Phase Angle

is an oscillatory shear strain.

is the oscillatory shear strain at time zero.

is the angular frequency of the oscillatory shear strain.

is the time.

is the stress (I am not sure why McCrum didn't call this "oscillatory shear stress.")

is stress at time zero.

is the phase angle by which the strain lags behind the stress.

G is the shear modulus.

J is the shear compliance.

[McCrum-115] For solids that are purely elastic, tan

equals zero.

Polymers can have values of of the order of several degrees; values as high as 30 degrees are possible.

Last Update- June 29, 1995- wld