Doctoral Thesis
Rißfortschrittsverhalten von Baustählen in der Nähe des Ermüdungsschwellwertes
(Fatigue Crack Propagation near Fatigue Threshold in various Structural Steels)
Division of Materials Science and Engineering, Department of Ferrous Metallurgy(IEHK), RWTH Aachen, Germany, 1996
ABSTRACT
The investigations have been conducted by measuring fatigue crack propagation in various structural steels differing in chemical composition and strength level. The fatigue crack propagation measurements were carried out using the constant-load-amplitude test in Paris-region, R-constant and Kmax-constant method in near fatigue threshold region. Scanning electron microscopy at fatigue crack front on fracture surface was applied to interpret the influence of crack closure effects on the measured fatigue threshold. Marked fretting oxide deposits distributed on the fracture surface at threshold level were observed in a low load ratio resulting from the combined action of plasticity- and oxide-induced crack closure at laboratory atmosphere. Fatigue threshold dependent on the load ratio appeared to be related to the extent of the crack closure effect. By considering the relationship of reversed plastic zone size and grain size the fatigue threshold in region of crack closure was calculated theoretically. The result has shown a good agreement with the experimentally measured values.
Master's Thesis
GFRP 복합재료의 섬유 배열방향에 따른 피로균열 진전거동
(Fatigue Crack Growth Behaviours of GFRP due to Change of Fiber Direction)
Department of Machine Design & Production Engineering, Hanyang University, Seoul, Korea, 1991