Papers by Author: Shi Hong Shi

Abstract: In this paper, coaxial inside-beam powder feeding technique was used. According to theoretical analysis and the single layer cladding experiments, the initial parameters and experimental scheme of width-changing layer cladding based on the coaxial inside-beam powder feeding were confirmed. The theory model of piecewise transition was established. The real-time control of scanning speed and the defocus amount to carry out the experiments were used while the laser power and powder feed rate were not changed. Finally, the layers with uniformly width changing and stable layer height were achieved. Performance analysis showed that the formed layer had smooth surface and a high rigidity without powder paste outside the surface, and the size was basically as same as the design value. Its microstructure was small and dense and good metallurgical combination was formed between part and substrate.

Abstract: In order to find out the correspond relationship of the outlet velocity and rotor speed in dry powder inhaler, the intermediate parameter was inserted in Workbench response surface based on CFD. The simulation of the suction drive rotor rotation mechanism was based on MRF model in FLUENT. It can be easily obtained the rotor’s performance curve under different aerodynamic conditions and found out the optimized flow rate is 66.127L/min. This method verifies the clinical phenomena and could guide the clinical research and machinery optimization.

Abstract: A numerical simulation model of laser cladding based on internal powder feeding through a hollow laser beam is set up by the Ansys Parametric Design Language (APDL). Through analyzing this model, the saddle-shaped distribution of energy absorbed in scanning direction is found and the molten pool temperature field of single laser cladding is observed like a comet^[. Base on the single laser cladding experiments, the initial parameters and test plans of laser cladding and the screwy thin-walled part forming are confirmed. The finite element model of laser cladding forming screwy thin-walled part is established. The evolution of temperature field and thermal cycle of the nodes are studied during the screwy thin-walled part forming process. In the emulation laser power is controlled real time according to the analyses above, and the changing value of laser power is obtained to keep the molten pool temperature steady. The screwy thin-walled part is formed successfully based on these data.

Abstract: Aimed at the lack of the cladding materials such as micro or nanopowder, the micro/nanocomposite powders prepared for experiment are feed directly, the key process parameters on the quality of the surface quality and microstructure analysis of the single-layer of laser cladding are studied in detail. Compared to the ordinary laser micro-cladding layer feeding by the micro powder, the cladding layer is more refined, which has more good mechanical properties. The results showed that: using reasonable parameters, the microstructure and macro-morphology of cladding layer with micro-nanocomposite powders feed directly are better than of micron powders.

Abstract: The paper is based on industrial PC with rich application developed resources under Windows environment and openness of PMAC numerical control system. With the consideration of characteristics and specific requirements of laser rapid prototyping, a third party software is developed by Visual C++ in Windows98 to communicate with the slave machine to get some forming parameters in the laser processing under control by calling PCOMM32PRO DLLs which is offered by Delta Tau company. Combining the developed third party software with the infrared radiation thermometer monitoring the real-time temperature of molten pool can improve the forming efficiency of workpiece obviously.

Abstract: The efficient implementation of Boolean operatio between STL models is a bottleneck problem to develop excellent RP data processing software, and the subdivision of the intersection is an important step of realization the Boolean operations. An algorithm is proposed in this paper. Based on the closed character of the STL model, the position relationship between the intersection lines and the triangle are classified, and the subdivision rules is summarized. The two data linked list of the intersection points and vertex points are created, a searching process to obtain the subdivision polygon is described.

Abstract: Analyze the contradiction of laser cladding rapid prototyping between cladding efficiency and cladding precision, this paper advanced laser variable-spot cladding process with small facula outlining border of workpiece and big facula filling in central section of workpiece in order to improve the influence of “Step effect”. Based on the patent technology of “Hollow laser beam and internal power feeding”, the experiments of laser variable-spot overlap cladding are carried out on the substrate of 45# steel with a novel device of coaxial inside-beam power feeding. The experimental results were analyzed to provide a theoretical basis for the promotion and application of laser variable -spot overlap cladding.

Abstract: Due to the present condition of temperature examination in laser molten pool which is mainly limited to infrared thermometer and thermal infrared imager ,a temperature measurement system based on monochrome CCD with high speed is developed. By transforming gray value to temperature , grayscale images of molten pool will be changed into 2 dimension distribution with color, making examination more intuitive and comprehensive .

Abstract: This experiment uses the shower nozzle of the ring laser inside-laser coaxial powder feeding for single channel /layer, defocusing, and multi-channel lap cladding. This study investigates the influence of process parameters (such as the laser power) on forming size and surface morphology. In certain limits, the cladding layer height and width are in positive correlation with laser power and powder feeding rate, and in negative correlation with scanning velocity. When the lap coefficient is 50%, the forming quality is high.

Abstract: The purpose of this study is to implement the dynamic control of single-storey height by adding hight detection devices based on PMAC in the existing three-dimensional laser processing systems.In order to overcome the rough topography of the forming parts and eliminate the phenomenon of jagged edge,it is important to ensure consistency between single-storey height- h and Z axis single-upgrade- Z.