Techno Press
Tp_Editing System.E (TES.E)
Login Search


You have a Free online access.
csm
 
CONTENTS
Volume 2, Number 3, September 2013
 

Abstract
This paper investigates the pull-in instability of functionally graded poly-SiGe micro-beams under the combined electrostatic and intermolecular forces and temperature change. The exponential distribution model and Voigt model are used to analyze the functionally graded materials (FGMs). Principle of virtual work is used to derive the nonlinear governing differential equation which is then solved using differential quadrature method (DQM). A parametric study is conducted to show the significant effects of material composition, geometric nonlinearity, temperature change and intermolecular Casimir force.

Key Words
functionally graded materials; micro-beam;pull-in instability;temperature change;Casimir force

Address
Xiao L. Jia and Shi M. Zhang: PetroleumCollege of Mechanical and Transportation Engineering, China University Petroleum-Beijing, 18 Fuxue Road, Changping, Beijing, CO 102249, China
Jie Yang: School of Aerospace, Mechanical and Manufacturing Engineering, RMIT University, PO Box 71, Bundoora, VIC 3083 Australia
Sritawat Kitipornchai: School of Civil Engineering, The University of Queensland, Brisbane, St Lucia 4072, Australia

Abstract
The impact of spar-nacelle-blade coupling on edgewise dynamic responses of spar-type floating wind turbines (S-FOWT) is investigated in this paper. Currently, this coupling is not considered explicitly by researchers. First of all, a coupled model of edgewise vibration of the S-FOWT considering the aerodynamic properties of the blade, variable mass and stiffness per unit length, gravity, the interactions among the blades, nacelle, spar and mooring system, the hydrodynamic effects, the restoring moment and the buoyancy force is proposed. The aerodynamic loads are combined of a steady wind (including the wind shear) and turbulence. Each blade is modeled as a cantilever beam vibrating in its fundamental mode. The mooring cables are modeled using an extended quasi-static method. The hydrodynamic effects calculated by using Morison\'s equation and strip theory consist of added mass, fluid inertia and viscous drag forces. The random sea state is simulated by superimposing a number of linear regular waves. The model shows that the vibration of the blades, nacelle, tower, and spar are coupled in all degrees of freedom and in all inertial, dissipative and elastic components. An uncoupled model of the S-FOWT is then formulated in which the blades and the nacelle are not coupled with the spar vibration. A 5MW S-FOWT is analyzed by using the two proposed models. In the no-wave sea, the coupling is found to contribute to spar responses only. When the wave loading is considered, the coupling is significant for the responses of both the nacelle and the spar.

Key Words
wind energy; floating offshore wind turbine; spar-type; edgewise vibration; blade-nacelle-spar coupling; hydrodynamic effects; Morison\'s equation

Address
Van-Nguyen Dinh and Biswajit Basu: School of Engineering, Trinity College Dublin, Dublin, Ireland
Soren R.K. Nielsen: Department of Civil Engineering, Aalborg University, Aalborg, Denmark

Abstract
This paper targets to investigate the solution of fuzzy quadratic Riccati differential equations with various types of fuzzy environment using Homotopy Perturbation Method (HPM). Fuzzy convex normalized sets are used for the fuzzy parameter and variables. Obtained results are depicted in term of plots to show the efficiency of the proposed method.

Key Words
fuzzy quadratic Riccati differential equation; fuzzy number; triangular fuzzy number; homotopy perturbation method

Address
Smita Tapaswini and S. Chakraverty: Department of Mathematics, National Institute of Technology Rourkela Odisha – 769 008, India

Abstract
In the present study an elastic-plastic strain analysis is carried out for fibrous composites by using numerical modeling. Application of homogeneous transversely-isotropic model was chosen based on problem solution of a square plate with a circular hole under uniaxial tension. The results obtained in this study correspond to the solution of fiber model trial problem, as well as to analytical solution. Further, numerical algorithm and software has been developed, based on simplified theory of small elastic strains for transversely-isotropic bodies, and FEM. The influence of holes and cracks on stress state of complicated configuration transversely-isotropic bodies has been studied. Strain curves and plasticity zones that are formed in vicinity of the concentrators has been provided. Numerical values of effective mechanical parameters calculated for unidirectional composites at different ratios of fiber volume content and matrix. Content volume proportions of fibers and matrix defined for fibrous composite material that enables to behave as elastic-plastic body or as a brittle material. The influences of the fibrous structure on stress concentration in vicinity of holes on boron/aluminum D16, used as an example.

Key Words
modeling; FEM; stress; strain; elastic-plastic; fiber; composite; hole; crack; boron/aluminum

Address
Askhad M. Polatov: Department of Mechanics and Mathematics, National University of Uzbekistan, 4 Universitetskaya,Tashkent 100174, Republic of Uzbekistan

Abstract
The piled raft is a geotechnical construction, consisting of the three elements- piles, raft and the soil, that is applied for the foundation of a tall buildings in an increasing number. The piled rafts nowadays are preferred as the foundation to reduce the overall and differential settlements; and also, provides an economical foundation option for circumstances where the performance of the raft alone does not satisfy the design requirements. The finite element analysis of the piled raft foundation is presented in this paper. The numerical procedure is programmed into finite element based software SAFE in order to conduct the parametric study wherein soil modulus and raft thickness is varied for constant pile diameter. The problems of piled raft for three different load patterns as considered in the available literature (Sawant et al. 2012) are analyzed here using SAFE. The results obtained for load pattern- I using SAFE are compared with those obtained by Sawant et al. (2012). The fair agreement is observed in the results which demonstrate the accuracy of the procedure employed in the present investigation. Further, substantial reduction in maximum deflections and moments are found in piled raft as compared to that in raft. The reduction in deflections is observed with increase in raft thickness and soil modulus. The decrease in maximum moments with increase in soil modulus is seen in raft whereas increase in maximum moments is seen in piled raft. The raft thickness and soil modulus affects the response of the type of the foundation considered in the present investigation.

Key Words
piled raft; raft; pile; load pattern; soil modulus; maximum deflection; maximum moment

Address
H.S. Chore: Department of Civil Engineering, Datta Meghe College of Engineering, Sector-3, Airoli, New Mumbai- 400708, India
M.J. Siddiqui: Department of Civil Engineering, Anjuman- E- Islam A.R. Kalsekar Polytechnic, New Panvel- 410206, India



Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2017 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-42-828-7997, Email: info@techno-press.com