Nanoscale amorphization effect on dislocation emission from an elliptical blunt crack tip in deformed nanocrystalline and ultrafine-grained materials

2019 ◽  
Vol 134 ◽  
pp. 98-105 ◽  
Author(s):  
Hui Feng ◽  
Jingwen Tang ◽  
Jun Peng ◽  
Hong Wu
Keyword(s):  
Crack Tip ◽  
Dislocation Emission ◽  
Blunt Crack ◽  
Ultrafine Grained ◽  
Ultrafine Grained Materials

Crack Blunting through Lattice Dislocation Slip in Nanocrystalline and Ultrafine-Grained Materials

2009 ◽  
Vol 633-634 ◽  
pp. 55-62
Author(s):  
Ilya A. Ovidko ◽  
A.G. Sheinerman
Keyword(s):  
Grain Size ◽  
Size Effect ◽  
Stress Fields ◽  
Dislocation Slip ◽  
Cubic Phase ◽  
Grain Size Effect ◽  
Dislocation Emission ◽  
Ultrafine Grained ◽  
Ultrafine Grained Materials ◽  
Crack Blunting

The grain size effect on blunting of cracks in nanocrystalline and ultrafine-grained materials (UFG) is theoretically described. Within our description, lattice dislocations emitted from cracks are stopped at grain boundaries. The stress fields of these dislocations suppress further dislocation emission from cracks in nanocrystalline and UFG materials, and the suppression depends on grain size. The dependences of the number of dislocations emitted by a crack on grain size (ranging from 10 to 300 nm) in Cu and 3C-SiC (the cubic phase of silicon carbide) are calculated which characterize the grain size effect on crack blunting that crucially influences ductility of these materials.

scholarly journals Effect Of Crack Blunting On Subsequent Crack Propagation

1995 ◽  
Vol 409 ◽  
Author(s):  
J. SchiØtz ◽  
A. E. Carlsson ◽  
L. -M. Canel ◽  
Robb Thomson
Keyword(s):  
Crack Propagation ◽  
Brittle Material ◽  
Crack Tip ◽  
Dislocation Emission ◽  
Dislocation Source ◽  
Blunt Crack ◽  
Ductile Materials ◽  
Noticeable Increase ◽  
Greens Function ◽  
Crack Blunting

AbstractTheories of toughness of materials depend on an understanding of the characteristic instabilities of the crack tip, and their possible interactions. In this paper we examine the effect of dislocation emission on subsequent cleavage of a crack and on further dislocation emission. The work is an extension of the previously published Lattice Greens Function methodology[1, 2, 3]. We have developed a Cavity Greens Function describing a blunt crack and used it to study the effect of crack blunting under a range of different force laws. As the crack is blunted, we find a small but noticeable increase in the crack loading needed to propagate the crack. This effect may be of importance in materials where a dislocation source near the crack tip in a brittle material causes the crack to absorb anti-shielding dislocations, and thus cause a blunting of the crack. It is obviously also relevant to cracks in more ductile materials where the crack itself may emit dislocations.

scholarly journals Effect of Crack Blunting on Subsequent Crack Propagation

1995 ◽  
Vol 408 ◽  
Author(s):  
J. Schiøtz ◽  
A. E. Carlsson ◽  
L. M. Canel ◽  
Robb Thomson
Keyword(s):  
Crack Propagation ◽  
Brittle Material ◽  
Crack Tip ◽  
Dislocation Emission ◽  
Dislocation Source ◽  
Blunt Crack ◽  
Ductile Materials ◽  
Noticeable Increase ◽  
Greens Function ◽  
Crack Blunting

AbstractTheories of toughness of materials depend on an understanding of the characteristic instabilities of the crack tip, and their possible interactions. In this paper we examine the effect of dislocation emission on subsequent cleavage of a crack and on further dislocation emission. The work is an extension of the previously published Lattice Greens Function methodology[l, 2, 3]. We have developed a Cavity Greens Function describing a blunt crack and used it to study the effect of crack blunting under a range of different force laws. As the crack is blunted, we find a small but noticeable increase in the crack loading needed to propagate the crack. This effect may be of importance in materials where a dislocation source near the crack tip in a brittle material causes the crack to absorb anti-shielding dislocations, and thus cause a blunting of the crack. It is obviously also relevant to cracks in more ductile materials where the crack itself may emit dislocations.

Superplastic Behavior in Ultrafine-Grained Materials Produced by Equal-Channel Angular Pressing

2008 ◽  
Vol 579 ◽  
pp. 29-40 ◽  
Author(s):  
Cheng Xu ◽  
Megumi Kawasaki ◽  
Roberto B. Figueiredo ◽  
Zhi Chao Duan ◽  
Terence G. Langdon
Keyword(s):  
Equal Channel Angular Pressing ◽  
High Strain ◽  
Processing Method ◽  
Strain Rates ◽  
Bulk Materials ◽  
Superplastic Behavior ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Ultrafine Grained Materials ◽  
Aluminum And Magnesium Alloys

Equal-channel angular pressing (ECAP) is a convenient processing method for refining the grain size of bulk materials to the submicrometer level. Metallic alloys processed by ECAP often exhibit excellent superplastic characteristics including superplasticity at high strain rates. This paper summarizes recent experiments designed to evaluate the occurrence of superplasticity in representative aluminum and magnesium alloys and in the Zn-22% Al eutectoid alloy.

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