Unformatted text preview: lags behind the stress. The tangent of 6 is often used as a measure of the internal friction of a linear viscoelastic material: imaginary part of M tan6 = real part of M * (4) For the Kelvin model, we have (5) M = 1 + iwr, E R 1 IMI= (1+w2r~)1'2ER, 1 f w".," 1 + iwr, When [MI and tan6 in (5) and (6) are plotted against the logarithm of w , curves as shown in Fig. 1.3:l are obtained. Experiments with torsional I I I I - ,n I -. c .- c Internal friction - 0 Y .- - 2 0.01 0. I 10 100 0- Fig. 131. Frequency dependence of internal friction and elastic modulus....
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- Fall '05