高速列车车顶铜导体压接开裂原因分析及改进措施

针对铜导体压接过程中出现的开裂失效现象, 通过分析微裂纹与压接显微组织, 结合有限元计算压接后铜导体等效应力应变, 确定了开裂原因, 并采用结构优化与去应力退火消除开裂倾向、提高加工质量。结果表明: 压接过程使铜导体内壁产生了严重的压缩变形, 等效应变高达0.985, 等效应力达458 MPa。内壁压应力集中超过了铜导体材料的极限强度, 产生了微裂纹进而导致压接开裂现象。在铜导体内套入外径19 mm、壁厚2~4 mm的小管进行压接, 可以达到无间隙无过盈的良好配合, 有效降低铜导体的应力应变, 消除铜导体压接开裂现象。压接后铜导体进行300 ℃退火2~3 h, 可以有效消除残余应力并保持较高硬度及力学性能, 提高了铜导体的加工质量。

Cause Analysis and Improving Measures for Cracking Failure in Crimping Process of Copper Conductor for High-Speed Train Roof

In view of the cracking failure occuring during the crimping process of copper conductor, the causes of cracking were determed by analyzing the microcracks and the microstructure of crimp, combined with the finite element calculation of equivalent stress and strain of copper conductor after crimping. Then, measures including structural optimization and stress-relief annealing were adopted to solve the problem and improve the machining quality. Results showed that during the crimping process, the inner wall of copper conductor was compressively deformed, with the equivalent strain up to 0.985 and the equivalent stress up to 458 MPa. The compressive stress concentration on the inner wall exceeds the ultimate strength of copper conductor material, thus the generated micro-cracks finally develop into crimping cracks. A tube with an outer diameter of 19 mm and a wall thickness of 2~4 mm is sleeved into the copper conductor for crimping, achieving a good fit without gap and interference, which can effectively reduce the stress and strain of the copper conductor, and eliminate the crimping cracking of the copper conductor. The copper conductor after crimping is subjected to annealing at 300 ℃ for 2~3 h, which can effectively eliminate residual stress, while maintaining high hardness and mechanical properties of copper conductor, thus the machining quality is improved.