Non-fickian three-dimensional hindered moisture absorption in polymeric composites: Model development and validation

2013 ◽  
Vol 34 (7) ◽  
pp. 1144-1157 ◽  
Author(s):  
L.R. Grace ◽  
M.C. Altan
Keyword(s):  
Moisture Absorption ◽  
Model Development ◽  
Three Dimensional ◽  
Polymeric Composites ◽  
Development And Validation

Residual Stress in Additive Manufactured Nickel Alloy 625 Parts

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Lindsey Bass ◽  
Justin Milner ◽  
Thomas Gnäupel-Herold ◽  
Shawn Moylan
Keyword(s):  
Residual Stress ◽  
Stress State ◽  
Nickel Alloy ◽  
Model Development ◽  
Three Dimensional ◽  
Powder Layer ◽  
Layer By Layer ◽  
Negative Effects ◽  
Alloy 625 ◽  
Development And Validation

One of the key barriers to widespread adoption of additive manufacturing (AM) for metal parts is the build-up of residual stresses. In the laser-based powder bed fusion process, a laser selectively fuses metal powder layer by layer, generating significant temperature gradients that cause residual stress within the part. This can lead to parts exceeding tolerances and experiencing severe deformations. In order to develop strategies to reduce the adverse effects of these stresses, the stresses first need to be quantified. Cylindrical Nickel Alloy 625 samples were designed with varied outer diameters, inner diameters, and heights. Neutron diffraction was used to characterize the three-dimensional (3D) stress state throughout the parts. The stress state of the parts was generally comprised of tensile exteriors and compressive interiors. Regardless of part height, only the topmost scan height of each part experienced large reductions in axial and hoop stress. Improved understanding of the residual stress trends will aid in model development and validation leading to techniques to reduce negative effects of the residual stress.

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