Sandwich structures with advanced composite facesheets are attracting much attention as a solution to maximize the potential of composite materials. However, the composite sandwich structures are prone to damage, such as impact damage and debonding. Although these damages are difficult to detect using conventional nondestructive inspection method, they cause significant reduction in the mechanical properties. Hence, several researchers have attempted to detect and suppress the damages using smart sensors and actuators. In this paper recent developments on smart technologies to improve reliability of the composite sandwich structures are reviewed. First, the state-of-the-art sandwich technology in aerospace application is presented. Next, typical damages in composite sandwich structures are described, which is essential to effectively apply the smart technologies to sandwich structures. Then, smart technologies which have been applied to sandwich structures are briefly shown with focusing specific properties of sandwich structures. It includes damage detection using dynamic response, wave propagation and optical fiber sensors. Finally, a smart honeycomb sandwich concept is also presented.

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In this article, the recent and original results on the effect of thermoelastic damping (TED) on the vibrational properties of micro- and nano-mechanical resonators are reviewed. Thermoelastic damping is recognized as a significant loss mechanism at room temperature in micro-scale resonators. The thermoelastic damping theory was first presented by Zener in 1937, and recently refined by Lifshitz and Roukes. A review of the thermoelastic damping process is presented. Also the theoretical and experimental advances in this field are introduced and discussed. Finally, some results gained by the authors are presented.

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For simulating the final failure of glassy polymers under impact loading, Shizawa's constitutive model was modified by introducing the craze density based softening law in which the phenomenological softening law using the craze density is employed. The material parameter identification procedure in the constitutive law was developed based on the sensitivity analysis. All parameters were identified with the measurement data which were obtained by both the dumbbell-shape tensile test specimen and the notched tensile test specimen. The dart impact test was also conducted. The load displacement curve and damage zone development were compared with those obtained by the finite element analysis using proposed constitutive equations. Both results were in good agreement and the usefulness of the constitutive equations was validated.

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This paper presents an analytical solution for an infinite strip having a circular inclusion, when the strip is subjected to pressure on both sides of the strip. In the analysis, two types of inclusions, i.e., perfectly bonded inclusion (displacements and tractions are continuous) and slipping inclusion (tractions and normal displacements are continuous and shear traction vanishes) are discussed. The solution is based on the Papcovich-Neuber displacement potentials approach and is deduced through making use of simple forms of Cartesian and cylindrical harmonics. The boundary conditions on both sides of the strip and around the inclusion are fully satisfied with the aid of the relationships between the Cartesian and cylindrical harmonics. The solution is represented in the form of graphs and the effects of the inclusions on the stress distribution are clarified.

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The main purpose of this paper is to explore a numerical algorithm for determining the contact stress when a circular crowned roller is compressed between two plates. To start with, the deformation curve on a plate surface will be derived by using the contact mechanical model. Then, the contact stress distribution along the roller which occurs on the plate surface is divided into three parts: from the center of contact to the edge, the edge and apart from the contact line. The first part is calculated by the elastic contact theorem for the contact subjected to nominal stress between non-crowned parts of roller and plates, the second part is obtained by the classical Hertzian contact solution for the contact between crowned parts of roller and plates, and the third part is simulated as exponential decay. In order to overcome the defect of the half space theorem, in which a plate with infinite thickness is assumed initially, a weighting method is introduced to find the contact stress of the plate with finite thickness. Comparisons with various finite element results indicate that the algorithm for estimating the contact stress of a circular crowned roller compressed between two plates derived in this paper can be a reasonably accurate when a heavy displacement load is applied. This is because the contact area is large under a heavy load, and the effect of stress concentration is smaller in comparison with the case under a light load.

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Multi-resolution display of highly detailed mesh models has been gaining considerable interest in recent years. However, most researches today are only focus on the geometric similarity. The mesh quality and machining acceptability are less concerned. In this paper, a multi-resolution mesh generation algorithm for sculptured surface machining is presented. The lower-resolution mesh can be used for rough-cut, and the higher-resolution mesh for finish-cut in machining. The proposed algorithm uses iterative edge collapse to simplify the input mesh. The approximation error is controlled by a local error metric VIV (Vertex Importance Value), and a global error bound. This multi-resolution mesh is capable of generating faithful approximations of the original model with high-quality mesh, and also capable of generating rough-cut models with simple geometric complexity and incremental volume, which is suitable for material removal process.

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One of the problems encountered in the design and implementation of a flexible transfer line (FTL) is the layout of the FTL in a restricted area. The layout of the FTL has an important impact on production cost. In this paper we propose efficient FTL layout design procedures for a FTL layout in an asymmetrical and restricted plant area. In order to find the layout of the FTL including the buffer size between each pair of FTL machines, an efficient FTL layout design procedure called a One by One Layout Method (OOLM) in conjunction with genetic algorithm (GA) is proposed. The OOLM generates an efficient solution for a set of irregularly shaped machines through a restricted plant area. A CAD system is linked to the OOLM to draw the FTL layout. The OOLM is not limited to a single static environment, but is highly flexible within the plant structure. An application example was developed, and after a number of operations based on OOLM, an efficient FTL layout design could be found.

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We developed a method to predict the change in the drain current in deep-sub-micron MOSFETs due to strain. The change in MOSFET drain current can be explained as a linear function of normal strains. The strain sensitivities of the MOSFETs drain current were clarified experimentally. The results indicated that drain current in N-MOSFETs increases with increases in in-plane tensile strains and normal compressive strain. Whereas, the results indicated the drain current of in P-MOSFETs increases with in-plane compressive strain parallel to the channel, and in-plane tensile strain perpendicular to the channel. The drain current also increases with normal tensile strain. The predicted values showed good agreement with the measured values. This method for predicting change in the drain current due to stress will help us to improve electronic performance of MOSFETs.

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This study deals with analytically evaluating the stress concentrations near loaded and initial fiber breaks in unidirectional composites with matrix yielding and interfacial sliding. To this end, by performing a detailed 3D finite element analysis, it is demonstrated that significant nonproportional straining occurs in the matrix near loaded fiber breaks in contrast to initial breaks, and that such nonproportional straining induces almost elastic developments of matrix shear stress near loaded fiber breaks. Then, the 3D shear-lag closed-form solution derived by the present authors, which is modified so as to be effective over a wide range of fiber volume fractions, is shown to be applicable to loaded, as well as initial, fiber breaks, provided the matrix shear modulus in the solution is prescribed by taking account of the nonproportional straining. It is thus demonstrated that the nonproportional straining in the matrix can lower the stress concentrations near loaded fiber breaks in the presence of matrix yielding.

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Slip deformation in symmetric type bicrystal models subjected to tensile load is analyzed by a finite element crystal plasticity analysis code and accumulation of geometrically necessary dislocations (GNDs) is studied in detail. Uniform deformation was expected to take place because mutual constraint of crystal grains through the grain boundary plane does not occur in symmetric type bicrystals, but, some results of the analysis show non-uniform deformation and the high density of GNDs accumulated in the form of band. Such kind of non-uniform deformation is observed regardless of the model size and the strain-hardening characteristics. Mechanism of non-uniform deformation and accumulation of GNDs in the form of band in the symmetric type bicrystals is discussed from the viewpoint of the boundary condition and shape change of grains after slip deformation

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For steels with lower yield stress, transgranular facet like fracture sometimes occurs under corrosive conditions. The occurrence mechanism of the transgranular facet like fracture has been analytically clarified under constant stress rate condition based on the concept of mechanical interaction between dislocations and hydrogen. In this paper, the analyses of the mechanical interaction between dislocations and hydrogen around a crack tip under cyclic loading condition were conducted to clarify the effect of stress wave forms on the feasibility of hydrogen embrittlement. This analysis showed the typical pile-up of dislocations occurs at the site of hydrogen similar as that under monotonous applied loading condition. Concerning the concentration of dislocations at the site of hydrogen atom, the dislocation pile-up intensity factor amplitude ΔA and power coefficient value of the singularity of dislocation density n were defined. ΔA under fatigue condition was found to concern the feasibility of the occurrence of facet like fracture due to dislocation pile-up caused by the interaction between dislocations and hydrogen. Furthermore, the condition of Fast-Slow stress wave form was found to promote the facet like transgranular fracture as compared with that of Slow-Fast stress wave form.

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Single crystals of lead zirconium titanate (PZT) are difficult to fabricate. Thus, not all material properties of PZT have been fully characterized. In this paper, the mechanical and electrical properties of a PZT single crystal, which can be assumed to be identical to those of a crystal grain in a polycrystal, have been computed from those of a polycrystalline PZT ceramic by the steepest decent method and multiscale finite element modeling based on crystallographic homogenization method. Crystallographic homogenization enables us to predict macroscopic properties of ceramics taking into account the inhomogeneous microstructure of an aggregate of crystal grains. The crystal morphology of the PZT ceramic was measured by the SEM·EBSD technique, and the result was used in the microscopic finite element model. Then, the mechanical and electrical properties of the crystal grain were derived by the steepest decent method so that its macroscopic properties would correspond to the measured properties of the PZT ceramic. The proposed computational method was applied to barium titanate (BT) and validated by comparison of the computed material properties with known properties of the BT single crystal. Finally, the computed material properties, such as the elastic compliance, and the dielectric and piezoelectric constants, were presented for the PZT single crystal.

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All arrows line in Fig. 2-8, Fig. 10-11, Fig. 15 and Table 1 disappeared due to PDF file conversion error. Also, word "Slow-Fast" in 5) of p.137 was wrong. The correct word is"Fast-Slow". The correct figures are attached behind this errata. Wrong:See PDF attached
Right:See PDF attached

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