فهرست مطالب

Mechanical Engineering Transactions of ISME - Volume:17 Issue: 1, Mar 2016

Iranian Journal of Mechanical Engineering Transactions of ISME
Volume:17 Issue: 1, Mar 2016

  • تاریخ انتشار: 1396/01/09
  • تعداد عناوین: 5
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  • Abdolamir Bakkhoshnevis, Amir Reza Mamouri *, Mahdieh Khodadadi Pages 5-25
    An experimental study is conducted on flow past a circular cylinder fitted with some tripping wires on its surface. The work investigates the dependency of the critical wire locations on the wire size and Reynolds numbers, and examines the wake and vortex shedding characteristics in an effort to advance the understanding of the critical wire effects beyond the existing literature. The primary aim of this investigation is to assess the significance of the angular locations of the surface trip wire. The wire size is 1.5 mm (wire_ to_ cylinder diameter ratio is 0.075), where in different angular locations attached in to the cylinder (by different number of trip wires, 2, 4, 6, 8, 10) and two Reynolds numbers (Re=10000 and Re=35000). Particularly, positioning the tripping wires at 45˚ (with 4 trip wires) maximally decreased the drag coefficients by 41.6% and 70.6% (Re=10000 and Re=35000, respectively), in comparison with the coefficients produced without the tripping wires. The variations of the Strouhal number is found to be, roughly, inversely related with drag coefficient.
    Keywords: Trip wire, Drag coefficient, Strouhal number, Velocity defect, Hot wire
  • Mojtaba Hasanlu *, Mostafa Siavashi, Ahmad Bagheri Pages 26-60
    The main objective of this study is to reduce optimal vibration suppression of Timoshenko beam under non-periodic step and impulse inputs. Cantilever beam was modeled by Timoshenko theory and finite element numerical method. Stiffness (K), mass (M), and damping (C) matrices are extracted. Then, in order to control structure vibration, piezoelectric patches were used due to simultaneous dual behavior, i.e. switching mechanical behavior to electrical behavior (sensor) and electrical behavior to mechanical behavior (actuator). Piezoelectric patches are used in two different arrays with equal dimensions and different elements for establishing feedback control. In the following, by using quadratic optimal controller (LQR), structure vibrations became attenuated. Weighting coefficients of R and Q matrices and piezoelectric patch location have been searched by multi-objective particle swarm optimization algorithm (MOPSO). Finally, the structure underwent standard inputs of impulse and step and the results are analyzed and compared.
    Keywords: Vibration Attenuation, Timoshenko beam, Optimal placement, PZT Patches, LQR-MOPSO
  • Mohsen Jabbari *, Masoud Rezaei, Arvin Mojahedin, Mohammad Reza Eslami Pages 61-78
    In this study buckling analysis of solid rectangular plate made of porous material in undrained condition is investigated. The mechanical properties of plate are assumed to vary through the thickness direction. Distributing of the pores through the plate thickness are assumed to be the nonlinear nonsymmetric, nonlinear symmetric, and monotonous distribution. The effect of pores and pores distribution on critical buckling load of porous plate are studied. Effect of fluid compressibility on critical buckling load is investigated in the undrained condition. Also, effect of temperature on fluid compressibility for symmetric porous material plate, choosing a linear function, is examined. A Direct and analytical method is used for solving governing equations usin Fourier expansion method. The results obtained for porous plates are verified with the known data in literature.
    Keywords: Buckling analysis, Rectangular plate, Functionally graded plate, Porous material
  • Mohammad Hossein Sharifi, Armin Sabetghadam-Isfahani *, Yegane Davoodbeygi Pages 79-95
    Herein, Compact-Testing (CT ) and Charpy V-Notch (CVN) testing have been done on four Friction-Stir-Processed (FSPed) samples: BM (Base-Metal), FS (FSPed-Sample), FN5 (FSP Nano-ZrO2-coated/560 rpm rotational speed) and FN9 (FSP Nano-ZrO2-coated/900 rpm), to investigate the KIC and the dominant parameters on it for St 37 steel. Experiments are also surveyed and validated by ABAQUS. Results showed the greatest KIC value for BM (CT: 110.40 /CVN: 98.72 MPa√m) and the least for FN9 (CT: 72.20/CVN: 60.08 MPa√m). FSP caused brittle behavior but not as much as FSP Nano-coating. The calculation of CT samples was done in Gerson theory by using of LEFM formulas. Investigations showed more reliability for CVN obtained results. The KIC and ductile fracture decreased after FSP for both CVN and CT.
    Keywords: KIC, CVN, CT, Crack propagation, FSP Nano-coating
  • Hirad Eghbalian, Mohammad Reza Eslami * Pages 96-110
    The generalized coupled thermo-viscoelasticity of hollow sphere subjected to thermal symmetric shock load is presented in this paper. To overcome the infinite speed of thermal wave propagation, the Lord-Shulman theory is considered. Two coupled equations, namely, the radial equation of motion and the energy equation of a hollow sphere are obtained in dimensionless form. Resulting equations are transformed into the Laplace domain using the Laplace transformation and discretized by means of the finite element method along the radius. Week's method is employed to obtain the unknowns in the time domain. The numerical results are provided to examine the propagation of thermal and mechanical waves. The results presented visually as temporal, radial and stress-strain plots to shown wave front of various field variables.
    Keywords: Thermo-viscoelasticity, Lord-Shulman model, Kelvin-Voigt model, Finite element model, Numerical Laplace inverse transformation