The test results show that the welding bubbles and depression in welding area, and the transgranular crack in heat affected area are the causes of the rail fracture.

• 结果表明，在焊料与基体金属间存在较大的孔洞或凹陷及热影响区内的穿晶裂纹构成了裂纹源，这些裂纹在外界疲劳荷载的作用下，逐渐扩展，最终导致了钢轨的断裂。