Fatigue crack growth behavior of marine steel under variable amplitude loading-combining DIC technique and SEM observation. (May 2023)

• Record Type: Journal Article
• Authors: Wang, Changzi; Wang, Shuqing; Xie, Lingjun; Liu, Yaping; Deng, Junlin; He, Wentao
• Is Part Of: International journal of fatigue. Volume 170(2023)
• Publication Date: 2023-05
• Subjects: DIC technique -- FCG behavior -- Overload retardation -- Strain evolution; Materials -- Fatigue -- Periodicals; Materials -- Fatigue; Periodicals; 620.1122
• DOI: 10.1016/j.ijfatigue.2023.107508
• Languages: English
• ISSNs: 0142-1123

Abstract

Highlights: FCG behavior of AH36 marine steel under variable amplitude loading is investigated. Strain evolution and cyclic fatigue characteristics is studied by DIC technique. Fracture surface morphological analysis is conducted through SEM observations. A crack tip locating method is proposed from displacement distribution. Abstract: This paper experimentally studies the fatigue crack growth (FCG) behavior of AH36 grade marine steel under variable amplitude loading. FCG testing is conducted using compact tension specimens. Digital image correlation technique (DIC) is employed to study the evolution of strain distribution and cyclic fatigue characteristics. Fractographic analysis is performed to explore the overload retardation mechanism. Results indicate that the FCG rate varies significantly under overload application, leading to the extension of fatigue life by 1.03, 1.18 and 2.42 times under the overload ratios (OLRs) of 1.5, 2.0 and 2.5. Reasonable evaluation of the fatigue performance depends on the loading history. Extension of the fatigue life for periodic overload (POL) cases is not a simple superposition of that under two single ones, the interaction effect between the adjacent tensile overloads cannot be neglected. Greater plastic dissipated energy corresponds to more severe plastic deformation at larger OLRs and crack lengths. The larger strain accumulation at the crack tip should account for the greater FCG resistance and more evident overload retardation effect. The fresh fracture surface is destroyed at a certain region after overload due to the premature contact of the crack flanks, confirming that overload induced crack closure exists.