A DAMAGE CONSTITUTIVE MODEL ACCOUNTING FOR INDUCED ANISOTROPY AND BIMODULAR ELASTIC RESPONSE

Abstract

IN SEVERAL CLASSES OF MATERIALS PROGRESSIVE DI®USE DAMAGE IS RESPONSIBLE BY SEVERE CHANGES OF THE MECHANICAL RESPONSE. CONTINUOUS DAMAGE MECHANICS (CDM) IS A PROPER TOOL TO FORMULATE DAMAGE CONSTITUTIVE RELATIONSHIPS INCLUDING SUCH KIND OF FEATURES. FOLLOWING CDM, A CONSTITUTIVE MODEL IS PROPOSED HERE BY EXPLORING THE FUNDAMENTAL HYPOTHESIS OF ENERGY EQUIVALENCE BETWEEN REAL AND CONTINUOUS MEDIUM. ACCORDING TO THE PROPOSED MODELING, THE MATERIAL IS ASSUMED AS AN INITIAL ELASTIC ISOTROPIC MEDIUM PRESENTING ANISOTROPY AND PERMANENT TRAINS INDUCED BY DAMAGE EVOLUTION. MOREOVER, DAMAGE CAN ALSO INDUCE A BIMODULAR RESPONSE IN THE MATERIAL, I.E., DISTINCT ELASTIC RESPONSES WHETHER TRACTION OR COMPRESSION STRESS STATES PREVAIL. TO CONVENIENTLY TAKE INTO ACCOUNT BIMODULARITY, TWO DAMAGE TENSORS GOVERNING THE RIGIDITY IN TRACTION OR COMPRESSION REGIMES ARE INTRODUCED. A CERTAIN CRITERIA ARE THEN PROPOSED IN ORDER TO CHARACTERIZE THE DOMINANT STATES. ON THE OTHER HAND, DAMAGE CRITERIA INDICATING THE INITIAL AND FURTHER EVOLUTION OF DAMAGE ARE EXPRESSED IN TERMS OF STRAIN ENERGY DENSITIES. THE MODEL ABILITY TO REPRODUCE BASIC EXPERIMENTAL RESPONSES IS ILLUSTRATED BY COMPARING SOME RESULTS VARYING FROM ONE TO THREE-AXIAL STRESS STATES. A FRAME STRUCTURE BEHAVIOR IS THEN SIMULATED IN ORDER TO SHOW THE POTENTIALITIES OF THE MODEL EMPLOYMENT TO HANDLE LARGE PROBLEMS.