鋼／アルミ異材スポット溶接接手の強度特性
-（第2報）疲労強度に関する調査-

各務　綾加・相本　光宏・梅野　栄介（トヨタ自動車）・松岡　秀明・尼子　龍幸（豊田中央研究所）

鋼板とアルミ合金のスポット溶接では，接合界面に生成される金属間化合物が接合強度と密接に関係することが知られている．本報では，鋼板とアルミ合金板のスポット溶接において，金属間化合物の脆さを克服する目的で突起状組織を形成した溶接継手を製作し，疲労強度について調査した．

応力集中部を有するステンレス鋼薄板の疲労におけるコーキシング効果

王　暁光（東京濾器）

ステンレス鋼薄板の応力集中部の疲労挙動を調査し，コーキシング効果が疲労限度に与える影響を明らかにした．ヒステリシスループや疲労線図から，応力比や応力振幅によるき裂の発生・進展の違いを観察し，き裂の伝播や破壊のメカニズムの解明を行った．コーキシング効果はき裂の停留や疲労寿命を左右する重要な要因であった．

Additively Manufactured HEA for Functional Integration and Weight Reduction in Mobility Systems

Hyomoon Joo (Hyndai Motor)

Recent mobility systems require structural materials with stable properties over wide temperature ranges. Conventional alloys degrade under extreme conditions. A Ni-based high-entropy alloy was fabricated via additive manufacturing, enabling precise microstructural control. The alloy exhibited temperature-insensitive tensile behavior due to its stable single-phase structure and sluggish diffusion. Grain boundary engineering enhanced strain hardening and mechanical robustness. The material shows strong potential for automotive applications, including electric powertrain and thermal components, offering improved durability and reliability for next-generation mobility systems.

A Study on Optimization of Two stage rolling process to Improve formability and Reduce springback of Pure titanium thin sheet for Fuel cell Separator

Jaebong Park･Sunghwan Kim (Hyundai Motor)

It was confirmed to improve the formability and reduce springback of titanium for separators through a two-stage rolling process with intermediate annealing. The effect of rolling texture dispersion due to inducing twin was verified. In addition, the analysis of rolling texture, grain, mechanical properties and springback was conducted based on the number of rolling stage, thickness reduction ratio, final annealing temperature and time. Through these results, the optimal two-stage rolling process that can improve formability and reduce springback were derived.