Non-dimensional process maps for residual stress in laser directed energy deposition

Chaitanya Vundru, Ramesh Singh, Wenyi Yan, Shyamprasad Karagadde

Research output: Chapter in Book/Report/Conference proceedingConference PaperOther

Abstract

The nature of the residual stress and substrate melting produced by laser directed energy deposition (DED) affects the quality and reliability of the additively manufactured part. The residual stresses are induced because of temperature gradients, differences in thermal expansion coefficients and the elastoplastic behavior of the deposit / substrate material. In addition, the high cooling rate in DED can lead to additional strains, such as transformation induced plasticity and volumetric dilatation. If tensile residual stress is induced in the deposited layer, it may compromise the service life due to accelerated fatigue. The residual stress evolution depends on the process parameters and selection of right process window can yield favorable residual stresses. A validated metallo-thermomechanical finite element model for directed energy deposition is used to predict the temperature distribution and residual stress for different process conditions. The model predictions at different process conditions have been used to develop a non-dimensional empirical relationship between the residual stress and the process parameters via a nonlinear regression analysis. Isopleth of residual stress free (~0 stress) state at the deposition-substrate interface is employed to divide the process parameter subspace into two distinct domains: a detrimental tensile zone and a desirable compressive zone. It may also be noted that in order to form a sound metallurgical bond a minimal dilution (DDmmiinn) is required which can ensure that the entire deposition melts with minimal substrate melting. Isopleth of normalized dilution of unity (DD/DDmmiinn = 1) can produce sound metallurgical bond between the deposited layer and substrate. These two isopleths in combination are crucial in identifying favorable and unfavorable domains. Such novel process maps serve as a theoretical framework in the choice of suitable process parameters to ensure the quality and integrity of the deposition.

Original languageEnglish
Title of host publication48th SME North American Manufacturing Research Conference
PublisherElsevier
Pages697-705
Number of pages9
Volume48
DOIs
Publication statusPublished - 2020
EventSME North American Manufacturing Research Conference 2020 - Cincinnati, United States of America
Duration: 22 Jun 202026 Jun 2020
Conference number: 48th

Publication series

NameProcedia Manufacturing
PublisherElsevier
Volume48
ISSN (Print)2351-9789

Conference

ConferenceSME North American Manufacturing Research Conference 2020
Abbreviated titleNAMRC 2020
CountryUnited States of America
CityCincinnati
Period22/06/2026/06/20

Keywords

  • Dilution
  • Laser directed energy deposition
  • Metallo-thermomechanical finite element model
  • Non-dimensional parameters
  • Process maps
  • Residual stress

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