A new prediction technique of master curve from limited data measured under temperature variance and constant frequency in a dynamic measurement tester has been proposed. The highlight of this technique is a high-accuracy prediction despite the use of the limited data. Our methodology requires that experimental storage and loss moduli satisfy a certain relationship derived from the linear viscoelastic theory. This requirement enables to predict a precise master curve in a wide range of frequencies from the limited data. Investigations of the method's effectiveness and stability have been performed with two materials: carbon-black-filled styrene-butadiene rubber (SBR) with a volume fraction of 10% and silica-filled SBR with a volume fraction of 25%. The mater curves predicted with the limit data on the basis of the new technique were successfully consistent with those predicted by the ordinary method which uses a lot of data measured under temperature and frequency variances and it was demonstrated that the new method showed an excellent predictive performance.
Automated thermoplastic tape laying (ATL) and automated fiber placement (AFP) are high-potential manufacturing methods for continuous carbon fiber reinforced thermoplastic (CFRTP) composites which can ensure operational safety even in highly loaded components such as aircraft wing skins and fuselages or construction large scaled structures. This study aimed to reveal the heating behavior of CFRTP in continuous tape layup molding. The material used for the experiment was unidirectional carbon fiber reinforced polyamide 6 (CF/PA6) prepreg tape. The effects of processing conditions such as output of infrared heater, feed speed of prepreg tapes and heating temperature of pressure rollers on the tape laying behavior of prepreg tape were investigated. In the case of only near infrared heating, it was revealed that the difference in temperature between the upside and downside prepreg tape was increased significantly. Then, the joining strength was decreased significantly compared with using the infrared heater, because the moisture in the prepreg tapes was not removed completely. On the other hand, when the near infrared heater and heating roller were used, the difference in temperature between the upside and downside prepreg tape was decreased considerably. It was also revealed that the surface temperature of CF/PA6 prepreg tape and singe lap tensile strength tends to increase with decreasing the feed speed of prepreg tapes.
In this paper, we propose the method of estimating the stress history from the measured state quantity data from operating machine by creating a stress estimation equation for each evaluation point. We also report how to create the stress estimation equation. We are able to estimate the stress history throughout the machine structure. To accurately verify the stress estimation equation, we performed excavation with actual machine and measured the quantity of state and the stress. We calculated the estimated stress history by using the measured data. As a result of comparing the estimated value with the measured value, the accuracy of estimation was good in the defined region of stress estimation equation.
Carbon fiber reinforced polymers (CFRPs) have high specific strength and many other advantages in mechanical properties compared with conventional metal materials. However, a small out-of-plane impact load can easily cause serious damage in a CFRP laminate because of its laminated structure composed of anisotropic layers. Although ultrasonic inspection is generally performed to detect the damage and estimate its location and size, the method usually requires both long inspection time and a large cost. Thus, a low-cost and in-situ system for monitoring collisions of foreign matters is required to identify the area where the ultrasonic inspection must be conducted. When a foreign matter, which is regarded as a charged body because any object is charged to a greater or lesser extent, approaches and hits grounded electric conductive materials such as a CFRP laminate, an electric current caused by electrostatic induction flows into the ground. We analyzed the electric current and conducted a falling-weight impact test to elucidate the mechanism of generation of the electric current. In addition, we proposed a collision monitoring system which utilizes the characteristic waveform of the electric current and the electrical anisotropy of a CFRP laminate, and conducted a falling-weight impact test to verify the validity of the proposed method. As a result, we succeeded in localizing the collision of the charged body in sufficiently high spatial resolution using the proposed system.
The flow characteristics of a vertical axis wind turbine with the hybrid blade which has the wing section with cutout trailing edge for purpose to make advantages of the drag type and the lift type wind turbine have been investigated by measuring the velocity vector fields using the conditional sampling PIV. The experimental apparatus is constructed using the PIV measurement system with the conditional sampling device and a new hybrid vertical axis wind turbine model installed in a circulating water channel. Four experimental conditions as the tip velocity ratio 0.5, 1.0 1.5 and 2.0 are investigated. The flows around the turbine which influence the efficiency of the vertical axis wind turbine are defined by the measured velocity vector fields. Moreover, the alternations of the angle of attack and the relative flow speed ratio of the rotating blades in the measured velocity vector fields are calculated by analyzing the mean velocity vectors along the circumference of rotating blades. The influences of the flow over the torque generated on the blades are clarified as follows. The drag torque increases, and the advantage of the hybrid blade is effective under the conditions of the tip velocity ratio 0.5 to 1.0. And the lift torque decreases under the conditions of the tip velocity ratio 0.5, and the lift torque increases under the conditions of the tip velocity ratio 1.0.
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, a new tension identification method in a thin plate using modal analysis method is investigated. We develop a simplified dynamic model of thin plate, and tension distribution is modeled by springs. A simplified model spring constants and bending stiffness are obtained by the least-squares method, which minimize the difference between a simplified model modal parameters and the given values. The authors apply the proposed identification method to a thin steel plate based on FEM analysis results. As a result, it is shown that identified tension distributions well corresponded to the FEM results.
The muscle-tendon units of human beings are helpful for minimizing the energy costs during walking. Therefore, proper use of characteristics of these units is effective for walking support and performance improvement. The knee orthosis proposed by the aurthors is composed of a ball screw and linear spring, and elastic energy during walking can be stored and reused. Walking experiments of the apparatus were carried out both on the flat ground and a slope, and the knee orthoses particularly reduced muscle activities for an upslope walking. Through the analysis of ankle equilibrium point trajectory and stiffness based on kinematics data and EMG signals, this study shows that the energy storage and reuse of the knee orthoses decreases muscle activities related to knee extension of radial direction during the stance phase and hip extension of argument direction during the swing phase.
Collision vibration systems are usually modeled as a nonlinear spring whose characteristics are described by the broken line model. These systems are called piecewise-linear systems. A piecewise-linear system is highly nonlinear, and it is usually difficult to predict the system response using any general analytical solution. If the effects of design parameters such as clearance size and dynamic nonlinearity of the systems are known, the structures can be designed to be safer and more comfortable. In a previous paper, forced collision vibration for 2nd order super harmonic resonance in a mass-spring system for two-degree-of-freedom was analyzed. The restoring force, which is generated when a mass collides elastically to another mass, was modeled as an asymmetric piecewise-linear system. In this research, the 1/2nd order sub-harmonic resonance is treated for the same system in the previous research. In order to analyze resulting vibration for the 1/2nd order sub-harmonic resonance, the Fourier series method is applied and analytical solutions for this system are derived. Next, following the analytical solutions, numerical calculations are performed, and the resonance curves are constructed by using resulting vibration. Effects of amplitude ratio of excitation, nonlinearity of the system and mass ratio on the resonance curves are shown numerically. For verification of the analytical solutions, numerical simulations are performed by the Runge-Kutta method, and numerical results based on analytical solutions are compared with numerical simulation results on the resonance curves. As a result, the analytical solutions are in a fairy good agreement with the numerical simulation results.
Heat sealing is a packaging technique for hermetic sealing of foods and medical supplies etc. Evaluation of seal strength is important to guarantee both airtightness and easiness to open which are conflicting requirements. There are few studies of nondestructive evaluation although conventional spot check with destructive evaluation costs a great deal. This study proposes a new nondestructive evaluation method for the seal strength with ultrasonic pulse. The proposed method focuses on instantaneous frequency of the ultrasonic pulse which is time varying frequency in waveform. This paper demonstrates that the instantaneous frequency is more effective to evaluate the seal strength than conventional indexes such as amplitude and arrival time of the pulse through experiments. The transmittance and reflectance on the welded boundary surface are supposed to vary depending on the seal strength because the welded condition does not affect only the seal strength but the characteristics on the welded boundary surface. We also analytically discuss the mechanism how the instantaneous frequency senses the change of the transmittance and reflectance on the welded boundary surface. Simulated instantaneous frequencies also vary according to the change of the transmittance and reflectance. This result indicates that our proposed method effectively senses the variation of the welded surface characteristics pertaining to heat strength.
A method for a six-legged robot of walking on terrain with various undulations by tripod gait is proposed. First the robot detects foot landing using touch sensors, and estimates the inclination angle of the ground from the landing positions; the estimated ground is called “reference ground”. Second the robot measures the inclination angle of its body using acceleration sensor. Then the legs move up and down so that the body may be parallel to and may keep a constant distance from the reference ground. If the robot encounters deep depressions or downward slopes, the robot suspends walking and actively inclines the reference ground. As a result the body inclines, and the swing leg goes further down. When the swing leg reaches the ground, the robot restarts walking. Due to the feedback gain of body orientation control, the robot does not respond to fine change of undulation. Hence the body keeps a constant orientation on short distance undulation or rugged surface, and gradually inclines its body on long distance undulation such as slopes and stairs. The ability of climbing up and down slopes and steps in longitudinal and transverse directions is evaluated by experiments. The maximum angle of climbing up slopes is 30 degree, and that of climbing down slopes is 40 degree. The maximum height of climbing up steps is 150 mm, and that of climbing down steps is 180 mm. The robot can also go through a bump of 125 mm width and 60 mm height.
We propose a set of constitutive equations of earthenware material subjected to the firing process and appropriate ways of determining their function forms and relevant material parameters from a series of respective experiments. The firing process under a specific heat curves is generally divided into three different phases; “thermal dilatation phase”, “sintering phase” and “thermal contraction phase”. These non-mechanical deformations are assumed not to be coincident, and the mechanical ones are assumed to be represented by viscoplastic constitutive model. Then, the key issue must be how to determine sintering strains by calibrating the employed function form of the densification rate with the data obtained from the stairway thermal cycle (STC) tests. Also, the presentations of the dependencies of the elastic and creep properties on both temperature and density are of particular importance to accurately predict the overall deformation of earthware. All the relevant material parameters as well as coefficients of thermal expansion and contraction are identified with the data obtained from respective mechanical experiments conducted in testing equipments for thermo-mechanical analysis (TMA) under several levels of termperature. The method of differential evolution, which is one of the metaheuristic optimization techniques, is employed to identify the creep parameters, since the mechanical responses to several levels of loading during firing processes involve all the non-mechanical and mechanical deformation of specimens simultaneously. The calculation results with the proposed constitutive equations are compared with the original experimental data to demonstrate the applicability for practical use of their function forms determined by the proposed strategy.
In a labor-intensive cell manufacturing system, effective training is an important issue. We have proposed "skill index" as a new human index in the previous study. We have also proposed operator allocation method using this index for effective training up to now under the stable order condition. However, the order condition is fluctuating in a real site. Since this method did not change task assignment, operators had to continue the same tasks after they became expert about assigned task. It has a potential which becomes the big restrictions under fluctuating order condition. In this study, we make a new operator allocation and scheduling method for fluctuating order condition. In particular, we add a new variable for representation of quantity in decision variable of task assignment. The operators have various tasks and we have to consider about the simultaneous tasks, parallel tasks and the preceding restriction for other operators in the same cell under scheduling method. As a result of the computer experiment, our new method can get the task assignment and schedule which achieve more effective training than the previous study.
Modularization and common module design have been discussed to comply with ever expanded global market. Although its ability to realize wide variety of product family are acknowledged, industries have still hesitated to take steps toward its actual implementation. One of the strongest concerns that industries have on product modularization is loss of competitive edge. Historically Japanese industries have advantages in their fine-tune integration - Suriawase. However, modular design may impede such Suriawase as interfaces among modules need to be agreed beforehand. By incorporating opportunity for Suriawase in a module that leads to competitiveness, common module design could be prominent way of design and development of product for Japanese industries. This paper proposes a computational support method for the planning of modular commonization structure of a product line that incorporates opportunity for Suriawase. While there have been several former study on modular commonization planning, this paper additionally discusses the aspect of Suriawase. The case study on planning of solar boat product line demonstrates the proposed method. Relevance of the proposed method was verified through audit with industrial partner as well.
Anteflexion of the spine is essential for many physical activities of daily living. However, this motion places the lumbar disks because it generats heavy load due to changes in the shape of the lumbar spine and can lead to low back pain. In older to reduce low back pain, here we proposed a wearable sensor system configuration that can estimate lumbosacral alignment and lumbar load by measuring the shape of the lumbar skin when the lumbosacral alignment changes. The shape of the lumbar skin and posture angle are measured by using curvature sensors and accelerometers. In addition, the system must be constructed in consideration of the physique, in order to absorb in a variety of human. We proposed this system by measuring the body parameters of anteflexion and studied the change in dimensions of the lumbar spine from changes in posture. By extracting the dimensions of the lumbosacral spine in X-ray images, the attitude angle, body surface area and the dimensions of the lumbosacral spine have relevance. The lumbosacral dimensions calibration method was developed by using that relation. Lumbosacral alignment estimation considering the difference in physiques is developed, and lumbosacral spine alignment was to improve the estimation accuracy. The proposed method could improve accuracy lumbosacral alignment estimation.
Holmium: YAG laser is effectively used for transurethral ureterolithotripsy (TUL). A single bubble is formed at a fiber tip when a laser with high absorption rate irradiates into water through an optical fiber. The bubble shows characteristic behavior when it grows and collapses. In the present study, the behavior of a bubble induced by the fiber type laser is observed with a high speed video camera. In addition, the impulse force is measured with a hand-made sensor. As the results, the instantaneous appearance and the strength of impulse force at bubble collapse are shown for various laser irradiation conditions. A bubble inception appears just after the laser irradiation at the fiber tip. The bubble grows to a characteristic form and collapses with a microjet near the fiber tip. In the case of a bubble generated near a solid wall, the bubble growth is suppressed with the adjacent wall, so that the impulsive force becomes weaker. The impulsive force on wall surface reaches to the maximum value at a distance from the wall to the fiber tip, where the bubble does not collapse at fiber tip but on the wall. It is pointed out that there is an optimum laser irradiation condition on the wall impact for TUL.
'Optimal Design' and ‘Fitting’ have received a lot of attention in golf market. 'Optimal Design' is defined as tailor made design and ‘Fitting’ is defined as a service choosing the best equipment for each player. Both of them have a same problem that they are only conducted by experts called 'Fitters' who have special knowledge and experience. The one reason is golf swings are very complex motions because of motion adjustment depending on the difference of gears. Thus, fitters are required for fitting but there are not enough numbers of advanced skilled fitters. Our objective is to develop a method of optimal design considering to swing motion adjustment and to establish a fitting system of golf shaft that can be used everybody who has not special knowledge. Firstly, we evaluated the validity of the calculated swing data using Design of Experiment and Response Surface Method to achieve our goal. The accuracy rates were over 80% with 9 skilled subjects whose handy caps were less than 40 including 3 professional golfers. On the other hand, the rates of 3 beginners were under 50%. Therefore, we limited the targets of this method to skilled golfers. Additionally, we developed a fitting system to choose the best golf shaft for each player and evaluated the accuracy. As a result, 89 players in 103 ones improved their distance, direction or both, using the optimal shaft recommend by our system.
Laboratory-scale experiments were carried out on simultaneous removal of NOx and SOx from a glass melting furnace using a semi-dry plasma and chemical hybrid process (PCHP). The experimental apparatus is simulated to the aftertreatment system for a full-scale semi-dry glass bottle manufacturing system, and NOx removal processes of plasma-induced ozone gas injection for the oxidation of NO followed by Na2SO3 solution reduction of NO2 and a dry neutralization removal of NO2 by NaHCO3 or Na2CO3. First, NO removal experiments are carried out with water sprayed to form a localized cooling area by heat removal of vaporization in the reactor. As a result, the NO oxidation efficiencies of 76% (Liquid-to-gas ratio, L/G = 0.7 L/m3) and 98% (L/G = 2.0 L/m3) are achieved by the injecting ozone into the localized cooling area. Next, for experiments with a mixed simulated gas of NO and SO2, when the mixed aqueous solution of Na2SO3 and NaOH is sprayed under the conditions of L/G = 0.7 L/m3 and 2.0 L/m3, NOx removal efficiencies of 45% and 48% with NO oxidation efficiencies of 62% and 70% are obtained, respectively. Simultaneously, more than 75% of SO2 is removed. Finally, the neutralization removal of NO2 is investigated for the reaction with NaHCO3 or Na2CO3 onto the filter in the reactor. It is clarified that Na2CO3 is more effective than NaHCO3 for the removal of NO2. The stable NO2 removal is achieved at the dry type reactor. It was confirmed from the experimental results that PCHP combined with dry reduction chemicals method was promising for effective exhaust gas aftertreatment for a glass manufacturing system.
This study examines the driver assistance system to judge whether a passage (GO) or a stop (NOGO) at a signalized intersection ahead. The assistance system indicates the evaluation indices on the road ahead virtually. The proposed assistance system informs a driver visually of the distance which the vehicle can traverse by maintaining the current velocity until the red signal onset using the signal information. If the remaining distance to the intersection is longer than the indicated distance, the system also indicates a stopping distance by assuming the ordinary deceleration. The driving simulator experiments are carried out to evaluate the proposed assistance system. The assistance system encourages the earlier deceleration before turning to the amber signal and prevents the emergency braking behavior or the risky passage through the intersection. In addition, the assistance system shortens drivers' reaction time to the emergency deceleration of the preceding vehicle compared with the onboard monitor indication in the own vehicle. Indicating evaluation indices on the road ahead virtually helps the driver to decelerate earlier and avoid the higher deceleration. These effects make it possible to suppress the collision risk to the preceding vehicle and contribute the safety driving.
The roll motion of the vehicle has an effect on the yaw natural frequency. Because the yaw natural frequency formula considering this effect is the solution to a quartic equation, the expression of the formula is thought to be complex and incomprehensible. Accordingly, a seemingly comprehensible approximate formula was suggested in the former paper. In this approximation process, it was assumed that the cornering forces of the front and rear wheels are generated simultaneously. On the other hand, a later report have indicated that the yaw resonance when the vehicle drives at a certain speed has a cornering forces phase difference of 90 degrees between the front and rear wheels. Therefore this paper formulates the yaw natural frequency and yaw damping ratio assuming the phase difference to be 90 degrees. As results of that, qualitatively, the design variables that dominate the characteristic equation are appropriately included in the yaw natural frequency and yaw damping ratio formulas, and quantitatively, the approximation error is reduced. Consequently, these formulas are believed to be more appropriate than the previously proposed formulas. These formulas indicate that, when the load distribution ratio of the front wheels becomes larger, the yaw natural frequency decreases and the yaw damping ratio increases. In addition, this paper also indicates the scope of these approximate formulas quantitatively.
Antenna surface forming by cable network is an essential design method to achieve high performance for communication services or high resolution observation for radio astronomy. The precision of the surface can be determined by a facet approximation error depending on their size. Uniform tensile force distribution among cables is measured by adjusting tension ratio of the edge cables and the center cables of the reflector. In general, the tensile forces of the edge cables become several times greater than those of the center cables. Therefore, total strain energy of the cables is decided based on the tensile force distribution including the edge cables. When the number of the cables of the network increases, the total strain energy of the cables raises. Consequently, a support structure, e.g., truss rib structures or hoop structures, must be improved its rigidity to prevent deformation of the surface. This paper describes a new surface forming concept in which the cable network is assembled by tensile and compression members. Several compression members are equipped instead of tensile cables. As a result, the total strain energy of the cables can be reduced, and the retentive force applied to the support structure can also be reduced by using this method.