Development of frame with high performance using hot stamping

Yumi SAITO･Naoki KIMOTO (Nippon Steel)

As the growing popularity of electric vehicles, both cost reduction and safety enhancement of battery packs are desired. In this study, we focused on frames in battery packs. Using hot stamping materials enabled the achievement of high-strength frames with continuous flanges due to the high strength and high formability of materials. Consequently, an increase in stiffness and load capacity was indicated.

The Influence of Secondary Forming on Sheared Edge Delayed Fracture

Yuichi Matsuki･Junya Tobata･Toyohisa Shinmiya･hideyuki Kimura･Tsuyoshi Shiozaki (JFE Steel)

The application of ultra-high-strength steel sheets is expanding to achieve both lightweight automotive body structures and improved collision characteristics; however, delayed fracture at the shear edge remains a challenge. In this study, shear processing was performed on ultra-high-strength steel sheets, and secondary forming involving tension and compression was applied to the shear edges. Subsequently, delayed fracture tests were conducted under stress loading conditions to investigate and discuss the effects on delayed fracture characteristics.

Consideration on Vibration Durability Evaluation Using Simultaneous Three-Axis Excitation

Katsuhiko Nakamura･Tatsuki Okunaga (IMV)･Kenji Yoshida･Tsukasa Ohzawa (DENSO)･Tetsuya Hyakutake (SOKEN)

In actual operating environments, products are subjected to multi-degree-of-freedom vibrations. While design evaluations have conventionally been conducted using sequential single-axis excitation in three directions, the adoption of simultaneous three-axis excitation is gaining attention. In this study, using a simple test specimen, the evaluation results of the different excitation methods were quantified using vibration energy. The differences in these results and their underlying factors are clarified and discussed.

Improving the Fatigue Limit of Spot-Welded Tensile Shear Joints Using 980MPa-class High-tensile Steel Plate as the Base Material
-Improving the Fatigue Limit due to a Single Overload-

Kotaro Tanaka (Graduate School of Science and Technology, Nihon University)･Akifumi Okabe･Noboru Tomioka (Nihon University)

A spot-welded tensile-shear joint with a base material of 980MPa-class high-tensile steel plate was subjected to a constant amplitude load fatigue test after applying a single overload in advance to impart compressive residual stress to the crack initiation site and its surroundings, and it was confirmed that the fatigue limit was improved by the single overload. It was also shown that the fatigue life with and without a single overload can be uniformly evaluated by using the effective strain range.

Fatigue Strength Evaluation of Spot Welded Joints Using Infrared Thermoelastic Method

Hideki Ueda･Hiroshi Shiromizu (Nippon Steel)･Reiji Tanaka (Nippon Steel Technology)

We investigated the effect of load frequency using thermoelastic finite element (FE) analysis on spot welded joint commonly used in automobile parts. To simulate the thermoelastic effect, we developed a stress field-temperature field thermoelastic FE analysis technique that calculates the heat transfer of heat generation and heat absorption according to compression and tensile stress. The calculated stress distribution showed a good agreement with thermoelastic stress distribution measured using an infrared ray method. Moreover, we verified the accuracy of estimating the fatigue limit obtained from the point of sudden increase in dissipated energy by infrared measurement.

Development of Analytical and Evaluation Techniques for Enhancing the Performance of Integrated Hot Stamped Components　

Masahiro Kubo･Naoki Kimoto･Tohru Okada･Satoshi Shirakami (Nippon Steel)

The application of hot-stamped steel sheets in integrated automotive structural components, such as cabin frame structures, is increasingly prevalent. This report focuses on the development of analytical and evaluation techniques aimed at enhancing the performance of these components, with a particular emphasis on the analysis and evaluation of overlapping sections.