【作者】 董安；

【导师】 罗震；

【作者基本信息】 天津大学 ， 材料加工工程， 2007， 硕士

【摘要】 铝合金点焊以其生产效率高易于实现自动化的优势在汽车、航空航天领域得于广泛应用。但由于铝合金自身物理化学的特点以及受现阶段焊接装备的先进程度的制约,铝合金点焊是一个高度非线性、有多变量耦合作用和大量随机不确定因素相互影响的过程,而且点焊形核过程处于封闭状态,故对熔核形成过程中物理量的监测有重要的意义。本研究分析研究了反演理论,计算机断层成像原理及其重建算法并率先把相关理论引入铝合金电阻点焊领域。根据电磁场基本理论,从比奥-萨伐尔定律及相关理论出发,根据铝合金点焊的特点提出建模参数与简化条件,建立了铝合金点焊焊接回路空间磁场的正演模型。设计了基于虚拟仪器LabVIEW、DAQ2000系列采集卡及霍尔传感器的磁场阵列的信号采集系统,并利用科学计算软件Matlab进行了数学建模及数据处理,实现了焊接过程空间磁场数据采集的高速、有效,保证了数据处理的计算精度。在正演计算的基础上,利用离散化手段建立了铝合金点焊熔核的面电流密度与磁感应强度的反演数学模型,并根据计算机断层成像技术的ART算法用Matlab编程实现反演计算,以可视化的手段直观的显示熔核面电流密度分布。最后通过实验,验证了本研究正反演理论模型的正确性,算法的可行性和有效性,为监测铝合金点焊熔核形成过程提出了一种新的研究方法及手段。更多还原

【Abstract】 Aluminum alloy spot welding is wildly implemented in auto and aerial industry because it is a welding technique which is easy to be automatized. Owing to the physical and chemical characteristic of aluminum alloy and restricted by the welding machines, aluminum spot welding is a process with high non-linearity, coupled with many parameters and affected by lots of random factors. Besides, the forming process of the nugget can not be inspected directly. Therefore, it has vital significance to inspect the forming process.The inverse problem, basic principles of Computerized Tomography, and reconstruction algorithm are analyzed in this research. The related theories are imported in aluminum alloy spot welding at the first time. According to the Biot-Savart law and related electromagnetic theory, mold parameters and predigestion conditions are brought forward based on the characteristic of aluminum alloy spot welding. A forward model of magnetic filed in aluminum alloy RSW are set up.A data sampling system based on virtual instrument LabVIEW, DAQ2000 series data acquisition hardware and Holl sensors array is designed to inspect the magnetic field. The scientific computing software Matlab is implemented to setup a mathematical model and make data processing. This data sampling and processing system actualized the high speed sampling and high precision data processing.On the foundation of forward model, a reversed model is set up by discrete method. The reversed model established the function relationship between plate current intensity of the nugget and magnetic intensity in 3D space. Eventually, all the data processing will be actualized with Matlab program. In this research, a new method was put forward to inspect the forming process of the nugget. And the feasibility of validity of the model and related algorithm was confirmed by experiments.更多还原