How this calculator works
Bulk stiffness relates a pressure increase to a reduction in volume. Enter volume change as final volume minus initial volume, so compression is negative. The secant relation assumes a nearly constant bulk modulus over a small pressure interval. Pressure here is a change, not an absolute pressure.
Formula
B = -Delta p / (Delta V / V0); volumetric strain = Delta V / V0.
Worked example
A pressure rise of 2 MPa compressing 1 m3 by 0.001 m3 gives B = 2 GPa. A 1 MPa rise in the same material gives a volume change of -0.0005 m3.
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Frequently asked questions
Why is there a minus sign?
A positive pressure rise normally produces a negative volume change, while bulk modulus remains positive.
Can I use this for a gas?
Only over a small interval with the correct isothermal or adiabatic modulus for that process.
Is strain a percentage?
The result is a dimensionless fraction. Multiply it by 100 to express percent.