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

这笔资金用于对先进高强度钢的电塑性效应及其在搅拌摩擦连接工艺中的潜在应用进行全面调查。在这项研究中，将进行微观结构分析，以了解电塑性效应的潜在机制。建立了关于应变率和电流参数的基本应力-应变模型。将引入一个考虑折合变形能与总电能输入之比的能量系数。此外，还将开发一种先进的混合搅拌摩擦连接工艺，用于利用上述电塑性效应连接不同材料。要连接的材料包括先进的高强度钢和铝合金。实验结果将从工艺参数和接头质量两个方面进行分析，还将建立有限元模型来预测混合搅拌摩擦连接过程中的下拉力。如果成功，本研究结果将指导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，高比强度的不同材料，如铝合金、镁合金和先进的高强度钢，正越来越多地被用于车辆结构中，以在不牺牲预期性能的情况下减轻车辆的重量。这些不同材料的连接是一项重大的技术挑战。这项研究将极大地扩大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立可用于表征电塑性效应和混合摩擦搅拌过程的建模和实验工具。

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.