Growth of Short Cracks

However, this behavior considered characteristic of small cracks is not always confirmed by experimental data. Several researchers [45—48] reports episodes of complete independency of FCGR of the crack length. An example of such a behavior is offered in Fig. 11.32 for quenched and tempered 4340 steel, 1187 MPa yield strength, whose FCGR of small cracks is practically the same of long cracks. 

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A. Fathulla, B. Weiss, R. Stickler, J. Fembdk The initiation and growth of short cracks in pm-Mo, Proc. 11th Plansee Seminar, Vol.l (Plansee AG, Reutte 1985) p.45... 

The application of microstructural fracture mechanisms (MFMs) has been successfully used to predict the growth of short cracks during fatigue in air [16], These models have been adapted to characterize and predict the uniaxial and multiaxial corrosion fatigue loading [17],... 

Leis, B.J., Ahmad, J., Kanninen, M.F. Effect of local stress state on the growth of short cracks. Multiaxial Fatigue ASTM-STP 853, 314-339 (1985)... 

Few experimental studies have been reported on the behavior of short cracks. However, in one study. Prater et al. [101] used an electrical potential drop method to monitor the growth oif surface cracks in carbon steel in oxygenated (8 ppm O2) high-temperature (288 °C) water. The cracks were semielliptical in shape and the crack... 

Perez Carbonell, E., Brown, M.W. A study of short crack growth in torsional low cycle fatigue for a medium carbon steel. Eng. Mater. Struct. 9, 15-33 (1986)... 

Hobson, P.D. The growth of short fatigue cracks in a medium carbon steel. Ph.D. thesis, University of Sheffield (1985)... 

Turnbull, A. and Newman, R. C., The influence of crack depth on electrochemistry and fatigue crack growth , Proc AIME Conf. on Short Crack Growth, AIME (1986)... 

Copper and silver tarnish readily in sulphide atmospheres, and copper in contact with sulphur-vulcanised rubber will sometimes react with the sulphur, devulcanising it in the process. The growth of conducting sulphide whiskers on silver is noteworthy as these whiskers may give rise to short circuits across silver-plated contacts. Ammonia has little effect on most metals, but traces will tarnish many copper alloys and cause stress-corrosion cracking of certain stressed brasses. 

Mechanisms of SCC. Crack initiation of EAC is complex and not well understood till now. Most of the SCC systems exhibit short initiation times ranging from minutes to weeks and cracking often occurs due to the change in the environment rather than to a very long initiation time. Stress-corrosion crack growth rates are usually 10 11 and 10-6 m s In systems such as stainless steels in chloride solutions, localized corrosion may create the local conditions prone to crack development, but it is still difficult to explain the initiation of the crack in the absence of localized corrosion in environmental conditions different from that of the crack propagation.95 It should be mentioned that dealloyed surface layers such as certain copper alloys in ammonia-containing solutions are believed to cause SCC.54... 

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