Hardness Vs Spring rate

[shivkug]

Is there any approximate relations for NR rubber hardness values to their Spring rates.

i.e, Different shore value - Spring rate

35 to 40 - xxx
41 to 45 - yyy + A% of immediate above range
46 to 50 - zzz + A% of immediate above range

expecting some constant A% value which can say that changing shore value from 46 Class to 40 Class will effect some A% of spring rate.

Regards,

Shivkumar

 

[tomaspin]

Shivkumar,

Hello again!

Spring stiffness is directly proportional to the rubber modulus.
The following figures are taken from 'Engineering Design with Natural Rubber', so you could use these as a starting point. Once you know the stiffness characteristics of a mounting in a particular hardness, then you can estimate the effect changing the compound will have

Hardness Youngs modulus(MN/m2) Shear Modulus (MN/m2)

30 0.92 0.30
35 1.18 0.37
40 1.50 0.45
45 1.80 0.54
50 2.20 0.64
55 3.25 0.81
60 4.45 1.06
65 5.85 1.37
70 7.35 1.73
75 9.40 2.22

The units are Mega newtons/ meter squared, and are for guidance only.Your test lab or compound supplier should be able to give you accurate data.


Regards

Tom