Collaborative Research: Modeling Material Microstructure Evolution and Fatigue Life of High Strength Metal Components Produced by Laser Melting Additive Process

合作研究：模拟激光熔化增材工艺生产的高强度金属部件的材料微观结构演变和疲劳寿命

• 批准号: 1563002
• 负责人: Jing Shi
• 金额: $ 14.99万
• 依托单位: University of Cincinnati Main Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-04-01 至 2020-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1563002&HistoricalAwards=false
• 关键词: Collaborative; Research; Modeling; Material; Microstructure

Additive manufacturing can enable industry to produce on-demand parts at a remote site, in space, or in a battlefield, with minimal inventory, delivery time, and tooling cost. It can also enable researchers to explore new material compositions leading to customized novel properties. To ensure quality of components in laser melting (one of the additive manufacturing processes) and reduce the lead time, it is critical to be able to evaluate material microstructure changes in response to the dynamic high thermal gradient in the process, and the strength of constructed materials under static and dynamic loads after the process. This award supports fundamental research to enable modeling and simulation methods that allow for realistic predictions, process design and optimization, and equipment design of laser melting additive process. The obtained knowledge provides the foundation for researchers and manufacturers to engineer new materials in small lot size at low cost by using laser melting additive process. It can also contribute to understanding the behavior of a broad range of materials in laser melting. Research results will enhance current engineering courses, and provide cross-disciplinary training opportunities for graduate students. The research objectives are to: (1) acquire knowledge on the mechanism of non-equilibrium solidification in laser melting, (2) determine the effects of non-uniform cyclic thermal history due to multilayer construction on microstructure changes, and (3) establish the relationship between the microstructure resulted from laser melting and the material performances. To achieve the first objective, a thermo-mechanical finite element analysis will be constructed to simulate the material addition process of laser melting, a phase-field approach will be created to calculate the time-dependent growth of alloy phase field based on the computed thermal history, and single-pass and multilayer laser melting experiments will be conducted on a medium carbon steel. The correlation between high thermal gradients from computation and the solute trapping phenomenon from experimental observation will be made to reveal the non-equilibrium solidification mechanism. To achieve the second objective, the microstructure evolutions under both single pass and multilayer laser melting processes are compared using the phase field approach, and verified by experiments. Microstructure variations in terms of grain size, phase composition and distribution will be obtained, resulting from different thermal histories of material points. To achieve the third objective, the analytical models for estimating strengths will be established based on the obtained material microstructure, and the fatigue crack initiation life will be estimated based on the minimum energy principle applied when a crack is created along the weakest material point and path.

增材制造可以使工业界能够在远程站点、太空或战场上生产按需零件，并以最少的库存、交付时间和工具成本。它还可以使研究人员探索新材料成分，从而获得定制的新颖特性。为了确保激光熔化（增材制造工艺之一）中部件的质量并减少交货时间，至关重要的是能够评估响应工艺中动态高热梯度的材料微观结构变化以及构造的强度加工后材料在静态和动态载荷下。该奖项支持基础研究，以实现建模和模拟方法，从而实现激光熔化增材工艺的现实预测、工艺设计和优化以及设备设计。所获得的知识为研究人员和制造商利用激光熔化增材工艺以低成本设计小批量新材料奠定了基础。它还有助于了解多种材料在激光熔化中的行为。研究成果将增强现有的工程课程，并为研究生提供跨学科的培训机会。研究目标是：(1) 获取有关激光熔化中非平衡凝固机制的知识，(2) 确定多层结构导致的不均匀循环热史对微观结构变化的影响，以及 (3) 建立激光熔化产生的微观结构与材料性能之间的关系。为了实现第一个目标，将构建热机械有限元分析来模拟激光熔化的材料添加过程，将创建相场方法来计算基于计算的热合金相场随时间的增长。历史，并将在中碳钢上进行单道次和多层激光熔化实验。将计算得出的高热梯度与实验观察到的溶质捕获现象之间的相关性，以揭示非平衡凝固机制。为了实现第二个目标，使用相场方法比较了单道和多层激光熔化工艺下的微观结构演变，并通过实验进行了验证。由于材料点的不同热历史，可以获得晶粒尺寸、相组成和分布方面的微观结构变化。为了实现第三个目标，将根据获得的材料微观结构建立估计强度的分析模型，并根据沿着最薄弱的材料点和路径产生裂纹时应用的最小能量原理来估计疲劳裂纹萌生寿命。