脉冲电流下对AL6061合金进行熔孔止裂与愈合的仿真研究

Al6061铝合金常应用于航空航天领域蒙皮制造,因其中等硬度与低强度的弱点,在承受复杂载荷时容易出现微裂纹,进而影响服役安全可靠性。脉冲电流是一种极速、非平衡的金属材料微小裂纹修复工艺,可以克服该材料不易焊接修复的短板。本文在既有的实验基础上建立单边预制裂纹缺口模型,采用有限元仿真手段,进行了热-电-力三场耦合数值模拟,计算不同参数下裂纹区域的电场、温度场和应力场分布。使用“生死单元”法模拟止裂熔孔的产生,并获得了不同几何、物理参数下止裂熔孔尺寸变化的规律。结果表明：焦耳热形成的止裂熔孔降低裂尖的集中应力,抑制裂纹扩展,裂纹区域高温区与基体常温区形成温度梯度相互约束产生巨大的热压应力促使裂纹宽度减小,进而直至愈合；初始熔孔尺寸与裂纹长度成正比、与板厚成反比,最佳尺寸直径为0.1mm以内；电流值和电流加载时间均能控制熔孔生长,电流值一定时,当时间达到0.12s形成的熔孔尺寸超出最佳止裂尺寸范围。研究成果为特定金属材料的裂纹止裂与愈合提供了机理参考和仿真方法。

Simulation Study on Melting Hole Crack Arrest of AL6061 under Pulse Current

Al6061 aluminum alloy is often used in the field of aerospace skin manufacturing. Due to the weakness of medium hardness and low strength, microcracks are prone to occur when subjected to complex loads, which affects the safety and reliability of service. pulse current is a very fast, non-equilibrium metal material micro-crack repair process, which can overcome the shortcomings of the material that is not easy to weld. In this paper, based on the existing experiments, a unilateral prefabricated crack notch model is established. The finite element simulation method is used to simulate the thermal-electric-mechanical three-field coupling numerical simulation, and the electric field, temperature field and stress field distribution of the crack area under different parameters are calculated. The '' birth and death element '' method was used to simulate the generation of crack arrest melting hole, and the law of size change of crack arrest melting hole under different geometric and physical parameters was obtained. The results show that the anti-crack fusion hole formed by Joule heat reduces the concentrated stress at the crack tip and inhibits the crack propagation. The temperature gradient formed by the high temperature zone in the crack area and the normal temperature zone of the matrix constrains each other to produce a huge hot-pressing stress, which causes the crack width to decrease until it heals. The initial melting hole size is proportional to the crack length and inversely proportional to the plate thickness, and the optimal size diameter is within 0.1 mm. Both the current value and the current loading time can control the growth of the melt hole. When the current value is constant, the size of the melt hole formed when the time reaches 0.12 s exceeds the optimal crack arrest size range. The research results provide a mechanism reference and simulation method for crack arrest and healing of specific metal materials.