The New Rheocasting process provides excellent mechanical properties with a positive solution for the cost of material that has been the weakness of the semi-solid casting process. The process is a kind of batch system. It uses a cup for each shot and a conventional automatic ladling system, which pours molten metal into the cup. This process produces semi-solid slurry including globular crystals directly from molten metal without stirring technique. The products made by this process showed good mechanical properties.

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The stress and displacement fields near the bonding edge, sharp notch, and contact edge show singularity behaviors, so methods of evaluating the strength of these points using maximum stresses calculated by a numerical stress analysis, such as the finite element method, are generally not valid. We have previously presented a new method of evaluating the strength of these singular points using two stress singularity parameters H and λ. The difficulty with this method was in obtaining the critical value of the intensity of the stress singularity parameter Hc for each order of stress singularity λ. We therefore present in this paper methods of formularizing Hc by λ based on typical strength parameters such as the fatigue limit σ_<w0> and the threshold stress intensity factor range ΔK_<th>. These critical value Hc (λ) agreed well with the experimental results. Using these easily obtained formularized critical value Hc (λ), we can estimate the fretting fatigue crack initiation criteria for each contact edge angle, and thus optimize the contact edge geometry. Finally, we discuss the development of these strength criteria in terms of stress singularity fields for general stress concentration fields.

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Polysilicon thin films were tensile tested by a thin film tensile tester developed for reliability evaluation of microelectromechanical (MEMS) devices. This tensile tester has a new specimen chucking system using electrostatic force. This method enables us to handle thin (few micrometer thick) specimens easily without damage. The tensile strength of polysilicon specimens is evaluated and some fracture properties are investigated. To study variation of the reported tensile strength of polysilicon films and to check accuracy of the tensile tester, we have participated the cross comparison of tensile testing techniques.

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In this paper, size effects on the mechanical properties of micro materials will be reviewed. Properties that will be addressed include yield strength, fatigue and creep behavior and fracture toughness of thin metallic films as studied by several specialized testing techniques including : (i) micro-tensile testing for yield strength and low cycle fatigue, (ii) nanoindentation and microbeam deflection for high cycle fatigue, and (iii) thermal cycling experiments for creep and fracture toughness. Cu thin films were investigated in all studies, only the fracture toughness experiments were carried out on NiAl thin films

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A decade ago Gilman proposed that the hardness of semi-conducting materials was controlled by a semi-conducting to metallic phase transformation at the very high hydrostatic compressive stresses developed under the indenter. In this work we report on a systematic investigation of the hardness and elastic modulus properties of a number of elemental semi-conductors (Si and Ge), as well as compound semi-conductors (GaAs, InP, GaN, ZnO) using nano-indentation and associated cross-sectional TEM. In all instances cross-section were made of impressions at various indentation loads using focused ion beam milling (FIB). Indentations were primarily made with a small spherical tipped indenter, which enabled the transition from elastic to elastic-plastic behaviour to be quantified. Complimentary observations of the residual impressions with AFM and Raman micro-probe spectroscopy were made as well as some electrical conductivity measurements during the indentation cycle. It was observed that only in the case of silicon was definitive evidence found for a pressure induced phase transformation beneath the indenter. In all other materials deformation occurred by classic plastic deformation, namely dislocation motion and twinning. In the case of silicon it was found that the resultant phase transformation observed in TEM sections from beneath the indenter depended strongly on the unloading rate. This presentation is based upon the PhD thesis of Ms J. Bradby.

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Microelectromechanical systems (MEMS) are expected to be applied to micro-photonics and bio-medical devices such as optical switches for electro-optical communications and micro-catheters for brain surgery. The size of the components used in such devices is considered to be in the order of microns. Therefore, the evaluation of mechanical properties of micro-sized materials are essential for practical applications of such MEMS devices. In particular, the fracture and fatigue properties of micro-sized components are of crucial importance to the structural integrity and long-term reliability of actual MEMS devices. In order to evaluate fracture and fatigue properties of such micro-sized specimens, we have developed a new type mechanical testing machine for micro-sized specimens, which can apply small amount of static and cyclic loads to the specimens. In this investigation, fracture and fatigue tests were carried out for micro-sized specimens prepared from an electroless deposited Ni-P amorphous alloy thin film using the mechanical testing machine which we have developed and the size effects on the fracture and fatigue crack growth behavior have been discussed. Cantilever beam type specimens (10×12×50(μm)^3) with notches were prepared from a Ni-P amorphous thin film by focused ion beam machining. This specimen size is approximately 1/1000 of ordinary sized specimen. Fatigue crack growth tests were carried out in air at room temperature under constant load amplitude using the testing machine for micro-sized specimens. Fracture tests were performed for the specimens with fatigue pre-cracks ahead of the notches. Fatigue crack growth resistance curves were obtained from the measurement of striation spacing on the fatigue surface and closure effects were observed even for micro-sized specimens. Once fatigue crack growth occurs, the specimens were failed after several thousand cycles. This indicates that the fatigue life of micro-sized specimens is dominated by a crack initiation. This also suggests that enen micro-sized surface flaw may be an initiation site of fatigue crack and this will shorten the fatigue life of micro-sized specimens. As the results of fracture toughness tests, plane strain fracture toughness, K_<IC>, values were not obtained since the criteria of plane strain were not satisfied for this size of specimens. As the plane strain requirements are determined by stress intensity, K, and yield stress of the material, it is rather difficult for micro-sized specimens to satisfy these requirements. Plane stress and plane strain dominated regions were clearly observed on the fracture surfaces and their sizes were consistent with those estimated by fracture mechanics calculations. This indicates that fracture mechanics is still valid for such micro-sized specimens. It is required to consider the results obtained in this investigation when designing actual MEMS devices.

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The present study investigates plasticity-induced martensitic transformation around a part-through crack in an austenitic stainless steel SUS304 fatigued at room temperature. Distributions of α' phase volume fraction ζ_<α'> around a semi-elliptic fatigue crack were measured with ferrite scope. The results were compared with the distributions of magnetic flux density B_z above the crack in a specimen magnetized by a strong magnet. It was revealed that the B_z distributions reflected the α' phase distributions around the crack : i.e., the distance between the points where B_z reached the maximum and the minimum values B_<zmax> and B_<zmin> had linear correlations with surface crack length 2a. The B_<zmax> and the B_<zmax> values also showed linear relations with maximum stress intensity factors at the surface tip K_<amax> and at the depth position K_<bmax>. These results imply that not only 2a but also K_<amax> and K_<bmax> values can be estimated in an electromagnetic non-destructive way.

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In this paper, the micro-macro interaction analyses of corrugated fiberboard are conducted by the finite element method in conjunction with the homogenization theory. It is assumed that corrugated fiberboard is piled periodically in quasi three-dimensional state. The updated Lagrangian method is adopted for the geometrically nonlinear analyses of microstructure and the scaled corrector method for detecting the buckling mode. The conclusions obtained in this study are summarized as follows. 1) The large deformation and buckling analysis based on the homogenization theory is conducted and the mechanical properties of corrugated fiberboard are investigated. 2) The micro-macro interaction analysis procedure for the buckling of the corrugated fiberboard based on the homogenization theory is newly proposed. The validity of the proposed procedure is clarified qualitatively by comparing with the experimental results.

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Sintering process of copper atom clusters is investigated by multi-resolution molecular dynamics (MRMD) simulation. This MRMD method is constructed as combination between calculation of atomic motion in boundary regions being done by ordinary MD method and calculation of rigid body motion of clusters being done by another kind of equation. Two dimensional array of 683 copper atom-clusters is studied, and it is found that adequate reappearance of the behavior about translation, collision, coalescence, and oscillation of clusters is capable to be obtained by MRMD method with new algorithm in determination of MD region.

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Zn-Al eutectoid alloy with nanocrystalline structure was developed by means of Thermo Mechanical controlling process (TMCP). In order to use the material as high performance and maintenance-free seismic damper, the deformation behavior was examined. The each phase was equixed with an average size of 1.7μm, and nanocrystalline Zn particles in Al-rich phases were observed. The tensile test revealed that the m-value exhibited about 0.3 in the low strain rate regime and the maximum value of 200% elongation at room temperature was obtained at a strain rate of (10)^<-5>s^<-1>. It was apparent that the materials had higher performance than the low yield point steel that was generally used as the seismic device.

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This study presents a complete set of effective elastic-stiffness coefficients of an Ni_<80>P_<20> amorphous-alloy thin film deposited on an aluminum-alloy substrate by electroless plating. The film thickness was 12 micrometers. The electromagnetic-acoustic-resonance method detected resonance frequencies of the triple-layered specimens (film/substrate/film), which enabled us to determine all five independent elastic-stiffness coefficients of the film using known substrate elastic properties. The resulting coefficients were those of a transverse isotropic material. There was strong anisotropy between the in-plane and normal directions; the in-plane Young's modulus is larger than the normal Young's modulus by 34%, for example. The anisotropic coefficients can be interpreted by considering a micromechanics model for local incomplete cohesion (thin ellipsoidal voids) aligned parallel to the film surface.

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We studied the elastic property of a lotus-type porous copper using the combination of resonance ultrasound spectroscopy and electromagnetic acoustic resonance methods to determine all the independent elastic constants. We observed the elastic anisotropy. The parallel Young's modulus E_<&parsl;> decreases linearly with porosity, while the normal E_<&bottom;> drops rapidly and then slowly. Micromechanics calculations considering the elastic anisotropy of the matrix (textured metal) can reproduce the measured anisotropic elastic constants. This indicates that the elastic properties of the various types of porous metals can be predicted and designed with the present approach using micromechanics modeling.

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Analysis on rubber modified epoxy resin is presented. In rubber modified epoxy resin, rubber particles are contained in Epoxy matrix. Epoxy can be regarded as a brittle matrix material and does not undergo much nonlinear deformation. It has been seen in literature that Epoxy undergoes a considerable amount of nonlinear deformation when it is mixed with rubber. Such a material is called rubber modified Epoxy resin. It has also pointed out in literature that the primary cause of nonlinear deformation is the cavitations (fracture) of rubber particles which are embedded in Epoxy matrix. In this paper, a BE (boundary element) based homogenization method is applied to analyze the deformation of rubber-modified Epoxy resin.

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