Papers by Keyword: Step Loading

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Authors: Si Feng Zhang, Xiu Guang Song, Yan Mei Li, Kai Yao
Abstract: The development and evolution regularity of the interface shear stress for the inner bond section of geotechnical prestressed anchorage structure is directly related to the ultimate bearing capacity and its long-term durability. By adopting the similar model test and embedding the strain brick at each interfaces of inner bond section, the interface mechanical properties under step loading were systematically studied. Conclusions can be drawn as follows: the interface shear stress along the axial direction of rod is not evenly distributed, and the interface distribution shape at different radial distance from the rod axis also varies. With the gradual increase of external load, the shear stress peak point continues to move into the deep areas, and resulting in the occurrence of gradual damage mode. In the process, the peak value of shear stress also augment gradually. Along radial direction of the rod, the shear stress concentration phenomenon just distributes within a small radius around the rod body. Adopting the two stage linear function to describe the relationship of shear stress and shear displacement at contact surface is suitable.
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Authors: Katsuaki Furukawa
Abstract: As a retardation of fatigue crack propagation occur under two step loading such as high to low loading, it is difficult to predictt the fatigue life in variable loading conditions. Therefore, the mechanism of retardation was investigated by changing the ratio of two step-loading in some materials in this paper. It is found in this study that when the ratio of low loading to high loading is less than 50 %, crack arrest occur in agreement with Elber’s formula about crack closure. We believe that crack closure phenomenon is the main problem in considering mechanism of crack propagation in the second stage. In this paper it is estimated that crack closure phenomenon arises because tensile plastic zone at crack tip is compressed by surrounding elastic zone. On the basis of the crack closure phenomenon, the mechanism of crack propagation in the second stage is proposed.
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