원공노치 인근에 발생한 결함의 위치변화가 균열성장률(da/dN) 및 응력확대계수범위(δK)의 관계에 미치는 영향 - 단일재 알루미늄과 Al/GFRP 적층재의 피로거동 비교 - = The Effect of Defect Location Near a Circular Hole Notch on the Relationship Between Crack Growth Rate (da/dN) and Stress Intensity Factor Range (δK) - Comparative Studies of Fatigue Behavior in the Case of Monolithic Al Alloy vs. Al/GFRP Laminate

다국어 초록 (Multilingual Abstract)

The objective of this study is to investigate the effect of arbitrarily located defect around the circular hole in the aircraft structural material such as Al/GFRP laminates and monolithic Al alloy sheet under cyclic bending moment. The fatigue behavior of these materials may be different due to the defect location. Material flaws in the from of pre-existing defects can severely affect the fatigue crack initiation and propagation behavior. The aim of this study is to evaluate effects of relative location of defects around the circular hole in monolithic Al alloy and Al/GFRP laminates under cyclic bending moment. The fatigue behavior i.e., the stress concentration factor($K_t$), the crack initiation life($N_i$), the relationship between crack length(a) and cycles(N), the relationship between crack growth rate(da/dN) and stress intensity factor range(${\Dalta}K$) near a circular hole are considered. Especially, the defects location at ${\theta}_1=0^{\circ}\;and\;{\theta}_2=30^{\circ}$ was strongly effective in stress concentration factor($K_t$) and crack initiation life($N_i$). The test results indicated the features of different fatigue crack propagation behavior and the different growing delamination shape according to each location of defect around the circular hole in Al/GFRP laminates.