It is well known that the compressibility or incompressibility of biological tissue stems from its microscopic structure, which is in general composed of varied material compressibility including incompressibility. This paper proposes a framework of homogenization method in which compressibility/incompressibility of the macrostructure properly reflects those of the microstructure. The formulation is based on the mixed variational principle with perturbed Lagrange-multiplier. It is shown that the rate of volumetric change of the macrostructure can be controlled through the homogenization procedure by introducing the constraint only for the microstructure. A couple of numerical examples is given so as to demonstrate the validity of the proposed method. By comparing the numerical results with theoretical solutions, the method is also confirmed to be free from locking.

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In this paper, effects of radial corrugation on crushing behaviors of circular tube are studied by using finite element method. The numerical analysis is carried out on two geometrically different types of corrugations, i.e. “Radial Corrugated Tube (RCT)” and “Radial Corrugated Tube with Corner (RCTC)”. In order to compare crushing behaviors with those of corrugated circular tubes, a simply circular tube (CT) is also analyzed. It is revealed that, in the crushing process, the crushing mode of RCT becomes more unstable than one of CT since the wavelength of fold becomes long, and the fold concentrates to the center of wavelength. However, when the length and the diameter of tubes set to be same levels, RCT demonstrates good energy absorption characteristics. Further, it is showed that the compressive load and the load efficiency of RCTC increase by the effect of corner part.

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We have investigated the interaction between dislocation cores of misfit dislocation on a semi-coherent interface and edge/screw dislocations gliding in a mono-lattice, by using molecular dynamics simulations. Edge dislocations, of which extra plane lies on the same side of that of misfit dislocation (same sign), bring about new dislocations from orthogonal line of misfit dislocation network to the cross-slip plane, keeping its Burgers vectors. Edge dislocations with opposite sign react with misfit dislocations, resulting in a new dislocation on the conjugate slip plane (parallel collision) or dislocation locks at the cross-sectional points (cross collision). Screw dislocations bounce at the interface by cross slip if they bump into misfit dislocation in parallel. On the other hand, a zig-zag dislocation is formed on the interface by crisscross cutting, due to the coincidence of Burgers vectors of screw and misfit (edge) dislocations. Then the zig-zag line is straightened with the line tension.

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A new technique for boundary element analysis of potential problems using a multipole expansion to obtain the solution quickly only in a target region has been developed. The capability of the present technique was verified by numerical simulations. In this technique, the multipole expansion is applied to boundary integral equations on non-target boundaries, and the expansion is truncated at the term where the error bound of the higher terms is guaranteed. This technique decreases the calculation amount by introducing multipole moments as the unknown in place of the unknown in the non-target region. To demonstrate the effectiveness of the method, some example analyses were performed. When the solutions only in the target region are needed, especially in large size boundary value problems, this technique enables us to obtain them quickly and precisely.

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This paper proposes an analytical method to determine the stress distribution in an elastic body using the stress measured on the surface. The basic equation is derived from the boundary integral equation approach introducing a point source which produces displacement and stress fields in the elastic body. The point source is called as a body force dipole and composed of two same body forces acting in the opposite directions at the same location. The basic solutions on the displacement and stress fields by a body force dipole are derived theoretically and are confirmed numerically that they produce the same fields generated by a pair of body forces. Then the input conditions are discussed how the location, the number and the components of known surface stress effect on the accuracy of the inverse analysis of the body force dipole distribution. The results show that only the tangential stress component measured on the surface should be used in the inverse analysis.

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In a structural material of the aircraft, the proportion of composite materials keeps rising more and more because of their excellent properties on specific strength and rigidity. The part where a metallic material is connected to the composite material increases by such circumstances, and how a structural integrity in such a place is secured becomes an important problem. In previous paper, a principle of a method to monitor the mechanical behaviors using axial strain in fastener bolt was proposed. Here, we actually made the fastener with an optical fiber sensor embedded in the shank of a titanium bolt, and applied it to the composite/titanium mechanical shear joint specimens to prove the function of it through the tensile tests. The results are summarized as follows, (1) proposed monitoring method is well available to monitor the load transfer mode around the fastener hole, (2) we can evaluate both the bearing loads acting to the shank of fastener bolt and the interfacial frictional loads between both materials by this method

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In this study, the theory proposed by the author to forecast distributions of length of visible part separated by other fibers and length of overlapping part covered with other fibers which could be observed under the surface of a short fiber reinforced composite was examined. For the examination, packing of fibers in space was computer simulated. The fibers were packed in a cubic space. Random numbers were used to assign position and orientation to the fibers. The computer-simulated short fiber reinforced composite was sectioned at a prescribed thickness. The sectioned simulated sample was observed from the surface, and the distributions of the length of the visible part and the overlapping part were measured. The obtained distributions and the average values of the length of those parts were compared with the distributions and the average values estimated by the theory. The distribution and average value of the length of the visible part estimated by the theory was almost corresponding to the simulational result. In the case that fiber orientation distribution was mostly random in three dimensions, the distribution and average value of the length of the overlapping part estimated by the theory was roughly corresponding to the simulational result.

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The tear characteristics of rubber can be improved by filling with ball-shaped filler (Exa. carbon black). We focused on the effect of vapor-grown carbon fiber (VGCF) filler on rubber tear characteristics. An experiment was conducted to study the tear strength of styrene-butadiene rubber (SBR) filled with various concentrations of carbon black (CB) and vapor-grown carbon fiber (VGCF). A trouser-leg tear test was used to determine tear initiation strength. VGCF has hardness similar to that of CB. It was found that the rubber tear strength increased with increasing VGCF concentration (only VGCF filling), and the sample tensile strength was degraded by filling with VGCF because of the untreated surface. The appropriate filling ratio of VGCF and CB was also found to be necessary to reinforce the rubber tear strength.

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In the assessment of structural integrity and remaining life of a power component operated at high temperatures, evaluation of crack-like damage is frequently required. When estimating crack propagation rates under creep-fatigue loading, J-integral type inelastic fracture mechanics parameters including elastic-plastic J-integral for elastic-plastic body and creep J-integral for creeping body are needed. Although these parameters may be estimated by detailed inelastic finite element analysis of a cracked component, this kind of analysis is usually laboring and costly. Therefore, employing simplified methods such as the reference stress approach is practical. Since the reference stress approach has been developed for an inelastic body subjected to external loading, a method to apply this to a component under secondary stress has not been established. This paper proposes an approach to apply the reference stress method to a cracked component subjected to displacement-controlled loading together with a clear definition of elastic follow-up factor

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The interfacial fracture toughness of anodic bonds between silicon and glass is quantitatively evaluated using the stress intensity factors of an interfacial crack between dissimilar anisotropic materials. Partial delaminations of anodic bonds were introduced using the photolithography and the BHF-etching. To investigate the effect of crystal anisotropy on the fracture toughness of an anodic bond, both the (100) and the (111) silicon wafers were used. The tensile fracture tests of anodic bonds between silicon chips and Pyrex glasses were performed to measure the fracture load. The stress intensity factors of interfacial cracks in anodic bonds at fracture were calculated using the combination between the finite element method and the modified virtual crack extension method which was developed in our previous study. The fracture mode of tensile tests were mixed mode and cracks kinked into Pyrex glass. The fracture toughness of specimens using the (100) and the (111) silicon wafers was almost identical. The thermal shock tests of anodic bonds between silicon chips and soda glasses were performed. The temperatures when the anodic bonds were broken were measured. The stress intensity factor under the thermal stress was almost pure mode II, and cracks were extended along the cleavage planes of silicon chips. The fracture toughness of an anodic bond using the (111) silicon wafer was higher than that using the (100) silicon wafer.

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If a shape-memory alloy (SMA) thin strip is applied to the elements subjected to torsion, a rotary driving element with a simple mechanism can be developed. In order to develop the rotary driving elements with the SMA thin strip, the torsion test, the recovery torque test and the torsion fatigue test were carried out for the TiNi SMA thin strip. The basic characteristics of the SMA thin strip for torsion were obtained. Torque increases in proportion to angle of twist and temperature. Recovery torque increases in proportion to angle of twist and temperature. The recoverable strain energy increases in proportion to temperature, but the dissipated work decreases slightly with an increase in temperature. Fatigue life decreases in proportion to amplitude of twisting angle. The fatigue life of the heat-treated material is longer than that of the as-received material. The fatigue limit of amplitude of twisting angle for the heat-treated material is almost the same as that for the as-received material. In order to develop the rotary driving elements, an opening or closing door driven by the SMA thin strip is demonstrated.

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The theromoelastic stress analysis system, which is a stress analysis technique based on the measurement of infrared emission from the surface of a body, was applied to inspection of a fatigue crack initiated at a weld toe in a welded joint and to evaluation of stress intensity factor ranges at crack tips in order to assess the validity of this technique as a nondestructive inspection method. As a result, the fatigue crack was detected from 0.75 mm in length by this technique, and the values of crack length estimated from the stress images were agreed with those measured by the optical microscope within 3%. Also, stress intensity factor ranges ΔK evaluated from stress distributions around a crack tip measured by this system coincided with comparable numerical values within 3%.

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It is examined by numerical calculation whether a finite plate with a 2D crack provides intrinsic natures of oscillation of an infinite plate, emphasizing the application to geometrical characterization of a geothermal reservoir crack. Boundary Integral Equation Method is employed for the numerical calculation. Two extreme cases are considered, i.e., a crack without fluid in it (dry) and a crack filled with fluid (wet). The results show that what happens depends on if the crack is dry or wet. If the crack is dry, no information on oscillation nature of the infinite plate is available from the data of oscillation of a finite plate. On the contrary to this, if the crack is wet, the intrinsic nature of an infinite plate oscillation appears clearly in the data of oscillation of the finite plate. Scale effect does exist, depending on the size ratio defined as the ratio of the plate half width to the crack half length. The scale effect shrinks rapidly with the increasing size ratio. It is found that the scale effect disappears for the size ratio that is larger than two.

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Acute coronary syndromes are caused by the rupture of unstable plaques on coronary arteries. The stability of plaque, which depends on biomechanical properties of fibrous cap, should be diagnosed crucially. Recently, Optical Coherence Straingraphy (OCS), e.g. an estimator of micro bio-strain distribution, has been being improved on the basis of Optical Coherence Tomography. This is composed of the recursive cross-correlation technique, which can provide the displacement vector distribution with high resolution. However, biomechanical characteristics have never estimated exhaustively, because OCT images severely include the speckle noise occurred by back-scattering light from tissue. In the present study, proposed is Adjacent Cross-correlation Multiplication (ACM) as speckle noise reduction method. Multiplying adjacent correlation maps can eliminate anomalies from speckle noise, and then enhance S/N in the determination of maximum correlation coefficient. Error propagation can be further prevented by recursively introducing to OCS algorithm. In this report, the proposed method was experimentally and numerically applied to compressed tissue samples to carry out the accuracy verifications. Consequently, it was quantitatively confirmed that its accuracy of displacement vectors could be enhanced by introducing ACM to OCS, thus, the proposed method can obtain the accurate strain map with high resolution.

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By processing triangle or square pyramid shaped indents on a flat sheet, panels with periodical indents in regular plane tiling patterns are manufactured. Highly rigid core panels are newly developed by setting this panel (as top panel) on a reversed one (as bottom panel), and gluing/ welding them at the apexes of pyramids to the vertexes of the tiling patterns in the bottom panel. The basic model named Dia-Core is a panel created in the form of Octet-Truss developed by Fuller which corresponds to the space filling model consisting of a combination of two tetrahedra and one octahedron. By varying the geometric patterns that appear on the panel surfaces, all possible patterns based on geometrical considerations are devised, systematically creating various modified models with larger welding portions.

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Non-contact torque sensor by using magnetostrictive alloy ring of polycrystalline FeGa (Galfenol) system was developed. For engineering sensor applications for automobile etc., it becomes necessary to increase the strength much more than that of the present binary FeGa alloy. Therefore, in the present paper, at first, ternary FeGaAl alloy with an additional C element was fabricated and then the magnetic property and mechanical property of that alloy were investigated. (Fe-13.6 Ga-6 Al) -1.5 C [at.%] sample showed the value of 50 ppm of maximum magnetostriction and value of 667 MPa of fracture stress which seem applicable as a torque sensor material. The torque sensor system was assembled using this alloy ring on the twisted shaft of non-ferromagnetic material and the output magnetic field was measured by ten adjacent Hall-sensor. The output voltage showed the almost linear relationship against applied torque and the sensitivity was 47.5 mOe/N·m, which seems a promising data for the proposed torque sensing system.

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