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Hardness Vs Spring rate

Hardness Vs Spring rate

Hardness Vs Spring rate

(OP)
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

RE: Hardness Vs Spring rate

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

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