Effect of process parameters on pulsed laser welding of AA5083 alloy using response surface methodology and pulse shape variation

Aluminium alloys exhibit eco-friendly aspects related to global environmental issues, such as almost unlimited recyclability. Nevertheless, some intrinsic characteristics are challenges to explore all their benefits. In the welding process, the high thermal conductivity and low melt point require high control of heat input. Alternatively, the pulsed laser mode provides a sharp beam focus with precise control enabling regulating the energy delivered. In this sense, this present work analysed the effect of pulsed laser welding parameters on 3-mm-thick AA5083 aluminium alloy sheets. Trials targeted to develop sound welds with minimum defect and high penetration depth adopting statistical methods. The optimum parameter arrangement was achieved by varying peak power, spot diameter, and pulse duration. Finally, the best parameter combination was applied using different pulse shapes to mitigate crack formation and pores. As a result, the pulse shape with step-down at the end of each pulse generated crack-free spot welds

Pulsed Laser Welding Applied to Metallic Materials-A Material Approach

Joining metallic alloys can be an intricate task, being necessary to take into account the material characteristics and the application in order to select the appropriate welding process. Among the variety of welding methods, pulsed laser technology is being successfully used in the industrial sector due to its beneficial aspects, for which most of them are related to the energy involved. Since the laser beam is focused in a concentrated area, a narrow and precise weld bead is created, with a reduced heat affected zone. This characteristic stands out for thinner material applications. As a non-contact process, the technique delivers flexibility and precision with high joining quality. In this sense, the present review addresses the most representative investigations developed in this welding process. A summary of these technological achievements in metallic metals, including steel, titanium, aluminium, and superalloys, is reported. Special attention is paid to the microstructural formation in the weld zone. Particular emphasis is given to the mechanical behaviour of the joints reported in terms of microhardness and strength performance. The main purpose of this work was to provide an overview of the results obtained with pulsed laser welding technology in diverse materials, including similar and dissimilar joints. In addition, outlook and remarks are addressed regarding the process characteristics and the state of knowledge

Low-Energy Pulsed-Laser Welding as a Root Pass in a GMAW Joint: An Investigation on the Microstructure and Mechanical Properties

Root pass is a fundamental step in multi-pass welding. In gas metal arc welding (GMAW), the weld bead qualities depend on the process parameters, filler materials, and welder abilities. This work investigates the effect of a Nd: YAG pulsed laser as a first pass to reduce the welders' reliance on the AH36 low-alloy steel with 5.5 mm thickness. This autogenous automatable process delivers reduced thermal impact due to the concentrated high-energy source, pulse overlap, and higher penetration depth-to-power ratio than continuous lasers. The outcomes indicate that the PL as a root welding generated a small HAZ compared to the GMAW condition. In addition, the subsequent arc passes positively affected the microstructure, reducing the hardness from around 500 to 230 HV. The PL + GMAW achieved similar strength results to the GMAW, although its Charpy impact values at -50 degrees C were around 15% lower than the arc condition.This work was financial supported from the Program for the Promotion and Impulse of Research and Transfer of the University of Cadiz (Reference project: IRTP02_UCA)

CENÁRIOS DISTINTOS PARA O MAPEAMENTO DE ÁREAS DE INUNDAÇÃO NOS BAIRROS DO MUNICÍPIO DE ALEGRE, ES

Inundação é um evento natural, entretanto vem ocasionando cada vez mais danos humanos e materiais. O mapeamento das áreas inundáveis é importante para eliminar os riscos de ocorrência do fenômeno e estabelecer o uso adequado de determinados locais da bacia. O objetivo deste trabalho foi elaborar e comparar dois cenários distintos obtidos por metodologias diferentes no mapeamento das áreas sujeitas à inundação em bairros do município de Alegre no Espírito Santo. O CENÁRIO 1 foi obtido aplicando a metodologia desenvolvida pelo Instituto de Pesquisas Tecnológicas (IPT), adaptada pelos autores, enquanto que o CENÁRIO 2 resulta da aplicação da metodologia proposta por Saaty em 1977. O método obtido pela análise de campo apresentou uma área inundável de risco muito alto – R4 18,64 há, e o Método proposto por Saaty (1977), apresentou uma área inundável de risco muito alto – R4 de 69,48 ha

Equipamento de solda por fricção a topo em elementos tubulares e método de solda por fricção a topo em elementos tubulares

Mattei, FabianoEngenhariaDepositad

Equipamento de movimentação e posicionamento de elementos tubulares para soldagem

PETROBRASUniversidade Federal do Rio Grande do SulEngenhariaDepositad

Tubo rígido metálico com extremidades mais espessas, riser submarino, processo e sistema de fabricação de tubo rígido metálico com extremidades mais espessas

PETROBRASUniversidade Federal do Rio Grande do SulEngenhari

Pan-Cancer Analysis of lncRNA Regulation Supports Their Targeting of Cancer Genes in Each Tumor Context

Long noncoding RNAs (lncRNAs) are commonly dys-regulated in tumors, but only a handful are known toplay pathophysiological roles in cancer. We inferredlncRNAs that dysregulate cancer pathways, onco-genes, and tumor suppressors (cancer genes) bymodeling their effects on the activity of transcriptionfactors, RNA-binding proteins, and microRNAs in5,185 TCGA tumors and 1,019 ENCODE assays.Our predictions included hundreds of candidateonco- and tumor-suppressor lncRNAs (cancerlncRNAs) whose somatic alterations account for thedysregulation of dozens of cancer genes and path-ways in each of 14 tumor contexts. To demonstrateproof of concept, we showed that perturbations tar-geting OIP5-AS1 (an inferred tumor suppressor) andTUG1 and WT1-AS (inferred onco-lncRNAs) dysre-gulated cancer genes and altered proliferation ofbreast and gynecologic cancer cells. Our analysis in-dicates that, although most lncRNAs are dysregu-lated in a tumor-specific manner, some, includingOIP5-AS1, TUG1, NEAT1, MEG3, and TSIX, synergis-tically dysregulate cancer pathways in multiple tumorcontexts