Abstract
Objectives of this study are to examine influence of the surface crackles fractal characteristics of CRTSII track slab on its propagation velocity and stress intensity factor (SIF) and to improve the service performance of track slab. In this paper, fractal dimension D of transverse crack on the surface of CRTSII track slab was calculated by image processing, digital image technology, and box-counting method. Based on the fractal structure of transverse crack on track slab surface, a fractal transverse crack propagation model was established. The impact of fractal effect on the surface crack propagation velocity and SIF of CRTSII track slab was analyzed quantitatively. The fractal dimension D of transverse crack is 1.0652 on the surface of CRTSII track slab. The actual measured crack propagation velocity V0 on the surface of the track slab can be corrected as the true crack propagation velocity V. When the V0/Cr=0.899<1, the SIF K′L1.0652,t,V of transverse dynamic fractal crack propagation on the surface of track slab has been equal to 0, and the V0 is always lower than Rayleigh wave velocity. In addition, the true attenuation rate of SIF for CRTSII track slab surface transverse dynamic crack propagation is faster than the actual measured value.
Highlights
CRTSII type ballastless track structure as concrete slab structure, subjected to train dynamic load, temperature load, and other complex environments, and the track slab surface will inevitably show a large number of cracks
Our research group has proved that the extended path of the transverse crack of CRTSII type track slab has fractal characteristics [10], and combined with the theory of fractal fracture mechanics, it focused on the investigation of the following problems: whether the surface crack propagation velocity and stress intensity factor (SIF) of CRTSII type track slab are affected by fractal effect, and whether the real crack propagation velocity can be obtained by the relationship between them
The results show that the fractal dimension D of CRTSII type track slab surface transverse crack studied in this paper is 1.0652, and it has a fractal structure
Summary
CRTSII type ballastless track structure as concrete slab structure, subjected to train dynamic load, temperature load, and other complex environments, and the track slab surface will inevitably show a large number of cracks. Surface crack of CRTSII type track slab is affected by the stress concentration effect of its own tip, and the possibility of continuous instability propagation is very great [8] This destruction is a gradual process with crack initiation, propagation, and series and develops in depth, forming cracks. Our research group has proved that the extended path of the transverse crack of CRTSII type track slab has fractal characteristics [10], and combined with the theory of fractal fracture mechanics, it focused on the investigation of the following problems: whether the surface crack propagation velocity and stress intensity factor (SIF) of CRTSII type track slab are affected by fractal effect, and whether the real crack propagation velocity can be obtained by the relationship between them
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