Block-Program-Volume Effect

A cantilever beam is 300 mm long, with a rectangular section of 100 x 10 mm. The beam is made of carbon steel already examined in sample problem 5 of Sect. 4.2 and is loaded at the edge by three different load histories A, B and C with R = 0 as follows 

56 S-N curve under completely reversed (dotted line, R = —1) and released tension (full R = 0) conditions and Haibach correction for the gear material 

The three load histories constitute the unit block-program. Knowing that 1,000 work pieces will be built, calculate the number m of blocks that can be tolerated by the beam without fatigue failure with 99.9 % of probability of survival Ps — I — P, P being the cumulative probability function. The three moments at the fix end of the cantilever beam corresponding to the three loads are 

Reference is made to Fig. 4.26 that follows reported as Fig. cycles for each load history are those of curve Pf99.9). Then, it follows 

Note that it has not been considered the Haibach correction as in the previous problem, but it should. The number of allowable blocks is 

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Block-Program-Volume Effect-Henry Approach... 

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