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Digital imagine correlation DIC: resolution

Hi everybody,

i tried to use the free opticist moire software for DIC. Big thanks to the developers for the work

done.

 So far i did not get the results i was expecting, but i think it is due to my camera / experiment

setup. I want to get the strain field in a traditional tensile test of a coupon using a universal test machine

(instron). The coupon is painted with a black-white speckle pattern. The camera lens does not allow

to get a close-up and focus closely at same time.  so in vertical direction the image covers circa 100mm and the imagine 

has 3000px in vertical direction.

So my question is, what is the minimum displacement one can measure in best case with the DIC in this case?

I thought that if everything shifts vertical by 1 pixel, the displacement would be 100mm/3000px*1px=0,03mm.

(So every pixel covers a vertical length of 0,03mm)

Which would be good in general, but in my case the length of coupon + load was low. Assuming the strain

was 0,1% one would need a measurement length of at least 1000x0,03mm=30mmin order to detect

ithe strain of 0,1% with 1pixel shift.

 I am not so sure f i thought is valid since DIC may interpret lots of pixel (not moving evenly) and maybe can increase the 

accurancy. But so far this my explaination to why i do not get reasonable patterns of strain (influence of errors is to big).

A comment on this would be apprecihated. Good night,

schuffe

 

jorgegdiaz's picture

I´d like to see the outcome of this.
I think you need(ed) find out your camera resolution

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