This paper presents the shrinkage behavior of unidirectionally reinforced plastics with glass fibers or carbon fibers in the hardening process. The matrix material is vinyl ester resin. The strains of fibers in the reinforced plastics during the hardening process were measured by strain gauges bonded on the surface. The shrinkage amounts in the hardening process were estimated by the apparent change of the density. The hardening model of fiber reinforced plastics was proposed, including the constraint effect of hardening the resin. The shrinkage strains calculated with the model were compared with the experimental results.

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According to the development of treatment of spinal deformity, information of the accurate three dimensional configuration of vertebra is needed. The accuracy of the measured locations and rotational angles by the developed photogrammetric system is studied. Errors are classified into three factors : The first is on the accuracy of the three dimensional reconstruction of location from two X-ray films. It is defined by the reference frame, calibration markers and reading of the landmarks using a digitizer. The second is on the calculating accuracy of a personal computer. This affects especially the calculated result of rotational angles. The third is on the identification accuracy of bony landmarks. They are recognized not as the point but as the region where the bone density is higher than the adjacent portion. The results show that the overall accuracies of the system are 1.5 mm on the location of the vertebral center, and 4° on the rotational angles of the vertebra.

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Fatigue crack growth retardation and complete arresting were experimentally observed in the CT specimens of grade A ship steel after compressive overloads were applied on the upper and lower sides of the ligament instead of loading at the pin positions. The degree of retardation depended on the magnitude of the compression and the crack arrested immediately after the compressive overload, K_OL/ΔK_base < -2(σ_c < -100 MPa), contrasting to the tensile overload case, K_OL/ΔK_base > 3, where the crack arrested after growing by a small amount. The current crack closure model admits of compressive yielding near the crack tip even when the load is suppressed. Additional compressive loads, hence, proceed to the compressive yielding and increase the compressive yield strength there, which causes the slower crack growth associated with less reversed plastic zone size ahead of the crack. Compressive pre-strain also raised the compressive yield strength in the material : slower growth rates, about 1/5 of the original rates were measured on the pre-strained specimen for -485 MPa.

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For the prevention of fatigue fracture, the prediction of the fatigue crak growth path is an important item. This paper deals with a fundamental study of this problem. Fatigue crack growth tests were carried out on SM 41 steel compact tention type specimens having drilled hole and the influence of hole location upon the crack growth path is investigated. The method of solution is based upon an application of Murakami's method, a convenience method for stress intensity factor solution by the finite element method. Solution results depend on mesh size that is crack growth size per one stage. The prediction of the fatigue crack growth path by a numerical approch using the finite element method agreed comparatively well with the experimental data.

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Flight-simulation tests were carried out using 2024-T3 specimens with constant gust cycles, and with the addition of a single overload at either the beginning or the end of each flight. Also, the effects of the stress level of the ground load on the fatigue crack propagation behavior were examined. The purpose was to reveal crack growth interaction effects (retardations and accelerations), and to measure the crack opening stress under variable amplitude loading, which might support crack growth prediction techniques. From the experimental results, the following conclusions were obtained. The crack growth retardations can occur by sequence effects. The crack propagation rate was closely related to the crack closure behavior of gust cycles in flight-simulation tests. The fracture surface transition from tensile mode to shear mode cracking was observed.

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Spheroidal graphite cast irons with both (a) as a perfectly cast pearlitic matrix structure and (b) as a predominantly ferritic matrix structure were austenitized, oil-quenched and tempered to the same hardness level. After heat treatment (a) is considered to have graphites compressed by the matrix, and (b) is considered to have graphites existing more loosely. With these samples, fatigue tests were carried out in order to investigate the effects of elasticity and compactness on the fatigue strength of spheroidal graphite cast iron. The following expected results were obtained : (a) had higher fatigue strength than (b) by about 24%, and the hypothesis proposed by the author was confirmed.

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Near-threshold fatigue crack growth behavior for SB 42 carbon steel and SUS 304 stainless steel was investigated at elevated temperatures of 200 and 400 °C at a frequency of 50 Hz. A new test procedure was attempted in order to avoid crack closure : ΔK was decreased under increasing minimum load while maintaining maximum load. A unique ΔK_th-value of about 2.8 MPa·m^1/2 was obtained independently of material and temperature by the closure-free test. The crack growth rate, however, was found to be accelerated in the ΔK region higher than 4 MPa·m^1/2 for both materials at elevated temperatures. The fractrographic features influenced by microstructure and environment were discussed in terms of the mechanism of crack growth.

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In the present study the effect of overstress on a non-propagating crak is investigated on the specimens with a small hole (dia. : 100μm, depth : 100μm). The effect of overstress on the behavior of the non-propagating crack under the first stress level is larger in this type of specimen than in the plain specimen. This phenomenon is closely related to the length of a non-propagating crack formed under the first stress level. This experimental result suggests that the existence of defects is more dangerous under varying stress amplitude than under constant stress amplitude. Moreover, the crack closure behaviors before and after overstress were measured by the S shaped unloading curve method in order to explain the effect of overstress.

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By using the extended body force method, a simulation analysis of fatigue crack propagation was carried out to investigate the delaying effects of overloads on fatigue crack propagation. It is shown that the transitional behavior of fatigue crack propagation after overloads can be demonstrated by the analytical results of the plasticity induced crack closure. The crack closure behavior after overloads was explained simply by taking into account the changes in δ^max_tip and δ_{R, tip} during the transitional process, where δ^max_tip is the crack tip opening displacement at the fully loaded state and δ_{R, tip} is the total thickness of the stretched meterial remaining on the upper and lower surfaces at the crack tip. The retardation of crack propagation due to overloads was discussed quantitatively based on the results of the present calculation. For the single peak overloads the δ^max_tip just after the peak overload is proposed to correlate the number of delay cycles for various combinations of load levels.

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This paper is concerned with the connection between the several analyses of plasticity induced crack closure which have been developed so far based on the Dugdale model. The simulation analysis developed by Newman can leave several stretched elements in the wake of an advancing crack tip. From this simulation analysis, when ΔK is constant the stretched material remaining at the upper and lower crack surfaces becomes constant, and when σ_∞ is constant it becomes proportional to the length of the crack. This means that the closure behaviours of the former can be represented by the constant residual stretch model in which the residual stretched material is assumed to by constant along the crack surfaces, and that the closure behaviours of the latter can be represented by the proportional residual stretch model. When the load is small, both the results from the constant residual stretch model and the proportional residual stretch model are close to the results obtained by Budiansky-Hutchinson analysis. Especially, if the stress ratio R<les>0 and σ_∞/σ_S tends to zero, all results are close to the result of Budiansky-Hutchinson analysis for the case of R=0.

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An experimental method for finding the A and N values of fatigue in ceramic radial turbine rotors is considered in this paper. In brittle materials like ceramics, slow crack growth behavior can be expressed by υ=A·K_I^N, where υ is crack velocity, A and N are constant, and K_I is stress intensity factor. These A and N values must be found in order to predict fatigue life. Rotating fatigue tests were, therefore, performed under constant stress using radial turbine rotors made of silicon nitride, and the A, N values were determined from the relation between fatigue life and survival probability. Considerable differences were found to exist between the A, N values obtained by these radial turbine tests and those obtained by tests using test pieces.

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The reliability evaluation system for ceramic gas turbine was developed. This system combined the results of a finite element stress analysis with a probabilistic analysis of ceramic structure. In this system, a new probabilistic method was used to estimate time or cycles to failure of multiaxially stressed ceramic structures.

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This work is concerned with the determination of transient thermal stress in a long circular cylinder inserted into a short rigid heated circular ring. It is assumed that a circular cylinder is perfectly bonded to a rigid ring. The problem is formulated in terms of a dual integral equation which is reduced to that of solving a simultaneous algebraic equation using the Fourier transform and Neumann series. The radial, hoop, axial and shear stresses have singularities at the end of a short rigid ring on a cylindrical surface. The factors are defined to evaluated the singularity of stresses ; and the relations between these factors are derived.

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In general, the stress at the first root of the ridge in a bolt seems to be beyond the yield stress. But the fastened parts which are made of ductile material have generally enough strength, since the regions deformed plastically may be limited around the root. In the case of evaluating the strength for dynamic load and cyclic load (fatigue strength) or the strength of the bolt made of high strength material, however, the stress concentration factor at the root of the ridge must be estimated correctly. In this paper, an analysis is carried out with a high accuracy for the case of bolt being both tensioned and fastened in order to obtain elementary knowledges concerning the stress concentration of the screw thread. The effects of the root radius and the friction coefficient of the contact surfaces upon the stress concentration at the root of screw thread are examined on the basis of the results by an axi-symmetric FEM which can deal with a three-body elastic contact problem.

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Large deformations of a fiber-reinforced straight beam with a central step attached on the beam bottom is analysed in the framework of the theory of ideal fiber-reinforced composite materials. The beam is reinforced in its axial direction and simply supported in two ways ; (A) with horizontally movable supports and (B) with fixed roller fulcrums. The equiliburium condition of the part of the beam corresponding to the step edge is reduced to a Fredholm type integral equation of the second kind with respect to the curvature radius of the uppermost fiber.

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The finite three-point bending of a cross-ply fiber-reinforced beam with an edged crack is analysed in the framework of the theory of ideal fiber-reinforced composite materials. The beam is reinforced in its axial and lateral directions and simply supported at its ends. Its deformed configurations are compared with those of a uni-directionally fiber-reinforced beam of the same dimensions. The results of the analysis are shown in figures with and emphasis on the crack opening angle and the singular fiber stress at the crack tip.

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In this paper, L shape joints, which are subjected to a bending moment in plane, are analyzed numerically by the finite element method proposed in the previous paper. The resultant shear stress at the adhesive layer concentrates at the boundaries between the adherend plates. The values increase with the decrease of the ratio h/t (h : the thickness of adhesive layer and t : the thickness of adherend plates). These results are compared with Yamaguchi's theory proposed previously. It is obvious that he theory is too approximate. On the other hand, a practical L shape joint test, of which the adherend is an aluminum plate and the adhesive is an epoxy resin bond, is performed. The joint strength are also compared with the values estimated by using the finite element method and the corresponding fracture criteria.

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The grain-size dependence of the strain-hardening exponent is experimentally investigated and is expressed as a simple power function of the mean-grain size, d_m, as n_{2, 3}=A(d_m)^B, (A, B : const.), where n_2.3 is the strain-hardening exponent obtained in the plastic strain range larger than about 4% in engineering sheet materials of copper, 6-4 brass, aluminum and a mild steel of SS41. Substituting this relation into the equation of σ_f=Kε_p^n_2.3 (K : a function of d_m), flow stress, σ_f, of these materials can be successfully expressed as a function of plastic strain, ε_p, and the mean-grain diameter. Another equation of σ_f=K'(a+ε_p)^n' where n' is the strain-hardening exponent (K', a : functions of d_m) is also applied to experimental data and their correlations with the values obtained in these equations are shown. A theoretical flow-stress equation containing a geometrically-necessary dislocation density, ρ^G, and a statistically-stored one, ρ^S is modified and it predicts the experimental grain-size dependence of strain-hardening exponent, n_2.3 in copper and 6-4 brass excellently. Is is also shown that the flow-stress dependence on the mean-grain diameter and plastic strain is satisfactorily expressed by these equations with copper.

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This paper is concerned with the compression experiment of carbon steel square pipes each with a circular hole in a short column range, supported with spherical seats. Consideration has been given to the diagram which is the combination of the analysis based on the energy method with the experimental result. The measurement reveals that this diagram is good design data, and is in good agreement with those obtained experimentally for a short column range. It was found that the agreement with those obtained experimentally for a short column range. It was found that the maximum compressive breaking load decreased as the opening ratio increased. Breaking of these carbon steel square pipes occurred as the local buckling of the flat wall with a circular hole.

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Stiffened aluminum-alloy plates under impulsive water pressure were tested, in order to obtain useful design data about elastic response, compared with the case of equal peak static pressure. Using test data, experimental equations about impulsive pressure and deflection were determined by substituting measured water contact conditions and viscous damping coefficients into them, respectively. In case of irregular impulsive pressure, statistical frequency analyses were pursued between pressure and deflection to certify their linear relation. Total responses, therefore, are given by summing up the response due to each pressure having a natural frequency obtained from the irregular pressure. Deflections and stresses are confirmed as showing about a 30 percent increase compared with the static case if the acting period impulsive pressure nears the natural frequency period of the stiffened plate.

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In ductile fracture, voids near a crack tip play an important role. From this point of view, taking into account the effects of microvoid nucleation and growth, a large deformation finite element analysis has been made to study the deformation, stress and strain, and void ratio near the crack tip under mixed mode plane strain conditions. The result shows that (i) the upper part of a crack tip sharpens while the lower part blunts, (ii) a field near a crack tip can be divided into four characteristic regions (the K field, HRR field, Blunted crack-tip field, and Damaged region), and (iii) the strain and void volume fraction become concentrated in the upper part of a crack tip with an increasing Mode II component.

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The J-integral resistance curve method is applied to RIM-polyurethan from which the skin layer is removed, as a porous and polymeric material. We have studied how the fracture toughness J_in and J_c values are affected by temperature and void. It is found that the stable fracture appears in the temperature range from -40 to 20°C and that the unstable fracture appears in the temperature range from -120 to -60°C. The J_in values are almost constant in the temperature range from -40 to 20°C and the J_c value have a maximum value at the temperature of about -60°C. It is considered that the ductile-brittle transition point exists at a temperature between -60 and -40°C. The J_in values increase with an increase of void content from 5 to 17% and decrease with an increase of void diameter on a constant void content at a temperature of 20°C. The J_c values decrease with an increase of void content from 5 to 17% and are not affected by the void diameter on a constant void content at the temperature of -80°C.

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The constitutive equations of unidirectionally fiber reinforced metals were derived. A modified fraction model's concept was applied to matrix and fiber separately. Additionally, equilibrium and compatibility were considered between matrix and fiber for deriving constitutive relations. The proposed theory is expected to describe the inelastic behaviour of FRM, and the strain rate dependency of stress-strain relations.

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Static and dynamic tensile tests were performed on unidirectional born/aluminum composites and cross-ply laminated plates. Static and dynamic stress-strain curves were obtained and the effect of the strain rate of the tensile strength was investigated. The 0° and laminated specimens showed no strain rate sensitivities regarding tensile strength : but in the case of the 45° and 90° specimens, the tensile strength increased as the strain rate increased. The previously proposed constitutive equations for unidirectional fiber reinforced metals were modified to take into account the strain rate controlled uniaxial tensile tests. The calculated results were compared with the experimental results. It was confirmed that the proposed constitutive equations gave a reasonable prediction of the stress-strain curves.

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The Stretching of peripherally clamped, thin, circular discs over rigid, cyrindrical punches is studied by means of an Updated Lagrangian type finite element method. The analysis is based on the elastic-plastic membrane theory ; it accounts for finite strain and displacement and embodies the classical J 2 flow law and the J 2 deformation theory. The geometry of the punch face varied between a hemispherical and a relatively shallow spherical (flat-bottomed) cap. Three models were employed to account for friction at the interface of the punch and disk. These were a no-friction, a full sticking condition and Coulomb friction hypothesis. The disk fails by excessive thinning. The region of strain localization and the rate at which the local neck grows are influenced by the punch geometry and the interfacial frictional conditions. The Coulomb friction and full-sticking models promote the formation of a local neck, and this is further accelerated the flatter the base of the punch. The material property n-value also affects the local neck. The calculations support the hypothesis that the higher the n-value, the better the material distributes the strain. It is also demonstrated that the result is not much affected by the different material models (J 2 F and J 2 D).

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A new form of integral constitutive equation for uniaxial stress conditions derived from the endochronic theory is shown to predict with computational ease cyclic plasticity of stable materials subjected to symmetric stress or strain loading. The detailed procedure to determine material constants is also given in this paper, based on the derived integral stress-strain relation. Close agreement between theoretical prediction and experiments for SUS 304 stainless steel and normalized mild steel shows the validity of the present constitutive modeling.

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A modified fraction model, which is one of the viscoplastic constitutive models, can be extended to represent the cyclic hardening or softening behavior of material by introducing the concept of a nonhardening strain region. The procedure for determining the material constants of the model is precisely described through the example of 21/4 Cr-1 Mo steel at 600°C. The data required for determining the material constants are the rate dependent stress-strain curves and the cyclic hardening or softening behavior of the material. Several example calculations and comparison with the test data have revealed that the proposed model can represent the plastic, creep and plastic creep interaction behavior of the material as well as the cyclic hardening or softening behavior in the viscoplastic regime.

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The backward extrusion of high-density polyethylene is experimentally investigated with relation to the effects of extrusion ratio R, semi-cone angle α of the punch nose, and extrusion rate V. The appearance of the extrudates was observed to be greatly affected by R, α and V ; it went bad as R or α increased, or V decreased. Dead material was formed only when α>75° and acted as a tip of the front end of the punch. Extrusion pressure P increased as R increased, but decreased as V increased : it was also affected by α. The tensile strength of the extrudates increased as R increased in the axial direction, but it was little affected by R in the hoop direction.

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The hydrafilm extrusion of high-density polyethylene (HDPE) is investigated and its behavior is compared with that of pure hydrostatic extrusion at extrusion ratios up to 11 and temperatures up to 100°C. Because of the use of a minimum amount of oil as lubricant and pressure-transmitting medium in hydrafilm extrusion, a serious problem of instability or stick-slip phenomena in the polymer extrusion was experimentally proved to be minimized. Also studied was the effect of the extrusion rate, which became more notable with the increase of the extrusion ratio. Billet temperature rise was found to affect the extrusion behavior to a great extent. The range of the extrusion rate for stable extrusion is delineated for a given value of the extrusion ratio.

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The dynamic elastic-plastic buckling behavior is analyzed numerically for a bar with initial deflection, whose end is struck by a rigid heavy hammer. The bending moment for each cross-section is evaluated by integrating the stress distribution over the section. The governing partial differential equations are approximated by means of finite-difference equations. It is shown that compressive and tensile plastic regions appear at the middle length of the bar even if the struck end remains elastic. The limiting velocity, which corresponds to the incipience of plasticity, for the bar of the large initial deflection or slenderness ratio is found to be low in comparison with one for a straight bar. The numerical results are in good agreement with the experimental results on aluminum bars.

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