DEFECTS IN METALS AND SIMULATION OF MECHANICAL ...

More documents

Recommendations

Info

DEFECTS IN METALS AND SIMULATION OF MECHANICAL PROPERTIES BY MEANS OF NANOINDENTATION Abstract by Elias K. Njeim, M.S. Washington State University December 2009 Chair: David F. Bahr Simulations of radiation damage in metals are of real interest when it comes to specifying the effect of radiation in terms of creation of defects such as vacancies, interstitials and dislocations. Molecular Dynamics is a helpful tool in modeling the process of radiation damage in metals on the small scale, since in MD we have a time scale comparable to the real time scale of radiation damage in metals. Zirconium is an important metal for nuclear applications such as for cladding fuel elements; it has a low absorption cross section for neutrons. We have modeled radiation damage in Zr using the PKA method or Displacement cascades that lead to the creation of defects which evolve with time and lead to changes in microstructure and macroscopic properties. Dependence on temperature and on the energy of the primary knocked on atom were studied; vacancies are the main defects generated for PKA energies ranging from 0.5 to 2 kev, and after around 5 ps of the excitation of the PKA the number of defects starts to stabilize. In addition, to characterize the effect of defects on the mechanical properties of metals, we have done molecular dynamics simulations of nanoindentation on Iron with vacancies and dislocations separately inside the metal, the effect of indenter velocity and the numbers of vacancies and iv
dislocations on yield load were also studied; the main results concerning the effect of vacancies and dislocations is that they both lower the yield load of the material during nanoindentation, and a higher concentration of vacancies will cause a higher deviation from the yield point with no vacancies following a weak power law relationship. v
Page 1 and 2: DEFECTS IN METALS AND SIMULATION OF
Page 3: ACKNOWLEDGMENTS The time and commit
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 and 44: The dislocation was created by remo
Page 45 and 46: Fig. 4-3: Edge dislocation in the (
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
show all

DEFECTS IN METALS AND SIMULATION OF MECHANICAL ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?