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Effects of Constrained Groove Pressing (CGP) on the plane stress fracture toughness of pure copper
Mohammadi, Bijan,Tavoli, Marzieh,Djavanroodi, Faramarz Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.5
Among severe plastic deformation methods, groove pressing is one of the prominent techniques for producing ultra-fine grained sheet materials. This process consists of imposing repetitive severe plastic deformation on the plate or sheet metals through alternate pressing. In the current study, a 2 mm pure Cu sheet has been subjected to repetitive shear deformation up to two passes. Hardness and tensile yield and ultimate stress were obtained after groove pressing. Fracture toughness tests have been performed and compared for three conditions of sheet material namely as received (initial annealed state), after one and two passes of groove pressing. Results of experiments indicate that a decrease in the values of fracture toughness attains as the number of constrained groove pressing (CGP) passes increase.
Effects of Constrained Groove Pressing (CGP) on the plane stress fracture toughness of pure copper
Bijan Mohammadi,Marzieh Tavoli,Faramarz Djavanroodi 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.5
Among severe plastic deformation methods, groove pressing is one of the prominent techniques for producing ultra-fine grained sheet materials. This process consists of imposing repetitive severe plastic deformation on the plate or sheet metals through alternate pressing. In the current study, a 2 mm pure Cu sheet has been subjected to repetitive shear deformation up to two passes. Hardness and tensile yield and ultimate stress were obtained after groove pressing. Fracture toughness tests have been performed and compared for three conditions of sheet material namely as received (initial annealed state), after one and two passes of groove pressing. Results of experiments indicate that a decrease in the values of fracture toughness attains as the number of constrained groove pressing (CGP) passes increase.
( Salimi,Ali ),( Fatemeh Yousefi ),( Marzieh Ghollasi ),( Sara Daneshjou ),( Hesam Tavoli ),( Sirous Ghobadi ),( Khosro Khajch ) 한국미생물 · 생명공학회 2012 Journal of microbiology and biotechnology Vol.22 No.8
Previously, an extracellular a-amylase (BKA) had been purified from the culture of Bacillus sp. KR8104. Subsequently, the crystal structure of the active enzyme revealed a 422 amino acids polypeptide. In this study, the bka was cloned into E. coli, which encoded a polypeptide of 659 amino acids including two additional fragments: one 44 residues N-terminal fragment and another 193 residues C-terminal fragment. In order to investigate the role of the C-terminal fragment, two constructs with and without this region [BKAΔ(N44) and BKAΔ(N44C193)] were designed and expressed in E. coli BL21. The optimum pH, thermal stability, and the end-products of starch hydrolysis were found to be similar in both constructs. The Km and Vmax values for BKAΔ (N44) were lower than BKAΔ (N44C193), using either starch or ethylidene-blocked 4-nitrophenylmaltoheptaoside as a substrate.