To develop non-destructive evaluation methods for oxidation damage on graphite components in High Temperature Gas-cooled Reactors (HTGRs), the applicability of ultrasonic wave and micro-indentation methods were investigated. Fine-grained isotropic graphites of IG-110 and IG-430, candidates for Very High Temperature reactor (VHTR), were used. Uniform oxidation condition of these graphites was given by air at 500^0C. The followings were obtained from this study. (1) Ultrasonic wave velocities with 1 MHz in the graphite samples were decreased with increasing the oxidation. For the IG-110 and IG-430, it can be expressed empirically by exponential formulas to burn-off, oxidation weight loss. (2) A wave propagation analysis with a wave-pore interaction model showed slightly less velocity reduction than experimental data of the oxidized IG-110. It implies uniform oxidation assumption in the analysis would not be precisely applicable. The possibility of the effect of the non-uniform oxidation such as un-unique pore growth and grain boundary oxidation was suggested. (3) Micro-indentation characteristics with the maximum indentation load of 10, 25 and 50 N on the graphite samples were changed to show oxidation-induced degradation. It is necessary to assess the variation of the test data with statistic method to specify the oxidation damage in the next study.

抄録全体を表示

For damage detection in CFRP laminates, health monitoring techniques using ultrasonic waves are effective. Currently, bulk piezo-ceramic elements are used for sending and receiving the ultrasonic waves. Hence the waves are generally narrowband. In this research, the authors developed a new damage detection system that can employ broadband ultrasonic waves in order to obtain more information in received waves. A macro fiber composite (MFC) actuator developed at NASA generates ultrasonic waves and a fiber Bragg grating (FBG) sensor receives the propagated wave. These elements do not have resonance frequency. Through the experiment for an aluminum plate and a CFRP laminate, it was confirmed that this system has the ability to propagate broadband waves.

抄録全体を表示

Ultrasonic flaw sizing is important issue for insuring structural reliabilities. Time-of-Flight Diffraction (TOFD) method is recognized as one of the most accurate flaw sizing method. However, the method is not applicable to high attenuation thick materials due to the low SN ratio of lateral wave and flaw tip diffraction wave. In order to overcome this problem, the pulse compression technique is often used for enhancing SN ratio of flaw tip diffraction wave and lateral wave. Although this method is effective to improve SN ratio, sometimes the time resolution of received signal becomes slightly lower than ordinary method. In this study, the new pulse compression technique utilizing wavelet transform was developed for enhancing time resolution of received signal. The pulse width and crack sizing accuracy were compared to the ordinary methods experimentally. As a result, the time resolution could be enhanced by wavelet modulation pulse compression technique compared ordinary pulse compression technique. Moreover, the sizing accuracy was enough for practical using.

抄録全体を表示

A contact-type line-focus ultrasonic probe that transmits SH wave is newly developed. The probe is composed of a quarter- or half-cylindrical wedge and a piezoelectric transducer attached to the cylindrical surface of the wedge. Cylindrical SH wave is excited from the transducer to the wedge and focuses on a line at the bottom surface of the wedge. Hence SH wave is incident upon the testing object at all angles from zero to 90 degrees simultaneously. The directivity of the probe is examined by a conventional method using a half-cylindrical testing block and compared with that of the longitudinal wave probe developed previously.

抄録全体を表示

Residual stresses caused by welding in T type butt-joint of a steel rolled-plate were nondestructively determined by an acoustoelastic method, proposed by the author. In an analysis ithe stress field is assumed to be plane-state and stress components are three. In the acoustoelastic method, two-velocities of shear waves propagatingu to the thickness direction of the weld plate and directions of their particle motions were experimentally measured by an ultrasonic technique.. Ultrasonic measurements were done on a position parallel to the weld line. The values of residual stresses determined from the data were reasonable.

抄録全体を表示

In the heating method it become problem that kowledge of temperature distribution and temperature dependent Young's modulus are necessary. In this paper a method to overcome of the problem is concerned with for the identification of welding resiudal stress in butt welded pipe. The method uses nonlinear least square method by Levenberg-Marquardt. The validity of the approach is demonstrated by numerical results and these shows usefullness of the proposed method.

抄録全体を表示

Non-destructive evaluation tests of defects for SS400 were performed by magnetic flux leakage technique using a fluxgate sensor. Changes in magnetic flux leakage due to the defects could be measured at 5 mm lift off height for the defect of 0.3mm width, and could be measured even at 7 mm lift off height for the defect of 3.0mm width. The sizes of defects were consistent with the peak to peak value of magnetic flux leakage ΔBz. In-situ magnetic flux measurements for permalloy under stress loading were also performed, and the magnetic flux measured by the fluxgate sensor increased with increasing stress.

抄録全体を表示

Eddy current method was applied to evaluate the mechanical properties of thin wall ductile cast iron. Thin wall ductile cast iron specimens with the thickness of 4mm and 6mm were prepared. Eddy current signal and Rockwell hardness were measured at the same position of the specimen. Correlation of the signal intensity and hardness of the thin wall specimen was compared with that of thick Y-Block. Hardness of the thin wall specimen was higher than that of Y-block specimen for the same eddy current signal intensity. Change in the eddy current signal with hardness of the thin wall specimen was smaller than that of the Y-block specimen. Tensile strength of the thin wall cast iron specimen can be estimated with the correlation of hardness and tensile strength for thick cast iron. Correlation of eddy current and hardness is needed to be clarified to eavluate mechanical properties of thin wall ductile cast iron by the eddy current method.

抄録全体を表示

Carbon fiber reinforced plastic (CFRP) laminates are now widely used in various fields. They are, however, very sensitive to an impact which causes delaminations in the laminate. Since delamination reduces the mechanical property of the laminate, nondestructive inspection is required to maintain the structural reliability of the CFRP structure. Eddy current method (ECT) has been studied to be applied to CFRP laminate. Strong electric anisotropy, however, makes application of the method difficult. Since delamination is in-plane damage in the laminate, conventional ECT has a problem for making current-loop which should be impeded by the damage to be detected. In the present paper, a new probe for electrically anisotropic CFRP laminate is introduced to resolve the problems. The probe is made of two coils put side-by-side to induce strong uniform electric current. Delamination was made in the CFRP laminate by means of the indentation test; the applicability of the ECT with new probe is examined experimentally.

抄録全体を表示

This paper investigates the identification of the location of delamination of CFRP laminates by using the response surface method. New technique is proposed that can reduce the required experimental cost by performing the analyses instead of experiments. The new delamination FEM model is proposed based on the detailed observation of actual delamination to perform FEM analysis that approximate the experimental result. As a result, the response surface is unstable for the experimental error when only FEM results are used to make the response surface. Newly proposed Robust Response Surface whose explanatory variables include the artificial noise can successfully improve the unstability and its applicability was confirmed by performing the identification of delamination location of CFRP laminate.

抄録全体を表示

Fiber waviness of composite structures decreases those compressive strength. Since existing NDT methods such as ultrasonic inspection do not detect the fiber waviness, a new method of detecting fiber waviness is required. In the present study, fiber waviness is monitored by measuring electrical resistance change during curing. Experimental investigation is conducted using cross-ply (90/0) composite laminate half cylinder. The generation of the waviness causes increase of the electric resistance due to the high deformation of carbon fibers. The feasibility of detecting fiber waviness is experimentally confirmed here.

抄録全体を表示

The PRPC (Porosity Reducing Post Compression) process, in which the product under the remaining heat of the die casting is compressed, has been investigated to enhance die-casting product reliability. In this study, the validity of PRPC was examined, mainly focused on the pore closure and bonding of the closed surfaces. The porosity inside die casting was observed non-destructively by using X-ray CT.

抄録全体を表示

Measurement of strain of tires in-service is effective to improve reliability of tires and ABS system. In previous studies, we developed a patch type strain sensor for automobile tires. The present study introduces the utilization model of strain data for an optimized braking control and road condition warning system. The relationship between strain changes on the inner surface of pneumatic tires, simulating sensor output, and mechanical tire parameters, such as contact patch length, effective radius, slip ratio, and friction coeffecient is examined. Calculations are carried out using finite element analysis with a simulation of the strain sensor signal when a tire rotates.

抄録全体を表示

In the present study, a measurement system for foot pressure distribution in walking are developed. This problem has some difficulties owing to the change of the boundary conditions in the contact area if sensors are directly put on the surface. In order to overcome the difficulties, this present system, the strain informations are measured apart from the contact area, and inverse analysis is applied to obtain pressure distribution acting on the surface of the structure. On the process of the inverse analysis, some regularization technique, Tikhonov method and truncating singular value decomposition (TSVD), are employed to avoid the instability of the numerical solutions. Pressure distribution measurement examination when walking acting on the load cell is performed to confirm the validity of the present method

抄録全体を表示

An easy and accurate displacement measurement method for structural health monitoring is proposed. The displacement distribution can be obtained from one image by capturing the attached reference grid and analyzing the phase information of moire pattern. In this paper, the basic principle and accuracy of in-plane displacement are described.

抄録全体を表示

Evaluation of fatigue strength under cyclic loading is one of the most basic issues for the design of engineering products. Fatigue limit of materials is usually evaluated by the fatigue test using some standard test piece. In addition, evaluation of fatigue limit of real parts of products is demanded nowadays in order to ensure the safety of engineering products from more practical viewpoint. However, fatigue limit evaluation of such real parts by usual testing methods costs too much to conduct in practice. To reduce the cost for fatigue limit evaluation, a newly developed technique utilizing the temperature rise due to energy dissipation under cyclic loading is paid attention recently. In this paper, this technique is applied to fatigue limit evaluation of a real product part made of stainless steel in order to verify its applicability. As a result, it is verified that the fatigue limit predicted by this technique coincides very well with that determined by usual fatigue testing method.

抄録全体を表示

There are two reasons why IR-thermography, as a nondestructive inspection method, can't work well for non-painted metal; It is difficult to measure a temperature of a low emissivity surface by IR-thermography device. In addition, radiant energy is hardly absorbed in such a surface. For solving these two problems, the surface of the target should have been painted with black ink which has high emissivity. But this method is hard to apply during operation. In this report, we proposed a new active-thermography method with a thin stainless film. The film is painted with black ink for giving higher emissivity and it can heat the specimen surface uniformly by Joule energy. On the other hand, because the film is very thin, the target temperature appears on the surface of the stainless film, which can be observed by IR-thermography. The flaw size and depth can be identified from two data, temperature difference and phase difference between the flaw and normal area. It was confirmed that FEM simulation results are similar to experimental results for flat-bottomed holes.

抄録全体を表示

This paper describes development of high speed data fusion system for infrared image and visible images. The method consists of two phases: (1) distortion adjustment of the infrared image on the basis of optical system for fitting the shapes of an object in the two images, (2) parallax error adjustment for fitting the positions and the sizes in two images. Using this method, data fusion of high speed infrared images were successfully conducted.

抄録全体を表示

The infrared thermography is a useful tool for the inspection of subsurface defects and damages, such as voids or delaminations, in concrete structures. As one of the NDT techniques by infrared thermography, passive thermographic NDT has been applied to the remote inspection of building wall and concrete structures. However, it is difficult to detect defects, when temperature difference between defect area and sound area is smaller than temperature resolution of thermal sensor. In this research, the self reference lock-in thermographic method is applied as the effective technique for signal to noise ratio improvement. Natural weather change from shine to cloud and sunset affects to temperature change on the objective surface. The wave forms of these temperature changes are measured by infrared thermography and processed by the lock-in analysis scheme. It is found from the experimental studies that the resolution of defect inspection was improved by the present the self-reference lock-in technique.

抄録全体を表示

Self-reference lock-in thermography was developed by the present authors. This technique enabled us to conduct lock-in temperature measurement without external reference signal. The reference signal for lock-in data processing is constructed from the same sequential temperature data. Temperature change in a region of interest was correlated with that in a region of reference signal construction. In this study, the feasibility of the proposed technique for active heating thermographic NDT was demonstrated for flat bottom hole material loss defects in steel plate.

抄録全体を表示

According to "Codes for Nuclear Power Generation Facilities -Rules on Fitness-for-Service for Nuclear Power Plants- version 2004", fully penetrated flaw should be assumed for uninspected region, when SCC is found and flaw evaluation is performed on cylindrical core internals such as core shroud. This postulation is considered to be too conservative, however, especially when the uninspected region is relatively wide. This study was performed on the better assumption of flaw existence in the uninspected region to develop a more appropriate flaw modeling. Based on comparison among some possible methods, a promising postulating method is proposed from the engineering viewpoints, also considering the inclination of flaw distribution seen in the field data.

抄録全体を表示

The SI-F method allows diagnosis of structure from data that will be acquired after set up. Presented method detects structural failure from statistical method that judges the equivalence of two data groups. One of these is called standard data group that will be acquired when structure is normal. Another is called diagnosis data group that will be acquired when structure is operated. However, there are many conditions in actual structure. Therefore, it is difficult to determine the only standard data group for long-term diagnosis. Therefore, it is necessary to prepare two or more standard data groups and to choose suitable group for the present condition. Therefore, a huge standard data groups cause a real-time decrease in the diagnosis. Optimal diagnosis needs optimization of the number of standard data groups. This report shows that the method of optimization of the number of standard data groups.

抄録全体を表示

Hydrogen embrittlement has been analyzed by using thermal desorption spectrometry (TDS). However, it is difficult to separate the states of trapped hydrogen at various lattice defects such as dislocation and vacancy. It is reported that peaks of hydrogen desorption are dependence on thickness of specimen, heating rate, binding energy and defect density. Thus, the objective of the present study is the separation of the hydrogen states in pure iron emphasized dislocation and vacancy using controlling thickness of specimen and heating rate.

抄録全体を表示

The main role of hydrogen in hydrogen embrittlement has been investigated for fcc and bcc metals. Both fcc and bcc metals show that hydrogen contents of the strained metals with hydrogen are more than those of strained metals without hydrogen. It suggested when including hydrogen promote the formation of the trapping site. In SSRT test, when stress was relieved before the fracture strain, held at 30℃ and reloaded. In this case, fracture strain was not recovered. While held at 200℃, fracture strain was completely recovered. These showed that the vacancy cluster contributed to the ductility reduction.

抄録全体を表示

Hydrogen embrittlemen mechanism is still remained issue to be clarified. Due to the recent studies, the interaction between dislocations and hydrogen is considered to plays an important role in hydrogen embrittlement. Therefore local hydrogen distribution or concentration around defects (e.g. dislocation) should be clarified. However the experimental investigations of the local hydrogen distribution have many difficulties due to the hydrogen character. In this study, the hydrogen diffusion behavior around an edge dislocation in pure iron is investigated based on molecular statics and molecular dynamics simulations. For an edge dislocation on the (112) slip plane, the potential energy distribution does not agree with the elastic theory near the dislocation core. Moreover, it is confirmed that the dislocation traps the hydrogen at the dislocation core and the exact slip plane by MD analysis. Therefore, on contrast with the elastic theory, the possibility of high hydrogen concentration along the slip plane near the dislocation core is proposed.

抄録全体を表示

Stainless steel has been expected for infrastructural materials for hydrogen energy society. However, metastable austenitic stainless steel is reported to deteriorate in high-pressure hydrogen. In the present study, to determine the cathodic charging condition of SUS 304, hydrogen absorption properties charged by high-pressure hydrogen and cathodic charging have been investigated. In addition, to clarify the mechanism for hydrogen degradation of SUS 304, the main factor affecting hydrogen degradation and recovery have been identified from the standpoint of hydrogen, vacancy, dislocation, and stress induced martensite.

抄録全体を表示

Though various experiments of hydrogen in metal have been studied, there is very little understanding of hydrogen trapping states and degradation in aluminum. This is because the hydrogen dissolution enthalpy of aluminum is very high. In the present study, pure aluminum (99%) was charged with hydrogen by electrochemical method in various conditions. Large hydrogen concentrations were introduced in invariant condition. There were two peaks at 120℃ and 400℃ in hydrogen evolution profile. For the first peak (120℃), hydrogen is solute in lattice or trapped at vacancies or dislocations. For the second peak (400℃), hydrogen is precipitated as hydrogen molecule in blisters in aluminum. Hydrogen trapping states at first peak affects decrease in ductility. In contrast, the second peak does not affect the degradation. The failure strain of aluminum charged hydrogen decreases with strain rates.

抄録全体を表示

The influence of hydrogen on fatigue crack tip plasticity of an austenitic stainless steel, SUS304, was investigated after exposing it to high-pressure hydrogen gas environment. The fatigue crack growth rate in the hydrogen-charged specimen was accelerated and hydrogen decreased the crack tortuosity and the crack opening displacement. Slip bands were lower and more discrete in the hydrogen-charged specimen than in the uncharged specimen. The hydrogen-charged specimen had less asperity along the crack on its surface compared with the uncharged specimen. These results suggest that hydrogen caused slip localization at crack tip and accordingly the acceleration in crack growth rate.

抄録全体を表示

Fatigue crack growth tests were conducted on hydrogen charged and uncharged specimens of a 0.08 mass%C low carbon steel sheet at test frequency 0.001 -10Hz. After fatigue crack growth tests, a stretch zone was formed in order to investigate the mechanisms of fatigue crack growth in the hydrogen environment. From the observation of striation and stretch zone on the fracture surface and slip bands on the specimen surface, it was revealed that uncharged specimens have no dependency of crack growth rate on test frequency and on the other hand, the crack growth rate of hydrogen charged specimens at the lower test frequency is approximately 10 times faster than that of uncharged specimens. There exists an upper limit of the increase in crack growth rate of the hydrogen charged specimens at test frequency below 0.01 Hz. The upper limit is almost equal to the maximum of stretch zone width which is inclined. The experimental results show that the fatigue crack growth of hydrogen charged specimen is related to the hydrogen enhanced localized plasticity.

抄録全体を表示

There are great expectations to hydrogen as a next generation energy or a medium of energy. However, it is well known that hydrogen weakens the strengths of metals. Despite the extensive investigations concerning hydrogen related fractures, the mechanisms have not been enough clarified yet. The difficulties to reveal the essential effects of hydrogen are mainly attributed to the characteristics of hydrogen such as ppm-order extremely low concentration, high diffusivity and high sensitivity to the defect-densities in metals. In this study, we applied molecular dynamics (MD) simulations to Mode I crack growth in α-iron single crystals with and without hydrogen, and analyzed the hydrogen effects from the atomistic viewpoints. We propose the mechanism of hydrogen related slip plane fracture based on the interaction between hydrogen atoms and dislocations around the crack tip.

抄録全体を表示

Fatigue tests have been conducted to investigate the influence of irreversible hydrogen and low temperature annealing on the fatigue strength for a cold drawn eutectoid steel specimen. For both as-received and annealed samples, crack initiated at internal inclusion. In the case of as-received samples, irreversible hydrogen had no influence on the fatigue strength. However, for the annealed samples, irreversible hydrogen caused a decrease in fatigue strength. These results indicate that a decrease in fatigue strength by absorbing irreversible hydrogen appears remarkably by low temperature annealing.

抄録全体を表示

High-strength steel has been required from the viewpoint of reduction in cost and environmental deterioration in recent years. However the probability of delayed fracture caused by hydrogen increases with steel strength. As universal mechanism of hydrogen embrittlement, hydrogen enhances the dislocation mobility and local plasticity and so stabilizes and increases vacancies. From these behaviors of hydrogen, high-strength steel with high resistance to delayed fracture was developed to suppression dislocation mobility and vacancy formation. Pre-strain and ageing method enable to improve the delayed fracture property of high-strength steel. The property of the delayed fracture was evaluated and the mechanism was examined.

抄録全体を表示

We investigated the effect of hydrogen and prestrain on the tensile properties of a low carbon steel plate JIS-SGP (0.078C-0.012Si-0.35Mn). The steel gas pipeline material JIS-SGP, which is one of candidates for hydrogen gas pipelines, is produced from the low carbon steel plate by plastic working and welding. The hydrogen content increased by hydrogen charge after prestraining. The reduction of area was not affected by prestraining in the uncharged specimens, but it was affected by prestraining in the hydrogen charged specimen. The reduction of area decreased linearly with increasing hydrogen content in the hydrogen charged specimens. The void growth in the specimen has a good correlation with the reduction of area. The voids were elongated along the tensile axis in the uncharged specimens. On the other hand, the voids were elongated in the direction perpendicular to the tensile axis in the hydrogen charged specimens. The mechanism of development of dimples and voids in the hydrogen charged specimens should be noted to understand the basic mechanism of hydrogen embrittlement.

抄録全体を表示

Tensile and fatigue properties of stainless steels exposed to highly pressurized hydrogen gaseous environment are investigated using small specimen. The hydrogen content distribution in the small specimen is nearly uniform, because the thickness of the specimen is very small (0.3mm). Metastable austenitic stainless steel SUS304 and SUS304L show the degradation of tensile ductility and the fatigue life by exposure to hydrogen gas environment. Even stable austenitic stainless steel SUS316L shows the little degradation of the tensile ductility in the high hydrogen content range, but doesn't show the degradation of the fatigue life.

抄録全体を表示

The effect of hydrogen on high-cycle fatigue property of shielded metal arc welded joints for gas piping was investigated. The thermal desorption spectroscopy (TDS) and the thermal desorption analysis (TDA) showed that a large amount of hydrogen was desorbed from weld metal, while hydrogen was not desorbed from HAZ and base metal. The hydrogen desorbed from weld metal is latent in the welded joint, because the welded joint is not hydrogen-charged. The hydrogen is considered to be nondiffusible, because it takes more than five months from welding. The growth of fatigue crack initiated from the small hole on the first layer of weld metal was faster at 0.2 Hz than at 2 and 20 Hz. The nondiffusible hydrogen in weld metal increased fatigue crack growth rate at the lower frequency of 0.2 Hz.

抄録全体を表示

The effect of hydrogen on fatigue crack growth behavior was investigated in SUS630 with hydrogen-charged specimens at different test frequencies. The fatigue crack growth rate was increased by hydrogen-charge. The fatigue crack growth rate of the hydrogen-charged specimen increased with decreasing test frequency from 20 Hz to 0.2 Hz. The fatigue crack path became thinner by hydrogen-charge. It was presumed to be caused by localization of slip at the crack tip by hydrogen. These factors cause the acceleration in fatigue crack growth rates in the hydrogen-charged specimens. Fatigue fracture surface observation shows that, in the hydrogen-charged specimens, there were a lot of circular-shaped patterns which were presumed to be formed by synergistic effect of cyclic loading and hydrogen concentration ahead of the main crack with a strong hydrostatic tension at the higher ΔK region. The coalescence of the main crack with advanced small cracks also causes the acceleration of fatigue crack growth rates in the hydrogen-charged specimens at the higher ΔK region.

抄録全体を表示

Fatigue tests were conducted on bearing steel, JIS-SUJ2 (SAE 52100) under cyclic torsion with compressive mean stress to simulate the stress condition of rolling bearing. Mode II fatigue cracks initiated and propagated along the axial direction of specimen in hydrogen-charged and uncharged specimens. Fatigue life was shorter by factor of 1/3-1/10 in hydrogen-charged specimens than that of uncharged specimens. More cracks were observed at the final stage in hydrogen-charged specimens (N/N_f=0.97) than in uncharged specimens (N/N_f=0.96). It is presumed that the slip deformation on the surface of the specimen was restricted and localized by hydrogen.

抄録全体を表示

The effects of interface roughness and thickness of TBC on the interfacial mechanical properties of EB-PVD TBC were examined in BC as-sprayed and polished with 200 μm and 500 μm TBC thickness systems using a barb test method. The residual compressive stress in TBC layer was measured, by using the Raman spectroscopy. The interface toughness related to the interface roughness and the thickness of TBC. The interface toughness was larger for BC as-sprayed TBC system than for BC polished TBC one. The delamination of TBC propagated within TBC layer adjacent to the interface for BC as-sprayed TBC, for BC polished TBC at the interface between the TGO and the BC. Moreover, the interface toughness was larger in 500 μm thickness TBC than in 200 μm thickness TBC. The relation of interface toughness to interface roughness and thickness of TBC was associated with the interface residual compressive stress and the interface sliding friction during the delamination of TBC.

抄録全体を表示

It has become popular to increase thermal efficiency by applying Thermal Barrier Coatings (TBC) to hot gas path parts in gas turbines. On the other hand, some uncertainty about the delamination life prediction method for TBC still remains. In this report, the influences of mechanical parameters on delamination behavior were investigated through thermo-mechanical fatigue tests, to improve the delamination life prediction method for TBC. The selected parameters were loading pattern, ceramic coating thickness, and high temperature pre exposure. Delamination behavior with an Out of Phase loading pattern seemed to better correspond to behavior under simulated loading than did that with In Phase loading. The results strongly suggest that an optimum ceramic coating thickness keeps the cooling performance consistent with delamination strength. However, high temperature pre-exposure seemed not to affect the delamination initiation life; pre-exposure appeared to decrease delamination growth resistance properties.

抄録全体を表示

Multiple crack simulations were conducted on the delamination process of thermal barrier coating applied to gas turbine blades using the polycrystal FEM model of thermal cycle test pieces. The simulation results of multiple cracks during the thermal cycle showed quite similar morphology to the observation on test pieces by modifying the Young's modulus of topcoat layer according to the fraction of pore. Moreover, statistical distribution of crack length also showed similar trend with the measured result.Therefore this polycrystal model could be an effective tool for the analysis of crack morphology and distribution in the delamination process of TBC.

抄録全体を表示

The correlation between the mechanical properties and the splat microstructure of an APSed TBC was studied by using the simple sintering model and the numerical simulation, i.e., the distinct element method. It was cleared from results of the numerical simulation that the mechanical properties of an APSed TBC were controlled with the change of the splat structure by the initial stage of the sintering. The change of mechanical properties in the APSed TBCs by the thermal exposure is predictable by using the proposed method in this work.

抄録全体を表示