Authors: Li Yun Li, F.X. Che, D.A. Liu
Abstract: Multi-crack problems are deeply involved in rock-like material and rock engineering. In order to study the influences of lateral stress and inclined crack angle on the failure load of the multi-cracked body, uniaxial and biaxial compression fracture tests are conducted on plate specimens with regular distributed multi-cracks. The stress distribution and the stress intensity factors KI and KII for every crack tips of the specimens are calculated by FEM. The experiment revealed that the failure load of the multi-cracked specimens increase obviously with the increase of the lateral pressure σ2 and the inclined crack angle α. And the multi-cracked specimens will hardly initiate propagation under equal biaxial compression. Analyses have been shown that these can be explained by the variation of KII with the σ2 and the α.
1523
Authors: Ozgur Inan, Serkan Dag, Fazil Erdogan
Abstract: In this study the three – dimensional surface cracking of a graded coating bonded to a homogeneous substrate is considered. The main objective is to model the subcritical crack growth process in the coated medium under a cyclic mechanical or thermal loading. Because of symmetry, along the crack front conditions of mode I fracture and plane strain deformations are assumed to be satisfied. Thus, at a given location on the crack front the crack propagation rate would be a function of the mode I stress intensity factor. A three – dimensional finite element technique for
nonhomogeneous elastic solids is used to solve the problem and the displacement correlation technique is used to calculate the stress intensity factor.
373
Authors: Jun Si, Fu Zhen Xuan, Shan Tung Tu
Abstract: The interaction behavior of two non-aligned through-wall cracks in flat plates is
investigated by the finite element method (FEM) under extensive creep condition. The
time-dependent fracture parameter C*-integral along the crack tips are calculated and compared to
the results of a single crack of the same size. For comparison purpose, the interaction of stress
intensity factors (SIFs) is also examined in the study. The results indicated that interaction of
multiple cracks is different between the time- dependent fracture characterized by C*-integral and
linear elastic fracture noted by SIF. The magnifying factors of time-dependent fracture are obviously
larger than that of the linear elastic fracture cases. Therefore, the current re-characterization rule for
multiple cracks developed from linear elastic fracture analysis may lead to a non-conservative result
and should be modified when it is used in the assessment of time dependent failure.
105
Authors: Masanori Kikuchi, Yoshitaka Wada, Masafumi Takahashi, Yu Long Li
Abstract: Fatigue crack growth under mixed mode loading conditions is simulated using S-FEM. By
using S-FEM technique, only local mesh should be re-meshed and it becomes easy to simulate crack
growth. By combining with auto-meshing technique, local mesh is re-meshed automatically, and
curved crack path is modeled easily. Plural fatigue crack problem is solved by this technique. For
two parallel crack problem, criteria of crack coalescence are proposed. By simulating this problem by
S-FEM, it is verified these criteria are conservative ones.
133
Authors: F. Ricci, F. Franco, Nicola Montefusco
Abstract: In this paper, the mechanisms of propagation of the damage in aluminum panels repaired with bonded composite patches of different mechanical characteristics is analyzed. The aim of this study is to analyze analytically, experimentally and numerically the advantage of the use of bonded composite patches to increase the fatigue life and to reduce the state of tension at the crack tips. The experimental results show that both static strength and fatigue life of the repaired aluminum panel has significantly increased due to the bonded composite patches. The different patches and adhesive, used for cracked panels, have provided about a 100-110% improvement in the fatigue life and a 30-35% decrease in the stress intensity factor. A comparison between finite elements calculations and experimental data has been carried out. The good agreement between the experimental data and the numerical ones has demonstrated the possibility to obtain an optimized design of bonded patches with the numerical tools.
597