A computational phase transformation model for selective laser melting processes

AbstractSelective laser melting (SLM) has gained large interest due to advanced manufacturing possibilities. However, the growing potential also necessitates reliable predictions of structures in particular regarding their long-term behaviour. The constitutive and structural response is thereby challenging to reproduce, due to the complex material behaviour. This motivates the aims of this contribution: To establish a material model that accounts for the behaviour of the different phases occurring during SLM but that still allows the use of (basic) process simulations. In particular, the present modelling framework explicitly takes into account the mass fractions of the different phases, their mass densities, and specific inelastic strain contributions. The thermomechanically fully coupled framework is implemented into the software Abaqus. The numerical examples emphasise the capabilities of the framework to predict, e.g., the residual stresses occurring in the final part. Furthermore, a postprocessing of averaged inelastic strains is presented yielding a micromechanics-based motivation for inherent strains.

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A thermomechanical modelling framework for selective laser melting based on phase transformations

PAMM ◽

10.1002/pamm.201900059 ◽

2019 ◽

Vol 19 (1) ◽

Author(s):

Isabelle Guschke ◽

Thorsten Bartel ◽

Andreas Menzel

Keyword(s):

Phase Transformations ◽

Selective Laser Melting ◽

Laser Melting ◽

Modelling Framework

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Simplified Inelastic Time Independent (SITI) Method for Predicting Creep

Volume 3: Design and Analysis ◽

10.1115/pvp2007-26060 ◽

2007 ◽

Author(s):

Jeries J. Abou-Hanna ◽

Osama Ali ◽

Venkata Tatikonda ◽

Timothy E. McGreevy

Keyword(s):

Creep Behavior ◽

Inelastic Strain ◽

Material Model ◽

Time Dependent ◽

Computationally Efficient ◽

Element Analysis ◽

State Variable ◽

Creep Analysis ◽

Inelastic Strains ◽

Very High

In an effort to address inelastic creep behavior for very high temperature (VHT) applications, a unified state variable material model was used in a time dependent finite element analysis to generate isochronous curves. The resulting isochronous curves were then used in an efficient time-independent plastic analysis to predict the creep behavior of components. This simplified inelastic time-independent (SITI) method can significantly reduce the geometric and load uncertainties, and the over-conservatism in predicting inelastic strain levels. SITI is an effective and computationally efficient approach for predicting inelastic strains of components operating at high and very high temperatures such as the case in the Next Generation Nuclear Plant. This work compares the SITI inelastic strains to those obtained using fully inelastic time-dependent elastic-plastic-creep analysis, and illustrates the effectiveness of the approach in obtaining creep strain predictions without elaborate full inelastic time-dependent simulation.

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