The interrelations between temperature, mechanical behaviour, phase transitions, and, in case of necessity, of carbon diffusion which are essential for distortion are investigated both mathematically and numerically. Even in the case of simplifying assumptions, models for these relations lead to a initial/boundary value problem for a coupled system of nonlinear, partial and ordinary differential equations, involving the time- and space-dependent fields of temperature, displacement, and phase fractions (of austenite, martensite, pearlite, e.g.). A special feature of steel is the transformation induced plasticity (TRIP), leading to plastic deformations even in the case of relatively small stresses. Dealing with TRIP and classical plasticity is a challenge for modelling as well as the mathematical and numerical analysis of these problems. Adaptive finite element methods are investigated for numerical simulations.

Key activities of the project C3 are:

• Simulations using adaptive FE methods with ALBERTA^TM and - when appropriate - with SYSWELD^TM and COMSOL^TM, respectively
• Modelling of single phenomena and of the bulk behaviour
• Evaluation of models of single phenomena using MATLAB^TM based on measured data

 

Currently, among others, we work on the following subjects, in cooperation with other groups of SFB570:

• Comparison and Evaluation of models of single phenomena by means of 3d simulations in ALBERTA^TM, COMSOL^TM and (when appropriate) in SYSWELD^TM based on measured data.
• Simulations in ALBERTA^TM, COMSOL^TM and SYSWELD^TM, respectively, concerning analysis of distortion for work pieces with and without phase changes.
• Testing and evaluation of models for phase transformations, TRIP and stress-dependent transformation behaviour for undereutectoid steels with different carbon content.
• Evaluation of relevant creep models based on measured data.