Overstrain and Load History Effect

Under load history A material fails prematurely relative to load history B. The rational is to be found in the mean stress effect. In case A, in fact, the overload has generated a hysteresis loop of initial path 0-1-2 ending with stress reversal in 2 that 

6 Strain-Based Fatigue Analysis Low Cycle Fatigue 

Using the Palmgren-Miner rule no difference would be found between the two cases. Conversely, experimental results show a rather large difference because the plate would withstand 4,60,000 cycles under load history A and only 63,000 cycles under load history B. Interesting enough, without any overload application at all the pane would has a life of 1,15,000 cycles. 

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