Joining of Dissimilar Materials through a Novel Hybrid Friction Stir Resistance Spot Welding Process

在许多工业应用（例如，汽车、航空航天和国防工业）。这种方法能够利用多材料结构并减轻车辆重量。 实现可靠的异种材料连接将为未来多材料飞行器结构的设计提供指导。该奖项支持基础研究，以提供创造一种新型，混合和高效的连接方法所需的知识，该方法将传统的电阻点焊方法与最近开发的摩擦搅拌工艺相结合。 研究结果可以大大有助于车辆轻量化的努力，从而提高运输车辆的燃油经济性和未来的可持续性。本研究的目标是：（1）确定脉冲电流对热应力场和机械应力场的影响，以及当通过使用电塑性增强摩擦搅拌点焊连接不同材料时的材料行为，以及（2）创建关键输入参数之间的数学关系（例如，脉冲电流大小和频率、摩擦搅拌工具的旋转速度、切入速度等）以及所得到的过程动态预测和相关的过程性能度量，例如接头质量、温度分布和焊接力和扭矩。本研究的范围包括模拟和分析的材料流动应力和形态在焊接区的异种材料通过搅拌摩擦技术在电阻点焊过程中融合。将采用多物理场模拟方法计算材料场、温度场和应力场。该模型还将用于分析与脉冲电流相关的电塑性和加热对焊接熔核中材料行为的影响。多相流理论将用于描述异种材料在焊接熔核中的行为。为了量化接头质量，将进行机械测试和微观结构分析。

A reliable, efficient, and economical method for joining dissimilar materials is highly desired in many industrial applications (e.g., automotive, aerospace, and defense industries). Such a method enables utilization of multi-material structures and reduction of vehicle weight. Achievement of reliable dissimilar material joints will provide design guidance for future multi-material vehicle structures. This award supports fundamental research to provide knowledge needed to create a novel, hybrid, and highly efficient joining method that integrates traditional resistance spot welding method with recently developed friction stir process. Research results can greatly contribute to the vehicle light-weighting efforts and thus to increased fuel economy of transportation vehicles and future sustainability.The objectives of this research are: (1) to determine the effects of pulsed electric currents on the thermal and mechanical stress fields, and material behaviors when joining dissimilar materials through the use of electro-plastically enhanced friction stir spot welding, and (2) to create the mathematical relationship between key input parameters (e.g., pulsed electric current magnitude and frequency, rotational speed of friction stir tool, plunge speed, etc.) and the resulting prediction of process dynamics and the associated process performance metrics such as joint quality, temperature distribution, and welding force and torque. The scope of this research includes the modeling and analysis of material flow stress and morphology in the welding zone where dissimilar materials are fused through the friction stir technique in resistance spot welding process. A multi-physics modeling approach will be utilized to calculate the material, temperature and stress distribution fields. This model will also be utilized to analyze the effects of electro-plasticity and heating associated with pulsed electric current on material behavior in the weld nuggets. Multiple phase flow theories will be used for describing dissimilar material behaviors in the weld nugget. In order to quantify the joint quality, both mechanical tests and microstructure analysis will be conducted.