Wrinkling of webs, such as papers, films and endless belts, is a serious problem in the operation of web handling machinery. In the paper-making process, out-of-plane deformation of webs, which will develop into wrinkling, often occurs owing to, e. g., low applied tension, misalignment of rolls and partial shrinkage of webs. In the numerical prediction of web wrinkling, we frequently encounter many difficulties in obtaining proper solutions, since the process of wrinkle development is highly nonlinear and unstable. This paper proposes a new analytical approach of web wrinkling which guarantees the stable calculation. The key for the stable calculation in the present geometrically nonlinear FEM is a novel numerical algorithm that the generalized inverse of the stiffness matrix is introduced when the calculation approaches the onset of buckling. Using this analytical method, numerical calculations were conducted on the deformation behavior of papers in a drying section of a printing machine, and also in an endless belt of a paper-making machine. The numerical results have shown a good agreement with the experimental observations.

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The Free Mesh Method (FMM), which is a kind of meshless method, is well compatible with parallel computing because it creates local elements around each node independently, and does not need global node-element connectivity data. The FMM using Delaunay tessellation to create local tetrahedral elements is here employed for the three dimensional stress analysis. When the traditional displacement method is used in the formulation of FMM (namely displacement based FMM), in which tetrahedral linear clement is employed as temporary local element, the accuracy is often poor. To improve the accuracy, a mixed formulation based upon the Hu Washizu's principle is combined here with FMM (namely Mixed FMM). Stress analyses of a cantilever beam under tip load are performed, by using displacement based FMM and Mixed FMM respectively. The results of the analyses are compared, and the remarkable improvement of accuracy of the latter is shown, compared to that of the former. Also, it is shown that the accuracy is of nearly the same grade as that of FEM using the 2nd order tetrahedral elements.

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In this paper, a new method to produce the functional continuum is proposed. The method is a topological optimization technique based on the function of a continuum and is composed of three steps. First, an initial mechanism model, which conforms to the given function, is determined using the Evolutionary L System (ELS). The ELS is a technique to obtain the optimum shape using L system and the genetic algorithms. The obtained mechanism model is changed to a framed structure as Rahmen model in the second step. The cross-section and length of members in the framed structure are optimized to maintain the original design requirement. In the final step, the framed structure is changed to the functional continuum using some well known shape optimization techniques. This method is applied to two problems of functional continuum. The first problem is to produce a device of which the displacement expands into the same direction. The second problem is to produce a microgripper of two fingers for the use in the medical fields. From the results, it is obvious that the proposed method is very useful to produce the functional continuum.

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Plate and shell structures with stiffeners are frequently adopted to acheive huge and light structures. A new design technique so called as growth method, which acheives a minimum compliance design, is suggested to obtain optimal layout pattern of the stiffeners for the plate and shell structures. The growth method starts from seed points distributed in advance, and grows gradually the stiffener layout along the grid nodes of the finite element by taking into account the design sensitivity of stiffener cross section. The method is applied to decide optimum layouts of stiffeners for square plates undr distributed and concentrated loads, and validity of the suggested technique is discussed.

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In this paper, a method for calculating the stress concentration factor or stress intensity factor is proposed and applied to the problem of the effect of gripped part in a plate specimen. This method is based on the combination of FEM and BFM (body force method). In this method first a given problem is analyzed by FEM and the surface stresses on an imaginary boundary including the source of stress concentration are calculated. Secondarily, BFM is applied to the partial body whose boundary is the imaginary boundary. In the analysis the boundary condition is given by the surface stresses on the imaginary boundary obtained by FEM. Because the accuracy of FEM on the imaginary boundary is comparatively high and the accuracy of BFM is extremely high, the accuracy of this method is high.

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In case of homogeneous isotropic half-space, the plane strain problem which a normal load is applied as the step function for the time on the surface is known as "Lamb's problem". To solve this problem H. Lamb performed the inverse transforms of the stress solution given as the Fourier and Laplace double transform by using the Cagniard method and deduced a closed form solution. Even if the material is inhomogeneous, the closed solution is obtained if the governing differential equation can be transformed by carrying out an appropriate coordinate transformation to be able to apply the Cagniard method. Here, as a comparatively easy impact problem the stress field for the case of generating SH elastic wave in a linear gradient inhomogeneous half-space is analyzed using the Cagniard method, and the inhomogeneous properties of this material subjected to the impulsive load are examined.

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Linear stress analysis without body force can be easily solved by means of the boundary-element method. Some cases of linear stress analysis with body force can also be solved without a domain integral. However, domain integrals are generally necessary to solve the linear stress problem with complicated body force distribution. This paper shows that the three-dimensional linear stress problem with complicated body force distribution can be solved approximately without a domain integral by the triple-reciprocity boundary element method. In this method, the distribution of complicated body forces is interpolated by integral equation. A new computer program is developed and applied to some problems.

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A plastic constitutive theory incorporating the directional dependence of the plastic strain increment dε^p on the stress increment dσ' was proposed by Goya and Ito. The expression was given in terms of two transition parameters μ(α) and β(α) which denote the magnitude and the direction angle of the plastic increment, where α denotes the direction angle of the stress increment measured from a particular direction n_N, named "natural direction", in which the direction of the stress increment coincide with that of the plastic strain increment. In this report, a computer code for a finite element polycrystalline model is used for the numerical investigation of the variation of the two constitutive parameters μ(α) and β(α) of anisotropic plastic materials. The results show that the approximate functions for the two transition parameters are numerically determined and the direction dependence rule can be naturally extended for anisotropic plastic materials. It is also suggested that several quadratic functions used for classical plastic potential may be introduced for the natural direction potential whose normal is identical to the natural direction.

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The roughening topography on the free surface of polycrystalline metal has important information for understanding the microscopic inhomogeneous deformation as well as the tribological behavior during metal forming processes. In the present study, three-dimensional surface roughening topographies of aluminum sheet in the deformation patterns with different strain ratios are investigated. The deformation with different strain ratio is achieved in the stretch forming test by using the specimens of different shapes. The three-dimensional filtering operation is applied to the measured topography, in order to distinguish the waviness and the roughness. By the newly introduced evaluation technique of the inplane anisotropy of the roughened shape, the differences in the characteristics of surface topography in various plastic deformations are well characterized. The influence of macroscopic deformation pattern on the roughening topography is also discussed concerning the deformation of respective grains.

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In this paper, a series of experiments, which showed the interaction between plasticity and creep, were carried out and the unified constitutive model was proposed. First, experiments such as pure tension, pure creep, cyclic loading, intermittent creep during cyclic loading and subsequent creep after cyclic loading were conducted using Type 304 stainless steel at room temperature. Then considering the equivalence of back stresses in plastic and creep deformations, the unified constitutive model was constructed and using the proposed model the experimental results were well simulated.

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In this study, the fatigue test has been carried out to investigate the effect of plastic deformation value by roller-working on the fatigue strength of notched specimen. Herein, the authors have tested four types of specimens whose deformation values have been changed by roller-working and final shape and dimensions are the same. The reason why fatigue strengh changes with different plastic deformation value, has been examined by analyzing the residual stress, hardness distribution and crack tip opening displacement etc. The main results obtained in this test are as follows : (1) The resistance of the fatigue crack initiation increases with the increase of plastic deformation value. (2) When deformation value becomes too large by roller working, the residual stress may be released by cycle stress and the critical stress of non-propagating crack tip opening becomes decrease. (3) The fatigue limit of notched specimen by roller-working tends to deteriorate gradually when the plastic deformation value becomes too large, the optimum deformation value would exist for improvement of fatigue limit of notched specimen by roller-working.

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This paper describes the shape memory effect of TiNi fiber reinforced/epoxy matrix smart composite on enhancement of its mechanical properties, especially fatigue resistance. Fatigue crack propagation behaviors are investigated by using the originally developed method of fine-grid which was engraved on the epoxy resin surface by photo-etching. The effects of pre-strain value in TiNi fiber on fatigue crack propagation and then, the decreasing crack propagation behavior in the very local domain region around the embedded TiNi fiber are investigated in detail by using fine-grid method. The retardation of fatigue crack propagation is attributed mainly to the compressive stress field in the matrix due to shrinkage of the prestrained TiNi fibers above A_f temperature. The local crack retardation at the interface region very near the TiNi fiber is experimentally confirmed by the change of local crack tip strain behavior. From crack-tip strain hysteresis in one load cycle, the compressive stress induced in the matrix and following fatigue crack closure phenomena play a key role to suppress the crack tip stress intensity and these fatigue crack propagation retardations. The comparison between the theoretical prediction and experimental results also is discussed.

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Damage evaluation method for 316FR stainless steel based on micro crack growth behavior has been investigated to improve the life prediction method for high temperature plant. Micro-crack growth was observed in the early stage of life in the coarse grain material even at lower strain ranges. On the other hand, crack growth started in the later stage of the life at lower strain ranges in the fine grain material. The initiation life of 0.2mm length micro-crack could be evaluated by a creep-fatigue damage estimation method using the ductility exhaustion method. In this evaluation, initiation life of 0.2-mm-length micro crack in pure fatigue and creep test was used to calculate the fatigue and creep damage. Crack growth life was also able to predict by a crack growth analysis based on nonlinear fracture mechanics. The failure life of the specimen was determined by the summation of initiation and growth life and this prediction was confirmed to give a reasonable accuracy. Micro-crack initiation and growth is the main mechanism of damage in creep fatigue and lives of real components strongly depend on their allowable crack size. Therefore, the life prediction method will be rationalized by relating the life or damage evaluating in the method with micro crack length as mentioned in this study.

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Two kinds of the as-received and the heat treated structural steel, the nickel chromium alloy and the copper alloy were selected for this investigation. The rolling contact fatigue tests with specific sliding 0, 3, 9, 20 and 30% were carried out measuring tangential force. The pulsating compression fatigue tests and the completely reversed torsion fatigue tests were carried out too. The effect of tangential force on the fatigue limit under the rolling contact fatigue were investigated. The relationships of the fatigue limit among the rolling contact fatigue, the pulsating compression fatigue and the completely reversed torsion fatigue were examined on the basis of the stress analyses under the contact surface. Then the fatigue limit p_s under the rolling contact fatigue could be estimated from the tensile strength σ_B, the yield stress σ_B, Young's modulus E and the coefficient of friction μ as p_s=0.07σ_B√(E/σ_y)(1-3μ).

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In order to clarify the fatigue behavior in a wide life region, fatigue tests in the life region of N=0.5∿(10)⁹ were performed for high strength steel of SUJ2, by means of a multi-type testing machine developed here. Thus, it was found that the S-N curve in the medium life region can be straightforwardly extrapolated to the low cycle region and connected to the static strength which provides the fatigue strength at N=0.5. It is another finding that S-N property of this steel in such a wide life region was successfully explained as duplex S-N characteristics corresponding to the surface induced fracture and interior inclusion induced fracture with a fish-eye, respectively. Characteristic fracture surface so-called fine granular area (FGA) was formed in the vicinity at the inclusion at the center of the fish-eye. Consequently, the long life fatigue fracture of this steel was caused through three different processes of (1) formation of FGA, (2) crack propagation to form the fish-eye and (3) rapid crack propagation to cause the catastrophic fracture.

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In this study, fatigue reliability of halogen free substrate noticed as an environmental harmony type printed circuit board backing was evaluated. And, the examination was demonstratively carried out on the difference of failure mechanism in fatigue breakdown and static destruction from the mesoscopic viewpoint. (1) There was a difference in both fatigue life, though mechanical property of halogen free material was almost equal to that of halogen material. That is to say, the fatigue life of halogen free material was longer than that of halogen material. (2) In halogen free material, the crack was comparatively generated in initial stage in fatigue life. In the meantime, in the halogen material, it immediately came to rupture, when crack was generated, and it was frailly destroyed. (3) From the fractographic study, it was indicated that the difference in fatigue life of halogen free material and fatigue life of halogen material was controlled by the difference of size (Unit Fracture Area) of the characteristic destruction pattern. (4) In fatigue breakdown, matrix resin is a weakest link. In the meantime, the effect of the difference of matrix resin does not appear in the static destruction in the sake glass fiber strength (that is to say, it is a strongest link).

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Recent development of OIM (Orientation Imaging Microscope) makes the measurement of crystal orientation easy and advanced computer technology allow us to conduct a detailed stress analysis of component with microstructure. In this study, a high cycle fatigue test was carried out for a copper polycrystal, where the shape and orientation of each crystal is measured by the OIM. 13PSBs are found along the grain boundaries, and the location and slip system are different from those expected by the Schmid factor. FEM analysis is conducted for the copper polycrystal with the same orientation and shape. It reveals that the increase of resolved shear stress, τ_rss, of specific slip system due to the constraint of deformation between grains causes the unique slip behavior near the grain boundary.

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A processing technique for Ceramic Matrix Composite (CMC) was developed using a polymer impregnation and pyrolysis method and the CMCs consisting of 2-dimensional SiC woven fabrics and SiC matrix were fabricated using this technique. Density and bending strength of the CMCs increased with the progress of the densification by repeating the impregnation and pyrolysis of the polymer and reached 2.24×(10)³kg/m³ and 520MPa after 9 densification cycles, respectively. Several tests were performed on the CMCs to investigate the basic properties. It was expected by the test results that the CMCs obtained by this processing technique had the excellent properties as heat resistance materials, which can be applied to large plane structure components.

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The interlaminar fracture toughness of carbon-fiber/epoxy composite laminates was investigated over wide ranges of loading rate, G=(10)^-1∿(10)⁷J/m²/s, and mode ratio, G_II/G_I=0∿∞, to study the effects of strain rate and mode mixture on micro- and macro-scopic fracture behavior. The MMF (Mixed Mode Flexure) and MMB (Mixed Mode Bending) specimens were employed to determine the mixed mode fracture toughness. The mode I, mode II and their mixed mode fracture toughness, G_IC, G_IIC, G_c, at the onset of crack growth was dependent on strain rate regardless of mode ratio; the fracture toughness at impact strain rate was about 10∿32% lower than the local maximum value at static strain rate. The mixed mode fracture toughness, G_c, obeyed the linear fracture criterion except for the region of low mode ratio, G_II/G_I≤3, and high strain rate, G≥(10)²J/m²/s. The microscopic fracture morphology was mainly dominated by the debonding of fiber/matrix interface at lower strain rate, whereas it was dominated by the cohesive fracture of matrix resin at higher strain rate.

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Dual phase stainless steels consist of the ferrite and austenite phase and have high strength and corrosion-resistance. They are often used for offshore structures. Microscopic stress is generated because of the difference in mechanical properties of each individual phase. In this study, X-ray diffraction technique and the theories of micromechanics models were used. Distributions of macrostress, microstresses and plastic strain near ground surface were investigated. Specimens ground in the Up-cut and the Down-cut direction with various depths of cut were prepared. In the results, residual tensile stresses in the ferrite phase increase with the depth of cut. However, the stresses in the austenite phase were independent of depth of cut. Furthermore, change of phase stress during bending tests were evaluated; the difference between experimental and theoretical results increases when tensile stress increases. It was concluded that the misfit of plastic strain is an important factor for deformation behavior of dual phase stainless steel.

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Matrix hybrid composites to improve mechanical properties and vibration damping properties at the same time have been proposed. High damping properties were confirmed by improving flexibility of matrix resin system and it has been confirmed to appear the shear deformation in the flexible matrix layer to be easy. This concept is applied to fiber/matrix interface, and the composite material that forms a flexible interphase has been developed. The porous material where the gap lies can improve the vibration damping. By setting up the gap in the composite material, it is also possible to urge the shear deformation, for high vibration damping to appear, and to reduce the weight of the structure. Therefore, this method is extremely effective to a high specific strength and a high specific rigidity. In this research, GF/PP foam composite materials which was the porous material had the structure to fix the glass fiber with the polypropylene was targeted. The flexural properties and the vibration damping properties that these possessed were examined based on the density distribution by which the foam rate was changed. In addition, the GF/PP foam sandwich laminates was proposed and the influence that the density distribution in skin and the core layer gave to various mechanical properties was examined.

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In this paper, the theoretical solutions for an circular lining tunnel under inclined to the far-field principal stress are presented. The rock, which is permeated by fluid, is assumed to behave as a poroelastic material with compressible constituents. And the circular lining is considered as a clasical elastic material. The poroelastic solutions are derived in the Laplace transform space, and are transformed to the time domain using an approximate numerical inversion technique. Several mumerical examples are shown by graphical representations.

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The stress-focusing effect in a solid sphere under instantaneous uniform heating is studied on the basis of the generalized thermoelastic theories, i. e. the Lord-Shulman (L-S) and the Green-Lindsay (G-L) theories. The combined governing equations of both theories are solved by the numerical inversion of Laplace transform. Calculations have been performed to exhibit the radial distributions and time variations of the radial and hoop thermal stresses on the basis of the L-S theory. The effects of the thermomechanical coupling and the relaxation time on the stress-focusing phenomena as well as the singularity of stresses are discussed.

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This study describes a reliability estimation method for the frame structures based on an adaptive importance sampling simulation. Both Normal and Non Normal probability distributions are treated in the original basic random variable space. First introducing a preliminary sampling simulation process for estimating the failure probabilities, the sample means and variances of the respective failure domains, several dominant failure modes are selected. For the selected failure domains, the local importance sampling densities are determined so as to have the same parameters as the estimated sample means and variances respectively. Then a multi-modal importance sampling density is constructed as a composite of the weighted local importance sampling densities by weighting the failure probabilities of the selected failure domains. The importance sampling simulation is carried out to estimate the structural failure probability and the respective local importance sampling densities are updated in the simulation process. Numerical examples are presented to show the validity of the proposed method.

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