Al-Alloy 2024-T4 Cumulative Biaxial Fatigue under Complex Loading (PDF)

Master's Thesis from the year 1997 in the subject Engineering - Mechanical Engineering, , language: English, abstract: A study of metal cumulative fatigue damage at multilevel stress programs using 2024- T 4 AI -Alloy is carried out in this investigation. Specimens are designed and fabricated. The tests are performed under multiaxial fatigue in phase combined loading bending and torsion, with zero mean stress (R=-l) at room temperature.
Five groups of multiaxial fatigue experiments are performed, constant amplitude, linear increasing and decreasing, Low-High loading sequence, High-Low loading sequence and equivalent flight loading fatigue.
Prediction of life specimens are studied at three methods:
Palmgren-Miner, Corten - Dolan, and Marsh. The methods are conservative to some specimens and non-conservative to another. The effects of stage life (ns) have been examined and fatigue life of specimens are decreased when the stage life is decreased.
Comparisons between High-Low & Low-High loading sequences in fatigue life (multi stress level) have been investigated. The Low-High loading sequence is less dangerous than High-Low loading sequence at the same stress range (equal loading stages).


Studies the effect of stress range fatigue life have been investigated and the fatigue life is decreased with increasing the stress range fatigue (having the same lowest stress).
For the fatigue of equivalent flight loading, the life is depend basically on stress range and the cruising interval this two parameters have been studied.