Application of normalization method to fracture resistance testing for storage tank A285 carbon steel

摘要

To determine the fracture resistance and its constraint effect for storage tank A285 carbon steel, a set of single edge notched bend (SENB) specimens with different crack lengths are tested under the guideline of ASTM standard E1820. Normalization method is adopted to develop J-R curves by directly using the load versus load-line displacement data without the need for online crack size measurement. For validation, the conventional electric potential drop method is also used to monitor crack extension, and to determine the J-R curves. The results indicate that the crack extension, J-R curves and fracture initiation toughness determined from both methods are nearly identical for the SENB specimens considered. The J-R curves obtained from the A285 SENB specimens show a strong dependence on crack size or fracture constraint. In reference to the J-A_2 fracture theory, the constraint effect is quantified by a constraint parameter A_2. Through experimental and numerical analyses of the specimens, a constraint-corrected J-R curve is obtained as a function of crack extension and the constraint parameter A_2. It is concluded that the normalization method is valid and cost-effective for the determination of J-R curves from both standard and nonstandard SENB specimens. In addition, the parameter A_2 can reasonably quantify the constraint effect on the experimental J-R curves.