THE EFFECT OF STRESS RATIO ON FATIGUE THRESHOLD OF CRAK IN MODE (I) | ||
| Al-Qadisiyah Journal for Engineering Sciences | ||
| Article 1, Volume 7, Issue 4, December 2014, Pages 187-200 PDF (0 K) | ||
| Abstract | ||
| In the present study, the effect of the stress ratio change on the threshold of the fatigue cracks for an aluminum alloy have been researched. This aluminum alloy was taken from a blade of Russian MI25 helicopter. A specimen of MI25 blade has been cut into testing specimens of standard dimensions; the stress intensity factor as a basic variable has been calculate and used by making an initial crack in the test specimens. The test have been conducted for five different stress ratio : ( R = - 1 , 0.0 , 0.1 , 0.3 , 0.5 ) : Several tested have been done to study the effect of these change on the threshold of fatigue crack , The result obtained in this research were compared to some well knows previous scientific theories and research in this field . At each stress ratio ( R ) , several specimens have been used to obtain the threshold stress intensity factor for that value of ( R ) . From the results obtained , it is clear that the value of the threshold stress intensity factor range (ΔK) decreases as the stress ratio increases. Whereas ; at a negative stress ratio: (ΔK) increase for threshold fatigue crack | ||
| Keywords | ||
| aluminum alloy; threshold of the fatigue; negative stress ratio; cracks | ||
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