Damage identification methods based on changes in natural frequencies and mode shapes using finite element methods have received wide attention for their high applicability to complex structures. In this paper, for truss structures we develop an effective damage identification method with a successive iteration method of bounding domain and a domain decomposition finite element technique. By means of the successive iteration method of bounding domain, a truss structure is subdivided successively into subdomains of truss structures, and finally a damaged truss member is identified. In order to reduce computational time, the domain decomposition finite element technique is also developed to give frequencies and mode shapes of the whole structure by assembling subdomain frequencies and mode shapes. We examine the validity of the domain decomposition finite element technique by performing the vibration analysis for a subdivided two-dimensional truss structure, and then a numerical damage identification study for a two-dimensional truss structure is conducted. It is recognized that the present damage identification method is effective and computationally efficient.

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Bending deformation of an ionic conducting polymer-metal composite (a platinum plated Nafion) upon applied low electric field across its thickness is dominated by internal water redistribution. Internal water redistribution is associated with two phenomena, electroosmosis of hydrated ions and self-diffusion of free water molecules. Two processes can be considered separately in the way that fast electroosmosis is followed by much slower self-diffusion. Consequently, there is strain distribution due to different water content throughout the thickness. In the present study, finite element formulation is conducted for the basic field equations governing electrochemical-mechanical response of a platinum plated Nafion actuator upon applied electric field. Some numerical studies are carried out in order to show the validity of the present formulation.

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Free Mesh Method (FMM) is a kind of node-based finite element method, which does not require mesh information. Therefore it has a main advantage of meshless method cutted cost of calculation by omitting mesh creation. Then it seems suitable for an adaptive method, a crack propagation problem, and a large-scale problem. Moreover, it still has merits of finite element method, i.e., it can use many existent techniques developed for finite element method. Although FMM has been demonstrated to be applied to many fields of research, no general purpose program based on FMM has been developed yet. So we designed Free Mesh Method program for 3D problem. Some of main features of this software are : (1) Large-scale : It can be executed in parallel environment, such as PC cluster with domain decomposition method (DDM) (2) Expandable : It is designed by object-oriented approach and new functions can be added very easily. Here we describe the local mesh generation of FMM, generalized recursive bisection method for DDM, the object-oriented design of the software, and the object-oriented parallel matrix solver.

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In order to obtain the Hertzian stress with high accuracy, very fine element division and enormous calculation time is needed for the FE & BE analysis. In addition, large-scale contact analysis to obtain accurate stress distribution, which is required to estimate strength of products such as turbine blade fixing on turbine disk, has been hardly possible. Authors developed a BEM program which include the following four techniques ; the p-version for the reduction of degree of freedom, the sparse method for the efficiency improvement of the calculation, the diagonal escalator method for the simultaneous linear equations, and the diagonal escalator method for iterative calculation. The performance of the developed program was verified by applications to demonstrative examples.

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A new boundary element method (BEM) for analyzing the potential field including thin plates is developed. It is known that the inaccurate solutions are encountered with the standard BEM for this potential problem. In case each source point on foreside and backside of the thin plate is close, the boundary integral equations for these sources nearly depend each other. This is because the fundamental solution distributions for each source are almost the same. In order to overcome this problem, the special weighting function whose form is not symmetric instead of the standard fundamental solution in the BEM is proposed. The weighting function for 2 D potential problem is derived. A few example problems are solved with this method to demonstrate its applicability and usefulness.

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It has been clearly shown that a can or PET bottle made by origami technique can be crushed with much smaller force. Furthermore, this structure is desirable to absorb more crash energy during automobile light collision or vehicles-pedestrian accidents. Thus, in this research, to minimize average crash force of the origami structure, the shape of the structure and the angle of polygonal folding lines are optimized by the method of MPOD, one kind of Response Surface Methods based on Holographic Neural Network (HNN).

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Propagation in a localized region of stress-induced phase transformation under strain variations in TiNi SMA is analyzed experimentally, by tension tests for wire and theoretically, by numerical simulation, FEM that is based on J 2 F theory. From the infrared thermograph during tension tests, it is found that a localized region of transformation appears near the end of the wire. The localized region of transformation propagates according to extension of the specimen, which gives rise to typical characteristics in the nominal stress-strain curve under strain variables of SMA wire (For example, the overshoots, the flat stress regions for reverse transformation and the nonlinear phenomena near the finishing points of transformation). Based on the constitutive assumptions of the softening type of the true stress-logarithmic strain curve, the simulated result exhibits the former typical behaviors associated with propagation of transformation. The validity of the constitutive assumptions and the mechanisms of the former behaviors are discussed by comparison of the experimental and the simulated results.

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In constrained optimization problems, many heuristic methods treat constraint functions as penalty function, and it is well known that penalty parameters depend on the problems. Generalized Random Tunneling Algorithm (GRTA) for global optimization has been proposed in the first report. GRTA does not need penalty parameters, and is a simple method. In this paper the accuracy of solutions and the efficiency between GRTA and heuristic methods are discussed through numerical examples. In numerical examples, some mathematical problems and structural optimization problem are treated. In case of mathematical problems, there are little differences of the accuracy of solution and the results between GRTA and heuristic methods. However, the efficiency of GRTA is excelent to find global minimum. Moreover there is big difference of the result in case of structural optimization problem. As a result, the validity and efficiency of GRTA are confirmed.

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In this paper, we propose a topology optimization method for two-dimensional structures. Virtual nodal forces are employed as design variables that are functions of parameters derived from boundary cycles in the homology theory. The density of material in each element is determined by the design variables so that the density of strain energy is equal to the prescribed value. The objective function is the volume of a plate, and it is minimized. The virtual nodal forces always satisfy the equilibrium at each node in the process of optimization without constraints on parameters, although all elastic equations are not satisfied until the process is completed. In other words, the finite element analysis and topology optimization progress simultaneously. This method does not require repeating finite element analysis. Although the optimum structures obtained by this method as numerical examples varied depending on values of constants in the optimization method or the size of elements, the conditions of the density of strain energy were almost satisfied. It can be said that the validity of the proposed method was proved.

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Numerical simulation method for analyzing the fracture behavior of brittle materials was developed on the basis of the initiation of micro-cracks. Deformation and fracture behavior of porous ceramics with initial cracks were numerically simulated.The mean stress model was abopted as the condition of the initiation and propagation of micro-cracks. The micro-cracks were located in a regular manner as the bonds of a square lattice. The stress distribution and stress intensity factors at micro-crack tips were calculated numerically by the body force method. As the variance of the critical strength increased, and as the initial crack length became long, the stress-strain relationship became nonlinear. When the initial crack length was small, the fracture occurred not from initial crack tip. The size of the non-damaging defects could be evaluated by the proposed method. The resistance curve calculated was independent of the initial crack length. The calculated results agreed very well with the experimental results.

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Damage development in piezoelectric ceramics under mechanical and electrical cyclic-loadings is represented by a damage variable based on the continuum damage mechanics, and an evolution equation of the damage variable is formulated by taking into account the effect of applied electric field on a fatigue life. In addition, the damage variable is incorporated into a constitutive equation of piezoelectric ceramics by using the modified cubes model i.e. material constants of the constitutive equation are expressed as a material function of the damage variable. Then, the damage evolution equation and the constitutive equation are applied to a prediction of a fatigue life under various applied electric fields. Results of the prediction are compared with experimental results, and the validity of formulating the damage evolution equation and the constitutive equation is discussed.

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The tensile deformation and rotating-bending fatigue life of a highelastic thin wire and a superelastic thin tube of NiTi alloy were investigated experimentally. The results obtained are summarized as follows. (1) The stress-strain curve of the highelastic thin wire is approximately straight till strain of 4% with stress of 1 400 MPa and depends little on temperature and strain rate. (2) Modulus of elasticity of both the wire and tube is low, having superior performance of flexibility which is necessary for medical application. (3) The strain-based fatigue curve of the alloy consists of two straight lines. The strain amplitude of fatigue limit is in the region of 0.6-0.8%. (4) In the tube, the fatigue crack initiates on the inner surface since the inner surface is rough, resulting in short fatigue life.

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The mechanism of shear mode fatigue crack growth in pure aluminum was investigated using pre-cracked specimen. The crack propagation tests were carried out by the cyclic torsion with a static axial load and the push-pull, respectively. In the case of the cyclic torsion, the fatigue crack grew by shear mode. The micro-cracks initiated perpendicular and parallel to the direction of main crack growth during the cyclic torsion. However, the interactions were not observed between the main crack and the micro-cracks, which directed perpendicular to the direction of main crack growth. The behavior of micro-cracks on pure aluminum was different from that of 4340 steel in which the pure shear mode crack growth hard to occurred. The crack growth behavior is related to the slip systems of the materials. The number of slip plane and the friction resistance between molecules of aluminum are smaller than those of steel. These and the loading conditions are related to the mechanism of the shear mode crack growth in aluminum. Under condition in the prenent study, the relation between the crack propagation rate and the stress intensity factor range was almost the same in the cases of the push-pull and the cyclic torsion with tension. However, the effects of friction between the crack surfaces on the crack propagation in a shear mode were not exactly evaluated.

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In this work, stress concentration factors (SCFs) of a round bar with a circular-arc or V-sharped notch Kt are considered on the basis of exact solutions for special cases and accurate numerical results. First, for the limiting cases of deep and shallow notches, the body force method is used to calculate the SCFs ; then, the formulas are obtained as Ktd and Kts. On the one hand, upon comparison of Kt and Ktd. it is found that Kt is nearly equal to Ktd if the notch is deep or blunt. On the other hand, if the notch is sharp or shallow, Kt is mainly controlled by Kts and the notch depth. The notch shape is classified into several groups according to the notch radius and notch depth ; then, the least squares method is applied for calculation of Kt/Ktd and Kt/Kts. Finally, a set of convenient formulas useful for any shape of notch in a round test specimen is proposed. The formulas yield SCFs with less than 1% error for any shape of notch. The effect of notch opening angle on the SCF is also considered for the limiting cases of deep and shallow notches.

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Initial fatigue damage process of plain woven CF/epoxy composites was studied with thermoelastic image technique. Thermoelastic damage analysis was conducted to evaluate the fatigue damage in the specimen. The experimental results showed that the damage initiation points were widely scattered in the location of the material. The each area, where the damage initiated, had different damage level at any fatigue cycles. The thermoelastic damage response can be an indicator for the state of fatigue damage of the composites. The thermoelastic damage analysis also predicted that the initial fatigue damage process of plain woven fabric composites changed when the local damage area was distributed in lateral direction of the specimen.

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Cavitation erosion data has been accumulated in our laboratory since 1970 for about 30 years. The database was constructed in the electrical data of the Excel file. The data file is able to offer the quick search in terms of test material, test method and test condition among 859 data. The carbon steel data were analyzed, excluding stainless steels that exhibit the high work hardening. The average of erosion rate under the standardized condition (ASTM G 32, stationary specimen method, standoff distance 1 mm) was determined for different carbon steels. Since the coefficient of variation was obtained in the range from 0.1 to 0.3, the standard deviation can be easily estimated for these steels. The erosion resistance was defined as a reciprocal of erosion rate, and it was normalized with the erosion resistance of SUS 304 steel. The normalized erosion resistance is equal to 2.1 E-06 x HV^2.4 (HV, Vickers hardness), and the correlation coefficient is 0.92. It was concluded that the erosion resistance could be estimated precisely by the material hardness for carbon steels.

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A number of rock types exhibit a nonlinear deformation induced by distributed microcracking, followed by a post-peak softening behavior due to grain bridging action, when subjected to a uniform tension. Numerical analyses of hydraulically induced geothermal reservoirs at great depths conducted to date neglect the effect of the distributed microcracking. In this paper, the formation of the distributed microcracking is studied using a numerical technique in order to characterize the growth of artificial subsurface cracks by hydraulic fracturing. A numerical fracture model based on a finite element method is developed. The progressive nonlinear deformation is analyzed on the basis of the Rankine criterion. A cohesive crack model is adopted to analyze the crack growth. In the numerical simulation, the crack is represented using an embedded crack element. The results obtained by numerical analyses show that the distributed microcrack zone induced by hydraulic fracturing at great depth conditions is significantly suppressed by tectonic stress. An energy consumption of the distributed microcrack zone is much smaller than that of the bridging zone.

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The new material fender is made from thermoplastic elastomer, and shape of the cross section is honeycomb. Honeycomb and foam are the two major classes of cellular solid, and commonly be used to absorb energy. Authors are performing the research that checks the characteristic of the new material fender to ship collision by the model test and numerical analysis. This report studies the influence of the bow collision condition by using the urethane form as the model. When rearranging the results, (1) Reaction force-bow penetration curve shows that the reaction force increases linearly with increase of bow penetration to a certain distance. Then, reaction force rapidly increases with little increase in the penetration distance. (2) When location of the penetration approaches the end of fender, the slope of the reaction force-bow penetration curve becomes moderate. In the case, the slope of the curve at the same penetration distance increases with the increase of the width of the fender, although this increase saturate to a certain value when the width/depth ratio exceeds 6.

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Equal-sized sphere packings were constructed using a sequential deposition method and then various statistical properties of the packing were examined. From the examination, we discovered that their packing structures are affected by the gravity ; more precisely, line segments connecting the centers of spheres in contact lie more frequently around the direction of 51 degrees from the vertical line, although they are uniformly distributed about the vertical line. Furthermore, with a parameter representing the degree of crystallization, we evaluated order/disorder of the packing structure ; the packing is found to contain some ordered structures, in which there are more structures of simple cubic packing than those of compact hexagonal packing. Using the packing constructed, we estimated effective thermal conductivities of the “sintered” ballons with various ratios of inner and outer diameters, which range from 0.0 to 0.9. It was found that the conductivity drops remarkably for the ratio larger than 0.7. This is good for heat insulation.

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The new method of stress separation was proposed in order to evaluate individual stress components from the sum of the principal stresses obtained from an infrared stress image. This method is based on the inverse problem analysis which uses the least squares method and the intelligent hybrid method. In order to prove this method, the experiment by infrared thermography was carried out using three kinds of materials and four kinds of the thickness of the specimen. The specimen with the thin thickness of 1mm was influenced greatly by heat conduction. The thickness effect on the stress intensity factor was not recognized in specimens thicker than 3mm. The error of a stress intensity factor increases linearly along with the increase in the thermal conductivity. The infrared hybrid method can evaluate the stress intensity factor of a low thermal conductivity material by high accuracy.

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The thermal recovery of internal stress becomes important in inelastic deformation at elevated temperatures such as creep or creep-plasticity interaction. In this paper the thermal recovery behavior of the internal stress is investigated by analyzing experimental stress-strain responses of JIS SCMV 4 steel at 550°C. The “bowing-out” behavior observed at the commencement of unloading in the cyclic stress-strain diagram is precisely investigated from which the recovery behavior of internal stress is obtained. Based on the obtained results, a thermal recovery term of evolution equation of internal stress is calibrated. Numerical simulation shows good agreement with the experimental data.

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In this paper, experimental and theoretical researches on the viscoplasticity of lead and lead-free solder alloys are conducted. First, experiments such as tension-compression loading with several stress amplitudes and strain rates, creep tests at several stress levels, and stress relaxation tests are conducted using specimens made of Sn-37 Pb as the lead solder alloys and Sn-3 Ag-0.5 Cu as the lead-free solder alloys at several temperatures. The test results show that the lead-free solder alloy has smaller strain rate effects, creep strain and stress relaxation than those of the lead solder alloy. The viscoplastic deformations of both lead and lead-free solder alloys are simulated by a viscoplastic constitutive model. The simulations show that the constitutive model can successfully apply to the pure sension, the cyclic loading, the creep deformation and the stress relaxation of both the lead and the lead-free solder alloys. FEM analysis of the bend of the substrate is also conducted by MSC. Marc, in which the constitutive model for viscoplasticity is incorporated. As a result, it is found that the bend of substrate using the lead-free solder joints has much larger bend than that using the lead solder joints.

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An investigation was performed on the interfacial control between polyphenyleneoxide (PPO) resin and copper conductor with a low temperature plasma treatment in order to find a new method for fabricating an insulation layer and a conductor layer. Various plasma treatments on the surface of PPO resin plate were carried out with three kinds of oxygen gas, nitrogen gas and argon gas under the constant treatment condition of pressure 30 Pa, power 50 W and time 600 s. The interfacial strength between PPO resin and copper plating was estimated by the peel test method. Furthermore, an XPS analysis and an AFM observation were carried out to investigate the surface characteristics of PPO resin. As a result, it was found that their surface energy largely increased, and functional groups (carboxyl group, hydroxyl group, carbonyl group) were formed on the surface after all plasma treatments. The peel strengths after plasma treatments were increased and the surface energy and these peel strengths showed a linear relation. And also, it became clear that the skewness value of surface roughness is an effective parameter for evaluating the peel strength of copper plating in the case of surface characterization formed by plasma etching.

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Ball-on-plate type rolling contact fatigue tests for a bearing steel JIS-SUJ 2 were carried out, and the influences of the applied load on the morphologies of the flaking failure were investigated.In order to try to describe the morphologies, stress intensity factor range ΔK_II, ΔK_III. for the subsurface crack subjected to cyclic loading of contact stress were estimated by using a simplified crack model. It was found that ΔK_II for a crack with a fixed radius indicated a maximum value at a certain depth, and the depth agreed well with the maximum flaking depth obtained experimentally. The length and the width of the flaking failure were also discussed by the variations of ΔK_II, ΔK_III. with the change of the crack radius. The flaking width estimated from the comparison of ΔK_III and its threshold value for fatigue crack growth was considerably close to experimental value.

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In atomic force microscopy (AFM), the deflection of the micro-machined cantilever equipped with a sensor tip measures an interactive force between a tip and a sample. Quantitative applications, including evaluation of elasticity and adhesion of sample surface in nano-scale, require AFM cantilevers to be measured accurately for the spring constants. Direct methods of determining spring constants, where the deflection of a cantilever is measured as a function of applied load, are reliable rather than indirect methods based on analysis of cantilever vibrations. This study proposes a novel direct method having the advantage of non-contact loading, where micro jet of inert gas from a micropipette produces a well-defined fluid force ranging from lnN to 10 pN. Combing the loading device with a laser interferometer for measuring sub-micro deflection of cantilevers makes possible the determination of spring constants with uncertainty of ±8%.

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