LONGITUDINAL STIFFNESS ANALYSES FOR THE PROPULSION SHAFTING SYSTEMS OF THE POLAR CLASS ICEBREAKERS

• Published in: Naval Engineers Journal
• Main Authors: VASSILOPOULOS, LYSSIMACHOS, HAMILTON, FRED M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1980
• Subjects: Antarctic; Polar Star; The Antarctic; Antarc*
• Online Access: http://dx.doi.org/10.1111/j.1559-3584.1980.tb05268.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1559-3584.1980.tb05268.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1559-3584.1980.tb05268.x

ABSTRACT During the first and second seasons of its deployment in the Antarctic region, the new United States Coast Guard Icebreaker, POLAR STAR, experienced longitudinal vibration problems in the center and wing shaft systems while breaking ice. To minimize and hopefully eliminate the vibratory responses, the USCG initiated several investigations, some of which will be treated In this paper. One of the items under study concerned the axial stiffness of the shafting systems that is contributed by the thrust bearings, their housings and the foundations on which they rest. Aside from model test studies, numerical assessments were made of these stiffnesses using finite element methods and other techniques. In all, three sets of thrust bearing foundations were analyzed in great detail. These include the original (as‐built) foundations, a modified configuration that was subsequently adopted for the wing shafts of the POLAR STAR and POLAR SEA, and a reinforced configuration that represents an upper bound on the foundation stiffness that can be achieved without drastic changes in shafting system architecture. The balk of the paper duals with the development of the there finite element models that were exercised with the NASTRAN Computer program to predict the stiffness of the three foundation designs. Various considerations that arise in model formulation are treated in some detail, especially the influence of chosen boundary conditions on the final answers. A simplified procedure is next outlined and need for estimating the stiffness of the thrust bearing itself. The estimate is based upon the use of simple structural models whose flexibilities are summed to get the net system flexibility. The results of all the calculations are reviewed in light of the broader objectives of the overall program and recommendations are given for further investigations that will aid in the understanding of the Icebreaker vibration problems.