Electro-thermo-mechanical modeling of Field Assisted Sintering Technology using high-order finite elements validated by experiments

现场辅助烧结技术（FAST）是一种现代制造工艺，在烧结过程中进行粉末压实。快速加热和冷却可缩短生产周期，改善材料性能。由于石墨工具和粉末材料在电势作用下产生的高温，对其内部过程的实验测量很难实现。因此，数值方法是足够的，但是，数值方法必须建立在实验模型的基础上，并考虑到测量中的不确定性，根据其可预测性进行验证。在本项目中，将对试验机中的整个过程进行汇总，并对工具和粉末工件进行本构模型建模。特别是，必须考虑耦合的电学、热学和力学性能。将本构模型实现为高阶时空有限元程序，并求解耦合三场问题。因此，利用应用于电-热-机械耦合的分区方法对耦合问题进行有效和稳健计算的新概念将得到发展，以便甚至可以考虑带反射的辐射。对于高阶有限元，需要有效的空间积分。采用自适应/分层有限单元法可以获得运动区域电热子问题的高精度结果，这意味着有限单元法在耦合问题中的进一步发展。这些高度复杂和具有挑战性的问题只有在来自不同学科（如材料科学、力学和数值）的合作伙伴之间才能实现，从而产生适用于进一步多物理问题的新贡献。

Field assisted sintering technology (FAST) is a modern manufacturing process, where during the sintering process powder compaction is performed. Fast heating and cooling yield shorter production periods and improved material properties. Caused by the high temperatures, which are induced in the graphite tools and the powder material by an electrical potential, an experimental measurement of the internal processes are hardly realizable. Thus, numerical methods are adequate, which, however, must be based on both experimental-based models as well as validated in view of their predictability under consideration of uncertainties in the measurements. In this project the entire process in the testing machine will be gathered and modeled with constitutive models for both the tools and the powder workpiece. Particularly, the coupled electrical, thermal and mechanical properties must be considered. The constitutive models are implemented into a high order space and time finite element program, where, additionally, the coupled three-field problem must be solved. Accordingly, new concepts for an efficient and robust computation of coupled problems using a partitioned approach applied to electro-thermo-mechanical coupling will be developed so that even radiation with reflection can be considered. In the case of high order finite elements an efficient space integration is required. Highly accurate results of the electro-thermal subproblem of the moving regions will be achieved using adaptive/hierarchical finite cell approach, which implies the further development of the finite cell method in view of coupled problems. These highly complex and challenging issues are only possible within collaborating partners coming from different disciplines such as material science, mechanics and numerics leading to new contributions applicable even to further multi-physical issues.