Among metal-based additive manufacturing, wire and arc additive manufacturing is receiving increasing attention for the production of components with medium to large dimensions. In the current research, the production of low-carbon steel thin-walled components by wire and arc additive manufacturing was addressed. Firstly, the influence of two depositing direction strategies on the wall shape was investigated. Subsequently, the effect of heat input on the shape stability and the microstructure evolution of the walls was studied. The results indicated that the alternating depositing direction strategy was more suited to build thin walls with relatively regular height. The heat input significantly influenced the shape stability, but had slight effects on the microstructure evolution. The microstructure of the walls varied from the top to the bottom regions, leading to a variation in hardness from 157 ± 3.11 to 192 ± 4.30 (HV5). The microstructure of the built thin walls can be distinguished in three regions: The upper region exhibited lamellar structures; the middle region dominantly featured granular structures of ferrites with a small proportion of pearlites, which appear in the boundaries of grains; and the lower region showed a mix of lamellar and equiaxed structures of ferrites. The tensile properties of the built material also exhibited anisotropic characteristics: The yield strength and ultimate tensile strength vary from 320 ± 6 to 362 ± 8 MPa and from 429 ± 8 to 479 ± 7 MPa, respectively.
Ba Lai Irrigation Project is located at coastal area in the Mekong Delta. In dry season when the flow rate decreases and the strong east wind blows into the delta, the salinity intrusion increases and seriously affects agricultural and domestic water use. Intakes of Ba Lai system have to be closed for 1-3 months depending on their locations, and no water supply during this period often causes water pollution in the project area. In order to solve such problems, this study aims to seek gate operation procedures for salinity control and water environment improvement. A numerical model is developed to simulate water movement, salinity concentration and duration of remaining water (water age) within the system under three scenarios: (1) without control structures, (2) with available control structures, (3) with the full control structures. Through the numerical simulations, control structures are confirmed to be an effective measure for the salinity control and suitable gate operation schedules are proposed to improve the water environment in the project.
Wire arc additive manufacturing (WAAM) is nowadays gaining much attention from both the academic and industrial sectors for the manufacture of medium and large dimension metal parts because of its high deposition rate and low costs of equipment investment. In the literature, WAAM has been extensively investigated in terms of the shape and dimension accuracy of built parts. However, limited research has focused on the effects of welding parameters on the microstructural characteristics of parts manufactured by this process. In this paper, the effects of welding current in the WAAM process on the shape and the microstructure formation of built thin-walled low-carbon steel components were studied. For this purpose, the thin-walled low-carbon steel samples were built layer-by-layer on the substrates by using an industrial gas metal arc welding robot with different levels of welding current. The shape, microstructures and mechanical properties of built samples were then analyzed. The obtained results show that the welding current plays an important role in the shape stability, but does not significantly influence on the microstructure formation of built thin-walled samples. The increase of the welding current only leads to coarser grain size and resulting in decreasing the hardness of built materials in each zone of the built sample. The mechanical properties (hardness and tensile properties) of the WAAM-built thin-walled low-carbon steel parts are also comparable to those of wrought low-carbon steel, and to be adequate with real applications.
3D printer technology has been applied to a lot of industrial branches such as automobile, aircraft, medicine, civil engineering, electronic engineering. Normally in Vietnam, the plastic fiber, raw material that is the most popular application is hot plastic fiber extruding through FDM nozzle... is being imported from China, Korea, and Taiwan. The paper represents our own research on the application of the technical design processes for design a plastic-bamboo fiber extruder that is sustainable, environmental friendliness, consumes domestic raw material and saving national budget for importation and mastering the technology of extruding plastic bamboo fiber.
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