초록 열기/닫기 버튼
To improve the durability of the turbocharger, it is important to suppress cracking of the turbine housing; therefore, we investigatedthe initiation and growth of these cracks. First, we initiated a crack in the turbine housing using endurance experiments. After the endurance test, cracks mainly occurred in the valve seat, the nozzle area, and the scroll part of the turbine housing. Theresults of a fracture analysis of the cracks showed that cracks in the valve seat were initiated by fatigue fracture. This seems to becaused by the accumulation of mechanical and thermal stresses due to vibration of the turbine wheel and high-temperature exhaustgas. Also, cracks in nozzle and scroll area were initiated by intergranular corrosion due to the exhaust gas. Thus, although there aredifferences in the cause of initiation according to the site, a concentric waveform was observed in all fracture planes. This phenomenonindicates that cracks gradually grow due to repeated stress changes, and the main causes are the temperature difference ofthe exhaust gas and the vibration caused by the turbine shaft.
