Recent developments in fracture surface examination are surveyed. Emphasis is placed on quantitative analysis of fracture surfaces. An X-ray analysis of a fracture surface is first described. The successful use of the residual stress distribution under the fracture surface is demonstrated for the estimation of the applied stress intensity factor under which the fracture occurred. A new technique using a laser profile meter is described for the measurement of fracture surface topographical information. A bird's-eye view of fracture surfaces is presented. The successful use of topographical information is demonstrated for matching of the conjugate fracture surfaces.

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Cavitation erosion is discussed through the measurements of the cavitation bubble collapse pressures and the observations of the erosion processes of various materials. The magnitude of impact pressures (impact loads) produced by the collapse of bubbles fluctuates over a wide range, but the number of bubble collapse impacts necessary to form erosion pits impulsively is remarkably small. Cavitation damage is found to be dominated by fatigue fracture due to the repetition of small impact loads as well as a small number of large impact loads. However, there is a threshold value at which impact load begins to contribute to the fatigue fracture of the surface. Comparing the distributions of impact loads with the hypothetical S-N curves of fatigue, Miner's law is followed for the incubation period and the erosion rate regardless of the testing apparatus, cavitation conditions and materials. The erosion resistances of the msterials are also discussed.

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An analytical solution is presented for a plane thermal stress problem in a nonhomogeneous hollow circular plate subjected to unaxisymmetric heating as an example of nonhomogeneous multiply connected regions. The nonhomogeneous plate has Young's modulus and thermal conductivity expressed in forms of different power laws of radial coordinate, the coefficient of linear thermal expansion given as an arbitrary function of radial coordinate, and constant Poisson's ratio. The governing equation of the thermoelastic problem formulated in terms of a stress function becomes Euler's differential equation. The single-valuedness of rotation in the symmetric thermal stress problem with respect to the x and y axes is assured based on the new Michell's conditions derived for arbitrary nonhomogeneous material properties in the previous report by the present author. Numerical calculations are carried out for the temperature and thermal stress distributions in the nonhomogeneous hollow circular plate subjected to unaxisymmetric heating on the inner boundary.

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A theoretical study is presented for the damping of the flexural vibration of a three-layered shallow spherical shell with a constrained viscoelastic layer. Expressing in-plane displacements in terms of auxiliary functions, general solutions of the equations of motion for nonaxially symmetric modes are given in terms of Bessel functions. When the opening angle changes with a constant base diameter, natural frequencies and loss factors of shallow spherical are calculated for axially and nonaxially symmetric modes. Effects of the opening angle, the shear parameter, the thickness of each layer, and boundary conditions on the damping properties are investigated.

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A torsional stress analysis and the expressions of torsional rigidity for the two types of nonsymmetrical three-layered rectangular rods such as sandwich rods with a viscoelastic core and covered rods having composition opposite to that of the sandwich rods, have been presented. The composite loss factors for these rods in torsional systems are also considered. The expressions of shear stress and torsional rigidity presented are briefly fonmulated and may be easily applicable to various two- and three-layered rods. Numerical results are discussed for typical sandwich rods and covered ones, and also those having geometrically similar compositions. These results decribe how to consider the suitable rod composition in order to reduce the maximum shear stress arising at the interfaces between the layers. Also, they indicate a remarkable difference of the damping characteristics between the symmetrical sandwich rod and the covered one such that the latter holds geometrical similarity, but the former does not presenting instead, an optimal rod composition. Therefore, it was clarified that the damping capacity of the symmetrical sandwich rod may be reduced if the viscoelastic core layer thickness exceeds its optimum.

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This paper is concerned with the contact problem of an elastic half-space subjected to torsional moment by a rigid elliptical punch. It is assumed that the contact is completely adhesive and that the normal pressure within the contact region cannot be neglected. This problem is equivalent to a mixed boundary value problem in which the displacements are specified inside the elliptical region and the surface stresses are specified and zero outside. The problem is reduced to solving simultaneous integral equations with kernels involving Bessel functions of the first kind of integer orders. It is further reduced to solving the Hilbert problem with infinite unknown functions by using the generalized Abel transform and the Plemelj formulae. A general method for solving the problem is shown. Numerical results for contact stresses and surface displacements are shown in graphical form for various aspect ratios of the ellipse.

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In linear fracture mechanics, stress intensity factors controlling fracture behavior of materials are calculated from stress distributions acting on the crack surface by the aid of superposition even for remote applied stresses: These stress distributions, however, cannot be measured directly in the crack opening state because of the stress relief, which is seen in tensile residual stress fields for instance. In this report, such stress distributions are assessed by measuring the opening displacements along a crack under tensile loading, using the equation that was derived based on the complex-valued formulas on the stress and displacement of a two - dimensional crack. The known analytical opening displacements for cracks whose surfaces are subjected to a given stress distribution are used for numerically checking the validity of the equation. Using a rectangular specimen, it was found that this method was useful for the estimation of the stress intensity factors of central cracks opened by axial tensile loading.

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A dynamic line-spring model is proposed for the simplified analysis of impact response of a part-through surface crack in an elastic plate. Bending of the plate is considered based on Mindlin's theory. Stiffness of the dynamic line-spring is simply evaluated following the static model of Rice and Levy. The procedure for evaluating the dynamic stress-intensity factor K<Id> is developed. The response of a semielliptical surface crack in a plate subjected to impact loading at its ends is analysed by using the present model. It is found that K<Id> takes its maximum value at the deepest penetration point of the surface crack and the maximum value is much larger than that in the static case.

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CT specimens with different thicknesses and a CCT specimen are analyzed precisely using the three-dimensional finite element method in the elastic-plastic stress states. The stress and displacement fields at the crack tip are compared with the HRR singular stress field and discussed. It is found that in the CT specimens, the thickness of them are greater than those recommended by the standard of fracture toughness testing, the stress and displacement fields agree very well with those of HRR fields. For the CT specimen, the thickness of which is a little less than the recommended value, the HRR field exists only at the center of the specimen. It is shown that there exist no HRR fields in the CCT specimen though the thickness is not small.

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The stress intensity factors of rectangular plates with single - or double - edge cracks under transverse bending are evaluated by the body-force doublet method. The stress field due to a pair of point moments (doublets) in a semi-infinite plate is used to solve these problems. According to the results, the effect of plate length on K_I is less under transverse bending than under uniform tension in rectangular plates of the same form.

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In this study, the body force method is extended to the analysis of elastodynamic problems. By inserting the region in question into the adjoint region, an arbitrary elastodynamic problem can be reduced to the elastodynamic problem of an infinite body. The general integral formula is obtained based on superposition of the elastodynamic fields of a point force and a discrepancy in the time-space region. Therefore, the analysis of the given elastodynamic problem is reduced to the calculation of unknown densities of force or discrepancy distributed along the imaginary boundary. The direct or indirect methods of BEM can be regarded as special cases of the general formula proposed in this study. The effectiveness of the method is shown by analyzing an example of the elastodynamic problems of a half space subjected to uniform surface pressure.

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A determination method for assessing redrawing ratios in the production of cylindrical shells is described. The redrawing ratios are calculated from the minimax optimization of a compromise solution of multiobjective optimization theory. The calculations indicate how the redrawing ratios are influenced by a number of processing parameters and certain material properties. The resulting computer package is aimed at providing a reasonable simulation of the redrawing operation and allowing the designer to rationalize and plan the production of cylindrical cups.

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Large elastic-plastic deformation in, for example, metal forming processes has been analyzed, so far, primarily on the basis of J₂-deformation theory, especially in situation where strain localization, such as shear-band formation in a block or localized necking in a sheet, takes place. In order to improve the J₂-deformation theory, three constitutive equaitons, one of which was previously proposed by the author, are introduced. By several FEM analyses of fundamental large elastic-plastic deformations, such as uniaxial tension and simple shear, it is demonstrated that these three constitutive equaitons are equivalently effective in predicting the strain localization phenomenon even in a quantitative sense.

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In order to estimate the number of roll passes necessary to form light-gauge steels for general structures, the relationship between the share factor and the number of roll passes for various sections is investigated by arranging the data collected from several companies. Furthermore, allotment of roll bend angle at any stage is carried out under the hypothesis that the locus of the edge of the section on the horizontal plane is modified by the cubic curve. An interactive computer graphic system, which introduces a floating index in an equation, is developed, and this new CAD system enables a roll designer to engage in dialogue with the computer. The roll flower for the sash section, track sections, keystone plate and deck plate sections and pipes sections designed by this new CAD system agreed well with actual roll drawings.

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The distribution of residual stress in the vicinity of fatigue crack tips and behind them for S15C and SK-5 were measured by X-ray microbeam equipment. Fatigue cracks were loaded and unloaded and then the behaviors of opening and closing were examined analytically. The results obtained are summarized as follows. ( 1 ) A monotonic plastic zone ahead of the crack tip and a cyclic plastic zone was found in the crack tip vicinity. ( 2 ) The ratios of fatigue crack opening and closing found by X-ray measurement were in good agreement with the value found by the microdisplacement method.

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The statistical property of the fatigue behavior was investigated for heat-treated 0.45% carbon steel plain specimens. The emphasis is to investigate separately the statistical properties of the initiation and propagation of microcracks through successive observations of the specimen surface through the plastic replica method. Results show that the Weibull distribution of the mixed type is well fitted to the microcrack initiation life distribution. On the other hand, the microcrack propagation life distribution and the crack length distribution are expressed as two- and three-parameter Weibull distributions, respectively.

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Low-cycle bending fatigue tests were carried out on annealed 0.45% C steel specimens with a blind hole inside a SEM. ΔCOD was measured from SEM photographs. The small-crack growth law was discussed based on the ΔCOD. The main results obtained were as follows : ( 1 ) When strain level is constant, the shapes of the rims of cracks are geometrically similar to each other and the crack opening ratio U is nearly constant. ( 2 ) When the dl/dN's in several specimens are equal, the ΔCOD's near the crack tip are also nearly equal. ( 3 ) The phenomena mentioned above support the small-crack growth law dl/dN∝l.

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In order to clarify the fatigue damage of smooth specimens under complex loading, it is important to investigate the effect of stress change through the behavior of a small crack because the fatigue life of specimens is occupied mainly by the propagation life of a small crack. However, such studies made in heat-treated carbon steels are few. In this research, fatigue tests on heat-treated carbon steel smooth specimens under two-step loading were carried out, and the effect of stress change on the behavior of a small crack was investigated. Results show that the value of the cumulative cycle ratio Σ(n/N_f) is smaller than unity when the first stress levelσ₁ is higher than the second oneσ₂; however, Σ(n/N_f) is about unity when σ₁ is lower than σ₂. This difference in the value of the cumulative cycle ratio is explained by the behavior of a small crack after stress change. Moreover, by using the results of annealed and prestrained steels, the effect of material properties on the fatigue damage under two-step loading is also examined.

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The cyclic characteristics of the shape memory effect (SME) in Ti-Ni alloy wires and helical springs are investigated in thermomechanical cycles. In the experiment on a helical spring, an offset crank shape memory alloy heat engine is used. The results obtained are summarized as follows. ( 1 ) The nonrecoverable elongation and the recovery rate vary significantly in the early cycles, but show slight variations in later cycles. ( 2 ) The two-way strain with reversible shape memory effect increases with the number of cycles. ( 3 ) The yield stress of stress-induced martensitic transformation decreases significantly in the early cycles, but decreases gradually in later cycles. The yield stress decreases for high shape memory processing temperature. ( 4 ) The stable cyclic properties of SME may be obtained by training before practical use. ( 5 ) When the maximum shear strain on the surface of the helical spring becomes larger than 2%, the rate of increase in nonrecoverable strain becomes greater while that for axial force decreases. ( 6 ) The number of cycles to failure decreases linearly with the range of torsional strain on the surface of the helical spring.

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In order to develop the shape memory alloy heat engine, basic output power characteristics of three types of heat engines are investigated. As a shape memory alloy, Ti-Ni alloy wire with an outer diameter of 0.75 mm is used. The heat engines employed are the twin crank engine, offset crank engine and simple pulley engine. The results are summarized as follows : ( 1 ) The output power of engines increases with the hot water temperature. ( 2 ) The range of rotational speed where the output power is maximized is wide. ( 3 ) Specific output power is 1-3 W/g. ( 4 ) The maximum output power increases with the number of wire loops of the shape memory alloy. Problems in development of the shape memory alloy heat engine are fatigue strength, welding and corrosion resistance of the material, and the efficiency and mechanism of the engine.

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To know the stress and strain distributions in the brain tissue as a solid is very important for understanding the state or biomechanism of hydrocephalus. But it is impossible to measure such mechanical factors directly in the human body. This paper proposes mechanical models of the brain, whose property has not been clarified, and discusses the adequacy of the models. Computer simulations are performed under the condition that the hydrostatic pressure of the cerebral ventricle is high. Elastic models show the principal stress distributions or distributions of other mechanical factors. Elastoplastic models taking large deformation into consideration show the deformation of the brain tissue. Moreover, simulations that include the "mechanical adaptation" of the living tissue are performed in elastoplastic models. It may be supposed from the result that a mechanical adaptation acts to make the stress distribution uniform in the brain and to promote ventricular enlargement.

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