The initiation and growth of crazes on the surface of PMMA were investigated under various levels of environmental temperature and applied stress. In this report, craze growth equations were derived on the basis of the rate process theory, considering the increase of activation energy for craze growth, and cessation of craze growth was discussed. Average craze length and total sum of craze length per unit area were calculated theoretically and experimentally and the theory agreed with the experimental results for low craze density. Crazing and uncrazing surfaces were observed by means of metallographical and interference microscopes. Slip lines were observed at the craze tip of unyielded specimens. It was found protuberances 0.1-0.2μm in height occurred around the craze due unloading.

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This paper presents the deformation and interlaminar strength in the transverse direction of carbon cloth laminated plastics. To obtain the mechanical properties in the laminated direction, a method using laminated thin walled tube specimens with fillet was proposed. The stress distributions in various specimens with fillet under tensile and torsional loads were analyzed by the finite element method. The shape of the specimen with fillet having flat tensile stress distributions were in good agreement with experimental ones under a combined stress state of tensile and torsional loads. The interlaminar strength of CFRP specimens with fillet under a combined stress was approximately expressed by Hoffman's fracture criterion. The fracture conditions of the specimens under various loadings were occurred in the interlaminar directions of laminated carbon cloths.

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Rotating bending fatigue tests were carried out on specimens of an annealed 0.42% C steel with a small blind hole at elevated temperatures of 200°C and 375°C. These results show that the small crack growth law, dl/dN=C₁σⁿ_al (σ_a : stress amplitude, l : crack length, C₁ and n : constants) holds well at elevated temperatures similarly as at room temperature. Moreover, at all of the tested temperatures, the values of ' n' in the above stated equation are nearly equal to 8, therefore, the effect of temperature on fatigue crack growth rate can be discussed through the change in C₁.

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Rotating bending fatigue tests of an austenitic stainless steel SUS304 were performed in the range of room temperature to 550°C. While the fatigue lives decreased with increasing temperature up to about 300°C, then in the temperature range of 400°C to 550°C, no decreases in the fatigue lives occurred. The preloading at 550°C caused microcrack growth at room temperature to retard or even to arrest. This retardation effect of crack growth observed at room temperature should be expected at 550°C too. It is concluded that the appearance of plateau in fatigue lives may be attributed to precipitation hardening occurring during cyclic stressing at elevated temperatures.

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Acoustic Emission techniques were applied to rapidly estimate the fatigue limits. At first monotonic and cyclic behaviors of AE were researched for S 25 C, SCM 4 and FCD 40 specimens. The first AE generating points correspond to the yield points for S 25 C spechimens in both tests. On the other hand, the first AE generating points were lower stresses rather than yield points for SCM 4 and FCD 40 specimens, which show certain turning points on log σ-log AE lines at cyclic tests. Each specimen was then fatigue tested to estimate fatigue limits. It is shown that the stresses at turning points (which mean the first AE generating points on S 25 C) in the cyclic tests correspond well to the fatigue limits for three kinds of materials containing smoothed and notched specimens.

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Attention has been focussed on the characteristics of the fatigue life of annealed low carbon steel in the extremely low cycle fatigue regime. In this regime, a transition of the fracture mode occurs from the surface to internal cracking with an increase in the plastic strain range. Results show that in this regime the final fracture occurs at a strain cycle count less than that expected from the Manson-Coffin law for an ordinary low cycle fatigue regime in which the development of small surface cracks leads to the fracture of the specimen. Such a reduction in fatigue life is caused by the cracking of pearlite inside the material at a high plastic strain range. The applicability of Miner's law to the prediction of the fatigue life under a variable plastic strain amplitude in the extremely low cycle fatigue regime has also been discussed.

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A prediction method for the erosion of mild steel by sand is studied. The prediction method is based on sand erosion results from the summation of erosion by a grain of sand and is proportional to the power law of particle diameter to erosion. Predicted erosion was compared with erosion test results which were done with a sand blast type test apparatus under a sand impact condition of 50 m/s air velocity and at 30° degrees to the test piece. Sieved sand and eleven kinds of logarithmic-normal size distributed commercial sands were used to compare calculated erosion with observed erosion. It is known that predicted erosion has an error of not over 18% for sieved sand and not over 56% for commercial sand.

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Creep of Hastelloy XR in steady and nonsteady multiaxial stress states was investigated experimentally by use of thin-walled tubular specimens at 900°C in air. The following stress conditions were applied to the specimens; (I) four kinds of combined constant tension-torsion, and (II) three kinds of constant tension superposed to cyclically reversed torsion. It was observed that, while only secondary creep prevails under steady stress conditions because of the very high test temperature, cyclically reversed torsion induces marked increase of creep strain rate (i.e., cyclic softening). However, this cyclic softening phenomenon was found to become less noticeable with increase of superposed constant tension. Moreover, the validity of Mises' flow rule was ascertained except just after nonproportional changes of stress state.

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The effect of probabilistic fiber orientations on the response of carbon fiber reinforced plastic laminated plates due to thermal load is analysed by the stochasic finite element method based on the first order perturbation technique. The fiber orientations are taken as two-dimensional spatial stochastic process, and the stochasticity is represented by a trigonometrical autocorrelation function. Numerical analyses are carried out in regard to rectangular CFRP laminated plates subjected to a uniform temperature rise or constant temperature gradient through the thickness. The variance of thermal deformation and stresses is discussed for the input statistical property of the orientations.

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This paper deals with elastic buckling and flexural vibration of annular plates whose thicknesses vary linearly in the radial direction. The annular plate is subjected to inplane forces along inner and outer edges, which vary in the circumferential direction. These problems are analyzed by the Galerkin method. Eigenfuctions of the natural vibration of a constant thickness annular plate without inplane forces are used as admissible functions. Two types of inplane forces are adopted; one with a sinusoidally varying nonuniformity along the outer edge, and the other is uniform along parts of the outer edge and zero along the remainder of the edge. The influences of the nonuniformity of the inplane forces on the buckling load and natural frequencies are investigated. It is found that the increse of the nonuniformity decreases the buckling load and the fundamental natural frequency. This tendency becomes more evident when the thickness of the plated at the inner edge is thinner.

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The buckling problem of compressed coiled springs was investigated by Haringx and that of twisted coiled springs by Hubbard. In this paper, the buckling condition of coiled springs is derived by considering coiled springs as elastic rods of equivalent rigidities. It is noticeable that the shearing-deformation of coiled springs is large enough to be taken into account in the analysis. Therefore, the equilibrium equation is set up by considering both bending and shearing deformation of the rods. The results satisfy the theories of Haringx and Hubbard. The experimental results on coiled springs under combined axial deformation and torsion shows good agreement with those predicted by the theory.

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The evaluation of moderately large deflections of inhomogeneous beam with fixed ends is presented using the Integral Equation Method (I.E.M.). The I.E.M. technique previously developed for the beam with fixed ends is here applied newly introducing internal zonal subdivisions. The nonlinearity due to fixed ends is included in the numerical method via an iterative procedure which has a numerical stability and a rapid convergence. In the analysis we consider the problem in which the flexural rigidity of the beam varies continuously along the length of the beam. A number of numerical examples of the beam with various boundary conditions are analyzed for deflections and the results are presented in the form of graphs.

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In this paper, the dynamic fracture phenomenon of a mixed mode is analyzed by using the dynamic photoelastic technique. The specimen is an obliquely cracked plate made of epoxy resin. A tensile pulse wave, whose height and width are controlled, is generated by an impact apparatus and travels through a plate. The dynamic fracture stresses and crack propagating angles for several cases are measured. These results are compared with the values calculated by the static fracture criterion of the mixed mode, that is Erdogan-Sih's criterion, and the adaptability of the criterion to dynamic fracture is discussed.

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Using the strength date of individual fiber fracture caused by the tensile-test of the bundle, a method for estimating the Weibull parameters has been proposed. This method has shown that the weakest fiber fractures firstly in a bundle, and the strength of the fractured fiber scatters by trying the bundle-test several times. That is to say, the strength is a random variable based on the concept of the order statistics, so the likelihood functions and equations necessary to estimate the Weibull parameters can be found on the condition that the fiber strength is given by a single or multi-modal Weibull distribution function. A bundle composed of ten boron fibers was tensile-tested, and the fiber strength equivalent to the first failure was calculated. The result is that the Weibull parameters estimated by the present method were almost in good agreement with the parameters obtained from the single-filament tests. To investigate the accuracy of the Weibull estimates, the present method was additionally compared with the method proposed by Chi, etc., from the simulation data on the basis of the Monte-Carlo method.

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Two-dimensional stress waves in a variety of elastic circular cylinder are analyzed numerically, when an axisymmetric impulsive load is applied to the end face of the cylinders. It is clearly demonstrated that, when the pulse length of the applied impulsive load is sufficiently short such as when a charge is detonated on the end face of the cylinder, stress distribution fluctuates violently with time, and so local parts are apt to be formed where a tensile stress arises concentrically. By examining a distribution of the maximum tensile stress arised in the cylinder, the generation of the peculiar fracture patterns to under impulsive loadings for a brittle body can be explained fairly well, whose patterns were summarized originally by Kolsky and Shearman.

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This paper deals with the stress concentration problems of an elastic strip with a pair of central notches and two pairs of supplemental notches under tension. The stress mitigations due to interference effects of stress concentrations by supplemental notches are investigated. Considerations are made for the influences of the distances between the central notches and the supplemental notches and the radii of the notches on the stress mitigations. The principle of the method of solution is to distribute body forces in the interior of a strip with no notch so as to satisfy the boundary conditions at the notches. For this purpose, we apply Green's functions for body force problems of a strip. The method of solution may be regarded as a kind of so-called indirect boundary element method with fictitious boundary.

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The tensile test is commonly used for determining the mechanical properties, especially strength, of sheet materials. In the tensile test, the top and the bottom sides of a specimen are gripped by the chucks which relatively move each other on a vertical line, without rotation. If the specimen is anisotropic and stretched along the direction different from the principal directions of anisotropy, each grip acts with not only vertical force, but also horizontal force, and no rotation of grips results to constrain the shear deformation brought about by the imbalance of strength. Horizontal force, in general, cannot be measured. Therefore, it is necessary that rotational freedom be given at each grip and that shear deformation not be constrained, but be measured. The rigorous treatment of the tensile test is described, taking the matter mentioned above into consideration. Next, the tensile test is simulated on specimens made from sheet metals showing the anisotropic property proposed by R. Hill. It does not necessarily seem to follow that maximum shear deformation always appears on specimens cut π/4 from the principal axes of anisotropy.

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In this paper, we consider the interaction between an edge dislocation, placed on the x-axis and having the glide plane inclined to the x-axis, and two circular inclusions in an infinite medium. They are placed in the order inclusion-inclusion-edge dislocation. The Airy's stress function is used with bipolar coodinates, for convenience. The solution is constructed by considering the relation between the real-edge dislocation and the imaginary one. The dislocation has a stable equilibrium position or an unstable equilibrium position at some intermediate distance from the inclusions under some combinations of elastic constants. The equilibrium positions are also affected by the inclination of glide plane.

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The synchrotron radiation source was used for X-ray stress measurement of sintered silicon nitride and alumina. X-ray diffraction was recorded with a position sensitive detector. The sin²ψ method was adopted to determine the X-ray elastic constants of the (323) plane for silicon nitride, and of the (1.0.10), (220), (146), and (4.0.10) planes for alumina. The X-ray values of Young's modulus E and Poisson's ratio ν for the (323) plane of silicon nitride were 305GPa and 0.285, which agreed with the values obtained by the ordinary parallel-beam method utilizing Cu-K α radiation. For alumina, the value of E/(1+ν) measured by X-rays decreased in the order of (146), (1.0.10), (220), and (4.0.10). This order agreed with that predicted from the elastic constants of a single crystal on the basis of the Reuss model. The measured value of E/(1+ν) decreased with decreasing purity and increasing porosity.

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In order to evaluate the fatigue fracture and the fracture toughness characteristics of rail steels, an axial residual stress determination, fatigue crack growth test, static and dynamic fracture toughness tests of samples from rails and the three point bending fatigue test of a full rail head were studied for six rail steels which differed in composition and processing histories. The rails consisted of a standard carbon rail, a full heat-treated rail, two Cr-Mo rails, a Cr-V rail and a head-hardened rail. All other rails except the head hardened rail had tensile residual stress in both sides of the head and the base, but the head-hardened rail had high compressive residual stress in the head which seemed to be desirable for fatigue and fracture toughness resistance. The head-hardened rail exhibited a high level of threshold and fatigue fracture toughness in the fatigue crack growth test, high static fracture toughness resistance and high fatigue resistance in the full rail head test. On the other hand, the Cr-V rail exhibited the most inferior characteristics in all tests. The fracture toughness values from all tests had the tendency to increase with an increase in the tensile ductility of each rail steel.

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Stress analysis of welded-type crane sheaves by measurement and the numerical analysis of the unloader traversing sheave is described. Stress of the welded joint between the web and the boss is concentrated on the loading side of the web due to the radial clearance of the roller bearing, which is well computed with gap elements by FEM. The fatigue equivalent stress during the unloading operation can be obtained from the stress range distribution which is modeled by the normal distribution. Variation of the stress range is mostly determined by the dynamic response factor of the wire rope.

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Crack energy density is the parameter which is defined without any restriction on constitutive equation and is expected to successfully describe all kinds of behaviors of a crack. In this paper, the fundamental properties of crack energy density subject to mixed mode loading are discussed and, moreover, the evaluation of crack energy density by FEM is tried. The contents are as follows; 1) It is shown that total crack energy density in an arbitraty direction ε_ψ can be separated into each deformation mode contribution. 2) It is shown that ε_ψ and each deformation mode contribution can be expressed by path independent integrals without any restriction on constitutive equation. 3) The elastic finite element analyses of ε_ψ and each deformation mode contribution are carried out using path independent integrals for a specimen under tension with a crack inclined to the loading axis. Through the results of these analyses, the evaluation method of each deformation mode contribution of ε_ψ is discussed.

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An analytical solution of the stress intensity factor for a double edge notched (DEN) specimen is first presented by using the two dimensional isotropic elasticity theory. Some approximate expressions, which have been widely used for the determination of the stress intensity factor, are compared with this solution in order to check their accuracy. Secondly, the influence of elastic anisotropy on the stress intensity factor of an orthotropic DEN specimen is examined within the framework of the two dimensional anisotopic elasticity theory. Lastly, the fracture toughness of plain weave fabric carbon fiber reinforced plastics (CFRP) is experimentally evaluated by taking into account their elastic anisotropy.

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The paper is concerned with the fracture toughness of glass fiber reinforced plastics at low temperature. By the use of compact tension specimens of a random chopped-strand SMC composite, fracture toughness tests were performed at temperatures, 298K, 200K, 77K and 4K. The main results are summarized as follows : (1) At the lower temperatures, the nonlinearity of load-crack mouth displacement curve becomes remarkable and the acoustic emission activity becomes higher. (2) From the microscopic observation, it was found that the zone of damage consisting of fiber debonding, matrix cracking and fiber breakage is formed in the vicinity of the notch tip. (3) The fracture toughness value K_AE, obtained as the stress intensity factor which corresponds to the onset of abrupt increase of the accumulated acoustic emission energy, is larger, as the temperature is lower. (4) At a low temperature, the fracture toughness value K_Q obtained by the 5% offset procedure of ASTM E 399 is extremely smaller than the fracture toughness value K_AE at the same temperature. Thus, the value K_Q could be inappropriate for the fracture toughness at a low temperature. (5) The equation involving the tensile strength of fibers is derived for the fracture toughness of the random chopped-strand SMC composite at a low temperature.

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This report studies the penetration of ductile thin metal sheet by conical bunches and tries to estimate the total work done which is absorbed during penetration. The penetration tests on circular thin sheets of mild steel, whose thicknesses are 1.0, 2.1 and 3.1mm 200mm diameter, are carried out at a quasistatical punch speed by using conical punches. The punch angles are 30, 45, 60 and 90 degrees and the point diameters of punch are 5.5 and 20mm. The total work done and the effect of plate thickness, punch angle and point diameter on the failure mode of plate and investigated experimentally. In addition, the authors present a formula for estimation of total work done for ductile thin metal sheets during penetration. By comparing estimated values with experimental ones of total work done, it is clear that the formula proposed by authors is valid for the estimation of total work done except by a large punch angle.

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Room temperature constant-loading fracture toughness tests on SUS304 stainless steel showed significant creep. Time-dependent crack growth was found in fracture toughness tests. The critical J-value at the stabilized load above which unstable fracture occurs, was significantly lower than the J_IC value. The crack growth resistance under constant-loading was also lower than that under the conventional displacement-controlled fracture toughness test. The stable crack under constant-loading seemed to propagate intermittently. The condition for general yielding of the specimen may be a necessary condition for unstable fracture under constant-loading.

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Fracture dynamics of Homalite-100, PMMA and epoxy were studied. Fracture surfaces were examined by a roughness meter to correlate the surface roughness λ with such fracture parameters as crack velocity a^^· and crack extension resistance R^*. High-speed photography of fracture caustic images gave those values. Correlations between λ and those parameters have shown that, although λdepends on a^^· or on R^*, λ is not a unique function of one of those parameters. It is found that λ has the best correlation with the product R^*· a^^·, i.e., dissipated energy per unit crack front and unit time.

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The conditions for crack propagation were varied from a constant load (or stress) condition to a constant elongation (or strain) condition while increasing a central crack length (2Co₁) from 6mm to 200mm in thin sheet plastic (Unsaturated Polyester Resin) specimens of 240mm width (2W), which were fractured under tension at room temperature. Numbers and various dimensions of fracture surface marks of both end close type (abbreviated BECM) and one end opened type (abbreviated OEOM) were measured under optical and scanning electron microscopes and analyzed. The marks observed in specimens fractured under a constant strain condition are excellently approximated by the equation of fracture marks proposed previously by us. Fracture strength and average values of their dimensions for each crack length decrease in a hyperbolic curve similar to the relative crack propagation distance at fracture W/Co₁ as the crack length increases. The experimental results for specimens having Co₁≒5.1mm, 23.85mm and 58.42mm are compared. Their dimensions and their gradients decrease as the length of the primary crack increases, and all these relations are predicted well by the equation of fracture marks.

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The ductile fracture mechanism of the in-plane stretching of 70/30 brass, OFHC copper, and 1100-O aluminum sheet alloys have been examined on the basis of fractography and modified M-K analysis. Dimples, which are a large number of elongated dimples and a small number of equiaxised dimples, and ripples are observed on every fracture site. The profiles of fracture are slant type for brass, cup-and cone type for copper, and chisel point type for aluminum. Observations of matched fracture sites by scanning electron microscope and on flow-line by optical microscope lead to the conclusion that the elongated dimples are shear dimples formed by a shear rupture toward the sheet thickness. The final strain conditions of the neck are almost identical to those assumed in the modified M-K analysis, indicating that the observed width of the fractured site is less than the theoretical one when the neck is reached under the plane-strain condition. These ductile fracture mechanisms are explained in terms of the shear deformation and dimple.

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A dynamic line-spring model is proposed for the simplified analysis of the dynamic stress-intensity factor for part-through surface cracks. A plate containing two surface cracks is modeled as a 2-D plate in plane stress with a through crack. Surfaces of the through crack are connected by dynamic line-springs distributed continuously along the through crack. In the case of static loading, the present model reduces to the static model proposed by Rice and Levy. As an example of the application of the present model, the dynamic response of a plate containing two semi-elliptical surface cracks is analysed where the plate is subjected to a vibrating stress at its ends. It is found that the dynamic stress-intensity factor takes its maximum value at the deepest penetration point of the surface crack and begins to increase markedly near the first resonance frequency as the frequency of the applied stress increases.

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The purpose of this paper is to confirm the effect of specimen length and the microstructure on the onset of precrack growth when an impact load is imposed on it. Impact, impact under static pretension and static tensile experiments were carried out using high strength aluminium alloy at 288 K and 77 K. The effect of specimen length on the critical condition for crack growth was discussed, based on the static stress intensity factor (K₁)_pre and the impact fracture stress σ_cd defined by the onset of crack growth. A linear relation between (K₁)_pre and D_f which was a summation of (K₁)_pre and σ_cd√(πa), where a was a precrack length, could be seen and this relation was independent of specimen length and temperature. Microstructural aspects near the crack tip region were also observed on the fracture surfaces. The results of microscopic deformation measured by the X-ray micro beam diffraction method and the dislocation distribution observed by TEM showed that they were almost the same at the same temperature and were independent of loading type and specimen length. Comparing above results with our previous ones for steel specimens, it is concluded that the effect of specimen length on crack growth is negligiable in the case of impact fracture when the microscopic deformation behavior at a crack tip is insensitive to a rapid stress rise, which depends on specimen length.

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J_IC tests were carried out on SUS 316 steel by means of the JSME R-curve method as well as the JSME stretched-zone width (SZW) method. The effect of side-grooves on the J_in value at stable crack growth initiation was investigated by using CCT specimens of two thicknesses (B=1, 2mm). The ratio of net thickness to gross thickness was kept at 0.5. The J_in values of the side-grooved CCT specimens of two thicknesses were considerably smaller than those of the 1TCT specimen. The J_in value of the side-grooved specimen of 2mm thickness was smaller than that of the standard CCT specimen. Further, as the thickness of the specimen becomes thinner, the J_in value decreases. In the case of 1mm thick CCT specimens with or without a side groove, the contraction percentage of thickness is very large so that it is not appropriate to use these specimens for the fracture toughness test. In the case of the thin or side-grooved CCT specimen, the J value which is evaluated from the load versus displacement curve by using Rice's formula cannot estimate the J-integral at the central part of the specimen. Therefore, a J-integral estimation method would have to be established by using 3-D elasto-plastic analysis.

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The uniaxial mechanical behavior of shape memory alloys is studied from the phenomenological point of view in the process of stress-induced martensitic transformation or of its reverse transformation. The phenomenological interpretation of the fraction of phase, which is identified as the internal state variable in the theory, is first discussed. The mechanical constitutive equation and the transformation kinetics are then proposed. They are shown to describe well such behaviors as the transformation pseudoelasticity, the partial transformation pseudoelasticity and the shape memory effect. The theory can also explain the strain recovery and the increase of the recoverable force during the heating process. The applicability of the theory is acknowledged by the numerical examples.

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In this paper, new crack elements are proposed for fracture mechanics analysis of two-and three-dimensional elastostatics by the boundary element method (BEM). In the proposed crack elements, arbitrary singularities of the stress or the traction near the crack front can be taken into account, and also the behavior of displacements near the crack front can be simulated in a reasonable manner. Three different kinds of interpolation function are used for modelling of the element geometry and the traction and displacement-variations, so that the nodal points of the crack element are located at their regular positions. Application is made to the stress intensity factor computation of some typical surface crack problems. Some interesting features are revealed through comparison of the results obtained with other available solutions.

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This paper presents an efficient calculation method which eliminates the LDU decomposition process of the stiffness matrix in numerical solutions of the finite element method (FEM). As an example, this method is applied to an elastic analysis of variable cross sectional beams. The FEM using the method decreases CPU time and memory capacity in comparison with conventional FEM using the LDU process. Moreover, the use of this method makes the FEM algorithm simple, and gives more accurate results. Therefore, this method is effective for microcomputer aided FEM.

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Many automatic mesh generators for FEM are popularly in use, but among them, the finite element approximation error is not considered. This paper is concerned with an adaptive mesh refinement for FEM, in which the finite element approximation error is considered. By the way, the interpolation error gives the upper bound of the approximation error. Here, we use interpolation error instead of approximation error, and calculate the error measure, then remesh by only relocating the nodes without increasing the total number of nodes and elements. The method is applied to 3-node triangular elements and the stress analysis of linearly elastic structures. The r-method is tested in two examples of stress analysis problems and its effects is confirmed.

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An expedient method to improve the accuracy in BEM and FEM is discussed in this paper. The concept of this method is based on the similarity of stress fields near notch roots. In this method, constant boundary elements are used for BEM and constant strain triangular finite elements for FEM. Therefore, personal computer programs can be used in order to analyze practical problems. This method is applied to some examples and its effectiveness is shown.

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In the low-cycle fatigue design based on testing of geometrically similar models, the scatter of fatigue life is taken into account using the factor for the statistical variation in test results, K_ss = 1.470 - 0.044γ, the formula given by the ASME Boiler and Pressure Vessel Code, where γ is the umber of replicate tests. In the present paper, this formula has been examined by calculating the upper confidence limit of the probability of failure P_fU for the design service cycles as determined using the above formula. It was found that P_fU varied with η and γ, where ηwas the coefficient of variation of the fatigue life. An alternative formula was proposed which made P_fU independent of η and γ.

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As many structural failures are caused by human errors, subjective uncertainties should be considered in conducting a reliability analysis. The author proposed a new reliability analysis method for structures considering objective reliability data, e.g. mean values and standard deviations of the load and/or strength, and linguistic evaluation of subjective uncertainties which were classified into three groups namely load, resistance and general. The objective data is fuzzified by a possibility function, the linguistic evaluation of each parameter is added and this method finally yields the fuzzified safety index. As the result of each linguistic evaluation corresponds to each safety index, the membership functions of the size, weight and kernel can be more easily defermined as compared with other methods. The result by this proposed method is less affected by some special linguistic values than those by conventional methods.

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Testing of Fast Breeder Reactor components is often conducted at an elevated temperature such as 550°C, where strain measurement using weldable strain gauges specially manufactured for high temperature use is costly and inappropriate for large and repeated strains. To solve this, a picture processing-utilized strain measurement method in combination with stereoscope is proposed. With this method, strain measurement of non-plane specimens can be performed remotely. A personal computer-based system that employs a solid state image sensor was also developed. The system satisfactorily distinguished marks from noise, and was easy to operate. A verification test performed on a bellows specimen showed that the strain error was reasonable considering the limitations of the hardware. The test also confirmed the validity of the present strain measurement system and the practicability of the proposed method for large strain measurement.

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There are many machine parts and structural members such as pile hammer, valve spring and power cut-off devices which are subjected to impact load. And impact fatigue failures are characterized in many cases by much shorter lives than predicted ones based on the usual life estimation technique. To prevent the failures of such parts and members, it is important to establish the design standard for the elements receiving impact load. Hydraulic-disc spring type high speed impact fatigue machine was developed using Hopkinson bar principle in order to obtain fundamental S-N data covering long life range under simple impact stress pattern. It was confirmed that the Hydraulic-disc spring device to drive an impact cylinder at high frequency gave good performance as Hopkinson bar type impact testing machine. And the feature of S-N data for two sorts of carbon steels obtained with this machine showed good agreement with the S-N characteristics of the carbon steels published hitherto.

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The Instrumented Charpy test was conducted on U-, V-, and fine notched specimens and a fatigue precracked specimen of A508 C1.3 steel and the effect of specimen configuration, test temperature and loading speed on the dynamic fracture toughness was investigated. Comparing the load-displacement curves of the U-notched and fatigue cracked specimen, the fracture toughness at the onset of crack extension was determined and proved to coincide with the lowest value of the dynamic fracture toughness. The J-integral and R-curve of the fatigue cracked specimen were corrected for crack extension by a proposed direct calculation procedure in place of ASTM's step-by-step one.

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Equipments and procedures for combined stress testing in a cryogenic state are presented. The combined axial load and torsion are applied to a thin wall tubular specimen in a cryostat. The specimen is cooled by liquid nitrogen and helium. A strain measuring system of a mechanical type is developed and the sensitivity of the system is calibrated. The cryogenic plastic behavior of SUS 304 is experimentally investigated under combined tensile stress and torsional stress. At 77 K, the plastic deformation follows the Mises low under combined stress states of tension and torsion, but the compressive flow-stress is greater than tensile or torsional. An unstable serrated flow by the proportional loading under stress control conditions is observed at 4.2 K.

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In this paper a constitutive model for cyclic plasticity incorporating the motion of the center of the loading surface and the plastic deformation-induced-anisotropy has been proposed. The Ramberg-Osgood law is applied to each cycle with respect to the current center of the loading surface. The computer simulation based on this model is verified by virtue of several kinds of experiments on type 304 austenitic stainless steel. As a result, this model is confirmed to be adequate for describing the essential features of proportional and nonproportional cyclic straining.

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The localized deformation of sheet strips of mild steel and aluminum with various thickness subjected to uniaxial tension are experimentally investigated by the use of the Moire method. These results are compared with theoretical ones calculated by the use of the elastic-plastic finite element method considering the effect of large deformation on the basis of J₂-flow theory and Gotoh's Vertex theory. The upper limit of thickness for the onset of localized necking of band-type is found to be dependent on the material properties. Gotoh's Vertex theory gives an evident localized necking of band-type in a diffusely necked thin strip, which clearly verifies its effectiveness over a large deformation range.

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