Failure Analysis of Micro Cracks and Alumina Inclusions Induced Insulator Pin’s Low Stress Mode of Fracture

Abstract

A tensile test must be conducted for each finished insulator in which a common but significant problem is a low stress mode of fracture. In order to investigate the cause of the low stress fracture in a batch of insulators, a series of failure analysis methods were carried out. As described in this paper, macro-fracture analysis, SEM observation, EDS examination, metallographic structure analysis, hardness test, and inclusion rating were all conducted on the investigation. The results of this investigation show that the major cause of incident fracture is micro cracks in the pin, which are the result of both the molding method and the heating treatment. However, the major reason for the macro cracks lies in the induction heating process, which lacked the accurate temperature control method and using of higher electric power. Furthermore, alumina inclusions in the pin were in excess of standard, so they may also have contributed to the low stress fracture of the pin.