SOFTWARE IMPLEMENTATION OF VISCOPLASTIC DEFORMATION AND DAMAGE ACCUMULATION PROCESSES IN STRUCTURAL ALLOYS UNDER THERMAL-MECHANICAL LOADING

Abstract

To evaluate service life characteristics of structural materials (metals and their alloys) subject to degradation mechanisms combining fatigue and creep of material under nonstationary thermal-mechanical loading, a mathematical model of damaged medium mechanics is developed, which consists of three interrelated parts: relations defining viscoplastic material behavior, accounting for the effect of the failure process; equations describing damage accumulation kinetics; strength criterion of the damaged material. The main characteristics of thermal-cyclic viscoplastic deformation and damage accumulation process (state parameters) are determined with a corresponding formulation of defining relations of damaged medium mechanics in increments which depend on the chosen integration step. Time step can be corrected when dealing with complex parts of the deformation path during the entire computation time, on condition of stability of the computational process. Material parameters and scalar functions of defining relations of damaged medium mechanics are determined using modern experimental-theoretical methodologies, combining numerical and realistic experiments. The issues of software implementation of the model of damaged medium mechanics are tackled. To verify the models of damaged medium mechanics, non-isothermal monotonous and cyclic deformation of laboratory specimens are analyzed. The models of damaged medium mechanics are verified by recovering the initial experimental creep curves, using numerical modeling. The used model of damaged medium mechanics, implemented in the EXPMODEL software product, quantitatively and qualitatively described the main effects of the viscoplastic deformation process of structural alloys.

Keywords: modeling, damaged medium mechanics, algorithm, software, structural element, hazardous zone, thermal-mechanical loading, viscoplastic deformation, stressed-strained state, damage, service life.