This study is conducted to clarify the influence that the dislocations left over around the fatigue crack have on the propagation rate through the computer simulation of the dislocation dynamics. The computer simulation is based on the equation concerning the elastic interaction of a semi-infinite crack with edge dislocations. The result of the basic analysis shows that the exisitence of dislocations near the crack-tip suppress the emission of new dislocations. This predicts that the shielding effect owing to the dislocations is one of the important factors which affect the propagation rate of the fatigue crack. Furthermore, the results of the computer simulation show that the transient fatigue crack propagation with the sudden change of the stress intensity factor amplitude can be qualitatively understood from the viewpoint of the change of the shielding effect which is induced by the dislocations left over around the crack.

抄録全体を表示

In the high cycle fatigue, the unique slip near the interface is caused by the increase of resolved shear stress, T_<rss>, due to the constraint of deformation at the interface. In this study, the stress field near the interphase boundary (IB) in a two-phase (α/γ) stainless steel bicrystal is analyzed by a finite element method. It was found that the increase of T_<rss> on the specific slip system is confined in a region near the junction of IB and the free face. Considering the critical resolved shear stress in the single crystal, the unique slip might be generated only near the junction in the high cycle fatigue.

抄録全体を表示

At the moment, the adhesion strength of the porcelain enamel does not quantitatively. So, it is necessary to discuss about evaluation of the adhesion. In this study, the steel ball drop test is applied to typical adhesion test, and steel ball indentation test using the porcelain enamel. The distribution and propagation of cracks, i. e, ring crack that occurs on the glass surface and the corn crack which propagate in the depth direction of the glass layer, are examined by a means of some observation technique. The stress distribution at the boundary between glass layer and steel plate was analyzed using the experimentation result by the 3-point bending test analysis. As a result of , (1) the steel ball indentation test is better than the steel ball drop test, because of stress analysis is easy. (2) the propagation angle of crack was arrived at about 35° from the boundary between glass layer and steel plate by the 3-point bending test analysis.

抄録全体を表示

The dispersion of fibers in the transverse direction of a unidirectional fiber-reinforced composite material has very strong influence on the local stress field occurred in the material and hence may be affect the transverse strength of the material. The distribution of areas of Dirichlet polygons obtained by the Dirichlet tessellations constructed upon such dispersion of fibers may be closely related with that of the nearest neighbour distances between fibers in the material. In the present research, therefore, the probability density function of the nearest neighbour distances is derived in order to characterize the inhomogeneous dispersion of fibers. By assuming that the area of the Dirichlet polygon is equal to that of a circle whose radius is half of the nearest neighbour distance and the outward region to the polygon is a homogeneous one whose elastic modulus is equal to the overall modulus of the composite material, the material can be modeled as a double inclusion. By analyzing the mean stresses occurred in the double inclusion model, the transverse strength of the material can be examined. Its value increases with increase in the degree of inhomogeneity of the dispersion of fibers. This is consistent with experimental results obtained by Pyrz.

抄録全体を表示

As a fundamental study of a smart structure having the functions of crack prevention and crack closure, the temperature distributions on the surface of multiple shape memory alloy (SMA) wires embedded in epoxy resin plates and heated by supplying electric current were investigated using an infrared themography technique and finite-element method (FEM). The temperature distributions of SMA in the air and of the specimen surface obtained using FEM were in good agreement with those obtained using the themography technique. The analytical results showed that the temperature of the SMA surface embedded in the plates were less than half of those in the air.

抄録全体を表示

The temperatures on the surfaces of heat-sealed areas in liquid packaging bags made of laminated plastic films were measured to investigate temperatures and rates of fluid filling into the bags suitable for the heat sealing. Thermal images were taken immediately after heat sealing using an infrared thermography technique at heat-sealing temperatures in the range of 100 and 190℃ at rates of film feed in the range of 10 and 25m/min in a automatic packing machine. After the tests, the relationship between the distributions of temperatures obtained from the images and adhesive property between the components consisting laminated plastic films in heat-sealed areas was investigated. The results showed that the distributions of temperatures on the surfaces of heat-sealed areas can be used to evaluate the adhesive property.

抄録全体を表示

A new nondestructive testing technique was developed based on the lock-in measurement of the surface temperature under the application of periodical xenon light heating. Experimental study was made on the applicability to the detection of flat bottom hole defects and delamination defects. Xenon light beam was periodically chopped by the electric shutter to generate thermal wave in the objective body. In-phase and out-of-phase temperature amplitude images were taken by the lock-in thermography, synchronized to the reference signal of the electric shutter operation. It was found that the location and size of the defects can be identified by the localized contrast change in the out-of-phase image. Further, the depths of the defects can be identified from the heat penetration depth, which was changed by the frequency of thermal wave stimulation.

抄録全体を表示

The temperature and spectral reflectance of the surfaces of intact Epipremunum Aureum leaves partially subjected to different intensities of ultraviolet (UV-B) irradiation as a function of time were investigated using a thermal video system and a spectrometer, respectively and compared with those for the cases of plant-upbringing irradiation. The results showed that the variations in the temperature and spectral reflectance for UV-B irradiation were different from those for case of plant-upbringing irradiation, and were depended on UV-B radiation intensity. Therefore, the temperature and spectral reflectance of the leaf surface suggested the possibility of applications in the prediction of the level of UV-B radiation.

抄録全体を表示

The purpose of this study is to develop the fatigue reliability estimation method of surface modified materials. Rotating-bending fatigue tests in air were carried out using smooth specimens of alloy tool steel, SKH51,with two kinds of surface treatment; TiCN thin film coating by the PVD method and duplex treatment with plasma nitriding followed by TiCN coating.

抄録全体を表示

Both X-ray image subtraction and CT are very useful for imaging inner structures of materials and components, and also for determination quantitatively the dimensions of those structures with fairly higher accuracy. In this paper we report the examples of sizing the diameters of pores in Si3N4 ceramics from the obtained images by both X-ray methods and compare them for discussion of the precision of those data. With the obtained data, both methods are confirmed to be very accurate to determine the sizes of inner structures.

抄録全体を表示

This paper is concerned with the development of Ultrasonic probe for detecting near surface discontinuity. Near surface discontinuity is difficult to detect for ultrasonic testing. To detect near surface discontinuity, a leaky surface acoustic wave (LSAW) experiment is carried out. But ordinarily it is difficult to separate the LSAW and the longitudinal waves along the central axis. In this study, a hollow is made in the center of the acoustic lens, and so the separation of LSAW becomes possible. The lens is named DH (Delaying Hole) lens. To verify the effect of the lens, the delamination and crack test samples are made, and sprayed coating surface are evaluated at the condition that surface are un-machined. The results show that with this method, delamination and crack parts are clearly detected and the acoustic image near the edge parts can also be clearly obtained.

抄録全体を表示

Linearized inverse scattering methods are formulated for the shape reconstruction of a defect in the three-dimensional elastic body. The linearized methods are besed on the Born and Kirchhoff approximations. The backscattering waveforms from the defect are fed into the linearized methods and the shape of the defect is reconstructed.

抄録全体を表示

This study deals with white light photoelasticity achieved using a combination of triphosphor fluorescent and mercury lamps and a tricolor filter, to reduce the attenuation of light intensities of isochromatics obtained from photoelastic experiments, and the multiplication and extraction of isochromatics. The proposed method requires the use of only a tricolor filter in addition to a circular polariscope, a color CCD camera, triphosphor fluorescent and mercury lamps and an image processor that are used in conventional white light photoelasticity. The method was applied to isochromatics obtained in an epoxy resin plate under four-point bending, and light intensities of the isochromatics were investigated. Then the isochromatics were multiplied and extracted using a technique developed by one of the authors. The results showed that a combination of the triphosphor fluorescent and mercury lamps and the tricolor filter improved the attenuation of light intensities of isochromatics, and increased the maximum fringe order of isochromatics which can be multiplied and extracted.

抄録全体を表示

The constant values such as Young's modulus, Poisson's ratio and the modulus of shering elasticity are obtained by using a Laser scanning micrometer. While pulling the test piece at high temperature, the diameter of the specimen with scanning laser light and the longitudinal elongation with an electronic micrometer are measured simultaneously. The resolving power of the laser scanning micrometer is 0.1μm. As a result of the experiment, the measured values obtained by this new technique are nearly equal to normal values.

抄録全体を表示

Due to the differences of the pretreated substrates' surface states, the adhesion between the thin film and the substrate will be influenced greatly. On the other hand, the adhesion depends on coating temperature. The dissimilarities will appear on the durability of the tools. Therefore, it is a very important subject for evaluation of the durability of the tool nondestructively. This article proposes a simplified evaluation method for the durability of CVD diamond coated cutting tools. Checking adhesion, we can determine whether the tool is a successful candidate or not by means of shot blast method. The effectiveness is verified with a great number of cutting tests.

抄録全体を表示

The measured values of interfacial strength much depend on the test method. One of the reason for this is the discrepancy between the actual fracture process and the applied mechanical criterion of the fracture, and the quantitative evaluation of interfacial strength has not yet been established. Couple Fiber Shear Method is a new method to evaluate the fiber/matrix interfacial strength. This model composite is composed of two filaments and one resin pocket, and is suitable for the in-situ observation in SEM. Interfacial stress was analyzed using finite element analysis including the influence of thermal stress. In the present study, the effect of fiber diameter was investigated. Experimental results were analyzed using the intensity of stress singularity, K_<ij>. The possibility of the evaluation of the interfacial strength using the parameter, K_<ij>, was discussed.

抄録全体を表示