Fatigue growth simulation for cracks in notched and unnotched round bars

Finite element modelling and analysis of crack shape evolution in mode-I fatigue Middle Cracked Tension specimens

“…Lazarus [17] analysed an embedded crack (elliptical or rectangular) in an infinite body loaded under mode-I and observed that after a certain time the crack becomes circular. Similar conclusions were presented in studies with cracks emanating from fastener holes and cracks in notched and unnotched round bars [9,10]. The cracks converge to shapes with constant fatigue crack growth along crack front and constant K (iso-K profile) [13].…”

“…A more sophisticated methodology work of external forces x c rate of crack shape variation x l transition limit of crack shape variation criterion f l transition limit of transient function criterion Da, Da max crack increment, maximum crack increment DK range of stress intensity factor DK eff effective range of stress intensity factor m Poisson's ratio was developed by Lin and Smith [5][6][7] considering several points along the crack front. This approach eliminates the crack shape constraint and was applied to planar cracks in fastener holes, to notched and unnotched round bars under tension, etc., by Lin and Smith [5][6][7][8][9][10]. Reliable predictions of crack shape evolution and stress intensity factors were also obtained by other authors.…”

“…Fig. 9 also indicates that the crack propagation can be divided into two main stages [9][10][11][17][18][19]: an initial transient stage (I) highly dependent on the initial crack shape and with high crack shape variation gradients; and a subsequent stable stage (stage II) where the crack follows preferred paths which are not affected by the initial crack shape. Only one single path can be followed by the dependent parameters for each initial crack shape.…”

“…The increase of m or B, decreases the optimum radial size. Multiple regressions were used to define a function relating these three variables, valid within B 2 [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] …”

Fatigue growth of a surface crack in a V-shaped notched round bar under cyclic tension

“…Lin and Smith (1998;1999) investigated crack shape evolution, crack shape deviation, and variation of the aspect ratio of a surface crack in a semi-circular notched round bar. They utilized a linear elastic 3D-FEA to estimate SIFs along the crack front and used Paris's equation for simulating fatigue crack growths.…”