Primary stress in scarred boiler tubes

The sensitivity of failure analysis of boiler tubes to the shape of elliptical external erosion flaws

“…Previous finite element analysis (FEA) studies on boiler tubes were done using flaw geometries such as: elliptical scar, triangular scar, rectangular scar, double rectangular scar and part-through rectangular scar [32][33][34]. These flaw geometries do not resemble the scenarios of localized external erosion which we observed in examples of failed boiler tubes [35].…”

“…In this initial investigation on failure pressure, the failure pressure of the tubes is defined as the internal pressure that results in a peak plastic strain of 5%, 𝑃 % . Previous research reported on limit load analysis using an elastic perfectly plastic model [3,26,28,32], with some also using 2% plastic strain, 𝑃 % [21,22], as an upper limit. Others used the Von Mises equivalent stress limit σ [23][24][25][26], without setting a limit on the amount of strain that should be allowed within the flaw area.…”

“…These comparative studies are then used to determine to what extent more complex flaw geometries need to be considered. A broad range of flaws are used for this study, unlike many of the general investigations performed on localized external erosion of boiler tubes, which usually focus on few flaws, sometimes only one or two [11,[17][18][19]32].…”