Evaluation of fatigue properties under four-point bending and fatigue crack propagation in austenitic stainless steel with a bimodal harmonic structure

Austenitic stainless steel (JIS-SUS304L) with a bimodal harmonic structure, which is defined as a coarse-grained structure surrounded by a network of fine grains, was fabricated using powder metallurgy to improve both the strength and ductility. Four-point bending fatigue tests and K-decreasing tests were conducted in air at room temperature under a stress ratio R of 0.1 to investigate fatigue crack propagation in SUS304L. The fatigue limit of this harmonic-structured material is higher than that of the material with a homogeneous coarse-grained structure. This is attributable to the formation of fine grains by mechanical milling and to the suppression of pore formation. In contrast, the threshold stress intensity range, ?Kth, for the harmonic-structured material is lower than that for the homogeneous coarse-grained material, while the crack growth rates, da/dN, are higher at comparable ?K. These results can be attributed to a reduction in the effective threshold stress intensity range, ?Keff,th, due to the presence of fine grains in the harmonic structure

Evaluation of Fatigue Properties under Four-point Bending and Fatigue Crack Propagation in Austenitic Stainless Steel with a Bimodal Harmonic Structure

Austenitic stainless steel (JIS-SUS304L) with a bimodal harmonic structure, which is defined as a coarse-grained structure surrounded by a network of fine grains, was fabricated using powder metallurgy to improve both the strength and ductility. Four-point bending fatigue tests and K-decreasing tests were conducted in air at room temperature under a stress ratio R of 0.1 to investigate fatigue crack propagation in SUS304L. The fatigue limit of this harmonic-structured material was higher than that of the material with a homogeneous coarse-grained structure. This is attributable to the formation of fine grains by mechanical milling and to the suppression of pore formation. In contrast, the threshold stress intensity range, DKth, for the harmonic-structured material was lower than that for the homogeneous coarse-grained material, while the crack growth rates, da/dN, were higher at comparable DK. These results can be attributed to a reduction in the effective threshold stress intensity range, DKeff,th, due to the presence of fine grains in the harmonic structure

Development and Practice of Staff Development Program with Faculty members, Administrators and Undergraduates in Higher Education

本稿では、関西大学において新たに開発及び実践されたSD (Staff Development) 研修プログラムを事例として、SD の開発における課題とその克服方法について検討する。本プログラムは、教員と職員がプロジェクトチームを組み開発したものである。その内容は、教育・学習支援をテーマとした全5 回にオリエンテーションと受講者による発表会をも含むものである。①職員だけでなく教員や学生も受講対象とし協同で学ぶ、②学習者のアクティブラーニングを促進する、③多様な学修環境で学ぶ、といった特色を持つものである。開発と実践にあたっては、プログラムを実施しやすくするための組織体制、テーマ設定、職員の関与、プログラムの評価、業務との連関といった面で課題があることを示した。本研究は，文部科学省科学研究補助金・基盤研究(C)（研究課題番号16K01143）の一部である。研究ノー