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On the determination of residual stresses in additively manufactured lattice structures
Author(s) -
Fritsch Tobias,
Sprengel Maximilian,
Evans Alexander,
Farahbod-Sternahl Lena,
Saliwan-Neumann Romeo,
Hofmann Michael,
Bruno Giovanni
Publication year - 2021
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s1600576720015344
Subject(s) - residual stress , neutron diffraction , materials science , lattice (music) , residual , diffraction , hydrostatic stress , stress field , hydrostatic equilibrium , cauchy stress tensor , structural engineering , composite material , optics , finite element method , mathematics , physics , classical mechanics , engineering , algorithm , quantum mechanics , acoustics
The determination of residual stresses becomes more complicated with increasing complexity of the structures investigated. Additive manufacturing techniques generally allow the production of `lattice structures' without any additional manufacturing step. These lattice structures consist of thin struts and are thus susceptible to internal stress‐induced distortion and even cracks. In most cases, internal stresses remain locked in the structures as residual stress. The determination of the residual stress in lattice structures through nondestructive neutron diffraction is described in this work. It is shown how two difficulties can be overcome: ( a ) the correct alignment of the lattice structures within the neutron beam and ( b ) the correct determination of the residual stress field in a representative part of the structure. The magnitude and the direction of residual stress are discussed. The residual stress in the strut was found to be uniaxial and to follow the orientation of the strut, while the residual stress in the knots was more hydrostatic. Additionally, it is shown that strain measurements in at least seven independent directions are necessary for the estimation of the principal stress directions. The measurement directions should be chosen according to the sample geometry and an informed choice on the possible strain field. If the most prominent direction is not measured, the error in the calculated stress magnitude increases considerably.