Current Issue : July - September Volume : 2013 Issue Number : 3 Articles : 5 Articles
Due to the lower dynamic load, the noise level during the operation in smaller automotive transmissions, helical gears have become the subject of attention. This paper explains about the comparison of the geometry of helical gears for two different modules and materials by modeling and mathematical equations, and the contact analysis of Helical gears using three-dimensional finite element method. The contact stresses were examined using three-dimensional finite element model. These stresses of different modules for different materials obtained from the finite element analysis were compared with the theoretical values. Both results agree very well. This indicates that the finite element method model is accurate....
The aim of this paper is to utilise genetic algorithm approach to investigate the effect of CNC drilling process variables such as spindle speed, drill diameter, material thickness, and feed rate on thrust force and torque generated during the drilling of mild steel plate using H.S.S drill. To find out the relationship between drilling process variable on thrust force and torque generated to the jig and work table, multiple regression model will be used. Regression model will be generated with the help of SPSS-19. Statistical validity, explanatory power and significance of the regression model will be tested at 95% confidence interval. High degree of correlation between drilling parameters and thrust force/torque has been found with almost negligible interaction amongst the drilling process parameter. Regression model developed explain thrust force and torque is found significant. Optimum combination of process variable to explain thrust force and torque generated is found with the help of MATLAB solver using genetic algorithm. Sensitivity analysis investigates the change in the solutions resulting from making changes in parameters of the GA model. In this research, sensitivity analysis shows how sensitive of solutions and decision variables to changes in weights in objective functions. It shows that the solutions of an aggregation method are affected by weight adjustment. Thus, in case of aggregation method, if the weights are not appropriately assigned, the GA may not give out good solutions. On the other hand, for the proposed Pareto method, it is not sensitive to weigh, so incorrect weights do not affect the solution outcome of Pareto based MOGA....
A general nonlinear time-varying (NLTV) dynamic model and linear time-varying (LTV) dynamic model are presented for\r\nshield tunnel boring machine (TBM) cutterhead driving system, respectively. Different gear backlashes and mesh damped and\r\ntransmission errors are considered in the NLTV dynamic model.The corresponding multiple-input and multiple-output (MIMO)\r\nstate space models are also presented.Through analyzing the linear dynamic model, the optimal reducer ratio (ORR) and optimal\r\ntransmission ratio (OTR) are obtained for the shield TBM cutterhead driving system, respectively.The NLTV and LTV dynamic\r\nmodels are numerically simulated, and the effects of physical parameters under various conditions of NLTV dynamic model are\r\nanalyzed. Physical parameters such as the load torque, gear backlash and transmission error, gear mesh stiffness and damped,\r\npinions inertia and damped, large gear inertia and damped, andmotor rotor inertia and damped are investigated in detail to analyze\r\ntheir effects on dynamic response and performances of the shield TBM cutterhead driving system. Some preliminary approaches\r\nare proposed to improve dynamic performances of the cutterhead driving system, and dynamic models will provide a foundation\r\nfor shield TBM cutterhead driving system�s cutterhead fault diagnosis, motion control, and torque synchronous control....
Rossby solitary waves generated by a wavy bottom are studied in stratified fluids. From the quasigeostrophic vorticity equation\r\nincluding a wavy bottom and dissipation, by employing perturbation expansions and stretching transforms of time and space,\r\na forced KdV-ILW-Burgers equation is derived through a new scale analysis, modelling the evolution of Rossby solitary waves.\r\nBy analysis and calculation, based on the conservation relations of the KdV-ILW-Burgers equation, the conservation laws of\r\nRossby solitary waves are obtained. Finally, the numerical solutions of the forced KdV-ILW-Burgers equation are given by using\r\nthe pseudospectral method, and the evolutional feature of solitary waves generated by a wavy bottom is discussed. The results\r\nshow that, besides the solitary waves, an additional harmonic wave appears in the wavy bottom forcing region, and they propagate\r\nindependently and do not interfere with each other. Furthermore, the wavy bottom forcing can prevent wave breaking to some\r\nextent.Meanwhile, the effect of dissipation and detuning parameter on Rossby solitary waves is also studied. Research on the wavy\r\nbottom effect on the Rossby solitary waves dynamics is of interest in analytical geophysical fluid dynamics....
There is a special circumfluence in the center region of cross-section for a tri-screw extruder. To study the effect of the dynamic\r\ncenter region on the flow and mixingmechanism of the tri-screw extruder, 2D finite elementmodeling was used to reduce the axial\r\neffects. Based on the particle tracking technology, the nonlinear dynamics of a typical particle motions in the center region was\r\ncarried out and the mixing process in the tri-screw extruder was analyzed with Poincar�´emaps.Moreover, mixing evaluations of the\r\ntri-screw and twin-screw extruders were analyzed and compared. The results show that there are many multiple and fractional\r\nexcitation frequencies in the Fast Fourier Transform(FFT) spectrums, and it shows a chaoticmotion in the center region. Poincar�´e\r\nsection maps in the tri-screw show the better particles diffusive ability than those in the twin-screw extrude due to the excellent\r\ndiffluent ability. Furthermore, the tri-screw extruder has the better dispersive, distributive mixing abilities and stretching mixing\r\nefficiency than the twin-screw extruder in the cross-section....
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