A review of the Effect of α/W ratio on fracture toughness （Ⅱ） experimental investigation in LEFM

In part I of this series, experimental investigation in EPFM （elastic-plastic fracture mechanics） had been discussed. In this paper, experimental investigation in LEFM （ linear elastic fracture mechanics） is given. Fracture toughness tests had been carried out on three different strength steels, using both through-cracked specimens with different α/W ratio and semi-elliptical cracked specimens with variable crack size and shape. Results show that the fracture toughness KIC increases with decreasing α/W when α/W 〈 0.3 for three-point-bend specimens, and that for α/W 〉 0.3, it is independent of α/W. Shallow crack specimens, both through-cracked and surface-cracked, gave markedly higher values than deeply notched specimens. However, the effect of crack shape on fracture toughness is negligible. Results also show that the LEFM approach to fracture is not tenable for design stresses where αc is often very small, far less than 2.5 （ KIC/σy）^2.

A review of the effect of a/W ratio on fracture toughness (II) —experimental investigation in LEFM

In part I of this series, experimental investigation in EPFM (elastic-plastic fracture mechanics) had been discussed. In this paper, experimental investigation in LEFM (linear elastic fracture mechanics) is given. Fracture toughness tests had been carried out on three different strength steels, using both through-cracked specimens with different a/W ratio and semi-elliptical cracked specimens with variable crack size and shape. Results show that the fracture toughness K _IC increases with decreasing a/W when a/W<0.3 for three-point-bend specimens, and that for a/W>0.3, it is independent of a/W. Shallow crack specimens, both through-cracked and surface-cracked, gave markedly higher values than deeply notched specimens. However, the effect of crack shape on fracture toughness is negligible. Results also show that the LEFM approach to fracture is not tenable for design stresses where a _c is often very small, far less than 2.5(K _IC/σ _y )². LI Qing-feng (1944–) graduated in Aeronautical Engineering from Harbin Military Engineering Institute in 1968. She is a professor in School of Mechanical & Electrical Engineering, Harbin Engineering University. 1980–1982: A Visiting Scholar in the Department of Mechanical Engineering, University of Sydney, N.S.W., Australia. 1996: Visiting Professor in the Department of Mechanical Engineering, University of Glasgow, Scotland, U.K. She is a member of Directorate of Modern Design Theory and Method Committee of China and has authored and co- authored 138 papers in national and international journals, and conference proceedings (58 papers were covered by SCI, EI and ISTP). Her research interests are in fracture mechanics, materials strength, materials design and machine design. FU YU-dong (1969–), a lecturer, is presently a PhD candidate in School of Mechanical and Electrical Engineering, Harbin Engineering University. He graduated from Harbin Engineering University and received his Bachelor degree in 1993, and Master degree in 1999. He has authored and co- authored 6 papers in journals and conference proceedings XU Xiao-xue (1980–), a postgraduate in School of Mechanical and Electrical Engineering, Harbin Engineering University. She graduated from Harbin Engineering University and received hers Bachelor degree in 2003.