Effect of Fatigue on Proof Strength of Gas Turbine Combustor Casing
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The objective of an aero-engine combustor structural design is primarily to provide the engine combustor with sufficient fatigue life and strength to permit its continuous operation until a scheduled engine overhaul and to withstand certain overload. During the service, combustor is subjected to cyclic pressure which may affect its overpressure capability. The combustor casing is considered as one of the critical parts in the engine. In this paper, the proof pressure capability of a combustor casing subjected to fatigue loading is evaluated. The effects of the fatigue damage on the proof pressure capability of the combustor casing are also established. During the testing of the casing, the pressure was continuously increased to evaluate the over pressure capability of the casing. The results of this experimental study on the casing of an aero-engine combustor are presented in this paper. A detailed post-fracture investigation of the fracture surfaces of the casing showed that two independent cracks, i.e., one along the circumference of the casing towards the front flange and the other one along the axial direction were developed. Further a detailed investigation of the fractured surface under stereo zoom microscope and scanning electron microscope showed that the presence of striations coupled with dimples indicated that the failure was initiated due to fatigue loading.
KeywordsCombustor Aero engines Proof strength Striations Fatigue Dimples Fracture
The authors express their gratitude to the Director, Gas Turbine Research Establishment, Bangalore for permitting to publish this work. Also the authors would like to thank the staff and scientists of Structural Integrity and Mechanical analysis Group, Structural Mechanics Group-2, Materials Group and Strain Gage Division for their cooperation in making various technical data available to prepare this report.
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