PEMODELAN DAN SIMULASI NUMERIK FATIGUE CRACK
GROWTH RATE AKIBAT CYCLIC LOADING PADA
STRUKTUR DOUBLER FUSELAGE SKIN STATION NUMBER
360–380 STRINGER 6L–7L PESAWAT BOEING 737-900
EXTENDED RANGE
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Institusion
INSTITUT TEKNOLOGI DIRGANTARA ADISUTJIPTO
Author
Rislya Prakasa, Lado
Subject
T Technology (General)
Datestamp
2024-07-19 08:27:52
Abstract :
In order to determine the strength of the doubler structure in resisting failure due to cracks caused by cyclic loading, a specific analysis excluded from Structural Repair Manual (SRM) is necessary. The cyclic loading can reduce the strength of the skin doubler in a gradual manner (i.e. fatigue) until reaching fracture. This research will analyze the crack growth rate and the number of loading cycles required to generate a crack with a certain length (i.e. fatigue cycle) in the doubler fuselage skin structure of the Boeing 737-900 Extended Range aircraft with a station number of 360-380 between 6L-7L stringers at certain crack lengths and simulated flight altitudes. The analysis was carried out by using a numerical approach employing Modified Virtual Crack Closure Integral (MVCCI) method to obtain the Stress Intensity Factor (SIF) value through a finite-element based software. Through the values obtained, it can be seen that the value of the crack growth rate and fatigue cycle is directly proportional to the certain crack lengths and simulated flight altitudes. The lowest crack growth rate was produced in the result of doubler structure with a crack length of 8,5 mm and a flight altitude of 5000 feet, which was 2,964 × 10?15 mm/cycle, and the highest value of 5,471 × 10?12 mm/cycle was found for doubler structure with a crack length of 51 mm and flight altitude of 40000 feet. Meanwhile, the lowest number of fatigue cycle value was obtained in the result of doubler structure with a crack length of 8,5 mm and a flight altitude of 40000 feet, which was 2,540 × 1013 cycle, and the highest value (i.e. 5,470 × 1015 cycle) was calculated in the case of doubler structure with a crack length of 51 mm and a flight altitude of 5000 feet.
In order to determine the strength of the doubler structure in resisting failure due to cracks caused by cyclic loading, a specific analysis excluded from Structural Repair Manual (SRM) is necessary. The cyclic loading can reduce the strength of the skin doubler in a gradual manner (i.e. fatigue) until reaching fracture. This research will analyze the crack growth rate and the number of loading cycles required to generate a crack with a certain length (i.e. fatigue cycle) in the doubler fuselage skin structure of the Boeing 737-900 Extended Range aircraft with a station number of 360-380 between 6L-7L stringers at certain crack lengths and simulated flight altitudes. The analysis was carried out by using a numerical approach employing Modified Virtual Crack Closure Integral (MVCCI) method to obtain the Stress Intensity Factor (SIF) value through a finite-element based software. Through the values obtained, it can be seen that the value of the crack growth rate and fatigue cycle is directly proportional to the certain crack lengths and simulated flight altitudes. The lowest crack growth rate was produced in the result of doubler structure with a crack length of 8,5 mm and a flight altitude of 5000 feet, which was 2,964 × 10?15 mm/cycle, and the highest value of 5,471 × 10?12 mm/cycle was found for doubler structure with a crack length of 51 mm and flight altitude of 40000 feet. Meanwhile, the lowest number of fatigue cycle value was obtained in the result of doubler structure with a crack length of 8,5 mm and a flight altitude of 40000 feet, which was 2,540 × 1013 cycle, and the highest value (i.e. 5,470 × 1015 cycle) was calculated in the case of doubler structure with a crack length of 51 mm and a flight altitude of 5000 feet.
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