A unified perspective of incremental J-integrals by the generalized Griffith framework

Experimental investigation on the correlation between critical storage of elastic strain energy and crack extension in elastic–plastic materials

“…Indeed, the aforesaid modified J ‐integrals are of importance in theoretical research and mechanism understanding during elastic–plastic crack extension, and some prominent problems have arisen at the same time. Conceptual issues in definitions are distinct, FPZ is embedded in ‐integral and theoretical analyses are hard to implement in FPZ for cracked materials and structures 17,40 . Besides, the physical meaning of the modified J ‐integrals will become ambiguous accompanied by the inevitable plastic unloading region 15,16,36 .…”

“…Next, the path independence of the revised J ‐integral is overemphasized, especially within the first modified category of integral‐type fracture parameters. Although these modified path‐independent J ‐integrals may be beneficial to numerical calculations, their derivation is in the regime of divergence theorem and they are all path‐dependent virtually 16,40–42 . Moreover, the judgment of whether a fracture parameter is suitable or not for elastic–plastic crack growth also depends on other properties and its physical meaning, not solely on whether it is path‐independent or not.…”

“…Conceptual issues in definitions are distinct, FPZ is embedded in b J-integral and theoretical analyses are hard to implement in FPZ for cracked materials and structures. 17,40 Besides, the physical meaning of the modified J-integrals will become ambiguous accompanied by the inevitable plastic unloading region. 15,16,36 Next, the path independence of the revised J-integral is overemphasized, especially within the first modified category of integraltype fracture parameters.…”

“…Although these modified pathindependent J-integrals may be beneficial to numerical calculations, their derivation is in the regime of divergence theorem and they are all path-dependent virtually. 16,[40][41][42] Moreover, the judgment of whether a fracture parameter is suitable or not for elastic-plastic crack growth also depends on other properties and its physical meaning, not solely on whether it is path-independent or not. Last but not the least, it remains controversial whether these modified J-integrals can be applicable to indicate the crack driving force and how to choose these fracture parameters for elastic-plastic crack growth, since the relationship is unclear between these revised Jintegrals and the pioneering works by Griffith.…”