Abstract
Selective laser melting (SLM) is a direct fabrication process that uses moving heat source for obtaining a 3D object from a digital design data. In the process, a steep temperature gradient develops due to localized heating causing differential expansion and contraction at different locations. Thus, stresses are generated, which remain in the material as residual stresses and affect the functionality of the part. This study presents an analysis of stresses developed in the SLM process. A thermo-mechanical model is developed for the prediction of residual stresses during processing of Ti-6Al-4V powder layer. The thermal model, considering Marangoni and natural convection in the melt pool, is used to deduce the temperature field, which is coupled with the mechanical model. Using the temperature field, an analysis is performed for the stresses developed due to solidification of the melt pool formed on the Ti-6Al-4V powder layer. The nature of the stresses during heating and cooling stages is studied. Stresses formed during melting in the vicinity of the melt pool region are compressive. During cooling, the stresses change their nature to tensile in the solidified melt pool region. These tensile stresses remain locked in the component as residual stresses even after cooling down period.
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Abbreviations
- \( C_{\text{p}} \) :
-
Specific heat capacity (J kg−1 K−1)
- K :
-
Thermal conductivity of the material (W m−1 K−1)
- L :
-
Latent heat of the fusion (J kg−1)
- \( p \) :
-
Pressure (Pa)
- \( T \) :
-
Temperature (K)
- \( \vec{u} \) :
-
Continuum velocity vector (m s−1)
- \( \phi \) :
-
Porosity of the powder material
- \( \rho \) :
-
Density of the material (kg m−3)
- \( \beta_{\text{T}} \) :
-
Coefficient of thermal expansion (K−1)
- \( \alpha_{\text{m}} \) :
-
Mass fraction
- \( \beta \) :
-
Volume fraction of liquid phase
- \( \mu \) :
-
Dynamic viscosity (kg m−1 s−1)
- \( \sigma_{ij} \) :
-
Stress tensor
- \( \upvarepsilon_{ij } \) :
-
Total strain tensor
- s:
-
Bulk solid
- p:
-
Powder
- solidus:
-
Solidus temperature
- liquidus:
-
Liquidus temperature
- ref:
-
Reference
- el:
-
Elastic
- th:
-
Thermal
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Sharma, R., Saxena, S., Kumar, A. (2019). Thermal Stress Analysis in Selective Laser Melting of Ti6Al4V Powder Layer. In: Dixit, U., Joshi, S., Davim, J. (eds) Application of Lasers in Manufacturing. Lecture Notes on Multidisciplinary Industrial Engineering. Springer, Singapore. https://doi.org/10.1007/978-981-13-0556-6_5
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DOI: https://doi.org/10.1007/978-981-13-0556-6_5
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