To evaluate the strength of cast iron on very small samples, an experimental study was performed on the influence of test piece dimension on the tensile strength and its scattering. Tensile tests on numerous specimens of 2 mm and 8 mm in diameter revealed that the average strength does not vary significantly with the test piece diameter, however, in gray iron, the scattering is large in small specimens. Weibull's formula of size effects does not apply, but Daniels theory on the strength of bundles of threads applies better. In ductile iron, neither the average strength nor the scattering is affected by specimen diameter, as the scattering is caused by variations in material strength.

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Dimensions of fracture surface marks of mostly one end opened marks (like parabolas) observed in a central notched sheet material of polymethyl methacrylate (abbreviated as PMMA) fractured in tension are measured using optical microphotographs. Those dimensions are an interference appearing distance (e-value) and a minimum chordal length at the secondary nucleus (l-value) of a mark. The e and l values increase as the primary crack propagates. The number of marks and heir density in a unit area increase as the primary crack propagates. The both end closed marks (like ellipses) and one end opened marks observed in PMMA are analytically expressed by the equation of marks using the e and l values and other necessary constants. The critical distance d--value, that is, the distance of the primary crack activating the secondary crack nucleus, is also calculated from the measured e-value by the equation of marks and the other constants. The variation of dynamic stress intensity factor K_D and the dynamic strain energy release-rate D_D due to the primary propagation are calculated. The experimental variation of e and d-values are shown to be supposedly controlled by these K_D and D_D values.

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Supersaturated solid-solutioning alloys of the Al-Cu system of up to 8at%Cu were prepared by means of heat treatments under the pressure of 5.4 GPa and the temperature of 720 °C for 10 hours. The elastic constants of the specimens obtained were measured by a three dimensional resonance method. The Young's modulus E and shear modulus G of the solid solutions were increased with Cu contents, and such features related to the number of electrons per atom ratio were discussed by free electron theory. The specimens of solid solutions were then isochronally aged up to 450 °C, and the variations of the elastic constants were measured step by step. The maximum shear modulus was observed during the precipitation of the θ' phase at 300°C-aging. Temperature coefficients of the moduli were also measured on the several specimens of different treatments.

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Pulsating compressive fatigue tests were conducted by using single-edge-notched specimens of a low-carbon steel under in-plane four-point bending. The development of crack growth was studied both experimentally and theoretically. Under cyclic compression, a crack initiated at the notch root, and then stopped at a certain crack length. The relation between the crack growth rate and the effective stress intensity range for short cracks at notches was identical to that obtained for long cracks. The crack opening stress calculated from the stress distribution at the applied minimum stress agreed with the experimental data except near the threshold. A method was proposed to estimate the upper bound of the non-propagating crack length.

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This paper deals with the dynamic interaction among penny-shaped cracks by radial shear impact load. Laplace and Hankel transforms are used to reduce the mixed boundary value problems to a set of dual integral equations. The solution is expressed in terms of a Fredholm integral equation of the second kind, having a kernel with fast rate of convergence. A numerical Laplace inversion technique is used to recover the time dependence of the solution. The dynamic stress intensity factor is determined, and its dependence on time and the geometry parameter is discussed.

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From the line image of the surface fatigue crack path, three parameters which showed the features of the crack shape and length were defined and measured as the crack deflection ratio, the initiation angle and the propagation angle. The rotating bending fatigue tests in a high cycle region were carried out for three metals, low carbon steel with four grain sizes, copper and austenitic stainless steel which had different crystal structure and slip character. The parameters measured for each metal were investigated in the relation to metallurgical structures. As a result, the parameters, especially, the crack initiation angle and the propagation angle represented well the effects of slip character and grain size respectively. The statistical scatters of the crack initiation lives and the crack propagation rates were discussed by using the parameters of crack path with regard to metallurgical factors.

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Recently, core based specimens have been proposed for standard fracture toughness testing rock, in a draft of the testing standard of the International society for Rock Mechanics (ISRM), which recommends two chevron-notched specimens. In this study, fracture toughness tests, according to the recommended testing procedure, were conducted on chevron-notched core based specimens of granite. In addition to these specimens, straight-notched core specimens with three different geometries were also tested, where the J-integral approach and AE technique were used to determine fracture toughness and the effect of specimen geometry on fracture toughness was examined. As a result it was found that the ISRM test method yields inconsistent fracture toughness values depending on the specimen geometry. Finally it was shown that the J-integral/AE method as applied to straight-notched specimens provides a suitable evaluation procedure for the fracture toughness testing of rock. Furthermore, the test method developed in this study was applied to other brittle materials which were nuclear grade graphites and mortar.

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Finite element methods are applied to calculate the squeeze effect of lubricant filling in semi-ellipitical surface cracks under unloading. The two-dimensional Reynolds equation for the lubricant and the three-dimensional elasticity equation for the surface crack specimen are solved simultaneously using an incremental iterative scheme. Although the external stress is zero, the crack opens due to the pressure rise caused by the squeeze effect. For shallow and deep semi-ellipitical surface cracks, the pressure distributions are roughly the same as in the case of a through crack in a thick plate. When the crack depth compared with the surface length is large, since the pressure of lubricant increases and the compliance of the crack opening displacement with the pressure decreases, the stress intensity factors due to the squeeze pressure are kept unchanged.

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A steady-state thermal stress problem is solved for a semi-infinite plate with a thermally insulated circular hole when a finite segment of its straight edge is heated with a prescribed temperature. Both the temperature and stress solutions are constructed by summing the temperature and stress fields due to point heat sources and loads distributed inside the hole. The intensity of heat sources and loads are determined from the boundary conditions on the hole using the least squares method. The boundary conditions on the straight edge are satisfied exactly. Extensive and detailed numerical calculations are carried out to clarify the effects of the length of heated segment and the distances of the hole from the straight edge ad the center of the heated segment on thermal stress concentration. The results show the power and flexibility of the method.

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Simplified inelastic methods of analysis are used to reduce the number of locations in a structure requiring detailed inelastic analysis. Three simplified inelastic models are proposed to calculated an inelastic strain range Δε_in produced in cyclic elastic follow-up process. Uniaxial cyclic elastic follow-up tests were carried out on SUS 304 steel at 700°C. The analytic model consists of elastic plastic material with/without strain hardening and stress relaxation to σ_r after a certain period. The parameters needed for analysis of the inelastic strain range Δε_in are stress ratios ξ(= σ_n/σ^^-_y), ζ(=σ_r/σ_y), and an elastic follow-up strain amplification factor p. A dimensionless inelastic strain range can be expressed by Δε_in/ε_y = (1+ζ)(1+p)(ξ-1). The shakedown condition in a structure can satisfy the following requirement ; ξ≤1. Using the relaxed stress based on pure relaxation tests makes the estimation of Δε_in/ε_y more conservative.

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Fundamental equations based on the linear-thermoviscoelastic theory were established to obtain the residual stress and deformation by cooling in a multi-layer laminated beam. The transient thermal stress distribution and deformation in an epoxy resin/Al alloy laminated beam during the cooling process were calculated using these fundamental equation, then these beams were actually subjected to the cooling process. The experimentally obtained values revealed a high level of correlation with values theoretically calculated by the thermoviscoelastic analysis. The results demonstrate the nesessity of thermoviscoelastic analysis for obtaining the residual stress and deformation by cooling of multi-layer laminated beams made of thermosetting resin.

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By observing slip lines in a copper foil with grown grain structure, the method of measuring cyclic stress acting on machine elements is studied. The features and distinction of this method in comparison with the copper electroplating method or the method using a recrystallized foil are examined. This method is superior to the method using a recrystallized foil from the point of ease of measurement and the strain sensitivity is much higher than that of the electroplating method. As an application of this method, the stress concentration factors in various types of circular shafts with a flat part under cyclic torsion are obtained, and the results are in good agreement with those obtained previously.

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A stress sending Si chip utilizing the piezoresistive effect of Si single crystals has been developed. This chip can measure 3-dimensional stress components, σ_x, σ_y, σ_z and shear stress τ_xy in the chip surface. The stress sensitivity is 0.1 MPa in the range of -100 MPa to 100 MPa. Temperature sensors are arranged in the chip and they have linear response between -100°C and 200°C. This chip is useful for the structural design and reliability tests of IC packages. The residual stress in a chip after the die bonding process is measured using this chip. It is found that rubber paste is useful in reducing stress in that process.

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As a basic study for the establishment of an accuracy estimation method in structural analysis using the zooming method, this second report deals also, as previous report, with the finite element analysis of the problems of transverse bending of thin, flat plates. In the previous report, we treated a small hole, if it was in a plate, as a hole. This treatment inconveniently led to an increase of nodal points and hence to an increase of the size of the system of simultaneous linear equations and computation time. To overcome this inconvenience, we propose in this second report a method where small holes are neglected and the whole region is divided into elements of nearly equal size at the initial two or more analyses prior to the start of the zooming process. But approximation error due to the neglect of small holes must be added to the error of the zooming method with consideration of holes. A computer program using this proposed method was developed and applied to several problems. The usefulness of this method was illustrated by these application results.

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A unified constitutive model and a continuous damage law are applied to analyze the deformation and life-time on 21/4 Cr-1Mo steel under time-varying temperature. The extended viscoplasticity model and the incremental life prediction law are employed and their material constants are determined at the temperature of 25°C to 600°C. Creep, tensile and cyclic loading tests are carried out under various temperature histories. The responses to sudden changes of temperature in the tensile tests are rather similar to those observed previously in the strain rate change tests. The viscoplasticity model is shown to reproduce the inelastic stress-strain behavior in the experiment, and its coupling with the damage model simulates the creep-fatigue damage accumulation of cyclic thermal fatigue tests.

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The present paper proposes a new law of cross and rotational hardening of yield surface in a form including the anisotropic hardening law of plasticity given in the first report. The kinematics of the yield surface are represented in 6-dimensional linear stress vector space. The evolutional equations for anisotropic hardening as well as isotropic and kinematic hardening are given in a unified form. The validity of the present theory will be confirmed by comparison with the previous experiment in a tension-torsion problem loaded along a strain path with a corner.

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In this paper, the theory is developed for the elasto/viscoplastic response of a transversely isotropic thick-walled spherical shell subjected to radially symmetric impact loadings. The dynamic response is studied by applying the theory of rays, which gives rise to the exact solution of the transient response. Numerical results are shown for internally applies pressure with a step function. The results show that the elasto/viscoplastic wave speed in a transversely isotropic sphere is not faster than the elastic wave speed.

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