EXPERIMENTAL AND FINITE ELEMENT INVESTIGATION OF A LOCAL DENT ON A PRESSURIZED PIPE

The problem of a local dent on a pressurized pipe is studied in this paper. Two case problems of dent are considered-a plain local dent (a smooth local dent without a surface defect), and a local dent associated with a loss of thickness defect. The strain gauging test and the finite element analysis on the plain local dent showed that the strain distributions in the local dent are different from those of a long and continuous dent. The maximum hoop strain in the local dent is located at the flank of the dent, along the dent axial axis, whereas in the case of the long dent, it is located at the root of the dent. In addition, the peak stress in the local dent is generally lower than that in the long dent. To estimate the stress concentration in the local dent using the analysis for the long dent would be grossly overestimated. The burst pipe tests on 17 dented pipes showed that the pipe failures were generally insensitive to the existence of the local dents. The pipe failures were found to be due to the loss-of-thickness defect. The comparison of results between the burst pipe tests and the plastic collapse formula shows reasonably good agreement.