Papers by Author: Xue Feng Yao

Abstract: The dynamic fracture behavior of PVB laminated glass during impact has been studied by both theoretic and finite element approaches. To make the analysis of cracking on PVB laminated glass more accurate and direct, high-speed photography method is introduced in this paper. Different crack patterns as well as their sequences of appearance are visualized. Finally, typical crack is measured in order to obtain important fracture characteristics such as crack velocity and acceleration.

Abstract: The fracture is an important failure behavior of cancellous bone. Three-point-bending experiment was used to study fracture behavior of cancellous bone. Three group specimens were taken from two human femoral head and there was a non-angled crack and an angled crack in every group respectively. By using Digital Speckle Correlation Method (DSCM), the displacement and strain field were obtained at the crack-tip and the full specimen. The initial crack path was always at the maximal strain location and could be predicted by the DSCM. In the macro-scope, the crack propagation paths towards the load tip, and are independent of the initial crack angle.

Abstract: In this paper, coherent gradient sensing (CGS) and digital speckle correlation method (DSCM) are introduced to study the K-dominance of static crack tip in functionally gradient materials (FGMs) with a crack oriented along the direction of the elastic gradient. And the numerical simulation is analyzed through finite element method (FEM). Firstly, the CGS and DSCM equations at the mode-I static crack tip of FGMs are developed, which can be used to calculate the stress intensity factors of FGMs. Secondly, three kinds of FGMs specimens with different variation of the modulus are prepared to observe the influences of the property variation on the K-dominance. Then three-point-bending experiments are carried out. The interference fringe pictures of CGS and the speckle patterns for DSCM on the specimens are shot through the camera. Thirdly, based on the results of the experiments, the stress intensity factors of three kinds of FGMs specimens are calculated by CGS and DSCM. Meanwhile, the stress intensity factors are obtained by FEM. Finally, comparing the results from CGS, DSCM and FEM, the K-dominance of mode-I static crack tip in FGMs is discussed in detail. It is found that the K-dominance of FGMs and homogenous material is almost same when the gradient index in FGMs is relatively small.

Abstract: A crack propagation perpendicular to gradient in a large scale functionally gradient materials, which has (1) a linear variation of Young’s modulus with a constant mass density and Poisson’s ratio, and (2) a exponential variation of Young’s modulus with a constant mass density and Poisson’s ratio, is modelled by finite element methods. Based on the experimental result of large scale functionally gradient materials, the dynamic propagation process of the FGMs is modelled and the dynamic parameters, like the energy release rate and crack tip opening angle, are calculated through a generation phase.