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

添加制造(AM)包括通过添加一层又一层材料来构建3D对象。纳米/微米颗粒的烧结是许多AM工艺的关键步骤之一。这一步骤往往会导致AM零件的形状变形，使其无法实现近净成形。这项学术与工业联系机会(GOALI)奖支持了一项综合的实验和理论研究，以充分了解AM中形状变形的控制机制这样的理解将能够识别关键的AM工艺参数，以便在不需要时消除失真，或者控制失真以实现4D打印的新方法。该项目的成果有可能降低AM部件的成本，对航空、汽车和核工业产生积极影响。这项工作带来的精密制造将有助于建立美国在工业4.0领域的领导地位。随着AM在航空航天工业中被用于制造大型部件(如飞机机翼)，该项目的研究成果将成为其制造的关键推动因素。近净形状AM将消除后处理，从而减少温室气体排放。该项目将涉及与来自贫困学校的K-12学生合作，让他们接触以STEM为基础的职业。该项目将通过开发跨学科课程，在先进制造、计算科学和纳米材料等跨学科领域培训不同的美国劳动力。该项目侧重于确定质量传输机制(S)及其对烧结型AM工艺中形状变形的相对贡献。初步研究表明，在烧结过程中的部分变形过程中，必须进行长程传质。该研究的实验部分将包括纳米和/或微米颗粒的三维结构的制造，在聚焦离子束(FIB)切割的切片中观察颗粒团簇在烧结过程中运动的操作显微镜，以及广泛的烧结后的非原位观察。紧密耦合的建模工作将涉及发展一个中尺度相场模型，以发现非均匀烧结中长程质量传输的物理机制。此外，还将开发一个宏观连续模型，该模型能够模拟全尺寸零件，并预测工业相关配置的形状变形和/或残余应力。将开发一个预测模型，以量化参数，如颗粒大小(S)、粘结剂含量、约束和温度梯度对零件变形的影响。这项研究将建立和实验验证设计指南，以最大限度地减少AM零件在烧结过程中的变形。最后，非均匀烧结将被作为一种实现可控失真的全新技术引入，即4D打印。该奖项反映了NSF的法定使命，并已通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.