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Unified characterisation of in‐plane and out‐of‐plane constraint based on crack‐tip equivalent plastic strain
Author(s) -
YANG J.,
WANG G. Z.,
XUAN F. Z.,
TU S. T.
Publication year - 2013
Publication title -
fatigue and fracture of engineering materials and structures
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.887
H-Index - 84
eISSN - 1460-2695
pISSN - 8756-758X
DOI - 10.1111/ffe.12019
Subject(s) - plane stress , fracture toughness , finite element method , constraint (computer aided design) , plane (geometry) , materials science , structural engineering , toughness , plasticity , measure (data warehouse) , mathematics , geometry , composite material , computer science , engineering , database
Constraint can be divided into two conditions of in‐plane and out‐of‐plane, and each of them has its own parameter to characterize. However, in most cases, there exists a compound change of both in‐plane and out‐of‐plane constraint in structures, a unified measure that can reflect both of them is needed. In this paper, the finite element method (FEM) was used to calculate the equivalent plastic strain ( ɛ p ) distribution ahead of crack tips for specimens with different in‐plane and out‐of‐plane constraints, and the FEM simulations based on Gurson–Tvergaard–Needleman (GTN) damage model and a small number of tests were used to obtain fracture toughness for the specimens with different constraints. Unified measure and characterisation parameter of in‐plane and out‐of‐plane constraints based on crack‐tip equivalent plastic strain has been investigated. The results show that the area A PEEQ surrounded by the ɛ p isoline ahead of crack tips can characterize both in‐plane and out‐of‐plane constraints. Based on the area A PEEQ , a unified constraint characterisation parameter A p was defined. It was found that there exists a sole linear relation between the normalised fracture toughness J IC /J ref and regardless of the in‐plane constraint, out‐of‐plane constraint and the selection of the ɛ p isolines. The unified J IC / J ref −reference line can be used to determine constraint‐dependent fracture toughness of materials. The FEM simulations with the GTN damage model (local approach) can be used in obtaining the unified J IC / J ref −reference line for materials with ductile fracture.