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Investigations into strain gradient ...

Saito, Yuki.

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Investigations into strain gradient plasticity.

紀錄類型:	書目-語言資料,印刷品 : Monograph/item
正題名/作者:	Investigations into strain gradient plasticity./
作者:	Saito, Yuki.
面頁冊數:	211 p.
附註:	Adviser: Jeffrey W. Kysar.
Contained By:	Dissertation Abstracts International68-09B.
標題:	Engineering, Materials Science. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3285157
ISBN:	9780549268444

Investigations into strain gradient plasticity.
Saito, Yuki.

Investigations into strain gradient plasticity. - 211 p.

Adviser: Jeffrey W. Kysar.

Thesis (Ph.D.)--Columbia University, 2007.

Experimental, numerical and analytical work of high strain gradient deformation in elastic-rigid plastic single crystals and bicrystals are studied. The purpose of this work is to examine the material mechanical behavior by simplifying the problem formulation in highly idealized situations. For example, wedge indentation of a single crystal in a specific direction allows the material to deform under plane strain conditions, and numerical simulations with elastic-ideally plastic constitutive relation yield the most fundamental features of the deformation field that are directly comparable to the experimental results. First, we provide the historical background of the current research and the organization of this work as an introduction. Next, we present the analytical solutions to stress states around a quasi-statically propagating singular point on the material surface, which is, in an essence, analogous to a quasi-statically healing crack problem. The analytical solution is then compared with the numerical simulation and they show a high correlation to each other. The analytical solution also gives some fundamental insights into the deformation fields of the material which is applied with various included angle of wedge indenters. Next, we present the experiment and numerical simulations of wedge indentation with various different included angles. The indenter angles are chosen to be 60°, 90° and 120° and are indented into a Face-Centered-Cubic (FCC) single crystal parallel to the [110] direction and in the [001] direction so that plane strain conditions are achieved. The midsection of the specimens is exposed and the lattice rotations are measured using Electron Backscatter Diffraction (EBSD). The important result is that no matter which angle of indenter is employed, the results show a similar characteristic lattice rotation field in both experiment and simulation. However, the magnitude of the in-plane lattice rotation differs in the experimental and the numerical results, which suggests the necessity of constructing a better constitutive relation for single crystal plasticity. The indentation experiment and simulation are performed for a FCC bicrystal also. The indenter is applied into one of the crystals of the bicrystal and indented 500 mum away from the grain boundary. The indentation depth is 200 mum. On the crystal on which the indenter is applied, the deformation field is very similar to that of the single crystal indentation experiment and simulation, however, in the other grain, the deformation is caused mainly by the curved grain boundary. There is a large discrepancy between the experiment and the simulation. This suggests the necessity of developing a better constitutive relationship for the grain boundary simulation based on the experimental result. Finally, we briefly mention the summary of conclusions and the future work.

ISBN: 9780549268444Subjects--Topical Terms:

1017759
Engineering, Materials Science.

Investigations into strain gradient plasticity.
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100 1 $a Saito, Yuki. $3 1278907
245 1 0 $a Investigations into strain gradient plasticity.
300 $a 211 p.
500 $a Adviser: Jeffrey W. Kysar.
500 $a Source: Dissertation Abstracts International, Volume: 68-09, Section: B, page: 6258.
502 $a Thesis (Ph.D.)--Columbia University, 2007.
520 $a Experimental, numerical and analytical work of high strain gradient deformation in elastic-rigid plastic single crystals and bicrystals are studied. The purpose of this work is to examine the material mechanical behavior by simplifying the problem formulation in highly idealized situations. For example, wedge indentation of a single crystal in a specific direction allows the material to deform under plane strain conditions, and numerical simulations with elastic-ideally plastic constitutive relation yield the most fundamental features of the deformation field that are directly comparable to the experimental results. First, we provide the historical background of the current research and the organization of this work as an introduction. Next, we present the analytical solutions to stress states around a quasi-statically propagating singular point on the material surface, which is, in an essence, analogous to a quasi-statically healing crack problem. The analytical solution is then compared with the numerical simulation and they show a high correlation to each other. The analytical solution also gives some fundamental insights into the deformation fields of the material which is applied with various included angle of wedge indenters. Next, we present the experiment and numerical simulations of wedge indentation with various different included angles. The indenter angles are chosen to be 60°, 90° and 120° and are indented into a Face-Centered-Cubic (FCC) single crystal parallel to the [110] direction and in the [001] direction so that plane strain conditions are achieved. The midsection of the specimens is exposed and the lattice rotations are measured using Electron Backscatter Diffraction (EBSD). The important result is that no matter which angle of indenter is employed, the results show a similar characteristic lattice rotation field in both experiment and simulation. However, the magnitude of the in-plane lattice rotation differs in the experimental and the numerical results, which suggests the necessity of constructing a better constitutive relation for single crystal plasticity. The indentation experiment and simulation are performed for a FCC bicrystal also. The indenter is applied into one of the crystals of the bicrystal and indented 500 mum away from the grain boundary. The indentation depth is 200 mum. On the crystal on which the indenter is applied, the deformation field is very similar to that of the single crystal indentation experiment and simulation, however, in the other grain, the deformation is caused mainly by the curved grain boundary. There is a large discrepancy between the experiment and the simulation. This suggests the necessity of developing a better constitutive relationship for the grain boundary simulation based on the experimental result. Finally, we briefly mention the summary of conclusions and the future work.
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