Abstract
The junctions of the flange girth weld and the struts longitudinal weld in the rear support shell exhibited multiple cracks after long-term test run of an aero-engine. Surface and fracture observations, metallographic examinations, hardness testing, and finite element analysis were utilized to explore the cracking cause of the shell. The results indicated that beach marks and fatigue striations were observed on the fractured surface, indicating a typical fatigue failure. The cracks originated from the inner wall surface at the junction of the girth and longitudinal welds, which were located in the stress concentration area of the shell and underwent stronger stress under thermal loading based on finite element analysis. Additionally, the α-case, which decreased the ductility and fatigue properties of titanium, was generated on the inner wall surface of the girth weld due to poor shielding gas during manual tungsten inert gas welding, which was the direct cause of cracking of the shell.
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