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Study on Formability and Weld-line Movment Countermeasures of Tailor-welded Blanks

Author: HeChunZuo
Tutor: ZhouJie
School: Chongqing University
Course: Materials Processing Engineering
Keywords: Tailor-Welded Blank FEM Formability The Means of Blank’s Movement The Compensatory Means
CLC: TG441.3
Type: Master's thesis
Year: 2008
Downloads: 153
Quote: 4
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Abstract

Considering the requirements of future automotive in environmental protection and safety, weight reducing of body-in-white, besides to the improvement of engine capability and aerodynamics character, has become an important goal of automotive manufacturing industry nowadays. So the forming technique of tailor-welded blanks (TWBs), which combine traditional materials with a new producing process, has developed quickly. Tailor welded blanks(TWBs)are defined as two or more sheets of blanks with equal or different thickness, mechanical properties, or surface coatings welded together by laser before stamping. TWBs have become a hot issue in the automobile industry and steel industry for its high quality, high profit and low cost of production,and have been widely used in automobile industry.In this paper, the application of TWBs in the automobile industry is discussed, and the development,characteristics, superiority and researches of TWBs are introduced. At the same time, the thickness ratio, the different mechanical properties combination and the draw bead which play important role in the process have been analyzed. As the shape of automobile’s covering parts is very complex and it is difficult to estimate the formality by means of experience,the finite element numerical simulation method and its software Dynaform are proposed to forecast the drawing formality of the TWB.At first, square box has been used, a typical part in sheet metal processes, for deep drawing simulation of TWB, to study on the movement law of welding-lines and the formability of TWB. With draw bead and without one separately, the formability of TWB square box has been analyzed in different conditions: same materials with different thickness, different materials with different thickness and different strength combination of TWB’s materials with same ratio of thickness. According to the result of simulation, it suggests the ratio of the thin blank to the thick one should be more than 0.5 and the ratio of strength be up to 3.0 in order to make the formability of TWB steady. Also, the affect of the draw bead on the displacement of weld-lines and the maximal vaulted height have been investigated. The maximal vaulted height is reduced as the single lessen width of draw bead is increased. When w∈[0,1.556], this is the most sensitive area. When w∈(1.556,8.556], this is the unsensitive area. When w>8.556, this is the sensitive area. The draw bead can reduce the formability of TWB to a large extent, and the displacement of weld-line. The reduction is more obvious on the flange than the bottom of the square box. So, An approach that is a strengthening rib vertical to weld-line, is proposed to reduce the displacement of weld-line.Secondly, the conclusions have been applied in the production of the front floor of automobile. Its formability and movement of weld-line are forecasted in the drawing process by selecting reasonable the ratio of thichness and strength. And a strengthening rib vertical to weld-line is designed.Finally, the means of blank’s movement and the compensatory means of curve weld-line have been studied to control movement of weld-line and ensure the assembly position of parts’weld-line. The eligible parts are gained.In this paper, the front floor has been studied to ensure the assembly position of parts’weld-line by numeric simulation. It is significative to production, light weight technologies in auto industry and wide application of TWBs.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Welding, metal cutting and metal bonding > Welding process > General approach > Weld method
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