Reason Analysis and Improvement of a Vehicle Door Latch Failed to Meet Anti-theft Requirement

A vehicle door latch failed to pass the anti-theft test.The direct cause was the fracture of a bolt in the latch.The fracture reason of bolt was analyzed by the methods of macro examination,fracture analysis,hardness testing,metallographic examination and so on.The results showed that overload was the main reason which led to ductile fracture in the bolt.Therefore the bolt strength grade was increased from 4.8 to 8.8 to avoid overload.The improved vehicle door latch successfully passed the anti-theft test.