A 1047 steel plate is subjected to a tensile stress of 120 MPa. Given its fractu

Question

A 1047 steel plate is subjected to a tensile stress of 120 MPa. Given its fracture toughness is 45 MPa?m and Y = 1, (a) Determine the critical crack length to assure the plate will not fail under static loading. (b) Consider the same plate under the action of cyclic tensile/compressive stresses of 120MPa and -30 MPa, respectively. If the component is to remain safe for 10 million cycles, what is the largest allowable crack length? (c) Compare the two critical crack lengths in (a) and (b), comment on the effect of the type ofloading on critical crack length.

Explanation / Answer

a. tensile stress = K/(Y(pi*a))

120 = 45/(1(3.14*a))

(3.14*a) = 0.375

a = 0.045m = 4.5 cm

b. compressive strees = K/(Y(pi*a))

-30 = 45/(1(3.14*a))

a = 0.72 m

tensile stress = K/(Y(pi*a))

120 = 45/(1(3.14*a))

(3.14*a) = 0.375

a = 0.045m = 4.5 cm

during cyclic loading crack length varies b/w 0.72 to 0.045 m

c. during cyclic loading crack length is high compared to normal loading

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