Repeated stress cycle

More formally if a component or structure is subjected to repeated stress cycles, like the loading on the connecting rod of a petrol engine or on the wings of an aircraft - it may... 

Figure 5.40 Variation of stress with time that accounts for fatigue failure by (a) a reversed stress cycle and (b) a repeated stress cycle. Reprinted, by permission, from W. Callister, Materials Science and Engineering An Introduction, 5th ed., p. 210. Copyright 2000 by John WUey Sons, Inc.

Equipment must be designed for pressures between 80-400 bar (8-40 ME ), as well as for the stress of repeated cycles. 

As seen from Figure 7, the area of the hysteresis loops decreases with the number of loading cycles following the second scenario indicating a possible decrease in the ability to carry of interfacial shear stress with repeated loading. This can be calculated as follows [1] ... 

Stress Cycle The smallest part of the stress-time function which is repeated periodically and identically. A stress cycle is a condition in which the alternating stress goes from an initial value to a maximum value, then to a minimum value and then returns to the initial value. A single operational cycle may result in one or more stress cycles. 

Fatigue is a phenomenon that leads to fracture under repeated or cyclic stresses having a maximum value less than the tensile strength of the material. Commonly, stresses alternate between tension and compression. Because the number of stress cycles, N, prior to fracture is a function of the applied stress, S, the graphic representation of stress versus the number of stress cycles or simply S-N plots are frequently used to report and describe the fatigue... 

Even in the best of designed machinery and plant failures can occur. When they do, the cause is normally investigated so that repetition can be prevented. Modes of failure relate to the type of stress under which the component has been working and the characteristic features of failures due to tension, compression, shear and torsion are well-known. Sometimes the failure is related more to the operating process than to the stress particularly when there is repeated stress cycling of the part and it can suffer fatigue failure. 

One such limitation was the tendency for pixels to delaminate, whereby the pixels would separate from its substrate. As these first-generation detectors were designed essentially for one use military applications, they could not cope with the thermal stresses of repeated heating-cooling cycles from liquid nitrogen cooling. 

The maximum repeated stress that can be endured by a metal without failure under definite conditions of corrosion and fatigue, and for a specific number of stress cycles and a specified period of time. 

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