiN-coated tool, the crater wear is small. (3) Even if the hardness of the workpiece is changed, the finished surface roughness is as small as 1 μm when cutting with the AlCrSiN-coated tool compared to other coated tools. (4) From the viewpoints of tool life, crater wearand finished surface roughness comprehensively, AlCrSiN-coated tool is effective when the hardness of the work material is changed.
Topology optimization has been widely used in industry for designing high performance structures, but these structures are often complicated shape and cannot be manufactured directly. To solve this problem, it is necessary that geometrical constraints for manufacturability be satisfied in the optimization process. This paper proposes a scheme for imposing geometrical constraints, known as overhang constraints, in topology optimization for additive manufacturing (AM). As a feature of AM, when the inclination angle of an overhang is lower than a certain angle, AM components require temporary support materials to prevent the components from collapsing during fabrication. After the fabrication, these support materials are removed mechanically or chemically. As the use of support materials increase, manufacturing costs increase. Consequently, in order to reduce support materials, it is necessary to control the minimal inclination angle of an overhang in topology optimization. In the proposed method, the inclination angle of an overhang is represented using a fictitious physical model described by a steady-state diffusion equation. The overhang constraint can be imposed in the optimization procedure by constraining the value of the fictitious physical field. Several numerical examples are given to show the validity and effectiveness of the proposed method.
In the present report, we attempted to construct a useful monitoring method to control laser via-hole drilling process of multi-layer printed wiring boards with a high speed video camera.Cu direct laser drilling was performed for the FR-4 type insulation layer, which made of glass fiber reinforced epoxy resin plastics, with a CO2 laser beam. First, we discussed the influence of laser irradiating conditions on the drilled via-hole quality based on estimating the visible video camera images. Second, we focused on two-color method to visualize the temperature distribution in monitoring image. As a result, the high speed video monitoring and the temperature visualization in video image are found to be effective to control the via-hole quality in laser processing.
This study proposes a modified response surface single loop (RSSL) method which improves both approximation accuracy of an optimal solution and the computational efficiency from an original RSSL method. The original RSSL method was proposed recently as one of the single loop methods for a reliability-based design optimization (RBDO) problem that evaluates the failure probability of the second-order limit state function directly by using Hermite polynomials without searching for the most probable point (MPP). When a limit state function is not described as the second-order polynomials, the function is approximated around the deterministic optimum point and then the single-loop searching for the RBDO is carried out. Though the method has sufficient accuracy regardless of the approximation point, two optimization runs; the deterministic and the reliability-based optimizations are required. In order to improve the computational efficiency, the concept of the single loop single vector (SLSV) method that approximate the limit state function around the approximated MPP every optimization searching step is introduced. Through numerical examples, it is demonstrated that the proposed method improves the approximation accuracy of the limit state function and also the searching efficiency.
In this research, we propose a numerical method to design surface texture with the desired friction characteristics, which are arbitrarily given according to the design purpose. The surface texture is parameterized, and the parameters are determined with the response surface method. The surface texture models are made based on the orthogonal array of Design of Experiments, and their friction characteristics between the surface texture model and the finger model are evaluated using the finite element sliding analysis. The three-dimensional multi-layered finger model with fingerprints is constructed based on the friction experiments and the sliding analyses in advance. The objective function and the constraint conditions are defined combining the desired friction characteristics, such as average friction coefficient, minimum friction coefficient, and average friction amplitude. The parameters of the surface texture is determined by the mathematical programming and the response surfaces. Numerical examples show that the proposed method is effective for the design of surface textures.
The demand for functional films with surface microstructures is increasing in industry. Functional films with multi-directional wavy components can be applied to fluid drag reduction in turbulent flow applications. In order to implement the high-efficiency manufacturing of functional films, it is necessary to machine wavy microgrooves onto the surfaces of roll molds first. The molds can then be used to imprint patterned films. However, the machining of complicated microgrooves with multi-directional wavy components has never been reported so far. In this study, the authors propose a two-directional wavy microgrooving process by introducing simultaneous reciprocating motions of a diamond cutting tool driven by a slow tool servo. First, microgrooving experiments were conducted by oscillating the tool in two single directions, namely tangential and normal directions of the surface, and the material removal mechanism in each experiment was investigated. In tangential direction tool oscillation, burrs formed on the edge of the groove, which were suppressed by appropriately setting the oscillation amplitude and the tool clearance angle. In normal direction oscillation, shear angle changed significantly with the groove depth, which in turn influenced the groove surface roughness. By synthesizing the results of single-direction oscillation cutting, wavy grooving was performed by reciprocating the tool in both directions simultaneously. As a result, two-directional wavy grooves were successfully machined with form accuracy of 1.2 μm P-V and surface roughness of 12.2 nm Ra. Then, the microgrooved roll molds were used in ultraviolet resin imprinting tests to fabricate films with wavy microstructures. The wavy microstructures were precisely transferred to the resin films with a transcription error of less than 0.7 μm P-V. The results of this study provide a new approach to rapid manufacturing of functional films with wavy microstructures.
CVT chains are widely used in vehicles because the slip between parts is small, which enables efficient power transmission. However, the intermittent motion of CVT chain pins entering and leaving the pulleys causes undesirable vibration in the whole chain, and affects the basic performance of the CVT. Therefore, it is important to investigate the influence of the geometrical specifications of the chain on this vibratory motion. This study focused on the pin-pulley slip length when the pins enter and leave the pulleys, and a mathematical model for the power loss of a CVT chain was developed. The validity of this model was verified and confirmed experimentally. In addition, the influence of the shape of chain components on power loss was also investigated. In particular, the influence of the position of the contact point between the pins and pulleys on power loss was investigated both theoretically and experimentally, and geometric parameters were optimized. As a result, the model formulated in this paper can be used to investigate measures for reducing CVT power loss.
This paper describes a methodology for probability estimation of derailment occurrence due to an earthquake by the use of seismic waveforms. Under the method proposed, an index for probability estimation of derailment is calculated using the estimated or measured seismic waveform of a track and the three types of running safety limit of the target railway vehicle to sinusoidal vibrations of tracks. The index is calibrated using dynamic simulations of the vehicle behavior with various seismic vibrations in order to obtain the relation between the value of the index and the derailment probability. The dynamic simulations can be executed previously. Therefore, when the seismic vibration of the track is obtained, the time to estimate probability of derailment using the method proposed is much shorter than using dynamic simulation of vehicle behavior. In the case of the Sinkansen train dealt with in the design standard of railway structures, if the calculated index is equal to 10, it means that the probability of derailment occurrence is about 50 %. If the index is larger than 30, the train running on the seismically vibrating track certainly derails due to the earthquake. The method is applicable to the following cases; (a) Quick extraction of sections with high probability of derailment occurrence from the whole train line, and support for the restoration of derailments in the event of a large earthquake. (b) Quantitative check of the effect of seismic countermeasures taken of the railway vehicles, tracks and structures from the standpoint of derailment occurrence probability.
Rail is the peculiar element constructing the railway system. The phenomenon such as wear or defect of rail will be caused by the repeated wheel and rail rolling contact on the rail surface. Especially, the cracks called head checks are generated continuously on the gauge corner side of the high rail due to the plastic deformation caused by the severe contact with the wheels. The occurrence situations and the initiation factors of the head checks are widely known because the head checks are generated in many curved sections of which radii are about 800m. On the other hand, some head checks are confirmed to appear on the low rail in the curved section. However, the occurrence situations of the head checks of the low rail are not clarified because the appearance of this type of the head checks is limited. Furthermore, the initiation factors of this type of the head check are also not clarified. In this research, we conducted the site investigation and the analysis of the rail which has the head checks to clarify the appearance situations of the head checks of the low rail. In addition, we conducted the wheel and the rail contact analysis by use of the multi-body dynamics tool by constructing a model of the site of the head checks appearance of the low rail to examine the initiation factors of the head checks of the low rail.