ABSTRACT Analysis of residual stresses in welded joints by TIG process using base metal ASTM A131 AH36 comparing different joint design, some specimens were machined with joint in “V” shape and others in “U” shape. It was also correlated with finishing with a single oscillating pass or with straight double pass. The results were performed using the DCP method (displacement of coordinated points). The specimens were welded according to the standards (manufacturing and qualification) AWS D1.1. After welding, holes were made in the thermally affected zone in the central region of the welding axis, which were then referenced on a coordinate measuring table. Then, the welds were subjected to a post weld heat treatment (PWHT) and measured the displacements of the holes caused after PWHT in coordinate plan, allowing the calculation of the residual stresses. The results demonstrated lower stress levels in “U” design joints and good applicability of the DPC method.

RESUMO Análise de tensões residuais realizada em juntas soldadas pelo processo TIG utilizando metal de base ASTM A131 AH36 comparando diferentes projetos de junta. Uma parte com chanfro usinado em formato de “V” e outra em forma de “U”. Também foi correlacionado variáveis de acabamento com passe único oscilante ou com passe duplo retilíneo. O resultado das tensões foi obtido através do método DPC (deslocamento de pontos coordenados). Os corpos de prova foram soldados segundo as normas (fabricação e qualificação) AWS D1.1. Após a soldagem foram realizadas furações na zona termicamente afetada nas mediações centrais do eixo de soldagem em uma mesa de medição por coordenadas. As soldas foram submetidas a tratamento térmico para alívio de tensões (TTAT) e mensurou-se os deslocamentos dos furos causados pelo TTAT, possibilitando o cálculo das tensões residuais. Os resultados demostraram menores níveis de tensões juntas em “U” e boa aplicabilidade do método DPC.

In the present work, a silver(I) complex with the antimycobacterial drug isoniazid (inh) is described. Elemental and thermogravimetric analyses confirmed a 1:1 metal:ligand ratio for the silver-isoniazid (Ag-inh) complex with molecular composition AgC6H7N3O·NO3. Infrared (IR) analysis suggests a bidentate coordination of isoniazid to silver by the nitrogen of the NH2 group and by the oxygen of the C=O group, and also confirms the presence of free nitrate anion. Coordination by the NH2 group was reinforced by NMR measurements. Computational simulations using the density functional theory (DFT) reinforced that the ligand coordinates to the silver atom by the NH2 and C=O groups. The silver complex presented a minimal inhibitory concentration (MIC90) of 0.78 µg/mL against the standard Mycobacterium tuberculosis strain H37Rv. The data reported herein warrants further investigation on Ag-inh complex as a potential agent against tuberculosis.

Resumo: As tensões residuais (TR) nas juntas soldadas do aço ASTM A131 AH36 foram analisadas pelo método DPC (deslocamento de pontos coordenados). A soldagem a arco foi realizada pelos processos eletrodo revestido (ER) e arame tubular (AT). As chapas de teste com dimensões de 200 mm x 65 mm e espessura 31,75 mm foram soldadas, segundo as normas (fabricação e qualificação) AWS D1.1 [1] e Petrobrás N-133 [2], respectivamente. Depois de soldadas foram realizados furos equidistantes com diâmetros de 2,00 mm por 2,00 mm de profundidade ao longo da zona termicamente afetada. Após a furação, tais furos foram referenciados em uma mesa de medição por coordenadas. Em seguida, as chapas de teste soldadas foram submetidas a um tratamento térmico para o alívio de tensões (TTAT) e, em seguida, foram medidos os deslocamentos dos furos causados pelo tratamento, o que possibilitou o cálculo das tensões residuais. Os resultados obtidos mostraram uma boa correlação do DPC com outros métodos de medições das TR.

Abstract: The residual stress (RS) in welded joints of ASTM A131 AH36 were analyzed by the method DPC (coordinated points displacement). The arc welding was performed using by Shielded Metal Arc Welding (SMAW) and Flux Cored Arc Welding (FCAW) processes. The test plates with dimensions of 200 mm x 65 mm and thickness of 31,75 mm were welded according to AWS D1.1 [1] and Petrobras N-133 [2] standards (manufacture and qualification), respectively. After welding, equidistant holes with diameters of 2.00 mm and depth of 2.00 mm were drilled along the heat affected zone. After drilling, the holes were referenced on a coordinate measuring table. Then, the welded test plates were subjected to Post Weld Heat Treatment (PWHT) and then the displacements of the holes caused by the treatment were measured, making possible the calculation of residual stresses. The results obtained showed a good correlation of the DPC with other methods of measurement for TR.