This research centers on the mechanical characterization of SS316L parts printed in 3D using laser powder bed fusion (LPBF) via selective laser melting, to estimate Poisson’s ratio via an ultrasound technique. This study aims to extend the application of ultrasonic waves to measure residual stresses in printed metallic specimens.
Density measurements and time-of-flight measurements of longitudinal and transverse waves along the specimen’s build direction were conducted on the printed parts to assess variations in Poisson’s ratio under non-heat-treated and heat-treated conditions.
The results show the influence of mass density, porosity, printing parameters and layer orientation on the values of Poisson’s ratio, and variations due to thermal treatment. Finally, a method for estimating the residual stresses in LPBF 3D-printed parts along the three principal layer orientations is proposed, and results are compared against X-ray diffraction (XRD) preliminary-based measurements, showing von Mises stress results within +20% to −14% relative error range, particularly along the z-build direction.
Residual stress estimation by ultrasound could only be resolved within acceptable values along the build orientation under the assumption of a plane stress condition.
Ultrasound measurement is a versatile nondestructive testing technique that allows for the accurate determination of mechanical properties such as Poisson′s ratio, which in turn can be used to estimate the average residual stress in an object along its thickness with almost zero modification of its material and geometrical integrity and whose accuracy will be determined by the resolution of the time of flight of the waves used, ideally in the nanosecond range.
Promoting the introduction of new, safe and functional products made by additive manufacturing into emerging world markets positively impacts our society and is enhanced by the utilization of nondestructive, fast and safe testing techniques, such as ultrasound, to determine the materials and mechanical integrity, such as residual stresses, of the current and future printed products.
A method for estimating the residual stresses in LPBF-printed parts along the three principal layer orientations is proposed and results are compared against XRD preliminary-based measurements, showing close results, particularly along the z-build direction.
