Cracking phenomena

It is possible to confuse SCC with other brittle cracking phenomena. Confirmation of SCC typically requires a metallographic examination. On thin-walled components, the surface from which the cracking originates may not be apparent. In these cases, a formal metallographic examination may be required to assure positive identification of the surface from which the cracks originate. 

It is important to underline that there may be more than one cracking phenomenon that can cause a failure. The following four main environmental cracking phenomena of concern can be observed when steels are exposed to wet H2S environments.139,140... 

The overlapping of cracking phenomena. There are a number of corrosion-related causes of the premature fracture of structural components. The most common of these... 

This package cracking phenomena must also be related to aluminum pattern deformation and passivation layer cracking. 

One of the outlet temperatures is bigger than the setpoint for the associated pass. This situation leads to a growing coking and cracking phenomena on this coil. Under conditions, the vaporized fraction diminishes, affecting the light oils efficiency. 

At 43 X magnification, one can visually track the cumulative mechanical UV damage by the appearance and subsequent growth of cracks in the tile surface. It turns out that fading and surface cracking phenomena always go together a sample... 

Similar cracking phenomena have been reported to be associated with the corrosion of electro-deposited y-phase Zn—Ni coatings that are of considerable interest as corrosion protective coatings for automotive appKcations [28-30]. However, the cause of this cracking may be more complex than in the case of S-Zn—Fe since the y-Zn—Ni phase is quoted rather ductile. Nevertheless, cracking is clearly linked with dealloying and appears to be important for the lifetime of the deposit. 

R. Valient, The influence of different Nb-contents on the hot-cracking susceptibility of Ni-base weld metals type 70/20, in T. BoUinghaus, H. Herold (Eds.), Hot Cracking Phenomena in Welds, Springer-Verlag, Berlin, 2005, pp. 141—164. 

Ikeda, K., and Satoh, H. (1989). An analysis of corrosion cracking phenomena of electrodeposited Zn-Ni alloy layers. Galvaiech 89, Iron and Steel Institute, Japan,... 

CF experiments are hindered by several common factors. Aggressive environments are difficult to contain at a constant condition, and hinder precise measurements of specimen displacement, load, and crack size. CF is influenced by many interactive mechanical, chemical, and microstructured variables that must be factored into experimental design. It is often necessary to investigate slow-rate deformation and cracking phenomena in a realistic time experiments must be conducted for one day to one year or more. CF damage is localized at surface slip structure and near the crack tip high resolution observations are not generally available and behavior must be interpreted from indirect measurements. 

Wu, X. and Weatherly, G. C. (1999), Cracking phenomena in Ino.25Gao.75As films on InP substrates, Acta Materialia 47, 3383-3394. 

Today, the general trend is to consider that transgranular crack propagation involves mechanical rupture and that the dissolution process may account for some intergranular cracking phenomena, particularly when the anodic behavior of grain boundaries is very different from the bulk material (for example, in sensitized stainless steels). 

The term cracking at simultaneous action of stress and environment was introduced for polymers (mainly polyethylenes) being in stressed state at mobile polar liquids presence. It has been shown [17], that in the end the most weak amorphous part of semicrystalline polymer is responsible for materials strength at this fracture kind. This allows to connect occurring at cracking phenomena to polar liquid diffusion in amorphous regions. 

Cracking phenomena includes corrosion fatigue, a mechanical phenomenon enhanced by nonspecific corrosive environments, and environmental cracking, in which a brittle failure is induced in an otherwise ductile material under tensile stress in an environment specific for the alloy system (stress corrosion cracking, fatigue). 

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