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NEAR‐THRESHOLD FATIGUE CRACK GROWTH AND CRACK CLOSURE IN A NODULAR CAST IRON
Author(s) -
Ogawa Takeshi,
Kobayashi Hideo
Publication year - 1987
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/j.1460-2695.1987.tb00206.x
Subject(s) - crack closure , materials science , paris' law , crack growth resistance curve , cast iron , composite material , stress concentration , graphite , stress intensity factor , modulus , crack tip opening displacement , closure (psychology) , stress (linguistics) , fracture mechanics , metallurgy , linguistics , philosophy , economics , market economy
— Near‐threshold fatigue crack growth and crack closure were investigated in a nodular cast iron. Fracture surface roughness was promoted by spheroidal graphites. The spheroidal graphites are partially crushed to form powder which accumulates within the crack and thus enhance crack closure. The marked influence of stress ratio on near‐threshold crack growth is due to graphite‐induced crack closure. When the contribution of graphite‐induced crack closure is excluded, the crack growth characteristics are insensitive to stress ratio, and the threshold behaviour for crack growth tends to disappear. In this case, Young's modulus becomes a controlling material parameter for the power law relationship between crack growth rate and stress intensity range.