Journal off Mechanical Design 1& l|i>««'M sJBM l^^A J Contributed by the Power Transmission and Gearing Committee for publication in the JOURNAL OF MECHANICAL DESIGN. Manuscript received

This paper presents an analytical expression of the time-varying contact length between perfect involute spur and helical gears. It is shown that contact lengths can be expressed as where AQ (r) and Bo ( T ) are 2 periodic piecewise linear functions represented in AO(T) and BO(T) can be easily decomposed in Fourier series as: AO(T) = -+ X «n • cos (InnT BO(T) * ao contact zone with: sin (2nn(ea + tp)IP)'\ Ea: transverse contact ratio eg: overlap contact ratio The length of a contact line starting at r = (' for either spur or helical gears can be deduced from (1) by: li(T) = lo(T -i) and the total contact length at T becomes: Lir) = S Zo(r -0 1=0 (5) 58

Kinematic Optimization of Energy Extraction Efficiency for Flapping Airfoil by using Response Surface Method and Genetic Algorithm

In this paper, numerical simulations have been performed to study the performance of a single fully activated flapping wing serving as energy harvester. The aims of the paper are predicting and maximizing the energy extraction efficiency by using optimization methodology. The metamodeling and the genetic algorithms are applied in order to find the optimal configuration improving the efficiency. A response surface method (RSM) based on Box–Behnken experimental design and genetic algorithm has been chosen to solve this problem. Three optimization factors have been manipulated, i.e. the dimensionless heaving amplitude h0, the pitching amplitude θ0 and the flapping frequency f. The ANSYS FLUENT 14 commercial software has been used to compute the governing flow equations at a Reynolds number of 1100, while the flapping movement combined from heaving and pitching of the NACA0015 foil has been carried out by using an in house user-defined function (UDF). A maximum predicted efficiency of 34.02% has been obtained with high accuracy of optimal kinematic factors of dimensionless heaving amplitude around the chord, high pitching amplitude and low flapping frequency of 0.304 hertz. Results have also showed that the interaction effect between optimization factors is important and the quadratic effect of the frequency is strong confirming the great potential of the applied optimization methodology

Dynamic behavior of a rotor supported by angular ball bearings

The wide range and large scale usage of rolling bearings indicates their necessity and vital contribution to the performance of modern industries. In this paper, a non linear model, predicting mechanical behavior of the loaded angular ball bearing, have been developed. The dynamic behavior of a rotor supported by two angular ball bearings is analyzed. The finite element method is used and the rotor is decritizied on beam elements. A mathematical modal taking account different sources of non linearity: the Hertzian contact force and the action of all balls on the bearings inner races, is developed. The Newmark algorithm coupled with Newton Raphson iterative method is used to solve the non linear differential equation iteratively

Role of lanthanum vacancy on the structural, magnetic and magnetocaloric properties in the lacunar perovskite manganites La 0.8−x □ x Na 0.2 MnO 3 (0 ≤ x ≤ 0.15)

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Sodium – Deficiency effects on the structural, magnetic and magnetocaloric properties of La 0.8 Na 0.2−x □ x MnO 3 (0 ≤ x ≤ 0.15)

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