ISSN:
1013-9826
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
How a crack initiates from the smooth surface of single crystals subjected to uniaxialcyclic loading is unclear. Experiments were conducted to observe in detail the dislocation microstructures during the saturation stage of cyclic deformation in a copper single crystal using scanning electron microscopy and the electron channeling contrast (SEM–ECC) technique. Some dark zones were found in the dislocation microstructures, which were located either at the edgeregion of the specimen or within the persistent slip bands (PSBs) at the matrix/PSB interfaces. Hence, fatigue cracks will initiate at these sites with high stress concentrations, i.e., the dark zones. Also, dislocation dynamics (DD) simulation was adopted to calculate internal stress distributionsinduced by dislocations, and finite element analysis (FEA) used to obtain stress distribution at the matrix/PSB interfaces and neighboring micro-regions caused by an externally applied load. Simulation results show that the external shear stresses distribute uniformly in all specimens; while near the free-surface regions, the maximum value of internal stresses not only occurs at interfacesbetween PSBs and dislocation matrix, but also at locations where these interfaces cross the freesurface. Consequently, the interfaces are most probable sites for nucleated cracks. Finally, the simulation results agree well with experimental observations
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/01/51/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.312.71.pdf
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