A toughness based deformation limit for fatigue-cracked X-joints under in-plane bending. (July 2015)

• Record Type: Journal Article
• Authors: Ahmed, Aziz; Qian, Xudong
• Is Part Of: Marine structures. Volume 42(2015)
• Page Start: 33
• Page End: 52
• Publication Date: 2015-07
• Subjects: Circular hollow section (CHS) -- Ductile tearing initiation -- Fracture deformation limit -- J-integral -- Tubular joint; Naval architecture -- Periodicals; Offshore structures -- Periodicals; Architecture navale -- Périodiques; Structures offshore -- Périodiques; Naval architecture; Offshore structures; Periodicals; 620.4162
• DOI: 10.1016/j.marstruc.2015.03.002
• Languages: English
• ISSNs: 0951-8339

Abstract

Abstract: This study reports a deformation limit for the initiation of ductile fracture failure in fatigue-cracked circular hollow section (CHS) X-joints subjected to brace in-plane bending. The proposed approach sets the deformation limit as the calculated crack driving force in a fatigue crack at the hot-spot location in the tubular joint reaches the material fracture toughness measured from standard fracture specimens. The calibration of the proposed approach and the numerical procedure utilizes two large-scale X-joint specimens with fatigue generated surface cracks. The subsequent numerical investigation covers X-joints with two different brace-to-chord intersection angles, a wide range of geometric parameters and a practical range of material parameters. The development of the deformation limit includes a non-dimensional material toughness, which covers both the geometric parameters and material properties. The lower-bound deformation limit thus developed exhibits a linear relationship with respect to the crack depth ratio and indicates consistent values among X-joints with different brace-to-chord intersection angles. Highlights: We propose a design deformation parameter based on the fracture toughness. The proposed critical deformation covers wide geometric and material parameters. The lower-bound deformation remains linear with respect to crack-depth ratios.