Constitutive Relations and Characterizations with COMSOL Multiphysics®

Keywords

structural mechanics, plasticity, viscoplasticity, kinematic hardening, heat transfer, welding, constitutive relations
 

Context / Goal

In order to prevent the risk of crack formation in welded assemblies, the knowledge of residual stresses after welding is essential. The modeling process can provide very helpful information but requires a precise characterization of the heated materials.

  • Thermo-mechanical characterization of a material (TA6V) on a large range of temperature (from 20°C to 1000°C) and for different strain rates

  • Adaptability of the model to industrial needs (welding) 
     

SIMTEC's Achievements / Results

The sequence of actions performed by SIMTEC to characterize this material is shown here :

  • bibliography to obtain the specificities of the material behavior (type of plasticity, type of hardening etc.),
  • building of a model in COMSOL Multiphysics® taking into account viscoplastic effects and non-linear kinematic hardening (inspired from LEMAITRE et CHABOCHE [LEMAITRE09]),
  • numerical tensile and relaxation tests in experimental data configurations [ROBERT07]:
Effective plastic strain Mechanical Displacement

 

  • numerical validation of the model and optimization of the different coefficients of the constitutive relations, and
  • confrontation with experimental data [ROBERT07].
     

Two examples of results obtained at two different temperatures (500°C and 800°C) are illustrated below (stress vs strain) for a strain rate set at:  :

Each experimental set of parameters (6 temperatures and 4 strain rates) has been modeled and compared with numerical results. Showing good agreements, the model has thus been validated. The client now has a model of the material behavior under thermomechanical stresses encountered in a welding process. The latter is now added to the complete modeling of the process, to obtain residual stresses and deformations after welding (see Thermo-metallo-mechanical Model of Pulsed Laser Welding with COMSOL Multiphysics®).