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.

增材制造可以使行业能够在偏远站点，太空或战场上生产按需零件，并具有最小的库存，交货时间和工具成本。它还可以使研究人员能够探索新的材料组成，从而导致定制的新型特性。为了确保激光熔化中的组件质量（添加剂制造过程之一）并减少交货时间，至关重要的是，能够评估材料微观结构的变化，以响应该过程中的动态高热梯度，以及在此过程后静态和动态载荷下构造材料的强度。该奖项支持基本研究，以实现建模和仿真方法，以实现现实的预测，过程设计和优化以及激光熔化添加剂过程的设备设计。获得的知识为研究人员和制造商提供了基础，以使用激光熔化添加剂工艺以低成本以低成本来设计新材料。它还可以有助于理解激光熔化中各种材料的行为。研究结果将增强当前的工程课程，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均衡固化机制的知识，（2）确定由于多层结构对微结构变化而导致的不均匀的环状热历史记录的影响，（3）建立由激光熔化和材料性能和材料表现而产生的微结构之间的关系。为了实现第一个目标，将构建热机械有限元分析以模拟激光熔化的材料添加过程，将创建一种相位场方法来计算基于计算的热历史的合金相位场的时间依赖性的生长，以及单通行和多层激光融化实验，将在中型碳钢上进行。将通过实验观察发现的高热梯度与溶质捕获现象之间的相关性将揭示出非平衡固化机制。为了实现第二个目标，使用相位场方法比较了单个Pass和多层激光熔化过程下的微观结构演变，并通过实验验证。由于材料点的不同热历史，将获得有关晶粒尺寸，相位组成和分布的微观结构变化。为了实现第三个目标，将基于获得的材料微观结构建立估计强度的分析模型，并根据沿最弱的材料点和路径创建裂纹时应用的最小能量原理来估算疲劳裂纹启动寿命。