The Shear Fatigue Tester for polyurethane foam consists of a reciprocating platform on which the test specimen can be held, a cylindrical roller to compress the test specimen, and an arrangement to either produce a constant deflection of the test specimen or to apply a constant load on it.The reciprocating platform is made of cast aluminium and is moved in a horizontal plane with the help of a motor, worm reduction gearbox, and a link. It moves on four wheels having ball bearings. The wheels run on two metallic rails. The platform has a large number of holes on its upper surface for rapid escape of air during compression. The test specimen is held on the platform with the help of either a double-sided adhesive tape or by holding fabric strips pasted on its ends under two bar shaped grips.
- The cylindrical roller is made of stainless steel and rests on the surface of the test specimen. Its axis is inclined at 15° to the direction of motion of the platform. The roller is mounted on two ball bearings and is held on the ends of two levers to permit a hinged vertical movement.
- The desired deflection is given by placing dead weights above the cylindrical roller. Test under constant deflection are conducted by restricting the vertical movement of the roller with the help of two adjustable knurled bolts. Tests under constant load are conducted by placing desired dead weights above the roller.
- A five digit pre-set type electronic counter with non-volatile memory is provided to record the number of compression of the test specimen and to automatically stop the motor after the desired number of compressions.
- The apparatus is finished in grey hammertone stoving painting and bright chrome / zinc plating to give it a corrosion resistant finish.
|Flexing frequency||28 cpm|
|Movement of platform||330 mm|
|Dimensions of the roller||75 mm diameter, 460 mm length|
|Dimensions of test specimen||380 x 380 mm|
|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|