Entity

Time filter

Source Type


Zhou Y.,Tsinghua University | Li Y.,Tsinghua University | Li Y.,Key Laboratory of Advanced Materials Processing Technology | Yuan J.,Tsinghua University
Gongneng Cailiao/Journal of Functional Materials | Year: 2015

Using gas injection foaming process, the influences of pure Al and hypoeutectic Al-Si alloy base materials on the average cell size, relative density, average cell wall thickness and other cell structure parameters of aluminum foams were studied. Compared with the aluminum foams produced from pure Al, the cell structures of the aluminum foams produced from hypoeutectic Al-Si alloy were much better, and the average cell size, relative density and average cell wall thickness of aluminum foams produced from hypoeutectic Al-Si alloy was smaller, lower and thinner. While these cell structure parameters were similar between the aluminum foams produced from different hypoeutectic Al-Si alloys. In terms of alloy phase diagram, surface tension, melt viscosity and the average rupture thickness of liquid films, the related reasons causing the above results are analyzed. This study showed that the kind of base material was an important factor in aluminum foam production, since it would significantly affect the quality of aluminum foams. © 2015, Chongqing Functional Materials Periodical Press Co. Ltd. All right reserved. Source


Wen P.,Tsinghua University | Wen P.,Key Laboratory of Advanced Materials Processing Technology | Zheng S.,Tsinghua University | Kenji S.,Hiroshima University | Motomichi Y.,Hiroshima University
Zhongguo Jiguang/Chinese Journal of Lasers | Year: 2011

Hot wire is used as the filler metal of high beam quality and long focal distance fiber laser for narrow gap welding. The austenite stainless steel base metal is molten by laser, and the Ni-based alloy wire is heated up by wire current. Both the stability and efficiency are improved a lot by using the hybrid heating sources. High speed camera is used to observe the movement of filler wire during laser welding and analyze the effect of welding parameters on wire transition. The solidification microstructure and the element distribution of narrow gap laser weld are studied. Consequently, it is found that wire current and filling wire speed are the two key processing parameters for laser hot wire welding quality. The side wall of base metal is bonded well with weld metal when defocused laser spot with a diameter close to the width of narrow gap is used. The laser reflection mainly contributes to the melting of side walls, rather than the laser beam itself. The solidification microstructure shows obvious epitaxial growth, while the dendrites grow vertically to the side wall due to the rapid cooling speed. No macro segregation is found. However, lack of fusion is found in the bottom of narrow gap with a 90° angle. This problem is solved by using U type narrow gap with arc transition in the bottom. The narrow gap laser weld is finally obtained without macro weld defects. Source


Li Y.,Key Laboratory of Advanced Materials Processing Technology | Li Y.,Tsinghua University | Lei L.-P.,Key Laboratory of Advanced Materials Processing Technology | Lei L.-P.,Tsinghua University | And 2 more authors.
Suxing Gongcheng Xuebao/Journal of Plasticity Engineering | Year: 2011

According to the character of shot peening process, an equivalent static loading method was employed to simulate the shot peening process, which can avoid the unstable factor in the dynamic explicit algorithm. The regularity of the average contact stress between shot and target was analyzed, based on which the shot peening process was divided into several different stages, then the equation of the equivalent static load was obtained. To evaluate the relationship between the indentations' distribution and compressive residual stress, an indentation array model was developed, and the simulation results show good agreement with the existed experiment data. Source


Liu F.-C.,Key Laboratory of Advanced Materials Processing Technology | Liu F.-C.,Tsinghua University | Lei L.-P.,Key Laboratory of Advanced Materials Processing Technology | Lei L.-P.,Tsinghua University | And 2 more authors.
Suxing Gongcheng Xuebao/Journal of Plasticity Engineering | Year: 2012

Surface rolling numerical simulation is a main theoretical tool for designing surface rolling process, predicting the distribution of compressive residual stress and evaluating the fatigue resistance after rolling. But up to present, it focused on the analysis of crankshaft and rotary bodies and the rare study on flat surface rolling only touched upon single round or lesser. A flat surface rolling FE model with multi-rolling was developed with ABAQUS python program. The relationships between the surface rolling parameters (rolling force, roll diameter, friction coefficient) and the compressive residual stress were obtained by the proposed model. Surface rolling experiment was carried out to verify the FE model results. Source

Discover hidden collaborations