A new data analysis technique to examine crack tip opening angle values tested in API X65 pipe steel

Abstract

ABSTRACTThis paper presents a new data analysis technique to rapidly identify the region of stable crack growth in crack tip opening angle (CTOA) testing of a modified double cantilever beam. The technique basically used the load–displacement data from CTOA testing on API X65 steel, which demonstrated a region of constant slope after the peak load. In total, 22 data points (out of 90) fell in this region, for which the variation of CTOA versus crack length remained almost constant. The CTOA measurement was conducted from crack edges and from a fine reference grid, using photographs from two cameras in front and rear sides of the CTOA specimen. As the visual analysis of the individual photographs is tedious and rather lengthy, the presented technique can be easily used for rapid and precise identification of the mean CTOA from those data in the constant slope region of the load–displacement plot.