Correlação digital de imagens; gradientes de deformação; deformações elastoplásticas; zonas plásticas; entalhes; trincas.
RESUMOFoi desenvolvida uma nova técnica de medição de tensões residuais, baseada em técnicas de seccionamento, remoção de camadas e na técnica do furo-cego. Trata-se de uma técnica destrutiva, proposta para uso em medições de tensões geradas por processos de fabricação. A técnica consiste na colagem de sensores de deformação na peça, seguida da usinagem de cortes longos próximos dos sensores. Os cortes aliviam as tensões existentes no material retirado e provocam variações nas deformações existentes em suas vizinhanças. Tais variações de deformações são medidas por extensômetros de resistência elétrica (strain gages). Para a formulação matemática da técnica, os cortes foram tratados como elipses, o que permitiu o uso das equações de Inglis para descrever os campos de tensão em sua vizinhança. Para avaliar e validar o equacionamento foram realizadas medições com esta técnica em dois espécimes tubulares API 5L X60 e X46 UOE-SAW. Nas medições, foram avaliados parâmetros como profundidade e comprimento dos cortes, e distância dos cortes para os strain gages, buscando estabelecer um procedimento experimental consistente. Os resultados destas medições foram comparados aos de medições realizadas com a técnica do furo-cego, já normalizada e consolidada. Os resultados das comparações foram satisfatórios, sustentando a validade das hipóteses assumidas para a modelagem analítica e a qualidade do procedimento experimental estabelecido para a nova técnica.Palavras chaves: Tensões Residuais, Formulações de Inglis, Furo Elíptico. Development and experimental evaluation of a new technique for the measurement of residual tensions ABSTRACTIt was developed a new technique for residual stress measurement, based on sectioning techniques, removing layers and on the blind-hole technique. This is a destructive technique, proposed for use on measurements of stresses generated by manufacturing processes. The technique consists in bonding strain gages in the sample, followed by the machining of long cuts next to the sensors. The cuts relieve stresses in due to the material removed and cause variations in the strain distribution existing in their vicinity. These changes in the strain fields are measured by the strain gages. For the mathematical formulation of the technique, the cuts were treated as ellipses, which allowed the use of equations described by Inglis to stress fields in the vicinity of the cuts. To evaluate and validate the equations and the proposed methodology experimental tests were applied to two tubular specimens made of steel pipes API 5L X60 and X46 UOE-SAW. Seeking to establish a consistent experimental procedure, the measurement results helped to analyze the influence of process variables such as the depth and the length of the cuts, distance of the cuts from the strain gages. Measurement results were compared against results determined with the application of the blind-hole technique, which is an already normalized and consolidated experimental technique to measure residual stresses. The results of the comparisons wer...
In this paper, it is proposed and experimentally investigated a sensor structure based on a core diameter mismatch technique for strain sensing. An uncoated short section of multimode fiber is spliced between two standard single mode fibers forming the sensor structure, called the SMS (single‐mode‐multimode‐single‐mode) sensor. The proposed SMS sensor, in the strain analysis, generates destructive or constructive interference patterns as load or strain are applied, changing the power of the optical signal only, without varying the wavelength. The sensor configuration offers several motivating attributes, such as easy fabrication, low‐cost, high‐efficiency and high sensitivity, moreover allows interrogation of the optical signal using the transmitted or reflected total optical power. The results and these advantages indicate that the proposed SMS sensor device is suitable for strain measurement, which is helpful in a broad range of applications, for instance, structural health monitoring.
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