Mode Analysis of Reset Section before the Nozzle of Some Certain Type of Engineer of Helicopter

Small cracks appeared in some certain type of engine's jet nozzle of helicopter recently,the trouble chiefly occurs around the reset section welding seam before the jet nozzle.In this paper,based on a jet nozzle structure in the engine,a calculation model was developed.The numerical results of free vibration frequencies and modes were also obtained through analyzing the integrated jet nozzle structure.Mutual comparison showed that the results of FEA estimation were in good agreement with those of testing.