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LammAdrienneValerie2004 jrm.pdf (3.62 MB)

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Dislocation Modeling of Mechanical Properties of Nanolayered Composite Materials

Lamm, Adrienne Valerie
http://rave.ohiolink.edu/etdc/view?acc_num=osu1363615565

Abstract Details

2004, Master of Science, Ohio State University, Materials Science and Engineering.
Nanoscale multilayered materials exhibit extraordinary strength, due to the ability of these systems to confine slip to individual layers. This work adopts a premise suggested by embedded atom simulations in copper-niobium multilayers that the tensile yield strength is determined approximately by the critical applied stress to eliminate the compressive biaxial stress in alternating layers of the composite. Yield strength maps are constructed for nanoscale multilayered composites consisting of alternating layer phases in which the volume fraction of the phases, bilayer thickness, and ratio of in-plane stressfree lattice parameters of the two phases are regarded as variables. Also, the degree of coherency of the interfaces and the internal biaxial stress state in each layer prior to loading are predicted as a function of these variables. The results suggest that decreasing bilayer thickness is a limited approach to increasing the biaxial yield strength of nanolayered composites. The consequences of growing multilayered thin films on substrates of finite size are also investigated. Substrates with lattice parameters less than or greater than those of either constituent, or possessing a lattice parameter between either of the constituent phases, were examined, with mixed results. Internal stress states of attached and detached multilayers were calculated and compared to the detached and heat-treated stress states determined as described in the proceeding paragraph. Attached multilayers showed masking effects that changed depending on the lattice parameter of the substrate. Detached multilayers consisted of internal stress contours with a similar shape of those displayed by the detached and heat-treated multilayers. The multilayer strength maps of each state revealed interesting results. The attached and detached strength maps were virtually indistinguishable, but when compared to the detached and heat-treated strength maps were very different quantitatively. The detached and heat-treated multilayers had strength gains that were 12% to 40% over the attached and detached conditions, with smaller gains occurring as the volume fraction of phase 1 was increased. The effects of adding structural resistance to the model were also examined. The strength maps for each condition showed an increase in overall multilayer strength, with the greatest increase occurring at small volume fractions of phase 1. This is in accordance with the values that resulted from heat-treating the multilayers. Comparisons of the theoretical results calculated by the model to experimental data collected by external scientists are also made, including changes and additions to the model that would create better agreement between the two data sets.
Peter Anderson (Advisor)
148 p.
Engineering; Materials Science

Recommended Citations

Citations

  • Lamm, A. V. (2004). Dislocation Modeling of Mechanical Properties of Nanolayered Composite Materials [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1363615565

    APA Style (7th edition)

  • Lamm, Adrienne. Dislocation Modeling of Mechanical Properties of Nanolayered Composite Materials. 2004. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1363615565.

    MLA Style (8th edition)

  • Lamm, Adrienne. "Dislocation Modeling of Mechanical Properties of Nanolayered Composite Materials." Master's thesis, Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1363615565

    Chicago Manual of Style (17th edition)

osu1363615565
154
© 2004, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.