Authors: Kazuhiro Oda, Yoshiyuki Muraoka, Naoaki Noda

297

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: Zhen Qing Wang, Ji Bin Wang, Wen Yan Liang, Juan Su

Abstract: The viscosity of material is considered at propagating crack-tip. Under the assumption
that the artificial viscosity coefficient is in inverse proportion to the power law of the plastic strain
rate, an elastic-viscoplastic asymptotic analysis is carried out for moving crack-tip fields in
power-hardening materials under plane-strain condition. A continuous solution is obtained
containing no discontinuities. The variations of the numerical solution are discussed for mode I
crack according to each parameter. It is shown that stress and strain both possess exponential
singularity. The elasticity, plasticity and viscosity of material at the crack-tip only can be matched
reasonably under linear-hardening condition. The tip field contains no elastic unloading zone for
mode I crack.

817

Authors: Zai Lin Yang, Hua Nan Xu, Mei Juan Xu, Bai Tao Sun

Abstract: In this paper, we study the problems of scattering of out-of-plane line source load by half-space shallow-embedded circular lining structure and a crack in the field of linearly elastic dynamic mechanics. This is an essential solution to the displacement field for the elastic space possessing shallow-embedded circular lining structure and a crack while bearing out-of-plane harmonic line source load at arbitrary point. The wave function of scattering of shallow-embedded circular lining structure impacted by incident steady SH-wave is constructed based on the symmetry of SH-wave scattering and the method of multi-polar coordinates system. Then a crack is made out using the method of “crack-division”. Thus expressions of displacement and stress are established when shallow-embedded circular lining structure and a crack are both in existent. Finally, with two different dimensionless parameters, numerical results of scattering of out-of-plane line source load by half-space shallow-embedded circular lining structure and a crack are obtained and numerical examples are provided to show the influence of wave number ratio, shear modulus ratio, thickness ratio and the ratio of distance between the center of the different cavity and ground surface and the radius of the circular lining structure upon the dynamic stress concentration factor(DSCF) and dynamic stress intensity factor(DSIF) at crack tip.

329

Authors: Hui Hua Zhang, Jia Xiang Yan

Abstract: The numerical manifold method (NMM) is a representative among different numerical methods for crack problems. Due to the independence of physical domain and the mathematical cover system, totally regular mathematical elements can be used in the NMM. In the present paper, the NMM is applied to solve 2-D linear elastic crack problems, together with the comparison study on the accuracy of n-sided regular mathematical elements, i.e., the triangular elements (n=3), the quadrilateral elements (n=4) and the hexagonal elements (n=6). Our numerical results show that among different elements, the regular hexagonal element is the best and the quadrilateral element is better than the triangular one.

1093