GOALI: Understanding the Physical Mechanisms of Distortion and Controlling its Effects in Sintering-based Additive Manufacturing Processes

Carnegie Mellon University, Pittsburgh PA

Investigators

Abstract

Additive Manufacturing (AM) involves building of 3D objects by adding layer upon layer of material. Sintering of nano/microparticles is one of the critical steps in many AM processes. This step often leads to shape distortion of AM parts, preventing their near-net-shape manufacture. This Grant Opportunities for Academic Liaison with Industry (GOALI) award supports an integrated experimental and theoretical research to fully understand the mechanisms controlling shape distortion in AM. Such understanding will enable identification of critical AM process parameters to either eliminate distortions when undesirable, or to control distortions to enable novel methods of 4D printing. The outcomes of this project have the potential to reduce cost of AM parts, positively impacting aviation, automotive, and nuclear industries. The precision manufacturing enabled by this work will help establish American leadership in Industry 4.0. As AM is adopted in aerospace industry for fabrication of large parts (e.g., aircraft wings), research outcomes from the project will be key enablers for their fabrication. Near-net-shape AM will eliminate post-processing, leading to a reduction in greenhouse gas emissions. The project will involve collaboration with K-12 students from disadvantaged schools to expose them to STEM-based careers. The project will train a diverse US workforce in the interdisciplinary areas of advanced manufacturing, computational sciences, and nanomaterials through the development of interdisciplinary curricula. This project focuses on identifying the mass transport mechanism(s) and their relative contributions to shape distortion in sintering-based AM processes. The preliminary studies have demonstrated that a long-range mass transport must be operational during part distortion in sintering. The experimental portion of the research will consist of fabrication of 3-D structures of nano and/or microparticles, operando microscopy to observe movement of particle clusters in Focused Ion Beam (FIB)-cut sections during sintering, and extensive ex-situ observations post sintering. A closely coupled modeling effort will involve the development of a mesoscale phase-field model to discover the physical mechanisms of long-range mass transport in non-homogeneous sintering. In addition, a macroscale continuum model will be developed that has capabilities to simulate full scale parts and predict shape distortion and/or residual stresses for industrially relevant configurations. A predictive model will be developed to quantify the effect of parameters such as particle size(s), binder content, constraints, and temperature gradients on part distortion. The research will establish and experimentally validate design guidelines to minimize distortion during sintering of AM parts. Lastly, inhomogeneous sintering will be introduced as a completely new technique to achieve controlled distortion, i.e., 4D printing. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.