Chong Teng

An Efficient Multi-Scale Simulation Architecture for the Prediction of Performance Metrics of Parts Fabricated Using Additive Manufacturing

In this study, an overview of the computational tools developed in the area of metal-based additively manufactured (AM) to simulate the performance metrics along with their experimental validations will be presented. The performance metrics of the AM fabricated parts such as the inter- and intra-layer strengths could be characterized in terms of the melt pool dimensions, solidification times, cooling rates, granular microstructure, and phase morphologies along with defect distributions which are a function of the energy source, scan pattern(s), and the material(s). The four major areas of AM simulation included in this study are thermo-mechanical constitutive relationships during fabrication and in-service, the use of Euler angles for gaging static and dynamic strengths, the use of algorithms involving intelligent use of matrix algebra and homogenization extracting the spatiotemporal nature of these processes, a fast GPU architecture, and specific challenges targeted toward attaining a faster than real-time simulation efficiency and accuracy.

The effects of material property assumptions on predicted meltpool shape for laser powder bed fusion based additive manufacturing

The objective of this study was to provide guidance on material specifications for powders used in laser powder bed fusion based additive manufacturing (AM) processes. The methodology was to investigate how different material property assumptions in a simulation affect meltpool prediction and by corrolary how different material properties affect meltpool formation in AM processes. The sensitvity of meltpool variations to each material property can be used as a guide to help drive future research and to help prioritize material specifications in requirements documents. By identifying which material properties have the greatest affect on outcomes, metrology can be tailored to focus on those properties which matter most; thus reducing costs by eliminating unnecessary testing and property charaterizations. Futhermore, this sensitivity study provides insight into which properties require more accurate measurements, thus motivating development of new metrology methods to measure those properties accurately.

A study of transverse laser modes using a novel multi-scale simulation architecture for laser-based manufacturing technologies

The present work presents an investigation of transverse laser modes in Selective Laser Melting (SLM). It includes detailed descriptions of process physics and various simulation tools that were developed at 3DSIM for SLM simulation. The SLM process depends on a focused laser directed towards a powder bed to selectively melt and solidify layers of powder to create a complex three dimensional geometry. The thermo-mechanical interaction of laser, powder bed and partially solidified part involves various nonlinear phenomena leading to final part microstructure, mechanical properties and geometrical accuracy. One important aspect of these interactions is the laser beam profile. Traditionally, Gaussian laser profiles with 00 transverse modes are used for SLM, since these are the only modes readily available for commercial purposes. The present work utilizes the SLM simulation tools at 3DSIM to study the potential for the use of transverse mode lasers for SLM. The interaction of transverse laser modes with characteristic thermal Eigenmodes of a typical powder bed has been modeled to further understand the effects of higher order laser modes on SLM performance.

Influence of small particles inclusion on selective laser melting of Ti-6Al-4V powder

The particle size distribution and powder morphology of metallic powders have an important effect on powder bed fusion based additive manufacturing processes, such as selective laser melting (SLM). The process development and parameter optimization require a fundamental understanding of the influence of powder on SLM. This study introduces a pre-alloyed titanium alloy Ti-6Al-4V powder, which has a certain amount of small particles, for SLM. The influence of small particle inclusion is investigated through microscopy of surface topography, elemental and microstructural analysis, and mechanical testing, compared to the Ti-6Al-4V powder provided by SLM machine vendor. It is found that the small particles inclusion in Ti-6Al-4V powder has a noticeable effect on extra laser energy absorption, which may develop imperfections and deteriorate the SLM fatigue performance.