In the present study, an interlaminer fracture toughness of cross-ply CFRP laminates under mixed mode state are evaluated by MMB (Mixed Mode Bending) tests. 2-Dimensional boundary element analysis are applied to determine complex stress intensity factors which are defined on the interface crack between dissimilar unisotropic laminates. The complex stress intensity factors and mixed mode ratio are extrapolated from stress distribution around the crack tip, then fracture toughness on the interface are calculated by the critical load defived from MMB test. It is shown that the fracture toughness of the cross-ply CFRP laminate depends on the mode ratio of the stress intensity factors K₁ and K₂. The criterion of the delamination growth is discussed from a standpoint of the mode dependency of the fracture toughness.

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The failure process of GFRP cross-ply laminates (up to final failure) is studied. In situ observations of ply cracks during tensile tests are carried out to obtain the damage process of the cross-ply laminates. Based on these experimental results, we propose a numerical simulation to investigate the damage process. In the present model, a ply crack is expressed by the cohesive element. Consequently, the stress-strain relationship and the density of ply cracks are simulated by choosing the strength and the critical energy release rate of the cohesive element.

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In this study, the dynamic response of a sandwiched piezoelectric strip containing a crack vertical to the interfaces under a normal impact load is considered. Based on the superposition principle and the integral transform techniques, the solutions in the Laplace transformed plane are obtained in terms of a singular integral equation. The singular integral equation is solved by using the Gauss-Jacobi integration formula, and the numerical Laplace inversion is then carried out to obtain the resulting dynamic stress and electric displacement intensities. The effects of the material properties and the geometric parameters on the dynamic stress intensity factors and the dynamic energy density factors are shown graphically.

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It is important to know the dynamic fracture behavior for the safety design of the brittle material board. However, to analyze the dynamic fracture behavior of the brittle material board is difficult because it is discontinuous fracture behavior. In this research, the impact penetration fracture behavior when the impact body collides with the center of the brittle material board is analyzed by using the Distinct Element Method (DEM). DEM is suitable for the analysis of the fracture behavior from the continuous body to discontinuous body. In addition to the analysis, an experiment of the impact penetration fracture is performed by using the glass plate. The experimental results are compared with the analytical results. From the result, it has been understood that the penetration speed and the loss energy increase as the impact velocity of the impact body increases. Moreover, the influences of material constants as the young's modulus, tensile and compressive strength are clarified.

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The characteristics of the off-axis strength reliability of notched UD composites is discussed. Tensile tests are carried out on polished specimens with various shaped notches introduced by a drill and a saw. The notches are observed with plastic replica and photographs to consider the effect of the machined damage. Moreover, each elastic field of specimens is analyzed with the Body Force Method to discuss the fracture process. The two parameter criterion proposed by Hashin is adopted as the fracture criterion, and the evaluation method for the strength reliability is proposed. It is found from the present data and the present evaluation method that the notch effect and the thickness effect can be expressed with the statistic factor.

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In this paper, finite element analysis for wrinkled interface in thermal barrier coating was performed. Particle binding layer model for an imperfect cohesion between ceramic thermal spray particles was developed here. Microstructure model consisted of ceramic coating, which is including a particle binding layer, and metallic bond coating layers with the wrinkled interface was used for examining the wrinkled interface stress filed in thermal barrier coating system. The analytical results showed that stress increases between peaks of the wrinkled interface in the side of ceramic coating layer when the microstructure model is subjected to transverse loading. The site of maximum stress was almost coincided with the micro crack initiation site observed in a cross section of the specimen. Energy release rates and stress intensity factors for isolated and periodic aligned small cracks in microstructure model with the wrinkled interface were shown with the term of the closed form.

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The residual stress and deformation behaviors of rectangular plate, induced by the inherent strain of coating layer due to thermal spraying, was clarified by a polynominal expression using the dimensionless parameters of σ· (1-ν_c) / (E_c·ε_I) and u·T/ (L²·ε_I). (σ : residual stress, ν_c : Poisson's ratio of coating, E_c : Young's modulus of coating, ε_I : inherent strain of coating layer, u : displacement, T : thickness of substrate and L : length of substrate). We made clear the rectangular plate size for measuring the inherent strain of coated member with high accuracy for preventing the plastic deformation effect of substrate and the cracking effect of coating layer in case of the MCrAIY coated IN738LC.

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Fatigue tests were conducted for Ti-6 Al-4 V alloy under stress ratios of R=-1, 0 and 0.3, and under the condition fixing the maximum stress at the yield stress without fixing stress ratios between each data point (σ_max=σ_y test). Internal fracture tended to occur under high stress ratios except R=-1, in spite of no occurrence in R=-1 test. The fracture sites of the internal fracture revealed no inclusion but serveral facets. The fatigue strength determined at 10⁸ cycles were below a modified Goodman line in the R=0 and 0.3 tests, although they were above under R=0.7. Besides, fatigue lives estimated with the modified Goodman line were much lower than actual results. These results meant high stress ratio tests were necessary in evaluating fatigue strength and life in the high stress ratio condition. For the high stress ratio tests, the σ_max=σ_y tests appeared to be a good solution.

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This paper presents numerical solutions for anisotropic medium with multi-layered elliptic inclusions. An arbitrary direction of principal axes of elasticity is considered in the anisotropic matrix. The solutions are obtained by using complex stress functions formulated by S. G. Lekhnitskii et al., and results of calculation are shown by several numerical examples. Then, stress intensity factors of Mode I, Mode II and Mode III at the tip of slit clack in layered elliptic inclusions are computed. The effect of the anisotropy of matrix on the stress concentration is examined.

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In this study, the thermal singular stresses in an elastic half-plane containing a crack perpendicular to the boundary is considered. The half-plane is subjected to a uniform heat flux and a uniform mechanical load, and the temperatures on the crack surfaces and free surface of the half-plane are maintained at uniform temperatures, respectively. The Fourier transform techniques are used to formulate the problem in terms of singular integral equations. The singular integral equations are solved by using the Gauss-Jacobi integration formula. Both the cases of an internal crack and an edge crack are studied. Numerical calculations are carried out, and the effects of the geometric parameters on the temperature-thermal stress distributions and the thermal stress intensity factors are shown graphically.

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Steady thermal stress analysis without heat generation can easily be solved by the boundary element method. However, for the case with arbitrary heat generation, a domain integral is necessary. This paper shows that the problem of three-dimensional steady thermal stress with heat generation can approximately be solved without the domain integral by triple-reciprocity boundary element Method. In this method, an arbitrary distribution of heat generation is interpolated by boundary integral equations. In order to solve the problem, the values of heat generation at internal points and on the boundary are used.

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The Genetic Algorithm (GA), which is optimization method based on the natural evolution theorem, is applicable to the wide scale problems. By using the GA, various evolutionary optimization methods are studied. But, in these methods, the meanings of genetic-code are not considered at all. In this study, the Special Feature Extracting GA (SFE-GA) is proposed. The SFE-GA is based on the idea that the genes possessing the suitable environment extend to all over the chromosome, and is the GA with an operation of stepping up the function. A superior group with the high fitness value includes the schemata of building blocks of good solutions. The schemata is extracted using the t-test, and the group with the low fitness value is overwritten to the extracted schemata. This method is applied to the problem that searches the maximum value in a simple function. The behavior in the search is clarified and it is confirmed to extract the effective schemata sequentially. Moreover, it's applied to the layout design problem of truss structure as the large scale problem.

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Heat-transfer coefficient distributions on both surfaces of a rotating disk are optimized to minimize Mises equivalent thermal stress by the combined use of genetic algorithm and analytical solutions to transient heat conduction and thermal stress problems in the rotating disk subjected to local heat generation near the outer radius. The transient temperature field in the rotating disk with arbitrary, radial change in the heat-transfer coefficient distribution is analyzed by the application of Vodicka's method. The optimized heat-transfer coefficient distributions show three patterns of distribution depending on the heat-transfer coefficient on the outer radius, the disk thickness and the area of the heat generation. Furthermore, it is discussed whether it is possible to realize the optimized heat-transfer coefficient distributions or not.

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In Renormalized Group Molecular Dynamics (RGMD), the temperature of individual clusters can not be determined, because individual velocity of atoms in a cluster is unable to resolve. This paper proposed a new method, in which temperatures of individual cluster can be determined by the velocity of atoms that are estimated by the velocity distribution of clusters obtained from RGMD using the central limit theorem. Simulations of heat conduction of silicon single-crystal have been carried out using the Molecular Dynamics (MD) and the RGMD. The temperature distributions in both MD and RGMD model have been compared. It was obtained that appropriate temperature distribution in MD model is exhibited using the RGMD, in which two statistical parameters contained in the proposed method are determined appropriately.

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Damage identification methods using finite element methods have received much attention for health monitoring systems. However, the damage identification methods need a long computational time for large and complex structures. In this paper, we develop an effective damage identification method for large truss structures using a successive iteration method of bounding domain and a domain decomposition finite element technique. The subdomain of truss structures which contains a damaged truss member is first determined by a flexibility method. The subdomain is subdivided into smaller subdomains using a successive iteration method of bounding domain, and finally the damaged truss member is identified. In order to reduce computational time, the domain decomposition finite element technique is used to get frequencies and mode shapes of the whole structure by assembling subdomain frequencies and mode shapes. To examine the effectiveness of the present damage identification method, the damage identification for large two-dimensional and three-dimensional truss structures is conducted. As the results, it is found that the damaged truss member and its residual stiffness can be identified precisely and the present damage identification method can reduce the computational time when the measurement errors are relatively small.

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In solving inverse problems, a priori assumption for the solution is needed in many cases. It is difficult to obtain a reasonable solution if the assumption has some errors. To conquer this problem, the authors have proposed a scheme which combines a method of discretizing a function using the delta functions with the boundary element method (BEM). In this study, the scheme is applied to the identification of bending rigidity of a beam. The method using the delta function is especially applicable to this problem because the second derivative of the objective function (bending rigidity) included in the basic integral equation must be treated. The new scheme will deal with it well while the usual element may lose its information due to differentiation. Besides, it will express a sudden change of the objective function such as a step change pretty well while it is difficult to interpolate such a function by the usual element. The new scheme is applied to identify the bending rigidity of beams with various shapes. It is demonstrated that sufficiently accurate results can be obtained regardless of the shape of the rigidity distribution, without the need for any a priori assumptions.

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Formulations of elastic deflection and bending stresses for anisotropic side plates (width 350, height h=300 and thickness 5.44mm, and longitudinal coefficients E _x =291 and E _y =153 N/mm² in width and height directions and Poison's ratio ν_xy=0.10 for width direction strain to height direction strain) in the case of the corrugated fiberboard box shape (CFCBS) under uniform compression p_y0 were expressed using the constrain of four edges, and behaviors of deflection iv and bending stresses for its box were discussed by these formulations. w and bending normal stresses σ_bx and σ_by in width and height directions of side plates distribute symmetrically to center lines in width and height directions, and shear stress τ_bxy distributes antisymmetrically to their center lines. Maximum wm of|w| is at side edge centers in the side plate, and maximum σ_bxm of σ_bx is at side edge centers and maximum σ_bym of |σby| is at positions of L/32 from the plate center in the width direction. And maximum τ_bxym of |τx_by| is at corners of the side plate. Ratios w (aniso) /w (iso), σ_bx (aniso) /σ_bx (iso), σ_by (aniso) /σ_by (iso) and τb_xy (aniso) /τ_bxy (iso) for the anisotropic plate to the isotropic plate (longitudinal coefficient E =E _x and Poison's ratio ν=ν_xy) are about 2, 2, 1 and 4/3 respectively.

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We have developed a theoretical model for predicting the in-plane mechanical properties of honeycombs based on the large deflection of the inclined and vertical members of the honeycomb cells. We have used the large deflection approach for a segment including honeycomb cells. Then we derive expressions for Elastic modulus and Poisson's ratios in two orthogonal directions, and the shear modulus of honeycombs. Elastic modulus, Poisson's ratios and the shear modulus of honey-combs are expressed using incomplete elliptic integrals. The results show that these mechanical properties are no longer constant at large deflections but vary significantly with the strain

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The purpose of the present study is to elucidate the micro-to macroscopic deformation behavior of an amorphous polymer with slightly heterogeneous distribution of molecular chain, in other words, the distribution of the initial strength of the polymer. The micro-to macroscopic deformation behavior of polymer blocks under macroscopically uniform tension, compression and shearing, and surface deformation of the plane strain block under compression were investigated by means of computational simulation with the nonaffine molecular chain network model. The results clarified the onset of microscopic shear bands emanating from the slightly weak points and their evolution, interaction and percolation of new shear band. The effect of distribution patterns and variation of initial shear strength on the deformation, the interaction of weak points, transition of microscopic shear bands to macroscopically inhomogeneous deformation including the evolution of surface undulation under compression have been demonstrated. In macroscopically homogeneous deformation as well as heterogeneous deformation, the deformation resistance increases with the introduction of heterogeneity of the initial shear strength.

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This research showed the procedure to search the proper welding condition, in lap joints of aluminum alloys made by laser welding. In this research, parameters of laser welding were the following three factors ; gap width, welding speed and laser power. By strength tests and observations of weld zone, the following conclusion was obtained. In order to search the laser welding condition range under which tensile strength and fatigue strength are stabilized, it is necessary to observe the states of weld zone and avoid following two matters. The one is lack of fusion by the shortage of heat input, and the other is weld cracking near toe of the weld by the excess of that.

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A finite element analysis of thin-walled tube which is simultaneously subjected to axial load and internal pressure is conducted. As for constitutive law, visco-plastic model is adopted. The present problem can be assumed in quasi-static state although the employed equation is described as rate form. Therefore an iteration solving method is utilized and a solution satisfying the equilibrium equation can be obtained. Axial load and internal pressure have to be independently controlled so that the ratio of longitudinal and circumferential stresses could be kept constant. To enable this, a novel arc-length method with two different loading modes is proposed. In the method, the ratio between longitudinal and circumferential stresses is controlled as an additional constraint condition. Plastic instability condition of thin-walled tube under combined loading is also presented. A numerical example demonstrates that the proposed method can keep the stress ratio constant through the analysis and evaluate the maximum loading points of thin-walled tube under combined loading.

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Cavitation erosion tests were carried out on 10 kinds of base metals such as irons and stainless steel castings, and 7 kinds of coatings used as pump materials. The cavitation erosion resistance was compared with the slurry wear resistance. For base metals, the ratio of the cavitation erosion rate to the slurry wear rate can be predicted by the breaking elongation obtained in the tensile test, because the cavitation erosion initiates at the weak second phase of the material which gives the low elongation. For thermal spray coatings, the cavitation volume loss increases rapidly in the initial stage due to the removal of the soft layer, and then it increases at a slower rate. It was concluded that the cavitation erosion resistance has a poor correlation with Vickers hardness of the material, and that the slurry wear resistance has a good correlation with the hardness, provided that the brittle material of the thermal sprayings are excluded.

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A tangent delta of a polymeric material, which influences the vibration damping capacity strongle, is high in value nearby the glass transition temperature of the material. Therefore, when the constituents of a polymer-based composite material are various in their glass transition temperatures, the magnitude of the macroscopic tangent delta of such a composite is expected to be high in wider range in temperature. In the present study, a shape memory polymer (SMP) particle/SMP matrix is used as a sample material and its macroscopic complex modulus and tangent delta are derived explicitly by using the equivalent inclusion method and the Mori-Tanaka's theorem. For the case of a four mode type of distribution of the glass transition temperatures of particles, the value of the macroscopic tangent delta becomes higher than that of the monolithic SMP at any temperature and it becomes constant in the temperature range from 20°C to 60°C.

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This study describes the micro evaluation methods for investigating the feedstock properties and the process conditions for industrial mass production of micro parts by Metal Injection Molding (MIM). The effects of feedstock properties such as particle size and powder loading on the sintered properties of micro-dumbbell specimens were investigated under various injection-molding conditions. Small particle size and high powder loading significantly improved the quality such as density and tensile strength, as well as yield percentage in producing sound micro-dumbbell sintered specimens. Deformation and fracture propagation behaviors were observed with the in-situSEM tensile test which was useful to comprehend the influences of feedstock properties on the mechanicalproperties of the micro MIM (μ-MIM) products

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A determination method for elastic-plastic material constants that obey the power-law hardening rule, from a couple of sharp micro-indentation tests, is proposed. Based on a similarity function that is determined from the three-dimensional FE simulation, it is shown that for plural triangular pyramid indenters with different apex angles unique values of representative strain correspond to each apex angle. It is also shown thatΠversusE^*/σ_rplot, which is constructed from FE simulation result, can be expressed as an interpolation between two analytical extremes : the elastic solution and the rigid/perfectly plastic solution. Based on these results, we propose a new method for determination of power-law hardening material constants, utilizing two triangular pyramid indenters with different apex angles. A simple method for determining the value of representative strain is also proposed.

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Stress corrosion cracking (SCC) occurs in shrouds and piping made of low carbon austenitic stainless steels at nuclear power plants. A work-hardened layer is considered to be one of the probable causes for this occurrence. The maximum Vickers hardness measured at the work-hardened layer is 400HV. It is important to determine the yield strength and tensile strength of the work-hardened layer in the investigation on the causes of SCC. However, the tensile specimen cannot be obtained since the thickness of the work-hardened layer is as mall as several hundred μm, therefore, it is useful if we can estimate these strengths from its Vickers hardness. Consequently, we investigated the relationships between Vickers hardness versus yield strength and tensile strength using the results obtained on various steels in a series of Fatigue Data Sheets published by the National Institute for Materials Science and results newly obtained on a parent material and rolled materials (reduction of area : 10-50%, maximum hardness : 350HV) for a low carbon stainless steel. The results showed that (1) the relationship between the 0.2% proof stress and the Vickers hardness can be described by a single straight line regardless of strength, structure, and rolling ratio, however, (2) the tensile strength is not correlated with the Vickers hardness, and the austenitic stainless steel in particular shows characteristics different from those of other steels.

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The investigation is done on the cognition about what degree of false step is caused by the students, when the teachers of Industrial Arts Course at Junior High School guided metalworking work. Questionnairing items are “the degree of false step of student”, “the necessity of study for students” and “the existence of instruction experiences of teacher”.
The investigation was done about the false step of student by the questionnaires and the interviews to the teachers. As the result, there were the correlations between “the degree of the false step of student and the existence of the instruction experiences of teacher”, “the necessity of study for students and the existence of instruction experiences, of teacher”, and “the degree of false step of student and the necessity of study for students”.

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