Authors: Tsutomu Ezumie, Kentaro Nishimura

Abstract: Fatigue and fractures such as blades and discs, which originate in the centrifugal force
caused in the rotor, become factors that often cause serious accidents. The enlargement of machine
and structure improves the possibility that do the latency of minute cracks and inclusion in materials
in manufacturing processes. Severe working conditions also promote the propagation of the crack
while operating. Thus, it is very important for the improvement in the safety of materials to analyze
the interference problem of inclusion and crack. In this study, an inclusion in the rotating disc and
the interference problem of the crack were examined. The influence of the mechanical property of
the inclusion and the distance to the crack tip was examined. The stress intensity factor was
determined by using photoelasticity and method of caustics. As a result, the stress intensity factor
was decreased when Young’s modulus of inclusion increased. Moreover, the stress intensity factor
decreased as the distance from the crack tip to the inclusion boundary became longer. The stress
intensity factor of the crack on the rotation center side increased more than the cracks on the
circumference side of the inclusion.

684

Authors: You Tang Li, Bo Chen, Rui Feng Wang

Abstract: Based on elasticity theory, the stress field and stress intensity factor of gear crack are discussed. The effect of friction coefficient and crack shape on equivalent stress, displacement at crack tip and stress intensity factor were analyzed by using general finite element software ANSYS, and the formula of stress intensity factor of gear crack was revised. The results showed that the equivalent stress, displacement at crack tip and stress intensity factor increased with the friction coefficient for the same crack. For the same f and different a/c, the front friction surface played a major role when a/B﹤0.05, and the post friction surface played a major role when a/B﹥0.05. The stress intensity factor increase at first, and then decrease with the increase of a/c.

493

Authors: Jin Feng Geng, Hong Sheng Cai, Xing Pei Liang, Hui Wang, Yu Jie Wang, Zhao Hua Wang

Abstract: The linear elastic problem for two welded thin-walled steel tubes containing circular arc weld defect subjected to bending load is analyzed in the present paper. The welding defect is firstly simplified as a circular arc crack and then the finite element based technique is used to calculate the corresponding energy release rate (J-integral), which is related to stress intensity factor directly. Finally, the arc length of welding defect is changed to investigate the variation of stress intensity factors.

1711

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

Abstract: Stress intensity factors are calculated for a cracked plate reinforced locally subject to mode I loading. The stiffeners are considered to have both longitudinal and transverse stiffness. There is no relative displacement between the plate and the stiffener. It is considered that the shear stresses are lumped at a finite number of locations, the result is obtained by summation. The influence of the stiffener location and the stiffener relative stiffness on cracked plate is included. The stress intensity factor depends on all these factors. Case study shows that the shear stress acting parallel to the stiffener gives more effect on the stress intensity factor than the shear stress acting perpendicular to the stiffener. To increase the relative stiffness of stiffener avails to reduce the stress intensity factor of the cracked plate.

493