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ASNE Day 2016 - Technical Paper Session 4 : Thursday, March 3, 2016 1100-1230

Additive Manufacturing


Authors: F. Abdi, F. Talagani, R. Miraj; A. Elwany, K. Nikbin

Title: Process Simulation for Metal-Based Additive Manufacturing



Summary- Additive manufacturing (AM) represents an alternative to traditional fabrication methodologies. In order to reduce lead time and improve quality, more and more commercial entities are considering the rapid prototyping and manufacture of critical time sensitive components using additive manufacturing. Selective Laser Melting (SLM) is an established technology that provides a means to additively construct metallic parts. Here, successive layers are created by selectively fusing metallic powder using a high-energy laser beam. SLM offers unique capabilities to produce physical objects with highly complex geometries. The SLM process is complex and involves many different physical phenomena such as absorption of the beam in the powder bed and the melt pool or the re-solidified melt, melting and re-solidification of a liquid pool, wetting of the powder particles with the liquid, diffusive and radiative heat conduction in the powders, diffusive and convective heat conduction in the melt pool, capillary effects, gravity, and others.

Problem- Metallic parts fabricated using current, conventional Directed Energy Deposition (DED) technologies are known to have: (i) high residual stresses, (ii) inconsistent density characterized by localized defects such as voids and inclusions and (iii) anisotropic microstructure due to complex thermal history and variable cooling rates. As a result, the mechanical behavior and thus the ‘trustworthiness’/durability, of engineering components fabricated via additive manufacturing processes are still not well understood.

Methodology- GENOA 3D printing software capability offers methodology for quantifying and certifying mechanical properties due to their anisotropic properties and variability in AM machines/processes: i) an automated finite element mesh generator; ii) ability to import from G-Code printer code file (from STL source); iii) Selective Laser Melting; iv) ability to re-simulate printing paths with width, angle and timing precision; v) resolution of solid element model from low to high fidelity; vi) preview or refined individual layers with an option to mesh and include bottom plate for additional heat transfer variables; vii) capability to export specific or all layers to multi-scale progressive failure analysis; viii) capability to generate an input deck compatible with commercial finite element codes such as ABAQUS and ANSYS and ix) capability to simulate coupled thermal structural analysis

Results- 3D printing process of Ti-6Al-4V component was simulated using MS-PFA: 1) to perform: 1) void initiation, growth, and surface roughness of the molten material cool down and determine the distorted shape of the material; 2) NDE test measurement of void and surface roughness compared with predictive results; 3) damage and fracture evolution and to determine the static stress strain curve of 3d printed material versus cast metal; 4) Fatigue of AS-Build material and prediction of crack growth versus cycle (a-N), and strength versus cycle (S-N) and considering the residual stress due to thermal distortion.

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