Authors: Akihide Saimoto, Yoshio Imai, Toshiyuki Hashida

327

Authors: Hong Liang Li, Hong Li, Yong Yang

Abstract: In mechanical engineering, circular hole is used widely in structure design. When the
structure is overloaded or the load is changed regularly, cracks emerge and spread. Based on the
former study of dynamic stress concentration problem of SH wave by a crack originating at a
circular hole edge, in this paper, the method of Green’s function is used to investigate the problem
of dynamic stress intensity problem of double linear cracks near a circular hole impacted by
incident SH-wave. The train of thought for this problem is that: Firstly, a Green’s function is
constructed for the problem, which is a fundamental solution of displacement field for an elastic
space possessing a circular hole and a linear crack while bearing out-of-plane harmonic line source
force at any point; Secondly, in terms of the solution of SH-wave’s scattering by an elastic space
with a circular hole and a linear crack, anti-plane stresses which are the same in quantity but
opposite in direction to those mentioned before, are loaded at the region where the second crack is
in existent actually, we called this process “crack-division”; Finally, the expressions of the
dynamic stress intensity factor(DSIF) of the cracks are given when the circular hole and double
linear crack exist at the same time. Then, by using the expressions, an example was provided to
show the effect of circular hole and cracks on the dynamic stress intensity factor of the cracks.

105

Authors: Yong Chang Guo, Han Lin Huang, Li Juan Li, Jun Deng, Gen Quan Zhong

Abstract: External bonding of fiber reinforced polymer (FRP) plates or sheets, because of their advantages, such as high strength to weight ratio and good resistance to corrosion, has become a popular technique for the strengthening and upgrading of structurally inadequate or damaged reinforced concrete (RC) structures. Interface debonding failure is one of the most common failure modes of the FRP strengthened RC structures. In this paper, the damaged concrete constitutive model is established and the effects of crack on the interfacial stresses of RC beam strengthened with CFRP are investigated. Longitudinal stress in the CFRP, shear stress in the adhesive layer and the first principal stress in the concrete at the crack tips of the retrofitted RC beams with cracks at different locations are analyzed. The results show that when cracks locate at the loading position, the longitudinal stress in the CFRP is the largest and the tensile failure of the CFRP is the most likely occurred.

559

Authors: Wei Wang, Zhao Peng Ni, Dong Zhu Chen, Guang Ming Yin, Peng Ding, Shi Chao Liao

Abstract: In this paper secondary lining of an underwater tunnel which had appeared I-longitudinal crack was taken as study object according to theory of fracture mechanics. Finite Element analysis was carried out to calculate the stress intensity factor at the tip of I-longitudinal crack which located in vault, then to analyze the extended state of crack based on double-K fracture criteria. The computation results indicate that the stress intensity factor at the tip of I-longitudinal cracks which appear within 20 degrees of the vault do not exceed unstable fracture toughness, lining is in stable growth stage and do not occur instable failure. The stress intensity factor at the tip of I-longitudinal cracks appeared in vault is maximum and appeared in both side of vault is minor, the further away from vault the less of stress intensity factor. When water level below the top of tunnel, with the rise of water level the stress intensity factor at the tip of I-longitudinal decrease and the external water pressure has restrain effect to the crack extension. When water level exceed the top of tunnel, with the rise of water level the stress intensity factor at the tip of large depth of crack decrease rapidly until arrive negative value, then increase backward until greater than unstable fracture toughness and cause lining structural local instable failure.

2472

Authors: Jing Fu Nan, Hui Qi, Chun Xiang Zhao

Abstract: The Green function and other complex functions were employed to study the problem of scatteing of SH wave by a interface semicircular debonded elastic lining of two-phase mediums and interface linear cracks originating at edge of lining. We divided the whole model into upper elastic half space with the semi-circular canyon and lower elastic half space with semi-circular lining hill.In lower half space. Semicircular debonded elastic lining is constructed by satisfing the continuous condition of displacement and stress on interface when upper half part and lower half part are conjoined,and linear cracks is constructed by using the method of crack incision, upper half part and lower half part are conjoined by method of “conjunction”.In the end some examples and results of dynamic stress intensify factor are given with discussions.

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