Investigation of Electro-Plastic Effect on Advanced High Strength Steels and Its Application in Friction Stir Joining of Dissimilar Material

这项拨款为高级高强度钢的电塑性效应及其在搅拌摩擦连接过程中的潜在应用的全面研究提供了资金。在本研究中，将进行微观结构分析，以了解电塑性效应的潜在机制。根据应变速率和电流参数建立基本应力应变模型。将引入考虑减少变形能与总输入电能之比的能量系数。此外，还将开发一种先进的混合搅拌摩擦连接工艺，利用上述电塑性效应进行不同材料的连接。要连接的材料包括高级高强度钢和铝合金。结合工艺参数和接头质量对实验结果进行了分析，并建立了混合搅拌摩擦连接过程中向下作用力的有限元模型。如果成功，这项研究的结果将导致针对不同材料的新连接工艺的优化设计。由于提高燃油经济性的挑战越来越大，不同的高比强度材料，如铝合金、镁合金和先进的高强度钢，越来越多地用于车辆结构，以减轻车辆的重量，同时又不牺牲预期的性能。这些不同材料的连接提出了一个重大的技术挑战。该研究将大大拓宽电塑性效应在各种制造工艺中的应用，包括传统的加工和成形等。所提出的工作也将有助于建模和实验工具可用于表征电塑性效应和混合摩擦搅拌过程。

This grant provides funding for a comprehensive investigation of the electro-plastic effect on advanced high strength steels and its potential applications to the friction stir joining processes. In this research, microstructure analysis will be carried out to understand the underlying mechanism of electro-plastic effect. Basic stress strain model will be established with regard to strain rate and current parameters. An energy coefficient considering the ratio of the reduced deformation energy to the total electrical energy input will be introduced. In addition, an advanced hybrid friction stir joining process will be developed for the joining of dissimilar materials utilizing the above-mentioned electro-plastic effect. The materials to be joined include advanced high strength steels and aluminum alloys. Experimental results will be analyzed considering both process parameters and joint quality and a Finite Element Model will also be developed to predict the downward force during the hybrid friction stir joining process.If successful, the results from this research will lead to optimized designs of new joining processes for dissimilar materials. Dissimilar materials with high specific strength, such as aluminum alloys, magnesium alloys and advanced high strength steels, are being increasingly used in vehicle structures to reduce the weight of vehicles without sacrificing desired performance due to the growing challenge of improving fuel economy. Joining of these dissimilar materials presents a significant technical challenge. This research will greatly widen the applications of electro-plastic effects into various manufacturing processes, including traditional machining and forming etc. The proposed work will also contribute to the modeling and experimental tools available for characterizing electro-plastic effects and hybrid friction stir processes.