双相钢电阻点焊性能特征与焊接机理分析-固体力学专业论文.docx

dual phase steel, derived the finite element equation of pre-pressure contact, and determined the initial conductive region. The thermo-electricity transient and thermal elastic-plastic mechanism of resistance spot welding for DP600 were analyzed by indirect coupling method and thermal elastic-plastic theory. By analyzing electric field and temperature field, the wave curve of welding nugget size was obtained under 50Hz AC, which provided a theoretical basis for controlling the welding nugget size. And by analyzing the contact pressure, stress and strain distribution, the deformation mechanism was revealed. It was concluded that the workpiece surface indentation and the wedge deformation were caused by the plastic strain of heat affected zone, and the deformation of workpiece area away from the welding range was not obvious. This result provided a theoretical guidance for the welding deformation controlling of dual phase steel.The contrast between numerical simulation and experimental results showed that, the simulated nugget sizes were consistency with experimental values under appropriate current, and there were significant errors when the current was too large. And the simulated deformation shape also showed good consistency with the experimental results. These showed that the analysis results of welding mechanism of the RSW for DP600 has good accuracy.Finally, based on the results, the relationships of the performance characteristics and welding mechanism were established. This study has practical significance for comprehensive understanding of the mechanism of RSW process as well as the application of dual phase steel and the quality controlling in the spot welding of automotive body.key words: Dual phase steel, Resistance spot welding, Mechanical properties, Micro- performance, Welding mechanism独创性声明本人声明所呈交的学位论文是我个人在导师指导下进行的研究工作及取得的研 究成果。尽我所知，除文中已经标明引用的内容外，本论文不包含任何其他个人或 集体已经发表或撰写过的研究成果。对本文的研究做出贡献的个人和集体，均已在 文中以明确方式标明。本人完全意识到本声明的法律结果由本人承担。学位论文作者签名： 日期：年 月 日学位论文版