The ability of polyurethane foam slabs to withstand the effect of repeated compressions is determined with the help of a Shear Fatigue Test.
In this test, a test specimen in shape of a square block is held over a flat reciprocating platform and is pressed down from top by a horizontal cylindrical roller inclined at an angle of 15° to the direction of motion of the platform. The platform is moved for a specified number of cycles and the effect of repeated compressions produced on the test specimen is evaluated by finding the change in its thickness and indentation hardness number.
IS 7888 – 1976 : Methods of Test for Flexible Polyurethane Foam
ASTM D 3574 – 1986 : Standard Methods of Testing Flexible Cellular Materials Slab, Bonded, and Moulded Urethane Foams.