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Re: Charpy Impact Test

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>1. The test temperature can be well above the minimum operating
>temperature and is dependent on the strain rate of the application
>(slow, moderate, impact).  For a strain rate of 1/1000 in/in/sec as in
>bridges, the difference is about 70 degree F. If you have the CVN value
>at test temp of 32 degree, i.e. it is good for min operating temperature
>of -38 degree. This value can be used for application that required test
>temperature at 70 on the safe side ( min operating temp is 0 degree).

I'll quibble with this. The ASME Code (UG-66) classes A-53 with A-515 gr 
60 and A-285 Gr A and B which have NDT above 32F. Your test value at 32F 
may indeed reflect the values at -38F because 32F is very near the lower 
energy shelf, anyway. 

Moreover you shouldn't go extrapolating Cv data to different strain 
rates. The 70 deg temperature shift reflects the effect of different 
testing speeds. If you're trying to qualify a material for toughness, the 
Charpy data shouldn't be fiddled to reflect another loading rate. 
Besides, ssuming that the loading rate equals the strain rate is 
incorrect, since the loading rate doesn't reflect the strain rate in 
front of a propagating crack. If you're looking for fracture toughness, 
A-53 is the wrong choice. 

>(ASTM STP 466, Impact Testing of Metal, 1970). Not for A53 specifically, 
The correlation includes A-36 with chemistry that overlaps that of A-53 
so it'll probably be as good for A-53 as for anything else. 


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