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Effect of residual stresses on fatigue strength of high strength steel sheets with punched holes |
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| Affiliation: | 1. Institute of Forming Technology and Lightweight Construction (IUL), TU Dortmund, Germany;2. Institute of Metal Forming and Casting (utg), Technische Universität München, Germany;1. Department of Materials Science and Engineering & RIAM, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea;3. Sheet Metal Development Team, Hyundai Motor Company, 150 Hyundaiyeonguso-ro, Namyang, Hwaseong-si, Gyeonggi-do 18220, Republic of Korea |
| Abstract: | The effect of residual stresses on the reverse bending fatigue strength of steel sheets with punched holes was studied for steels with tensile strength grades of 540 MPa and 780 MPa. Tensile and compressive residual stresses were induced around the punched holes. Heat treatment of the specimens with punched holes at 873 K for 1 h decreased the residual stresses around the holes and improved the fatigue strength of the sheets. This result means that the tensile residual stresses induced in the sidewalls of the holes and near the hole edges by punching reduced fatigue strength. The effect of the residual stresses on the fatigue limits of the edges was estimated by the modified Goodman relation using the residual stresses after cyclic loading and the ultimate tensile strength at the fatigue crack initiation sites. |
| Keywords: | Carbon steel Automotive components Fatigue limit Residual stresses Punched edge |
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