In this paper, the Finite Element Method (FEM) and the previously proposed inverse theory for bimorph piezoelectric actuators are applied into a real time control algorithm of connected piezoelectric actuators. Most control schemes handle an entire system in series, which becomes a drawback when some elements lose their function in a higher redundancy system. On the other hand, the FEM can handle the system in parallel by subdividing it into discrete finite elements, and can cope with flexibility in the change of form and material properties. Noncompatible finite elements are used to express the actuators in the control algorithm, and empirical formulae considering time-dependent charactristics such as creep and residual stain, are also implemented. A real time FEM control system, which consists of a PC, a bipolar DC unit and a signal-distributing controller, is developed. The system is verified by experiments on quasi-static displacement control of connected piezoelectric actuators. The results show the possibility of highly accurate, real time control of the atcuators using the FEM.

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The injection-molded sheets of Polypropylene were used in this study. The tensile damage property in relation with the inner microstructure was examined on the testing temperatures ranging from -30 to 50°C and different rolling ratio. The results are following as: (1) For the injection molded speciment treated by rolling the crystal structure has been broken together with the specimen material softens. The hardness of fracture surface and inhomogeneous distribution of orientation has been improved and the fracture surface becomes more uniform. (2) For the tensile testing of unrolling specimen under the temperature below 10°C, the strain within 10% is probable to the brittle fracture. However, the rolled specimen has a high stretch ratio at a relative lower temperature (-30°C) and the yield stress and the stretch ratio become higher with the increase of the rolling ratio. (3) For low rolling ratio the improvement of the mechanical property is impossible. However, the crystal was broken on the high ratio (60%). Because the non-crystal around crystal section became a more uniform, the orientation of molecular link was improved. It results in the increase in the plastic characterization and strength. (4) It is effective methods that increase in the material strength and ductile property by rolling processing. For low temperature, the obvious effect was understood as opposite to high temperature.

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Effect of the stress amplitude on the fatigue property was investigated on the injection molding PP. The experimental conditions were designed as follows that the load was sin wave of 5 Hz, the ratio of stress was 0.02, temperature was from -10°C to 25°C and the stress amplitude was a range of 8∼26 MPa. In order to determine the change of the material property in the fatigue process, the change of dynamic visco elasticity E' and tan δ was continuously measured. The results are following as (1) the fatigue property was very influenced by the different three-layer structure in skin, intermediate and core of injection molded specimen. (2) for the fatigue test at room temperature, the increase in stress amplitude resulted in decreasing in E', the increase in tan δ was gradated rapidly, and the damage produced a trend from the brittle fracture to the ductile fracture. The damage of specimen passed through three steps of the origin, development and propagation of the crack on the low stress level, but the large stress companion with heating quickly resulted in high temperature tensile damage on the high stress level. (3) for the fatigue damage at low temperature (10, -10°C), the damage mechanism on the low stress level was the same as that at room temperature, however, the damage mechanism on the high stress showed a strong trend of the brittle fracture. (4) the fatigue damage mechanism of the polymer materials is strongly depended on the environment temperature and stress amplitude.

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The method of caustics in combination with a Cranz-Schardin high-speed camera was utilized to study dynamic crack propagation in PMMA. Stress intensity factor K_ID was evaluated in the course of crack propagation which included crack acceleration, deceleration and re-acceleration in one fracture event. Crack velocity a and acceleration a were also measured to correlate with K_ID, and the following findings were obtained : (1) K_ID was an increasing function of a, but their relation was not unique. (2) For a constant velocity a, K_ID was larger when the crack was decelerated than when it was accelerated. (3) K_ID was dependent on both a and a, and K_ID for a constant acceleration a could be uniquely related to a.

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To improve the fatigue reliability for Mn-Si-C Steel by an environmentally sound surface modification, the influence of the modification on fracture mechanism was studied experimentally. The fatigue properties of Mn-Si-C Steel are found to be obviously improved by a Super-Rapid Induction Quenching, so that they can no longer be estimated by using a concept of "S-N Globe" which has successfully been applied to many surface-treated materials. The detailed observations have revealed that fatigue crack initiation in a Super-Rapid Induction Quenched specimen occurs in a hardened region near surface not in a subsurface region with virgin microstructure. The fatigue crack was induced by slip in the ferritic matrix. And the fatigue crack propagation in the hardened reagion was restricted by the presence of the martensite phase and compressive residual stress. Such a crack initiation mechanism is different from that previously observed in other surface treated materials, explaining the reason why the S-N Globe concept can not be applied to the present case.

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Estimation for surface properties has been studied for diamond-like carbon coated PEEK [poly (etheretherketon)]. Especially, Relationship between DLC coating and impression patterns in the hardness test were experimentally investigated. As the results, Vickers hardness of DLC coated PEEK increased. It was found that the factors of the increase of Vickers hardness occurred because of lower shearing force by high hardness and low friction of DLC film. Impression patterns at hardness test were classified into the following three types. Type I;Cross type occurred by viscoelasticity, Type II;Lozenge type occurred by viscoplasticity, Type III;Crack type occurred by overload. These impression patterns were depended on indentation.

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Surface crack growth behavior of a Si₃N₄ plate from small pre-indentations was investigated under ball-on-plant contact. The cracks located in the border of contact area were observed, where the cracks were little affected by the fluid pressure by "hydraulic pressure mechanisms". Near surface contact stresses under the spherical Hertzian contact were calculated. The crack growth behavior was discussed in terms of the calculated contact stresses and the stress intensity factors under sliding-including-rolling contact and under rolling contact. The cracks were observed to grow in the parallel direction and in the perpendicular direction to the motion of the ball, which indicates that the cracks are predominantly propagated by the contact stresses in the border. The stress intensity factor ranges, ΔK_II, ΔK_III, and the maximum value of K_I, K_Imax increase with the increase in crack length both under rolling contact and under sliding-including-rolling contact. It was found that the crack growth is controlled by ΔK_II combined with K_Imax and ΔK_III. It was also found that the crack growth is promoted by K_II combined with K_I in the parallel direction.

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The micro Vickers hardness distribution just beneath the fatigue crack propagation surface was measured for SUS 316 stainless steel. The increase of hardness occurred in the plastic zone because of the strain hardening. A good correlation was found between the hardened region size and the maximum stress intensity factor K_max. The relationship can be used to estimete the maximum applied stress on the cracked component which failed by fatigue.

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If fatigue crack initiation and growth behavior in structures and materials can be detected based on strain information on the surface, the detecting method becomes a practical one for evaluating the fatigue damage and the residual life. From this standpoint, the strain interference method of detecting crack initiation and crack growth becavior was proposed by one of authors and the effectiveness of the method has been shown mainly through the fatigue tests using center-cracked specimens. In this paper, the applicability of the strain interference method to double V-notched specimens is investigated. First, the finite element analyses are carried out for double V-notched specimens, which are subjected to the tension-compression axial loading. The locations of strain measurement for detecting crack initiation and crack tip opening and closing points are discussed. After that, the exial loading fatigue tests of the specimen are carried out referring to the result obtained in finite element analyses. As a result of the experiment, it is shown that the crack initiation and crack growth behavior can also be detected by the strain interference method.

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A laser speckle biaxial strain gauge was developed to measure local strains at notch roots. Measurements were made on single edge-notched type 304 stainless specimens under fully reversed cyclic loading at both 637 K and room temperature. The change in the cyclic total strain range was more significant when blunt notched specimens were subjected to a higher applied stress. The measured biaxial strains were discussed in terms of a proposed dimensionless notch deformation constraint parameter which consisted of a notch root radius, a thickness of the plate and a nominal stress level. It was found that the biaxial strain ratio was uniquely correlated with the proposed parameter for all the tested notches. It was also found that the change in the cyclic strain range was correlated with the proposed parameter, and the material didn't show cyclic softening or hardening under an increased value of the parameter. Furthermore, the measured strains were compared with the estimated values by the Neuber's rule.

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Stress field in the vicinity of fast propagating crack is measured just before and just after crack bifurcation. Cracks are of opening mode and propagate in PMMA specimens at a speed more than 600 m/s. Interferometry is applied to measure the stress field around the crack tips. High-speed holographic microscopy is used to take three successive photographs of cracks and interference fringes with high spatial resolution of 180 lines/mm. The measurement results show that the neartip stress field deviates from the K-field not only after crack bifurcation but also before bifurcation. This fact indicates that the near tip field at bifurcation is affected both by micro cracks or attempted branches around the crack tips and by the higher-order terms of stress field. And it can explain the experimental result that the bifurcation angle depends on specimen's shape and experimental conditions.

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Rubber-modified epoxy resin is used in engineering components as adhesive. The failure behaviour of an interface crack in an adhesive joint is important from the viewpoint of the structural integrity of the adhesive joint. In the present tsudy, the damage zones around crack tips in two-phase adhesive joints consisting of aluminum and rubber-modified epoxy resin are compared with those around crack tips in the rubber-modified epoxy resin alone which are called bulk specimens hereafter. Damage zones around crack tips are observed by a polarization microscope and an atomic force microscope (AFM). As a result, damage zones generated by cavitation in rubber particles in the bulk specimen are not observed around crack tips in the two-phase adhenive joints.

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The creep-burst mechanism is based on a creep-burst test and the crack growth analysis of seam-welded high temperature reheat steam piping elbows. The creep-burst test was performed under conditions with the inside steam pressure at 3.04 MPa and a test temperature 70°C above that of the serviced plant. As a result, the center of the elbow's inner side bursted after 2948 hours. Observing the bursted cross section, the greatest areal creep voids density was 12 mm in depth from the outer surface. The thickness of the oxide scale from 12 mm in depth to the outer surface was greater than the other. After Burst, a specimen near the crack was used to perform a crack growth test. This test indicated that after cracks generate inner side of a pipe, they run through the outer surface, causing the pipe to burst. Based on these findings, the creep-burst mechanism in serviced pipes can be estimated as follows. Life Fraction:Creep-burst mechanism on high energy piping. 80%:Many voids generated on the outer surface. 86%∼88%:It is presumed that cracks generate the inner side of the pipe. 92%:Microcracks generate at about a single grain boundary on the outer surface or creep void joints on the outer surface. 96%∼99%:It is presumed that microcracks run through the outer surface from the inner side of the pipe. 100%:The specimen bursts.

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This paper proposes a new numerical method of a creep damage evaluation for modified 9Cr-1Mo steel welded joints. The creep damage mechanisms of this steel are mainly the nucleation of creep voids, their growth and coalescence in a softening region of its heat affected zone. Creep constitutive equations have been formulated using the Gurson Model which was originally developed for the ductile fracture analysis of porous materials. The damage parameter of this model is the void volume fraction that is easy to compare with measured damage values. To include the coupling effects between damage and deformation, the locally coupled technique has been employed, because the damaged area in a welded joint of this steel is small in comparison with the wall thickness. The accuracy of this proposed method has been examined by simulating uniaxial creep tests on round bar specimens of welded joints. Their lives have been predicted within a factor of two.

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FRP materials show a rather complex damage behavior under cyclic loading, for example, matrix cracking, fiber-matrix debonding, void growth, fiber breakage, etc. Therefore, it is very difficult to evaluate the fatigue damage and remaining life of the FRP. Heat generation is often observed due to damping in the material, which has hysteresis loss, subjected to cyclic load. A part of the heat accumulates with the number of fatigue cycles in the material. FRP materials show temperatures rise remarkably under fatigue test, since the matrix resin is viscoelasticity. It is considered that there is the relation on this fact with the fatigue damage. In this study, we attempted to evaluate the fatigue damage of the glass fiber mat reinforced CP-resin composites by the infrared thermography. Fatigue thermal curves with the various conditions are represented with one line by means of correction according to the stress and the frequency.

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With the increase of the FRP use, the method of detect flaws and evaluate damages in the FRP are being tried variously. The advancement in resolution of the infrared detectors showed the usefulness of the infrared thermographic imaging method as a detection method of flaws. However, the quantitative evaluation of the damage in the FRP is yet difficult. We obtained the temperature rise curve of the specimen surface of the GFRP, which depend on fatigue damage. The purpose of this study is to evaluate the fatigue damage of the glass fiber mat reinforced CP-resin composites by the infrared thermography. For this purpose, two step fatigue tests are carried out. The specimens were damaged by first test, and evaluate the damage of the GFRP by temperature rise with the second test.

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This paper discusses about the characteristics of distributed genetic algorithms (DGAs). Among the several types of models for DGAs, this paper focused on a rendomized migration island model. In this model, the island of the migration is decided as every migration opportunity at random. When there are a lot of islands, this model is very useful. The efficiency of this model is discussed through the numerical examples. In this study, Distributed Genetic Algorithm with Distributed Environment (DEGA) is also introduced. Usually, the parameters in GAs are the same in each island but they are different in DEGAs. This approach makes designers free from setting appropriate GA parameters. Applying this algorithm to solve numerical examples, it is also clarified that there are several advantages in this approach.

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Designs of experiments to obtain approximate response surfaces of laminated composites are described in the present study. For genetic algorithms for stacking sequence optimizations, a large number of evaluations require high computational cost, and the evaluation cost can be reduced by approximation with response surfaces. For the sesponse surface of stacking sequence optimizations, lamination parameters are adopted as variables of the entire design space instead of the ply angles. In the present study, a new method of design of experiments is proposed and investigated in detail. For most of the analysis tools, stacking sequences are the demanded input date and lamination parameters can not be applied directly. Therefore, in the present study, lamination D-optimal design is proposed and applied to the stacking sequence optimizations of the problem of maximization of buckling load of a composite cylinder. The new design of experiment is a set of stacking sequemces selected from the candidate stacks using a D-optimal design. As a result, the lamination D-optimal design is shown to be effective for the design of experiments of the response surfaces.

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A deterministic method is presented to obtain the global optima of optimization problems having both objective and constraint functions which are nonconvex. A branch and bound algorithm is developed based on the interval analysis and using the first order derivatives of the functions. Kuhn-Tucker optimality criteria are generated within the divided design space (interval box) and are solved by using preconditioned interval Gaussian elimination technique for Kuhn-Tucker multipliers. If all the K-T multipliers are nonnegative in an interval box, it is divided further to improve the accuracy of the solution and the optimality is checked again. Iteration is recursively continued until the given convergency criteria is satisfied. Several test problems and a practical design problem are solved to illustrate the computational sense of the algorithm involved in finding the global optimum.

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The cross-over of a rope wound around a drum in multi-layers is analyzed as a geometrically nonlinear problem of the linearly elastic rope by means of differential geometry and variational method with movable boundaries. The rope is assumed to be a thin and long elastic rod with a uniform circular cross-section and to be capable of large bend. The centerline of the cross-over is considered as a space curve, which is constrained by the surface of the rope of the lower layer. The work of the non-conservative tension and the bending energy of the cross-over are obtained by considering the parameters of the constraining surface. The boundaries condition are obtained by defining arc-length of the cross-over as a variables which presents movable boundaries, and by considering the geometrical boundaries at ends and the center point of cross-over. Euler equation of the variational problem is changed into an implicit form. The expression for the centerline of cross-over has been formulated, in which all parameters of a hoisting mechanism have been included in dimensionless form. Geometrical shape of the cross-over are measured in radius, winding lead and rotation angle of the drum. Using the theoretical result and measured bending stiffness, the radius, the z-axis and the arc-length of cross-over are calculated and compared with experimental data. The good correspondence with the theoretical analysis is obtained.

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Based on the three dimensional anisotropic thermoelasticity theory, Green's function solutions are presented for a two-phase transversely isotropic solid with a steady heat source in lower halfspace. The mirror reflection method is used and a general expression of the solutions in the Cartesian coordinate system is obtained. It is also shown that the solution includes the special case of a homogeneous transversely isotropic elastic solid of infinite space and semi-infinite space. In addition, numerical examples for the magnesium-titanium composites are given.

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Green's functions are shown for axisymmetric body force problems of an elastic thick infinite plate. The Green's functions are defined as solutions to the problem of an elastic thick infinite plate subjected to axisymmetric body forces acting along a circle in the interior of the plate. The axisymmetric body forces considered here are a radial force and an axial force in cylindrical coordinates. Green's functions for torsional body force problems have been shown in a previous paper. In order to obtain the Green's functions, we apply stress functions for axisymmetric problems of elasticity. As an example of application of the Green's functions shown, we consider a stress concentration problem of a thick plate with a spherical cavity. It is assumed that a uniform pressure acts on the plane surfaces of the plate with a spherical cavity. The problem is formulated by an integral equation with unknown body forces. By numerical calculations, stress distributions around the cavity are shown. The results are compared with the exact solution for an infinite elastic solid with a spherical cavity.

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A pair of integral equations are derived for a non-uniformly pressurized vertical planar crack of arbitrary shape in a fluid-saturated, poroelastic, infinite space of transversely isotropic permeability with its anisotropy axis perpendicular to crack surface, by using the fundamental solutions obtained in a previous paper and the concept of a dislocation segment. This anisotropy assumption is more realistic for many oil reservoirs. The equations obtained relate normal tractions and fluid pressure on the crack faces to crack opening gradients and fluid injection rate per unit fracture area and include the known integral equations for an isotropic permeability as a limiting case. These integral equations are intended to be implanted in a 3D hydraulic fracturing simulator.

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In recent years, composite materials contained synthetic resin are used widely as structural materials. In these materials, large deformations are often allowed and analysises of large deformation problems are often required. But analytical method by finite deformation theory is complex and take large time for calculation. Especially on unsteady state large deformation, it is more complex and hard to deal with this method. Therefore simplified analytical methods for large deformation are needed. We adopt one of them that updates only locations of nodal points of finite elements with its displacements at each incremental step. It is the purpose of this paper that we show efficiency of this method, and we'll estimate exactitude of it by a exact mrthod that is formulated on the convected coordinates. Examples for analysis are uniformly loaded thick circular plates with a hole on several support conditions and the 3-dimensional finite element method is used as a numerical method.

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It is very important to know the characteristics of wave propagating on the surface of anisotropic materials for estimating the property of materials. It is known that crystal structures near the surface are different from those in bulk. The author deduced the boundary condition taking into consideration of surface density and surface stresses of materials in a previous paper. In the present paper, the boundary condition is used for examining the velocity of the surface wave against wave number. The dispersion of the surface wave in an isotropic material is first investigated, and it is shown that the wave velocity decreases with decreasing the wavelength in the case where the surface density and the surface stresses are taken into account. The dispersion properties of surface wave in anisotropic materials, in particular, Ni (001) and W (110) are next investigated, and the dispersion relationship obtained by a continuum approach is compared to the experimental results of surface phonon. The theoretical results considering the surface density and the surface stresses are almost agreed with the experimental ones. In this analysis, the surface density plays an important role for the explanation of behavior of surface phonon against the wave number.

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In the present study, the plastic singular stress occurring in a wedge is studied by using the finite element analysis. The results so obtained are in a good agreement with the results by the asymptotic analysis obtained by the authors previously. Based on the numerical results, the K_p of plastic stress intensity factor and the K_c of elastic stress intensity factor for various notch tip are determined. It is found that value of K^1-λe_p/K^1-λp_c is independent of the strength of the singular stress field, where 1-λ_e and 1-λ_p are the orders of elastic and plastic singularity, respectively. Also, it is found that K^1-λe_p/K^1-λp_e is almost comstant with respect to γ for γ≤90°. These facts enable one to evaluate K_p without using a plastic stress analysis.

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Nuclear power plants have the greatest potential for use in space ships, underwater vehicles, and so on. Because the space and the weight for those plants have limitation, it is very important to develop new radiation shielding materials which have excellent mechanical strength and heat-resistant characteristics. Chromium carbide ceramics (Cr₃C₂) is the neutron absorber which is more excellent than titanium boride ceramics and has been investigated as a radiation shielding material. This report presents an evaluation of thermal shock strength by the laser irradiation technique for chromium carbide ceramics. Their temperature and thermal stress distributions are analyzed by the finite element method (FEM), and critical fracture curves, which can specify a critical power density for a given laser beam spot diameter, are obtained from the relationships between the spot diameter of the laser beam and the maximum tensile thermal stress. And furthermore, size effects to the fracture criterion of chromium carbide ceramics are examined, and the laser irradiation experiments are performed on chromium carbide ceramics using a CO₂ laser. Finally, theoretical results are compared with experimental ones, and the thermal shock strength P_L of Cr₃C₂ ceramics with laser irradiation is ∼3.4 W/mm² for tension by the FEM analyses.

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Effects of various basic factors of combustion gas flow conditions on SiC degradation phenomenon have been experimentally clarified. SiC degradation phenomenon was signified as the weight loss, the weight loss became larger with increase of the partial pressure of water vapor in combustion gas, and its rate was also greatly dependent on the partial pressure of water vapor. The effect of the partial pressure of oxygen on the weight loss was small, and the weight loss decreased with increase of the partial pressure of oxygen. By considering the effect of partial pressures of water vapor and oxygen, the gas temperature, the pressure and the gas flow rate in combustion gas conditions did not have such a significant effect on the weight loss in the extent of test conditions. Based on experimental results, it was clarified that the partial pressure of water vapor is a major factor on SiC degradation.

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This paper describes an analytical formulation and a numerical solution of the thermal stress and deformation for moderately thick shells of revolution made of functionally graded material (FGM) subjected to thermal impulsive loading. The material properties of the shell are continuously inhomogeneous along the shell thickness. The temperature distribution through the shell thickness is expressed with a curve of high order, and the equations of motion and the relations between the strains and displacements are derived from the Reissner-Naghdi shell theory. The fundamental equations derived are numerically solved using the finite difference method. As numerical examples, functionally graded cylindrical shells subjected to the following two kinds of thermal impulsive loads are treated;one is the thermal loads due to fluid and another is the loads due to heat generation in the shell body. In comparison with the results from the characteristic method, good agreement is obtained. And it is found that the temperature distributions, stress distributions and deformations with time are significantly varied depending on the compositional distribution profiles in FGM.

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The cementless prostheses used in the total hip replacement (THR) have been predominantly developed in Western countries. Although many cementless prostheses developed in Western have been applied to THR of Japanese osteoarthrosis (OA) patients, they have not been always fitted to shape of Japanese OA femurs. Because they have been designed for the primary OA which is general in Western but not the secondary OA. There are many cases of the secondary OA which has large deformation of femoral head caused of longterm subluxation in Japan. Unfitted prosthesis design gives a worse influence on its stability and stress distribution in proximal femur, and then it can cause serious stress-shielding. To develop the prosthesis suitable for Japanese OA, it is important to consider their characteristic shape of proximal femur. In this study, 3-dimensional models of proximal femur with the secondary OA were constructed by using CAD based on computed topographic (CT) images, and canal shapes of the femurs were geometrically classified by comparing these models. The cementless prosthetic stems were designed due to the classification. Furthermore, finite-element analyses were carried out for the OA femurs with the fitted or unfitted stem. Effectiveness of the prosthetic stem designs is discussed from the result.

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