The prediction of failure lives and the estimation of remaining lives of various buried pipelines are very important to protect human-being' daily lives from unexpected accidents. The fracture mechanics approach may do a good role to reduce to check the degree of the integrity of buried pipelines by using both stress (circumferential stresses) induced by varying boundary conditions in buried pipelines are reviewed in detail. The boundary conditions include the soil pressure, the width of trench, and the vehicle loading. The effect of hoop stresses on the external circumferential crack in buried pipelines are investigated by using a simple model proposed by this study, This study may be extended to investigate axial and mixed mode loading cracks as well.

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In order to evaluate the structural integrity of fuel assemblies associated with seismic loads in a PWR reactor, detailed fuel assembly model and core series models with 7 and 17 assemblies have been developed using the super-element capability of the MSC/NASTRAN code. The detailed fuel assembly model has been verified by comparison of the analysis results and test results. Nonlinear transient analysis has been performed on the core series models. The detailed fuel assembly model and core series models for a PWR developed with the MSC/NASTRAN code have a good correlation with test results and in-reactor impact behavior of fuel assemblies under applied seismic loads.

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The purpose of this paper is to study the possibility of compounded mesh pattern for evaluating the singularities in three-dimensional dissimilar materials. Because of the plural singularities in those materials, it is generally not easy to make a mesh pattern that can correspond to all of the singularities. To solve this problem, it is tried to use a compounded mesh pattern of two different mesh patterns. One is for one singularity and the other for the other singularity. The displacements for each mesh pattern are superposed. The formulation corresponding to finite element method is given based on the principle of virtual work and the applicability of the method is studied through numerical examples.

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Finite element computation had been undertaken to evaluate the J-integral of bi-material interfacial crack of three points bending specimens (TPB) loaded normally. The numerical results indicated that the path-independence of total J-integral and the expression of J = J_I + J_<II> are still valid even the interface is involved, whereas J_<II> and J_I respectively increased and decreased as the crack tip is approached. The fracture toughness for crack growth along the interface can be characterized by J-integral, which could be obtained directly from TPB testing because the J values from the path integrals are agreed well with those from the P 〜 δ curves described in ASTM E813-87. The mechanical property mismatch causes an opposite kind of deformation (sharpening-blunting) at the two sides of the crack tip and a high stress triaxiality on the softer metal side even for the symmetrical loading. That is, a crack may grow along the interface or deviate into the softer metal, but never turn into the harder one. A new parameter is proposed to represent the mixed ratio of loading mode, which is sensitive only to the mismatch in mechanical properties but not to the loading level and the distance from the crack tip.

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A method was proposed for multiplying and extracting continuous isochromatics from color photoelastic fringes obtained in plane polariscopes with a tricolor light source. In the method, isochromatics are taken using a color CCD camera in dark- and light-field plane polariscopes. The four color images, which contain both isochromatic and isoclinics, for the dark and light fields are used to obtain only color isochromatics. The color isochromatic images are separated into R, G and B images. The number of fringes is sextupled when the three color images with extracted fringes of 0.25, 0.75, 1.25, … order are superimposed. In order to investigate the effectiveness of the multiplication and extraction, this method was applied to color photoelastic fringes obtained in a circular disk subjected to a diametrically compressive load. As a result, continuous isochromatics with a width of one pixel increased by 6 times were accurately extracted.

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Recently, a lot of advanced materials have been developed. Therefore, the cutting conditions suitable for such materials are diversified, and the damage of the tool becomes complex. For example, temperature damage, steadily propagating wear, chipping of the tool edge, failure, etc, and those damages are created by the various causes. To analyze the tool damages, it is very important to make clear the stress induced in the tool under cutting operation. Main purpose of this research is to measure the dynamic cutting stress, especially in orthogonal cutting, momentarily by applying the caustic experimental method. The cutting conditions employed are; the cutting speed is 26.4 〜 659.7 m/min, the relief angle is kept as +15 degree constant, the rake angle is adjusted to +15 degree, 0 degree, -15 degree and the feed rate is 0.1 〜 0.5 mm/rev. The laser ray is irradiated to the cutting region, and the reflected and the caustic patterns created by the reflected light ray are observed. We investigated the effect of cutting conditions on the caustic patterns. As the result, it was obtained that the size of the caustic pattern increases with the cutting resistance. In addition, the shape of the caustic curves becomes smaller gradually with the decrease of the rake angle.

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In this paper, the photoelastic technique was employed to investigate the interfacial stresses in bimaterial structures. The effect of thermal loading was studied. The whole-field stress distribution of the test specimen can be observed during the thermal loading. The experimental results revealed that severe local stress concentrations were induced in the vicinity of the edges in the interface. The maximum fringe order near the interface was found to be about six times of that near the top surface of the photoelastic material when the heating temperature was raised to 65 ℃. In comparison with the theories developed by other investigators, severe stress gradient was found across the specimen's height. The numerical analysis was also performed and compared with the experimental results.

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In this paper, static and dynamic stress intensity factors of the interfacial crack were determined by photoelasticity and caustics method, and the fracture toughness of the interfacial crack was examined. The shearing deformation behavior of the interfacial crack was experimented on with the ENF specimen. Epoxy resin and the polycarbonate were used for the attendant test material. As a result, the fracture toughness and the direction of the crack propagation in the interfacial crack showed a result different according to the bonding condition. When the upper phase material was brittle material, the fracture toughness of the interfacial crack was a low value. And, the crack propagated to the upper phase, and the crack propagation angle was 1.22 rad. However, when the upper phase was ductile material, the fracture toughness was a high value. And, the crack has propagated to the joint surface of the interface. The fracture toughness of the upper phase material influences these tendencies. In addition, these became similar tendencies because of the static and impact test. Therefore, the fracture toughness of the material, which receives the load, determines the fracture toughness of the interfacial crack and the direction of the crack propagation.

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This paper describes a phase measuring technique that uses eight images through a circular polariscope. The phase measuring technique is applied to the digital measurements of isochromatics and isoclinics, respectively, from photoelastic fringes. Isochromatics can directly be obtained by using wrapped isoclinic phases calculated by the arc tangent operator which is the four-quadrant operator from - π to π. It is not required to unwrap isoclinic phases for the calculations of isochromatics. Isoclinic parameters are directly determined from unwrapped isochromatic parameters. The developed technique is applied to obtain the distributions of isochromatics and isoclinics along a horizontal line and an inclined line of a horseshoe-type curved beam under tension load. Generally, digitally measured isochromatics using the developed phase-shifting method agree with those expected by theory. Experimental isochromatics on the horizontal line, where isoclinics are almost constant and near zeroes, are in close agreement to theoretical calculations. However, experimental isochromatics along the inclined line, where isoclinics are changed at every point, are more or less different from theoretical expectations. Distributions of isoclinics are directly obtained by using unwrapped isochromatic parameters. Distributions of digitally measured isoclinics are in good agreement to those of theoretical calculations except in a few region.

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In the field of linear elastic fracture mechanics, the stress intensity factor approach has been widely accepted as a valid means for predicting the behavior of a material in the presence of a crack or flaw. To optimize their dimension and to ensure their safety in service, a practical study of the strength under centrifugal force is important. In this paper, it is investigated that the stress intensity factors K_I and K_<II> on the rotating elliptic disks having outside cracks by means of combining the photoelastic freezing method and the caustics method. Stress intensity factors K_I and K_<II> were determined by using tow experimental methods, as a function of ellipticity of the elliptic disk and at two different velocities. The results of these experimental methods was nearly agreement, and attracted the interest.

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In this paper, when the initial propagation angle of branched crack is calculated from the maximum tangential stress criterion (MTSC) and the minimum strain energy density criterion (MSEDC), we had better use stress components in which higher order terms are considered and stress components at the position in a distance 0.005mm from the crack tip (= r). When interfacial crack propagates along the interface with constant velocity, the initial propagation angle of branched crack is similar to the mode mixity and the theoretical values obtained from MTSC and MSEDC. The initial propagation angle of branched crack is considerably depended on the stress intensity factor K_2.

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A new method for measurement of the three dimensional surface profile and the deformation of continuously moving objects is proposed. A grid pattern made of an interference of plane wave is projected on a moving object. The deformed grid patterns projected on an object are acquired by three linear sensors continuously. Since a liner sensor records the light intensity on a single line along the original (reference) grid pattern, the result of the image forms a moire fringe pattern showing a profile of the object, like a scanning moire method. Using three images obtained by three linear sensors, the phase distribution of the moire fringe pattern is calculated by a phase-shifting method. The phase of the moire fringe pattern is simply proportional to the height of the object. This method can be used for not only the inspection of moving products on a belt conveyor but also health monitoring of huge structures, such as a tunnel from a moving train. The principle, and the accuracy of the proposed method are described in this paper. A simulation and an experiment for evaluating effectiveness of this method are explained.

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We previously developed a shape measurement method by grating projection method using two reference planes. Because this method does not use lens center positions of a projector and a camera and uses two reference planes, the resultant shape is accurate. But the method has a problem that the accuracy is worse at intermediate positions between the two reference planes than at positions near the reference planes. In this paper, we develop an accurate shape measurement system using multiple reference planes to overcome the above problem. The principle of the shape measurement and the result of an experiment are shown.

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Safety Monitoring System using a laser and 2-D arrayed photo sensors to monitor the deformation and small rotation of structure is developed. Developed optical system using 2-D photo sensor array was used to detect the variation of optical orbit of laser which was induced by deformation of the structure. Also, operating program to manage the system and an algorithm for the data acquisition and the database are introduced. In the present study, an attempt was made to examine applicability of the Safety Monitoring System through several experiments in laboratory before applying to the field.

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An ESPI system which make it possible to observe dynamic phenomena of a whole object field was applied to observe plastic deformation process in tensile experiments of aluminum alloy samples. Dynamic behavior of strain-localized band (SLB) caused by Potevin-LeChaterie effect was clearly observed on an animating picture. We found that the propagating behavior of the SLB consisted of pulsating variation which we called Localized Strain Pulsation (LSP). There are two stages in lire whole process of plastic deformation. In the earlier half process, moving fringes vary drastically corresponding to stress concentration and relaxation accompanied by large amplitude of serrated variation of the stress curve. On the other hand in the later half process, fringe movement is rather gentle. Switching of the orientation of the SLB was also observed. These phenomena which were newly discovered by the ESPI suggest wavy propagation of plastic deformation.

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Phase shifting method for speckle ineterferometry is performed by a quarter wave plate with a linear polarizer instead of PZT controller. The quarter wave plate with the linear polarizer is analyzed with Jones matrices for measurement of in-plane displacement. In order to test performance of phase shifting by the quarter wave plate with the linear polarizer, optical experiments to measure in-plane displacement in several specimens are carried out. The results show that the quarter wave plate with the linear polarizer can be used in phase shifting method for speckle interferometry.

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A dynamic process in tensile experiment of austenitic stainless steel was observed by digital speckle pattern interferometry (DSPI) which enables us to observe entire process of whole field deformation. In plastic deformation state, localized deformation appeared as concentrated correlation fringes in a narrow band, which run over the specimen repeatedly. Correspondingly, a stress curve took some hills. In microscopic surface observation of a fractured specimens, martensite were found together with collapsed grain. It means that strain-induced martensitic transformation generates in part in heterogeneous structure of the material. These phenomena vary depending on carbon content. Dynamic DSPI presented here is expected as a new tool to invenstigate dynamic behavior of plastic deformation and fracture.

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A two-directional simultaneous measurement system of a surface deformation is proposed by using a speckle pattern. The speckle pattern is generated in the diffusely reflected light, when a rough surface is illuminated by a laser. Measurement methods using the speckle are divided into the two groups that are a speckle correlation method and a speckle interferometry method. The resolutions of the displacements of the speckle correlation and interferometry methods are about several to several 10 μm and less than 1 μm, respectively. The speckle correlation method is obtained in-plane components of displacement. The speckle interferometry method is obtained the component of the displacement in the direction of a laser radiation. So, in order to obtain in-plane components, the laser light is separated two beams that are illuminated to the two-direction (a vertical and horizontal directions) by using high-speed-switching-based methods. In this study, a measurement system is constructed by using the speckle interferometry method for the purpose of performing the two-directional simultaneous measurement. It consists of a He-Ne laser, Ar^+ laser, and optical parts. These lasers separately illuminate to the vertical and horizontal directions at the same time. The wavelengths of these lasers are selected by using optical filters, and in-plane components are simultaneously obtained.

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We investigated a method to measure deformation using image correlation technique. If we put random pattern on material surface as target marks, we can measure deformation distribution on the surface by comparing two images before and after deformation taken with CCD devices. In this method, searching method of the corresponding points on the two images is important. We considered a method to search quickly and with high accuracy. We employed two-stage method of searching, coarse and fine search to make search in short time. In these search methods, we derived a new iteration method to search corresponding points with sub-pixel accuracy. We investigated the interpolation method for the estimation of gray level using neighboring pixel data with linear, third-order polynomial and fifth-order polynomial functions. The results showed that interpolation is more accurate using higher order polynomials. We obtained about 0.01 pixel accuracy using this interpolation method using fifth-order polynomials. We applied this method for strain measurement on metal plate under tensile test. The result showed that we could measure strain up to 10^<-4> using a normal NTSC CCD camera with VGA resolution.

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Recently, based on the smart structure concept, optical fiber sensors have been increasingly applied to monitor the various engineering and civil structural components. These fiber optic smart structures allow engineers to add nervous systems to their designs, giving structures capabilities that would be very difficult to achieve by other means, including continuous assessment of damage processes. Several studies associated with crack monitoring using optical fiber sensors have been reported. In this study we combined the fracture mechanics concept with the optical fiber technology using TEFPI (Transmission-type Extrinsic Fabry-Perot Interferometric) optical fiber sensors. The fracture mechanics concept means that crack growth causes the redistribution of the displacement field around the crack. This idea has been utilized as the basis of compliance technique that is a useful indirect method for fatigue crack length measurement in the laboratory. The objective of this study is to evaluate the potentiality of application of TEFPI optical fiber sensors to the monitoring of crack growth behavior of composite patch repaired structures. The sensing system of TEFPI and the data reduction principle for the detection of compliance changes are presented. Finally, experimental results from the tests of center-cracked-tension aluminum specimens repaired with bonded composite patch is presented and discussed.

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Scattered light from the surface of a specimen will broaden as the surface roughness increases. The surface of ground specimens was illuminated with a halogen light beam. The scattered light intensity distribution was measured with a CCD camera and it was approximated by a two-dimensional Gaussian function; the surface roughness in two orthogonal directions was evaluated using the standard deviations σ_x and σ_y with respect to the x- and y-axes of the function, the y- axis being taken as the grinding direction of the specimen. The half-width B and integrated width C which represent the broadness of the scattered intensity distribution can be expressed in terms of the standard deviations σ_x and σ_y of the function as B_x=2.35σ_x, B_y=235σ_y, C_x=2.51σ_x, C_y=2.51σ_y and they can also be used for evaluating the surface roughness. The standard deviations σ_x, the half-width B_x and the integrated width C_x of the cross section of the intensity distribution perpendicular to the grinding direction increased rapidly with increasing the root-mean-square deviation of the profile R_q, while the values for the cross section parallel to the grinding direction remained almost unchanged. The scattered intensity distribution has a close correlation with the slope angle distribution of the surface roughness profile measured with a stylus profilometer.

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This paper presents the effect of the level of plastic deformation on the ductility of a mild steel (0.06 mass % C). The steel was cold rolled to five degrees of 2, 5, 10, 25 and 50 % in thickness reduction (R). Tensile tests for smooth and notched specimens were carried out to examine the effect of the level of plastic deformation on the change of ductile-brittle transition temperature (T_c). The specimens were tested at any desired temperatures between 293 K and 77 K and at a strain rate of 4.2 × 10^<-3> s^<-1>. The results obtained in this work are summarized as follows: (1) As-annealed smooth specimen was fractured including the ductile elongation even if the testing temperature was lowered to 90 K, but it was ruptured without any elongation at 77 K and the ductile-brittle transition temperature was determined to be 90 K. After the specimen was rolled to the reductions of 5 % to 25 % in thickness, the values of the transition temperature increased up to 113 K. In contrast with this, the transition temperature was lowered to below 77 K for the heavily hardened specimen with 50 % thickness reduction. (2) The presence of a notch causes the transition temperature to increase by 43 K to 100 K over the thickness reduction range of 0 % to 50 %.

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The surface of material can be transmitted into nanocrystalline structure by some treatments such as ultrasonic peening (USP). The surface nanocrystalline (SNC) can play a significant role in promoting the strength, stiffness and fatigue life. The effect of surface nanocrystallization for stainless-steel sheet on its static mechanical behaviors is investigted. SNC treatment leads to the yield stress and the ultimate stress of the material to rise by about 96% and 13% respectively. The nanostructured layer acts as a very strong wall to block the dislocations and slips moving out of the surface of the structure so as to harden the material. A measurement of the stress distribution in sample section is carried out by means of moire interferometry and the experimental results show that the nanostructured layer shares rather portion of load because of its high stiffness.

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It is predicted that next generation micromachines and electronic equipments will be made much lighter and smaller. Consequently the micron-sized parts as the structural members are required, however, it is expected that the micro materials are different from the bulk materials on the mechanical properties. It is important to understand the mechanical property of the micro materials for using as the structural members. Therefore, the establishment of the test method for the micro materials is very necessary. The effects of the test method, the processing method, the shape, the size and the grain size of specimens on the tensile strength of the micro materials have been reported until now. However, the reliability and the accumulation of the experimental data are insufficient, and the evaluation method of the tensile strength for thin sheet materials has not been established. The purpose of this study is to establish a test method of tensile strength and to investigate the strength characteristics of the micro materials. Then, the tensile strength tests of SUS304 thin sheets were carried out using a microforce testing system (MTS Tytron250), and the effect of sheet thickness and grain size of the test specimen on tensile strength and Young modulus was investigated. As results, it was found that though scatter of Young's modulus was large, and the mean values of Young's modulus were E=191GPa regardless of the gage length. Also, it was found that the 0.2% proof stress σ_<0.2> increases as t/d increased up to t/d=2〜4, and that it was almost constant over t/d=2〜4. The causes for these are discussed

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Spot welding causes several problems, deformation of structure by welding heat and decrease of durability, precision and productivity by residual stress. Adhesive bonded joint has bigger bonded area than welded one does. Stress is uniformly distributed on adhesive bonded joint. It is known that adhesive bonded joint is more durable than welded one. Recently adhesive bonding method is highly recommended as method of structure bonding in mobile field. Purposes of this research are to find how to replace spot welding with adhesive bonding and which way is proper to use adhesive bonding together with welding. Standard of design for adhesive bonded structure is proposed through this research. Therefore durability and productivity will be increased by adopting the adhesive bonding.

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Adhesion between the anionic and the cationic gels were observed. This adhesion force varies according to the pH and the ion strength of the solutions bathing the gels. It exhibits the quite strong adhesion in the neutral and lower ion strength solution, but it decays in the highly acidic or basic and higher ion strength solution and even comes to exhibit no adhesion at all. The cause of this adhesion phenomenon was proved to be primarily due to the electrostatic interaction between the anionic and the cationic fixed groups contained in the respective gels. That is, the formation of the salt-linkages between the dissociated -COOH and -NH_2 groups, which are -COO^-…^+H_3N-. They were found in the amphoteric gels, too, and proved to play a role of the reinforcement of the gels hardness. They work as the crosslinkings in the gels in addition to the permanently formed chemical crosslinkings consisting of N,N-methylenebisacrylamide. The degree of the reinforcement (the formation of the salt-linkages) can be controlled reversibly by their formation and disruption with the control of temperature or the pH or the ion strength of the bathing solution. Namely, the amphoteric gels hardness can be controlled reversibly without permanently modifying the gel's molecular structure. Since the reversible hardness change is also observed in the real human muscle, the reversible harness control by the use of the salt-linkage is the promising method to realize the gel artificial muscles.

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The Vickers microhardness, elastic modulus, bending strength and mineral density of ninety cortical bone specimens from ten bovine femora were determined. The relationship between Vickers microhardness number and elastic modulus was found to be approximately linear. Similar relationship existed between Vickers microhardness and bending strength. The bone mineral density of the plexiform bone was also correlated with microhardness. These relationships found suggest that Vickers microhardness was a good predictor of the elastic modulus, bending strength and mineral density of cortical bone.

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The welded joint has a gradient of microstructure and mechanical properties from fusion line to the unaffected base metal. But, conventional mechanical tests, which require large specimen and complex testing sequences, have difficulties in evaluating the mechanical properties of local zones of the in-service pipeline. Therefore, a simple and non-destructive mechanical testing method using small specimen is needed. An advanced indentation test meets these requirements. The advanced indentation test measures indentation load and depth during indentation. Various mechanical properties related to deformation are evaluated through the quantification of indentation stress field and the analysis of the load-depth curve. In this study, we concerned with the variation of tensile properties within the weldment of API 5L X65 steel, generally used for natural gas pipeline. The macroscopic and microscopic change in tensile properties such as true stress-strain curve, yield and tensile strengths are evaluated using advanced indentation tests, and the results are discussed.

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There have been many studies on superplasticity in ceramics and its application is believed as a promising method to produce ceramic components of required shapes and sizes. The authors have investigated the superplastic deformation induced variations in mechanical properties of 3mol% yttria stabilized tetragonal zirconia polycrystals (3Y-TZP) in relation to its microstructure. Superplastically deformed specimens were prepared by a high temperature tensile test. Their morphological characteristics were examined by Scanning Electron Microscope (SEM). A micro-indentation test was carried out to evaluate mechanical properties at micro-regions of the specimens. As a result, the dynamic hardness and the Young's modulus are decreased with the increase in an average grain size caused by the deformation. From a statistical viewpoint, it is suggested that the crystal phase transformation in 3Y-TZP caused by the deformation is a crucial factor on the hardness change and that the deformation induced cavity formation is also an important factor on the apparent Young's modulus.

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The general yield criterion proposed in [5] is originally for shape memory alloys, which undergo martensitc transformation and martensite reorientation upon loading/unloading. It is based on the principle that the driving energy for transformation at a given temperature is a constant. In this paper, a brief review and recent progress on this criterion are presented. It is followed by the applications in two non-crystalline materials, namely, concrete and grey cast iron. The yield surfaces and strain-stress curves under proportional loads are simulated against the experimental results reported in the literature.

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Current micro assembly techniques mainly include soldering, welding, plastic deformation, adhesive and "through hole". Each of them has some advantages, but also unavoidably associates with intrinsic problems in practice. In this paper, we propose a novel method for micro-assembly using shape memory alloy. A finite element package, ANSYS, with a material element dedicated for shape memory alloys, is used to simulate the assembly of aluminum with PZT by shape memory alloy wire.

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The characteristics of cycle strain relaxation for spring steel 35SiMnVB, 50CrMn and 50CrVA under the various cycle stress are investigated. The cycle strain relaxation for three spring steels having various hardness under the different cycle stress is measured and the microstructures of three spring steels are observed. The results show that the cycle strain relaxation increases with increasing of cycle numbers under the giving cycle stress, and with increasing of cycle stress under the giving cycle number. The cycle strain relaxation value for new spring steel 35SiMnVB is less than that of spring steel 50CrMn, but more than that of spring steel 50CrVA. This shows that the cycle relaxation resistance of new spring steel 35SiMnVB is satisfactory for using in the automobile. The mentioned results are discussed.

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The mechanical behavior of Ti-48Al-2Mn-2Nb alloy produced by centrifugal spray deposition (CSD) was investigated. Tensile, compression and fracture toughness tests of CSD Ti-48Al-2Mn-2Nb alloy were carried out at room temperature (RT), and the comparison was made with the ingot metallurgy (IM) Ti-48Al-2Mn alloy at RT, as well as at 600 and 800℃. The results show that CSD Ti-48Al-2Mn-2Nb alloy exhibits a better elongation of 2.8%, and excellent compression properties with compressive strength of 2210MPa and compressive ratio of 33.9% at room temperature, furthermore, higher compressive strength of 2625 MPa and better compressive ratio of 58.8% at 600℃. CSD alloy with a refined lamellar structure exhibits higher tensile and compressive properties and better plastic strain ability than that of IM alloy. CSD alloy also has a better fracture toughness of 23.6 MPa √<m> at RT, however, the IM alloy with coarse lamellar structure exhibits higher fracture toughness of 25.34 MPa √<m> at RT, and 31.5 MPa √<m> at 800℃.

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In the reflow soldering process, the IC package is heated over 270℃ by the infrared rays. In a delamination interface, the stress field near a crack tip will always be in a mixed-mode state. It was assumed that the initial defects were generated among the corner part of die pad and epoxy molding compound. The 3-D finite element analysis was carried out to evaluate the strain energy release rate (SERR) of delamination interface in IC packages subjected to non-steady thermal stress. SERR of mixed mode was evaluated by the modified crack-closure integral (MCCI) and virtual crack extension method (VCEM). The maximum difference of SERR between MCCI and VCEM was about 8%. Therefore, it is considered that MCCI is useful as the simple evaluation method of SERR. The stress intensity factor K was examined from 3-D VCEM. VCEM can evaluate stress intensity factors of the interface crack under a mixed-mode loading accurately.

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Silicon single crystal is commonly used for electronic devices. Because an integrated circuit consists of various micro-materials, their deformation mismatch brings about stress concentration in the substrate. A defect such as dislocation induced by the stress concentration aggravates the subtle electronic property of silicon. As the substrate possesses high purity with no initial dislocation, the ideal strength under the resolved shear stress might be an important measure to predict dislocation nucleation. In this study, in order to precisely evaluate the critical shear strength, a numerical ab initio simulation is conducted on the silicon single crystal (slip plane: (111), slip direction: [101]). Especially, the focus is set on the effects of normal stress and the inner displacement of atoms in the cell under the shear strain. The normal stress strongly affects on the instability strain, and the inner displacement remarkably decreases the strength. The peak stress of silicon crystal is about lOGPa at the shear strain of 0.3. The band gap becomes narrow as the strain increases. Since it disappears at the shear strain of 0.2, the deterioration of electronic property is more sensitive to the shear deformation than the mechanical one.

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In this paper the authors have investigated the thermal fatigue reliability of lead-free solder joints. They have focused their attention to the formation of the intermetallic compound and its effect on the initiation and propagation behaviors of fatigue cracks. An isothermal fatigue test method was used in this study to improve the efficiency of fatigue study, and several different lead-free solder alloys, Sn-Ag-Cu, Sn-Ag-Cu-Bi, Sn-Cu and Sn-Zn-Bi were investigated. There are two kinds of fracture mode in lead-free solder joints, one is solder fatigue mode, and the other is an interface fatigue mode. Based upon the experimental results, it was found that not only is the mode transition of the fatigue crack affected by the properties of the intermetallic layer but also is affected by the tension strength of the solder material.

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Low cycle fatigue tests of as-casted Ag-Sn eutectic solder (3.5Ag/96.5Sn) were carried out using the non-contact strain controlled system at 20 ℃. The fatigue behavior followed the Coffin-Manson equation with the fatigue ductility exponent of 0.76. Without local deformation and stress concentration at contact points between the extensometer and the specimen surface in strain-controlled fatigue tests, crack initiation and propagation behavior during fatigue test was observed on the specimen surface by replication technique. After failure, the longitudinal cross sections as well as fracture surface were examined under an SEM. Steps at the boundary between Sn-dendrite and Ag-Sn eutectic structure, and cavities along the boundaries and especially around the Ag_3Sn paticles, were the initiation sites of microcracks. Stage II crack propagated in mixed manner, i.e. intergranular along Sn-dendrite boundaries, transgranular through Sn-dendrites and Ag-Sn eutectic structure. After fatigue tests, small grains were observed in Sn-dendrites near fracture surface.

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Moire interferometry technique was applied to the thermo-mechanical analysis of flip-chip packages. Thermal deformations of two kinds of flip-chip structures, no-underfill and underfill flip-chip packages, were studied. The differences of the thermal deformations between the two packages were measured to clarify the effect of underfill. The experimental results showed that the underfill plays an important role to give similar curvatures at the lower side of the silicon chip and the upper side of the substrate. The shear deformation of the solder ball decreased due to the underfill, while the tensile deformation increased.

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Recently, the drilling of small hole in FRP is occasionally required. However there are many difficult problems, such as shortened tool life, rough machined surface, some cracks and so on, during drilling by using drill press. And the smaller size of hole is difficult to be drilled by such a traditional procedure. We can find only some papers about laser drilling for FRP plates, especially for AFRP plate. Therefore, we tried to get the smaller size hole with deep depth further the higher quality by using a laser machining that never induces tool wear. In this report, as a first step, we tried to investigate the effect of laser condition on the hole shapes and its appearance. Aramid fiber and glass fiber are chosen as reinforcing materials in the FRP composite and one bundle of those fibers is placed in the polyester. We used the CO_2 laser equipment for drilling and the various kinds of irradiating conditions are employed to investigate the phenomena in machining process. Observing the effect of laser irradiating conditions on the shapes of machined hole quality, we obtained the following results; it is clarified that the maximum diameter of machined hole increases with irradiating time and laser power. And the maximum depth was affected mainly by laser power and by a presence of fibers. The presence of fibers, especially glass fiber, causes difficulty to drill the deeper hole under the conditions of lower laser power and shorter irradiating time. The high quality drilling beyond the fiber bundle is not easy to realize, but HAZ (Heat Affected Zone) is created easily along the bundle of fibers.

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The stress field near a contact edge in fretting fatigue tests depends on the deformation type at the contact edge. During one cycle of loading in a fretting fatigue test, nine types and six independent types of the stress field are possible to exist. In this study, the detailed forms of the singular stress variation range near the contact edge for these basic types have been theoretically deduced. The theoretical results were compared with numerical results obtained by the boundary element analysis. It was found that the singular order of the stress field obtained by the theoretical solution agrees well with the numerical results. It should be noted that the stress variation range presents different singular behavior for different deformation types. Therefore, the fatigue strength evaluation should be carried out in the corresponding way to the stress variation range type. It was found that a fretting fatigue crack initiated in the maximum shear stress range direction, and then kinked into the maximum tangential stress range direction following the initiation stage of the crack.

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The fretting characteristics of TiN coated Zircaloy-4 tube were investigated experimentally. The fretting experiment was performed using TiN coated Zircaloy-4 tube as the fuel rod cladding material and uncoated Zircaloy-4 tube as one of grids. TiN coating is probably one of the most frequently and successfully used PVD coatings for the mitigation of fretting. In this study, TiN coating by PVD was employed for improvement of Zircaloy-4 tube fretting characteristics. The fretting tester was designed and manufactured for this experiment. The number of cycles, slip amplitude and normal load were selected as main factors of fretting. The results of this research showed that the wear volume of TiN coated Zircaloy-4 tube increased as number of cycles, normal load and slip amplitude increase but the quantity of volume was lower than the case of uncoated Zircaloy-4 tube pairs.

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TiN films were deposited on pure titanium specimens by reactive RF magnetron sputtering and gas nitriding methods. Pin-on-disk type wear tests were carried out to evaluate the effect of interfacial strength on the wear resistance of TiN films. The results showed that the wear property was improved remarkably by both methods, but the effect quickly disappeared after a large number of rotation cycles. Optical observation of wear scars during wear tests showed that delamination of a small part of the film occurred and the area extended within a small increase in rotation cycles. The delamination process of film during the wear test was discussed from a viewpoint of fracture mechanics, and the equation to evaluate the interfacial fracture toughness was derived. The interfacial fracture toughness of the sputtered and gas nitrided specimens decreased with increasing pin load and film thickness by fatigue damage along the interface accumulated during rotation cycles.

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The low speed motion of the journal with surface modified micro porous film in solid-lubricant mixed oil bearing in response to an applied torque is experimented. The main results obtained are as follows: (1) Micro porous structure and hardness film was coating by HAE anodization for Mg. (2) As results of torque test by the journal bearing, only oil using, micro porous and unmodified materials showed the similar torque characteristic. Because of thin film by the oil is formed on the surface, and it becomes a boundary surface. Therefore effects of the micro porous film function made cancelled. (3) By using solid-lubrication mixed oil (MoS_2 include oil), slide characteristics were improved. It was found that these results formed MoS_2 thin film on sliding surface.

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The titanium nitride (TiN) films with the thickness of 0.5, 1.0, 2.0μm were coated on a steel substrate by the ion beam mixing method. The film had a strong fiber texture with <110> axis perpendicular to the film surface. The initial residual stresses are equi-biaxial compression between -4200 to -5500MPa. For all thickness cases, the initial part of the changes of the in-plane stresses in the film due to external tensile loading agreed well with the prediction based on elasticity. While the substrate is under uniaxial stresses, the film was in the biaxial state of stress because of the mismatch of Poisson's ratio. When the measured stress in the film exceeds a certain value, the stress departs from the linear relation and levels off. The onset of nonlinearity is coincident with the first appearance of cracks. The stresses at the onset of nonlinearity and leveling-off decrease with increasing film thickness. The ratio of Young's modulus between loading and unloading decreases as the film thickness increases, suggesting the increasing disjointed area.

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In the investigation, the piezoelectric thin film Pb(Zr_xTi_<1-x>)O_3(PZT) was prepared by a pulse laser deposition method. The properties of PZT films were strongly dependent on substrate temperature and oxygen pressures. The residual stress in piezoelectric thin film was tested by indentation fracture method. The relation of properties such as microstructures, piezoelectric response with residual stress was investigated. A theoretical model for the formation of residual stress is proposed. The model is based on the combined effects of the difference of thermal mismatch between substrate and thin film, the phase transformation and the different of lattice constant between thin film and substrate.

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Ferroelectric thin films Pb(Zr_xTi_<1-x>)O_3(PZT) with x=0.58 were deposited on Pt/Ti/Si(001) by pulsed laser deposition (PLD) and the fracture toughness of the film was tested by indentation fracture method. The fracture pattern diagram as a function of indentation load and thin film thickness is introduced. Radial and lateral cracks are observed in indentation with a Vickers diamond indenter. The fracture toughness of PZT thin was determined as 0.47MPa.m^<1/2> and it is much lower than the correspond bulk material. The interfacial fracture toughness for PZT thin film/Si substrate was determined as 3×10^<-4>〜2.3×10^<-3> MPa.m^<1/2>. The interfacial fracture toughness is much lower than the fracture toughness of PZT thin film. In the case of brittle thin film deposited on a brittle substrate, the interface is very weak.

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Using a new film fatigue testing method by which fatigue cracks can be initiated and propagated in a film adhered to cover a circular through-hole in a base plate subjected to push-pull cyclic loads, rolled iron films annealed at 873 K and 1173 K were fatigued with a stress ratio of R=0. From the crystallographic information of rolling textures in annealed iron films obtained by EBSD (Electron Backscatter Diffraction) method, the anisotropy of rolling texture remained after annealing. In order to discuss the effect of rolling texture on fatigue crack propagation properties of iron films with the thickness of 100 μm, the two types of specimen that rolling direction was parallel and perpendicular to loading direction were prepared in film fatigue testing. The cracks in the film annealed at 873 K propagated along the grain boundary and the crack propagation rate is approximately the same for the two types of specimen. The cracks in the film annealed at 1173 K propagated across the grain and there was a difference between the two types of specimen in crack propagation behavior and crystallographic information around the fatigue crack obtained from the EBSD method. The reason was probably that the slip system of the rolling texture in iron film annealed at 1173 K is different in accordance with the relationship between rolling direction and crack propagation direction.

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In this paper an analytical model, based upon the line spring model installed in ABAQUS, has been proposed in order to simulate the low cycle fatigue crack propagation. And a series of computer simulations have been carried out in order to investigate the experimental behaviors of the degraded pipes. It has been shown that the leak behavior of circumferentially cracked piping can be simulated well by the proposed method.

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There is a large difference in the atomic size between aluminum and magnesium atoms. They are mutually solved in solid solution and make the stronger alloys at high temperatures. The crystal structure of aluminum alloy is face centered cubic and that of magnesium alloy hexagonal. Both alloys, A5083 aluminum (Al-Mg) and AZ91 magnesium (Mg-Al) alloys were tested under a condition of constant stress in tensile at high temperatures. The creep tests were conducted until the rupture of the specimens. The creep curves were discussed from the viewpoints of the strain rate and the creep life. Both alloys do not present the steady state creep, of which the strain rate is constant against the creep time and the creep strain. The simple relationship between the minimum creep rate and the creep life is observed for both alloys. The Monkman-Grant constant, which is the product of them, is about unity for Al-Mg alloy and less than unity for Mg-Al alloy.

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We investigate the mechanical behavior of the fiber reinforced organic composites in high vacuum and temperature condition. The material used in this study is short carbon fiber reinforced thermoplastic polyimide composites (SCFR-PI) with various fiber contents. Tension tests were carried out with the aid of AE method. After the tests, we observed the damage propagation in SCFR-PI specimens by scanning electron microscope photographs and optical microscope photographs. The main results are summarized, as follows: (1) Even though tested at the same temperature 298 K (25℃), the SCFR-PI composite specimen kept in high vacuum condition has higher tensile strength and higher equivalent Young's modulus than that in the atmospheric condition. (2) The fiber pull-out length of the specimen in high vacuum condition is shorter than that in the atmospheric condition and the fracture surfaces are not flat. The strength of the interfacial bonding between carbon fibers and the thermoplastic polyimide resin matrix becomes better in high vacuum condition. The degas and/or moisture desorption may change the performance of each materials and microfractures of SCFR-PI composites. (3) It is found that there exists the effect of vacuum condition on the tensile strength and Young's modulus of SCFR-PI composites and the microfractures.

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