This paper describes an approach of physical property measurement of molten metals by SR x-ray diffraction. Metal samples were laser-heated on the aerodynamic levitation system installed on the x-ray diffractometer equipped with the IP detector at BL19B2 in SPring-8. Lattice constants and expansion coefficients were estimated from measured diffraction data for heated metal samples. Further heating under vacuum condition will provides us dynamic physical properties of molten metals.

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The surface tension of the molten stainless steels was measured under plasma conditions. The sessile drop method was adopted and a low pressure plasma was generated between the sample and the electrode above the sample. The measurement was carried out for several types of stainless steel, which contains different amounts of sulfur, 10ppm and 100ppm, at the temperature from 1773K to 1873K. No significant effect of the plasma on the surface tension of the molten stainless steel was observed. The sulfur content significantly affects the temperature coefficients of the surface tension, and the coefficient is negative for the low sulfur content and positive for the high sulfur content.

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Viscosities of molten Fe-Cr and Fe-Ni binary melts have been measured up to 1600℃ by using the oscillating viscometer developed for precise measurement. Viscosities obtained for all the compositions showed very good Arrhenian temperature dependence. Isothermal viscosity of Fe-Cr melt increases monotonously with increasing Cr content, and that of Fe-Ni alloy decreases monotonously with increasing Ni content. Activation energy for viscous flow of the binary alloy also increases and decreases monotonously with increasing the content of chromium and nickel, respectively. The order of the viscosity value of the elements is same to that of the melting point that reflects the cohesive energy in the melt and affects the viscosity of the alloy.

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The thermal conductivity of liquid iron and its commercial alloys has been measured under microgravity, where there is no convection in liquid metals. The hot wire method was employed for the measurements and the hot wire was coated with alumina thin layer which was produced using a electrophoresis method. The thermal conductivities were smaller than the estimated values from the electric conductivities using the Wiedemann-Frantz law.

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The problem of emissivity change on metal surface complicates the radiation thermometry measurement of weld pools. Therefore, in the conventional radiation thermometry, an emissivity correction has been one of the most important subjects. The objective of the present investigation is to develop an ultraviolet (UV) radiation thermometry, which is tolerance to an emissivity change. Because, according to the Planck's law of radiation, it is evident that the effect of temperature on the spectral radiance is greater at the shorter wavelength, and radiation thermometry in UV range is expected to reduce the error caused by this emissivity change. Generally, the radiation energy in UV range is lower than that in IR range at the same temperature. A measurement system that is sensitive to the UV radiation has been developed in the present work. The system consists of an image intensifier, and multiple optical band-pass filters.

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The observation of the welding arc and molten metal behavior is necessary in order to model the welding phenomenon. A tracer, which is made of zirconium oxide, is floated in order to visualize the molten metal behavior. The flow direction and speed of the molten metal can be quantitatively measured by tracking the locus of the tracer. Experiments are carried out under the following parameters; the kinds of shield gas and the sulfur content in the 304 stainless steel test piece. We have succeeded in visualization and measurement of the molten metal behavior in GTAW by use of the high-speed camera and the tracer.

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In order to investigate the effects of the gravity, surface tension electromagnetic force and plasma stream on convection in a molten pool, electron beam (EB) welding and gas tungsten arc (GTA) welding were performed under both terrestrial and microgravity conditions. For iron alloys, pure iron, an iron-tungsten alloy (SKD4), and for aluminum alloys, pure aluminum and an aluminum-copper alloy (A2219), were used for the specimens. The cross sections of the specimens were analyzed by EPMA after the welding. During the EB welding, the surface tension and the buoyancy determine the convection. Under microgravity, only the surface tension causes the convection because the buoyancy is considered to be negligible. As a result, it is found that the convection due to the surface tension is dominant for iron alloys but it is very weak for aluminum alloys. Accordingly, when aluminum alloys are welded by arc welding under microgravity, only the electromagnetic force and plasma stream are the dominant effects on the convection. Therefore, the convection can be controlled by changing the arc length to break the balance between the electromagnetic force and the plasma stream.

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Automation of arc welding process is very important to improve weld quality and cost performance. However, arc welding process has not fully understood, because of less knowledge on arc behavior. Behavior of heat transfer during arc welding is much influenced by metal composite, arc voltage, arc current and shielding gas. The welding process was captured by high-speed video systems in high pressure chamber. Three-dimensional behavior of heat transfer and motion of liquid metal surface has been analyzed. Full color image and near infrared monochrome image have different information on arc and metal condition. Then, deeper consideration on defect formation during welding process becomes possible.

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One of the important problems in the welding engineering is to construct a mathematical model for the computer simulation of the welding process in a manufacturing environment. In the first part of the present work, a simple mathematical model for MAG (Metal Active Gas) arc welding, based on the heat flow equation and the molten pool balance equation, has been introduced to make clear the influence of various process parameters on the weld bead formation. And it is made clear that the model is capable of predicting the MAG arc welding process, including multi-pass welding. In the second part, a simulation-software for the virtual welding system, based on the MAG welding process model, has been proposed. In the software, the process model has been linked to a metallurgical and mechanical model, developed in the project, to simulate the MAG arc welding comprehensively. According to the software, the weld-geometry and the weld-deformation including the temperature history in the work-piece for the inputted process parameters are easily estimated, and the dynamic behavior of molten pool and weld-deformation are reproduced visually by using an animation technique.

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The flow-field of a molten pool of the laser welding was simulated by solving the 3-dimensional Navier-Stokes equation. The keyhole diameter and depth were assumed to be 1mm and 6mm for the 4.8kW CO2 laser welding condition. The body force of (10)^7N/m3 by the evaporation reaction was given at the keyhole front region. The temperature gradient of the surface tension was assumed to be -0.5mN/mK. and the Marangoni effect was considered. The descending flow was formed at the front of the keyhole, and its velocity was about from 0.2m/s to 0.5m/s. It is enough for the bubble of 0.3mm∿1mm diameter of to be separated from the keyhole by the fluid force against the surface tension and the buoyancy. Some of the bubbles were trapped in the solidification region, which remained as the porosity.

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In order to clarify the formative mechanism of weld penetration in an arc welding process, the development of a numerical model of the process is quite useful for understanding quantitative values of the balances of mass, energy and force in the welding phenomena, because there is still a lack of understanding due to the existence of complicated interactive phenomena between the arc plasma and the weld pool. The present paper is focused on a stationary gas tungsten arc (GTA) welding process for simplification, but the whole region of GTA welding, namely, tungsten cathode, arc plasma, work-piece and weld pool is treated in a unified numerical model taking into account the close interaction between the arc plasma and the weld pool. The two-dimensional distributions of temperature and velocity in the whole region of GTA welding process are predicted. The weld penetration geometry is also predicted.

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A 3D-numerical model, which predicts both fields of temperature and liquid metal flow in weld pool and time-dependent penetration process by both of spot and moving gas tungsten arc, was developed. In order to examine the validation of the model, penetration shapes in helium gas shielded GTA welding were experimentally and theoretically investigated for two heats of stainless steel having different sulfur contents. Weld penetration of high sulfur stainless steel (250ppm S) was deeper than that of low sulfur stainless steel (10ppm S) for current of 100A in welding speed range up to 10 mm/s. A ratio of depth to width in penetration shape of high sulfur stainless steel decreases with increase of welding speed. Whereas, that of low sulfur stainless steel was almost constant and not dependent on welding speed. It is shown that calculated results agree well with experimental results.

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It is very valuable to develop a numerical model for various welding styles in order to understand the welding phenomena. The welding simulation models for a target work could be available for off-line robot programming or on-line robot control. The objective of this study is to develop a GTA welding simulation model for various works. Present model may apply to several work configurations with comparative ease. This paper discusses on a model for welding of pipes and a model for all position welding of plate and pipe, and the model applies to aluminum and aluminum alloys. According to calculated results, it is made clear that homogenous weld is difficult to get for the fixed pipe welding due to the gravity effect, and that the weld bead shape on welding of plate and pipe is sensitive to changes in plate thickness. The calculated result by the model has been compared with the experimental result, and good correspondence between them has been obtained. Accordingly, the model, proposed in this work, is concluded to be useful for a simple simulation of GTA welding, and offers a powerful means for the estimation of optimum process parameters in the process.

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The welding distortion of a plate structure during the assembly process is influenced not only by the local shrinkage due to the welding thermal cycle but also by the root gap and the misalignment. The former is governed by the heat input. Meanwhile, the latter is strongly affected by the welding procedure, such as the welding sequence and restraint on the joint to be welded. A method to predict the welding distortion considering these factors is developed. The welding cracking problem is important as well as the distortion. A method for the simulation of welding hot cracking is also developed.

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The experiment for measurement of welding distortion generated by fillet welding was carried out and the experiment was simulated by 3D program (three-dimensional thermal elastic-plastic analysis by FEM) developed by the author. The tendency of the longitudinal bending distortion was well simulated but the absolute value of the analysis results was larger than that of the experiment. Although the tendency coincided well in the angle distortion like as in the longitudinal bending distortion, the absolute value of the analysis results was smaller than that of the experiment. It is difficult to say that the experiment was accurately simulated by 3D program. It can be considered as the reason that the initial distortion of the skin plate had been ignored and that the welds metal had been assumed as a simple isosceles triangle. It is the future problem to be solved.

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The thermal elastic-plastic analysis for the welding transient and residual stresses and deformations needs the huge computation time to obtain the accurate results. In this study, a new method, a step iterative total strain method, will be developed to shorten the computation time largely, keeping high accuracy. For the large increment of temperature the basic theory of the step iterative total strain method was developed for the thermal elastic-plastic state, taking into account the change from elastic state to elastic-plastic state in one increment and the temperature-dependencies of the mechanical properties. Based on the theory (the thermal elastic-plastic constitutive equation), the equilibrium equation (the stiffness equation) was developed for the finite element method. New FEM program for thermal elastic-plastic analysis is under development, based on the above theory, now.

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It is well known that porosities were easily formed in welds and its toughness was low when steels were laser welded. In this study, the weld was austenitized by adding a filler wire with laser welding. It is confirmed that fracture surface of welds was changed from brittle to ductile with increasing amount of filler wire.

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Three-dimensional (3D) morphology and growth behavior of acicular ferrite formed in low carbon steel weld deposit (0.11%C) was studied by serial sectioning and computer-aided visualization. The specimens taken from the weld deposit were austenitized at 1350℃ and reacted at 570℃ for varying times. The length, width and thickness of individual ferrite plates, measured from 3D-reconstructed images, were ranging from several microns to ∿25μm, less than ∿8μm and from 0.2 to ∿3μm, respectively. The change in the aspect ratio with holding time indicates that the lengthening occurred first and thickening followed after the plate tips impinged mainly on other plates. Multi-variant ferrite plates were observed to be nucleated at inclusions and grow in the specific directions in the matrix, probably keeping a fixed orientation relationship with austenite.

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A mesh-divided model for prediction of mechanical properties of weld metals was developed This model consist of two main parts. First part is microstructure evolution model that predicts fraction and size of transformation products. Second part is mechanical properties model that predicts hardness, tensile strength and Charpy impact value etc in each mesh. Mechanical properties of whole deposit metals were well predicted by summation of those of each mesh.

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An investigation has been made of the effects of heat input and shielding gas composition on the properties and microstructure of welds which was produced on 950 MPa class high strength steel by gas metal arc welding. The microstructure of the weld obtained, consisting principally of martensite and bainite, was altered from martenstic to bainitic, as the CO_2 content in the shielding gas of Ar was increased from 0 to 25%. The effect of the increase in the heat input from 2.5 to 4.5 kJ/mm on the microstructure exhibited a similar tendency, but the observed difference was less significant. The weld metal produced by shielding gas of less than 10% CO_2 contents at heat inputs less than 4 kJ/mm had superior mechanical properties. It was also found that the M-A constituent, embrittlement microstructure, formed in the granular bainitic area, whose volume fraction was increased with the CO_2 content and heat input.

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The present work deal with the construction of a basic simulation system of the evolution of microstructure during cyclic heat treatment in order to estimate and propose a suitable welding condition for fabricating sound joint. Potts model containing hexagonal array of 200×200 sites was generated for representing polycrystalline structure. Monte Carlo simulation technique was utilized to realize migration of phase boundaries and grain boundaries at elevated temperature. The pattern of temperature cycle was settled to alter the microstructure by precipitation and grain growth at higher temperature where the solution treatment proceeds. The present system can provide any number of nucleation site on each grain boundary and also nucleation site in grain interior. Precipitation nucleated at grain boundaries was successfully realized and successive grain growth at higher temperature was also represented.

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Ceramics has been excellent mechanical and thermal properties. These characteristics are noticed recently and ceramics is utilized as structural materials for a heat resistant material. The knowledge of the behavior in the high temperature of grain boundary layer including sintered additive is necessary, on using ceramics as a heat resistant material. In this study, internal friction characteristic of three kinds of ceramics, i.e., the silicon nitride, the silicon carbide and the zirconia is investigated. The measurement is conducted from the room temperature to 1000℃ by an inverted torsion pendulum testing equipment. The result shows the internal friction value of the zirconia and silicon nitride has a peak. However, a peak didn't appear in the silicon carbide.

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The constitutive relation of silicon nitride at high temperature and high strain rate was investigated using split Hopkinson pressure bar method. Experiments were conducted at the strain rates 10-(10)^2 and the temperature up to 1300℃ and the stress-strain relation was obtained. The numerical simulation was also performed using 4-element visco-elastic model, and compared with the experimental results.

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The fracture modes, i.e., brittle fracture and ductile fracture are studied comparing the criteria in macroscopic and microscopic aspects. In this study, as the macroscopic criterion, the stress triaxiality and the critical stress intensity factor are used. As the microscopic criterion, the idea of fractal is applied to the fracture surfaces. The tensile fracture tests and the three points bending tests were carried out using S35C, S55C and FC200. Fractal dimension are calculated based on the method of box-counting and hight-hight correlation. The relationship between the fracture modes and the fractal dimension of the fracture surfaces is discussed.

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Spacecraft structures in low earth orbit (LEO) encounter a degradation problem caused by atomic oxygen in the space environment. This study presents an experiment of degradation due to atomic oxygen on the ground. The experiment was carried out in a vacuum space chamber. Atomic oxygen produced at a plasma torch was accelerated fluid-dynamically with argon working gas. As target materials, isotropic high density graphite and highly oriented pyrolytic graphite (HOPG) were used. In this study, the effect of the bombardment direction is investigated. The macroscopic mass loss was measured and the microscopic degradation mode was observed. The mass loss of isotropic graphite depends on bombardment direction; however, the effect of the bombardment direction is not large considering the reduction of the bombardment area due to the inclination of the surface of the target material. The mass loss of HOPG is negligible compared with that of isotropic graphite. The eroded surfaces of both materials were observed with SEM. In case of isotropic graphite, the erosion occurred mainly at grain boundary area. On the other hand, the surface of HOPG after bombardment remains flat. It suggests that degradation of HOPG occurs by not only each atom but also by grain.

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It is well known that when a uniformly heated glass plate is lowered into cold water gradually in its in-plane direction, sinusoidal cracks often propagate due to thermal stress. The object of this study is to clarify the mechanism of the propagation of such sinusoidal cracks. Experiments were conducted changing the temperature and the descent speed of the glass plates. It has been observed that the larger the descent speed of the glass plate is, the larger the wavelength of the sinusoidal crack becomes. Furthermore, the stress distribution of the glass plate was calculated in order to investigate the effect of thermal stress on the crack propagation. At the first stage of the stress analysis, no cracks were assumed in the glass plate. The principal stress distribution suggests that cracks may propagate vertically below the surface of the water but that cracks turn to the horizontal direction after crossing the surface of the water.

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The effect of converting SiC shape form particle to whisker and addiction of Y_2O_3 on the crack-healing ability and mechanical properties of the SiC particle reinforced alumina composite, which have excellent crack-healing ability, were investigated. Fracture strength at high temperatures as well as at room temperature and fracture toughness have been excellent improved by converting SiC shape. Fracture strength at high temperatures has been also improved by addiction of Y_2O_3. Moreover, Crack-healing ability has not been reduced by converting SiC shape and addiction of Y_2O_3.

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Small-diameter fiber Bragg grating (FBG) sensors were embedded into the 90°ply on the border of the lower 0°ply of carbon fiber reinforced plastic (CFRP) cross-ply [0_4/(90)_4/0_4] laminates. When impact loading was applied to the specimens with a drop-weight impact tester, reflection spectrum from the sensors changed sensitively. In order to clarify these results, the spectrum was simulated theoretically. Furthermore, the intensity ratio of two peaks in the spectrum was found to be a good indicator for the quantitative evaluation of impact damage in real time.

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This paper describes embedment of a FBG (Fiber Bragg Grating) sensor in an aluminum matrix for deformation monitoring of aluminum based composites as a new application of FBG sensors in the field of structural materials. As FBG sensors are normally not handled at high temperatures, there high temperature stability was investigated to select a method of embedding them in aluminum matrix. Taking the results into consideration, a FBG sensor was successfully embedded in pure aluminum by the interphase forming/bonding method using copper insert. The aluminum specimen was tensile tested under monitoring the peak wavelength shift of the reflected light from the embedded FBG sensor and the level of optical transmissionloss. The obtained results show that it is working as a strain sensor in aluminum matrix even when the strain becomes larger than that of optical fiber fracture.

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This paper describes a study of smart structure composed of Ti-Ni shape memory alloys (SMA) and elastic materials. SMA is one of the effective materials which posses actuator function for start structure. However, in the conventional application of SMA, its shape change is non-reversible. Under certain conditions, SMA can show two-way shape memory effect (SME). But conventional two-way SMA is not used for smart structure because stability of the effect and strength of generated force is not sufficient. Composing SMA with elastic materials, the structures can response reversibly depending on temperature. In this paper, ring-shape type, which contains CFRP as the elastic materials, is investigated. Analytical models of reversible shape change and generated forces are led based on beam theory. The validity of the models is shown by comparison with experimental results.

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Joule heating deformation of laminated rectangular plates shown in the title was examined theoretically and experimentally. The room-temperature shape of a rectangular plate is decided by the plane dimension, and it becomes a saddle shape or a cylindrical shape. The boundary is shown in the fixed relationship between width and length of the plates. All rectangular plates become saddle shape, if the length of one edge is 127mm or less. With the temperature rise, the deformation by Joule heating simply shifts to flat plate from room-temperature shape. The transition from the cylinder to the saddle shape, estimated by the theory at intermediate temperature, is not generated

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This paper describes development of CFRP/metal active laminates. The active laminates were made by hot-pressing of various kinds of metal plates as high CTE material, unidirectional CFRP prepreg as low CTE material and electric resistance heater, KFRP prepreg as low CTE material and insulator between them, and copper foils as electrodes. In this study, the effect of the kind of metal and its thickness on the deformation and output force of the active laminate was investigated. As the results, it became clear that 1) aluminum is a suitable material for the metal plate to realize unidirectional actuation, and 2) it realizes both of high actuation capability and large output force.

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A microgrid was inscribed on the electro-chemically polished 347 austenitic stainless steels specimen surface and creep tests were carried out in argon atmosphere. B-added steel exhibited lower total creep strain and grain boundary sliding rates than those in the B-free steel. The contribution of the sliding strain to the total creep strain was found more in the B-free steel than that in B-added steel. Creep cavity nucleation and growth in the steel were suppressed with B addition, resulting in higher creep strength coupled with higher creep ductility in B-added steel.

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Al_2O_3 and mullite composite ceramics rein-forced by SiC whisker were sintered. Three point bending specimen was made from the composite ceramics. A semi-elliptical surface crack up to 450μm in diameter (aspect ratio ≒ 0.9) was introduced on the specimen. Basic crack-healing behavior of the cracked-sample was studied systematically as a function of crack-healing temperature, and also bending strength of crack-healed sample was tested systematically. Followings are main conclusion obtained; (1) Alumina and mullite rein-forced by SiC whisker exhibited large crack-healing ability. (2) The fracture toughness K_<IC>s of the composite alumina and mullite were increased by the SiC whisker reinforcement by about 100% and 60%, respectively. (3) The crack-healed alumina exhibited same level bending strength (σ_B) to the base material and very high σ_B up to 1473K. (4) The crack-healed mullite exhibited lower bending strength (σ_B) than that of crack-healed base material by 150 &acd; 200MPa.

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Al_2O_3/SiC composite ceramics was sintered by hot pressing. Three point bend tests were conducted according to JIS standard. Semi-elliptical surface crack of 40-350μm in diameter was made on the specimen. Four kinds of specimens (as-received, heal treated, pre-cracked and heal treated cracked), crack healing behavior and high temperature strength were tested systematically. The main conclusions were obtained as follows : (a) Al_2O_3/SiC composite ceramic has ability to heal crack. (b) Pre-cracked Al_2O_3/SiC composite ceramic to be healed completely at 1273K, 1473K and 1573K, for 300h, 10h and 1h, in air each other. (c) The maximum crack size to be healed is semi-elliptical crack of about 300μm in diameter. (d) Crack healed part has approximately the same strength of smooth specimen up to 1373K and most specimen failed outside the pre-cracked zone.

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This paper describes development of an active and sensitive metal-based composite. To realize this material system, continuous titanium fiber was embedded in an aluminum matrix, of which surface was oxidized to be insulated from the matrix to form a heater and a temperature/strain sensor. It successfully actuated and sensed temperature and electric resistance change during heating by its heating capability.

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A new apparatus has been developed to fabricate micro-structures and micro-devices. The apparatus is equipped with a tungsten microprobe, a stage system, a power source of 10V-10kV and two optical microscopes for monitoring. Fine particles can be picked up, transported, arranged and, if necessary, welded one by one, In this paper, the process of manipulation and welding using the apparatus is introduced, and two examples of the application are shown. One is arrangement of polymer particles coated with solder for the flip chip, andf another is a micro conveyer actuated by the alternative magnetic field.

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The PTC and NTC materials are defined that the electric resistance are steeply increased and decreased with an increase in temperature at around the Curie point, respectively. Composite particles of BaTiO_3 and In are fabricated by the forced electrification method. The packed bed of the composite particles have a good PTC property almost the same with the disk samples. The composite particles of NTC and In are also fabricated and their packed bed showed the NTC property. When the packed bed of PTC composite particles are piled up on that of the NTC composite particles, the layered packed bed shows V-type property. The V-type temperature dependency of the resistance is an addition of PTC and NTC. Furthemore, the composite particles of PTC, NTC and In are fabricated as follows. The PTC composite particles and NTC composite particles are composed by the forced electrification method. The packed bed of the two-step composite particles has also a V-type property. This is a good example of the particle assemblage that the multi-functional materials are created by integrating different kinds of particles.

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Magnetostrictive bulky Fe-17at%Ga alloy was fabricated by combining lamination of rapid-solidified ribbons (80 μm in thickness) and spark plasma sintering/joining (SPSJ). The laminated sample maintained the polycrystalline texture of columnar grains in as-spun ribbons because of the feature of short time and low temperature heating process in SPSJ. The excellent sintered sample was obtained under a condition of the compressive stress of 100 MPa at the temperature 973K. The magnetostriction considerably depended on compressive pre-stress for specimen and reached about 100 ppm which is a half of value obtained from the ribbon sample.

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A metallic 3-dimentional micro-honeycomb structural material containing heat resistant polymer for smart systems has been developed. Heat resistant polymer particles coated with a nickel-phosphorus alloy layer using electroless plating were pressed into green pellets and sintered at high temperatures in a vacuum. A metallic 3-dimentional micro-honeycomb structural material containing heat resistant polymer was then fabricated. The compressive and damping tests were carried out to measure the mechanical and damping properties of this material, respectively. The results showed that the stress-strain curve had a liner region, long plateau region and wavy region, and the sintering temperatures of the specimens affected the compressive strength of each specimen. The damping capacity of this material were shown to be very large. These results indicate that this metallic closed cellular material can be utilized as a material for energy-absorbing and passive-damping systems.

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CFRP has some pecular electrical properties. Taking advantage of these properties, CFRP unidirectional laminates can be used as smart patches to detect the maximum strain applied on structures. In order to confirm the possibility of the practical use of the CFRP smart parch, the change in the voltage distribution due to the damages in CFRP laminate was firstly investigated. As a result, it was revealed to be more effective to measure the total electrical resistance of unidirectional CFRP laminates than to measure the electrical distribution on their surface. Secondly, it was confirmed that the residual resistance change of the unidirectional laminate increased according to the maximum strain by both the loading/unloading test and the analysis using modified δ_<ec> model. From these results, the CFRP smart patch was found to be effective to measure the maximum strain.

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Property of interface materials used as boundary against sever environments seems to be gradually varied along to the distance from the surface. Material integrity might be influenced by the surface property degradation. Target vessel materials used in spallation neutron source will be exposed to proton and neutron irradiation and mercury immersion environments. In order to evaluate the surface degradation due to such environments, triple ions beam irradiation was carried out to the surface hardening treated materials that are candidate materials for a beam window in the target vessel. The mechanical property of the irradiated gradient surface layer was evaluated by the indentation technique with inverse analysis using multi-layer model. As a result, it was confirmed that the ductility loss of the surface-hardening-treated layer was hardly enhanced by irradiation, as compared with the changes of substrates.

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We examined the deformation behavior of CFRP laminates with delaminations by the buckling analysis based on nonlinear FEM. First, the buckling mode is estimated by linearlized eigenvalue buckling analysis. The result shows that local buckling is generated due to the existing interlaminar delamination in CFRP laminates under compression. Next, we calculated the reflection spectra of FBG sensors embedded at the delaminated region in the laminate, using post-buckling analysis and coupled-mode theory. From the result, we confirmed that the local buckling can be detected by reflection spectrum of the embedded FBG sensor.

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Although FBG sensors are useful for the strain measurement, they are influenced by the temperature change. In the present research, the center wavelength shift of an FBG sensor embedded in an unidirectional CFRP laminate was measured under the cryogenic temperature, and the relation between the temperature change and the wavelength shift was determined. Then, the accurate strain applied to the laminate was obtained by subtraction of the wavelength shift caused by the temperature change. The result showed that the temperature-compensated strain measurement could be carried out appropriately.

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Crack growth behavior from precrack in AlN under thrmal shock was evaluated by the Disk-on-Rod test. In this test, the heated specimen was quenched by means of contacting with a cool metal rod. The temperature distribution in the specimen was measured by IR camera, and AE signals during crack growth were detected by an AE sensor attached on the metal rod. In the present study, video camera system was applied to observe the crack growth behavior. Then, thermal stress and stress intensity factor were calculated by FEM analysis using temperature distribution. Deflection angles showed good agreement with the angles determined from two types of the mixed made fracture criteria. Consequently, the crack growth behavior under thermal shock was characterized.

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