Acoustic anisotropy as a factor to determine residual stresses in GMAW and CW-GMAW welds

In the areas of construction and maintenance of welded implements, the acoustic anisotropy of the as received material exerts a great influence on the generated residual stresses levels. In this context, several measurements were taken in order to obtain the acoustic anisotropy, as well as the residual stresses values of welds in simple deposition performed via GMAW (Gas Metal Arc Welding) and CW-GMAW (Cold Wire-Gas Metal Arc Welding). The acoustic anisotropy of the present material, ASTM 131 steel, was determined before and after the welding process using an ultrasonic technique called acoustic birefringence. It was verified that the stress levels at the same point varied with four adopted anisotropy parameters (punctual, mean, maximum and minimum). The maximum stress difference (σE) obtained at the same point with the maximum and minimum anisotropy was about 38 MPa, and for the mean and punctual, the maximum stress was 21 MPa. It is assumed that the non-uniform distribution of acoustic anisotropy in the as received material has generated such stresses variation. The punctual or mean anisotropy of the as received material is the most recommended to be used in the stresses calculations, as the maximum stresses difference calculated by these values represented an only 6%, error, whereas the maximum and minimum anisotropy obtained an error of 11% in relation to the yield strength of the material.