Estimation of internal defect size by means of radial deformations in pipes subjected to internal pressure

Metals like carbon steel are used extensively in pipeline industries due to simplicity and economy. However, flaws such as cracks, pitting, local wall thinning can be generated by corrosion, erosion, and environmental exposure to various substances. In this paper, an analysis of asymmetric radial deformation in pipe with local wall thinning under internal pressure is proposed. The deformation is asymmetric with respect to the axis and consists of a radial displacement of all points in the wall of the pipe. Here, only the vertical and horizontal displacements in pipe are taken into account and they are calculated by means of strain energy method based on the classical Castigliano's theorem. In order to validate the results, a commercially available finite element code is used. The agreement between the theoretical predictions and numerical results is very close. It is found that the internal defect sizes can be estimated knowing the horizontal and vertical displacements.