DEFECTS IN METALS AND SIMULATION OF MECHANICAL ...

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existing dislocation deviates from the other curve at a load of around 300 nN which is suggested by Johnson [ 30 , 50 ] who suggested that when the stress field around a contact load generated by the application of a load-controlled testing system encounters an existing dislocation; there could be a gradual yielding in which the curve gradually deviates from the elastic loading curve and exhibits increasing amounts of plasticity, this description fits the result shown in Fig. 4-2. Considering the case when nanoindentation is performed in the direction (Z direction) as shown in Fig. 4-3; the important aspect is that the dislocation didn’t move in the its slip plane since the load is applied in a direction that the dislocation does move on, so the dislocation stayed fixed in its initial position, but still Fig. 4-2 shows that even if the dislocation is not moving during elastic deformation its effect on yielding is important, which brings the idea of the effect of the stress field around the dislocation that has its effect on the nucleation of new dislocations under the indenter tip and subsequently on the onset of plasticity or the yield load. 34
Fig. 4-3: Edge dislocation in the (1 1 -2) plane while indenting in the Z direction, yielding at a depth of 7 A. Atoms with a co-ordination number less than 8 are shown. All other atoms are removed. Fig. 4-4 shows the same scenario as Fig. 4-3 but at a higher depth; showing the interaction of the edge dislocation with the emitted dislocations under the indentation surface. 35
Page 1 and 2: DEFECTS IN METALS AND SIMULATION OF
Page 3 and 4: ACKNOWLEDGMENTS The time and commit
Page 5 and 6: dislocations on yield load were als
Page 7 and 8: LIST OF TABLES Page Table.2-1: Forc
Page 9 and 10: Fig. 3-2: Defects formation at the
Page 11 and 12: Chapter 1 Motivation The motivation
Page 13 and 14: experiments, the advantage is that
Page 15 and 16: Chapter 2 Vacancies effect on metal
Page 17 and 18: showing no dislocation nucleation b
Page 19 and 20: Fig. 2-3: Force displacement curves
Page 21 and 22: Fig.2-5: Indentation with 0% Vacanc
Page 23 and 24: In Fig. 2-6 a) and b) we can see th
Page 25 and 26: Vacancy concentrations were varied
Page 27 and 28: The load at yielding is also sensit
Page 29 and 30: Fig. 2-9 shows that with a higher s
Page 31 and 32: Atomistic computer simulation techn
Page 33 and 34: Figure 3-1 shows the simulation box
Page 35 and 36: Fig. 3-4a: Defects after the initia
Page 37 and 38: In Fig. 3-5 we can see the evolutio
Page 39 and 40: Fig. 3-6: Fraction Nv/n of survivin
Page 41 and 42: Chapter 4 Dislocations effect on Me
Page 43: The dislocation was created by remo
Page 47 and 48: For iron the shear modulus, µ, is
Page 49 and 50: Fig.4-6: Simulatin showing dislocat
Page 51 and 52: Chapter 5 Conclusion Defects in met
Page 53 and 54: [ 14 ] D.F. Bahr, D.E. Kramer, and
Page 55: [ 47 ] H. G. M. Kreuzer and R. Pipp

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