CMMI-EPSRC: Thermoacoustic Response of Additively Manufactured Metals: A Multi-Scale Study from Grain to Component Scales

这项研究项目是由NSF工程-UKRI工程和物理科学研究理事会机会基金资助的，NSF 20-510。这笔赠款将支持研究，以了解在极端热机械激励下生产金属部件的添加制造(AM)的潜力。在高温和振动载荷相结合的苛刻环境中的结构(例如，持续的高超声速飞行、空间再入、排气洗涤结构、聚变反应堆中的增殖包层)通常会经历疲劳，从而缩短其生命周期。这些类型的结构很可能只会小批量生产，因此适合考虑在其建造过程中使用加工法。此类部件的成功设计、制造和服务部署需要了解部件从初始状态、经过拆卸、开始可检测到的非关键损坏，最后到故障的过程。到目前为止，对于传统减法制造的金属来说，这种失效演变过程是相当清楚的。然而，对AM金属失效的多尺度材料-结构相互作用的基本认识非常有限。由于AM金属独特的微观结构，制造过程中复杂的热历史，以及显著的残余应力的存在，假设它们在极端热声载荷下的响应将与传统的对应材料显著不同，特别是在缺陷驱动的过程中，例如失效。通过了解AM金属在极端热声载荷下这一失效过程的细节，这项研究的结果将阐明如何更好地定制添加剂制造方法，以生产最适合在这种不利环境中运行的材料和结构。这项研究将由PI与英国利物浦大学的研究人员合作进行，重点放在将材料级别(微观和中尺度)响应与结构级别(宏观)响应联系起来的关键方面。将使用高分辨率数字图像相关来量化在循环加载以及全局和局部温度梯度作用下添加制造的金属在微观尺度上的损伤累积。在更大的长度尺度上，将使用实时光学和热成像来研究几何增强的附加制造的板在热机械激励下的热屈曲。一个关键的方面将是探索AM金属复杂的热加工历史(包括任何现有的残余应力)与施加的瞬时和耦合热机械载荷之间的相互作用。最后，该项目将确定管理用于受高温宽带激励的可靠部件的AM的基本规则。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。

This research project was funded under the NSF Engineering–UKRI Engineering and Physical Sciences Research Council opportunity, NSF 20-510. The grant will support research towards understanding the potential for additive manufacturing (AM) in the production of metallic components subject to extreme thermomechanical excitation. Structures in demanding environments where high temperatures and vibratory loads are combined (e.g., sustained hypersonic flight, space re-entry, exhaust-wash structures, breeder blankets in fusion reactors) often experience fatigue which shortens their lifecycle. It is likely that these types of structures will be produced only in small quantities, making it appropriate to consider additive manufacturing for their construction. Successful design, manufacture and service deployment of such components requires an understanding of the component's progression from its virgin state, through shake-down, towards initiation of detectable non-critical damage, and ultimately to failure. To date, this failure evolution process is fairly well understood for traditional subtractive-manufactured metals. However, there is very limited fundamental understanding of the multi-scale material-structure interactions for failure of AM metals. Because of the unique microstructure of AM metals, their complex thermal history during manufacture, and the presence of significant residual stresses, it is hypothesized that their response under extreme thermoacoustic loading will be significantly different from their traditional counterparts, especially in defect-driven processes such as failure. By understanding the details of this failure process in AM metals under extreme thermoacoustic loading, the results of this study will shed light onto how to better tailor the additive manufacturing approach to produce materials and structures most suitable for operating in such adverse environments.The research will be undertaken jointly by the PI in collaboration with researchers at the University of Liverpool in the United Kingdom, focusing on key aspects that link material-level (micro- and mesoscale) response to the structural-level (macroscale) response. Damage accumulation at the microscale for additively-manufactured metals subjected to cyclic loading and global and local thermal gradients will be quantified using high resolution digital image correlation. At a larger length scale, additively-manufactured plates with geometric reinforcement subjected to thermal buckling during thermo-mechanical excitation will be studied using real-time optical and thermal imaging. A key aspect will be to explore the interaction of the complex thermal processing history of AM metals (including any existing residual stresses) with the transient and coupled thermomechanical loading applied. Finally, the project will identify the fundamental rules governing AM for reliable components subject to high-temperature broadband excitation.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.