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Experimental and Theoretical Investigation of Crystallographic Orientation Dependence of Nanoscratching of Single Crystalline Copper.

Geng Y, Zhang J, Yan Y, Yu B, Geng L, Sun T - PLoS ONE (2015)

Bottom Line: The correlation of microscopic deformation behavior of the material with macroscopically-observed machining results is revealed.Moreover, the influence of crystallographic orientation on the nanoscratching of single crystalline copper is examined.Both experiments and MD simulations demonstrate that the machined surface morphologies in terms of groove depth and surface pile-up exhibit strong crystallographic orientation dependence, because of different geometries of activated slip planes cutting with free surfaces and strain hardening abilities associated with different crystallographic orientations.

View Article: PubMed Central - PubMed

Affiliation: The State Key Laboratory of Robotics and Systems, Robotics Institute, Harbin Institute of Technology, Harbin, Heilongjiang, 150008, P. R. China; Center for Precision Engineering, Harbin Institute of Technology, Harbin, Heilongjiang, 150001, P. R. China.

ABSTRACT
In the present work, we perform experiments and molecular dynamics simulations to elucidate the underlying deformation mechanisms of single crystalline copper under the load-controlled multi-passes nanoscratching using a triangular pyramidal probe. The correlation of microscopic deformation behavior of the material with macroscopically-observed machining results is revealed. Moreover, the influence of crystallographic orientation on the nanoscratching of single crystalline copper is examined. Our simulation results indicate that the plastic deformation of single crystalline Cu under the nanoscratching is exclusively governed by dislocation mechanisms. However, there is no glissile dislocation structure formed due to the probe oscillation under the load-controlled mode. Both experiments and MD simulations demonstrate that the machined surface morphologies in terms of groove depth and surface pile-up exhibit strong crystallographic orientation dependence, because of different geometries of activated slip planes cutting with free surfaces and strain hardening abilities associated with different crystallographic orientations.

No MeSH data available.


Related in: MedlinePlus

MD snapshots of defect evolution during load-controlled multi-passes nanoscratching of single crystalline Cu(010).Instantaneous defect structures after the (a) penetration and (b) scratching phase of the first scratching pass. Instantaneous defect structures after the scratching pass of the (c) 2nd and (d) 3rd scratching pass.
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pone.0131886.g005: MD snapshots of defect evolution during load-controlled multi-passes nanoscratching of single crystalline Cu(010).Instantaneous defect structures after the (a) penetration and (b) scratching phase of the first scratching pass. Instantaneous defect structures after the scratching pass of the (c) 2nd and (d) 3rd scratching pass.

Mentions: To reveal the underlying deformation mechanisms of single crystalline Cu(010), dynamic analysis of defect evolutions during the load-controlled multi-passes nanoscratching is carried out. Fig 5 presents representative MD snapshots of instantaneous defect structures during the nanoscratching process. For the single scratching pass, the deformation mechanisms of single crystalline Cu(010) can be summarized as follows: in the penetration phase, the defect-free material first undergoes first elastic deformation, followed by plastic deformation initiated by the nucleation of dislocations from the penetrated surface. In the plastic deformation the nucleated dislocations subsequently glide on {111} slip planes below the (010) free surface, and their reaction and cross-slip lead to the formation of sessile dislocation structures shown in Fig 5(A). However, there is no glissile dislocation structure such as prismatic dislocation loop formed, which is significantly different from previous MD simulations of the displacement-controlled penetration [30]. The discrepancy of dislocation structures between different penetration modes can be attributed to the oscillating displacement of the probe in the load-controlled mode, which releases accumulated plastic strain in the vicinity of the probe. In the following scratching phase, dislocation evolution is much more complex than that in the penetration phase because of more complex stress state of multi-axis. It is found from Fig 5(B) that while there are fresh dislocations nucleated from free surface in front of the probe due to the shear stress applied by the probe, dislocation annihilations occur at the free surface behind the probe because of the release of applied normal stress. Furthermore, there is still no glissile prismatic dislocation structures formed within the material in the scratching phase. Correspondingly, there are considerable displaced material accumulated on the sample surface, due to the glide of dislocations on {111} slip planes towards the surface and the annihilation of dislocation at the surface [30]. In the final retraction phase, the release of applied stress leads to considerable strain energy recovery, and the defect zone beneath the free surface shrinks slightly.


Experimental and Theoretical Investigation of Crystallographic Orientation Dependence of Nanoscratching of Single Crystalline Copper.

Geng Y, Zhang J, Yan Y, Yu B, Geng L, Sun T - PLoS ONE (2015)

MD snapshots of defect evolution during load-controlled multi-passes nanoscratching of single crystalline Cu(010).Instantaneous defect structures after the (a) penetration and (b) scratching phase of the first scratching pass. Instantaneous defect structures after the scratching pass of the (c) 2nd and (d) 3rd scratching pass.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4492598&req=5

pone.0131886.g005: MD snapshots of defect evolution during load-controlled multi-passes nanoscratching of single crystalline Cu(010).Instantaneous defect structures after the (a) penetration and (b) scratching phase of the first scratching pass. Instantaneous defect structures after the scratching pass of the (c) 2nd and (d) 3rd scratching pass.
Mentions: To reveal the underlying deformation mechanisms of single crystalline Cu(010), dynamic analysis of defect evolutions during the load-controlled multi-passes nanoscratching is carried out. Fig 5 presents representative MD snapshots of instantaneous defect structures during the nanoscratching process. For the single scratching pass, the deformation mechanisms of single crystalline Cu(010) can be summarized as follows: in the penetration phase, the defect-free material first undergoes first elastic deformation, followed by plastic deformation initiated by the nucleation of dislocations from the penetrated surface. In the plastic deformation the nucleated dislocations subsequently glide on {111} slip planes below the (010) free surface, and their reaction and cross-slip lead to the formation of sessile dislocation structures shown in Fig 5(A). However, there is no glissile dislocation structure such as prismatic dislocation loop formed, which is significantly different from previous MD simulations of the displacement-controlled penetration [30]. The discrepancy of dislocation structures between different penetration modes can be attributed to the oscillating displacement of the probe in the load-controlled mode, which releases accumulated plastic strain in the vicinity of the probe. In the following scratching phase, dislocation evolution is much more complex than that in the penetration phase because of more complex stress state of multi-axis. It is found from Fig 5(B) that while there are fresh dislocations nucleated from free surface in front of the probe due to the shear stress applied by the probe, dislocation annihilations occur at the free surface behind the probe because of the release of applied normal stress. Furthermore, there is still no glissile prismatic dislocation structures formed within the material in the scratching phase. Correspondingly, there are considerable displaced material accumulated on the sample surface, due to the glide of dislocations on {111} slip planes towards the surface and the annihilation of dislocation at the surface [30]. In the final retraction phase, the release of applied stress leads to considerable strain energy recovery, and the defect zone beneath the free surface shrinks slightly.

Bottom Line: The correlation of microscopic deformation behavior of the material with macroscopically-observed machining results is revealed.Moreover, the influence of crystallographic orientation on the nanoscratching of single crystalline copper is examined.Both experiments and MD simulations demonstrate that the machined surface morphologies in terms of groove depth and surface pile-up exhibit strong crystallographic orientation dependence, because of different geometries of activated slip planes cutting with free surfaces and strain hardening abilities associated with different crystallographic orientations.

View Article: PubMed Central - PubMed

Affiliation: The State Key Laboratory of Robotics and Systems, Robotics Institute, Harbin Institute of Technology, Harbin, Heilongjiang, 150008, P. R. China; Center for Precision Engineering, Harbin Institute of Technology, Harbin, Heilongjiang, 150001, P. R. China.

ABSTRACT
In the present work, we perform experiments and molecular dynamics simulations to elucidate the underlying deformation mechanisms of single crystalline copper under the load-controlled multi-passes nanoscratching using a triangular pyramidal probe. The correlation of microscopic deformation behavior of the material with macroscopically-observed machining results is revealed. Moreover, the influence of crystallographic orientation on the nanoscratching of single crystalline copper is examined. Our simulation results indicate that the plastic deformation of single crystalline Cu under the nanoscratching is exclusively governed by dislocation mechanisms. However, there is no glissile dislocation structure formed due to the probe oscillation under the load-controlled mode. Both experiments and MD simulations demonstrate that the machined surface morphologies in terms of groove depth and surface pile-up exhibit strong crystallographic orientation dependence, because of different geometries of activated slip planes cutting with free surfaces and strain hardening abilities associated with different crystallographic orientations.

No MeSH data available.


Related in: MedlinePlus