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다단 성형 공정 시 고-Mn 강의 타원형 용기 헤드에서의 변형률 분포: 유한요소해석
Preetham Alluri,Lalit Kaushik,최시훈 한국소성∙가공학회 2023 소성가공 : 한국소성가공학회지 Vol.32 No.5
ISO 21029 cryogenic vessel is used to transport cryogenic fluids. High-manganese steel (High-Mn steel) is widely regarded as suitable for use at cryogenic temperatures. The conventional way of manufacturing an ellipsoidal vessel head involves incremental stretching, followed by a spinning process. In this study, an alternative method for forming an ellipsoidal vessel head was proposed. Finite element analysis (FEA) was used to theoretically examine the strain evolution during a multi-stage forming process, which involved progressive stretching, deep drawing, and spinning of High-Mn steel. The distribution of effective strain and strain components were analyzed at different regions of the formed part. The FEA results revealed that only normal strains were evident in the dished region of the vessel head due to the stretching process. However, the flange region experienced complex strain evolution during the subsequent deep drawing and spinning process.
Jain Pawan Kumar,Kaushik Shiv Kumar,Vashisht Lalit Kumar Korean Mathematical Society 2007 대한수학회보 Vol.44 No.1
Some stability theorems (Paley-Wiener type) for Banach frames in Banach spaces have been derived.
Mahesh Panchal,K. R. Ravi,Lalit Kaushik,Rajesh Khatirkar,Shi‑Hoon Choi,Jaiveer Singh 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.12
Magnesium (Mg) alloys are the lightest among the structural metallic materials and have attracted great interest due to theirhigh specific strength and specific stiffness. However, Mg alloys show poor formability particularly at room temperature(RT), due to the development of strong basal texture and thus limiting their structural applications. Therefore, many techniquesbeing constantly proposed to alter the crystallographic texture in Mg alloys, such as microalloying, especially withrare-earth (RE) elements, severe plastic deformation (SPD), thermomechanical processing (TMP), pre-twinning/stretchingin the recent past. Pre-twinning remains the most effective technique that controls the crystallographic texture in Mg alloysby introducing 1012 extension twins (ETs) which work out for alloys prepared through various prior processing conditionsand compositions. Interestingly, only a small fraction of ETs during pre-twinning imparts significant improvement in the RTstretch formability. Therefore, this manuscript critically reviews the underlying mechanisms of pre-twinning and texturecontrol via practical pre-twinning methods such as in-plane compression and compares its effectiveness with other texturecontrol methods through alloy design, TMP, and SPD processes. In addition, the effect of initial microstructure and variousdeformation conditions on the contribution of twin, twin-orientation control during thermal treatment and also their influenceon the RT stretch formability are discussed.