Extrusions and Intrusions

2 Morphological Aspects of Fatigue Crack Formation and Growth 

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Fig. 8.60 Schematic diagrams showing common surface profiles produced during fatigue (a) coarse slip and crack initiation adjacent to grain boundaries (b) extrusions and intrusions (c) coarse slip within a persistent slip band (after Lynch Y...

The geology of the study area comprises mainly limestones, shales, alluvial deposits and basic extrusive and intrusive rocks. 

The feldspars crystallize from the magma in both extrusive and intrusive rocks they occur as contact minerals in veins, and they are developed in many sorts of tnelamorphic rocks, e g., albile schists. They may also he found as mechanical deposits in various sedimentary nicks. 

Precrack cyclic deformation that includes the formation of persistent slip bands, formation of extrusions and intrusions. 

Figure 6.48 Extrusions and intrusions in the copper7 after 6 x 70s cycles in air. Sample covered with silver and mounted at an angle to magnify surface protuberances x20...

Kovalev V. P. and Malyasova Z. V. (1971) The content of mobile uranium in extrusive and intrusive rocks of the eastern margins of the South Minusinsk Basin. Geokhimiya 7, 855-865. 

They include continental flood basalts of the type found in the Deccan plateau in India or the Karoo province of southern Africa, and, where the volcanism is within oceanic crust, oceanic plateaus. Most Mesozoic and Cenozoic LIPs had an original areal extent of more than a million km2 and represent magma volumes of up to 4 million km3. The Ontong Java oceanic plateau has a lava volume of 6 million km3 and when extrusive and intrusive components are aggregated a total volume of 44.4 million km3 (Ernst et al., 2005). 

Fie. 7.118 Model of local plastic deformation by dislocation glide producing surface extrusions and intrusions that initiate fatigue cracks. Source Ref 162... 

Figure 1.19 Extrusions and intrusions in copper after 6 X 10 cycles in air. (Reproduced by permission, John Wiley and Sons (8).)...

Figure 8.19. Extrusions and intrusions in copper after 6 x 10 cycles in air. Specimen plated with silver after test and mounted at an angle to magnify surface protuberances by about 20x. Overall magnification about SOOx. [Figure 3 from W. Wood and H. Bendler, The fatigue process in copper as studied by electron metallography, Trans. Metall. Soc. AIME 224, 182...

Figure 10.8 illustrates how dislocation movement on slip planes can roughen a surface by forming extrusions and intrusions. Steps on the surface formed by slip of the material (figure 10.8(b)) are not completely removed upon load reversal since a dislocation that has moved in one direction will not necessarily revert to its original position. Instead, another dislocation may move and cause the plastic deformation, leading to a roughening of the initially smooth surface. Furthermore, a thin oxide layer of a few nanometre... 

Fig. 10.8. Formation of intrusions and extrusions due to cyclic loading. During the cycles, small irreversible plastic deformations occur on parallel shp bands that cause accumulation of extrusions and intrusions on the surface. The number of cycles increases from the left to the right...

Figure 4.74 Schematic example of mechanisms leading to a fatigue crack initiation (a) extrusion and intrusion in slip region due to cyclic stress (b) slip band intrusions and extrusions prior to crack initiation (Note the stress concentration is formed on the sur ce in this process). (From Fuchs, H.O. and Stephans, R.1. (1980). Metal Fatigue in Engineering, New York John Wiley Sons Inc, p. 28. By kind permission of John Wiley, New York, USA)...

Cottrell, A.H., Hull, D. Extrusions and intrusions by cyclic slip in copper. Proc. Roy. Soc. A242, 211-213 (1957)... 

The value for the "correct" contact angle used to calculate area or porosity using mercury penetration/exlrusion data is not certain. Likewise, it is not certain whether the same contact angle should be used in making calculations using both extrusion and intrusion data. Davis (15) made a comparison of the surface area... 

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