Clevis Pin Failure

A turnbuckle clevis pin used to hoist and hold the mast of a sail boat in place failed, resulting in the mast falling into the ocean. A metallurgical failure analysis was requested on the failed turnbuckle pin. Metallurgical testing included macro/microphotography, EDS analysis, and scanning electron microscopy (SEM). The failed clevis pin fracture surface is shown in Photograph A.

Photograph A: Overall view of the subject failed turnbuckle and fractured clevis pin.

Upon examination, the subject fractured turnbuckle clevis pin was found to contain massive amounts of interdendrite casting  porosity. This interdendrite casting porosity was the result of insufficient liquid feed metal into the casting mold during the casting process. In addition, the chemical composition of the subject turnbuckle clevis pin was not of marine quality bronze.

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