Integration of tube end forming in wire arc additive manufacturing: An experimental and numerical investigation

Abstract

Integration of tube end forming operations in metal additive manufacturing routes has a great potential for the fabrication of customized features in additively deposited hollow parts. This paper is focused on the integration of tube expansion with rigid tapered conical mandrels to highlight the advantages in the construction of overhanging flares derived from the elimination of support structures and prevention of humping. The work draws from the mechanical and formability characterization of stainless steel AISI 316L tubes produced by wire arc additive manufacturing (WAAM) to the experimental and numerical simulation of the construction of overhanging flares by tube expansion. Strain loading paths obtained from digital image correlation and finite element analysis combined with the strain values at the onset of necking and fracture allow determining the critical ductile damage that additively deposited tubes can safely withstand. Results show that despite formability of additively deposited tubes being influenced by a dendritic based microstructure, their performance is adequate for tube end forming operations, such as tube expansion, to be successfully integrated in metal additive manufacturing without the need of using expensive hardware and complex deposition strategies.

Description of anisotropic material response of wire and arc additively manufactured thin-walled stainless steel elements

“…In contrast to conventionally-produced structural steel and stainless steel, which generally behave isotropically (i.e. the mechanical properties are independent of orientation at any given point in the material), anisotropy in additively manufactured metals can be significant [28,29,30,31,32].…”

Hybrid Manufacturing of Stiffening Grooves in Additive Deposited Thin Parts

“…By determining the critical meridional strain ε crit φ under plane strain deformation conditions through the intersection of the FFL with the vertical axis of Figure 4, and subsequently obtaining the critical meridional stress σ crit φ by replacement of the average values by the critical values in Equation (10), and identifying the minimum thickness t min under the limiting material formability conditions of…”

“…The need for additional reinforcements is not exclusive to large panels because there are other thin metal parts of smaller dimensions that have bends in more than one plane which also need to be strengthened in order to withstand the efforts that are applied to them in service. This is particularly important in the case of lightweight additive manufactured parts, which require the use of support structures whenever complex out-ofplane-shaped features are to be included to preserve the overall geometric integrity of the parts, and prevent the occurrence of defects and failures, such as deformations, dross formation or warpage [10]. In such cases, it makes sense to investigate the possibility of implementing a new hybrid metal additive manufacturing approach [11] that combines additive manufacturing and in-plane stretching by SPIF to produce local, customized, stiff- Direct manufacture of stringers through additive manufacturing has recently been proposed for the self-reinforcement of aircraft fuselage panels [5].…”

In Situ Ultrasonic Testing for Wire Arc Additive Manufacturing Applications

“…However, there are some downsides to this technology that affect the quality of WAAM parts, limiting their ability to satisfy standard industrial requirements [3,4]. The most noticeable downsides concern the rough surface quality and low geometric precision of WAAM parts, which can usually be circumvented by employing fine machining operations in postprocessing steps [5].…”