Description / Abstract: Purpose.

A Johnstone test apparatus or equivalent (see SAE J1864) is used to conduct this test. A sealed steel cylinder (of initial volume of 150.76 cc) is filled completely, with material to be tested, loaded into the check load frame and subjected to a progressive increase in loading upon the pressure cap. This load is applied in a manner which increases the internal hydrostatic pressure of the material by a measured increment (usually 13.8 bar (200 psi)). Any displacement of the pressure cap is measured by means of a dial extensometer or Linear Voltage Displacement Transducer (LVDT). Two (2) additional measurements are taken at each material pressure increment – the air pressure in the loading cylinder (total applied load), and the displacement of the pressure cylinder cap (total compression). By calculating and plotting the material hydrostatic pressure against the percentage compression of the material, a stress-strain plot for the material can be constructed and used to determine effective compressive modulus (resistance to compression) and filler yield point (failure limit of pressure sensitive filler components). Finally, the total material compression for a peak loading pressure can be separated into rebound (elastic) and crush (permanent) compressive elements.

Applicability.

This test procedure is applicable to ultralight sealer materials approved under the following specifications: GMW16070, GMW16680 or any other materials containing glass bubbles as lightweight fillers