Fatigue crack growth model for collinear semi-elliptical cracks including coalescence and recharacterization

Book · Wed Nov 01 04:00:00 EST 1995

OSTI ID:122494

Bell, R; Zhang, H; Harrington, D S ^[1]

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1. Carleton Univ., Ottawa, Ontario (Canada). Dept. of Mechanical and Aerospace Engineering

The coalescence and recharacterization of two adjacent semi-elliptical cracks as they evolve into a single crack has for some time been an interesting and challenging research topic. The design codes which provide guidance on the treatment of fatigue crack growth and coalescence are the ASME Boiler and Pressure Vessel Code Section XI and the British Standards Code PD6439. This paper presents a computer prediction crack growth model which investigates the fatigue crack growth and coalescence of several colinear semi-elliptical cracks. So far the coalescence process which encompasses a significant portion of the total fatigue life is not clearly understood, therefore this investigation includes in the model empirical equations based on the crack shape development of coalescing cracks. Experimental results of fatigue crack growth and crack shape development, including the coalescence phase, is also presented for semi-elliptical surface cracks in steel plate specimens loaded in four point bending. In these tests the fatigue crack growth and crack shape development are monitored using a novel mobile DCPD (direct current potential drop) probe arrangement. The results from these experimental tests are used to develop empirical relationships which describe the coalescence and recharacterization of adjacent cracks in the prediction model. The results from the prediction model are compared with the results obtained using the guidance rules given in the international codes.

• OSTI ID: 122494
• Report Number(s): CONF-950740--; ISBN 0-7918-1331-2
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
42 ENGINEERING
COMPARATIVE EVALUATIONS
CRACK PROPAGATION
EXPERIMENTAL DATA
FATIGUE
MATHEMATICAL MODELS
MECHANICAL STRUCTURES
STEELS
THEORETICAL DATA