Journal of the Korean Society of Industry Convergence (한국산업융합학회 논문집)

The Korean Society of Industry Convergence (한국산업융합학회)
권호 표지
DOI QR코드

DOI QR Code

A Study on Improvement of Dimensional Accuracy in 2-axis Bending for Automotive Blow Motor Case

차량용 블로우 모터 케이스 2축 굽힘 공정의 치수 정밀도 향상에 관한 연구

  • Kwon, Il-Keun (Division of Mechanical Eng., Dongeui Institute of Technology) ;
  • Kim, Gug-Yong (Division of Mechanical Eng., Dongeui Institute of Technology) ;
  • Park, Jun-Woo (Hang Seong Industrial Co., Ltd.)
  • Received : 2018.10.12
  • Accepted : 2018.12.05
  • Published : 2018.12.31
Download PDF
⟨ Previous Next ⟩

Abstract

In case high strength steels are applied for press-formed automotive parts, it is very difficult to secure forming accuracy due to large springback compared to moderate strength steels. In this study, a repetitive step-wise forming analyses based on secant method was proposed as the die design method for mandrel(bending tool) for the 2-axis bending equipments. A bending die with circular mandrel was designed for the DP780 blow motor case of which diameter and thickness are 70.8mm and 2.0mm respectively. Forming tests were performed to verify the validity of established die design and the results were compared with that of conventional HGI(Hot galvanized iron steel) blow motor case. For additional improvement in forming accuracy, an elliptical mandrel was proposed and its validity was verified using forming analyses based on secant method.

Keywords

SOOOB6_2018_v21n6_419_f0001.png 이미지

Fig. 1 Configuration 2-axis bending equipment for blow motor case

SOOOB6_2018_v21n6_419_f0002.png 이미지

Fig. 2 Comparison of mechanical properties, HGI vs. DP780

SOOOB6_2018_v21n6_419_f0003.png 이미지

Fig. 3 True stress – true strain curves for HGI and DP 780

SOOOB6_2018_v21n6_419_f0004.png 이미지

Fig. 4 Diagram for optimization of bending tool geometry

SOOOB6_2018_v21n6_419_f0005.png 이미지

Fig. 5 Secant method for optimization of bending tool geometry(x-axis: diameter of bending tool, y-axis: error in diameter of formed part

SOOOB6_2018_v21n6_419_f0006.png 이미지

Fig. 6 Finite element model for bending analysis

SOOOB6_2018_v21n6_419_f0007.png 이미지

Fig. 8 Error in diameter of formed part for each optimization steps

SOOOB6_2018_v21n6_419_f0008.png 이미지

Fig. 9 Forming test((a) equipment for forming test, (b) formed part)

SOOOB6_2018_v21n6_419_f0009.png 이미지

Fig. 10 Error in diameter and out of roundness (mandrel with elliptical section)

SOOOB6_2018_v21n6_419_f0010.png 이미지

Fig. 11 Error in diameter of formed part (mandrel with circular section vs. with elliptical section)

SOOOB6_2018_v21n6_419_f0011.png 이미지

Fig. 12 Error in out of roundness of formed part (mandrel with circular section vs. with elliptical section)

SOOOB6_2018_v21n6_419_f0012.png 이미지

Fig. 7 Major stress of upper fiber((a) after forming, (b) after springback)

Table 1. Diameters of mandrel(bending tool) for each optimization step(Unit:mm)

SOOOB6_2018_v21n6_419_t0001.png 이미지

Table 2. Error in diameter and out of roundness of formed parts(DP780, 2.0mm thickness, unit:mm)

SOOOB6_2018_v21n6_419_t0002.png 이미지

Table 3. Error in diameter and out of roundness of formed parts(HGI, 2.6mmt, unit:mm)

SOOOB6_2018_v21n6_419_t0003.png 이미지

Table 4. Vertical and horizontal length of mandrel(bending tool) and formed part for each optimization steps(Unit:mm)

SOOOB6_2018_v21n6_419_t0004.png 이미지

References

  1. C. H. Cha, S. K. Lee, D. C. Ko, B. M. Kim, "A study on the forming of automotive front side member part with ultra high strength steel of DP980", Transactions of Materials Processing 18(1), pp.39-44 (2009). https://doi.org/10.5228/KSPP.2009.18.1.039
  2. C. H. Suh, H. D. Shin, Y-C. Jung, C. D. Park, Y. H. Lim, Y. S. Kim, "A study on the forming process of stair type side sill for automobile using DP780", Transactions of Materials Processing 18(8), pp.601-606 (2009). https://doi.org/10.5228/KSPP.2009.18.8.601
  3. D. C. Ko, J. H. An, M. J. Jang, J. H. Bae, C. H. Kim, B. M. Kim, "Process design of seat rail in automobile by the advanced high strength steel of DP780", Transactions of Materials Processing, 17(3), pp.197-202 (2008). https://doi.org/10.5228/KSPP.2008.17.3.197
  4. M. K. Choi, H. Huh, "Investigation of springback behavior of DP780 steel sheets after the U-bending process ", Transactions of Materials Processing, 21(6), pp.384-388 (2012). https://doi.org/10.5228/KSTP.2012.21.6.384
  5. K. H. Kang, S. H. Kim, H. C. Ro, "Change in springback tendency during forming of a hat-type product with high strength steel using a digital servo press", Transactions of Materials Processing, 25(1), pp.21-28 (2016). https://doi.org/10.5228/KSTP.25.1.21
  6. Gug-Yong Kim, Il-Keun Kwon, Jun-Woo Park, "Study on prediction of mechanical joining strength of blow motor case joint", Journal of The Korean Society of Industry Convergence 20(1), pp.81-87 (2017). https://doi.org/10.21289/KSIC.2017.20.1.081
  7. Jin-Woo Lee, "Advanced method for an initial pole position estimation of a PMLSM", the transactions of korean institute of power electronics, 10(2), pp.124-129 (2005).