Complementary Measurements of Residual Stresses Before and After Base Plate Removal in an Intricate Additively-Manufactured Stainless-Steel Valve Housing

Abstract

Residual stress measurements using neutron diffraction and the contour method were performed on a valve housing made from 316L stainless steel powder with intricate three-dimensional internal features using laser powder-bed fusion additive manufacturing. The measurements captured the evolution of the residual stress fields from a state where the valve housing was attached to the base plate to a state where the housing was cut free from the base plate. Making use of this cut, thus making it a nondestructive measurement in this application, the contour method mapped the residual stress component normal to the cut plane (this stress field is completely relieved by cutting) over the whole cut plane, as well as the change in all stresses in the entire housing due to the cut. The non-destructive nature of the neutron diffraction measurements enabled measurements of residual stress at various points in the build prior to cutting and again after cutting. Good agreement was observed between the two measurement techniques, which showed large, tensile build-direction residual stresses in the outer regions of the housing. The contour results showed large changes in multiple stress components upon removal of the build from the base plate in two distinct regions: near the plane where the build was cut free from the base plate and near the internal features that act as stress concentrators. These observations should be useful in understanding the driving mechanisms for builds cracking near the base plate and to identify regions of concern for structural integrity. Neutron diffraction measurements were also used to show the shear stresses near the base plate were significantly lower than normal stresses, an important assumption for the contour method because of the asymmetric cut.

Residual stress evaluation in innovative layer-level continuous functionally graded materials produced by Powder Bed Fusion-Laser Beam

“…In addition, it has been reported in [50][51][52] that for parallelepiped-shaped specimens residual stress relaxation subsequent to detachment is more pronounced in the longitudinal direction, while the stress component in transverse direction is minimally impacted and remains present even at high values. Furthermore, Clausen et al in [53] stated that for samples without internal features, residual stress changes due to build platform removal decrease monotonically with increasing distance from the cut surface, in accordance with the St. Venant's principle [54].…”

Residual stress and distortion in thick-plate weld joint of AF1410 steel: finite element simulations and experimental studies

“…As a new way developed in recent years to measure residual stress through destruction, the contour method was first proposed by Prime [17]. Clausen et al [18] used the neutron diffraction and contour method to measure the residual stress of a valve housing made from 316 L stainless steel powder. Sun et al [19] investigated the residual stress in stationary shoulder friction stir welded plate by neutron diffraction and contour method.…”