Multiscale Structure-Mechanical Property Investigation of Additive Manufactured Components for Development of a Reliable Qualification Method

增材制造（也称为3D打印）现在能够生产/构建复杂形状的金属部件，其强度足以用于结构应用。然而，传统制造的标准鉴定方法并不适用于增材制造的零件，因为增材制造的零件的力学行为与传统方法制造的零件有本质的不同。因此，本研究的目标是基于经过验证的计算机模拟和无损评估技术相结合的方法，开发一种高度可靠、低成本和高效的增材制造部件鉴定方法。这种鉴定方法将有可能导致增材制造的更广泛采用，并将影响需要复杂、高价值、时间敏感和定制产品和原型的应用，如汽车和航空航天零件（即复杂设计）、破损零件更换（即时间敏感）和医疗植入物（即高度定制）。学生在这个项目中获得的技能和知识将为他们在确保美国在未来几代制造工程中的领导地位方面发挥积极作用做好准备。为了实现这一目标，本项目有以下目标：1)在多个长度尺度上表征关键的微观结构特征和力学性能；2)建立概率本构模型，捕捉亚微米力学行为；3)基于各种无损评价技术的微观结构数据建立宏观模型；4)在复杂零件上测试鉴定方法。本研究解决了增材制造结构部件的可靠性鉴定问题，这些部件的局部微观结构和力学行为在同一部件的不同构建中可能存在很大差异。x射线微计算机断层扫描的使用保证了被扫描材料中的任何微尺度缺陷都可以被检测到，因此在设计组件中直接模拟其机械行为是可能的。通过多尺度研究，将建立一个本构模型来捕捉缺陷、晶粒尺寸和残余应力的力学效应。将各种无损评估技术与基于物理的建模相结合，将为增材制造部件提供一种快速、可靠、低成本的鉴定方法。

Additive manufacturing (also called 3D printing) is now capable of producing/building complex-shaped metal components strong enough for structural applications. However, standard qualification methods for traditional manufacturing are not suitable for additive manufactured parts because the mechanical behavior of these parts is fundamentally different from those made by traditional means. Hence, the goal of this research is to develop a highly reliable, low-cost, and efficient qualification method for additive manufactured components based on a combined approach of validated computer simulations and non-destructive evaluation techniques. This qualification method will potentially lead to much wider adoption of additive manufacturing and will impact applications requiring complex, high value, time-sensitive, and customized products and prototypes such as automobile and aerospace parts (i.e., complex designs), broken part replacement (i.e. time-sensitive), and medical implants (i.e., highly customized). The skills and knowledge the students gain in this project will prepare them for active roles in securing the the United States' leadership in manufacturing engineering for future generations. To achieve its goal, this project has the following objectives: 1) Characterize key microstructure features and mechanical properties across multiple length scales; 2) Develop a probabilistic constitutive model to capture sub-micron mechanical behavior; 3) Develop a macroscopic model based on microstructure data from various non-destructive evaluation techniques; and 4) Test the qualification method on a complex part. This research tackles a challenging problem in the reliable qualification of additive manufactured structural components whose local microstructure and mechanical behavior may vary widely among different builds of the same component. The utilization of X-ray micro computed tomography guarantees that any microscale flaws in the materials being scanned can be detected so that direct simulation of their mechanical behavior in the design component is possible. Through the multiscale investigation, a constitutive model will be developed to capture the mechanical effects of flaws, grain size, and residual stress. The integration of various nondestructive evaluation techniques with physics-based modeling will thus enable a rapid, reliable, and low-cost qualification method for additive manufactured components.