Papers by Keyword: Gradient Distribution

Abstract: Bamboo is a fiber-reinforced bio-composite with superior structural behavior. For the purpose of analyzing the correlations between the mechanical properties of bamboo and fiber volume fraction, tensile tests were performed on bamboo test specimen, and the corresponding volume fractions of fiber and parenchymatous ground tissue were measured. Linear and curvilinear regressions were done from tested data of elastic modulus, tensile strength and volume fractions of fiber. The results display that there is an obvious correlation between bamboo tensile properties and fiber volume fraction. In order to analyze the effects of fiber gradient distribution on bamboo structural behavior, models composed of fiber and parenchymatous tissue were built based on different fiber distribution for comparative analysis. The analysis results show that the maximum deformation of 4 layers model is 3.86% less than 1 layer model, and the maximum deformation of 8 layers model is 8.87% less than 4 layers model. In the part of maximum axial stress, the maximum axial stress of 4 layers model is 3.27% less than 1 layer model, and the maximum axial stress of 8 layers model is 8.90% less than 4 layers model. Conclusion can be drawn from the comparison that the strength and stiffness of the model appear to be growing with the degree of fiber gradient distribution deepening from 1 layer model to 4 layers model, and 4 layers model to 8 layers model.It can be concluded that the mechanical properties of bamboo structure are significantly improved because of fiber gradient distribution.

Abstract: Gradient Zirconia toughened alumina (ZTA) ceramics with high fracture strength and toughness were prepared using centrifugal slip casting method. Aqueous Al2O3-20vol% ZrO2 slurries with different solid contents were prepared and the rheological characteristic of the slurries were investigated. The effect of solid loading of slurries on green density difference of ZTA ceramic compacts was observed. Mass segregation of Al2O3 and ZrO2 particles were studied. Microstructure and bending property of the sintered ZTA ceramics were investigated. The results show that the segregation phenomenon of Al2O3-ZrO2 slurries comes form the difference of settling velocity of Al2O3 and ZrO2 particles. With the increase of solid content of slurries, the gradient distribution of green density becomes unconspicuous. After sintered at 1550○C for 2 h, the gradient ZTA ceramics centrifuged with 20vol% slurries have high sintered density (99.2% TD) and continuous gradient distribution of Al2O3 and ZrO2 particles. The fracture strength and toughness of gradient ZTA ceramic are 732MPa and 5.4MPam1/2, respectively.

Abstract: Abstract. Based on the electro-thermal property of carbon fiber-reinforced concrete, two groups of carbon fiber with equal quality dispersed in cement mortar deferring to layered and gradient distribution separately. The heat change of electro-thermal layer (with carbon fiber) and non- electro-thermal layer (without carbon fiber) of the two kinds of specimen was contrasted, and the corresponding thermal stress value among each layer was calculated theoretically. The results indicate that comparing with the carbon fiber layered distribution, carbon fiber gradient distribution decreases the thermal stress maximum of neighboring layers from 15.42MPa to 5.21MPa. The decrease of heating stress increases heat stability, by which can enhance cement mortar service life.

Abstract: High speed milling experiments are performed for hardened H13 die steel by using coated ball end milling cutter, the residual stress of the work-piece surface on the feed and cross feed direction are measured, and the distribution characteristics of residual stress is analyzed. The result shows that the residual stress presents gradient distribution on feed direction, and furthermore, the three-dimensional surface micro topography has no close relation with the residual stress. In addition, the cumulative effect is discussed for explaining the phenomena.