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Marine propeller shafts transmit power from engine to propeller assembled at the end of shaft. These shafts are long and have large diameters. They are supported on bushed bearings mounted on supports using bolts. Due to large diameter and large self weight, these shafts undergo large deflection. Estimation of deflection and stresses induced due to self weight are important at the time of normal operation as well as at the time of assembly and mounting of shafts, bearing and bolts. Even if the shaft is designed taking into account the stresses induced at the time of normal operation after it is properly installed and supported, it may fail at the time of mounting and assembly due to excessive deflections and stresses arising because partial support and constraints encountered during handling and assembly. Further, even under completely assembled condition, the deformation and compliance of bearings and bolts cause the deflection and stresses to be different than those estimated using classical methods of mechanics. Kozousek and Davies (2000) outlined the new shaft alignment rules and explained their impact on shaft alignment. They have suggested that shafts can be modeled using classical continuous beam theories. Further, they suggested that bearings can also be modeled and point of support can be considered in mid span of bearing length. Murawski (2005) studied shaft line alignment taking into consideration hull deformations. According to his work, intermediate bearings are flexible member of propulsion system, but they can be considered heavy and stiff. Low and Lim (2004) also studied the effect of hull deflection on shaft line alignment. They have suggested that pre-tilting the projected shaft line downwards is necessary in order to counter the problem of inherent upward tilting of the shaft in floating condition of ship. Lei et al. (2010) analyzed propeller shaft misalignment considering ship weight and its buoyancy. In this work, a method of propeller alignment is proposed considering hull deformations. They proposed that attention should be paid to negative influence of temperature fields during shaft installation and alignment work. Propulsion shaft alignment should be done considering flexibility of bearing foundation (IRS, 2010). In analytical calculations or strain gauge measurement technique, the bearing supports are considered rigid, and results obtained do not account for bearing or bush deformation. Most of the shaft alignment calculations are done based on theoretical modeling analysis of the shafting which calculates bearing loads, bearing reaction and slope at the theoretical static aligned condition. These results do not provide comprehensive information for actual situation. In all these works, earlier researchers have not considered the effects of deformation and compliance of support bearings and bolts. When the deflection and stresses are calculated using classical beam theory, it is not possible to account for deformation of bearings, bolts and compliance of base. In this paper, an analysis is done using finite element method by which such factors can be taken into account. An elementary analysis of effect to bolt size is also included in this work. Foundation bolt size affects the flexibility and compliance of the overall shaft system. Bush deformation is also considered while studying the shaft stresses. The results are compared with those obtained using the classical theory. The method of analysis and the results should be useful in estimating the deflections and stresses in heavy and long shafts with better accuracy compared to the approaches and results given in earlier research. This proposed method of analysis should also be useful in estimating the possibility of failure due to excessive stresses and deflections during mounting and assembly of such shafts.
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