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# Brittle fracture under constant K and negative temperature gradient

## Brittle fracture under constant K and negative temperature gradient

(OP)
Hello all,

It seems like a fairly straightforward question but I cannot find any information in the literature.

Let's suppose we apply a crack driving force K1=45 MPa.m^0.5 to a notched specimen with an upper shelf fracture toughness K_mat = 50 MPa.m^0.5 at room temperature T0=20 oC.

Under a constant K1=45 MPa.m^0.5 (let's ignore the effect of thermal expansion here), the temperature drops to T1=-10 oC and the fracture toughness of the material is now K_mat=40 MPa.m^0.5 (now lower shelf).

Is the specimen going to fail ?

Could you please suggest some references describing similar experiments/theoretical analyses ?

Yohann

### RE: Brittle fracture under constant K and negative temperature gradient

"Is the specimen going to fail ?" yes ... this is like the proof testing the USAF did on the F111 when they found the critical flaw (at room temp) was undetectable. They cool the airplane down and apply a load that proved a crack size that'd permit flying to the next proof test.

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