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Sunusi Marwana Manladan - One of the best experts on this subject based on the ideXlab platform.
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Resistance Element welding of magnesium alloy and austenitic stainless steel in three-sheet configurations
Journal of Materials Processing Technology, 2019Co-Authors: Sunusi Marwana Manladan, Singh Ramesh, Yangchuan Cai, Y Zhang, Zhen LuoAbstract:Abstract The Mg alloy and two austenitic stainless steel sheets were joined together by a metallurgical bond across the rivet and two austenitic stainless steel sheets. More heat was generated at the austenitic stainless/austenitic stainless interface than at the rivet/ austenitic stainless steel interface, leading to larger nugget size at the austenitic stainless steel /austenitic stainless steel interface at all welding currents. Thus, the nugget size at the austenitic stainless steel /austenitic stainless steel interface mainly influenced the transition from interfacial to pullout failure modes. The fusion zone microstructure consisted of ferrite and austenite. The microstructure in the edges of the nugget (both in the rivet and ASS) consisted of fine columnar dendritic grains. Owing to variation of temperature gradient and solidification growth rate, the grains morphology changed from columnar dendritic to equiaxed dendritic in the nugget center. The fine grains resulted in high fusion zone hardness. Digital image correlation analysis revealed that the joints could experience joining zone rotation/out-of-plane displacement during lap-shear tests, which reduced the magnitude of strain sustained by the joints in the loading direction. The joint configuration that did not undergo joining zone rotation and failed via pullout failure in the austenitic stainless steel sheet exhibited superior lap-shear performance.
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microstructure and mechanical properties of Resistance spot welded in welding brazing mode and Resistance Element welded magnesium alloy austenitic stainless steel joints
Journal of Materials Processing Technology, 2017Co-Authors: Singh Ramesh, Sunusi Marwana Manladan, Y Zhang, Zhen Luo, Farazila Yusof, Zhanxiang LingAbstract:Abstract An AZ31 Mg alloy and 316L austenitic stainless steel (ASS) were joined via Resistance spot welding (RSW) and Resistance Element welding (REW). The RSW joints were found to be produced through welding-brazing mode, in which the Mg alloy melted and spread on the solid steel, forming a nugget only in the Mg alloy. The microstructure of the nugget consisted of columnar dendritic structure, indicating that columnar-to-equiaxed transition was interrupted. Shrinkage porosity and cracking were also observed in the RSW nugget. In contrast, a two-zone nugget was formed during REW, consisting of a peripheral nugget on the ASS side and the main nugget. Compared with the RSW joints, the REW joints were obtained at lower welding currents, and they exhibited superior mechanical performance, with 63% higher peak load and 9 times higher energy absorption. Irrespective of the welding current, the RSW joints failed in interfacial failure mode, while the failure mode of the REW joints transited from interfacial to pull out with increased welding current.
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a review on Resistance spot welding of aluminum alloys
The International Journal of Advanced Manufacturing Technology, 2017Co-Authors: Sunusi Marwana Manladan, Farazila Yusof, S Ramesh, M Fadzil, Zhen LuoAbstract:This paper presents a review on the Resistance spot welding (RSW) of Al/Al alloys, Al alloys/steel, Al/Mg alloys, and Al/Ti alloys, with focus on structure, properties, and performance relationships. It also includes weld bonding, effect of welding parameters on joint quality, main metallurgical defects in Al spot welds, and electrode degradation. The high contact Resistance, induced by the presence of oxide layer on the surface of Al alloys, and the need for application of high welding current during RSW of Al alloys result in rapid electrode tip wear and inconsistency in weld quality. Studies have shown that cleaning the oxide layer, sliding of a few microns between sheets, enhancing the electrode force, and the application of a low-current pre-heating can significantly reduce the contact Resistance and improve joint quality. For Al/steel dissimilar RSW, the technique of Resistance Element welding, the use of optimized electrode morphology, the technique of RSW with cover plates, and the use of interlayers such as Al-Mg, AlSi12, and AlCu28 alloys were found to suppress the formation of brittle intermetallic compounds (IMC) and improve the joint quality. The employment of pure Ni foil, Au-coated Ni foil, Sn-coated steel, and Zn-coated steel interlayers was also found to restrict the formation of brittle IMCs during RSW of Al/Mg alloys. Furthermore, the techniques of RSW with cover plates and RSW under the influence of electromagnetic stirring effect were found to improve the weldability of Al/Ti dissimilar alloys.
Zhen Luo - One of the best experts on this subject based on the ideXlab platform.
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Resistance Element welding of magnesium alloy and austenitic stainless steel in three-sheet configurations
Journal of Materials Processing Technology, 2019Co-Authors: Sunusi Marwana Manladan, Singh Ramesh, Yangchuan Cai, Y Zhang, Zhen LuoAbstract:Abstract The Mg alloy and two austenitic stainless steel sheets were joined together by a metallurgical bond across the rivet and two austenitic stainless steel sheets. More heat was generated at the austenitic stainless/austenitic stainless interface than at the rivet/ austenitic stainless steel interface, leading to larger nugget size at the austenitic stainless steel /austenitic stainless steel interface at all welding currents. Thus, the nugget size at the austenitic stainless steel /austenitic stainless steel interface mainly influenced the transition from interfacial to pullout failure modes. The fusion zone microstructure consisted of ferrite and austenite. The microstructure in the edges of the nugget (both in the rivet and ASS) consisted of fine columnar dendritic grains. Owing to variation of temperature gradient and solidification growth rate, the grains morphology changed from columnar dendritic to equiaxed dendritic in the nugget center. The fine grains resulted in high fusion zone hardness. Digital image correlation analysis revealed that the joints could experience joining zone rotation/out-of-plane displacement during lap-shear tests, which reduced the magnitude of strain sustained by the joints in the loading direction. The joint configuration that did not undergo joining zone rotation and failed via pullout failure in the austenitic stainless steel sheet exhibited superior lap-shear performance.
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microstructure and mechanical properties of Resistance spot welded in welding brazing mode and Resistance Element welded magnesium alloy austenitic stainless steel joints
Journal of Materials Processing Technology, 2017Co-Authors: Singh Ramesh, Sunusi Marwana Manladan, Y Zhang, Zhen Luo, Farazila Yusof, Zhanxiang LingAbstract:Abstract An AZ31 Mg alloy and 316L austenitic stainless steel (ASS) were joined via Resistance spot welding (RSW) and Resistance Element welding (REW). The RSW joints were found to be produced through welding-brazing mode, in which the Mg alloy melted and spread on the solid steel, forming a nugget only in the Mg alloy. The microstructure of the nugget consisted of columnar dendritic structure, indicating that columnar-to-equiaxed transition was interrupted. Shrinkage porosity and cracking were also observed in the RSW nugget. In contrast, a two-zone nugget was formed during REW, consisting of a peripheral nugget on the ASS side and the main nugget. Compared with the RSW joints, the REW joints were obtained at lower welding currents, and they exhibited superior mechanical performance, with 63% higher peak load and 9 times higher energy absorption. Irrespective of the welding current, the RSW joints failed in interfacial failure mode, while the failure mode of the REW joints transited from interfacial to pull out with increased welding current.
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a review on Resistance spot welding of aluminum alloys
The International Journal of Advanced Manufacturing Technology, 2017Co-Authors: Sunusi Marwana Manladan, Farazila Yusof, S Ramesh, M Fadzil, Zhen LuoAbstract:This paper presents a review on the Resistance spot welding (RSW) of Al/Al alloys, Al alloys/steel, Al/Mg alloys, and Al/Ti alloys, with focus on structure, properties, and performance relationships. It also includes weld bonding, effect of welding parameters on joint quality, main metallurgical defects in Al spot welds, and electrode degradation. The high contact Resistance, induced by the presence of oxide layer on the surface of Al alloys, and the need for application of high welding current during RSW of Al alloys result in rapid electrode tip wear and inconsistency in weld quality. Studies have shown that cleaning the oxide layer, sliding of a few microns between sheets, enhancing the electrode force, and the application of a low-current pre-heating can significantly reduce the contact Resistance and improve joint quality. For Al/steel dissimilar RSW, the technique of Resistance Element welding, the use of optimized electrode morphology, the technique of RSW with cover plates, and the use of interlayers such as Al-Mg, AlSi12, and AlCu28 alloys were found to suppress the formation of brittle intermetallic compounds (IMC) and improve the joint quality. The employment of pure Ni foil, Au-coated Ni foil, Sn-coated steel, and Zn-coated steel interlayers was also found to restrict the formation of brittle IMCs during RSW of Al/Mg alloys. Furthermore, the techniques of RSW with cover plates and RSW under the influence of electromagnetic stirring effect were found to improve the weldability of Al/Ti dissimilar alloys.
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Resistance Element welding of 6061 aluminum alloy to uncoated 22mnmob boron steel
Materials and Manufacturing Processes, 2016Co-Authors: Zhanxiang Ling, Zhen Luo, Yueqiao Feng, Zhengmin WangAbstract:A novel Resistance Element welding technology was applied to join 6061 Al alloy and uncoated 22MnMoB boron steel. To conduct the Resistance Element welding process, a technological hole was drilled in the Al sheet into which a Q235 steel rivet was inserted. Resistance spot welding was carried out at the rivet. The mechanical properties, fracture morphology, nugget formation process, dynamic Resistance, microstructure, and hardness distribution of the Resistance Element welding were investigated. Traditional Resistance spot weld joints were also prepared for comparison. Resistance spot welding could barely join Al 6061 and boron steel, and had a maximum tensile shear force of less than 1000 N. Novel Resistance Element welding could join the metals reliably with a maximum tensile shear force of over 7000 N and a relatively high toughness. Nugget formed at the interface of rivet and steel acted as loading position, and IMC interlayer connected rivet and aluminum.
Zhanxiang Ling - One of the best experts on this subject based on the ideXlab platform.
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microstructure and mechanical properties of Resistance spot welded in welding brazing mode and Resistance Element welded magnesium alloy austenitic stainless steel joints
Journal of Materials Processing Technology, 2017Co-Authors: Singh Ramesh, Sunusi Marwana Manladan, Y Zhang, Zhen Luo, Farazila Yusof, Zhanxiang LingAbstract:Abstract An AZ31 Mg alloy and 316L austenitic stainless steel (ASS) were joined via Resistance spot welding (RSW) and Resistance Element welding (REW). The RSW joints were found to be produced through welding-brazing mode, in which the Mg alloy melted and spread on the solid steel, forming a nugget only in the Mg alloy. The microstructure of the nugget consisted of columnar dendritic structure, indicating that columnar-to-equiaxed transition was interrupted. Shrinkage porosity and cracking were also observed in the RSW nugget. In contrast, a two-zone nugget was formed during REW, consisting of a peripheral nugget on the ASS side and the main nugget. Compared with the RSW joints, the REW joints were obtained at lower welding currents, and they exhibited superior mechanical performance, with 63% higher peak load and 9 times higher energy absorption. Irrespective of the welding current, the RSW joints failed in interfacial failure mode, while the failure mode of the REW joints transited from interfacial to pull out with increased welding current.
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Resistance Element welding of 6061 aluminum alloy to uncoated 22mnmob boron steel
Materials and Manufacturing Processes, 2016Co-Authors: Zhanxiang Ling, Zhen Luo, Yueqiao Feng, Zhengmin WangAbstract:A novel Resistance Element welding technology was applied to join 6061 Al alloy and uncoated 22MnMoB boron steel. To conduct the Resistance Element welding process, a technological hole was drilled in the Al sheet into which a Q235 steel rivet was inserted. Resistance spot welding was carried out at the rivet. The mechanical properties, fracture morphology, nugget formation process, dynamic Resistance, microstructure, and hardness distribution of the Resistance Element welding were investigated. Traditional Resistance spot weld joints were also prepared for comparison. Resistance spot welding could barely join Al 6061 and boron steel, and had a maximum tensile shear force of less than 1000 N. Novel Resistance Element welding could join the metals reliably with a maximum tensile shear force of over 7000 N and a relatively high toughness. Nugget formed at the interface of rivet and steel acted as loading position, and IMC interlayer connected rivet and aluminum.
Bernard La Scola - One of the best experts on this subject based on the ideXlab platform.
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giant viruses of amoebae a journey through innovative research and paradigm changes
Annual Review of Virology, 2017Co-Authors: Philippe Colson, Bernard La Scola, Didier RaoultAbstract:Giant viruses of amoebae were discovered serendipitously in 2003; they are visible via optical microscopy, making them bona fide microbes. Their lifestyle, structure, and genomes break the mold of classical viruses. Giant viruses of amoebae are complex microorganisms. Their genomes harbor between 444 and 2,544 genes, including many that are unique to viruses, and encode translation components; their virions contain >100 proteins as well as mRNAs. Mimiviruses have a specific mobilome, including virophages, provirophages, and transpovirons, and can resist virophages through a system known as MIMIVIRE (mimivirus virophage Resistance Element). Giant viruses of amoebae bring upheaval to the definition of viruses and tend to separate the current virosphere into two categories: very simple viruses and viruses with complexity similar to that of other microbes. This new paradigm is propitious for enhanced detection and characterization of giant viruses of amoebae, and a particular focus on their role in humans is ...
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mimivirus leading the way in the discovery of giant viruses of amoebae
Nature Reviews Microbiology, 2017Co-Authors: Philippe Colson, Bernard La Scola, Anthony Levasseur, Gustavo CaetanoanollesAbstract:The discovery of the giant amoebal virus mimivirus, in 2003, opened up a new area of virology. Extended studies, including those of mimiviruses, have since revealed that these viruses have genetic, proteomic and structural features that are more complex than those of conventional viruses. The accidental discovery of the giant virus of amoeba — Acanthamoeba polyphaga mimivirus (APMV; more commonly known as mimivirus) — in 2003 changed the field of virology. Viruses were previously defined by their submicroscopic size, which probably prevented the search for giant viruses, which are visible by light microscopy. Extended studies of giant viruses of amoebae revealed that they have genetic, proteomic and structural complexities that were not thought to exist among viruses and that are comparable to those of bacteria, archaea and small eukaryotes. The giant virus particles contain mRNA and more than 100 proteins, they have gene repertoires that are broader than those of other viruses and, notably, some encode translation components. The infection cycles of giant viruses of amoebae involve virus entry by amoebal phagocytosis and replication in viral factories. In addition, mimiviruses are infected by virophages, defend against them through the mimivirus virophage Resistance Element (MIMIVIRE) system and have a unique mobilome. Overall, giant viruses of amoebae, including mimiviruses, marseilleviruses, pandoraviruses, pithoviruses, faustoviruses and molliviruses, challenge the definition and classification of viruses, and have increasingly been detected in humans.
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MIMIVIRE is a defence system in mimivirus that confers Resistance to virophage
Nature, 2016Co-Authors: Anthony Levasseur, Meriem Bekliz, Pierre Pontarotti, Eric Chabriere, Bernard La ScolaAbstract:MIMIVIRE is a novel nucleic-acid-based immune system against virophage infection in the giant virus mimivirus. The B and C lineages of mimivirus, a giant virus with predatory amoebae as its natural host, can be infected by a unique virophage known as Zamilon. Lineage A, however, is resistant to Zamilon infection. Here Didier Raoult and colleagues identify a nucleic-acid-based defence mechanism present in lineage A mimivirus which protects against Zamilon infection. These lineage A viruses contain an insertion of a repeated Zamilon sequence, termed mimivirus virophage Resistance Element or MIMIVIRE, within an operon that also encodes nuclease and helicase functions. Silencing the repeated sequences and the related genes restores susceptibility to Zamilon. This work demonstrates that MIMIVIRE acts as a virophage Resistance factor, just as CRISPR acts as a Resistance factor against bacteriophages. Since their discovery, giant viruses have revealed several unique features that challenge the conventional definition of a virus, such as their large and complex genomes, their infection by virophages and their presence of transferable short Element transpovirons1,2,3,4,5. Here we investigate the sensitivity of mimivirus to virophage infection in a collection of 59 viral strains and demonstrate lineage specificity in the Resistance of mimivirus to Zamilon6, a unique virophage that can infect lineages B and C of mimivirus but not lineage A. We hypothesized that mimiviruses harbour a defence mechanism resembling the clustered regularly interspaced short palindromic repeat (CRISPR)-Cas system that is widely present in bacteria and archaea7,8,9,10. We performed de novo sequencing of 45 new mimivirus strains and searched for sequences specific to Zamilon in a total of 60 mimivirus genomes. We found that lineage A strains are resistant to Zamilon and contain the insertion of a repeated Zamilon sequence within an operon, here named the ‘mimivirus virophage Resistance Element’ (MIMIVIRE). Further analyses of the surrounding sequences showed that this locus is reminiscent of a defence mechanism related to the CRISPR–Cas system. Silencing the repeated sequence and the MIMIVIRE genes restores mimivirus susceptibility to Zamilon. The MIMIVIRE proteins possess the typical functions (nuclease and helicase) involved in the degradation of foreign nucleic acids. The viral defence system, MIMIVIRE, represents a nucleic-acid-based immunity against virophage infection.
Julian I Rood - One of the best experts on this subject based on the ideXlab platform.
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functional analysis of a bacitracin Resistance determinant located on icecp1 a novel tn916 like Element from a conjugative plasmid in clostridium perfringens
Antimicrobial Agents and Chemotherapy, 2015Co-Authors: Xiaoyan Han, Torsten Seemann, Dieter M Bulach, Luke Southey, Xuxia Yan, Trudi L Bannam, Julian I RoodAbstract:ABSTRACT Bacitracins are mixtures of structurally related cyclic polypeptides with antibiotic properties. They act by interfering with the biosynthesis of the bacterial cell wall. In this study, we analyzed an avian necrotic enteritis strain of Clostridium perfringens that was resistant to bacitracin and produced NetB toxin. We identified a bacitracin Resistance locus that resembled a bacitracin Resistance determinant from Enterococcus faecalis. It contained the structural genes bcrABD and a putative regulatory gene, bcrR . Mutagenesis studies provided evidence that both bcrA and bcrB are essential for bacitracin Resistance, and that evidence was supported by the results of experiments in which the introduction of both the bcrA and bcrB genes into a bacitracin-susceptible C. perfringens strain was required to confer bacitracin Resistance. The wild-type strain was shown to contain at least three large, putatively conjugative plasmids, and the bcrRABD locus was localized to an 89.7-kb plasmid, pJIR4150. This plasmid was experimentally shown to be conjugative and was sequenced. The sequence revealed that it also carries a tpeL toxin gene and is related to the pCW3 family of conjugative antibiotic Resistance and toxin plasmids from C. perfringens. The bcr genes were located on a genetic Element, ICE Cp1 , which is related to the Tn 916 family of integrative conjugative Elements (ICEs). ICE Cp1 appears to be the first Tn 916 -like Element shown to confer bacitracin Resistance. In summary, we identified in a toxin-producing C. perfringens strain a novel mobile bacitracin Resistance Element which was experimentally shown to be essential for bacitracin Resistance and is carried by a putative ICE located on a conjugative plasmid.
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tiscpe8 an is1595 family lincomycin Resistance Element located on a conjugative plasmid in clostridium perfringens
Journal of Bacteriology, 2009Co-Authors: Dena Lyras, Trudi L Bannam, Julian I Rood, Victoria Michelle Adams, Susan Alicia Ballard, Wee Lin Teng, Pauline Howarth, Paul K Crellin, Glenn J SongerAbstract:Clostridium perfringens is a normal gastrointestinal organism that is a reservoir for antibiotic Resistance genes and can potentially act as a source from which mobile Elements and their associated Resistance determinants can be transferred to other bacterial pathogens. Lincomycin Resistance in C. perfringens is common and is usually encoded by erm genes that confer macrolide-lincosamide-streptogramin B Resistance. In this study we identified strains that are lincomycin resistant but erythromycin sensitive and showed that the lincomycin Resistance determinant was plasmid borne and could be transferred to other C. perfringens isolates by conjugation. The plasmid, pJIR2774, is the first conjugative C. perfringens R-plasmid to be identified that does not confer tetracycline Resistance. Further analysis showed that Resistance was encoded by the lnuP gene, which encoded a putative lincosamide nucleotidyltransferase and was located on tISCpe8, a functional transposable genetic Element that was a member of the IS1595 family of transposon-like insertion sequences. This Element had significant similarity to the mobilizable lincomycin Resistance Element tISSag10 from Streptococcus agalactiae. Like tISSag10, tISCpe8 carries a functional origin of transfer within the Resistance gene, allowing the Element to be mobilized by the conjugative transposon Tn916. The similarity of these Elements and the finding that they both contain an oriT-like region support the hypothesis that conjugation may result in the movement of DNA modules that are not obviously mobile since they are not linked to conjugation or mobilization functions. This process likely plays a significant role in bacterial adaptation and evolution.