Failure Analysis On Fracture Of P4.9 Tube Of Aviation Turbo Fan Engine V2500

It is healthy condition of engines that decided the safety of whole aircraft.The engine studied in this thesis was made by a famous turbo fan engine manufacturer IAE-V2500.It was chosen by A320 series.The P4.9 tube around low pressure turbine was designed to provide outlet air pressure data for engine control.Due to high temperature and corrosion environment,multiple fracture failure events happened during 2012-2014,which caused unsafe events such as returns or diversions.To prevent the same problem happening again,we need to study the reason of fracture.This thesis is working on one of those failure events with normal failure analysis ways.Possibility of fatigue fracture or corrosion fatigue was found by scanning electron microscope(SEM).Fatigue striations spread out from the center of silicon oxide impurity to the entire surface;Energy dispersive spectrometer(EDM)proved that the content of silicon was beyond the limit and the metallographic experiment made on sample proved that organization structure inside was complete--austenitic stainless steel.To get a better understanding for stress state of the P4.9 tube,finite element method software ANSYS was used to simulate the static and dynamic loadings on failure part.The simulation results about static proved that there was stress concentration around the fracture area but which could not be the main cause for the structure failure;the results for dynamic analysis proved that there existed alternating loadings during engine running.And the possibility of thermal stress influence from LPT case was excluded with comparison.Combining the results of ANSYS and observation we know that the main reason for fracture failure is corrosion fatigue.Considering limiting practical condition for operation,two ways in material and structure for improvement were given.The stress results of Incoloy825 and Incone1690 were almost the same,but when compared to the stainless steel,load value decreased about 10%;On the other hand,the structure was enhanced with supplementary material and welding.Stress condition under static and dynamic loadings was improved.Depending on the analysis results of finite element method,both ways were proved to be practicable because they could decrease stress levels for the tube.