A metallurgical failure analysis was requested on a failed automated welding equipment door after the door unexpectedly fell on a worker’s arm. The analysis was to determine whether a design and/or manufacturing defect caused the failure. The failure was found to have occurred in the aluminum door-header beam. Visual examination revealed that the header beam failed in three separate locations: at a large milled notch in the center, and at both header beam ends.
Microscopic and macroscopic examination further revealed that the beam failed due to progressive overload. Design analysis showed that the door was safe under normal usage conditions. Reconstruction of the incident was attempted through building and testing an exact copy of the door. Photograph A is an overall view of the replica door.
Photograph A Replica door positioned for testing.
Mechanical and metallurgical testing of the replica door revealed that the door functioned safely if properly maintained. The three distinct and separate failures in the header beam prior to the actual door accident attest to the fact that the header beam failure was not due to improper design or manufacture.
The final result of the metallurgical failure analysis was that improper maintenance was the cause of this failure. Loose bolts and improper maintenance by the operator caused the door failure.
Photograph B Cracked beam in center of automated door header.