Browsing by Author "Nguyen, Van Anh"

Now showing 1 - 7 of 7
  • Thumbnail Image
    ItemOpen Access
    Development of a novel GTAW process for joining ultra-thin metal sheets
    (Elsevier, 2022-06-23) Manh, Ngo Huu; Nguyen, Van Anh; Duy, Han Le; Akihisa, Murata; Le, Van Thao; Ngoc, Trinh Quang; Gandham, Bharat
    The butt weld of ultra-thin sheet raw material coils in production lines is a crucial challenge with traditional welding processes because of the troubles related to the control of heat input, arc stability, application reliability, and investment costs. To overcome such challenges, a novel GTAW process has been developed for joining ultra-thin metal sheets for the first time. The novel welding torch with a novel orifice is the main discovered point of this process. In this paper, the novelties of the developed technology are clarified by comparing it with the conventional GTAW process. The results show that the novel GTAW process features much distinctiveness as compared to the conventional GTAW process: (i) the arc plasma column is more concentrated; (ii) the heat input is considerably reduced, but the temperature at the arc center is greatly increased; (iii) the metal evaporation and the metal vapor amount attached to the tungsten electrode surface are enormously reduced, and (iv) the corrosion of the tungsten electrode tip is vastly reduced. As a result, the novel GTAW process can successfully perform the butt weld of thin/ultra-thin metal sheets (up to 0.03 mm) with high quality and reliability.
  • Thumbnail Image
    ItemOpen Access
    On the connection of the heat input to the forming quality in wire-and-arc additive manufacturing of stainless steels
    (Elsevier, 2023-01-03) Le, Van Thao; Bui, Manh Cuong; Nguyen, Thuy Duong; Nguyen, Van Anh; Nguyen, Van Canh
    WAAM (wire-and-arc additive manufacturing) is recently gaining much interest for the fabrication of parts with wide size. A crucial issue associated to this technology is how to control the process variables to achieve expected qualities of parts. The aim of this investigation is to explore the relationship of the heat input (Q) with the forming quality of 308L stainless steel. The outcomes demonstrate that the heat input has significant effects on the shape, microstructures, and mechanical properties of the walls. Both the height and width of single weld beads increase with an increment in Q. The walls fabricated with the low heat inputs feature better mechanical properties and lower surface roughness. The tensile strengths (YS0.2% and UTS) and the surface roughness (Sa) of the walls built with the lower heat input (230 J/mm) are 292 ± 4.95 MPa, 523 ± 4.24 MPa, and 106 μm, respectively, whilst YS0.2% = 273 ± 4.34, UTS = 482 ± 5.66 MPa, and Sa = 179 μm for the wall fabricated with the higher heat input (576 J/mm). This investigation contributes to enriching the understanding on the WAAM process of steels and helping operators to select a proper heat input for specific applications.
  • Thumbnail Image
    ItemOpen Access
    Optimization of weld parameters in wire and arc-based directed energy deposition of high strength low alloy steels
    (Taiwan Association of Engineering and Technology Innovation, 2022-12-28) Le, Van Thao; Mai, Dinh Si; Dang, Van Thuc; Dinh, Duc Manh; Cao, Thi Hong; Nguyen, Van Anh
    This paper aims to investigate the fabrication of high strength low alloy (HSLA) steels by wire and arc-based directed energy deposition (WADED). Firstly, the relationship between the process variables (including the travel speed-V, the current-C, and the voltage-U) and the geometrical characteristics of weld beads (including the bead height (BH), bead width (BW), and melting pool length (MPL)) was investigated. Secondly, the optimal process variables were identified using the desirability approach. The results indicate that voltage-U has the highest impact on BW and MPL, meanwhile the travel speed-V is the most impacting factor on BH. The optimal variables for the WADED process of HSAL steels are V = 0.3 m/min, C = 160 A, and U = 19 V. The component fabricated with the optimal variables is fully dense without spatters and defects, confirming the efficiency of the WADED process for HSLA steels.
  • Thumbnail Image
    ItemOpen Access
    Penetration and microstructure of steel joints by ultrasonic-assisted gas metal arc welding
    (IOP Publishing, 2022-01-20) Tran-The Chung, Vinh; Nguyen, Cong Thai; Bui, Khanh Duy; Nguyen, Huu Loc; Nguyen, Van Anh; Nguyen, Thanh-Hai
    his work investigates the application of ultrasonic vibration to steel joints formed by gas metal arc welding. Welding is done using a metal active gas welding source with welding current of 120–160 A, 0.8-mm-diameter welding wire and 10 L/min CO2 flow. The distance from the torch to the ultrasonic horn is 120 mm. Ultrasonic vibration most affects the weld when ultrasonic vibration position is 120 mm from torch and increases the penetration when welding speed is 190 (275) mm/min for a 5-mm-thick (10-mm-thick) plate. Moreover, weld width increases when welding speed is 190 mm/min for 10-mm-thick plate. Although ultrasonic vibration does not affect the hardness of welding zones, it modifies the microstructure of the diffusion and welding-pool zones.
  • Thumbnail Image
    ItemOpen Access
    Prediction and optimization of processing parameters in wire and arc-based additively manufacturing of 316L stainless steel
    (Springer, 2022-08-10) Le, Van Thao; Doan, Quang Thanh; Mai, Dinh Si; Bui, Manh Cuong; Tran, Hoang Son; Tran, Xuan Van; Nguyen, Van Anh
    Wire and arc-based additively manufacturing (WAAM) is a potential metallic additively manufacturing (AM) technologies for producing large-size metallic components. 316L is one of the most common stainless-steel grades used in WAAM. However, most of previous studies normally adopted process parameters for the WAAM process based on recommendations of welding wire manufacturers for traditional welding processes. In this article, we focus on predicting and optimizing process parameters for the WAAM process of 316L stainless steel. The experiment was designed by using Taguchi method and L16 orthogonal array. Three parameters, consisting of voltage (U), welding current (I), and travel speed (v), were considered as the input variables, and the responses are four geometrical characteristics of single weld beads, including width, height, penetration, and dilution of weld beads (WWB, HWB, PWB, and DWB, respectively). The effects of each input variable on the responses were determined through analysis of variance (ANOVA). The optimal process parameters were identified by using GRA (grey-relational analysis) and TOPSIS (techniques for order-preferences by similarity-to-ideal solution) methods. The obtained results show that the travel speed has the most important effect on WWB and HWB, while the voltage has the highest impact on PWB and DWD. Both GRA and TOPSIS methods give the same optimum process parameters, namely U = 22 V, I = 110 A, and v = 0.3 m/min, which are validated by confirmation experiments. The predicted models of WWB, HWB, PWB, and DWB were also demonstrated to be adequate for selecting the process parameters in specific applications.
  • Thumbnail Image
    ItemOpen Access
    Relationship among welding defects with convection and material flow dynamic considering principal forces in plasma arc welding
    (MDPI, 2021-09-13) Nguyen, Huu Loc; Nguyen, Van Anh; Duy, Han Le; Nguyen, Thanh-Hai; Tashiro, Shinichi; Tanaka, Manabu
    The material flow dynamic and velocity distribution on the melted domain surface play a crucial role on the joint quality and formation of welding defects. In this study, authors investigated the effects of the low and high currents of plasma arc welding on the material flow and thermodynamics of molten pool and its relationship to the welding defects. The high-speed video camera (HSVC) was used to observe the convection of the melted domain and welded-joint appearance. Furthermore, to consider the Marangoni force activation, the temperature on the melted domain was measured by a thermal HSVC. The results revealed that the velocity distribution on the weld pool surface was higher than that inside the molten weld pool. Moreover, in the case of 80 A welding current, the convection speed of molten was faster than that in other cases (120 A and 160 A). The serious undercut and humping could be seen on the top surface (upper side) and unstable weld bead was visualized on the back side (bottom surface). In the case of 160 A welding current, the convection on the weld pool surface was much more complex in comparison with 80 A and 120 A cases. The excessive convex defect at the bottom side and the concave defect at the top surface were observed. In the case of 120 A welding current, two convection patterns with the main flow in the backward direction were seen. Almost no welding defect could be found. The interaction between the shear force and Marangoni force played a solid state on the convection and heat transportation processes in the plasma arc welding process.
  • Thumbnail Image
    ItemOpen Access
    Unique characteristics of the novel-GTAW process for the butt joint of ultra-thin silicon steel sheets
    (Elsevier, 2022-12-17) Ngo, Manh Huu; Le, Van Thao; Gandham, Bharat; Nguyen, Van Anh; Le, Duy Han; Van, Truong Nguyen; Van, Tuan Nguyen
    Butt joining of ultra-thin silicon steel sheets is a major challenge because of the ultra-thin thickness, high silicon content, and the coating layer on their surfaces. For the first time, welding butt-joint of the 0.2 mm ultra-thin silicon steel sheets has been performed successfully and reported in this paper. The results show that the weld beads fabricated by the novel-GTAW process are straight, stable, and without defects. They have a narrower width on the top and a larger width on the bottom side compared to the conventional-GTAW process. The mechanical properties of the welding joints also overmatch that of the base metal, confirming good qualities of the weldment. The success of the novel GTAW process in butt weld of ultra-thin silicon steel sheets is because of its unique characteristics: First, the mechanism of the novel-GTAW torch allows removing and blowing the insulation coating layer to prevent its penetration into the melting point and its accumulation on the electrode during the welding process; thus, eliminating welding defects and electrode wear and maintaining the arc stability. Second, the novel-GTAW process enables superiorly reducing the heat input and increasing the cooling rate, which ensures the high quality of the butt weld of ultra-thin silicon steel sheets. Lastly, the shielding efficiency of the melting pool is enhanced to prevent silicon oxidation and welding defects.