Analysis of environmentally assisted cracking processes in notched steels using the point method

This paper proposes the use of the Point Method (PM) to analyse Environmentally Assisted Cracking (EAC) processes in steels containing U-shaped notches. The PM, a methodology included within the Theory of Critical Distances (TCD), has been extensively validated by many authors for the analysis of fracture and fatigue phenomena of different types of materials containing notches. However, it has never been applied to other critical or subcritical cracking processes such as EAC or creep crack propagation. This work provides a PM-based analysis of EAC emanating from notches, which is validated by testing CT notched specimens of X80 and S420 steels subjected to aggressive environments under hydrogen embrittlement conditions. The results reveal that the PM accurately predicts the crack propagation onset condition, as well as the evolution of the materials apparent EAC resistance.This work was supported by the Spanish Ministry of Science and Innovation through the research projects MAT2014-58443-P and MAT2014-58738-C3-3-R

The Influence of Connection Geometry on the Fatigue Life of National Pipe Thread Threaded Pipe Couplings

In this paper, four-point bending experiments are performed to determine the fatigue life of several threaded pipe couplings. It is shown that fatigue life of these couplings can be improved by designing them with more uniform load distribution in the threads, achieved through reducing the global and local stiffness of the coupling. Finite element simulations of a 2D axisymmetric model show consistence between experimental observation and analytical modeling. A 3D finite element simulation, which includes nonlinear material behavior, elaborate contact properties and represents the coupling geometry more accurately, is also performed to evaluate the 2D axisymmetric finite element model