Trabalho de Conclusão de Curso de Graduação
Medição de tensões residuais em juntas soldadas pelo processo de soldagem a arco elétrico com atmosfera gasosa (GMAW) utilizando ondas longitudinais criticamente refratadas (ondas LCR)
Fecha
2019-12-13Autor
Gryzbowski, Igor Felipe
Institución
Resumen
Welding is a manufacturing process widely used in industry to join metal parts permanently.
However, the welding process may induce residual stresses, affecting the mechanical
performance of the component negatively. Residual stresses are generated intrinsically by
fabrication processes and it is very important to know the residual stress state since it can
directly contribute to the reduction of the component life. Destructive and non-destructive
tests are performed to quantify such stresses. Nevertheless, destructive approaches, unlike
non-destructive ones, don’t enable the components to be used after the test and consequently
are not applied in many cases, such as railway wheels, pumps, nuclear equipment and oil
pipelines. Among non-destructive methods is the ultrasonic stress measuring method using
critically refracted longitudinal waves (LCR waves). This type of wave propagates slightly
below the surface of the material and the time it takes for the wave to travel through it is
influenced by the presence of stresses in the medium. Thus, knowing the variation in time of
flight (TOF) of the wave, it is possible to determine the stress difference through the
acoustoelastic theory, which studies the change in the propagation velocity of ultrasonic
waves due to the presence of stress in a specific material. In this paper, specimens of plain
carbon steel ASTM A36, very used in structural components, were tested. All samples have
weld beads generated using different welding voltages, wire feed speeds and welding speeds
and produced by the gas metal arc welding (GMAW) process. The experimental results show
residual stress profiles as a function of the transverse distance to the weld bead in accordance
with the literature, contributing to increase the reliability of the method. In addition, it was
concluded that the welding parameters analyzed have a significant influence on the maximum
residual stress generated in the welded joint. This influence was quantified, enabling the
appropriate selection of welding parameters in order to attenuate the residual stresses
generated in the process.