It′s used especially to test the static compression for tuber. Place one standard specimen between parallel flat plates, revolve then compress it a certain range of percentage and then put into the oven under the specified temperature for a certain time period then take it off cooling for 30 minutes to measure its thickness for calculating its permanent deformation rate.
Compression Deformation Rate Formula:
(Uncompressed Thickness - Compressed Thickness)÷(Uncompressed Thickness - Plate Thickness)×100