tailieunhanh - High Cycle Fatigue: A Mechanics of Materials Perspective part 64

High Cycle Fatigue: A Mechanics of Materials Perspective part 64. The nomenclature used in this book may differ somewhat from what is considered standard or common usage. In such instances, this has been noted in a footnote. Additionally, units of measurement are not standard in many cases. While technical publications typically adhere to SI units these days, much of the work published by the engine manufacturers in the United States is presented using English units (pounds, inches, for example), because these are the units used as standard practice in that industry. The graphs and calculations came in those units and no attempt was made to convert. | 616 Appendix H is provided it shall be demonstrated once during each shut down. Components such as air-oil coolers with exposure to inlet sand and dust conditions shall be considered inlets for this test but a rig test may be performed to satisfy the requirements herein. Following the post-test performance check the engine shall be disassembled to determine the extent of sand erosion and the degree to which sand may have entered critical areas in the engine. The test will be considered satisfactorily completed when the criteria of have been met and the teardown inspection reveals no failure or evidence of impending failure. Background The recommended text decreases the operational time in the extreme sand and dust environment from ten hours to two hours for turbofan and turbojet engines. Engine contractors have been unwilling in the past to guarantee their engines for ten hours helicopter subjected to the severe Vietnam sand and dust environment typically used inlet filtration systems . The time requirement will have to be negotiated with each engine contractor in specific future specification negotiations based upon the intended usage in regions of the world where sand will be a concern. The sand concentration should be calculated with customer bleed air extraction. The anti-icing switch should be activated five times during each hour of sand ingestion at equally spaced intervals. The test should be conducted with a thrust bed and load cell measurement of thrust in lieu of calculating thrust by EPR. Disassembly and inspection between the coarse and fine sand tests should be conducted for kg s 100lb. sec airflow or smaller engines. VERIFICATION LESSONS LEARNED The Engine V sand and dust test did not use the recommended sand and dust mixture due to commercial unavailability of the mixture. The specification for fine sand calls for a particle size distribution which cannot be obtained commercially. Specifically calcite and gypsum could not be .