Compression behavior of porous aluminum was examined by the experiment, elastic and elastic-plastic finite element analyses. The finite element model was constructed by the image-based modeling technique using the three-dimensional images obtained by the micro-focus X-ray computed tomography. Use was made of the voxel meshing which convert a voxel into a cubic finite element for simplicity. The elastic analysis showed that the elastic stress concentration was extremely high and occurred around the junction of cell walls, while the evaluated stiffness was extremely higher than the experimental result. Moreover, the post stress-smoothing filter worked effectively to reduce the error stress arising from the step-like surface shape of the voxel model. The elastic-plastic analysis showed that the actual stress concentration was relatively low and the experimental initial stiffness must be affected by the plastic deformation.

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Microcellular injection molding is a technology to create very small cells in the wall of plastic parts. Microcellular injection molding needs specially designed equipment to create single phase solution from molten polymer and supercritical fluid and to create micro cells in molten polymer by quick pressure drop. Microcellular parts are used in automotive industries and electric/electronics industries. Recently the combination of microcellular injection molding and Heat&Cool technologies are studied actively to avoid swirl mark on the surface. To get high expansion ratio, core back technology is studied.

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Surface pores of a closed-cell type aluminum foam were filled with aluminum powder by selective laser melting (SLM). The relationship between the laser irradiation conditions and solidification characteristics of aluminum powder was investigated with one-line laser irradiation. The aluminum powder was continuously melted and solidified with a laser spot diameter of 0.6 mm and a scanning speed of 10-20 mm/s. According to the successful melting and solidification conditions, SLM was applied to the surface pores of a closed-cell type aluminum foam supplied with aluminum powder. The supplied aluminum powder was melted and welded to the aluminum foam. As the result, the aluminum foam with nonporous surface layer (sandwich structure) was successfully fabricated.

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To stabilize graded foaming of aluminum alloy precursors, the adjustment of the amounts of TiH_2 foaming agent and SiC stabilizing agent may be important. On the other hand, the usage of prealloyed powder and the granulation of ceramic particle additives were found be effective to the stabilization of foaming, in the previous study. In the present study, the effects of the combination adjustment of SiC / TiH_2 on the foaming behavior of the prealloyed powder precursor with SiC granules were examined. Consequently, both large expansion and high height-to-width ratio of the foam specimens were attained to some extent with an appropriate combination of SiC and TiH_2 contents.

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Porous aluminum sandwiches with the aluminum foam and dense steel sheets were fabricated by the friction stir processing (FSP) route. Using the fabricated sandwiches, failure tests were carried out under combined loading of tensile type and shear type. Under only shear type loading, two types of failure (i.e., tensile type failure and shear type failure) were observed. Under combined loading, tensile type failure firstly occurred, then shear type deformation markedly increased. The tensile strength and shear strength of porous aluminum could be approximately defined by the maximum principal stress and maximum shear stress, respectively.

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In this report, we show the preparation of self-organized honeycomb-patterned porous polymer films and their applications for superhydrophobic surface and etching masks. The preparation method of honeycomb-patterned porous polymer films was easy and simple; casting a hydrophobic polymer solution containing hydrophobic polymer and surfactant on a solid substrate under humid condition. After several minutes, honeycomb-patterned porous polymer films were formed by using condensed water droplet arrays as template. Honeycomb-patterned films are consisted of three parts: top porous layer, bottom dimpled layer and pillar structures. Because of these pillar structures are mechanically weak, we can divide honeycomb-patterned films into top porous layer and bottom dimpled layer by using adhesive. The dimpled bottom layer, pincushion films, shows superhydrophobicity, and top porous layer can be used as etching masks. By using top porous layer as wet etching masks, dimpled iron surface can be obtained. Top porous layer also can be used as dry etching masks, and the silicon nanospike-array structure, which was reflected 3-dimensional structures of top porous layer, was formed. These surfaces have functions of anti-seizure property and superhydrophobicity, respectively. Detail preparation methods and functions will be discussed.

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Sintered aluminum fiber is one of the open-cell porous metals. Present study examines the potential application for landing gear of SLIM (Smart Lander for Investigating Moon) explorer. Quasi-static and dynamic compressive tests were carried out using a universal testing machine and a drop hammer type impact testing machine, respectively. Plateau stress of the sintered aluminum fiber reduce with reducing the specimen size, which is called size effect. On the other hand, plateau stress is independent of the initial compressive strain rate. Free fall experiments using a real size model of SLIM explorer revealed advantages of sintered aluminum fiber for impact energy absorbing material.

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A bi-modal porous ceramics with cylindrical pores and communicated pores were fabricated through unidirectional solidification of water slurry containing CO_2 gas. The cylindrical pores were formed during the unidirectional solidification under reduced pressure and a composite of ice and ceramics powder was obtained. Since the composite was formed by segregation of ice during the solidification, a communicated structure of ice was obtained. The ice was removed by vacuum freeze drying method. The porous bulk with cylindrical pores and communicated pores was sintered at 1250℃ for 5 hours. The porosity and pore size was well controlled by the pressure during the solidification and sintering temperature and time.

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A bi-modal porous SiC with cylindrical pores and communicated pores were fabricated through unidirectional solidification of water slurry containing CO_2 gas and microwave sintering. The cylindrical pores were formed during the unidirectional solidification under reduced pressure and a composite of ice and SiC powder was obtained. Since the composite was formed by segregation of ice during the solidification, a communicated structure of ice was obtained. The ice was removed by vacuum freeze drying method. The porous bulk with cylindrical pores and communicated pores was sintered using microwave sintering for 5 minutes. Since the dielectric loss factor for SiC is larger than that of the other ceramics, a rapid heating of SiC bulk can be achieved by microwave sintering. The porosity and pore size was well controlled by the pressure during the solidification and sintering time. The degree of shrinkage can be controlled by adding a sintering agent.

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In bone tissue engineering, porous composite materials of biopolymers and bioactive ceramics have been planned to be utilized as scaffolds for tissue regeneration with stem cells. Continuous porous structure is one of the key factors for scaffolds in order to ensure cell growth and formation of extra-cellular matrix (ECM) inside the scaffolds. In the present study, different kinds of porous composite scaffolds were developed for bone tissue engineering applications and their mechanical and biological properties were examined. For example, β-TCP particle filled collagen sponge exhibited an excellent biocompatibility with mesenchymal stem cells although its compressive properties were quite low compared to natural cancellous bone. On the contrary, sintered porous bioceramic structures with introduction of secondary polymer phase possessed better mechanical properties with proper biocompatibility. A novel porous scaffold with drug release function was also successfully developed to activate regeneration of bone. In this paper, the fabrication methods and the fundamental properties of those porous composite materials developed for bone regeneration are summarized.

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Porous metals like aluminum foam, which has relatively large closed cells around several millimeters, are expected as an ultra lightweight structural material in various industrial fields. Research and development of such porous metals are increased in the 1980s and some industrial applications were proposed and increased in 1990s. Focusing on a precursor method for metallic foams, the movement of related technology, innovative development in our laboratory and future possibility and issue are surveyed in the present paper.

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This study clarified the relationship of fatigue strength reduction factors of engineering plastics PBT and PEEK between theoretical stress concentration factor, stress concentration factor and strain concentration factor in the region of high and low cycle fatigue. In this study, we carried out elastic-plastic simulation FEM analysis and elastic-plastic fatigue tests on specimens with four kinds of elliptical hole which are made of PBT and PEEK. As results of experiments and calculation, it is clarified that there is the proper relation between fatigue strength reduction factor and stress concentration factor in PBT, on the other hand, there is also the other relation between fatigue strength reduction factor and theoretical stress concentration factor in PEEK

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Lanthanum (La) doping porous Silica (Si) material for adsorption of carbon dioxide (CO_2) was synthesized by a precursor solution method accessed the adsorption properties, and studied the relation between the microstructure and CO_2 adsorption properties by transmission electron microscopy (TEM), X-ray diffraction (XRD), automated gas sorption system (Autosorb). As a result, CO_2 adsorption of the Si-La materials exhibit better result at 373 K than at 673 K. The Si : La ratio 4:1 composite material showed best function of CO_2 adsorption as compare with Si : La=2:1 specimen, which suggested that CO_2 adsorption might depend on the surface site of activated La_2O_3 in Silica.

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Porous aluminum (Al) is a lightweight with high energy absorption properties and expected as structural materials. In this study, porous Al core filled in Al pipe composite material (porous core pipe) was fabricated by friction welding. Precursor of porous Al was fabricated by mixing the Al plates and blowing agent powder by friction stir welding. Precursor was put into the Al pipe, and rotating tool was pressed into the precursor. Then, bonding Al precursor to Al pipe can be conducted. Porous core pipe with metal bonding was successfully fabricated by heating the precursor. By using X-ray CT, pore structures of porous Al was observed.

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In order to improve fuel consumption and collision safety of a car, application of ultra-light porous metals having high specific rigidity and good impact energy absorption to various car parts are hopeful. Generally, it is thought that the applicable porous metals include closed cells and their relative density is less than 0.3. Especially, metallic hollow sphere (MHS) structure is comparatively homogeneous and has high reliability to apply it to the car parts. However, production cost, insufficient controllability of performance and weak tensile strength have been problems yet. To solve these problems, we propose a new ball-chain type MHS structure. Many strings of metallic hollow spheres are precisely produced from thin metal sheets by plastic working with dies and then the strings are arranged and consolidated. Since the neighboring hollow spheres are connected by a bridge, the tensile strength may be improved. By changing thickness of metal sheet and die dimension, density of the structure or mechanical performance can be controlled easily. In this paper, the fabrication method and results of simple compression and 3-point bending tests of the structure are reported.

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In this study, the tensile properties of the quasi-static and the impact tests for 7075 aluminum alloys subjected to pre-fatigue deformation in a humid environment were investigated. An impact tensile test was performed by means of the Split Hopkinson pressure bar method. The flow stress in both the quasi-static and the impact tests was unaffected by the pre-fatigue deformation. On the other hand, it was clarified that the ductility of the pre-fatigue specimen was slightly lower than that of the non-fatigue specimen. The ductility of the quasi-static test was decreased as compared with the impact test. It is thought that the ductility loss occurred due to changes in the microstructure, such as dislocations caused by the presence of hydrogen in the specimen due to pre-fatigue deformation in a high-humidity environment.

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In the present study, the effect of strain rate on compressive properties of the foamed polyethylene (PE) film was experimentally investigated. The foamed PE film has characteristics of thin and closed-cell structure. The impact test was carried out at the strain rate of 10^3 to 10^4s^<-1> using split Hopkinson pressure bar method. The dynamic test was carried out at the strain rate of 10^1 to 10^2s^<-1> using a drop weight testing machine with opposed load cell, which can evaluate the dynamic stress equilibrium during the deformation. Quasi-static test was carried out at strain rates of 10^<-4> to 10^<-1>s^<-1>. Within the set of experiments, the compressive stress was increased, and the densification strain was decreased with increasing the strain rate. The plateau deformation was observed immediately after the compressive testing started with no linear-elastic response phase. It was clarified that the change of strain rate sensitivity was appeared at the strain rate of 10^<-2>s^<-1>.

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Effect of microstructure on mechanical properties and thermal stability of high strength flame resistance magnesium alloy were investigated. In this present study, we used Mg-Al-Ca (Ca=1 mass%) cast alloys by antigravity cast process with rapid cooling. Sheet of this alloy subjected to a multi-pass rolling process at 300℃ showed a yield stress and ultimate tensile strength were 340 MPa and UTS 350 MPa, respectively. During the multi-passes rolling process, grain refinement occurred as a result of dynamic recrystallization of the Mg phase and dynamic crushing of Al-Ca compounds. Rolled flame resistance magnesium alloy was formed of non-recrystallized grain region was elongated to rolling direction with shear deformation. After annealing treatment, the grain growth was showed 3 to 5 μm at 400℃ for 1 hr because Al-Ca compound fine dispersion in Mg phase and the Al-Ca compound controlled grain growth at high annealing temperature. The thermal stability of this alloy was improved by addition Ca element.

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The effect of crystal orientation on indentation hardness and its microstructural evolution in HCP metals, i.e., magnesium, was investigated by experiments and calculations. The experimental results obtained by nanoindentation showed that the hardness of prismatic plane was slightly harder compared to that of basal plane. The deformed microstructural observations revealed the formation of {10-12}-type deformation twins without any relations to indented planes. Analysis of finite element (FE) simulation considering Hill's potential function indicated that the prismatic plane tended to have harder hardness. In addition, the location of deformation twins analyzed by FE simulation was the same as that of experiments.

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We investigated the effect of alloy composition on mechanical properties and formability of flame resistance magnesium cast alloys prepared by antigravity suction casting. It was well known that the combustion temperature of the Mg alloy is increased 200 K by the addition of 1 mass% of Ca. In addition, mechanical properties and corrosion resistance is improved adding Al to Mg alloy. In this present study, by using the various Mg cast alloy with varying Al content prepared by antigravity suction casting, and to investigate the formability, rollability and mechanical properties of the cast material, and investigated the optimal amount of Al added. The Vickers hardness and yield stress were improved with increases of the Al content, but Tensile strength and elongation were reduced Al content more than 8 mass%. In order to increase the limited reduction ratio and formability, fine dispersion of Al-Ca compounds to Mg phase is very effective, it is necessary to obtained fine initial grain size about 100 μm of the cast material. By performing a multi-pass warm and hot rolling process, the Mg phase is occurred the dynamic recrystallization and the Al-Ca compound is crashed during rolling process, the strength is improved, but, edge crack easily formed that Al content is increased.

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The deformation mechanism of the extruded AZ31 magnesium alloy rod under various deformation conditions was studied. From the result, the yield mechanism of AZ31 magnesium alloy is a non basal slip from 423K to 673K when this material is subjected to tensile stress parallel to the extruded direction to which transgranular sliding and grain boundary sliding are restrained. The non basal slip keeps working until fracture after the yield under the temperature below 523K. At a temperature of 523K or higher, grain boundary sliding is activated. The influence not only of temperature but also of strain rate on these deformation mechanism is implied.

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It was well known that commercial AZ series Mg alloy show the easily ignition at low temperature comparison with Ca added Mg alloys. While magnesium alloys have long been drawing strong interest as the lightest structural materials available, their application has been limited mostly to die casting parts. The request for low cost magnesium sheet materials has been drastically increased for the application to automotive and electronic industries. In this study, deep drawing behavior and tensile properties of twin-roll casted subjected warm rolling Mg-6Al-1Zn-1Ca alloy (AZX611; 1 mm in thickness) have been investigated in comparison with AZ61 rolled alloy. In order to form the Al-Ca compound in AZX611 alloy, yield stress is higher than that of AZ61 alloy, but tensile strength and elongation was reduced due to it is unable to secure sufficient plastic deformation. On the other hands, changed the punch and die condition, limited drawing ratio (LDR) of AZX611 showed the 1.8 to 2.4 in which testing temperature at 250 to 350℃. As a result, there was formed an Al-Ca compound by addition of Ca, it was possible to obtain the drawability same to AZ61 alloy and structural refinement by dynamic recrystallization and crushed of Al-Ca compound during warm rolling process was effective.

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Estimation methods for the creep properties by measuring the micro size deformation is required for finite element method (FEM) analysis considering the creep deformation of the solder joint in-situ. The indentation creep test is one of the effective methods to directly evaluate the creep deformation of solder joint. However, the indentation test cannot give the same creep properties as the creep properties obtained by the uniaxial creep tests using a bulk specimen. The authors proposed an indentation test conducted under a constant depth to determine a suitable reference area, which leads to the same creep characteristics as those obtained by the uniaxial creep test. One of the remaining problems of the indentation test is the reference area cannot be determined without the creep data obtained by the uniaxial creep test. In this paper, a method to determine the reference area without the uniaxial creep tests using a bulk specimen is proposed. For the determination of the new reference area, numerical indentation tests under a constant depth process for four kinds of solder alloys were conducted by FEM. The numerical simulation showed that the reference area obtained considering the distribution of the principal stress gives the almost same creep characteristic as that obtained by the uniaxial creep using bulk specimens.

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Creep constitutive equation is needed to conduct damage evaluation for welded part in a high temperature component. However uniaxial creep test has been done to identify some parameter included in the constitutive equation, the typical testing method cannot be applied to the local region in the HAZ. The purpose of this study is to develop the indentation creep test method and to establish the method for estimating the creep constitutive equation. First of all, the problem of semi-infinite creep media indented with a rigid spherical ball was solved analytically, and the simple formula which can identify the parameters was introduced. Next, the validity of the formula was confirmed through comparing with the results by inelastic-contact finite element analysis. Finally, the high-temperature indentation test for 12Cr steel was performed and the creep constitutive equation was estimated for the test results. As a result, it was found that the creep constitutive equation was estimated adequately by this method.

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In order to handle easily, Bainite transformation is treated as a kind of diffusive transformation in heat treatment analysis research. There are no reports about transformation progress of Ferrite-Pearlite-Bainite phase as far as we know. However, autocatalytic nucleation due to the precipitation of cementite occurs in the Bainite transformation, as proposed by Bhadeshia et al. In the past, we introduced the autocatalytic nucleation coefficient β, and examined the utility of the development type of phase transformation extended equation. In this study, we tested its usefulness by applying it to the structure as well as the coupled high-frequency induction heating and comparing the measured phase fraction with the analytical prediction.

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In order to evaluate the delamination strength of hard films bonded on ductile substrates, a convex edge indent method was proposed. A transparent glass plate was bonded on an transparent acrylic resin substrate, and one end of the specimen was machined to a rectangular shape. A conical indenter was gradually pressed to a glass plate at a distance from the edge observing the formation and propagation of the interfacial crack. The result showed that the interfacial crack initiated around the indent point at an indentation load about 1/3 of the delamination load, and propagated with increasing the indentation load. Delamination of the glass plate occurred after the crack front approached the edge. The interfacial fracture toughness was derived fracture mechanically, and applied to the. The interfacial fracture toughness ranged between 2-7kJ/m^2, decreased with increasing the width of the edge.

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The purpose of this study is to clarify the possibility of the sphere indentation test to evaluate properties of crack initiation and wear progress in ceramic thin films deposited on cemented carbide. Three kinds of ceramic thin films were deposited onto cemented carbide WC-Co substrates. Cyclic sphere indentation tests were carried out by using spherical indenter to investigate the aspects of crack initiation, wear progress in ceramic film and to obtain the influence of the applied maximum load P_<max> and load ratio L_s on the cyclic number of crack initiation N_i and wear value in thin films. The main conclusions are the following. (1) The loading cycle of ring crack initiation N_i increase with increasing L_s. (2) The wear value of S=S/(d_1-d_2) linearly increase accordance with P_<max> and loading cycles N, where S is obtained by measuring the cross-sectional shape of contact area and d_1, d_2 are diameter of wear region in the contact area. (3) The values of S^^-/(P_<max>×N) is almost constant independent of L_s, P_<max> and N.

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Bolted joints are widely used in various structures as fastening method because of the convenience in assembly-disassembly. However, loosening of the bolt may cause failure of the structure by reduction of the clamping load. Therefore, it is important to monitor the clamping load of the bolt. According to some previous studies, it has been clarified that the reduction of the clamping load of the bolt decreases the natural frequency of the structure with the bolted joints. This main cause is reduction of the contact stiffness in the jointed part that depends on the contact pressure and the surface topography of the jointed part. In this study, an identification technique using inverse analysis for clamping load from natural frequency of structure with bolted joints has been developed. This technique preliminarily estimates the parameters of the surface topography of the jointed part by using the natural frequency obtained from the known clamping load. And then, the unknown clamping load is estimated by the natural frequency and the parameters estimated preliminarily. In order to verify the effectiveness of the proposed technique, numerical simulations were carried out by using finite element models of the structure with the hollow cylindrical bolt.

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The elasto-viscoplastic constitutive equation based on the concept of continuum damage mechanics was formulated for the niobium alloy (C103) which was used for a thruster chamber material in a satellite. Fatigue life analysis based on damage mechanics was conducted to simulate the experimental data obtained by the strain controlled fatigue tests using round bar specimens made of the niobium alloy. The material parameters in the constitutive equation are determined based on the experimental data. Stress-Strain curves and damage value evolutions were also evaluated and the validity of material parameters was illustrated by comparing calculated values with test results.

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When honeycomb core sandwich panel (hereafter, HSP for brevity) is used as a floor panel, a dent is formed on the face sheet of the HSP. When the crack occurred on the face sheet makes the depth of the dent becomes deeper. Then the panel change into a new panel. If the high stiffness material such as Carbon fiber reinforced plastics (hereafter, CFRP for brevity) is used for face sheet, it is thought that the period for use as the floor panel extends. In this study, a series of static local compression tests and local compression fatigue tests by using peripherally clamped HSP of which CFRP was used for face sheet was carried out in consideration of usage condition as floor panel. From the obtained results of static local compression tests, the follows were observed; 1) No crack occurred on the face sheet used one-ply CFRP. On the other hand, there were cracks occurred on each layer of two-ply or more-ply CFRP. 2) The crack initiation occurred depends on the curvature of the dent. From the obtained results of local compression fatigue tests, the follows were observed that the stiffness of panel became higher with increasing the CFRP laminated number.

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A simple method to predict fatigue life is the linear cumulative damage rule. It is sometimes difficult to predict precisely the crack growth life under random loading in this method, because there is an effect of crack closure behavior on the fatigue life. In order to predict precisely, a new prediction method of fatigue life under random loading has been proposed. In the proposed method, the fatigue life was divided into 2 stages: the crack initiation stage and the crack propagation stage. The initiation stage was calculated by using the linear cumulative damage rule. The propagation stage was calculated by using the effective stress range to consider the crack closure effect. When the fatigue stage changes from the crack initiation stage to the crack propagation stage, there is a period where only the larger stress amplitude propagate's the crack. This study also proposed a method to consider that period hereafter, to the propagation stage, called the transition stage, by using the degree of fatigue and diving the fatigue life into 3 stages: the initiation stage, the transition stage and the propagation stage for brevity. To evaluate the validity of the proposed methods, a series of fatigue tests were carried out under several two step loading waves changed a ratio of high load amplitude to low amplitude. From obtained test results, it was found that the proposed life prediction became more accurate compared to the linear cumulative damage rule.

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Thin polyimide (PI) films have been widely used for spacecraft polymeric materials. However, small defects often initiate at the surface of PI films by the erosion caused by atomic oxygen present in space environment, and decreases mechanical strength significantly. Our previous experiments determined fracture toughness J_<IC> of PI films in the direction of film thickness considering the crack propagation from a surface short crack. In this paper, tensile tests were carried out using the same PI films used in our previous report, and CTOD values were measured by 3D laser scanning microscope to confirm the validity of J_<IC>. Fracture toughness tests were carried out with two types of specimens with different pre-crack lengths, 20μm and 40μm. As a result, CTOD_<IC> values of 20μm and 40μm pre-cracked specimens were determined to be 4.43μm and 6.08μm, respectively. It was found that CTOD was proportional to J, which corresponded well with generally accepted relationship between these two parameters. Therefore, J_<IC> values obtained in our previous work are valid as fracture toughness of PI films when crack propagates in the direction of film thickness.

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The fatigue life of solder alloys for the slow-fast cyclic loading condition is much shorter than that for the fast-slow cyclic loading condition, despite the two loading conditions having almost equal inelastic strain amplitudes. This suggests that the inelastic strain amplitude is not the best parameter used for evaluating the fatigue life which shows the strain rate dependency. In the previous study, we conducted the fatigue tests using the Sn-3.0Ag-0.5Cu (SAC) solder at RT. The tests employed the cyclic tension-compression loading using the stepped ramp wave (SW) to analyze the stress-creep strain relations during the tests. The analysis result showed that the creep strain amplitude obtained from the stress-creep strain relation had a higher correlation with the fatigue life than the inelastic strain amplitude. In addition, the equation indicating the relationship between the creep strain amplitude and the fatigue life at RT was likely to be useful to predict the fatigue lives at the other temperature. In this study, we investigated the relationships between the creep strain amplitude and the fatigue life for the SAC solder at 343 K and 393 K by conducting the fatigue tests with cyclic tension-compression loading using the SW. Then we attempted to describe the investigated relations at these two temperatures by the above-mentioned equation. As a result, the equation almost expressed the relationships between the creep strain and the fatigue life at 343 K and 393K even though it had been derived from the test results at RT.

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A new decision procedure on fretting fatigue and wear process analysis integrating total wear behaviour was proposed as a simulation technique used commercial FEM cord. The validity of this approach was verified using a simple wear model under elastic and elastic-plastic analysis condition. The fatigue lives near fatigue limit were exactly predicted by considering total-wear behaviour in wear process analysis. A procedure of simulating the accumulation of wear debris was proposed for discussing the location of fatigue crack initiation at fretting contact area.

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The non-direction ultrasonic sensor is developed for the purpose of the high-speed non-destructive test of a structure. First, the ultrasonic sensor using the electromagnetic Acoustic Transducer has been developed as a non-contact sensor. This paper has reported the experimental result direction ultrasonic sensor, and performance assessment. The performance assessment is evaluation of the trial sensor. The evaluation result indicated that developed sensor could be used to inspect the large area of a structure.

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Underground storage tanks are used for a long time after they were installed. Leak accidents occurred on the walls of tanks owing to local corrosion. Such tanks are monitored and checked by pressure test. However, the corrosion can not be detected before tank leakage occurred. The acoustic emission (AE) method is one of the powerful tools to detect local corrosion. We developed optical fiber AE sensor for monitoring underground storage tank. However, sensitivity of the sensor was not enough to detect weak AE signals. In this study, we simulated elastic wave propagated in underground storage tank that filled with liquid by using the finite-difference time-domain (FDTD) method. The shapes of the immersion type AE sensor was developed and designed by using the result of simulation. Amplitude of the signals that propagated in the liquid, simulated and compared. We estimated that AE sensor was mounted on the inner bottom surface, upper side and bottom side of sensor box.

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We investigated non-contact nonlinear ultrasonic characterization of the aluminum alloy plates subjected to zero-to-tension fatigue loading. We used two nonlinear methods; NRUS and three-wave mixing method, which were resonance-based techniques exploiting the significant nonlinear behavior of damaged materials. In NRUS, the resonant frequency of an object is studied as a function of the excitation level. As the excitation level increases, the elastic nonlinearity is manifest by a shift in the resonance frequency. In nonlinear three-wave mixing method, two intersecting ultrasonic waves produced a scattered wave when the resonance condition is satisfied. The wave amplitude was measured. NRUS and nonlinear three-wave interaction methods exhibited high sensitivity to micro-structural change of the damaged material. It rapidly increases from 60 % of fatigue life to the fracture. Three-wave interaction methods sensitivity is higher than NRUS. These noncontact resonance-EMAT measurements can monitor the evolution of NRUS throughout the fatigue life and has a potential to assess the damage advance and to predict the fatigue life of metals.

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Acoustic properties, e.g., acoustic impedance, sound velocity, etc., are used for characterizing polymer materials. It has been reported that the acoustic properties of thin polymer films can be characterized using acoustic resonance phenomenon occurring among the water, polymer film and reflection plate. We observe acoustic resonance phenomenon at both surfaces of the reflection plate contacted with a polymer film, and measure the sound velocity of the film from the resonant frequency.

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Nondestructive inspection of a high temperature structure is required to guarantee the safety of it. However, there are not any useful sensors for high-temperature structure. Some of them can't work at high temperature over 50℃. Another one is too expensive to use it. Therefore, the sensing system which can transmit and receives an ultrasonic wave which travel long distance by using a long waveguide has been studied. It means that an ultrasonic sensor could be driven at atmospheric temperature. We could finally confirm that a guided ultrasonic wave generated by a trial electromagnetic acoustic transducer (EMATs)with Ni-thin sheet on the surface of th pipe can travel more than 10m using a thin bar with a 2mm - diameter as a wave guide. Next, we tried to transmit and receive a guided wave in to a pipe using the developed system. It is indicated that an additional T-shaped or Y-shaped waveguide on the pipe is useful.

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In this study, we investigated the relationship between microstructural change and the evolutions of two nonlinear acoustic characterizations, resonant frequency shift and other three-wave mixing, with electromagnetic acoustic resonance (EMAR) throughout the creep life in welded joint for high Cr terrific heat resisting steel, ASME Grade 122. EMAR was a combination of the resonant acoustic technique with a non-contact electromagnetic acoustic transducer (EMAT). We used bulk shear-wave EMAT. Creep tests of thick welded joints specimens were interrupted at several time steps at 873 K, and100 MPa. Two nonlinear acoustic parameters and ultrasonic attenuation decreased from the start to 40% of creep life. After that, they gradually increased to rupture. Creep void initiated from 40% of life, and slightly increased to 90 % creep life. After that it rapidly increased to the rupture. The changes of two nonlinear acoustic parameters, attenuation caused by the microstructural change related to creep void initiation and growth. This noncontact resonance-EMAT measurement can monitor the evolution of nonlinear acoustics throughout the creep life and has a potential to assess the Type IV creep damage advance and to predict the creep life of high Cr ferritic heat resisting steels.

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Piezoelectric ring-shaped sensor (PeRS) has been widely used for guided wave inspection of piping. The PeRS is normally consisted of plural transducer elements located along circumference at regular interval. Due to the structure, in addition to the axially propagating torsional mode guided waves, circumferential (C-) Lamb waves have also been generated as spurious waves at the same time. Especially in the resonant conditions determined by both the specific frequencies and locations of sensor elements, the C-Lamb waves are dominantly and preferentially generated as actual spurious signals that may distort axially propagating waves. In this paper, this troublesome phenomenon is used not for the axially propagating guided waves but usefully for the measurements of wall thicknesses. The Principle, the verification and the accuracy of the measurements were shown.

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A new ultrasonic coupling powder has been developed where the gel of conventional contact mediums is replaced with powder. In this method, ultrasonic testing is carried out while compressing the powder between probes and concrete surfaces by applying pressure to the probes. Even though the powder usually prevents the transmission of elastic waves, they can be transmitted through it under pressurized conditions. In addition, the acoustic impedance can be matched to that of mortar or concrete by controlling the pressure applied to the powder. In this paper, this ultrasonic coupling powder was applied to the testing of mortar test specimens. The results were that the amplitudes of the back reflection increase as the pressure of the powder increases. These results were compared to those from grease coupling. The problem with the coupling powder is the necessity of high pressure applied to the powder. Our solutions to this problem are outlined in the last section.

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In this research, phase-shifted FBG (PS-FBG) sensor was employed to practical AE detection for carbon fiber reinforced plastic (CFRP) composite laminate. Firstly, we evaluated the characteristics of AE signals detected by this kind of sensor. Secondly, through the experiment and simulation concerning AE source orientation, quantitative information about the standard for discriminating the AE signals due to transverse cracks and delaminations was obtained. Finally, according to the standard, we identified the occurrence of those two damage types successfully from the actually detected AE signals under three point bending and tensile tests.

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In Japan, concrete slabs of highway bridges, especially ones constructed before 1970, have suffered fatigue damage due to repeated traffic loads. "Steel plate bonding method" has been widely used for over 30 years to strengthen damaged concrete slabs. In recent years, however, the repaired structures have also been damaged due to the debonding of adhesive resin between a steel plate and concrete. In this study, a laser based ultrasonic method is developed for remote inspection of bonded steel plates. Some results are obtained in a laboratory measurement of specimens, and are discussed in comparison with impact hammer method and numerical results. It is shown that the laser based method has a promising possibility of effective nondestructive evaluation for steel plate bonding of highway bridges.

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Pipes in power plants tend to be damaged at the pipe elbows and lower reach of orifices by Flow accelerated corrosion and erosion. As one of the conventional techniques, an ultrasonic thickness meter is generally used to measure the main pipe thickness and detect the corrosion wastage in power generation plants. However, this requires plant outage time and cost to dismantle and reassemble the heat-insulating coat of the pipes. To solve these problems, we developed a new measuring technology by combining Electromagnetic Acoustic Transducer (EMAT) and Fiber-Optic sensors. Since it can be put between the pipe and the heat insulator, this sensor enables us to measure and monitor the thickness of the pipe online. This report describes how to detect scale adhesion to inner surface of pipes with EMAT and Fiber-Optic sensor.

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Efficient transduction of a circumferential (C-) Lamb waves by a pair of noncontact air-coupled ultrasonic transducers (NAUT) was presented. A line focus type (LFT-) of the NAUT was employed for the efficient transduction of the C-Lamb wave, which was designed so as to take an almost same angle of the incident longitudinal beam on the circular pipe surface. Outstanding characteristics of the LFT-NAUT for the C-Lamb wave transduction were theoretically and experimentally shown in comparison to those of the conventional plane type (CPT-) NAUT.

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This paper demonstrates a new approach for generating ultrasound, utilizing evanescent light. Evanescent light generated during total internal reflection at the prism surface, is utilized for generating ultrasound in aluminum specimen. A pulsed ND:YAG laser operated at 1064 nm optical wavelength, with duration time of 3〜5 nsec, and energy density of 0.03〜0.85 J/cm^2 is used. It has been found that ultrasound can be generated in the aluminum specimen only by evanescent light. The amplitudes of ultrasound generated by evanescent light were unexpectedly nine times larger than the ones generated by direct laser irradiation. The obtained directivity pattern shows considerable intensity at 0°, which reveals that the ultrasound in this experiment is generated by ablation effect. According to the theoretical speculation, when the plasma generated by laser irradiation is confined geometrically, its impulse pressure is significantly enhanced. These results indicate that the possibility of a novel ultrasound pulse-echo transducer with near-field optics for measuring objects smaller than the wavelength of light.

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Nowadays thin films are essential materials for modem engineering, and the demand for high quality thin films is getting larger. Understanding the dynamics of initial growth mechanism during deposition is important to control the quality of films. In this research, we monitored the structure evolution of thin film during and after deposition by using antenna transmission acoustic resonance (ATAR) method. We observed the structure evolutions from island structure to continuous film and vice versa. During deposition, structure changed from island structure to continuous film. However, by increasing the temperature, continuous film changed to island structure. We thus succeeded to monitor the structural evolution by temperature variation.

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By using a burst sine wave pulser of 100MHz range, high-pass filters, an amplifier and imaging software, we imaged non-metallic inclusions in a SUS 304 steel plate, interface disbond of a SiC/Ti composite by tensile loading and local plastic deformation in SUS 304 plate. The images of anormalies obtained by 35MHz sine wave of 2 cycles and 80 MHz high-pass filter have much higher resolution than those obtained by 20MHz sine wave of 2 cycles and 40 MHz high-pass filter. By a local resonance technique, image resolution of local plastic deformation in a SUS 304 perforated plate subjected to 30% plastic strain at maximum is also improved markedly.

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