Analysis on Cracking of Oil-in Mouthpiece of Oil Radiator

An oil radiator in the main retarder of a helicopter cracked at the welded joint between the oil-in mouthpiece and the cover of the radiator during service. In order to find out the failure mode and failure cause, micro and macro observation as well as metallographic examination were carried out. The results show that crack of the oil-in mouthpiece of the oil radiator is high-cycle fatigue crack, and the cracking of the oil-in mouthpiece is mainly due to the improper design of the structure. The cracking of the oil-in mouthpiece could be avoided by reducing the length of the oil-in mouthpiece and increasing the thickness of the radiator cover.