CONSTITUTIVE MODELING AND FINITE ELEMENT
METHODS FOR TRIP STEELS

Prof. Nikolaos Aravas
Department of Mechanical and Industrial Engineering
University of Thessaly, GREECE

Abstract

A constitutive model that describes the mechanical behavior of steels exhibiting “Transformation Induced Plasticity” (TRIP) during martensitic transformation is presented.  Multiphase TRIP steels are considered as composite materials with a ferritic matrix containing bainite and retained austenite, which gradually transforms into martensite.  The effective properties and overall behavior of TRIP steels are determined by using homogenization techniques for non-linear composites.  A methodology for the numerical integration of the resulting elastoplastic constitutive equations in the context of the finite element method is developed and the constitutive model is implemented in a general-purpose finite element program.  The model is calibrated by using experimental data of uniaxial tension tests in TRIP steels.  The problem of necking of a bar in uniaxial tension is studied in detail.  The constitutive model is used also for the calculation of “forming limit diagrams” for sheets made of TRIP steels; it is found that the TRIP phenomenon increases the strain at which local necking results from a gradual localization of the strains at an initial thickness imperfection in the sheet.

 Thursday, November 8th
337 Towne Building
2:00 – 3:00 p.m.