- Elastic Torque, S′
- The peak amplitude torque component which is in phase with a sinusoidally applied strain.
- Viscous Torque, S′′
- The peak amplitude torque component which is 90° out of phase with a sinusoidally applied strain.
- Complex Torque, S*
- The peak amplitude torque response measured by a reaction torque transducer for a sinusoidally applied strain.
Mathematically, S* = (S′² + S′′²)^1/2
- Loss Angle, delta
- The phase angle by which the complex torque (S*) leads a sinusoidally applied strain.
- Storage Shear Modulus, G′
- The ratio of (elastic) peak amplitude shear stress to peak amplitude shear strain for the torque component in phase with a sinusoidally applied strain.
Mathematically, G′ = [(S′/Area)/Peak Strain]
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- Loss Shear Modulus, G′′
- The ratio of (viscous) peak amplitude shear stress to peak amplitude shear strain for the torque component 90° out of phase with a sinusoidally applied strain.
Mathematically, G′′ = [(S′′/Area)/Peak Strain]
- Complex Shear Modulus, G*
- The ratio of peak amplitude shear stress to peak amplitude shear strain.
Mathematically, G* = [(S*/Area)/Peak Strain] = (G′² + G′′²)^1/2
- Loss Factor, Tan delta
- The ratio of loss modulus to storage modulus, or the ratio of viscous torque to elastic torque.
Mathematically, tan delta = G′′/G′ = S′′/S′
- Dynamic Complex Viscosity, n*
- The ratio of the complex shear modulus, G*, to the oscillation frequency in rads/sec.
- Real Dynamic Viscosity, n′
- The ratio of the loss shear modulus, G′′, to the oscillation frequency in rads/sec.
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