INTEMA   05428
INSTITUTO DE INVESTIGACIONES EN CIENCIA Y TECNOLOGIA DE MATERIALES
Unidad Ejecutora - UE
artículos
Título:
Two competing crack growth mechanisms in very high pressures tubes
Autor/es:
J,L. OTEGUI; H. KUNERT; J. BOOMAN; P. BARCIA; G. GUIDI
Revista:
ENGINEERING FAILURE ANALYSIS
Editorial:
PERGAMON-ELSEVIER SCIENCE LTD
Referencias:
Año: 2011 vol. 18 p. 564 - 571
ISSN:
1350-6307
Resumen:
This work addresses the influence of autofrettage in the occurrence of repeated leaks of
thick wall straight and curved 4333M4 steel tubes from a high pressure petrochemical
reactor, comprised by straight and curved tubes subjected to autofrettage. Recent leaks
in straight tubes are due to fatigue transgranular growth of cracks initiating from machining
groves in the inner surface, driven by pressure cycles during many years of normal
operation. Experimental measurement of residual stresses verified that high temperature
service relieved most of the compressive residual stresses imposed by the autofrettage.
Previous failures in curved tubes were found to be due to metallurgical susceptibility to
intergranular cracking, related to a phenomenon similar to Temper Embrittlement. Repeating
autofrettage to mitigate fatigue failures would reproduce the deformation mechanisms
that favored intergranular cracking of the tubes. Recently developed life extension strategies
include early detection of leaks by acoustic emission and an improved manufacturing
method of replacement bends.