Search

Abstract: This paper study the effect of Casimir intermolecular force on stress distribution of electrostatic cantilever nano-electromechanical systems (NEMS) using homotopy perturbation method (HPM). An analytical closed-form solution has been obtained in terms of convergent series with easily computable components. The shear force, bending moment and stress distribution along the cantilevers at the onset of instability, which are important parameters for designing electromechanical systems are computed and compared with numerical solution. Furthermore, the results computed by HPM method agree with numerical solutions and those from the literature. [Copyright &y& Elsevier]

Abstract: Herein, homotopy perturbation method (HPM) is used to investigate the effect of van der Waals force on the pull-in parameters and stress distribution and the instability of electrostatic actuators at nano-scale separations. The shear force, bending moment and stress distribution along the cantilevers at the onset of instability, which are important parameters for designing and manufacturing nano-actuators, are computed. An analytical closed-form solution is obtained and compared with numerical solution and those from literature. It has been shown that van der Waals attraction can highly influences the pull-in parameters and internal stress field of the nano-actuator. [Copyright &y& Elsevier]

Abstract: Spinning is frequently used for manufacturing axisymmetric shapes where press tooling might not be justified on grounds of size and production volumes. Spinning also has the possibility of producing parts that could not be deep drawn. The temperature effect is significant on the metal forming processes; for the quality of products and the tools life are extremely affected by it. In this paper, a three-dimensional explicit finite-element analysis (FEA) is employed to simulate the spinning process of an aluminium circular sheet and also we investigate the thermal effects on the conventional spinning process by the explicit finite element method. The energy terms in this study include the plastic strain energy, the frictional sliding energy, and the heat transfer energy. The various mesh types are examined in the simulations. The main benefit of the proposed model will save the tremendous costs in the die designing and the experimental works. The parameters and techniques using in the numerical model are helpful for the design of forming process and the coupling thermal-mechanical analysis. [Copyright &y& Elsevier]

• Adobe is one of the main constituents of old heritage and current buildings in world. • Adobe is a sustainable, inexpensive and environmentally friendly material. • Novel strengthening and reinforcement methods of adobe material is necessary. • Laser shock process enhances mechanical properties of the adobe. • Laser treatment reduces water absorption of the adobe. • Microstructure analysis confirm improved integrity and homogeneity of adobe surface by laser treatment. Many of the old heritage buildings and even many current buildings in the world are made of adobe, which is a sustainable, inexpensive, and environmentally friendly material. The adobe buildings react harmoniously against gravity or lateral forces, but structural fractures and sudden forces such as natural disasters or moisture leakage are the main causes of making them vulnerable, especially against earthquakes. Strengthening and reinforcement of adobe materials have long been discussed, and techniques such as adding materials to adobe or plastering adobe walls have been used to increase its resistance. Here, laser shock processing operation is exploited to analyze the extent of change in mechanical strength and moisture resistance of adobe material and ultimately to test its applicability to heritage buildings. The distance between the focal point of the laser beam and the surface of the adobe is optimized while an optimum value is also obtained for laser intensity. Laser radiation increases the compressive strength and flexural strength of the adobe by 348% and 12%, with respect to the raw material, whereas no significant difference is observed in the tensile strength. Nevertheless, the hydrophobicity of the samples increases by upper defocus and increasing the defocus, improves the soil adhesion, and escalates the homogeneity and integrity of the surface. Microstructural analysis such as SEM, EDAX and XRD of raw, and laser-treated adobe material confirm these improvements and overall render laser treatments an interesting, beneficial candidate among adobe reinforcement techniques. [ABSTRACT FROM AUTHOR]