Aspecimen of a 4340 steel alloy with a plane strain fracture toughness of 54.8 mpa m (50 ksi in. ) is exposed to a stress of 1090 mpa (158100 psi). assume that the parameter y has a value of 1.11. (a) if the largest surface crack is 0.8 mm (0.03150 in.) long, determine the critical stress σc.

To solve this problem it is necessary to apply the concepts related to stress failure, stress and last module Young.

Critical stress by definition is given as,

Where,

Strain fracture toughness

Y = Young's module

a = Length surface crack

Our values are given as,

Replacing in our previous equation we have,

Therefore the critical stress is 984.77Mpa

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