Crack Paths 2012

NumericalSimulationof Fatigue CrackGrowthin

HeterogeneousMaterial

MasanoriKikuchil, Yoshitaka Wada2,KazuhiroSuga1 and YulongLi3

1 TokyoUniversity of Science, 2641 Yamazaki,Noda,Chiba, 278-8510,Japan

kik@rs.noda.tus.ac.ip , ksuga@rs.noda.tus.ac.ip

2 TokyoUniversity of Science, Suwa, 5000-1, Toyohira, Chino, Nagano,391-0292Japan

wada@rs.suwa.tu.sac.jp

3NorthwesternPolytechnical University, 127 Youyi Xilu, Xian 710072Shaanxi, P.R.China

li loon n w u.edu.cn

A B S T R A C T .Fully automatic fatigue crack growth simulation system is developed

using S-version F E M(S-FEA/I). This system is extended to fracture in heterogeneous

material. In the heterogeneous material, crack tip stress field becomes mixed mode

condition, and crack growth path is affected by inhomogeneous materials and mixed

modeconditions. Stress Intensity Factors (SIF) in mixedmodecondition are evaluated

using Virtual Crack Closure Method(VCCM). Criteria for crack growth amountand

crack growth path are used based on these SIFs, andgrowing crack configurations are

obtained. Atfirst, basic problem is solved, and results are comparedwith previously

reported ones. It is shown that this system gives adequately accurate estimation ofSIFs.

Then Z-dimentional fatigue crack growth problems are simulated using this system.

crack growthproblems are simulated using this system. Thefirst example is a plate with

interface between hard and soft materials. Crack tends to grow into soft material

through interface. Second example is a plte with distributed hard inclusions. Crack

takes zig-zag path by keeping awayfrom hard inclusions. In each cases, crack growth

path changes in complicated manner. Changes ofSIFs are also shown and discussed

Finally it is shown that this system is useful for the prediction ofresidual fatigue life in

heterogeneous material.

I N T R O D U C T I O N

Fatigue crack growth is important problem for the integrity of structures. To avoid

catastrophic accident, predictions of crack growth path and fatigue life are key

technologies. As fatigue crack growth occurs in complicated structures, these

predictions have met serious difficulties. F E Mis usually used for these predictions, but

re-meshing process is needed for modeling of growing crack configurations, it has been

a bottleneck for the application of F E Mto fatigue crack growth problems, especially in

three-dimensional field.

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