Temperature control in friction stir welding

搅拌摩擦焊(FSW)是一种固态连接工艺，由于材料的温度保持在固相线以下，因此可产生高焊接质量。由于这一特点和良好的重复性，搅拌摩擦焊在工业应用中得到了迅速的推广，焊缝区的温度不能直接受到影响，而是由所选择的工艺参数、刀具几何形状和其他边界条件决定的。然而，这些自变量与焊接温度之间的关系还没有得到充分的研究。特别是在复杂的焊接任务中，改变热边界条件会影响焊缝区的温度，从而对接头的力学性能产生负面影响。因此，控制热输入是保证高焊接质量的关键。所要求的研究项目的目的是探索理论背景，并实施和验证原型控制系统。总而言之，主要问题可以概括为：开发一种近似实时确定焊接区温度的方法；开发关于焊接区温度分布的工艺原理；确定主要影响焊接区温度的相关工艺参数；实施温度控制系统并在特征应用中演示其功能。

Friction stir welding (FSW) is a solid state joining process producing high weld quality, since the temperature of the material remains below its solidus. Due to this characteristic and the good repeatability FSW has quickly spread in industrial application.The temperature in the weld zone cannot be directly influenced, but results from the chosen process parameters, the tool geometry and other boundary conditions. Yet, the relationship between those independent variables and the weld temperature has been insufficiently in-vestigated. Especially in complex weld tasks changing thermal boundary conditions can affect the weld zone temperature with negative impact on the mechanical joint properties. Thus, controlling the heat input is essential to ensure high weld quality. The aims of the requested research project are to explore the theoretical background and to implement and validate a prototypic control system. Concluding, the main issues can be summarized as: development of a method to determine the weld zone temperature approximately in real-time; development of the process principles regarding the temperature profile in the weld zone; determination of relevant process parameters, which mainly affect the weld zone temperature; implementation of a system for temperature control and demonstration of its functionality in characteristic applications.