Scaling laws for fatigue crack growth of large cracks in steels

Journal Article · Mon Nov 01 00:00:00 EST 1993 · Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States)

DOI:https://doi.org/10.1007/BF02646526· OSTI ID:5842816

Chan, K S ^[1]

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1. Southwest Research Inst., San Antonio, TX (United States). Mechanics Dept.

A set of scaling laws has been developed for intermittent as well as continuous fatigue crack growth of large cracks in steels in the power-law regime. The proposed scaling laws are developed on the basis that fatigue crack growth occurs as the result of low-cycle fatigue (LCF) failure of a crack-tip element whose width and height correspond to the dislocation cell size and barrier spacing, respectively. The results show that the effects of microstructure on fatigue crack growth can be described entirely in terms of a dimensionless microstructural parameter, [xi], which is defined in terms of yield stress, fatigue ductility, dislocation cell size, and dislocation barrier spacing. For both discontinuous and continuum crack growth, the crack extension rate, da/dN, scales with [xi] and ([Delta]K/E)[sup m], where [Delta]K is the stress intensity range, m is the crack growth exponent, and E is Young's modulus. Application of the model to high-strength low-alloy (HSLA) and conventional ferritic, ferritic/pearlitic, and martensitic steels reveals that the lack of a strong microstructural influence on fatigue crack growth in the power-law regime is due to increasing yield stress and fatigue ductility with decreasing dislocation barrier spacing, which leads to a narrow range of [xi] values and crack growth rates. Variation of da/dN data with microstructure in HSLA-80 steels is explained in terms of the proposed model. Other implications of the scaling laws are also presented and discussed in conjunction with several fatigue models in the literature.

• OSTI ID: 5842816
• Journal Information: Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States), Vol. 24:11; ISSN 0360-2133
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
STEELS
CRACK PROPAGATION
DISLOCATIONS
DUCTILITY
FATIGUE
MICROSTRUCTURE
SCALING LAWS
YIELD STRENGTH
YOUNG MODULUS
ALLOYS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
IRON ALLOYS
IRON BASE ALLOYS
LINE DEFECTS
MECHANICAL PROPERTIES
TENSILE PROPERTIES
360103* - Metals & Alloys- Mechanical Properties