Evaluation for rheological constitutive relations, using the indentation technique
Abstract
A simple experimental method of determining the rheological constitutive relations is proposed. The method relies upon an analysis of the frictionless contact of a rigid spherical indenter and the rheological materials. The proposal addresses problems in two fields: rheological constitutive models and contact mechanics. It attempts to evaluate the rheological constitutive relations using an indentation technique. A systematic, optimizationbased material parameter/function indentation model is proposed. The identification algorithm is based on a modified MarquardtLevenberg method. A new integral constitutive equation for viscoelastic materials is derived. The derivation is carried out so that a damage function is included in the model in a relatively convenient form. Inclusion of damage effects makes this constitutive equation considerably more general than the widely accepted KBKZ integral model. The singlestep and doublestep stress relaxation indentation experiments on asphalt materials were performed. The KBKZ, Wagner, and nonlinear Volterra models were evaluated. It is demonstrated that the new integral constitutive model shows a very good agreement with the experimental data. The idea of damage function is introduced not only to have a better fit of data, but the damage (or irreversibility) is observed experimentally. Also, the creep indentation tests on composites were presented. A multiaxial theory of creep deformation for particlestrengthened metal matrix composites (ZhuWeng Theory) was evaluated. The goal of the proposed research is to develop the indentation technique for use in basic mechanical studies. From the indentation test, material response is measured. The data are used in conjunction with the material parameter identification model to optimally back calculate the constitutive relations. <Comparing the experimental data between the indentation test and other experiment method demonstrates the viability of the proposed approach.
 Publication:

Ph.D. Thesis
 Pub Date:
 January 1992
 Bibcode:
 1992PhDT........14F
 Keywords:

 Constitutive Equations;
 Creep Tests;
 Impact Tests;
 Integral Equations;
 Mathematical Models;
 Metal Matrix Composites;
 Creep Properties;
 Indentation;
 Parameter Identification;
 Viscoelasticity;
 Physics (General)