This paper is about damage diagnosis using discriminant analysis via the support vector machine(SVM). For evaluation of reliability of the structure, condition of the structure is divided to several condition levels by the threshold in many cases. At these cases, identification of the damage as the discriminant levels is sufficient for the damage identification model. This paper is focused on the improvement of the identification accuracy of damage identification using discriminant analysis. SVM is one of linear learning machine which conduct 2 groups discrimination which used for discriminant analysis and pattern recognition. SVM is enable to use for the analysis which the boundary of the groups has nonlinear relation. About the damage identification, measurement data is affected by location and stage of the damage and simple linear discrimination is difficult to adopt as the method. In this paper, SVM is applied to identification of a delamination cracks in CFRP beams using the electric resistance change method. The effectiveness of this method is investigated from FEM model of electric resistance change due to the growth of the delamination crack. As a result, with weighted method for avoiding the risk side evaluation, the risk side evaluation which cause degradation of the reliability of structure was reduced.
Research and development on a composite material named as Fiber-Metal Laminates (FML) for its airplane structural applications have been focused on in recent years. These materials laminate FRP (Fiber Reinforced Plastic) of susceptibility to out-of-plane loads and metal of high impact resistance together to mutually compensating the weaknesses of FRP and metals. To date, a typical one of FML is GLARE (Glass Laminate Aluminum Reinforced Epoxy) which laminates the aluminum alloy (Al) and the Glass-fiber reinforced plastic (GFRP) together. In this work, interlaminar mechanical properties, e.g., fracture toughness, of GLARE are improved by acid treatment to Al and adding Vapor Grown Carbon Fiber (VGCF) between Al and GFRP layers. The influence of VGCF addition and acid treatment on the mechanical properties of GLARE is examined by End Notched Flexure (ENF) tests. On the surface of an Al plate, the “line” induced during rolling manufacturing process appears clearly by acid treatment. Furthermore, VGCF addition amount is changed as 0, 10, 20 and 30 g/m2. From the results of ENF tests for Mode-Ⅱ properties, when 10g/m2 of VGCF are added between Al with acid treatment and GFRP layers in GLARE, critical load (PC) and critical strain energy release rate in Mode-Ⅱ(GⅡC) increase most significantly due to the fiber bridging effect, i.e., 118% and 345%, respectively. The present results also reveal that properly adding VGCF, e.g., 10g/m2, has an effect on deterrence of crack growth. However, GⅡC decreases when the VGCF loading is too high due to poor VGCF dispersion, e.g., 30 g/m2 here. Moreover, the anisotropy of interlaminar mechanical properties depending on the “line” and fiber directions appears more obviously by adding VGCF.
The objective of this study is to evaluate fatigue crack propagating behavior in surface modification layer treated by peening. A load-controlled plate bending fatigue tester has been developed in this study. This makes possible to evaluate relation between stress intensity factor range and fatigue crack growth rate, i.e., da/dN-ΔK diagram, in the surface modification layer, since the tester keeps the load constant differently from a displacement-controlled tester. Although the displacement-controlled fatigue tester which keeps displacement constant has been widely used to evaluate the fatigue crack propagating behavior, an applied load, i.e., stress ratio, changes along with crack propagating. In this study, the fatigue crack propagation test was conducted on specimens treated by cavitation peening, which is one of the surface modification techniques, and mechanical properties were also evaluated, including residual stress, yield stress and Vickers hardness, so as to reveal the effect of such mechanical properties varied by the peeing on the fatigue crack propagating behavior. It was concluded that the da/dN-ΔK diagram determined by the tester follows the Paris law and ΔK at da/dN = 10-9 ～ 10-8 was increased more than twice by cavitation peening. The increment has a relation with the mechanical properties varied by the peening.
Particle diffusion from a continuous point source was experimentally investigated to clarify the mechanism of turbulent diffusion for a wide range of turbulent Reynolds number Rλ. The values of Rλ were systematically changed from 43 to 445 by controlling turbulent intensity and vortex scale, using an active turbulent generator. Particle concentration was measured by a laser system. The mean concentration profiles agree with Gaussian distribution, and streamwise growth rate of the variance became larger as Rλ increased, as predicted by the Taylor's diffusion theory. Lagrangian properties (TL，vL，T0) were determined from the streamwise growth rate of the variance σT2. Diffusion fields shifted from the short-time diffusion dominated by meandering diffusion to the long-time diffusion dominated by relative diffusion as Rλ increased. Then we discussed the ratio, β(=TL/TE), between the Lagrangian and Eulerian time scales. The contributions of the relative and meandering diffusions to the total diffusion were evaluated by the Lee & Stone's model.
The tip vortex has an important role on the aerodynamic performance and noise of half-ducted propeller fans. The present paper provides better understanding on the three-dimensional structure of the tip vortex in a half-ducted propeller fan, aiming at the effective control of it. A numerical analysis was carried out using a detached eddy simulation (DES). DES results were validated by the comparison with LDV measurement data. Vortex centers around the propeller fan were identified by the critical point theory. The numerical results show that the tip vortex in the opened region upstream of the shroud leading edge is advected nearly along main stream, whereas the tip vortex in the ducted region covered by the shroud is turned toward the tangential direction by the interaction of the tip vortex with the shroud wall. The behavior of the tip vortex in its inception region does not depend on the flow rate, because the relative inflow angle at the leading edge near the blade tip is independent of the flow rate. On the other hand, the behavior of the tip vortex in the ducted region is sensitive to the flow rate. As the flow rate is decreased, the tip vortex interacts more strongly with the shroud wall, and as a result, its trajectory is inclined more largely in the tangential direction in the ducted region. In the opened region, the core radius and circulation of the tip vortex increase rapidly at constant growth rate in the streamwise direction. In the ducted region, on the other hand, the tip vortex decays gradually in the downstream direction. The maximum circulation of the tip vortex amounts to 60～75% of the circulation of the bound vortices released from the near tip region of the blade. It is found that the jet-like axial velocity distribution is formed around the tip vortex center by the favorable pressure gradient along the tip vortex center resulting from its rapid growth in the opened region.
The pressure waves which is caused by high-intensity proton beam injection into mercury is a critical issue to keep the steady operation in the high-power spallation neutron source, because the pressure waves induces cavitation and imposes severe erosion damage on the target vessel due to bubble collapsing. A double-walled structure of the beam window portion is adopted for the advanced mercury target vessel in the Japan Proton Accelerator Research Complex (J-PARC). The double-walled structure which has the narrow gap between the inner and outer walls is expected to reduce cavitation erosion in the beam window portion by deforming the shape of cavitation bubbles due to the flowing and gap boundary effects. In order to understand the cavitation damage in the narrow gap, cavitation damage tests of the type 316 stainless steels were conducted using mechanically-induced pressure waves under stagnant mercury with parametrically changing gap width and machine power. Furthermore, numerical simulation was carried out to estimate the pressure and cavitation bubble behavior in the narrow channel. The results showed that the clear damage reduction which was attributed to the deformation of bubble collapse due to the channel wall boundary was confirmed. On the other hand, the damage in the narrow gap was not directly related to the imposed power. The severe damage caused by the secondary cavitation bubble collapse predicted through the numerical simulation was observed at the lowest power.
Hot water in a main pipe flows into a branch pipe and forms a thermally stratified layer with cold water at a bent section. Fluctuation of the thermally stratified layer may initiates thermal fatigue crack in the branch pipe. Penetration depth of the main flow and the fluctuation characteristics into the branch pipe with a closed end were investigated experimentally for the branch pipe inner diameters ( = Db) from 7 mm to 43 mm under uniform temperature conditions. The penetration depth of the main flow was correlated by the Reynolds number defined by the main flow velocity ( = Um) and Db. The fluctuation width of the penetration depth ( = ΔL) was large for Db less than 30 mm and small for Db more than 34 mm. It increased with increasing Um for Db less than 30 mm and was almost constant for Db more than 34 mm. Periods for the fluctuation of the penetration depth increased with increasing Um and Db. The maximum penetration depth predicted by the obtained correlation is available to the design preventing thermal fatigue in the branch pipe with a closed end.
Turbulent jets are utilized in various industrial devices such as combustors and ejectors. To control jets and enhance mixing, several devices have been developed, and mixing process also has been studied. For the practical applications, such devices should be simple, reasonable and durable. In this study, a flapping jet is focused for mixing passively. The flapping jet is a self-induced oscillating flow which emerges from a fluidic device. The fluidic device used here is referred to by Mi et al., 2001 and it consists of a slit and a rectangular duct. The objectives of this study are to specify occurring condition of the flapping jet and to clarify the characteristics and the mechanism of it by means of flow visualization and velocity measurement. It is found that the flapping jet occurs depending on the rectangular nozzle dimension, and periodic flapping occurs when the ratio of duct width to slit width is about 1.6 and the ratio of duct height to duct length is 0.4～0.65. It is noticed that flapping frequency depends on the dimension of the duct and Strouhal number is almost constant against Reynolds number, but it decreases with an increase in duct height. It also becomes apparent that the flapping jet spreads widely and the half width becomes about 3 times wider than that of no flapping. In addition, the deflection of flapping jet is revealed to be caused by the vortex in the rectangular duct, which is generated between the main flow and the reverse flow from the outside of the rectangular duct.
In order to evaluate sensory disturbance, a subjective method is performed, in which the patient answers orally to the given stimulation. On the other hand, fMRI is a technique for observing brain activity. Therefore fMRI can be used for objective evaluation of sensory disturbance. The purpose of this study is to develop an MR-compatible device which provides both pin and brush stimulations to the surface of the human skin, and to confirm the feasibility of the device by the evaluation of the basic operations and the fMRI trial. The developed device consists of both an MR-compatible stimulator placed inside the MRI room and a driver placed outside the MRI room. The tube-rod mechanism is adopted for power transmission from the driver to the stimulator. For the evaluation of the basic operations, we measure both the pressing force and the period of the pin stimulation, and the stimulation position of the brush stimulation. For the fMRI trial, the MR-compatibility test is performed, and pin and brush stimulations are provided to the hand of a healthy subject. As a result, the standard deviations of the pressing force, period, and position were less than 0.1 N, less than 1.0 ms and less than 0.1 mm. These results were smaller than the standard deviations of manual stimulation by human. Also, MR-compatibility of the device was verified experimentally. Finally, both pin and brush stimulations activated the somatosensory areas. In conclusion, we developed an MR-compatible device which provides both pin and brush stimulations, confirming the feasibility of the device.
An absolute displacement sensor has been proposed for anti-vibration. Until now, it has been shown that the absolute displacement sensor is effective as a feedback sensor. Then, we would like to apply the same sensor to semiconductor exposure apparatuses, however detection bandwidth is limited due to resonances called high frequency dynamics. Since the proposed sensor is constructed by servo-type velocity sensor and original feedback circuits, the sensor has the same characteristics in high frequency dynamics. We have found that the pendulum of the velocity sensor have vibration modes on each resonance frequency by experimental modal analysis. In shaking test, same resonances appeared. Then, we conducted to suppress the resonances by loading viscoelastic materials, metal pieces, and TMD (Tuned Mass Damper). As a result, the resonances can be most suppressed by loading TMD. Moreover, we tried loading TMD in consideration of vibration modes, loading point, and constitution of TMD. The resonances were drastically suppressed by loading TMD on multiple points. In addition, we confirmed effects of high frequency dynamics and its suppression under the feedback of the absolute displacement sensor's velocity signal. As result, the resonances can be suppressed by loading TMD under the feedback. In this paper, suppression methods of high frequency dynamics are described and the absolute displacement sensor is applied to FB control.
In a mechanical structure development focusing on the noise and vibration, numerical analysis method like finite element method and structural optimization is widely used to predict and improve a frequency response of the structure. But, the results of these method are idealized and uncertainties in structure like parts shape and connecting part are neglected in many cases. In recent years, the mechanical structure is becoming slim and light weight to save a energy. Therefore, the influence of the uncertainties becomes large relatively, so it is necessary to take in the uncertainties to the numerical analysis. In this paper, as a one of the numerical analysis with uncertainties, robust design method based on stochastic finite element method and structural optimization will be discussed to minimize frequency response variance of structure by the uncertainties. In this paper, the robust design method were explained in detail. And, as an example of application, the robust design method was applied to an FE model. It showed that the structure which minimize the frequency response variance can be find efficiently by the robust design method.
Assembly of fine particles on three dimensional curved structure enables a lot of applications such as biochemical sensors. Dip coating method is often used because of its high productivity, but this method has been applied only to planar substrates. The spreading shape of suspension on the three dimensional curved structure is different from the planer substrate and changes the assembly process mechanism. This paper aims to assemble particles on a three dimensional curved structure of which shape continuously changes by extending the assembly model for planar substrate. When the drawing speed from the suspension that contains particles is constant, the recession speed of the contact line changes depending on location of the curved structure. Spreading shape and recession speed with 5 mm quartz cylinder has been investigated based on microscopic observation. The effects of cylinder diameter and contact angle on the recession speed analyzed with finite element method. From the results, we modeled the relationship between the drawing speed and the recession speed. The effect of the recession speed on the self-assembly of 500 nm silica particle was investigated analyzing the particle coverage for verification. The assembly model of planer substrate was extended to three-dimensional curved one. Finally, we applied the model to the assembly on a convex lens.
In this paper, modeling and simulation of nanofilled crosslinked rubber using beads spring model was reported, and the effects of the crosslinking density, the dispersibility of nanofiller and the strength of filler-polymer interactions on the reinforcement in an elongation simulation were discussed. The models were consisted two fillers, five polymer-chains, and crosslinkers with four types of filler-rubber interaction based on the Lennard-Jones potential. From the uniaxial elongation simulation, it was confirmed that the strength of interaction was affected to the stress. Furthermore, the dependency of the elongation stress and the mobility of polymer beads around filler on temperature was carried out, and it was found that the presence of low-mobility phase around filler by a strong interaction lead to the reinforcement of filled crosslinked rubber.
In reciprocating sliding, it is not yet specified the difference of effects between higher frequency and lower frequency on friction and wear under a given sliding velocity. In the study of cast irons, focus seems to be mainly on behaviors of graphite flakes. In this report, sliding characteristics of marine cylinder liner materials were studied on an SRV tester in terms of contact frequency by varying frequency and stroke under a given sliding velocity in base oils and oils with EP-additives, DBDS ( Dibenzyl Disulphide ). In higher contact frequency, or a combination of higher frequency and a smaller stroke, friction was observed to become higher than at lower frequency under severe lubricating conditions. However, run-in process was promoted under higher contact frequency with increase in viscosity and sliding velocity. Hard-phase particles, steadite, showed a tendency to chip from rubbed surfaces because of higher contact frequency, causing higher friction. The effects of frequency and stroke in base oils reflected on those of EP-additives. In DBDS-added oil, higher friction under higher contact frequency was also observed for severe lubricating conditions. Larger value of S/O ratio was confirmed by X-ray analysis of worn surfaces under higher friction. The ratio of S/O ratio decreased to less than one with improved lubricating conditions.
In this paper, the cutting mechanism and cutting performance of a ball end mill on an inclined surface using the straight-line path method are investigated. Ball end mills are used to make a variety of products such as molds and dies. However, due to the complexity of the edge shape, the cutting process is not clear, so it becomes difficult to select the tool and an effective method to achieve good cutting performance. Therefore, in this study, the purpose is proposal of high efficient and accurate cutting method using a 5-axis control machine tool. First, a cutting model assembled by a ball end mill and a workpiece with and inclined surface is carried out using 3D-CAD (SolidWorks). Next, the cross-sectional cutting area is calculated by the interference of the rake surface of the tool and the uncut chip volume which can be removed by one cutting operation. Then, the evaluation value corresponding to a cutting torque is defined and calculated. After that, the cutting experiments are done in order to measure the cutting force and machined surface roughness. In addition, the cutting torques are calculated based on these results. Finally, high efficient and accurate cutting method are discussed using the analytical and experimental results, and then the cutting conditions which are expected good cutting performance are shown.
This paper describes a parameter-free free-form optimization method for reducing the radiated noise from vibrating shell structures in an open space. Squared sound pressure, which is evaluated by solving fully coupled shell-acoustic interaction system, is selected as the objective function to be minimized. The optimum design problem is formulated as a distributedparameter shape optimization problem under the assumptions that shell structures are varied in the out-of-plane direction to the surface and the thickness is constant. The shape gradient function and the optimality conditions are derived by using the material derivative method, and they are applied to the free-form optimization method for shell, where the shape gradient function is applied to the shell surface as a fictitious distributed force under Robin condition for varying the surface, for minimizing the objective functional and for regularizing the mesh. With this method, the smooth optimal free-form of shell structures are obtained without any shape design parameterization, while minimizing the objective functional. The validity of this method for the radiated noise reduction from vibrating shell structures is verified through design examples.
The purpose of this paper is to clarify the factors which influenced the development of the technology in the Edo period. Especially, this paper tries to consider the influence on the mechanical technology development by the “Shinki-hatto”. “Shinki-hatto” law was promulgated in 1721. It has been proposed in the field of the history of engineering and intellectual property that invention is strictly prohibited by this law and the law causes Japan's stagnant technology development in the Edo period. This paper makes clear that the principal purpose of the law was to maintain the economic and institutional status quo. In addition, the paper suggests the possibility that the law fell short of expectations in terms of effectiveness.