Friction stir welding (FSW) is a solid-state welding process that is finding increasing use in a variety of industries, owing to its ability to create high-quality welds with less heat input than fusion welding. While the modeling of FSW has been an active effort for at least 15 years, two input parameters, namely the friction coefficient and the heat transfer coefficient, are still adjustable quantities that are difficult to measure. This lack of information compromises the predictive capability of FSW models. While the modeling of friction between the tool and workpiece remains a complex task, the measurement of heat transfer should be possible, but has not been adequately addressed because of the difficulty of accessing the relevant interface with thermocouples. This paper presents a multi-layered frequency-domain thermoreflectance (FDTR) method and transducer design to measure the heat transfer coefficient between the spinning tool and the workpiece. Due to constraints of the welding process, a multi-layered structure is needed for a useable measurement to maximize the heat flow from the modulated heating surface through the heat transfer interface into the welded workpiece. An analytical 2D thermal quadrupole model is shown to be useful in determining layer properties. A multi-layered structure for a specific tool design is validated using COMSOL and optimized. This process can be used to determine the ideal transducer structure to maximize the signal from an FDTR measurement during a friction stir welding process.

中文翻译：

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搅拌摩擦焊热接触电导测量装置的优化设计

搅拌摩擦焊 (FSW) 是一种固态焊接工艺，在各种行业中得到越来越多的使用，因为它能够以比熔焊更少的热输入创建高质量的焊缝。虽然 FSW 的建模已经积极努力至少 15 年，但两个输入参数，即摩擦系数和传热系数，仍然是难以测量的可调量。这种信息的缺乏损害了 FSW 模型的预测能力。虽然工具和工件之间的摩擦建模仍然是一项复杂的任务，热传递的测量应该是可能的，但由于难以使用热电偶访问相关接口，因此尚未得到充分解决。本文提出了一种多层频域热反射 (FDTR) 方法和换能器设计，用于测量旋压工具和工件之间的传热系数。由于焊接过程的限制，需要多层结构才能进行可用的测量，以最大限度地提高从调制加热表面通过传热界面进入焊接工件的热流。分析 2D 热四极杆模型显示可用于确定层属性。特定工具设计的多层结构使用 COMSOL 进行了验证和优化。该过程可用于确定理想的换能器结构，以在搅拌摩擦焊接过程中最大化来自 FDTR 测量的信号。