Second Airframe Division, National Aerospace Laboratory(NAL)
Second Airframe Division, National Aerospace Laboratory(NAL)
Second Airframe Division, National Aerospace Laboratory(NAL)
Second Airframe Division, National Aerospace Laboratory(NAL)
First Airframe Division, National Aerospace Laboratory(NAL)
出版者
航空宇宙技術研究所
出版者（英）
National Aerospace Laboratory(NAL)
雑誌名
航空宇宙技術研究所報告
雑誌名(英)
Technical Report of National Aerospace Laboratory TR-683
Since the USB flap of the NAL-STOL experimental aircraft is one of the primary design modifications of the original C-1 transport aircraft, an acoustic fatigue test of sub-structural models at elevated temperature was conducted to verify the safety of the flap structure during the planned flight evaluation program. The following five structral models were provided: upper surface (A) and lower surface (B) substructures of the main flap, upper surface substructures of the fore flap (C), and additional models for upper (D) and lower (E) surfaces with reduced panel thickness. All structural models consist of the face panel with stringers and ribs rivetted on the backside in # shape. Thus they are called “nine-bay” models, with the center bay being of primary importance. Test panels (A), (B), (D) and (E) are all flat but (C) has the same curveture as the actural flap structure. The material of the face panels and stiffeners of (A), (C) and (D) is Ti-6A1-4V alloy and that of (B) and (E) is 2024C-T3 alloy. The present test program comprises the following four items: (1)Static thermal loading up to 200C to detect the thermal buckling temperature of test panels (A),(C) and (D). (2)Vibration test by an electric shaker and impact test to identify the resonant frequencies, mode shapes and damping coeffidients. (3)The dynamic strain response measurement and its data processing to compare the results with the numerical simulation solution. (4)Acoustic fatigue test on test panels (A), (C) and (D) at elevated temperature and on (B) and (E) at room temperature. The conclusions reached by the present experiment are summarized as follows: (1)Thermal buckling occured on test panels (A) and (D), but not on (C). (2)Resonant frequencies of the flat test panels (A),(B), (D) and (E) fall in the range between those of clamped and those of simply supported plates. However resonant frequencies of (C) are very close to those of the simply supported plate. (3)The dynamic response strain spectrum has a significant frequency content in the 100～200Hz range besides the peaks at the resonant frequencies. (4)Through the prescribed fatigue test period, all structural models have proven themselves to be strong enough to resist both acoustic and thermal loading. No detectable damage was found on the panel face or around the rivet holes. Besides the laboratory verification, analytical treatment on the strain response has been analyzed and the fatigue life has been estimated on the assumption that the flat test panel was uniformly loaded by heat and noise. The strain responses of simply supported panel qualitively agreed with experiments in terms of the spectrum, but their R.M.S. values were larger than those determined measurement. All estimated lives based on both simulated and experimental strain histories suggested confirmation of the fatigue test results.
USBフラップ構造模型の高温における音響疲労試験について
naltr00683.pdf
(4.7MB)
