This paper evaluates the reliability of an aluminum based composite including vapor growth carbon fibers (VGCF) and carbon nanotubes (CNT). The composite is fabricated using spark plasma sintering and has high thermal conductivity. For the reliability evaluation, the correlation between the inelastic deformation and thermal conductivity of the composite is discussed both with experiments and simulation conducted by the finite element method (FEM). Specimens made from the composite are first subjected to tensile loading until inelastic strain occurs. After the tensile loading, the thermal conductivities of the specimens were measured to establish the differences between the thermal conductivity before and after the tensile loading. The FEM analyses are also conducted to evaluate the reliability of the composites. It was found that the thermal conductivity changed due to the inelastic deformation of the composites and that a FEM analysis considering the damage due to the deformation qualitatively estimates the differences in the thermal conductivity before and after the tensile loading.

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When a thin film/substrate system is indented, the measured indentation hardness is always regarded as a weighted average of the hardness of film and that of the substrate material. That is, one usually takes it for granted that the measured hardness should be bounded between that of the film and substrate, and with the increase of indentation depth, the measured hardness should vary monotonically from the intrinsic film hardness to the intrinsic substrate hardness. Using finite element simulations of sharp indentation on film/substrate systems, here we show an “abnormal” behavior that if the film and substrate have close hardness but different plastic behaviors, within a certain range of indentation depth, in some cases the measured hardness may “overshoot” and be higher than both the film and substrate hardness; when the film and substrate materials are reversed, then the measured hardness may “undershoot” and be lower than both the film and substrate hardness. In both cases, the indentation hardness varies non-monotonically with indentation depth. This unconventional behavior may provide some physical insights on correctly interpreting the indentation measurements on thin film/substrate systems.

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Equivalent stiffness of plates clamped by bolted joints for designing should be evaluated according to not only the strength of bolted joints but also the deformation and vibration characteristics of the structures. When the applied external axial load or the bending moment is sufficiently small, the contact surfaces of the bolted joint are stuck together, and thus both the bolt and the clamped plates deform linearly. Although the sophisticated VDI 2230 code gives the appropriate stiffness of clamped plates for the infinitesimal deformation, the stiffness may vary nonlinearly with increasing the loading because of changing the contact state. Therefore, the present paper focuses on the nonlinear behaviour of the bending stiffness of clamped plates by using Finite Element (FE) analyses, taking the contact condition on bearing surfaces and between the plates into account. The FE models of the plates with thicknesses of 3.2, 4.5, 6.0 and 9.0 mm tightened with M8, 10, 12 and 16 bolts were constructed. The relation between bending moment and bending compliance of clamped plates is found to be categorized into three regions, namely, (i) constant compliance with fully stuck contact surfaces, (ii) transition showing the nonlinear compliance, and (iii) constant compliance with one-side contact surfaces. The mechanical models for these three regions are proposed and compared with FEM solutions. The prediction on the bounds of three regions is in a fairly good agreement except the case with smaller bolts and thicker plates.

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The stress singularity fields are one of the main factors responsible for debonding under mechanical or thermal loading. Stress singularity frequently occurs at a vertex in an interface of joints due to a discontinuity of materials. Stress singularity is related to debonding and delamination at interface of the bonded joint. However, the singularity at a vertex in two-phase transversely isotropic piezoelectric dissimilar material joints has not been made clear until now. In this paper, intensity of singularity at a vertex is investigated in transversely isotropic piezoelectric dissimilar material joints. The orders of singularity at a vertex and at a point on singularity lines for piezoelectric bonded joints are determined using eigenanalysis. The stress and electric displacement distributions on an interface and the intensity of singularity at the vertex are investigated using BEM. From the numerical results, it is shown that the 3D intensity of stress singularity increases and the 3D intensity of electric displacement singularity decreases with the increase of material thickness in joint.

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This paper presents an analytical solution for an infinite circular cylinder having a spherical inclusion when the cylinder is subjected to tension at infinity. In this analysis, two types of inclusions, i.e., a perfectly bonded inclusion (displacements and tractions are continuous) and a slipping inclusion (tractions and normal displacements are continuous and shear traction vanishes) are discussed. The solution is based on the Dougall's displacement potentials approach and is deduced through making use of simple forms of spherical and cylindrical harmonics. The boundary conditions on the cylinder at infinity and around the inclusion are fully satisfied with the aid of the relationships between the spherical and cylindrical harmonics. The solution is represented in the form of graphs and the effects of the inclusions on the stress distribution are clarified. From the analyzed results, it is found that the stresses around the inclusion are considerably affected by the interface conditions.

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