The influence of the constraint effect on the mechanical properties and weldability of the mismatched weld joints

The process of welding has dynamic character and is related with the local change of the internal energy E of welded system and can be defined by general dependence between intensive φ_j and extensive ψ_j parameters. The knowledge of the run of thermo-dynamical process under welding indicates on the possibility of active modelling of weldability and the control of welding process: φ_j = ∂E/∂ψ_j. Hence, these process can be enhanced by mathematical modelling and numerical analysis of weldability models of, i.e. welding processes of material behaviour in welding and the strength of welded structures. The main attention is focused on the assessment of susceptibility of materials under defined welding conditions using fracture mechanics parameters. The analysis is based on the normalised parameters such as: ∂/∂_c, K_Ith/K_IC, as a measure of the susceptibility of materials in welding process. The deformation process and fracture parameters calibrations are influenced by constraint; hence the importance of determining the deformation behaviour and fracture parameters as a function of constraint. Furthermore, there established analytically the condition of welding process in mismatched weld joints for strength equal to base metal. Finally, same analytical examples which present new capabilities of weldability estimates and mechanical properties of mismatched weld joints are presented.