A computational approach for fatigue crack propagation in ship structures under random sequence of clustered loading

The authors have developed a simulation program, CP-System, for multiple cracks propagating in a three-dimensional stiffened panel structure, where through-the-thickness crack propagation is formulated as a two-dimensional in-plane problem, and the crack propagation behavior is simulated by step-by-step finite element analyses. In order to evaluate the fatigue lives of marine structures accurately, it is necessary to take into account the load histories induced by sea waves, which may be composed of a random sequence of certain clustered loads with variable stress range. In the proposed crack growth model, the crack opening and closure behavior is simulated by using the modified strip yielding model, and the effective tensile plastic stress intensity range, ΔKRP, is calculated by considering the contact of plastic wake along the crack surfaces. The adequacy of the proposed crack growth model is examined by comparison with fatigue tests under non-constant-amplitude loading. The usefulness of the developed method is demonstrated for a ship structural detail under certain simulated load sequences. It is shown that the fatigue crack growth of a ship structure is significantly retarded due to the load interaction effects, so that the conventional method for fatigue life assessment may predict a relatively conservative fatigue life of a structure.

[1]  R. Salganik,et al.  Brittle fracture of solids with arbitrary cracks , 1974 .

[2]  大川 鉄平.  Simulation-based fatigue crack management of ship structural details applied to longitudinal and transverse connections , 2008 .

[3]  Y. Sumi,et al.  On crack branching and curving in a finite body , 1983 .

[4]  Torgeir Moan,et al.  A unique crack growth rate curve method for fatigue life prediction of steel structures , 2009 .

[5]  Yoichi Sumi,et al.  A note on the first order perturbation solution of a straight crack with slightly branched and curved extension under a general geometric and loading condition , 1986 .

[6]  Yoichi Sumi,et al.  Morphological aspects of fatigue crack propagation Part II—effects of stress biaxiality and welding residual stress , 1996 .

[7]  Masanori Kawahara,et al.  An Expression of Fatigue Crack Propagation Rates under Wide Ranged Stress Ratios , 1983 .

[8]  Y Tomita,et al.  STOCHASTIC CHARACTERISTIC OF LONG TERM DISTRIBUTION OF WAVE-INDUCED LOADING AND SIMULATION METHOD FOR FATIGUE STRENGTH ANALYSIS OF SHIP STRUCTURAL MEMBER (3RD REPORT: FATIGUE TEST RESULT UNDER VARIABLE STRESS AMPLITUDE ACCORDING TO "STORM MODEL") , 1995 .

[9]  J. Newman.  A crack-closure model for predicting fatigue crack growth under aircraft spectrum loading , 1981 .

[10]  Yoichi Sumi,et al.  Morphological aspects of fatigue crack propagation Part I—Computational procedure , 1996 .

[11]  Masahiro Toyosada,et al.  Fatigue crack propagation for a through thickness crack: a crack propagation law considering cyclic plasticity near the crack tip , 2004 .

[12]  Yoichi Sumi,et al.  Computational prediction of fatigue crack paths in ship structural details , 2005 .

[13]  Yang Mu,et al.  Development of an Automatic Quadrilateral Mesh Generator for the Simulation of Curved Crack Growth , 1999 .

[14]  Yoichi Sumi,et al.  Fatigue crack propagation and computational remaining life assessment of ship structures , 1998 .

[15]  Yoshiyuki Yamamoto,et al.  Determination of stress intensity factors in cracked plates by the finite element method , 1973 .

[16]  Masahiro Toyosada,et al.  Fatigue life assessment for welded structures without initial defects: an algorithm for predicting fatigue crack growth from a sound site , 2004 .

[17]  Yoichi Sumi,et al.  A finite-element simulation method for a system of growing cracks in a heterogeneous material , 1998 .