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The piezoelectric properties of bone play an important role in the bone remodeling process and can be employed in clinical bone repair. In this study, the piezo-voltage of bone between two surfaces of a bone beam under bending deformation was measured using an ultra-high-input impedance bioamplifier. The influence of shear stress on the signs of piezo-voltages in bone was determined by comparing and contrasting the results from three-point and four-point bending experiments. From the three-point bending experiment, the study found that the signs of piezo-voltages depend only on shear stress and are not sensitive to the normal stress. [ABSTRACT FROM AUTHOR]

Special hole elements are presented for analyzing the stress behavior of an isotropic elastic solid containing an elliptical hole. The special hole elements are constructed using the special fundamental solutions for an infinite domain containing a single elliptical hole, which are derived based on complex conformal mapping and Cauchy integrals. During the construction of the special elements, the interior displacement and stress fields are assumed to be the combination of fundamental solutions at a number of source points, and the frame displacement field defined over the element boundary is independently approximated with conventional shape functions. The hybrid finite element model is formulated based on a hybrid functional that provides a link between the two assumed independent fields. Because the fundamental solutions used exactly satisfy both the traction-free boundary conditions of the elliptical hole under consideration and the governing equations of the problems of interest, all integrals can be converted into integrals along the element boundary and there is no need to model the elliptical hole boundary. Thus, the mesh effort near the elliptical hole is significantly reduced. Finally, the numerical model is verified through three examples, and the numerical results obtained for the prediction of stress concentration factors caused by elliptical holes are extremely accurate. [ABSTRACT FROM AUTHOR]

Abstract: This paper studies interfacial mechanical behavior of laminate beams, consisting of two piezoelectric facial sheets and an elastic core. The study is based on coupled multi-filed finite element formulation. The emphasis is placed on mechanical and electric behavior of interfaces between piezoelectric material and elastic material, including effect of geometrical parameters, stress distribution and stress concentration near free edge of the beam subjected to coupling electric and mechanical loads. In particular, various parametric effect of laminate beam is explored and some conclusions are presented which may be useful for designing laminate beam and minimizing stress concentration at the free edges of the beam. [Copyright &y& Elsevier]

A theoretical model of a single piezoelectric fibre pull-out is developed to study the interaction between fibre deformation, pull-out stress and corresponding electrical field. Computer simulation of the stress–displacement curve of the fibre pull-out process is presented. Numerical examples show that the piezoelectric fibre pull-out behaviour can be both described and affected by its electrical field. Therefore, the interactions between the mechanical and electric fields of the fibre/matrix system can be employed to monitor and control the fracture behaviour of active fibre composites. [Copyright &y& Elsevier]

This paper presents a study on interfacial stresses of a concrete column confined by fiber-reinforced plastic (FRP) plate, which has been widely applied in the civil engineering for rehabilitation and retrofitting of conventional structures. It is assumed that both the FRP plate and concrete structures are elastic and the interface between them is perfectly bonded. An analytical model for analysis of the interfacial stresses is developed and the finite element modeling is carried out for an axisymmetric FRP–concrete hybrid column. Components of the FRP plate with different geometric and material properties are considered to study their effects on the interfacial stresses. The study shows that the interfacial stresses are influenced by several factors, such as modulus ratio of FRP and concrete and thickness of FRP. This work provides a comprehensive investigation on the mechanical behavior of the interface in hybrid structures. [Copyright &y& Elsevier]

The evolution of real-time stress in porous silicon (PS) during drying is investigated using micro-Raman spectroscopy. The results show that the PS sample underwent non-negligible stress when immersed in liquid and suffered a stress impulsion during drying. Such nonlinear transformation and nonhomogeneneous distribution of stress are regarded as the coupling effects of several physical phenomena attributable to the intricate topological structure of PS. The effect of dynamic capillarity can induce microcracks and even collapse in PS structures during manufacture and storage. [ABSTRACT FROM AUTHOR]

In this work, an analytical solution for layered magneto-electro-elastic (MEE) cylindrical shell adhesively bonded by viscoelastic interlayer is developed to predict its time-dependent mechanical, electric and magnetic behaviors. The viscoelastic characteristic of the interlayer is modelled by the standard linear solid model. Each MEE layer is governed by the equations of magneto-electro-elasticity. The imperfect electric conditions between adjacent MEE layers are also considered. Using the Pseudo-Stroh formalism, a general solution with unknown coefficients is derived for each MEE layer. The Laplace transformation is applied to the constitutive equations of the viscoelastic interlayer. The coefficients are determined by the surface conditions as well as the interface conditions. The present solution can be used as the benchmark to assess results from numerical approaches. It is shown that the finite element solution converges to the present one as the mesh density increases; however, the finite element method is time-consuming in mesh division and calculation. Finally, the effects of time, shell angle, interlayer thickness and imperfect electric coefficient on the mechanical, electric and magnetic behaviors are investigated. [ABSTRACT FROM AUTHOR]

Abstract: Based on the concepts of eigenstrain and equivalent inclusion of Eshelby for inhomogeneity problems, a computational model and its solution procedure are presented using the proposed three-dimensional (3D) eigenstrain formulation of boundary integral equations (BIE) for simulating ellipsoidal particle-reinforced (and/or void-weakened) inhomogeneous materials. In the model, the eigenstrains characterizing deformation behaviors of each particle embedded in the matrix are determined using an iterative scheme with the aid of the corresponding Eshelby tensors, which can be obtained beforehand either analytically or numerically. With the proposed numerical model, the unknowns of the problem appear only on the boundary of the solution domain, since the interface condition between particles/voids and the matrix is satisfied naturally. The solution scale of the inhomogeneity problem can thus be significantly reduced. Using the algorithm, the stress distribution and the overall elastic properties are identified for ellipsoidal particle-reinforced/void-weakened inhomogeneous materials over a representative volume element (RVE). The effects of a variety of factors on the overall properties of the materials as well as the convergence behavior of the algorithm are studied numerically, showing the validity and efficiency of the proposed algorithm. [Copyright &y& Elsevier]

Abstract: We present a Raman spectroscopy study on a film of carbon nanotubes (CNTs) acting as a wireless sensor for measuring strain at the microscale. A model for the CNT strain sensor was proposed by evaluating the quantitative contributions of individual deformed CNTs to the entire Raman spectrum. The proposed model provides an analytical relationship between the in-plane strain components to be measured and the spectral parameters detected directly through polarized Raman tests on the CNT film sensor. Based on this model, a noncontact technique for strain measurements is developed. The experiments using this technique confirmed that the CNT strain sensor described is appropriate for measuring the in-plane strain components at the microscale by using polarized Raman spectroscopy. [Copyright &y& Elsevier]