FINITE-ELEMENT MODELING OF FREQUENCY-DEPENDENT AND TEMPERATURE-DEPENDENT DYNAMIC BEHAVIOR OF VISCOELASTIC MATERIALS IN SIMPLE SHEAR

Material dynamic mechanical behavior can depend strongly on frequency and temperature. This dependence is especially significant for elastom ers and polymers, such as those used in bearings and damping treatment s. Previous research has yielded a time-domain model of linear viscoel astic material and structural behavior that captures characteristic fr equency-dependent behavior; continuing research has addressed the acco mmodation of temperature dependence as well, The resulting approach is based on the notion of lime-temperature superposition for thermorheol ogically-simple materials. In such materials, temperature effects are experienced primarily through a temperature-dependent factor multiplyi ng the time scale. The phenomenon of ''thermal runaway'', observed in some tests of helicopter elastomeric dampers, motivates a numerical ex ample of forced vibration of a 40 x 16 x 5 mm elastomeric lest specime n in simple shear. For forcing at 1500 N and 4 Hz, and the temperature on one face held constant, the temperature at the thermally free face increases by about 3 K. For forcing at 3000 N, the temperature rapidl y increases more than 35 K, and displacement amplitudes increase by mo re than a factor of 4. The coupled-field finite element simulation evi dently captures the key features of observed material response, includ ing a rapidly increasing rate of temperature change and an accompanyin g stiffness reduction.