Deformation Analysis of Dented Pipeline via Surface Interpolation

Advances in the interpolation techniques of discrete data points and its application to monitoring the displacement of physical infrastructure has led to improved analytical strain evaluation procedures. In order to generate a detailed mathematical model of the strain state of a dented pipeline, it is necessary to decompose the deformation data obtained from monitoring devices into the corresponding radial, longitudinal and circumferential components. In this paper, a technique for analytically evaluating the strains in dented pipelines based on the coordinates of the geometric profile of the dent is investigated and the strains predicted from the said method are benchmarked against the strains predicted from a numerical model generated using nonlinear finite element analysis (FEA) and the codified equations for evaluating strains in dented pipes. This novel technique to strain analysis is an application of the principles of shell theory to a deformed pipeline in order to evaluate the components of the displacements in the cylindrical coordinate system. The coordinates of the deformed profile are obtained from the FEA model and interpolated with B-Splines curves equipped with second order continuity. The resulting strain distribution along the thickness of the pipe wall is evaluated analytically by performing derivatives on the spline functions. The good agreement obtained in the strains predicted by our model and FEA indicates a possibility of conducting in-depth strain analysis of thin-walled structures without the need for the rigorous FEA.