This research is about method for estimate the risk for the risk based maintenance of non static equipment based on the monitoring data. Generally, evaluation of probability of failure is conducted by the prediction of the damage based on the hazard data base for the static equipment. But, for the non static equipment, it's damage is mainly caused accidently, so it is difficult to evaluate the damage based on them. Therefore, for the non static equipment, damage evaluation based on the monitoring data is practical. And the SI-F method proposed by authors that is evaluated by the change of relation between measurement of several sensors is used to process the large amount of data statistically. Then in this research, the method to evaluate the probability of failure via SI-F method based on the monitoring data is proposed and the validity of the method is experimentally confirmed.

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The SI-F method is statistical damage diagnostic method which diagnose existence of the damage from detecting the change of correlation between sensors as instead of change of single sensor measurement. Since the damage diagnosis is conducted by using parameter which shows change of correlation, this method has high tolerance to the noise and change of environments. However, deviation from a theoretical result occurs in the status under too high noise condition. Then in this paper, the noise condition evaluation parameter for SI-F method was proposed.

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This research is about improvement of diagnostic accuracy of the damage identification applying the generalized linear mixed model to the inverse problem. Generalized linear mixed model (GLMM) is the extend method of the linear regression analysis include the random effect. When the damage diagnosis conducted by the inverse problem, this unknown fluctuation is caused by not only the difference of the lot of test piece, but also the unknown parameters of the damage. For example, for the damage size identification problem, location of the damage is the unknown parameter. This unknown parameter is unknown at the time of damage identification but this unknown parameter is known at the time of constructing the model of the inverse problem and the time of deciding the parameter for the inverse problem model. Then in this research, improvement of diagnostic accuracy of the damage identification using inverse problem via the GLMM is conducted. The method is applied to the delamination identification via electric potential method of CFRP laminate. FEM analyses are conducted to obtain electric potential changes due to delamination crack creations with seven-electrode type specimens. By comparisons of the estimations without the random effect and with the effect, a better diagnostic tool is discussed in detail. As a result, GLMM improve the diagnostic accuracy and the generalization capability of size identification of the delamination crack.

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The present paper investigates Electrical Resistance Change Method (ERCM) for thick CFRP laminates with a dent. The authors have proposed the damage identification method for CFRP using the ERCM and confirmed its applicability for beams and thin plate-type specimens in the previous studies. However, the dent is made for thick CFRP and the dent causes electrical resistance decreases. In the present study, we focus on the dent and the electrical resistance decrease is adopted for monitoring delamination location. FEM analyses are used to obtain electrical resistance decrease distributions. Response surfaces are adopted to estimate the delamination location here. The results show good agreements with the experimental data.

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In the previous study, unsupervised detection of delamination cracks in CFRP plates using statistical analysis of temperature characteristic of resistance were developed to prevent electrical resistance changes caused by damages of electrical contact at electrodes. Delamination cracks change temperature characteristic of resistance of CFRP laminates. To detect delaminations without learning processes, electrical resistances of multiple segments of a CFRP laminate at high temperature are compared with those at low temperature and a statistical analysis method discriminates the change. Electrical resistance changes caused by damages of electrical contact at electrodes do not affect the temperature characteristic of resistance. This method has applicability to existing structures and can also detect initial defects. As a result of the previous study, delamination at least 5.3 mm in diameter subjected to a quasi-static load in a quasi-isotropic-plied CFRP plate was detectable without intact data. The diagnosis was not affected by damages of electrical contact at electrodes except for perforated lack of an electrode. The present study employs the unsupervised detection method of delamination cracks and damages of electrical contact at an electrode subjected to falling weight impact loads, and dents subjected to quasi-static loads.

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The current work investigates full-field monitoring of resin flow during a VaRTM using an area-sensor array. The squared area sensors are aligned as a matrix on a thin polyimide film without any un-sensing space; thus the film measures the full-field flow monitoring, and never misses a dry spot that may occur anywhere on the film. To identify the precise flow front and dry spots, the impregnated area is estimated by minimizing the residual sum of squares between the measured and estimated impregnated area ratios. To demonstrate the applicability of the proposed method, the area-sensor array is applied to monitoring a VaRTM resin flow on glass fiber reinforced plastic (GFRP) and foam-cored structures. As a result, the precise figurations of the flow front and the dry spot were successfully estimated in real time.

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Carbon Fiber Reinforced Polymer (CFRP) laminated structures are applied to many aerospace structures. Although the CFRP laminates have high specific strength and specific stiffness, delamination cracks are easily created and the delamination cracks are usually difficult to be detected by visual inspections. Recently, high toughness CFRP laminates are adopted to primary structures. The tough CFRP yields small fiber breakages when delamination crack is made in many cases. This requires a detection system of fiber breakages at low cost for large structures. In the present study, Time Domain Reflectometry (TDR) is adopted. TDR uses an electrical pulse wave and observes the reflected wavefrom. The method is applied to a 2m CFRP strip specimen and notches are detected from the reflected pulse waveform.

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A broadband ultrasonic wave propagation system had been already developed, in which a macro fiber composite (MFC) actuator and fiber Bragg grating (FBG) sensors were used because of their thinness and high fracture strain. A structural health monitoring technique using the broadband ultrasonic wave propagation system was proposed to detect debondings in carbon fiber reinforced plastic (CFRP) bonding structures. In the technique, the debondings were detected by using changes in modal dispersions of received Lamb waves propagated through the debonding. As the first step in this study, propagation tests using specimens, in which a 180^L×60^W×3.4^T mm CFRP plate was bonded to a 180^L×25^W×3.4^T mm CFRP plate to simulate a skin-stringer bonded structure, were carried out. In the tests, the changes in the modal dispersions corresponding to various propagation lengths, CFRP plate thicknesses, and debonding lengths, were circumstantially investigated. Thorough the tests, the feasibility of the structural health monitoring technique using the broadband ultrasonic wave propagation system for the debonding detection was demonstrated.

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The authors developed an ultrasonic wave propagation system using FBG sensors in the previous study. The purpose of this study is to extend the function of this system with an AWG filter as an FBG wavelength filter to detection of impact loads. First, tensile test was conducted to obtain the relation between the strain and the output from each port of the AWG filter. Then impact test was carried out, and inverse analysis was applied to the measured output ratio of multiple ports of the AWG using the fitted curves defined by the result of the tensile test. From the inverse analysis, the strain wave caused by the impact load was able to be obtained. Hence this system has an ability to detect impact behavior precisely through the inverse analysis

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The strain or temperature distribution can be measured by optical frequency domain reflectometry (OFDR) using fiber Bragg gratings (FBG) with high spatial resolution. In general, however, one needs to compensate temperature/strain effects during strain/temperature measurement because of the Bragg wavelength sensitivity to both of them. In this paper, we implemented simultaneous strain and temperature sensing with FBG inscribed into polarization-maintaining fiber. First we constructed a numerical model of OFDR using polarization-maintaining FBG for the necessity of analysis about polarization interference and polarized Bragg wavelengths behavior. After assessments of simultaneous measurement capability through numerical simulations, we implemented simultaneous strain and temperature sensing experiments with OFDR distributed sensing. The results showed the practical capability of simultaneous measurement with distributed sensing.

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Load identification is useful for structural health monitoring. Predecessors proposed one load identification method, and confirmed by simulation that this method is applicable to real structure. We need to confirm the applicability to real structure by experiment too. So , we focus on wind tunnel experiment, and tried to measure strain and deformation distribution on wind tunnel experiment. We measured strain by FBG (one of optical fiber strain sensors), and estimated deformation by using beam theory. And by experiment and simulation of simply supported beam subjected to bending loads, we confirmed that load can be identified by using strain and deformation information with almost the same accuracy and stability.

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This report shows the results of the feasibility study to examine the applicability of fiber Bragg gratings (FBG) sensors to structural health monitoring of solid rocket motor cases, especially which are made of CFRP. For the study, a trial apparatus for a few FBG sensors which monitors strains and acoustic emission (AE) signal was designed and manufactured. The verification of the apparatus was carried out by the pressure test of a subscale motor case which was made of CFRP. The apparatus was manufactured by combining with DWDM components and CDWM components for large strain change. In the test, signals of FBG sensors were compared with conventional electrical resistance strain gages and piezoelectric AE sensors. The strain measurement results of FBG sensors and strain gages showed good agreement.

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Ti-Nb shape memory alloys were fabricated in six compositions of Ti-(18-28)at%Nb by powder metallurgy (P/M) process. Microstructure, elastic modulus and shape recovery properties of the alloys were investigated. Ti-(18-20)at%Nb and Ti-(22-28)at%Nb alloys consisted of the α+β phase and the β phase at 300 K, respectively. This change in crystal structure possibly lowered the transformation temperature of the alloy with increasing Nb content of the alloy. The elastic modules of the P/M alloys were higher than that of the wrought alloys. This may be due to increase in oxygen content of the P/M alloys and difference in crystal structure between the wrought alloy and the P/M alloy. Annealing after cold-rolling resulted in recrystallization texture of β phase of the cold-rolled alloy, which improved the shape recovery properties of the alloy. Ti-22at%Nb alloy annealed at 1273 K for 0.18 ks had a recovery strain of 0.34 %.

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To obtain the two-way shape memory effect, a shot-peening treatment is applied to a shape memory alloy. The shot-peening region works as a bias spring. The experimental result shows that 0.2 % two-way strain can be obtained by this treatment. In addition, a simple model which can estimate the residual stress measure and the effective depth of the shot-peening is proposed.

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The mechanical property of a cast shape memory alloy (SMA) plate from self-propagating high temperature synthesis (SHS) ingot was investigated. DSC and Tensile test specimens were cast by lost-wax process from SHS ingot. The compositions of these ingots were Ti-50.0at%Ni and Ti-50.8at%Ni. The heat treatment conditions were 400℃-600℃ for DSC and tensile test. Transformation temperatures were measured by differential scanning calorimetry (DSC). Mechanical properties were measured by a tensile test at 17 degree Celsius. The effect of heat treatment conditions were investigated this study.

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Uniaxial tensile deformation properties of the TiNi shape memory alloy were investigated for the subloop loading under the stress-controlled condition. The results obtained are summarized as follows. (1) The stress-induced martensitic transformation on the surface of the material can be observed by using the microscope and the thermography. (2) In the subloop loading of the stress-controlled condition, the martensitic transformation progresses and strain increases in the initial stage of the unloading process since the temperature of the material decreases during unloading.

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In order to develop a brain spatula or a brain retractor made of a shape memory alloy (SMA), the bending fatigue characteristics of the brain spatula of TiNi SMA made by the precision casting were discussed. The results obtained can be summarized as follows. (1) At the room temperature, the fatigue life in pulsating-plane bending is longer than that in alternating-plane bending. (2) The fatigue life with heating and cooling is longer than that at room temperature under constant frequency when bending strain is larger than 2 %. (3) The above mentioned characteristics of the SMA-brain spatula obtained in this study can be substantially applied to the development not only for the brain spatula but also for other retractors and instruments used in other surgery operations.

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In this study, a semi-active vibration suppression system comprising piezoelectric elements is developed for flexible structures. The vibration suppression system comprises a cantilevered beam with bimorph piezoelectric ceramic tiles shunted by a RL electrical circuit with a switching part. This study shows that the resonant shunt circuit functions as a type of a dynamic damper for mechanical systems and the proposed switching control, inspired by a sliding-mode control law, is more effective than the passive damping system especially for the multi-mode vibration suppression.

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This paper proposes a simple identification system of generalized electromechanical coupling coefficient for passive vibration suppression system by piezoelectric element. In the proposed method the method of excitation and measuring of the resonant oscillations are realized by electric and electronic components Consequently, the proposed system can be realized in compact and simple configuration and the identification can be realized in simple procedure. Passive vibration suppression system is designed by the use of the parameter which is identified by the proposed method and experiment of the vibration suppression validates the proposed method.

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An electrical power generating device using piezoelectric element (PZT) has been developed to convert structural vibration energy into electrical energy. This paper describes the electrical generation characteristics of PZT and PZT including Nb under vibration load. Vibration tests are performed by using an experimental equipment composed of PZT, weights and a support frame structure. Sinusoidal wave excitation tests are carried out under the condition of the constant initial compressive load acting on PZT. Effects of the concentration of Nb, vibration frequency and vibration load on generated voltage and electric power are evaluated by the vibration test.

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This paper presents fabrication and characterization of a metal-core lead zirconate titanate fiber/aluminum composite. In order to embed the fragile fiber, the IF/B method was used. The effects of fabrication conditions such as hot-pressing condition on the composite microstructure were investigated, and the optimum condition to embed it in the matrix without fracture and chemical reaction was obtained. Then, the effect of the very high compressive thermal residual stress working on the piezofiber on the output voltage characteristic of the composite was investigated by an impact test. The result obtained in this study indicated that the output voltage linearly increases with increasing strain up to the level much higher than that of the fracture strain of the fiber itself. Sensing capability of the composite embedded with several fibers was also investigated by another impact test. The results showed that the embedded fibers have possibilities to be able to work as distributed sensors to identify impact positions, and so on.

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This paper presents characterization of output power of the metal-core piezoelectric ceramic (PZT) fiber/aluminum composite. As the piezofiber is very fragile, the interphase forming/bonding (IF/B) method proposed by Asanuma was used for embedding it in an aluminum matrix without its fracture. In this study, output power characterization of the piezo-composite specimen was done by an oscillation test, and it was found that 1) the output power generated from the specimen increases with increasing the square of its strain, and 2) the output power increases in proportion to its oscillation frequency.

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Polycrystalline Galfenol (Fe-Ga-Al-C system) alloys were fabricated as a bulk sample by ark-melting or as an ribbon samples by rapid-solidification melt-spinning method. Their metallurgical characterization, the magnetic characteristic and strength property after appropriate heat-treatments were studied. Based on this result, we will introduce an application as a torque sensor for steering-by-wire system of automobile because this Galfenol alloy with large magnetostriction also has high strength and workability for torque-ring around the steering shafts.

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This paper reports the piezoresistive behavior of a strain sensor made from a polymer/carbon nanotube nanocomposite experimentally and numerically. The sensor was experimentally fabricated from a polymer nanocomposite with multi-walled carbon nanotube (MWNT) fillers. The piezoresistivity of this sensor under tensile and compressive strains was measured. From the obtained experimental results, it is shown that the sensitivity of the sensor is inversely proportional to its nanotube loading. Furthermore, under a tensile strain, the sensitivity of the sensor is much higher than that of a conventional strain gage, whereas the sensitivity of the sensor under a compressive strain is only slightly higher than that of a conventional strain gage. This phenomenon is caused by the different patterns of conductive network change under tensile and compressive strains. On the other hand, from the numerical results, the CNT addition content dependency is coincident to the experimental measurement results qualitatively. Moreover, the sensitivity of nanocomposite strain sensors increases as the ratio of the tunneling resistance among nanofillers in the total sensor resistance increases.

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Micro-sensor that embedded in die was fabricated by using semiconductor processing technology. A sensing system for V-bending process was developed and its characteristics were evaluated. The influent factors on sensing accuracy were investigated. Sensitivity of micro sensor was very high, and the process parameters, such as stress distribution, bend angle, can be monitored from multi sensors allocated on one sensor chip in-process. However, it is found that the accuracy of sensor embedding and joining processes influence on the sensor properties significantly. A novel process in which the micro sensor was deposited on the die surface directly using 3D photolithography process was proposed as an alternate method.

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The usage of composite materials in the space and aircraft structure was enlarged for minimizing of the structure weight. As a full composite structure is difficult, there are some joint structures between composite parts and metallic parts, then, the monitoring of the joint structure was important to keep safety. Applying the fastener, embedded the optical fiber sensor, showed good results for detecting damages around the joint in the previous studies. The possibilities of the strength reduction, due to the hole for the embedded sensor, were failed, prior to the failure of the bolt. The finite element analysis showed that there was a stress concentration around the drilling hole, however, this concentration did not affect to the higher stress region around the contacted area. The strength reduction was concluded to negligible in this study.

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This paper presents a new viscous sensor using piezoelectric fiber matrices. The produced viscous sensor is the structure which embedded the piezo electric fiber containing a metal core in aluminum matrices. When aluminum covers a piezo electric fiber, the sensor part is mechanically protected from the outside. Moreover, the aluminum cover is used also as an electrode. Voltage is applied between an internal core and aluminum, a tip is vibrated, and viscosity is calculated from change of resonance frequency. By embedding into aluminum, it is possible to conquer the weakness of ceramics and to remove an electric noise. Therefore, measurement of the viscosity in inferior environment is also possible. The application to monitoring of the viscosity of the engine oil of an automobile is expected.

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The objective of this study is to characterize a piezoelectric composite and evaluate its suitability for viscosity-measuring applications. The composite is manufactured of a platinum-core lead zirconate titanate fiber inserted into an aluminum matrix. This study characterizes it by testing its impedance, capacitance, voltage sensitivity response to vibrational inputs, and deformation due to electrical input. Additional tests in air, water, and deionized water are carried out to evaluate its suitability for measuring viscosity using two probes: one as an actuator and another as a sensor. Results of the gain and phase between the probes indicate that the phase shift may be used as an indicator of viscosity changes. The first significant phase shift was measured as 2.45, 2.77, and 4.065 x 1O^7Hz, for water, air, and oil which is directly proportional to the kinematic viscosity of each fluid.

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Water distribution in the adhesively bonded joint was investigated using the electrode sensors. Suitable electrode patterns for the experiment were investigated. Electrode sensors were made using the patterns. Capacitance and impedance in the adhesively bonded joint interface were determined with the electrode sensors, and water distribution along the interface was determined.

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Recently, an electrically dismantlable adhesive has been introduced. This adhesive can be applied to separation systems. However, the fundamental properties of the adhesive, which is essential to design the separation systems, have not been studied yet. In this paper, the effect of electrical treatment conditions on the strength of the joints bonded with the adhesive is investigated experimentally.

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Adhesive joints have a lot of merits. For instance, it is easy to bond different types of materials and realize light weight structures. However, the bonded adherend has been difficult to be recycled. Currently, dismantlable adhesives that can be separated by a trigger have been developed. In this case, the adherends are recyclable. The adhesives include thermally expansive microcapsules (TEM). However, some properties of TEM are still unknown. In this research, the effect of the size and position of TEM in adhesives is studied using FEA.

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For the stabilization of insulation performance in resin-molded insulators, strong adhesion between the resin and ceramic is required. In this paper, a new technique for the control of the interfacial strength in resin-molded structures has been proposed. The adhesive strength of the internal interface in a resin-molded structure was estimated as the interfacial fracture energy by using the molecular dynamics method. The interfacial fracture energy was qualitatively in agreement with the adhesive strength index obtained by a shear experiment. Based on the simulation results, the control of the interfacial strength was performed, and it became clear from the result that the interfacial strength between resin and ceramic can be improved up to the strength level of the glaze adhesion.

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In this study, we present stress analysis for 3D bonded structures based on the mesh free method. Stress singularity occurs at vertex on interface in bonded structure when external load is applied to upper surface of the structure, and it might be induced delamination or crack. Therefore, it is necessary to employ appropriate computed stress value for design of bonded structure to increase reliability of bonded structure. In this study, the mesh free and the finite element methods are used for discretization techniques, and computed results are compared. As a computational model, Fe and Al boned structure is employed.

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A mismatch of different material properties in joints may cause stress singularities at the edge of the interface, which lead to the failure of the bonding part in structures. Therefore, it is important for the bonding strength of the joints to estimate three-dimensional stress sigularity at the vertex. In the present study, a boundary element method is used for evaluating the intensity of stress singularity. A model for analysis is three-layered joints consisting of Si, resin and FR-4.5. The singular stress field at the vertex under an external load is investigated.

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This research is about stress analysis of loosening process of bolted joint of CFRP Plate via contact analysis using FEM. Carbon fiber reinforced plastic (CFRP) has high specific tensile strength and stiffness, and are good for the structures of airplanes and space instruments. In recent years, CFRP becomes to use as the major structure of the large airplane like A380. Since the matrix of CFRP is epoxy resin in general, compressive strength of thickness direction is low and the fastening force of bolted joint of CFRP plate is low than that of metal plate joint. When the joint is vibrated by external force, side of the bolt hole is compressed by side of the bolt. Then in this research, influence the washer stiffness of the bolted composite joint and compression force of side of the bolt hole to the loosening process and the internal stress distribution of CFRP plate is investigated by the analysis of loosening process via FEM contact analysis.

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This study is about the effect of the fastening holes side contact to the looseness behavior of CFRP / metal flat plate fastener. In recent years, because of its high stillness and strength per weight, CFRP becomes applied to large-scale structure. To fastening the CFRP to the large-scale structure, mechanical fastening method like bolt nut joint is desired because of ease of the maintenance. Since compressive strength of the CFRP is low, to prevent the compressive damage, fastening force is set up to low value. However, it is easy to break at around the bolt holes because of the fastening holes side contact. In addition, it is thinkable to accelerate looseness. Therefore, in order to show the effect of the fastening holes side contact CFRP / metal plate fastener with contact analysis was conducted.

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Mechanical behavior of a bolted joint subjected to a rotational loading and a combined loading of a rotational and a transverse load is investigated. It is confirmed that the joint behavior obtained using the proposed analytical model reproduces that obtained by FEM analysis. As to the rotational loading case, the thread surface undergoes complete slip and bolt rotates in the loosening direction in the loosening process while the bearing surface undergoes complete slip and bolt does not rotate in the tightening process. As to the combined loading case in which the joint is subjected to rotation angle of 0.12 degree and transverse displacement of 0.04 mm, the progress of loosening decreases because the bolt rotates in the tightening direction in the tightening process.

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Loosening of setscrew joints is the possible problem under the dynamical environment. Therefore, choosing the setscrew which is hard to loose is very important. In this report, loosening of several type of setscrew under axial cyclic loading was examined by the experiments. As a result, the reason of setscrew loosening under axial cyclic loading is due to decrease in axial force which is caused by the plastic deformation of contact surface. In addition, it is confirmed that the setscrew which tip is flat, is effective to prevent loosening under axial cyclic loading.

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The impulsive riveting method can join the sheets without drilling as well as disjoin easily the jointed sheets. The joints made by the method have high joint strength and the deformation of the joints is also small. However, the equipment for the impulsive riveting is large in order to utilize the impulsive energy. Therefore, miniaturization and simplification of the equipment are necessary for the practical application. In this study, the self-punching riveting method is applied to the joining of cold-reduced carbon steel sheets. The proposed method uses a press machine. The sheets are joined by compressing the rivet at the quasi-static speed without drilling of the sheets. The deformation and the strength of the joints made by the method are examined in comparison with those of the joints made by caulking and the impulsive riveting method.

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In this paper, the application of mechanical clinching to a built-up aluminum beam is studied. At first, tensile-shear tests and fatigue tests are carried out on clinched joints of 6063-T5 aluminum alloy sheet to investigate the tensile-shear strength and fatigue strength. Then, based on the joint strength results of clinched joint, the joint pitch of the built-up beam is designed. Lastly, static bending test and cyclic bending test are carried out on the built-up beam to investigate the deformation behavior and the flexural rigidity. The built-up beam is proved to have the same flexural rigidity as that of one type beam. Cyclic bending test results show that cyclic loading gives no influence to clinched joints and the flexural rigidity of the built-up beam. All results demonstrate that mechanical clinching is an effective connection method in a built-up beam.

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Press-fit joint was combined to spline joint to prevent fretting fatigue failure of the spline teeth. This study focused on the effect of press-fit allowance on torsional fretting fatigue strength of the combined jointed shaft. The fretting fatigue strength was drastically increased. While fretting fatigue failure occurred at the press-fitted part when the press-fit allowance was relatively small, the combined jointed shaft had four times higher fretting fatigue strength than conventional splined shaft. Increase of the allowance in which amount of relative slip in fretting was significantly reduced prevented fretting fatigue failure and brought further increase of fatigue strength.

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A practical residual decision approach which provides significant effectiveness in computational time and the stability of wear solution was proposed for analyzing the wear process with fretting fatigue cycles. The range of the incremental wear step and smoothing of total wear curve were determined by the residual decision approach. The RMS error between the computed wear curve and smoothed one obtained by law frequent filtering techniques was calculated in this approach. The changes of contact surface configuration, contact pressure and tangential surface stress with fretting fatigue cycles were discussed as a demonstrational example under the partial slip and fretting fatigue limit condition.

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The solder joint between 61.9Sn-38.1Pb lead solder and Sn-3.5Ag-0.75Cu lead-free solder were studied.The study focuses on the relation between the solder joint with loading rate,bonding thickness and bonding surface. In this study, the tensile test at room temperature were carried out for lead-solder and lead-free solder ,in order to investigate the mechanical properties of both solder. Based on the experiment result, the bonding increase with the loading rate but decrease with the bonding thickness.For the bonding surface experiment,the result shows that the effect of the bonding surface towards the solder joint are small.Comparisons in term of mechanical properties for lead-free solder and eutectic solder alloy also has been discussed.

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The mechanical properties of friction stir welded 7075-T6 and 7075-O aluminum alloy joints at room temperature were investigated. In comparison with the base metal, the stir zone of the T6 joints had smaller Vickers hardness but that of the O joints had greater hardness. The application of natural aging for 5 months caused the hardness in the stir zones of both joints to be greater than that of as-welded joints. On the other hand, the tensile properties of the naturally aged joints were generally lower to those of the base metals. The results were suggested that the existence of the welding defects in the joints to affect the tensile properties.

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Friction surfacing is an effective way to fabricate thick coating with high strength, wear resistance and corrosion resistance. A rotating consumable rod is pressed down on a substrate, and generates frictional heat at the interface with the substrate. This heat plasticize the rod, and form the plasticized layer. To elucidate mechanism of the coating, temperature distribution of the rod, material flow and adhesion strengh were investigated for SUS304 coating of friction surfacing. The maximum temperature of 1570 K was obtained above rotational plane inside of the rod. From the material flow observation, The coating had layered structure and changed with heat input during process. The adhesion strength of the coating decreased with cross feeding speed (Vx).

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Dissimilar materials spot welding between PET (Polyethylene Terephthalate) and metals has been carried out by using pulse YAG laser. Metals used were A5052, commercially pure Cu and SUS304. PET/SUS304 joint was obtained with relatively lower heat input compared to other joints. Shear tensile test was carried out to evaluate strength of the joints. Size of welded area and failure load of the joints increase with increasing in heat input in case of PET/A5052 and PET/Cu joint. However, in case of PET/SUS304 joint, failure load was not only depending on heat input. Apparent strength was almost constant for PET/Cu joint regardless heat input. In contrast, the strength increases with increasing of heat input for PET/A5052 and PET/SUS304 joint. According to cross sectional observation, baubles were formed near the interface in all joints. Molten pool was formed in PET/A5052 and PET/SUS304 joint, but not in PET/Cu joint. Molten pool shape and formation of baubles might be affect on the strength of the joint.

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An acoustic resonance technique for measuring the coating thickness on a steel plate is reported. The acoustic resonance phenomenon at the back-side of the plate structure, i.e., the steel/coating/air interface, is able to be observed at which the quarter wavelength of the transmitted wave corresponds to the thickness of the back-side coating. The thickness of the back-side coating is determined from the measured resonant frequency and the results are compared with the results of direct observation by a microscope.

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In this study, we evaluated the evolution of the ultrasonic attenuation and velocity in a carbon steel, subjected to zero-to-tension cyclic loading, by monitoring of ultrasonic characteristics, using EMAR (Electromagnetic Acoustic Resonance), which is a contactless resonant method with the use of an EMAT and is free from extra energy losses, resulting in the measurement of intrinsic attenuation in solids. We launched polarized shear wave in the thickness direction of the plate sample to obtain the ultrasonic velocity from the resonant frequency and the attenuation coefficient from the ring-down curve at resonance. Ultrasonic attenuation was more sensitivity than velocity and showed a peak at 10% of the total life. This phenomenon is not depend on amplitude of stress range EMAR method has possibility of predicting the remaining life of a metal and metal fatigue breakdown.

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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 both the durability test of junction of sensors with pipes and the field test of this system.

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