The determination of service-life estimates for large marine machinery components subjected to resonance under transient and continuous operating conditions is discussed, and information is presented on the assessment of safe torsional vibration limits using standards of comparison. For a given service-life duration, the limiting standards for resonance amplitudes were considered for intermediate shafts, i.e., those between the crankshaft and screwshaft. It is shown that the usual deterministic description of steady vibrations is insufficient in this case, and that the special features of nonsteady-state vibrations under transient conditions, the random nature of the deviations of resonance amplitudes from the average, and the reliability of the damper system as a whole should be taken into account. It has been ascertained that the recurrence of transient conditions and the duration of continuous-operation conditions are subject to statistical distributions reflecting the working conditions of vessels used for various purposes and of their classes. Such statistics, combined with the dynamics of the shaft, make it possible to reproduce the shaftings loadlife-long spectrum, i.e., to determine its service-life when designing the shafting. The first macrocrack occurring over a stress-concentration area is considered to be the maximum damage condition of the shaft, and a certain curve at the lower edge of the model-specimen lifes distribution is considered to be the fatigue curve. Two approaches were considered: the calculation of the shaft under continuous-operation conditions with unrestricted service-life and of a shaft under transient conditions for a given service-life period. Apparently for the first time, a theoretical basis was given to the two stated torsional-stress limit standards circulated by vessel-classification societies and by the Registers of Shipping. A comparison of the limit standards theoretically obtained in this manner with those available at the Register has shown a qualitative and a close quantitative correspondence. The need for further development of the theory of the nonsteady-state vibration process, and for the introduction of differential equations of motion for random damping functions is noted.

  • Authors:
    • Vagapov, R D
    • Shishorina, O I
    • Yakovleva, M V
  • Publication Date: 1968

Media Info

  • Features: Figures; Tables;
  • Pagination: p. 51-63
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00014963
  • Record Type: Publication
  • Source Agency: Joint Publications Research Service
  • Files: TRIS
  • Created Date: May 7 1973 12:00AM