Several P/M (Powder Metallurgy) high-speed steels with different sizes of carbide particles, which is one of the predominant factors influencing wear properties, strength etc., were prepared. In the plain fatigue tests, the plain fatigue strength of the specimen with large carbide particles was lower than that with small carbide particles. This result is obtained because fatigue cracks are initiated at carbide particles. In fretting fatigue tests, the fretting fatigue strength decreased with increasing carbide particle size. This is mainly because the frictional coefficient of the materials decreased with decreasing carbide particle size. According to the results of the fatigue crack growth tests, the carbide particle has no significant influence on the fatigue crack growth rate. The predicted lives based on the fracture mechandcs model of fretting fatigue were in good agreement with the experimental results.

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Fretting fatigue tests were carried out using HIP-sintered silicon nitride to study the effect of relative slip amplitude between the specimen and the contact piece on fretting fatigue behavior. Fretting fatigue strength decreased with increasing relative slip amplitude. Application of static contact without fretting motion had no influence on static fatigue strength. Therefore, fretting action with relative slip will be essential to the degradation of fatigue strength. Fretting fatigue life prediction based on the fracture mechanics analysis was also carried out, where the frictional force between the specimen and the contact piece was taken into consideration. The predicted fretting fatigue lives agreed well with the experimental results.

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Crack propagation tests were carried out in various environments from water to vacuum using CT specimens. The main results obtained are as follows. (1) In vacuum, cyclic load accelerated crack propagation rate faster as compared with that under static load. Cyclic fatigue can occur without the presence of vapor. This behavior is substantial cyclic fatigue in this material. (2) Degree of the acceleration in creased as partial pressure of water vapor rose. (3) These results are explained successfully by the mechanism in which the origin of cyclic effect is the decrease in the stress shielding effect by cyclic load. In this respect, the only necessary condition for cyclic fatigue is not stress corrosion cracking due to water vapor but load cycling.

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The evolution and healing process of creep-fatigue damage are discussed on the basis of the experimental observation of cavities and small cracks. Multiple cavities and small cracks are formed along grain boundaries inside a smooth specimen of a Cr-Mo-V steel in creep-fatigue with slow-tension and fast-compression cycling at the relatively high temperature of 923 K. The cracks begin to appear at the middle stage of life, while the cavities initiate in the very early stage. The failure is brought about by the coalescence of cracks in the late stage. It is also found that these cavities and cracks caused by the diffusive creep in tension disappear during successive compression creep in creep-fatigue with fast-tension and slow-compression cycling. The failure life of the specimen can be extended by the healing cavities and cracks.

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The stress-strain field was assessed by means of the elastic-plastic finite-element method in the vicinity of the crack tip of the through-thickness-center cracked specimen subjected to cyclic loading under test conditions where ratchet deformation occurs. Then the cyclic J-integral range was calculated and its validity was examined. Both the maximum and minimum axial total strains at the crack tip during one stress cycle were greatly increased when ratchet deformation was generated. The path independence of ΔJ_op failed with the beginning of ratchet deformation, where ΔJ_op is cyclic J-integral range corresponding to load ranges above a crack opening point. Cyclic J-integral range ΔJ calculated through Dowling's conventional method, which was plotted against the crack tip opening displacement range ΔΦ_t calculated at 200μm behind crack tip, was situated on the smaller ΔJ side under test condition accompanied with ratchet deformation than under that without ratchet deformation. Meanwhile, the modified parameterΔJ/(1-Φ^min_c/Φ^max_c)^0.2 showed a good linear correlation with ΔΦ_t under all the test conditions with and without ratchet deformation. The earlier work in which one of the authors showed that the elastic-plastic fatigue crack growth rates were controlled quite well by means of the parameter ΔJ/(1-Φ^min_c/Φ^max_c)^0.2 might be realized in this way.

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Recently, it has been reported that the fracture stress σ_f and the fracture toughness K_c of engineering ceramics, measured by use of short precracks, have values lower than, σ_f = K_IC/(πc)^1/2 and K_C = K_IC, which might be expected from the conventional fracture mechanics. In the present study, assuming that these phenomena are due to the effect of a microdefect formed ahead of a main crack under applied stress, we propose a main crack-microdefect interaction model and formulate it using the theory of continuous distribution of dislocation in order to explain the above experimental results. As a result, we obtain the stress intensity factor K at the tip of the microdefect in a closed form. Supposing that macroscopic fracture would be caused when the stress intensity factor K reaches the plane-strain fracture toughness K_IC, we can obtain the analytical expressions of the fracture stress σ_f and the fracture toughness K_c and explain the above phenomena theoretically.

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In the previous paper, an approximate solution to the main crack-microdefect interaction model was derived using a main crack stress field, and the effect of a microdefect ahead of a main crack on the strength of solids was discussed in terms of the model. In the present paper, in order to investigate more precisely the above effect, the main crack-microdefect interaction model is formulated more specifically based on the continuous distribution theory of dislocations, and the distribution functions for both a main crack and a microdefect are obtained. As a result, we obtain stress intensity factor K both at the tip of a main crack and at a microdefect in a closed form. Using these K values, we can elucidate the effective range of the above interaction model and the crack shielding effect by a microdefect. Furthermore, the crack length dependence of fracture stress and fracture toughness of engineering ceramics can be explained well theoretically using the present model.

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The percolation model for rapid extension of a crack is proposed. In this model, a crack progresses through a two-dimensional lattice when the initially closed "bond", defined at each square, is broken. The fracture surface corresponds to the percolated region of the "broken square" and the tip of the crack is identified as the periphery of this percolated region. The probability P of breaking a bond is defined as P = K/√(R) for R ≤ R_IC, where K(≤1) is a parameter to be varied and R is a row or column distance from the crack tip. R_IC is the critical distance within which the bond breaks with the probability P. The initially plane crack tip progresses through a 60×270 lattice with the probability P during a unit time step, and a new crack tip is identified. The velocity of a crack for various values of K and R_IC is measured. Various aspects of the simulation are examined and the correspondence between this simulation and the well known experimental result is discussed. We find that the behavior of the velocity of a crack is reasonable, which indicates that the present model can be used to investigate dynamic behavior of a crack.

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In order to investigate the influence of oil on crack growth behavior, torsional fatigue tests were carried out on three kinds of age-hardened Al alloy specimens, 2017-T4 extruded, 20l7-T4 drawn and 7075-T6 extruded, with a small blind hole, in air and in oil. In both environments, the initial crack growth mode is the macroscopic tensile type in all materials. The crack leading to the final failure, however, is a shear-mode crack which is initiated after the initial tensile-type crack, except in the case of 7075-T6 extruded in air which propagates in the tensile mode. The crack growth rate is higher in oil than in air as a result of the lubricating action of the oil when the crack propagates in shear mode. On the other hand, this rate is decelerated in oil by the oil wedging action when the crack growth mode is the tensile type.

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The fracture mechanisms of short-fiber-reinforced PET (FRPET) are studied by the acoustic emission (AE) method to examine the effects of fiber content and loading direction. The maximum loads of test specimens increase with increase in the fiber content, and the loads decrease with increase in the angle between the directions of injection and loading. The cumulative AE event count and the total AE energy are affected by the fiber content and the loading direction. The effects of the fiber content and the loading direction on the total AE energy can be explained by AE amplitude distribution. The loads of P_b and P_c determined by the stress intensity factor method are in agreement with the loads determined by the AE energy gradient method. Damage is generated by the debonding between fiber and resin at the load point of P_b and by the fiber breaking at the load point of P_c in materials with fiber content of 15 and 30% by weight.

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In this paper, we describe the effects of cryogenic temperature at 77 K and water absorption on the mechanical properties and fatigue strength of intermediate-temperature cured carbon fiber reinforced epoxy matrix composites. Tensile and tension-tension fatigue tests were conducted on both dry and wet specimens, which had been preconditioned in laboratory air and in water for two months, respectively. The test results showed that i) an increase in the strength of the fiber/matrix interface and matrix material and in the elastic modulus of the matrix at cryogenic temperature, ii) a decrease in interlaminar strength at cryogenic temperature, and iii) a decrease in fiber/matrix interfacial and interlaminar strength by water absorption severely influenced the mechanical and fatigue fracture behavior of the composites. Internal damage was non-destructively examined with a scanning acoustic microscope, the fracture surfaces were closely examined with a scanning electron microscope, and the influence of cryogenic temperature and water absorption on fracture mechanisms was discussed.

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The effect of temperature on fracture toughness was investigated using Double Cantilever Beam (DCB) specimens of two kinds of unidirectional CFRP : APC-2 (fiber : AS4, matrix : poly-ether-ether-ketone (PEEK)) and T800H/PMR-15 (fiber : T800H, matrix : polyimide (PMR-15)). The tests were conducted at temperatures from 293K to 523K and 293K to 573K for APC-2 and T800H/PMR-15, respectively. The fracture toughness of APC-2 increased up to 473K due to larger ductility of matrix, while it decreased at higher temperatures because of the matrix creep. On the other hand, fracture toughness of T800H/PMR-15 was not influenced by the matrix creep even at 573K, though the toughness was lower than that of APC-2.

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The relationship between oxygen penetration depth into ground silicon carbide ceramics during oxidation and the extent of the affected layer has been studied. The penetration depth was deter-mined by measuring oxygen profile using the SIMS technique. The depths of ground ceramics oxidized at 1200 and 1500°C were expressed as the function of the maximum grain depth of cut g which is related to the depth of median crack in grinding. The penetration depth was smaller than the crack size. The increase in oxidation time hardly affected the penetration depth at 1200°C. It is suggested that the oxide film prevents further oxygen penetration and that the oxygen penetration has little effect on the strength at elevated temperatures.

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We analyzed microscopic stress and strain of hybrid laminate composed of two plain-woven-fabric-reinforced plastic (PW-RP) lamina and an unidirectional FRP lamina, applying our previous FEM approach for PW-RP lamina, and verified its results by the photoelastic experiment. The results of 3-D analysis show that the surface of hybrid laminate subjected to a uniform tensile deformation in the fiber direction of fabric is somewhat smoother than that of PW-RP lamina, but surface depression values of both hybrid laminate and PW-RP lamina are almost the same as that for tensile deformation in the direction of 45 degrees. Interlaminar stress is generated by restraint of the warp, and the highest value of interlaminar maximum shear stress appears at the portion closest to the weft.

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A new parameter, C_ij, is proposed for taking into account the effects of the interaction of multi-bonding layers on the strains of bonding layers with nonelastic behavior in semiconductor chip bonding structures under temperature changes. The previously proposed strain solution of a single bonding layer is extended to the solution of multi-bonding layers through use of this new parameter. This solution shows good agreement with FEM results. It is found from the consideration of sample structures that C_ij is a useful parameter for optimizing multi-bonding layer structures.

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In this paper, propagation of SV wave in two jointed dissimilar half spaces and layered half space is considered. Reflection and transmission coefficients at an imperfectly bonded interface are analyzed. The bonding strength at the interface is assumed using joint coefficients D_x and D_y, as well as our part 2 report. In the case of two jointed dissimilar half spaces, the coefficient of transmission for SV wave has a singularity at the critical angle of reflected P wave. On the other hands, in the case of a layered half space, it is shown that the plate vibrated by joint coefficients D_x and D_y when the interface is imperfectly bonded. The relationship between bonding strength and the two coefficients is discussed.

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In the previous work, strain rate change tests were conducted for high-purity polycrystalline aluminum at very high strain strain rates. This paper presents the results of reduction tests applied to copper. The experimental apparatus devised in the previous work is used to attain a sufficiently steep reduction in the strain rate. The flow stress obtained from the reduction tests is analyzed by means of the deconvolution method. The results indicate that the instantaneous strain rate plays a more important role than the strain rate history in the dynamic flow stress at a very high strain rate where a steep increase in the strain rate sensitivity of the flow stress is observed. The above-mentioned results are the same as those found in the previous work.

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In the previous papers, the numerical analysis method was proposed for estimating the mechanical behavior of braided composites, and its validity was confirmed. An analytical model can be developed for considering the continuity and crimp of fibers, and can be faithfully expressed in reinforcement configuration. The purpose of this study is to extend this analysis method to estimation of the mechanical properties of textile composites such as woven, braided and knitted fabrics. In this paper, the tensile properties and fracture behavior of weft-knitted fabric composite were estimated. The validity of this analysis method was examined by comparing predicted results with experiment data. Consequently, deformation properties and the stress state of weft-knitted fabric composite could be expressed using this analytical model. The predicted tensile modulus agreed well with the experimental results. Accordingly, it was clear that the tensile properties of weft-knitted fabric composite could be estimated using this analysis method.

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Longitudinal fibers, also called middle-end fibers, can be inserted into braided fabric during the braiding process. In the previous paper, it was confirmed that the braided composite with the middle-end fibers had superior mechanical properties compared to the braided composite without them. In this paper, a numerical analysis method is proposed for estimating the mechanical behavior of braided composites. This model considers the continuity and orientation of fibers. With this model, the tensile properties and fracture behavior of braided composites with the middle-end fibers were estimated and compared with the experimentdata presented in the previous papers. The tensile properties predicted by this method agreed well with the experimental data. Moreover, it was clear hat the fracture process of braided composites with the middle-end fibers could be simulated using this analysis method.

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A new phase called "quasicrystals" was discovered in 1984. The phase has a unique atomic structure, i.e., quasi-periodic structure and fivefold rotation symmetry in crystallography, which makes it neither crystalline nor amorphous (noncrystalline). Because of this atomic structure, superior mechanical properties have been expected. However, it is very difficult to obtain bulk samples of the quasicrystalline alloys, so the research on the mechanical properties and the application is very restricted. In this investigation, the quasicrystalline powder in Mg-Al-Zn alloy made by a mechanical alloying method is consolidated using a high-pressure technique of up to 5.4 GPa, and the pressure-temperature conditions of the quasicrystalline compacts are investigated. The mechanical properties of the obtained samples are also clarified in comparison with crystaline samples.

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In the present paper we examine the compressive buckling characteristics of symmetrically laminated plates with bending-twisting coupling. With use of lamination parameters, the effect of bending twisting coupling on compressive buckling loads is discussed for the case of simply-supported or clamped edges where the Rayleigh-Ritz method and the Galerkin method are respectively applied in the buckling analysis of simply-supported and clamped plates. The paper also examines the effect of the aspect ratio of rectangular plates on compressive buckling characteristics. The representation of the buckling load on the lamination parameter plane gives a comprehensive explanation of the coupling effect, since any laminate configuration in symmetrically laminated plates can be expressed in terms of four out-of-plane lamination parameters.

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There are certain kinds of microstructural characteristics such as second-phase particles, solute atoms, grain size and grain orientation, which affect the impact strength of aluminum alloys. In this paper we discuss the influence of distribution of second-phase particles in various commericial Al-Mg-Si system alloys. Test alloys were prepared with five kinds of heat treatment : T4, under aging, T6, over aging and O temper. The deformation behavior of these alloys was investigated using a compression test at room temperature. Dynamic tests (4×10²∼2×10³s^-1) were performed using a Hopkinson pressure bar system, and static tests (1×10^-3∼1×10^-ls^-1) were performed with an Instron machine for reference. It has been revealed that strain rate sensitivity of flow stress varies with the interaction between second-phase particles and dislocations.

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Certain microstructural characteristics, such as second-phase particles, solute atoms, gain size and grain orientation, affect the impact strength of aluminum alloys. In this paper, we discuss the influence of solute magnesium atoms on impact strength and ductility. In order to investigate the influence of solute magnesium atoms, five kinds of binary Al-Mg alloys with 2∼8 wt.% magnesium concentration and high-purity aluminum were used. Dynamic tensile tests (1.5×10³s^-1) were performed using a Hopkinson pressure bar system, and static tests (1×10^-4, 2×10^-3s^-1) were performed with an Instron machine for reference. The values of flow stress at certain strain can be described as a linear function of magnesium concentration beyond 2.7 wt.%. Total elongation increases with increasing strain rate and decreases with increasing magnesium concentration.

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A universal program of this matrix method with numerical Laplace transform was developed in the 1st report. Impulsive responses of simple framed structures can be analyzed with its use. For complex structures or those with a large number of elements, the program takes much cpu-time and extensive memory area. Thus the substructure synthesis method is applied to the matrix method in this paper. A comparison of analytical results obtained from the two programs shows that the new program takes less cpu-time and memory area without sacrificing accuracy. Then this method is applied to recalculation after rearrangement of structures and analysis of structures having the same substructures.

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This paper deals with a three-dimensional stress analysis for link chains subjected to tensile loads. The analysis was done using the finite-element method to examine the strength of the link chains. The effects of the dimensions of link chains on Misess's stress at the border between the curved part and the straight part in the link, and at the outer part, of which the inner part contacted with the inner part of the other link, were shown through numerical calculations. For verification, photoelastic experiments and measurement of strain were performed. The analytical results were in fairly good agreement with the experimental results. It was clarified that the strength of link chains can be improved by optimizing the link pitch, the link width, shape of the link section and compressed depth. Discussion is also presented on the estimation of the strength of the link chain subjected to tensile loads.

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This paper deals with the two-dimensional thermoelastic contact problem of a rolling rigid cylinder of specified shape, which induces effects of friction and heat generation in the contact region, moving with constant velocity in an elastic half-space containing two surface cracks located close to each other. In the present temperature analysis, the speed of the moving heat source is assumed to be much greater than the ratio of the thermal diffusivity and the contact length. The problem is solved using complex-variable techniques and is reduced to a pair of singular integral equations which are solved numerically. Numerical results of stress intensity factors are obtained for the case of two of two parallel cracks. The variance in interference effects on the stress intensity factors with the distance between two cracks, and the effects of the frictional coefficient, the sliding/rolling ratio and the distribution of heat generation on the results are considered.

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In this paper, fundamental solutions are given for two-dimensional infinite and semi-infinite problems in one-dimensional nonlocal elastic material. Solutions for nonlocal stress and displacement are obtained by means of closed forms assuming nonlocal coefficient shape. Their solutions are illustrated graphically and compared with the classical solutions.

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The stress field with logarithmic singularity is studied for the bonded wedges with a resultant configuration of a half-plane. Bogy has reported the stress field near the jointed corner tip due to arbitrary normal and shearing traction in an explicit form for the case in which the angle of the wedge γis 90°. In this study, the general expression of the stress field is given for an arbitrary value ofγ.

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Based on the general solution obtained in the first report, the stress field with logarithmic singularity is studied for bonded wedges with the resultant configuration of a half plane. It is found that surface traction is necessary for production of the logarithmic singular stress field. When the traction is uniform for all surfaces of the wedges, there is no singular stress field with the form of σ∼γ^λ-1 logγ, where γ is the distance measured from the corner tip. In this case, the logarithmic singular stress field with the form of σ∼logγ may exist ; however, it can exist only when the condition ofα=β(cos2γ-1)/cos2γ or α=π/[2tanγ+π-2γ] is satisfied, where α and β are the composite parameters and γ is the corner angle of the wedge.

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In this study, the interaction effect among cracks and fillets in a round and flat test specimen under tension is analyzed using the body force method. The stress field induced by a ring force acting in the radial and axial directions in an infinite body and a point force in a semi-infinite plate are used as a fundamental solution to solve these problems. The stress concentration factors of the fillet in a stepped round bar are systematically calculated under various geometrical conditions. Through the comparison of the present results with those of previous research studies, it is found that the Peterson's stress concentration charts based on photoelastic tests give stress concentration factors underestimated by about 13%. The stress distribution at the narrow section of the test specimen without cracks and the stress intensity factor of the test specimen with cracks are systematically investigated and the geometrical condition whereby the interaction effect between the fillet and crack disappears is discussed.

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This paper is concerned with an analytical formulation and a numerical solution of the thermo-elasto/visco-plastic deformation of general, moderately thick shells of revolution subjected to thermal loads due to fluid. Firstly, the temperature distribution through the thickness is assumed to be a curve of the second order, and the temperature field in the shell under the appropriate initial and boundary conditions is determined using the equations of heat conduction and heat transfer. Secondly, the stresses and deformations are derived from the thermal stress equations. The equations of equilibrium and the relations between the strains and displacements are developed by extending the Reissner-Naghdi theory for elastic shells. For the constitutive relations, the Perzyna elasto/visco-plastic equations including the temperature effect are employed. The fundamental equations derived are numerically solved by the finite difference method. As a numerical example, a simply supported cylindrical shell made of mild steel under thermal loading due to fluid is analyzed, and the results are compared with those from classical theory, which neglects the effect of shear deformation.

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A dynamic rigid-plastic finite element method for simulating high-speed plastic deformation in the shot-peening processes is proposed on the basis of the finite deformation theory of plasticity. In the present method, the inertial force due to the decelerating shot is equilibrated with the force caused by plastic deformation of the workpiece at the interface in each deformation step. By the use of the stress distribution at the time of maximum inertial force calculated from the rigid-plastic analysis, the residual stress distribution in the shot-peened workpiece is obtained via the elastic finite element method. Three-dimensional plastic deformation and residual stress distributions in rectangular blocks peened with a single rigid shot are computed. The calculated shape and residual stress distribution of the shot-peened workpiece are in reasonable agreement with the experimental ones for mild steel, copper and aluminium blocks.

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Cyclic plastic deformation of stainless steel 304 was experimentally investigated at low temperature of liquid nitrogen (77K) under combined loading conditions. Tubular specimens were subjected to cyclic loading under stress-controlled conditions. At low temperature, the material showed magnitudes of different hardening for the same strain in tensile and compressive loading directions. The characteristic hardening behavior caused a kind of mechanical ratchetting under cyclic loading. The hysteresis loops of stress-strain curves in cyclic loading were saturated with increasing cycle numbers. The saturated stress values depended on the loading condition. The values were represented by an equation accounting for cumulative plastic strain.

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Thermal ratcheting tests were performed on SUS304 large stainless steel cylinder specimens (610 mm in diameter), which were subjected to axially shifting temperature. In the experiment, we investigated the effects of four types of shifting temperature distributions : cold-front cycling and hot-front cycling with large movements, changing temperature distribution with fast movement, and no movement (stationary) cycling. Considerable thermal ratcheting strain was observed in the early cycles, but became saturated after many cycles. The increment in thermal ratcheting strain during each cycle, Δε, can be expressed as an inverse power law of the number of cycles N, such that Δε=C·N^-m(C, m are constants). During stationary cycling, the thermal ratcheting strain became saturated after several cycles and was very small. The relationship between transversed distance l and ratcheting strain Δε is explained quantitatively. A method for evaluating thermal ratcheting strain accumulated after a large number of cycles is proposed and its possibilities are examined. Under changing temperature distribution conditions, thermal ratcheting strain can be conservatively estimated by considering temperature distribution with shifting constant maximum stress.

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An alternative form of the auxiliary hardening rule is developed to describe the anisotropic creep behavior under multiaxial nonproportional repeated stress changes. The auxiliary hardening rule controls the combined isotropic and kinematic hardening with a memory surface in which isotropic hardening is suppressed and kinematic promoted. Differences from the previous studies are found in the alternative definitions of the memory surface and its evolution equations. A method for the enhancement of the creep recovery is also proposed within the present constitutive framework. The applicability and insufficiency of the creep model are elucidated by comparison with the typical experimental results on multiaxial nonproportional repeated creep. The simulated results of the isotropic and kinematic hardening models, which are derived as special cases of the present model, are included.

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In conventional design sensitivity analysis using the boundary element method, all boundaries must be discretized. Therefore, the size of the coefficient matrix of the resulting system of linear algebraic equations becomes quite large for a field with small circular holes. In this paper, we present an efficient sensitivity analysis approach for two-dimensional steady-state heat conduction problems. In the boundary element formulation, the temperature and the heat flux over the boundary of a circular hole are approximated by simple trigonometrical functions. Then, the boundary integral equation is differentiated directly with respect to a design variable. The resulting boundary integral equation relates the sensitivity coefficients of temperature and heat flux over the boundary. The effectiveness of the proposed approach is illustrated through several numerical examples.

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In the case of analyzing various problems by means of the boundary element method, special treatment is required for corner points and discontinuous boundary conditions. In this paper, a method for reasonable treatment of discontinuous boundary conditions is proposed in the analysis of potential problems, plane stress problems and plate bending problems. Numerical examples of the present method are shown and compared with values obtained by means of other methods.

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The present paper describes new algorithm for the optimization problem under the condition of constraint. The algorithms on the following concept are referred collectively to as constructive algorithms (CAs). Two types of chromosomes are introduced in these algorithms. One is called the main chromosome and the other the subchromosome. The condition of constraint is always satisfied with the genome on the main chromosome. The subchromosome controls the transformation of the genes on the main chromosome in the surrounding environment. The genetic algorithms (GAs) are applied only to the subchromosomes. Finally, the main chromosome acquires the required functions for optimization. To demonstrate the effectiveness of the proposed new algorithm, the algorithm is applied to the design problem of the strongest column.

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For life extension of fossil power plants, one of the most important subjects is to evaluate creep damage in high-temperature components such as boilers and turbines. A creep void area fraction rate method, by which damage is evaluated based on visible information from a material texture image, is a useful method with applicability to damage detection in actual plants. In this study, an evaluation system for creep void area fraction rate assisted by an image-processing technique was newly developed. It was ascertained that the developed system enabled efficient and objective evaluation with the same accuracy as the conventional manual method. Statistical properties of creep void distribution were studied using data acquired with the system. The relation between measurement conditions and evaluation accuracy was examined, and reasonable measurement conditions were proposed.

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