A mesomechanical analysis of the stress–strain localisation in friction stir welds of polycrystalline aluminium alloys

Abstract

A numerical analysis is presented of the microstructural effects on the deformation and fracture of friction stir welds in aluminium alloys. A dynamic boundary-value problem in a plane strain formulation is solved numerically by the finite-difference method. Experimental polycrystalline microstructures inherent in different weld zones-base material, weld nugget, and thermo-mechanically affected zones-were accounted for explicitly in the calculations. To simulate the mechanical response of individual grains, use was made of an elastic-plastic formulation of the problem accounting for isotropic strain hardening, including the Hall-Petch effect, and of a fracture model allowing for crack initiation and growth in the regions of maximum equivalent plastic strains. Plastic strain and fracture localisation is shown to depend on the strength of welded materials.

A Numerical Study of the Microscale Plastic Strain Localization in Friction Stir Weld Zones

“…The strength of the material was found to depend on the degree of ordering of the microstructure. A similar numerical analysis for a microstructure containing fine and coarse grains in the nugget and base materials and elongated grains in the TMAZ was performed in [10]. Maximum plastic strain localization and fracture sites were found to depend on the specimen strain and strength of the material.…”

“…Maximum plastic strain localization and fracture sites were found to depend on the specimen strain and strength of the material. Both sets of calculations [9,10], however, were performed for rather idealized 2D microstructures, with the isotropic elastic-plastic models being used to describe the deformation response of individual grains. It is, therefore, a challenge to perform a more realistic 3D analysis of microscale stress and strain fields formed in different FSW microvolumes under loading with accounting for an anisotropic elastic-plastic material response on the grain scale.…”

The influence of the mechanical properties of a steel substrate on the macroscopic strength of a coated material

“…A plane strain boundary-value problem is solved by the finite difference method with the use of the Wilkins scheme [1][2][3][4]. A ceramic coating and steel substrate are described as elastic-brittle and elastic-plastic solids, respectively.…”

Investigation on Effect of Strain Rate and Heat Generation on Traverse Force in FSW of Dissimilar Aerospace Grade Aluminium Alloys

“…FSW, invented in 1991 by W.M. Thomas at TWI [3], finds numerous applications [4,5,6,7] in a short time span compared to other welding processes. However, a coherent understanding of FSW process has not yet been achieved and there persists the quest for even better understanding of various aspects of the process, such as strain, strain rate, evolution of process forces, etc.…”