Papers by Author: Yan Chun Liu

Abstract: Spherical alumina powder and dispersant were mixed with distilled and deionized water, and ball milled to make alumina slurry. The slurry was dried in a high magnetic field to make a compact. Subsequently, the compact was cold-isostatic-pressed (CIP) to enhance the homogeneity in particle packing density. Anisotropy of shrinkage during sintering was examined for the alumina compacts in detail. Particle orientation existed in the spherical alumina powder compacts prepared in 10T, and made them shrink anisotropically during sintering. Sintering shrinkage was larger in the direction parallel to magnetic field direction (i.e., the c-axis direction of alumina crystal) than that in its perpendicular direction. The particle orientation structure in the compacts was confirmed with the immersion liquid method of polarized light microscope, and the grain alignment structure in the sintered bodies was also observed with X-ray diffraction, the c-plane was perpendicular to the magnetic field direction. On the other hand, isotropic sintering shrinkage occurred in the spherical alumina powder compacts prepared in 0T, which did not hold the particle orientation. The experimental results indicate that sintering shrinkage of spherical alumina powder compact depends on alumina crystal axis direction. Origin of the sintering shrinkage anisotropy for the spherical alumina powder compacts can be attributed to the particle orientation caused by high magnetic field.

Abstract: A damage detection method reflecting initial damage of the elastic structure is presented. It is based on the idea that the damage will decrease the structure stiffness. From eigenvalue issue, regard Poison ratio and elastic modulus as a constant and a random variable, respectively, and in terms of known data and a combination of the FEM, then equations solving random modulus of the undamaged and the damaged structure are obtained, respectively. Based on the element damage indicator, initial damage of the structure can be detected. At last, a five-storey shearing structure is simulated, and the results indicate that initial damage situation can be accurately calculated, and initial damage locations can be estimated based on the proposed method, which is simple and effective, and contributes to the application in Engineering.