CMMI-EPSRC: Thermoacoustic response of Additively Manufactured metals: A multi-scale study from grain to component scales

该提案建立在现有合作的基础上，该合作的重点是在750 K和800 Hz的热声激励下，使用详细的实验和模拟，在传统制造的金属板和梁中，从铝到Hastelloy X，实现对材料结构响应的多尺度理解。结果表明，在微观尺度上，变形倾向于集中在材料微观结构内的低聚晶体的较大晶粒中，其位置与宏观尺度均匀分析预测的位置不同（卡罗尔等人，国际疲劳杂志，57：140-150，2013），证明了微观结构的不均匀性可能导致预测失效时的显著和服务临界误差。进一步的实验室规模的实验，使用在宽带热声激励期间测量的表面变形图，已经证实了当不均匀加热产生热屈曲时存在模式跳跃和转移（Lopez-Alba等人，J. Sound & Vibration 439：241-250，2019）。考虑到这一点，研究小组将这些测试缩放到组件规模，建立简单组件的热声激励的耦合模型的定量验证程序（Berke等人，Expl.机械、56（2）：231-243，2016）。在此过程中，该团队开发了两种独特的实验设备：在伊利诺伊州，用于局部加热和试样的模态激励;在利物浦，提供21千瓦的空间分布加热，同时对小部件施加随机宽带激励。这两种钻机都具有实时、全场温度和位移测量能力。Lambros和Patterson在极端载荷下的多尺度材料力学（Lambros）和结构响应的测量、模拟和验证（Patterson）方面具有相应的互补专业知识。建议利用这些发现、设施和专业知识来了解增材制造在苛刻环境中生产受到极端热机械激励的组件的潜力。这种类型的结构可能会以小批量生产，因此适合考虑增材制造;然而，温度和机械载荷的极端条件使其成为任何材料的挑战性应用。成功的设计，制造和服务部署这样的组件需要了解多尺度的材料-结构响应的加载和它的演变与组件的进展，从其原始状态，通过安定到启动可检测的非关键损伤。对于减材制造的金属，这些响应在基本水平上被理解;然而，对于增材制造的金属，在室温下，对这些材料-结构相互作用的基本理解非常有限（Attar等人，IJ Mach.工具和手册，133：85-102，2018，Foehring等人，Mat. Sci. Eng. A，724：536-546，2018）或升高的温度（Roberts等人，Progress. Add. Manu.，1-8，2018）。据推测，由于独特的微观结构包含先前研究的较大晶粒的低聚晶体，其制造的复杂的热机械历史和显着的残余应力的存在下，极端热声负载下的增材制造的金属的响应将显着不同于减材制造的对应物，特别是在缺陷驱动的过程，如故障。该提案扩展了Lambros和Patterson的研究，增加了Sutcliffe（雷尼绍AMPD研发总监，2018年RAe银奖得主，拥有20多年研究金属增材制造的经验）提供的增材制造专业知识和设施，Sutcliffe对最新的增材制造技术拥有无与伦比的访问权。

The proposal builds on an existing collaboration which has focussed on achieving a multi-scale understanding of the material-structure response to thermoacoustic excitation at up to 750K and 800 Hz using detailed experiments and simulations, in plates and beams of conventionally-manufactured metals, ranging from aluminium to Hastelloy X. Results have shown, at a microscale, a tendency for deformation to concentrate in the larger grains of oligocrystal within the material microstructure at locations disparate from where macroscale homogeneous analysis predicts (Carroll et al., Int. J. Fatigue, 57: 140-150, 2013), demonstrating that non-uniformity in the microstructure can lead to significant and service critical errors in predicting failure.Further laboratory-scale experiments, using maps of surface deformation measured during broadband thermoacoustic excitation, have confirmed the presence of mode jumping and shifting when non-uniform heating generates thermal buckling (Lopez-Alba et al, J. Sound & Vibration 439:241-250, 2019). With this in mind, the research team scaled these tests to component scale, establishing quantitative validation procedures for coupled models of thermoacoustic excitation of simple components (Berke et al, Exptl. Mech., 56(2):231-243, 2016). In doing so, the team developed two unique pieces of experimental apparatus: in Illinois, for localised heating and modal excitation of coupons; and in Liverpool, to deliver spatially distributed heating at 21kW while simultaneously applying random broadband excitation to small components. Both rigs have real-time, full-field temperature and displacement measurement capability. Lambros and Patterson have correspondingly complementary expertise in multi-scale mechanics of materials under extreme loading (Lambros) and in measurement, simulation and validation of structural responses (Patterson).It is proposed to exploit these findings, facilities and expertise to understand the potential for additive manufacturing in the production of components subject to extreme thermomechanical excitation in demanding environments. It is likely that this type of structure will be produced in small quantities rendering it appropriate to consider additive manufacturing; however, the extreme conditions of temperature and mechanical loading make it a challenging application for any material. Successful design, manufacture and service deployment of such components requires an understanding of the multi-scale material-structure response to loading and its evolution with a component's progression from its virgin state through shake-down towards initiation of detectable non-critical damage. These responses are understood at a fundamental level for subtractively-manufactured metals; however, there is very limited fundamental understanding of these material-structural interactions for additively-manufactured metals, at either room temperature (Attar et al, IJ Mach. Tools & Manu., 133: 85-102, 2018, Foehring et al, Mat. Sci. Eng. A, 724: 536-546, 2018) or elevated temperatures (Roberts et al, Progress. Add. Manu., 1-8, 2018). It is hypothesized, because of the unique microstructure containing the previously studied larger grains of oligocrystal, the complex thermomechanical history of their manufacture and the presence of significant residual stresses, that the response of additively-manufactured metals under extreme thermoacoustic loading will be significantly different from their subtractively-manufactured counterparts, especially in defect-driven processes such as failure. This proposal extends the research of Lambros and Patterson by adding the additive manufacturing expertise and facilities provided by Sutcliffe (R&D Director at Renishaw AMPD, RAe Silver Medallist 2018 with over 20 years researching metal additive manufacturing) who has unparalleled access to the latest additive manufacturing technology.