Abstract:A screw failure was found when the line joints were taken apart. This paper records the results of
macroscopic observation, the microscopic observation and measurement, the observation of the screw, and the material
tests of the failure part, such as hardness test and metallographic analysis. The results indicated a seizure of the
threads on the line joints which originated in an adhesive wear, the type of which causes most severe damage. Combined
with the assembly mechanism of the screw thread connection, it is concluded that using the same material is the
internal cause of the adhesive wear of the line joint. Too little interspaces between the joint which leading the screw
thread of the joint broken during installation and the remainders accumulate made the nut deflexion is the main cause
of the adhesive wear of the line joint.
