The Effect of Stress Relaxation on Complex Modulus Measurements.
Summary rept. May-Jul 70,
OHIO STATE UNIV RESEARCH FOUNDATION COLUMBUS
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The governing equations of motion for the shear response of a viscoelastic specimen subjected to initial stresses are presented. It is shown that relaxation of the initial stresses leads to apparent complex moduli which increase with time. This explains various time dependent anomalies observed experimentally by Fitzgerald. The effect on the real part of the apparent complex modulus is typically small. The effect on the imaginary part is more pronounced and can, under certain conditions, lead to an apparent negative material damping. The implications of these findings with regard to material testing are discussed. Author-PL
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