Failure analysis of inlet guide vane (IGV) actuator and bellcrank assembly used on J85 turbojet engines

This study presents the metallurgical analysis results of fracture failure occurred on the arm of Inlet Guide Vane (IGV) actuator and bellcrank assembly that used on J85-GE-5 turbojet engine. The broken arm material is determined to be AMS4134 Aluminum Alloy Forging. Material composition of Aluminum alloy consists of 93.35%-Al, 4.5%-Cu, 0.85%-Si, 0.8%-Mn and 0.5% -Mg. The average hardness value of the material is measured to be 75 HRB. The metallurgical analysis results indicate that the corrosion assisted fatigue under the influence of repeated loading and corrosion started the micro fractures and cracks on the IGV actuator and bellcrank assembly arm surface, then residual cross-section surface were completely sheared off because the residual cross-section surface did not endure the over load effects overcoming on it. The fatigue area of the arm covers approximately 1/3 of the total cross-sectional area.