Abstract The dislocation structure evolution of polycrystalline copper at constant strain amplitude during low cycle fatigue has been studied sufficiently. The dislocation structure develops loop patches, vein structure, persistent slip bands (PSBs), dislocation walls, dislocation cells, and misorientation dislocation cells step-by-step by increasing fatigue cycles. However, the dislocation structure evolution will change as the strain amplitude decreasing from high to low. In order to realize that the dislocation structure of polycrystalline copper how to evolve with reducing strain amplitude during low cycle fatigue, I use the copper of 99.99% purity in this experiment. The test is controlled 4¡Ñ103 cycles at 0.2% strain amplitude, and the strain amplitude is decreased from 0.2% to 0.1%. It keeps the 0.1% strain amplitude after 4¡Ñ103 cycles. I chose the four steps of the low cycle fatigue at 5¡Ñ103 , 9¡Ñ103, 15¡Ñ103 cycles, and the specimen cracking then observe the dislocation structure. Then we can know the dislocation morphology under evolution process after decreasing the strain amplitude. From the fatigue tests data by dropping the strain amplitude we can see the dislocation cells fast creaking to loop patches at 5¡Ñ103 cycles; The dislocation cells scatter and become vein structure with loop patches like a band at 9¡Ñ103 cycles. To observe clearly that the scattering loop patches normal develop dislocation walls near the grain boundary at 15¡Ñ103 cycles; At last, all of the dislocations form dislocation cells again and progress misorientation when becoming equiaxis cell. The morphology is between 0.2% strain amplitude and 0.1% strain amplitude. So we can understand the process of dislocation reverse evolution is the dislocation cells diffusing to bands. Then the bands creak to loop patches.

Abstract IF steel with two grain sizes ( 70£gm and 210£gm ) strain amplitude of 2%¡B1.6%¡B1%¡B0.8%¡B0.6%¡B0.4%¡B0.3%¡B0.2%¡B0.1%¡B0.05% were fatigued in order to obtain basic fatigue properties. By use TEM , we can know that we can observe dislocation cells from £G£`t = 0.05% ~£G£`t = 2% . When £G£`t > 1.6% , hardening will occur , if not , softening will be observed . The more strain amplitude is , the more plastic deformation will be observed . When£G£`t > 0.3% , the elastic deformation will smaller than plastic deformation . When£G£`t =0.2% ~£G£`t = 0.4% , we can observe secondary hardening from the specimen of 70£gm . When £G£`t > 1% , the n¡¦ of 70£gm is more than the n¡¦ of 210£gm , that means the specimen of 70£gm has bigger hardening . By the ¡¥ Stress amplitude v.s. Plastic deformation amplitude ¡¦ plot of 70£gm and 210£gm , we can know that there is no ¡¥ pleatue ¡¦ . The more strain amplitude is , the more difference between long axis and short axis of dislocation cell will occur .

Fatigue cracking is one of the fundamental distresses that occur in the life of a Hot Mix Asphalt Concrete (HMAC) pavement. This load induced distress leads to structural collapse of the entire pavement ultimately and can only be remedied by rehabilitation. There is the need, therefore, for a total understanding of the phenomenon to be able to counter its occurrence. The fatigue resistance of hot mix asphalt concrete (HMAC) has been estimated using approaches ranging from empirical methods to mechanistic-empirical methods to purely mechanistic methods. A continuum mechanics based approach called the Calibrated Mechanistic with Surface Energy (CMSE) measurements was developed at Texas A&M University and recommended after comparison with other approaches in predicting fatigue lives of two Texas HMAC mixtures. The CMSE approach which includes fundamental material properties such as fracture, aging, healing, and anisotropy has been shown to effectively model the parameters that affect the performance of HMAC pavements exposed to repetitive traffic loads. Polymer modified asphalt (PMA) improves pavement performance by providing additional resistance to the primary distresses in flexible pavements, including permanent deformation or rutting, thermal cracking, and fatigue cracking. In this research, the CMSE approach was utilized to estimate the fatigue resistance of HMAC fabricated with asphalts modified with Styrene-butadiene-Styrene (SBS) co-block polymer. These HMAC mixtures were fabricated from materials used on three different road sections in Texas and one test pavement in Minnesota. The CMSE approach was validated as an effective approach for estimating the fatigue resistance of HMAC mixtures with PMA. The effect of oxidative aging on the fatigue resistance of the HMAC mixtures was also verified. Oxidative aging of the mixtures resulted in a corresponding decrease in mixture fatigue resistance. In addition, for two HMAC mixtures with the same binder content and aggregate gradation, the mixture with the softer of the two Performance Grade (PG) binders exhibited greater fatigue resistance. The use of the Utility Theory revealed the possible effects of aggregate geometric properties on the HMAC mixture properties and consequently on their fatigue resistance.

Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains xi, 86 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 79-86).

Thèse Linköping : Univ., 2003. / Härtill 4 uppsatser.

Reproduction de : Thèse de doctorat : Génie mécanique : Clermont-Ferrand 2 : 2005. / Thèse avec annexes. Titre provenant de l'écran-titre. Bibliogr. p. 146-149.

Thesis (DClinPsychol)--Salomons Centre. BLDSC no. DXN049059.

Thesis (M.S. in Human Systems Integration)--Naval Postgraduate School, December 2009. / Thesis Advisor(s): Miller, Nita Lewis. Second Reader: Schiffman, David L. "December 2009." Description based on title screen as viewed on January 26, 2010. Author(s) subject terms: Navy Standard Workweek, fatigue, sleep, circadian rhythm. Includes bibliographical references (p. 95-97). Also available in print.

Thesis (Ph.D.)--Indiana University, 2009. / Title from screen (viewed on February 2, 2010). School of Nursing, Indiana University-Purdue University Indianapolis (IUPUI). Advisor(s): Janet L. Welch, Juanita F. Keck, Janet S. Fulton, Barbara Manz Friesth. Includes vitae. Includes bibliographical references (leaves 150-164).

Thesis (Ph. D.)--University of Michigan, 1915. / Kansas State Documents Classification Number: E50.13 : v. 9, no. 17. Includes bibliographical references (p. 241-243).