某车辆在下线时发生横拉杆断裂失效。使用扫描电镜、光谱仪、硬度计等仪器设备对断裂的横拉杆进行了失效分析，并利用二维有限元数值计算方法模拟了钢材冷挤压过程中心部裂纹的形成过程。结果表明：该失效件是在冷挤压变形加工过程中受到了过大的载荷，内部产生了多处开裂，使有效连接面积大幅减小，因而当车辆行驶时，横拉杆即发生断裂失效。

A tie rod fracture failure occurred when the car got off the production line. The fractured tie rod was analyzed by using scanning electron microscope, spectrometer, hardness tester and other equipments, and two-dimensional finite element numerical calculation method was used to simulate the crack formation process in the center of the rod during cold extrusion. The results show that the failure tie rod was subjected to excessive load during the cold extrusion deformation process, which resulted in multiple internal cracking, so the effective linked area was greatly reduced. Therefore, the tie rod fractured when the car moved.