Abstract

The phenomenon where welding heat reduces the structure strength performance of hot-stamped materials used in automobile bodies was clarified. Tests using test pieces demonstrated that continuous welding methods, such as laser welding, that transmit heat over a wide range may reduce the structure strength performance compared to resistance spot welding. CAE analysis was performed to clarify the mechanism of this phenomenon. The material strength properties were obtained using micro tensile test specimens and applied to CAE models to reproduce the phenomenon where welding heat softens the area around the weld. The calculation results closely matched the test results, which showed that the drop in structure strength performance is due to material softening. In addition, the relationship between the material softening range and structure strength performance was investigated, and showed that softening of the welding flange area has a small effect, and softening of the hinge line areas has a large effect. This is because the hinge line areas bear a large share of the structural stress, and softening occurred in these areas. These results provided useful knowledge for future investigation of body structures and welding methods.

References

1. (1) Marukawa, T., Shoji, Y., Nakamura, M.: Euro Car Body 2017, Honda ACCORD, (2017)
2. (2) Palmquist, N., D’Elia, A., Nedic, S.: Euro Car Body 2016, Volvo V90, (2016)
3. (3) Yamazaki, K., Satoh, K., Tokunaga, Y.: Static and Fatigue Strength of Spot Welded Joints of Ultrahigh Strength Steel Sheets, Quarterly Journal of the Japan Welding Society, Vol. 17, No. 4, p. 553-560, (1999) (in Japanese)
4. (4) Fujimoto, H., Yasuyama, M., Ueda, H., Ueji, R., Fujii, H.: Static Strength of Hot-stamped Spot Welded Joints, Quarterly Journal of the Japan Welding Society, Vol. 33, No. 2, p. 144-152, (2015) (in Japanese)
5. (5) Fujimoto, H., Fukui, K., Okamura, K., Miyahara, M., Nakayama, E.: A Study on Strength and Fracture Mode of Spot Welds for High Tensile Strength Steels, 2002 JSAE Annual Congress Proceedings, No. 105-02, p. 5-8, (2002) (in Japanese)
6. (6) Tarr, S.: Body Technology of Honda New NSX, 2017 JSAE Annual Congress (Spring) Forum, New Automotive Body Technologies 2017, No. 17, FORUM-Y8, p. 1-20, (2017) (in Japanese)
7. (7) Ooka, H., Suzuki, A., Goto, M., Otsuka, K., Okada, Y.: Development of Short Pitch Resistance Spot Welding Technology, Honda R&D Technical Review, Vol. 25, No. 2, p. 85-91
8. (8) http://www.honda.co.jp/factbook/auto/N-WGN/201311/p22.pdf
9. (9) Ooka, H., Nomura, T.: Weight Reduction of Car Body Using Short Pitch Resistance Spot Welding, Journal of The Japan Welding Society, Vol. 84, No. 7, p. 509-513, (2015) (in Japanese)

Author (organization or company)

• Hisayasu OOKA（Automobile R&D Center）
• Tomohiro NOMURA（Automobile R&D Center）
• Masahiro KAWAZU（Automobile R&D Center）

Publication Information

Article of Honda R&D Technical Review Vol.30 No.1 (74 - 81)

PDF

Citation Information