Introduction: 

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Residual stresses are an unavoidable consequence of additive manufacturing (AM) of metallic parts due to the inherent thermo-mechanical effects. The unpredictable nature of these processes makes it difficult to fully understand the magnitude and distribution of these stresses. This study addresses the challenge by utilising a voxel-based eigenstrain reconstruction method.

 

Voxel-based Eigenstrain Reconstruction: 

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The voxel-based eigenstrain method enables full-field reconstruction of residual stresses in discontinuous processing bodies. It operates without the need for simplifying assumptions or regularisation functions, providing detailed mapping at a resolution dictated by the quality of experimental data. The method calculates residual stresses, elastic strains, and displacements through a cost-effective linear elastic computational framework.

 

Experimental Method: Height Digital Image Correlation (hDIC): 

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To capture high-quality experimental data, the height Digital Image Correlation (hDIC) technique was employed. This method measures triaxial displacements corresponding to the elastic response of a CM 247 LC powder bed fusion (PBF) AM part after detachment from its base. Optical profilometry was used at an optimised resolution to reconstruct Type I residual stresses.

 

Results and Validation: 

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The hDIC-calculated displacements were used to map the eigenstrain components, leading to the reconstruction of residual stresses, elastic strains, and displacements both before and after detachment from the base. To ensure accuracy, the results were validated using synchrotron X-ray diffraction measurements, confirming the reliability of the reconstruction process.

 

Conclusion: 

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This study demonstrates the effectiveness of voxel-based eigenstrain reconstruction in mapping complex residual stress fields in AM parts, without relying on regularisation assumptions. The use of hDIC and synchrotron X-ray beams enhances the precision and reliability of this method, offering a robust approach for understanding and managing residual stresses in additive manufacturing.