Effect of welded joint imperfection on the integrity of pipe elbows subjected to internal pressure

Abstract

Imajući u vidu da lokalna oštećenja smanjuju nosivost i mogućnost deformiranja cjevovoda, analiziran je utjecaj grešaka u zavarenom spoju na integritet cijevnih lukova izloženih djelovanju unutarnjeg tlaka. Ispitivane su greške tipa neprovarenosti, jer su defekti ovog tipa prethodno otkriveni ultrazvučnim ispitivanjem na unutarnjoj površini cjevovoda u hidroelektrani. Trodimenzijska analiza metodom konačnih elemenata je urađena uporabom programskog paketa Abaqus. Određen je utjecaj geometrije defekta u zavarenom spoju (dubina, duljina i položaj) na integritet cijevnih lukova. Također je određen pad nosivosti u slučaju da postoji pukotina na dnu defekta. Ispitan je utjecaj tipa konačnih elemenata (rabljeni su elementi oblika heksaedra i tetraedra).Since local defects reduce the load-carrying capacity and deformation ability of a piping system, an analysis is undertaken to quantify the influence of weld defects on integrity of the pipe elbows subjected to internal pressure. Incompletely filled groove is examined, because this type of defect was previously detected by ultrasonic measurement on the inner surface of the pipeline from a hydro-power plant. Three-dimensional finite element analysis is conducted using Abaqus software package. The influence of weld defect geometry (its depth, length and location) on the elbow integrity is determined. Additionally, decrease of load carrying capacity is determined for the case when a crack has initiated at the bottom of the defect. The influence of finite element type (hexahedral or tetrahedral) is examined