Anisotropic yielding in AM Ti-6Al-4V: Experimental methods, models, and case study justifications

增材制造（AM）相对于传统的减法方法的优势是众所周知的。AM将带来令人兴奋的机会。具有复杂外部和内部特征的高效结构在增材制造中成为可能，允许更广泛的设计信封和优化系统。对于采用增材制造材料和先进的设计来说，最重要的是了解材料在复杂的加载配置下是如何变形和失效的。目前，支持预测模型的实验研究（通常）仅限于单轴条件。从这些观察可以推断出多轴行为。然而，结果容易受到很大程度的不确定性的影响。这反过来又限制了在预测模型中表征各向异性的程度。预测材料模型中不可接受的不确定性水平限制了对增材制造新设计的信心，从而破坏了增材制造的潜在影响。我们需要的是一种智能测试方法，探索增材制造材料的各向异性，以及一种通用的建模方法，允许在设计阶段做出准确的预测。这里提议的项目将利用UNOTT新的测试能力发展这些方法。将建立通用的多轴试验券。通过与雷尼绍的合作，这些将在Ti-6Al- 4V（作为示范材料）中制造，并使用新的屈服轨迹探测技术进行测试（由UNOTT新的多轴测试框架实现）。Hill的各向异性屈服准则（或对其进行修改）将用于开发Ti-6Al-4V材料的通用塑性模型。结果将通过沿非标准加载轴的附加测试来验证。最后，工作的价值将通过AM支架的设计案例研究量化地展示。传统的（由于建模不确定性导致的大但合理的安全因素）和先进的（在项目中开发的）材料模型将用于分析增材制造支架组件，以确定安全的工作负载。在超前变形的情况下，其价值将通过更大的结构能力得到体现。

The advantages of additive manufacturing (AM) over traditional subtractive methods are well known. Exciting opportunities will be enabled by AM. Efficient structures with complex external and internal features are made possible in AM, allowing for broader design envelopes and optimised systems. Paramount to the adoption of both AM materials and the advanced designs that they promote is an understanding of how materials deform and fail in complex loading configurations. At present, the experimental studies that underpin predictive models are (often) limited to uniaxial conditions. Multiaxial behaviours can be inferred from these observations. However, the results are susceptible to large levels of uncertainty. This, in turn, limits the degree to which anisotropy can be represented in the predictive models.Unacceptable levels of uncertainty in predictive material models limit confidence in novel designs enabled in AM, thereby undermining the potential impacts of AM. What is required is both an intelligent testing methodology that explores anisotropy in AM materials and a general modelling approach that allows accurate predictions to be made at the design stage.The project proposed here will develop these approaches using new testing capabilities at UNOTT. Generic multiaxial test coupons will be established. These will be built in Ti-6Al- 4V (as a demonstration material) through collaborations with Renishaw and tested using novel yield locus probing techniques (enabled by the new multiaxial test frame at UNOTT). Hill's anisotropic yield criterion (or a modification of it) will then be used to develop generic plasticity models for the Ti-6Al-4V material. Results will be verified through additional testing along non-standard loading axes. Finally, the value of the work will be quantifiably demonstrated through a design case study of an AM bracket. Conventional (with large but justifiable safety factors resulting from modelling uncertainty) and advanced (developed in the project) material models will be used to analyse an AM bracket component to determine safe working loads. The value will be demonstrated through a greater structural capacity in the case of advanced deformation representations.