In this study, we propose a suitable blanking velocity for the blanking of different materials using a screw drive servo press. Under this blanking velocity, press blanking can be carried out without causing an increase in blanking vibration. Blanking noise and vibration are causes of pollution. Moreover, blanking vibration reduces the precision of press work products and the lifetimes of the press machine and press die. Recently, a servo press has been developed for advanced press work. A screw drive servo press does not have a mechanical bottom dead center but location of its slide is constantly measured, and highly precise location and speed control are achieved by a feedback control system. However, blanking vibration is increased at high blanking velocities using this machine. Our previous study clarified that the blanking velocity and blanking time affect of blanking vibration. However, the influence of the material is not clear. Thus, we studied the relationship between the material and the vibration in blanking with a screw drive servo press both experimentally, and by simulation. At the experiment, we compared the blanking vibration of four materials with different tensile strengths. As a result, we found that the blanking time is different for each material, because the blanking distance depends on each material. And finally, we propose an equation as a general formula which calculates the threshold of blanking velocity vt to prevent an increase in blanking vibration.
A new process is proposed to fabricate an aluminum alloy matrix composite dispersed with intermetallic compound particles by using the reaction between porous nickel and molten aluminum alloy. The intermetallic compound particles reinforced aluminum alloy matrix composite was manufactured with the infiltration-reaction method. Four different specific surface areas of porous nickel were used to fabricate the composites and then the porosity inside composites were investigated. Porous nickel reacted with molten aluminum alloy at 973 K, and the intermetallic compound, Al3Ni was generated on the surface of the porous nickel. The generated intermetallic compound Al3Ni, was delaminated according to the difference of thermal expiation coefficient with nickel. And the intermetallic compounds moves in the direction of aluminum matrix. The area fraction of the intermetallic compounds increased with the increasing specific surface area of porous nickel. In addition, the hardness of composite increased by the increasing specific surface area of porous nickel.
FEM simulation for the orthogonal cutting of Ti-6Al-4V alloy was investigated. Johnson-Cook's model was used for a flow stress equation of material. Rigid-plastic analysis was carried out using DEFORM-2D and AdvantEdge which were commercial software. For the constants in this model, the initial yield strength, the strain-hardening coefficient, the strain-rate sensitivity, the strain-hardening exponent and the thermal-softening exponent were used a reported value by Meyer-Kleponis. Failure accumulation in the Johnson-Cook model was considered by applying the Cockcroft & Latham law to the failure condition of materials. Some constants of material model and fracture limit value were estimated from the orthogonal cutting test. The friction between the chip and cutting tool was assumed the Coulomb friction μ=0.382. The friction coefficient that applied to simulation was calculated by the results of the cutting test. The validity of the calculation results were considered by comparing with the experimental results that were the cutting force, tool temperature and chip shape. When a ductile fracture condition was not considered (Df=0), the chip shape was calculated the flow type, the characteristic saw-tooth type in titanium alloy was not calculated. The chip shape was varied according to a limit value of the ductile fracture. The calculation result of the tool temperature was approximately accorded with an actual value. It was found that the cutting simulation of the titanium alloy was possible by the Johnson-Cook model that applied a ductile fracture condition as Df=0.1.
The goal of the present work was developing the software for calculating the electrical conductivity of aluminum-based particle-dispersed composites by using the actual microstructure images and by performing conduction simulations. However, the electrical conductivity calculated using the microstructure image was supposed to be not equivalent to the electrical conductivity measured by using any of the existing experimental methods, because the microstructure image is a two-dimensional source of information, although the experimental conductivity is obtained from three-dimensional microstructures. Therefore, the statistical relationship between three- and two-dimensional electrical conductivities was investigated by performing the conduction simulations. The electrical potential distribution in the steady state was calculated by using the finite volume method, and the electrical conductivity of the composites was evaluated. The average electrical conductivity of two-dimensional cross-sections was lower than that of a three-dimensional cell, and the difference increased with increasing volume fraction. When the difference between the matrix and reinforcement electrical conductivities was small, the difference between the two- and three-dimensional electrical conductivities was small as well. The difference between the two- and three-dimensional electrical conductivities was constant for all volume fractions even when dispersibility changed. A correction for converting the two-dimensional electrical conductivity to the three-dimensional electrical conductivity was suggested. The electrical conductivity of Al/TiB2 was evaluated from the actual microstructure image by performing the conduction simulation.
This study aims at clarifying the effects of delamination on fretting wear behaviors of plasma-sprayed hydroxyapatite coating. Plasma-sprayed hydroxyapatite (HAp) coating has been widely used as a bond between human bone with artificial metallic implants in order to smoothly transmit loads by gaits. However, HAp coating is susceptible to be failed due to brittle fracture, fatigue cracks, wears by fretting or corrosion etc. Wear particles made by fretting are concerned for activating inflammatory reactions at surrounding organs, which lead to loosening of implants or subsequent failures. Delamination in interfaces of HAp coating can accelerate the wear behaviors in fretting fatigue. Moreover, adhesive conditions between human bone with artificial implants can affect such the delamination / wear behaviors of HAp coating. Adhered contact surfaces between human bone with artificial implants are practically believed to suppress such wear behaviors. However, no experimental study to observe the behaviors has been conducted. An in-situ observation system of fretting fatigue was facilitated. The in-situ observations revealed that higher stress amplitudes and lower contact pressures promoted growth rates of delamination. Furthermore, delamination between HAp coating with metal substrates could accelerate the wear amounts from both the artificial human bone and HAp coatings. Adhered contact conditions between contact pads with coated substrates demonstrated lower delamination growth rates in HAp coating. Even in the cases of adhered contacts conditions, delaminaion continued propagations, which indicated that wear behaviors would occur once delamination reached a certain length. Finite element analyses also revealed that delamiantion length in HAp coating could mainly promote wear behaviors of HAp coating.
In multi-stage closed die forging, an optimum shape of a preform is required to economically manufacture more complicate and precise products. This preform promotes to distribute an appropriate volume, and it helps to reduce material loss and forging load at the final stage for the final products. However, it is difficult for beginners to design the preforms, especially, in processes of locally-lateral upsetting. The preform is needed to make automobile parts such as a connecting rod, a crank shaft, and a knuckle arm. In this paper, locally-lateral upsetting of a rod billet for the typical preform is tried by using different punches and configuration to promote the asymmetric flow of the work material. The punch has each cylindrical nose with a different radius. Furthermore, the punch is set at a different rotating angle from the axial direction of the rod to promote the asymmetric material flow. As the results, the largest asymmetric material flow is appeared when the cylindrical punch with the large radius and rotating 45° is used.
For high sensitivity in micro bio-analysis devices (MBD), the fabrication of the micro-structured reaction field using vertically aligned carbon nanotubes (VACNTs) which is pillar-structured by two methods was performed. The first method is the combination of photolithography and thermal chemical vapor deposition (CVD). The second method is the molding process of polydimethylsiloxane (PDMS) substrate with micro-pillars array and the transfer press of VACNTs synthesized by thermal CVD on PDMS substrate for lower cost in mass production compared with photolithography process. In the first method, circular-pattered metal film on silicon (Si) substrate as the catalyst for VACNTs synthesis was fabricated by photolithography and VACNTs-pillars array was successfully fabricated using the substrate with circular-pattered metal film by thermal CVD. Furthermore, the protein adsorption property of these structures was evaluated as the reaction field of MBD by ultraviolet (UV) spectroscopy. The results show that the protein adsorption property was improved considering the design of micro pattern in VACNTs structures. On the other hand, in the second method, pillar-structured PDMS substrate was molded using a photoresist mold by photolithography and VACNTs was transferred on PDMS substrate by transfer-press equipment. The results indicate that VACNTs can be transferred on the top of micro pillar of PDMS substrate controlling the load of transfer press. Furthermore, it is indicated that micro-pillar VACNTs structures can be fabricated by molding and transfer press with lower cost than the combination of photolithography and thermal CVD.
This paper proposes a method for measuring the tool temperature during burnishing by using a diamond tip. The proposed method was used to examine the influence of tool wear behavior and burnishing conditions on the tool temperature. The experiment focused on the inner circumferential surface of a cylindrical geometric workpiece rotated by the main spindle of a lathe. The tool temperature was measured by using a two-color pyrometer with an optical fiber as a noncontact thermometer. An optical fiber was embedded in the workpiece in the radial direction, and it was rotated with the workpiece. The optical fiber accepted the infrared rays that radiated from the burnishing point of the diamond tip. Another optical fiber that was fixed on the outside of the lathe guided the accepted infrared rays to the two-color pyrometer. The accelerometer was fixed on the tool shank to detect the position of the burnishing point. The output pulses from the two-color pyrometer and accelerometer were stably observed during each rotation of the workpiece. The influence of the tool wear behavior on the tool temperature was observed. The tool temperature increased when the profile of the wear region of the diamond tip became rough. In contrast, the tool temperature decreased during the initial stage of burnishing. The circumferential speed of the target surface (burnishing speed) and the indentation force of the diamond tip on the target surface influenced the tool temperature.
Hard chromium coating is mainly used to improve the surface performance of pistons, brake disks and gears. In the future, better abrasion resistance and better corrosion resistance of hard Cr coating are demanded. Co-deposition of ceramic particles in Cr coating improved these characteristics. The Cr-ZrO2 composite coating is one of the prospective candidates for improvements of mechanical properties. In the present work, the measurement of polarization behavior of low carbon steel in CrO3-H2SO4 electrolyte with ZrO2 addition was conducted to investigate corrosion resistance. Microstructure of coating surface was observed with Electron Prove Micro Analyzer (EPMA) and Transmission Electron Microscope (TEM). Vickers hardness of coating surface was measured. The addition of ZrO2 had no effect on pH. Electrolyte was still strong acid. The shape of polarization curve was changed by the addition of ZrO2 particles. Polarization point was shifted higher by the addition of ZrO2 particles. The corrosion resistance was improved by the addition of ZrO2 particles. ZrO2 particles made the reduction reaction slowly. Coating surface consisted of Cr nano-crystal whose average size was 32.7 nm. Aggregation of ZrO2 particles was not observed in the resolution of EPMA. Addition of ZrO2 particles improved Vickers hardness of coating surface.
Poly(lactic acid) (PLA) attracts much attention as a typical biodegradable and biocompatible polymer, because it degrades to nontoxic lactic acid through non-enzymatic hydrolytic degradation. Processing of PLA bone fixation devices have been investigated to improve their mechanical properties. Among fixations, screws are referred as one of the most general bone fixation device. The purpose of the present study is to clarify the effect of initial higher-order structure on degradation behavior and associated mechanical properties for self-reinforced PLA screws. PLA screws were prepared through a series of routes including casting extrusion drawing and forging. These screws were immersed in phosphate buffer solution (PBS) for 0, 8, 16 and 24 weeks, and orientation function, crystallinity, molecular weight and shear strength were measured. As a result, initial shear strength increased and degradation ratio decreased with orientation. This is due to lower water absorption caused by orientation crystallization. Shear strength decreased approximately 15 % at least with 24 weeks immersion. The results of the crystallinity showed that the screws were selectively hydrolyzed in amorphous region. This fact suggested that shear strength retention depends on hydrolysis in amorphous region. Initial shear strength for extrusion ratio (ER) 2 is the highest although the orientation function is the lowest. And the strength rapidly decreased with 8 weeks immersion. This might be due to hydrolysis of oriented tie chains. Although β crystals emerged only at ER 4, there was not clear difference in molecular weights and shear strength. This result suggested that the crystal form has little effects on degradation behavior and mechanical properties.
Performance of self-sustaining methanol auto-thermal reforming (ATR) was investigated experimentally in order to elucidate a reforming reaction mechanism and a condition required for high purity H2 production for compact reformer. The reformer consists of vaporizing and reforming sections in a single unit. The exothermic oxidation and endothermic steam reforming (STR) take place simultaneously in the reforming section. The reforming section is surrounded by the vaporizing section and then the heat for vaporization is supplied from the reforming section. Two types of exothermic oxidation reaction were investigated as the heat source for STR; one is a partial oxidation (POX) and the other is a total oxidation (TOX). CuO/ZnO/Al2O3 catalyst and Pt/Al2O3 catalyst were used for STR and POX, respectively. While, only CuO/ZnO/Al2O3 catalyst was needed for TOX because TOX took place when fuel and oxygen were supplied to the CuO/ZnO/Al2O3 catalyst. Experiments were investigated in the range of oxygen/carbon ratio (O/C ratio) 0.1-1.5, steam/carbon ratio (S/C ratio) 1.0-3.0 and N2 mole ratio 79-50 % in oxidizer. The results showed that the H2 formation reached maximum at around O/C=0.4 in both STR/POX and STR/TOX cases in the present study. When O/C ratio is decreased from 0.4, heat formation by the oxidation reactions decreases and is insufficient to reform residual CH3OH by STR. As a result, H2 formation and the methanol conversion ratio decrease. When O/C ratio is increased from 0.4, the H2 formation decreases, because methanol is consumed with the excess O2 by TOX and CH3OH for STR decreases. After all, O/C=0.4 gives an appropriate balance of heat supply and methanol for H2 production. These results elucidate that the reaction rate of oxidation reactions, POX and TOX, is much faster than that of STR. In other words, methanol is first consumed by the oxidation reaction and the residual methanol is used for STR. For S/C ratio, H2 formation is decreased in the higher S/C ratio. N2 mole ratio in oxidizer has few influence over the reforming gas. The chemical equilibrium calculations support the experimental results.
One of the inherently safe technologies currently under development is a system to prevent hydrogen explosion during severe accidents (SAs). This hydrogen explosion prevention system consists of a high-temperature resistant fuel cladding of silicon carbide (SiC), and a passive autocatalytic recombiner (PAR). Replacing the zircaloy (Zry) fuel claddings currently used in LWRs with the SiC fuel cladding decreases the amount of hydrogen generated and thus decreases the risk of hydrogen leakage from the primary containment vessel (PCV) to the reactor building (R/B), including the operation floor. The PAR recombines the leaked hydrogen gas so as to maintain the hydrogen concentration at less than the explosion limit of 4 % in the R/B. The SiC fuel cladding being considered consists of an inner metallic layer, an SiC/SiC composite substrate, and an outer environment barrier coating (EBC). A thin inner metallic layer in combination with the SiC/SiC composite substrate functions as a barrier for fission products release. The EBC is introduced to provide both corrosion resistance in high temperature water environments during normal operation and oxidation resistance in high temperature steam environments during SAs. The advantages of using the SiC fuel cladding in the system were examined through experiments and SA analysis. Results of steam oxidation tests confirmed that SiC had 2 to 3 orders of magnitude lower hydrogen generation rates during oxidation in a high temperature steam environment than Zry. Results of SA analysis showed that the total amount of hydrogen generated from the SiC fuel cladding was reduced to one eightieth or less than that of Zry claddings. Calculation also showed that the lower heat and the lower reaction rate of the oxidation reaction of SiC moderated the hydrogen generation with time. It is expected this moderated generation will lessen the pressure increase in the PCV.
A novel alternate-current (AC) magnetic suspension using magnetic resonant coupling is proposed and studied both theoretically and experimentally. An AC magnetic suspension with energy transfer function has been developed to achieve magnetic suspension and energy transfer to the suspended object simultaneously. However, the energy transfer efficiency was low in the developed system mainly because there existed a rather wide gap between the primary and secondary circuits. In contrast, the energy transfer technique using magnetic resonant coupling has high efficiency even if there is a wide gap. In this work, this technique is combined with AC magnetic suspension. The fundamental characteristics of the proposed system are studied for a basic model. It is shown analytically that the coupled circuits has two resonant frequencies and attractive force is generated at the lower resonant frequency while repulsive force is generated at the higher resonant frequency. In addition, the self-stabilizing characteristic, which is proper in the tuned LCR circuit levitation, is achievable in the proposed suspension system. A see-saw type experimental apparatus was fabricated for basic experimental study. The theoretical predictions were confirmed experimentally. The self-stabilization was achieved in the fabricated apparatus. It was also shown experimentally that the stiffness and damping characteristics depend on the gap, the amplitude and frequency of the AC voltage source.
This study formulates a three-link and three-joint optimal control model for simulating human squat movements, clarifies its performance, and examines the strategy for generating squat movements from a computational viewpoint. The model is characterized by sequentially minimizing its two criterion functions for the crouching-down and rising-up processes of the squat movements and predicting the desired value of the state-variable vector in the crouching-down process and the overall movement duration necessary for optimization. Each criterion function consists of three kinds of energy costs, a center-of-gravity cost, and a torque-change cost. The model is applied to reproduction or generation of trajectories of human squat movements, and the following results are obtained: (1) the desired value of the state-variable vector and the overall movement duration can be predicted as linear functions of the minimum height of the center of gravity at the switching time when the mode of motion switches from the crouching-down process to the rising-up one; (2) there exists an optimal switching time to minimize the sum of the two criterion functions; (3) the reproduced squat movement trajectories agree well with the measured ones; and (4) the reproduced trajectories are hardly affected by which one of the criterion function’s costs is minimized. These results suggest that the formulated model can be effective in simulating human squat movements and that three kinds of strategies-which individually minimize the energy, center-of-gravity, and torque-change costs-can be equivalent to one another in terms of the reproduced trajectories as far as human squat movements are concerned. The results also suggest that the minimum height of the center of gravity can be minimum information indispensable for generating squat movements.
Receding horizon control is a type of optimal feedback control in which control performance over a finite future is optimized with a performance index that has a moving initial time and terminal time. Spatiotemporal dynamic systems characterized by both spatial and temporal variables often occur in many research fields. In this study, we develop a novel design method of receding horizon control for a generalized class of spatiotemporal dynamic systems. Using the variational principle, we first derive the exact stationary conditions that must be satisfied for a performance index to be optimized. Next, we provide a numerical algorithm to solve the stationary conditions via a finite-dimensional approximation. Finally, the effectiveness of the proposed method is verified by numerical simulations.
An inertia damper with a long spiral bypass pipe was developed in order to obtain a series inertia effects for vibration suppression of structures in practical use. The damper comprised a cylinder, piston, and MR fluid. The gap was spirally formed around the outside of a cylinder, and acted as a long bypass pipe. MR fluid is well known for its changeable damping effect, but the mass of the fluid is the focus of this study. It is obvious from previous studies that a fluid inertia effect is caused by quick motion in the long bypass pipe, and it depends on the length of the bypass pipe, compression ratio of area, and density. A large inertia effect can be derived if the fluid has a heavy mass. In order to confirm the inertia effect, a prototype damper was manufactured, and resisting force characteristics were measured. Seismic response tests using a 3-story structure were then performed using a shaking table with the damper installed. Each story of the structure had a height of 3 m, and a weight of 6 tons with a total height of 9 m and a total weight of 18 tons. Several types of earthquakes were input, and the response acceleration, relative displacement, and reaction force were measured. Finally the effects of vibration reduction were confirmed experimentally, and a feasibility study was discussed.
Humans can evaluate roughness on various shaped surfaces. Conventional roughness measurement sensors are difficult to apply to curved surface or small product's surface. In this paper, a simple tactile sensor utilizing human ability based on haptic bidirectionality is developed for the roughness evaluation. Humans can move their fingers while perceiving tactile sensations and change exploratory movements like contact force, scanning velocity, direction, etc. according to haptic perception and task objective. Our developed sensor is composed of two microphones and is mounted on a human fingertip. It allows users to touch the object without haptic obstruction. Users can apply the sensor while retaining their normal haptic perception and simultaneously obtaining vibrations and sound based on the mechanical interaction between the finger and the object. First, influence of contact force and scanning velocity on the sensor output is investigated. The experimental results show that the sensor output increases with a rise in the contact force but the influence of the scanning velocity varies between individuals. Then, on the basis of the results, experiment of roughness evaluation is conducted for flat surface and curved surface. A constant normal force and scanning velocity are exerted and the collected sensor output is calibrated by using the sensor output for the middle-roughness sample. The results show that the sensor is capable of evaluating roughness on both flat surface and curved surface in the same rating.
An electro-conjugate fluid (ECF) is a type of functional fluid that produces a jet flow under a non-uniform electric field. We use an ECF to generate a rotational flow in a tiny cylindrical chamber. When multiple droplets are dripped into the rotational flow of the ECF, they may be subjected to a centripetal force because of the difference in density between the droplets and ECF. This causes the droplets to move to the center of the chamber and mix with each other. In this paper, we conducted luminance measurements using a bioluminescence reaction to verify the suitability of this device for biological applications. We observed the luminescence produced by mixing droplets of luciferin and luciferase, and measured luminance maxima and area to assess the mixing ability of the device. In addition, because the enzyme luciferase can be deactivated by surroundings, we confirmed whether the proposed mixing method has any harmful influence on biological samples or not. To better understand the properties of the device, we conducted control experiments with two other set of conditions; i.e., without ECF and with still ECF. Our results confirmed that there was no difference in mixing ability between the three systems, and the influence of an electric- and centrifugal-field generated in the device on mixing might be negligible for biological applications.
Golfers' swings vary with each individual and golf club manufacturers provide the service called “Fitting”, to select an appropriate golf club for each swing, to an each golfer. In order to find the appropriate golf club for each golfer, it is necessary to measure the position and orientation of a golf club head. It can be supposed that the measurement error needs to be less than 0.5 degree. There is an existing method whereby the three-dimensional (3D) orientation of a golf club head is measured from the 3D positions of points on the golf club head. This method is generally used in the area of motion analysis, and has problems in that the system has many restrictions in its installation, large installation space is required, and costs are incurred to the future expansion of the fitting service to many locations, as two or more cameras are needed. The “Fitting” service requires a method that needs small space, low cost and little calculation time. Therefore, A method was developed, whereby the 3D orientation of a golf club head was calculated based on one image from just one camera using the Newton-Raphson method, which needs little calculation time, and the measurement accuracy was validated compared with the experimental results. It was proved that the developed method is useful to a golf club fitting service because the measurement error is less than 0.5 degree of our target even when various golfers' swings are measured, whereby markers are attached possibly near the outline of the head in the case of the farthest distance between markers from 80 to 95 mm, and then the coordinates of the marker center are identified by calculation from luminance and coordinates of each pixel in an area surrounding the marker.
Gantry cranes used for container handling at container terminals (hereinafter referred to as cranes) have experienced unexpected runaways caused by wind. In the present paper, a method of dynamic simulation analysis for runaway of cranes caused by wind is described and the dynamic behavior of a standard-size crane while approaching runaway and after runaway as a result of a wind gust was clarified. In the dynamic simulation analysis, the crane was modeled by combining three-dimensional finite elements. The interaction forces generated between the wheels and the rails and the braking force of the rail clamps used to prevent crane runaway as a result of wind were modeled and calculated. The time change of wind velocity of a wind gust was modeled in terms of the increase ratio and the time change rate, and the wind load acting on the crane was calculated. Based on these models, a standard-size crane was analyzed herein. According to the analysis results, when the gust acted in the rail direction under the condition in which the friction coefficients between the pads of the rail clamps and the rails and those between the wheels and the rails decreased, the sea-side clamp pads and driving wheels entered the slip state, after which the land-side clamp pads and driving wheels entered the slip state. Then, the entire crane started to run away. Due to the time lag like this, the crane may run away even though the total wind load is smaller than the total resistance force acting to prevent runaway, which is simply calculated as the sum of the maximum static friction forces generated between the clamp pads and the rails and between the wheels and the rails. Moreover, although the increase ratio of the wind velocity is small, if a wind gust having a large time change rate blows and the fluctuation of the inertial force in the rail direction becomes large as a result of the swinging of the upper part of the crane, the probability of crane runaway increases when the inertial force increases in the runaway direction.
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