Springback Characteristics of Tailor-Welded Strips in U-Draw Bending

Seo, Dae Gyo,Chang, Sung Ho,Heo, Young Moo 대한금속재료학회 2003 METALS AND MATERIALS International Vol.9 No.6

The purpose of this study is to investigate the springback characteristics of tailor-welded strips in U-draw bending. Two different welded strips were adopted to compare the effects of weld-line locations on the springback. One was welded along the centerline of the strip-width and the other was welded along the centerline of the strip-length. To investigate the effect of different thickness combinations on the springback, the tailorwelded strips were joined by a laser welding process. Three sheet thickness combinations were assessed, SCP1 0.8 t * SCP1 1.2 t, SCP1 0.8 t * SCP1 1.6 t and SCP1 0.8 t * TRIP 1.0 t. Three punch profile radii of 3, 6, and 9 mm and three die profile radii of 5, 10, and 15 mm were prepared and three blank holding forces (BHF) of 125 kgf, 250 kgf, and 500 kgf were applied to investigate the effects of punch profile radius (Rp), die profile radius (Rd), and BHF on the springback of tailor-welded strips. With consideration for the thickness of the sheet and the material properties, the extent of the springback on the sidewall of unloaded sheet shapes increases as the thickness and the yield strength of the sheet increase in the U-draw bending process. For longitudinally welded strips, the amount of springback of the TRIP steel sheet in TWB could be reduced through a springback combination of the thinner side and weld-line. For the thinner side (0.8 t) of the centrally welded strips, the deformed shapes after the springback were almost the same regardless of the thickness combination, and the extent of the springback decreased compared with that of non-welded SCP1 0.8 t. Some experimental results are compared with analytical results obtained by using the finite element method.

용접판재 딥드로잉 공정에서의 드로비드 설치가 용접선 이동에 미치는 영향에 대한 고찰

허영무,최유호,서대교 기계기술연구소 2000 성균관대학교 논문집 기계기술편 Vol.2 No.1

The purpose of this study is to investigate the weld line movements of the laser welded tailor-sheets during the deep drawing process with or without round drawbeads. Square blanks have been used and they have the three different weld line locations, respectively. The differences of the weld-line movements and the tendencies of the strain distributions in thickness were investigated by thickness strain in central and diagonal direction, the larger the values, the longer the distances from the center line. The drawbead adds the additional restraining forces to the blank, so the movement of weld line is reduced and the thickness strain distribution is changed.

LASER TAILOR-WELDED BLANKS FOR HOT-PRESS-FORMING STEEL WITH ARC PRETREATMENT

M. KANG,C. KIM,배성민 한국자동차공학회 2015 International journal of automotive technology Vol.16 No.2

Tailor-welded blanks (TWBs) are made of sheets with various strengths or thicknesses that ensure increased material strength without significantly increasing the weight. In this study, Al–Si-coated hot-press-forming steel sheets were subjected to laser butt welding for making TWBs. After laser welding, the welded blanks were heated and subsequently quenched to simulate a thermal cycle in the hot-press-forming process, and the properties of the welded joints were examined. Arc pretreatment was applied before laser welding, and its influence on the mechanical and metallurgical properties of the welds was analysed.

Manufacturing of tailor-rolled blanks with thickness variations in both the longitudinal and latitudinal directions

Han, Sangwook,Hwang, Taewoo,Oh, Ilyeong,Choi, Moonseok,Moon, Young Hoon Elsevier 2018 Journal of materials processing technology Vol.256 No.-

<P>A tailor-rolled blank is a semi-finished part that can be used to produce stamping parts with continuous thickness variations. This study investigates a cold manufacturing process to fabricate a TRB with variable thickness variations in both the longitudinal and latitudinal directions. The effect of the rolling process on the characteristics of the transition zone and the deformation behaviors of the blanks were investigated using various processing conditions. The dimensional variations at the transition zones were analyzed based on the cross-sectional thickness profiles of the formed blanks. The results show that manufacturing such a TRB requires an extra process to reduce dimensional instabilities caused by superimposed transition zones in both directions. To manufacture sound blanks with acceptable dimensions, this study proposes a trial method that uses blanks with circular and square holes instead of solid blank.</P>

유한요소 해석을 이용한 TWB 기술의 자동차용 측면 외부 보강재 부품 적용 연구

김기주,이재웅 대한기계학회 2022 大韓機械學會論文集A Vol.46 No.7

Tailor welded blanks are the technique to form the welded two or more sheets having different thickness and mechanical properties for saving the weight reduction. Because TWB (tailor welded blank) technique makes it possible to deform the welded sheets with one process, there should be a good effectiveness on precise dimension control, productivity, costs and weight reduction during forming processes. In this study, basic mechanical properties, formability, and finite element analysis were performed to investigate the application performance for the process of processing the side external reinforcement by forming the TWB plate joined by laser welding. For parts with TWB technology applied to the side external reinforcement, it was possible to delete the part corresponding to the door reinforcement. In addition, it was possible to reduce the number of molds and the number of steps such as spot welding at the same time.

Macro-performance evaluation of friction stir welded automotive tailor-welded blank sheets: Part I - Material properties

Chung, K.,Lee, W.,Kim, D.,Kim, J.,Chung, K.H.,Kim, C.,Okamoto, K.,Wagoner, R.H. Pergamon Press ; Elsevier Science Ltd 2010 International journal of solids and structures Vol.47 No.7

In order to evaluate the macroscopic performance of friction stir welded automotive tailor-welded blank (TWB) sheets, the hardening behavior, anisotropic yielding properties and forming limit diagram were characterized both for base (material) and weld zones. In order to describe the Bauschinger and transient hardening behaviors as well as permanent softening during reverse loading, the modified Chaboche type combined isotropic-kinematic hardening law was applied. As for anisotropic yielding, the non-quadratic anisotropic yield function, Yld2000-2d, was utilized for base material zones, while isotropy was assumed for weld zones for simplicity. As for weld zones, hardening properties were obtained using the rule of mixture and selectively by direct measurement using sub-sized specimens. Forming limit diagrams were measured for base materials but calculated for weld zones based on Hill's bifurcation and M-K theories. In this work, four automotive sheets were considered: aluminum alloy 6111-T4, 5083-H18, 5083-O and dual-phase steel DP590 sheets, each having one or two thicknesses. Base sheets with the same and different thicknesses were friction-stir welded for tailor-welded blank (TWB) samples.

Influence of Workpiece Tilting Angle on Joint Properties in Tailor Friction Stir Welded Blanks of Aluminium Alloy 5052-H32

Chan-Seung Ro,Hee-Seon Bang,Han-Sur Bang,Seung-Ji Yoo,Jong-Hee Kim,Eun-Gyeol Choi 대한용접·접합학회 2018 대한용접·접합학회지 Vol.36 No.5

The application of aluminium tailor-welded blanks (TWB) is progressively increasing in automotive industries due to its high strength to weight ratio, superior corrosion resistance and crashworthiness. The weldments produced by Friction stir welding (FSW) retains high strength and formability as the process yields the sound joints at relatively lower temperatures in comparison to that of the conventional fusion welding processes. However, the FSW of aluminium alloy of different thicknesses in butt configuration is rarely studied. The primary objective of the present work is to investigate the feasibility of FSW process in joining of 1.5 to 2.5 mm thick AA5052 alloy tailored blank by tilting the workpiece with respect to machine bed. The effects of workpiece tilting angle with welding and rotational speeds on mechanical and metallurgical properties of the joints are studied. Minimum effective sheet thickness is found to be around 1.34 mm for tool rotational speed of 400 rpm and tilting angle of 0°. The highest joint strength around 212.6 MPa (95% of base metal strength) is achieved at a workpiece tilt angle of 1° for rotational and travel speed of 400 rpm and 1 mm/s, respectively. The maximum measured hardness is 60 Hv at tool roational speed of 400 rpm with tilting angle of 1°.

Macro-performance evaluation of friction stir welded automotive tailor-welded blank sheets: Part II - Formability

Kim, D.,Lee, W.,Kim, J.,Chung, K.H.,Kim, C.,Okamoto, K.,Wagoner, R.H.,Chung, K. Pergamon Press ; Elsevier Science Ltd 2010 International journal of solids and structures Vol.47 No.7

Formability of automotive friction stir welded TWB (tailor-welded blank) sheets was experimentally and numerically investigated in this work for four automotive sheets, aluminum alloy 6111-T4, 5083-H18, 5083-O and DP590 steel sheets, each having one or two different thicknesses. In particular, formability in three applications including the simple tension test with various weld line directions, hemisphere dome stretching and cylindrical cup drawing tests was evaluated. For numerical simulations, mechanical properties previously characterized in a joint paper (Chung et al., 2010) were utilized. To represent the mechanical properties, the non-quadratic orthogonal anisotropic yield function, Yld2000-2d, was utilized along with the (full) isotropic hardening law, while the anisotropy of the weld zone was ignored for simplicity.

극저탄소강의 Mash Seam TB 용접성 평가에 관한 연구

한창우,이창희,이명호 대한용접접합학회 2002 대한용접·접합학회지 Vol.20 No.4

M/S TB(Mash Seam Tailored Blank) is a production method for blanks by welding together blanks of different material, thickness and coating, and is an attractive method for manufacturing car body because it makes parts lighter and can save the cost and time to manufacture. However, there have not been quantified criteria to evaluate the quality of TB weld. This study introduced FHR (failure height ratio) in order to assess formability or/and weldability of the M/S welds and the applicability of FHR was confirmed by actual auto body forming and FLD tests. Furthermore, a new parameter, HN(heat number) based on the heat input of "$Q=I^2Rt$" was proposed and assessed. It was found that the concept of HN could be utilized to evaluate the soundness of M/S welds without any destructive tests.ive tests.

DISCRETE OPTIMIZATION DESIGN OF TAILOR-WELDED BLANKS (TWBs) THIN-WALLED STRUCTURES UNDER DYNAMIC CRASHING

Yisong Chen,Fengxiang Xu,Suo Zhang,Kunying Wu,Zhinan Dong 한국자동차공학회 2019 International journal of automotive technology Vol.20 No.2

Tailor-welded blanks (TWBs) thin-walled structures have been widely applied in field of automotive and construction due to their significant advantages in saving weight and improving crashworthiness. To further understand and improve crashing performance of TWB structures, this paper conducts parametric analysis and optimization design on TWB thin-walled tubes. Firstly, the numerical model of dynamic crashing event of different TWB tubes is derived from physical experiments. The parametric analysis results show that the material and thickness combinations have significant effects on the crashing performance. The energy-absorbed characteristics and deformed modes of TWBs are superior to those of tubes with uniform thickness. Then, two optimization cases of TWB tubes are presented through analysis of mean (ANOM) and updating orthogonal array, in which the thickness property and material types are considered as design variables. The results demonstrated that the performances of the optimized structure are much better than those of the initial counterpart.