A dislocation shielding model for the fracture of semibrittle polycrystals

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

DOI:https://doi.org/10.1007/BF02657321· OSTI ID:6354080

Katz, Y ^[1]; Keller, R R ^[2]; Huang, H; Gerberich, W W ^[3]

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1. Nuclear Research Center, Beer-Sheva (Israel)
2. Univ. of Erlangen-Nuernberg (Germany)
3. Univ. of Minnesota, Minneapolis (United States)

Using a dislocation mechanics-based crack-tip shielding model, a zeroth-order estimate of the grain size and yield strength dependence of fracture toughness is made for mild steel. This model, appropriate to cleavage fracture in the lower shelf regime, is shown to predict the fracture toughness determined over a temperature regime of 100 to 240 K in both quasi-static and dynamic tests and for two different grain sizes. Two grain size terms in the proposed model result. One is associated with grain boundary blockage effects on crack-tip shielding, while the other is proposed to affect the far-field stresses and, indirectly, the local crack-tip stress field. Differences between the present approach and the classic Cottrell-Petch model are in how the friction stress and grain size affect local stresses at the crack tip rather than at a carbide or a grain boundary.

• DOE Contract Number: FG02-88ER45337
• OSTI ID: 6354080
• Journal Information: Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States), Vol. 24:2; ISSN 0360-2133
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
STEELS
FRACTURE PROPERTIES
BRITTLENESS
DISLOCATIONS
GRAIN BOUNDARIES
GRAIN SIZE
MATHEMATICAL MODELS
POLYCRYSTALS
STRESSES
TEMPERATURE RANGE 0065-0273 K
YIELD STRENGTH
ALLOYS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
CRYSTALS
IRON ALLOYS
IRON BASE ALLOYS
LINE DEFECTS
MECHANICAL PROPERTIES
MICROSTRUCTURE
SIZE
TEMPERATURE RANGE
360103* - Metals & Alloys- Mechanical Properties