Papers by Author: Xiao Bo Lu

Abstract: The system uses B / S mode and ASP as the web-based support and connects with the SQL Server 2005 database, which realizes the automatic and manual assessment of Photoshop course exam management operations. At the same time, it will be able to generate paper reference to test the difficulty levels of papers.

Abstract: Nowadays, the computer is increasingly popular, and college examination is developing in the direction of traditional examination means to automation and intelligence ones gradually, all these make it inevitable to construct question bank for courses, and to generate test paper using computers. This paper uses the Delphi technique, to make improvements to existing components, combining with VBA programming, and use of SQL Server to implement the question bank management and test paper auto-generation system, which could generate test paper in Word Document. A large number of tests show that the software is running stably and system features are functioning correctly on Windows 2000/XP/2003 platform with Office XP/2003 environment.

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: The composite ceramics that contains nano-fibers and transformation particles, fabricated through SHS process, is performed with high fracture toughness and high plasticity. The matrix of composite ceramics was mainly composed of fiber eutectics with nano-fibers. The transformation particles were distributed along boundaries of the fiber eutectic structures. First, Mori-Tanaka method was used to predict the stiffness of the fiber eutectic. The fiber eutectic is transverse isotropy and has five independent elastic constants. Then considering random orientation of the fiber eutectic, the Young’s modulus and Poisson’s ratio of the matrix is determined by even strain. The matrix is isotropy. Finely, assuming the transformation particles as spheres distributed in the matrix, the effective stiffness for composite ceramics was computed. When the volume fraction of fibers and particles increase, the Young’s modulus of composite ceramics decrease and are little smaller than the volume average value, the Poisson’s ratio of composite ceramics decrease and are little bigger than the volume average value.

Abstract: By the use of comprehensive transformation criterion and the method of weight function, the fracture enhancement of mixed-mode II-III crack in transformation toughened ceramics is predicated. The theoretical expressions of the toughening effect for both the stationary and steady-state growing crack are given respectively. The results show there is no toughening effect for the stationary crack and the toughening effect for the steady-state growing crack is associated with the modulus of elasticity, the width of transformation and its volume fraction.

Abstract: Based on the SEM observation on cracks in lined ceramics of the composite pipes, the stress fields in lined ceramics were analyzed. The results indicated that there are the compressive field and heat stress field in lined ceramics, resulting in the existence of radial cracks and net cracks; besides being influenced by wall thickness of ceramic layer, the strength of compressive stress field is also dependent on bonding strength between metal and ceramics, and the strength of heat stress field is dependent on temperature gradient in lined ceramics during cooling of the ceramics.