Failure Analysis of Ball Clevis of 320KN Hardware Fittings

Abstract

Failure analysis of ball clevis of 320 KN hardware fittings was carried out through microstructural analysis, mechanical properties evaluation and SEM analysis. Chemical composition and mechanical properties of the component conforms to the standard specification. The microstructure consists of tempered martensite. However, fractographic studies of the failed component revealed the presence of a large number of secondary cracks on the fracture surface. This indicates that the probable cause of failure of the component could be delayed cracking, a kind of hydrogen embrittlements that involves initiation and propagation of cracks under the condition of relatively slow strain rate or sustained load controlled by diffusion of hydrogen present in the materials, and leading to the failure of the component at a significantly low load. This hydrogen might have been introduced into the material during manufacturing process.