Papers by Author: Lei Wang

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Authors: Kai Zhang, Lei Wang, Xiao Feng Shang
Abstract: The fabrication of metal parts is the backbone of the modern manufacturing industry. Laser forming is combination of five common technologies: lasers, rapid prototyping (RP), computer-aided design (CAD), computer-aided manufacturing (CAM), and powder metallurgy. The resulting process creates part by focusing an industrial laser beam on the surface of processing work piece to create a molten pool of metal. A small stream of powdered alloy is then injected into the molten pool to build up the part gradually. By moving the laser beam back and forth and tracing out a pattern determined by a CAD, the solid metal part is fabricated line by line, one layer at a time. By this method, a material having a very fine microstructure due to rapid solidification process can be produced. In the present work, a type of direct laser deposition process, called Laser Metal Deposition Shaping (LMDS), has been employed and developed to fabricate metal parts. In the LMDS process, the powder delivery system is an important component to perform the powder transport from powder storage box to powder nozzle, which supplies the raw material for the as-deposited metal parts. Consequently, the stability and precision of powder delivery during LMDS is essential to achieve the metal parts with high quality, so it is critical to evaluate the main factors closely related to the stability and precision of powder delivery. The shielding gas flow and the powder feeding rate were ascertained through experimental measure and formula calculation. The results prove that the suitable shielding gas flow and powder feeding rate can promote the stability and precision of powder delivery, which is the basis for the fabrication of as-deposited metal parts with flying colors.
Authors: Kai Zhang, Xiao Feng Shang, Lei Wang
Abstract: The laser additive manufacturing technology is a laser assisted direct metal manufacturing process. This process offers the ability to make a metal component directly from CAD drawings. The manufacturing equipment consists of some components. Among them, the laser transmission component plays an important role in the whole fabricating process. It provides the energy source to melt the metal powder, so it is necessary to develop the laser transmission technology. This technology is achieved primarily by laser generator system and optical path transmission system. The related structure design and function implementation prove that the laser transmission technology can generate desirable laser power at precise assigned position, and complete the manufacturing process with flying colors.
Authors: Kai Zhang, Lei Wang, Xin Min Zhang
Abstract: Laser Metal Deposition Shaping (LMDS) is an emerging manufacturing technique that ensures significant reduction of process time between initial design and final components. The fabrication of fully dense parts with appropriate properties using the LMDS process requires an in-depth understanding of the entire thermal behavior of the process. In this paper, the thermal behavior during LMDS was studied, both numerically and experimentally. Temperature distribution and gradient in the fabricated part were obtained by finite element method (FEM) simulation. The numerical results are in good agreement with the experimental observations. The numerical method contributes to the comprehension and control of the thermal behavior, and may be used to optimize process parameters and predict the thermal response of LMDS fabricated components.
Authors: Zhong Feng Guo, Shi Jie Wang, Lei Wang, Yi Zhang, Zhong Wei Ren
Abstract: For studying physical properties of Nitrile Butadiene Rubber(NBR) stator of Electrical Submersible-motor-driven Progressive Cavity Pumping (ESPCP) with oil erosion, two different formulations of NBR soaked in crude oil at 90 °C for 168h. Variation rule with time of rubber quality, hardness, volume, tensile strength and elongation rate are got. The results show that erosion in the same temperature, rubber quality increase rapidly in the first 24h, increase slowly down in 24~168h. Rubber hardness does not change significantly soaked within 168h. Rubber volume change obviously in the first 72h and change slowly in 72~168h. In the first 96h, the rubber's tensile strength and elongation rate change quickly, slowly changes in 96~168h. The study has a certain reference of design of ESPCP stator under certain operating conditions.
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