Papers by Author: Bao Feng Li

Abstract: According to the microstructures in eutectic composite ceramic containing lamellae, the four phase model, which is composed of lamellae, eutectic interphase, matrix-atmosphere and effective medium, is put forward. Three phase cell that is composed of lamellae, eutectic interphase and matrix-atmosphere can be regarded as a composite inclusion. In view of Eshelby theory, the effective thermal expansion coefficients of eutectic composite ceramic containing the same orientation lamellae are determined. The eutectic composite ceramic is transverse isotropy and has two independent thermal expansion coefficients. The quantitative analysis shows that the effective thermal expansion coefficients have obvious size dependence.

Abstract: It is studied in this paper that in the manual SHS Welding, the amount of Ni added affects the quality of the welding, especially in view of the cracks. When the proportion of Ni is between 1.57％～7.86％, welding external appearances are in good condition. No welding cracks can be spotted. The strength of tension also reaches an optimum condition. When the proportion of Ni is 7.86％. there are internal cracks by the examination of machine. When the proportion of Ni is between 10.2% and 15.7%, there are obvious external and internal welding cracks and the strength of tension is also the lowest, about 193MPa.

Abstract: Rod-shaped oxide eutectic ceramics fabricated through SHS process can acquire outstanding mechanical properties. First, Four-phase model method was used to study effective disturbance strain of rod-shaped oxide eutectic ceramics produced by nano fibers with inter-phases, then average strain of rod-shaped oxide eutectic ceramics aroused thermal inconsistency is obtained. The effective thermal expansion longitudinal strain and transverse strain of rod-shaped oxide eutectic ceramics are determined by the average strain. Rod-shaped oxide eutectic ceramics is transverse isotropy and has two independent thermal expansion coefficients. The results show that the thermal expansion coefficients of rod shaped oxide eutectic ceramics are dependent on the diameter of nano-fiber. The thermal expansion coefficients will decrease when the diameter of nano-fiber decrease.

Abstract: The partial debonding interphase has large influence on the behaviors of composite ceramic. The emerging cause of partial debonding interphase is interpreted and the interaction between particles and partial debonding interphase is accounted for determining the equivalent eigen strains by using the four phase model method. Then the effective stiffness of composite ceramic is estimated. The results show the effective stiffness is associated with the stiffness of the matrix and particles, the volume fractions of particles and partial debonding interphase, the subtending angle and thickness of partial debonding interphase.

Abstract: Rod-shaped oxide eutectic ceramics fabricated through SHS process can acquire outstanding mechanical properties. First, Eshebly-Mori-Tanaka method was used to study Thermal Stress Field of rod-shaped oxide eutectic ceramics, and then average strain of rod-shaped oxide eutectic ceramics aroused thermal inconsistency is obtained. The effective thermal expansion longitudinal strain and transverse strain of rod-shaped oxide eutectic ceramics are determined by the average strain. Rod-shaped oxide eutectic ceramics is transverse isotropy and has two independent thermal expansion coefficients. The results show that the thermal expansion coefficients of rod shaped oxide eutectic ceramics are dependent on the diameter of nano-fiber. The thermal expansion coefficients will decrease when the diameter of nano-fiber decrease. When the diameter of nano-fiber is bigger than 300nm, the thermal expansion coefficients of rod shaped oxide eutectic ceramics is constants.

Abstract: The interfacial arc-microcracks have large influence on the behaviors of cermets. The emerging cause of arc-microcracks is interpreted and the interaction between ceramic particles and arc-microcracks is accounted for determining the equivalent eigen strains by using the random two phase element method. Then the effective volumetric modulus and shear modulus of the cermets is estimated. The results show the effective volumetric modulus and shear modulus of the cermets is associated with the stiffness of the matrix and ceramic particles, the volume fractions of ceramic particles and arc-microcracks, the subtending angle and thickness of arc-microcrack..

Abstract: Ni base alloy ceramic composite coating fabricated through vacuum fusion sintering process can acquire high strength and good thermal fatigue resistance. Composite coating was mainly composed of Ni base alloy and ellipsoidal ceramic particles with random orientation. The three-phases model is used to study the thermal expansion strains in composite coating. First, Eshebly-Mori-Tanaka method was used to determine effective eigen strain of two-phases model formed by the ellipsoidal matrix shell being around a ellipsoidal ceramic particle, then disturbance strain in two-phases model aroused thermal inconsistency is obtained. Finally thinking average stress in effective matrix vanish, the residual stress field in Ni base alloy and particles can be gotten by considering random orientation of two-phases models. It will exert influence on strength and fatigue life of the composite coating.