System Calibration Procedure
Yerzley Oscillograph is an efficient means of obtaining the mechanical properties of rubber and similar materials. The calculations for dynamic properties rely on the “moment of inertia – I” of “the beam”. The component of the oscillograph, called “the beam” does not have a simple geometry; so it is not easy to determine it’s “I” value purely from geometry. Furthermore, there are many components attached to this beam that affect the actual moment of inertia. The ASTM Standard D945-06 on page 9, in paragraph 13.10 mentions that 0.100 slug-ft.sq is an approximate value that has historical acceptance.
It is possible to determine the moment of inertia of the beam together with all it’s attached components experimentally. The method is based on the paper by Dr. F.L.Yerzley, published in the proceedings of the ASTM in volume 39, 1939.