EPSRC supported EngD project: Thermo-Mechanical Modelling for Structural Ceramics

疲劳断裂是工程陶瓷材料在循环热载荷作用下裂纹萌生、扩展并最终失效的失效模式之一。疲劳裂纹扩展的有效预测有助于产品耐久性的工程决策。传统的Paris定律或J积分不足以预测复杂的3D几何形状中的裂纹扩展，例如来自附加层制造的3D周期结构。作为一种替代方法，相场模型受到了越来越多的关注。在这种方法中，可以对微裂纹陶瓷中的塑性和弹性变形随时间进行建模。模型预测还可以用来跟踪结构中的薄弱区域和施加载荷条件对产品耐久性的严重程度。在扩展弹塑性陶瓷相场模型和测量蜂窝等复杂结构的断裂韧性、分离能、粘结强度、疲劳参数等模型输入参数方面存在知识空白。在这项工作中，将开发相场模型来了解微裂纹系统的耐久性，并将开发新的实验技术来测量模型参数，利用高温弯曲试验、动态力学分析仪、高温脉冲激励和纳米压痕等设备。模型预测将在热冲击载荷条件下的模型材料上得到验证。同样，这些模型将被用来解释微裂纹陶瓷弹性性能中显露的颗粒生长和滞后现象。这个项目将专门解决JM的一些产品开发和质量控制需求。英语专业的学生将作为热处理小组和质量控制团队中不可或缺的一员工作。JM正在这一领域建立增强的能力，支持模型驱动的制造和设计。EngD研究员将在这个团队中发挥关键作用；为给定的产品配方开发定制的测量方法、骨折模型。EngD的重点将是集团的基本研发需求，但也将参与商业环境中模型的试验和实施，并支持欧洲不同的制造基地。对于任何对英国退欧的担忧，这一职位都是全额支付和赞助的。

Fatigue fracture is one of the failure modes in engineering ceramics where crack initiates, propagates, and finally results in failure under cyclic thermal loading. The efficient prediction of fatigue crack growth helps make engineering decisions on product durability. The conventional Paris law or J-integrals are not enough to predict crack growth in complex 3D geometries such as 3D perioidic structures from additive layer manufacturing. As an alternative method, the Phase Field models have been receiving increasing attention. In this approach it is possible to model both plastic and elastic deformations with a time in microcracked ceramics. The model predictions can also be used to track weaker zones in the structure and the severity of the applied loading conditions on the product durability. There is a knowledge gap in extending the Phase Fieldd models for elasto-plastic ceramics and measuring model input parameters such as fracture toughness, separation energy, cohesive strength, fatigue parameters for such complex structures such as honeycombs. In this work, Phase Field models will be developed to understand the durability of the microcracked systems and novel experimental techniques will be developed for measuring model parameters by utilizing facilities like high temperature bending test, Dynamic Mechanical Analyser, high-temperature impulse excitation, and nanoindentation. The model predictions will be validated on model materials under thermal shock load conditions. Similarly, these models will be used to explain the revesible grain growth and hysteresis in the elastic properties of microcracked ceramics.This project will specifically address some of the product development and quality control needs of JM. The EngD student will work as an integral part of thermal processing group and quality control teams. JM is building an enhanced capability in this area, enabling the model driven manufacturing & design. The EngD researcher will play a key role within this team; developing bespoke measurement methods, fracture model for a given product formulations. The focus of the EngD will be the fundamental R&D needs of the group, but also being involved in trials and implementation of models in commercial environment and support different manufacturing sites in Europe. For any concern with Brexit, this position is fully paid and sponsored.