This paper solves a plane elasto-static problem for two bonded elastic and isotropic strips with a T-shaped crack. The T-shaped crack consists of a crack perpendicular to the interface and an interface crack. By means of the Airy stresss function and Fourier transforms the problem is formulated as a system of integral equations. A new numerical method using only the Gauss-Chebyshev integral formula is proposed to evaluate the integral equations, though the complicated Jacobi polynomials expansion and integral formula were used in the previous literature. Stress intensity factors are obtained numerically for various material and geometrical parameters, where the interaction between the cracks perpendicular to and on the interface is clearly shown.

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This paper deals with a mechanical model for estimation of the deformation behavior of two-phase sintered materials. Two-phase sintered materials can be regarded as an assemblage of unit cells which consist of a hard grain and its surrounding soft binder. From a consideration of deformation characteristics of the unit cell, a mechanical model, which can predict not only overall elastic moduli and overall instantaneous elastic-plastic moduli but also microscopic stresses and strains of the two-phase sintered materials, has been proposed. This model has been applied to estimate the deformation behavior of WC-Co hardmetals with various volume fractions of Co. The analytical results of the overall elastic moduli and the overall stress-strain relations under uniaxial tensile tests agree well with the experimental results in references.

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The interaction of crack growth on multiple ended fatigue cracks is examined with the coupled compact tension specimens of 0.45% C carbon steel under high cyclic stresses. The crack propagation behaviour of coupled specimens fatigued under the stress ratio of 0.05 and 0.7 is compared with that of single specimen. The deviation of crack propagation rate from the stable relation between the rate and ΔK of a single specimen is found to take place with the difference of crack closure and the onset of the ratcheting extension of specimens. The crack growth acceleration is affected by another specimen coupled because of the incomplete reversal of plastic deformation in ratcheting deformation. Based on the theoretical prediction of an interaction curve for crack growth of a coupled specimen, it is concluded that multiple ended fatigue cracks under high cyclic stresses propagate with a mechanism such that the increment of total strain energy release per cycle in a body including some cracks is distributed to each crack with the ratio of the strain constraint factor.

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Rotating bending fatigue tests were made on specimens which were polished longitudinally or circumferentially with two kinds of silicon carbide papers. The material used was a quenched and tempered SCM 435 steel. The specimen surfaces were observed by the two stage plastic replica method. The effects of surface finishes on the fatigue strengths of the specimens were investigated. The main results obtained are as follows : (1) Non-propagating micro-cracks are observed on the surfaces of the specimens after 10⁷ cycles of the fatigue limit. In specimens polished under different conditions, the physical meaning of the fatigue limit σ_wb is the same. That is, it can be defined as the limiting stress for the propagation of a micro-crack which is initiated under the repetitions of σ_wb. (2) The geometric features of the starting points of cracks affect the fatigue strengths of surface-finished specimens.

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The brittle fracture behavior in the static tension of notched specimens of polycarbonate has been studied for a wide range of notch tip radii. The nominal stress at the brittle fracture decreases with decreasing notch tip radius, and it approaches a constant value when the notch tip radius is less than about 0.1 mm. For notch tip radii less than 0.1 mm, the fracture is well explained on the basis of linear elastic fracture mechanics. For notch tip radii larger than 0.1 mm, the specimens failed in an apparently brittle manner after the formation of a small plastic zone at the notch tip. The experimental results of these specimens have been discussed in terms of a combination of the critical maximum elastic stress and the notch tip radius from the standpoint of linear notch mechanics. It is shown that the maximum elastic stress for brittle fracture is governed by the notch tip radius alone.

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Mode I interlaminar fracture toughness of CFRP has been examined using DCB (Double Cantilever Beam) specimenn in this paper. A new DCB specimen has been developed in order to obtain the accurate fracture toughness value, G_c, using the compliance method. Interpolation equations of crack length, energy release rate and compliance are obtained using the finite element method. Based on the equations, a computer-aided testing system has been developed, by which the relation between the crack length and G_c can be obtained automatically. Unidirectionally reinforced Carbon/Epoxy laminates have been used for the test. The initial cracks were introduced in two ways, by inserting PTFE film on the midplane during fabrication and by cutting mechanically after curing. Behavior of the acoustic emission (AE) has also been measured during the test, and the relation between the amplitude distribution and G_c has been examined. Effects of the initial crack on G_c have been examined and reasonable fracture toughness values have been obtained by the proposed method for the specimens with cracks prepared by both of the mechanical crack with width of three plies and PTFE film.

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The elastic-plastic fracture toughness (J_IC) and fracture resistance (J-R curve) of a carbon steel, STS42, used for piping in a nuclear reactor were evaluated according to the several evaluating methods recommended or proposed so far to discuss their applicability and utility. The results obtained are as follows: (1) In evaluating J_IC, the multiple specimen method recommended by the Japan Society for Mechanical Engineers (JSME standard S001) gives the most reliable results by using smaller sized specimens. (2) The single specimen methods by using the compliance technique, adopted in the ASTM standard (E813, E813 modified, Tentative test procedure for determining the plain strain J-R curve), do not give an accurate J-R curve of J_IC, due to an error in the calculated crack length. (3) In evaluating the J-R curve, it is necessary to account for crack extension in calculating the J-integral. (4) According to the above results, a new standard method for determining the J-R curve including the J_IC test method should be poprosed.

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Rice has shown a simplified method for estimating the J-integral for a deeply cracked bend bar. For a compact specimen used in the elastic-plastic fracture toughness J_IC test, Merkle and Corten have shown a simplified method for estimating the J-integral which is taken into account the axial force. Now, a modified Merkle-Corten formula is generally used in the J_IC test. In this study, an applicable range of these J estimation formulas for a compact specimen is analytically studied for three materials ; linear elastic, rigid perfectly-plastic and elastic perfectly-plastic. Results show that the original Merkle-Corten formula is superior to the modified one and the Rice formula in accuracy. Based on the results, use of the original Merkle-Corten formula and a recommended precrack length for the compact specimen in the J_IC test are proposed.

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A plane-stress thermoelastic problem in a nonhomogeneous rectangular region with a circular hole subjected to transient heating on the circular hole has been formulated by the stress function method. The system of fundamental equations obtained has been solved numerically by the finite difference method. To analyse numerically the plane-stress thermoelastic problem in the non-homogeneous region, with two distinct boundary geometries, by the use of the less number of grids, we introduce two types of finite difference grid parallel to each co-ordinate curve of rectangular co-ordinate and polar co-ordinate systems. Numerical calculations are carried out for the thermal conductivity, Young's modulus and the coefficient of linear thermal expansion which vary exponentially with the distance from the co-ordinate origin.

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The determination of thermal stresses in plates with variable thickness, which is applicable to the design of commonly used structural elements such as fins, rotating discs and turbine brades, is presented analytically. A hollow circular plate of variable thickness considered here is subjected to asymmetric heating on the inner boundary and has a decreasing thickness from the inner boundary toward the outer boundary with the radial position. Analytical solutions are given for the transient temperature field in the plate of variable thickness insulated on the upper and lower surfaces and the steady-state temperature field in the same plate with a uniform heat transfer coefficient on both surfaces. The associated plane-stress thermoelastic problem is formulated in terms of a stress function, and the Michell's condition derived before and expressed in cylindrical co-ordinates here is used as an assurance of the single-valuedness of rotation in the plate of variable thickness. Numerical calculations are carried out for the distributions of temperature and thermal stress in the hollow circular plate of variable thickness for the various cases of thickness variation and heat transfer coefficient on the upper and lower surfaces.

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In case of some kinds of material, distinct difference between pre-tensed and pre-compressed Bauschinger's stress-strain curves occurs. Experiments of copper test pieces were conducted in pre-strain region to about 30% in this paper. From the test data, the ratio of two stress values in the narrowest point between simple stress-strain curve in pre-strain direction and reversely loaded stress-strain curve which is shifted by pre-strain value and shown in pre-strain direction is approximately 0.94, not depending on kinds of pre-strain and pre-strain value. Therefore the above said difference of Bauschinger's curve is derived from difference between simple tensile and compressive stress-strain curves in some kinds of material. And also this phenomenon can be explained by observation of slip bands.

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A bar is made by hot rolling, so it is important to make the temperature distribution clear for a precise estimation of the material shape and controlling texture. We analyzed the flow of material in bar rolling by the energy method using finite element division. In this paper we deal with the temperature distribution in bar rolling. The temperature distribution near the material-roll contact surface changes sharply. So we propose the following new method for the analysis in the neighboring region of the contact surface. We apply the finite differences method to this region, and the finite element method to the other region. Consequently, the following results are obtained. (i) The temperature at the material-roll contact surface depends highly on the frictional condition and the circumferential velocity of the roll. (ii) The temperature becomes high at the central part of the material near the roll contact surface in square-diamond pass and round-oval pass, whereas in square-oval pass the temperature becomes high at the side part of the material near the roll contact surface.

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Fracture of blades or disks due to centrifugal force in rotary machines has often caused serious accidents. To estimate the strength of a structure, a precise knowledge of stress intensity factors for the mixed mode in rotating disks is important. In this paper, stress intensity factors K_I and K_II has been determined by using the photoelastic and caustics method, as a function of the inclination crack of length 2 a (2a = 4, 8, 12, 16, 21 mm) and at different values of the inclination crack angles φ(φ = 0, 15, 30, 45, 60, 75, 90°) at a velocity of 2 100 rpm. The results of these experimental methods coincided favorable with the theoretical analysis results of Ishida and Terada.

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In this report, the principle of structural analysis by the ε-method is discussed for two-dimensional multi-storied and multi-span rectangular rigid frames loaded vertically or horizontally, in cases where the bases of columns of the rigid frame are all hinged. A digital computing program for the structural analysis of the rigid frame was constructed on the basis of the ε-method and various quantities were computed by this program. The ε-method, named by the authors, is one of the slope-deflection methods and is of practical use in the structural analysis of rigid frames. Finally the results calculated by the digital computing program are shown in several figures in the present paper.

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A supercomputer based software, which enables re-construction of a three-dimensional shape without human assistance using a stereo-pair of scanning electron micrographs, has been developed. It is based upon computer image processing and pattern recognition techniques, and can re-construct a three-dimensional shape of a wide variety of fracture surfaces of corrosion fatigue as well as crack initiation sites in an aggressive environment like a corrosion pit. We discuss the optimum algorithm according to the morphology of fracture surfaces. A sequential similarity detection algorithm is available in transgranular fatigued surfaces, whereas in the case of corrosion fatigue fracture surfaces and crack initiation sites, the mutual correlation coefficient technique is well suited. The shape and size of the window area, and the run time required in re-construction are also discussed.

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