Microstructural examination of fatigue crack tip in high strength steel

Journal Article · Fri Oct 01 00:00:00 EDT 1993 · Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States)

DOI:https://doi.org/10.1007/BF02648595· OSTI ID:5729079

Fukuoka, C; Yoshizawa, H; Nakagawa, Y G ^[1]; Lapides, M E ^[2]

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1. Ishikawajima-Harima Heavy Industries Co., Tokyo (Japan). Research Lab.
2. Electric Power Research Inst., Palo Alto, CA (United States)

Fatigue tests were performed to examine how microstructural conditioning influences crack initiation and propagation in SA508 class 3 low-carbon steel. A 3-mm-long crack was introduced in compact tension (CT) fatigue test specimens under four different loads in order to obtain crack tip plastic zones at different stress intensity factor ranges, [Delta]K = 18, 36, 54, and 72 MPa[radical]m. The microstructure of the plastic zones around the crack tip were examined by transmission electron microscopy (TEM) and selected area electron diffraction (SAD). Micro-orientation of the dislocation cells in the plastic zones of all of the CT samples increased to 4 deg from the level of an as-received sample. Four-point bending fatigue tests were performed for plate shape samples with a large cyclic strain range. The SAD value of the bending samples was also 4 deg in the damaged area where cracks already initiated at an early stage of the fatigue process. These test results indicate that the microstructural conditioning is a prerequisite for the fatigue crack initiation and propagation in SA508. These observations may lead to better understanding of how fatigue initiation processes transit to cracks.

• OSTI ID: 5729079
• Journal Information: Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States), Vol. 24A:10; ISSN 0360-2133
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
STEEL-ASTM-A508
CRACK PROPAGATION
MICROSTRUCTURE
BENDING
EXPERIMENTAL DATA
FATIGUE
MECHANICAL TESTS
STRESS INTENSITY FACTORS
ALLOYS
DATA
DEFORMATION
INFORMATION
IRON ALLOYS
IRON BASE ALLOYS
LOW ALLOY STEELS
MATERIALS TESTING
MECHANICAL PROPERTIES
NUMERICAL DATA
STEELS
TESTING
360103* - Metals & Alloys- Mechanical Properties
360102 - Metals & Alloys- Structure & Phase Studies