Fatigue of welded steel in sea water is evaluated and discussed from the standpoints of tubular connection design and the phenomenology of crack initiation and propagation. The role of selected critical variables, including electrochemical potential, stress state as affected by notches and steel strength level, are incorporated with consideration of the interactive nature of these and the influence of each upon initiation and propagation. Experimental results are reported for butt welded ABS-DH32 steel which indicate that at -1.00v. (Cu-CuSO4) small cracks at the weld toe arrest, whereas these propagate to failure at potentials either positive or negative to the above value. Possible explanations for this crack arrest are discussed, and it is concluded that the role played by electrochemical potential was most influential. The concept of a "significant crack size" below which fatigue crack initiation plays a major role in fatigue and above which crack growth dominates is reviewed. It is proposed that appropriate microstructure and weld quality control, such that initial weld toe cracks are less than the significant size, represents an effective technique for enhancing fatigue resistance.

Subject
Crack growth, Corrosion fatigue, Water, Materials, Offshore structures, Crack initiation, Crack propagation, Fatigue crack growth rate, Stress cracking, Stress, Negative potentials, Steel, Fatigue
© 1986 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
1986
Association for Materials Protection and Performance (AMPP)
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