Failure analysis of compressor blades of a helicopter engine

摘要

This paper presents a detailed analysis of the failure of compressor blades from a helicopter engine. The analysis presented in this paper is a result of a preflight inspection carried out by a line mechanic where damage was detected in the compressor rotor blades of stage 1, which exceeded the limit specified by the manufacturer for the turbine. It has been found abnormal data values for the left engine occurred during the operating phase of the last flight and after opening the engine, it was found that several blades of the stages 1, 7, 8, 9 and 12 and some blades of inlet guide vanes were damaged. In order to determine the causes of the failure, a material analysis was performed, followed by a detailed study of the fracture's surface both visually and using optical and scanning electron microscopies. The observations of fracture surfaces of the stage 1 compressor blade revealed a large plastic deformation of the blade normally associated with the collision of different components. The fracture surface shows facies similar over the entire surface, typically observed in over stress fractures, showing however along the fracture surface different levels of plastic deformation caused by the contact, with no visible initiation of fracture that may be associated with an indentation caused by a foreign object. Having contact between the blade of stage 1 with inlet vanes blades, it appears that this impact was the cause of the fracture of the stage 1 blade. The blades of stage 7, 8, 9 and 12 present damage clearly caused by the collision of foreign object, which may have originated by the fracture of the stage 1 blade.