Brittle Fracture of a Lifting Stud During Assembly Operations

A lifting stud from a stator frame broke during assembly operations. The part was hot rolled from a 50 W grade low-carbon steel (according to the Canadian standard CSA G40.21-04), which is the equivalent of AISI 1022 grade. Complete metallurgical characterization of the material showed that the chemical and mechanical requirements of the aforementioned standard were met. Moreover, the tensile testing showed that the material had good ductility. Fractographic investigation, both at the macroscale and microscale levels, indicated that the lifting stud failed under bending overload, in a brittle mode. It was found that brittle behavior of the ductile material was caused by the sudden application of the load combined with triaxial stresses promoted by the threaded geometry.