The present paper proposes a formlation simpler than previous investigations for the static bending problem of beam-stiffened elastic plates. This problem has been analyzed so far using the Timoshenko thin plate theory in which the equivalent shear force and bending moments are assumed to act to the beam stiffener. Since they include at most fourth-order derivatives of unknown displacements, at least fourth-order polynomials must be used as the interpolation functions in numerical implementation of the formulation. In this paper, the forces and moments acting between the plate and the stiffener are treated as line distributed unknown loads. The numerical implementation of the formulation, therefore, these forces can be interpolated using any type of interpolation functions. In this study, however, the resulting set of integral equations are discretized using constant elements for interpolation of these forces. The numerical results obtained by the computer code developed in this study are discussed, whereby the versatility of the proposed analysis method is demonstrated.

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Currently, in order to evaluate the residual life of a welded area of an actual boiler, the Void Area Fraction is usually measured at the evaluation points. The residual life is calculated from the life fraction Master curve prepared in the laboratory. But since such Master curves are obtained from a series of partially completed creep tests and since the effects of temperature, stress, and weld-heat-affected-zone structure have not been satisfactorily examined, a lower limit of 99% of the data band has been adopted for safety. In order to achieve high-accuracy evaluations, differences in creep void generation and growth processes resulting from differences in heat, stress, and weld-heat-affected zone structure were observed in detail. As a result, the method described below is proposed as a high-accuracy method of Residual Life Asessment. (1) Clarification of damage evaluation position. a. Evaluate the coarse-grained areas of the circumferential joints of pipes subject to internal pressure. b. Evaluate the fine-grained areas of the longitudinal joints of pipes subject to internal pressure, longitudinal joints of elbows, and circumferential joints of pipes subject to system stress. (2) Use of Different Master curves for the evaluation positions. Use the different Master curves (which was conventionally a single curve) for the HAZ fine grain section and the coarse grain section. The Void Area Fraction method is appropriate for the HAZ fine grain section, and is not appropriate for the coarse grain section.

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Interaction between plastic and creep deformation is an important matter to construct a constitutive model for viscoplasticity. Praticularly, equivalence of back stress affecting plastic deformation and affecting creep deformation takes an important role to descreibe cyclic viscoplastic deformation by a constitutive model. In this paper, to clarify the eqivalence, a serise of tests such as (1) Creep tests during pure tension and cyclic tension-compression loading, (2) cyclic tension-compression loading tests after both creep and pure tensile deformation, and (3) subsequent creep tests at a maximum stress after cyclic tension-compression loading, were carried out using Type 304 stainless steel at room temperature. The test results of (1) and (2) showed that the back stresses affecting plasticity and affecting creep have a same value. However, the difference subsequent creep curves were observed due to number of cycle of loading after the stress-strain relation were stabilized, irrespective of the same value of back stresses. Then, we tried to explaine the difference of the continuous creep curves using Bailey-Norton's transient creep law employed an activation energy.

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In this study, influence of specimen geometry on creep and creep-fatigue strength was discussed based on experimental and FE analysis results of weld joints. Increase of creep strain under the creep condition in the fine grain region is faster than that in other portion both in the standard and large size weld joint specimens. Increase of creep strain of fine grain region in the large specimen is faster than that in the standard specimen resulting in the difference of creep rupture time. It was found that difference of stress multiaxiality, which is larger in the large specimen, caused the difference of creep strength. On the other hand, failure life of the large weld joint specimen is shorter than that of the standard specimen in the creep-fatigue loading. The main crack propagated through fine grain region in the standard specimen and it propagated through coarse grain region in the large specimen. These difference can be interpreted by the difference of plastic and creep strains under creep-fatigue condition between two specimens. Failure location and life of the weld joint specimens could be well predicted by the nolinear damage accumulation model based on FE analysis results.

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Thermal fatigue damage of solder joint is considered to be closely related to microstructural phase growth. In order to evaluate the relation between the microstructural change and thermal fatigue crack initiation, thermal cycle tests were carried out by using fabricated PCB on which various chip capacitors were mounted. Following results were obtained through the microstructural observation. The phase growth is characterized by phase growth parameter S which is defined as average phase size to the 4th power d⁴ and proceeds such that S increases proportional to the number of thermal cycles N. Furthermore, there exists simple relation between average number of cycles to thermai fatigue crack initiation N_i and average increase in parameter S_c per one cycle 〓S_c, where S_c is component of S, represents strain induced phase growth and corresponds to total equivalent creep strain approximately. That is, power law relation 〓S_c=CN^-β_i is found out. The relation enables us to evaluate the thermal crack initiation of solder joint based on the observation of microstructural evolution.

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The influence of dual phase microstructure and TiAlN films on the fatigue mechanism of TiAl intermetallic alloy coated with TiAlN film by the physical vapor deposition (PVD) was studied in vacuum at 1073 K from the view point of mesoscopic size which is 1 μm-1 mm size range. The crack initiation and crack growth was observed and photographed under high resolution condition using elevated-temperature loading cyclic stage for the scanning electron microscope. The results indicated that the fatigue strength of coated TiAl alloy was higher than that of uncoated TiAl alloy at an elevated temperature. TiAlN films reduced plastic deformation and crack initiation in γ phase. Therefore the fatigue process of coated TiAl alloy was dominated by initiation and growth mechanism of some mesocracks, which is 200-300 mm length. The fatigue property of coated TiAl was controlled by meso-structure, which was composed of films and substrate.

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Mode II fatigue crack growth behaviors were investigated with two kinds of unidirectional carbon/epoxy laminates, M 40 J/2500 and T 300/3601, under constant 〓K_II conditions. The crack growth tests were conducted with end notched flexure (ENF) speciments. Tests were carried out from 1 to 20 Hz at a load ratio of 0.5 either in air or in water. In M 40 J/2500 laminates, either in air or in water, the crack propagation rate was almost constant with crack extension, and the crack growth was cycle-dependent. The crack propagation rate in air was almost identical to that in water. In T 300/3601 laminates, either in air or in water, the crack propagation rate was also constant with crack extension, and the crack growth was time-dependent. The crack propagation rate in water was faster than that in air, and it increased with prior-immersion period in water. The crack propagation rate at 70°C was slightly higher than that at 25°C.

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Rotating bending fatigue tests were carried out on semi-liquid die casting aluminum alloys. Compared with the conventional casting, the semi-liquid die casting could reduce cast defects and porosities of casting aluminum alloys, and could miniatureize structrue size, therefore fatigue life of semi-liquid die casting aluminum alloys were expected to be improved. And fatigue crack initiation sites were alternative of cast defects and eutectic silicon particles. According to crack initiation sites, the crack initiation life varied, and crack propagation property depended on the form and the distribution of eutectic silicon particles. Therefore the fatigue strength of aluminum alloys was higher in turn of the semi-liquid die cast material that cracked from eutectic silicon particles, the same material that cracked from porosity and the conventional die cast material (AC 4CH). As a result, as to aluminum alloys, the fatigue life was estimated from the crack initiation life and the crack propagation life, and obtained fatigue life prediction gave good agreement with the experiment value.

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In this paper, a versatile method for a quarter-infinite body with a corner crack of an arbitrary shape is proposed under two types of pressure;which are constant and linear. And new numerical results are obtained in many cases. Fatigue crack propagation from a corner crack is analized successively with the present method. Moreover, a stress intensity factor of a corner crack is proposed in a simple form for an arbitrary shape.

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Solution of the mixed boundary value problem for thin plate bending with two external force and two displacement boundaries is derived. General solution is derived using a rational mapping and complex stress functions. A semi-infinite plate with two displacemen constraints within a semi-elliptic notch under uniform bending is considered as an application. Stress distributions, stress intensity of debonding at the tip of the displacement constraint, stress concentration factors at the bottom of the semi-elliptic notch, and stress intensity factors when the semi-elliptic notch is changed into an edge crack are calculated. Besides, a general solution for one external force boundary and one displacement boundary is also derived.

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In this study, generalized stress intensity factors K_{III, λ4} are calculated for a V-shaped notched round bar under torsion using the singular integral equation of the body force method. The body force method is used to formulate the problem as a singular integral equation, where unknown functions are densities of body forces distributed in an infinite body. In order to analyze the problem accurately, the unknown functions are expressed as piecewise smooth, functions using a fundamental density and power series, where the fundamental density is chosen to represent the skew-symmetric stress singularity of the form 1/γ^1-λ4. Then, generalized stress intensity factors at the notch tip are systematically calculated for various shapes of V-shaped notches. The accuracy of Benthem-Koiter's formula proposed for a circumferential crack is also examined through the comparison with the present analysis.

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We propose a neural network technique for estimating precisely the stress concentration factor of specimens with arbitrary configuration parameters, based on the finite number of values obtained discretely by Body Force Method. The validity of values estimated by the neural network technique is checked and confirmed by treating a problem of 60 degress V-notched cylindrical specimens under tension as an example. Finally, we make it clear how to select the rational training data necessary to train the neural network.

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Inelastic deformation of 316 FR stainless steel under biaxial ratcheting and nonproportional straining is discussed based on viscoplasticity theory by Krempl. It is pointed out that the multiaxial ratcheting can be regraded as a special case of nonproportional loading and that the simultaneous modeling is necessary for the both behaviors. In the one of the author's previous study a viscoplastic constitutive equation was developed for nonproportional loading based on the viscoplasticity theory proposed by Krempl. An idea similar to Ohno-Wang model for ratcheting is used to extend this previous model and a viscoplastic constitutive model is developed for biaxial ratcheting and nonproportional loading. A critical value is assumed for the dynamic recovery of thekinematic hardening parameter. It is also assumed that the activating the dynamic recovery of the kinematic hardening reduces the additional hardening under nonproportional loading. It is shown that the developed model well reproduces both biaxial ratcheting and stress response under nonproportional loading.

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Three-dimensional viscoelastic FEM code was developed to simulate thermoforming processes of polymer sheet. The integral constitutive equation known as the K-BKZ model, where the stress is considered the integral of the time domain and some functions, is adopted and the model is newly formulated to solid element. In order to adequately represent the real physical response of polymers, the entire domain history is needed to keep in memory to carry out the integration. A scheme to optimize time step of memory function is proposed. Thermoforming of a circular cup and traveler's case were simulated and compared with the experimental results. The validity of this method is demonstrated by comparing the experimental results.

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This paper presents the study on the stability of a clamped elliptical plate on the elastic foundation subjected to uniform compression in the middle plane of the plate according to the ordinary thin plate theory. The analysis is rigorously made by the use of Mathieu functions and modified Mathieu functions which are the solutions of the equibrium equation of the buckled plate. The stability condition equations are derived by applying the orthogonality of the Mathieu function. The calculated eigenvalues of buckling are given in tables for various aspect ratios and dimensionless foundation moduli.

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In order to clarify the conditions for fracture morphology of monolithic ceramics subjected to a solid particle collision, the stress analysis of ceramic circle plate subjected to compressive contact load by a small ball was carried out for the various circle plate thicknesses. The maximum stresses of three critical points were compared in the relation with the plate thickness. As fracture criteria the stress intensity factor on the basis of stress distribution were analyzed for each critical points. The behaviors of fracture morphology depending to the plate thickness were successfully clarified by estimating K_I for fracture criteria. On the basis of small ball collision test results, the collision velocity, which converted from impact load, can express the conditions for the fracture morphology. The critical collision velocity is found to change depending to plate thickness and fracture toughness of ceramics.

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Two methods (IT-a and IT-b methods) for estimating temperatures in steady wave fronts in a thermo-viscous material are established. To this end, two irreversible thermodynamic equations for the temperature in the wave front are derived under the fundamental assumption that the material in the wave front is approximately in an equilibrium state. In addition, heat transport is neglected in the IT-a method, while in the IT-b method, the work done by the thermal stress is offset by heat transport. The two equations are connected with the Hugoniot function and the Mie-Gruneisen equation, respectively. The efficacy of the two methods is examined qualitatively by three temperature distributions estimated qualitatively using three equations for entropy which include no assumption on heat transport, the assumption used in the IT-a method, and that in the IT-b method, respectively. These three distributions suggest that the temperatures are overestimated by the IT-a method, while the IT-b method is effective if the effect of viscosity is distinguished.

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In the Previous study, two Inside Temperature (IT-a and IT-b) methods for estimating the temperature distributions in steady wave fronts in a thermo-viscous material were established and the IT-b method was shown qualitatively to be effective if the effect of viscosity was distinguished. In this paper, these two methods are applied to the shock compressions of Yittria-doped Tetragonal Zirconia (YTZ) that is a thermo-viscous material with a multiple shock Hugoniot. The YTZ Hugoniot consists of three partial curves including two kinks, that are the Hugoniot Elastic Limit (HEL)and the phase transition point. The shock temperatures evaluated by the IT-b method were close to the accurate temperatures obtained by the Shock-Temperature method in the whole stress range to 140 GPa examined here. Furthermore, the inside temperature distributions were approximately accurate because the effect of viscosity was distinguished in the shock compression. By these facts, it was considered that the fundamental assumption and the assumption on heat transport used in the IT-b method were valid and as a result, this method was effective. In addition, the influences of heat transport on the temperatures and thermo-elastic stresses were examined.

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Development and utility of a novel three-dimensional dynamic contact algorithm based on an approximate Riemann solver to define contact forces are discussed. According to the resulting solver a smooth force field which prevent Lagrangian grids from overlapping is obtained by numerical iterations. Though the proposed method evolves from a hydrocode slideline methodology in the 60's, it has not recourse to the master-slave treatment which may cause numerical instabilities when the element size of the slave (impactor) element is larger than the one of the master (target) element. The method is implemented in an general-purpose explicit Lagrangian program. Numerical results are presented for a series of test problems and are compared with theoretical solutions as well as with these obtained by the penalty method.

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In this study, the element free Galerkin method is applied to the structural analyses which has material or geometrical discontinuity. The conventional element free Galerkin method, the first mesh free method proposed by Belytschko et al. in 1994, has an advantage that the continuous displacement derivatives are obtained due to the moving least squares interpolation for the approximation of the field function. Therefore, in order to evaluate discontinuous derivatives, the special treatments should be given at the discontinuity and the penalty method is adopted in this study. The proposed method is firstly applied to several structural analyses including material discontinuity and the appropriate size of domain of influence and the effect of nodal distribution as well as the accuracy of the method is investigated. Finally, it is applied to a geometrically nonlinear analysis of membrane structure, which has discontinuous slopes, and the effectiveness of analyses using the present method is demonstrated.

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A diamond-like carbon (DLC) film is mainly composed of both sp³-bonded atoms as in diamond and sp²-bonded atmos as in graphite. Many reports concerning their mechanical and tribological properties have been published, while there have not been enough studies on deformation mechanism yet. In the present paper, the change of bonding form under uniaxial loading is investigated using the molecular dynamics. From uniaxial tension analyses of the DLC film obtained by the random walk method, the content rate of sp³-bonded atom decreases as opposed to that of sp²-bonded atom under the tension. The morphological changes of bonding which are accompanied by the annihilation and the generation of the bonding forms are observed. Moreover, rearrangement of bonding caused by the combination of these changes is confirmed. By these changes, local atomic environment which includes the back-bond interaction comes to stabilize energetically. The first peak of the radial distribution function has almost the same position between the initial state and the loading state of ε₁1=0.1. Therefore, it is concluded that bending and torsion effects between atoms induced by the employed interatomic potential are more predominant rather than bond-stretching under the deformation. However, the well-established Tersoff type potential for diamond structure cannot represent its torsion effect which has been acknowledged by the molecular orbital calculations.

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The relationship between mechanical properties and microstructure, especially volume ratio of Pearlite and Bainite, has been investigated. Using three type of specimens which have experienced different heat-treatment, tensile properties and fracture toughness (K_IC)have been evaluated. The tensile strength and elongation of 50% Bainite mixed structure showed the mean characteristics of Pearlite and Bainite, while its 0.2 proof stress showed similar value of Pearlite. The result of COD test showed that the charactristics of mixed structure is closer to 100% Pearlite, which is due to the plastic deformation of Pearlite at the edge of crack. Such difference of fracture mechanism is considered to cause the above results described.

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The cross section of main frame structure is preferable to be a cylinder for plants and animals in order to adapt to their environment. There are some exceptionals. One of those is a hemp palm branch. It has an up side-down isosceles triangular shape. Since the hemp palm branch has unusually large leaves and a relatively slender branch stem as compared with other trees, the branches must be subjected a large twisting moment. A triangular cross section reinfored by a functionally graded distribution of fibers must be a solution for that problem, which can reduce the induced stress. This paper presents a torsional analysis of a triangular bar based on the 2-layerd model. Deriving an analytic solution using conformal mapping and complex warping function, the stress distributions and torque were computed. The two layerd bar reduced the maximum shear stress as compared with the one of a homogeneous bar.

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A tilt-disk offset crank heat engine using shape memory alloy was developed and output power characteristics of the engine were investigated. The output power characteristics were discussed based on the thermomecanical properties of shape memory alloy. The results are summarized as follows. (1) The output power characteristics are prescribed based on the properties of recovery stress which appears in shape memory alloy. (2) The equation describing the influence of center distance of two disks, inclined angle, heating temperature and velocity of air flow on output power was proposed based on the properties of the recovery stress. The output power characteristics are expressed quantitatively by the proposed equation. (3) The relationship on output power is useful for development and design of a shape-memory alloy heat engine.

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