Rinehart, Adam James (2003-08). Effects of localized geometric imperfections on the stress behavior of pressurized cylindrical shells. Doctoral Dissertation. Thesis uri icon

abstract

  • The influence of dent imperfections on the elastic stress behavior of cylindrical shells is explored. This problem is of central importance to the prediction of fatigue failure due to dents in petroleum pipelines. Using an approximate technique called the Equivalent Load Method, a semi-analytical model of two-dimensional dent stress behavior is developed. In the three-dimensional situation, decreased dent localization, in particular dent length, and increased dent depth are confirmed to cause dent stress concentration behavior to shift from having a single peak at the dent center to having peaks at the dent periphery. It is demonstrated that the equivalent load method does not predict this shift in stress behavior and cannot be relied upon to analyze relatively small, deep imperfections. The two stress modes of dents are associated with two modes of dent fatigue behavior that have significantly different fatigue lives. A method for distinguishing longer lived Mode P dents from shorter lived Mode C dents based on two measured features of dent geometry is developed and validated. An approach for implementing this analysis in the evaluation of real dents is also suggested.
  • The influence of dent imperfections on the elastic stress behavior of cylindrical shells

    is explored. This problem is of central importance to the prediction of fatigue failure

    due to dents in petroleum pipelines. Using an approximate technique called the

    Equivalent Load Method, a semi-analytical model of two-dimensional dent stress

    behavior is developed. In the three-dimensional situation, decreased dent localization,

    in particular dent length, and increased dent depth are confirmed to cause dent stress

    concentration behavior to shift from having a single peak at the dent center to having

    peaks at the dent periphery. It is demonstrated that the equivalent load method

    does not predict this shift in stress behavior and cannot be relied upon to analyze

    relatively small, deep imperfections. The two stress modes of dents are associated

    with two modes of dent fatigue behavior that have significantly different fatigue lives.

    A method for distinguishing longer lived Mode P dents from shorter lived Mode C

    dents based on two measured features of dent geometry is developed and validated.

    An approach for implementing this analysis in the evaluation of real dents is also

    suggested.

publication date

  • August 2003