東華大學圖書館 |

語系: 繁體中文

說明(常見問題)

回圖書館首頁

手機版館藏查詢

登入

回首頁

切換: 標籤 | MARC模式 | ISBD

Fatigue behavior and encrustation ch...

University of California, Irvine., Materials Science and Engineering - Ph.D.

FindBook

Google Book

Amazon

博客來

Fatigue behavior and encrustation characteristics of nanocrystalline metals.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Fatigue behavior and encrustation characteristics of nanocrystalline metals./
作者:	Lai, Li-Chung.
面頁冊數:	114 p.
附註:	Adviser: James Earthman.
Contained By:	Dissertation Abstracts International70-05B.
標題:	Engineering, Materials Science. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3355697
ISBN:	9781109149906

Fatigue behavior and encrustation characteristics of nanocrystalline metals.
Lai, Li-Chung.

Fatigue behavior and encrustation characteristics of nanocrystalline metals. - 114 p.

Adviser: James Earthman.

Thesis (Ph.D.)--University of California, Irvine, 2009.

The nanocrstalline (NC) metals have been reported to have high mechanical performance owing to it's small grain interior and a large volume fraction of grain boundary (GB) atoms. Small grain leads to the forbidden dislocation activities in grain interior while GB activities become dominant due to a higher volume fraction of GB atoms. Regarding the fatigue response to nanocrstalline metals, it has been reported that decreasing grain led to both significantly improvement on the fatigue-endurance limit and deleterious effect on the resistance to subcritical fatigue crack propagation. The increases endurance limit has been attributed to the greater resistance to fatigue crack initiation at near-surface regions. On the other hand, the less resistance to fatigue crack growth were resulted from less tortuous fatigue crack profiles supported by the deflection/closure theory.

ISBN: 9781109149906Subjects--Topical Terms:

1017759
Engineering, Materials Science.

Fatigue behavior and encrustation characteristics of nanocrystalline metals.
LDR:04875nmm 2200349 a 45 001 867005
005 20100802
008 100802s2009 ||||||||||||||||| ||eng d
020 $a 9781109149906
035 $a (UMI)AAI3355697
035 $a AAI3355697
040 $a UMI $c UMI
100 1 $a Lai, Li-Chung. $3 1035701
245 1 0 $a Fatigue behavior and encrustation characteristics of nanocrystalline metals.
300 $a 114 p.
500 $a Adviser: James Earthman.
500 $a Source: Dissertation Abstracts International, Volume: 70-05, Section: B, page: 3123.
502 $a Thesis (Ph.D.)--University of California, Irvine, 2009.
520 $a The nanocrstalline (NC) metals have been reported to have high mechanical performance owing to it's small grain interior and a large volume fraction of grain boundary (GB) atoms. Small grain leads to the forbidden dislocation activities in grain interior while GB activities become dominant due to a higher volume fraction of GB atoms. Regarding the fatigue response to nanocrstalline metals, it has been reported that decreasing grain led to both significantly improvement on the fatigue-endurance limit and deleterious effect on the resistance to subcritical fatigue crack propagation. The increases endurance limit has been attributed to the greater resistance to fatigue crack initiation at near-surface regions. On the other hand, the less resistance to fatigue crack growth were resulted from less tortuous fatigue crack profiles supported by the deflection/closure theory.
520 $a However, it has never been studied the influence of proceeding and pre-existing defects on the fatigue performance considering the difference response of NC structure from than coarse grain (CG) structure. In the present work, the influence of electrical discharge machining (EDM) and surface defects on the fatigue behavior of both conventional cold-rolled CG and electro-deposited (ED) NC Ni were investigated. The experimental results revealed considerable influence by EDM on the fatigue strength of NC Ni, while it has little or no affect on that for CG Ni. Specifically, EDM led to a 50 to 75% reduction in fatigue strength for NC Ni despite a relatively small depth of EDM affected material (&sim; 1% of width). Rationale for this effect can be attributed to grain growth, microcracks, and a higher sulfur content at the GBs in the EDM affected zone. In addition, the pre-existing surface defects that appear to be due to impurity segregation near the electro-deposition substrate significantly reduced the fatigue resistance of ED NC Ni.
520 $a In order to understand the fatigued behavior in NC Ni, crack tip grain structures were investigated using transmission electron microscope (TEM). Crack tip grain growth was observed at early state of crack propagation with low stress intensity factor (K &sim; 6 MPa m 1/2). As K increased, the size of grain growth zone increased exponentially in width and crack propagation behavior transmitted from interganular to transgranular. It appears that this transmission is associated with grain growth. The coalesced grains due to grain rotation/GB diffusion created larger paths for more extended dislocation movement. Dislocation activities become less forbidden and the dislocation-slip mechanism can be dominant leading to a more plastically transgranular fracture.
520 $a In addition to fatigue study of ED NC Ni, encrustation on ED NC Ti was investigated. The use of materials for medical applications in the urinary tract is hampered by the formation of calcium-based crystalline deposits, generally referred to as encrustation, that act as precursors to urinary stones. Anecdotal evidence suggests that titanium can possess encrustation-resistant properties in vivo and may be useful in urologic applications. To test the utility of coating surfaces with nanostructured titanium, several forms of materials were submersed in artificial urine with saturating concentrations of calcium for a period of 14 days. The specimens were then analyzed using scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS) to determine the extent of encrustation on the surface of the various samples. Our observations indicate that nanostructured titanium offers superior resistance to encrustation when compared to polyurethane, polyvinyl chloride or conventional coarser grained titanium. Further studies investigating the use of nanostructured titanium in urologic applications are warranted.
590 $a School code: 0030.
650 4 $a Engineering, Materials Science. $3 1017759
650 4 $a Engineering, Mechanical. $3 783786
650 4 $a Engineering, Metallurgy. $3 1023648
690 $a 0548
690 $a 0743
690 $a 0794
710 2 $a University of California, Irvine. $b Materials Science and Engineering - Ph.D. $3 1035700
773 0 $t Dissertation Abstracts International $g 70-05B.
790 $a 0030
790 1 0 $a Earthman, James, $e advisor
790 1 0 $a Mohamed, Farghalli $e committee member
790 1 0 $a Shi, Frank $e committee member
791 $a Ph.D.
792 $a 2009
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3355697