Failure due to synergistic fracture and pitting corrosion of ruptured bolts in a LARZAC engine of Alpha Jet

Abstract:

In one of the front bearing support of LARZAC engine from one of the factories in Egypt; a case of material failure occurred in six bolts due to a synergistic effect between corrosion and vibration (corrosion fatigue). This chapter studies the reasons for the failure and investigates the possible reasons for corrosion and stresses. Materials examination was performed by visual inspection, macrograph, and SEM-EDS. The results of the materials examination showed that the main mode of failure was transgranular fracture with pitting corrosion by the proven presence of chloride and sulfur. The scanning electron microscopy (SEM) micrographs showed the presence of well-defined pitting corrosion. Microprobe surface analysis of the corrosion products formed at the pitting areas was performed using EDS and revealed presence of chloride and sulfur. Surface examination also revealed well-defined area of fracture and cracks initiation. The occurrence of fracture and cracks can be attributed to the vibration originated in the bearing system. (A failure has been identified in the bearing rolling system which resulted in noise during running. However, the reasons for such failure are not the topic of this chapter.).

Año de publicación:

2016

Keywords:

• Failure analysis
• Fracture
• Ruptured bolts
• vibration
• Pitting corrosion
• LARZAC engine

Fuente:

scopus