Failure analysis of pipe fitting hydro-burst test

Andrew Ruggiero, Nicola Bonora

Techdyn Engineering

Gabriel Testa

University of Cassino and Southern Lazio

Paolo Folgarait

Allied International Srl and Seamthesis

Sergio Coroli

Tectubi Raccordi


The possibility to use continuum damage mechanics to predict failure of a tee in a hydro-burst test with finite element analysis was investigated. In the test, capped pup pieces are welded at the branch and run pipe end sections and the tee is pressurized with water up to rupture. The tee material was characterized determining the plastic flow curve and damage model parameters from traction tests on smooth and round notched bar samples. Hydro-burst test revealed that fracture occurs first at the pup piece weld. Therefore, the weld metal plastic flow curve were determined using an inverse calibration technique, using modeFRONTIER, having as objective function the thickness measured in critical locations. Similarly, the weld damage parameters were calibrated on the experimental burst pressure. Successively, finite element analysis was performed to investigate the capability of the model to predict the correct location of fracture initiation and tee size and geometry effect on predicted burst test pressure.