Eren GÜVEN 514111006 (1st Week Unanswered Term)

High Cycle Fatigue (Material)- Previus answer

High numbers of cycles to produce fatigue failure, It is called High Cycle Fatigue.  High Cycle Fatigue occurs when the numbers of cycles are greater than about 10^4 or 10^5 cycles. 
Jack A. Collins, Failure Of Materials In Mechanical Desing : Analysis, Prediction, Prevnetion P.179

High Cycle Fatigue (Material) – New answer / Better

High Cycle Fatigue has been a serious engineering problem in many industries since the 1800s. Around 1995 there were a series of gas turbine engine failures on US Air Force fighter jets that caused great concern because of excessive maintenance costs andpotential costs of redesigns, but mostly because of the threat to operational readiness.

Fatigue is not a technical subject that has been around hundreds of years. In fact, it came into being in the 1800s because of numerous accidents associatedwith railroad axles and railroad bridges, both of which were subjected to repeated loading.Although the terminology “High Cycle Fatigue” (HCF) was not used in connection withthese accidents and the subsequent investigations, the high cycle counts associated withsome of these incidents put them in the high cycle category, values of stress at or near the fatigue limit corresponding to a large number of cycles in the HCF regime, typically 10⁷ cycles or greater.

For HCF, the emphasis is on the value of stress at the fatigue limit and the data arerepresented on a Goodman diagram which is a plot of alternating stress against meanstress as shown in (b). Each value of R is represented as a straight line drawnradially outward from the origin and the plot is the locus of points having a constant lifein the HCF such as 10⁷ cycles.(The Goodman diagram, which should correctly be called a Haigh diagram.)

(*High Cycle Fatigue, A Mechanics of Material Perspective, Theodore Nicholas, Air Force Institute of Technology / Department of Aeronautics and Astronautics, Ohio,USA, P- x,xi,3,8.

*Fundamentals of Material Science, E. J. Mittemeijer , P568.)