The results indicated that the crack was caused by the mutual actions both surface shear friction stress and distorting stress, and the cracks developed in the way of stress corrosion.

• 结果表明：上轴裂纹是在较大的表面剪切摩擦应力与扭转应力的共同作用下发生的开裂，裂纹开裂后以应力腐蚀的方式扩展。