Abstract: A finite element model was established for resistance spot welding of DC01 with a thickness of 1.0 mm, DP590 with thicknesses of 1.2 mm and 1.5 mm. The energy distribution and stress-strain during the spot welding processes were analyzed using the multi-field coupling of thermal field, electric field, and force field. The test results show that the numerical simulation results are in good agree with the test ones. The peak current density decreases with time, and the distribution area is different from that of the two-layer plates, with a significantly larger area of distribution in the upper and lower plates compared with the middle plate. The potential changes indicate that initial heat generation in spot welding is mainly through contact resistance, which later transforms into bulk resistance. The temperature distribution on dissimilar unequal-thickness plates is uneven, with nucleation preferentially occurs on the lower part of the middle plate and on the DP590/DP590 contact surfaces. After the formation of the nugget, the middle part is under compressive stress, while the base material zone is under tensile stress at the nugget zone. The maximum strain value exists at the DP590/DP590 location.

Key words: dissimilar steel, resistance spot welding, nucleation process, numerical simulation, multi-field coupling

摘要： 针对厚度1.0 mm的DC01、厚度1.2 mm和1.5 mm的DP590样片组，建立了电阻点焊的有限元模型，采用热场、电场、力场多场耦合分析了点焊过程能量分布和应力应变。试验结果表明：焊核尺寸的数值模拟计算结果与试验结果吻合良好，电流密度峰值随时间减小，其分布区域与两层板不同，与中板相比，在上板和下板分布的区域明显更大，电势变化说明点焊初期主要通过接触电阻产热，后期变成体电阻，温度在异种不等厚板材上分布不均匀，优先在中板下部和 DP590/DP590接触面上形核，熔核形成后中部受到压应力，母材区受到熔核拉应力，应变最大值存在于 DP590/DP590处。

关键词: 异种钢, 电阻点焊, 形核过程, 数值模拟, 多场耦合