It is very important industrially to estimate the degree of large deflection appearing in such members as a plate spring, plastics and so on. In this report, the problem of large deflection of a simply supported beam in a symmetrical four-point bending test was treated. It was shown that the desired specific quantities such as the maximum deflection, maximum curvature, maximum bending stress and end slope, which are especially matters of great concern in the material testing, were able to be predicted easily from a conventional linear bending theory and three reduction factors derived here newly.
For the convenience of applications, the nomographs of the reduction factors were given graphically in terms of the vertical load, the large deflection at midpoint and the end slope.
The experiment of large deflection in which a PVC thin plate was utilized was carried out to confirm the availability of the newly proposed reduction method. The experimental results obtained were in good agreement with the predicted ones by the reduction method. Therefore, the present simple reduction method can be put into practical use.

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Uniaxial tensile strength tests were carried out on several engineering ceramics in air at temperatures ranging from room temperature up to 1600°C. The materials chosen for the present study were silicon nitride, silicon carbide and partially stabilized zirconia ceramics, which are in the process of development for gas turbine applications.
The tensile strength of silicon nitride rapidly decreased at temperatures above 800-1000°C. When the temperature rose as high as 1300°C, the strength decreased to about 10 percent of the room temperature strength. On the other hand, the strength of silicon carbide did not change appreciably with temperature. The strength of zirconia decreased with increasing temperature; at 1000°C the strength was reduced to 8 percent of the room temperature strength.

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By utilizing a simple Arrhenius-type equation, the strain rate dependence of the lower yield stress of plain carbon steels was characterized in a wide range of strain rate from a conventional low strain rate to a high strain rate (ε=10³-5×10⁴/s). For pure iron and a mild steel, the strain rate dependence was well expressed by (p, q)=(1/2, 1) when the activation energy was given by ΔG∝{1-(σ^*/σ^*_m)^p}^q (σ^*; the thermal component of the stress, σ^*_m; the σ^* at 0K). For a low carbon (C=0.1-0.2%) and a medium carbon (C-0.45%) steel, it became clear that (p, q)=(1/2, 3/2) and (1/2, 2) were suitable to characterize the dependence, respectively.
By applying the equation with (p, q)=(1/2, 3/2) to the experimental data of double shear impact tests (Campbell and Ferguson, 0.12%C steel) which are often quoted to exemplify the dislocation damping mechanism at extremely high rates of strain, the data were re-analyzed in order to discuss whether or not the strain rate dependence can be expressed by the thermally activated process. Except at 195K, the calculated rate-dependence coincided fairly well with the experimental one. This suggests that in steel, the single thermally activated process is still predominant up to an extremely high rates of strain (ε-5×10⁴/s).

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The simplified equations for estimating the J contour integral by the use of a load-displacement curve have been developed to analyze various crack problems. These equations were derived by setting certain assumptions, for example, a deep crack or a shallow crack, etc.. In this paper, the distinction between the shallow crack and the deep crack was made by paying attention to the elastic-plastic deformation behavior of cracked plates. The validity of the present equations for non-liner materials were demonstrated by comparing their prediction with the available finite element analysis results, which were obtained for different shapes of various test specimens; for example, the center cracked tension plate, double edge cracked tension plate, single edge cracked tension plate, and single edge cracked bending plate. The way to use the simplified estimating equations was given. Also, the new simplified equations for estimating the J-value were derived for elastic-plastic materials by paying attention to their elastic-plastic deformation behavior which is characterized by full yielding or general yielding.

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This paper shows a simple analysis method based on the finite element method for dynamic response of two layered laminates subjected to impact load. The two layered laminates consists of two stiff plates and an adhesive layer which connects both stiff plates. Visco-elastic characteristics of the adhesive were represented by a simple Voigt model. An experiment that a bonded beam specimen made of two aluminum strips as stiff plates was hit by an impact hammer, was conducted. Both time-deformation history at the free end and surface strains of the beam were compared with the calculated results. The comparison showed that the present method was effective to predict the time dependent interlaminar stress of two layered laminates under impact loading. The basic equations of motion for multi-layered laminates were also given in this paper.

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The correlation between the fractographic features and the underlying microstructure and the effect of impact velocity on the correlation were studied by noting the cleavage facets.
The observed cleavage facets were divided into three groups according to the features of their surfaces. The ratio of the cleavage facets made from one grain to all the observed facets decreased, the ratio of those made from a part of one grain increased and the ratio of those made from two grains and over was constant with an increase of impact velocity.
This fact is considered to be caused by the propagation and interference of stress waves. Thus, an understanding of stress waves is needed to analyze the fracture surface caused by impact loads. It was also observed that a twin parttern occasionally made a tongue or a cleavege step.

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Two kinds of carbon felt reinforced carbon composite of pitch fiber (C/C-A) and of PAN fiber (C/C-B) have been developed to improve the fracture mechanics properties of regular grade graphite. The tensile properties and the fracture toughness values of these new composites were determined as a function of temperature up to 2400°C. These results were compared with those of a carbon fiber cloth reinforced carbon composite of rayon fiber (C/C-C) and a fine grain isostatic graphite (IG-11), and these distinctive features were discussed.

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Ductile unstable failure test has been made on the high strength control-rolled steel over a wide temperature range. The effects of separation, compliance of the loading system and also temperature on the ductile unstable failure features have been investigated in detail by using compact specimens. The test results were mainly analysed with respect to material and applied tearing moduli. The main conclusions are as follows.
(1) Stable-unstable behavior is in good agreement with theoretical prediction except that material tearing modulus at instability is larger than 300.
(2) Even at the low temperature range where separation is notable, the specimen showed high resistance to tearing instability.
(3) Separation which initiated before the maximum load point, did not induce brittle fracture and also tearing instability. On the contrary, it prevents the initiation of brittle fracture by decreasing the plastic constraint.

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In fracture toughness testing of ceramics, it is well known that notch sharpness gives a large effect on the fracture toughness. In this respect, the fracture toughness tests were carried out on acrylic resin. Plate specimens with different notch sharpness were prepared. The different artificial notches were introduced into the specimens by means of micro-grinding disk, fret saw, laser machining, razor and fatigue pre-cracking. It was found that the fracture toughness K_Ic decreased with increasing the notch sharpness. As a fracture criterion, it was found that the fracture occurred when the stress at a definite point ahead of the notch tip reached the critical value. In addition, it was also clarified that the specimen thickness (5-15mm) hardly influenced the the value of K_Ic.

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Specimens of a mild steel (JIS-S20C), with a shallow notch made by cold-form-rolling, were subjected to rotary bending fatigue tests, and a large increase in fatigue strength by the rolling was exhibited. The specimen cycled to more than 10⁷ cycles at a stress just below the fatigue limit contained a stage II non-propagating crack. The limit for the formation of the crack was proportional to the hardness near the surface, indicating that the work-hardening caused by the rolling increased the resistance against the crack initiation. This effect of the work-hardening constituted about 90% of the observed increase in the fatigue limit caused by the cold-form-rolling. The cause of the appearance of the non-propagating crack was examined by estimating the relation between the crack length and the stress intensity factor range ΔK_I, taking into acount the observed residual stress distribution at the form-rolled notch. The threshold value for the crack to become dormant was about 5MPa√m. This value was close to that for annealed S20C steel, so that the effect of the form-rolling on the crack propagation resistance was not particularly larger than that of ordinary prestaining.

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The effect of stress frequency on fatigue crack initiation in 99.5% pure titanium plate, which has remarkable strain rate dependence in plastic region and notable orthotropy, was studied.
Fatigue crack initiation tests were carried out under three kinds of stress frequencies (0.2Hz, 1Hz, 20Hz). The test specimens were cut out from the rolling direction and transverse to the rolling direction of the plate. An anisotropic elasto/visco-plastic analysis was performed by the use of the orthotropic elasto/visco-plastic overlay model, and the comparison between the cycles to crack initiation and the viscoplastic strain range at the notch root obtained by the analysis was made.
The results obtained in this study are summarized as follows:
(1) It was found from the experiment that the cycles to fatigue crack initiation depended on the cutting-out direction of the specimen because of the anisotropy of titanium plate, and was approximately in proportion to fⁿ(n>0), where f is the stress frequency.
(2) A parameter related closely to the fatigue crack initiation is the visco-plastic strain range at the notch root, and the cycles to fatigue crack initiation is approximately in inverse proportion to the nth power of the visco-plastic strain range at the notch root.
(3) The effect of stress frequency on fatigue crack initiation may be explained by the variation of visco-plastic strain range at the notch root based on the strain rate dependence and the anisotropy of the material.

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In this paper, examinations have been made on the intra-specimen variability model as a stochastic model of the fatigue crack propagation rate. This model assumes that the parameter C in the Paris' law da/dN=C(ΔK)^m is a spatial random variable within a specimen. The examinations were made with respect to the following two points. The first examination was concerned with the relation between the experimentally observed inter-specimen variability of the parameters in the Paris' law and this model. When the equation da/dN=C_s(ΔK)^m_s is applied to each specimen, inter-specimen variability of C_s and m_s is observed experimentally. It is known that log C_s and m_s are normally distributed approximately and there exists a strong correlation between log C_s and m_s. This paper first examined if these experimental characteristics can be interpreted by the model. From the analysis, it was shown that the above mentioned experimental characteristics could be interpreted by the intra-specimen variability model both qualitatively and quantitatively. The second examination was concerned with the correlation distance which appears in this model. It was attempted to estimate the value of the correlation distance, and a rather large value was obtained. Thus, it was pointed out that a detailed consideration is necessary on the relation between the correlation distance and the microstructure of the material. Finally, a possibility of a modified model was suggested in which the parameter C was assumed to be a random variable among specimens as well as within a specimen.

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The relationship between the threshold stress intensity (K_ISCC) and hydrogen content in SNCM 439 steel subjected to various heat-treatments was examined. K_ISCC was obtained from the compact tension (CT) and wedge opening loading (WOL) type specimens immersed in artificial sea water. The hydrogen content in the steel was measured by an electrochemical method (Ni-plating method).
The results showed that the diffusion coefficient of hydrogen decreased and the hydrogen content increased with increasing yield strength of steel. K_ISCC decreased with increasing hydrogen content, but the relationship between K_ISCC and hydrogen content became different at the yield strength of 1275MPa. This phenomenon was discussed in relation to metallographic observation of the fractured surface of steel.

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A probabilistic method for estimating the compressive strength of concrete containing weaker aggregates than mortar matrix is presented.
At first, for the aggregate of constant size, it is proposed that the strength of concrete can be estimated by determining the effective number of weak aggregates which exist randomly in a given cross section of the specimen. Then, an experimental program is performed to prove the propriety of the proposed method and to show the necessity to take into account the size of aggregate which is not considered in Bache's empirical equation. Moreover, for the mixed aggregate of different sizes, an equation for the estimation of the strength of concrete is also proposed as an extension of the case of constant size. On the basis of the present results, the compatibility of Bache's empirical equation is discussed.

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In this paper, segregation tendency of aggregate particles with different size fractions caused by self-floating or sinking was investigated. After washing analysis of concrete samples picked from every portion in the vertical direction of a prismatic specimen, sieve analyses of fine and coarse aggregates were made and the unit contents of the particles retained on each of sieve series were determined. The segregation tendency in a portion was evaluated by the ratio (R_i) of the unit content to that in the specified mix. If the particle content increases or decreases as compared with the specified one, R_i>1 or R_i<1, and the closer R_i to unity, the milder the tendency.
The subtraction of the ratio in the top portion from that in the bottom portion was adopted as the segregation factor (SA) of the particles for the whole specimen in the height direction. If the content of particles with a certain size fraction is highest in the top portion due to self-floating and decreases down ward, SA<0, and if the content is lowest due to self-sinking and increases downward, SA>0. The higher the absolute value, the more the segregation tendency, and the distribution of the particles corresponding to SA=0 remains unchanged. The conclusions obtained were as follows;
(1) In the top portion of concrete with 25mm maximum particle size, R_i≈1 for the particles with 2.5-5mm size fraction, R_i>1 for those with smaller one than that and R_i<1 for those with larger one. The smaller the size fraction, the higher the ratio. Also, the larger the one, the lower the ratio. In the bottom portion, the opposite trend was more or less observed on the whole.
(2) In the case of concrete with 25mm maximum particle size, SA≈0 for the particles with 2.5-5mm size fraction, SA<0 for those with smaller one than that and SA>0 for those with larger one. The smaller or the larger the size fraction, the higher the absolute value.
(3) Except the particles corresponding to SA=0, the higher the maximum particle size, the slump value, the frequency and the amplitude of vibrator, the higher the segregation tendency.
(4) As the correlation was observed between the segregation indicator of concrete expressed by the ratio relative to the coarse aggregate content and the factor of the particles with each size fraction, the factor could be estimated from the indicator readily. Under the adequate consolidating condition, it was estimated that SA≈0.5 and SA≈-0.2 for the particles with 20-25mm and 0.15-0.3mm size fraction, respectively.

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The corrosion product of aluminum appearing in mortar has been studied with XRD, EPMA and EDX methods. The corrosion product consisted of two layers which were the mixtures of bayerite, hydrargillite and nordstrandite. The inner layer was gel-like in which sodium and chloride ions concentrated. The outer layer was crystalline and flake-like. Sodium ions in the inner layer reacted with Al(OH)₄^- ions to form hydrated sodium aluminate, which easily dissolved and changed to crystalline trihydrated aluminum oxide and kept the high concentration of hydroxide ions, causing severe corrosion.

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The corrosion behavior of aluminum alloys in mortar has been studied by electrochemical measurements. In mortar without NaCl, the corrosion rate calculated from the weight loss agreed fairly well with the limiting diffusion current of oxygen, and also with the passivation current. The corrosion mechanism changed from the hydrogen evolution type to the oxygen reduction type with immersion time, which brought the reduction in corrosion rate. On the other hand, the addition of 3%NaCl in mortar made the corrosion of hydrogen evolution type to continue.

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In the present investigation, composite materials consisting of the particles of SiC or Si₃N₄ and aluminum-silicon alloy were prepared. The thermal diffusivity (a) and the specific heat (c_p) were measured in the range from room temperature to about 400°C and the thermal conductivity (λ) was calculated from the relation of λ=a·c_p·ρ.
The results obtained are summarized as follows:
(1) The thermal diffusivity of each specimen gradually decreased with increasing temperature and its temperature dependence was similar to that of the aluminum alloy. The thermal diffusivity also decreased with an increase in the content of SiC or Si₃N₄.
(2) The specific heat of each specimen increased with increasing temperature and slightly decreased with an increase in SiC or Si₃N₄ content below 200°C.
(3) The thermal conductivity did not increase with increasing temperature below about 250°C, above which they started to increase gradually with increasing temperature.

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