IDENTIFYING MECHANICAL PROPERTIES OF VISCOELASTIC MATERIALS IN TIME DOMAIN USING THE FRACTIONAL ZENER MODEL

Abstract

THE PRESENT PAPER AIMS AT PRESENTING A METHODOLOGY FOR CHARACTERIZING VISCOELASTIC MATERIALS IN TIME DOMAIN, TAKING INTO ACCOUNT THE FRACTIONAL ZENER CONSTITUTIVE MODEL AND THE INFLUENCE OF TEMPERATURE THROUGH WILLIAMS, LANDEL, AND FERRYÂS MODEL. TO THAT EFFECT, A SET OF POINTS OBTAINED EXPERIMENTALLY THROUGH UNIAXIAL TENSILE TESTS WITH DIFFERENT CONSTANT STRAIN RATES IS CONSIDERED. THE APPROACH IS BASED ON THE MINIMIZATION OF THE QUADRATIC DISTANCE BETWEEN THE EXPERIMENTAL STRESS-STRAIN CURVES AND THE CORRESPONDING ONES GIVEN BY THE THEORETICAL MODEL. IN ORDER TO AVOID THE LOCAL MINIMA IN THE PROCESS OF OPTIMIZATION, A HYBRID TECHNIQUE BASED ON GENETIC ALGORITHMS AND NON-LINEAR PROGRAMMING TECHNIQUES IS USED. THE METHODOLOGY IS APPLIED IN THE CHARACTERIZATION OF TWO DIFFERENT COMMERCIAL VISCOELASTIC MATERIALS. THE RESULTS INDICATE THAT THE PROPOSED METHODOLOGY IS EFFECTIVE IN IDENTIFYING THERMORHEOLOGICALLY SIMPLE VISCOELASTIC MATERIALS.