Metallurgical Investigation of a Cracked Splice Plate Used in a Power Transmission Line Tower

Abstract

Steel splice plates are used in power transmission line towers. During service, some of these plates may fail due the loading stress as well as stress generated due to inclement weather condition. One such failed splice plate, cracked in the heel region of the plate has been studied in detail to find out genesis of such failure. Metallographic study of the failed plate material near the crack and away from the crack indicated presence of white hard martensite layer near the crack. Evaluation of mechanical properties of the plate material carried out at heel and edge regions had also supported the above findings. There was enhancement of hardness, yield strength, tensile strength of the plate near heel which had indicated localized hardening of the plate in this region due to presence of martensite. A substantial deterioration of the Charpy impact toughness of the material at the heel region could also be observed particularly at subzero testing temperatures due to the same reason. The material inadequacies and operational stresses must have caused the initiation and propagation of the cracks in the heel region of the plate leading to its premature failure.