Monday  |  Lakeshore C  |  11:00 AM–11:20 AM

#19684, Influence of Mechanical Restraint and Thermal History on Triaxial Residual Stress in AM Right Isosceles Prisms

Additively manufactured right isosceles triangular prisms are built via laser-based powder bed fusion from 316L stainless steel powder with distinct mechanical restraints and thermal histories to study their influence on bulk triaxial residual stress. Residual stress is determined using diverse measurements and data are compared to thermomechanical model predictions. Two samples are constructed with right leg lengths of 19.5 mm and out-of-plane thickness of 25.4 mm. A first sample is built with one 19.5 mm by 25.4 mm plane at the build plate (no support structure) and a second sample is built with that plane in the final build layer (requiring a lattice support structure along the 27.6 mm isosceles hypotenuse). Bulk triaxial residual stress measurements are conducted through a combination of techniques. The contour method is used to assess normal residual stress at the mid-thickness plane and synchrotron X-ray diffraction measurements to assess in-plane stress components in a removed thin triangular plate; then these data were combined to determine the triaxial residual stress near the prism mid-thickness. Residual stress estimates are obtained from a thermomechanical model that considers powder solidification and thermo-elasto-plastic behavior of the material. High tensile stresses (500 MPa) are found along the specimen free surfaces, balanced by compressive stresses (around -200 MPa) in the sample interiors. Relatively low magnitudes of in-plane shear stress are observed (less than 150 MPa). By adopting a geometry dependent cartesian coordinate system, rather than build direction dependent coordinate system, the samples are found to have similar in-plane residual stress states (differences < 100 MPa). The lack of build direction dependence is noteworthy in the measurements but more pronounced in the model results.

Nicholas Bachus   University of California, Davis
Levente Balogh   Queen's University
Bjorn Clausen   Los Alamos National Laboratory
Christopher D'Elia   University of California, Davis
Michael Hill   University of California, Davis
Lucas Ravkov   Queen's University
Donald Brown   Los Alamos National Laboratory