ACCELERATED CORROSION TEST FOR THE QUALITATIVE EVALUATION OF CORROSION IN CONCRETE

This paper is devoted to simulate the behavior of reinforced concrete in saline solution through the accelerated corrosion test. During this test, this method was evaluating the behavior of the steel bars that reinforce concrete for corrosion, according to the NACE 0775 standard. After the corrosion test, the steel bars were cleaned and dried according to the ASTM A380 standard and evaluated according to the NACE RP 0775, NACE SP0308, and NACE SP0187 standards. From the results obtained, the steel bars concrete showedhigh corrosion rates with structural impairment of the metal armor according to the NACE standards

Soldagem por fricção convencional entre a liga de alumínio 6351-T6 e o aço SAE 1020 assistida por indução eletromagnética

Exportado OPUSMade available in DSpace on 2019-08-11T03:38:06Z (GMT). No. of bitstreams: 1 disserta__o__soldagem_por_fric__o_convencional_entre_a_liga_de_alum_nio__6351_t6_e_o_a_o_sae_1020.pdf: 4268789 bytes, checksum: 9def2dc25b5f38047520faa60681fa8f (MD5) Previous issue date: 7A soldagem por fricção tem tomado um rumo muito interessante quanto às aplicações. O presente trabalho teve como objetivo avaliar o efeito do preaquecimento na soldagem de topo por fricção convencional entre a liga de alumínio AA 6351-T6 e o aço de baixo teor de carbono SAE 1020. Para o desenvolvimento do mesmo, uma furadeira de coluna foi adaptada e instrumentada para produzir as juntas dissimilares. As soldagens foram realizadas em duas condições: sem preaquecimento e com preaquecimento de 350°C induzido eletromagneticamente na interface aço-alumínio. A força de compressão e o torque durante a soldagem puderam ser monitorados através de uma célula de carga acoplada na mesa da furadeira. Os parâmetros de soldagem, com exceção do tempo de fricção, foram mantidos constantes para as duas condições, pois uma nova variável foi inserida ao processo, a temperatura de preaquecimento. A caracterização da interface de ligação foi realizada por microscópio óptico (MO) e microscópio eletrônico de varredura (MEV-EDX). A resistência mecânica da solda foi avaliada pelos ensaios de microdureza Vickers e tração. Os resultados obtidos mostraram que a utilização do preaquecimento diminui o tempo total de processo pela metade. A análise via MEV-EDX evidenciou que houve interdifusão entres os principais elementos presentes nos materiais envolvidos. Para as duas condições de soldagem, a ruptura dos corpos de prova ocorreu na interface de ligação. A temperatura registrada no aço para as soldas sem preaquecimento foi de 400°C e para as soldas com preaquecimento 418°C.Friction welding has become interesting in terms of its application. In this context, this paper aimed to evaluate the effect of preheating the conventional friction butt welding between the aluminum alloy AA 6351-T6 and low-carbon steel SAE 1020. For developing this work, an adapted and instrumented drill press was used to make dissimilar joints. The welding was done under two conditions: without preheating and with electromagnetically induced preheating to about 350°C, applied to the steel-aluminum interface. The compression stress and torque could be monitored during welding by using a load cell attached to the drill table. The welding parameters, with the exception of friction time, were kept constant for both conditions because a new variable was introduced to the process, namely the preheating temperature. The bonding interface characterisation was done using an optical microscopy (OM) and scanning electron microscopy (SEM-EDX). Vickers microhardness and traction testing were used to evaluate the welding mechanical strength. The results obtained shown that preheating application decreases the total time of the process by 50%. The SEM-EDX analysis showed that there was interdiffusion amid the main elements contained in the materials applied. For both welding conditions, the failure occurred on the bonding interface of the specimens. The temperature recorded in the steel for welds without preheating was 400°C and welds with preheating 418°C

Comparative Study About Mechanical Properties of Strutural Standard Concrete and Concrete with Addition of Vegetable Fibers

<div><p>This paper explored the effect of adding organic fibers from either bamboo or sugarcane on the mechanical properties of concrete. Cylindrical and prismatic specimens were made containing 2% and 5% v/w (volume to weight) of vegetable fibers to concrete. Following 28 days of curing period, the samples were evaluated for compressive strength, tensile strength using diametric compression, tensile strength during bending and static modulus. It was discovered that all concretes produced met the minimum strength of 20 MPa recommended by NBR 6118 for structural purposes, and it was observed an increase of the compressive strength on the specimens with addition of organic fibers. Moreover, an increase in the compressive strength was observed in the specimens with fiber addition, although no significant variation of water absorption was noticed when compared with the standard concrete. In conclusion, the concrete containing 2% v/w of bamboo fibers showed better mechanical strength and static modulus of elasticity when compared to both concrete with sugar cane fibers addition and the concrete without any additional fibers.</p></div